JP4805291B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device. In particular, the present invention relates to an alignment treatment technique for an alignment film of a liquid crystal display device.

  A liquid crystal display device is sandwiched between a pair of substrates facing each other with a gap, an electrode and an alignment film formed on one substrate, an electrode and an alignment film formed on the other substrate, and the pair of substrates. LCD. The electrode on one substrate is a common electrode, and the electrode on the other substrate is formed as a pixel electrode. The pixel electrode can be provided with an active matrix. Further, a black matrix or a color filter is provided on any substrate.

  When the liquid crystal display device is viewed, a certain portion of the pixel electrode becomes brighter or darker depending on on / off of the voltage. That is, the pixel electrode defines the pixel display portion. The opening of the black matrix is disposed so as to overlap with the pixel electrode, and the area of the opening of the black matrix is formed smaller than the area of the pixel electrode. Therefore, when there is a black matrix, the pixel display portion is defined by the opening of the black matrix. In either case, the portion around the pixel display portion is a non-display portion.

  The alignment film is classified into a horizontal alignment film and a vertical alignment film. When the horizontal alignment film is used, the liquid crystal molecules are aligned substantially parallel to the surface of the substrate, and when a voltage is applied, the liquid crystal molecules are tilted with respect to the surface of the substrate. When the vertical alignment film is used, the liquid crystal molecules are aligned substantially perpendicular to the surface of the substrate, and when a voltage is applied, the liquid crystal molecules tilt obliquely from the surface of the substrate. In any case, the alignment film is subjected to an alignment process such as rubbing. In the case of a TN liquid crystal display device, the liquid crystal is twisted from one alignment film toward the other alignment film. Further, the rubbing causes the liquid crystal molecules to pretilt with a pretilt angle with respect to the alignment film.

  In the TN liquid crystal display device, when the liquid crystal display device is viewed in an assembled state, the two alignment films are rubbed in a direction that forms a predetermined angle (90 degrees) with each other, and the liquid crystal is aligned from one alignment film to the other alignment film. Try to twist towards the membrane. Here, if the liquid crystal molecules are aligned in one plane ignoring the twist, the pretilt direction of the liquid crystal molecules located near one alignment film and the liquid crystal molecules located near the other alignment film The liquid crystal molecules positioned in the middle are aligned according to the pretilt direction of the liquid crystal molecules positioned near both alignment films.

  If the pretilt direction of the liquid crystal molecules located near one alignment film and the pretilt direction of the liquid crystal molecules located near the other alignment film are opposite, the liquid crystal molecules located in the middle are either alignment film. It is not known whether the liquid crystal molecules may be aligned according to the pretilt direction of liquid crystal molecules located near the liquid crystal molecules, and the liquid crystal molecules do not tilt in a certain direction. This alignment state is splay alignment when the pretilt angle of the alignment film is close to horizontal alignment, and bend alignment when the pretilt angle of the alignment film is high, for example, 30 ° or more, or close to vertical alignment.

  However, the applicant of the present application is that even if the pretilt direction of the liquid crystal molecules located near one alignment film is opposite to the pretilt direction of the liquid crystal molecules located near the other alignment film, If there is a difference between the pretilt angle of the liquid crystal molecules near the liquid crystal molecule and the pretilt angle of the liquid crystal molecules near the other alignment film, the liquid crystal molecules located in the middle follow the pretilt direction of the liquid crystal molecules having a large (or small) pretilt angle. It is found that it is oriented, and this is applied to the orientation division described below. When a horizontal alignment film is used, the liquid crystal molecules located in the middle are aligned according to the pretilt direction of the liquid crystal molecules having a large pretilt angle. When the vertical alignment film is used, the liquid crystal molecules located in the middle are pretilt. Alignment is performed according to the pretilt direction of liquid crystal molecules having a small angle.

  The liquid crystal display device includes a problem of so-called viewing angle characteristics that it looks whitish or blackish according to the viewing direction of the display surface. As a proposal for improving the problem of viewing angle characteristics, there is an alignment division technique. In the alignment division, one pixel is divided into two domains. In one domain, liquid crystal molecules located in the middle between both alignment films are tilted in one direction, and in the other domain, between the alignment films. The liquid crystal molecules located in the middle are tilted in the opposite direction. By the orientation division, the characteristic that looks whitish and the characteristic that looks blackish are averaged, and a good display can be obtained when the display surface is viewed from any direction. However, in order to perform alignment division, it is necessary to perform rubbing for each domain, and it is necessary to perform rubbing twice for each alignment film using a mask.

  Patent Document 1 filed by the applicant of the present application discloses various alignment division techniques. It is particularly advantageous that the alignment division can be performed by performing rubbing once for each alignment film. In this alignment division technique, each alignment film is rubbed and irradiated with ultraviolet rays through a mask. As a result, the liquid crystal molecules are aligned at the first pretilt angle due to the rubbing effect in the portion not irradiated with the ultraviolet rays, and the pretilt angle of the liquid crystal molecules is increased (or decreased) in the portion irradiated with the ultraviolet rays. Orientation is performed at the second pretilt angle. The part of the first alignment film that forms the first pretilt angle and the part of the other alignment film that forms the second pretilt angle are arranged to face each other. The rubbing of both alignment films is the bend alignment or splay alignment described above, but due to the difference in the pretilt angle of the liquid crystal molecules near both alignment films, the intermediate liquid crystal molecules follow the pretilt direction of the specific pretilt angle liquid crystal molecules. Orient. Since the substantial part and the opening of the mask appear alternately, the alignment direction of the liquid crystal also alternates accordingly.

  Further, the liquid crystal display device has a pixel display portion and a non-display portion, but the pixel display portion and the non-display portion are rubbed simultaneously. As an exception, Patent Document 2 proposes that the alignment process be performed so that the anchoring energy of the display portion is larger than the anchoring energy of the pixel display portion. According to this publication, when a constant voltage is applied, the liquid crystal molecules in the pixel display portion are likely to rise, and the liquid crystal molecules in the non-display portion are difficult to rise, so that they are not affected by the bus line voltage applied to the non-display portion. I have to.

  There is also a problem with rubbing. The rubbing is rubbing the alignment film with a cloth such as rayon, and dust generation occurs when the cloth such as rayon is brought into a clean room. Further, static electricity is generated by rubbing, and the active matrix TFT (thin film transistor) may be destroyed. Therefore, there is a demand for alignment treatment other than rubbing, for example, by ultraviolet irradiation.

For example, Patent Document 3, Patent Document 4, and Patent Document 5 disclose performing alignment processing using polarized ultraviolet rays. In Patent Document 3, a homogeneously aligned liquid crystal cell is partially irradiated with polarized ultraviolet rays, and the alignment direction of the irradiated portion changes from the original homogeneous alignment direction. Patent Literature 4 and Patent Literature 5 disclose that a polymer network (PPN) capable of photo-orientation is irradiated with UV light polarized perpendicularly to realize orientation of liquid crystal molecules. However, this method has a problem that polarized ultraviolet rays must be used. Furthermore, the only polarizers that can be used to obtain polarized UV light are currently Glan Taylor type polarizers, but Glan Taylor type polarizers are manufactured by cutting out naturally occurring calcite and are actually used. Not suitable for. Therefore, it is desired that the alignment treatment can be performed using non-polarized ultraviolet rays.
US Pat. No. 5,473,455 JP-A-8-152638 US Pat. No. 4,974,941 JP-A-6-289374 JP-A-8-015681

  If the alignment processing of the pixel display portion of the opposing alignment film is different, a large amount of charge remains in the vicinity of one alignment film when a voltage is applied to the pixel during use of the liquid crystal display device and the voltage is turned off. Even when the voltage is turned off, the image displayed previously is thinly burned by the residual charge. In particular, in the alignment division using the above-described ultraviolet rays, one alignment film has a portion irradiated with ultraviolet rays, and the other alignment film portion opposite thereto is not irradiated with ultraviolet rays. There is a difference in the alignment treatment of the portions facing each other, and there is a tendency that a large amount of charge remains in the vicinity of one alignment film.

  It is an object of the present invention to prevent a large amount of electric charge from remaining in the vicinity of one alignment film in an opposing alignment film, and even in a state where the voltage is turned off, a previously displayed image is thinly burned by the residual charge. It is an object of the present invention to provide a liquid crystal display device that can be used. Another object of the present invention is to provide a liquid crystal display device in which alignment processing of opposing alignment films can be performed equally and easily in a liquid crystal display device divided in alignment.

  Another object of the present invention is to provide a liquid crystal display device capable of performing an alignment treatment instead of rubbing. Another object of the present invention is to provide a liquid crystal display device capable of performing a combination of rubbing and other alignment treatments.

  A liquid crystal display device according to the present invention includes a pair of substrates opposed to each other with an interval, an electrode and an alignment film formed on one substrate, an electrode and an alignment film formed on the other substrate, and the pair of substrates A liquid crystal sandwiched therebetween, and a means for partitioning a pixel display portion and a non-display portion at least partially surrounding the pixel display portion, and the alignment film controls the alignment of the liquid crystal molecules in the pixel display portion. Alignment treatment is performed so as to be regulated by the alignment of the liquid crystal molecules in the display portion.

  In this configuration, the alignment processing is changed between the pixel display portion and the non-display portion. In the pixel display portion, the alignment treatments of the opposing alignment films are not substantially different, thereby preventing a large amount of charge from remaining in the vicinity of one alignment film. In the non-display portion, even if there is a substantial difference in the alignment treatment of the opposing alignment films, this does not affect the display. Thus, if the orientation of the liquid crystal molecules in the pixel display portion is regulated by the orientation of the liquid crystal molecules in the non-display portion, a desired display can be performed in the pixel display portion.

In addition to this configuration, the following configuration can be adopted.
The alignment processing of the pixel display portion is different from the alignment processing of the non-display portion.
The alignment film is made of a uniform alignment material.
The alignment film is only rubbed in the pixel display portion, and is rubbed and irradiated with ultraviolet rays in the non-display portion.
The pixel display portion has at least two domains in which the alignment directions of liquid crystal molecules are opposite to each other.
The alignment film includes at least two material layers in the non-display portion.
Only the non-display portion is rubbed.
The alignment film is rubbed in at least two directions in the non-display portion.

An electrode of one substrate is a pixel electrode, and one substrate is provided with a black matrix having a black stripe and an opening, and the pixel display portion is defined by the opening of the black matrix.
Furthermore, the liquid crystal display device according to the present invention includes a pair of substrates facing each other with a gap, an electrode and an alignment film formed on one substrate, an electrode and an alignment film formed on the other substrate, and the pair of substrates. A liquid crystal sandwiched between substrates, and the alignment film is an alignment film exhibiting vertical alignment, and alignment with a pretilt angle is realized by irradiating non-polarized ultraviolet rays from an oblique direction. It is characterized by being.

In this configuration, it was found that an alignment with a pretilt angle can be realized by obliquely irradiating non-polarized ultraviolet rays without rubbing in the case of a vertical alignment film.
In addition to this configuration, the following configuration can be adopted.
The irradiated ultraviolet ray includes a component having a wavelength of 280 nm or less.

The parallelism of ultraviolet rays is within ± 10 degrees.
Furthermore, the liquid crystal display device according to the present invention includes a pair of substrates facing each other with a gap, an electrode and an alignment film formed on one substrate, an electrode and an alignment film formed on the other substrate, and the pair of substrates. A liquid crystal sandwiched between the substrates, the alignment film is rubbed, and is irradiated with ultraviolet rays from an oblique direction.

According to this configuration, a new alignment process can be performed by combining rubbing and ultraviolet irradiation.
In addition to this configuration, the following configuration can be adopted.
The alignment film is uniformly rubbed and irradiated with ultraviolet rays from different oblique directions for each domain.

The irradiated ultraviolet ray includes a component having a wavelength of 280 nm or less.
The parallelism of ultraviolet rays is within ± 10 degrees.
Further, the present invention provides a pair of substrates opposed to each other with an interval, an electrode and an alignment film formed on one substrate, an electrode and an alignment film formed on the other substrate, and the pair of substrates between the pair of substrates. The alignment film is irradiated with ultraviolet rays so that alignment with a pretilt angle of liquid crystal molecules adjacent to the alignment film is realized, and the substrate is irradiated to realize alignment. A liquid crystal display device comprising a material that absorbs an ultraviolet wavelength region is provided.

