JPH08292425A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To solve the problem of the degradation in contrast while maintaining an effect of lessening the degradation of display on visual angles by providing a liquid crystal display device with a light scattering layer within a liquid crystal display panel and adequately selecting the positions where color filter layers are disposed. CONSTITUTION: This liquid crystal display device is formed by interposing a TN type liquid crystal layer 34 between a glass substrate 21 successively laminated and formed with the color filter layers 23, the light scattering layer 25 and a polarizing plate layer 26 and an ITO layer 28 and a TFT substrate 30 having an ITO layer 31 and a polarizing plate layer 33.

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 having reduced viewing angle dependence of display.

At present, liquid crystal display devices are strongly required to have high definition and large screen. Therefore, it is necessary to improve display quality. As a part thereof, the viewing angle characteristics are improved or the light utilization efficiency is improved. Improvements need to be made and the present invention can address them.

[0003]

2. Description of the Related Art In order to improve viewing angle characteristics in a liquid crystal display device, twisted nematic (twisted) is used.
There is known a liquid crystal display device in which the alignment of nematic (TN) type liquid crystal is changed within a pixel (if necessary, JP-A-63-106624, JP-A-4-212928, and JP-A-5-27242). See the bulletin, etc.).

FIG. 7 is a perspective view of a principal part for explaining the liquid crystal display panel disclosed in Japanese Patent Laid-Open No. 63-106624.

In the figure, 3 and 4 are glass substrates having an alignment film on the liquid crystal surface side, and the arrow shown in the figure indicates the direction of the rubbing treatment. In each of the glass substrates 3 and 4, It can be seen that the rubbing process is performed in the opposite directions in the areas 1 and 2.

By adopting the above-mentioned means, it is said that the change in electro-optical characteristics depending on the viewing angle of the liquid crystal display device is reduced and a good display can be obtained in a wide field of view.

However, even in the conventional liquid crystal display device described with reference to FIG. 7, when the display is viewed at a position at a large angle from the direction normal to the display surface, the contrast is lowered or the display is inverted. Was.

FIG. 8 is a side view for explaining a liquid crystal display device disclosed in Japanese Patent Laid-Open No. 4-212928. Incidentally, (A) shows the state where the display is "bright", and (B) shows the state where the display is "dark".

In the figure, 11 and 12 are glass substrates, 13 is a polymer resin, 14 is a liquid crystal material, and 15 and 1.
6 is a polarizing plate arranged orthogonally, 17 is a power source, and 18 is a switch.

As is clear from the figure, the structure of the liquid crystal display device shown in FIG.
Is composed of a polymer-dispersed liquid crystal panel and a pair of polarizing plates 15 and 16 in which liquid crystals are dispersed in the form of droplets.

When no voltage is applied to the liquid crystal display panel, a light-transmitting plate transmission component is generated due to the depolarization property of the liquid crystal,
The display becomes "bright", and when voltage is applied, the linearly polarized light reaches the polarizing plate as it is, all the light is absorbed, and the display becomes "dark".
It is said to have achieved 0 degrees.

However, in the conventional liquid crystal display device described with reference to FIG. 8, since the absorption axis of the polarizing plate is apparently deviated, the viewing angle dependence characteristic is essentially generated. That is, light leakage is seen depending on the viewing angle, and the contrast is reduced.

In addition to the above, as a means for reducing the viewing angle dependence of display, light transmitted through a liquid crystal display panel is first projected on a scattering plate, and display is performed according to the scattered light.

The display by the method using the scattered light is apt to cause "bleeding" in the periphery, and in order to avoid this, a light source whose light flux is perfectly controlled, that is, parallel light is required, and therefore, the optical There is a problem that the system becomes complicated, a large space is required for the optical system, and the light incident from the front surface is backscattered (scattered on the front surface) to lower the contrast.

In order to solve this problem, there is known an invention in which a light scattering layer is provided in a liquid crystal display panel to perform projection (if necessary, see JP-A-4-81816).

[0016]

[Patent Document 1] Japanese Patent Laid-Open No. 4-81816
In the invention disclosed in Japanese Patent Laid-Open Publication No. 2004-242242, in which a light scattering layer is provided in a liquid crystal display panel for projection, a color filter is disposed after the light scattering layer, and therefore, there is a drawback that the contrast is easily deteriorated by external light. is there.

