JP3306407B2 - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which can prevent the display quality of the device from deteriorating and which can improve the viewing angle characteristics in all viewing angle directions without drastically increasing the manufacturing steps. SOLUTION: A vertical alignment region 22 is provided on an alignment layer which has a property to horizontally align liquid crystals. Besides the vertical alignment region 22 is provided on a central part of a pixel 21. Since the liquid crystal has continuity, surrounding liquid crystal molecules 23 are radially arranged centering the vertical alignment region 22 so as to make excellent viewing angle characteristics obtained throughout the full display region. Moreover, there is an advantage of making alignment treatment such as rubbing unnecessary in the manufacturing process. Because a light irradiation method as a means for partial homeotropic alignment is simply to irradiate the alignment layer with light, a problem of a longer process is solved.

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 utilizing the anisotropy of the refractive index of a liquid crystal.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal display (LCD) has
The display is performed by changing the orientation of liquid crystal molecules of a liquid crystal layer sandwiched between a pair of substrates and utilizing the optical refractive index change of the liquid crystal layer caused by the change. Therefore, it is important that the liquid crystal molecules of the liquid crystal cell are arranged as regularly as possible. The arrangement of the liquid crystal molecules is regulated by the surface state of the substrate constituting the liquid crystal cell and the interaction with the liquid crystal molecules near the substrate surface. Currently, the most widely used method for initially aligning liquid crystal molecules in a certain direction is to apply a liquid crystal alignment film material to opposing surfaces of a pair of substrates, and dry and cure the applied material. This is a method in which an alignment film is formed, and the surface of the alignment film is rubbed to have alignment characteristics. The liquid crystal molecules in contact with the alignment film can be aligned by the rubbed alignment film. Since the rubbing process is performed in a uniform direction on the substrate, all pretilt angles in the liquid crystal cell become uniform. Therefore, the pretilt angle becomes uniform within each picture element.

[0003] General liquid crystal display device (TFT-LCD)
As a twisted nematic type (hereinafter referred to as TN type)
There is a liquid crystal panel. In this TN type liquid crystal display device, the liquid crystal molecules are oriented so as to be twisted by 90 degrees between the two substrates. The viewing angle direction of this liquid crystal display device follows the direction of the liquid crystal molecules in the liquid crystal layer.

FIG. 11 shows a cross section of a cell in a conventional TN type liquid crystal display device. In FIG. 11, a substrate 4 on which a transparent electrode 2 and an alignment film 3 are further formed on a glass substrate 1,
A transparent electrode 6 and a substrate 8 having an alignment film 7 formed thereon are arranged on a glass substrate 5 such that the alignment films 3 and 7 face each other. That is, one substrate 4 has a transparent electrode 2 formed on one surface of the glass substrate 1 and an alignment film 3 formed on the entire surface to cover the transparent electrode 2. The same applies to the substrate 8 opposing the substrate 4. These alignment films 3,
The liquid crystal molecules 9 are twisted by 90 degrees between 7. Here, δ indicates the pretilt angle as the tilt angle of the liquid crystal molecules in contact with the alignment films 3 and 7, and when the liquid crystal molecules rise,
The direction in which the major axis faces is the normal viewing angle direction 10. Polarizing plates 11 and 12 are provided on the surfaces of the glass substrates 1 and 5 opposite to the alignment films 3 and 7, respectively.
Since the polarizing plate 11 has a polarizing axis in a direction perpendicular to the plane of FIG. 11 and the polarizing plate 12 has a polarizing axis in a direction horizontal to the plane of FIG. 11, light is generally transmitted when no voltage is applied. And a white display is obtained. This method is called a normally white mode (NW mode). In this NW mode liquid crystal display device, when the liquid crystal display screen is viewed from directly above the liquid crystal display device (in a direction perpendicular to the substrate surfaces 4 and 8) with a voltage applied to the liquid crystal cell, FIG. As shown by L1, the light transmittance decreases as the applied voltage value increases. The light transmittance of the liquid crystal cell becomes substantially zero when the applied voltage reaches a certain value, and remains substantially zero even when the applied voltage is further increased. However, if the viewing direction of viewing the liquid crystal display screen is changed obliquely, the relationship between the applied voltage and the transmittance characteristics changes.

