JP2001242453A - Color image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a higher uniformity of a light-emitting surface, while making total thickness of a liquid crystal display device smaller. SOLUTION: The color image display device is equipped with a liquid display part 2, a backlight part 1 with at least two or more sets of organic EL (electroluminescence) element groups, respectively comprising plural organic EL elements 17, respectively emitting plural colors provided in proximity in a row arrangement, as a light source, a light diffusing plate 15 diffusing light from the backlight part 1 and a control part for controlling the plural organic EL elements 17, in such a way that the plural organic EL elements 17 emit lights of respective colors successively, so as to display color pictures via the liquid crystal display part 2. A distance L, between the organic EL elements 17 of the backlight part 1 and the light diffusion plate 15, is set so as to establish the relation (1/50)P<L*H<100P, where the pitch between the identically colored elements of the plural organic EL elements 17 is expressed as P, and the haze of the light diffusion plate 15 is expressed as H.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image display device, and more particularly to a color image display device suitable for use in a backlight type transmissive color liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, a TFT type color liquid crystal display device is often used in a color image display section of a personal computer, OA equipment, PDA (portable information terminal), or the like. This uses a white cold-cathode tube as a backlight, separates colors through three color filters of red, green, and blue, and uses a liquid crystal cell having a TFT for each color as a light-transmitting shutter. The color display is realized by three colors of blue.

[0003]

However, such a color liquid crystal display device has a problem that it is difficult to reduce the cost because color filters and driver ICs are expensive. The light transmittance of the color filter is 10 to 30.
%, There is also a problem that power consumption per light emission luminance increases.

For this reason, in order to display a color image without using a color filter, a three-color backlight and a monochrome liquid crystal cell are combined, and a field sequential color system (F) for switching these cells at high speed.
An SC type liquid crystal device (FSC-LCD) has been proposed (Liquid Crystal, Vol. 3, No. 3, 190-194, 199).
9).

According to such an FSC system, not only is a color filter unnecessary, but it is easier to achieve a higher resolution than a liquid crystal cell having a color filter by using a monochrome liquid crystal cell. Parts can be reduced. At first, it was pointed out that there was a problem with the high-speed response of liquid crystal, but ferroelectric liquid crystal and O
A sufficient response speed has been obtained by using an CB (Optically Compensated Birefringence) system, a fast response STN liquid crystal, or the like (for example, Nikkei Electronics 1999.10.25 (No. 75)).
5), JP-A-9-101497, etc.).

On the other hand, as a three-color backlight of the above-mentioned FSC type liquid crystal device, a method using a three-color LED array, a method using a three-color cold cathode tube, and the like have been proposed (for example, Japanese Patent Application Laid-Open No. HEI 9-208572). 9-90135). But,
In the method using three-color LEDs for the backlight, since the LEDs are point light sources, it is necessary to increase the number of LEDs with an increase in the size of the display unit, which inevitably increases the cost.

[0007] The method using a three-color cold-cathode tube requires an expensive inverter for each color, and the speed of deterioration of the cold-cathode tube due to repeated blinking becomes a problem. Further, when these light sources are arranged on the back of the display unit as a backlight, it is necessary to secure a sufficient distance between the light source and the display unit in order to obtain a uniform light emitting surface. In order to increase the thickness of the entire device or to reduce the distance, the number of light emitting sources must be increased, resulting in an increase in cost. Furthermore, LEDs and cold cathode tubes are basically 1
Since it is necessary to mount each light source, there is a limit in increasing the number of light emitting sources to increase the light source density.

Further, when an LED or a cold-cathode tube is used as an edge-light type backlight, a waveguide plate is required, the luminance per light source needs to be increased, or a light-emitting source is housed. For example, there is a problem that the frame outside the display unit becomes large. For this reason, in order to solve the above-mentioned problems, the FSC type liquid crystal device 3
It is conceivable to use an organic EL element as a color backlight. In this regard, SID99DIGEST No. 1
Pages 098 to 1101 describe that field sequential control (FSC) is performed using an organic electroluminescent element (organic EL element) as a light source of a three-color backlight.

However, in the field sequential control, it is necessary to provide a light diffusion plate between the light source of the backlight and the liquid crystal display screen in order to obtain uniformity of the light emitting surface. In order to obtain the uniformity of the surface, it is important to dispose the light diffusion plate in consideration of the distance between the light source of the backlight and the light diffusion plate. When an organic EL element is specifically used as a three-color backlight, it is necessary to specifically examine how to configure an electric circuit for injecting holes and electrons into the organic EL element. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has no need for a color filter to reduce the cost, reduce power consumption per light emission luminance, and use an LED or a cold cathode as a light source for a backlight. Compared to the case where a tube is used, the cost can be reduced, and the overall thickness of the liquid crystal display device can be reduced without increasing the frame portion of the liquid crystal display device. It is an object of the present invention to provide a color image display device in which higher light emitting surface uniformity can be obtained by disposing a light diffusing plate in consideration of the distance and the like.

