JP2001242460A - Liquid crystal display - Google Patents

Abstract

(57) [Object] To provide a liquid crystal display device provided with a color filter, which can prevent coloring when viewed obliquely (high viewing angle region) without lowering light use efficiency. . A blue colored layer 1 among red (R), green (G), and blue (B) colored layers 11-R, 11-G, and 11-B.
Only 1-B is made of a material having a larger retardation (phase difference) than the other coloring layers 11-R and 11-G. As a result, the transmittance of blue light in the high viewing angle region is increased to offset the coloring of yellow. In the case where coloring other than yellow is included, a difference in retardation value is appropriately provided between the red (R) and green (G) coloring layers 11-R and 11-G. Completely remove coloring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device having a color filter. In particular, the present invention relates to a liquid crystal display device provided with a phase difference plate for expanding a viewing angle.

[0002]

2. Description of the Related Art Liquid crystal display devices have been widely used as display devices for notebooks and desktops, as well as televisions and graphic displays, because of their advantages such as space saving and low power consumption. Has become.

However, the liquid crystal display device has a problem that the viewing angle is generally narrower than that of a cathode ray tube display device (CRT) or the like. The viewing angle is the maximum angle at which display characteristics such as predetermined contrast can be obtained when viewed obliquely from the front direction (the normal direction of the display panel). That is, it is the maximum value of the viewing angle (the angle between the line of sight and the front direction) at which a predetermined display characteristic is obtained.

[0004] As a method for improving the viewing angle characteristics, the following several methods are used.

[0005] One is a method generally called a multi-domain method, in which one pixel (dot) is divided into a plurality of regions and the alignment direction of liquid crystal is controlled for each divided region. With this method, although the viewing angle can be considerably improved, it is necessary to provide a structure for multi-domain, so that the manufacturing process becomes considerably complicated and the yield is greatly reduced.

As another method, there is a method such as an IPS (In-Plane Switching) mode for controlling the movement of liquid crystal molecules by lateral electrolysis. According to this method, although a high viewing angle can be obtained, there is a problem that the response speed is low and the efficiency of use of the backlight light is low because the aperture ratio is low.

On the other hand, there is a method using an optically anisotropic element called a retardation plate (viewing angle expanding film). For example, in a liquid crystal display device described in JP-A-8-95032, a discotic compound forming a discotic liquid crystal is
It is arranged on the front and back sides of the liquid crystal panel by being included in a transparent resin film. This retardation plate has optically negative uniaxiality, and has characteristics as an optically anisotropic element in which the optical axis is the same as the normal direction of the film and slightly inclined. That is, it is a film in which a layer containing an optically anisotropic compound having a refractive index nx, ny in the plane of the film larger than the refractive index nz in the thickness direction is appropriately laminated.

In the method using the retardation plate, it is only necessary to attach the liquid crystal panel to the conventional liquid crystal panel, so that the manufacturing process of the liquid crystal panel does not need to be changed, and the conventional manufacturing apparatus and manufacturing technology can be used. Can be used.
In addition, sufficient viewing angle characteristics can be obtained.

[0009]

However, according to this method, when performing color display, when viewed from an oblique direction that is greatly deviated from the front direction, that is, in a high viewing angle region,
There was a problem that "coloring" was seen. Generally,
The whole is colored yellow.

As a method of avoiding the coloring, adjustment of the retardation (phase difference) of the liquid crystal layer itself in the liquid crystal panel is also performed. However, this method has a problem that the light transmittance of the liquid crystal panel is reduced and the light use efficiency is reduced.

The inventors of the present invention have made intensive studies in view of the above problems, and found that among the films that can be used as the coloring layers of the color filters, certain films have retardation. Reached. The film used as the coloring layer of the color filter broke the stereotype of those skilled in the art that had been determined to have no retardation.

As a result of further studies, the inventor of the present invention has come up with the idea that coloring can be eliminated based on the retardation of the colored layer.

According to the present invention, based on such a completely new idea, a liquid crystal display device having a color filter is provided.
An object of the present invention is to provide a display device capable of preventing coloring in a high viewing angle region without reducing light use efficiency.

[0014]

According to the first aspect of the present invention, a pair of transparent insulating substrates, a liquid crystal layer held between the transparent insulating substrates,
An alignment film formed on a surface of the transparent insulating substrate in contact with the liquid crystal layer, and a plurality of colored layers arranged on any of the transparent insulating substrates, and each pixel constituting a display region, In a liquid crystal display device including a color filter that sequentially allocates one color at a time from the plurality of colors, and a retardation plate and a polarizing plate disposed on the outer surfaces of the pair of transparent insulating substrates, the colored layer performs retardation based on optical anisotropy. Have
The color layer of one color has a retardation value different from that of the color layer of another color.

With the above-described structure, in the high viewing angle region, coloring can be eliminated and excellent color rendering can be obtained.

