JPH09185058A - Liquid crystal display device and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device with which the improvement in its visual field angle characteristic is possible by orienting the liquid crystal parts corresponding to plural regions varying in imidization rates at different pretilt angles meeting the imidization rates. SOLUTION: This liquid crystal display device has liquid crystals 4 and polyimide oriented films 7, 8 for orienting these liquid crystals 4. The polyimide oriented films 7, 8 have the plural regions varying in the imidization rates and the liquid crystal parts corresponding to the respective regions are thereby oriented at the pretilt angles varying in accordance with the imidization rates. The threshold voltage for driving the liquid crystals 4 is varied by varying these pretilt angles, by which the changing of the visual field angle is made possible. The regions having the different visual field angles may, therefore, be arranged over the entire part of the display region. Then, the regions having the different preferential visual field angles are formable within one pixel by forming the plural regions varying in the imidization rates within the pixel.

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 and a manufacturing method thereof, and more particularly to a structure of a liquid crystal display device having a viewing angle improved by changing a pretilt angle of liquid crystal and a manufacturing method thereof. It is a thing.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal display device, a TN has been used.
Type liquid crystal display devices, such as liquid crystal display devices of STN type, STN type liquid crystal display device, and liquid crystal display device using ferroelectric liquid crystal, are known, and a driving method of the liquid crystal display device is also a simple matrix type liquid crystal display device. , And active matrix type liquid crystal display devices are known.

In these liquid crystal display devices, in general,
The liquid crystal is sandwiched and held between a pair of substrates, and an alignment film for aligning the liquid crystal is provided inside the substrate. With such an alignment film, liquid crystal molecules are aligned so as to have a constant pretilt angle.

In the conventional liquid crystal display device, the entire display area is set to have substantially the same pretilt angle, so that the angle at which the display contents can be clearly observed is limited and the so-called viewing angle is narrow. there were.

An object of the present invention is to provide a liquid crystal display device capable of improving viewing angle characteristics and a manufacturing method thereof.

[0006]

A liquid crystal display device according to a first aspect of the present invention includes a liquid crystal and a polyimide alignment film for aligning the liquid crystal, and the polyimide alignment film has a plurality of regions having different imidization ratios. Therefore, the liquid crystal portion corresponding to each region is aligned with different pretilt angles according to the imidization ratio.

In the first aspect, it is preferable that a plurality of regions having different imidization ratios of the polyimide alignment film be formed in each pixel. According to the first aspect, by varying the imidization ratio of the polyimide alignment film, the pretilt angle of the liquid crystal is changed according to the imidization ratio. In a liquid crystal display device, mutual dependence is recognized between the pretilt angle of liquid crystal molecules and the threshold voltage for driving the liquid crystal. Therefore, by changing the pretilt angle, it is possible to change the threshold voltage for driving the liquid crystal and change the viewing angle. Therefore, regions having different viewing angles can be arranged in the entire display region. By forming a plurality of regions having different imidization ratios within a pixel, regions having different preferential viewing angles can be formed within one pixel.

A manufacturing method according to a second aspect of the present invention is a method capable of manufacturing the liquid crystal display device according to the first aspect of the present invention. A manufacturing method according to the second aspect is a manufacturing method of a liquid crystal display device having a polyimide alignment film for aligning liquid crystals, which includes a step of forming a polyimide alignment film, a step of prebaking the polyimide alignment film, and a polyimide alignment film. And irradiating it with a laser to change the imidization ratio of the irradiation region.

As the polyimide alignment film, polyamic acid and soluble polyimide are usually used as starting materials. Polyamic acid is a compound that becomes a polyimide compound by heating to increase the imidization ratio. Soluble polyimide is a polyimide compound that is not partially imidized, and is soluble only in a specific solvent. Therefore, by forming a polyimide alignment film using such a polyamic acid or soluble polyimide and irradiating the polyimide alignment film with a laser, the imidization ratio of the irradiation region can be changed. Therefore, by irradiating only a specific region with laser, the imidization ratio of the irradiation region can be changed, and a plurality of regions having different imidization ratios can be formed in the polyimide alignment film.

Since the polyamic acid used in the present invention originally has a low imidization ratio (about 50% or less), the imidization ratio can be greatly changed. Further, since the soluble polyimide used in the present invention originally has a higher imidization ratio than polyamic acid (about 50% or more), a polyimide alignment film having a high imidization ratio can be obtained by a slight heat treatment.

In this aspect, the prebaking temperature is 50.
-150 degreeC is preferable, More preferably, it is 100-15.
0 ° C. By prebaking, the polyimide alignment film can reach a predetermined imidization ratio.

The prebaking may be performed by laser irradiation. By performing the pre-baking by the laser irradiation, it becomes possible to continuously perform the laser irradiation for changing the imidization ratio after the pre-baking.

The imidization ratio can be changed by increasing the imidization ratio or decreasing the imidization ratio by appropriately selecting the wavelength or energy density of the laser used.

The wavelength of the laser irradiated to increase the imidization ratio is preferably 400 nm or more.
If the wavelength is shorter than this, polymer bonds such as polyimide bonds in the polyimide alignment film may be broken or the alignment film itself may be broken, as described later. The energy density is preferably 0.01 to 1 J / cm ² ,
More preferably, it is 0.01 to 0.1 J / cm ² .

The wavelength of the laser irradiated to reduce the imidization ratio is preferably 300 to 400 nm.
If the wavelength is less than 300 nm, the alignment film itself may be easily broken, and the performance of aligning the liquid crystal may be deteriorated. If the wavelength is longer than 400 nm, the bonds such as imide bonds in the alignment film may not be sufficiently broken, and the imidization ratio may not be sufficiently reduced. The energy density is preferably 1~90mJ / cm ^2, more preferably 30~70mJ / cm ^2.

The manufacturing method according to the third aspect of the present invention is a method of manufacturing a liquid crystal display device having a polyimide alignment film for aligning liquid crystals, and forms a film of polyamic acid as a precursor of the polyimide alignment film. The method includes a step, a step of prebaking the polyamic acid film by heat treatment to imidize it, and a step of irradiating a part of the imidized film with a laser to increase the imidization rate of the irradiation region. The temperature of the heat treatment for heating the polyamic acid to imidize it is preferably about 100 to 150 ° C.

Further, the wavelength of the laser to be irradiated to increase the imidization ratio is preferably 400 nm or more. If the wavelength of the laser is shorter than this, the bond in the film may be broken or the film may be broken. The energy density is 0.01 to 1 J / cm ^2.
Is preferred, and 0.01 to 0.1 J / cm ² is more preferred. The heat treatment of the polyamic acid film is not particularly limited, and the heat treatment may be performed by laser irradiation, for example.

A manufacturing method according to a fourth aspect of the present invention is a method of manufacturing a liquid crystal display device having a polyimide alignment film for aligning liquid crystals, which comprises a step of forming a polyimide alignment film and a part of the polyimide alignment film. Laser irradiation to reduce the imidization ratio of the irradiation region.

As the polyimide alignment film used in the fourth aspect, a polyamic acid and a soluble polyimide can be used as in the second aspect. Therefore, after the polyimide alignment film is formed, it may be pre-baked and then irradiated with laser to reduce the imidization ratio of the irradiation region.

A liquid crystal display device according to a fifth aspect of the present invention comprises a liquid crystal and a photosensitive polymer alignment film for aligning the liquid crystal, and the photosensitive polymer alignment film has a plurality of regions having different degrees of polymerization. Thus, the liquid crystal portions corresponding to the respective regions are aligned with different pretilt angles according to the degree of polymerization.

As the photosensitive polymer alignment film, a negative or positive photosensitive polymer used in photolithography or the like can be used. By varying the degree of polymerization of such a photosensitive polymer alignment film, it is possible to align the liquid crystal with different pretilt angles according to the degree of polymerization, forming regions with different pretilt angles, thereby improving the viewing angle. can do.

According to the fifth aspect, the photosensitive polymer alignment film is used as the alignment film and the degree of polymerization of the photosensitive polymer alignment film is changed without changing the pixel structure of the liquid crystal display device. The liquid crystal can be aligned with different pretilt angles. Therefore, the viewing angle can be improved more easily than the conventional method of dividing the pixels.

A manufacturing method according to a sixth aspect of the present invention is a method capable of manufacturing the liquid crystal display device according to the fifth aspect of the present invention, which comprises a step of forming a photosensitive polymer alignment film, and a photosensitive layer. And irradiating the functional polymer alignment film with ultraviolet rays to change the degree of polymerization in the irradiated region.

By irradiating a part of the photosensitive polymer alignment film with ultraviolet rays and changing the degree of polymerization only in the irradiated region, a plurality of regions having different degrees of polymerization can be formed in the photosensitive polymer alignment film. . It is preferable that a plurality of regions having different degrees of polymerization are formed in each pixel.

Further, in the sixth aspect, it is preferable that the photosensitive polymer alignment film is subjected to a development treatment after being irradiated with ultraviolet rays. By carrying out the development treatment in this way, the surface shape such as the surface roughness can be made different according to the degree of polymerization, whereby regions having different pretilt angles can be formed.