[0011]

According to the first aspect of the present invention, there is provided a color image display apparatus which can emit a plurality of colors necessary for displaying a color image and a liquid crystal display section for displaying a color image. A backlight unit serving as a light source by arranging at least two or more sets of one set of organic EL elements in which a plurality of organic EL elements are arranged in parallel, and being disposed between the liquid crystal display unit and the backlight unit; A light diffusion plate for diffusing light from the backlight unit, and a control unit for controlling the plurality of organic EL elements so that the plurality of organic EL elements sequentially emit light for each color so as to display a color image through the liquid crystal display unit. The distance L between the organic EL element and the light diffusion plate in the backlight portion is represented by (1/50) P, where P is the pitch between the same colors of the plurality of organic EL elements and H is the haze of the light diffusion plate. <L * H <10
It is characterized in that it is set so that the relationship of 0P is established.

According to a second aspect of the present invention, there is provided a color image display device, wherein one set of the organic EL element group comprises an organic EL element emitting red light.
It is characterized by comprising an element, an organic EL element emitting green light, and an organic EL element emitting blue light. According to a third aspect of the present invention, there is provided a color image display device comprising: an organic layer in which a plurality of organic EL elements are arranged in a stripe shape, each of which can emit light of each color; and an electric circuit for flowing a current through the organic layer. An electric circuit, a common electrode connected to all of the plurality of organic layers, a plurality of opposed electrodes independently connected to each of the plurality of organic layers, and an organic light emitting device capable of emitting the same color among the plurality of opposed electrodes. A plurality of conductive layers connecting a counter electrode connected to the layer at a portion extending from the counter electrode connected to the organic layer capable of emitting another color, and a power supply connecting the common electrode and the plurality of conductive layers Wherein an insulating layer is provided between at least one of the plurality of conductive layers and another counter electrode different from the counter electrode to which the one conductive layer is connected.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a color image display device according to an embodiment of the present invention will be described in detail with reference to the drawings. In addition, each drawing is a diagram schematically illustrating a main part of the color image display device according to the present embodiment for describing the color image display device, and illustrates all components of the color image display device according to the present embodiment. Do not mean.

This color image display device is a color liquid crystal display device in which an organic EL element is used as a backlight and color display can be performed by field sequential control (FSC). Hereinafter, the contents will be described in detail. Here, FIG. 1 is a cross-sectional view schematically illustrating the color image display device according to the present embodiment.

As shown in FIG. 1, the present color image display device includes a backlight unit 1 and a liquid crystal display unit 2 for displaying a color image. First, backlight unit 1
As shown in FIG. 1, a plurality of colors necessary for displaying a color image as a backlight light source (light emitting source, light emitting element) are provided so as to be located on the back surface of the liquid crystal display unit 2. Then, red (R), green (G), blue (B)
Organic EL (electrolumin
luminescence) element 17.

As shown in FIG. 1, a plurality of organic EL elements 17 are provided on the surface of a single transparent substrate for backlight 12 supported on a support substrate 11 via a seal member 13 (for backlight). On the back side of the transparent substrate 12), it is formed in a band shape (rectangular shape) so as to extend in the height direction (vertical direction in FIG. 2) of the backlight transparent substrate 12, and is arranged in a stripe shape. The seal member 13 is adhered and sealed to each of the support substrate 11 and the transparent substrate for backlight 12, and the plurality of organic EL elements 17 are bonded to the support substrate 11, the seal member 13, and the transparent substrate for backlight (for example, glass). The substrate 12 is hermetically covered.

Here, as shown in FIG. 1, each organic EL element 17 has a transparent electrode 16 serving as an anode shared by each element 17, an organic layer 30 that emits light, and a counter electrode for an organic layer (cathode, cathode). (Metal cathode) 18. Then, holes are injected from the electrode 16, electrons are injected from the electrode 18, and when a current flows through the organic layer 30, the organic layer 30 emits light. In FIG. 1, different components are given different patterns in order to easily distinguish each component.

Here, the organic layer 30, the organic layer counter electrode 1
8 is provided for each organic EL element 17, and the organic layer 30 includes a red organic layer 30R that emits red light, a green organic layer 30G that emits green light, and a blue organic layer 30B that emits blue light. The opposing electrode 18 is provided with three types of opposing electrodes 18R for a red organic layer, an opposing electrode 18G for a green organic layer, and an opposing electrode 18B for a blue organic layer, corresponding to the organic layer 30. The organic E having the red organic layer 30R
The L element 17 is referred to as a red organic EL element 17R, the organic EL element 17 including the green organic layer 30G is referred to as a green organic EL element 17G, and the organic EL element 17 including the blue organic layer 30B is referred to as a blue organic EL element 17B.

Here, a plurality of organic EL elements 17 (here, three colors of red, green, and blue) required to display a color image can be emitted.
A set of organic EL element groups each including three red organic EL elements 17R, one green organic EL element 17G, and one blue organic EL element 17B) are arranged side by side.
At least two or more sets are repeatedly arranged along the width direction (horizontal direction in FIG. 2) of the backlight transparent substrate 12 to be used as a light source of the backlight unit 1.