According to a second aspect of the present invention, the plurality of colors include blue, and the blue colored layer has a higher retardation value than any of the other colored layers. .

With this configuration, yellow coloring can be sufficiently prevented.

According to a third aspect of the present invention, the plurality of colors include red, green, and blue, and a difference is provided in a retardation value between the red coloring layer and the green coloring layer. And

With such a configuration, it is possible to completely prevent coloring.

According to a fourth aspect of the present invention, the colored layer is made of a resin material, and the one colored layer is made of a resin material different from the other colored layer.

With such a configuration, the production can be easily performed, and the production cost does not increase.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display device according to an embodiment will be described with reference to FIGS.

FIG. 1 is a schematic diagram for explaining the basic structure of the liquid crystal display device 10 when attention is paid to optical anisotropy. FIG. 2 is a vertical sectional view schematically showing the basic structure of the liquid crystal display device 10. FIG.

As shown in FIG. 2, the liquid crystal display device 10 comprises:
The first glass substrate 1 on which 960 signal line electrodes 13 are arranged in parallel with each other, and the 234 scanning line electrodes 21
However, the second glass substrate 2 arranged perpendicularly to the signal line electrode 13 and parallel to each other is combined so that the electrode forming surfaces face each other and the liquid crystal layer 31 is sandwiched therebetween. Spherical spacers 32 for making the thickness of the liquid crystal layer 31 uniform are substantially uniformly distributed between the first and second glass substrates 1 and 2. It is sealed by the agent 34.

Each of the signal line electrode 13 and the scanning line electrode 21 is a transparent pixel electrode and has a wide linear shape, that is, a stripe shape. Signal line electrode 13 and scanning line electrode 21
At the intersection of the two, a minute liquid crystal cell composed of these electrodes 13 and 21 and the liquid crystal layer 31 therebetween is formed. If this minute liquid crystal cell is one dot (display pixel), 234 (vertical) × 960 (horizontal) = 224,460 dots are arranged in a matrix to form an image display area. The pitch of one dot was 320 μm vertically and 110 μm horizontally.

A black matrix (BM) 12 is formed on the first glass substrate 1 so as to separate the dots.
They are arranged in a stripe or matrix.
Red (R), green (G), and blue (B) colored layers 11-are arranged in a grid-shaped or striped area separated by the black matrix (BM) 12, that is, at a location corresponding to the dot. R, 11-G and 11-B are regularly arranged. As a result, a color filter 11 in which any one of red (R), green (G), and blue (B) is sequentially assigned to each dot is formed.

On the outer surfaces of the first and second glass substrates 1 and 2, retardation plates 41 and 42 and polarizing plates 51 and 52 are adhered in this order.

The retardation plates 41 and 42 increase the viewing angle by compensating for the retardation of the liquid crystal layer 31 so as to prevent light leakage in a high viewing angle region.

Here, the liquid crystal layer 31 is made of a twisted nematic (TN) type liquid crystal material as shown in FIG. The liquid crystal molecules have a rugby ball shape or a rod shape, are oriented in the thickness direction as a whole, and are arranged in a substantially spiral shape when no voltage is applied. The liquid crystal molecule optically forms an index ellipsoid having a shape similar to its actual shape, and thus has optically positive uniaxiality.

Therefore, the liquid crystal layer as a whole has a large refractive index in the thickness direction and has a positive retardation.

On the other hand, the retardation plates 41 and 42 contain, for example, disc-shaped liquid crystal molecules in a resin film, and are optically negative uniaxial layers, or substantially biaxial. Include layers that are more negative uniaxial. Phase difference plates 41 and 42
Generally, as shown in FIG. 1, a structure in which layers of an optically anisotropic substance are laminated so as to perform optical compensation in accordance with the inclination and distribution of liquid crystal molecules in the liquid crystal layer 31 is shown. Have.

In the liquid crystal display device 10 of the embodiment, red (R), green (G), and blue (B) colored layers 11-R, 1
1-G and 11-B are as shown in Table 1 below for constituent materials, film thickness, and optical anisotropy.

For example, the red colored layer 11-R is formed by coating an acrylic resin in which a red pigment is dispersed to obtain a film having a thickness of 1.1 μm, and then, by photolithography, a portion of a display pixel to which a red color is assigned. Only to be left.

The retardation (phase difference) at the right end of the following table is
It is equal to birefringence (Δn) × film thickness (d). Birefringence (Δ
n) can be appropriately designed depending on the type, composition, film forming conditions and the like of the resin material.

[0035]

[Table 1] As shown in Table 1, in Examples, red (R) and green (G)
The colored layers 11-R and 11-G are made of an acrylic resin, while the colored layer 11-B of blue (B) is made of a polyimide resin. Since the birefringence (Δn) of the polyimide resin is higher by one digit than that of the acrylic resin, the retardation of the blue colored layer 11-B is higher by one digit than that of the other colors. Note that the film thicknesses are all the same.

