Liquid crystal display device

The present invention provides a liquid crystal display device that prevents a decrease in the voltage holding ratio (VHR) and an increase in the ion density (ID) in the liquid crystal layer, and resolves the problems of display defects, such as white streaks, variations in alignment, and image sticking. Since a liquid crystal display device according to the present invention has a feature of preventing a decrease in the voltage holding ratio (VHR) and an increase in the ion density (ID) in the liquid crystal layer, and suppressing the occurrence of display defects such as image sticking, the liquid crystal display device is particularly useful for active matrix driving liquid crystal display devices with an IPS mode or an FFS mode and can be applied to liquid crystal display devices such as liquid crystal televisions, monitors, cellular phones, and smart phones.

TECHNICAL FIELD

BACKGROUND ART

Liquid crystal display devices have come to be used in, for example, watches, calculators, various home electric appliances, measuring instruments, automobile panels, word processors, electronic organizers, printers, computers, and televisions. Representative examples of liquid crystal display modes include TN (twisted nematic) mode, STN (super twisted nematic) mode, DS (dynamic scattering) mode, GH (guest host) mode, IPS (in-plane switching) mode, OCB (optically compensated birefringence) mode, ECB (electrically controlled birefringence) mode, VA (vertical alignment) mode, CSH (color super homeotropic) mode, and FLC (ferroelectric liquid crystal). The drive mode shifted from the conventional static driving to multiplex driving, which is commonly used. The mainstream technology is a simple matrix mode and recently an active matrix (AM) mode in which devices are driven with TFTs (thin film transistors) and TFDs (thin film diodes), for example.

Referring toFIG. 1, a typical liquid crystal color display device includes two substrates (1) each having an alignment film (4), a transparent electrode layer (3a) serving as a common electrode and a color filter layer (2) which are disposed between one of the substrates and the alignment film of the one substrate, and a pixel electrode layer (3b) between the other substrate and the alignment film of that other substrate. The substrates are arranged so that the alignment films face each other and a liquid crystal layer (5) is sandwiched between the alignment films.

The color filter layer is constituted by a color filter that includes a black matrix, a red colored layer (R), a green colored layer (G), a blue colored layer (B), and, if needed, a yellow colored layer (Y).

Liquid crystal materials constituting such liquid crystal layers have been subjected to high levels of impurity control since impurities remaining in the materials significantly affect electrical properties of display devices. Regarding the materials that form alignment films, it has been known that the alignment films come into direct contact with the liquid crystal layer and impurities remaining in alignment films migrate to the liquid crystal layer, so that the impurities affect electrical properties of the liquid crystal layer. Studies are now being made in order to determine the properties of liquid crystal display devices affected by the impurities in the alignment film materials.

Materials, such as organic pigments, used in the color filter layer are also presumed to affect the liquid crystal layer due to impurities contained in the materials as with the case of the alignment film materials. However, since an alignment film and a transparent electrode are interposed between the color filter layer and the liquid crystal layer, the direct effects on the liquid crystal layer have been considered to be significantly low compared to those of the alignment film materials. However, alignment films are usually as thin as 0.1 μm or less in thickness. Transparent electrodes that serve as color-filter-layer-side common electrodes are thick so as to enhance the electrical conductivity; however, the thickness thereof is usually only as large as 0.5 μm or less. Accordingly, the color filter layer and the liquid crystal layer are not completely separated from each other. There is a possibility that impurities contained in the color filter layer may migrate through the alignment film and the transparent electrode and cause a decrease in the voltage holding ratio (VHR) and an increase in the ion density (ID) in the liquid crystal layer, thereby leading to display defects such as white streaks, variations in alignment, and image sticking.

Studies have been made to find a way to resolve display defects caused by impurities contained in pigments in color filters: a method of controlling release of impurities into liquid crystals by using a pigment in which the content of extracts obtained with ethyl formate is limited to a particular value or less (PTL 1) and a method of controlling release of impurities into liquid crystals by specifying the pigment in the blue colored layer (PTL 2). However, these methods do not differ much from simply decreasing the amounts of impurities in the pigment and fail to provide sufficient improvements that resolve the display defects even under the recent progress in pigment purification technologies.

Also disclosed are a method that focuses on the relationship between organic impurities contained in the color filter and a liquid crystal composition, in which insolubility of the organic impurities in the liquid crystal layer is indicated by a hydrophobicity parameter of liquid crystal molecules contained in the liquid crystal layer and the value of this hydrophobicity parameter is controlled to a particular value or higher and a method of preparing a liquid crystal composition that contains a particular fraction or more of a liquid crystal compound having a —OCF3group at an end of the liquid crystal molecule since there is a correlation between this hydrophobicity parameter and the —OCF3group at an end of a liquid crystal molecule (PTL 3).

However, the essence of the invention disclosed in this literature is to suppress effects of impurities in the pigment on the liquid crystal layer and thus a direct relationship between the structure of the liquid crystal material and the structure of the coloring material such as dyes and pigments used in the color filter has not been investigated. This literature does not resolve the problems related to display defects of liquid crystal display devices that have become increasingly complicated.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

The present invention provides a liquid crystal display device that includes a particular liquid crystal composition and a color filter containing a particular pigment, to thereby prevent a decrease in the voltage holding ratio (VHR) and an increase in the ion density (ID) in the liquid crystal layer, and to resolve the problems of display defects, such as white streaks, variations in alignment, and image sticking.

Solution to Problem

The inventors of this application have extensively studied the combination of the structure of the liquid crystal materials constituting the liquid crystal layer and the coloring materials, such as dyes and pigments, that constitute the color filter to address the problems described above. As a result, the inventors have found that a liquid crystal display device that includes a particular liquid crystal material and a color filter containing a particular pigment is capable of preventing a decrease in the voltage holding ratio (VHR) and an increase in the ion density (ID) in the liquid crystal layer and resolving the problems of display defects such as white streaks, variations in alignment, and image sticking. Thus, the inventors have accomplished the invention of this application.

In other words, the present invention provides

a liquid crystal display device including: a first substrate; a second substrate; a liquid crystal composition layer sandwiched between the first substrate and the second substrate; a color filter including a black matrix and at least RGB three-color pixel portions; a pixel electrode; and a common electrode,

wherein the liquid crystal composition layer contains a liquid crystal composition that contains at least one compound represented by a general formula (I)

(in the formula, R31represents an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkenyloxy group having 2 to 10 carbon atoms; M31to M33each independently represent a trans-1,4-cyclohexylene group or a 1,4-phenylene group in which one or two —CH2— in the trans-1,4-cyclohexylene group may be replaced by —O— such that oxygen atoms are not directly next to each other, and one or two hydrogen atoms in the phenylene group may be replaced by fluorine atoms; X31and X32each independently represent a hydrogen atom or a fluorine atom; Z31represents a fluorine atom, a trifluoromethoxy group, or a trifluoromethyl group; n31and n32each independently represent 0, 1, or 2 and n31+n32is 0, 1, or 2; and in a case where there are a plurality of M31and M33, the plurality of M31and M33may be the same or different), and that contains at least one compound selected from the group consisting of compounds represented by a general formula (II-a) to a general formula (II-f),

(in the formulae, R19to R30each independently represent an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms; and X21represents a hydrogen atom or a fluorine atom), and

the RGB three-color pixel portions contain, as a coloring material in the R pixel portion, a diketopyrrolopyrrole-based red pigment having an average primary particle size of 5 to 50 nm measured by a small angle X-ray scattering method.

Advantageous Effects of Invention

A liquid crystal display device according to the present invention includes a particular liquid crystal composition and a color filter that contains a particular pigment, so that a decrease in the voltage holding ratio (VHR) and an increase in the ion density (ID) in the liquid crystal layer can be prevented and display defects such as white streaks, variations in alignment, and image sticking can be prevented.

REFERENCE SIGNS LIST

1substrate2color filter layer2acolor filter layer containing a particular pigment3atransparent electrode layer (common electrode)3bpixel electrode layer4alignment film5liquid crystal layer5aliquid crystal layer containing a particular liquid crystal composition

DESCRIPTION OF EMBODIMENTS

FIG. 2shows an example of a liquid crystal display device according to the present invention. A transparent electrode layer (3a) that serves as a common electrode and a color filter layer (2a) that contains a particular pigment are disposed between one of two substrates (1), i.e., a first substrate and a second substrate, each having an alignment film (4), and the alignment film of that one substrate. A pixel electrode layer (3b) is disposed between the other substrate and the alignment film of that substrate. These substrates are arranged so that the alignment films face each other and a liquid crystal layer (5a) containing a particular liquid crystal composition is sandwiched between the alignment films.

The two substrates of the display device are bonded to each other with a sealer and a sealing material disposed in the peripheral region. In most cases, granular spacers or resin spacer columns formed by photolithography are disposed between the two substrates to maintain the substrate-to-substrate distance.

A liquid crystal composition layer in a liquid crystal display device according to the present invention contains a liquid crystal composition that contains at least one compound represented by a general formula (I)

(in the formula, R31represents an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkenyloxy group having 2 to 10 carbon atoms; M31to M33each independently represent a trans-1,4-cyclohexylene group or a 1,4-phenylene group in which one or two —CH2— in the trans-1,4-cyclohexylene group may be replaced by —O— such that oxygen atoms are not directly next to each other, and one or two hydrogen atoms in the phenylene group may be replaced by fluorine atoms; X31and X32each independently represent a hydrogen atom or a fluorine atom; Z31represents a fluorine atom, a trifluoromethoxy group, or a trifluoromethyl group; n31and n32each independently represent 0, 1, or 2 and n31+n32is 0, 1, or 2; and in a case where there are a plurality of M31and M33, the plurality of M31and M33may be the same or different), and that contains at least one compound selected from the group consisting of compounds represented by a general formula (II-a) to a general formula (II-f),

(in the formulae, R19to R30each independently represent an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms; and X21represents a hydrogen atom or a fluorine atom).

In the general formula (I), in a case where the ring structure to which R31is bonded is a phenyl group (aromatic), R31preferably represents a linear alkyl group having 1 to 5 carbon atoms, a linear alkoxy group having 1 to 4 (or more) carbon atoms, or an alkenyl group having 4 to 5 carbon atoms; and, in a case where the ring structure to which R31is bonded is a saturated ring structure such as cyclohexane, pyran, or dioxane, R31preferably represents a linear alkyl group having 1 to 5 carbon atoms, a linear alkoxy group having 1 to 4 (or more) carbon atoms, or a linear alkenyl group having 2 to 5 carbon atoms.

