JP2009282366A - Liquid crystal display panel and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing liquid crystal display panel capable of photo alignment with a simpler process than heretofore, and to provide a liquid crystal display panel which can be manufactured according to such a manufacturing method. <P>SOLUTION: The method of manufacturing liquid crystal display panel includes: a step of preparing a glass substrate 11; a step of forming embedded lines 12a, 12b extended in a first azimuth on a first main surface of the glass substrate 11; a step of forming a photo alignment layer 18 on the first main surface of the glass substrate 11 on which embedded lines are formed; a step of defining a pretilt direction on a first region of the photo alignment layer by selectively applying linearly polarized light only to the first region 18A1 or 18A2 of the photo alignment layer from a direction inclined to a second azimuth approximately orthogonal to the first azimuth from the second main surface side; a step of preparing the glass substrate 21 having an alignment layer 28; and a step of preparing a liquid crystal cell in which the glass substrate 11 and the glass substrate 21 are attached to each other, such that the photo alignment layer 18 and the alignment layer 28 face each other via a liquid crystal layer 30 containing a liquid crystal material having negative dielectric anisotropy. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal display panel and a method for manufacturing the same.

  In recent years, in a method for manufacturing a liquid crystal display panel, a photo-alignment method has attracted attention as a method for setting a pretilt direction of liquid crystal molecules (for example, Non-Patent Document 1). The photo-alignment method sets the pretilt direction by irradiating the photo-alignment film with polarized light. Since the photo-alignment method is a non-contact process unlike the conventional rubbing method, it has an advantage that problems such as generation of static electricity do not occur.

  On the other hand, a multi-domain technique is used as a technique for improving the viewing angle characteristics of a liquid crystal display panel. Multi-domain technology is a method of forming a plurality of domains having different alignment directions of liquid crystal molecules in one pixel (agreeing with a liquid crystal domain), and averaging the viewing angle characteristics of the plurality of domains to This is to improve the angular characteristics.

  In order to form a plurality of domains in a pixel using the photo-alignment method, it is necessary to perform the photo-alignment process a plurality of times, which complicates the process. For example, after a predetermined pretilt direction is given by selectively irradiating only a part of the region in the pixel using a photomask, the other part of the region in the pixel using another photomask. By selectively irradiating light only to the other direction, another pretilt direction is given. Therefore, it is necessary to prepare a plurality of photomasks, and there is a problem that the positions where the domains are formed vary depending on the alignment accuracy of the photomask.

  Therefore, Patent Document 1 discloses a photo-alignment method characterized in that a block (which can be used as a spacer) is formed on a substrate constituting a liquid crystal display panel, and this block is used as a photomask.

The use of the photo-alignment method described in Patent Document 1 has the advantage that the number of photomasks can be reduced and that photo-alignment processing can be performed in a self-aligned manner on blocks formed on the substrate. It is done.
JP 2001-296526 A Japanese Patent Laid-Open No. 2003-66864 "Liquid crystal alignment", published by Kunihiro Ichimura, Yoneda Publishing, March 2007

  However, when the technique described in Patent Document 1 is used, there is a problem that the block formed on the substrate disturbs the alignment of the liquid crystal molecules. Further, since the block obstructs the injection of the liquid crystal material, there arises a problem that the injection takes a long time.

  The present invention has been made to solve the above-mentioned problems, and its main object is to manufacture a liquid crystal display panel capable of performing photo-alignment processing by a simpler process than before and to manufacture by such a manufacturing method. An object of the present invention is to provide a liquid crystal display panel that can be used.

  The method for manufacturing a liquid crystal display panel of the present invention includes a step (a) of preparing a first glass substrate having first and second main surfaces, and a first main surface of the first glass substrate. A step (b) of forming a buried wiring extending in an orientation; a step (c) of forming a photo-alignment film on the first main surface of the first glass substrate on which the buried wiring is formed; By selectively irradiating only the first region of the photo-alignment film with linearly polarized light from a direction inclined in a second direction substantially orthogonal to the first direction from the two principal surface sides, the first of the photo-alignment film A step (d) for defining the pretilt direction of one region, a step (e) for preparing a second glass substrate having an alignment film, and a liquid crystal layer containing a nematic liquid crystal material having a negative dielectric anisotropy. The first alignment layer and the alignment layer are opposed to each other. Comprising a step (f) to produce a glass substrate and the second glass substrate and the bonding was a liquid crystal cell. The “azimuth” indicates a direction in a plane and does not include a polar angle (elevation angle) component.

  In one embodiment, the second region adjacent to the first region of the photo-alignment film is irradiated with linearly polarized light from a direction inclined in a third direction that is substantially 180 ° different from the second direction from the second main surface side. Thus, the method further includes a step (g) of defining the pretilt direction of the second region of the photo-alignment film in a direction different from the pretilt direction of the first region by approximately 180 °.

