A novel organic compound is provided. That is, a novel organic compound that is effective in improving the element characteristics and reliability is provided. An organic compound has a benzonaphthofuran skeleton and a triazine skeleton and is represented by General Formula (G1) below. (In the formula, Ar1, Ar2, and Ar3 separately represent a substituted or unsubstituted phenylene group, and each of m and n is independently 0 or 1. R1 and R2 separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. B1 to B3 separately represent nitrogen or carbon, and at least one of B1 to B3 represents nitrogen. In addition, A is represented by General Formula (G1-1). Any one of R3 to R12 is bonded to Ar1, and the others separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. Furthermore, Q represents S or O.)

BACKGROUND OF THE INVENTION

1. Field of the Invention

One embodiment of the present invention relates to an organic compound, a light-emitting element, a light-emitting device, an electronic device, and a lighting device. Note that one embodiment of the present invention is not limited thereto. That is, one embodiment of the present invention relates to an object, a method, a manufacturing method, or a driving method. One embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Specific examples include a semiconductor device, a display device, a liquid crystal display device, and the like.

2. Description of the Related Art

A light-emitting element including an electroluminescent (EL) layer between a pair of electrodes (also referred to as an organic EL element) has characteristics such as thinness, light weight, high-speed response to input signals, and low power consumption; thus, a display including such a light-emitting element has attracted attention as a next-generation flat panel display.

In a light-emitting element, voltage application between a pair of electrodes causes, in an EL layer, recombination of electrons and holes injected from the electrodes, which brings a light-emitting substance (organic compound) contained in the EL layer into an excited state. Light is emitted when the light-emitting substance returns to the ground state from the excited state. The excited state can be a singlet excited state (S*) and a triplet excited state (T′). Light emission from a singlet excited state is referred to as fluorescence, and light emission from a triplet excited state is referred to as phosphorescence. The statistical generation ratio thereof in the light-emitting element is considered to be S*:T*=1:3. Since the spectrum of light emitted from a light-emitting substance depends on the light-emitting substance, the use of different types of organic compounds as light-emitting substances makes it possible to obtain light-emitting elements which exhibit various colors.

In order to improve element characteristics of such a light-emitting element, improvement of an element structure, development of a material, and the like have been actively carried out (see Patent Document 1, for example).

REFERENCE

SUMMARY OF THE INVENTION

In development of light-emitting elements, organic compounds used in the light-emitting element are very important for improving the characteristics and reliability. Thus, an object of one embodiment of the present invention is to provide a novel organic compound. That is, an object is to provide a novel organic compound that is effective in improving the element characteristics and reliability. Another object of one embodiment of the present invention is to provide a novel organic compound that can be used in a light-emitting element. Another object of one embodiment of the present invention is to provide a novel organic compound that can be used in an EL layer of a light-emitting element. Another object is to provide a highly efficient, highly reliable, and novel light-emitting element using a novel organic compound of one embodiment of the present invention. Another object is to provide a novel light-emitting device, a novel electronic device, or a novel lighting device. Note that the description of these objects does not disturb the existence of other objects. In one embodiment of the present invention, there is not necessarily a need to achieve all the objects. Other objects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.

In General Formula (G1), Ar1, Ar2, and Ar3separately represent a substituted or unsubstituted phenylene group, and each of m and n is independently 0 or 1. R1and R2separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. B1to B3separately represent nitrogen or carbon, and at least one of B1to B3represents nitrogen. In addition, A is represented by General Formula (G1-1). Any one of R3to R12is bonded to Ar1, and the others separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. Furthermore, Q represents S or O.

In General Formula (G2), R1and R2separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. R13to R20separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. In addition, A is represented by General Formula (G2-1). Any one of R3to R12is bonded to Ar1, and the others separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. Furthermore, Q represents S or O.

In General Formula (G3), R1, R2, R3to R5, and R7to R20separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. In addition, Q represents S or O.

In General Formula (G4), R1, R2, R3to R6, and R8to R20separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. In addition, Q represents S or O.

Another embodiment of the present invention is an organic compound represented by General Formula (G5) below.

In General Formula (G5), R3to R5and R7to R30separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. In addition, Q represents S or O.

In General Formula (G6), R3to R6and R8to R30separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. In addition, Q represents S or O.

The organic compound of each of the above embodiments of the present invention has a benzonaphthofuran structure or a benzonaphthothiophene structure. In the structure, dibenzofuran or dibenzothiophene, in which two benzene rings are fused to a heteroaromatic ring, is further fused. The organic compound having such a fused benzonaphthofuran structure or benzonaphthothiophene structure can improve reliability. In addition, by bonding a substituent to a benzene skeleton fused to a furan skeleton or a thiophene skeleton in a benzonaphthofuran structure or a benzonaphthothiophene structure, extension of conjugation can be suppressed, and broadening of spin density distribution at T1 (triplet excitation level) can be suppressed. This enables high reliability without lowering T1.

Another embodiment of the present invention is an organic compound represented by Structural Formula (100) or Structural Formula (121).

Another embodiment of the present invention is a light-emitting element containing an organic compound having a benzonaphthofuran skeleton and a triazine skeleton. The present invention also includes a light-emitting element containing the above organic compound and a substance that converts triplet excitation energy into light emission, such as a phosphorescent material including an organometallic complex or a thermally activated delayed fluorescence (TADF) material.

Another embodiment of the present invention is a light-emitting element containing the organic compound of one embodiment of the present invention. Note that the present invention also includes a light-emitting element in which an EL layer provided between a pair of electrodes or a light-emitting layer included in the EL layer contains the organic compound of one embodiment of the present invention. In addition to the above light-emitting elements, a light-emitting device including a transistor, a substrate, or the like is also included in the scope of the invention. Furthermore, in addition to the light-emitting device, an electronic device and a lighting device that include a microphone, a camera, an operation button, an external connection portion, a housing, a cover, a support, a speaker, or the like are also included in the scope of the invention.

The organic compound of one embodiment of the present invention can be used as a light-emitting substance. Alternatively, the organic compound of one embodiment of the present invention can be used in combination with a light-emitting substance that emits phosphorescence (phosphorescent compound) for a light-emitting layer of a light-emitting element. That is, light emission from a triplet excited state can be obtained from the light-emitting layer; thus, the efficiency of the light-emitting element can be improved, which is very effective. Accordingly, one embodiment of the present invention also includes a light-emitting element in which the organic compound of one embodiment of the present invention and a phosphorescent compound are used in combination in a light-emitting layer. A structure in which the light-emitting layer further contains a third substance may also be employed.

One embodiment of the present invention includes, in its scope, a light-emitting device including a light-emitting element, and a lighting device including the light-emitting device. Accordingly, the light-emitting device in this specification refers to an image display device and a light source (including a lighting device). In addition, the light-emitting device includes, in its category, all of a module in which a connector such as a flexible printed circuit (FPC) or a tape carrier package (TCP) is connected to a light-emitting device, a module in which a printed wiring board is provided at the end of a TCP, and a module in which an integrated circuit (IC) is directly mounted on a light-emitting element by a chip on glass (COG) method.

According to one embodiment of the present invention, a novel organic compound can be provided. In other words, a novel organic compound that is effective in improving the element characteristics and reliability can be provided. According to one embodiment of the present invention, a novel organic compound that can be used in a light-emitting element can be provided. According to one embodiment of the present invention, a novel organic compound that can be used in an EL layer of a light-emitting element can be provided. According to one embodiment of the present invention, a highly efficient, highly reliable, and novel light-emitting element using a novel organic compound of one embodiment of the present invention can be provided. In addition, a novel light-emitting device, a novel electronic device, or a novel lighting device can be provided. Note that the description of these effects does not disturb the existence of other effects. In one embodiment of the present invention, there is not necessarily a need to achieve all the effects. Other effects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following description, and the modes and details of the present invention can be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description in the following embodiments.

Note that the position, size, range, or the like of each component illustrated in drawings and the like is not accurately represented in some cases for easy understanding. Therefore, the disclosed invention is not necessarily limited to the position, size, range, or the like disclosed in the drawings and the like.

In the description of modes of the present invention with reference to the drawings in this specification and the like, the same components in different diagrams are commonly denoted by the same reference numeral.

In this embodiment, organic compounds each of which is one embodiment of the present invention are described.

The organic compound of one embodiment of the present invention has a benzonaphthofuran skeleton and a triazine skeleton and has a structure represented by General Formula (G1) below.

In General Formula (G1), Ar1, Ar2, and Ar3separately represent a substituted or unsubstituted phenylene group, and each of m and n is independently 0 or 1. R1and R2separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. B1to B3separately represent nitrogen or carbon, and at least one of B1to B3represents nitrogen. In addition, A is represented by General Formula (G1-1). Any one of R3to R12is bonded to Ar1, and the others separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. Furthermore, Q represents S or O.

An organic compound described in this embodiment is represented by General Formula (G2) below.

In General Formula (G2), R1and R2separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. R13to R20separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. In addition, A is represented by General Formula (G2-1). Any one of R3to R12is bonded to Ar1, and the others separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. Furthermore, Q represents S or O.

An organic compound described in this embodiment is represented by General Formula (G3) below.

In General Formula (G3), R1, R2, R3to R5, and R7to R20separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. In addition, Q represents S or O.

An organic compound described in this embodiment is represented by General Formula (G4) below.

In General Formula (G4), R1, R2, R3to R6, and R8to R20separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. In addition, Q represents S or O.

An organic compound described in this embodiment is represented by General Formula (G5) below.

In General Formula (G5), R3to R5and R7to R30separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. In addition, Q represents S or O.

An organic compound described in this embodiment is represented by General Formula (G6) below.

In General Formula (G6), R3to R6and R8to R30separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. In addition, Q represents S or O.

In any of General Formulae (G1) to (G6), when any of the substituted or unsubstituted phenyl group, the substituted or unsubstituted biphenyl group, the substituted or unsubstituted terphenyl group, the substituted or unsubstituted fluorenyl group, the substituted or unsubstituted methylfluorenyl group, the substituted or unsubstituted dimethylfluorenyl group, the substituted or unsubstituted spirofluorenyl group, the substituted or unsubstituted naphthyl group, or the substituted or unsubstituted phenanthrenyl group has a substituent, examples of the substituent include an alkyl group having 1 to 6 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, or a hexyl group; a cycloalkyl group having 5 to 7 carbon atoms, such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a 1-norbornyl group, or a 2-norbornyl group; and an aryl group having 6 to 12 carbon atoms, such as a phenyl group or a biphenyl group. These substituents may be bonded to each other to form a ring.

Specific examples of the alkyl group having 1 to 6 carbon atoms which is represented by any of R1to R30in General Formulae (G1) to (G6) include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a neopentyl group, a hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, a neohexyl group, a 3-methylpentyl group, a 2-methylpentyl group, a 2-ethylbutyl group, a 1,2-dimethylbutyl group, a 2,3-dimethylbutyl group, and the like.

The organic compound of one embodiment of the present invention which is represented by any of General Formulae (G1) to (G6) has a benzonaphthofuran structure or a benzonaphthothiophene structure. In the structure, dibenzofuran or dibenzothiophene, in which two benzene rings are fused to a heteroaromatic ring, is further fused. The organic compound having such a fused benzonaphthofuran structure or benzonaphthothiophene structure can improve reliability. In addition, by bonding a substituent to a benzene skeleton fused to a furan skeleton or a thiophene skeleton in a benzonaphthofuran structure or a benzonaphthothiophene structure, extension of conjugation can be suppressed, and broadening of spin density distribution at T1 (triplet excitation level) can be suppressed. This enables high reliability without lowering T1.

Next, specific structural formulae of the above-described organic compounds, each of which is one embodiment of the present invention, are shown below. Note that the present invention is not limited to these formulae.

Note that organic compounds represented by Structural Formulae (100) to (171) are examples of the organic compound represented by General Formula (G1). The organic compound of one embodiment of the present invention is not limited thereto.

Next, an example of a method for synthesizing the organic compound of one embodiment of the present invention is described.

<<Method for Synthesizing Organic Compound Represented by General Formula (G1)>>

First, an example of a method for synthesizing the organic compound represented by General Formula (G1) will be described.

In General Formula (G1), Ar1, Ar2, and Ar3separately represent a substituted or unsubstituted phenylene group, and each of m and n is independently 0 or 1. R1and R2separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. B1to B3separately represent nitrogen or carbon, and at least one of B1to B3represents nitrogen. In addition, A is represented by General Formula (G1-1). Any one of R3to R12is bonded to Ar1, and the others separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. Furthermore, Q represents S (sulfur) or O (oxygen).

The organic compound (G1) of one embodiment of the present invention can be synthesized by Synthesis Scheme (A-1) shown below. That is, a halogen compound or a compound having a triflate group of a heterocyclic compound (a1) is coupled with a boronic acid or an organoboron compound of a benzo[b]naphtho[1,2-d]furan compound or a benzo[b]naphtho[1,2-d]thiophene compound (a2) by the Suzuki-Miyaura reaction using a palladium catalyst, whereby the organic compound (G1) of one embodiment of the present invention can be obtained.

In Synthesis Scheme (A-1), Ar1, Ar2, and Ar3in the compound (a1) separately represent a substituted or unsubstituted phenylene group, and each of m and n is independently 0 or 1. R1and R2separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. B1to B3separately represent nitrogen or carbon, and at least one of B1to B3represents nitrogen. In addition, X represents a halogen or a triflate group. When X represents a halogen, chlorine, bromine, or iodine is particularly preferable as the halogen.

In addition, A in the compound (a2) is represented by General Formula (G1-1) below. In the case where the compound (a2) is a boronic acid, R51and R52each represent hydrogen. The boronic acid of the compound (a2) may be protected by ethylene glycol or the like, and in this case, R51and R52in the compound (a2) each represent an alkyl group having 1 to 6 carbon atoms. In the case where the compound (a2) is an organoboron compound, R51and R52may be the same or different and may be bonded to each other to form a ring.

In General Formula (G1-1), any one of R3to R12is bonded to Ar1, and the others separately represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted methylfluorenyl group, a substituted or unsubstituted dimethylfluorenyl group, a substituted or unsubstituted spirofluorenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthrenyl group. Furthermore, Q represents S (sulfur) or O (oxygen).

For Synthesis Scheme (A-1), palladium(II) acetate, tetrakis(triphenylphosphine)palladium(0), or the like can be used as the palladium catalyst. Examples of a ligand of the palladium catalyst include tri(ortho-tolyl)phosphine, triphenylphosphine, and tricyclohexylphosphine. As a base, an organic base such as sodium tert-butoxide, an inorganic base such as potassium carbonate or sodium carbonate, or the like can be used. As a solvent, any of the following can be used: toluene, xylene, benzene, an ether (e.g., 1,2-dimethoxyethane), an alcohol (e.g., ethanol), water, and a mixed solvent of any of them (e.g., a mixed solvent of toluene and ethanol, a mixed solvent of toluene and water, a mixed solvent of xylene and ethanol, a mixed solvent of xylene and water, or a mixed solvent of benzene and ethanol).

