JPH07261169A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal panel which is particularly excellent in contrast, has display characteristics of a wide visual field angle without deteriorating the display characteristics of the liquid crystal panel and is easily obtainable by providing this device with substrates, one of which has transparency, and providing the surfaces of the substrates with color filters, polarizing layer and pixel electrodes in this order. CONSTITUTION:At least one of the substrates 2 have transparency, and the color filters 10, the polarizing layer 8 and the pixel electrodes 6 are laminated thereon successively from the substrates 2. (The pixel electrodes, the color filters and the polarizing layer are laminated successively from the substrates as the production method). The device is, therefore, made into a structure in which the light polarized by the polarizing plate 7 (acting as a polarizer) on the incident side passes the polarizing layer 8 (acting as an analyzer) on the outlet side before passage through the layer 10 of the color filters. Then, the deterioration in the display characteristics of the liquid crystal panel including contrast does not arise even if a disturbance in polarizability is generated by the layer 10 of the color filters after passing through the polarizing layer 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device used for displays of so-called electronic devices such as computers, liquid crystal televisions, displays for car navigation systems, and the like.

[0002]

2. Description of the Related Art In recent years, display devices have been required to be space-saving and portable as display devices for personal computers, portable information terminals, and portable televisions. Under such circumstances, liquid crystal display devices have rapidly become popular as display devices in place of conventional CRTs because of the feature that they can be flat, and they are gaining momentum. Since the liquid crystal display device is originally a non-emissive device,
An external light source such as a backlight is required for displaying. And to perform color display on a liquid crystal display device,
A color filter method is generally used.

Now, an example of a conventional liquid crystal display device will be described with reference to FIG. FIG. 3 is a schematic sectional view of a conventional liquid crystal display device. As shown in FIG. 3, a pixel electrode 9 and an alignment film 3 are formed on a transparent substrate 1 typified by glass, and the alignment film 3 is subjected to an alignment treatment such as rubbing to align the liquid crystal. Has been done. On the other hand, color filters 10R, 10G, and 10B having R, G, and B color patterns are provided on the transparent substrate 2 on the opposite side, and a counter electrode 6 and an alignment film 4 are provided on the color filters 10R, 10G, 10B. Alignment treatment is carried out almost in the same manner as 3.

Here, in order to construct a liquid crystal display device, as shown in the figure, the transparent substrates 1 and 2 on which these electrodes are formed are made to face each other so that the electrodes face each other, and the liquid crystal 5 is placed between them. Encapsulate. The liquid crystal used at this time is usually TN (Twisted Nematic) liquid crystal or STN (Super
Twisted Nematic liquid crystal, which is set and controlled so that the liquid crystal molecules are twisted and aligned according to each liquid crystal mode in the range of 90 to 270 °. Hereinafter, the liquid crystal display device in this state will be referred to as a liquid crystal panel.

In order to perform display with such a liquid crystal panel, the optical shutter effect due to the electro-optical characteristics of liquid crystal is utilized. That is, generally, the polarizing plates 7 and 11 are provided on both outer sides of the liquid crystal panel, and the optical shutter effect is exhibited by using the change in the optical rotatory power of the liquid crystal due to the electric field.

By the way, in recent years, the performance of liquid crystal panels has been dramatically improved, and the fields of application thereof have been gradually expanded, so that high gradation display such as full color display typified by television image display has been required. ing. In order to meet this demand, it is important to make the display contrast (the ratio of the brightness of the non-display portion to that of the display portion) as large as possible.