  Further, the present invention provides a pair of substrates opposed to each other with an interval, an electrode and an alignment film formed on one substrate, an electrode and an alignment film formed on the other substrate, and the pair of substrates between the pair of substrates. A region in which the alignment film of the at least one substrate is divided into a plurality of stripe-like regions extending in parallel to each other and the alignment direction of the liquid crystal molecules in one region is adjacent thereto The liquid crystal display device is characterized in that the alignment treatment is performed so that the alignment direction is opposite to the alignment direction of the liquid crystal molecules and the alignment direction is parallel to the stripes.

  Further, the present invention provides a pair of substrates opposed to each other with an interval, an electrode and an alignment film formed on one substrate, an electrode and an alignment film formed on the other substrate, and the pair of substrates between the pair of substrates. Each of the pixels has four alignment regions different from each other, and the four alignment regions are formed so that the liquid crystal molecules are oriented in four directions at 90 degrees with respect to each other. A liquid crystal display device is provided.

  Further, the present invention provides a pair of substrates opposed to each other with an interval, an electrode and an alignment film formed on one substrate, an electrode and an alignment film formed on the other substrate, and the pair of substrates between the pair of substrates. The alignment film is formed so that one pixel has at least two regions having different threshold voltages, and the alignment film is subjected to an alignment process with a pretilt by irradiation of ultraviolet rays. A liquid crystal display device is provided. According to this configuration, the rubbing is not used by a relatively simple means such as ultraviolet irradiation (therefore, the rubbing does not form groove-like rubbing marks on the surfaces of the alignment films 20 and 24). The alignment can be realized, and a plurality of regions having different threshold voltages can be formed in one pixel, and the viewing angle characteristics of the liquid crystal display device can be improved without increasing the manufacturing cost.

  Further, the present invention provides a pair of substrates opposed to each other with an interval, an electrode and an alignment film formed on one substrate, an electrode and an alignment film formed on the other substrate, and the pair of substrates between the pair of substrates. The alignment film is formed so that one pixel has four regions in which the alignment of the liquid crystal is different by a boundary line extending in a cross shape, and a light-shielding film covering the boundary line extending in the cross shape is formed Provided is a liquid crystal display device. According to this configuration, it is possible to prevent an excessively bright portion from occurring in the cross-line extending from the four regions.

  According to the present invention, a large amount of electric charge remains in the vicinity of one alignment film in the opposite alignment film, and even when the voltage is cut off, this residual charge prevents the previously displayed image from being thinly burned. can do. Further, the alignment treatment can be performed using ultraviolet irradiation instead of rubbing, or the alignment treatment can be performed by combining rubbing and ultraviolet irradiation.

  1 is a schematic plan view showing a part of a liquid crystal display device according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view showing the liquid crystal display device of FIG. 1, and FIG. 3 is an active view formed on one substrate of FIG. It is a figure which shows a matrix. 2A is a sectional view taken along line 2A-2A in FIG. 1, FIG. 2B is a sectional view taken along line 2B-2B in FIG. 1, and FIG. 3 is taken along line 2C-2C. It is sectional drawing.

  In FIG. 2, the liquid crystal display device 10 includes a pair of transparent glass substrates 12 and 14 that are opposed to each other with a space therebetween, and a liquid crystal layer 16 that is sandwiched between the substrates 12 and 14. A transparent pixel electrode 18 and a transparent alignment film 20 are formed on one substrate (referred to as a lower substrate) 12, and a transparent common electrode 22 and a transparent alignment film 24 are formed on the other substrate (referred to as an upper substrate) 14. Has been.

  The pixel electrode 18 of the lower substrate 12 is formed together with the active matrix shown in FIG. A color filter 26 and a black matrix 28 are further formed on the upper substrate 14. Polarizers 29 </ b> A and 29 </ b> B are disposed outside the lower substrate 12 and the upper substrate 14.

  In FIG. 3, the active matrix includes a gate bus line 32, a drain bus line 30, and a TFT (thin film transistor) 34. The TFT 34 is connected to the gate bus line 32 and the drain bus line 30, and further connected to the pixel electrode 18. In the liquid crystal display device 10, alignment division is applied, and each pixel electrode 18 is divided into two domains A and B by a line 36 that passes through substantially the center of the pixel electrode 18.

  In FIG. 2, the color filter 26 includes R, G, and B color elements, and each pixel electrode 18 is disposed corresponding to each of the R, G, and B color elements of the color filter 26. The openings 28 a of the black matrix 28 are arranged so as to overlap the pixel electrodes 18, and the area of the openings 28 a of the black matrix 28 is smaller than the area of the pixel electrodes 18.

  Further, a storage capacitor electrode 40 is provided below the pixel electrode 18 so as to pass through substantially the center of the pixel electrode 18. Reference numeral 27 denotes an insulating layer. The black matrix 28, the bus lines 30, 32, the storage capacitor electrode 40, and the pixel electrode 18 are electrically separated by an insulating layer (not shown) disposed therebetween.

  The opening 28a of the black matrix 28 defines the pixel display portion C. Around the pixel display portion C, there is a non-display portion D defined by the black stripes of the black matrix 28. The storage capacitor electrode 40 becomes a non-display portion E. Also in FIG. 2, for each pixel electrode 18, two domains A and B divided by a line 36 passing through the center of the pixel electrode 18 are shown. The line 36 passes through the center of the storage capacitor electrode 40.

  FIG. 1 is a diagram showing one pixel electrode 18 of FIG. 3 and its peripheral region, and the elements of FIG. 2 are also shown superimposed. In FIG. 1, in the domain A of FIG. 2, a portion that overlaps the pixel display portion C is indicated by CA, a portion that overlaps the non-display portion D is indicated by DA, and a portion that overlaps the non-display portion E is indicated by EA. Has been. Similarly, in the domain B of FIG. 2, a portion overlapping the pixel display portion C is indicated by CB, a portion overlapping the non-display portion D is indicated by DB, and a portion overlapping the non-display portion E is indicated by EB. Yes.

  In FIG. 1, the pixel display portions CA and CB are indicated by white, and the non-display portions DA, EA, DB, and EB are indicated by hatching. The hatching of the non-display portions DA and EA and the hatching of the non-display portions DB and EB are reversed, indicating that the orientation processing of these portions is changed. That is, the pixel display portion C and the non-display portions D and E are divided into two domains CA, DA, and EA; CB, DB, and EB by the center line of the storage capacitor electrode 40 and the center line of the black stripe of the black matrix 28. ing.

  4 and 5 are diagrams showing an example of the alignment process of FIG. 1. FIG. 4 shows the state of the liquid crystal when no voltage is applied, and FIG. 5 shows the state of the liquid crystal when voltage is applied. In the following drawings, the alignment films 20 and 24 are shown, but other pixel electrodes, a black matrix, and the like are omitted or simplified. 4 and 5 show examples in which the alignment films 20 and 24 are vertical alignment films, and for the sake of simplicity, the twist is ignored and all the liquid crystal molecules 16A are shown in the same plane.

  One domain A will be described with reference to FIG. The liquid crystal molecules 16A close to the lower alignment film 20 are pretilted at a small pretilt angle (for example, 85 °) in the non-display portions DA and EA, and at a large pretilt angle (for example, 89 °) in the pixel display portion CA. Pretilt. The liquid crystal molecules 16A close to the upper alignment film 24 facing this are pretilted uniformly at a large pretilt angle (for example, 89 °) in the non-display portions DA and EA and the pixel display portion CA.

  The pretilt direction of the liquid crystal molecules 16A close to the lower alignment film 20 and the pretilt direction of the liquid crystal molecules 16A close to the upper alignment film 24 are opposite to each other. In this example using the vertical alignment film, The liquid crystal layer 16 between the upper alignment film 24 is bend aligned as a whole. In the pixel display portion CA, the pretilt angle of the liquid crystal molecules 16A close to the lower alignment film 20 and the pretilt angle of the liquid crystal molecules 16A close to the upper alignment film 24 are substantially the same and bend-aligned. When the pixel display portion CA having such an alignment state is present alone, the liquid crystal molecules 16A positioned between the upper and lower alignment films 20 and 24 when a voltage is applied are liquid crystal molecules close to the lower alignment film 20. Whether tilting according to the pretilt angle of 16A or tilting according to the pretilt angle of the liquid crystal molecules 16A close to the upper alignment film 24 is indefinite, and does not change in a predetermined direction. In order to make the pixel display portion CA in such an unstable state, the pixel display portion CA may be left without rubbing.

  On the other hand, in the non-display portions DA and EA, the liquid crystal molecules 16A close to the lower alignment film 20 are pretilted at a small pretilt angle, and the liquid crystal molecules 16A close to the upper alignment film 24 are at a large pretilt angle. Pretilt. Thus, if the pretilt angles of the liquid crystal molecules 16A near the upper and lower alignment films 20 and 24 are different, even if they are bend aligned, they are positioned between the upper and lower alignment films 20 and 24 when a voltage is applied. It has been found that the liquid crystal molecules 16A tilt according to the orientation with the smaller pretilt angle.

  Accordingly, as shown in FIG. 5, in the non-display portions DA and EA, when a voltage is applied, the liquid crystal molecules 16A are tilted in the upward direction according to the alignment treatment of the lower alignment film 20. . This state is further exaggerated in FIG. Although it is not known in which direction the liquid crystal molecules 16A of the pixel display portion CA are tilted alone, the liquid crystal molecules of the pixel display portion CA are surrounded by the non-display portions DA and EA. 16A is regulated by the orientation of the liquid crystal molecules 16A of the non-display portions DA and EA, and tilts in the direction in which the liquid crystal molecules 16A of the non-display portions DA and EA tilt with application of voltage. This state is further exaggerated in FIG.

  Here, it is important that in the pixel display portion CA, the lower alignment film 20 and the upper alignment film 24 are subjected to the same alignment treatment, whereby a symmetrical alternating voltage is applied. When the voltage is turned off later, there is no difference between the charge remaining near the lower alignment film 20 and the charge remaining near the upper alignment film 24, and image burn-in can be prevented. . In the non-display portions DA and EA, there is a difference in the alignment process, so there may be a difference in the residual charge.

  The same applies to the domain B if the alignment process of the lower alignment film 20 and the upper alignment film 24 is reversed. In FIG. 4, the liquid crystal molecules 16A close to the lower alignment film 20 are pretilted uniformly at a large pretilt angle (for example, 89 °) in the non-display portions DB and EB and the pixel display portion CB. The liquid crystal molecules 16A close to the upper alignment film 24 facing this are pretilted at a small pretilt angle (for example, 85 °) in the non-display portions DB and EB, and a large pretilt angle (for example, in the pixel display portion CB). 89 °).

  Also in this case, the pretilt direction of the liquid crystal molecules 16A close to the lower alignment film 20 and the pretilt direction of the liquid crystal molecules 16A close to the upper alignment film 24 are opposite to each other, and the lower alignment film 20 and the upper alignment film The liquid crystal layer 16 between them is bend-oriented as a whole.

  In the pixel display portion CB, the pretilt angle of the liquid crystal molecules 16A close to the lower alignment film 20 and the pretilt angle of the liquid crystal molecules 16A close to the upper alignment film 24 are substantially the same and bend-aligned. If the pixel display portion CB in such an alignment state exists alone, the liquid crystal molecules 16A located in the middle of the upper and lower alignment films 20 and 24 when the voltage is applied are liquid crystals close to the lower alignment film 20. Whether to tilt according to the pretilt angle of the molecules 16A or to tilt according to the pretilt angle of the liquid crystal molecules 16A close to the upper alignment film 24 is indefinite, and does not change in a predetermined direction.

  On the other hand, in the non-display portions DB and EB, the liquid crystal molecules 16A close to the lower alignment film 20 are pretilted at a large pretilt angle, and the liquid crystal molecules 16A close to the upper alignment film 24 are at a small pretilt angle. The liquid crystal molecules 16A, which are pretilted and are positioned between the upper and lower alignment films 20 and 24 when a voltage is applied, are tilted in accordance with the orientation with the smaller pretilt angle.

  Therefore, as shown in FIG. 5, in the non-display portions DB and EB, when a voltage is applied, the liquid crystal molecules 16 </ b> A are tilted in the right downward direction. Although the liquid crystal molecules 16A of the pixel display portion CB alone do not know in which direction they fall, the pixel display portion CB is surrounded by the non-display portions DB and EB, so the liquid crystal molecules 16A of the pixel display portion CB. Is regulated by the orientation of the liquid crystal molecules 16A of the non-display portions DB and EB, and tilts in the same manner as the tilt direction of the liquid crystal molecules 16A of the non-display portions DB and EB.