A liquid crystal display device according to a seventh aspect of the present invention includes a liquid crystal and an alignment film for aligning the liquid crystal,
An uneven shape is formed on the surface of the alignment film, whereby the liquid crystal is aligned at different pretilt angles according to the uneven shape. The pretilt angle of the liquid crystal is also affected by the uneven shape of the alignment film as described above.

As a method for forming unevenness on the surface of the alignment film, there is a method of dispersing fine particles in the alignment film. According to such a method, an uneven shape is formed on the surface of the alignment film along the shape of the fine particles. Regarding the particle size of the particles, particles having a substantially uniform particle size may be used, or particles having different particle sizes may be mixed to have a wide particle size distribution. According to this method, the pretilt angle can be easily changed by changing the particle size of the fine particles added to the alignment film without changing the pixel structure of the liquid crystal display device.

Further, as the alignment film, a porous alignment film may be formed, and the alignment film may have unevenness on the surface. In such a case, it may be in a state in which liquid crystal molecules have entered the inside of the hole formed on the surface in contact with the liquid crystal.

It is also possible to provide a base layer below the alignment film, form a concavo-convex shape on the surface of the base layer, and form a concavo-convex shape that reflects the surface shape of the base layer on the surface of the alignment film. Examples of such an underlayer include an auxiliary capacitance electrode, an insulating film, and a transparent electrode provided on the surface of the substrate or above the substrate.

Further, the uneven shape formed on the surface of the alignment film is
An uneven shape having a tapered convex portion may be used. When reflecting the uneven shape of the underlayer on the uneven shape of the alignment film,
By making the uneven shape of the underlying layer an uneven shape having a tapered convex portion, the uneven shape of the surface of the alignment film can be made an uneven shape having a tapered convex portion.

A liquid crystal display device according to an eighth aspect of the present invention includes a liquid crystal and an alignment film for aligning the liquid crystal,
On the surface of the alignment film, there are formed a plurality of groove regions formed by arranging grooves having different groove shapes and / or groove forming directions. The liquid crystal portion corresponding to each groove region is different. Oriented with a pretilt angle.

In the eighth aspect, the pretilt angle of the liquid crystal is changed by changing the groove shape or the groove forming direction. In the eighth aspect, depending on the shape of the groove formed on the surface of the alignment film, that is, the groove depth, the groove width and the groove pitch, and the groove forming direction, the pretilt angle of the liquid crystal introduced onto the groove is determined. Take advantage of different things,
The liquid crystal parts corresponding to the respective groove regions are aligned with different pretilt angles.

Also in the eighth aspect, it is possible to form a groove region in the underlying layer provided below the alignment film and thereby form a groove region on the surface of the alignment film that reflects the shape of the groove region of the underlying layer. it can.

As such an underlayer, a substrate surface, an auxiliary capacitance electrode, an insulating film, a transparent electrode or the like can be similarly mentioned. In the present invention, the imidization ratio can be quantitatively calculated by measuring an IR spectrum and using the following formula.

[0035]

[Equation 1]

Therefore, in the above calculation formula, the imidation rate is calculated by setting the imidation rate as 100% for the one heat-treated at 295 ° C. Further, the present invention includes the following technical contents.

(1) In a liquid crystal display device having an alignment film for aligning liquid crystals, the pretilt angle in at least one liquid crystal region among a plurality of liquid crystal regions on the alignment film is the same as the pretilt angle in another liquid crystal region. A liquid crystal display device characterized by being different.

(2) The alignment film is composed of a polyimide alignment film having a plurality of regions having different imidization ratios, and the plurality of liquid crystal regions having different pretilt angles have different imidization ratios of the alignment film. The liquid crystal display device according to (1) above, which is formed so as to correspond to a plurality of regions.

(3) The above-mentioned (2), wherein at least one of the pair of alignment films arranged so as to face each other with the liquid crystal layer interposed therebetween has the plurality of regions having different imidization ratios. Liquid crystal display device.

(4) The pair of the alignment films is characterized in that a plurality of regions having different imidization ratios are formed at positions symmetrical to each other with the liquid crystal layer sandwiched therebetween. Liquid crystal display device.

(5) A method of manufacturing a liquid crystal display device having an alignment film for aligning a liquid crystal, wherein the imidization ratio is partially changed after the polyimide alignment film is formed. Manufacturing method of display device.

(6) The method for producing a liquid crystal display device according to (5), wherein the imidization ratio is partially changed by irradiating the surface of the polyimide alignment film with a laser.

(7) The laser irradiation is performed with a laser intensity that does not break the polymer bond of the polyimide alignment film, thereby partially increasing the imidization rate, and the above (6) is described. Liquid crystal display device manufacturing method.

(8) The liquid crystal display according to the above (6), wherein the laser irradiation is performed at a laser intensity that can break the polymer bond of the polyimide alignment film to reduce the imidization ratio. Device manufacturing method.

(9) The alignment film is composed of a photosensitive polymer alignment film having a plurality of regions having different degrees of polymerization, and the plurality of liquid crystal regions having different pretilt angles have a degree of polymerization of the alignment film. The liquid crystal display device according to (1) above, which is formed corresponding to a plurality of different regions.

(10) A method of manufacturing a liquid crystal display device having an alignment film for aligning liquid crystals, comprising forming a photosensitive polymer alignment film as the alignment film, and then irradiating with ultraviolet rays,
A method of manufacturing a liquid crystal display device, wherein the degree of polymerization of the photosensitive polymer alignment film is changed by selectively exposing the photosensitive polymer alignment film to light.

(11) By selectively developing the photosensitive polymer alignment film in which regions having different degrees of polymerization are formed,
The method for producing a liquid crystal display device according to (10) above, wherein regions having different surface shapes are formed on the surface of the photosensitive polymer alignment film.

(12) Concavities and convexities are formed on the surface of the alignment film in contact with the liquid crystal, and the liquid crystal regions arranged on the concave and convex surface of the alignment film have different pretilt angles corresponding to the concavo-convex surface shape. The liquid crystal display device according to (1) above.

(13) The liquid crystal display device according to the above (12), wherein the alignment film is composed of a porous alignment film. (14) The liquid crystal display device according to (13), wherein the alignment film has adhesiveness.

(15) The liquid crystal display as described in (13) or (14) above, wherein the liquid crystal molecules penetrate into the holes formed in the surface of the alignment film in contact with the liquid crystal. apparatus.

(16) Fine particles are dispersed in the alignment film, and irregularities are formed on the surface of the alignment film along the shape of the dispersed fine particles.
The liquid crystal display device according to (12).

(17) The liquid crystal display device according to the above (16), wherein the fine particles dispersed in the alignment film have a substantially uniform particle size. (18) The liquid crystal display device according to (16) above, wherein the fine particles dispersed in the alignment film have a plurality of different particle sizes.

(19) A transparent substrate and a transparent electrode formed in each pixel region on the surface of the transparent substrate, wherein the transparent electrode has a surface shape having a tapered convex portion. And the surface of the alignment film that covers the surface of the transparent electrode is formed in a shape having a tapered convex portion that reflects the surface shape of the transparent electrode. The liquid crystal display device according to 12).

(20) The translucent substrate, which has a translucent substrate, an auxiliary capacitance electrode sequentially laminated for each pixel region on the surface of the translucent substrate, an insulating film, and a transparent electrode, Of the auxiliary capacitance electrode, the insulating film, the transparent electrode, the surface of any one layer is formed in an uneven shape having a tapered convex portion, the surface of the alignment film covering the transparent electrode, The liquid crystal display device according to (12) above, wherein the liquid crystal display device is formed in a concavo-convex shape having a tapered convex part that reflects the surface shape of the one layer.

(21) The above-mentioned (2) to (4), characterized in that the surface of the alignment film is subjected to a rubbing treatment.
(9) The liquid crystal display device according to any one of (12) to (20). (22) On the surface of the alignment film, a plurality of groove regions in which a plurality of grooves having different groove depths or groove directions are arranged are formed, and a plurality of liquid crystal regions having different pretilt angles are formed. The liquid crystal display device according to (1), wherein the liquid crystal display device is formed so as to correspond to the plurality of groove regions.

(23) A transparent substrate and a transparent electrode formed for each pixel region on the surface of the transparent substrate are provided, and the surface of the transparent electrode has a groove depth or a groove. A groove region is formed in which a plurality of grooves in which at least one of the directions is different is arranged, and the surface of the alignment film that covers the surface of the transparent electrode is formed in a groove shape that reflects the surface shape of the transparent electrode. The liquid crystal display device according to (22) above.

(24) The transparent substrate, which has a transparent substrate, an auxiliary capacitance electrode sequentially laminated for each pixel region on the surface of the transparent substrate, an insulating film, and a transparent electrode. The surface of any one of the auxiliary capacitance electrode, the insulating film, and the transparent electrode has a groove region in which a plurality of grooves having different groove depths or groove directions are arranged. The liquid crystal display device according to (22) above, wherein the surface of the alignment film that covers the transparent electrode is formed with a groove shape that reflects the surface shape of the one layer.