An organoboron compound or a boronic acid of a quinoxaline derivative may be coupled with a halogen compound or a compound having a triflate group of an aryl derivative by the Suzuki-Miyaura reaction shown by Synthesis Scheme (A-1).

The above is the description of a method for synthesizing the organic compound (G1) of one embodiment of the present invention; however, the present invention is not limited thereto, and another synthesis method may be employed.

Note that the above organic compounds which are embodiments of the present invention each have an electron-transport property and a hole-transport property and can thus be used as a host material in a light-emitting layer or can be used in an electron-transport layer or a hole-transport layer. Furthermore, the above organic compounds are preferably used in combination with a substance that emits phosphorescence (phosphorescent material), as host materials. In addition, the above organic compounds emit fluorescence and can thus be used as light-emitting substances of light-emitting elements. Accordingly, light-emitting elements containing these organic compounds are also included as embodiments of the present invention.

With the use of the organic compound of one embodiment of the present invention, a light-emitting element, a light-emitting device, an electronic device, or a lighting device with high emission efficiency can be obtained. In addition, a light-emitting element, a light-emitting device, an electronic device, or a lighting device with low power consumption can be obtained.

In this embodiment, one embodiment of the present invention has been described. Other embodiments of the present invention are described in the other embodiments. Note that one embodiment of the present invention is not limited thereto. In other words, since various embodiments of the invention are described in this embodiment and the other embodiments, one embodiment of the present invention is not limited to a particular embodiment. For example, although an example of use in a light-emitting element is described in this embodiment, one embodiment of the present invention is not limited thereto. Depending on circumstances, one embodiment of the present invention may be used in objects other than a light-emitting element. Furthermore, depending on circumstances, one embodiment of the present invention does not necessarily need to be used in a light-emitting element.

The structures described in this embodiment can be combined with any of the structures described in the other embodiments as appropriate.

In this embodiment, a light-emitting element including any of the organic compounds described in Embodiment 1 is described with reference toFIGS. 1A to 1D.

A basic structure of a light-emitting element will be described.FIG. 1Aillustrates a light-emitting element including, between a pair of electrodes, an EL layer having a light-emitting layer. Specifically, an EL layer103is provided between a first electrode101and a second electrode102.

FIG. 1Billustrates a light-emitting element that has a stacked-layer structure (tandem structure) in which a plurality of EL layers (two EL layers103aand103binFIG. 1B) are provided between a pair of electrodes and a charge-generation layer104is provided between the EL layers. With the use of such a tandem light-emitting element, a light-emitting device which can be driven at low voltage with low power consumption can be obtained.

The charge-generation layer104has a function of injecting electrons into one of the EL layers (103aor103b) and injecting holes into the other of the EL layers (103bor103a) when voltage is applied between the first electrode101and the second electrode102. Thus, when voltage is applied inFIG. 1Bsuch that the potential of the first electrode101is higher than that of the second electrode102, the charge-generation layer104injects electrons into the EL layer103aand injects holes into the EL layer103b.

Note that in terms of light extraction efficiency, the charge-generation layer104preferably has a property of transmitting visible light (specifically, the charge-generation layer104has a visible light transmittance of 40% or more). The charge-generation layer104functions even when it has lower conductivity than the first electrode101or the second electrode102.

FIG. 1Cillustrates a stacked-layer structure of the EL layer103in the light-emitting element of one embodiment of the present invention. In this case, the first electrode101is regarded as functioning as an anode. The EL layer103has a structure in which a hole-injection layer111, a hole-transport layer112, a light-emitting layer113, an electron-transport layer114, and an electron-injection layer115are stacked in this order over the first electrode101. Even in the case where a plurality of EL layers are provided as in the tandem structure illustrated inFIG. 1B, the layers in each EL layer are sequentially stacked from the anode side as described above. When the first electrode101is a cathode and the second electrode102is an anode, the stacking order is reversed.

The light-emitting layer113included in the EL layers (103,103a, and103b) contains an appropriate combination of a light-emitting substance and a plurality of substances, so that fluorescence or phosphorescence of a desired emission color can be obtained. The light-emitting layer113may have a stacked-layer structure having different emission colors. In that case, the light-emitting substance and other substances are different between the stacked light-emitting layers. Alternatively, the plurality of EL layers (103aand103b) inFIG. 1Bmay exhibit their respective emission colors. Also in that case, the light-emitting substance and other substances are different between the light-emitting layers.

In the light-emitting element of one embodiment of the present invention, for example, a micro optical resonator (microcavity) structure in which the first electrode101is a reflective electrode and the second electrode102is a transflective electrode can be employed inFIG. 1C, whereby light emission from the light-emitting layer113in the EL layer103can be resonated between the electrodes and light emission obtained through the second electrode102can be intensified.

Note that when the first electrode101of the light-emitting element is a reflective electrode having a structure in which a reflective conductive material and a light-transmitting conductive material (transparent conductive film) are stacked, optical adjustment can be performed by controlling the thickness of the transparent conductive film. Specifically, when the wavelength of light obtained from the light-emitting layer113is λ, the distance between the first electrode101and the second electrode102is preferably adjusted to around mλ/2 (m is a natural number).

To amplify desired light (wavelength: λ) obtained from the light-emitting layer113, the optical path length from the first electrode101to a region where the desired light is obtained in the light-emitting layer113(light-emitting region) and the optical path length from the second electrode102to the region where the desired light is obtained in the light-emitting layer113(light-emitting region) are preferably adjusted to around (2m′+1)λ/4 (m′ is a natural number). Here, the light-emitting region means a region where holes and electrons are recombined in the light-emitting layer113.

By such optical adjustment, the spectrum of specific monochromatic light obtained from the light-emitting layer113can be narrowed and light emission with high color purity can be obtained.

In that case, the optical path length between the first electrode101and the second electrode102is, to be exact, the total thickness from a reflective region in the first electrode101to a reflective region in the second electrode102. However, it is difficult to exactly determine the reflective regions in the first electrode101and the second electrode102; thus, it is assumed that the above effect can be sufficiently obtained wherever the reflective regions may be set in the first electrode101and the second electrode102. Furthermore, the optical path length between the first electrode101and the light-emitting layer emitting the desired light is, to be exact, the optical path length between the reflective region in the first electrode101and the light-emitting region in the light-emitting layer emitting the desired light. However, it is difficult to precisely determine the reflective region in the first electrode101and the light-emitting region in the light-emitting layer emitting the desired light; thus, it is assumed that the above effect can be sufficiently obtained wherever the reflective region and the light-emitting region may be set in the first electrode101and the light-emitting layer emitting the desired light.

The light-emitting element inFIG. 1Chas a microcavity structure, so that light (monochromatic light) with different wavelengths can be extracted even if the same EL layer is used. Thus, separate coloring for obtaining a plurality of emission colors (e.g., R, G, and B) is not necessary. Therefore, high resolution can be easily achieved. Note that a combination with coloring layers (color filters) is also possible. Furthermore, emission intensity of light with a specific wavelength in the front direction can be increased, whereby power consumption can be reduced.

In the light-emitting element of one embodiment of the present invention, at least one of the first electrode101and the second electrode102is a light-transmitting electrode (e.g., a transparent electrode or a transflective electrode). In the case where the light-transmitting electrode is a transparent electrode, the transparent electrode has a visible light transmittance of higher than or equal to 40%. In the case where the light-transmitting electrode is a transflective electrode, the transflective electrode has a visible light reflectance of higher than or equal to 20% and lower than or equal to 80%, and preferably higher than or equal to 40% and lower than or equal to 70%. These electrodes preferably have a resistivity of 1×10−2Ωcm or less.

Furthermore, when one of the first electrode101and the second electrode102is a reflective electrode in the light-emitting element of one embodiment of the present invention, the visible light reflectance of the reflective electrode is higher than or equal to 40% and lower than or equal to 100%, and preferably higher than or equal to 70% and lower than or equal to 100%. This electrode preferably has a resistivity of 1×10−2Ωcm or less.

<<Specific Structure and Fabrication Method of Light-Emitting Element>>

Specific structures and specific fabrication methods of light-emitting elements of embodiments of the present invention will be described. Here, a light-emitting element having the tandem structure inFIG. 1Band a microcavity structure will be described with reference toFIG. 1D. In the light-emitting element inFIG. 1D, the first electrode101is formed as a reflective electrode and the second electrode102is formed as a transflective electrode. Thus, a single-layer structure or a stacked-layer structure can be formed using one or more kinds of desired electrode materials. Note that the second electrode102is formed after formation of the EL layer103b, with the use of a material selected as described above. For fabrication of these electrodes, a sputtering method or a vacuum evaporation method can be used.

<First Electrode and Second Electrode>

As materials used for the first electrode101and the second electrode102, any of the following materials can be used in an appropriate combination as long as the functions of the electrodes described above can be fulfilled. For example, a metal, an alloy, an electrically conductive compound, a mixture of these, and the like can be appropriately used. Specifically, an In—Sn oxide (also referred to as ITO), an In—Si—Sn oxide (also referred to as ITSO), an In—Zn oxide, an In—W—Zn oxide, or the like can be used. In addition, it is possible to use a metal such as aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo), tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt), silver (Ag), yttrium (Y), or neodymium (Nd) or an alloy containing an appropriate combination of any of these metals. It is also possible to use a Group 1 element or a Group 2 element in the periodic table, which is not described above (e.g., lithium (Li), cesium (Cs), calcium (Ca), or strontium (Sr)), a rare earth metal such as europium (Eu) or ytterbium (Yb), an alloy containing an appropriate combination of any of these elements, graphene, or the like.

In the light-emitting element inFIG. 1D, when the first electrode101is an anode, a hole-injection layer111aand a hole-transport layer112aof the EL layer103aare sequentially stacked over the first electrode101by a vacuum evaporation method. After the EL layer103aand the charge-generation layer104are formed, a hole-injection layer111band a hole-transport layer112bof the EL layer103bare sequentially stacked over the charge-generation layer104in a similar manner.

The hole-injection layers (111,111a, and111b) inject holes from the first electrode101that is an anode and the charge-generation layer (104) to the EL layers (103,103a, and103b) and each contain a material with a high hole-injection property.

As examples of the material with a high hole-injection property, transition metal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide can be given. Alternatively, it is possible to use any of the following materials: phthalocyanine-based compounds such as phthalocyanine (abbreviation: H2Pc) and copper phthalocyanine (abbreviation: CuPc); aromatic amine compounds such as 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB) and N,N′-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (abbreviation: DNTPD); high molecular compounds such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (abbreviation: PEDOT/PSS); and the like.

Alternatively, as the material with a high hole-injection property, a composite material containing a hole-transport material and an acceptor material (an electron-accepting material) can also be used. In that case, the acceptor material extracts electrons from the hole-transport material, so that holes are generated in the hole-injection layers (111,111a, and111b) and the holes are injected into the light-emitting layers (113,113a, and113b) through the hole-transport layers (112,112a, and112b). Note that each of the hole-injection layers (111,111a, and111b) may be formed to have a single-layer structure using a composite material containing a hole-transport material and an acceptor material (electron-accepting material), or a stacked-layer structure in which a layer including a hole-transport material and a layer including an acceptor material (electron-accepting material) are stacked.

The hole-transport layers (112,112a, and112b) transport the holes, which are injected from the first electrode101and the charge-generation layer (104) by the hole-injection layers (111,111a, and111b), to the light-emitting layers (113,113a, and113b). Note that the hole-transport layers (112,112a, and112b) each contain a hole-transport material. It is particularly preferable that the HOMO level of the hole-transport material included in the hole-transport layers (112,112a, and112b) be the same as or close to that of the hole-injection layers (111,111a, and111b).

Examples of the acceptor material used for the hole-injection layers (111,111a, and111b) include an oxide of a metal belonging to any of Groups 4 to 8 of the periodic table. Specifically, molybdenum oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, tungsten oxide, manganese oxide, and rhenium oxide can be given. Among these, molybdenum oxide is especially preferable since it is stable in the air, has a low hygroscopic property, and is easy to handle. Alternatively, organic acceptors such as a quinodimethane derivative, a chloranil derivative, and a hexaazatriphenylene derivative can be used. Specifically, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), and the like can be used.

The hole-transport materials used for the hole-injection layers (111,111a, and111b) and the hole-transport layers (112,112a, and112b) are preferably substances with a hole mobility of greater than or equal to 10−6cm2/Vs. Note that other substances may be used as long as the substances have a hole-transport property higher than an electron-transport property.

Note that the hole-transport material is not limited to the above examples and may be one of or a combination of various known materials when used for the hole-injection layers (111,111a, and111b) and the hole-transport layers (112,112a, and112b).

Next, in the light-emitting element inFIG. 1D, the light-emitting layer113ais formed over the hole-transport layer112aof the EL layer103aby a vacuum evaporation method. After the EL layer103aand the charge-generation layer104are formed, the light-emitting layer113bis formed over the hole-transport layer112bof the EL layer103bby a vacuum evaporation method.

The light-emitting layers (113,113a, and113b) each contain a light-emitting substance. Note that as the light-emitting substance, a substance whose emission color is blue, violet, bluish violet, green, yellowish green, yellow, orange, red, or the like is appropriately used. When the plurality of light-emitting layers (113aand113b) are formed using different light-emitting substances, different emission colors can be exhibited (for example, complementary emission colors are combined to achieve white light emission). Furthermore, a stacked-layer structure in which one light-emitting layer contains two or more kinds of light-emitting substances may be employed.

The light-emitting layers (113,113a, and113b) may each contain one or more kinds of organic compounds (a host material and an assist material) in addition to a light-emitting substance (guest material). As the one or more kinds of organic compounds, one or both of the hole-transport material and the electron-transport material described in this embodiment can be used.

There is no particular limitation on light-emitting substances other than the above that can be used for the light-emitting layers (113,113a, and113b), and a light-emitting substance that converts singlet excitation energy into light emission in the visible light range or a light-emitting substance that converts triplet excitation energy into light emission in the visible light range can be used. Examples of the light-emitting substance are given below.

As an example of the light-emitting substance that converts singlet excitation energy into light emission, a substance that emits fluorescence (fluorescent material) can be given. Examples of the substance that emits fluorescence include a pyrene derivative, an anthracene derivative, a triphenylene derivative, a fluorene derivative, a carbazole derivative, a dibenzothiophene derivative, a dibenzofuran derivative, a dibenzoquinoxaline derivative, a quinoxaline derivative, a pyridine derivative, a pyrimidine derivative, a phenanthrene derivative, and a naphthalene derivative. A pyrene derivative is particularly preferable because it has a high emission quantum yield. Specific examples of the pyrene derivative include N,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N′-diphenyl-N,N′-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N′-bis(dibenzofuran-2-yl)-N,N′-diphenylpyrene-1,6-diamine (abbreviation: 1,6FrAPrn), N,N′-bis(dibenzothiophen-2-yl)-N,N′-diphenylpyrene-1,6-diamine (abbreviation: 1,6ThAPrn), N,N′-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-6-amine](abbreviation: 1,6BnfAPrn), N,N′-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-02), and N,N′-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-03).