  Here, in the pixel display portion CB, both the lower alignment film 20 and the upper alignment film 24 are subjected to the same alignment treatment, whereby when the voltage is turned off after the voltage is applied, Thus, there is no difference between the charge remaining near the alignment film 20 and the charge remaining near the upper alignment film 24, and image burn-in can be prevented. In the non-display portions DB and EB, there is a difference in the alignment process, so there may be a difference in residual charge. However, since this portion is a non-display portion, there is no effect on image formation.

  When the domain A and the domain B are compared, the liquid crystal molecules 16A in the domain A as a whole tilt to the right and the liquid crystals 16A in the domain B as a whole tilt to the right. Thus, the effect of orientation division can be obtained. 8 and 9 are diagrams showing the effect of the alignment division. In FIG. 8, in the domain A, the liquid crystal molecules 16A positioned in the middle of the upper and lower alignment films 20 and 24 tilt to the right, and in the domain B, the liquid crystal molecules 16A positioned in the middle of the upper and lower alignment films 20 and 24. Tilt to the right. This is the same when a horizontal alignment film is used and when a vertical alignment film is used. The difference between using a horizontal alignment film and using a vertical alignment film is that a small pretilt angle in the case of a vertical alignment film is equivalent to a large pretilt angle in the case of a horizontal alignment film. In the case of a vertical alignment film, a liquid crystal having a negative dielectric anisotropy is preferable, and in the case of a horizontal alignment film, a liquid crystal having a positive dielectric anisotropy is preferable.

  9A and 9B are diagrams showing viewing angle characteristics when the domain B in FIG. 8 is viewed from the directions of arrows U, N, and L. FIG. 9A shows the case where a horizontal alignment film is used, and FIG. 9B shows the case where a vertical alignment film is used. For example, in (A), when the domain B is viewed from the direction of the arrow N, as shown by the curve N, when the voltage is increased, the transmittance decreases proportionally, and a good display can be obtained. When the domain B is viewed from the direction of the arrow U, when the voltage is increased as shown by the curve U, the transmittance decreases rapidly, and the display looks dark. When the domain B is viewed from the direction of the arrow L, even if the voltage is increased as shown by the curve L, the transmittance does not decrease so much and the display looks whitish. As described above, in the TN liquid crystal display device, the viewing angle characteristic (the display quality in the viewing direction) changes according to the tilt direction of the liquid crystal molecules 16A.

  Since the tilt direction of the liquid crystal molecules 16A in the domain A is opposite to the tilt direction of the liquid crystal molecules 16B in the domain B, the viewing angle characteristics of the domain A are opposite to the viewing angle characteristics of the domain B. That is, the characteristics when the domain A is viewed from the direction of the arrow U are the same as the characteristics when the domain B is viewed from the direction of the arrow L. Therefore, the characteristic when the domain A and the domain B are simultaneously viewed from the direction of the arrow U is the characteristic of the curve I that is the average value of the curve U and the curve L in FIG. The characteristic of the curve I approaches the characteristic of the curve N, and a relatively good display can be obtained from any direction. The same applies to the case of FIG. 9B.

  Therefore, in order to perform the alignment division, the direction of inclination of the liquid crystal molecules 16A located in the middle of the domain A may be opposite to the direction of inclination of the liquid crystal molecules 16A located in the middle of the domain B. In the configuration of FIG. 1, the alignment process of the non-display areas DA and EA is performed so that the tilt direction of the liquid crystal molecules 16A in the pixel display area CA is the same as the tilt direction of the liquid crystal molecules 16A in the domain A. Well, the means for the alignment treatment is not limited. Similarly, the alignment process of the non-display areas DB and EB may be performed so that the tilt direction of the liquid crystal molecules 16A in the pixel display area CB is the same as the tilt direction of the liquid crystal molecules 16A in the domain B. The means is not limited.

  10 and 11 are diagrams showing an example of a basic alignment process for performing alignment division. In this example, a horizontal alignment film is used. The lower alignment film 20 is rubbed in the direction of Ria in the domain A, and is rubbed in the direction of Rib in the domain B. The upper alignment film 24 is rubbed in the Roa direction in the domain A, and is rubbed in the Rob direction in the domain B. The rubbing direction Ria and the rubbing Rib are opposite to each other, and the rubbing direction Roa and the rubbing Rob are opposite to each other. Therefore, in order to perform such rubbing, it is necessary to perform rubbing twice for each of the alignment films 20 and 24 using a mask.

  In this way, for the domain A, the liquid crystal is twisted from the rubbing direction Ria of the lower alignment film 20 toward the rubbing direction Roa of the upper alignment film 24, and the lower alignment film 20 and the upper alignment film 24 are twisted. As shown in FIG. 10, the liquid crystal molecules 16A located in the middle of the tilt tilt upward, for example. Also for the domain B, the liquid crystal is twisted from the rubbing direction Rib of the lower alignment film 20 toward the rubbing direction Rob of the upper alignment film 24, and between the lower alignment film 20 and the upper alignment film 24. For example, the liquid crystal molecules 16A located in the position are aligned in the left-up direction as shown in FIG.

  Such an alignment process can be performed on the non-display areas DA, EA, DB, and EB of FIG. The pixel display areas CA and CB are bend aligned or spray aligned. In an extreme case, it is not necessary to know how the liquid crystal changes in the pixel display areas CA and CB. Therefore, the pixel display areas CA and CB need not be subjected to an alignment process such as rubbing. This tendency is particularly remarkable in the case of vertical alignment.

  12 and 13 are diagrams showing another example of an alignment process for performing alignment division. In FIG. 13, the lower alignment film 20 is rubbed in the direction of Ri for both domains A and B, and the upper alignment film 24 is rubbed in the direction of Ro for both domains A and B. Then, as shown in FIG. 12, the alignment treatment of the lower alignment film 20 is such that the liquid crystal molecules 16A close to the lower alignment film 20 are pretilted in the domain B with a large pretilt angle α. In FIG. 2, pretilt is performed at a small pretilt angle β. Further, the alignment treatment of the upper alignment film 24 is such that the liquid crystal molecules 16A close to the upper alignment film 24 are pretilted with a large pretilt angle α in the domain A and pretilt with a small pretilt angle β in the domain B. Has been made.

  Therefore, in each of the domains A and B of the alignment films 20 and 24 facing each other, a large pretilt angle α can be formed near one alignment film, and a small pretilt angle β can be formed near the other alignment film. In this case, the liquid crystal molecules 16A between the alignment films 20 and 24 facing each other are tilted according to the liquid crystal molecules 16A having a large pretilt angle α. Accordingly, in the domain A, the intermediate liquid crystal molecules 16A are tilted in the same direction as the tilt of the liquid crystal molecules 16A near the upper alignment film 24, and in the domain B, the intermediate liquid crystal molecules 16A are close to the lower alignment film 20. Tilt in the same direction as the tilt of the liquid crystal molecules 16A. Therefore, in the domain A and the domain B, the intermediate liquid crystal molecules 16A are tilted in the opposite directions, and the alignment division is achieved.

  The alignment process of FIGS. 4 and 5 is based on the alignment division process of FIGS. 12 and 13. The only difference is whether to use a horizontal alignment film or a vertical alignment film. Such an alignment process is performed on the non-display areas DA, EA, DB, and EB of FIG. 1, and the pixel display areas CA and CB are bent or sprayed.

  FIG. 14 is a diagram showing an example of means for realizing the different pretilt angles α and β shown in FIG. In this example, the alignment film 20 is formed of two alignment film layers 20A and 20B, and the alignment film 24 is formed of two alignment film layers 24A and 24B. The upper alignment film layers 20B and 24B are patterned according to the sizes of the domains A and B, and the lower alignment film layers 20A and 24A are exposed from the openings. In the domain A, the alignment film layer 20A and the alignment film layer 24B face each other, and in the domain B, the alignment film layer 20B and the alignment film layer 24A face each other.

  The alignment film layers 20B and 24B are made of a material in which the liquid crystal molecules 16A are aligned at a pretilt angle α when a constant rubbing is performed, and the alignment film layers 20A and 24A are pretilted when the rubbing is performed in the same manner as described above. Made of material that is oriented at an angle β. That is, different pretilt angles α and β are realized depending on the alignment material. Therefore, when the alignment films 20 and 24 having the configuration shown in FIG. 14 are rubbed in FIG. 13, the alignment shown in FIG. 12 is obtained.

  FIG. 15 is a diagram showing another example of means for realizing the different pretilt angles α and β shown in FIG. In this example, the alignment films 20 and 24 are formed of a uniform alignment film layer. However, ultraviolet irradiation is performed to change the pretilt angle. That is, in (A), the entire surface of the alignment film 20 (24) is rubbed with a rubbing roll 50, and in (B), ultraviolet rays (UV) are irradiated. At this time, a mask 52 having an opening 52a is used. As shown in (C), when the rubbed alignment film 20 (24) is partially irradiated with ultraviolet rays, the pretilt angle α of the liquid crystal molecules 16A is realized in the portion of the alignment film 20 (24) irradiated with ultraviolet rays, The pretilt angle β of the liquid crystal molecules 16A is realized in the portion of the alignment film 20 (24) that has not been irradiated with ultraviolet rays. In the case of the vertical alignment film, the pretilt angle α is smaller than the pretilt angle β in both cases of the horizontal alignment film.

  FIG. 16 is a diagram showing a second embodiment of the present invention. As in the example of FIG. 2, the liquid crystal display device 10 includes a pair of transparent glass substrates 12 and 14 that are opposed to each other with a space therebetween, and a liquid crystal layer 16 that is sandwiched between the substrates 12 and 14. A transparent pixel electrode 18 and a transparent alignment film 20 are formed on one substrate 12, and a transparent common electrode 22 and a transparent alignment film 24 are formed on the other substrate 14. A color filter 26 is further formed on the upper substrate 14, and a black matrix 28 is formed on the lower substrate 12. The color filter 26 includes R, G, and B color elements. A storage capacitor electrode 40 is also provided. This alignment film achieves alignment with a pretilt angle without rubbing.

  FIG. 17 shows an alignment processing apparatus 60 for the alignment film 20 (24). The alignment processing device 60 includes a light source 62 that emits unpolarized ultraviolet light, a mirror 64, and a holder 66 that supports the substrate 12 (14) on which the alignment film 20 (24) is provided. The holder 66 supports the substrate 12 (14) at an angle of 45 degrees with respect to the optical axis. That is, parallel ultraviolet rays from the light source 62 are incident on the alignment film 20 (24) at an angle of 45 degrees.

  The light source 62 includes a parabolic reflector 62a and irradiates non-polarized ultraviolet rays substantially in parallel. A preferred spectral distribution of the light source 62 is shown in FIG. This spectral distribution has a peak in the vicinity of a wavelength of 250 nm. The irradiated ultraviolet light preferably contains a component having a wavelength of 280 nm or less. The alignment film 20 (24) processed by the alignment processing apparatus 60 is an alignment film exhibiting vertical alignment, and alignment with a pretilt angle is realized by irradiating non-polarized ultraviolet rays from an oblique direction.

  The alignment film 20 (24) is an alignment film exhibiting vertical alignment in a state where it is applied and baked, and an example of the structure is shown below.

  FIG. 18 is a diagram showing the principle of orientation processing, and FIG. 19 is a simplified diagram of FIG. The alignment film 20 (24) shown in the chemical formula 1 has an alkyl group R that realizes vertical alignment. The alkyl group R is indicated by the numeral 70 in FIG. It is considered that the alkyl group 70 protrudes randomly on the surface of the alignment film 20 (24).

  The ultraviolet rays 68 are irradiated obliquely from the X direction to the alignment film 20 (24), and the pretilt direction (azimuth line) of the liquid crystal is parallel to the incident direction of the ultraviolet rays 68. The unpolarized ultraviolet light 68 includes P wave and S wave polarized light, but the S wave does not contribute to the directionality of the alignment. That is, the S wave does not act at all in the X direction, but acts in the Y direction, but the magnitude of the action is the same in the positive direction and the negative direction of the Y axis. Does not contribute.