FIG. 13 is a perspective view of a liquid crystal cell sandwiched between a pair of substrates 4 and 8 opposed to each other in the conventional TN type liquid crystal display device of FIG. In FIG. 13, the substrate 4
The rubbing direction 14 of the alignment film 3 on the substrate 8 and the rubbing direction 15 of the alignment film 7 on the substrate 8 are perpendicular to each other. Here, in a state where a voltage is applied to the liquid crystal cell 16, the sight is inclined in a normal viewing angle direction 10 from a direction perpendicular to the surface of the substrate 4, and the relationship between the applied voltage and the transmittance characteristic in the normal viewing angle direction 10 is illustrated. The characteristic changes from the curve L1 in FIG. 12 to the characteristic shown by the curve L2. That is, the transmittance decreases as the applied voltage increases, but the transmittance increases again when the applied voltage exceeds a specific voltage value, and then gradually decreases again. For this reason, when the visual sense is inclined in the normal viewing angle direction, a grayscale inversion phenomenon occurs in which the black and white (negative / positive) of the image is inverted at a specific angle. this is,
This is a phenomenon that occurs because the liquid crystal molecules 9 in the liquid crystal layer are inclined with a pretilt angle δ, and the refractive index changes visually. This phenomenon is a great obstacle for the viewer of the image.

FIGS. 14A to 14C are schematic diagrams for explaining a grayscale inversion phenomenon in a conventional liquid crystal display device. FIG.
As shown in a, when the applied voltage is zero or a relatively low voltage, the observer 17 in the normal viewing direction sees the central liquid crystal molecule 9 in the liquid crystal layer as an ellipse. When the height is increased, the major axis direction of the liquid crystal molecules 9 is oriented in the electric field direction (substrate 4,
14b), the observer 17 has a moment when the liquid crystal molecules 9 look round as shown in FIG. 14b. Further, when the applied voltage increases, the liquid crystal molecules 9 become substantially parallel along the direction of the electric field, and as shown in FIG. In the same phenomenon, even in a visual direction other than the normal viewing angle direction 10, even when the gradation inversion phenomenon does not occur due to the difference in the characteristics of the transmittance and the voltage, when the vision is deepened,
A visual characteristic such as a curve L2 in FIG. 12 that the contrast ratio between black and white is reduced appears. In the TN type liquid crystal display device, such a gradation inversion phenomenon in the normal viewing angle direction 10 and a decrease in the contrast ratio in a viewing angle direction other than the normal viewing angle direction become a great obstacle for a viewer, and the display characteristics of the liquid crystal display device itself are reduced. The result is a decrease.

[0007] In order to improve the viewing angle characteristic peculiar to such a TN type liquid crystal display device and to improve the display quality, the following methods have conventionally been announced. For example, Japanese Patent Application Laid-Open No. Sho 60-212424 and IEICE Technical Report (February 1993, pp. 35-41, “Complementary T
N (CTN) -TN with wide viewing angle "),
188374 discloses a method of dividing a picture element into two or more different orientation directions. Japanese Patent Application Laid-Open No. 3-230120 discloses a method using a compensating plate.

[0008]

Various methods have been disclosed as methods for improving the viewing angle characteristics of conventional liquid crystal display devices, but these methods have the following problems.

For example, the picture element as described above is divided into 2
As a method of giving two or more different orientation directions, there are a method of etching an alignment film composed of an organic film, and a method of forming a mask on the alignment film and performing an alignment treatment. All of these methods are performed by the photolithography method.Either method may cause impurities to be attached to the alignment film by etching or the like or to be damaged when the alignment processing is performed by attaching a metal mask to the alignment film. The display quality of the liquid crystal display device may be reduced. In addition, since the number of manufacturing steps is significantly increased, manufacturing cost and manufacturing time are deteriorated. Also,
In the method using the compensator, the viewing angle cannot be increased in both of the opposite viewing angle directions.

The present invention solves the above-mentioned conventional problems, and suppresses a decrease in display quality of a liquid crystal display device, and improves viewing angle characteristics in all viewing angle directions without greatly increasing the number of manufacturing steps. It is an object of the present invention to provide a liquid crystal display device capable of performing the above-described operations.