As examples of a light-emitting substance that converts triplet excitation energy into light emission, a substance that emits phosphorescence (phosphorescent material) and a thermally activated delayed fluorescence (TADF) material that exhibits thermally activated delayed fluorescence can be given.

Examples of a phosphorescent material include an organometallic complex, a metal complex (platinum complex), and a rare earth metal complex. These substances exhibit the respective emission colors (emission peaks) and thus, any of them is appropriately selected according to need.

As examples of a phosphorescent material which emits blue or green light and whose emission spectrum has a peak wavelength at greater than or equal to 450 nm and less than or equal to 570 nm, the following substances can be given.

As examples of a phosphorescent material which emits green or yellow light and whose emission spectrum has a peak wavelength at greater than or equal to 495 nm and less than or equal to 590 nm, the following substances can be given.

As examples of a phosphorescent material which emits yellow or red light and whose emission spectrum has a peak wavelength at greater than or equal to 570 nm and less than or equal to 750 nm, the following substances can be given.

As the organic compounds (the host material and the assist material) used in the light-emitting layers (113,113a, and113b), one or more kinds of substances having a larger energy gap than the light-emitting substance (the guest material) are used. Note that any of the hole-transport materials listed above and the electron-transport materials given below may be used as the organic compounds (the host material and the assist material).

When the light-emitting substance is a fluorescent material, it is preferable to use, as the host material, an organic compound that has a high energy level in a singlet excited state and has a low energy level in a triplet excited state. For example, an anthracene derivative or a tetracene derivative is preferably used. Specific examples include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl}anthracene (abbreviation: FLPPA), 5,12-diphenyltetracene, and 5,12-bis(biphenyl-2-yl)tetracene.

In the case where the light-emitting substance is a phosphorescent material, an organic compound having triplet excitation energy (energy difference between a ground state and a triplet excited state) which is higher than that of the light-emitting substance is preferably selected as the host material. In that case, it is possible to use a zinc- or aluminum-based metal complex, an oxadiazole derivative, a triazole derivative, a benzimidazole derivative, a quinoxaline derivative, a dibenzoquinoxaline derivative, a dibenzothiophene derivative, a dibenzofuran derivative, a pyrimidine derivative, a triazine derivative, a pyridine derivative, a bipyridine derivative, a phenanthroline derivative, an aromatic amine, a carbazole derivative, and the like.

In the case where a plurality of organic compounds are used for the light-emitting layers (113,113a, and113b), compounds that form an exciplex are preferably used in combination with a phosphorescent substance. With such a structure, light emission can be obtained by exciplex-triplet energy transfer (ExTET), which is energy transfer from an exciplex to a phosphorescent substance. In that case, although any of various organic compounds can be used in an appropriate combination, in order to form an exciplex efficiently, it is particularly preferable to combine a compound that easily accepts holes (hole-transport material) and a compound that easily accepts electrons (electron-transport material). As the hole-transport material and the electron-transport material, specifically, any of the materials described in this embodiment can be used.

The TADF material is a material that can up-convert a triplet excited state into a singlet excited state (i.e., reverse intersystem crossing is possible) using a little thermal energy and efficiently exhibits light emission (fluorescence) from the singlet excited state. The TADF is efficiently obtained under the condition where the difference in energy between the triplet excited level and the singlet excited level is greater than or equal to 0 eV and less than or equal to 0.2 eV, preferably greater than or equal to 0 eV and less than or equal to 0.1 eV. Note that “delayed fluorescence” exhibited by the TADF material refers to light emission having the same spectrum as normal fluorescence and an extremely long lifetime. The lifetime is 10−6seconds or longer, preferably 10−3seconds or longer.

Examples of the TADF material include fullerene, a derivative thereof, an acridine derivative such as proflavine, and eosin. Other examples include a metal-containing porphyrin, such as a porphyrin containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd). Examples of the metal-containing porphyrin include a protoporphyrin-tin fluoride complex (abbreviation: SnF2(Proto IX)), a mesoporphyrin-tin fluoride complex (abbreviation: SnF2(Meso IX)), a hematoporphyrin-tin fluoride complex (abbreviation: SnF2(Hemato IX)), a coproporphyrin tetramethyl ester-tin fluoride complex (abbreviation: SnF2(Copro III-4Me)), an octaethylporphyrin-tin fluoride complex (abbreviation: SnF2(OEP)), an etioporphyrin-tin fluoride complex (abbreviation: SnF2(Etio I)), and an octaethylporphyrin-platinum chloride complex (abbreviation: PtCl2OEP).

Alternatively, a heterocyclic compound having a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring, such as 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), or 10-phenyl-10H,10′H-spiro[acridin-9,9′-anthracen]-10′-one (abbreviation: ACRSA) can be used. Note that a substance in which the π-electron rich heteroaromatic ring is directly bonded to the π-electron deficient heteroaromatic ring is particularly preferable because both the donor property of the π-electron rich heteroaromatic ring and the acceptor property of the π-electron deficient heteroaromatic ring are increased and the energy difference between the singlet excited state and the triplet excited state becomes small.

Note that when a TADF material is used, the TADF material can be combined with another organic compound.

In the light-emitting element inFIG. 1D, the electron-transport layer114ais formed over the light-emitting layer113aof the EL layer103aby a vacuum evaporation method. After the EL layer103aand the charge-generation layer104are formed, the electron-transport layer114bis formed over the light-emitting layer113bof the EL layer103bby a vacuum evaporation method.

The electron-transport layers (114,114a, and114b) transport the electrons, which are injected from the second electrode102and the charge-generation layer (104) by the electron-injection layers (115,115a, and115b), to the light-emitting layers (113,113a, and113b). Note that the electron-transport layers (114,114a, and114b) each contain an electron-transport material. It is preferable that the electron-transport materials included in the electron-transport layers (114,114a, and114b) be substances with an electron mobility of higher than or equal to 1×10−6cm2/Vs. Note that other substances may also be used as long as the substances have an electron-transport property higher than a hole-transport property.

Examples of the electron-transport material include metal complexes having a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, and a thiazole ligand; an oxadiazole derivative; a triazole derivative; a phenanthroline derivative; a pyridine derivative; and a bipyridine derivative. In addition, a π-electron deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound can also be used.

Each of the electron-transport layers (114,114a, and114b) is not limited to a single layer, but may be a stack of two or more layers each containing any of the above substances.

Next, in the light-emitting element inFIG. 1D, the electron-injection layer115ais formed over the electron-transport layer114aof the EL layer103aby a vacuum evaporation method. Subsequently, the EL layer103aand the charge-generation layer104are formed, the components up to the electron-transport layer114bof the EL layer103bare formed, and then the electron-injection layer115bis formed thereover by a vacuum evaporation method.

The electron-injection layers (115,115a, and115b) each contain a substance having a high electron-injection property. The electron-injection layers (115,115a, and115b) can each be formed using an alkali metal, an alkaline earth metal, or a compound thereof, such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), or lithium oxide (LiOx). A rare earth metal compound like erbium fluoride (ErF3) can also be used. Electride may also be used for the electron-injection layers (115,115a, and115b). Examples of the electride include a substance in which electrons are added at high concentration to calcium oxide-aluminum oxide. Any of the substances for forming the electron-transport layers (114,114a, and114b), which are given above, can also be used.

A composite material in which an organic compound and an electron donor (donor) are mixed may also be used for the electron-injection layers (115,115a, and115b). Such a composite material is excellent in an electron-injection property and an electron-transport property because electrons are generated in the organic compound by the electron donor. The organic compound here is preferably a material excellent in transporting the generated electrons; specifically, for example, the electron-transport materials for forming the electron-transport layers (114,114a, and114b) (e.g., a metal complex or a heteroaromatic compound) can be used. As the electron donor, a substance showing an electron-donating property with respect to the organic compound may be used. Preferable examples are an alkali metal, an alkaline earth metal, and a rare earth metal. Specifically, lithium, cesium, magnesium, calcium, erbium, ytterbium, and the like can be given. Furthermore, an alkali metal oxide and an alkaline earth metal oxide are preferable, and a lithium oxide, a calcium oxide, a barium oxide, and the like can be given. Alternatively, a Lewis base such as magnesium oxide can be used. Further alternatively, an organic compound such as tetrathiafulvalene (abbreviation: TTF) can be used.

In the case where light obtained from the light-emitting layer113bis amplified in the light-emitting element illustrated inFIG. 1D, for example, the optical path length between the second electrode102and the light-emitting layer113bis preferably less than one fourth of the wavelength λ of light emitted from the light-emitting layer113b. In that case, the optical path length can be adjusted by changing the thickness of the electron-transport layer114bor the electron-injection layer115b.

The charge-generation layer104has a function of injecting electrons into the EL layer103aand injecting holes into the EL layer103bwhen a voltage is applied between the first electrode (anode)101and the second electrode (cathode)102. The charge-generation layer104may have either a structure in which an electron acceptor (acceptor) is added to a hole-transport material or a structure in which an electron donor (donor) is added to an electron-transport material. Alternatively, both of these structures may be stacked. Note that forming the charge-generation layer104by using any of the above materials can suppress an increase in drive voltage caused by the stack of the EL layers.

In the case where the charge-generation layer104has a structure in which an electron acceptor is added to a hole-transport material, any of the materials described in this embodiment can be used as the hole-transport material. As the electron acceptor, it is possible to use 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, and the like. In addition, oxides of metals that belong to Group 4 to Group 8 of the periodic table can be given. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, or the like is used.

In the case where the charge-generation layer104has a structure in which an electron donor is added to an electron-transport material, any of the materials described in this embodiment can be used as the electron-transport material. As the electron donor, it is possible to use an alkali metal, an alkaline earth metal, a rare earth metal, metals that belong to Groups 2 and 13 of the periodic table, or an oxide or carbonate thereof. Specifically, lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb), indium (In), lithium oxide, cesium carbonate, or the like is preferably used. Alternatively, an organic compound such as tetrathianaphthacene may be used as the electron donor.

The light-emitting element described in this embodiment can be formed over any of a variety of substrates. Note that the type of the substrate is not limited to a certain type. Examples of the substrate include a semiconductor substrate (e.g., a single crystal substrate or a silicon substrate), an SOI substrate, a glass substrate, a quartz substrate, a plastic substrate, a metal substrate, a stainless steel substrate, a substrate including stainless steel foil, a tungsten substrate, a substrate including tungsten foil, a flexible substrate, an attachment film, paper including a fibrous material, and a base material film.

Examples of the glass substrate include a barium borosilicate glass substrate, an aluminoborosilicate glass substrate, and a soda lime glass substrate. Examples of the flexible substrate, the attachment film, and the base material film include plastics typified by polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyether sulfone (PES); a synthetic resin such as acrylic; polypropylene; polyester; polyvinyl fluoride; polyvinyl chloride; polyamide; polyimide; aramid; epoxy; an inorganic vapor deposition film; and paper.

For fabrication of the light-emitting element in this embodiment, a vacuum process such as an evaporation method or a solution process such as a spin coating method or an ink-jet method can be used. When an evaporation method is used, a physical vapor deposition method (PVD method) such as a sputtering method, an ion plating method, an ion beam evaporation method, a molecular beam evaporation method, or a vacuum evaporation method, a chemical vapor deposition method (CVD method), or the like can be used. Specifically, the functional layers (the hole-injection layers (111aand111b), the hole-transport layers (112aand112b), the light-emitting layers (113aand113b), the electron-transport layers (114aand114b), the electron-injection layers (115aand115b)) included in the EL layers and the charge-generation layer104of the light-emitting element can be formed by an evaporation method (e.g., a vacuum evaporation method), a coating method (e.g., a dip coating method, a die coating method, a bar coating method, a spin coating method, or a spray coating method), a printing method (e.g., an ink-jet method, screen printing (stencil), offset printing (planography), flexography (relief printing), gravure printing, micro-contact printing, or nanoimprinting), or the like.

Note that materials that can be used for the functional layers (the hole-injection layers (111aand111b), the hole-transport layers (112aand112b), the light-emitting layers (113aand113b), the electron-transport layers (114aand114b), and the electron-injection layers (115aand115b)) that are included in the EL layers (103aand103b) and the charge-generation layer104in the light-emitting element described in this embodiment are not limited to the above materials, and other materials can be used in combination as long as the functions of the layers are fulfilled. For example, a high molecular compound (e.g., an oligomer, a dendrimer, or a polymer), a middle molecular compound (a compound between a low molecular compound and a high molecular compound with a molecular weight of 400 to 4000), an inorganic compound (e.g., a quantum dot material), or the like can be used. The quantum dot may be a colloidal quantum dot, an alloyed quantum dot, a core-shell quantum dot, a core quantum dot, or the like.

The structures described in this embodiment can be combined with any of the structures described in the other embodiments as appropriate.

In this embodiment, a light-emitting device of one embodiment of the present invention is described. Note that a light-emitting device illustrated inFIG. 2Ais an active-matrix light-emitting device in which transistors (FETs)202are electrically connected to light-emitting elements (203R,203G,203B, and203W) over a first substrate201. The light-emitting elements (203R,203G,203B, and203W) include a common EL layer204and each have a microcavity structure in which the optical path length between electrodes is adjusted depending on the emission color of the light-emitting element. The light-emitting device is a top-emission light-emitting device in which light is emitted from the EL layer204through color filters (206R,206G, and206B) formed on a second substrate205.

The light-emitting device illustrated inFIG. 2Ais fabricated such that a first electrode207functions as a reflective electrode and a second electrode208functions as a transflective electrode. Note that description in any of the other embodiments can be referred to as appropriate for electrode materials for the first electrode207and the second electrode208.

In the case where the light-emitting element203R functions as a red light-emitting element, the light-emitting element203G functions as a green light-emitting element, the light-emitting element203B functions as a blue light-emitting element, and the light-emitting element203W functions as a white light-emitting element inFIG. 2A, for example, a gap between the first electrode207and the second electrode208in the light-emitting element203R is adjusted to have an optical path length200R, a gap between the first electrode207and the second electrode208in the light-emitting element203G is adjusted to have an optical path length200G, and a gap between the first electrode207and the second electrode208in the light-emitting element203B is adjusted to have an optical path length200B as illustrated inFIG. 2B. Note that optical adjustment can be performed in such a manner that a conductive layer207R is stacked over the first electrode207in the light-emitting element203R and a conductive layer207G is stacked over the first electrode207in the light-emitting element203G as illustrated inFIG. 2B.