  The P wave acts on the portion including the alkyl group 70 in a plane parallel to the incident direction of the ultraviolet ray 68, and affects the orientation direction. FIG. 19 is a part of FIG. 18 taken along a plane parallel to the incident direction of the ultraviolet ray 68, that is, a plane parallel to the vibration surface of the P wave. In FIG. 19, the alkyl group 70 can be divided into two that are inclined in opposite directions with respect to the vibration direction of the P wave of the ultraviolet ray 68. The component a of the alkyl group 70 is inclined so as to be nearly perpendicular to the vibration direction of the P wave, and the component b of the alkyl group 70 is nearly horizontal with respect to the vibration direction of the P wave. It is inclined to become. In general, it is unlikely that the alkyl group itself is destroyed by ultraviolet rays. It is easy to understand that the part supporting the alkyl group or the part tilting the alkyl group is broken by ultraviolet rays. A portion a (corresponding to the component a) in which the alkyl group is inclined so as to be perpendicular to the vibration direction of the P wave and an alkyl group are inclined so as to be parallel to the vibration direction of the P wave. The ratio of being broken by ultraviolet rays is different from the portion b (corresponding to the component b). The portion b where the alkyl group is inclined is susceptible to energy and is easily broken by the energy of ultraviolet rays. Therefore, the component b decreases and the component a remains unbroken by irradiation with ultraviolet rays. Therefore, when the alignment film 20 (24) is used in the liquid crystal display device 10, the liquid crystal molecules are pretilted according to the inclination of the component a in the alkyl group 70 of the alignment film 20 (24).

  FIG. 20 is a diagram showing a modification of FIG. In FIG. 19, it is assumed that the components a and b of the alkyl group 70 are uniformly subjected to the action of ultraviolet irradiation, but FIG. 20 shows that some of the components a and bb of the components a and b of the alkyl group 70 are This is particularly the case when it is strongly affected by ultraviolet irradiation. These portions aa and bb are bent opposite to most of the components a and b of the alkyl group 70, respectively.

  Therefore, the portion aa is easily broken by the energy of ultraviolet rays, but the portion bb is hardly broken by the energy of ultraviolet rays. Therefore, when the component b having the part bb remains and the alignment film 20 (24) is used in the liquid crystal display device 10, the liquid crystal molecules are pretilted according to the inclination of the component b in the alkyl group 70 of the alignment film 20 (24). It becomes like this. In both cases of FIG. 19 and FIG. 20, the liquid crystal molecules are aligned with a certain pretilt angle. Therefore, in the case of a vertical alignment film, alignment with a pretilt angle can be realized by obliquely irradiating non-polarized ultraviolet rays without rubbing.

  However, in FIGS. 19 and 20, it may be difficult to determine which of the a component and the b component is likely to be broken before ultraviolet irradiation. However, when ultraviolet rays are irradiated obliquely, one of the a component and the b component is broken and the other remains, whereby the liquid crystal molecules are aligned with a pretilt angle without rubbing. As an example, alignment treatment was performed under the following conditions. As the material of the vertical alignment film 20 (24), for example, RN722, RN783, RN784 marketed by Nissan Chemical Co., Ltd., or JALS-204 manufactured by Nippon Synthetic Rubber Co., Ltd. was used. First, the alignment film material was applied to the substrate 12 (14) at 2000 rpm by spin coating. The thickness of the alignment film at this time is about 80 nm. This was baked at 180 ° C. for 2 hours. Next, the alignment film was irradiated with ultraviolet rays using the alignment processing apparatus 60 of FIG. At this time, a deep UV irradiation device made by USHIO was used as the light source 62. In the light source 62, the size of the ultraviolet light emitting portion was about 5 mm, and substantially parallel ultraviolet rays were obtained by the reflector 62a. Several samples were made by irradiating ultraviolet rays in the range of 1 to 30 minutes, and assembled as a liquid crystal display device. In a liquid crystal display device including a sample irradiated for 10 seconds or more, a pretilt of liquid crystal molecules was developed, and the pretilt angle was lowered from 90 degrees in the vertical direction to 88 degrees.

  The spectral distribution shown in FIG. 21 includes a wavelength component near 250 nm, and this component is effective. As described above, a short arc type lamp is used as the light source, and ultraviolet rays near 250 nm are mainly used, and the parallelism of the ultraviolet rays is made ± 10 degrees or less, preferably ± 3 degrees or less by the reflector. A test using the light source light having the spectrum distribution shown in FIG. 21 as it is and a test in which ultraviolet light with a wavelength component of 300 nm or more of the light source light cut was performed, and the results were compared. Expression was confirmed. From this result, it was found that it is effective to irradiate ultraviolet rays of 280 nm or less in order to develop the pretilt in the vertical alignment film 20 (24).

  Thus, in this example, it was possible to impart pretilt expression to the vertical alignment film 20 (24) using non-polarized ultraviolet rays. Although it can be said that only the P wave of the non-polarized ultraviolet rays is actually effective, the advantage of being able to use the non-polarized ultraviolet rays is still great. Conventionally, there has been a proposal for imparting pretilt expression by irradiating polarized ultraviolet rays to a horizontal alignment film, but in this case, it has not been possible to obtain pretilt expression using non-polarized ultraviolet rays. For this reason, a polarizer for obtaining polarized ultraviolet rays is required, and such a polarizer is currently only a Grand Taylor type polarizer, but a Gran Taylor type polarizer cuts out calcite that naturally occurs. Are not suitable for actual use. Therefore, the ability to perform alignment treatment using non-polarized ultraviolet rays eliminates the need to use a polarizer for ultraviolet irradiation, which is extremely preferable.

  In this embodiment, non-polarized ultraviolet rays are uniformly applied to the entire surface of the vertical alignment film 20 (24). Therefore, in order to perform the alignment division, as shown in FIG. 22, each of the divided domains A and B is irradiated with ultraviolet rays 68A and 68B from opposite directions. By doing so, as shown in FIG. 23, two domains A and B in which liquid crystal molecules located in the middle tilt in opposite directions are obtained. In this case, there is no difference in the pretilt angle of the liquid crystal molecules between the two domains A and B.

  FIG. 24 shows an example in which the ultraviolet rays 68A and 68B are simultaneously irradiated from the opposite direction for each of the domains A and B. In this case, a mask 74 having an opening 74A is used. The ultraviolet rays 68A and 68B in the opposite directions enter from one opening 74A, and the conditions under which the ultraviolet rays 68A and 68B in the opposite directions are just distributed to the two domains A and B are as follows. When the pitch of the openings 74A of the mask 74 (the pitch of one pixel) is P, the interval between the mask 74 and the alignment film 20 (24) is Q, and the incident angles of the ultraviolet rays 68A and 68B are θ, Q = ( P / 4) It is assumed that sin θ.

  As shown in FIG. 25, when this principle is applied, four different domains Aa, Ab, Ba, Bb can be formed by simultaneously irradiating ultraviolet rays from four directions. FIG. 26 is a diagram showing an alignment process according to the third embodiment of the present invention. The alignment film 20 (24) shown here can be used in the liquid crystal display device shown in FIG. In (A), the entire surface of the alignment film 20 is rubbed with a rubbing roll 50 so that the liquid crystal molecules 16A exhibit a certain pretilt as shown in (B). Then, in (C), unpolarized ultraviolet rays 68A and 68B are irradiated from opposite directions. Then, as shown in (D), in domain A and domain B, the realized pretilt angle is the sum of the pretilt angle by rubbing and the pretilt angle by ultraviolet irradiation. Therefore, the difference in the pretilt angle of the liquid crystal molecules can be made between the two domains A and B.

  Irradiation with ultraviolet rays can be performed as in the previous example. As the light source, a short arc lamp is used, and ultraviolet rays of 280 nm or less, preferably around 250 nm are mainly used, and the parallelism of the ultraviolet rays is made ± 10 degrees or less, preferably ± 3 degrees or less by a reflector. Further, as the alignment film, polyimide exhibiting vertical alignment can be used.

  As shown in FIG. 27, the other alignment film 24 is similarly rubbed and irradiated with ultraviolet rays. The rubbing directions of the two alignment films 20 and 24 are, for example, as shown in FIG. Then, when the liquid crystal display device is assembled using the alignment films 20 and 24, as shown in FIG. 28, two domains A and B in which liquid crystal molecules located in the middle tilt in opposite directions are obtained. Splitting is achieved. In this case, since the alignment films 20 and 24 are respectively rubbed and irradiated with ultraviolet rays, the alignment films 20 and 24 are partially irradiated with ultraviolet rays using the mask 52 described with reference to FIG. There is no difference in alignment treatment between the alignment films 20 and 24 facing each other. Therefore, in the case of the alignment processing according to FIGS. 26 to 28, it is not necessary to divide and process the pixel display portion and the non-display portion as shown in FIG.

  In the alignment treatment according to FIGS. 16 to 24, rubbing is not performed. When the pretilt angle of the liquid crystal molecules expressed by ultraviolet irradiation is small without rubbing, combining the rubbing and ultraviolet irradiation as in this example, the effects of the examples of FIGS. 16 to 24 are maintained. A sufficient pretilt angle can be obtained.

  FIG. 29 is a diagram showing the characteristics of the glass substrates 12 and 14 of the liquid crystal display device of FIG. As shown in FIG. 29, the glass substrates 12 and 14 are characterized by being made of a material that absorbs ultraviolet rays irradiated to achieve orientation. FIG. 29 shows a case where the alignment film 20 (24) is irradiated with ultraviolet rays. The ultraviolet rays 68 are irradiated in a state where the glass substrate 12 (14) provided with the alignment film 20 (24) is supported on the sample table 76. In this case, since the glass substrate 12 (14) absorbs the ultraviolet rays 68, the ultraviolet rays 68 irradiated to the alignment film 20 (24) pass through the alignment film 20 (24) and then are absorbed by the glass substrate 12 (14). .

  FIG. 30 shows a case where the alignment films 20 and 24 are irradiated with ultraviolet rays 68 when the glass substrate 12 (14) is made of a material that does not absorb the ultraviolet rays 68. The ultraviolet rays 68 are irradiated in a state where the glass substrate 12 (14) provided with the alignment film 20 (24) is supported on the sample table 76. In this case, the ultraviolet rays 68 irradiated to the alignment film 20 (24) pass through the alignment film 20 (24), then pass through the glass substrate 12 (14), and are reflected by the surface of the sample stage 76, so that the glass substrate 12 ( 14) and the alignment film 20 (24).

  In this case, the vibration direction of the P wave of the ultraviolet ray 68 incident on the alignment film 20 (24) is the direction connecting the upper left and the lower right in FIG. The vibration direction of the P wave of the ultraviolet ray 68 passing through the film 20 (24) is a direction connecting the lower left and the upper right in FIG. That is, the alignment film 20 (24) is the same as that irradiated from the opposite oblique directions (without the mask).

  As described with reference to FIGS. 18 to 20, the orientation is realized by the P wave of the obliquely incident ultraviolet ray 68 breaking one of the a component and the b component inclined in opposite directions of the alkyl group 70 1. . When there is reflected light as shown in FIG. 30, for example, if the P wave of the incident ultraviolet ray 68 breaks the a component, the P wave of the reflected ultraviolet ray 68 breaks the b component, and eventually all the alkyl groups 70 are broken. As a result, the alkyl group 70 standing obliquely does not remain, so that there is a problem that the alignment action cannot be obtained or the alignment is disturbed.

  Therefore, as shown in FIG. 29, the glass substrate 12 (14) does not absorb the ultraviolet rays 68, and the incident ultraviolet rays 68 are absorbed by the glass substrate 12 (14) after acting on the alignment film 20 (24). Thus, reflection at the sample stage 76 below the glass substrate or reflection at the interface between the glass substrate 12 (14) and air is eliminated. Therefore, as described with reference to FIG. 30, by preventing the reflected ultraviolet rays from acting on the alignment film 20 (24), the alignment can be reliably modified by the irradiation of ultraviolet rays.

  FIG. 31 is a diagram showing the characteristics of the used ultraviolet light (light source light) and the glass substrate. The intensity of the ultraviolet light without the substrate is shown by a black bar graph, and the ultraviolet light with the substrate (transmitted through the substrate) is shown. Intensity is indicated by a white bar graph. As indicated by the black bar graph, the light source used emits the strongest UV light, particularly in the wavelength region around 250 nm and 300 nm. And the glass substrate 12 (14) used what absorbs these low wavelength region ultraviolet rays well. As shown by the white bar graph in the case of the presence of the substrate, in the light that has passed through the glass substrate 12 (14), the ultraviolet rays of about 300 nm or less are cut. There is no peak near 250 nm. Thereby, the passage state of ultraviolet rays as shown in FIG. 29 was confirmed.

