JP3722870B2 - Liquid crystal display panel and manufacturing method thereof - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a liquid crystal display panel and a method for manufacturing the same, and more particularly to a liquid crystal display panel having an orientation parallel or nearly parallel to a substrate surface on at least one substrate surface side and a method for manufacturing the same.
[0002]
[Prior art]
Conventionally, as a method for aligning liquid crystal molecules, a rubbing method, an oblique deposition method, and a diffraction grating method are known.
[0003]
The rubbing method is a method of rubbing (rubbing) a roll around which a nylon-based or vinyl-based fiber is wound on an alignment film formed on the surface of the substrate on the liquid crystal layer side. According to this method, static electricity of about 100 V to 10 kV is generated during the rubbing process. Due to static electricity, an active element such as a thin film transistor (TFT) formed on the substrate surface may be destroyed.
[0004]
The oblique deposition method is a method in which an inorganic film such as SiO is deposited on a substrate from an oblique direction. According to this method, the element is not destroyed due to the generation of static electricity. However, it is not suitable for mass production.
[0005]
The diffraction grating method is a method in which fine stripe-shaped grooves are formed on the surface of a substrate and liquid crystal molecules are aligned along the grooves. In this method, it is necessary to pattern the entire surface of the substrate using photolithography.
[0006]
[Problems to be solved by the invention]
As described above, the rubbing method is not suitable for the alignment treatment of the substrate on which an active element such as a TFT is formed. Further, the oblique deposition method and the diffraction grating method are disadvantageous in terms of mass productivity.
[0007]
An object of the present invention is to provide a liquid crystal display panel using an alignment treatment technique that does not generate static electricity and is suitable for mass production, and a method for manufacturing the same.
[0008]
[Means for Solving the Problems]
According to one aspect of the present invention, a step of forming an alignment film whose surface energy is changed by light irradiation on the surface of a transparent substrate, and by irradiating the alignment film with linearly polarized light, a step of changing the surface energy of the region formed by a plurality of parallel arrangement of elongated in direction, after the step of changing the surface energy, have a a step of manufacturing a liquid crystal panel using the transparent substrate A method of manufacturing a liquid crystal display panel , wherein the amount of change in surface energy that changes in the step of changing the surface energy is a level at which liquid crystal molecules in the liquid crystal panel receive a region in which the surface energy has changed and is oriented in a specific direction. Is provided.
[0009]
According to another aspect of the present invention, a step of forming an alignment film whose surface energy is changed by light irradiation on the surface of a transparent substrate, and a plurality of patterns that are long in one direction among the surfaces of the alignment film The alignment film is formed by irradiating light to a region having a shape arranged so that the longitudinal directions of the two are substantially parallel to each other, and making the surface energy of the region irradiated with light different from the surface energy of other regions. possess a step of imparting orientation, the difference between the surface energy of the surface energy and other areas of the irradiated region of the light, the liquid crystal molecules in contact with the alignment film is affected differently of the surface energy particular A method for manufacturing a liquid crystal display panel having a level oriented in the direction is provided.
[0010]
According to another aspect of the present invention, there is provided a method for manufacturing a liquid crystal display panel, wherein the shape that is long in one direction includes a portion whose width changes monotonously with respect to the longitudinal direction.
[0011]
According to another aspect of the present invention, a pair of transparent substrates arranged in parallel and an alignment film formed on the opposite surface side of at least one of the pair of transparent substrates and whose surface energy is changed by light irradiation. And a liquid crystal layer sandwiched between the pair of transparent substrates, the surface of the alignment film is flat on the order of the size of the liquid crystal molecules of the liquid crystal layer, and in one direction of the surfaces Unlike surface energy of the light illuminated area has an arrangement shape as long plurality of patterns longitudinal direction of each pattern substantially parallel to each other and the surface energy of the other regions, the difference in the surface energy, A liquid crystal display panel is provided in which liquid crystal molecules in contact with the alignment film are aligned in a specific direction under the influence of different surface energy .