(25) A liquid crystal and an alignment film for orienting the liquid crystal are provided, and an uneven shape is formed on the surface of the alignment film, whereby the liquid crystal has different pretilt angles according to the uneven shape. Aligned liquid crystal display device.

(26) The liquid crystal display device according to the above (25), further comprising fine particles dispersed in the alignment film, and the uneven shape of the surface of the alignment film is formed along the shape of the fine particles.

(27) An underlayer provided below the alignment film is further provided, and an uneven shape is formed on the surface of the underlayer, whereby the unevenness on the surface of the alignment film reflects the surface shape of the underlayer. The liquid crystal display device according to (25), wherein the liquid crystal display device has a shape.

(28) The liquid crystal display device according to the above (27), wherein the uneven shape of the underlayer is a tapered convex shape that is convex in substantially the center of each pixel. (29) A plurality of groove regions, each of which has a liquid crystal and an alignment film for aligning the liquid crystal, and in which a groove in which at least one of a groove shape and a groove forming direction is different is arranged on the surface of the alignment film A liquid crystal display device in which the liquid crystal portions corresponding to the respective groove regions are aligned with different pretilt angles.

(30) A base layer provided below the alignment film is further provided, and a plurality of grooves are formed on the surface of the base layer in which at least one of the groove shape and the groove forming direction is arranged differently. The liquid crystal display device according to (29), wherein a groove region is formed, and thereby a groove region reflecting the shape of the groove region of the underlying layer is formed on the surface of the alignment film.

[0063]

1 is a sectional view showing an example of the structure of a display portion of a liquid crystal display device. Referring to FIG. 1, in liquid crystal display device 1, liquid crystal 4 is injected between substrates 2 and 3 made of a transparent material such as glass. Transparent conductive films 5 and 6 are provided on the surfaces of the substrates 2 and 3 on the liquid crystal 4 side as electrodes for applying a voltage to the liquid crystals. An alignment film 7 for aligning the liquid crystal 4 is formed on the transparent conductive films 5 and 6.
8 are formed. The transparent conductive films 5 and 6 are, for example, IT
It is formed of O (indium tin oxide). The alignment films 7 and 8 are made of synthetic resin such as polyimide.

In the conventional liquid crystal display device, the alignment films 7 and 8 are uniformly formed on the entire surface of the display region, and therefore the pretilt angles of the liquid crystal molecules are set to be the same in the entire display region.

According to the first aspect, the second aspect, the third aspect, and the fourth aspect of the present invention, a polyimide alignment film is used as the alignment film, and the polyimide alignment film has a plurality of different imidization ratios. Forming a region. Thereby, the liquid crystal portion corresponding to each region is aligned with different pretilt angles according to the imidization ratio.

According to the fifth and sixth aspects of the present invention, a photosensitive polymer alignment film is used as the alignment film, and a plurality of regions having different degrees of polymerization are formed in the photosensitive polymer alignment film. . Thereby, the liquid crystal portions corresponding to the respective regions are aligned with different pretilt angles according to the degree of polymerization.

According to the seventh aspect of the present invention, a concave-convex shape is formed on the surface of the alignment film, whereby the liquid crystal is aligned at different pretilt angles according to the concave-convex shape. According to the eighth aspect of the present invention, a plurality of grooves having different groove shapes and / or different groove forming directions are arranged on the surface of the alignment film to form groove areas, and the groove areas are formed in plural. As a result, the liquid crystal portions corresponding to the respective groove regions are aligned with different pretilt angles.

Embodiments according to the above aspects of the present invention will be described below. First, an embodiment according to the first aspect to the fourth aspect of the present invention will be described. FIG. 2 is a cross-sectional view showing the main parts of the liquid crystal display device of the embodiment according to the first aspect of the present invention. Referring to FIG. 2, the liquid crystal display device includes a transparent substrate 10 made of glass or a transparent synthetic resin, and a conductive film 2 formed on the surface of the transparent substrate 10.
0, and an alignment film 30 formed on the surface thereof. Liquid crystal 40 is injected on the alignment film 30. Although not shown, the same configuration as the alignment film 30, the conductive film 20, and the translucent substrate 10 is symmetrically provided on the upper surface of the liquid crystal 40 above.

The conductive film 20 functions as an electrode for applying a voltage to the liquid crystal 40, and is made of a transparent conductive material such as ITO. Alignment film 30
Is made of a polyimide resin, and its surface is subjected to a rubbing treatment. The polyimide alignment film 30 has regions 30a and 30b having different imidization ratios. If the imidization ratio of the polyimide alignment film is different, the pretilt angle in the initial alignment state of the liquid crystal 40 injected on the surface is different. For example, as shown in FIG. 2, the pretilt angle A of the liquid crystal on the region 30a having a high imidization ratio is larger than the pretilt angle B of the liquid crystal on the region 30b having a low imidization ratio.

Next, a method of manufacturing the liquid crystal display device according to the second and third aspects of the present invention will be described. FIG.
Referring to, a conductive film made of a transparent conductive material such as an ITO film is formed on the surface of the transparent substrate 10 and patterned (S10).

Next, the material of the alignment film is applied on the surface of the conductive film 20. Here, an example of using a polyamic acid as the alignment film material according to the third aspect and an example of using soluble polyimide according to the second aspect will be described.

First, in the case of using polyamic acid,
A polyamic acid film is formed on the surface of the conductive film 20 (S1).
2). After that, prebaking is performed at a low temperature, for example, 50 ° C., and imidization is performed over the whole until a predetermined imidization rate is reached (S14).

When soluble polyimide is used, after the soluble polyimide is coated on the surface of the conductive film 20 (S12), a predetermined temperature, for example, 50 to 70 is used.
A pre-baking process is performed at C (S14).

Next, the alignment film formed on the conductive film 20 is irradiated with laser. As the type of laser, a laser having an intensity that does not break the polymer bond of polyimide is selected. Specifically, a laser having a wavelength of 400 nm or more is preferable, and for example, a CO ₂ laser is used. Table 1 below shows the average bond energy between the molecules contained in the polyimide.

[0075]

[Table 1]

With respect to the binding energies shown in Table 1, the CO ₂ laser intensity is, for example, 10.6
μm and energy of 0.12 eV are set. When the surface of the alignment film 30 is irradiated with laser under such conditions, the region irradiated with laser is heated, and the imidization ratio of that portion changes. The imidization reaction by the heat treatment is a reaction in which polyamic acid is changed to polyimide, and is generally expressed by the following formula. This reaction increases the imide bond (imide ring) and increases the imidization ratio.

[0077]

Embedded image

For example, FIG. 4A shows a polyamic acid P.
The relationship between the heating temperature and the imidization ratio of the polyimide film formed from A-1 and the soluble polyimide PI-1 is shown. It has been shown that the imidization ratio of both increases as the heating temperature increases. In particular, this tendency is remarkable when a polyamic acid is used.

The pretilt angle of the initial alignment state of the liquid crystal injected onto the surface of the alignment film 30 varies depending on the degree of imidization of the alignment film 30. This is shown in FIG.
For example, when viewed at a temperature of 150 ° C., as shown in FIG. 4A, the pretilt angle is 7.5 ° for an imidization ratio of 96% when a soluble polyimide is used, whereas polyamic acid is used. When used, the pretilt angle is about 2.8 ° for an imidization ratio of 20%. Further, the pretilt angle changes according to the baking temperature (heating temperature). As is clear from FIG. 4B, in the case of the polyamic acid film, the pretilt angle increases as the baking temperature rises, but conversely in the case of the soluble polyimide film, the pretilt angle decreases as the temperature rises. There is.
Therefore, it is necessary to select a region in which the pretilt angle is changed by laser irradiation, depending on which film material is used (S16).

FIG. 5 is a diagram showing the relationship between the baking temperature, the imidization ratio, and the pretilt angle of different types of soluble polyimide (PI-2). In addition, in FIG.
The scale of the imidization ratio on the vertical axis is enlarged to make it easier to see the change in imidization ratio. FIG. 5 (a) and (b)
As is clear from the results, as the baking temperature increases, the imidization ratio increases and the pretilt angle decreases.

When the imidization treatment by the above laser heating is completed, the surface of the alignment film 14 is rubbed,
The process of forming the alignment film is completed (S18). Note that the rubbing treatment of the alignment film may be performed before the imidization treatment by laser irradiation. Further, after that, the process of assembling the liquid crystal panel and the process of injecting the liquid crystal are performed, but the detailed description is omitted here.