  In one embodiment, in the step (d), the pretilt direction of the first region is defined as the second orientation.

  In one embodiment, a vertical alignment film that does not define a pretilt direction is used as the alignment film.

  In one embodiment, the method further includes a step of forming a gate bus line, a source bus line, and a TFT on the first main surface of the first glass substrate, and the embedded wiring is the gate bus line. The method may further include forming a CS bus line extending in parallel with the gate bus line, and the embedded wiring may include the CS bus line.

  The liquid crystal display panel of the present invention includes a plurality of pixels arranged in a matrix having rows and columns, a TFT substrate, a counter substrate, and a dielectric anisotropy provided between the TFT substrate and the counter substrate. A liquid crystal layer including a negative nematic liquid crystal material, and the TFT substrate includes a glass substrate, a gate bus line formed on the glass substrate, a source bus line, the gate bus line, and the source bus. A TFT connected to a line; and a photo-alignment film; the counter substrate has a vertical alignment film that does not define a pretilt direction; the gate bus line is embedded in the glass substrate; and the liquid crystal layer Each of the plurality of pixels has two domains divided by a boundary parallel to the gate bus line, and a liquid near the photo-alignment film in the two domains. Orientation direction of molecules of the gate bus line and the substantially orthogonal, and, different substantially 180 ° from each other.

  In one embodiment, the liquid crystal molecules in contact with the photo-alignment film in the two domains rise from the photo-alignment film toward the boundary when no voltage is applied.

  According to the present invention, the photo-alignment process can be performed by a simple process because the photo-alignment process can be performed using the embedded wiring formed on the TFT substrate as a photomask. Further, since the wiring used as the photomask is embedded, the alignment of the liquid crystal molecules is not disturbed.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings, but the present invention is not limited to the illustrated embodiments.

  FIG. 1 schematically shows the structure of a liquid crystal display panel 100 according to an embodiment of the present invention. FIG. 1 schematically shows a structure of a portion corresponding to one pixel among a plurality of pixels arranged in a matrix form having rows and columns of the liquid crystal display panel 100. FIG. 1A is a schematic plan view, and FIG. 1B is a schematic cross-sectional view taken along line B-B ′ in FIG.

  The liquid crystal display panel 100 includes a TFT substrate 10, a counter substrate 20, and a liquid crystal layer 30 including a nematic liquid crystal material having a negative dielectric anisotropy provided between the TFT substrate 10 and the counter substrate 20.

  The TFT substrate 10 includes a glass substrate 11, a gate bus line 12a formed on the glass substrate 11, a source bus line (not shown), and a TFT (not shown) connected to the gate bus line 12a and the source bus line. The pixel electrode 15 (sub-pixel electrodes 15a and 15b) and the photo-alignment film 18 are provided.

  The TFT includes a gate electrode (not shown) formed from the same conductive layer as the gate bus line 12a, a gate insulating film 13 covering the gate electrode, and a semiconductor formed on the gate insulating film 13 so as to face the gate electrode. A layer (not shown) and a source electrode and a drain electrode (both not shown) formed from the same conductive layer as the source bus line are included, and these are covered with a passivation film 14. The pixel electrode 15 is formed on the passivation film 14 and connected to the drain electrode in a contact hole (not shown).

  Further, the TFT substrate 10 has a CS bus line 12b formed of the same conductive film as the gate bus line 12a. As is well known, the CS bus line 12b is connected to one electrode of an auxiliary capacitor (Storage Capacitor) electrically connected in parallel with the liquid crystal capacitor constituting the pixel. The CS bus line 12b is provided so as to extend in parallel (in the row direction) with the gate bus line 12a.

  In the liquid crystal display panel 100 illustrated here, one pixel is divided into two sub-pixels (upper and lower sides of the gate bus line 12a in FIG. 1A). Specifically, the pixel electrode 15 is composed of two subpixel electrodes 15a and 15b, and the subpixel electrodes 15a and 15b each have a liquid crystal capacitance for each subpixel by the counter electrode 25 and the liquid crystal layer 30, respectively. Form. The source bus line is common to the two subpixels, and the TFT is provided corresponding to each of the two subpixels. The gates of the two TFTs are connected to a common gate bus line 12a.

  The CS bus line 12b is provided corresponding to each of the two sub-pixels, and the liquid crystal of the two sub-pixels is supplied by a voltage (for example, vibration voltage) supplied from the CS bus line 12b after the TFT is turned off. The effective voltage applied to the capacitors is configured to be different (for example, Japanese Patent Application Laid-Open No. 2004-62146). Thus, a structure that displays the luminance to be displayed by one pixel as an average of the luminances of two or more sub-pixels (sometimes referred to as a “multi-pixel structure”) is preferable from the viewpoint of viewing angle characteristics. The liquid crystal display panel of the embodiment of the present invention is not limited to this.