In a case where high chemical stability with respect to heat or light is a priority, R31preferably represents an alkyl group. Alternatively, in a case where low viscosity and production of a liquid crystal display element having a high response speed are priorities, R31preferably represents an alkenyl group. In addition, in order to achieve low viscosity, a high nematic-isotropic phase transition temperature (Tni), and a faster response speed, preferably used is an alkenyl group in which the unsaturated bond is not present at the end, particularly preferred is an alkenyl group and a methyl group that is at the end and next to the alkenyl group. In a case where high solubility at low temperature is a priority, R31preferably represents an alkoxy group; alternatively, multiple types of R31are preferably used in combination. For example, regarding R31, compounds having alkyl or alkenyl groups having 2, 3, and 4 carbon atoms are preferably used in combination; compounds having 3 and 5 carbon atoms are preferably used in combination; or compounds having 3, 4, and 5 carbon atoms are preferably used in combination.

M31preferably represents the following structures.

M31more preferably represents the following structures.

M32preferably represents the following structures.

M32more preferably represents the following structures.

M32still more preferably represents the following structures.

M33preferably represents the following structures.

M33more preferably represents the following structures.

M33still more preferably represents the following structure.

At least one of X31and X32preferably represents a fluorine atom and both of X31and X32more preferably represent fluorine atoms.

Z31preferably represents a fluorine atom or a trifluoromethoxy group.

Regarding the combination of X31, X32, and Z31, in one embodiment, X31═F, X32═F, and Z31═F. In another embodiment, X31═F, X32═H, and Z31═F. In still another embodiment, X31═F, X32═H, and Z31═OCF3. In still another embodiment, X31═F, X32═F, and Z31═OCF3. In still another embodiment, X31═H, X32═H, and Z31═OCF3.

n31preferably represents 1 or 2, n32preferably represents 0 or 1 and more preferably 0, and n31+n32is preferably 1 or 2 and more preferably 2.

More specifically, compounds represented by the general formula (I) are preferably compounds represented by a general formula (I-a) to a general formula (I-f) below.

(In the formulae, R32represents an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkenyloxy group having 2 to 10 carbon atoms; X31to X38each independently represent a hydrogen atom or a fluorine atom; and Z31represents a fluorine atom, a trifluoromethoxy group or a trifluoromethyl group).

In the general formula (Ia) to the general formula (If), in a case where the ring structure to which R32is bonded is a phenyl group (aromatic), R32preferably represents a linear alkyl group having 1 to 5 carbon atoms, a linear alkoxy group having 1 to 4 (or more) carbon atoms, or an alkenyl group having 4 to 5 carbon atoms; and, in a case where the ring structure to which R32is bonded is a saturated ring structure such as cyclohexane, pyran, or dioxane, R32preferably represents a linear alkyl group having 1 to 5 carbon atoms, a linear alkoxy group having 1 to 4 (or more) carbon atoms, or a linear alkenyl group having 2 to 5 carbon atoms.

In a case where high chemical stability with respect to heat or light is a priority, R31preferably represents an alkyl group. Alternatively, in a case where low viscosity and production of a liquid crystal display element having a high response speed are priorities, R31preferably represents an alkenyl group. In addition, in order to achieve low viscosity, a high nematic-isotropic phase transition temperature (Tni), and a faster response speed, preferably used is an alkenyl group in which the unsaturated bond is not present at the end, particularly preferred is an alkenyl group and a methyl group that is at the end and next to the alkenyl group. In a case where high solubility at low temperature is a priority, R31preferably represents an alkoxy group; alternatively, multiple types of R31are preferably used in combination. For example, regarding R31, compounds having alkyl or alkenyl groups having 2, 3, and 4 carbon atoms are preferably used in combination; compounds having 3 and 5 carbon atoms are preferably used in combination; or compounds having 3, 4, and 5 carbon atoms are preferably used in combination.

At least one of X31and X32preferably represents a fluorine atom and both of X31and X32more preferably represent fluorine atoms.

Z31preferably represents a fluorine atom or a trifluoromethoxy group.

Regarding the combination of X31, X32, and Z31, in one embodiment, X31═F, X32═F, and Z31═F. In another embodiment, X31═F, X32═H, and Z31═F. In still another embodiment, X31═F, X32═H, and Z31═OCF3. In still another embodiment, X31═F, X32═F, and Z31═OCF3. In still another embodiment, X31═H, X32═H, and Z31═OCF3.

n31preferably represents 1 or 2, n32preferably represents 0 or 1 and more preferably 0, and n31+n32is preferably 1 or 2 and more preferably 2.

At least one of X33and X34preferably represents a fluorine atom and both of X33and X34more preferably represent fluorine atoms.

At least one of X35and X36preferably represents a fluorine atom. However, it is not preferred that both of X35and X36represent fluorine atoms in view of Tni, solubility at low temperature, and chemical stability in the form of a liquid crystal display element, though it is effective in an increase in Δ∈.

At least one of X37and X38preferably represents a hydrogen atom and both of X37and X38preferably represent hydrogen atoms. It is not preferred that at least one of X37and X38represent a fluorine atom in view of Tni, solubility at low temperature, and chemical stability in the form of a liquid crystal display element.

One to eight of the compounds represented by the general formula (I) are preferably contained and one to five of the compounds are particularly preferably contained. The content of the compounds is preferably 3% to 50% by mass and more preferably 5% to 40% by mass.

In the general formula (IIa) to the general formula (IIf), in a case where the ring structures to which R19to R30are bonded are phenyl groups (aromatics), R19to R30preferably represent a linear alkyl group having 1 to 5 carbon atoms, a linear alkoxy group having 1 to 4 (or more) carbon atoms, or an alkenyl group having 4 to 5 carbon atoms; and, in a case where the ring structures to which R19to R30are bonded are saturated ring structures such as cyclohexane, pyran, and dioxane, R19to R30preferably represent a linear alkyl group having 1 to 5 carbon atoms, a linear alkoxy group having 1 to 4 (or more) carbon atoms, or a linear alkenyl group having 2 to 5 carbon atoms.

In a case where high chemical stability with respect to heat or light is a priority, R19to R30preferably represent an alkyl group. Alternatively, in a case where low viscosity and production of a liquid crystal display element having a high response speed are priorities, R19to R30preferably represent an alkenyl group. In addition, in order to achieve low viscosity, a high nematic-isotropic phase transition temperature (Tni), and a faster response speed, preferably used is an alkenyl group in which the unsaturated bond is not present at the end, particularly preferred is an alkenyl group and a methyl group that is at the end and next to the alkenyl group. In a case where high solubility at low temperature is a priority, R19to R30preferably represent an alkoxy group; alternatively, multiple types of R19to R30are preferably used in combination. For example, regarding R19to R30, compounds having alkyl or alkenyl groups having 2, 3, and 4 carbon atoms are preferably used in combination; compounds having 3 and 5 carbon atoms are preferably used in combination; or compounds having 3, 4, and 5 carbon atoms are preferably used in combination.

R19and R20preferably represent an alkyl group or an alkoxy group and at least one of R19and R20preferably represents an alkoxy group. More preferred is a case where R19represents an alkyl group and R20represents an alkoxy group. Still more preferred is a case where R19represents an alkyl group having 3 to 5 carbon atoms and R20represents an alkoxy group having 1 to 2 carbon atoms.

R21and R22preferably represent an alkyl group or an alkenyl group and at least one of R21and R22preferably represents an alkenyl group. A compound in which both R21and R22are alkenyl groups is suitably used to improve the response speed, but is not preferred in a case where the chemical stability of a liquid crystal display element is improved.

At least one of R23and R24preferably represents an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or an alkenyl group having 4 to 5 carbon atoms. In order to achieve good balance between response speed and Tni, at least one of R23and R24preferably represents an alkenyl group. In order to achieve good balance between response speed and solubility at low temperature, at least one of R23and R24preferably represents an alkoxy group.

At least one of R25and R26preferably represents an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or an alkenyl group having 2 to 5 carbon atoms. In order to achieve good balance between response speed and Tni, at least one of R25and R26preferably represents an alkenyl group. In order to achieve good balance between response speed and solubility at low temperature, at least one of R25and R26preferably represents an alkoxy group. More preferably, R25represents an alkenyl group and R26represents an alkyl group. It is also preferred that R25represent an alkyl group and R26represent an alkoxy group.

At least one of R27and R28preferably represents an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or an alkenyl group having 2 to 5 carbon atoms. In order to achieve good balance between response speed and Tni, at least one of R27and R28preferably represents an alkenyl group. In order to achieve good balance between response speed and solubility at low temperature, at least one of R27and R28preferably represents an alkoxy group. More preferably, R27represents an alkyl group or an alkenyl group and R28represents an alkyl group. It is also preferred that R27represent an alkyl group and R28represent an alkoxy group. Furthermore, it is particularly preferred that R27represent an alkyl group and R28represent an alkyl group.

At least one of R29and R30preferably represents an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 4 to 5 carbon atoms. In order to achieve good balance between response speed and Tni, at least one of R29and R30preferably represents an alkenyl group. In order to achieve high reliability, at least one of R29and R30preferably represents an alkyl group. More preferably, R29represents an alkyl group or an alkenyl group and R30represents an alkyl group or an alkenyl group. It is also preferred that R29represent an alkyl group and R30represent an alkenyl group. Furthermore, it is also preferred that R29represent an alkyl group and R30represent an alkyl group.

One to ten of the compounds represented by the general formula (II-a) to the general formula (II-f) are preferably contained and one to eight of the compounds are particularly preferably contained. The content of the compounds is preferably 5% to 80% by mass, more preferably 10% to 70% by mass, and particularly preferably 20% to 60% by mass.

A liquid crystal composition layer in a liquid crystal display device according to the present invention may further contain at least one compound selected from the group consisting of compounds represented by a general formula (III-a) to a general formula (III-f).

(In the formulae, R41represents an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkenyloxy group having 2 to 10 carbon atoms; X41to X48each independently represent a hydrogen atom or a fluorine atom; and Z41represents a fluorine atom, a trifluoromethoxy group, or a trifluoromethyl group.)