In the liquid crystal display device manufactured by the above steps, the area imidized by laser irradiation has a different imidization rate compared to other areas. Then, if the imidization ratio is different, as described above, the pretilt angle in the initial alignment state of the liquid crystal injected on the surface is different. Further, when the pretilt angles are different, the threshold voltage in each region changes when a predetermined voltage is applied to the conductive film. This state is shown in FIG.
(A) and (b) show. Here, the vertical axis of FIG.
The threshold voltage V ₁₀ is shown when the luminance changes from 100% to 10%, and the vertical axis of FIG. 6B shows the threshold voltage V ₉₀ when the luminance is changed to 90%. In both figures, when the temperature is constant, the values of the threshold voltages V ₁₀ and V ₉₀ decrease as the pretilt angle increases in both cases. As can be seen from this, in the regions having different pretilt angles, even if a uniform voltage is applied from the conductive film, the effective driving of the liquid crystal is different due to the different threshold voltages. Becomes For this reason, the viewing angles in the respective areas are different, and in particular, the priority viewing angles have different values. Therefore, in the liquid crystal display device as a whole, the viewing angle is widened and the viewable range of the display screen is widened.

In the above embodiment, the case where the imidization ratio of each region of the alignment film is variously changed by increasing the imidization ratio of the irradiation region by laser irradiation has been described. According to this aspect, the laser intensity may be increased, the bond between the imidized polymers may be cut to reduce the imidization ratio, and the imidization ratio in each region of the alignment film may be variously changed. In this case, the laser intensity is selected to be larger than the binding energy of the polymer bond of polyimide. The embodiment according to the fourth aspect will be described later.

Further, an example of arrangement of regions having different pretilt angles, that is, regions having different imidization ratios of the alignment film in the flat display region of the liquid crystal display device will be described below.

For example, FIG. 7A shows a plan view when regions having different imidization ratios are formed in a pixel.
In this example, in the pixel 131, a region 131A having the highest imidization ratio is formed in a stripe shape in the central portion, and regions 131B and 131C having a lower imidization ratio than the region 131A are formed in stripes on both sides thereof. There is. Further, regions 131D and 131E having a lower imidization ratio are formed on both sides thereof.

In the example shown in FIG. 7B, the pixel 13
2, regions 132A, 13 having a relatively high imidization ratio
2B and regions 132D, 13 having a relatively low imidization ratio
2C and 2C are alternately formed in a stripe shape. Such a structure not only contributes to an increase in the viewing angle but can also be used for gradation display. That is, the difference in pretilt angle appears as the difference in contrast between the regions. Therefore, by setting the pretilt angle of each stripe area set in the pixel area in a stepwise manner, it is possible to perform gradation display according to the setting.

Further, the example shown in FIGS. 8A and 8B also shows another example of the divided area in the pixel, as in the case of FIG. That is, in FIG.
Region 133 having the highest imidization ratio in the central part of 3
A to 133D are formed, and regions 133E to 133L with the next highest imidization ratio are formed on the outside thereof, and regions 133M to with the lowest imidization ratio are formed at the corners of the pixel.
133P is formed. In this structure, the imidization ratio is set in three stages.

Further, in FIG. 8B, one pixel 134
In the inner part of the
A is formed, and a region 134 having a low imidization ratio is formed around it.
B is formed.

The regions having different imidization ratios according to the present invention may be set not only in the pixel region but also in the entire display panel region of the liquid crystal display device. FIG. 9 shows that the central portion of the panel 135 is
A region 135A having a relatively high imidization ratio is provided with respect to the peripheral region 135B.

FIG. 10 is a perspective view for explaining an arrangement example of laser irradiation regions in a pixel, that is, regions having different imidization ratios. Referring to FIG. 10, alignment film 13
Reference numerals 6 and 137 are alignment films on the substrate side on which a driving unit such as a TFT is provided. The alignment films 138 and 139 are alignment films on the counter substrate side, respectively. The alignment film 138 is located in the pixel region facing the alignment film 136, and
39 is located in the pixel region facing the alignment film 137. The alignment films 138 and 139 are formed on the common electrode, and are actually formed continuously on the entire surface. In FIG. 10, the correspondence between the pixels is shown in a divided state for easy viewing.

In FIG. 10, the region where the imidization ratio of the alignment film is changed by laser irradiation is shown by hatching. In the alignment films 136 and 137, TF is used.
A laser irradiation area 136 is provided in each of the divided areas distant from T.
A and 137A are formed. Opposing alignment film 13
Also in 8 and 139, laser irradiation regions 138A and 139A are formed in regions facing the laser irradiation regions 136A and 137A.

The laser irradiation may be performed while continuously irradiating from one end to the other end of the alignment film, or the laser irradiation may be performed only on the portion where the laser irradiation is necessary and not on the portion where the laser irradiation is not necessary. Alternatively, scanning may be performed while repeating irradiation and non-irradiation. For example, the laser may be scanned while irradiating only the alignment film portion in the pixel region and not irradiating the black matrix portion between the pixels. The laser spot diameter and the spot shape are not particularly limited, and can be appropriately selected according to the size and shape of the pixel. For example, the spot diameter of the laser can be changed from several μm to a size of 5 cm square. For example, when scanning is performed while irradiating a laser beam having a spot diameter of 30 μm at a frequency of 50 Hz, the scanning can be performed at a speed of 1.5 mm / sec.

FIG. 11 is a perspective view showing another example of the laser irradiation area in the pixel. Here, the laser irradiation regions 136A and 137A of the alignment films 136 and 137, and the laser irradiation regions 138A of the alignment films 138 and 139 facing each other.
And 139A are arranged so as not to face each other. Therefore, the laser irradiation regions 136A and 137A face the regions of the facing alignment films 138 and 139 which are not irradiated with the laser. Also, laser irradiation areas 138A and 1
39A faces the regions of the facing alignment films 136 and 137 which are not irradiated with the laser.

FIG. 12 is a perspective view showing still another example of the laser irradiation area in the pixel. Here, the laser irradiation regions 136A and 138A are formed so as not to face each other between the alignment film 136 and the facing alignment film 138. On the other hand, the alignment film 137 and the alignment film 139 facing each other
Between the laser irradiation area 137A and the laser irradiation area 1
39A are arranged so as to face each other. In this embodiment, every other pixel is configured to have such a laser irradiation region positional relationship.

FIG. 13 is a perspective view showing still another example of the laser irradiation area in the pixel. Here, the laser irradiation regions 136A and 138A face each other between the alignment film 136 and the facing alignment film 138, while the laser irradiation region 137A moves between the alignment film 137 and the facing alignment film 139. The 139A are configured so as not to face each other.

FIG. 14 is a perspective view showing still another example of the laser irradiation area in the pixel. In this embodiment,
The laser irradiation region is formed in the direction perpendicular to the direction of the laser irradiation region of the above embodiment. Between the alignment film 136 and the facing alignment film 138, the laser irradiation regions 136A and 138A are formed to face each other. Similarly, between the alignment film 137 and the facing alignment film 139, the laser irradiation regions 137A and 139A are formed to face each other.

FIG. 15 is a perspective view showing still another example of the laser irradiation area in the pixel. In this embodiment,
Laser irradiation region 1 formed on the alignment films 136 and 137
The laser irradiation regions are formed so that the directions of 36A and 137A and the laser irradiation regions 138A and 139A of the facing alignment films 138 and 139 are perpendicular to each other. Therefore, the laser irradiation region 136A and the laser irradiation region 138A partially overlap and face each other. Similarly, the laser irradiation region 137A and the laser irradiation region 139A partially overlap and face each other. Therefore, both the regions where both alignment films facing each other are irradiated with laser,
A region in which only one or the other is a laser irradiation region and three types of regions in which neither is a laser irradiation region are formed. Therefore, the areas with different pretilt angles are
Types can be formed, and the viewing angle characteristics can be further improved.

Next, the alignment film of each pixel is divided into two so that the laser irradiation region is arranged as shown in FIG.
A liquid crystal display device was manufactured in which only one region was irradiated with laser and the imidization ratio of the laser irradiation region was higher than that of the laser non-irradiation region. Specifically, soluble polyimide is applied to form a polyimide alignment film,
After prebaking at 0 ° C, heat treatment was performed at 150 ° C to adjust the imidization ratio to 96.2%. Next, wavelength 632.8 nm
The He-Ne laser of was used, the spot diameter was set to 30 μm, and a half region of a pixel having a size of 60 μm × 60 μm was irradiated with laser light twice. The laser frequency is 5
The laser scanning speed was 0.7 Hz and the laser scanning speed was 0.75 mm / sec. By such laser irradiation, the imidization ratio in the laser irradiation region increased to 98.6%. Note that when the laser spot shape is a rectangular shape with a size of 30 μm × 60 μm, half the region of a pixel can be irradiated with laser by one oscillation.

As described above, a TN type liquid crystal display device having an alignment film in which a region having a high imidization ratio was formed in a part of the pixel region was produced, and the viewing angle characteristics were evaluated. For comparison, the same soluble polyimide was used to form a polyimide alignment film, which was then prebaked at 50 ° C. and then heat-treated at 150 ° C. An alignment film having a uniform imidization ratio (imidization ratio 96.2%). A TN type liquid crystal display device having the above was manufactured and evaluated in the same manner.