The second substrate205is provided with the color filters (206R,206G, and206B). Note that the color filters each transmit visible light in a specific wavelength range and blocks visible light in a specific wavelength range. Thus, as illustrated inFIG. 2A, the color filter206R that transmits only light in the red wavelength range is provided in a position overlapping with the light-emitting element203R, whereby red light emission can be obtained from the light-emitting element203R. Furthermore, the color filter206G that transmits only light in the green wavelength range is provided in a position overlapping with the light-emitting element203G, whereby green light emission can be obtained from the light-emitting element203G. Moreover, the color filter206B that transmits only light in the blue wavelength range is provided in a position overlapping with the light-emitting element203B, whereby blue light emission can be obtained from the light-emitting element203B. Note that the light-emitting element203W can emit white light without a color filter. Note that a black layer (black matrix)209may be provided at an end portion of each color filter. The color filters (206R,206G, and206B) and the black layer209may be covered with an overcoat layer formed using a transparent material.

Although the light-emitting device inFIG. 2Ahas a structure in which light is extracted from the second substrate205side (top emission structure), a structure in which light is extracted from the first substrate201side where the FETs202are formed (bottom emission structure) may be employed as illustrated inFIG. 2C. In the case of a bottom-emission light-emitting device, the first electrode207is formed as a transflective electrode and the second electrode208is formed as a reflective electrode. As the first substrate201, a substrate having at least a light-transmitting property is used. As illustrated inFIG. 2C, color filters (206R′,206G′, and206B′) are provided so as to be closer to the first substrate201than the light-emitting elements (203R,203G, and203B) are.

InFIG. 2A, the light-emitting elements are the red light-emitting element, the green light-emitting element, the blue light-emitting element, and the white light-emitting element; however, the light-emitting elements of one embodiment of the present invention are not limited to the above, and a yellow light-emitting element or an orange light-emitting element may be used. Note that description in any of the other embodiments can be referred to as appropriate for materials that are used for the EL layers (a light-emitting layer, a hole-injection layer, a hole-transport layer, an electron-transport layer, an electron-injection layer, a charge-generation layer, and the like) to fabricate each of the light-emitting elements. In that case, a color filter needs to be appropriately selected depending on the emission color of the light-emitting element.

With the above structure, a light-emitting device including light-emitting elements that exhibit a plurality of emission colors can be fabricated.

Note that the structures described in this embodiment can be combined with any of the structures described in the other embodiments as appropriate.

In this embodiment, a light-emitting device of one embodiment of the present invention is described.

The use of the element structure of the light-emitting element of one embodiment of the present invention allows fabrication of an active-matrix light-emitting device or a passive-matrix light-emitting device. Note that an active-matrix light-emitting device has a structure including a combination of a light-emitting element and a transistor (FET). Thus, each of a passive-matrix light-emitting device and an active-matrix light-emitting device is one embodiment of the present invention. Note that any of the light-emitting elements described in other embodiments can be used in the light-emitting device described in this embodiment.

In this embodiment, an active-matrix light-emitting device will be described with reference toFIGS. 3A and 3B.

FIG. 3Ais a top view illustrating the light-emitting device, andFIG. 3Bis a cross-sectional view taken along chain line A-A′ inFIG. 3A. The active-matrix light-emitting device includes a pixel portion302, a driver circuit portion (source line driver circuit)303, and driver circuit portions (gate line driver circuits) (304aand304b) that are provided over a first substrate301. The pixel portion302and the driver circuit portions (303,304a, and304b) are sealed between the first substrate301and a second substrate306with a sealant305.

A lead wiring307is provided over the first substrate301. The lead wiring307is connected to an FPC308that is an external input terminal. Note that the FPC308transmits a signal (e.g., a video signal, a clock signal, a start signal, or a reset signal) or a potential from the outside to the driver circuit portions (303,304a, and304b). The FPC308may be provided with a printed wiring board (PWB). Note that the light-emitting device provided with an FPC or a PWB is included in the category of a light-emitting device.

FIG. 3Billustrates a cross-sectional structure of the light-emitting device.

The pixel portion302includes a plurality of pixels each of which includes an FET (switching FET)311, an FET (current control FET)312, and a first electrode313electrically connected to the FET312. Note that the number of FETs included in each pixel is not particularly limited and can be set appropriately.

As FETs309,310,311, and312, for example, a staggered transistor or an inverted staggered transistor can be used without particular limitation. A top-gate transistor, a bottom-gate transistor, or the like may be used.

Note that there is no particular limitation on the crystallinity of a semiconductor that can be used for the FETs309,310,311, and312, and an amorphous semiconductor or a semiconductor having crystallinity (a microcrystalline semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a semiconductor partly including crystal regions) may be used. A semiconductor having crystallinity is preferably used, in which case deterioration of the transistor characteristics can be suppressed.

For the semiconductor, a Group 14 element, a compound semiconductor, an oxide semiconductor, an organic semiconductor, or the like can be used, for example. As a typical example, a semiconductor containing silicon, a semiconductor containing gallium arsenide, or an oxide semiconductor containing indium can be used.

The driver circuit portion303includes the FET309and the FET310. The FET309and the FET310may be formed with a circuit including transistors having the same conductivity type (either n-channel transistors or p-channel transistors) or a CMOS circuit including an n-channel transistor and a p-channel transistor. Furthermore, a driver circuit may be provided outside.

An end portion of the first electrode313is covered with an insulator314. The insulator314can be formed using an organic compound such as a negative photosensitive resin or a positive photosensitive resin (acrylic resin), or an inorganic compound such as silicon oxide, silicon oxynitride, or silicon nitride. The insulator314preferably has a curved surface with curvature at an upper end portion or a lower end portion thereof. In that case, favorable coverage with a film formed over the insulator314can be obtained.

An EL layer315and a second electrode316are stacked over the first electrode313. The EL layer315includes a light-emitting layer, a hole-injection layer, a hole-transport layer, an electron-transport layer, an electron-injection layer, a charge-generation layer, and the like.

The structure and materials described in any of the other embodiments can be used for the components of a light-emitting element317described in this embodiment. Although not illustrated, the second electrode316is electrically connected to the FPC308that is an external input terminal.

Although the cross-sectional view inFIG. 3Billustrates only one light-emitting element317, a plurality of light-emitting elements are arranged in a matrix in the pixel portion302. Light-emitting elements that emit light of three kinds of colors (R, G, and B) are selectively formed in the pixel portion302, whereby a light-emitting device capable of displaying a full-color image can be obtained. In addition to the light-emitting elements that emit light of three kinds of colors (R, G, and B), for example, light-emitting elements that emit light of white (W), yellow (Y), magenta (M), cyan (C), and the like may be formed. For example, the light-emitting elements that emit light of some of the above colors are used in combination with the light-emitting elements that emit light of three kinds of colors (R, G, and B), whereby effects such as an improvement in color purity and a reduction in power consumption can be achieved. Alternatively, a light-emitting device which is capable of displaying a full-color image may be fabricated by a combination with color filters. As color filters, red (R), green (G), blue (B), cyan (C), magenta (M), and yellow (Y) color filters and the like can be used.

When the second substrate306and the first substrate301are bonded to each other with the sealant305, the FETs (309,310,311, and312) and the light-emitting element317over the first substrate301are provided in a space318surrounded by the first substrate301, the second substrate306, and the sealant305. Note that the space318may be filled with an inert gas (e.g., nitrogen or argon) or an organic substance (including the sealant305).

An epoxy-based resin, glass frit, or the like can be used for the sealant305. It is preferable to use a material that is permeable to as little moisture and oxygen as possible for the sealant305. As the second substrate306, a substrate that can be used as the first substrate301can be similarly used. Thus, any of the various substrates described in the other embodiments can be appropriately used. As the substrate, a glass substrate, a quartz substrate, or a plastic substrate made of fiber-reinforced plastic (FRP), polyvinyl fluoride (PVF), polyester, acrylic, or the like can be used. In the case where glass frit is used for the sealant, the first substrate301and the second substrate306are preferably glass substrates in terms of adhesion.

Accordingly, the active-matrix light-emitting device can be obtained.

In the case where the active-matrix light-emitting device is provided over a flexible substrate, the FETs and the light-emitting element may be directly formed over the flexible substrate; alternatively, the FETs and the light-emitting element may be formed over a substrate provided with a separation layer and then separated at the separation layer by application of heat, force, laser, or the like to be transferred to a flexible substrate. For the separation layer, a stack including inorganic films such as a tungsten film and a silicon oxide film, or an organic resin film of polyimide or the like can be used, for example. Examples of the flexible substrate include, in addition to a substrate over which a transistor can be formed, a paper substrate, a cellophane substrate, an aramid film substrate, a polyimide film substrate, a cloth substrate (including a natural fiber (e.g., silk, cotton, or hemp), a synthetic fiber (e.g., nylon, polyurethane, or polyester), a regenerated fiber (e.g., acetate, cupra, rayon, or regenerated polyester), or the like), a leather substrate, and a rubber substrate. With the use of any of these substrates, an increase in durability, an increase in heat resistance, a reduction in weight, and a reduction in thickness can be achieved.

Note that the structures described in this embodiment can be combined with any of the structures described in the other embodiments as appropriate.

In this embodiment, examples of a variety of electronic devices and an automobile manufactured using the light-emitting device of one embodiment of the present invention or a display device including the light-emitting element of one embodiment of the present invention are described.

FIG. 4Aillustrates a mobile computer that can include a switch7009, an infrared port7010, and the like in addition to the above components.

FIG. 4Billustrates a portable image reproducing device (e.g., a DVD player) that is provided with a recording medium and can include a second display portion7002, a recording medium reading portion7011, and the like in addition to the above components.

FIG. 4Cillustrates a goggle-type display that can include the second display portion7002, a support7012, an earphone7013, and the like in addition to the above components.

FIG. 4Dillustrates a digital camera that has a television reception function and can include an antenna7014, a shutter button7015, an image receiving portion7016, and the like in addition to the above components.

FIG. 4Eillustrates a cellular phone (including a smartphone) and can include the display portion7001, a microphone7019, the speaker7003, a camera7020, an external connection portion7021, an operation button7022, the like in the housing7000.

FIG. 4Fillustrates a large-size television set (also referred to as TV or a television receiver) and can include the housing7000, the display portion7001, the speaker7003, and the like. In addition, here, the housing7000is supported by a stand7018.

The electronic devices illustrated inFIGS. 4A to 4Fcan have a variety of functions, such as a function of displaying a variety of data (a still image, a moving image, a text image, and the like) on the display portion, a touch panel function, a function of displaying a calendar, date, time, and the like, a function of controlling a process with a variety of types of software (programs), a wireless communication function, a function of connecting to a variety of computer networks with a wireless communication function, a function of transmitting and receiving a variety of data with a wireless communication function, a function of reading a program or data stored in a recording medium and displaying the program or data on the display portion, and the like. Furthermore, an electronic device including a plurality of display portions can have a function of displaying image data mainly on one display portion while displaying text data on another display portion, a function of displaying a three-dimensional image by displaying images on a plurality of display portions with a parallax taken into account, or the like. Furthermore, the electronic device including an image receiving portion can have a function of taking a still image, a function of taking a moving image, a function of automatically or manually correcting a taken image, a function of storing a taken image in a recording medium (an external recording medium or a recording medium incorporated in the camera), a function of displaying a taken image on the display portion, or the like. Note that functions that can be provided for the electronic devices illustrated inFIGS. 4A to 4Fare not limited to those described above, and the electronic devices can have a variety of functions.

FIG. 4Gillustrates a smart watch, which includes the housing7000, the display portion7001, operation buttons7022and7023, a connection terminal7024, a band7025, a clasp7026, and the like.

The display portion7001mounted in the housing7000serving as a bezel includes a non-rectangular display region. The display portion7001can display an icon7027indicating time, another icon7028, and the like. The display portion7001may be a touch panel (an input/output device) including a touch sensor (an input device).

The smart watch illustrated inFIG. 4Gcan have a variety of functions, such as a function of displaying a variety of information (e.g., a still image, a moving image, and a text image) on a display portion, a touch panel function, a function of displaying a calendar, date, time, and the like, a function of controlling processing with a variety of software (programs), a wireless communication function, a function of being connected to a variety of computer networks with a wireless communication function, a function of transmitting and receiving a variety of data with a wireless communication function, and a function of reading a program or data stored in a recording medium and displaying the program or data on a display portion.

Note that the light-emitting device of one embodiment of the present invention or the display device including the light-emitting element of one embodiment of the present invention can be used in the display portion of each electronic device described in this embodiment, enabling display with high color purity.

Another electronic device including the light-emitting device is a foldable portable information terminal illustrated inFIGS. 5A to 5C.FIG. 5Aillustrates a portable information terminal9310which is opened.FIG. 5Billustrates the portable information terminal9310which is being opened or being folded.FIG. 5Cillustrates the portable information terminal9310which is folded. The portable information terminal9310is highly portable when folded. The portable information terminal9310is highly browsable when opened because of a seamless large display region.

A display portion9311is supported by three housings9315joined together by hinges9313. Note that the display portion9311may be a touch panel (an input/output device) including a touch sensor (an input device). By bending the display portion9311at a connection portion between two housings9315with the use of the hinges9313, the portable information terminal9310can be reversibly changed in shape from an opened state to a folded state. The light-emitting device of one embodiment of the present invention can be used for the display portion9311. In addition, display with high color purity can be performed. A display region9312in the display portion9311is a display region that is positioned at a side surface of the portable information terminal9310which is folded. On the display region9312, information icons, file shortcuts of frequently used applications or programs, and the like can be displayed, and confirmation of information and start of application and the like can be smoothly performed.

Examples of the use of an electronic device will be described with reference toFIGS. 35A and 35B. Note that the electronic device described here includes the display device including the light-emitting element of one embodiment of the present invention in a display portion thereof. Thus, the display portion can perform display both in a reflective mode with a reflective liquid crystal element and in a transmissive mode with the light-emitting element.FIG. 35Aillustrates an example of the use of the electronic device in an outdoor environment in the daytime with high illuminance, andFIG. 35Billustrates an example of the use of the electronic device in an outdoor environment at night with low illuminance.

In the high-illuminance environment, an electronic device6000is operated in a reflective display mode or a reflective-emissive display mode, and display is performed using reflected light6003obtained by reflecting external light6002, as illustrated inFIG. 35A. This operation enables high visibility to be ensured also in the high-illuminance environment, and can achieve high display quality and low power consumption.

In the low-illuminance environment, the electronic device6000is operated in an emissive display mode or a reflective-emissive display mode, and display is performed using emitted light6004from the display device, as illustrated inFIG. 35B. This operation enables high visibility to be ensured also in the low-illuminance environment.

FIGS. 6A and 6Billustrate an automobile including the light-emitting device. The light-emitting device can be incorporated in the automobile, and specifically, can be included in lights5101(including lights of the rear part of the car), a wheel cover5102, a part or whole of a door5103, or the like on the outer side of the automobile which is illustrated inFIG. 6A. The light-emitting device can also be included in a display portion5104, a steering wheel5105, a gear lever5106, a seat5107, an inner rearview mirror5108, or the like on the inner side of the automobile which is illustrated inFIG. 6B, or in a part of a glass window.