Considering a high-quality display represented by, for example, a high-definition television, there is an urgent need to further improve the contrast particularly in a liquid crystal display device.
Generally, in the liquid crystal panel having the structure shown in (FIG. 3), incident light from a light source such as a backlight is linearly polarized by the polarizing plate 7, is incident on the liquid crystal 5, and is then twisted and aligned at 90 °. It is rotated 90 ° by 5. At this time, if the polarization axis of the polarizing plate 11 on the opposite side is set to form an angle of 90 ° with respect to the polarizing plate 7, the polarization axis of the light transmitted through the liquid crystal panel and the polarization axis of the polarizing plate 11 are aligned. Light is transmitted to match. On the other hand, when a voltage is applied to the electrodes of the liquid crystal panel, the liquid crystal 5 rises in parallel with the electric field, but at this time, since the above-mentioned optical rotatory power of light disappears, light is blocked by the polarizing plate 11 on the exit side. In addition, a combination of the directions of the polarizing plates 7 and 11,
The liquid crystal alignment is not limited to the above combination, and it is not contrary to the known art that other combinations can be applied. For example, if the polarization axes are aligned so as to be parallel to each other, the action of the optical shutter effect is reversed.

[0008]

If the contrast is defined as the ratio of the brightness of the light in the transmission state to the brightness of the light in the light blocking state, the value of the contrast becomes infinite in the ideal case. However, in practice, typical values for the contrast are between approximately 40 and 100. This is because the liquid crystal panel surface has leaked light in a reflected or shielded state. Therefore, in order to improve the contrast, it is important to reduce the leakage light in the light-shielded state. In a liquid crystal panel having a conventional structure, a material in which a pigment is dispersed in a polymer binder is used as a color filter layer, so that the polarization of incident light is disturbed at the pigment portion and an elliptically polarized light component is generated. The leakage light is generated, and as a result, the contrast of the liquid crystal panel is deteriorated, so that the deterioration of the contrast cannot be prevented. Further, in the conventional liquid crystal display device, the color filter and the polarizing plate are installed in such a manner that a glass substrate is sandwiched between them, and the thickness of the glass substrate is usually 1 m.
Since it is about m, it is impossible to make the distance between the color filter and the polarizing plate close to each other, so that the sharpness of the display is lost when the screen of the liquid crystal display device is viewed obliquely. The drawbacks are unavoidable, and it is a big problem to improve the display quality.

The present invention was created as a result of intensive studies to solve the above-mentioned problems of the conventional liquid crystal panel. The purpose of the present invention is that the contrast is higher than the conventional one and the viewing angle dependency is high. It is to be able to easily provide a small number of liquid crystal panels.

[0010]

Means provided by the present invention as means for solving the above-mentioned problems are as follows:
A liquid crystal is sandwiched between substrates on which a pair of electrodes are formed, and a deflecting layer is provided on both sides of a layer having the liquid crystal, and an electric field is applied through the electrodes to change the electro-optical characteristics of the liquid crystal. In a liquid crystal panel for displaying by this, at least one of the substrates is transparent, and a color filter, a polarizing layer, and electrodes are provided on the substrate in this order from the substrate. A characteristic liquid crystal panel. Further, as another means, the present invention provides that at least one of the substrates has transparency, and an electrode, a color filter, and a polarizing layer are laminated in this order on the substrate. The liquid crystal panel is characterized by being provided.

The present invention will be described in more detail below with reference to the drawings. FIG. 1 is a sectional view showing a liquid crystal panel of the present invention. Color filters 10R, 10 made of red, green, and blue are formed on a transparent substrate 2 such as glass or plastic.
G and 10B are installed. The material of the color filter at this time is a printing method, a photo-etching method, a photo-etching method in which R, G, and B pigments are dispersed in a polymer compound such as polyimide resin, acrylic resin, polyamide resin, or PVA resin. A known method such as a polymer method, an electrodeposition method, or an electrophotographic method is appropriately used to form a pixel pattern. Further, a black matrix is formed as a light-shielding pattern between each pixel by a known photolithography method from a thin film of a metal material such as Cr or photo black.