FIG. 16 is a diagram showing the viewing angle characteristics of the liquid crystal display device obtained as described above. The horizontal axis represents the viewing angle, and the vertical axis represents the gradation brightness. The solid line shows the liquid crystal display device according to the present invention, and the dotted line shows the liquid crystal display device of the comparative example.

As is apparent from FIG. 16, in the liquid crystal display device according to the present invention in which the imidization ratio of a part of the alignment film in the pixel is made different and the regions having different pretilt angles are formed in the pixel, the comparative liquid crystal display Compared with the device, the viewing angle characteristics are improved,
It can be seen that the decrease in the luminance and the contrast ratio due to the shift in the viewing angle direction when observed facing the display is small.

Further, in the above embodiment, when the polyimide alignment film is formed by using polyamic acid instead of the soluble polyimide and a part of the region is irradiated with the laser, the similar viewing angle characteristics are improved. Was observed.

In the above embodiment, the heat treatment of the pre-bake is performed by the heat treatment in the furnace such as a heating furnace.
Prebaking may be performed by laser irradiation. In this case, the laser irradiation for prebaking and the laser irradiation for changing the imidization ratio can be continuously performed as a series of steps. Further, since heating is performed by laser irradiation, only the alignment film can be heat-treated without heating a portion which is not desired to be heated such as a transistor portion.

Next, an embodiment according to the fourth aspect of the present invention will be described. According to the fourth aspect, by irradiating a part of the polyimide alignment film with a laser, the imidization ratio of the irradiation region is reduced. Such lasers include:
As described above, laser light having a wavelength of 300 to 400 nm is preferable. For example, a XeF laser (wavelength 353 nm), a XeCl laser (wavelength 308 nm), etc. can be mentioned.

Specific experimental examples will be described below.
A polyimide alignment film formed from soluble polyimide is used.
After prebaking at 180 ° C., heat treatment was performed at 180 ° C. to obtain a polyimide alignment film having an imidization ratio of 96.8%. An XeF laser with an energy density of 50 m is applied to this polyimide alignment film.
Upon irradiation with J / cm ² , the imidization ratio decreased to 85%. Therefore, by irradiating the XeF laser,
The imidization rate could be reduced.

In FIG. 17, liquid crystal was introduced onto the polyimide alignment film thus laser-irradiated, and the reflection luminance peak intensity of the liquid crystal by the polarized laser light at the interface between the liquid crystal of one substrate and the alignment film was measured. It is a figure which shows the result. The horizontal axis represents the orientation angle of the liquid crystal, and the vertical axis represents the relative value of the reflection luminance peak intensity. The solid line represents the alignment film before laser irradiation, and the dotted line represents the alignment film after laser irradiation.
As is clear from FIG. 17, before the laser treatment, the orientation which is almost the same as that after the laser treatment is shown, and it can be seen that the function of the orientation film is not lost.

The pretilt angle was 4.9 ° when the alignment film before laser irradiation was used and 5.6 ° when the alignment film after laser irradiation was used. Therefore, it is understood that the pretilt angle is increased due to the reduction of the imidization ratio.

As a comparison, a KrF laser (wavelength 248 nm) having a wavelength of 300 nm or less was used to irradiate the polyimide alignment film with a laser at an energy density of 70 mJ / cm ² in the same manner as above. It collapsed and the film was scattered. Therefore, it is understood that it is preferable to use a laser having a wavelength of about 300 to 400 nm.

Next, embodiments according to the fifth aspect and the sixth aspect of the present invention will be described. FIG. 18 is a cross-sectional view showing the main parts of the liquid crystal display device of the embodiment according to the fifth aspect of the present invention. The liquid crystal display device includes a translucent substrate 10 made of glass or translucent synthetic resin, a conductive film 20 formed on the surface of the translucent substrate 10, and further formed on the surface. The alignment film 31 is provided. And
Liquid crystal 40 is injected on the alignment film 31. Also,
Although not shown, the same structure as the alignment film 31, the conductive film 20, and the transparent substrate 10 is symmetrically provided on the upper surface of the liquid crystal 40 above.

The alignment film 31 is a photosensitive polymer alignment film material,
For example, it is composed of acrylic resin type photosensitive material,
The surface is rubbing treated. The alignment film 31 made of a photosensitive polymer material has regions 31a and 31b formed by a method described later and having different degrees of polymerization. If the degree of polymerization of the alignment film is different, the pretilt angle in the initial alignment state of the liquid crystal 40 injected on the surface is different. For example, in FIG. 18, a region 31a having a high degree of polymerization is
The pretilt angle A of the liquid crystal 40a of
It is set to be larger than the pretilt angle B of the liquid crystal 40b on 1b.

Now, a method of manufacturing the liquid crystal display device shown in FIG. 18 will be described with reference to FIGS. 19 and 20. First, a transparent conductive material such as an ITO film is formed on the surface of the transparent substrate 10 and patterned (S20).

Next, an alignment film material is applied on the surface of the conductive film 20. As the alignment film material, a negative type or positive type photosensitive polymer material is used. The negative photosensitive polymer material improves the degree of polymerization in the region exposed to light such as ultraviolet rays, and the positive photosensitive polymer material decreases the degree of polymerization in the region exposed to light. Such a photosensitive polymer material is applied by spin coating or roll coating on the surface of the transparent substrate 10 on which the conductive film 20 is formed (S22).

Then, after pre-baking the photosensitive polymer alignment film, a gradation mask 210 having different transmittances is formed on the surface of the alignment film. As shown in FIG. 20, the gradation mask 210 has different thickness regions 2
By forming 10a and 210b, or by partially combining different materials, a region having different transmittance with respect to the irradiation light beam is formed (S2).
4).

After that, an irradiation light beam 220 such as an ultraviolet ray is transmitted through the gradation mask 210 to irradiate the surface of the photosensitive polymer alignment film 31 to expose the photosensitive polymer alignment film 31. For example, in FIG. 20, the alignment film region 31a located under the thin film thickness region 210a of the grayscale mask 210 is smaller than the alignment film region 31b located under the thick film thickness region 210b of the grayscale mask 210. The exposure amount becomes large. And
Regions having a high degree of polymerization and regions having a low degree of polymerization are formed in the alignment film 31 depending on the exposure amount. That is, when the negative type alignment film material is used, the region 31a having a large exposure amount has a higher degree of polymerization than the region 31b having a small exposure amount.
On the other hand, when a positive type alignment film material is used, conversely, the degree of polymerization of the region 31a having a large exposure amount is low in the region 3 having a small exposure amount.
It is lower than the polymerization degree of 1b.

After the above exposure processing is performed, the alignment film 31 is formed.
A post-baking process is performed on (S26). Further, the surface of the alignment film 31 is rubbed (S2
8) The process of forming the alignment film 31 is completed.

Through the above steps, a plurality of regions having different degrees of polymerization are formed in the photosensitive polymer alignment film 31. Further, in the present embodiment, the exposed photosensitive polymer alignment film,
Post-baking processing may be performed after further development processing. When the developing process is performed, the residual film rate varies depending on the amount of exposure, and thus regions having different surface states such as the surface shape are formed in the photosensitive polymer alignment film 31.

A specific example of forming an alignment film using a negative acrylic resin as a photosensitive polymer alignment film material will be described below. A solution of a photosensitive polymer material (trade name “JNPC-10”; manufactured by Japan Synthetic Rubber Co., Ltd.) is dropped on the surface of the conductive film 20, and a thin film of an alignment film material having a predetermined thickness is formed by spin coating. Next, prebaking treatment is performed at a temperature of 80 ° C. for 3 minutes. Further, a gradation mask 210 having a plurality of regions having different light transmittances is arranged on the surface of the alignment film material thin film. Here, in each region of the gradation mask 210, the exposure amount to the alignment film material is 50 to 1000 mJ / c.
It was previously adjusted to be m ² .

After arranging the gradation mask 210, an ultraviolet ray 2 having a wavelength of 450 nm is provided by a mercury short arc lamp or the like.
20 is transmitted through the gradation mask 210 for 10 seconds to irradiate the alignment film material thin film to expose the alignment film material to light. By this exposure processing, regions having different exposure amounts are formed in the alignment film material thin film corresponding to the film thickness of the gradation mask.

Further, after removing the gradation mask 210,
Post baking treatment is performed at a temperature of 180 ° C. for 30 minutes, and the manufacturing process of the alignment film 31 is completed. In another embodiment, the development process can be performed on the alignment film material thin film exposed by using the gradation mask 210. This causes a difference in the surface condition such as the surface roughness of the alignment film, and then a post-baking process is performed at a temperature of 180 ° C. for 30 minutes to complete the manufacturing process of the alignment film 31.

When a negative acrylic resin is used as the photosensitive polymer material, the degree of polymerization of the portion exposed to a large amount of light is higher than the degree of polymerization of the portion exposed to a small amount of light. As a result, in the initial alignment state of the liquid crystal after manufacturing the liquid crystal panel, the pretilt angle of the liquid crystal on the region having a high degree of polymerization is set to be larger than the pretilt angle of the liquid crystal aligned on the region having a low degree of polymerization.