As described above, the electronic devices and automobiles can be obtained using the light-emitting device or the display device of one embodiment of the present invention. In that case, display with high color purity can be performed. Note that the light-emitting device or the display device can be used for electronic devices and automobiles in a variety of fields without being limited to those described in this embodiment.

Note that the structures described in this embodiment can be combined with any of the structures described in the other embodiments as appropriate.

In this embodiment, a structure of a lighting device fabricated using the light-emitting device of one embodiment of the present invention or the light-emitting element which is a part of the light-emitting device is described with reference toFIGS. 7A to 7D.

FIGS. 7A to 7Dare examples of cross-sectional views of lighting devices.FIGS. 7A and 7Billustrate bottom-emission lighting devices in which light is extracted from the substrate side, andFIGS. 7C and 7Dillustrate top-emission lighting devices in which light is extracted from the sealing substrate side.

A lighting device4000illustrated inFIG. 7Aincludes a light-emitting element4002over a substrate4001. In addition, the lighting device4000includes a substrate4003with unevenness on the outside of the substrate4001. The light-emitting element4002includes a first electrode4004, an EL layer4005, and a second electrode4006.

The first electrode4004is electrically connected to an electrode4007, and the second electrode4006is electrically connected to an electrode4008. In addition, an auxiliary wiring4009electrically connected to the first electrode4004may be provided. Note that an insulating layer4010is formed over the auxiliary wiring4009.

The substrate4001and a sealing substrate4011are bonded to each other with a sealant4012. A desiccant4013is preferably provided between the sealing substrate4011and the light-emitting element4002. The substrate4003has the unevenness illustrated inFIG. 7A, whereby the extraction efficiency of light emitted from the light-emitting element4002can be increased.

Instead of the substrate4003, a diffusion plate4015may be provided on the outside of the substrate4001as in a lighting device4100illustrated inFIG. 7B.

A lighting device4200illustrated inFIG. 7Cincludes a light-emitting element4202over a substrate4201. The light-emitting element4202includes a first electrode4204, an EL layer4205, and a second electrode4206.

The first electrode4204is electrically connected to an electrode4207, and the second electrode4206is electrically connected to an electrode4208. An auxiliary wiring4209electrically connected to the second electrode4206may be provided. An insulating layer4210may be provided under the auxiliary wiring4209.

The substrate4201and a sealing substrate4211with unevenness are bonded to each other with a sealant4212. A barrier film4213and a planarization film4214may be provided between the sealing substrate4211and the light-emitting element4202. The sealing substrate4211has the unevenness illustrated inFIG. 7C, whereby the extraction efficiency of light emitted from the light-emitting element4202can be increased.

Instead of the sealing substrate4211, a diffusion plate4215may be provided over the light-emitting element4202as in a lighting device4300illustrated inFIG. 7D.

Note that with the use of the light-emitting device of one embodiment of the present invention or the light-emitting element which is a part of the light-emitting device as described in this embodiment, a lighting device having desired chromaticity can be provided.

Note that the structures described in this embodiment can be combined with any of the structures described in the other embodiments as appropriate.

In this embodiment, application examples of lighting devices fabricated using the light-emitting device of one embodiment of the present invention or the light-emitting element which is a part of the light-emitting device will be described with reference toFIG. 8.

A ceiling light8001can be used as an indoor lighting device. Examples of the ceiling light8001include a direct-mount light and an embedded light. Such a lighting device is fabricated using the light-emitting device and a housing or a cover in combination. Besides, application to a cord pendant light (light that is suspended from a ceiling by a cord) is also possible.

A foot light8002lights a floor so that safety on the floor can be improved. For example, it can be effectively used in a bedroom, on a staircase, or on a passage. In that case, the size or shape of the foot light can be changed depending on the area or structure of a room. The foot light8002can be a stationary lighting device fabricated using the light-emitting device and a support base in combination.

A sheet-like lighting8003is a thin sheet-like lighting device. The sheet-like lighting, which is attached to a wall when used, is space-saving and thus can be used for a wide variety of uses. Furthermore, the area of the sheet-like lighting can be increased. The sheet-like lighting can also be used on a wall or housing having a curved surface.

In addition, a lighting device8004in which the direction of light from a light source is controlled to be only a desired direction can be used.

Besides the above examples, when the light-emitting device of one embodiment of the present invention or the light-emitting element which is a part of the light-emitting device is used as part of furniture in a room, a lighting device that functions as the furniture can be obtained.

As described above, a variety of lighting devices that include the light-emitting device can be obtained. Note that these lighting devices are also embodiments of the present invention.

The structures described in this embodiment can be combined with any of the structures described in the other embodiments as appropriate.

In this embodiment, touch panels including the light-emitting device of one embodiment of the present invention will be described with reference toFIGS. 9A and 9B,FIGS. 10A and 10B,FIGS. 11A and 11B,FIGS. 12A and 12B, andFIG. 13.

FIGS. 9A and 9Bare perspective views of a touch panel2000. Note thatFIGS. 9A and 9Billustrate only main components of the touch panel2000for simplicity.

The touch panel2000includes a display panel2501and a touch sensor2595(seeFIG. 9B). The touch panel2000includes a substrate2510, a substrate2570, and a substrate2590.

The display panel2501includes, over the substrate2510, a plurality of pixels and a plurality of wirings2511through which signals are supplied to the pixels. The plurality of wirings2511are led to a peripheral portion of the substrate2510, and parts of the plurality of wirings2511form a terminal2519. The terminal2519is electrically connected to an FPC2509(1).

The substrate2590includes the touch sensor2595and a plurality of wirings2598electrically connected to the touch sensor2595. The plurality of wirings2598are led to a peripheral portion of the substrate2590, and parts of the plurality of wirings2598form a terminal2599. The terminal2599is electrically connected to an FPC2509(2). Note that inFIG. 9B, electrodes, wirings, and the like of the touch sensor2595provided on the back side of the substrate2590(the side facing the substrate2510) are indicated by solid lines for clarity.

As the touch sensor2595, a capacitive touch sensor can be used, for example. Examples of the capacitive touch sensor include a surface capacitive touch sensor, a projected capacitive touch sensor, and the like.

Examples of the projected capacitive touch sensor are a self-capacitive touch sensor, a mutual capacitive touch sensor, and the like, which differ mainly in the driving method. The use of a mutual capacitive type is preferable because multiple points can be sensed simultaneously.

First, an example of using a projected capacitive touch sensor will be described below with reference toFIG. 9B. Note that in the case of a projected capacitive touch sensor, a variety of sensors that can sense proximity or touch of a sensing target such as a finger can be used.

The projected capacitive touch sensor2595includes electrodes2591and electrodes2592. The electrodes2591are electrically connected to any of the plurality of wirings2598, and the electrodes2592are electrically connected to any of the other wirings2598. The electrodes2592each have a shape of a plurality of quadrangles arranged in one direction with one corner of a quadrangle connected to one corner of another quadrangle with a wiring2594, as illustrated inFIGS. 9A and 9B. In the same manner, the electrodes2591each have a shape of a plurality of quadrangles arranged with one corner of a quadrangle connected to one corner of another quadrangle; however, the direction in which the electrodes2591are connected is a direction crossing the direction in which the electrodes2592are connected. Note that the direction in which the electrodes2591are connected and the direction in which the electrodes2592are connected are not necessarily perpendicular to each other, and the electrodes2591may be arranged to intersect with the electrodes2592at an angle greater than 0° and less than 90°.

The intersecting area of the electrode2592and the wiring2594is preferably as small as possible. Such a structure allows a reduction in the area of a region where the electrodes are not provided, reducing variation in transmittance. As a result, variation in luminance of light passing through the touch sensor2595can be reduced.

Note that the shapes of the electrodes2591and the electrodes2592are not limited thereto and can be any of a variety of shapes. For example, the plurality of electrodes2591may be provided so that a space between the electrodes2591is reduced as much as possible, and the plurality of electrodes2592may be provided with an insulating layer located between the electrodes2591and2592. In this case, it is preferable to provide, between two adjacent electrodes2592, a dummy electrode electrically insulated from these electrodes because the area of regions having different transmittances can be reduced.

Next, the touch panel2000will be described in detail with reference toFIGS. 10A and 10B.FIGS. 10A and 10Bcorrespond to cross-sectional views taken along dashed-dotted line X1-X2inFIG. 9A.

The touch panel2000includes the touch sensor2595and the display panel2501.

The touch sensor2595includes the electrodes2591and the electrodes2592provided in a staggered arrangement in contact with the substrate2590, an insulating layer2593covering the electrodes2591and the electrodes2592, and the wiring2594that electrically connects the adjacent electrodes2591to each other. Between the adjacent electrodes2591, the electrode2592is provided.

The electrodes2591and the electrodes2592can be formed using a light-transmitting conductive material. As the light-transmitting conductive material, an In—Sn oxide (also referred to as ITO), an In—Si—Sn oxide (also referred to as ITSO), an In—Zn oxide, an In—W—Zn oxide, or the like can be used. In addition, it is possible to use a metal such as aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo), tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt), silver (Ag), yttrium (Y), or neodymium (Nd) or an alloy containing an appropriate combination of any of these metals. A graphene compound may be used as well. When a graphene compound is used, it can be formed, for example, by reducing a graphene oxide film. As a reducing method, a method with application of heat, a method with laser irradiation, or the like can be employed.

For example, the electrodes2591and2592can be formed by depositing a light-transmitting conductive material on the substrate2590by a sputtering method and then removing an unneeded portion by any of various patterning techniques such as photolithography.

Examples of a material for the insulating layer2593include a resin such as an acrylic resin or an epoxy resin, a resin having a siloxane bond, and an inorganic insulating material such as silicon oxide, silicon oxynitride, or aluminum oxide.

The adjacent electrodes2591are electrically connected to each other with the wiring2594formed in part of the insulating layer2593. Note that a material for the wiring2594preferably has higher conductivity than materials for the electrodes2591and2592to reduce electrical resistance.

The wiring2598is electrically connected to any of the electrodes2591and2592. Part of the wiring2598functions as a terminal. For the wiring2598, a metal material such as aluminum, gold, platinum, silver, nickel, titanium, tungsten, chromium, molybdenum, iron, cobalt, copper, or palladium or an alloy material containing any of these metal materials can be used.

Through the terminal2599, the wiring2598and the FPC2509(2) are electrically connected to each other. The terminal2599can be formed using any of various kinds of anisotropic conductive films (ACF), anisotropic conductive pastes (ACP), and the like.

An adhesive layer2597is provided in contact with the wiring2594. That is, the touch sensor2595is attached to the display panel2501so that they overlap with each other with the adhesive layer2597provided therebetween. Note that the substrate2570as illustrated inFIG. 10Amay be provided over the surface of the display panel2501that is in contact with the adhesive layer2597; however, the substrate2570is not always needed.

The adhesive layer2597has a light-transmitting property. For example, a thermosetting resin or an ultraviolet curable resin can be used; specifically, a resin such as an acrylic-based resin, a urethane-based resin, an epoxy-based resin, or a siloxane-based resin can be used.

The display panel2501inFIG. 10Aincludes, between the substrate2510and the substrate2570, a plurality of pixels arranged in a matrix and a driver circuit. Each pixel includes a light-emitting element and a pixel circuit that drives the light-emitting element.

InFIG. 10A, a pixel2502R is shown as an example of the pixel of the display panel2501, and a scan line driver circuit2503gis shown as an example of the driver circuit.

The pixel2502R includes a light-emitting element2550R and a transistor2502tthat can supply electric power to the light-emitting element2550R.

The transistor2502tis covered with an insulating layer2521. The insulating layer2521has a function of providing a flat surface by covering unevenness caused by the transistor and the like that have been already formed. The insulating layer2521may serve also as a layer for preventing diffusion of impurities. That is preferable because a reduction in the reliability of the transistor or the like due to diffusion of impurities can be prevented.

The light-emitting element2550R is electrically connected to the transistor2502tthrough a wiring. It is one electrode of the light-emitting element2550R that is directly connected to the wiring. An end portion of the one electrode of the light-emitting element2550R is covered with an insulator2528.

The light-emitting element2550R includes an EL layer between a pair of electrodes. A coloring layer2567R is provided to overlap with the light-emitting element2550R, and part of light emitted from the light-emitting element2550R is transmitted through the coloring layer2567R and extracted in the direction indicated by an arrow in the drawing. A light-blocking layer2567BM is provided at an end portion of the coloring layer, and a sealing layer2560is provided between the light-emitting element2550R and the coloring layer2567R.

Note that when the sealing layer2560is provided on the side from which light from the light-emitting element2550R is extracted, the sealing layer2560preferably has a light-transmitting property. The sealing layer2560preferably has a higher refractive index than the air.

The scan line driver circuit2503gincludes a transistor2503tand a capacitor2503c. Note that the driver circuit and the pixel circuits can be formed in the same process over the same substrate. Thus, in a manner similar to that of the transistor2502tin the pixel circuit, the transistor2503tin the driver circuit (the scan line driver circuit2503g) is also covered with the insulating layer2521.

The wirings2511through which a signal can be supplied to the transistor2503tare provided. The terminal2519is provided in contact with the wiring2511. The terminal2519is electrically connected to the FPC2509(1), and the FPC2509(1) has a function of supplying signals such as an image signal and a synchronization signal. Note that a printed wiring board (PWB) may be attached to the FPC2509(1).

Although the case where the display panel2501illustrated inFIG. 10Aincludes a bottom-gate transistor is described, the structure of the transistor is not limited thereto, and any of transistors with various structures can be used. In each of the transistors2502tand2503tillustrated inFIG. 10A, a semiconductor layer containing an oxide semiconductor can be used for a channel region. Alternatively, a semiconductor layer containing amorphous silicon or a semiconductor layer containing polycrystalline silicon that is obtained by crystallization process such as laser annealing can be used for a channel region.

FIG. 10Billustrates the structure that includes a top-gate transistor instead of the bottom-gate transistor illustrated inFIG. 10A. The kind of the semiconductor layer that can be used for the channel region does not depend on the structure of the transistor.

In the touch panel2000illustrated inFIG. 10A, an anti-reflection layer2567poverlapping with at least the pixel is preferably provided on a surface of the touch panel on the side from which light from the pixel is extracted, as illustrated inFIG. 10A. As the anti-reflection layer2567p, a circular polarizing plate or the like can be used.

For the substrates2510,2570, and2590inFIG. 10A, for example, a flexible material having a vapor permeability of 1×10−5g/(m2·day) or lower, preferably 1×10−6g/(m2·day) or lower, can be favorably used. Alternatively, it is preferable to use the materials that make these substrates have substantially the same coefficient of thermal expansion. For example, the coefficients of linear expansion of the materials are 1×10−3/K or lower, preferably 5×10−5/K or lower, and further preferably 1×10−5/K or lower.