[0012]
[Action]
By irradiating the alignment film whose properties change by light irradiation with linearly polarized light, the alignment film can be provided with alignment. In addition, the alignment film can be aligned by irradiating light to a region having a shape in which a plurality of long patterns in one direction are arranged so that the longitudinal directions of the patterns are substantially parallel to each other. Can be granted. The reason why orientation is imparted by these methods is considered as follows.
[0013]
Irradiation with light partially changes the surface energy of the alignment film. The shape of the region where the surface energy changes depends on the polarization direction of linearly polarized light or the shape of the region irradiated with light, and is considered to have directionality in the plane. The liquid crystal molecules are considered to be oriented in a specific direction under the influence of the region where the surface energy has changed.
[0014]
By making the shape of the region that irradiates light a shape whose width changes monotonously in the longitudinal direction, the shape of the region that irradiates light can have directivity in the longitudinal direction. Since the shape of the region irradiated with light has directivity in the longitudinal direction, it is expected that a pretilt can be imparted to liquid crystal molecules aligned along the longitudinal direction.
[0015]
【Example】
A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a partial sectional view of a liquid crystal display panel according to the first embodiment. The liquid crystal display panel is composed of substrates 10 and 20 and a liquid crystal layer 30.
[0016]
The substrate 10 is configured by laminating a color filter 12, a transparent electrode 13, and an alignment film 14 in this order on the surface of the transparent substrate 11. The color filter 12 includes a region R that transmits red light, a region G that transmits green light, and a region B that transmits blue light. The transparent electrode 13 and the alignment film 14 are formed on almost the entire surface of the substrate. The alignment film 14 is subjected to a rubbing process to give an alignment property and a pretilt angle α.
[0017]
The substrate 20 includes a TFT substrate 21 and an alignment film 24. On the TFT substrate 21, TFTs, pixel electrodes, and wirings not shown in the figure are formed. The alignment film 24 is formed on almost the entire surface of the TFT substrate 21. The alignment film 24 is given orientation by a method described later.
[0018]
FIG. 2 is a schematic view of an alignment processing apparatus for explaining a method for imparting alignment to an alignment film. The alignment processing apparatus includes an excimer laser light source 42, a beam attenuator 41, and a polarizer 40. In the drawing, a substrate 45 having an alignment film 44 formed on the left side of the polarizer 40 is disposed with the surface on the alignment film side facing the polarizer 40.
[0019]
The excimer laser light source 42 is a KrF laser light source having an emission wavelength of 248 nm. The laser light emitted from the excimer laser light source 42 propagates along the optical axis 43 and enters the beam attenuator 41. The beam attenuator 41 adjusts the fluence of the laser beam.
[0020]
The laser light transmitted through the beam attenuator 41 enters the polarizer 40 at an incident angle of 56.5 °. The polarizer 40 is PL248 made by Showa Optronics. The laser light transmitted through the polarizer 40 becomes linearly polarized light. The surface of the alignment film 44 is irradiated with linearly polarized laser light.
[0021]
Using the above alignment treatment apparatus, the fluence on the surface of the alignment film 44 was 25, 20, 15, 10, and 5 mJ / cm ^2, and 1000 shots were irradiated at a repetition frequency of 3 Hz. The used substrate 45 is a glass substrate with a transparent electrode. The alignment film 44 is formed by applying and baking a soluble polyimide-based alignment film material (JALS214 manufactured by JSR) on the surface of the substrate 45.
[0022]
A twisted nematic (TN) type liquid crystal panel was manufactured using the substrate 45 irradiated with laser light under the above conditions, and the refractive index was measured to evaluate the orientation of the liquid crystal layer. Note that the alignment film of the substrate facing the substrate irradiated with the laser light is rubbed, and the pretilt angle is 5 °. It was found that good orientation was obtained when the fluence was 10 mJ and 5 mJ.
[0023]
The reason why the alignment film can be oriented by irradiation with linearly polarized laser light is considered as follows.