In the general formula (IIIa) to the general formula (IIIf), in a case where the ring structure to which R41is bonded is a phenyl group (aromatic), R41preferably represents a linear alkyl group having 1 to 5 carbon atoms, a linear alkoxy group having 1 to 4 (or more) carbon atoms, or an alkenyl group having 4 to 5 carbon atoms. In a case where the ring structure to which R41is bonded is a saturated ring structure such as cyclohexane, pyran, or dioxane, R41preferably represents a linear alkyl group having 1 to 5 carbon atoms, a linear alkoxy group having 1 to 4 (or more) carbon atoms, or a linear alkenyl group having 2 to 5 carbon atoms.

In a case where high chemical stability with respect to heat or light is a priority, R41preferably represents an alkyl group. Alternatively, in a case where low viscosity and production of a liquid crystal display element having a high response speed are priorities, R41preferably represents an alkenyl group. In addition, in order to achieve low viscosity, a high nematic-isotropic phase transition temperature (Tni), and a faster response speed, preferably used is an alkenyl group in which the unsaturated bond is not present at the end, particularly preferred is an alkenyl group and a methyl group that is at the end and next to the alkenyl group. In a case where high solubility at low temperature is a priority, R41preferably represents an alkoxy group; alternatively, multiple types of R41are preferably used in combination. For example, regarding R41, compounds having alkyl or alkenyl groups having 2, 3, and 4 carbon atoms are preferably used in combination; compounds having 3 and 5 carbon atoms are preferably used in combination; or compounds having 3, 4, and 5 carbon atoms are preferably used in combination.

At least one of X41and X42preferably represents a fluorine atom and both of X41and X42more preferably represent fluorine atoms.

Z41preferably represents a fluorine atom or a trifluoromethoxy group.

Regarding the combination of X41, X42, and Z41, in one embodiment, X41═F, X42═F, and Z41═F. In another embodiment, X41═F, X42═H, and Z41═F. In still another embodiment, X41═F, X42═H, and Z41═OCF3. In still another embodiment, X41═F, X42═F, and Z41═OCF3. In still another embodiment, X41═H, X42═H, and Z41═OCF3.

At least one of X43and X44preferably represents a fluorine atom and both of X43and X44preferably represent fluorine atoms in order to achieve high Δ∈. However, it is not preferred that both of X43and X44represent fluorine atoms for achieving high solubility at low temperature.

At least one of X45and X46preferably represents a hydrogen atom and both of X45and X46more preferably represent hydrogen atoms. The use of fluorine atoms in a large amount is not preferred in view of Tni, solubility at low temperature, and chemical stability in the form of a liquid crystal display element.

At least one of X47and X48preferably represents a hydrogen atom and both of X47and X48more preferably represent hydrogen atoms. It is not preferred that at least one of X47and X48represent a fluorine atom in view of Tni, solubility at low temperature, and chemical stability in the form of a liquid crystal display element.

One to ten of the compounds selected from the group consisting of the compounds represented by the general formula (III-a) to the general formula (III-f) are preferably contained and one to eight of the compounds are more preferably contained. The content of the compounds is preferably 5% to 50% by mass and more preferably 10% to 40% by mass.

In the liquid crystal composition of a liquid crystal composition layer in a liquid crystal display device according to the present invention, Δ∈ at 25° C. is preferably +1.5 or more. In order to achieve high speed response, Δ∈ is preferably +1.5 to +4.0, more preferably +1.5 to +3.0. In order to achieve low voltage driving, Δ∈ is preferably +8.0 to +18.0, more preferably +10.0 to +15.0. Furthermore, Δn at 25° C. is preferably 0.08 to 0.14 and more preferably 0.09 to 0.13. More specifically, Δn is preferably 0.10 to 0.13 in a case where a small cell gap is employed; and Δn is preferably 0.08 to 0.10 in a case where a large cell gap is employed. Moreover, η at 20° C. is preferably 5 to 45 mPa·s, more preferably 5 to 25 mPa·s, and particularly preferably 10 to 20 mPa·s. Tniis preferably 60° C. to 120° C., more preferably 70° C. to 100° C., and particularly preferably 70° C. to 85° C.

In addition to the above-described compounds, a liquid crystal composition in the present invention may contain standard nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, or the like.

A liquid crystal composition in the present invention may contain at least one polymerizable compound for the purpose of producing a liquid crystal display element with, for example, a PS mode, a transverse electric field-type PSA mode, or a transverse electric field-type PSVA mode. For example, a photopolymerizable monomer whose polymerization proceeds with energy rays such as light can be used as the polymerizable compound. In terms of structure, a polymerizable compound having a liquid crystal skeleton formed by bonding a plurality of six-membered rings, such as a biphenyl derivative or a terphenyl derivative, is exemplified. More specifically, the polymerizable compound is preferably a bifunctional monomer represented by a general formula (V).

(In the formula, X51and X52each independently represent a hydrogen atom or a methyl group; Sp1and Sp2each independently represent a single bond, an alkylene group having 1 to 8 carbon atoms, or —O—(CH2)s— (where s represents an integer of 2 to 7 and the oxygen atom is bonded to the aromatic ring); Z51represents —OCH2—, —CH2O—, —COO—, —OCO—, —CF2O—, —OCF2—, —CH2CH2—, —CF2CF2—, —CH═CH—OCO—, —CH═CH—OCO—, —COO—CH═CH—, —OCO—CH═CH—, —COO—CH2CH2—, —OCO—CH2CH2—, —CH2CH2—COO—, —CH2CH2—OCO—, —COO—CH2—, —OCO—CH2—, —CH2—OCO—, —CH2—OCO—, —CY1═CY2— (where Y1and Y2each independently represent a fluorine atom or a hydrogen atom), —C≡C—, or a single bond; M51represents a 1,4-phenylene group, a trans-1,4-cyclohexylene group, or a single bond; and any hydrogen atom in all 1,4-phenylene groups in the formula may be replaced by a fluorine atom).

The polymerizable compound is preferably any of a diacrylate derivative in which X51and X52each represent a hydrogen atom and a dimethacrylate derivative in which X51and X52each represent a methyl group, and is also preferably a compound in which one of X51and X52represents a hydrogen atom and the other represents a methyl group. Among these compounds, the diacrylate derivative has the highest rate of polymerization, the dimethacrylate derivative has a low rate of polymerization, and the asymmetrical compound has an intermediate rate of polymerization. A preferred one can be used in accordance with the applications. In a PSA display element, the dimethacrylate derivative is particularly preferred.

Sp1and Sp2each independently represent a single bond, an alkylene group having 1 to 8 carbon atoms, or —O—(CH2)s—. In a PSA display element, at least one of Sp1and Sp2preferably represents a single bond. A compound in which Sp1and Sp2each represent a single bond or a compound in which one of Sp1and Sp2represents a single bond and the other represents an alkylene group having 1 to 8 carbon atoms or —O—(CH2)s— is preferred. In this case, a 1-4 alkyl group is preferred and s is preferably 1 to 4.

M51represents a 1,4-phenylene group in which any of hydrogen atoms may be replaced by fluorine atoms, a trans-1,4-cyclohexylene group, or a single bond and preferably represents a 1,4-phenylene group or a single bond. In a case where C represents a ring structure other than a single bond, Z51preferably represents a linking group other than a single bond. In a case where M51represents a single bond, Z51preferably represents a single bond.

In view of the foregoing, specifically, the ring structure between Sp1and Sp2in the general formula (V) is preferably the following structure.

In a case where M51represents a single bond and the ring structure is constituted by two rings in the general formula (V), the ring structure is preferably represented by a formula (Va-1) to a formula (Va-5) below, more preferably represented by the formula (Va-1) to the formula (Va-3), and particularly preferably represented by the formula (Va-1).

(In the formulae, both ends are bonded to Sp1and Sp2.)

A polymerizable compound having such a skeleton is polymerized to provide an anchoring strength that is optimal for PSA-type liquid crystal display elements, so that a good alignment state is achieved. Therefore, unevenness in displaying is suppressed or completely prevented.

Accordingly, the polymerizable compound is particularly preferably represented by a general formula (V-1) to a general formula (V-4) and most preferably represented by the general formula (V-2).

In a case where such a polymerizable compound is added to a liquid crystal composition in the present invention, polymerization proceeds even in the absence of a polymerization initiator, but a polymerization initiator may be contained to facilitate the polymerization. Examples of the polymerization initiator include benzoin ethers, benzophenones, acetophenones, benzylketals, and acylphosphine oxides.

A liquid crystal composition containing a polymerizable compound in the present invention is provided with a liquid crystal alignment capability by polymerizing the polymerizable compound therein through irradiation with ultraviolet rays and is used for liquid crystal display elements that control the amount of transmitted light by using the birefringence of the liquid crystal composition. The liquid crystal composition is useful for liquid crystal display elements such as an AM-LCD (active matrix liquid crystal display element), a TN (nematic liquid crystal display element), an STN-LCD (super-twisted nematic liquid crystal display element), an OCB-LCD, and an IPS-LCD (in-plane switching liquid crystal display element). The liquid crystal composition is particularly useful for AM-LCDs and can be used for transmission or reflection-type liquid crystal display elements.

A color filter in the present invention includes a black matrix and at least RGB three-color pixel portions. The RGB three-color pixel portions contain, as a coloring material in the R pixel portion, a diketopyrrolopyrrole-based red pigment having an average primary particle size of 5 to 50 nm measured by a small angle X-ray scattering method.

The R pixel portion contains a diketopyrrolopyrrole-based red pigment having an average primary particle size of 5 to 50 nm, more preferably 10 to 30 nm, measured by a small angle X-ray scattering method. Specifically, the diketopyrrolopyrrole pigment is preferably at least one selected from C.I. Pigment Red 254, 255, 264, and 272 and Orange 71 and 73, more preferably at least one selected from Red 254, 255, 264, and 272, particularly preferably C.I. Pigment Red 254.

In addition, a pigment derivative is preferably contained as a dispersion aid. Such a pigment derivative contained is preferably at least one of a quinacridone-based pigment derivative, a diketopyrrolopyrrole-based pigment derivative, an anthraquinone-based pigment derivative, and a thiazine-based pigment derivative. The derivative moiety may be a phthalimidemethyl group, a sulfonic group, an N-(dialkylamino)methyl group, or an N-(dialkylaminoalkyl)sulfonamide group. Among such derivatives, two or more different derivatives may be used in combination.