FIG. 2 shows these organic EL elements 1
FIG. 7 is a rear view schematically showing a front view 7 (a front view when viewed from a direction A in FIG. 1). In FIG. 2, different components are given different patterns in order to easily distinguish each component.
First, the organic layer 30 generally has a laminated structure. That is, as shown in FIG. 3, the organic layer 30 is
0a, a light emitting layer 30b, and an electron transport layer 30c. Here, the light emitting layer 3 that emits each color
Ob is formed on the transparent substrate for backlight 12 by adding a luminescent material that emits a plurality of colors such as red, green, and blue at the time of its formation. In order to improve the luminous efficiency, the organic layer 30 may be formed by adding layers such as a hole injection layer, an electron injection layer, a hole blocking layer, and an electron blocking layer. In FIG. 3, different components are given different patterns in order to easily distinguish each component.

The organic layer 30 is generally formed by a coating method or a vacuum deposition method. Here, the organic layer 30
Is manufactured by a vacuum evaporation method. First, the hole transport material is put into a crucible installed in a vacuum vessel, and the inside of the vacuum vessel is moved to about 133 × 10 − by a suitable vacuum pump.
After evacuating to 6 Pa (about 1 × 10 −6 Torr),
The hole transporting material is evaporated by heating the crucible to form the hole transporting layer 30a on the transparent electrode 16 on the transparent substrate 12 placed facing the crucible. The thickness of the hole transport layer 30a thus formed is usually about 10 to about 300.
nm, preferably about 30 to about 100 nm.

Next, when forming a red light emitting layer among the light emitting layers 30b, a red light emitting material is placed in a vacuum vessel, and the red light emitting material is evaporated to form a red light emitting material on the hole transport layer 30a. Form a layer. At this time, a portion other than the formation region is covered with a metal mask or the like so that a red light emission layer is not formed outside the red light emission region. Similarly, a green light emitting layer and a blue light emitting layer are formed. The thickness of the light emitting layer 30b is usually
About 10 to about 300 nm, preferably about 30 to about 100 n
m. In order to optimize the light emission characteristics of each color,
The film thickness may be changed for each emission color.

Next, the electron transporting material is placed in a vacuum vessel, and the electron transporting material is evaporated to form an electron transporting layer 30c on the light emitting layer. The compound used for the electron transport layer 30c needs to be a compound having a high electron injection efficiency from the counter electrode 18 as a cathode and capable of efficiently transporting the injected electrons. Therefore, the electron affinity is large, the electron mobility is large,
Further, it is required that the compound is excellent in stability and hardly generates impurities serving as traps during production or use. The thickness of the electron transport layer 30c is generally about 10 to about 200
nm, preferably about 30 to about 100 nm.

In this manner, the organic layer 30 as the RGB light emitting source having a thickness of the light emitting source including the transparent substrate for backlight 12 of about 1 mm or less is manufactured. Since the emission colors such as red, green, and blue are mainly determined by the material used for forming the light emitting layer, it is possible to easily produce a light emitting layer of any color such as yellow or orange by changing the light emitting material. What can be achieved is a characteristic of the organic EL element 17. Because of this,
As long as a color image can be displayed by a plurality of colors other than green and blue, a plurality of organic EL elements each emitting another plurality of colors may be used.

The arrangement and shape of the organic EL element 17 may be changed by changing the light emitting area for each color in consideration of uniformity of light emission, or by changing the width of a stripe in consideration of luminance reduction due to a voltage drop. May be. In addition, since the light emitting region can be easily controlled by a metal mask or the like at the time of vapor deposition, the number of stripes and the density (light source density) can be easily increased without increasing the cost.

Further, for the same reason, the organic EL element 1
Since the shape of 7 can be easily formed into a shape such as a curve, a circle, and a star, a backlight of a color liquid crystal display device meeting various needs can be provided. Further, as described above, the organic E of each color is applied to the light emitting region.
The L elements 17 are not limited to those arranged in a stripe shape.
For example, they may be arranged in a matrix (mosaic arrangement) or in a triangle (delta arrangement). In such an arrangement, an auxiliary electrode line connecting elements of the same color may be provided as necessary. Even in such an arrangement, the pitch P used for calculating the haze may be set in the same manner as in the case of arrangement in a stripe shape.

By the way, the plurality of organic EL elements 17 thus configured are each provided with a transparent electrode 1 as an anode.
6 and a counter electrode 18 for an organic layer as a cathode are connected. Of these, as shown in FIG.
It is configured as a comb-like electrode extending on the surface of a single transparent substrate for backlight 12 in the width direction (horizontal direction in FIG. 2) of the transparent substrate for backlight 12. That is, as shown in FIG. 2, the transparent electrode 16 connects the comb portion 16A composed of a plurality of strip-shaped electrodes arranged in parallel in a stripe shape, and connects each strip-shaped electrode at one end of these strip-shaped electrodes. And a handle portion 16B.
Current is supplied from the B electrode.