Next, a touch panel2000′ having a structure different from that of the touch panel2000illustrated inFIGS. 10A and 10Bwill be described with reference toFIGS. 11A and 11B. It can be used as a touch panel like the touch panel2000.

FIGS. 11A and 11Bare cross-sectional views of the touch panel2000′. In the touch panel2000′ illustrated inFIGS. 11A and 11B, the position of the touch sensor2595relative to the display panel2501is different from that in the touch panel2000illustrated inFIGS. 10A and 10B. Only different structures will be described below, and the above description of the touch panel2000can be referred to for the other similar structures.

The coloring layer2567R overlaps with the light-emitting element2550R. The light-emitting element2550R illustrated inFIG. 11Aemits light to the side where the transistor2502tis provided. That is, (part of) light emitted from the light-emitting element2550R passes through the coloring layer2567R and is extracted in the direction indicated by an arrow inFIG. 11A. Note that the light-blocking layer2567BM is provided at an end portion of the coloring layer2567R.

The touch sensor2595is provided on the transistor2502tside (the far side from the light-emitting element2550R) of the display panel2501(seeFIG. 11A).

The adhesive layer2597is in contact with the substrate2510of the display panel2501and attaches the display panel2501and the touch sensor2595to each other in the structure illustrated inFIG. 11A. The substrate2510is not necessarily provided between the display panel2501and the touch sensor2595that are attached to each other by the adhesive layer2597.

As in the touch panel2000, transistors with any of a variety of structures can be used for the display panel2501in the touch panel2000′. Although a bottom-gate transistor is used inFIG. 11A, a top-gate transistor may be used as illustrated inFIG. 11B.

An example of a driving method of the touch panel will be described with reference toFIGS. 12A and 12B.

FIG. 12Ais a block diagram illustrating the structure of a mutual capacitive touch sensor.FIG. 12Aillustrates a pulse voltage output circuit2601and a current sensing circuit2602. Note that inFIG. 12A, six wirings X1to X6represent electrodes2621to which a pulse voltage is applied, and six wirings Y1to Y6represent electrodes2622that detect changes in current.FIG. 12Aalso illustrates capacitors2603that are each formed in a region where the electrodes2621and2622overlap with each other. Note that functional replacement between the electrodes2621and2622is possible.

The pulse voltage output circuit2601is a circuit for sequentially applying a pulse voltage to the wirings X1to X6. By application of a pulse voltage to the wirings X1to X6, an electric field is generated between the electrodes2621and2622of the capacitor2603. When the electric field between the electrodes is shielded, for example, a change occurs in the capacitor2603(mutual capacitance). The approach or contact of a sensing target can be sensed by utilizing this change.

The current sensing circuit2602is a circuit for detecting changes in current flowing through the wirings Y1to Y6that are caused by the change in mutual capacitance in the capacitor2603. No change in current value is detected in the wirings Y1to Y6when there is no approach or contact of a sensing target, whereas a decrease in current value is detected when mutual capacitance is decreased owing to the approach or contact of a sensing target. Note that an integrator circuit or the like is used for sensing of current values.

FIG. 12Bis a timing chart showing input and output waveforms in the mutual capacitive touch sensor illustrated inFIG. 12A. InFIG. 12B, sensing of a sensing target is performed in all the rows and columns in one frame period.FIG. 12Bshows a period when a sensing target is not sensed (not touched) and a period when a sensing target is sensed (touched). Sensed current values of the wirings Y1to Y6are shown as the waveforms of voltage values.

A pulse voltage is sequentially applied to the wirings X1to X6, and the waveforms of the wirings Y1to Y6change in response to the pulse voltage. When there is no approach or contact of a sensing target, the waveforms of the wirings Y1to Y6change uniformly in response to changes in the voltages of the wirings X1to X6. The current value is decreased at the point of approach or contact of a sensing target and accordingly the waveform of the voltage value changes. By detecting a change in mutual capacitance in this manner, the approach or contact of a sensing target can be sensed.

AlthoughFIG. 12Aillustrates a passive-type touch sensor in which only the capacitor2603is provided at the intersection of wirings as a touch sensor, an active-type touch sensor including a transistor and a capacitor may be used.FIG. 13illustrates an example of a sensor circuit included in an active-type touch sensor.

A signal G2is input to a gate of the transistor2613. A voltage VRES is applied to one of a source and a drain of the transistor2613, and one electrode of the capacitor2603and a gate of the transistor2611are electrically connected to the other of the source and the drain of the transistor2613. One of a source and a drain of the transistor2611is electrically connected to one of a source and a drain of the transistor2612, and a voltage VSS is applied to the other of the source and the drain of the transistor2611. A signal G1is input to a gate of the transistor2612, and a wiring ML is electrically connected to the other of the source and the drain of the transistor2612. The voltage VSS is applied to the other electrode of the capacitor2603.

Next, the operation of the sensor circuit inFIG. 13will be described. First, a potential for turning on the transistor2613is supplied as the signal G2, and a potential with respect to the voltage VRES is thus applied to a node n connected to the gate of the transistor2611. Then, a potential for turning off the transistor2613is applied as the signal G2, whereby the potential of the node n is maintained. Then, mutual capacitance of the capacitor2603changes owing to the approach or contact of a sensing target such as a finger, and accordingly the potential of the node n is changed from VRES.

In reading operation, a potential for turning on the transistor2612is supplied as the signal G1. A current flowing through the transistor2611, that is, a current flowing through the wiring ML is changed depending on the potential of the node n. By sensing this current, the approach or contact of a sensing target can be sensed.

In each of the transistors2611,2612, and2613, an oxide semiconductor layer is preferably used as a semiconductor layer in which a channel region is formed. In particular, it is preferable to use such a transistor as the transistor2613because the potential of the node n can be held for a long time and the frequency of operation of resupplying VRES to the node n (refresh operation) can be reduced.

Note that the structures described in this embodiment can be combined with any of the structures described in the other embodiments as appropriate.

In this embodiment, a display device that includes the light-emitting element of one embodiment of the present invention and a reflective liquid crystal element and that can display an image both in a transmissive mode and in a reflective mode will be described with reference toFIGS. 14A,14B1, and14B2,FIG. 15, andFIG. 16.

The display device described in this embodiment can be driven with extremely low power consumption for displaying an image using the reflective mode in a bright place such as outdoors. Meanwhile, in a dark place such as indoors or in a night environment, an image with a wide color gamut and high color reproducibility can be displayed with the use of the transmissive mode. Thus, by combination of these modes, the display device can display an image with low power consumption and high color reproducibility as compared with the case of a conventional display panel.

As an example of the display device of this embodiment, description will be made of a display device in which a liquid crystal element provided with a reflective electrode and a light-emitting element are stacked and an opening in the reflective electrode is provided in a position overlapping with the light-emitting element. Visible light is reflected by the reflective electrode in the reflective mode and light emitted from the light-emitting element is emitted through the opening in the reflective electrode in the transmissive mode. Note that transistors used for driving these elements (the liquid crystal element and the light-emitting element) are preferably formed on the same plane. It is preferable that the liquid crystal element and the light-emitting element be stacked with an insulating layer therebetween.

FIG. 14Ais a block diagram illustrating a display device described in this embodiment. A display device3000includes a circuit (G)3001, a circuit (S)3002, and a display portion3003. In the display portion3003, a plurality of pixels3004are arranged in an R direction and a C direction in a matrix. A plurality of wirings G1, a plurality of wirings G2, a plurality of wirings ANO, and a plurality of wirings CSCOM are electrically connected to the circuit (G)3001. These wirings are also electrically connected to the plurality of pixels3004arranged in the R direction. A plurality of wirings S1and a plurality of wirings S2are electrically connected to the circuit (S)3002, and these wirings are also electrically connected to the plurality of pixels3004arranged in the C direction.

Each of the plurality of pixels3004includes a liquid crystal element and a light-emitting element. The liquid crystal element and the light-emitting element include portions overlapping with each other.

FIG.14B1shows the shape of a conductive film3005serving as a reflective electrode of the liquid crystal element included in the pixel3004. Note that an opening3007is provided in a position3006which is part of the conductive film3005and which overlaps with the light-emitting element. That is, light emitted from the light-emitting element is emitted through the opening3007.

The pixels3004in FIG.14B1are arranged such that the adjacent pixels3004in the R direction exhibit different colors. Furthermore, the openings3007are provided so as not to be arranged in a line in the R direction. Such arrangement has an effect of suppressing crosstalk between the light-emitting elements of adjacent pixels3004. Furthermore, there is an advantage that element formation is facilitated owing to a reduction in the degree of miniaturization.

The opening3007can have a polygonal shape, a quadrangular shape, an elliptical shape, a circular shape, a cross shape, a stripe shape, or a slit-like shape, for example.

FIG.14B2illustrates another example of the arrangement of the conductive films3005.

The ratio of the opening3007to the total area of the conductive film3005(excluding the opening3007) affects the display of the display device. That is, a problem is caused in that as the area of the opening3007is larger, the display using the liquid crystal element becomes darker; in contrast, as the area of the opening3007is smaller, the display using the light-emitting element becomes darker. Furthermore, in addition to the problem of the ratio of the opening, a small area of the opening3007itself also causes a problem in that extraction efficiency of light emitted from the light-emitting element is decreased. The ratio of the opening3007to the total area of the conductive film3005(excluding the opening3007) is preferably 5% or more and 60% or less because the display quality can be maintained even when the liquid crystal element and the light-emitting element are used in a combination.

Next, an example of a circuit configuration of the pixel3004is described with reference toFIG. 15.FIG. 15illustrates two adjacent pixels3004.

The pixel3004includes a transistor SW1, a capacitor C1, a liquid crystal element3010, a transistor SW2, a transistor M, a capacitor C2, a light-emitting element3011, and the like. Note that these components are electrically connected to any of the wiring G1, the wiring G2, the wiring ANO, the wiring CSCOM, the wiring S1, and the wiring S2in the pixel3004. The liquid crystal element3010and the light-emitting element3011are electrically connected to a wiring VCOM1and a wiring VCOM2, respectively.

A gate of the transistor SW1is connected to the wiring G1. One of a source and a drain of the transistor SW1is connected to the wiring Si, and the other of the source and the drain is connected to one electrode of the capacitor C1and one electrode of the liquid crystal element3010. The other electrode of the capacitor C1is connected to the wiring CSCOM. The other electrode of the liquid crystal element3010is connected to the wiring VCOM1.

A gate of the transistor SW2is connected to the wiring G2. One of a source and a drain of the transistor SW2is connected to the wiring S2, and the other of the source and the drain is connected to one electrode of the capacitor C2and a gate of the transistor M. The other electrode of the capacitor C2is connected to one of a source and a drain of the transistor M and the wiring ANO. The other of the source and the drain of the transistor M is connected to one electrode of the light-emitting element3011. Furthermore, the other electrode of the light-emitting element3011is connected to the wiring VCOM2.

Note that the transistor M includes two gates between which a semiconductor is provided and which are electrically connected to each other. With such a structure, the amount of current flowing through the transistor M can be increased.

The on/off state of the transistor SW1is controlled by a signal from the wiring G1. A predetermined potential is applied from the wiring VCOM1. Furthermore, orientation of liquid crystals of the liquid crystal element3010can be controlled by a signal from the wiring S1. A predetermined potential is applied from the wiring CSCOM.

The on/off state of the transistor SW2is controlled by a signal from the wiring G2. By the difference between the potentials applied from the wiring VCOM2and the wiring ANO, the light-emitting element3011can emit light. Furthermore, the conduction state of the transistor M can be controlled by a signal from the wiring S2.

Accordingly, in the structure of this embodiment, in the case of the reflective mode, the liquid crystal element3010is controlled by the signals supplied from the wiring G1and the wiring Si and optical modulation is utilized, whereby an image can be displayed. In the case of the transmissive mode, the light-emitting element3011can emit light when the signals are supplied from the wiring G2and the wiring S2. In the case where both modes are performed at the same time, desired driving can be performed on the basis of the signals from the wiring G1, the wiring G2, the wiring S1, and the wiring S2.

Next, specific description will be given with reference toFIG. 16, a schematic cross-sectional view of the display device3000described in this embodiment.

The display device3000includes a light-emitting element3023and a liquid crystal element3024between substrates3021and3022. Note that the light-emitting element3023and the liquid crystal element3024are formed with an insulating layer3025positioned therebetween. That is, the light-emitting element3023is positioned between the substrate3021and the insulating layer3025, and the liquid crystal element3024is positioned between the substrate3022and the insulating layer3025.

A transistor3015, a transistor3016, a transistor3017, a coloring layer3028, and the like are provided between the insulating layer3025and the light-emitting element3023.

A bonding layer3029is provided between the substrate3021and the light-emitting element3023. The light-emitting element3023includes a conductive layer3030serving as one electrode, an EL layer3031, and a conductive layer3032serving as the other electrode which are stacked in this order over the insulating layer3025. In the light-emitting element3023that is a bottom emission light-emitting element, the conductive layer3032and the conductive layer3030contain a material that reflects visible light and a material that transmits visible light, respectively. Light emitted from the light-emitting element3023is transmitted through the coloring layer3028and the insulating layer3025and then transmitted through the liquid crystal element3024via an opening3033, thereby being emitted to the outside of the substrate3022.

In addition to the liquid crystal element3024, a coloring layer3034, a light-blocking layer3035, an insulating layer3046, a structure3036, and the like are provided between the insulating layer3025and the substrate3022. The liquid crystal element3024includes a conductive layer3037serving as one electrode, a liquid crystal3038, a conductive layer3039serving as the other electrode, alignment films3040and3041, and the like. Note that the liquid crystal element3024is a reflective liquid crystal element and the conductive layer3039serves as a reflective electrode; thus, the conductive layer3039is formed using a material with high reflectivity. Furthermore, the conductive layer3037serves as a transparent electrode, and thus is formed using a material that transmits visible light. The alignment films3040and3041are provided on the conductive layers3037and3039and in contact with the liquid crystal3038. The insulating layer3046is provided so as to cover the coloring layer3034and the light-blocking layer3035and serves as an overcoat. Note that the alignment films3040and3041are not necessarily provided.

The opening3033is provided in part of the conductive layer3039. A conductive layer3043is provided in contact with the conductive layer3039. Since the conductive layer3043has a light-transmitting property, a material transmitting visible light is used for the conductive layer3043.

The structure3036serves as a spacer that prevents the substrate3022from coming closer to the insulating layer3025than required. The structure3036is not necessarily provided.

One of a source and a drain of the transistor3015is electrically connected to the conductive layer3030in the light-emitting element3023. For example, the transistor3015corresponds to the transistor M inFIG. 15.

One of a source and a drain of the transistor3016is electrically connected to the conductive layer3039and the conductive layer3043in the liquid crystal element3024through a terminal portion3018. That is, the terminal portion3018has a function of electrically connecting the conductive layers provided on both surfaces of the insulating layer3025. The transistor3016corresponds to the transistor SW1inFIG. 15.

