Light emitting module and method of driving the same, and optical sensor

The object of the present invention is to provide a light emitting module which is excellent in visibility and can reduce power consumption.The light emitting module includes a light emitting device containing at least a pixel section 101 and a sensor section 104, which are formed on the same insulating body, and further includes means for sensing illuminance of a use environment with the sensor section 104 and for adjusting luminance of a light emitting element according to the illuminance to keep a ratio of the luminance to the illuminance of the use environment at a constant value.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a module (hereinafter referred to as a light emitting module) including a device (hereinafter referred to as a light emitting device) comprising an element sandwiching a light emitting material (hereinafter referred to as a light emitting element) between electrodes. In particular, the present invention relates to a light emitting module comprising a light emitting element (hereinafter referred to as an EL element) using a compound producing EL (Electro Luminescence) as the light emitting material. Here, an organic EL display and an organic light emitting diode (hereinafter referred to as an OLED) is included in the light emitting device in accordance with the present invention.

Further, the light emitting material used in the present invention includes all materials emitting light (phosphorescence and/or fluorescence) through singlet excitation, triplet excitation or both of them.

2. Description of the Related Art

In recent years, the development of an EL element using an organic compound (hereinafter referred to as an organic EL film ) producing EL (Electro Luminescence) as a light emitting layer has advanced and EL elements using various kinds of organic EL films have been proposed. A flat panel display using such an EL element as a light emitting element has been developed.

A passive matrix type light emitting device and an active matrix type light emitting device have been known as a light emitting device employing an EL element. The passive matrix type light emitting device is a light emitting device employing an EL element with a structure in which an EL film is sandwiched between stripe-like anodes and cathodes provided to intersect at right angles. Also, the active matrix type light emitting device is a light emitting device in which each pixel has a thin film transistor (hereinafter referred to as a TFT) and the TFT connected to one of the anode and the cathode of the EL element controls a current flowing through the EL element.

The passive type light emitting device has an advantage that it has a simple structure which reduces manufacturing costs, but it has a problem that as the pixel is of higher definition (the number of pixels increases), the luminous intensity of the EL element needs to be increased, that is, a larger current is required with results of an increase in power consumption and a reduction in life.

On the other hand, in the active matrix type light emitting device, the pixel is capable of holding data because it is controlled by the TFT and the luminance of the EL element can be made constant irrespective of the number of pixels: that is, the luminance of the EL element can be reduced to a minimum as long as a user can see to prevent an increase in power consumption and a decrease in life.

From the above description, it is thought that the active matrix type light emitting device has smaller power consumption. However, because the active matrix type light emitting device is driven by a current, it is required to decrease the power consumption.

One object of the present invention is to provide a light emitting device having small power consumption and excellent visibility. Further, another object of the present invention is to provide an electrical appliance having a display section employing such a light emitting device and having small power consumption and excellent visibility.

SUMMARY OF THE INVENTION

A light emitting module in accordance with the present invention is characterized in that it includes a sensor section to sense the illuminance of an environment where the light emitting module is used (hereinafter referred to as environmental illuminance) and means for adjusting the luminance of a light emitting element according to the environmental illuminance and for keeping the ratio of the luminance of the light emitting element to the environmental illuminance (contrast ratio between the luminance of the light emitting element and the environmental illuminance) at a constant value.

In other words, the light emitting module in accordance with the present invention is characterized in that the luminance of an EL element can be increased in a bright use environment to improve visibility and that the luminance of the EL element can be decreased in a dark use environment to reduce power consumption without degrading visibility.

It is recommended that the environmental illuminance be sensed (monitored) by an optical sensor. The present invention is characterized also in that a sensor section including one or a plurality of optical sensors (typically, photodiodes) and a pixel section for displaying an image are formed on the same insulating body. That is, the present invention is characterized also in that the sensor section including photodiodes is formed with the same process as a transistor (including a thin film transistor and a MOS transistor using bulk silicon) and the EL element on the pixel section.

In the light emitting module in accordance with the present invention, the environmental illuminance is sensed by the sensor section formed in the light emitting device, and the correct luminance of the EL element and a correction signal which is necessary for obtaining the correct luminance of the EL element are calculated by a correction circuit based on the output signal of the sensor section. Then, the amount of current flowing through the EL element is corrected based on the correction signal to keep the ratio of the luminance of the EL element to the environmental illuminance (contrast ratio) at a constant value.

The light emitting module in accordance with the present invention is excellent in visibility in a bright environment because of a sufficiently bright display and reduces power consumption in a dark environment because it is possible to decrease brightness to a minimum while ensuring good visibility. Therefore, an electric appliance employing the light emitting module in accordance with the present invention has excellent visibility in a display section and can reduce power consumption.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments in accordance with the present invention will be described.FIG. 1Ais a circuit block diagram of a light emitting module in accordance with the present invention. A light emitting device100includes a pixel section101, a data signal (video signal) side driving circuit102, gate signal side driving circuit103, and a sensor section104, and a correction circuit105is connected to the light emitting device100. The correction circuit105has an arithmetic circuit for computing the luminance of the light emitting element of the pixel section101based on a signal transmitted by the sensor section104.

A monolithic IC, a hybrid IC, or a MCM (Multi Chip Module) may be used as the correction circuit105. When the monolithic IC is used, it may be directly packaged into the light emitting device100and may be packaged on a TAB (Tape Automated Bonding) tape and be connected to the light emitting device100as a TCP (Tape Carrier Package). Also, when the hybrid IC or the MCM is used, it is recommended to be connected to the light emitting device100with the use of the TAB tape.

Next,FIG. 1Bshows one example of a circuit configuration of the sensor section104. Here, the sensor section104includes a photodiode106, a reset TFT107, a buffer TFT108, and a constant current TFT109.