The transparent electrode 16 is formed as a common electrode that faces all of a red organic layer counter electrode 18R, a green organic layer counter electrode 18G, and a blue organic layer counter electrode 18B as a cathode described later. Also, the transparent electrode 16
Generally, metals such as aluminum, gold, silver, nickel, palladium and tellurium, metal oxides such as oxides of indium and / or tin, copper iodide, carbon black,
Alternatively, it is made of a conductive polymer such as poly (3-methylthiophene). The transparent electrode 16 is generally formed by a sputtering method, a vacuum evaporation method, or the like.

Further, the thickness of the transparent electrode 16 depends on the required transparency. If transparency is required, the visible light transmittance is about 60% or more, preferably about 80%.
% Or more, and in this case, the thickness of the conductive layer 2 is generally about 5 to about 1000 nm, preferably about 10 to about 500 nm. On the other hand, a plurality of organic layer counter electrodes 18 are provided for each of the plurality of organic layers 30 that are repeatedly arranged in the order of red (R), green (G), and blue (B) as described above. These organic layer opposing electrodes 18 are formed in a strip shape on the surface of the plurality of organic layers 30 so as to extend over the entire length of the organic layers 30. The organic layer counter electrode formed on the red organic layer 30R is referred to as a red organic layer counter electrode 18R, and the organic layer counter electrode formed on the green organic layer 30G is referred to as a green organic layer counter electrode 18G. In other words, the organic layer counter electrode formed on the blue organic layer 30B is referred to as a blue organic layer counter electrode 18B. Further, the organic layer counter electrode 18 may have a laminated structure of two or more layers of different substances.

The plurality of opposing electrodes for organic layers 18
It serves as a cathode (cathode) to inject electrons into a plurality (three in this case) of organic layers 30. For this reason, it is preferable to use a metal having a low work function to enable efficient electron injection.
A suitable metal such as magnesium, indium, aluminum, silver or the like or an alloy thereof is used. The thickness of the organic layer counter electrode 18 is generally the same as that of the transparent electrode 16.

Each of the organic layer opposing electrodes 18 is connected to an EL drive circuit 42 described later via the conductive layer 19. In other words, the plurality of red organic layer opposed electrodes 18R include:
As shown in FIG. 2, a conductive layer 19R for a red organic layer for connecting these electrodes 18R to an EL drive circuit 42 described later is connected.
R extends in the width direction (horizontal direction in FIG. 2) of the backlight transparent substrate 12 and is drawn out from one end (the left end in FIG. 2) of the backlight transparent substrate 12. .
Further, the plurality of red organic layer opposing electrodes 18R are different from the other green organic layer opposing electrodes 18G and blue organic layer opposing electrodes 18R.
One end (upper end in FIG. 2) is formed longer than B, thereby forming the red organic layer conductive layer 19R.
However, it does not contact the other green organic layer counter electrode 18G and blue organic layer counter electrode 18B. Here, the conductive layer 19R for the red organic layer is drawn from one end of the transparent substrate for backlight 12, but may be drawn from the other end (the right end in FIG. 2). good.

Similarly, a plurality of green organic layer opposing electrodes 18
As shown in FIG. 2, a green organic layer conductive layer 19G for connecting these electrodes 18G together to an EL drive circuit 42, which will be described later, is also connected to G. The backlight transparent substrate 1 extends in the width direction of the backlight transparent substrate 12 (the horizontal direction in FIG. 2).
2 is drawn out from the other end (the right end in FIG. 2). The plurality of green organic layer opposed electrodes 18G are
The other end of the red organic layer counter electrode 18R (FIG. 2)
The middle and lower ends are formed long so as not to contact the red organic layer counter electrode 18R. In this case, the green organic layer conductive layer 19G is drawn from the other end of the backlight transparent substrate 12, but may be drawn from one end (the left end in FIG. 2). good.

Similarly, a plurality of blue organic layer opposing electrodes 18B are also provided on these electrodes 18B as shown in FIG.
Is connected to an EL driving circuit 42, which will be described later, and the blue organic layer conductive layer 19B is connected to the backlight transparent substrate 12 in the width direction (the horizontal direction in FIG. 2). ), And is drawn out from one end of the transparent substrate for backlight 12 (the left end in FIG. 2). Also, a plurality of blue organic layer counter electrodes 18B
The other end (the lower end in FIG. 2) is formed longer than the red organic layer counter electrode 18R and the green organic layer counter electrode 18G, and is in contact with the red organic layer counter electrode 18R. I try not to.

Further, the opposing electrode 18B for a blue organic layer is provided with an electric insulating layer 20G at a position where the green organic layer conductive layer 19G on the other end (the lower end in FIG. 2) is provided.
Is formed, and the insulating layer 20 insulates the blue organic layer counter electrode 18B from the green organic layer counter electrode 18G. That is, the green organic layer conductive layer 19G and the other red organic layer counter electrode 18R and blue organic layer counter electrode 18B different from the green organic layer counter electrode 18G to which the green organic layer conductive layer 19G is connected.
And an insulating layer 20 is provided between them. Note that, here, the conductive layer 19B for a blue organic layer is drawn out from one end of the transparent substrate for backlight 12, but may be drawn out from the other end (the right end in FIG. 2). good.