The cross-sectional structure of the liquid crystal display device shown in FIGS. 18 and 20 is shown by focusing on one pixel region, and regions having different degrees of polymerization are displayed inside one pixel region. Various settings are made. As for the arrangement of the regions having different degrees of polymerization, the arrangements shown in FIGS. 7 and 8 and FIGS. 10 to 15 in the first to fourth embodiments can be applied. Further, without being limited to one pixel area, for example, area setting as shown in FIG. 9 can be performed. Then, in the liquid crystal display device according to the fifth aspect, similarly to the first to fourth aspects, the pretilt angle of the initial alignment state of the liquid crystal is changed by appropriately changing the degree of polymerization of the alignment film for each predetermined region. Various settings can be made. As a result, the preferential viewing angles can be changed, and as a result, the effect of improving the viewing angle characteristics can be exhibited.

The alignment film according to the fifth aspect may be applied to only one of the two alignment films facing each other with the liquid crystal layer in between, or may be applied to both of the alignment films facing each other. Next, an embodiment according to the seventh aspect of the present invention will be described.

FIG. 21 is a sectional view showing a main part of a liquid crystal display device of an embodiment according to the seventh aspect of the present invention. The liquid crystal display device includes translucent substrates 10 and 70 made of glass or translucent synthetic resin, conductive films 20 and 60 formed on the translucent substrates 10 and 70, and further above them. And the alignment films 32 and 52 formed on. The liquid crystal 40 is injected between the pair of alignment films 32 and 52. The pair of conductive films 20 and 60 function as a pair of counter electrodes for applying a voltage to the liquid crystal 40.

The orientation films 32 and 52 are composed of a thin film having small holes on at least the surface thereof. Alignment film 32,
The small holes on the surface of 52 have a function of forming unevenness on the surface of the alignment film, and the initial alignment state of the liquid crystal 40 is defined along the uneven shape. That is, in the initial alignment state of the liquid crystal, the liquid crystal is aligned along the uneven shape on the surface of the alignment film, so that domains having different pretilt angles of the liquid crystal are formed in a minute region corresponding to the uneven shape. The preferential viewing angles are different in each domain, and the domains appear to be averaged as one pixel, so that a wide viewing angle can be obtained.

The alignment films 32 and 52 having irregularities on the surface are
It is formed by various materials and methods. The first example is a polymer alignment film formed from a mixed material of liquid crystal and polymer by a solvent evaporation method. This polymer alignment film is
For example, CPHOB (4-cyanophenyl 4'-hexyloxybenzoate), 5OCB (4-cyano 4'-pentoxybiphenyl), 7OCB (4-cyano 4'-heptoxybiphenyl), HPPB (4-hexyloxyphenyl 4 '. -Pentylbenzoate) and other liquid crystals, for example polyvinyl chloride, PMMA (polymethylmethacrylate), polystyrene, polydiisopropyl fumarate,
After mixing a polymer such as acrylonitrile-butadiene rubber or polyimide and applying it on the conductive films 20 and 60,
It is formed by extracting only the liquid crystal component by immersing it in a solvent that dissolves only the liquid crystal, such as ethanol or acetone. Many small holes are formed in the portion of the film where only the liquid crystal component is extracted. In particular, minute irregularities are formed on the surface of the alignment film. The size of the unevenness is larger than the liquid crystal molecule and smaller than the pixel size, preferably a few μm.
It is formed in the m order. Then, in the initial alignment state in which the liquid crystal 40 is injected into the liquid crystal panel, the liquid crystal is more preferably inside the irregularities on the surfaces of the alignment films 32 and 52, and more preferably,
It is also injected inside the pores in the membrane. By injecting the liquid crystal molecules into the uneven portion of the surface, the orientation of the liquid crystal molecules varies along the uneven shape of the surface, and the pretilt angles are set differently. Further, when the liquid crystal is injected into the holes in the film, light scattering occurs when a voltage is not applied between the pixel electrodes, and the effect of improving the light transmittance can be obtained.

By adjusting the mixing ratio of the liquid crystal and the polymer material at the time of forming the alignment film, it is possible to control the size or formation density of the unevenness of the alignment film. Also,
When an ultraviolet curable resin or a thermosetting resin is used as the polymer material, it is possible to form an adhesive alignment film. Therefore, the adhesiveness of the alignment film can be used to fix the substrate and the spacer.

The second example of the alignment films 32 and 52 is formed by using a foaming resin. In this case, expanded polystyrene resin, expanded polyethylene resin, expanded polyvinyl chloride resin or the like is used as the expandable resin material. Conductive film 20
By applying a foaming resin material on the surface of (60) and then performing a foaming treatment, a concavo-convex surface having a large number of small holes can be formed at least on the surface of the alignment film.

The alignment films 32 and 52 formed by the first and second examples described above are subjected to rubbing treatment on their surfaces. However, this rubbing process is not always necessary.

The surface irregularities are preferably formed on the alignment films 32 and 52 arranged on both upper and lower surfaces of the liquid crystal layer 40, but the same effect can be obtained by forming only one of them. be able to.

FIG. 22 is a sectional view showing a main portion of a liquid crystal display device of another embodiment according to the seventh aspect of the present invention. The illustrated structure schematically shows a region corresponding to one pixel. The liquid crystal display device includes a transparent substrate 10 made of glass, a transparent synthetic resin, or the like, a conductive film 20 formed on the transparent substrate 10, and an alignment film formed on the conductive film 20. And 33. Then, the liquid crystal 40 is injected on the alignment film 33. Although not shown, the same configuration as the alignment film 33, the conductive film 20 and the transparent substrate 10 is symmetrically formed on the upper surface of the liquid crystal 40 above.

In this liquid crystal display device, unevenness is formed on the surface of the alignment film 33 by mixing spacers into the alignment film. Spacers 330a, 330b
As the spacer, a spherical spacer such as silica, polystyrene resin, polyolefin resin, or benzoguanamine resin is used. The size of the spacer may be uniform, or several types may be mixed. The spherical diameter is preferably in the range of 0.3 to 1.5 μm.
In the present embodiment, two types of spherical spacers 330a, 3
30b, for example, spacers having spherical diameters of 0.5 μm and 1.0 μm are used. The alignment film 33 is formed by spin-coating on the surface of the conductive film 20 after mixing spherical spacers 330a and 330b into a solution of a polymer alignment film material made of a material such as polyimide, polyamide, PVA, polyester, or polyethylene, and mixing them. It is formed by applying by coating or printing and heating. Then, a rubbing process is performed.

On the surface of the alignment film 33 thus formed, uneven surfaces are formed along the shapes of the spherical spacers 330a and 330b dispersed on the surface of the conductive film 20. Therefore, the liquid crystal arranged on the uneven surface is oriented with different pretilt angles A and B depending on the shape of the uneven surface. For example, in the illustrated example, the pretilt angle is set larger as the size of the convex portion increases. As a result, the liquid crystal regions 40a, 40b, 40c having various pretilt angles are formed even in the illustrated one pixel region, so that the preferential viewing angles of the respective regions are different from each other, and a wide viewing angle is obtained as a whole. .

FIG. 23 shows another example of this embodiment. In the liquid crystal display device according to this modification, an insulating film 80 is formed on the surface of the conductive film (transparent electrode) 20. The insulating films 80 are formed on both surfaces facing each other with the liquid crystal layer 40 in between, and are provided to prevent a short circuit between the pair of conductive films 20. In such a liquid crystal display device, spherical spacers 330a, 330 are formed in the insulating film 80.
b is mixed to form an uneven surface.

That is, SiO ₂ is formed on the surface of the conductive film 20.
By mixing spherical spacers of different sizes in the coating liquid for forming the film and forming them by spin coating, the insulating film 80 having an uneven surface can be formed. Then, the polymer alignment film 3 is formed on the surface of the insulating film 80.
Form 3 In this case, the surface of the polymer alignment film 33 is
The uneven shape is formed following the uneven shape of the surface of the lower insulating film 80. Therefore, it is possible to form the regions 40a to 40c having different pretilt angles as in the embodiment shown in FIG.

The selection of the material, size and the like of the spherical spacer can be applied in the same manner as in the above embodiment. Further, the uneven shape according to the above-described embodiment and its modification may be applied to either one of a pair of alignment films (or insulating films) that are opposed to each other with the liquid crystal 40 interposed therebetween, or to both. Good.

FIG. 27 is a perspective view schematically showing a structure of a liquid crystal panel in still another embodiment according to the seventh aspect of the present invention. The liquid crystal panel includes a pair of translucent substrates 10 and 70 arranged to face each other with a liquid crystal 40 interposed therebetween, and a conductive film 20 forming a pair of counter electrodes formed on the translucent substrates 10 and 70, respectively. , 60, and an alignment film (not shown) formed on the surface thereof. Further, a color filter 90 is provided on the transparent substrate 70 on the counter electrode side.
Is provided.