The reset TFT107is a TFT for applying a reverse bias voltage to the photodiode106to return (reset) to the initial state, and a timing of returning to the initial state is controlled by a signal transmitted to a reset signal line110which is a gate. Further, the buffer TFT108is a TFT for amplifying a signal sensed by the photodiode106and the constant current TFT109is a TFT which functions as a constant current power source. Here, the buffer TFT108and the constant current TFT109function as a source follower and an output signal is transmitted to an output line111.

Here, constant voltages V1 to V3 are fixed voltages applied to the photodiode106, the reset TFT107, the buffer TFT108, and the constant current TFT109. Typically, a power source voltage or an earth voltage is employed as the fixed voltage.

Here, the circuit configuration shown inFIG. 1Bis one example and any publicly known circuit configuration may be employed providing that the circuit configuration functions as an optical sensor. Further, while the TFT is used as an active device in this example, in the case where the pixel section is formed of a MOS transistor (a transistor with a MOS structure formed on a semiconductor substrate), naturally, the MOS transistor is used.

Next,FIG. 1Cshows one example of a circuit configuration of the pixel section101. Here, the pixel section101includes an EL element112, a switching TFT113, a current control TFT114, and a capacitor115.

The switching TFT113is a TFT for controlling the gate of the current control TFT114and transmits a signal transmitted to a data line (video line)117to the gate of the current control TFT114by using a gate line116as a gate. Also, the current control TFT114is a TFT for controlling a current flowing through the EL element112and transmits a signal transmitted to a current supply line118to the EL element112.

Here, the circuit configuration shown inFIG. 1Cis one example and any publicly known circuit configuration may be employed if the circuit configuration can control the light emission of the EL element. Further, while the TFT is used as an active device in this example, there may be the case where the pixel section is formed of the MOS transistor.

Next, examples of the configuration of the correction circuit105will be shown in FIG.2and FIG.3. Here,FIG. 2is a case where the light emitting device100is driven by an analog signal (analog driving system) andFIG. 3is a case where the light emitting device100is driven by a digital signal (digital driving system).

InFIG. 2, the correction circuit105includes an AID conversion circuit (A/D converter)201, an arithmetic circuit202, a correction memory203, and a D/A conversion circuit (D/A converter)204. Here, it is preferable that the arithmetic circuit202and the correction memory203are formed of the MCM because the MCM can increase the transmission speed of data.

Here, the correction memory203is a memory for storing correction data for correcting the luminance of the EL element so as to make the ratio of luminance to environmental illuminance constant, that is, a memory for storing (memorizing) correct value data of luminance corresponding to the environmental illuminance so as to ensure a constant contrast ratio of the luminance to the environmental illuminance. Of course, it is necessary to previously get and store the correct value data of the luminance corresponding to the environmental illuminance.

Here, the flow of a signal in the case of the analog driving system shown inFIG. 2will be described. In the case of the analog driving system, a signal which determines the amount of current to the EL element is a signal transmitted to the data line117in FIG.1C.

Data of environmental illuminance transmitted from the sensor section104(sensor output signal) is converted into a digital signal by the A/D conversion circuit201and is inputted to the arithmetic circuit202. The arithmetic circuit202calculates a correct value of a data signal (video signal) for obtaining correct luminance with respect to the environmental illuminance based on the inputted sensor output signal and the data stored in the correction memory203.

In this manner, the data signal (video signal) from a signal generator205is corrected to the correct value based on the sensor output signal and the data stored in the correction memory203, and the corrected data signal is again converted into an analog signal by the D/A conversion circuit204and is inputted to the data signal side driving circuit102.

Next, the flow of a signal in the case of the digital driving system shown inFIG. 3will be described. In the case of the digital driving system, a signal which determines the amount of current to the EL element is a signal transmitted to the current supply line118in FIG.1C.

Data of environmental illuminance transmitted from the sensor section104(sensor output signal) is converted into a digital signal by the A/D conversion circuit301and is inputted to the arithmetic circuit302. The arithmetic circuit302calculates a correct value of the amount of current which is necessary for obtaining correct luminance with respect to the environmental illuminance based on the inputted sensor output signal and the data stored in the correction memory303, and a correction signal with its information is outputted.

In this manner, the correction signal calculated based on the sensor output signal and the data stored in the correction memory303is converted into an analog signal by the D/A conversion circuit304and is inputted to an EL driving power source305. The EL driving power source305is a power source of a signal (hereinafter referred to as a power source data signal) transmitted to the current supply line of the pixel section101, and a power source for finally determining a current flowing to the EL element. A voltage varying device306is connected to the EL driving power source305and a power source data signal is corrected based on the correction signal transmitted from the correction circuit105and the corrected power source data signal is inputted to the pixel section101.

In this manner, first, the environmental illuminance is sensed by the sensor section104provided in the light emitting device and the correction circuit105calculates a data signal or a correction signal which is necessary for obtaining the correct luminance of the EL element based on the output signal (sensor output signal). Then, the amount of current flowing to the EL element is corrected based on this data signal or correction signal to produce luminance of a correct contrast ratio.

The light emitting module described in the preferred embodiment in accordance with the present invention is excellent in visibility in a bright environment because of a sufficiently bright display and reduces power consumption in a dark environment because it is possible to reduce brightness to a minimum while ensuring good visibility. Accordingly, in an electric appliance using a light emitting module of the present invention, a display is excellent in visibility and power consumption is reduced.

In the present embodiment, a cross-sectional structure (in a state before sealing) included in a light emitting module in accordance with the present invention will be described. In the present embodiment, there will be described an example of a light emitting device (in a state before sealing) which has a sensor section, a pixel section, and a driving circuit for driving the pixel section on the same insulating body. Here, the sensor section shows a reset TFT and a photodiode connected to the reset TFT, and the driving circuit shows a CMOS circuit which is a basic unit, and the pixel section shows one pixel.