Next, the polarizing layer 8 is formed on the color filter layer, but before this, if necessary, the color filter layer 1 is formed.
The surface of 0 is flattened. As a treatment method, known means such as pressing, polishing, and formation of a flattening layer is used. As a method of forming the polarizing layer 8, a polymer film of poly (vinyl alcohol), polyimide, polyetherimide, polyamideimide, polyvinyl chloride or the like is applied and a rubbing treatment is performed. Here, the rubbing treatment is a treatment method of rubbing the polymer film in one direction with a rubbing cloth by a known means such as a rubbing device to form fine grooves on the polymer surface. At this time, since the rubbing direction defines the direction of the deflection axis, the rubbing direction is performed so as to have a predetermined angle with the alignment direction of the liquid crystal to be sealed thereafter. Next, the rubbed polymer film is coated or dipped with an aqueous solution of potassium iodide or a mixture of iodine and potassium iodide, or an aqueous solution in which a suitable dichroic dye such as disazo, trisazo, or dianisidine is dispersed. Thus, the polarizing layer 8 is formed. Further, if necessary, a protective film made of an inorganic material such as an organic polymer such as acrylic resin, urethane resin, or epoxy resin, silicon dioxide, alumina, or silicon nitride is appropriately provided on the polarizing layer 8.

Next, a thin film made of a transparent conductive material such as ITO (Indium-Thin-Oxide) and tin oxide is formed by a known means such as a sputtering method, and if necessary, photoetching and lift-off methods. And the like using the pixel electrode 6
To form. Further, an alignment film 4 made of polyimide for liquid crystal alignment is applied on this substrate, and an alignment treatment is performed by the rubbing method. At this time, the alignment direction is determined to be an appropriate direction in consideration of the display mode of the liquid crystal used and the polarization direction of the polarizing layer 8 formed below. On the other hand, the transparent conductive thin film described above is patterned as a counter substrate on a transparent substrate made of glass, a plastic film or the like to form a pixel electrode 9, and an alignment film 3 made of polyimide is applied thereon, and similarly rubbed or the like. Alignment treatment is performed by.

Next, the transparent substrates 1 and 2 are combined so that the pixel electrodes 9 and 6 face each other at a predetermined distance (generally 2 to 15 μm), and the liquid crystal 5 is interposed therebetween.
Is enclosed. The liquid crystal to be sealed at this time is generally a nematic liquid crystal, but is not limited to this. Finally, in this liquid crystal panel, a polarizing plate 7 is combined with the outside of the transparent substrate 1 to complete the liquid crystal panel.

Next, the liquid crystal panel according to claim 2 will be described with reference to FIG. FIG. 2 is a sectional view showing the outline of the liquid crystal panel of the present invention. ITO (Indium-Tin-Oxide) on transparent substrate 2 such as glass or plastic
A thin film having a transparent conductivity such as tin oxide is formed by a known method such as a sputtering method, and the pixel electrode 6 is formed by using a photoetching method, a lift-off method or the like, if necessary.

Further, color filters 10R, 10G, and 10B made of red, green, and blue are installed on this. The material of the color filter at this time is a printing method in which R, G, and B pigments are dispersed in polymer compounds such as polyimide resin, acrylic resin, polyamide resin, and PVA resin.
A pixel pattern is formed by appropriately using a known means such as a photoetching method, a photopolymer method, an electrodeposition method, and an electrophotography method. In addition, a black matrix 12 is provided between each pixel.
Are formed by photo black or a printing method.

Next, the polarizing layer 8 is formed on the color filter layer, but before this, if necessary, the color filter layer 1 is formed.
The surface of 0 is flattened. As a treatment method, known means such as pressing, polishing, and formation of a flattening layer is used. As a method of forming the polarizing layer 8, a polymer film of poly (vinyl alcohol), polyimide, polyetherimide, polyamideimide, polyvinyl chloride or the like is applied and a rubbing treatment is performed. It is desirable that the thickness of the organic polymer film is appropriately selected within the range of 100 nm to 10 μm. Here, the rubbing treatment is a treatment method of rubbing the polymer film in one direction with a rubbing cloth by a known means such as a rubbing device to form fine grooves on the polymer surface. At this time, since the rubbing direction defines the direction of the polarization axis, the rubbing direction is performed so as to have a predetermined angle with the alignment direction of the liquid crystal to be sealed thereafter.