According to the present invention, by providing a light scattering layer in the liquid crystal display panel and appropriately selecting the arrangement position of the color filter layer, the contrast of the display is reduced while maintaining the effect of reducing the viewing angle dependence of the display. Eliminate the problem of deterioration.

[0018]

In the present invention, a light scattering layer is arranged in a liquid crystal display panel and a color filter layer is arranged in front of the light scattering layer.

That is, in the liquid crystal display device according to the present invention, (1) at least a color filter layer (eg color filter layer 23) and a light scattering layer (eg light scattering layer 2)
5), a transparent insulating substrate (for example, glass substrate 21) in which a polarizing plate layer (for example, polarizing plate layer 26) and a driving transparent electrode layer (for example, ITO layer 28) are sequentially stacked, and at least a driving transparent electrode (for example, ITO). TFT substrate (eg TF) having layer 31) and polarizing plate layer (eg polarizing plate layer 33)
A liquid crystal layer (for example, a TN type liquid crystal layer 3) between the T substrate 30 and
4) is interposed, or

(2) In the above (1), the light scattering layer is also used as a color filter layer having a light scattering property (for example, a color filter layer in which a white pigment such as MgO is dispersed). Or

(3) In the above (1), the light scattering layer is a polymer dispersion type liquid crystal layer (for example, the polymer dispersion type liquid crystal layer 5).
2), or

(4) In (1), (2), or (3), the light scattering layer corresponding to each pixel of the color filter layer or each pixel of the color filter layer is surrounded by adjacent pixels. A light-blocking wall (for example, a light-blocking wall 41) that blocks scattered light is formed, or

(5) In (1) or (2) or (3) or (4) above, a passivation layer (for example, passivation layer 27) is interposed between the polarizing plate layer and the driving transparent electrode layer. It is characterized by

[0024]

By adopting the above means, the effect of reducing the viewing angle dependence of the display by the light scattering layer can be enjoyed as in the conventional case.
Moreover, since the color filter layer is arranged on the front side of the light scattering layer, light incident from the front side of the liquid crystal display panel is transmitted through the color filter layer and then scattered to the front side.
Therefore, most of the scattered light is absorbed by the color filter layer, and as a result, the reduction in contrast is suppressed. Further, since the liquid crystal layer for switching light and the light scattering layer are relatively close to each other, it is possible to realize a display with less "bleeding" even if the light source is not a parallel light beam.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a side sectional view showing an essential part of a liquid crystal display device for explaining a first embodiment of the present invention.

In the figure, 21 is a glass substrate, 22 is a black matrix, 23R is a red color filter layer, 23G is a green color filter layer, 23B is a blue color filter layer, and 23 is a red color filter layer. 23
R and green color filter layer 23G and blue color
A color filter layer composed of the filter layer 23B, 24 is a flattening layer, 25 is a light scattering layer, 26 is a polarizing layer, 27 is a passivation layer, 28 is ITO (indium ti).
(n oxide) layer, 29 is an alignment film layer, and 30 is a TFT
(Thin film transistor) substrate,
31 is an ITO layer, 32 is an alignment film layer, 33 is a polarizing plate layer, 3
Reference numeral 4 denotes a TN type liquid crystal layer, and 35 denotes a directional backlight.

2 to 4 are side sectional views showing the main part of the liquid crystal display device in the process steps for explaining the process of manufacturing the first embodiment shown in FIG. It will be explained with reference to the figure. In each drawing, the same symbols as those used in FIG. 1 represent the same parts or have the same meanings.

2 (A). 2- (1) A Cr film having a thickness of, for example, 0.1 [μm] is formed on the glass substrate 21 by applying the sputtering method.

2- (2) Resist process in lithography technology, and
By applying a wet etching method using an etchant as an aqueous solution of ceric ammonium nitrate,
The black film 22 is formed by etching the Cr film formed in the step 2- (1).

2- (3) By applying the spin coating method, an ultraviolet curable resin film having a thickness of, for example, 1.5 [μm] in which a red pigment is dispersed is formed on the entire surface.

2- (4) Exposure to ultraviolet rays is carried out through a mask to carry out the step 2
-Selective curing of the red ultraviolet curing resin film formed in (3) is performed.

2- (5) The red color filter layer 23R is obtained by immersing in an alkaline developing solution and removing the uncured ultraviolet curable resin film.

2- (6) The pigment dispersed in the UV-curable resin film is changed to green or blue, and the steps 2- (3) to 2- (5) are repeated to repeat the green color filter 23G and the blue color filter.
The filter 23B is formed. The thickness of these may be 1.5 [μm] as in the red color filter 23R. In addition, the color filter layers of the respective colors are collectively referred to as a color filter layer 23.