InFIG. 4, a reference numeral400is an insulting body (made of an insulating substrate, an insulating film, or a substrate with an insulating film on the surface) on which a sensor section, a driving circuit, and a pixel section are formed. The sensor section is provided with a reset TFT451and a photodiode452. Also, the driving circuit has an n-channel type TFT453and a p-channel type TFT454which constitute a CMOS circuit. Further, the pixel section has a switching TFT455, a current control TFT456, and an EL element457. In this respect, the respective TFTs may be TFTs with any publicly known structure. In the present embodiment, the respective TFTs are bottom gate type TFTs (specifically, inverse stagger type TFT), but top gate type TFTs (typically, planar type TFT) may be used.

Further, the circuit configuration of the sensor section in the present embodiment has a structure shown in FIG.1B and the circuit configuration of the pixel section has a structure shown in FIG.1C. However, not only such a circuit configuration but also a circuit with three or more TFTs can produce the effects of the present invention.

Here, the structures of the respective TFTs formed on the insulating body400will be described. In the n-channel type TFT453, a reference numeral401designates a gate electrode,402designates a gate insulating film,403designates a source region made of an n-type semiconductor region (hereinafter referred to as n-type region),404designates a drain region made of an n-type region,405aand405bdesignate an LDD (lightly doped drain) region,406designates a channel forming region,407designates a channel protecting film,408designates a first interlayer insulating film,409designates a source wiring, and410designates a drain wiring.

Further, in the p-channel type TFT454, a reference numeral411designates a gate electrode,402designates a gate insulating film,412designates a source region made of a p-type semiconductor region (hereinafter referred to as p-type region),413designates a drain region made of a p-type region,414designates a channel forming region,415designates a channel protecting film,408designates a first interlayer insulating film,416designates a source wiring, and410designates a drain wiring which is a wiring common to the n-channel type TFT453.

Further, basically, the reset TFT451has the same structure as the n-channel type TFT453(they are different from each other only in the structure of the source wiring or the drain wiring) and hence the detailed description thereof will be omitted. Here, it is also possible that the reset TFT451has the same structure as the p-channel type TFT454. In the case of the reset TFT451, an amorphous semiconductor film (typically, an amorphous silicon film)419is formed between a drain region417made of an n-type region and a p-type region418to form a photodiode452with a PIN junction. Here, a reference numeral420designates a wiring for applying voltage to the p-type region418.

Further, basically, the switching TFT455has the same structure as the n-channel type TFT453and hence the detailed description thereof will be omitted. Here, it is also possible to form the switching TFT455with the same structure as the p-channel type TFT454. Further, it is also possible to form the switching TFT455with a structure in which two or more channel forming regions are formed between the source region and the drain region (multi-gate structure).

Further, basically, the current control TFT456has the same structure as the p-channel type TFT454(they are different from each other in that the drain wiring is a pixel electrode423) and hence the detailed description thereof will be omitted. Here, it is also possible to form the current control TFT456having the same structure as the n-channel type TFT453.

Then, there is formed a second interlayer insulating film (leveling film)421covering the reset TFT451, the photodiode452, the n-channel type TFT453, the p-channel type TFT454, the switching TFT455, and the current control TFT456.

Still further, the second interlayer insulating film421has a contact hole extending to the drain region422of the current control TFT456and a pixel electrode423is connected to the drain region422. The pixel electrode423functions as an anode of the EL element and is formed of a conductive film with a large work function, typically, an oxide conductive film. It is recommended that the oxide conductive film be made of indium oxide, tin oxide, zinc oxide, or a compound thereof. Also, gallium oxide may be added to the oxide conductive film.

Next, a reference numeral424designates an insulating film covering the end portion of the pixel electrode423and is called a bank in the present specification. It is recommended that the bank424be formed of an insulating film containing silicon or a resin film. In the case of using the resin film, a dielectric breakdown can be prevented in the film formation if carbon particles or metal particles are added to the resin film so that the specific resistance of the resin film becomes from 1×106Ωm to 1×1012Ωm (preferably, from 1×108Ωm to 1×1010Ωm).

Next, a reference numeral425designates an EL layer. In this respect, in the present specification, a laminated body of a combination of layers selected from a hole injection layer, a hole transport layer, a hole prevention layer, an electron transport layer, an electron injection layer and an electron prevention layer is defined as an EL layer with respect to a light emitting layer. The light emitting layer may be formed of any publicly known material and a publicly known dopant (typically, fluorescent dye) may added to the light emitting layer. Further, it is preferable that an organic material which emits light through triplet excitation is used as the dopant since high luminous efficiency can be produced.

Next, a reference numeral426designates a cathode of the EL element and is formed of a conductive film with a small work function. It is recommended that a conductive film containing an element which belongs to the first or second group of a periodic table be used as the conductive film with a small work function. In the present embodiment, a conductive film made of a compound of lithium and aluminum is used.

In this respect, a laminated body457of the pixel electrode (anode)423, the EL layer425, and the cathode426is an EL element. Light generated by the EL element457is emitted to the insulating body400(in the direction shown by an arrow in FIG.4). Also, in the case of using the p-channel type TFT as the current control TFT, as described in the present embodiment, it is preferable that the anode of the EL element is connected to the drain of the current control TFT.

In this respect, it is effective that a protective film (passivation film)427completely covering the EL element457is formed after the cathode426is formed. A single layer of an insulating film of a carbon film, a silicon nitride film, or a silicon nitride oxide film or a laminated layer of a combination of the above insulating films is used as the protective film427.