[0011]

A liquid crystal display device according to the present invention is a liquid crystal display device having a liquid crystal layer sandwiched between a pair of substrates and an alignment film between the substrates and the liquid crystal layer. The liquid crystal display is characterized in that an alignment region for vertically aligning liquid crystal is arranged in an alignment film having a property of performing horizontal alignment and having not been subjected to alignment processing. Also, align the liquid crystal vertically
Has the property of
It is characterized by having an alignment area for horizontal alignment of liquid crystal.
are doing.

Further, the alignment region is patterned in a dot-like manner, and liquid crystal molecules are radially or concentrically arranged around the alignment region.

[0013] The present invention is characterized in that the alignment region is patterned in a curved line, a straight line, or a combination thereof.

Further, the present invention is characterized in that the alignment region is formed so as to overlap a black mask.

[0015]

According to the above structure, for example, a vertical alignment region for vertically aligning the liquid crystal is arbitrarily arranged in an alignment film which has a property of horizontally aligning the liquid crystal and has not been subjected to the alignment treatment. Are vertically aligned. Since the liquid crystal has continuity, the liquid crystal molecules tend to be aligned in the vertical alignment direction even in a portion in contact with the vertical alignment region. Accordingly, the liquid crystal molecules are arranged radially or concentrically around the dot when the vertical alignment region is a dot, and are arranged in two directions with the vertical alignment region being a straight line when the vertical alignment region is a straight line. Similarly, in the case where the shape is changed even in the case of a straight line, or in the case of a curved line, the liquid crystal molecules can have various orientations close to a point in the alignment direction. Further, since the range in which the vertical alignment has a regulating force is several tens of microns, by forming a single or a plurality of vertical alignment regions according to the size of the display region, it is possible to improve the entire display region. And excellent viewing angle characteristics. Further, the vertically aligned portion always displays black and substantially reduces the aperture ratio. Therefore, it is desirable that the area of the vertical alignment region be suppressed to 50% or less of the display area. Also,
If the vertical alignment region is formed so as to overlap the black mask, the aperture ratio does not decrease at all.

Further, by subjecting at least a predetermined region of the alignment film of the substrate to a surface treatment for roughening the surface, and optionally arranging a vertical alignment region for vertically aligning the liquid crystal, a part of the display region can be selectively formed. A liquid crystal display device having uniform viewing angle characteristics from all directions can be obtained only by vertically aligning the liquid crystal. In addition, when etching or the like is not used in the manufacturing process, no impurities adhere to the alignment film, and the display quality of the liquid crystal display device does not deteriorate. Further, there is an advantage that there is no need for an alignment treatment such as rubbing. As means for partially vertical alignment, a vertical alignment film may be formed at a predetermined location, or a chemical solution such as an alkali or an acid, or a method of performing a surface treatment to roughen the alignment film surface by irradiating light or the like. There is also. Above all, the method of irradiating light only needs to irradiate the alignment film with light, so that there is no problem that the step, which is a drawback of the process of the conventional viewing angle improving method, becomes longer.

[0018]

Embodiments of the present invention will be described below.

(Embodiment 1) FIGS. 1a and 1b are plan views of a liquid crystal display device according to a first embodiment of the present invention when a picture element is enlarged and viewed from directly above, and FIG. 1c is a sectional view thereof. It is.
As shown in FIG. 1A, a vertical alignment region 22 is provided at the center of a picture element 21, and liquid crystal molecules 23 around the vertical alignment region 22 are arranged radially around the vertical alignment region 22. When a voltage is applied to this liquid crystal display device, the liquid crystal molecules 23 rise so that the side of the vertical alignment region 22 rises.
In this case, the liquid crystal molecules 23 do not include a chiral component. When the liquid crystal molecule 23 contains a chiral component,
As shown in FIG. 1B, the liquid crystal molecules 24 are easily arranged concentrically. In FIG. 1C, a vertical alignment region 22 is formed in an upper alignment film 25, and liquid crystal molecules 23 below the vertical alignment region 22 are vertically aligned.