  The counter substrate 20 includes a glass substrate 21, a color filter layer 22, a counter electrode 25, and an alignment film 28. Here, the alignment film 28 is a vertical alignment film that does not define the pretilt direction. The color filter layer 22 includes a black matrix 23. The black matrix 23 is provided so as to overlap with the source bus line and the TFT of the TFT substrate 10 when viewed from the display surface normal line of the liquid crystal display panel 100.

  Here, the gate bus line 12 a and the CS bus line 12 b included in the TFT substrate 10 are embedded in the glass substrate 11. By using the gate bus line 12a and the CS bus line 12b embedded in the glass substrate 11 (sometimes referred to as “embedded wiring”) as a photomask, the photo-alignment film 18 is subjected to photo-alignment treatment. ing. Details of the photo-alignment process will be described later.

  As shown in FIG. 1A, two domains 18A1 and 18B1 and domains 18A2 and 18B2 are formed in each sub-pixel by the photo-alignment film 18 that has been subjected to the photo-alignment treatment (alignment division). Sometimes it is.) The boundary between the two domains of each subpixel is parallel to the gate bus line 12a (and CS bus line 12b).

  Further, the orientation directions (pretilt directions) of the liquid crystal molecules 30a in the vicinity of the photo-alignment film 18 in the two domains (18A1 and 18B1 or 18A2 and 18B2) are as indicated by cones 30A and 30B in FIG. The gate bus lines 12a are substantially orthogonal to each other and are different from each other by about 180 °. Each of the cones 30A and 30B is illustrated with the end of the liquid crystal molecules 30a close to the viewer side as the bottom surface of the cone when the liquid crystal layer 30 is observed from the counter substrate 20 side. Accordingly, the two domains of each subpixel in the liquid crystal display panel 100 rise from the photo-alignment film 18 toward the boundary.

  The alignment film 28 of the counter substrate 20 is a vertical alignment film that has not been subjected to alignment treatment, and the liquid crystal molecules 30a in the vicinity of the alignment film 28 are aligned as schematically shown in FIG. It is oriented almost perpendicular to the surface of the film 28. However, since the liquid crystal molecules 30a are aligned so that the alignment is continuous, the liquid crystal molecules 30a in the vicinity of the alignment film 28 are aligned so as to be aligned with the alignment direction of the liquid crystal molecules 30a by the opposing photo alignment film 18. Therefore, when a voltage is applied to the liquid crystal layer 30, the liquid crystal molecules 30a of the domains 18A1, 18B1, 18A2, and 18B2 fall in the directions indicated by the cones 30A and 30B, respectively. The cones 30A and 30B also indicate the direction of the director of each domain.

  The liquid crystal display panel 100 has a polarizing plate and a retardation plate on both sides of a liquid crystal cell composed of the TFT substrate 10, the counter substrate 20, and the liquid crystal layer 30 shown in FIG. In FIG. 1B, a pair of polarizing plates is arranged so as to sandwich the TFT substrate 10 and the counter substrate 20. The pair of polarizing plates have their polarization axes (transmission axes) orthogonal to each other (in a crossed Nicols state) as shown by a pair of double arrows in FIG. 1A (the broken line is the polarization axis of the lower polarizing plate). Has been placed. The director orientation of each domain bisects the angle formed by the polarization axes of the pair of polarizing plates. The configuration of the retardation plate is, for example, a C plate (a negative uniaxial retardation plate having a fast axis in the surface normal direction) in order from the liquid crystal layer 30 side between the TFT substrate 10 and the lower polarizing plate. ) And a TAC layer. Further, an A plate (a positive uniaxial retardation plate having a slow axis in the plane) and a TAC layer are provided between the counter substrate 20 and the upper polarizing plate in order from the liquid crystal layer 30 side.

  The liquid crystal display panel 100 can be manufactured as follows, for example.

  First, a glass substrate 11 is prepared, and circuit elements such as a gate bus line, a source bus line, a CS bus line, and a TFT are formed on one main surface of the glass substrate 11 by a known method. At this time, a buried wiring extending in the first direction is formed. Here, the gate bus line 12a and the CS bus line 12b extending in the row direction are embedded wirings. The embedded wiring can be formed by the method described in Patent Document 2, for example. Since the gate bus line is generally required to have a lower resistance than the source bus line, the gate bus line is wider than the source bus line. When the gate bus line is an embedded wiring, the thickness can be increased and the width can be reduced, so that the aperture ratio of the pixel can be increased.