  As the alignment film 20 (24), for example, RN-722, RN-783, or RN-784 commercially available from Nissan Chemical Industries, Ltd. was used. First, the alignment film 20 (24) was applied on the glass substrate 12 (14) by spin coating at 2000 rpm. At this time, the thickness of the alignment film 20 (24) is about 80 nm. This was baked at 180 ° C. for 2 hours. Next, ultraviolet rays were irradiated as ultraviolet rays using a deep UV irradiation device manufactured by Ushio Electric. In this ultraviolet irradiation apparatus, the size of the ultraviolet light emitting portion is about 5 mm, and an almost parallel ultraviolet beam was obtained by assembling an optical system using this. The spectrum of this ultraviolet beam is shown by the black bar graph in FIG.

  As the glass substrate 12 (14), an OA2 glass substrate made of Asahi Glass was used. This is a kind of glass substrate called borosilicate glass or non-alkali glass, and a substrate similar to this exhibits ultraviolet transmission characteristics equivalent to those shown in FIG. Here, as the energy of the ultraviolet light, the short wavelength energy is high, and the effect of modifying the alignment film 20 (24) is stronger in the light of 250 nm. For this reason, if possible, a light source including light near 250 nm is desirable as the light source. However, even when using a light source that does not contain light in the vicinity of 250 nm, there is ultraviolet light in a wavelength region that has an effect of modifying the alignment film. In this case, the glass substrate absorbs light in such a wavelength region. By doing so, a predetermined purpose can be achieved.

  Examples of the light source that generates ultraviolet rays include a high-pressure mercury lamp, a low-pressure mercury lamp, and a xenon lamp. A glass substrate that absorbs light effective for improving the alignment film may be used. For example, when light near 250 nm is effectively used, such an effect can be obtained by using soda lime glass as the glass substrate.

  As an example of a combination of a light source and a glass substrate, a combination of a high-pressure mercury lamp and soda lime glass, a xenon lamp and soda lime glass, borosilicate glass or non-alkali glass is preferable. When the substrate 12 (14) is made of plastic, the substrate material is preferably selected from polycarbonate, polyethylene, and polystyrene.

  32 to 34 are views showing another embodiment of the present invention. This embodiment is an improvement in the feature that realizes a plurality of different orientations by irradiating the alignment film 20 (24) with ultraviolet rays obliquely as in the embodiments shown in FIGS. FIG. 32 shows that the alignment film 20 (24) is subjected to an alignment process. FIG. 33 shows a state where liquid crystal molecules are aligned with respect to the alignment film 20 (24) when the alignment film 20 (24) thus subjected to the alignment treatment is assembled as a liquid crystal display device (FIG. 16).

  FIG. 34 shows a mask used in the alignment film processing of FIG. The liquid crystal 16 used had a negative dielectric anisotropy, and the alignment film 20 (24) used vertical alignment polyimide.

  32 and 33, the alignment film 20 (24) includes a plurality of regions 78A and 78B divided in a stripe shape. The region 78A includes a plurality of unit regions P that are continuously connected, and the region 78B includes a plurality of unit regions Q that are continuously connected. Referring to the X axis and Y axis orthogonal to each other, the regions 78A and 78B extend long in parallel with the X axis. The ultraviolet rays 68A are obliquely applied to the region 78A of the alignment film 20 (24) from a direction parallel to the X axis. As a result, the liquid crystal molecules 16A in the region 78A are tilted upward in FIG. 33 and pretilt. On the other hand, the ultraviolet rays 68B in the opposite direction are obliquely applied to the region 78B of the alignment film 20 (24) from a direction parallel to the X axis. As a result, the liquid crystal molecules 16B in the region 78B are tilted downward and pretilt in FIG. However, as described above, the liquid crystal molecules 16A in the region 78A may be tilted downward and pretilt in FIG. 33, and the liquid crystal molecules 16B in the region 78B may be tilted upward and pretilt in FIG.

  In FIG. 34, a mask 80 is formed by vapor-depositing chromium 80B on a synthetic quartz plate 80A. The portion of chromium 80B serves as a light shielding portion, and the portion between chromium 80B and chromium 80B serves as an opening. Chrome 80B extends in the X-axis direction. The width of the chrome 80B and the width of the opening of the mask 80 coincide with the widths of the regions 78A and 78B. Therefore, in the ultraviolet irradiation of FIG. 32, this mask 80 is used, the ultraviolet ray 68A is irradiated with the opening of the mask 80 above the region 78A, and then the mask 80 is shifted laterally by one pitch to obtain the region 78B. An ultraviolet ray 68 </ b> B is irradiated with an opening of the mask 80 on the top.

  Here, as a method of irradiating the ultraviolet rays 68A and 68B, two lamps for irradiating the ultraviolet rays are prepared and the ultraviolet rays are irradiated from the above two directions. There is a method of irradiating ultraviolet rays by rotating 180 degrees in an integrated state. FIG. 37 shows an example using two lamps 82A and 82B. The first lamp 82A is used for the first ultraviolet irradiation, and the second lamp 82B is used for the second ultraviolet irradiation from the opposite direction. In this case, the mask 80 is shifted in the direction perpendicular to the stripe direction of the regions 78A and 78B (in the direction of the arrow) and the same distance as the stripe width between the first ultraviolet irradiation and the second ultraviolet irradiation.

  FIG. 38 shows an example in which one lamp 82 is used. In this case, after the first ultraviolet irradiation, the substrate 12 (14) or both the substrate and the mask (20 (24)) are rotated 180 degrees (as indicated by the arrows), and the ultraviolet rays are not irradiated for the first time. In this case, both the substrate 12 (14) and the mask 80 are rotated 180 degrees, and the relative position of the mask with respect to the substrate is shifted to perform the second ultraviolet irradiation. It is also possible to irradiate ultraviolet rays after shifting the relative position of the substrate and the mask and rotating the position of the ultraviolet light source by 180 degrees.

  FIG. 35 shows a case where the ultraviolet rays 68 are irradiated along the Y-axis direction of the mask 80. In this case, the ultraviolet rays 68 travel in a direction orthogonal to the chromium (light-shielding portion) 80B of the mask 80, and when the distance between the mask 80 and the alignment film 20 (24) is shifted by d ′, the exposure position on the alignment film 20 (24) Is shifted laterally by d ″. On the other hand, when the ultraviolet rays 68 are irradiated along the Y-axis direction of the mask 80 as shown in FIGS. Even if the interval of (24) is shifted by d ′, the exposure position on the alignment film 20 (24) is not shifted laterally.

  In the example of FIG. 24, a single mask 74 is used, and ultraviolet rays are obliquely irradiated from opposite directions to realize a plurality of different orientations. However, in such a method, if the distance between the mask 74 and the alignment film 20 (24) is deviated by 10 μm, the exposure position on the alignment film 20 (24) may be deviated by 10 μm horizontally. . Further, when the glass substrate 12 (14) is enlarged, the glass substrate 12 (14) or the mask 74 is bent due to its own weight, and the deflection between the mask 74 and the alignment film 20 (24) is shifted. Similar problems arise. For example, it is known that a chromium mask having a thickness of 400 × 500 mm and a thickness of 20 mm bends about 10 μm at the center. Therefore, such a problem can be solved if it is described with reference to FIGS.

  FIG. 36 is a diagram showing the relationship between the irradiation angle of the ultraviolet rays 68A and 68B and the pretilt angle realized. This irradiation angle is an angle taken from a direction perpendicular to the alignment film 20 (24). When the ultraviolet rays 68A and 68B are applied to the alignment film 20 (24) from an oblique direction of 45 degrees, a pretilt angle of 88 degrees can be stably realized. FIG. 32 shows that the ultraviolet rays 68A and 68B are irradiated from an oblique direction of 45 degrees with respect to the alignment film 20 (24).

  When the irradiation angle of ultraviolet rays deviates from 45 degrees, the stability of the alignment decreases. For this reason, for example, even when it is desired to realize a pretilt angle of 88 degrees, a pretilt angle of 88 degrees may not be realized. In order to stably achieve a desired pretilt angle, the irradiation angle is preferably in the range of 20 degrees to 70 degrees, and more preferably in the range of 30 degrees to 60 degrees. The stability of alignment and the uniformity of alignment were the best at 45 degrees.

  FIG. 39 shows a case where the pair of substrates 12 and 14 are bonded so that the stripe directions of the regions 78A and 78B of the alignment films 20 and 24 are perpendicular to each other. At this time, as shown in FIG. 40, four types of domains (alignment regions) J, K, L, and M are formed. In FIG. 40, a solid line nail indicates a liquid crystal molecule in front of the paper surface, and a broken line nail indicates a liquid crystal molecule beyond the paper surface. In this way, a total of four types of liquid crystal alignments are realized with two types of rotation starting points and two types of rotation directions, and the twist angles of the domains J, K, L, and M are each 90 degrees.

  When no voltage is applied, the liquid crystal molecules stand substantially perpendicular to the substrate surface at a pretilt angle of 88 degrees, but when a voltage is applied, the liquid crystal molecules fall asleep while rotating. The azimuth angles of the rotation centers are different from each other by 90 degrees. That is, in domain J, the liquid crystal is twisted to the left (twisted to the right in the figure but is defined in this manner in the field of liquid crystal panels). Twisted by twist, the starting point is the upward direction in the figure.

  The direction in which the liquid crystal molecules positioned in the middle between the two substrates when the voltage is applied is in the lower left direction as indicated by the arrow a in the domain J, the lower right direction as indicated by the arrow b in the domain K, and the domain In L, the upper left direction is indicated by the arrow c, and in the domain M, the upper right direction is indicated by the arrow d. Each pixel includes four domains J, K, L, and M. Since the viewing angle characteristics are different in the four domains J, K, L, and M and different viewing angle characteristics are mixed, a favorable viewing angle characteristic can be obtained as a whole.

  FIG. 41 shows a case where the pair of substrates 12 and 14 are bonded so that the stripe directions of the regions 78A and 78B of the alignment films 20 and 24 are parallel to each other. At this time, the directions of the tilt of the liquid crystals are the same in the opposing portions of the upper and lower substrates. By laminating the upper substrate region 78A so as to face the lower substrate 78B, the liquid crystal tilt directions are opposite to each other at the opposite portions of the upper and lower substrates. In the latter case, when a voltage is applied, the liquid crystal is uniformly tilted in one direction (+ X direction) within the region. In the other region of the stripe, the liquid crystal is still tilted in one direction, but its azimuth direction is the -X azimuth direction. In this way, the orientation can be divided into two types.

  Here, as shown in FIG. 42, when the alignment is only divided into two types, the irradiation of ultraviolet rays through the mask 80 is performed only on the alignment film 24 of one substrate, and the alignment film 20 of the opposite substrate is performed. It is also possible to adopt a configuration in which no ultraviolet ray is irradiated. In this case, although the alignment stability is somewhat inferior, it is possible to suppress the number of times of ultraviolet irradiation.

  Further, examples will be described. As the alignment film, a vertical alignment type having an alkyl side chain was used. This alignment film was applied by spin coating and baked at 180 ° C. A stripe-shaped mask 80 was prepared, and ultraviolet rays were irradiated obliquely from the direction of the stripe direction. As the ultraviolet rays, a mercury arc xenon lamp short arc type was used, and ultraviolet rays having substantially uniform directions were irradiated.

  The center wavelength of ultraviolet irradiation is preferably around 250 nm. Unlike the rubbing method in which the alignment film surface is rubbed, the alignment film surface is characterized in that no streak-like grooves are formed on the surface of the alignment film. Here, different orientations are realized using the mask 80, and a plurality of regions having different orientations are provided in each pixel. Here, it goes without saying that the number of regions having different orientations may be any number as long as it is plural, even if there are two or four types of orientation of the regions. For example, if the pitch of each region is sufficiently smaller than the pixel pitch, there is no need to worry about misalignment.