FIG. 2 is a view showing a manufacturing process of the liquid crystal display device according to the first embodiment of the present invention. As shown in FIG. 2, first, picture elements 32 and 33 are formed on a substrate 31. Next, an alignment film 34 is formed on the entire surface of the substrate 31 so as to cover the picture elements 32 and 33. As the alignment film 34, an organic polymer film 1
One polyimide film is used. The alignment film 34 has a property of horizontally aligning liquid crystal molecules. This substrate 3
A mask 35 for a light irradiation step, which will be described later, is arranged at a position facing the surface 1. In the mask 35, a hatched portion 35a is a light-shielding portion that does not transmit the light 36, and a portion 35b that is not hatched.
Is a transmitting portion for transmitting the light 36. This transmission part 35
b corresponds to the center of the picture elements 32 and 33. After forming the orientation film 34, light 36 is irradiated on the orientation film 34 through the mask 35, and the center of each of the picture elements 32 and 33 is formed. A surface treatment for roughening the surface is performed to form a vertical alignment region of liquid crystal molecules. This light irradiation is performed on one of the substrates 31 constituting the liquid crystal display device. After irradiation with the light 36, the liquid crystal cell is assembled without performing an alignment treatment such as rubbing.
The present invention is applicable to all substrate structures conventionally used in liquid crystal display devices.

The irradiation step of the light 36 can be performed at any time after the formation of the alignment film 34. Specifically, the alignment film 3
4 After application, after preliminary firing, or after main firing.
In the present embodiment, the vertical alignment region obtained by irradiating light using the mask 35 is a perfect circle having a diameter of 10 μm and occupying 3% of the pixel area. Also, the mask 35
For example, a mask similar to a commonly used photomask can be used. Further, as the light 36 applied to the alignment film 34 made of a polyimide film, any of ultraviolet light, visible light, infrared light, or laser light of a predetermined wavelength for the material of the alignment film 34 may be used. Ultraviolet light having a wavelength of 400 nm or less is preferable as a light source that easily obtains high energy for changing the wavelength.
Light of such a wavelength can be easily obtained with a high-pressure mercury lamp, a low-pressure mercury lamp, a mercury-xenon lamp, or the like. When irradiating this ultraviolet light, it irradiates on condition of 30 J / cm < ² > or more.

As described above, the effect of providing the vertical alignment region on the alignment film 34 was observed at about 50 μm around the vertical alignment region which is the irradiation point. When the optical characteristics of this liquid crystal panel were measured, characteristics equivalent to the curve L3 shown in the transmittance-applied voltage characteristics in FIG. 3 could be measured.

Here, the principle of expanding the viewing angle will be described. 3A to 3C are schematic diagrams for explaining the principle of expansion of the viewing angle in the liquid crystal display device of FIG. 1, wherein a is a cross-sectional view of a TN type liquid crystal panel, and b is a view of the pixel of a viewed from directly above. FIG. 2C is a sectional view of a pixel when the liquid crystal display device is a guest-host (GH) type liquid crystal panel. In FIG. 3a,
Reference numerals 41 and 42 denote polarizing plates, which have a direct Nicol relationship so as to form an NW mode in a TN type liquid crystal panel. Transparent substrates 43 and 44 are provided inside the polarizing plates 41 and 42, respectively. Further, the alignment film 4 horizontally aligned inside the transparent substrates 43 and 44 is provided.
5, 46 are applied and provided. At this time, although the horizontal alignment film 45 has not been subjected to the alignment process,
A predetermined amount of ultraviolet light is irradiated on a predetermined portion of the substrate 5 to obtain a vertical alignment region 47. The vertical alignment region 47 includes liquid crystal molecules 48
Has the function of vertically orienting. Therefore, the liquid crystal molecules 48 in the liquid crystal are vertically aligned between the transparent substrates 43 and 44, and the liquid crystal molecules 48a around the vertically aligned liquid crystal molecules 48 are influenced by the liquid crystal molecules and are sequentially inclined at an angle.
Therefore, as shown in FIG. 3B, the liquid crystal molecules 48a can have an optimal viewing angle direction in all directions around the vertical alignment region 47. 49 indicates the position of the observer.