  A photo-alignment film 18 is formed so as to cover almost the entire surface of the TFT substrate 10 thus obtained, and a photo-alignment process is performed. One of the features of the liquid crystal display panel manufacturing method of the present embodiment is that the photo-alignment treatment is performed by irradiating light from the back surface of the TFT substrate 10 (opposite side of the main surface on which the photo-alignment film 18 is formed). is there.

  The photo-alignment process for the photo-alignment film 18 of the TFT substrate 10 can be performed as follows. With reference to FIG. 2 (a) and (b), the method of a photo-alignment process is demonstrated.

  As schematically shown in FIG. 2A, the photo-alignment film 18 is irradiated with light from the back surface through the glass substrate 11.

  The incident angle θ of light is, for example, about 45 ° with respect to the normal line of the photo-alignment film 18. The light incident azimuth is an azimuth (column direction) orthogonal to a direction (row direction) in which the gate bus line 12a and the CS bus line 12b extend. The light irradiated from the glass substrate 11 side is blocked by the gate bus line 12a and the CS bus line 12b which are embedded wirings, so that the region is half of the region (subpixel) between the gate bus line 12a and the CS bus line 12b. Only irradiated. In the example shown in FIG. 2A, only the left half of the photo-alignment film 18 in the sub-pixel is selectively irradiated with light. Thereafter, light irradiation is performed from the opposite side of the gate bus line 12a and the CS bus line 12b (left side in FIG. 2A), so that only the right half of the photo-alignment film 18 in the sub-pixel is selectively irradiated. Is done. In this manner, two regions having a pretilt direction different by about 180 ° can be formed in the photo-alignment film 18 in the sub-pixel. Of course, you may perform a photo-alignment process only to one area | region as needed.

  As the photo-alignment film 18, as shown in FIG. 2B, a film that exhibits an alignment regulating force that pre-tilts the liquid crystal molecules 30 a in a direction orthogonal to the incident light by irradiating linearly polarized light (ultraviolet rays) is used. . As such a material, for example, a material having a chemical structure as shown in FIG. 2C is known (Non-Patent Document 1). When such a material is used, the pretilt direction can be defined in the light incident direction for the photo-alignment treatment. That is, as shown in FIG. 2B, the liquid crystal molecules 30a can be pretilted to the right side by irradiating light from the right side in the figure. At this time, when a P wave (polarization direction is in the plane of incidence) is used as linearly polarized light, better alignment can be obtained.

  A liquid crystal cell is manufactured using the TFT substrate 10 thus obtained and the counter substrate 20 having an alignment film prepared separately. The liquid crystal cell is manufactured so that the photo-alignment film 18 and the alignment film 28 face each other with a liquid crystal layer including a nematic liquid crystal material having negative dielectric anisotropy interposed therebetween. The liquid crystal material may be injected after the liquid crystal cell is formed using a vacuum injection method, or may be applied to any one of the substrates before the liquid crystal cell is formed using a drop injection method.

  The photo-alignment process for the photo-alignment film 18 is performed from the back side of the glass substrate 11 as described above. Therefore, the photo-alignment treatment for the photo-alignment film 18 may be performed after the liquid crystal cell is assembled. Further, when an alignment defect is found after the liquid crystal display panel is completed, the alignment defect can be repaired by performing the optical alignment process again. However, it is necessary to remove the polarizing plate in the second photo-alignment treatment.

  Next, a structure of another liquid crystal display panel 200 according to the embodiment of the present invention and a manufacturing method thereof will be described with reference to FIG.

  FIG. 3A schematically shows the structure of a portion corresponding to one pixel among a plurality of pixels arranged in a matrix form having rows and columns of the liquid crystal display panel 200, as in FIG. FIG. The liquid crystal display panel 200 is the same as the liquid crystal display device 100 except that the arrangement of the two domains formed in each subpixel is reversed. Components common to the liquid crystal display device 100 are denoted by common reference numerals, and description thereof is omitted here. The cross-sectional structure of the liquid crystal display panel 200 taken along the line BB ′ in FIG. 3A is such that the pretilt direction of the liquid crystal molecules 30a on the photo-alignment film 18 is the same as that in FIG. Except for the above, the liquid crystal display device 100 is the same as the liquid crystal display device 100, and the cross-sectional view is omitted.

  As shown in FIG. 3A, the orientation direction (pretilt direction) of the liquid crystal molecules 30a in the vicinity of the photo-alignment film 18 in the two domains (18A1 and 18B1 or 18A2, 18B2) of the subpixel of the liquid crystal display panel 200 is In contrast to the liquid crystal display panel 100 shown in FIG. 1A, the two domains are tilted from the photo-alignment film 18 toward the boundary.