The positions where the conductive layers 19R, 19G, and 19B are provided are not limited to those described above, and may be, for example, on one end (upper end in FIG. 2) of the organic layer counter electrode 18. May be provided with a green organic layer conductive layer 19G or a blue organic layer conductive layer 19B, or any two conductive layers may be provided on one end side of the organic layer counter electrode 18. Although the anode is used as the common electrode here, the cathode may be used as the common electrode.

As described above, in the present embodiment, in order to inject holes and electrons into the organic layer 30 of the organic EL element 17, the common electrode 1 connected to all of the plurality of organic layers 30 of each color is used.
6, a plurality of opposing electrodes 18 independently connected to each of the plurality of organic layers 30 of each color, and an organic layer 30 (30R, 30G, 3) capable of emitting the same color among the plurality of opposing electrodes 18.
0B) connected to the opposite electrode 18 (18R, 18G, 1).
8B) to the organic layer 30 (30R, 30) capable of emitting another color.
G, 30B) connected to the opposite electrode 18 (18R, 18B).
G, 18B), a plurality of conductive layers 19 (19R, 19G, 19B) connected at a portion extending from the common electrode 16 and a power source (19R, 19G, 19B) connected to the plurality of conductive layers 19 (19R, 19G, 19B). (Not shown)).

As described above, the red light emitting layer 30R of the red organic EL element 17R, the green light emitting layer 30G of the green organic EL element 17G, and the blue light emitting layer 30B of the blue organic EL element 17B
The electrodes connected for injecting holes or electrons into each of the electrodes have one of the anode and the cathode as one common electrode, and the other electrode is provided for each light emitting layer 30. Are connected to a conductive layer 19 for each color (this conductive layer is also considered to be a part of the electrode), so that a total of four electrodes are used to form a red organic EL element 17R, a green organic EL element 17G, and a blue organic EL element. It is possible to control each of the light emitting elements 17B to emit light. With such a circuit configuration, the circuit configuration can be simplified, and all circuits are formed on one substrate. As a result, cost reduction can be achieved. Further, the circuit can be easily manufactured and the yield can be improved.

In this embodiment, as shown in FIG. 1, a light diffusing plate 15 is also provided so as to diffuse the light from the organic EL elements 17 to obtain uniform light. The light diffusion plate 15 is configured as a substrate (or sheet) that has been subjected to light diffusion processing, and as shown in FIG.
It is mounted on the surface of a liquid crystal transparent substrate 21 of the liquid crystal display unit 2 (described later) supported on the support substrate 11 via the support member 14 (the rear surface of the liquid crystal transparent substrate 21 and the light incident surface of the liquid crystal display unit 2). ing. That is, the light diffusion plate 15 is interposed between the organic EL element 17 as a light source of the backlight unit 1 and the liquid crystal display unit 2 described later.

The support member 14 is bonded to the support substrate 11 and a liquid crystal transparent substrate 21 of the liquid crystal display unit 2 described later, and the light diffusing plate 15 is joined together with the organic EL element 17 to the support substrate 11 and the support member. 14 and transparent substrate 2 for liquid crystal
Covered by one. Therefore, the light diffusion plate 15 can be regarded as a part of the backlight unit 1. by the way,
In order to display a color image, it is necessary to provide a plurality of organic EL elements 17 capable of emitting each color. In this case, it is necessary to provide an organic EL element 17 in order to sequentially arrange the plurality of organic EL elements 17 capable of emitting each color. Since the element 17 is formed in a linear or dot shape, the light diffusing plate 15 is required to obtain uniform light without unevenness.
Role is important.

For this reason, in the present embodiment, the distance between the light emitting surface of the organic EL element 17 and the surface of the light diffusion plate 15 is reduced (that is, the overall thickness of the color image display device is reduced). , In order to obtain a more uniform light emitting surface,
The light diffusing plate 15 is arranged so as to satisfy the following relational expression (1). That is, the light emitting surface of the organic EL element 17 (FIG. 1)
1 and 2 and the surface of the light diffusion plate 15 (light diffusion processing surface,
(L, G, B), and the same color among a plurality of organic EL elements 17 repeatedly arranged at least in two or more sets. When the pitch P between the light emitting organic EL elements 17 is set and the haze of the light diffusion plate 15 is H, the light diffusion plate 15 is arranged so as to satisfy the following relational expression (1).

(1/50) P <L * H <100P (1) Preferably, the range is (1/5) P <L * H <10P. Here, the haze H of the light diffusion plate 15 is
Let Tt be the total light transmittance that transmits light, and let T be the diffuse light transmittance.
When d is set, it is defined as a quantity represented by the following equation (2).