2- (7) A transparent thermosetting resin film having a thickness of, for example, 1.5 [μm] is formed by applying the spin coating method.

2- (8) A heat treatment for thermosetting the thermosetting resin film formed in the step 2- (7) is performed. The thermosetting resin film after the heat treatment is the flattening layer 24.

See FIG. 2B. 2- (9) By applying the spin coating method, an ultraviolet curable resin film having a thickness of, for example, 10 [μm] in which a white pigment such as MgO is dispersed is formed on the entire surface. Form.

2- (10) Exposure to ultraviolet rays is performed to cure the white ultraviolet curable resin film formed in the step 2- (9) to form the light scattering layer 25.

See FIG. 3 (A) 3- (1) Stretching to adsorb iodine allows the thickness to be, for example, about 20 [μm].
Polyvinyl alcohol (polyvinyl)
A thin film of alcohol (PVA) is adhered on the light scattering layer 25 to form a polarizing plate layer 26.

See FIG. 3B. 3- (2) By applying the spin coating method, a passivation film 27 made of an acrylate prepolymer having a thickness of 3 [μm] is formed on the entire surface. The passivation film 27 plays a role of protecting the polarizing plate layer 26 made of a PVA thin film.

See FIG. 4 4- (1) By applying the low temperature sputtering method, an ITO layer 28 having a thickness of, for example, 0.1 [μm] is formed on the entire surface.
Here, the reason for applying the low temperature sputtering method to the formation of the ITO layer 28 is that the heat resistance of the polarizing plate layer 26 made of a PVA thin film is low.

4- (2) After a horizontal aligning agent of polyimide is applied on the ITO layer 28, rubbing is performed to form an alignment film layer 29.

The first substrate obtained through the above steps is bonded to the second substrate having the TFT matrix array obtained through another step, and the TN type liquid crystal layer 34 is provided between the substrates. Is enclosed and the liquid crystal display panel is completed.

The second substrate is a TFT substrate 30 on which a TFT matrix array is formed, on which an ITO layer 31, an alignment film layer 32, and a polarizing plate layer 33 are formed. The technique for manufacturing the first substrate is used. It can be applied and manufactured.

As is apparent from FIG. 1, in this embodiment,
The color filter layer 23 is a front surface of the light scattering layer 25, that is,
Since it is arranged on the outer side, the contrast can be maintained high, and of course, the effect of using the light scattering layer can be sufficiently maintained, and the viewing angle dependence of the display is hardly present.
The directional backlight 3 used in this embodiment is used.
5 is effective in reducing "bleeding" in the display.

FIG. 5 is a side sectional view showing a main part of a liquid crystal display device for explaining a second embodiment of the present invention.
The same symbols as those used in FIG. 4 represent the same parts or have the same meanings.

In the figure, reference numeral 41 designates a light shielding wall made of an ultraviolet curable resin colored black.

When manufacturing the liquid crystal display device of this embodiment,
Since the points relating to the formation of the light shielding wall 41 and the light scattering layer 25 are different from the first embodiment, only those points will be described next.

To form the light shielding wall 41, the spin coating method is applied after the color filter layer 23 is formed and before the light scattering layer 25 is formed. Is formed on the entire surface with an ultraviolet curable resin film of 10 [μm] colored in black.

Next, ultraviolet rays are applied to the black-colored ultraviolet curable resin film through a mask formed so that ultraviolet rays are irradiated between the pixels, and patterning is performed to form the light shielding wall 41. Since the light blocking wall 41 is formed thicker than the color filter layer 23, a recess surrounded by the light blocking wall 41 is formed on the surface of the color filter layer 23.

Next, by applying a spin coating method, an ultraviolet curable resin in which a white pigment such as MgO is dispersed is coated so as to fill the recess surrounded by the light shielding wall 41, and an exposure by ultraviolet light is performed. Then, the white UV curable resin film is cured to form the light scattering layer 25.

FIG. 6 is a side sectional view showing a main part of a liquid crystal display device for explaining a third embodiment of the present invention.
The same symbols as those used in FIG. 4 represent the same parts or have the same meanings.

In the figure, 51 is an ITO layer, 52 is a polymer dispersion type liquid crystal layer, and 53 is an ITO layer.