  Such an alignment division structure can be obtained by performing a photo-alignment process on the photo-alignment film 18 as follows.

  Here, as shown in FIG. 3B, the photo-alignment film 18 exhibits an alignment regulating force that pre-tilts the liquid crystal molecules 30a in a direction parallel to the incident light by irradiating linearly polarized light (ultraviolet rays). Use things. As such a material, for example, a material having a chemical structure such as cinnamate group or coumarin group as X shown in FIG. 3C is known (Non-Patent Document 1). When such a material is used, the pretilt direction can be defined in a direction 180 ° different from the incident direction of light for the photo-alignment treatment. That is, as shown in FIG. 3B, the liquid crystal molecules 30a can be pretilted to the left side by irradiating light from the right side in the figure.

  Next, the viewing angle characteristics of the liquid crystal display panels 100 and 200 will be described with reference to FIG. 4 (a) and 4 (b) show the transmissivity of the liquid crystal display panels 100 and 200 in the vertical direction (in-plane along the line BB 'in FIGS. The viewing angle (polar angle) dependence at 12 o'clock to 6 o'clock of the board) is shown. That is, the viewing angle characteristic in the column direction orthogonal to the row direction in which the embedded wiring extends is shown. Here, a case where the pixel size is 600 μ × 200 μ (length in the column direction × length in the row direction), the depth of the embedded wiring is about 300 μm, and the photo-alignment process is performed at an incident angle θ of 45 ° is illustrated.

  As is clear from the comparison between FIG. 4A and FIG. 4B, in the liquid crystal display panel 200, when the absolute value of the viewing angle exceeds 45 °, the transmittance becomes extremely large as compared with the liquid crystal display panel 100. descend. When the absolute value of the viewing angle exceeds 45 °, the light passing through one of the two domains is blocked by the embedded wiring and thus does not contribute to display. Referring now to FIG. 1B, the liquid crystal molecules 30a of the domain that does not contribute to display when the viewing angle is tilted among the two domains of the liquid crystal layer 30 of the liquid crystal display panel 100 is tilted. The liquid crystal molecules 30a are inclined toward the surface (the bottom surface of the cone faces the viewing angle direction). Since the apparent refractive index anisotropy of the liquid crystal molecules 30a inclined toward the viewing angle direction is small, the influence on the display is small. Referring to FIG. 1A, when the viewing angle is tilted in the B direction along the line B-B ', the domains 18A1 and 18A2 do not contribute to display. At this time, the apparent refractive index anisotropy of the liquid crystal molecules 30a in the domains 18A1 and 18A2 is smaller than the apparent refractive index anisotropy of the liquid crystal molecules 30a in the domains 18B1 and 18B2, so that the contribution to display is small.

  On the other hand, in the liquid crystal display panel 200, contrary to the liquid crystal display panel 100, the liquid crystal molecules 30a in the domain that does not contribute to display when the viewing angle is tilted are tilted opposite to the tilted viewing angle direction. . Referring to FIG. 3A, when the viewing angle is tilted in the B direction along the line B-B ', the domains 18B1 and 18B2 do not contribute to the display. At this time, the apparent refractive index anisotropy of the liquid crystal molecules 30a in the domains 18B1 and 18B2 is larger than the apparent refractive index anisotropy of the liquid crystal molecules 30a in the domains 18A1 and 18A2, so that the contribution to display is large. That is, in the liquid crystal display panel 200, when the absolute value of the viewing angle exceeds 45 °, the domains 18B1 and 18B2 having the larger contribution to the display do not contribute to the display, so that the transmittance is extremely lowered.

  Therefore, the liquid crystal display panel 100 is preferable for obtaining a wide viewing angle, and the liquid crystal display panel 200 is preferable for obtaining a narrow viewing angle. Any one may be selected according to the use of the liquid crystal display panel.

  Next, with reference to FIGS. 5A to 5D, preferred shapes of the subpixel electrodes of the liquid crystal display panels 100 and 200 will be described. FIG. 5A is a plan view for explaining the structure of one pixel of the liquid crystal display panel 100 ′, and FIG. 5B is a plan view for explaining the structure of one pixel of the liquid crystal display panel 200 ′. FIG. The liquid crystal display panels 100 'and 200' are the same as the liquid crystal display panels 100 and 200, respectively, except for the shape of the subpixel electrodes. In the figure, the polarization axes (transmission axes) of the pair of polarizing plates are indicated by a pair of double arrows (the broken line indicates the polarization axis of the lower polarizing plate). The same applies to FIGS. 6 and 7.