Next, the rubbed polymer film is treated with an aqueous solution of potassium iodide or a mixture of iodine and potassium iodide, or an aqueous solution in which a suitable dichroic dye such as disazo, trisazo or dianisidine is dispersed. The polarizing layer 8 is formed by coating or dipping. Further, if necessary, a protective film 8 ′ made of an inorganic material such as an organic polymer such as acrylic resin, urethane resin, or epoxy resin, silicon dioxide, alumina, or silicon nitride is appropriately provided on the polarizing layer 8.

Next, an alignment film 4 made of polyimide for liquid crystal alignment is applied on this substrate, and an alignment treatment is performed by the rubbing method described above. At this time, the alignment direction is determined in consideration of the display mode of the liquid crystal used and the polarization direction of the polarizing layer 8 formed below. On the other hand, by patterning the transparent conductive thin film on a transparent substrate made of glass, plastic film or the like as a counter substrate, the pixel electrode 9
Is formed, an alignment film 3 made of polyimide is applied thereon, and similarly, an alignment treatment is performed by rubbing or the like.

Next, these transparent substrates 1 and 2 are combined so as to hold a predetermined interval (generally 2 to 15 μm) in which the pixel electrodes 9 and 6 face each other, and the liquid crystal 5 is interposed therebetween.
Is enclosed. The liquid crystal to be filled at this time is generally a nematic liquid crystal, but the technique disclosed by the present invention is not limited to this. Finally, in this liquid crystal panel, a polarizing plate 7 is combined with the outside of the transparent substrate 1 to complete the liquid crystal panel.

[0021]

According to the liquid crystal panel of the present invention, at least one of the substrates has transparency, and the color filter, the polarizing layer, and the pixel electrode are laminated on the substrate in this order (or alternatively, Since the pixel electrode, the color filter, and the polarizing layer are sequentially laminated from the substrate), the incident side polarizing plate (this polarizing plate functions as a so-called polarizer).
Since the light polarized by means of a structure that passes through the polarizing layer on the exit side (this polarizing layer acts as a so-called analyzer) before passing through the layer of the color filter, the layer of the color filter after passing through the polarizing layer. Even if the polarization is disturbed, the deterioration of display characteristics of the liquid crystal panel such as contrast does not occur.

[0022]

EXAMPLE An example of the present invention will be described with reference to FIG.

Example 1 A transparent substrate made of low alkali glass (7059 glass manufactured by Corning Co., Ltd.) was formed as a low reflection layer of a chromium oxide thin film to a thickness of 20 nm by a sputtering method, and then chromium was formed. Thin film 100n
It was laminated in a film thickness of m. Next, the pattern of the black matrix 12 was formed by the photo etching method.

Then, on the substrate, a color paste in which a red pigment is dispersed in a photopolymer mainly composed of an acrylic resin is applied by a spin coater, dried, and then exposed and developed by using a photomask to obtain a red color filter 10.
R was formed. The same process was repeated to form the green and blue color filter layers 10G and 10B to complete the color filter layer 10. After that, in order to flatten the color filter layer, the surface is polished so that the surface level difference is ± 0.2.
It was controlled to be not more than μm.

Next, a polyvinyl alcohol resin (manufactured by Fuji Yakuhin Kogyo Co., Ltd.) was applied onto the color filter layer by a spin coater and dried. At this time, the film thickness of the polyvinyl alcohol resin was about 1 μm. Next, the surface was rubbed by using a commercially available rubbing device. The rubbing cloth used at this time was made of nylon and had a bristle tip length of 1 mm. Next, this substrate is immersed in an aqueous solution of potassium iodide (0.5% by weight of iodine, 8% by weight of potassium iodide) to form a polarizing layer 8, and an acrylic resin is spin-coated thereon to a film thickness of 1 μm. To form a protective layer 8 '.