A terminal portion3019is provided in a region where the substrates3021and3022do not overlap with each other. The terminal portion3019electrically connects the conductive layers provided on both surfaces of the insulating layer3025like the terminal portion3018. The terminal portion3019is electrically connected to a conductive layer obtained by processing the same conductive film as the conductive layer3043. Thus, the terminal portion3019and an FPC3044can be electrically connected to each other through a connection layer3045.

A connection portion3047is provided in part of a region where a bonding layer3042is provided. In the connection portion3047, the conductive layer obtained by processing the same conductive film as the conductive layer3043and part of the conductive layer3037are electrically connected with a connector3048. Accordingly, a signal or a potential input from the FPC3044can be supplied to the conductive layer3037through the connector3048.

The structure3036is provided between the conductive layer3037and the conductive layer3043. The structure3036has a function of maintaining a cell gap of the liquid crystal element3024.

As the conductive layer3043, a metal oxide, a metal nitride, or an oxide such as an oxide semiconductor whose resistance is reduced is preferably used. In the case of using an oxide semiconductor, a material in which at least one of the concentrations of hydrogen, boron, phosphorus, nitrogen, and other impurities and the number of oxygen vacancies is made to be higher than those in a semiconductor layer of a transistor is used for the conductive layer3043.

Note that the structures described in this embodiment can be combined with any of the structures described in the other embodiments as appropriate.

Synthesis Example 1

In this example is described a method for synthesizing the organic compound of one embodiment of the present invention, 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn), which is represented by Structural Formula (100) in Embodiment 1. A structure of mBnfBPTzn is shown below.

Step 1: Synthesis of 1-(3-chloro-2-fluorophenyl)-2-naphthol

Into a 200 mL three-neck flask were put 3.4 g (19 mmol) of 3-chloro-2-fluorophenylboronic acid, 4.0 g (18 mmol) of 1-bromo-2-naphthol, 0.13 g (0.36 mmol) of di(1-adamantyl)-n-butylphosphine, and 7.6 g (72 mmol) of sodium carbonate, and the atmosphere in the flask was replaced with nitrogen. To the mixture were added 90 mL of toluene and 36 mL of water, and the resulting mixture was degassed by being stirred while the pressure was reduced. After the degasification, 40 mg (0.18 mmol) of palladium(II) acetate was added to the mixture, and the resulting mixture was stirred at approximately 80° C. for 15 hours. After the stirring, the aqueous layer of this mixture was subjected to extraction with toluene, and the solution of the obtained extract and the organic layer were combined and washed with a saturated aqueous solution of sodium chloride. The obtained organic layer was dried with magnesium sulfate. This mixture was gravity-filtered, and the obtained filtrate was concentrated to give a brown oily substance. This oily substance was purified by silica gel column chromatography (using a developing solvent of toluene) to give 4.5 g of a target brown oily substance in a yield of 91%. The synthesis scheme of Step 1 is shown in (a-1) below.

Step 2: Synthesis of 8-chlorobenzo[b]naphtho[1,2-d]furan

Next, 4.5 g (16 mmol) of 1-(3-chloro-2-fluorophenyl)-2-naphthol, 80 mL of N-methyl-2-pyrrolidone (NMP), and 4.4 g (32 mmol) of potassium carbonate were put into a 500 mL three-neck flask. This flask was subjected to stirring at 150° C. for 2 hours under a nitrogen stream. After the stirring, this mixture was cooled down to room temperature and added to approximately 200 mL of toluene, and approximately 100 mL of water was added to the mixture. The aqueous layer of the mixture was subjected to extraction with toluene, and the solution of the extract and the organic layer were combined and washed with dilute hydrochloric acid (1.0 mol/L) and a saturated aqueous solution of sodium chloride. The organic layer was dried with magnesium sulfate, and after the drying, this mixture was gravity-filtered. The obtained filtrate was concentrated to give an oily substance. The obtained oily substance was dissolved in approximately 50 mL of toluene, and this solution was subjected to suction filtration through Celite, alumina, and Florisil. A solid obtained by concentrating the resulting filtrate was recrystallized from toluene/hexane to give 3.2 g of target white needle-like crystals in a yield of 79%. The synthesis scheme of Step 2 is shown in (a-2) below.

Step 3: Synthesis of 4,4,5,5-tetramethyl-2-(benzo[b]naphtho[1,2-d]furan-8-yl)-1,3,2-dioxaborolane

Step 4: Synthesis of 2-(3-chlorophenyl)-4,6-diphenyl-1,3,5-triazine

Into a 200 mL three-neck flask were added 10 g (37 mmol) of 2-chloro-4,6-diphenyl-1,3,5-triazine, 5.8 g (37 mmol) of 3-chlorophenylboronic acid, and 7.8 g (74 mmol) of sodium carbonate, and the atmosphere in the flask was replaced with nitrogen. To the mixture were added 150 mL of toluene, 35 mL of ethanol, and 37 mL of water, and the resulting mixture was degassed by being stirred while the pressure was reduced. After the degasification, 0.43 g (0.37 mmol) of tetrakis(triphenylphosphine)palladium(0) was added to the mixture, and the resulting mixture was stirred at approximately 80° C. for 3 hours. After the stirring, the aqueous layer of this mixture was subjected to extraction with toluene, and the solution of the obtained extract and the organic layer were combined and washed with a saturated aqueous solution of sodium chloride. The obtained organic layer was dried with magnesium sulfate. This mixture was gravity-filtered, and the obtained filtrate was concentrated to give a solid. The obtained solid was dissolved in approximately 30 mL of hot toluene, and this solution was subjected to suction filtration through Celite, alumina, and Florisil. A solid obtained by concentration of the obtained filtrate was washed with methanol, and the solid was collected by suction filtration to give 11 g of a target white solid in a yield of 86%. The synthesis scheme of Step 4 is shown in (a-4) below.

Step 5: Synthesis of 4,4,5,5-tetramethyl-2-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-1,3,2-dioxaborolane

Into a 200 mL three-neck flask were put 5.0 g (15 mmol) of 2-(3-chlorophenyl)-4,6-diphenyl-1,3,5-triazine, 4.1 g (16 mmol) of bis(pinacolato)diboron, 0.21 g (0.60 mmol) of di(1-adamantyl)-n-butylphosphine, and 4.4 g (45 mmol) of potassium acetate, and the atmosphere in the flask was replaced with nitrogen. To this mixture was added 74 mL of xylene, and the resulting mixture was degassed by being stirred while the pressure was reduced. To this mixture heated to 40° C. was added 0.12 g (0.15 mmol) of [1,1′-bis(diphenylphosphino)ferrocene]palladium(II) dichloride dichloromethane adduct, and the resulting mixture was stirred at 130° C. for 24 hours under a nitrogen stream. After the stirring, this mixture was suction-filtered, and the obtained filtrate was concentrated to give an oily substance. The obtained oily substance was purified by silica gel column chromatography (using a developing solvent of hexane:toluene=6:1) to give a white solid. The obtained solid was washed with hexane to give 3.4 g of a target white solid in a yield of 53%. The synthesis scheme of Step 5 is shown in (a-5) below.

Step 6: Synthesis of 2-[3-(3-chlorophenyl)phenyl]-4,6-diphenyl-1,3,5-triazine

Into a 200 mL three-neck flask were added 3.0 g (6.9 mmol) of 4,4,5,5-tetramethyl-2-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-1,3,2-dioxaborolane, 2.4 g (10 mmol) of 3-chloroiodobenzene, 43 mg (0.14 mmol) of tri(o-tolyl)phosphine, and 1.9 g (14 mmol) of potassium carbonate, and the atmosphere in the flask was replaced with nitrogen. To the mixture were added 25 mL of toluene, 10 mL of ethanol, and 7.0 mL of water, and the resulting mixture was degassed by being stirred while the pressure was reduced. After the degasification, 16 mg (0.070 mmol) of palladium(II) acetate was added to the mixture heated at 40° C., and the resulting mixture was stirred at approximately 80° C. for 7 hours, whereby a solid was precipitated. The precipitated solid was collected by suction filtration and dissolved in approximately 30 mL of hot toluene, and this solution was subjected to suction filtration through Celite, alumina, and Florisil. A solid obtained by concentration of the obtained filtrate was recrystallized from toluene to give 2.2 g of a target white solid in a yield of 77%. The synthesis scheme of Step 6 is shown in (a-6) below.

Step 7: Synthesis of 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine

Into a 200 mL three-neck flask were added 2.1 g (5.0 mmol) of 2-[3-(3-chlorophenyl)phenyl]-4,6-diphenyl-1,3,5-triazine, 1.7 g (5.0 mmol) of 4,4,5,5-tetramethyl-2-(benzo[b]naphtho[1,2-d]furan-8-yl)-1,3,2-dioxaborolane, 3.2 g (15 mmol) of tripotassium phosphate, and 36 mg (0.10 mmol) of di(1-adamantyl)-n-butylphosphine, and the atmosphere in the flask was replaced with nitrogen.

To this mixture, 25 mL of diethylene glycol dimethyl ether and 1.2 g (15 mmol) of tert-butyl alcohol were added. The resulting mixture was degassed by being stirred while the pressure was reduced. To this mixture was added 12 mg (0.050 mmol) of palladium(II) acetate, and the resulting mixture was stirred at 80° C. for 7 hours under a nitrogen stream, whereby a solid was precipitated.

After the stirring, water was added to the mixture, and the resulting mixture was stirred and suction-filtered to collect a solid. The collected solid was dissolved in approximately 500 mL of hot toluene, and this solution was subjected to suction filtration through Celite, alumina, and Florisil. A solid obtained by concentration of the obtained filtrate was recrystallized from toluene to give 1.8 g of a target white powder in a yield of 58%. The synthesis scheme of Step 7 is shown in (a-7) below.

By a train sublimation method, 1.7 g of the obtained white powder was purified under a pressure of 0.018 Pa at 280° C. After the sublimation purification, 0.76 g of a white solid of mBnfBPTzn was obtained at a collection rate of 44%.

Analysis results by nuclear magnetic resonance (1H-NMR) spectroscopy of the white solid obtained by Step 7 are shown below.FIG. 17shows the1H-NMR chart. These results reveal that the organic compound of one embodiment of the present invention, mBnfBPTzn represented by Structural Formula (100), was obtained in this example.

Next, ultraviolet-visible absorption spectra (hereinafter, simply referred to as “absorption spectra”) of mBnfBPTzn in a toluene solution and that in a solid thin film and emission spectra thereof were measured. The solid thin film was formed over a quartz substrate by a vacuum evaporation method. The absorption spectra were measured using ultraviolet-visible spectrophotometers (V-550 manufactured by JASCO Corporation for the solution and U-4100 manufactured by Hitachi, Ltd. for the thin film). Note that the absorption spectrum in the solution was calculated by subtraction of the measured absorption spectrum of only toluene in a quartz cell, and the absorption spectrum in the thin film was calculated using an absorbance (−log10[% T/(100−% R)]) obtained from a transmittance and a reflectance of a substrate and the thin film. Note that % T represents transmittance and % R represents reflectance. The emission spectra were measured using a fluorescence spectrophotometer (FS920 manufactured by Hamamatsu Photonics K.K.). Measurement results of the obtained absorption and emission spectra in the toluene solution are shown inFIG. 18A, in which the horizontal axis represents wavelength and the vertical axes represent absorption intensity and emission intensity. Measurement results of the absorption and emission spectra in the solid thin film are shown inFIG. 18B, in which the horizontal axis represents wavelength and the vertical axes represent absorption intensity and emission intensity.

FIG. 18Ashows that mBnfBPTzn in the toluene solution has absorption peaks at around 284 nm, 314 nm, 327 nm, and 342 nm, and emission wavelength peaks at 348 nm, 362 nm, and 379 nm.FIG. 18Bshows that mBnfBPTzn in the solid thin film has absorption peaks at around 217 nm, 260 nm, 316 nm, 330 nm, and 347 nm, and an emission wavelength peak at 416 nm (an excitation wavelength of 330 nm).

The ionization potential of mBnfBPTzn in the thin film state was measured in the air with a photoelectron spectrometer (AC-3 manufactured by Riken Keiki Co., Ltd.). The obtained value was converted into a negative value, so that the HOMO level of mBnfBPTzn was −6.17 eV. From the data of the absorption spectrum in the thin film inFIG. 18B, the absorption edge of mBnfBPTzn, which was obtained from Tauc plot with an assumption of direct transition, was 3.49 eV. Thus, the optical energy gap of mBnfBPTzn in the solid state can be estimated to be 3.49 eV; from the values of the HOMO level obtained above and this energy gap, the LUMO level of mBnfBPTzn can be estimated to be −2.68 eV. This reveals that mBnfBPTzn in the solid state has an energy gap as wide as 3.49 eV.

Next, mBnfBPTzn obtained in this example was subjected to an analysis by liquid chromatography-mass spectrometry (LC-MS). In the LC-MS analysis, liquid chromatography (LC) separation was carried out with UltiMate 3000 manufactured by Thermo Fisher Scientific K.K., and mass spectrometry (MS) was carried out with Q Exactive manufactured by Thermo Fisher Scientific K.K. In the LC separation, a given column was used at a column temperature of 40° C., and solution sending was performed in such a manner that an appropriate solvent was selected, the sample was prepared by dissolving mBnfBPTzn in an organic solvent at an arbitrary concentration, and the injection amount was 5.0 μL. In the MS analysis, ionization was carried out by an electrospray ionization (ESI) method, and measurement was carried out using Full MS-SIM. The Full MS-SIM measurement was carried out in a mass range of m/z=150 to nm/z=2000, and detection was performed in a positive mode. The obtained MS spectrum is shown inFIG. 19.

The results inFIG. 19show m/z=602, which corresponds to the sum of the exact mass of mBnfBPTzn and the mass of a proton. This confirms that mBnfBPTzn was obtained.

Thermogravimetry-differential thermal analysis (TG-DTA) of mBnfBPTzn was performed. A high vacuum differential type differential thermal balance (TG/DTA 2410SA, manufactured by Bruker AXS K.K.) was used for the measurement. The measurement was carried out under a nitrogen stream (a flow rate of 200 mL/min) and a normal pressure at a temperature rising rate of 10° C./min. From the relationship between weight and temperature (thermogravimetry), it has been found that mBnfBPTzn has a 5% weight-loss temperature of 462° C., which is indicative of high heat resistance of mBnfBPTzn.

Differential scanning calorimetry (DSC) was also performed on mBnfBPTzn. For the calorimetry, Pyris 1 DSC manufactured by PerkinElmer, Inc. was used. In the differential scanning calorimetry, after the temperature was raised from −10° C. to 300° C. at a temperature rising rate of 40° C./min, the temperature was held for a minute and then lowered to −10° C. at a temperature decreasing rate of 40° C./min. This operation was the first measurement. Then, the same operation with the temperature rising and decreasing rates changed to 10° C./min was performed as the second measurement, and the second measurement result was employed. The DSC measurement shows that the glass transition point of mBnfBPTzn is 97° C. In addition, the measurement was also performed on 2-{3-[3-(dibenzothiophen-4-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mDBtBPTzn). The measurement shows that the glass transition point of mDBtBPTzn is 81° C. and is lower than that of mBnfBPTzn. This reveals that mBnfBPTzn has higher heat resistance than mDBtBPTzn.