The amount of such a pigment derivative used with respect to 100 parts of the diketopyrrolopyrrole-based red pigment is preferably 4 parts or more and 17 parts or less, more preferably 6 parts or more and 13 parts or less.

The G pixel portion preferably contains at least one selected from the group consisting of a halogenated metal phthalocyanine pigment, a phthalocyanine-based green dye, and a mixture of a phthalocyanine-based blue dye and an azo-based yellow organic dye. Preferably, the halogenated metal phthalocyanine pigment has, as a central metal, a metal selected from the group consisting of Al, Si, Sc, Ti, V, Mg, Fe, Co, Ni, Zn, Cu, Ga, Ge, Y, Zr, Nb, In, Sn, and Pb; in a case where the central metal is trivalent, the central metal is bonded to any one of a halogen atom, a hydroxy group, and a sulfonic group, or the central metal is oxo- or thio-bridged; and, in a case where the central metal is a tetravalent metal, the central metal is bonded to one oxygen atom or two selected from halogen atoms, hydroxy groups, and sulfonic groups, the selected two being the same or different. Such halogenated metal phthalocyanine pigments may be halogenated metal phthalocyanine pigments that belong to the following two groups.

A halogenated metal phthalocyanine pigment having, as a central metal, a metal selected from the group consisting of Al, Si, Sc, Ti, V, Mg, Fe, Co, Ni, Zn, Cu, Ga, Ge, Y, Zr, Nb, In, Sn, and Pb and having a structure in which 8 to 16 halogen atoms per molecule of phthalocyanine are bonded to benzene rings of a phthalocyanine molecule; in a case where the central metal is trivalent, the central metal is bonded to any one of a halogen atom, a hydroxy group, and a sulfonic group (—SO3H); and, in a case where the central metal is a tetravalent metal, the central metal is bonded to one oxygen atom or two selected from halogen atoms, hydroxy groups, and sulfonic groups, the selected two being the same or different.

A pigment composed of a halogenated metal phthalocyanine dimer including, as constitutional units, two molecules of a halogenated metal phthalocyanine having, as a central metal, a trivalent metal selected from the group consisting of Al, Sc, Ga, Y, and In and having a structure in which 8 to 16 halogen atoms per molecule of phthalocyanine are bonded to benzene rings of a phthalocyanine molecule; and the central metals of the constitutional units are bonded to each other through a divalent atomic group selected from the group consisting of an oxygen atom, a sulfur atom, sulfinyl (—SO—), and sulfonyl (—SO2-).

In such a halogenated metal phthalocyanine pigment, all the halogen atoms that are bonded to the benzene rings may be the same or different from each other. Different halogen atoms may be bonded to a single benzene ring.

A halogenated metal phthalocyanine pigment in which 9 to 15 bromine atoms among 8 to 16 halogen atoms per molecule of phthalocyanine are bonded to benzene rings of a phthalocyanine molecule assumes yellowish bright green and is optimally used for a green pixel portion of a color filter. The halogenated metal phthalocyanine pigment is insoluble or sparingly soluble in water or an organic solvent. The halogenated metal phthalocyanine pigment may be a pigment (also referred to as a “crude pigment”) not subjected to a finishing treatment described below or a pigment having been subjected to the finishing treatment.

The halogenated metal phthalocyanine pigments that belong to the first group and the second group can be represented by a general formula (PIG-1) below.

In the general formula (PIG-1), the halogenated metal phthalocyanine pigment that belongs to the first group is as follows.

In the general formula (PIG-1), X1ito X16irepresent a hydrogen atom, a chlorine atom, a bromine atom, or an iodine atom. Four X atoms that are bonded to a single benzene ring may be the same or different. Among X1ito X16ithat are bonded to four benzene rings, 8 to 16 of them are chlorine atoms, bromine atoms, or iodine atoms. M represents a central metal. Among halogenated metal phthalocyanine pigments having the same Y, which will be described below, and the same number m of Y, pigments having chlorine atoms, bromine atoms, and iodine atoms in a total number of less than 8 among 16 atoms of X1ito X16iassume blue, and pigments having chlorine atoms, bromine atoms, and iodine atoms in a total number of 8 or more among 16 atoms of X1ito X16iassume more yellowish as the total number increases. Y that is bonded to the central metal M is a monovalent atomic group selected from the group consisting of a halogen atom such as fluorine, chlorine, bromine, or iodine, an oxygen atom, a hydroxy group, and a sulfonic group; and m represents the number of Y that is bonded to the central metal M, m being an integer of 0 to 2.

The value of m is determined on the basis of the valence of the central metal M. In a case where the central metal M is a trivalent metal such as Al, Sc, Ga, Y, or In, m=1 and any one group selected from the group consisting of fluorine, chlorine, bromine, iodine, a hydroxy group, and a sulfonic group is bonded to the central metal. In a case where the central metal M is a tetravalent metal such as Si, Ti, V, Ge, Zr, or Sn, m=2 and one oxygen atom is bonded to the central metal or two groups each selected from the group consisting of fluorine, chlorine, bromine, iodine, a hydroxy group, and a sulfonic group are bonded to the central metal. In a case where the central metal M is a divalent metal such as Mg, Fe, Co, Ni, Zn, Cu, Zr, Sn, or Pb, Y is not present.

In the general formula (PIG-1) above, the halogenated metal phthalocyanine pigment that belongs to the second group is as follows.

In the general formula (PIG-1), X1ito X16ihave the same definition as above; the central metal M represents a trivalent metal selected from the group consisting of Al, Sc, Ga, Y, and In; m represents 1; and Y represents the following atomic group.

In the chemical structure of the atomic group Y, the central metal M has the same definition as above and X17ito X32ihave the same definition as that of X1ito X16idescribed above in the general formula (PIG-1). A represents a divalent atomic group selected from the group consisting of an oxygen atom, a sulfur atom, sulfinyl (—SO—), and sulfonyl (—SO2-). M in the general formula (PIG-1) and M in the atomic group Y are bonded to each other through the divalent atomic group A.

In other words, the halogenated metal phthalocyanine pigment that belongs to the second group is composed of a halogenated metal phthalocyanine dimer including, as constitutional units, two molecules of a halogenated metal phthalocyanine, the two molecules being bonded to each other through the divalent atomic group.

Specific examples of the halogenated metal phthalocyanine pigment represented by the general formula (PIG-1) include the following (1) to (4).

(1) A halogenated metal phthalocyanine pigment such as a halogenated copper phthalocyanine pigment, a halogenated tin phthalocyanine pigment, a halogenated nickel phthalocyanine pigment, or a halogenated zinc phthalocyanine pigment, in which the central metal is a divalent metal selected from the group consisting of Mg, Fe, Co, Ni, Zn, Cu, Zr, Sn, and Pb and 8 to 16 halogen atoms per molecule of phthalocyanine are bonded to four benzene rings. Note that, among the phthalocyanine pigments, a chlorinated/brominated zinc phthalocyanine pigment, which corresponds to C.I. Pigment Green 58, is particularly preferred.

(2) A halogenated metal phthalocyanine pigment such as a halogenated chloroaluminum phthalocyanine, in which the central metal is a trivalent metal selected from the group consisting of Al, Sc, Ga, Y, and In, the central metal has any one of a halogen atom, a hydroxy group, and a sulfonic group, and 8 to 16 halogen atoms per molecule of phthalocyanine are bonded to four benzene rings.

(3) A halogenated metal phthalocyanine pigment such as a halogenated oxytitanium phthalocyanine or a halogenated oxyvanadium phthalocyanine, in which the central metal is a tetravalent metal selected from the group consisting of Si, Ti, V, Ge, Zr, and Sn, the central metal has one oxygen atom or two selected from halogen atoms, hydroxy groups, and sulfonic groups, the selected two being the same or different, and 8 to 16 halogen atoms per molecule of phthalocyanine are bonded to four benzene rings.

(4) A pigment composed of a halogenated metal phthalocyanine dimer, such as a halogenated μ-oxo-aluminum phthalocyanine dimer or a halogenated μ-thio-aluminum phthalocyanine dimer, that includes, as constitutional units, two molecules of a halogenated metal phthalocyanine having, as a central metal, a trivalent metal selected from the group consisting of Al, Sc, Ga, Y and In and having a structure in which 8 to 16 halogen atoms per molecule of phthalocyanine are bonded to four benzene rings, the central metals of the constitutional units being bonded to each other through a divalent atomic group selected from the group consisting of an oxygen atom, a sulfur atom, sulfinyl, and sulfonyl.

Specifically, the halogenated metal phthalocyanine pigment is preferably at least one selected from C.I. Pigment Green 7, 36, and 58, more preferably at least one selected from Green 36 and 58. Specifically, the phthalocyanine-based green dye is preferably at least one selected from C.I. Solvent Green 4, 5, 7, and 28. Specifically, the phthalocyanine-based blue dye is preferably at least one selected from C.I. Solvent Blue 4, 5, 25, 35, 36, 38, 58, 59, 67, and 70, more preferably at least one selected from Blue 25, 38, 67, and 70. Specifically, the azo-based yellow organic dye is preferably at least one selected from C.I. Solvent Yellow 2, 4, 14, 16, 18, 21, 56, 72, 124, 162, and 163, more preferably at least one selected from Yellow 82 and 162.

The B pixel portion preferably contains at least one selected from the group consisting of an ∈-type copper phthalocyanine pigment, a triarylmethane pigment, and a cationic blue organic dye. As the cationic blue organic dye, C.I. Solvent Blue 7 is preferably contained. The ∈-type copper phthalocyanine pigment is preferably C.I. Pigment Blue 15:6.

The triarylmethane pigment is preferably represented by the following general formula (1).

(In the formula, R11jto R16jeach independently represent a hydrogen atom, an alkyl group having 1 to 8 carbons that may be substituted, or an aryl group that may be substituted; in a case where R11jto R16jrepresent an alkyl group that may be substituted, neighboring R11jand R12j, R13jand R14j, and R15jand R16jmay be bonded so as to form ring structures; X11jand X12jeach independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 8 carbons that may be substituted; Z−represents at least one anion selected from a heteropolyoxometalate anion represented by (P2MoyW18-yO62)6−/6 where y represents an integer of 0, 1, 2, or 3, a heteropolyoxometalate anion represented by (SiMoW11O40)4−/4, and a lacunary Dawson phosphotungstic heteropolyoxometalate anion; and, in a case where a single molecule contains a plurality of the formula (1), the plurality of the formula (1) may represent the same structure or different structures).