Next, an ITO film was formed on this substrate as a transparent electrode by using a sputtering device. At this time,
In order to form the ITO film in a predetermined pixel electrode pattern, a region other than the film forming portion was covered with a mask made of a thin metal plate, and then the film was formed to form the pixel electrode 6. The ITO film thickness here was about 100 nm, and the sheet resistance value of the film was about 30 Ω / □. Further, a polyimide film (trade name: LQT-120, manufactured by Nippon Synthetic Rubber Co., Ltd.) as an orientation material was applied on this substrate to a film thickness of about 90 nm, and then rubbing was performed using a rubbing device to perform orientation treatment. The alignment film 4 is formed. The orientation treatment direction at this time was set to a direction parallel to the polarization axis of the polarizing layer.

As the counter substrate, an active matrix element substrate composed of a TFT using amorphous Si as a semiconductor and a pixel electrode 9 connected to the TFT was manufactured by a semiconductor process on a transparent substrate 1 also composed of a low alkali glass substrate. The number of pixels at this time was 300 × 240 pixels, and the display area had a diagonal distance of about 6 cm. Further, polyimide was applied to this substrate as an alignment material and subjected to rubbing treatment to form an alignment film 3. The materials used at this time are the same as those described above. The rubbing direction at this time is 90 ° with the alignment direction of the color filter side substrate.
I went so as to make the angle.

Next, spacers are sprayed on these substrates so as to have a predetermined distance (generally referred to as a cell gap), and an epoxy resin sealing material (trade name: Struct Bond, Mitsui Toatsu Kagaku) is applied to the peripheral portion. (Manufactured by KK) was used for adhesion to prepare a liquid crystal cell. At this time, the cell gap was set to about 5 μm. Next, this liquid crystal cell was filled with a nematic liquid crystal 5 (trade name: ZLI-4792, manufactured by Merck Japan Co., Ltd.) from the filling port, and then the filling port was sealed with a sealing material to produce a liquid crystal panel. .

Finally, the polarizing plate 7 was attached on the outside counter substrate side of the liquid crystal panel so that the polarization axis of the polarizing plate 7 forms an angle of 90 ° with the alignment axis of the polarizing layer inside the liquid crystal panel. The liquid crystal panel was completed so that it would be in the Mari White mode. When the display test of the completed liquid crystal panel was performed and the brightness of the lit pixels and the non-lit pixels were measured to obtain the contrast, the contrast of the conventional liquid crystal panel was about 70. With the related liquid crystal panel, the contrast reaches about 150,
The display quality was remarkably improved.

<Embodiment 2> Another embodiment of the liquid crystal panel according to the present invention will be described with reference to FIG. Low-alkali glass (Corning 7059 glass)
An ITO film was formed into a film having a thickness of 200 nm on the transparent substrate 1 made of (4) by a sputtering method. The sheet resistance value at this time was 10 Ω / □. Next, the ITO film was patterned by photoetching to form the pixel electrode 6.

Next, a color paste in which a black pigment was dispersed was first applied to a photopolymer mainly composed of an acrylic resin by a spin coater, dried, and then exposed and developed using a photomask to form a black matrix 12. Then, in the same manner as above, the color filter layers of red 10R, green 10G, and blue 10B were formed by using the photosensitive color paste, and the color filter layer 10 was completed. Then, in order to flatten the color filter layer, the surface was polished to control the step difference of the surface to ± 0.2 μm or less.

Next, a polyvinyl alcohol resin (manufactured by Fuji Yakuhin Co., Ltd.) was applied on the color filter layer by a spin coater and dried. At this time, the film thickness of the polyvinyl alcohol resin was about 1 μm. Next, the surface was rubbed by a commercially available rubbing device. The rubbing cloth used at this time is made of nylon, and the length of the tips is 1 m.
m was used. Next, this substrate is immersed in an aqueous solution of potassium iodide (0.5% by weight of iodine, 8% by weight of potassium iodide) to form a polarizing layer 8, and a 1 μm thick acrylic resin film is further formed thereon by spin coating. It was applied thickly to form a protective layer 8 '.

Furthermore, a polyimide film (trade name: LQT-120, manufactured by Nippon Synthetic Rubber Co., Ltd.) as an orientation material on this substrate.
After coating a film having a thickness of about 90 nm, rubbing was performed using a rubbing device to form an alignment film 4. The orientation treatment direction at this time was set to a direction parallel to the polarization axis of the polarizing layer.