With such a configuration, in a high viewing angle region, the leakage rate of blue light is somewhat higher than that of red and green light, and the overall state is as if a blue filter has been applied. Therefore, it is possible to cancel the coloring of yellow having a complementary color relationship with blue.

When the liquid crystal display device 10 of the embodiment was actually operated by incorporating a drive circuit system and the like, no coloring was observed even when viewed obliquely. In addition, no change was observed in the color rendering properties when viewed from the front direction.

Further, compared to the case where only the color filter was a conventional general filter, and the others were the same as in the embodiment, no decrease in luminance, ie, no decrease in light transmittance was observed.

In the above embodiment, the retardation was the same for the red (R) and green (G) colored layers 11-R and 11-G. By appropriately changing the value of the retardation between the colored layers, coloring can be almost completely eliminated.

Also, since it does not adjust the retardation of the liquid crystal layer 31 itself and does not add a new layer to the light transmission path, the transmittance of the backlight light,
That is, there is no reduction in light use efficiency.

Further, a colored layer is formed by a resin layer,
Since the difference in retardation value is provided only by changing the type of the resin material, the manufacturing process and cost are not increased, and the manufacturing can be performed reliably and easily. Further, there is no need to provide a difference in the thickness of the coloring layer, and the thickness of the liquid crystal layer can be kept uniform.

In the above embodiment, an acrylic resin and a polyimide resin were used. However, if an appropriate retardation and a difference between the values can be obtained and the resin has sufficient transparency, an arbitrary resin may be selected. It is also possible to use inorganic materials other than resins.

In the above embodiment, the retardation is changed by changing the kind of the resin in which the pigment is dispersed. However, in some cases, the thickness can be changed somewhat.

The retardation plate composed of discotic liquid crystal described above naturally includes a combination of a layer having positive optical characteristics and a discotic layer having negative optical characteristics. Further, as the retardation plate, various ones having optical compensation characteristics for enlarging the viewing angle, such as those composed of simply rod-shaped liquid crystal molecules, can be used.

In the above description, the liquid crystal display device has been described as a simple matrix drive type.
The same applies to an active matrix driving type having a switching element such as a TFT as long as it is a type using a TN liquid crystal. Further, the same applies to a liquid crystal display device of a reflection type.

The color filter may be provided on either side of the pair of transparent insulating substrates, and the color filter may be provided on one substrate and the black matrix may be provided on the other substrate.

[0047]

According to the present invention, there is provided a liquid crystal display device provided with a color filter which can prevent coloring in a high viewing angle region without lowering light use efficiency.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a basic configuration of a liquid crystal display device according to an example when attention is paid to optical anisotropy.

FIG. 2 is a longitudinal sectional view schematically showing a basic structure of the liquid crystal display device of the embodiment.

[Explanation of symbols]

Reference Signs List 10 liquid crystal display device 11 color filter 11-R red coloring layer made of acrylic resin (retardation 0.0055) 11-G green coloring layer made of acrylic resin (retardation 0.0055) 11-B blue coloring layer made of polyimide resin (retardation) 0.044) 12 Black matrix 31 Liquid crystal layer 41, 42 Phase difference plate

Claims (7)

[Claims] 1. A transparent insulating substrate comprising: a pair of transparent insulating substrates; a liquid crystal layer held therebetween; an alignment film formed on a surface of the transparent insulating substrate in contact with the liquid crystal layer; A color filter composed of a plurality of colored layers disposed on the color filter and sequentially assigning each color from the plurality of colors to each pixel constituting the display area; and a phase difference disposed on an outer surface of the pair of transparent insulating substrates. In a liquid crystal display device comprising a plate and a polarizing plate, the colored layer has a retardation based on optical anisotropy, and the colored layer of one color has a different retardation value from the colored layer of another color. Characteristic liquid crystal display device. 2. The method according to claim 1, wherein the plurality of colors include blue, and the colored layer of blue has a higher retardation value than the colored layers of any other colors. Liquid crystal display. 3. The method according to claim 1, wherein the plurality of colors are red, green, and blue, and a difference in retardation value is provided between the red coloring layer and the green coloring layer. Or 2
The liquid crystal display device as described in the above. 4. The liquid crystal display device according to claim 1, wherein said colored layer is made of a resin material, and said one colored layer is made of a resin material different from that of said other colored layer. 5. The liquid crystal display device according to claim 1, wherein said retardation plate has substantially negative uniaxiality. 6. The liquid crystal display device is of a simple matrix drive type, wherein a linear transparent electrode formed on one of the pair of transparent insulating substrates and a transparent electrode on the other transparent insulating substrate. 2. The liquid crystal display device according to claim 1, wherein each intersection with the formed linear electrode forms a display pixel. 7. The liquid crystal display device according to claim 1, wherein said liquid crystal display device is of an active matrix type.