In the general formula (1), R11jto R16jmay be the same or different. Accordingly, an —NRR (RR represents any one combination of R11jR12j, R13jR14j, and R15jR16j) group may be symmetrical or asymmetrical.

In a case where neighboring R's (R's are among R11jto R16j) are bonded so as to form rings, these rings may be formed via hetero atoms. Specific examples of the rings are illustrated below. These rings may be substituted.

From the standpoint of chemical stability, R11jto R16jpreferably each independently represent a hydrogen atom, an alkyl group that may be substituted, or an aryl group that may be substituted.

In particular, more preferably, R11jto R16jeach independently represent a hydrogen atom; an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a cyclopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, or a 2-ethylhexyl group; or an aryl group such as a phenyl group or a naphthyl group.

In a case where R11jto R16jrepresent an alkyl group or an aryl group, the alkyl group or the aryl group may have a desired substituent. Examples of the desired substituent that the alkyl group or the aryl group may have include the following [substituent group Y].

Examples include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a cyclopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, and a 2-ethylhexyl group; aryl groups such as a phenyl group and a naphthyl group; halogen atoms such as a fluorine atom and a chlorine atom; a cyano group; a hydroxy group; alkoxy groups having 1 to 8 carbon atoms such as a methoxy group, an ethoxy group, a propoxy group, and a butoxy group; amino groups that may be substituted such as an amino group, a diethylamino group, a dibutylamino group, and an acetylamino group; acyl groups such as an acetyl group and a benzoyl group; and acyloxy groups such as an acetyloxy group and a benzoyloxy group.

R11jto R16jmore preferably represent alkyl groups that have 1 to 8 carbon atoms and may have substituents. Specific examples include unsubstituted alkyl groups 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 pentyl group, a hexyl group, and a 2-ethylhexyl group; alkoxyalkyl groups such as a 2-methoxyethyl group and a 2-ethoxyethyl group; acyloxy groups such as a 2-acetyloxyethyl group; cyanoalkyl groups such as a 2-cyanoethyl group; and fluoroalkyl groups such as a 2,2,2-trifluoroethyl group and a 4,4,4-trifluorobutyl group.

In a case where X11jand X12jrepresent such an alkyl group, the alkyl group may have a desired substituent. Examples of such a substituent include halogen atoms such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom; and alkoxy groups such as a methoxy group, an ethoxy group, and a propoxy group. Specific examples of X11jand X12jinclude haloalkyl groups such as a fluoromethyl group, a trifluoromethyl group, a trichloromethyl group, and 2,2,2-trifluoroethyl group; and alkoxyalkyl groups such as a methoxymethyl group.

X11jand X12jpreferably represent a substituent that causes such appropriate steric hindrance that does not affect torsion, such as a hydrogen atom, a methyl group, a chlorine atom, or a trifluoromethyl group. X11jand X12jmost preferably represent a hydrogen atom, a methyl group, or a chlorine atom from the standpoint of color tone and heat resistance.

Z−represents at least one anionic triarylmethane compound selected from a heteropolyoxometalate anion represented by (P2MoyW18-yO62)6−/6 where y represents an integer of 0, 1, 2, or 3, a heteropolyoxometalate anion represented by (SiMoW11O40)4−/4, and a lacunary Dawson phosphotungstic heteropolyoxometalate anion. Specifically, the lacunary Dawson phosphotungstic acid is preferably monolacunary Dawson phosphotungstic heteropolyoxometalate anion (P2W17O61)10−/10 from the standpoint of durability.

Specific examples of a triarylmethane pigment represented by the general formula (1) include compounds described in Tables 1 to 7 below; however, the present invention is not limited to these compounds without departing from the spirit and scope of the present invention.

The RGB three-color pixel portions preferably contain, as a coloring material in the R pixel portion, C.I. Pigment Red 254 having an average primary particle size of 5 to 50 nm measured by a small angle X-ray scattering method; as a coloring material in the G pixel portion, a mixture of C.I. Solvent Blue 67 and C.I. Solvent Yellow 82 and/or 162; and, as a coloring material in the B pixel portion, a triarylmethane pigment represented by the general formula (1).

The RGB three-color pixel portions also preferably contain, as a coloring material in the R pixel portion, C.I. Pigment Red 254 having an average primary particle size of 5 to 50 nm measured by a small angle X-ray scattering method; as a coloring material in the G pixel portion, at least one selected from C.I. Pigment Green 7, 36, and 58; and, as a coloring material in the B pixel portion, a triarylmethane pigment represented by the general formula (1).

The RGB three-color pixel portions preferably further contain, as a coloring material in the R pixel portion, at least one organic dye or pigment selected from the group consisting of C.I. Pigment Red 177, 242, 166, 167, and 179, C.I. Pigment Orange 38 and 71, C.I. Pigment Yellow 150, 215, 185, 138, and 139, C.I. Solvent Red 89, C.I. Solvent Orange 56, and C.I. Solvent Yellow 21, 82, 83:1, 33, and 162.

The RGB three-color pixel portions preferably further contain, as a coloring material in the G pixel portion, at least one organic dye or pigment selected from the group consisting of C.I. Pigment Yellow 150, 215, 185, and 138 and C.I. Solvent Yellow 21, 82, 83:1, and 33.

The RGB three-color pixel portions preferably further contain, as a coloring material in the B pixel portion, at least one organic dye or pigment selected from the group consisting of C.I. Pigment Blue 1, C.I. Pigment Violet 23, C.I. Basic Blue 7, C.I. Basic Violet 10, C.I. Acid Blue 1, 90, and 83, C.I. Direct Blue 86, and C.I. Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, and 15:6.

It is also preferred that the color filter include a black matrix, the RGB three-color pixel portions, and a Y pixel portion, and the Y pixel portion contain, as a coloring material, at least one yellow organic dye or pigment selected from the group consisting of C.I. Pigment Yellow 150, 215, 185, 138, and 139 and C.I. Solvent Yellow 21, 82, 83:1, 33, and 162.

In a color filter according to the present invention, the chromaticity x and chromaticity y in the XYZ color system of each pixel portion with use of a C light source are preferably as follows from the viewpoint of preventing a decrease in the voltage holding ratio (VHR) and an increase in the ion density (ID) in the liquid crystal layer and suppressing problems of display defects such as white streaks, variations in alignment, and image sticking.

In the XYZ color system of the R pixel portion with use of a C light source, the chromaticity x is preferably 0.58 to 0.69 and more preferably 0.62 to 0.68 and the chromaticity y is preferably 0.31 to 0.36 and more preferably 0.32 to 0.35. More preferably, the chromaticity x is 0.58 to 0.69 and the chromaticity y is 0.31 to 0.36. More preferably, the chromaticity x is 0.62 to 0.68 and the chromaticity y is 0.32 to 0.35.

In the XYZ color system of the G pixel portion with use of a C light source, the chromaticity x is preferably 0.19 to 0.35 and more preferably 0.20 to 0.26 and the chromaticity y is preferably 0.54 to 0.76 and more preferably 0.64 to 0.73. More preferably, the chromaticity x is 0.19 to 0.35 and the chromaticity y is 0.54 to 0.76. More preferably, the chromaticity x is 0.20 to 0.26 and the chromaticity y is 0.64 to 0.73.

In the XYZ color system of the B pixel portion with use of a C light source, the chromaticity x is preferably 0.12 to 0.19 and more preferably 0.12 to 0.17 and the chromaticity y is preferably 0.04 to 0.14 and more preferably 0.05 to 0.12. More preferably, the chromaticity x is 0.11 to 0.19 and the chromaticity y is 0.04 to 0.14. More preferably, the chromaticity x is 0.12 to 0.17 and the chromaticity y is 0.05 to 0.12.

In the XYZ color system of the Y pixel portion with use of a C light source, the chromaticity x is preferably 0.46 to 0.50 and more preferably 0.47 to 0.48 and the chromaticity y is preferably 0.48 to 0.53 and more preferably 0.50 to 0.52. More preferably, the chromaticity x is 0.46 to 0.50 and the chromaticity y is 0.48 to 0.53. More preferably, the chromaticity x is 0.47 to 0.48 and the chromaticity y is 0.50 to 0.52.

Herein, the XYZ color system is a color system approved as the standard color system by the CIE (International Commission on Illumination) in 1931.

Such chromaticity in each pixel portion can be adjusted by changing the types of dyes and pigments used and the mixing ratio of the dyes and pigments. For example, in the case of the R pixel, the chromaticity can be adjusted by adding an appropriate amount of a yellow dye/pigment and/or an orange pigment to the red dye/pigment. In the case of the G pixel, the chromaticity can be adjusted by adding an appropriate amount of a yellow dye/pigment to the green dye/pigment. In the case of the B pixel, the chromaticity can be adjusted by adding an appropriate amount of a purple dye/pigment or a yellowish blue dye/pigment to the blue dye/pigment. The chromaticity can also be adjusted by appropriately controlling the particle size of a pigment.

In the color filter, color filter pixel portions can be formed by a publicly known method. A representative example of a method for forming pixel portions is a photolithography method. In this method, a photo-curable composition described below is applied onto a black-matrix-side surface of a transparent substrate for color filters and dried by performing heating (pre-baked); pattern exposure is then performed by irradiating the photo-curable composition with ultraviolet rays through a photomask to cure the photo-curable compound in portions corresponding to pixel portions; and unexposed portions are then developed with a developer to remove portions other than the pixel portions, whereby the pixel portions are fixed on the transparent substrate. In this method, pixel portions composed of a cured colored coating film of the photo-curable composition are formed on the transparent substrate.

The photo-curable composition described below is prepared for each of the R pixel, G pixel, B pixel, and optionally other pixels of different colors, such as the Y pixel and the above-described process is repeatedly performed. Thus, a color filter including colored pixel portions of the R pixel, G pixel, B pixel, and Y pixel at predetermined positions can be produced.

Examples of a method for applying the photo-curable composition described below onto the transparent substrate composed of glass or the like include a spin coating method, a slit coating method, a roll coating method, and an ink-jet method.