Here, it is preferable that a film with good coverage is used as the protective film427, and a carbon film, a DLC (diamond like carbon) film in particular, is effectively used. The DLC film can be formed in a temperature range of the room temperature to 100° C. and hence can be easily formed also on the EL layer425with low heat resistance. Further, the DLC film has a high blocking effect to oxygen and it is possible to effectively prevent oxidation of the EL layer425. Accordingly, the DLC film can prevent the EL layer425from being oxidized during the following sealing process.

Here, a manufacturing process for producing the structure shown inFIG. 4will be shown in FIG.5. First, gate electrodes502to506are formed of chromium film on a glass substrate501and a gate insulating film507is formed thereon of a silicon nitride oxide film (insulating film expressed by SiOXNY). An amorphous silicon film is formed on the gate insulating film507and crystallized by laser annealing to form semiconductor films508to513of a crystalline silicon film by patterning. The process up to this point may be performed by using the publicly known materials and technology (see FIG.5A).

Here, the distance between the semiconductor film508and the semiconductor film509is not more than 1 μm, preferably, from 0.3 μm to 0.5 μm.

Next, insulating films514to519made of a silicon oxide film are formed on the semiconductor films508to513and phosphorus or arsenic is added thereto by the publicly known method. In this way, n-type regions520to525are formed. The n-type regions520to525contain phosphorus or arsenic with a concentration of 1×1020atoms/cm3to 1×1021atoms/cm3(see FIG.5B).

Next, the insulating films514to519are patterned by back-surface lithography with using the gate electrodes502to506as masks to form insulating films (channel protecting film)526to530. Then, in this state, phosphorus or arsenic is again added thereto by the publicly known method. In this way, n-type regions531to541are formed. The n-type regions531to541contain phosphorus or arsenic with a concentration of 1×1017atoms/cm3to 1×1019atoms/cm3(see FIG.5C).

Next, resist films542to544are formed and boron is added thereto by the publicly known method. In this way, p-type regions545to549are formed. The p-type regions545to549contain boron with a concentration of 3×1020atoms/cm3to 5×1021atoms/cm . Here, although phosphorus or arsenic is already added to the p-type regions545to549, the concentration of boron is three or more times that of phosphorus or arsenic and hence the p-type regions545to549are completely inverted from n type to p type. (see FIG.5D).

Next, the resist films542to544are removed and a first interlayer insulating film550with a laminated structure of a silicon oxide film and a silicon nitride oxide film is formed. Contact holes are made in the first interlayer insulating film550and wirings551to558with a laminated structure of molybdenum and tungsten are formed. Then, a conversion layer559made of a semiconductor film is formed. The conversion layer559is a layer for absorbing light and generating carriers in the photodiode and corresponds to the i- layer (photoelectric conversion layer) of a solar cell. (see FIG.5E).

In this respect, a publicly known layer structure with a PIN junction can be used as the conversion layer559. Also, the conversion layer559may have a PIN junction or a NIP junction in viewing from the incident side of light. Further, an amorphous semiconductor film, a crystalline semiconductor film, or a microcrystalline semiconductor film may be used as the material of the conversion layer559.

Then, as shown inFIG. 4, a second interlayer insulating film421, a pixel electrode423, a bank424, an EL layer425, a cathode426, and a protective film427are formed to complete a light emitting device with a cross-sectional structure shown in FIG.4.

If a light emitting device with the cross-sectional structure of the present embodiment is employed, it is possible to provide a light emitting module which is excellent in visibility in the bright environment and can ensure good visibility while reducing power consumption in the dark environment. Here, in the present embodiment, the configurations shown in FIG.1andFIG. 2or FIG.1andFIG. 3may be combined.

In the present embodiment, there will be described an example of a light emitting device (however, in the state before sealing) with a structure different from the embodiment 1. Here, in the present embodiment, description will be made in the different parts from the embodiment 1. The description of the embodiment 1 may be referred to on parts with the same reference symbols as the parts in FIG.4.

InFIG. 6, a sensor section, a driving circuit, and a pixel section are formed on an insulating body400. The sensor section includes a reset TFT451and a photodiode (photo-sensor)601, and the driving circuit includes a CMOS circuit comprising an n-channel type TFT453and a p-channel type TFT454, and the pixel section includes a switching TFT455, a current control TFT456, and an EL element457.

The present embodiment is different from the embodiment 1 in the structure of the photodiode601. The photodiode is formed of a wiring603which is to be the source or drain of the reset TFT451, a conversion layer604, and a reflection side electrode (electrode at the reflecting side of light)605. Also, in the present embodiment, a buffer layer606made of an insulating film containing silicon is formed on a second interlayer insulating film421. The buffer layer606makes the wiring603put into close contact with the second interlayer insulating film421and allows second interlayer insulating film421to be prevented from being etched when the conversion layer604is formed.

Here, the wiring603is transparent with respect to visible light because it is formed by the same process as the pixel electrode423. Also, a conductive film to be the reflection side electrode is preferably a conductive film with a high reflectivity, and it is recommended that a conductive film containing aluminum or silver as a main component be used. Here, if an oxide conductive film is formed as a buffer layer between the conversion layer604and the reflection side electrode605, the conversion layer604can be prevented from reacting with the reflection side electrode605.

If a light emitting device with the cross-sectional structure of the present embodiment is employed, it is possible to provide a light emitting module which is excellent in visibility in the bright environment and can ensure good visibility while reducing power consumption in the dark environment. Here, in the present embodiment, the configurations shown in FIG.1andFIG. 2or FIG.1andFIG. 3may be combined.