H = Td / Tt (2) The arrangement of the light diffusion plate 15 is determined for the following reason. That is, when the distance L is set such that the value of (L * H) defined by the relational expression (1) is smaller than (1/50) P with respect to the haze H of the light diffusion plate 15 used [ L * H <(1/50) P], the light diffusing plate 1
5 is too close to the organic EL element 17 as a light emitting source, and the light of each color (here, three colors) emitted from the plurality of organic EL elements 17 is not sufficiently mixed, and color unevenness occurs, which is preferable. Absent.

On the other hand, when the distance L is set so that the value of (L * H) becomes larger than 100P, [L * H> (1 /
In 50) P], although the light of each color emitted from the plurality of organic EL elements 17 becomes uniform, the thickness of the backlight unit 1 is undesirably increased. This is a practically large limitation for a color image display device.

As described above, the light diffusing plate 15 configured as an independent substrate may be attached to the lower surface of the transparent substrate for liquid crystal 21. However, the present invention is not limited to this. It may be mounted on the upper surface of the substrate 12, or may be provided as a light diffusion processing layer on the lower surface of the transparent substrate for liquid crystal 21. In this case, the light diffusion processing layer can be manufactured by, for example, providing minute unevenness or forming a minute lens on the surface of the backlight transparent substrate 12.

The liquid crystal display unit 2 can function as a shutter for displaying a color image by exposing light from the backlight unit 1 and, for example, a high-speed response type STN (Super Twisted Nematic). A liquid crystal panel is used. In addition, as the liquid crystal panel as the liquid crystal display unit 2, a polymer dispersed liquid crystal (PDL) may be used.
C), a liquid crystal panel having a high response speed such as a ferroelectric liquid crystal (FLC) or an antiferroelectric liquid crystal can be used.

More specifically, as shown in FIG. 1, the liquid crystal display section 2 includes a transparent substrate for liquid crystal 21, an electronic circuit 22, a liquid crystal seal member 23, a front cover 24, and a liquid crystal cell 25. It is composed. That is, the electronic circuit 22 and the liquid crystal cell 25 are laminated on the surface of the liquid crystal transparent substrate 21, and the electronic circuit 22 and the liquid crystal cell 25 are supported on the liquid crystal transparent substrate 21 via the liquid crystal seal member 23. It is covered with a front cover 24 and is sealed and sealed by a liquid crystal seal member 23.

Note that the liquid crystal display unit 2 thus configured is
Are supported on the support substrate 11 of the backlight unit 2 via the support member 14 of the backlight unit 2. By the way, the backlight unit 1 and the liquid crystal display unit 2 according to the present embodiment are configured as described above, and an EL drive circuit 42 is connected to the backlight unit 1 as shown in FIG. The EL drive circuit 42 is connected to the control circuit 40. 4, a liquid crystal drive circuit 41 is connected to the liquid crystal display unit 2, and the liquid crystal drive circuit 41 is connected to the control circuit 40. In FIG. 4, the liquid crystal display unit 2, the light diffusion plate 15 and the backlight unit 1 are disassembled to show the main part only for easy understanding. In FIG. 4, different components are given different patterns in order to easily distinguish each component.

In the present embodiment, the control circuit 40 and the EL drive circuit 42 as the control section perform field sequential control (FSC control) for causing the organic EL elements 17 of each color to emit light in a time-division manner. . That is, the control circuit 40 and the EL drive circuit 42 control the plurality of organic EL elements 17 so that the plurality of organic EL elements 17 sequentially emit light for each color so as to display a color image through the liquid crystal display unit 2. ing. The control circuit 40 and the liquid crystal drive circuit 41 can control the lighting of each organic EL element 17 independently for each color, and perform control to expose light in synchronization with the lighting of these organic EL elements 17. It is supposed to be.

Here, as shown in FIG. 5, the control circuit 40 and the EL drive circuit 42 turn on a color synthesis field (color image display field) for displaying a color image at predetermined time intervals (for example, about 1/60 second). This color synthesis field is divided into three fields for each of the colors R, G, and B constituting the backlight unit 1 and each field is divided by the organic EL element 17 of each color for a predetermined time (for example, R → G → B → R
And the control circuit 40 and the liquid crystal driving circuit 41 drive the liquid crystal cell (liquid crystal display element) 25 at a predetermined dot position on / off in synchronization with the lighting cycle of one color combining field (that is, back-up). The liquid crystal shutter constituting the liquid crystal display unit 2 is operated in synchronization with the light emission from the light unit 1, and an arbitrary color image display is obtained by the visual afterimage phenomenon that occurs at that time.

Therefore, according to the color image display device of this embodiment, the light diffusion plate 15 and the organic EL element 1
7 is set so as to satisfy the above-described relational expression (1), so that the overall thickness of the color image display device can be reduced and higher uniformity of the light emitting surface can be obtained. There are advantages. In addition, since it has a monochrome liquid crystal cell 25 of high-speed response and further has a backlight unit 1 for performing field-sequential control in which three colors of red, green and blue are switched at high speed, a conventional color TFT type liquid crystal image display device is provided. Since it is not necessary to provide an expensive color filter, the cost can be reduced, the power consumption per emission luminance can be suppressed low, and further, there is an advantage that high luminance and high resolution can be obtained.