  The subpixel electrode 15a ′ of the liquid crystal display panel 100 ′ shown in FIG. 5A is rectangular, whereas the subpixel electrode 15a of the liquid crystal display panel 100a has two domains as shown in FIG. It is a hexagon whose boundary line portion is swollen. As shown in FIG. 5A, when the subpixel electrode 15a 'is rectangular, the dark line DL is formed not only at the boundary between the two domains but also along the edge in the column direction of the subpixel electrode 15a'. This is because the orientation of the liquid crystal molecules is twisted when the pretilt direction of the liquid crystal molecules makes an angle of 90 ° or more with respect to the direction of the oblique electric field (fringe electric field) generated at the edge portion of the sub-pixel electrode 15a ′. This is because there are liquid crystal molecules that are aligned parallel to the absorption axis (perpendicular to the polarization axis). On the other hand, the subpixel electrode 15a has an edge inclined by α with respect to the column direction, and as a result, the generation of the dark line DL is suppressed. α is preferably 1 ° or more and less than 45 °.

  While the subpixel electrode 15c ′ of the liquid crystal display panel 200 ′ shown in FIG. 5B is rectangular, the subpixel electrode 15c shown in FIG. It is square. As shown in FIG. 5B, when the subpixel electrode 15c ′ is rectangular, the dark line DL is formed not only at the boundary between the two domains but also along the edge in the row direction and the column direction of the subpixel electrode 15c ′. The On the other hand, the subpixel electrode 15c has an edge inclined by β with respect to the column direction, and as a result, the generation of the dark line DL along the edge in the column direction is suppressed. β is preferably 1 ° or more and less than 45 °.

  As shown in FIGS. 5C and 5D, the edge (edge defining the width in the row direction) extending in the column direction of the subpixel electrode is an angle (α) of 1 ° or more and less than 45 ° with respect to the column direction. , Β), the liquid crystal molecules in the vicinity of the edge of the sub-pixel electrode are affected by the oblique electric field, but are aligned almost parallel to the direction indicated by the cone in the figure, and thus parallel to the absorption axis of the polarizing plate. There are no liquid crystal molecules that are aligned with each other, and the dark line DL is not generated. This was confirmed experimentally by making a sample.

  Next, with reference to FIGS. 6A to 6C, structures and manufacturing methods of liquid crystal display panels 300A and 300B according to other embodiments of the present invention will be described.

  The liquid crystal display panels 300A and 300B have a photo-alignment film not only on the TFT substrate side but also on the counter substrate side, and are each subjected to photo-alignment processing by backside illumination. The black matrix 23A of the counter substrate (corresponding to the counter substrate 20 of FIG. 1B) included in the liquid crystal display panels 300A and 300B has a buried structure. A photo-alignment process is performed on the photo-alignment film on the counter substrate side (corresponding to the alignment film 28 in FIG. 1B) using this embedded black matrix 23A.

  In the liquid crystal display panel 300A shown in FIG. 6A, the embedded wiring (gate bus line 12a and CS bus line 12b) is used as a photomask for the photo-alignment film of the TFT substrate by the method shown in FIG. 3B. The photo-alignment process is performed, and the photo-alignment process is performed on the photo-alignment film of the counter substrate by using the embedded black matrix 23A as a photomask by the method shown in FIG. ing. As a result, each subpixel is divided into four domains. The orientation direction of the liquid crystal molecules near the center of the thickness direction of the liquid crystal layer of each domain is a direction that bisects two orthogonal pretilt directions defined by a pair of photo-alignment films as indicated by a cone. .

  On the other hand, in the liquid crystal display panel 300B shown in FIG. 6B, the photo-alignment film of the TFT substrate is filled with the embedded wiring (gate bus line 12a and CS bus line 12b) by the method shown in FIG. 2B. As shown in FIG. 2B, the photo-alignment process is performed using the embedded black matrix 23A as a photomask by the method shown in FIG. 2B. It has been subjected. As a result, each subpixel is divided into four domains.

  The liquid crystal display panels 300A and 300B, like the liquid crystal display panels 100 and 200, are subjected to photo-alignment treatment from the back surface of the glass substrate. However, when alignment failure is found after the liquid crystal display panel is completed, the photo-alignment is performed again. Even if the treatment is performed, the alignment failure cannot be repaired. As shown in FIG. 6C, when light is irradiated from the back surface of the TFT substrate, the light alignment film on the counter substrate side is also irradiated with light. It will be impossible to obtain.

  Thus, when using a photo-alignment film also on the counter substrate side, it is necessary to perform a photo-alignment process on each photo-alignment film before assembling the liquid crystal cell. Furthermore, since the counter substrate usually has a color filter layer, and the color filter layer absorbs ultraviolet rays, when the light alignment film of the counter substrate is irradiated with light from the back surface, it is necessary to have a configuration without the color filter layer. is there. Of course, color display can be performed by adopting a field sequential driving method without providing a color filter layer on the counter substrate.