Synthesis Example 2

In this example is described a method for synthesizing the organic compound of one embodiment of the present invention, 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn-02), which is represented by Structural Formula (121) in Embodiment 1. A structure of mBnfBPTzn-02 is shown below.

Into a 200 mL three-neck flask were added 0.54 g (1.3 mmol) of 2-[3-(3-chlorophenyl)phenyl]-4,6-diphenyl-1,3,5-triazine, 0.36 g (1.4 mmol) of (benzo[b]naphtho[1,2-d]furan-6-yl)boronic acid, 0.85 g (4.0 mmol) of tripotassium phosphate, and 47 mg (0.13 mmol) of di(1-adamantyl)-n-butylphosphine, and the atmosphere in the flask was replaced with nitrogen. To this mixture, 7.0 mL of diethylene glycol dimethyl ether and 0.30 g (4.0 mmol) of tert-butyl alcohol were added. The resulting mixture was degassed by being stirred while the pressure was reduced. To this mixture was added 15 mg (0.065 mmol) of palladium(II) acetate, and the resulting mixture was stirred at 160° C. for 7 hours under a nitrogen stream.

After the stirring, toluene and water were added to the mixture, and the resulting mixture was stirred. Then, the aqueous layer of the mixture was subjected to extraction with toluene. The solution of the obtained extract and the organic layer were combined and washed with a saturated aqueous solution of sodium chloride. The obtained organic layer was dried with magnesium sulfate. This mixture was gravity-filtered, and the obtained filtrate was concentrated to give a black oily substance. The oily substance was purified by silica gel column chromatography (using a developing solvent of toluene:hexane=5:1) to give a solid. The obtained solid was purified by HPLC and washed with hexane to give 0.19 g of a target white solid in a yield of 24%.

By a train sublimation method, 0.19 g of the obtained white solid was purified under a pressure of 3.4 Pa at 280° C. After the sublimation purification, 0.15 g of a white solid of mBnfBPTzn-02 was obtained at a collection rate of 79%. The synthesis scheme of the above synthesis method is shown in (b-1) below.

Analysis results by nuclear magnetic resonance (1H-NMR) spectroscopy of the white solid obtained by the above synthesis method are shown below.FIGS. 20A and 20Bshow the1H-NMR chart. Note thatFIG. 20Bis a chart where the range of from 7.20 ppm to 9.20 ppm inFIG. 20Ais enlarged. These results reveal that the organic compound of one embodiment of the present invention, mBnfBPTzn-02 represented by Structural Formula (121), was obtained in this example.

Next, an ultraviolet-visible absorption spectrum (hereinafter, simply referred to as “absorption spectrum”) of mBnfBPTzn-02 in a toluene solution and an emission spectrum thereof were measured. The absorption spectrum was measured using an ultraviolet-visible spectrophotometer (V-550 manufactured by JASCO Corporation). Note that the absorption spectrum in the solution was calculated by subtraction of the measured absorption spectrum of only toluene in a quartz cell. The emission spectrum was measured using a fluorescence spectrophotometer (FS920 manufactured by Hamamatsu Photonics K.K.). Measurement results of the obtained absorption and emission spectra in the toluene solution are shown inFIG. 21, in which the horizontal axis represents wavelength and the vertical axes represent absorption intensity and emission intensity.

FIG. 21shows that mBnfBPTzn-02 in the toluene solution has absorption peaks at around 285 nm, 317 nm, and 342 nm, and emission wavelength peaks at 368 nm and 381 nm.

Thermogravimetry-differential thermal analysis (TG-DTA) of mBnfBPTzn-02 was performed. The measurement was carried out under a nitrogen stream (a flow rate of 200 mL/min) and a normal pressure at a temperature rising rate of 10° C./min. From the relationship between weight and temperature (thermogravimetry), it has been found that rBnfBPTzn-02 has a 5% weight-loss temperature of 444° C., which is indicative of high heat resistance of mBnfBPTzn-02.

Differential scanning calorimetry (DSC) was also performed on mBnfBPTzn-02 using Pyris 1 DSC manufactured by PerkinElmer, Inc. In the differential scanning calorimetry, after the temperature was raised from −10° C. to 300° C. at a temperature rising rate of 40° C./min, the temperature was held for a minute and then lowered to −10° C. at a temperature decreasing rate of 40° C./min. This operation was the first measurement. The same operation with the temperature rising and decreasing rates changed to 10° C./min was performed as the second measurement, and the second measurement result was employed. The DSC measurement shows that the glass transition point of mBnfBPTzn-02 is 111° C. In contrast, the glass transition point of mDBtBPTzn is 81° C. and is lower than that of mBnfBPTzn-02. This reveals that mBnfBPTzn-02 has higher heat resistance than mDBtBPTzn.

In this example, element structures, fabrication methods, and properties of a light-emitting element1(a light-emitting element of one embodiment of the present invention) in which mBnfBPTzn (Structural Formula (100)) described in Example 1 is used in a light-emitting layer and a comparative light-emitting element2in which the comparative organic compound 2-{3-[3-(dibenzothiophen-4-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mDBtBPTzn) (Structural Formula (200)) is used in a light-emitting layer will be described. Note thatFIG. 22illustrates an element structure of the light-emitting elements used in this example, and Table 1 shows specific structures. Chemical formulae of materials used in this example are shown below.

In each of the light-emitting elements described in this example, as illustrated inFIG. 22, a hole-injection layer911, a hole-transport layer912, a light-emitting layer913, an electron-transport layer914, and an electron-injection layer915were stacked in this order over a first electrode901formed over a substrate900, and a second electrode903was stacked over the electron-injection layer915.

First, the first electrode901was formed over the substrate900. The electrode area was set to 4 mm2(2 mm×2 mm). A glass substrate was used as the substrate900. The first electrode901was formed to a thickness of 70 nm using indium tin oxide containing silicon oxide (ITSO) by a sputtering method.

As pretreatment, a surface of the substrate was washed with water, baking was performed at 200° C. for 1 hour, and then UV ozone treatment was performed for 370 seconds. After that, the substrate was transferred into a vacuum evaporation apparatus where the pressure had been reduced to approximately 10−4Pa, and was subjected to vacuum baking at 170° C. for 60 minutes in a heating chamber of the vacuum evaporation apparatus, and then the substrate was cooled down for about 30 minutes.

Next, the hole-injection layer911was formed over the first electrode901. After the pressure in the vacuum evaporation apparatus was reduced to 10−4Pa, the hole-injection layer911was formed by co-evaporation to have a mass ratio of 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) to molybdenum oxide of 4:2 and a thickness of 60 nm.

Then, the hole-transport layer912was formed over the hole-injection layer911. The hole-transport layer912was formed to a thickness of 20 nm by evaporation of 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP).

The light-emitting layer913in the light-emitting element1was formed by co-evaporation using mBnfBPTzn as a host material, using PCBBiF as an assist material, and using [Ir(dppm)2(acac)] as a guest material (phosphorescent material) to have a weight ratio of mBnfBPTzn to PCBBiF and [Ir(dppm)2(acac)] of 0.7:0.3:0.05. The thickness was set to 20 nm. Furthermore, mBnfBPTzn, PCBBiF, and [Ir(dppm)2(acac)] were deposited by co-evaporation to have a mass ratio of mBnfBPTzn:PCBBiF:[Ir(dppm)2(acac)] of 0.8:0.2:0.05. The thickness was set to 20 nm. Accordingly, the light-emitting layer913had a stacked-layer structure with a thickness of 40 nm.

The light-emitting layer913in the comparative light-emitting element2was formed by co-evaporation using mDBtBPTzn as a host material, using PCBBiF as an assist material, and using [Ir(dppm)2(acac)] as a guest material (phosphorescent material) to have a weight ratio of mDBtBPTzn to PCBBiF and [Ir(dppm)2(acac)] of 0.7:0.3:0.05. The thickness was set to 20 nm. Furthermore, mDBtBPTzn, PCBBiF, and [Ir(dppm)2(acac)] were deposited by co-evaporation to have a mass ratio of mDBtBPTzn:PCBBiF:[Ir(dppm)2(acac)] of 0.8:0.2:0.05. The thickness was set to 20 nm. Accordingly, the light-emitting layer913had a stacked-layer structure with a thickness of 40 nm.

Next, the electron-transport layer914was formed over the light-emitting layer913. The electron-transport layer914in the light-emitting element1was formed in the following manner: mBnfBPTzn and bathophenanthroline (abbreviation: Bphen) were sequentially deposited by evaporation to thicknesses of 20 nm and 10 nm, respectively. The electron-transport layer914in the comparative light-emitting element2was formed in the following manner: mDBtBPTzn and bathophenanthroline (abbreviation: Bphen) were sequentially deposited by evaporation to thicknesses of 20 nm and 10 nm, respectively.

Then, the electron-injection layer915was formed over the electron-transport layer914. The electron-injection layer915was formed to a thickness of 1 nm by evaporation of lithium fluoride (LiF).

After that, the second electrode903was formed over the electron-injection layer915. The second electrode903was formed using aluminum to a thickness of 200 nm by an evaporation method. In this example, the second electrode903functioned as a cathode.

Through the above steps, the light-emitting elements in each of which the EL layer was provided between a pair of electrodes over the substrate900were fabricated. The hole-injection layer911, the hole-transport layer912, the light-emitting layer913, the electron-transport layer914, and the electron-injection layer915described above were functional layers forming the EL layer of one embodiment of the present invention. Furthermore, in all the evaporation steps in the above fabrication method, evaporation was performed by a resistance-heating method.

Each of the light-emitting elements fabricated as described above was sealed using another substrate (not illustrated) in such a manner that the substrate (not illustrated) was fixed to the substrate900with a sealing material in a glove box containing a nitrogen atmosphere, a sealant was applied so as to surround the light-emitting element formed over the substrate900, and then irradiation with 365-nm ultraviolet light at 6 J/cm2was performed and heat treatment was performed at 80° C. for 1 hour.

Operation characteristics of the fabricated light-emitting elements were measured. Note that the measurement was performed at room temperature (in an atmosphere kept at 25° C.). The results are shown inFIGS. 23 to 26.

Table 2 shows initial values of main characteristics of the light-emitting elements at around 1000 cd/m2.

The above results show that the light-emitting element1fabricated in this example has high current efficiency and high external quantum efficiency. Note that the comparative light-emitting element2exhibits comparably favorable characteristics. The results reveal that favorable element characteristics can be obtained in the case of having not only a structure common to mBnfBPTzn and mDBtBPTzn but also a structure in which two benzene rings are fused to a heteroaromatic ring.

FIG. 27shows emission spectra when current at a current density of 25 mA/cm2was applied to the light-emitting element1and the comparative light-emitting element2. As shown inFIG. 27, the emission spectrum of each of the light-emitting element1and the comparative light-emitting element2has a peak at around 584 nm that is derived from light emission of the organometallic complex [Ir(dppm)2(acac)] contained in the light-emitting layer913.

Next, reliability tests were performed on the light-emitting element1and the comparative light-emitting element2.FIG. 28shows results of the reliability tests. InFIG. 28, the vertical axis represents normalized luminance (%) with an initial luminance of 100%, and the horizontal axis represents driving time (h) of the elements. Note that in the reliability tests, the light-emitting elements were driven under the conditions where the initial luminance was set to 5000 cd/m2and the current density was constant.

These results reveal that the light-emitting element of one embodiment of the present invention (the light-emitting element1) is comparable to the comparative light-emitting element2in current efficiency and external quantum efficiency, but is superior thereto in reliability.

As a result of a comparison between structures of mBnfBPTzn and mDBtBPTzn, it can be understood that the improvement in reliability of mBnfBPTzn is attributable to the benzonaphthofuran structure in which dibenzofuran (where two benzene rings are fused to a heteroaromatic ring) is further fused.

In this example, element structures, fabrication methods, and properties of a light-emitting element3(a light-emitting element of one embodiment of the present invention) in which mBnfBPTzn (Structural Formula (100)) described in Example 1 is used in a light-emitting layer and a comparative light-emitting element4in which the comparative organic compound mDBtBPTzn (Structural Formula (200)) is used in a light-emitting layer will be described. Note that the light-emitting elements described in this example are similar to those described in Example 3 except for the light-emitting substance (dopant) used in the light-emitting layers; thus,FIG. 22can be referred to, and the fabrication method is not described. Table 3 shows the specific structures of the light-emitting element3and the comparative light-emitting element4described in this example. Chemical formulae of materials used in this example are shown below.

Operation characteristics of the fabricated light-emitting elements were measured. Note that the measurement was performed at room temperature (in an atmosphere kept at 25° C.). The results are shown inFIGS. 29 to 32.

Table 4 shows initial values of main characteristics of the light-emitting elements at around 1000 cd/m2.

The above results show that the light-emitting element3fabricated in this example has high current efficiency and high external quantum efficiency. Note that the comparative light-emitting element4exhibits comparably favorable characteristics. The results reveal that favorable element characteristics can be obtained in the case of having not only a structure common to mBnfBPTzn and mDBtBPTzn but also a structure in which two benzene rings are fused to a heteroaromatic ring (dibenzofuran or dibenzothiophene).

FIG. 33shows emission spectra when current at a current density of 25 mA/cm2was applied to the light-emitting element3and the comparative light-emitting element4. As shown inFIG. 33, the emission spectrum of each of the light-emitting element3and the comparative light-emitting element4has a peak at around 546 nm that is derived from light emission of the organometallic complex [Ir(tBuppm)2(acac)] contained in the light-emitting layer913.

Next, reliability tests were performed on the light-emitting element3and the comparative light-emitting element4.FIG. 34shows results of the reliability tests. InFIG. 34, the vertical axis represents normalized luminance (%) with an initial luminance of 100%, and the horizontal axis represents driving time (h) of the elements. Note that in the reliability tests, the light-emitting elements were driven under the conditions where the initial luminance was set to 5000 cd/m2and the current density was constant.

These results reveal that the light-emitting element of one embodiment of the present invention (the light-emitting element3) is comparable to the comparative light-emitting element4in current efficiency and external quantum efficiency, but is superior thereto in reliability.

As a result of a comparison between structures of mBnfBPTzn and mDBtBPTzn, it can be understood that the improvement in reliability of mBnfBPTzn is attributable to the benzonaphthofuran structure in which dibenzofuran (where two benzene rings are fused to a heteroaromatic ring) is further fused.

This application is based on Japanese Patent Application Serial No. 2016-202251 filed with Japan Patent Office on Oct. 14, 2016, the entire contents of which are hereby incorporated by reference.