In particular, by using the organic EL element 17 as a light source for the backlight unit 1, the cost can be reduced as compared with a conventional case where a cold cathode tube or LED is used as a light source for the backlight unit. In addition, there is an advantage that the density of the light emitting region can be increased. Further, the backlight unit 1 including the light diffusing plate 15 can be made thinner, which has an advantage that the thickness of the entire liquid crystal display device can be reduced without increasing the frame portion of the liquid crystal display device.

Further, the organic EL element 17 can be driven at a low voltage by direct current, and has the advantage that the EL drive circuit 42 can be manufactured simply and at low cost. Further, the organic EL element 17
Red, green,
Colors other than blue can be easily produced, and the backlight unit 1 having a color that meets various needs can be produced.

Note that such a color image display apparatus is a flat panel display (for example, an OA computer, a wall-mounted TV, a display of a camera or a home appliance).
It can be applied to displays, sign boards, and sign lights, and its technical value is high.

[0054]

Next, the present invention will be described in more detail with reference to one embodiment. However, the present invention is not limited to the description of the following embodiment unless departing from the gist of the present invention. (Example 1) First, as an example of the present invention, an organic EL element 17 was manufactured as a light source of the backlight unit 1. The plurality of organic EL elements 17 emit three colors of red, green and blue. The size of the organic layer 30 of each of the plurality of organic EL elements 17 is about 1 mm in width × about 20 mm in length, and the space between the organic layers 30 is about 1 mm, respectively, on the transparent substrate 12 for backlight. One red organic EL element 17R and one green organic E are arranged in order of red → green → blue.
With the L element 17G and one blue organic EL element 17B as one set, seven sets of organic EL element groups were repeatedly arranged. Thereby, the light emitting surface of the organic EL element 17 is about 20 mm long ×
The backlight unit 1 using the organic EL element 17 having a width of about 41 mm and a thickness of about 1 mm as a light source was manufactured. In this case, the pitch P between the same colors of the organic EL element 17 was about 6 mm.

FIG. 6 shows the emission spectrum of each color of the backlight unit 1 using the organic EL element 17 produced as described above as a light source. As shown in FIG. 6, the peak wavelength of the backlight unit 1 is approximately 62 for red.
1 nm, green was about 542 nm, and blue was about 471 nm. Then, the organic EL element 17 as the light emitting source is
Lighting was repeated by setting the lighting time of the color to about 1/180 second and the lighting time in one cycle of R → G → B to about 1/60 second.

Here, FIG. 7 shows a photograph of the light emitting surface of the backlight unit 1 when the lighting control is performed as described above. Here, since the shutter speed is made slower than 1/60 second in accordance with the afterimage characteristics of human eyes,
Captures all green and blue light emission. On the other hand, FIG. 8 shows a photograph in which the light emitting surface of the backlight unit 1 is photographed through the light diffusion plate 15 when repeatedly turned on under the same conditions as described above. The photographing conditions were the same as above, but when photographing was performed through the light diffusing plate 15, white light was obtained by mixing the three colors. Here, the light diffusing plate 15 (light-up 100 PBU manufactured by Kimoto: total light transmittance Tt =
66%, haze H = 0.9) was arranged such that the distance L from the light emitting surface of the organic EL element 17 was about 5 mm. The distance L between the light diffusion plate 15 and the light emitting surface of the organic EL element 17 (= about 5 mm), the pitch P between the same colors of the organic EL element 17 (= about 6 mm), the haze H of the light diffusion plate 15 ( =
0.9) was set so as to satisfy the above-mentioned relational expression (1).

When the liquid crystal display unit 2 is mounted on the backlight unit 1 using the organic EL element 17 as a light source and the liquid crystal display unit 2 is driven in synchronization with the lighting cycle of the backlight unit 1, a clear color is obtained. An image was obtained. (Comparative Example 1) Next, as a comparative example, a backlight portion was produced using a commercially available cold-cathode tube of three colors.

Here, the size of one cold-cathode tube is about 3 mm (φ3 mm) × about 100 mm in length, and the pitch P between adjacent cold-cathode tubes is about 20 mm. A total of 9 tubes were arranged by repeating the tubes in order. In this case, the pitch P of the cold-cathode tubes of the same color is about 60 m.
m. A light diffusing plate was placed on the thus obtained backlight portion at a distance of about 5 mm from the light emitting surface of the backlight portion as in the example, and the light emitting surface was observed through the light diffusing plate. A light emission pattern with a blurred line was observed. The lighting cycle and shutter speed at this time were the same as in the example.

When a liquid crystal display section was connected to the backlight section, and the displayed color image was observed in synchronization with the driving in the same manner as in the embodiment, the red, green, and blue colors affected by the light emission pattern of the backlight section were observed. Only a color image having color unevenness was obtained. The color image display device according to the present invention uses an organic EL element as a backlight,
Since color display can be performed by field sequential control (FSC), and the light diffusion plate 15 is arranged under predetermined conditions, the liquid crystal display unit 2 may be configured without departing from the spirit of the invention. And light diffusion plate 1
Various changes can be made to the configuration of the fifth embodiment, the configuration of the organic EL element 17, and the configuration of the control system.