  Further, since the liquid crystal display panels 300A and 300B have the black matrix 23A embedded in the counter substrate in addition to the embedded wiring of the TFT substrate, the viewing angle is limited not only in the vertical direction but also in the horizontal direction. Is inferior to the liquid crystal display panels 100 and 200.

  Next, with reference to FIG. 7 and FIG. 8, the structure and manufacturing method of liquid crystal display panels 400A and 400B according to still another embodiment of the present invention will be described.

  In the liquid crystal display panels 400A and 400B, the TFT substrate side is subjected to photo-alignment processing by back surface illumination as in the previous embodiment, but the counter substrate is subjected to photo-alignment processing by front surface irradiation.

  In the liquid crystal display panel 400A shown in FIG. 7A, the embedded wiring (gate bus line 12a and CS bus line 12b) is used as a photomask for the photo-alignment film of the TFT substrate by the method shown in FIG. 3B. Thus, a photo-alignment process is performed. On the other hand, the photo-alignment film of the counter substrate is irradiated with light from the front surface of the photo-alignment film (without passing through the glass substrate) by the method shown in FIG. The black matrix 23 does not have an embedded structure. As a material for this photo-alignment film, a material that exhibits an alignment regulating force that pre-tilts the liquid crystal molecules 30a in a direction parallel to the incident light is used (see FIG. 3C). The irradiation direction of the light with respect to the photo-alignment film of the counter substrate is a direction indicated by a dashed arrow in FIG. Since the pretilt direction by the photo-alignment film on the TFT substrate and the pretilt direction by the photo-alignment film on the counter substrate are different by 90 °, the pretilt direction of the liquid crystal molecules near the center of the thickness direction of the liquid crystal layer is a direction that bisects them (See the cone in FIG. 7 (a)). As a result, two domains different in pretilt direction by 180 ° are formed in each sub-pixel.

  On the other hand, in the liquid crystal display panel 400B shown in FIG. 7B, a buried mask (gate bus line 12a and CS bus line 12b) is photomasked in the photo-alignment film of the TFT substrate by the method shown in FIG. 2B. The photo-alignment processing is performed using as. On the other hand, the photo-alignment film of the counter substrate is irradiated with light from the front surface of the photo-alignment film (without passing through the glass substrate) by the method shown in FIG. The black matrix 23 does not have an embedded structure. As such a material, for example, a material having a chemical structure as shown in FIG. 2C is known (Non-Patent Document 1). When such a material is used, the pretilt direction can be defined in the light incident direction for the photo-alignment treatment (Non-Patent Document 1). The light irradiation direction with respect to the photo-alignment film of the counter substrate is the direction indicated by the broken-line arrow in FIG. Since the pretilt direction by the photo-alignment film on the TFT substrate and the pretilt direction by the photo-alignment film on the counter substrate are different by 90 °, the pretilt direction of the liquid crystal molecules near the center of the thickness direction of the liquid crystal layer is a direction that bisects them. (See the cone in FIG. 7B). As a result, two domains different in pretilt direction by 180 ° are formed in each sub-pixel.

  Since the liquid crystal display panels 400A and 400B do not have an embedded black matrix like the liquid crystal display panels 300A and 300B, the viewing angle range in the left-right direction is wide. However, the liquid crystal display panels 400A and 400B, like the liquid crystal display panels 300A and 300B, can be repaired even if the photo-alignment process is performed again if alignment failure is found after the liquid crystal display panel is completed. Absent. As shown in FIG. 7C, when light is irradiated from the back surface of the TFT substrate, light is also irradiated to the photo-alignment film on the counter substrate side. It will be impossible to obtain.

  Also in the manufacturing process of the liquid crystal display panels 400A and 400B, it is necessary to perform a photo-alignment treatment on each photo-alignment film before assembling the liquid crystal cell. In the liquid crystal display panels 300A and 300B, since the light alignment film on the counter substrate is irradiated with light from the back surface, it is necessary to have a configuration without the color filter layer. In the liquid crystal display panels 400A and 400B, the photo alignment film on the counter substrate is used. Since light irradiation is performed from the front surface, the present invention can also be applied to a configuration having a color filter layer.

  The present invention can be widely applied to liquid crystal display panels.