The liquid crystal display device manufactured by this method has a viewing angle characteristic L3 as shown in FIG. That is, when the liquid crystal cell is viewed obliquely, that is, the voltage-transmittance curve (VT curve) in the optimal viewing angle direction when measured from a position inclined by 40 degrees with respect to the direction perpendicular to the alignment films 45 and 46 is , A gradation inversion occurs at a certain voltage as shown by the curve L2. However, since the liquid crystal molecules in the direction completely opposite to the optimum viewing angle direction can be observed at the same time, the viewing angle characteristics of the curve L1 are mixed with the viewing angle characteristics of the curve L2. That is, since there are various optimal viewing angle directions for one point, various transmittance curves are synthesized, and a screen without gradation inversion such as the characteristic shown by the curve L3 can be viewed.

A guest-host (GH) type liquid crystal panel shown in FIG. 3c is applied to a device other than the TN type liquid crystal panel by a similar method. Reference numeral 50 denotes a GH dye. In this system, the display can be confirmed without the polarizing plates 41 and 42 shown in FIG.
The effect by the above can be obtained.

In this embodiment, the shape of the light transmitting portion 35b of the mask 35 is a perfect circle. However, the light transmitting portion 35b may be an ellipse, a square such as a triangle or a quadrangle, or an irregular shape such as a star. It may have a certain shape. In this case, the mask 3
The shape of the light transmitting portion 35b of No. 5 becomes the shape of the vertical alignment region formed in the alignment film 34.

In the present embodiment, the diameter of the light transmitting portion 35b of the mask 35 is 10 microns (3% of the pixel area), but it is preferably 20 microns or less. What is necessary is just below percent. This is because when the area of the vertical alignment region is 50% or more of the pixel area, the vertical alignment region is recognized as a black point.

Further, in this embodiment, a mask similar to a photomask is used as the mask 35. However, a mask pattern is formed directly on the alignment film 34 by using the photolithography technique, and the mask is irradiated with light. May be peeled off. Further, the condensed light may be applied to the boundary region without using the mask 35.

Further, in this embodiment, ultraviolet light is used as a means for roughening the surface of the alignment film 34 in order to form a vertical alignment region. However, irradiation with an electron beam, ion beam, X-ray, or the like is also possible.

Further, in this embodiment, a polyimide film is used as the alignment film 34, but an alignment film made of another material may be used. For example, silicon nitride, silicon oxide, magnesium fluoride, gold or the like may be used. An inorganic alignment film as a main component may be used. In this case, irradiation with high energy light such as an ultraviolet laser or an electron beam is required.

Further, in the present embodiment, the light irradiation is performed on one side of the substrate constituting the liquid crystal display device, but may be performed on both sides. In general, irradiation of both substrates has a stronger alignment regulating force.

(Embodiment 2) FIG. 5 is an enlarged plan view of a picture element of a liquid crystal display device according to a second embodiment of the present invention when viewed from directly above. In FIG. 5, when the size of the picture element 51 is large and the orientation of the entire picture element 51 cannot be controlled in one vertical alignment area, a plurality of vertical alignment areas 52 are provided in this way. The number, shape and arrangement of the vertical alignment regions 52 are arbitrary. In this embodiment, square vertical alignment regions 52 of 10 μm square are arranged at a pitch of 70 μm, and the ratio occupied by the vertical alignment regions 52 is 2% of the whole. In this embodiment, a vertical alignment characteristic 52 is imparted to the alignment film by performing a surface treatment for roughening the surface of the alignment film, similarly to the above-described light irradiation. The substrate structure and the like are the same as those in the first embodiment.

FIG. 6 is a view showing a method of manufacturing a liquid crystal display device according to a second embodiment of the present invention. As shown in FIG. 6, an alignment film 62 is formed on a glass
At any time after the formation of the resist pattern 2, a resist pattern 63 is formed on the alignment film 62 using a photolithography technique.
The alignment film 62 is covered with the resist pattern 63 except for the region to be vertically aligned. Thereafter, the surface of the alignment film 62 is brought into contact with an alkaline solution shown by an arrow 64 to roughen only the contact surface. As the alkaline solution, 0.5
% NaOH aqueous solution or 2.38% TMAH aqueous solution. In this surface treatment, an acid solution can be used instead of the alkali solution. One example is nitric acid. Further, a reactive gas such as ozone or ammonia gas may be used.