The drying conditions of the coating film of the photo-curable composition applied onto the transparent substrate are normally 50° C. to 150° C. and about 1 to 15 minutes though depending on, for example, the types of components and the mixing ratio. The light used for the photo-curing of the photo-curable composition is preferably ultraviolet light or visible light in a wavelength range of 200 to 500 nm. Various light sources that emit light in this wavelength range can be used.

Examples of a developing method include a puddling method, a dipping method, and a spraying method. After the exposure and development of the photo-curable composition, the transparent substrate on which pixel portions of necessary colors have been formed is washed with water and dried. The thus-produced color filter is heat-treated (post-baked) at 90° C. to 280° C. for a predetermined time using a heating device such as a hot plate, an oven, or the like to remove volatile components in the colored coating film and, at the same time, heat-cure an unreacted photo-curable compound remaining in the cured colored coating film of the photo-curable composition, whereby the color filter is completed.

By using a coloring material for a color filter of the present invention together with a liquid crystal composition of the present invention, there can be provided a liquid crystal display device in which a decrease in the voltage holding ratio (VHR) and an increase in the ion density (ID) in the liquid crystal layer are prevented and problems of display defects such as white streaks, variations in alignment, and image sticking are resolved.

In general, the photo-curable composition is produced by the method below. A dye and/or pigment composition for a color filter of the present invention, an organic solvent, and a dispersant serving as essential components are stirred and dispersed so as to be uniformly mixed with each other in order to prepare a pigment dispersion liquid for forming a pixel portion of a color filter. A photo-curable compound and optionally a thermoplastic resin, a photopolymerization initiator, and the like are added to the pigment dispersion liquid to produce the photo-curable composition.

Examples of the organic solvent used herein include aromatic solvents such as toluene, xylene, and methoxybenzene; acetate solvents such as ethyl acetate, propyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, diethylene glycol methyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol propyl ether acetate, and diethylene glycol butyl ether acetate; propionate solvents such as ethoxyethyl propionate; alcohol solvents such as methanol and ethanol; ether solvents such as butyl cellosolve, propylene glycol monomethyl ether, diethylene glycol ethyl ether, and diethylene glycol dimethyl ether; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aliphatic hydrocarbon solvents such as hexane; nitrogen compound solvents such as N,N-dimethyl formamide, γ-butyrolactam, N-methyl-2-pyrrolidone, aniline, and pyridine; lactone solvents such as γ-butyrolactone; and carbamates such as a mixture containing methyl carbamate and ethyl carbamate in a ratio of 48:52.

Examples of a dispersion aid that can be contained include organic pigment derivatives such as phthalimidemethyl derivatives, sulfonic acid derivatives, N-(dialkylamino)methyl derivatives, and N-(dialkylaminoalkyl)sulfonamide derivatives. It is obvious that two or more different types of these derivatives can be used in combination.

Examples of the thermoplastic resin used to prepare the photo-curable composition include urethane resins, acrylic resins, polyamide resins, polyimide resins, styrene-maleic acid resins, and styrene-maleic anhydride resins.

A publicly known and commonly used photosensitizer can also be used together with the photopolymerization initiator. Examples of the photosensitizer include amines, urea compounds, compounds containing a sulfur atom, compounds containing a phosphorus atom, compounds containing a chlorine atom, nitriles, and other compounds containing a nitrogen atom. They can be used alone or in combination of two or more thereof.

The mixing ratio of the photopolymerization initiator added is not particularly limited, but is preferably in the range of 0.1% to 30% by mass relative to the compound having a photo-polymerizable or photo-curable functional group. In a case where the ratio is less than 0.1%, the sensitivity during photocuring tends to decrease. In a case where the ratio is more than 30%, a crystal of the photopolymerization initiator is precipitated during drying of a pigment dispersion resist coating film and thus the physical properties of the coating film may be degraded.

A photo-curable composition for forming a pixel portion of a color filter can be prepared using the materials described above. Specifically, 300 to 1000 parts by mass of the organic solvent and 1 to 100 parts by mass of the dispersant relative to 100 parts by mass of the dye and/or pigment composition for a color filter of the present invention are stirred and dispersed so as to be uniformly mixed with each other. Thus, the die/pigment liquid can be prepared. Subsequently, 3 to 20 parts by mass in total of the thermoplastic resin and photo-curable compound relative to 1 part by mass of the pigment composition for a color filter of the present invention, 0.05 to 3 parts by mass of the photopolymerization initiator relative to 1 part by mass of the photo-curable compound, and optionally an organic solvent are added to the pigment dispersion liquid and stirred and dispersed so as to be uniformly mixed with each other.

A publicly known and commonly used organic solvent or aqueous alkali solution can be used as the developer. In particular, in a case where the photo-curable composition contains a thermoplastic resin or a photo-curable compound and at least one of the thermoplastic resin and photo-curable compound has an acid value and exhibits alkali solubility, washing with an aqueous alkali solution is effective for formation of color filter pixel portions.

The method for forming color filter pixel portions by a photolithography method has been described in detail. The color filter pixel portions formed by using pigment compositions for a color filter of the present invention may be formed by another method such as an electrodeposition method, a transfer method, a micelle electrolysis method, a PVED (photovoltaic electrodeposition) method, an ink-jet method, a reverse printing method, or a heat curing method, so that a color filter is produced.

In a liquid crystal display device of the present invention, in a case where an alignment film for aligning a liquid crystal composition needs to be formed on surfaces of first and second substrates that contact the liquid crystal composition, the alignment film is disposed between a color filter and a liquid crystal layer. However, the thickness of the alignment film is small and at most 100 nm or less, which does not completely block the interaction between a coloring agent such as a pigment constituting the color filter and a liquid crystal compound constituting the liquid crystal layer.

In a liquid crystal display device that does not use an alignment film, there is a higher degree of interaction between a coloring agent such as a pigment constituting the color filter and a liquid crystal compound constituting the liquid crystal layer.

The alignment film can be composed of a transparent organic material such as polyimide, polyamide, BCB (benzocyclobutene polymer), or polyvinyl alcohol. In particular, the alignment film is preferably a polyimide alignment film formed by imidizing polyamic acid synthesized from a diamine such as an aliphatic or alicyclic diamine, e.g., p-phenylene diamine or 4,4′-diaminodiphenylmethane, and an aliphatic or alicyclic tetracarboxylic acid anhydride such as butanetetracarboxylic acid anhydride or 2,3,5-tricarboxycyclopentylacetic acid anhydride, or an aromatic tetracarboxylic acid anhydride such as pyromellitic acid dianhydride. In this case, the alignment is generally provided by rubbing, but the alignment film can also be used without being provided with alignment when used as a vertical alignment film or the like.

The alignment film can be composed of a material containing chalcone, cinnamate, cinnamoyl, or an azo group in a compound, and such a material may be used in combination with a material such as polyimide and polyamide. In this case, rubbing or an optical alignment technique may be used for the alignment film.

Regarding the alignment film, in general, a resin film is formed by applying the alignment film material onto a substrate by a method such as a spin coating method. Alternatively, a uniaxially stretching method, a Langmuir-Blodgett method, or the like can also be employed.

In a liquid crystal display device of the present invention, the transparent electrode can be composed of a material such as a conductive metal oxide. The metal oxide can be indium oxide (In2O3), tin oxide (SnO2), zinc oxide (ZnO), indium tin oxide (In2O3—SnO2), indium zinc oxide (In2O3—ZnO), niobium-added titanium dioxide (Ti1-xNbxO2), fluorine-doped tin oxide, graphene nanoribbon, or metal nanowire and is preferably zinc oxide (ZnO), indium tin oxide (In2O3—SnO2), or indium zinc oxide (In2O3—ZnO). The transparent conductive film can be patterned by, for example, a photo-etching method or a method that uses a mask.

A liquid crystal display device of the present invention is particularly useful for active matrix driving liquid crystal display devices and can be applied to liquid crystal display devices with a TN mode, an IPS mode, a polymer-stabilized IPS mode, an FFS mode, an OCB mode, a VA mode, or an ECB mode.

The liquid crystal display device, in combination with a backlight, is used in various applications such as monitors of liquid crystal televisions and personal computers, displays of cellular phones and smart phones, notebook computers, mobile information terminals, and digital signage. Examples of the backlight include a cold-cathode tube backlight, and a pseudo-white backlight with two wavelength peaks and a backlight with three wavelength peaks that use a light-emitting diode composed of an inorganic material or an organic EL element.

EXAMPLES

Hereinafter, the present invention will be described further in detail with reference to Examples, but the present invention is not limited to these Examples. In compositions of Examples and Comparative Examples below, “%” means “% by mass”.

In Examples, the measured properties are as follows.

(a value, which is expressed as a percentage, of the ratio of a measured voltage to an initial applied voltage, the measured voltage being obtained by injecting a liquid crystal composition into a cell having a thickness of 3.5 μm and performing measurement at an application voltage of 5 V, a frame time of 200 ms, and a pulse duration of 64 μs)

(an ion density obtained by injecting a liquid crystal composition into a cell having a thickness of 3.5 μm and performing measurement at an application voltage of 20 V and a frequency of 0.05 Hz using MTR-1 (manufactured by TOYO Corporation))

Image sticking of a liquid crystal display element was evaluated as follows. A predetermined fixed pattern was displayed in a display area for 1000 hours, and a uniform image was then displayed on the full screen. The level of a residual image of the fixed pattern was evaluated through visual inspection on the basis of the four-level criteria described below.

A: No residual image was observed.

B: A residual image was slightly observed, but was at an acceptable level.

C: A residual image was observed, and was at an unacceptable level.

D: A residual image was observed, and was at a very poor level.

In Examples, the following abbreviations are used for the description of compounds.