(A) And (b) is a schematic diagram which shows one pixel of the liquid crystal display panel 100 of embodiment by this invention, (a) is a top view, (b) is a BB 'line | wire in (a). FIG. (A)-(c) is a figure for demonstrating the manufacturing method of the liquid crystal display panel 100, (a) is typical sectional drawing of the liquid crystal display panel 100, (b) is a photo-alignment process direction. (C) is a figure which shows the chemical structure of photo-alignment film | membrane material. (A) is a schematic top view which shows one pixel of the other liquid crystal display panel 200 of embodiment by this invention, (b) is a schematic diagram which shows a photo-alignment process direction, (c) is light It is a figure which shows the chemical structure of alignment film material. (A) And (b) is a graph which shows the viewing angle (polar angle) dependence in the up-down direction of the transmittance | permeability of the liquid crystal display panels 100 and 200, respectively. (A) is a top view for demonstrating the structure of one pixel of liquid crystal display panel 100 ', (b) is a top view for demonstrating the structure of one pixel of liquid crystal display panel 200', (C) is a plan view showing a sub-pixel electrode 15 a of the liquid crystal display panel 100, and (d) is a plan view showing a sub-pixel electrode 15 c of the liquid crystal display panel 200. (A) And (b) is a typical top view which shows one pixel of liquid crystal display panel 300A and 300B of other embodiment by this invention, (c) is light again to the pixel of liquid crystal display panel 300A. It is a schematic diagram which shows the orientation state at the time of performing an orientation process. (A) And (b) is a schematic top view which shows one pixel of liquid crystal display panel 400A and 400B of further another embodiment by this invention, (c) is again to the pixel of liquid crystal display panel 400A. It is a schematic diagram which shows the orientation state at the time of performing a photo-alignment process. (A) And (b) is a schematic diagram which shows the photo-alignment processing method by irradiating light from a front surface to a photo-alignment film.

Explanation of symbols

10 TFT substrate 11, 21 Glass substrate 12a Gate bus line 12b CS bus line (auxiliary capacitance wiring)
13 Gate insulating film 14 Passivation film 15 Pixel electrode 15a, 15b, 15c, 15d, 15a ′, 15c ′ Subpixel electrode 18 Photo-alignment film 18A1, 18A2, 18B1, 18B2 Domain 20 Counter substrate 28 Alignment film 30 Liquid crystal layer 30a Liquid crystal molecule 30A, 30B Cone 100, 200, 300, 400 Liquid crystal display panel

Claims (7)

Preparing a first glass substrate having first and second main surfaces (a);
Forming a buried wiring extending in a first orientation on the first main surface of the first glass substrate (b);
(C) forming a photo-alignment film on the first main surface of the first glass substrate on which the embedded wiring is formed;
By selectively irradiating only the first region of the photo-alignment film with linearly polarized light from a direction inclined in a second direction substantially orthogonal to the first direction from the second main surface side, the photo-alignment film Defining the pretilt direction of the first region (d);
A step (e) of preparing a second glass substrate having an alignment film;
The first glass substrate and the second glass substrate are bonded so that the photo-alignment film and the alignment film face each other with a liquid crystal layer containing a nematic liquid crystal material having a negative dielectric anisotropy interposed therebetween. Producing a combined liquid crystal cell (f);
A method for producing a liquid crystal display panel, comprising:   By irradiating the second region adjacent to the first region of the photo-alignment film from the second principal surface side from a direction inclined in a third direction different from the second direction by about 180 ° from the second direction, 2. The method of manufacturing a liquid crystal display panel according to claim 1, further comprising a step (g) of defining a pretilt direction of the second region of the photo-alignment film in a direction different from the pretilt direction of the first region by approximately 180 °.   3. The method of manufacturing a liquid crystal display panel according to claim 1, wherein, in the step (d), a pretilt direction of the first region is defined as the second orientation.   The method for manufacturing a liquid crystal display panel according to claim 1, wherein a vertical alignment film that does not define a pretilt direction is used as the alignment film. Forming a gate bus line, a source bus line, and a TFT on the first main surface of the first glass substrate;
The method for manufacturing a liquid crystal display panel according to claim 1, wherein the embedded wiring is the gate bus line. A plurality of pixels arranged in a matrix having rows and columns;
A TFT substrate;
A counter substrate;
A liquid crystal layer including a nematic liquid crystal material having a negative dielectric anisotropy provided between the TFT substrate and the counter substrate;
Have
The TFT substrate has a glass substrate, a gate bus line formed on the glass substrate, a source bus line, a TFT connected to the gate bus line and the source bus line, and a photo-alignment film,
The counter substrate has a vertical alignment film that does not define a pretilt direction,
The gate bus line is embedded in the glass substrate, and the liquid crystal layer has two domains divided by a boundary parallel to the gate bus line in each of the plurality of pixels.
The liquid crystal display panel in which the orientation directions of liquid crystal molecules in the vicinity of the photo-alignment film in the two domains are substantially orthogonal to the gate bus line and differ from each other by about 180 °.   The liquid crystal display panel according to claim 6, wherein the liquid crystal molecules in contact with the photo-alignment film in the two domains rise from the photo-alignment film toward the boundary when no voltage is applied.

Images