FIGS. 1 to 6 used for describing the present embodiment show an example of a color image display device of the present embodiment, and the present invention is not limited to the drawings unless departing from the gist thereof. However, the present invention is not limited to this.

[0061]

According to the color image display device of the present invention, the distance L between the light diffusion plate and the organic EL element is reduced.
Is set so as to satisfy a predetermined condition, there is an advantage that higher uniformity of the light emitting surface can be obtained. In addition, since the field sequential control is performed, a color filter is not required, thereby reducing costs and power consumption per light emission luminance. Furthermore, an organic EL is used as a light source for the backlight unit.
Since the element is used, the light source of the backlight is LE
There is an advantage that the cost can be reduced as compared with the case where a D or a cold cathode tube is used, and the thickness of the entire liquid crystal display device can be reduced without enlarging the frame portion of the liquid crystal display device.

According to the color image display device of the present invention, there is an advantage that the circuit configuration for supplying a current to the organic EL element can be simplified and the circuit can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating an overall configuration of a color image display device according to an embodiment of the present invention.

FIG. 2 is a schematic plan view showing a structure of an organic EL element of the color image display device according to one embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view showing a structure of an organic EL element of the color image display device according to one embodiment of the present invention.

FIG. 4 is a diagram illustrating a control system of a backlight unit and a liquid crystal display unit of the color image display device according to the embodiment of the present invention.

FIG. 5 is a time chart illustrating field sequential control of the color image display device according to the embodiment of the present invention.

FIG. 6 is a diagram showing emission spectra of respective colors of a backlight unit using an organic EL element as a light source according to one embodiment of the present invention.

FIG. 7 is a photograph as a drawing showing a light emitting surface of a backlight unit using an organic EL element as a light source according to one embodiment of the present invention.

FIG. 8 is a photograph as a drawing showing a light-emitting surface of a backlight unit passing through a light diffusion plate using an organic EL element as a light source according to one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 backlight part 2 liquid crystal display part 11 support substrate 12 transparent substrate for backlight 13 sealing member 14 support member 15 light diffusion plate 16 transparent electrode 17 organic EL element 18 counter electrode for organic layer 18R counter electrode for red organic layer 18G green organic Counter electrode for layer 18B Counter electrode for blue organic layer 19 Conductive layer 19R Conductive layer for red organic layer 19G Conductive layer for green organic layer 19B Conductive layer for blue organic layer 20 Insulating layer 21 Transparent substrate for liquid crystal 22 Electronic circuit 23 Liquid crystal sealing member Reference Signs List 24 front cover 25 liquid crystal cell 30 organic layer 30a hole transport layer 30b light emitting layer 30c electron transport layer 30R red organic layer 30G green organic layer 30B blue organic layer 40 control circuit (control unit) 41 liquid crystal drive circuit 42 EL drive circuit (control) Part)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H091 FA31Z FA44Z FD01 FD03 GA11 HA10 HA12 JA02 LA11 LA18 MA10 5G435 AA01 AA18 BB05 BB12 BB15 CC12 EE26 EE30 FF06 GG25 GG27

Claims (3)

[Claims] 1. An organic EL element group comprising a liquid crystal display section for displaying a color image and a plurality of organic EL elements each capable of emitting a plurality of colors necessary for displaying a color image. A backlight unit provided as a light source by arranging at least two or more sets, a light diffusion plate disposed between the liquid crystal display unit and the backlight unit, and diffusing light from the backlight unit; A control unit for controlling the plurality of organic EL elements so that the plurality of organic EL elements sequentially emit light for each color so as to display a color image through a liquid crystal display unit; The distance L between the element and the light diffusing plate is represented by P, the pitch between the same colors of the plurality of organic EL elements is represented by P, and the haze of the light diffusing plate is represented by H,
(1/50) A color image display device characterized by being set so as to satisfy the relationship of P <L * H <100P. 2. The organic EL element group of one set includes an organic EL element that emits red light, an organic EL element that emits green light,
The color image display device according to claim 1, comprising an organic EL element emitting blue light. 3. The plurality of organic EL elements are arranged in a stripe pattern, each comprising: an organic layer capable of emitting light of each color; and an electric circuit for causing a current to flow through the organic layer. A common electrode connected to all of the plurality of organic layers; a plurality of counter electrodes independently connected to each of the plurality of organic layers; and the same color among the plurality of counter electrodes can emit light. A plurality of conductive layers connecting a counter electrode connected to the organic layer at a portion extending from the counter electrode connected to the organic layer capable of emitting another color, and the common electrode and the plurality of conductive layers A power supply to be connected, at least one conductive layer of the plurality of conductive layers,
An insulating layer is provided between the counter electrode to which the one conductive layer is connected and another counter electrode different from the counter electrode.
The color image display device according to claim 1.