(Embodiment 3) FIG. 7 is a plan view of a liquid crystal display device according to a third embodiment of the present invention when a picture element is enlarged and viewed from directly above. In FIG. 7, a vertical alignment region 72 is selectively provided at a predetermined position of a picture element 71 in a wavy stripe shape. The line width of this waveform is 5 microns and the picture element 7
1 occupies about 15% of the total area. In the vertical alignment region 72, the liquid crystal molecules 73 are vertically aligned. The liquid crystal molecules 73 around the vertical alignment region 72 are sequentially inclined at an angle under the influence. Therefore, the liquid crystal molecules 73
Can have an optimal viewing angle direction in all directions around the linear and wavy vertical alignment region 72.

FIG. 8 is a view showing a method of manufacturing a liquid crystal display device according to a third embodiment of the present invention. As shown in FIG. 8A, at an arbitrary point after the formation of the horizontal alignment film 74, a resist pattern 75 is formed on the horizontally aligned alignment film 74 by using a photolithography technique. Except for the region to be vertically aligned, the alignment film 7 is formed by the resist pattern 75.
4 is coated. Thereafter, the alignment film 74 is removed as shown in FIG. 8B, and a vertical alignment film 76 is applied as shown in FIG. 8C. Next, when the resist pattern 75 is removed as shown in FIG. 8D, a vertical alignment region 72 is formed. As described above, by selectively forming the vertical alignment film 76 on the horizontal alignment film 74, the vertical alignment region 72 can be formed in the same manner as the light irradiation described above. Thus, the conventional rubbing step can be omitted. Otherwise, the substrate structure and the like are the same as in the case of the first embodiment.

In the present invention, the vertical alignment region 72 is provided in the form of a stripe with a waveform. However, the vertical alignment region 72 is not limited to the waveform and may be a mountain or a saw, or may be a shape in which points of various shapes are continuous. That is, the linear vertical alignment region may be a single or a plurality of vertical alignment regions patterned in a curve or a straight line or a combination thereof, depending on the pixel area, and only one in the center. May be.

(Embodiment 4) FIGS. 9a to 9c are plan views of enlarged picture elements of a liquid crystal display device according to a fourth embodiment of the present invention, as viewed from directly above. As shown in FIG. 9A, the vertical alignment region 82 is provided in a linear stripe shape for each picture element 81. The line width of the vertical alignment region 82 is 10 microns and the area ratio is about 20%. Since the liquid crystal molecules 83 in the horizontal alignment region are vertically arranged in the vertical alignment region 82, in this case, they are arranged in two directions. A
Is a boundary between these two directions. In this case, a rubbing process may be performed.

Even in the case of the linear vertical alignment region 82, for example, as shown in FIGS. 9b and 9c, by forming vertical alignment regions 84 and 85 having a shape in which several straight lines are combined, uniformity in all directions can be achieved. It is possible. When the size of the picture element 81 is several tens of microns both vertically and horizontally, the vertical alignment region 8 shown in FIG.
5, the vertical alignment region 82c may be provided so as to overlap the black mask. In this case, the viewing angles in all directions can be made uniform without lowering the aperture ratio.

Here, as in the first embodiment, a method of irradiating light using a photomask is used as a method of forming the vertical alignment region 82 in the alignment film. By irradiating appropriate light to a region other than the alignment region 82, the pretilt angle may be reduced and horizontal alignment may be performed. The amount of light to be applied varies depending on the orientation film, but is required to be 10 J / cm ² or more. This allows
The pre-tilt angle of the light irradiating section becomes 10 degrees or less.

As shown in the sectional view of the picture element in FIG. 10, the areas of the vertical alignment regions 93 and 94 are changed by the alignment films 91 and 92 on the upper and lower substrates,
By shifting the 3,94 pattern by several microns, the alignment regulating force was also enhanced.