  Ultraviolet rays were irradiated from the right direction of FIG. 37 through this mask. As the irradiation angle of ultraviolet rays, the direction of 45 degrees was optimal. Although it was oriented at 30 ° or 60 °, the orientation stability and orientation uniformity were the best when it was 45 °. Next, the position of the mask was shifted by half the stripe pitch, that is, the stripe width, in the direction perpendicular to the azimuth direction of the stripe of the mask. That is, the same mask was used. Then, ultraviolet rays were irradiated obliquely from the direction opposite to the first ultraviolet irradiation.

  FIG. 43 is a diagram showing the relationship between the alignment films 20 and 22 having the regions 78A and 78B subjected to the alignment treatment of FIGS. 39 and 40 and the pixels formed on the substrates 12 and. As described above, FIG. 39 and FIG. 40 show that each pixel has four different domains (alignment regions) J, K, L, and M, in which the liquid crystal molecules form 90 degrees with respect to each other. It shows that it is formed so as to face four directions a, b, c, and d.

FIG. 43 is intended to make the configuration of FIGS. 39 and 40 more advantageous. Here, each pixel includes a display part C and a half of the non-display part D in FIGS. 1 to 3 (the black matrix is divided at the center between two adjacent pixel electrodes 18). In other words, it is assumed that the surfaces of the substrates 12 and 14 are simply partitioned by diagonal lines. Therefore, each pixel has a substantially rectangular shape, and the direction of the stripe forming the regions 78A and 78B is at an angle of 45 degrees with respect to the sides of the rectangle.
When each pixel is divided into four domains J, K, L, and M, as shown in FIG. 45, the size is typically ¼ that is similar to the shape of the pixel along the size of the pixel. It is conceivable to divide the area. This is also an embodiment of the present invention. However, in this case, as shown in FIG. 46, when the exposure position is shifted when the alignment films 20 and 24 are irradiated with ultraviolet rays, a part of the four regions is hidden in the bus line or the black matrix. As a result, the ratio of the pixel to the pixel decreases, the other part becomes relatively large, and there is a possibility that the viewing angle characteristic deteriorates. For this reason, in the case of obliquely irradiating ultraviolet rays, proximity exposure is adopted, but it is necessary to align the mask and the workpiece more accurately. In this case, the apparatus becomes large. Alternatively, it may take time for alignment and may cause problems such as affecting the throughput.

  The configuration shown in FIG. 43 solves this problem, and the stripe pattern of the mask 80 for irradiating ultraviolet rays is inclined with respect to the pixel arrangement. The inclination angle and the width of the stripe (the width of one region 78A, 78B) are selected so that eight or more domains J, K, L, M are at least partially included in one pixel. For this reason, even if the exposure position shifts when the alignment films 20 and 24 are irradiated with ultraviolet rays, the domains J, K, L, and M always exist at a uniform rate, and the viewing angle characteristics do not deteriorate. .

  Preferably, the stripe direction (direction in which the regions 78A and 78B extend) forms an angle of 45 degrees with respect to the rectangular side of the pixel. When the width of the stripe is W and the pitch on the short side of the rectangular pixel is p, W = (√2) / 3 × p.

  In the examples, a TFT type liquid crystal panel was applied. Three pixels of RGB constitute one display unit. The pixel pitch was 300 μm in the RGB set, and the size of each RGB pixel was 100 μm × 300 μm. First, a vertical alignment type polyimide was applied to each of the substrates 12 and 14 and as a counter CF alignment film. Then, the TFT substrate 12 was first irradiated with ultraviolet rays having substantially the same direction through the mask 80. Here, a stripe-shaped mask 80 was used, and the stripe width of the mask 80 was set to 100 μm × √2 ÷ 3≈47.14 μm. The mask was designed with care so that the stripes were at 45 degrees with respect to the pixel direction, and ultraviolet rays were irradiated from an oblique angle of 45 degrees from an azimuth direction parallel to the stripes.

  Next, the mask 80 is shifted in the direction perpendicular to the stripe by the width of the stripe, and the ultraviolet light is obliquely inclined at an inclination angle of 45 degrees in an azimuth direction parallel to the stripe and opposite to the direction in which the ultraviolet light is first irradiated. Irradiated from. Thereby, first, an orientation as shown in FIG. 33 was obtained. Next, the color filter substrate 14 was also irradiated with ultraviolet rays in the same manner, but here, as shown in FIG. 39, when the color filter substrate 14 and the TFT substrate 12 are bonded to each other as the azimuth direction in which the ultraviolet rays are irradiated. In order to obtain a positional relationship, the direction of the stripe (as viewed in the assembled state) was irradiated from an azimuth of 90 degrees with respect to the irradiation direction of the ultraviolet rays with respect to the previous TFT substrate 12.

  A pair of substrates 12 and 14 having the orientation obtained in this way were bonded together. Thus, the configuration of FIG. 43 was obtained. Each pixel includes four types of domains J, K, L, and M, and there are about 20 domains J, K, L, and M in each pixel. A series of domains (M, K, J, L) exist completely within one pixel, the other domains J ′, M ′ are located on the left data bus line, and the other domains L ′, K 'Is located on the right data bus line.

  FIG. 44 shows an example in which the position is shifted from the state of FIG. Even if the exposure position is deviated, the proportion of each area in the pixels can be made almost unchanged. For example, the area of the rounded domain J located below is large in FIG. 43 and small in FIG. In contrast, the area of the rounded domain J located above is small in FIG. 43 and large in FIG. This eliminates the need to worry about the positional relationship as long as the angle is set to 45 degrees when aligning the mask with the workpiece for photo-alignment. The loss in any region is comparable when the stripe width is (√2) / 3 × p. Therefore, even if a positional deviation occurs, the influence is reduced as a result.

  Since ultraviolet rays can be irradiated regardless of the mutual positional relationship between the mask and the substrate, the time required for alignment is unnecessary, the apparatus is simplified, and the throughput is improved. For example, in the configuration of FIG. 45, the alignment takes 15 to 30 seconds. Since the viewing angle characteristics of the four types of regions are different and complementary, good viewing angle characteristics can be obtained.

  47 to 59 are views showing still another embodiment of the present invention. FIG. 47A shows that alignment treatment is performed on the alignment film 20 by obliquely irradiating ultraviolet rays as in FIG. In this example, ultraviolet rays 68 that are parallel light are irradiated on the entire surface of the alignment film 20 from a direction at an angle of 45 degrees with respect to the alignment film 20. The alignment film 20 is shown to include a plurality of regions 78A and 78B divided into stripes as in the case of FIG. 32, but at the time of FIG. 47 (A), the ultraviolet rays 68 are directed in a single direction. Since the alignment film 20 is irradiated, the alignment film 20 is not yet divided into a plurality of regions 78A and 78B. The plurality of regions 78A and 78B are divided in this way later, and are shown in FIG. 47A for convenience of explanation.

  FIG. 48A shows a state where liquid crystal molecules are aligned with respect to the alignment film 20 when the alignment film 20 thus subjected to the alignment treatment is assembled as a liquid crystal display device. Also in this case, the plurality of regions 78A and 78B are shown for convenience. The liquid crystal molecules 16A and 16B adjacent to the alignment film 20 (regions 78A and 78B thereof) are pretilted with a substantially constant pretilt angle with respect to the alignment film 20. The liquid crystal 16 used had a negative dielectric anisotropy, and the alignment film 20 (24) used vertical alignment polyimide.

  FIG. 47B shows that alignment treatment is further performed on the alignment film 20 after the step of FIG. Here, for example, a mask 80 similar to that shown in FIG. 34 is used, and the alignment film 20 is irradiated with ultraviolet rays 68 obliquely through the mask 80. The mask 80 has a transmissive portion 80A and a non-transmissive portion 80B. The region 78A of the alignment film 20 is a portion where the ultraviolet ray 68 has hit the alignment film 20 through the transmission portion 80A of the mask 80, and the region 78B is blocked by the non-transmission portion 80B of the mask 80 and the ultraviolet ray 68 is blocked by the alignment film 20. This is the portion of the alignment film 20 that did not hit.

  FIG. 48B shows a state where liquid crystal molecules are aligned with respect to the alignment film 20 when the alignment film 20 thus subjected to the alignment treatment is assembled as a liquid crystal display device. When the alignment of the liquid crystal is realized by irradiating the vertical alignment film 20 with ultraviolet rays, the larger the amount of irradiated ultraviolet rays, the larger the destruction energy of the vertical alignment function and the smaller the pretilt angle with respect to the alignment film 20. Become. Since the region 78A of the alignment film 20 is irradiated with ultraviolet rays twice and the region 78B is irradiated only once with ultraviolet rays, the region 78A has a larger amount of ultraviolet irradiation than the region 78B.

  Accordingly, the pretilt angle of the liquid crystal molecules 16A adjacent to the region 78A of the alignment film 20 is smaller than the pretilt angle of the liquid crystal molecules 16B adjacent to the region 78B of the alignment film 20. As a result, when a voltage is applied, the liquid crystal molecules 16A adjacent to the region 78A are more likely to change from a substantially vertical position to a substantially horizontal position than the liquid crystal molecules 16B adjacent to the region 78B, and drive the liquid crystal in the region 78A. The threshold voltage is lower than the threshold voltage for driving the liquid crystal in region 78B.

  49A and 49B show that the alignment process is performed on the other alignment film 24 in the same manner as the alignment film 20. In FIG. 49A, ultraviolet rays 68 which are parallel lights are applied to the entire surface of the alignment film 24 from an oblique 45 ° direction with respect to the alignment film 24. In FIG. 47A, the ultraviolet rays 68 are irradiated along the direction (X direction) parallel to the stripes forming the plurality of regions 78A and 78B, whereas in FIG. 49A, the ultraviolet rays 68 are irradiated. Is irradiated along a direction (Y direction) perpendicular to the stripe forming the plurality of regions 78A and 78B.

  Therefore, as shown in FIG. 50A, the liquid crystal molecules 16A and 16B adjacent to the alignment film 24 (regions 78A and 78B thereof) are pretilted with a substantially constant pretilt angle in the Y-axis direction with respect to the alignment film 24. It becomes like this. In FIG. 49B, the alignment film 24 is irradiated with ultraviolet rays 68 obliquely through a mask 80. Also in this case, as shown in FIG. 50B, the pretilt angle of the liquid crystal molecules 16A adjacent to the region 78A of the alignment film 24 is larger than the pretilt angle of the liquid crystal molecules 16B adjacent to the region 78B of the alignment film 24. Get smaller. As a result, when a voltage is applied, the liquid crystal molecules 16A adjacent to the region 78A are more likely to change from a substantially vertical position to a substantially horizontal position than the liquid crystal molecules 16B adjacent to the region 78B.

  The pretilt direction of the liquid crystal molecules with respect to the alignment film 20 in FIG. 48B is the X direction, and the pretilt direction of the liquid crystal molecules with respect to the alignment film 24 in FIG. 50B is the Y direction. Therefore, when the alignment film 20 in FIG. 48B and the alignment film 24 in FIG. 50B are directly overlapped, the liquid crystal is twisted by 90 degrees. Here, it is defined in FIG. 49 that the body is tilted in the Y direction, but the same argument holds for the X direction.

  FIG. 51 is a diagram showing the liquid crystal display device 10 formed as described above. In one alignment film 20 (24), the amount of ultraviolet irradiation differs for each of the regions 78 A and 78 B, and the amount of ultraviolet irradiation to the region 78 A (or 78 B) of one alignment film 20 is different from that of the other alignment film 24. This is substantially the same as the amount of ultraviolet irradiation to the corresponding region 78A (or 78B).

  Therefore, in the region 78A, the pretilt angle of the liquid crystal molecules adjacent to the alignment film 20 is δ, and the pretilt angle of the liquid crystal molecules adjacent to the alignment film 24 is also δ, and both are equal. Similarly, in the region 78B, the pretilt angle of the liquid crystal molecules adjacent to the alignment film 20 is γ, and the pretilt angle of the liquid crystal molecules adjacent to the alignment film 24 is also γ, and both are equal. Therefore, the symmetry of the behavior of the liquid crystal is maintained in the regions 78A and 78B of the opposing alignment films 20 and 24, respectively.

  FIG. 54 is a diagram showing the relationship between the applied voltage and the transmittance of the liquid crystal display device 10 of FIGS. A curve 79A is a diagram showing a relationship between the applied voltage and transmittance of the region 78A, and a curve 79B is a diagram showing a relationship between the applied voltage and transmittance of the region 78B. Each of the curve 79A and the curve 79B has bumps P and P ', and if the liquid crystal display device has a single characteristic of the region 78A or 78B, the bump P when the display is viewed from an oblique direction. , P ′ has a problem that the display is reversed in black and white.