(Side Chain Structure and Linking Structure)

Into a plastic bottle, 10 parts of a red pigment 1 (C.I. Pigment Red 254) having an average primary particle size of 25 nm and a normalized dispersion of 40% measured by a small angle X-ray scattering method was placed; 55 parts of propylene glycol monomethyl ether acetate, 7.0 parts of DISPERBYK LPN21116 (manufactured by BYK-Chemie GmbH), and 0.3 to 0.4 mmφ zirconia beads “ER-120S” manufactured by Saint-Gobain were added; and they were dispersed with a paint conditioner (manufactured by Toyo Seiki Seisaku-sho, Ltd.) for four hours and then filtered with a 1-μm filter to obtain a pigment dispersion liquid. Then, 75.00 parts of the pigment dispersion liquid, 5.50 parts of polyester acrylate resin (Aronix (trademark) M7100 manufactured by TOAGOSEI CO., LTD.), 5.00 parts of dipentaerythritol hexaacrylate (KAYARAD (trademark) DPHA manufactured by Nippon Kayaku Co., Ltd.), 1.00 part of benzophenone (KAYACURE (trademark) BP-100 manufactured by Nippon Kayaku Co., Ltd.), and 13.5 parts of UCAR Ester EEP were stirred with a mixer and filtered with a filter having a pore size of 1.0 μm to obtain a red pigment-colored composition 1.

Note that the average primary particle size and the particle size distribution of the organic pigment were obtained from a small angle X-ray scattering profile (measured scattering profile) of the organic pigment dispersion based on a small angle X-ray scattering method in Japanese Unexamined Patent Application Publication No. 2006-113042.

A red pigment-colored composition 2 was prepared in the same manner as above, except that 9.95 parts of a red pigment 2 (C.I. Pigment Red 254) having an average primary particle size of 15 nm and a normalized dispersion of 55% measured by the small angle X-ray scattering method and 0.05 parts of a sulfonic acid derivative of diketopyrrolopyrrole were used instead of 10 parts of the red pigment 1 of the red pigment-colored composition 1.

A red pigment-colored composition 3 was prepared in the same manner as above, except that 9.95 parts of a red pigment 3 (C.I. Pigment Red 255) having an average primary particle size of 20 nm and a normalized dispersion of 48% measured by the small angle X-ray scattering method and 0.04 parts of a phthalimidemethyl derivative of dichloroquinacridone were used instead of 10 parts of the red pigment 1 of the red pigment-colored composition 1.

A red pigment-colored composition 4 was prepared in the same manner as above, except that 7.36 parts of a red pigment 3 having an average primary particle size of 10 nm and a normalized dispersion of 60% measured by the small angle X-ray scattering method, 0.64 parts of a sulfonic acid derivative of diaminoanthraquinonyl, and 2 parts of a yellow pigment 2 (C.I. Pigment Yellow 139) were used instead of 10 parts of the red pigment 1 of the red pigment-colored composition 1.

A green pigment-colored composition 1 was prepared in the same manner as above, except that 6 parts of a green pigment 1 (C.I. Pigment Green 36, “FASTOGEN GREEN 2YK-CF” manufactured by DIC Corporation) and 4 parts of a yellow pigment 1 (C.I. Pigment Yellow 150, FANCHON FAST YELLOW E4GN manufactured by BAYER) were used instead of 10 parts of the red pigment 1 of the red pigment-colored composition 1.

A green pigment-colored composition 2 was prepared in the same manner as above, except that 4 parts of a green pigment 2 (C.I. Pigment Green 58, FASTOGEN GREEN A110 manufactured by DIC Corporation) and 6 parts of a yellow pigment 2 (C.I. Pigment Yellow 138) were used instead of 6 parts of the green pigment 1 and 4 parts of the yellow pigment 1 of the green pigment-colored composition 1.

A blue pigment-colored composition 1 was prepared in the same manner as above, except that 9 parts of a blue pigment 1 (C.I. Pigment Blue 15:6, “FASTOGEN BLUE EP-210” manufactured by DIC Corporation) and 1 part of a purple pigment 1 (C.I. Pigment VIOLET 23) were used instead of 10 parts of the red pigment 1 of the red pigment-colored composition 1.

Into a plastic bottle, 1.80 parts of a triarylmethane pigment represented by the general formula (1) above (Compound No. 2 in Table 1), 2.10 parts of BYK-2164 (BYK-Chemie GmbH), 11.10 parts of propylene glycol monomethyl ether acetate, and 0.3 to 0.4 mmφ SEPR beads were placed, and they were dispersed with a paint conditioner (manufactured by Toyo Seiki Seisaku-sho, Ltd.) for four hours to obtain a pigment dispersion liquid. Then, 75.00 parts of the pigment dispersion liquid, 5.50 parts of polyester acrylate resin (Aronix (trademark) M7100 manufactured by TOAGOSEI CO., LTD.), 5.00 parts of dipentaerythritol hexaacrylate (KAYARAD (trademark) DPHA manufactured by Nippon Kayaku Co., Ltd.), 1.00 part of benzophenone (KAYACURE (trademark) BP-100 manufactured by Nippon Kayaku Co., Ltd.), and 13.5 parts of UCAR Ester EEP (manufactured by Union Carbide Corporation) were stirred with a mixer and filtered with a filter having a pore size of 1.0 μm to obtain a blue pigment-colored composition 2.

A blue pigment-colored composition 3 was prepared in the same manner as above, except that a triarylmethane pigment represented by the general formula (1) above (Compound No. 5 in Table 1) was used instead of the triarylmethane pigment of the blue pigment-colored composition 2.

A yellow pigment-colored composition 1 was prepared in the same manner as above, except that 10 parts of a yellow pigment 1 (C.I. Pigment Yellow 150, FANCHON FAST YELLOW E4GN manufactured by LANXESS) was used instead of 10 parts of the red pigment 1 of the red pigment-colored composition 1.

Into a plastic bottle, 10 parts of a red dye 1 (C.I. Solvent Red 1) was placed; 55 parts of propylene glycol monomethyl ether acetate and 0.3 to 0.4 mmφ SEPR beads were added; and they were dispersed with a paint conditioner (manufactured by Toyo Seiki Seisaku-sho, Ltd.) for four hours and then filtered with a 5-μm filter to obtain a dye-colored liquid. Then, 75.00 parts of the dye-colored liquid, 5.50 parts of polyester acrylate resin (Aronix (trademark) M7100 manufactured by TOAGOSEI CO., LTD.), 5.00 parts of dipentaerythritol hexaacrylate (KAYARAD (trademark) DPHA manufactured by Nippon Kayaku Co., Ltd.), 1.00 part of benzophenone (KAYACURE (trademark) BP-100 manufactured by Nippon Kayaku Co., Ltd.), and 13.5 parts of UCAR Ester EEP were stirred with a mixer and filtered with a filter having a pore size of 1.0 μm to obtain a red dye-colored composition 1.

A green dye-colored composition 1 was prepared in the same manner as above, except that 3 parts of a blue dye 1 (C.I. Solvent Blue 67) and 7 parts of a yellow dye 1 (C.I. Solvent Yellow 162) were used instead of 10 parts of the red dye 1 of the red dye-colored composition 1.

A green dye-colored composition 2 was prepared in the same manner as above, except that 4 parts of a yellow dye 1 (C.I. Solvent Yellow 162) and 3 parts of a yellow dye 3 (C.I. Solvent Yellow 82) were used instead of 7 parts of the yellow dye 1 of the green dye-colored composition 1.

A green dye-colored composition 3 was prepared in the same manner as above, except that 10 parts of a green dye 1 (C.I. Solvent Green 7) was used instead of 3 parts of the blue dye 1 and 7 parts of the yellow dye 1 of the green dye-colored composition 1.

A yellow dye-colored composition 1 was prepared in the same manner as above, except that 10 parts of a yellow dye 1 (C.I. Solvent Yellow 21) was used instead of 10 parts of the red dye 1 of the red dye-colored composition 1.

A yellow dye-colored composition 2 was prepared in the same manner as above, except that 10 parts of a yellow dye 4 (C.I. Solvent Yellow 2) was used instead of 10 parts of the yellow dye 1 of the yellow dye-colored composition 1.

A blue dye-colored composition 1 was prepared in the same manner as above, except that 10 parts of a blue dye 1 (C.I. Solvent Blue 7) was used instead of the red dye 1 of the red dye-colored composition 1.

A blue dye-colored composition 2 was prepared in the same manner as above, except that 10 parts of a blue dye 2 (C.I. Solvent Blue 12) was used instead of 10 parts of the blue dye 1 of the blue dye-colored composition 1.

[Production of Color Filter]

The red colored composition was applied by spin coating onto a glass substrate on which a black matrix was formed in advance, so as to form a film having a thickness of 2 μm. The film was dried at 70° C. for 20 minutes and then exposed to ultraviolet rays through a photomask in a striped pattern using an exposure device equipped with an ultrahigh-pressure mercury lamp. The film was subjected to spray development with an alkali developer for 90 seconds, washed with ion-exchanged water, and air-dried. Subsequently, the film was post-baked in a clean oven at 230° C. for 30 minutes to form a red pixel, which was a striped colored layer, on the transparent substrate.

Next, the green colored composition was applied by spin coating in the same manner so as to form a film having a thickness of 2 μm. After drying, exposure and development were performed with an exposure device so that a striped colored layer was formed in a place shifted from the place of the red pixel. Thus, a green pixel adjacent to the red pixel was formed.

Next, the blue colored composition was applied by spin coating in the same manner so as to form a blue pixel having a film thickness of 2 μm and disposed adjacent to the red pixel and green pixel. Thus, a three-color filter including red, green, and blue striped pixels was produced on the transparent substrate.

When necessary, the yellow colored composition was applied by spin coating in the same manner so as to form a blue pixel having a film thickness of 2 μm and disposed adjacent to the red pixel and green pixel. Thus, a four-color filter including red, green, blue, and yellow striped pixels was produced on the transparent substrate.

Color filters 1 to 4 and a comparative color filter 1 were produced using dye-colored compositions or pigment-colored compositions listed in Table 9.

In each of the pixel portions of the color filter, the x value and y value in the CIE 1931 XYZ color system with use of a C light source were measured with a microspectrophotometer including a microscope MX-50 manufactured by Olympus Corporation and a spectrophotometer MCPD-3000 manufactured by Otsuka Electronics Co., Ltd. The following Table 10 shows the results.

Examples 1 to 4

An electrode structure was formed on at least one of first and second substrates, and an alignment film having a horizontal alignment property was formed on each of surfaces of the first and second substrates facing each other. Then, a weak rubbing treatment was performed, an IPS cell was made, and a liquid crystal composition 1 described below was sandwiched between the first substrate and the second substrate. Table 11 shows the physical properties of the liquid crystal composition 1. Subsequently, liquid crystal display devices of Examples 1 to 4 were produced using the color filters 1 to 4 listed in Table 9 (dgap=4.0 μm, alignment film AL-1051). The VHR and ID of the produced liquid crystal display devices were measured. The image sticking of the produced liquid crystal display devices was also evaluated. Table 12 shows the results.