Next, as an opposing substrate, an active matrix element substrate having pixel electrodes 9 connected to the MIM element as a non-linear element was produced by a semiconductor process on the transparent substrate 1 made of low alkali glass. The number of pixels at this time was 300 × 200 pixels, and the display area was diagonally about 5 cm. Furthermore, polyimide was applied to this substrate as an alignment material, and a rubbing treatment was performed to form an alignment film 3. The materials used at this time are the same as those described above. The rubbing direction at this time was 90 ° with respect to the alignment direction of the color filter side substrate.

Next, spacers are spread over these substrates so as to have a constant space (called a cell gap), and an epoxy resin-based sealing material (trade name: struct bond,
A liquid crystal cell was produced by bonding with Mitsui Toatsu Chemical Co., Ltd. At this time, the distance between the substrates was set to about 5 μm. Next, the nematic liquid crystal 5 (trade name Z
LI-4792, manufactured by Merck Japan Co., Ltd. was sealed, and then the sealing port was sealed with a sealing material to produce a liquid crystal panel. Finally, the polarizing axis of the polarizing plate on the outer counter substrate side of this liquid crystal panel is set to 9 ° with respect to the alignment axis of the polarizing layer inside the liquid crystal panel.
The liquid crystal panel was completed by sticking it so as to form an angle of 0 ° and setting it in a normally white mode.

A display test of the completed liquid crystal panel is conducted,
When the contrast was obtained by measuring the brightness of the lit pixels and the non-lit pixels, the contrast was about 5 in the conventional liquid crystal panel.
While the contrast was 0, the contrast of the liquid crystal panel of the present invention reached about 80, and the display quality was remarkably improved.

[0037]

According to the liquid crystal panel of the present invention, at least one has a transparent substrate, and the color filter, the polarizing layer, and the pixel electrode are provided on the substrate in this order, or alternatively, as a pixel. Since the electrodes, the color filter, and the polarizing layer are provided in this order, the light polarized by the polarizing plate (polarizer) on the incident side, before passing through the color filter layer, the polarizing layer (analyzer) on the outlet side. Since it has a structure that passes through, even if the polarization property is disturbed in the color filter layer thereafter, it does not cause deterioration of display characteristics of the liquid crystal panel such as contrast, and further Since the distance is short, the viewing angle dependence can be reduced. In other words, as a result, it was possible to provide a liquid crystal panel which is particularly excellent in contrast, has a wide viewing angle display characteristic, and is easily obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an outline of an embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a sectional view showing the outline of another embodiment of the liquid crystal display device according to the present invention.

FIG. 3 is a cross-sectional view schematically showing an example of a liquid crystal display device according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transparent substrate 2 ... Transparent substrate 3 ... Alignment film 4 ... Alignment film 5 ... Liquid crystal 6 ... Pixel electrode 7 ... Polarizing plate 8 ... Polarizing layer 8 '. -Protective layer 9 ... Pixel electrode 10R-Red color filter layer 10G-Green color filter layer 10B-Blue color filter layer 11 ... Polarizing plate 12 ... Black matrix (light-shielding pattern)

Claims (2)

[Claims] 1. A liquid crystal is sandwiched between a pair of substrates on which electrodes are formed, and a polarizing layer is provided on both sides of a layer composed of the liquid crystal. In a liquid crystal display device that performs display by changing electro-optical characteristics, at least one of the substrates has transparency, and a color filter, a polarizing layer, and an electrode are provided in this order on the substrate. Characteristic liquid crystal display device. 2. A liquid crystal is sandwiched between a pair of substrates on which electrodes are formed, a polarizing layer is provided on both sides of a layer made of the liquid crystal, and an electric field is applied using the electrodes to form a liquid crystal. In a liquid crystal display device that performs display by changing the electro-optical characteristics, at least one of the substrates has transparency, and an electrode, a color filter, and a polarizing layer are provided in this order on the substrate. Liquid crystal display device characterized by.