In the present embodiment, the ITO dispersion layers 51 and 53 sandwich the polymer dispersion type liquid crystal layer 52 to act as a light scattering layer, and the light distribution depends on the electric field applied to the polymer dispersion type liquid crystal layer 52. It is possible to control the scattering intensity, and thus it is possible to adjust the directivity of the display brightness with the electric field.

The polymer-dispersed liquid crystal layer 52 in the third embodiment is known in the art, for example, JP-A-58-501631.
It can be easily manufactured by applying the technique disclosed in the publication.

The present invention is not limited to the above embodiments, and many other modifications can be realized. For example, by dispersing a white pigment such as MgO in the color filter layer 23. It is also possible to play a role of light scattering. In this case, the effect of absorbing the light incident from the front surface by the color filter layer 23 is reduced, but the manufacturing process is simplified.

[0056]

In the liquid crystal display device according to the present invention,
A liquid crystal layer is provided between a transparent insulating substrate in which at least a color filter layer, a light scattering layer, a polarizing plate layer, and a driving transparent electrode layer are laminated in order, and a TFT substrate having at least a driving transparent electrode and a polarizing plate layer. Intervene.

By adopting the above structure, the effect of reducing the viewing angle dependence of the display by the light scattering layer can be enjoyed as in the conventional case, and further, the color filter layer is disposed on the front side of the light scattering layer. Since the light incident from the front surface of the liquid crystal display panel is transmitted through the color filter layer and then scattered to the front surface, most of the scattered light is absorbed by the color filter layer, resulting in a decrease in contrast. Be deterred.
Further, since the liquid crystal layer for switching light and the light scattering layer are relatively close to each other, it is possible to realize a display with less "bleeding" even if the light source is not a parallel light beam.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a main part of a liquid crystal display device for explaining a first embodiment of the present invention.

FIG. 2 is a side sectional view showing an essential part of a liquid crystal display device at a process step for explaining a process of manufacturing the first embodiment shown in FIG.

FIG. 3 is a side sectional view showing a main part of a liquid crystal display device at a process step for explaining a process of manufacturing the first embodiment shown in FIG.

FIG. 4 is a side sectional view showing an essential part of a liquid crystal display device at a process step for explaining a process of manufacturing the first embodiment shown in FIG.

FIG. 5 is a side sectional view showing a main part of a liquid crystal display device for explaining a second embodiment of the present invention.

FIG. 6 is a side sectional view showing a main part of a liquid crystal display device for explaining a third embodiment of the present invention.

FIG. 7 is a perspective view of a main portion for explaining the liquid crystal display panel disclosed in Japanese Patent Laid-Open No. 63-106624.

FIG. 8 is a side view of a main part for explaining the liquid crystal display device disclosed in Japanese Patent Laid-Open No. 4-212928.

[Explanation of symbols]

 21 glass substrate 22 black matrix 23R red color filter layer 23G green color filter layer 23B blue color filter layer 23 color filter layer 24 planarizing layer 25 light scattering layer 26 polarizing plate layer 27 passivation layer 28 ITO layer 29 orientation Film layer 30 TFT substrate 31 ITO layer 32 Alignment film layer 33 Polarizing layer 34 TN type liquid crystal layer 35 Directional backlight 41 Light shielding wall 51 ITO layer 52 Polymer dispersion type liquid crystal layer 53 ITO layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazutaka Hanaoka 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Hideaki Tsuda 1015, Kamedotachu, Nakahara-ku, Kawasaki, Kanagawa Prefecture Fujitsu Limited ( 72) Inventor Hideo Senda 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa, Fujitsu Limited

Claims (5)

[Claims] 1. A transparent insulating substrate in which at least a color filter layer, a light scattering layer, a polarizing plate layer and a driving transparent electrode layer are laminated in order, and a TFT substrate having at least a driving transparent electrode and a polarizing plate layer. A liquid crystal display device having a liquid crystal layer interposed therebetween. 2. The liquid crystal display device according to claim 1, wherein the light scattering layer also serves as a color filter layer having a light scattering property. 3. The liquid crystal display device according to claim 1, wherein the light-scattering layer comprises a polymer-dispersed liquid crystal layer. 4. A light-scattering layer corresponding to each pixel of the color filter layer or a light-shielding wall for shielding scattered light from an adjacent pixel is formed around each pixel of the color filter layer. The liquid crystal display device according to claim 1, 2 or 3. 5. The liquid crystal display device according to claim 1, wherein a passivation layer is interposed between the polarizing plate layer and the driving transparent electrode layer.