It was found that the liquid crystal composition 1 had a liquid crystal phase temperature range of 75.8° C., which was practical for use as a liquid crystal composition for TVs, a high absolute value of dielectric anisotropy, low viscosity, and an optimal value of Δn.

In the liquid crystal display devices of Examples 1 to 4, high VHRs and low IDs were achieved. In the evaluation of image sticking, no residual image was observed or a residual image was slightly observed, which was at an acceptable level.

Examples 5 to 12

Liquid crystal compositions 2 and 3 listed in Table 13 were sandwiched as in Example 1. Liquid crystal display devices of Examples 5 to 12 were produced using the color filters listed in Table 9 and the VHR and ID were measured. The image sticking of the liquid crystal display devices was also evaluated. Tables 14 and 15 show the results.

In the liquid crystal display devices of Examples 5 to 12, high VHRs and low IDs were achieved. In the evaluation of image sticking, no residual image was observed or a residual image was slightly observed, which was at an acceptable level.

Examples 13 to 24

Liquid crystal compositions 4 to 6 listed in Table 16 were sandwiched as in Example 1. Liquid crystal display devices of Examples 13 to 24 were produced using the color filters listed in Table 9 and the VHR and ID were measured. The image sticking of the liquid crystal display devices was also evaluated. Tables 17 to 19 show the results.

In the liquid crystal display devices of Examples 13 to 24, high VHRs and low IDs were achieved. In the evaluation of image sticking, no residual image was observed or a residual image was slightly observed, which was at an acceptable level.

Examples 25 to 36

An electrode structure was formed on first and second substrates, and an alignment film having a horizontal alignment property was formed on each of surfaces of the first and second substrates facing each other. Then, a weak rubbing treatment was performed, a TN cell was made, and liquid crystal compositions 7 to 9 described in Table 20 were sandwiched between the first substrate and the second substrate. Subsequently, liquid crystal display devices of Examples 25 to 36 were produced using the color filters 1 to 4 listed in Table 9 (dgap=3.5 μm, alignment film SE-7492). The VHR and ID of the produced liquid crystal display devices were measured. The image sticking of the produced liquid crystal display devices was also evaluated. Tables 21 to 23 show the results.

In the liquid crystal display devices of Examples 25 to 36, high VHRs and low IDs were achieved. In the evaluation of image sticking, no residual image was observed or a residual image was slightly observed, which was at an acceptable level.

Examples 37 to 44

An electrode structure was formed on at least one of first and second substrates, and an alignment film having a horizontal alignment property was formed on each of surfaces of the first and second substrates facing each other. Then, a weak rubbing treatment was performed, an FFS cell was made, and liquid crystal compositions 10 and 11 described in Table 24 were sandwiched between the first substrate and the second substrate. Subsequently, liquid crystal display devices of Examples 37 to 44 were produced using the color filters 1 to 4 listed in Table 9 (dgap=4.0 μm, alignment film AL-1051). The VHR and ID of the produced liquid crystal display devices were measured. The image sticking of the produced liquid crystal display devices was also evaluated. Tables 25 and 26 show the results.

In the liquid crystal display devices of Examples 37 to 44, high VHRs and low IDs were achieved. In the evaluation of image sticking, no residual image was observed or a residual image was slightly observed, which was at an acceptable level.

Examples 45 to 56

Liquid crystal compositions 12 to 14 listed in Table 27 were sandwiched as in Example 37. Liquid crystal display devices of Examples 45 to 56 were produced using the color filters listed in Table 9 and the VHR and ID were measured. The image sticking of the liquid crystal display devices was also evaluated. Tables 28 to 30 show the results.

In the liquid crystal display devices of Examples 45 to 56, high VHRs and low IDs were achieved. In the evaluation of image sticking, no residual image was observed or a residual image was slightly observed, which was at an acceptable level.

Examples 57 to 60

A liquid crystal composition 15 was prepared by mixing 0.3% by mass of bismethacrylic acid biphenyl-4,4′-diyl with the liquid crystal composition 10 used in Example 37. The liquid crystal composition 15 was sandwiched in the TN cell. A polymerization treatment was performed by performing irradiation with ultraviolet rays (3.0 J/cm2) for 600 seconds while applying a driving voltage between electrodes. Liquid crystal display devices of Examples 57 to 60 were then produced using the color filters 1 to 4 listed in Table 9 and the VHR and ID were measured. The image sticking of the liquid crystal display devices was also evaluated.

Table 31 shows the results.

In the liquid crystal display devices of Examples 57 to 60, high VHRs and low IDs were achieved. In the evaluation of image sticking, no residual image was observed or a residual image was slightly observed, which was at an acceptable level.

Examples 61 to 64

A liquid crystal composition 16 was prepared by mixing 0.3% by mass of bismethacrylic acid biphenyl-4,4′-diyl with the liquid crystal composition 8 used in Example 29. The liquid crystal composition 16 was sandwiched in the IPS cell. A polymerization treatment was performed by performing irradiation with ultraviolet rays (3.0 J/cm2) for 600 seconds while applying a driving voltage between electrodes. Liquid crystal display devices of Examples 61 to 64 were then produced using the color filters 1 to 4 listed in Table 9 and the VHR and ID were measured. The image sticking of the liquid crystal display devices was also evaluated.

Table 32 shows the results.

In the liquid crystal display devices of Examples 61 to 64, high VHRs and low IDs were achieved. In the evaluation of image sticking, no residual image was observed or a residual image was slightly observed, which was at an acceptable level.

Examples 65 to 68

A liquid crystal composition 17 was prepared by mixing 0.3% by mass of bismethacrylic acid 3-fluorobiphenyl-4,4′-diyl with the liquid crystal composition 6 used in Example 21. The liquid crystal composition 17 was sandwiched in the FFS cell. A polymerization treatment was performed by performing irradiation with ultraviolet rays (3.0 J/cm2) for 600 seconds while applying a driving voltage between electrodes. Liquid crystal display devices of Examples 65 to 68 were then produced using the color filters 1 to 4 listed in Table 9 and the VHR and ID were measured. The image sticking of the liquid crystal display devices was also evaluated. Table 33 shows the results.

In the liquid crystal display devices of Examples 65 to 68, high VHRs and low IDs were achieved. In the evaluation of image sticking, no residual image was observed or a residual image was slightly observed, which was at an acceptable level.

Comparative Examples 1 to 4

A comparative liquid crystal composition 1 described below was sandwiched in the IPS cell used in Example 1. Table 34 shows the physical properties of the comparative liquid crystal composition. Liquid crystal display devices of Comparative Examples 1 to 4 were produced using the color filters 1 to 4 listed in Table 9 and the VHR and ID were measured. The image sticking of the liquid crystal display devices was also evaluated. Table 35 shows the results.

In the liquid crystal display devices of Comparative Examples 1 to 4, the VHRs were decreased and the IDs were increased compared with the liquid crystal display devices of the invention of this application. In the evaluation of image sticking, a residual image was observed, which was at an unacceptable level.

Comparative Examples 5 to 12

Comparative liquid crystal compositions 2 and 3 listed in Table 36 were sandwiched as in Example 1. Liquid crystal display devices of Comparative Examples 5 to 12 were produced using the color filters 1 to 4 listed in Table 9 and the VHR and ID were measured. The image sticking of the liquid crystal display devices was also evaluated. Tables 37 and 38 show the results.

In the liquid crystal display devices of Comparative Examples 5 to 12, the VHRs were decreased and the IDs were increased compared with the liquid crystal display devices of the invention of this application. In the evaluation of image sticking, a residual image was observed, which was at an unacceptable level.

Comparative Examples 13 to 20

Comparative liquid crystal compositions 4 and 5 listed in Table 39 were sandwiched as in Example 1. Liquid crystal display devices of Comparative Examples 13 to 24 were produced using the color filters 1 to 4 listed in Table 9 and the VHR and ID were measured. The image sticking of the liquid crystal display devices was also evaluated. Tables 40 and 41 show the results.

In the liquid crystal display devices of Comparative Examples 13 to 20, the VHRs were decreased and the IDs were increased compared with the liquid crystal display devices of the invention of this application. In the evaluation of image sticking, a residual image was observed, which was at an unacceptable level.

Comparative Examples 21 to 32

Comparative liquid crystal compositions 6 to 8 listed in Table 42 were sandwiched as in Example 1. Liquid crystal display devices of Comparative Examples 21 to 32 were produced using the color filters 1 to 4 listed in Table 9 and the VHR and ID were measured. The image sticking of the liquid crystal display devices was also evaluated. Tables 43 to 45 show the results.

In the liquid crystal display devices of Comparative Examples 21 to 32, the VHRs were decreased and the IDs were increased compared with the liquid crystal display devices of the invention of this application. In the evaluation of image sticking, a residual image was observed, which was at an unacceptable level.

Comparative Examples 33 to 44

Comparative liquid crystal compositions 9 to 11 listed in Table 46 were sandwiched as in Example 1. Liquid crystal display devices of Comparative Examples 33 to 44 were produced using the color filters 1 to 4 listed in Table 9 and the VHR and ID were measured. The image sticking of the liquid crystal display devices was also evaluated. Tables 47 to 49 show the results.

In the liquid crystal display devices of Comparative Examples 33 to 44, the VHRs were decreased and the IDs were increased compared with the liquid crystal display devices of the invention of this application. In the evaluation of image sticking, a residual image was observed, which was at an unacceptable level.

Comparative Examples 45 to 52

Liquid crystal display devices of Comparative Examples 45 to 52 were produced in the same manner, except that the comparative color filter 1 listed in Table 9 was used instead of the color filter 1 in Examples 5, 13, 17, 25, 37, 45, 61, and 65. The VHR and ID were measured. The image sticking of the liquid crystal display devices was also evaluated. Tables 50 and 51 show the results.

In the liquid crystal display devices of Comparative Examples 45 to 52, the VHRs were decreased and the IDs were increased compared with the liquid crystal display devices of the invention of this application. In the evaluation of image sticking, a residual image was observed, which was at an unacceptable level.