In the present embodiment, there will be described an example of a light emitting device (however, in the state before sealing) with a different structure from the embodiment 1. Here, in the present embodiment, description will be made in the different parts from the embodiment 1. The description of the embodiment 1 may be referred to on parts with the same reference symbols as the parts in FIG.4.

InFIG. 7, a sensor section, a driving circuit, and a pixel section are formed on an insulating body400. The sensor section includes a reset TFT701and a photodiode (photo-sensor)702, and the driving circuit includes a CMOS circuit comprising an n-channel type TFT703and a p-channel type TFT704, and the pixel section includes a switching TFT705, a current control TFT706, and an EL element457.

First, the present embodiment is characterized in that the source line or the drain line of each TFTs is formed so as to cover a channel region. The structure of the present embodiment is formed in the shape shown inFIG. 7in order to obstruct light which directly enters to the channel forming region of the TFT to prevent an increase in leakage current.

Further, in the present embodiment, an n-channel type TFT is used as a current control TFT706. Here, the current control TFT706has basically the same structure as the n-channel type TFT453shown inFIG. 4(they are different from each other only in the shape of a source electrode), so the detailed description thereof will be omitted. Here, the current control TFT706can have the same structure as the p-channel type TFT454shown in FIG.4.

Still further, the present embodiment is different from the embodiment 1 in the structure of a photodiode702and the photodiode702is formed of a wiring711to be the source or drain of the reset TFT701, a conversion layer712, and a transmission side electrode (electrode at the side where light transmits)713, and a leader line714is connected to the transmission side electrode713. The conversion layer712can be formed in the same configuration as the conversion layer604of the embodiment 2. Also, it is recommended that the transmission side electrode713be formed of an oxide conductive film.

In a pixel section, a pixel electrode715is formed in the same process as the leader line714. The pixel electrode715is an electrode which functions as the cathode of an EL element707and is formed of a conductive film containing an element which belongs to the first group or the second group of the periodic table. In the present embodiment, a conductive film made of a compound of lithium and aluminum is used. Here, in the case where a cathode is connected to the current control TFT as described in the present embodiment, it is preferable that an n-channel type TFT is used as the current control TFT.

After the pixel electrode715is formed, an insulating film (bank)424, an EL layer716, an anode717made of an oxide conductive film, and a protective film718are formed to complete a light emitting device (however, in the state before sealing) with the structure shown in FIG.7. It is recommended that the material and the structure of the EL layer716, the anode717, and the protective film718be referred to the embodiment 1.

If a light emitting device with the cross-sectional structure of the present embodiment is employed, it is possible to provide a light emitting module which is excellent in visibility in the bright environment and can ensure good visibility while reducing power consumption in the dark environment. Here, in the present embodiment, the configurations shown in FIG.1andFIG. 2or FIG.1andFIG. 3may be combined.

In the present embodiment, there will be described an example of a light emitting device (however, in the state before sealing) with a different structure from the embodiment 1. Here, in the present embodiment, description will be made in the different parts from the embodiment 1. The description of the embodiment 1 may be referred to on parts with the same reference symbols as the parts in FIG.4.

InFIG. 17, a sensor section and a pixel section are formed on an insulating body400. Here, a driving circuit can be formed on the same insulating body as the embodiment 2 or the embodiment 3.

The sensor section includes a reset TFT1701and a photodiode (photosensor)1702and the pixel section includes a switching TFT1703, a current control TFT1704, and an EL element1705.

In the present embodiment, a p-channel type TFT is used as the current control TFT1704. Here, the current control TFT1704basically has the same structure as the current control TFT456shown inFIG. 4 and, hence, the detailed description will be omitted. Here, the current control TFT1704can also have the same structure as the n-channel type TFT455shown in FIG.4.

Further, the present embodiment is different from the embodiment 1 in the structure of the photodiode1702, and the photodiode1702is formed of a wiring1711made of an oxide conductive film to be the source or the drain of the reset TFT1701, an n-type semiconductor layer1712, a conversion layer (i-type semiconductor layer)1713, a p-type semiconductor layer1714, and a light receiving side electrode (electrode at the side where light is received)1715.

Here, the wiring1711is formed in the same process as the pixel electrode (anode of the EL element1705)1716. Also, the light receiving side electrode1715may be formed of an oxide conductive film. Here, in the pixel section, the pixel electrode1716formed in the same process as the wiring1711is electrically connected to the drain of the current control TFT1704.

After the pixel electrode1716is formed, an insulating film (bank)424, an EL layer425, a cathode426, and a protective film427are formed to complete a light emitting device (however, in the state before sealing) with the structure shown in FIG.17. It is recommended that the material and the structure of the EL layer425, the cathode426, and the protective film427be referred to the embodiment 1.

If a light emitting device with the cross-sectional structure of the present embodiment is employed, it is possible to provide a light emitting module which is excellent in visibility in the bright environment and can ensure good visibility while reducing power consumption in the dark environment. Here, in the present embodiment, the configurations shown in FIG.1andFIG. 2or FIG.1andFIG. 3may be combined.

In the present embodiment, a light emitting device, in which a sensor section, a correction circuit, a driving circuit, and a pixel section are formed on the same insulating body, will be described.

InFIG. 8, a reference numeral800designates a light emitting device of the present embodiment,801designates a pixel section,802designates a data signal side driving circuit,803designates a gate signal side driving circuit,804designates a sensor section, and805designates a correction circuit. Here, it is recommended that the configuration of the pixel section801be referred to FIG.1C and that the configuration of the sensor section804be referred to FIG.1B.

The present embodiment is characterized in that the correction circuit805with the configuration shown inFIG. 2orFIG. 3is formed on the same insulating body as the sensor section, the driving circuit, the pixel section. That is, in the light emitting device800of the present embodiment, a corrected data signal is outputted from a correction circuit805based on the environmental illuminance sensed by the sensor section804to adjust the luminance of the pixel section801to a correct intensity.