This liquid crystal display device is characterized in that the surface of the alignment film is formed in a shape having an inclined surface such as a cone or a quadrangular pyramid. 28 to 30 show various examples of the shape of the alignment film having the inclined surface.

First, as shown in FIGS. 28A and 28B, in one pixel region defined by the gate line GL and the data line DL, the auxiliary capacitance electrode SC has a conical shape such as a conical shape or a quadrangular pyramid shape. Is formed in. The insulating film 81 formed by stacking on the auxiliary capacitance electrode SC
The surface of each of the a, the conductive film 20, and the alignment film 37a is formed in a pyramid shape according to the surface shape of the auxiliary capacitance electrode SC. Also, the surface of the alignment film is subjected to rubbing treatment.
The rubbing direction is performed in parallel with the gate line GL or the data line DL or with an inclination of 45 degrees.

With the above structure, the liquid crystals on the surface of the alignment film 37a are aligned at different pretilt angles along the inclined surface of the alignment film 37a. As a result, the preferential viewing angles of the respective areas are different, and a wide viewing angle can be obtained. Table 2 shows the relationship between the inclined surface of the alignment film surface and the pretilt angle of the liquid crystal on the inclined surface.

[0140]

[Table 2]

As is clear from Table 2, the liquid crystal is oriented with different pretilt angles depending on the tilt angle of the tilted surface. Next, in the example shown in FIG. 29, only the pixel electrode (conductive film) 20 is formed in a pyramid shape having an inclined surface.
Therefore, the alignment film 37b formed on the surface of the pixel electrode 20 has a pyramid shape similarly to the surface shape of the pixel electrode 20.

Further, in the example shown in FIG. 30, the insulating film 8 laminated between the auxiliary capacitance electrode SC and the pixel electrode 20.
1a is formed in a pyramid shape as in the above example, and the pixel electrode 20 and the alignment film 37c formed on the surface thereof are formed in a pyramid shape conforming to the surface shape.

In any of the examples shown in FIGS. 28 to 30, as a result, the surface of the alignment film is formed into a pyramid having an inclined surface, and as a result, the liquid crystal is aligned with a different pretilt angle for each inclined surface. Can be made.

Each of the above-mentioned auxiliary capacitance electrode SC, insulating film 81, and pixel electrode 20 is formed into a taper shape by taper etching after film formation. As a taper etching method, the following method can be applied.

For example, by adjusting the etching selection ratio between the etching mask and the film to be etched, the etching mask is side-etched in the etching process, and the side surface of the film to be etched is tapered as the side surface recedes and the etching proceeds. There is a method of etching.

Alternatively, there is a method of utilizing a multi-step etching process. In this method, film formation and etching of an etching target film are alternately repeated, and the etching mask width is gradually narrowed to stack the etching target film in a pyramid shape.

Further, there is a method of utilizing the side wall formation of the polymer film. In this method, a polymer film forming component is mixed with a reactive gas such as dry etching to perform etching, so that a polymer film is formed on the sidewall of the etching mask in the course of etching and the width of the mask is widened. This is a method in which the side surface of the film to be etched is tapered.

The surface shape of a cone or the like having an inclined surface formed by taper etching may be performed on a pixel-by-pixel basis as shown in FIGS. 28 to 30, and a wider area beyond one pixel area may be formed. You may form. Further, it may be formed not only on each layer on the pixel electrode 20 side in the drawing but also on a conductive film, an insulating film or the like on the counter electrode side. Moreover,
You may form in each layer of both sides which oppose.

Further, as shown in FIG. 31, a conical inclined surface may be formed on the surface of the color filter 90. Further, the surface shape is not limited to the conical shape, and may be a shape such as a truncated cone or a truncated pyramid.

FIG. 32 is a cross sectional view showing still another embodiment according to the seventh aspect. In the present embodiment, one pyramid-shaped convex portion is formed in four adjacent pixels. Therefore, as shown in FIG. 32, the alignment films 37d and 37e are formed so as to be higher toward the central data line DL. In this embodiment, the insulating film 81a of each pixel is formed so as to have an inclined surface, and thus the alignment film 37d and the alignment film 37e formed thereon are inclined. As described above, the tapered convex portion of the alignment film does not necessarily have to be formed in one pixel, and one tapered convex portion may be formed in a plurality of adjacent pixel regions.

In the above embodiment, the alignment film is tilted by forming the tilted surface on the insulating film, but the alignment film may be tilted by forming the tilted surface on the pixel electrode or the auxiliary capacitance electrode.

Next, an embodiment according to the eighth aspect of the present invention will be described. FIG. 24 is a cross-sectional view showing the main parts of the liquid crystal display device of the embodiment according to the eighth aspect of the present invention.
The structure of a region corresponding to one pixel is schematically shown. This liquid crystal display device includes a translucent substrate 10 made of glass or translucent synthetic resin, a conductive film 20 formed on the translucent substrate 10, and an alignment formed on the conductive film 20. Membrane 3
4 is provided. The liquid crystal 4 is formed on the alignment film 34.
0 is injected. Although not shown,
On the upper surface of the liquid crystal 40, the same configuration as the alignment film 34, the conductive film 20, and the translucent substrate 10 is symmetrically provided above.

In this liquid crystal display device, microgroove regions 34a and 34b having different shapes are formed on the surface of the alignment film 34. Micro groove areas 34a, 34b
Has a plurality of V-shaped grooves formed along the surface of the alignment film 34, and the groove pitch, the groove depth, the groove width, or the extending direction of the grooves is different depending on each region. There is. When the micro-groove regions 34a and 34b having different shapes are formed on the surface of the alignment film 34, the liquid crystal 40 is formed.
Are oriented so that the pretilt angles in the initial alignment state are different from each other. For example, as shown in the figure, in the region 34a where the groove formation density is high, the pretilt angle is set to be larger than that in the region 34b where the groove formation density is relatively low (A> B). Thereby, a wide viewing angle can be obtained by forming various regions having different preferential viewing angles corresponding to the different pretilt angles.

This micro-groove region can be formed by the following method. One of them is a method using shape transfer. In this method, first, a metal plate or the like having a desired microgroove shape processed on the surface is prepared, and the processed surface of the metal plate is pressed against the surface of the alignment film 34, or is further heated to micro-process the surface of the metal plate. The groove shape is transferred to the surface of the alignment film 34. For example, on the surface of the alignment film 34 having a film thickness of 1000 to 1500 Å, micro-grooves having different groove depths in the range of groove depth 100 to 500 Å and different groove pitches in the range of 0.1 to 5 μm. The area is transferred and formed. In addition, as the alignment film material, a material having flexibility such that shape transfer is possible, for example, polyimide, PVA,
Polyamide, polyester, polyethylene and the like are used.

As another method, the surface of the alignment film can be directly processed by using a laser to form a micro-groove shape. Next, a modified example will be described. FIG.
5 is a cross-sectional view showing a main part of a liquid crystal display device of a modified example. In this modification, an insulating film 80 is formed between the conductive film 20 and the alignment film 35, and a microgroove region is formed on the surface of the insulating film 80. It is formed as follows.

First, a SiO ₂ film 80 having a film thickness of 1000 to 2000 is formed on the surface of the conductive film 20 by using, for example, a sputtering method.
Form with Å. Then, various microgroove regions having different groove shapes are formed on the surface of the SiO ₂ film 80 by using the shape transfer method as described above. After that, when the alignment film 35 is formed on the surface of the insulating film 80, the alignment film 35 is formed.
Is a micro-groove shape on the surface of the insulating film 80,
A micro-groove shape is formed on the surface. In this case, the alignment film 35 has a thickness such that the microgroove shape on the surface of the insulating film 80 is reflected on the surface, for example, 100.
It is formed by spin coating or printing to about 1000 Å.

Further, another modification will be described with reference to FIG. In the modification shown in FIG. 26, a translucent substrate 10 is formed with microgroove shapes on its surface. As a method of forming a groove shape on the surface of the transparent substrate 10,
An etching method can be used. For example, when a resist having a groove-shaped pattern to be formed on the surface of the transparent substrate 11 is formed and wet etching is performed with diluted hydrofluoric acid (HF: H ₂ O = 1: 50), the groove corresponding to the resist pattern is formed. Are formed on the surface of the transparent substrate 10. The depth of the groove is controlled by adjusting the etching time, and the depth is set to, for example, about 100 to 1000Å.
Further, instead of wet etching, plasma dry etching in an atmosphere of carbon tetrafluoride and oxygen can be used to form the groove in the same manner.

When the conductive film 20, the insulating film if necessary, and the alignment film 36 are sequentially formed on the surface of the substrate having the grooves formed by such an etching method, the surface of each film is a transparent substrate. Reflecting the groove shape on the surface of 11, the groove shape is formed on the surface.

The surface irregularity is not only formed on one of the alignment films, the insulating film, or the predetermined underlayer on the surface of the light-transmitting substrate, which face each other with the liquid crystal 40 interposed therebetween.
It may be formed on both surfaces of the facing alignment film, insulating film or translucent substrate. Further, the microgroove regions having different groove shapes are shown in FIG. 7 described in the first to fourth aspects.
8 and FIGS. 10 to 15 can be set. Further, the area setting as shown in FIG. 9 is possible without being limited to one pixel area.