  In this embodiment, the two regions 78A and 78B are configured to form one pixel. By including at least two regions 78A and 78B having different threshold voltages in one pixel, it is possible to solve the problem of black and white inversion of display. That is, in the region 78A where the irradiation amount of ultraviolet rays is large, the pretilt angle δ is small, and the liquid crystal molecules easily fall toward the alignment films 20 and 24, and the threshold voltage becomes low. On the other hand, in the region 78B where the irradiation amount of ultraviolet rays is small, the pretilt angle γ is large, and the liquid crystal molecules are aligned substantially perpendicular to the alignment films 20 and 24. The threshold voltage is high.

  When a voltage is applied to the liquid crystal display device 10, the applied voltage exceeds a certain threshold voltage corresponding to the halftone display in the region 78A. However, since the applied voltage does not reach the threshold voltage corresponding to the halftone display in the other region 78B, the display is not inverted in the region 78B. In the present invention, since the two regions 78A and 78B form one pixel, the display having these different threshold voltage characteristics is mixed, and the tendency of the display to be inverted as a whole pixel is reduced. The A curve 79C in FIG. 54 shows the relationship between the applied voltage and transmittance of one synthesized pixel, and the bending of the TV characteristic is reduced as compared with the curves 79A and 79B.

  Thus, there is a conventional technique for dividing one pixel into two regions having different threshold voltages. For example, FIG. 55 shows a conventional threshold division. In FIG. 55, a dielectric 90 is provided in one region to make it difficult for voltage to be applied to that region, and the threshold voltage of the liquid crystal itself is increased to realize two regions having different threshold voltages. Yes. However, in the case of such a configuration, the process of providing the dielectric 90 increases, and the process becomes complicated, leading to a decrease in yield and an increase in unit price. In addition, the required applied voltage increases due to the installation of the dielectric 90.

  According to the present embodiment, the liquid crystal can be obtained without using rubbing by a relatively simple means such as irradiation of ultraviolet rays (thus, without rubbing rubbing traces on the surfaces of the alignment films 20 and 24). In addition, a plurality of regions having different threshold voltages can be formed in one pixel, and the viewing angle characteristics of the liquid crystal display device can be improved without increasing the manufacturing cost.

  Preferably, as shown in FIG. 51 and as described above, in each of the two regions 78A and 78B in one pixel, the irradiation amount of the ultraviolet rays to one region of one alignment film is the same as that of the other alignment film. Therefore, the pretilt angle of the liquid crystal molecules adjacent to the alignment films 20 and 24 is γ in the region 78A, and the alignment film 20 in the region 78B. , 24 so that the pretilt angle of the liquid crystal molecules adjacent to each other is δ.

  However, FIG. 52 is a diagram illustrating a change example of the alignment process. In FIG. 52, in the region 78B, the pretilt angle of the liquid crystal molecules adjacent to the alignment film 20 is γ, and the pretilt angle of the liquid crystal molecules adjacent to the alignment film 24 is 90 degrees (substantially no pretilt). . In this case, when a voltage is applied, the liquid crystal molecules as a whole fall down with respect to the substrate surface according to the pretilt of the liquid crystal molecules adjacent to the alignment film 20. In the other region 78A, the pretilt angles of the liquid crystal molecules adjacent to the alignment films 20 and 24 are both δ. In this case, the alignment film 20 is aligned as shown in FIG. 47, but the alignment film 24 is aligned only once using the mask 80.

  FIG. 53 is a diagram showing another example of the alignment process. 53, in the region 78A, the pretilt angles of the liquid crystal molecules adjacent to the alignment films 20 and 24 are γ and δ, respectively, and in the other region 78, the liquid crystal molecules adjacent to the alignment films 20 and 24 are. The pretilt angles are δ and γ, respectively. The tilting direction is constant on each of the alignment films 24 and 20. In such a configuration, in the regions 78A and 78B, the orientation in which the liquid crystal molecules are tilted is reversed by the application of voltage, and a favorable viewing angle characteristic is realized.

  FIG. 56 is a diagram showing another example of the alignment process. This alignment process is performed by a procedure reverse to the procedure shown in FIG. That is, as shown in FIG. 56A, the mask 80 is used to irradiate the regions 78A and 78B of the alignment film 20 with ultraviolet rays at different doses. Then, as shown in FIG. 56B, the entire surface of the alignment film 20 is irradiated with ultraviolet rays from a single direction without using the mask 80. Then, the alignment film 24 is also subjected to an alignment process in the reverse order of the procedure shown in FIG. As a result of such alignment treatment, the same liquid crystal display device as that shown in FIG. 51 can be obtained.

  FIG. 57 is a diagram showing another example of the alignment process. This alignment process is performed by a procedure similar to the procedure shown in FIG. That is, as shown in FIG. 57A, the entire surface of the alignment film 20 is irradiated with ultraviolet rays from a single direction without using the mask 80. Then, as shown in FIG. 57 (B), using a mask 80, the regions 78A and 78B of the alignment film 20 are irradiated with ultraviolet rays while changing the dose. The ultraviolet irradiation angle in FIG. 57A and the ultraviolet irradiation angle in FIG. 57B are not equal.

  In FIG. 57 (A), ultraviolet rays are irradiated at an angle of 45 degrees with respect to the alignment film 20, and in FIG. 57 (B), ultraviolet rays are irradiated at an angle of 90 degrees with respect to the alignment film 20. Irradiation of ultraviolet rays at an angle of 45 degrees with respect to the alignment film 20 is necessary for the alignment film 20 to have an alignment with a pretilt. If an orientation with a pretilt is provided in this way, thereafter, it is not always necessary to irradiate the alignment film 20 with ultraviolet rays at an angle of 45 degrees. Anything that changes The same applies to the alignment film 24. Further, although the process (B) is performed after (A) in FIG. 57, it is also effective to perform the process (A) after (B).

  In the above example, the mask 80 has the transmission part 80A and the non-transmission part 80B. However, the non-transmission part 80B not only completely blocks ultraviolet rays but also blocks ultraviolet rays to some extent and It may be transparent to some extent. Further, the transmission portion 80A and the non-transmission portion 80B do not need to be completely separated, and the transmission characteristics may change continuously. In the above example, the ultraviolet irradiation is performed only twice, but the ultraviolet irradiation can be performed several times.

  FIG. 58 is a diagram showing another example in which the alignment film 20 (24) is irradiated with ultraviolet rays using the mask 80. FIG. The mask 80 has a transmissive portion 80A and a non-transmissive portion 80B. 47, 49, 56 and 57, the mask 80 is arranged in parallel to the alignment film 20 (24) and in proximity to the alignment film 20 (24). However, in FIG. The film 20 (24) is not arranged in parallel. For example, the mask 80 is disposed at an angle of 45 degrees with respect to the alignment film 20 (24).

  In order to provide the regions 78A and 78B having different threshold voltages, it is only necessary to provide regions having different ultraviolet irradiation amounts, but there is no problem even if the ultraviolet irradiation amounts are continuously changed. Since the liquid crystal molecules are tilted in the same direction in the regions 78A and 78B, it may be desirable that the amount of ultraviolet irradiation is rather continuously changed. For this reason, it is not necessary for the amount of UV irradiation to be completely discontinuous by the mask 80. Accordingly, as shown in FIG. 58, the mask 80 can be disposed at an angle with respect to the alignment film 20 (24), away from the alignment film 20 (24). In this case, it is only necessary to simply install the substrate for irradiating ultraviolet rays with respect to the existing ultraviolet irradiation device.

  In FIG. 58, the ultraviolet rays 68 are transmitted through the transmission portion 80A of the mask 80 and blocked by the non-transmission portion 80B. Although the ultraviolet rays 68 are supplied as parallel light, they are not completely parallel light. The ultraviolet ray 68 includes a light component 68C incident obliquely with respect to the mask 80. The light component 68C passes through the transmissive portion 80A, travels below the non-transmissive portion 80B, and is to be covered by the non-transmissive portion 80B. 20 (24) is incident.

  FIG. 59 is a diagram showing another example in which the alignment film 20 (24) is irradiated with ultraviolet rays. In this case, the mask 80 is omitted, but the mask 80 is used for both the first and second ultraviolet irradiations, and the respective ultraviolet irradiation amounts of the first and second ultraviolet irradiations are aligned. The regions 78A and 78B of the films 20 and 24 are changed. For example, the region 78A of the alignment film 20 is irradiated with ultraviolet rays at 3.0 (arbitrary unit), and the region 78B of the alignment film 20 is irradiated with ultraviolet rays at 1.5. On the other hand, the region 78A of the alignment film 24 is irradiated with ultraviolet rays at 2.0, and the region 78B of the alignment film 24 is irradiated with ultraviolet rays at 1.0.

  If the alignment films 20 and 24 are overlapped as shown in FIG. 59, the sum of the ultraviolet irradiation amounts of the facing alignment films 20 and 24 is 2.5 (1 + 1.5), 3.5 (2 + 1.5). ) 4 regions, 4 (1 + 3) and 5 (2 + 3), are formed. In this manner, four types of threshold characteristics can be realized, and regions with different voltages overlap each other, so that display inversion can be suppressed.

  60 to 66 are views showing still another embodiment of the present invention. 60 shows a portion of one pixel of the liquid crystal display device 10, and FIG. 61 is a view showing the alignment of the liquid crystal of the portion of one pixel of the liquid crystal display device 10. The alignment of the liquid crystal in FIG. 61 is the same as the alignment of the liquid crystal shown in FIG. 40, and one pixel includes four regions J, K, L, and M. The four areas J, K, L, and M are divided by boundary lines extending in a cross shape within one pixel.

  As shown in FIG. 60, the liquid crystal display device 10 includes a liquid crystal sandwiched between a pair of substrates as in the above embodiment, and each substrate includes an electrode and an alignment film. The alignment film is subjected to an alignment process with a pretilt by irradiation with ultraviolet rays. The liquid crystal display device 10 has an active matrix structure including pixel electrodes 18, drain bus lines 30, gate bus lines 32, and TFTs 34. The liquid crystal display device 10 further includes a storage capacitor electrode 40.

  The storage capacitor electrode 40 extends in a cross shape horizontally and vertically through almost the center of the pixel electrode 28. That is, the storage capacitor electrode 40 is formed as a light-shielding film that achieves its original function and covers the boundary line extending in a cross shape that partitions the four regions J, K, L, and M. The storage capacitor electrode 40 is made of chromium and does not transmit light.

  FIG. 62 is a diagram showing the relationship between the voltage application time and the transmittance of the four-divided vertical alignment type liquid crystal display device without the storage capacitor electrode 40. A wide viewing angle can be realized by the quadrant vertical alignment type liquid crystal display device. In such an orientation like a blade of a windmill, when white display is performed by applying a high voltage from a voltage-off state, a boundary line extending in a cross shape that divides the four regions J, K, L, and M In FIG. 5, a phenomenon was observed in which the luminance once increased considerably as indicated by a point H and then decreased and stabilized. This is because at the moment when a voltage is applied, the behavior of the liquid crystal molecules is not stable at the cross-shaped boundary line, the brightness rises extremely, and then the lateral interaction between the liquid crystal molecules begins to work. This is considered to settle down to a stable value.

  In the case of the conventional liquid crystal display device having the storage capacitor electrode 40 extending only in the horizontal direction, there is no problem because the horizontal portion of the portion shining in the cross shape is hidden by the storage capacitor electrode 40, but in the cross shape. The vertical portion of the shining portion has been a problem in the conventional liquid crystal display device. In the present invention, since the storage capacitor electrode 40 is formed as a light-shielding film covering the boundary line extending in a cross shape, such an extremely bright portion can be eliminated. FIG. 63 is a diagram showing the relationship between the voltage application time and the transmissivity of the four-divided vertical alignment type liquid crystal display device with the storage capacitor electrode 40 extending in a cross shape. As shown in FIG. 62, it can be seen that the extreme increase in transmittance is eliminated. When the auxiliary capacity electrode 40 is extended in the vertical direction, the horizontally extending portion of the auxiliary capacity electrode 40 is thinned and the portion is provided in the vertical direction. As a result, it is possible to eliminate a portion having extreme luminance without impairing the aperture ratio. However, it is necessary to consider the resistance of the auxiliary capacitance electrode.