Of course, in the configuration of the present embodiment, the correction circuit805is formed only of transistors (TFT or MOS transistor). Here, it is recommended that the correction circuit be designed by using a CMOS circuit comprising the n-channel type TFT453and p-channel type TFT454inFIG. 4as a basic section.

In this respect, the configuration of the present embodiment can be carried out with any of the configurations of the embodiment 1 to the embodiment 4. Since the light emitting module including the light emitting device of the present embodiment has a built-in correction circuit, the weight can be reduced as compared with the structure shown in FIG.1and the number of pins which is necessary for connecting the correction circuit to the driving circuit can be reduced.

A circuit which functions as an optical sensor (photo sensor) can be used as a sensor section included in a light emitting module of the present invention. In the present embodiment, examples of the circuit configuration of an active type optical sensor will be shown inFIGS. 9A and 9B.

The optical sensor shown inFIG. 9Aincludes a photodiode901, a first reset TFT902, a buffer TFT903, a load capacitance904, a second reset TFT905. Also, a first reset signal line906is connected to the gate of the first reset TFT902and a second reset signal line907is connected to the gate of the second reset TFT905. Further, a reference numeral908designates an output line.

Further, the optical sensor shown inFIG. 9Bincludes a photodiode911, a reset TFT912, a buffer TFT913, a load resistance (or a load capacitance)914. Also, a reset signal line915is connected to the gate of the reset TFT912. Further, a reference numeral916designates an output line.

Here, inFIGS. 9A and 9B, constant voltages V1 and V2 are the fixed voltages applied to the photodiode, the reset TFT, and the buffer TFT. Typically, a power source voltage or an earth voltage is employed as the fixed voltage.

One or a plurality of optical sensors with the circuit configuration shown inFIG. 9AorFIG. 9Bmay be provided in the sensor section of the light emitting module in accordance with the present invention. Further, the circuit configurations shown inFIGS. 9A and 9Bare simply examples. While the TFTs are used as active elements here, a MOS transistor is used naturally in the case where the pixel section is formed of the MOS transistor. Still further, in the case where the TFT is used, a top gate type TFT or a bottom gate type TFT may be used.

In this respect, the configuration of the present embodiment can be carried out with any of the configurations of the embodiment 1 to the embodiment 5.

A circuit which functions as an optical sensor can be used as a sensor section included in a light emitting module of the present invention. In the present embodiment, an example of the circuit configuration of an passive type optical sensor will be shown in FIG.10.

The optical sensor shown inFIG. 10includes a photodiode1001and a reset TFT1002. Also, a reset signal line1003is connected to the gate of the reset TFT1002. Further, a reference numeral1004designates an output line.

Here, inFIG. 10, a constant voltage V1 is the fixed voltage applied to the photodiode. Typically, a power source voltage or an earth voltage is employed as the fixed voltage.

One or a plurality of optical sensors with the circuit configuration shown inFIG. 10may be provided in the sensor section of the light emitting module in accordance with the present invention. Further, the circuit configurations shown inFIG. 10is simply an example. While the TFTs are used as active elements here, a MOS transistor is used naturally in the case where the pixel section is formed of the MOS transistor. Still further, in the case where the TFT is used, a top gate type TFT or a bottom gate type TFT may be used.

In this respect, the configuration of the present embodiment can be carried out with any of the configurations of the embodiment 1 to the embodiment 5.

In the present embodiment, the case will be described, where a structure of a pixel in a pixel section is different in from the FIG.1B. Here, the description ofFIG. 1Bmay be referred to on the parts with the same reference symbols as in FIG.1B.

The configuration shown inFIG. 11Ais characterized in that an erasing TFT1101is disposed between a switching TFT113and the gate of a current control TFT114. The erasing TFT1101is a TFT for forcibly transforming the gate voltage applied to the current control TFT114to 0 volt. One of the source and drain of the erasing TFT1101is connected to the gate of a current control TFT114and the other is connected to the current supply line118and the gate thereof is connected to a wiring (erasing gate line)1102to be the gate of the erasing TFT1101.

Further, the configuration shown inFIG. 11Bis a publicly known configuration in which a first TFT1103, a second TFT1104, a third TFT1105, a fourth TFT1106, a first capacitor1107and a second capacitor1108are provided. Still further, there is provided a data line1109, a first gate line1110, a second gate line1111, a third gate line1112, and a current supply line1113as shown inFIG. 11Bin order to transmit signals to the respective TFTs.

A plurality of pixels with the circuit configuration shown inFIG. 11Aor11B may be formed in the pixel section of the light emitting module in accordance with the present embodiment. Further, the circuit configurations shown inFIG. 11A and 11Bare simply examples. While the TFTs are used as active elements here, the pixel section may be formed of MOS transistors. Still further, a top gate type TFT or a bottom gate type TFT may be used.

In this respect, the configuration of the present embodiment can be carried out with any of the configurations of the embodiment 1 to the embodiment 7.

In a light emitting module in accordance with present invention, it can make an operating frequency reduced to drive a data signal side driving circuit by a publicly known split driving method. The split driving method is a driving method for reducing the operating frequency by writing a data signal in a plurality of pixels at the same time in performing a driving method by a dot sequential type driving method.

In this case, n data signals (video signals) are necessary for split-driving by n splits. A data signal is written in a block of n pixels in synchronization with the output timing of a shift register. In this way, the operating frequency of the data signal side driving circuit can be reduced to 1/n.

Further, it is possible to write a data signal every n pixels in synchronization with the output timing of a shift register. Also in this case, the operating frequency of the data signal side driving circuit can be reduced to 1/n.