In the above Examples 1 to 4, it is based on the following principle that the alignment of the liquid crystal can be changed depending on the roughness of the alignment film surface. That is, when the surface of the alignment film having the horizontal alignment characteristic is roughened, the pretilt angle of the liquid crystal molecules in that portion is reduced, but when the surface of the alignment film is sufficiently roughened, the liquid crystal molecules are vertically aligned. Become. Since the liquid crystal has continuity, the liquid crystal molecules 23 tend to align in the vertical alignment direction even in a portion in contact with the vertical alignment region 22 as shown in FIG. 1C. Thereby, the liquid crystal molecules 23
If the vertical alignment region 22 is point-like, such as a circle, a corner, or a star, the center of the vertical alignment region 22 is radially aligned with FIG.
9a, and the vertically aligned regions 8 as shown in FIG.
When 2 is a straight line, it is arranged in two directions with that being interposed.
Similarly, as shown in FIG. 7, when the shape of the liquid crystal molecules 73 changes in a straight line, such as an intricate uneven shape such as a wavy shape or a chevron shape, the alignment direction of the liquid crystal molecules 73 changes to a point-like shape. It can have various directions. Further, since the range in which the vertical alignment has a regulating force is several tens of microns, by forming a plurality of vertical alignment regions according to the size of the display region, good viewing angle characteristics can be obtained over the entire display region. Can be obtained. Further, the vertically aligned portion always displays black and substantially reduces the aperture ratio. Therefore, it is desirable that the area of the vertical alignment region be suppressed to 50% or less of the display area.

Conversely, a vertical alignment film can be used as the alignment film. In this case, the pre-tilt angle is reduced by performing a surface treatment for appropriately roughening the alignment film other than the vertical region.
What is necessary is just to make it a horizontal orientation state.

As described above, according to the first to fourth embodiments, regions having different viewing angles can be formed only by vertically aligning a part of the display region of the liquid crystal display device. Specifically, a part of the display area is shown in FIGS.
A liquid crystal display device having a uniform viewing angle characteristic from all directions can be obtained only by selectively vertically orienting in a shape as shown in FIGS. 7, 9b and 9c. In addition, there is an advantage that an alignment treatment such as rubbing is not required in the manufacturing process. As means for partially vertically aligning, a vertical alignment film may be formed at a predetermined place, or a chemical solution such as an alkali or an acid, or a method of performing a surface treatment to roughen the alignment film surface by irradiating light. is there. Among them, the method of irradiating light, for example, only needs to irradiate the alignment film with light through a photomask, so that it is possible to solve the problem that the step which is a drawback of the conventional viewing angle improving method becomes longer. it can.

Further, by vertically orienting a part of the display area in a shape as shown in FIG. 9A, the viewing angle characteristics in the forward and reverse directions can be made uniform. In this case, an alignment treatment such as rubbing may be performed. If a method of roughening the surface of the alignment film with light is used as a means for partially vertically aligning, the problem that the process, which is a drawback of the conventional viewing angle improving method, becomes longer can be solved. Alternatively, a vertical alignment film may be partially formed, or a method of roughening the alignment film surface with a chemical such as an alkali or an acid may be used. In such a case, each of them is the same as the conventional one in that the photolithography technique is used, but is advantageous in that an alignment treatment such as rubbing is not required.

In the present invention, the vertical alignment regions obtained by various methods are provided in various shapes. However, the combination of the shape, the number, and the forming method of the vertical alignment regions is arbitrary. In the step of arranging the vertical alignment region, the surface shape of the alignment film may be selectively formed in a predetermined region of the alignment film on at least one substrate so that the surface shape of the alignment film is vertically aligned with respect to the liquid crystal molecules. A surface treatment may be performed on the alignment film by providing a rough surface and coating the alignment film thereon.

FIG. 3 of the first embodiment is shown in FIG.
23 and 24 in Japanese Patent Application Laid-Open No. 173138/1992, the purpose of Japanese Patent Application Laid-Open No. Hei 5-173138 is to suppress disclination lines generated at the boundary where alignment processing has been performed first. It does not solve the problem described above, but is fundamentally different from the present invention. Similarly, in Japanese Patent Application Laid-Open No. Hei 5-5886, a vertical alignment region is provided by irradiating ultraviolet light or the like, but Japanese Patent Application Laid-Open No. Hei 5-5886 discloses a method for preventing light leakage outside picture elements. However, this does not solve the problem of the present invention, and is fundamentally different from the present invention.

[0047]

As described above, according to the present invention, a liquid crystal display device having a uniform viewing angle characteristic in all directions can be obtained. Further, according to the liquid crystal display device of the present invention, it is possible to easily obtain a liquid crystal display device in which the viewing angle characteristics in two directions are uniform. In particular, if the light irradiation method is used,
By simply adding a step of irradiating light through a mask, an easy and high-quality wide viewing angle liquid crystal display device can be obtained,
The display quality of the liquid crystal display device can be improved.