  In FIG. 64, a part of the light shielding film covering the boundary line extending in a cross shape that divides the four regions J, K, L, and M is formed by the storage capacitor electrode 40 extending in the horizontal direction, and another part of the light shielding film is formed. It is a figure which shows the example which forms a part with the member 28X integral with the black matrix 28. FIG. This can also eliminate the extreme increase in transmittance. FIG. 65 is a diagram showing another example for preventing an excessively bright portion from occurring in a cross-shaped boundary line that divides four regions J, K, L, and M. FIG. In the liquid crystal display device to which the feature of FIG. 65 is applied, the alignment films 20 and 24 are formed so as to have four regions in which the alignment of the liquid crystal differs by the boundary line in which one pixel extends in a cross shape (see FIGS. 61 and 62). ) And polarizers 29A and 29B (FIG. 2) arranged in crossed Nicols.

  FIG. 65 shows that the setting directions of the polarizers 29A and 29B are shifted in the range of 5 degrees to 20 degrees with respect to the vertical direction 100 and the horizontal direction 102 in which the boundary line extends. That is, the transmission axes of the polarizers 29A and 29B are within the range I. Furthermore, in FIG. 65, the setting directions of the polarizers 29A and 29B are shifted in the range of 5 to 20 degrees with respect to the directions 104 and 106 that are 45 degrees oblique to the vertical direction 100 and the horizontal direction 102 in which the boundary line extends. It is shown that. That is, the transmission axes of the polarizers 29A and 29B are within the range J. On the other hand, the polarizers 29A and 29B are generally installed in the vertical direction 100 and the horizontal direction 102, or in the directions 104 and 106 at 45 degrees.

  FIG. 66 is a diagram showing the relationship between the time and the transmittance when the polarizers 29A and 29B are shifted from each other. A curve R shows the characteristics when the transmission axes of the polarizers 29A and 29B are arranged vertically and horizontally, which is consistent with the characteristics shown in FIG. A curve S shows characteristics when the transmission axes of the polarizers 29A and 29B are shifted by 20 degrees with respect to the vertical and horizontal directions, and a curve T shows a characteristic when the transmission axes of the polarizers 29A and 29B are shifted by 10 degrees with respect to the vertical and horizontal directions. The characteristics of the case are shown.

  From the comparison between the curves S and T and the curve R, it can be seen that the point H where the curve R becomes extremely bright can be eliminated according to the curves S and T. As a result of the test, a preferable result was obtained by disposing the transmission axes of the polarizers 29A and 29B within the above-mentioned range. Although a configuration in which the angle is shifted from 5 degrees to 20 degrees is effective, 10 degrees to 15 degrees is more desirable.

  FIG. 67 shows still another embodiment. The liquid crystal display device 10 includes a spacer 110 together with the liquid crystal 16 between the pair of substrates 12 and 14. The spacer 110 is a small sphere that maintains a constant gap between the pair of substrates 12 and 14. In this embodiment, the vertical alignment process is performed on the surface of the spacer 110. As the vertical alignment treatment, a silane coupling agent or a vertical alignment film material is preferably applied to the surface of the spacer 110.

  As shown in FIG. 68, when the surface of the spacer 110 is not subjected to the vertical alignment treatment, the liquid crystal molecules around the spacer 110 have a property of being aligned (horizontal alignment) along the surface of the spacer 110. In the liquid crystal display device 10 that achieves vertical alignment with a pretilt by irradiating the vertical alignment films 20 and 24 with ultraviolet rays, if there is horizontal alignment around the spacer 110, the liquid crystal molecules around the spacer 110 are It is regulated by the horizontal alignment regulating force and is prevented from being oriented in the desired vertical direction. Therefore, there is a problem that the display becomes dark.

  On the other hand, if the surface of the spacer 110 is subjected to the vertical alignment treatment, the liquid crystal molecules around the spacer 110 are not subjected to such a horizontal alignment regulating force and the vertical alignment regulating force is relatively weak. , It can be oriented in the desired vertical direction, and a coarse display can be obtained. This feature can be applied to all the embodiments of the liquid crystal display device 10 in which vertical alignment with a pretilt is realized by irradiating the vertical alignment films 20 and 24 with ultraviolet rays.

  As described above, according to the present invention, a large amount of charge remains in the vicinity of one alignment film in the opposite alignment film, and the image displayed previously is thinly burned by this residual charge even in a state where the voltage is turned off. It can be prevented from becoming a state. Further, the alignment treatment can be performed using ultraviolet irradiation instead of rubbing, or the alignment treatment can be performed by combining rubbing and ultraviolet irradiation.

1 is a schematic plan view showing a part of a liquid crystal display device according to a first embodiment of the present invention. It is sectional drawing which shows the liquid crystal display device of FIG. It is a figure which shows the active matrix formed in one board | substrate of FIG. It is sectional drawing of the liquid crystal display device for demonstrating an example of the alignment process of the alignment film of FIG. It is sectional drawing at the time of the voltage application of the liquid crystal display device of FIG. FIG. 6 is a diagram showing a first stage of behavior of liquid crystal molecules in one domain of FIG. 5. It is a figure which shows the 2nd step of the behavior of the liquid crystal molecule of FIG. It is sectional drawing of the liquid crystal display device for demonstrating alignment division. It is a figure which shows the viewing angle characteristic achieved by the orientation division | segmentation of FIG. It is a figure which shows the basic example of orientation division | segmentation. It is a figure which shows the orientation process for obtaining the orientation division | segmentation of FIG. It is a figure which shows the other example of orientation division | segmentation. It is a figure which shows the orientation process for obtaining the orientation division | segmentation of FIG. It is a figure which shows an example which implement | achieves the orientation division | segmentation of FIG. It is a figure which shows the other example which implement | achieves the orientation division | segmentation of FIG. It is a figure which shows 2nd Example of this invention. It is a figure which shows the alignment processing apparatus of the alignment film of FIG. It is a figure which shows the principle of the alignment process of the alignment film of FIG. It is the figure which simplified FIG. It is a figure which shows the modification of FIG. It is a figure which shows the spectrum distribution of the ultraviolet-ray used with the apparatus of FIG. It is a figure which shows performing an orientation process to two domains. It is a figure which shows the orientation division achieved by the orientation process of FIG. It is a figure which shows the mask which performs the orientation process of FIG.22 and FIG.23. It is a figure which shows the modification of FIG. It is a figure which shows 3rd Example of this invention. It is a figure which shows the orientation process of 3rd Example. It is a figure which shows the liquid crystal molecule with respect to the alignment film processed by the alignment process of 3rd Example. It is a figure which shows the characteristic of the glass substrate of the liquid crystal display device of FIG. FIG. 30 is a comparative diagram for explaining the feature of FIG. 29. It is a figure which shows the transmitted light intensity of the light source to be used with and without a substrate. It is a figure which shows 4th Example of this invention. It is a figure which shows the place where the liquid crystal molecule is orientating with respect to the alignment film which carried out the alignment process in FIG. It is a figure which shows the mask used by the alignment film process of FIG. It is a figure explaining that a problem arises with the relationship between a mask and an ultraviolet irradiation direction. It is a figure which shows the relationship between the irradiation angle of an ultraviolet-ray, and the pretilt angle implement | achieved. It is a figure which shows the example which performs ultraviolet irradiation using two lamps. It is a figure which shows the example which performs ultraviolet irradiation using one lamp. It is a figure which shows the example which has arrange | positioned two alignment films obtained by the ultraviolet irradiation of FIG. 32 so that stripes may mutually orthogonally cross. It is a figure which shows four orientations obtained by arrangement | positioning of FIG. FIG. 33 is a diagram showing an example in which two alignment films obtained by ultraviolet irradiation of FIG. 32 are arranged in parallel with each other. It is a figure which shows the example which performed the ultraviolet irradiation only to one alignment film. It is a figure which shows the relationship between the orientation film which has the area | region where the orientation process of FIG.39 and FIG.40 was performed, and a pixel. It is a figure which shows the case where the alignment film of FIG. 43 has shifted | deviated with respect to the pixel. FIG. 41 is a diagram showing another relationship between an alignment film having a region subjected to the alignment process of FIGS. 39 and 40 and a pixel. It is a figure which shows the case where the alignment film of FIG. 43 has shifted | deviated with respect to the pixel. It is a figure which shows 5th Example of this invention. It is a figure which shows the orientation of the liquid crystal achieved when using the orientation film | membrane shown in FIG. It is a figure which shows the alignment process of the alignment film facing the alignment film shown by FIG. It is a figure which shows the orientation of the liquid crystal achieved when using the orientation film by which the orientation process was shown by FIG. It is a figure which shows the orientation of the liquid crystal in the liquid crystal display device containing the orientation film which performed the orientation process of FIG.47 and FIG.49. It is a figure which shows the example of a change of the orientation process of FIG. It is a figure which shows the other example of the orientation process of FIG. FIG. 52 is a diagram illustrating a relationship between applied voltage and transmittance of the liquid crystal display devices of FIGS. 47 to 51. It is a figure which shows the prior art example of threshold value division | segmentation. It is a figure which shows the example of a change of orientation processing. It is a figure which shows the example of a change of orientation processing. It is a figure which shows the other example which irradiates an alignment film with an ultraviolet-ray using a mask. It is a figure which shows the example of a change of orientation processing. It is a figure which shows 6th Example of this invention. FIG. 61 is a diagram showing the alignment of liquid crystal in a portion of one pixel of the liquid crystal display device of FIG. 60. It is a figure which shows the relationship between the voltage application time of a 4-part dividing vertical alignment type liquid crystal display device when there is no storage capacity electrode, and the transmittance | permeability. FIG. 61 is a diagram illustrating a relationship between voltage application time and transmittance of the liquid crystal display device of FIG. 60. It is a figure which shows the other example of a light shielding film. FIG. 63 is a diagram showing another example for solving the problem shown in FIG. 62. FIG. 66 is a diagram showing a relationship between voltage application time and transmittance of a liquid crystal display device adopting the characteristics of FIG. 65. It is a figure which shows the example of the liquid crystal display device containing the spacer which performed the vertical alignment process. It is a figure which shows the spacer which does not perform a vertical alignment process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display device 12, 14 ... Substrate 16 ... Liquid crystal layer 18 ... Pixel electrode 20 ... Orientation film 22 ... Common electrode 24 ... Orientation film 28 ... Black matrix 40 ... Storage capacity electrode 68 ... Ultraviolet ray 80 ... Mask

Claims (6)

A pair of substrates facing each other at an interval;
An electrode and an alignment film formed on one of the pair of substrates;
An electrode and an alignment film formed on the other of the pair of substrates;
A liquid crystal disposed between the pair of substrates,
The alignment film is processed so that four regions having different liquid crystal alignments are formed in the pixel, separated by a boundary line extending in a cross shape.
A light shielding film covering the boundary line extending in the cross shape is provided in the pixel ;
One alignment film of the pair of substrates has two regions extending in parallel to each other, and one of the two regions is subjected to an alignment treatment so that the liquid crystal is inclined in a first orientation, and the two regions On the other side, the alignment treatment is performed so that the liquid crystal is tilted in the opposite direction to the first direction.
The other alignment film of the pair of substrates has two other regions extending in parallel to each other, and the liquid crystal is inclined in a second direction orthogonal to the first direction in one of the other two regions. alignment treatment is performed as to the other of said other two areas, the liquid crystal in the liquid crystal display device includes a second orientation, characterized that you have made to the alignment treatment so as to be inclined in opposite directions.   The liquid crystal display device according to claim 1, wherein the alignment film is subjected to an alignment process with a pretilt by irradiation with ultraviolet rays. An auxiliary capacitance electrode extending in a cross shape in the pixel,
The liquid crystal display device according to claim 1, wherein the auxiliary capacitance electrode functions as the light shielding film. An auxiliary capacitance electrode and the black matrix extends into said pixels,
The liquid crystal display device according to claim 1, wherein the light shielding film is configured by both the auxiliary capacitance electrode and the black matrix.   The liquid crystal display device according to claim 1, wherein the light shielding film extends in a cross shape through substantially the center of the pixel. The one and the alignment film formed on the other of the pair of substrates is a oriented film of vertical alignment type liquid crystal display device according to any one of claims 1 to 5.

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