Further, as the microgroove shape formed on the surface of the alignment film, the insulating film or the transparent substrate, a uniform groove shape may be formed on the entire surface of the display region. Even in this case, the pretilt angle of the initial alignment state of the liquid crystal varies along the groove-shaped surface of the alignment film that follows the microgroove shape, and the priority viewing angle is set accordingly to increase the viewing angle. Can be made.

[0161]

According to the first aspect of the present invention, the liquid crystal is aligned at different pretilt angles by changing the imidization ratio of the polyimide alignment film. Therefore, a plurality of regions having different preferential viewing angles can be formed in the display region, the viewing angle can be widened, and the viewing angle characteristics can be improved.

Second, Third and Fourth Aspects of the Present Invention
According to this aspect, the imidization ratio of the polyimide alignment film is changed by irradiating the laser, and thereby the liquid crystal is aligned at different pretilt angles. Therefore, the pretilt angle can be varied in a fine region by a simple method.

According to the fifth and sixth aspects of the present invention, a plurality of regions having different degrees of polymerization are formed in the photosensitive polymer alignment film, and thereby liquid crystals are aligned at different pretilt angles. Therefore, similarly to the above, the viewing angle characteristics can be improved.

According to the seventh aspect of the present invention, the unevenness is formed on the surface of the alignment film to align the liquid crystal with different pretilt angles. Therefore, similar to the above, the viewing angle characteristics can be improved.

According to the eighth aspect of the present invention, a plurality of groove regions are formed on the surface of the alignment film, the groove regions having different groove shapes and / or groove forming directions, and thereby different pretilt angles are formed. The liquid crystal is aligned. Therefore,
Similar to the above, the viewing angle characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a structure of a liquid crystal display device of the present invention.

FIG. 2 is a cross-sectional view showing a main part of the liquid crystal display device of the embodiment according to the first aspect of the present invention.

FIG. 3 is a flowchart showing manufacturing steps of the liquid crystal display device shown in FIG.

FIG. 4 is a diagram showing a relationship between a baking temperature of an alignment film, an imidization ratio and a pretilt angle.

FIG. 5 is a diagram showing a relationship between a baking temperature of an alignment film, an imidization ratio and a pretilt angle.

FIG. 6 is a diagram showing a relationship between operating temperature and threshold voltages V ₁₀ and V ₉₀ .

FIG. 7 is a plan view showing an example of arrangement of regions having different imidization ratios.

FIG. 8 is a plan view showing another example of arrangement of regions having different imidization ratios.

FIG. 9 is a plan view showing still another example of arrangement of regions having different imidization ratios.

FIG. 10 is a plan view showing still another example of arrangement of regions having different imidization ratios.

FIG. 11 is a plan view showing still another example of arrangement of regions having different imidization ratios.

FIG. 12 is a plan view showing still another example of arrangement of regions having different imidization ratios.

FIG. 13 is a plan view showing still another example of arrangement of regions having different imidization ratios.

FIG. 14 is a plan view showing still another example of arrangement of regions having different imidization ratios.

FIG. 15 is a plan view showing still another example of arrangement of regions having different imidization ratios.

FIG. 16 is a diagram showing a relationship between a viewing angle and brightness in the embodiment according to the present invention.

FIG. 17 is an alignment angle of liquid crystal according to an embodiment of the present invention,
The figure which shows the relationship with the relative value of the reflection brightness peak intensity of the liquid crystal by polarized laser light.

FIG. 18 is a sectional view showing a main part of a liquid crystal display device of an embodiment according to a fifth aspect of the present invention.

FIG. 19 is a flowchart showing a manufacturing process in the embodiment according to the sixth aspect of the present invention.

FIG. 20 is a sectional view showing a process for manufacturing the embodiment shown in FIG.

FIG. 21 is a cross-sectional view showing the main parts of the liquid crystal display device of the embodiment according to the seventh aspect of the present invention.

FIG. 22 is a sectional view showing a main portion of a liquid crystal display device of another embodiment according to the seventh aspect of the present invention.

FIG. 23 is a cross-sectional view showing the main parts of a liquid crystal display device of still another embodiment according to the seventh aspect of the present invention.

FIG. 24 is a sectional view showing a main part of a liquid crystal display device of an embodiment according to an eighth aspect of the present invention.

FIG. 25 is a cross-sectional view showing the main parts of a liquid crystal display device of another embodiment according to the eighth aspect of the present invention.

FIG. 26 is a cross-sectional view showing the main parts of a liquid crystal display device of still another embodiment according to the eighth aspect of the present invention.

FIG. 27 is a perspective view showing a liquid crystal display panel of an embodiment according to the seventh aspect of the present invention.

FIG. 28 is a cross-sectional view showing the main parts of a liquid crystal display device of still another embodiment according to the seventh aspect of the present invention.

FIG. 29 is a cross-sectional view showing the main parts of a liquid crystal display device of still another embodiment according to the seventh aspect of the present invention.

FIG. 30 is a cross-sectional view showing the main parts of a liquid crystal display device of still another embodiment according to the seventh aspect of the present invention.

FIG. 31 is a cross-sectional view showing the main parts of a liquid crystal display device of still another embodiment according to the seventh aspect of the present invention.

FIG. 32 is a cross-sectional view showing the main parts of a liquid crystal display device of still another embodiment according to the seventh aspect of the present invention.

[Explanation of symbols]

 10 ... Translucent substrate 20 ... Conductive film 30-37 ... Alignment film 40 ... Liquid crystal 80 ... Insulating film 90 ... Color filter

Front Page Continuation (72) Inventor Kazuhiro Inoue 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (16)

[Claims] 1. A liquid crystal and a polyimide alignment film for aligning the liquid crystal, wherein the polyimide alignment film has a plurality of regions having different imidization ratios, whereby the liquid crystal portion corresponding to each region is formed. A liquid crystal display device that is aligned at different pretilt angles according to the imidization ratio. 2. The liquid crystal display device according to claim 1, wherein a plurality of regions having different imidization ratios of the polyimide alignment film are formed in each pixel. 3. A method of manufacturing a liquid crystal display device having a polyimide alignment film for aligning liquid crystal, comprising the steps of forming the polyimide alignment film, prebaking the polyimide alignment film, and the polyimide alignment film. A step of irradiating the substrate with a laser to change the imidization ratio of the irradiation region. 4. The method for manufacturing a liquid crystal display device according to claim 3, wherein the polyimide alignment film is made of polyamic acid. 5. The method for manufacturing a liquid crystal display device according to claim 3, wherein the polyimide alignment film is made of soluble polyimide. 6. The method for manufacturing a liquid crystal display device according to claim 3, wherein the temperature of the heat treatment in the prebaking step is 50 to 150 ° C. 7. The method of manufacturing a liquid crystal display device according to claim 6, wherein the pre-baking step is performed by laser irradiation. 8. The laser for irradiating has a wavelength of 400 nm.
The method for manufacturing a liquid crystal display device according to claim 7, which is the laser described above. 9. The method of manufacturing a liquid crystal display device according to claim 3, wherein the step of irradiating with the laser is a step of increasing an imidization ratio of an irradiation region. 10. The method for manufacturing a liquid crystal display device according to claim 9, wherein the laser irradiated to increase the imidization ratio is a laser having a wavelength of 400 nm or more. 11. The method for manufacturing a liquid crystal display device according to claim 3, wherein the step of irradiating with the laser is a step of reducing an imidization ratio of an irradiation region. 12. The method for manufacturing a liquid crystal display device according to claim 11, wherein the laser irradiated to reduce the imidization ratio is a laser having a wavelength of 300 to 400 nm. 13. A liquid crystal and a photosensitive polymer alignment film for orienting the liquid crystal, wherein the photosensitive polymer alignment film has a plurality of regions having different degrees of polymerization, thereby corresponding to each region. A liquid crystal display device in which the liquid crystal portion is aligned with different pretilt angles according to the degree of polymerization. 14. A method of manufacturing a liquid crystal display device having a photosensitive polymer alignment film for aligning liquid crystal, comprising: forming the photosensitive polymer alignment film; A method of manufacturing a liquid crystal display device, which comprises a step of irradiating ultraviolet rays to change a degree of polymerization of an irradiation region. 15. A method of manufacturing a liquid crystal display device having a photosensitive polymer alignment film for aligning liquid crystal, comprising: forming the photosensitive polymer alignment film; A method of manufacturing a liquid crystal display device, comprising: a step of irradiating an ultraviolet ray to change a degree of polymerization of an irradiation region; 16. A liquid crystal, an alignment film for aligning the liquid crystal, and fine particles dispersed in the alignment film, wherein an uneven shape is formed on the surface of the alignment film along the shape of the fine particles. Accordingly, the liquid crystal display device in which the liquid crystal is oriented at different pretilt angles according to the uneven shape.