[Brief description of the drawings]

FIGS. 1A and 1B are plan views of a picture element of a liquid crystal display device according to a first embodiment of the present invention when the picture element is enlarged and viewed from directly above, and FIG. It is.

FIG. 2 is a schematic manufacturing process diagram of the present liquid crystal display device according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram for explaining the principle of expanding the viewing angle in the liquid crystal display device according to the first embodiment of the present invention;
(a) is a sectional view of a picture element of a TN type liquid crystal panel, (b) is a view of the picture element of (a) viewed from directly above, and (c) is a liquid crystal display device which is a guest-host (GH) type liquid crystal. It is a picture element sectional view in the case of a panel.

FIG. 4 is a graph showing an applied voltage-transmittance characteristic in the liquid crystal display device according to the first embodiment of the present invention.

FIG. 5 is an enlarged plan view of a picture element of a liquid crystal display device according to a second embodiment of the present invention when viewed from directly above.

FIG. 6 is a diagram illustrating a method for manufacturing a liquid crystal display device according to a second embodiment of the present invention.

FIG. 7 is a plan view of a picture element of a liquid crystal display device according to a third embodiment of the present invention, which is enlarged and viewed from directly above.

FIG. 8 is a diagram illustrating a method for manufacturing a liquid crystal display device according to a third embodiment of the present invention.

FIGS. 9A to 9C are plan views of enlarged picture elements of a liquid crystal display device according to a fourth embodiment of the present invention, as viewed from directly above.

FIG. 10 is a sectional view of a picture element of a liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 11 is a sectional view of a liquid crystal cell in a conventional TN type liquid crystal display device.

FIG. 12 is a graph showing an applied voltage-transmittance characteristic in a conventional TN type liquid crystal display device.

FIG. 13 is a perspective view of a liquid crystal cell sandwiched between a pair of substrates 4 and 8 opposed to each other in the conventional TN liquid crystal display device of FIG.

FIGS. 14A to 14C are schematic diagrams for explaining a grayscale inversion phenomenon in a conventional liquid crystal display device.

[Explanation of symbols]

21, 32, 33, 51, 71, 81 Picture elements 22, 47, 52, 72, 82, 84, 85, 93, 9
4 Vertical alignment regions 23, 24, 48, 48a, 73, 83 Liquid crystal molecules 25, 34, 45, 46, 62, 74, 76, 91, 9
2 Alignment film 31 Substrate 35 Mask 36 Light 63, 75 Resist pattern

Continuation of the front page (56) References JP-A-7-168187 (JP, A) JP-A-6-214235 (JP, A) JP-A-6-82788 (JP, A) JP-A-2-251821 (JP) JP-A-3-267919 (JP, A) JP-A-63-14123 (JP, A) JP-A-64-76029 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) G02F 1/1337 505 G02F 1/1335 500

Claims (5)

(57) [Claims] 1. A liquid crystal display device having a liquid crystal layer sandwiched between a pair of substrates and an alignment film between the substrates and the liquid crystal layer, the liquid crystal display device having a property of horizontally aligning the liquid crystal and performing an alignment process. A liquid crystal display device in which an alignment region for vertically aligning liquid crystal is arranged on an alignment film that has not been subjected to the alignment. 2. A liquid crystal display device having a liquid crystal layer sandwiched between a pair of substrates and having an alignment film between the substrates and the liquid crystal layer, the liquid crystal display device having a property of vertically aligning the liquid crystal and performing an alignment process. A liquid crystal display device in which an alignment region for horizontally aligning a liquid crystal is arranged in an alignment film that has not been subjected to the alignment. 3. The method according to claim 1, wherein the alignment region is patterned in a point shape.
2. The liquid crystal display device according to claim 1, wherein the liquid crystal molecules are arranged radially or concentrically around the alignment region. 4. The liquid crystal display device according to claim 1, wherein the alignment region is patterned in a curved line, a straight line, or a combination thereof. 5. The liquid crystal display device according to claim 1 , wherein the alignment region is formed so as to overlap a black mask.