In this respect, the configuration of the present embodiment can be carried out with any of the configurations of the embodiment 1 to the embodiment 7.

In the present embodiment, a light emitting module in accordance with the present invention after a sealing process for protecting an EL element will be described with reference toFIGS. 12A and 12B. Here, the sealing structure of the present embodiment can be applied to any structure shown in the embodiment 1 to the embodiment 4. The reference symbols inFIG. 4are referred to if necessary.

FIG. 12Ais a plan view to show a state in which the process has been advanced to the step of sealing the EL element andFIG. 12Bis a cross-sectional view taken on line A—A′ inFIG. 12A. Asection1200indicated by a dotted line is a pixel section and a section1201is a source signal side driving circuit and a section1202is a gate signal side driving circuit and a section1203is a sensor section. Also, a reference numeral1204designates a covering member and1205designates a first sealing member and1206designates a second sealing member.

Further, a reference numeral1207designates a TAB tape to be an external input terminal that receives a video signal or a clock signal from an external driving circuit and a correction circuit. Here, while only the TAB is shown, the TAB tape may be provided with a printed wiring board (PWB) or be a TCP.

Next, the cross-sectional structure will be described with reference to FIG.12B. On an insulating body400are formed a pixel section1200, a source signal side driving circuit1201and a sensor section1203. The pixel section1200includes a plurality of pixels each of which includes a current control TFT456and a pixel electrode423electrically connected to the drain of the current control TFT456. Further, the source signal side driving circuit1201includes a CMOS circuit made of a combination of an n-channel type TFT453and a p-channel type TFT454. Still further, the sensor section1203includes a photodiode452connected to a reset TFT451. Here, a polarizing plate (typically, a circular polarizing plate) may be placed to the insulating body400.

The pixel electrode423functions as the anode of the EL element. Also, banks424are formed on both ends of the pixel electrode423, and an EL layer425and the cathode426of the EL element are formed on the pixel electrode423. The cathode426functions also as a wiring common to all the pixels and finally is electrically connected to a TAB tape1207. Further, all the elements included in the pixel section1200, the source signal side driving circuit1201, and the sensor section1203are covered with a protective film427.

Further, the covering member1204is placed to the insulating body400with the first sealing member1205. Here, a spacer may be provided so as to ensure a gap between the covering member1204and the EL element. A space1208is formed inside the first sealing member1205. Here, it is preferable that the first sealing member1205is made of a material which does not allow moisture or oxygen to pass through. Further, it is effective that a substance having effects of absorbing moisture or preventing oxidation is disposed in the space1208.

In this respect, it is recommended that carbon films (specifically, a diamond like carbon film)1209a,1209bhaving a thickness of from 2 nm to 30 nm be formed as protective films on the obverse surface and the reverse surface of the covering member1204. Such a carbon film prevents the entry of oxygen and water and mechanically protects the surface of the covering member1204.

Further, after the covering member1204is bonded, a second sealing member1206is formed such that it covers the exposed surface of the first sealing member1205. The second sealing member1206can be formed of the same material as the first sealing member1205.

By sealing the EL element by the structure described above, the EL element can be completely shielded from the outside to prevent a substance for degrading the EL layer by oxidation such as moisture and oxygen from entering from the outside. Accordingly, this can provide a light emitting device having high reliability.

A shown inFIGS. 12A and 12B, a light emitting module with a pixel section, a driving circuit, and a sensor section which are formed on the same insulating body, and further provided with a TAB tape, is referred to as a light emitting module of a built-in driving circuit type in the present specification.

In the embodiment 10, the light emitting module of a built-in driving circuit type shown inFIGS. 12A and 12Bis an example in which a pixel section and a driving circuit are integrally formed on the same insulating body, but the driving circuit may be provided as an external IC (integrated circuit). In this case, the structure will be shown in FIG.13A.

In the module shown inFIG. 13A, a TAB tape14is attached to a substrate (active matrix substrate)10(including a pixel section11, wirings12a,12band a sensor section13) on which a pixel section including a TFT and an EL element is formed and a printed wiring board15is connected thereto through the TAB tape14. Here, the circuit block diagram of the printed wiring board15is shown in FIG.13B.

As shown inFIG. 13B, at least I/O ports (also referred to as an input/output section)16,19, a source signal side driving circuit17, a gate signal side driving circuit18and an IC which functions as a correction circuit20are mounted in the printed wiring board15.

As described above, a module with a configuration, in which a substrate with a pixel section and a sensor section which are formed on the same insulating body is provided with a TAB tape and a printed wiring board which functions as a driving circuit is provided via the TAB tape, is referred to as a light emitting module of an external driving circuit type in the present specification.

Further, in the module shown inFIG. 14A, a light emitting module of a built-in driving circuit type30(including a pixel section31, a source signal side driving circuit32, a gate signal side driving circuit33, wirings32a,33a, a sensor section34, and a TAB tape35) is provided with a printed wiring board36via the TAB tape35. Here, the circuit block diagram of the printed wiring board36is shown in FIG.14B.

As shown inFIG. 14B, at least I/O ports37,40, a control section38and an IC which functions as a memory section39are provided in the printed wiring board36. Here, the memory section39functions as the correction memory shown inFIG. 2or FIG.3and luminance is adjusted by the correction circuit included in the control section38. Also the control section38can control various kinds of signals such as a signal transmitted to the driving circuit or a timing signal.

As described above, a module with the configuration, in which a light emitting module of a built-in driving circuit type with a pixel section, a driving circuit and a sensor section which are formed on the same insulating body is provided with a printed wiring board which functions as a controller, is referred to as a light emitting module of an external controller type.

A light emitting module formed by the use of the present invention is applied to various kinds of electric appliances and a pixel section is used as an image display section. The electric appliances in accordance with the present invention include a video camera, a digital camera, a goggle type display (head-mounted display), a navigation system, an audio unit, a note-type personal computer, a game device, a portable device (a mobile computer, a portable telephone, a portable game device or an electronic book), and an image reproducing device provided with a recording medium. The specific examples of these electric appliances will be shown inFIGS. 15Ato16B.

FIG. 15Ais an EL display and includes a box2001, a support2002, and a display section2003. A light emitting module in accordance with the present invention can be used as the display section2003. By applying the light emitting module in accordance with the present invention to the display section, it is possible to improve the visibility of the EL display and to reduce power consumption.

FIG. 15Bis a video camera and includes a main body2101, a display section2102, a voice input section2103, an operating switch2104, a battery2105, and an image receiving section2106. The light emitting module in accordance with the present invention can be used as the display section2102.

FIG. 15Cis a digital camera and includes a main body2201, a display section2202, an eyepiece section2203, and an operating switch2204. The light emitting module in accordance with the present invention can be used as the display section2202.

FIG. 15Dis an image reproducing device provided with a recording medium (specifically, a DVD reproducing device) and includes a main body2301, a recording medium (a CD, an LD, or a DVD)2302, an operating switch2303, a display section (a)2304and a display section (b)2305. The display section (a)2304mainly displays image information and the display section (b)2305mainly displays textual information and a light emitting module in accordance with the present invention can be used as the display sections (a), (b). Here, the image reproducing device provided with the recording medium includes a CD reproduction device, a game device and the like.

FIG. 15Eis a portable (mobile) computer and includes a main body2401, a display section2402, a image receiving section2403, an operating switch2404, and a memory slot2405. The light emitting module in accordance with the present invention can be used as the display section2402. This portable computer can record information on a recording medium in which flash memories and non-volatile memories are integrated and can reproduce the information.

FIG. 15Fis a personal computer and includes a main body2501, a box2502, a display section2503, and a keyboard2504. The light emitting module in accordance with the present invention can be used as the display section2503.

Further, occasions are increasing when the above-mentioned electric appliances display information allotted through an electronic communication line such as an internet, a CATV (cable TV), and the like and, in particular, occasions are increasing when the appliances display motion pictures. In the case where a light emitting module using an EL element is used as a display section, it is possible to display motion pictures without delay because the EL element has a vary high response speed.

Still further, since the light emitting section consumes electric power in the light emitting module, it is preferable that information be displayed such that the light emitting section is made as small as possible. Accordingly, in the case a light emitting module is used as a display section mainly displaying textual information such as a portable information terminal, in particular, a portable telephone, an audio unit, or the like, it is preferable that the light emitting module be driven in such a way that textual information is formed of the light emitting section against the background of non-light emitting section.

Here,FIG. 16Ashows a portable telephone and has a key operating section (operation section)2601and an information displaying section (information display section)2602which is connected to the operation section2601with a connection section2603. Also, the operation section2601is provided with a voice input section2604and an operating key2605and the information display section2602is provided with a voice output section2606and a display section2607.

The light emitting module in accordance with the present invention can be used as the display section2607. In this respect, in the case where the light emitting module is used as the display section2607, displaying white letters against a black background can reduce power consumption of the portable telephone.

In the case of the portable telephone shown inFIG. 16A, it is also possible to use the portable telephone as a certification system terminal for certifying a user by reading his fingerprint or palm by building a sensor made of a CMOS circuit (CMOS sensor) in the light emitting module used as the display section2604. Further, it is possible to read the brightness (illuminance) of the outside and to emit light such that information is displayed in a set contrast.

Still further, it is possible to reduce the power consumption of the portable telephone by decreasing the luminance of the display section2604while the operating switch2605is being used and increasing the luminance after the use of the operating switch is finished. Still further, it is possible to reduce the power consumption of the portable telephone by increasing the luminance of the display section2604when a signal is received and decreasing the luminance during a telephone conversation. Still further, it is possible to reduce the power consumption of the portable telephone by providing it with a function of turning off the display by a time control unless reset while it is continuously used. Here, these functions may be manually controlled.

Still further.FIG. 16Bshows an audio unit mounted in a motor vehicle and includes a box2701, a display section2702, and operating switches2703,2704. The light emitting module in accordance with the present invention can be used as the display section2702. While an audio unit (car audio unit) mounted in a motor vehicle is shown as an example of the audio unit in the present embodiment, the light emitting module in accordance with the present invention can be applied to an audio unit mounted in the house (audio component). Here, in the case where the light emitting module is used as the display section2704, it is possible to reduce power consumption by displaying white letters against a black background.

As described above, the present invention has a wide range of application and can be applied to various kinds of electric appliances. As a result, it is possible to improve the visibility of the display section of the electric appliance and to reduce the power consumption by using a light emitting module which is excellent in visibility in the bright environment and the dark environment and further can reduce power consumption to a minimum in the dark environment. Further, the light emitting module including any of the configurations of from the embodiment 1 to the embodiment 11 may be applied to the electric appliances of the present embodiment.

(Effects of the Invention)

According to the present invention, environmental illuminance is sensed by a sensor section provided in a light emitting device, and the correct luminance of an EL element and a correction signal necessary for obtaining the correct luminance are calculated by a correction circuit based on the output signal of the sensor section. Then, the amount of current flowing through the EL element is corrected based on the correction signal to keep the ratio of the luminance of the EL element to the environmental illuminance at a constant value.

As a result, according to the present invention, it is possible to obtain a light emitting module which is excellent in visibility in the bright environment and in the dark environment and can reduce power consumption to a minimum in the dark environment. Therefore, an electric appliance employing the light emitting module in accordance with the present invention can have excellent visibility in a display section and reduce power consumption.