FIG. 3 is a partial perspective view of a substrate and an alignment film that have been subjected to alignment treatment by irradiating linearly polarized laser light. An alignment film 44 is formed on the surface of the substrate 45. It is considered that when the alignment film 44 is irradiated with linearly polarized laser light, the surface of the alignment film 44 is modified and a region 46 having a partially different surface energy is formed. The shape of the region 46 having different surface energy depends on the polarization direction of the laser beam to be irradiated, and is considered to be long in the direction parallel to the polarization direction as shown in FIG.
[0024]
The liquid crystal molecules are considered to be aligned such that the major axis thereof is along the longitudinal direction of the region 46 under the influence of the region 46 having different surface energy. That is, the liquid crystal molecules are aligned in a direction parallel to the polarization direction of the irradiation light.
[0025]
In FIG. 1, the alignment film 24 on the TFT substrate 21 side can be subjected to the alignment process without being subjected to the rubbing process, so that the TFT can be prevented from being broken due to static electricity or the like. In addition, alignment and pretilt can be imparted by performing a rubbing treatment on the alignment film 14 on the side opposite to the TFT substrate 21. Since no active elements such as TFTs are formed on the substrate 10 on the alignment film 14 side, there is no adverse effect of static electricity due to the rubbing process.
[0026]
In this manner, a liquid crystal display panel having a pretilt can be manufactured without subjecting the alignment film on the TFT substrate side to rubbing treatment. Although FIG. 1 shows the case where the liquid crystal molecules are homogeneously arranged, the present invention can also be applied to other arrangements in which the liquid crystal molecules are aligned parallel or nearly parallel to the substrate surface. For example, it could be applied to twisted nematic arrangement.
[0027]
In the first embodiment, the case of irradiating laser light with a wavelength of 248 nm has been described, but laser light with other wavelengths may be used. Preferably, laser light with a wavelength of 300 nm or less is irradiated. The fluence of the laser beam is preferably not more than 1/2 of the ablation threshold value of the alignment film. Moreover, although the case where the soluble polyimide type alignment film material was used was demonstrated, as long as the surface is modified by light irradiation, other alignment film materials may be used.
[0028]
The first embodiment is particularly effective when performing an alignment process on the alignment film on the TFT substrate side. However, the first embodiment is suitable for an alignment process on an alignment film formed on a substrate on which no active element such as a TFT is formed. Is also applicable. For example, the present invention can be applied to alignment processing of a simple matrix type liquid crystal display panel.
[0029]
Next, a second embodiment of the present invention will be described with reference to FIGS.
FIG. 4 is a diagram for explaining an alignment processing method according to the second embodiment. An alignment film 51 is formed on the surface of the transparent substrate 50. The material of the alignment film 51 is the same as that used in the first embodiment. A photomask 54 is arranged in parallel on the alignment film 51 with a gap therebetween. The photomask 54 includes a glass substrate 52 and a mask pattern 53. The mask pattern 53 is a striped pattern with a pitch of 1 μm.
[0030]
The surface of the alignment film 51 is irradiated with KrF excimer laser light through the photomask 54. The fluence of the laser beam was 10 mJ / cm ² , and 2000 shots were irradiated at a repetition frequency of 3 Hz. The laser light used in this embodiment is not linearly polarized light but includes various polarized light.
[0031]
Using the substrate irradiated with laser light by the method shown in FIG. 4, a TN liquid crystal panel similar to that in the first example was manufactured. As a result of measuring the refractive index of the liquid crystal panel and evaluating the orientation of the liquid crystal layer, it was possible to confirm a good orientation.
[0032]
In the second embodiment, the case of irradiating KrF excimer laser light has been described. However, ultraviolet light from a low-pressure mercury lamp may be irradiated. However, since the ultraviolet light from the low-pressure mercury lamp is diverging light, it is preferable that the photomask and the alignment film surface are in close contact with each other. The photomask and the alignment film surface were brought into close contact, and irradiation was performed at an irradiation intensity of 10 mW / cm ² and an irradiation time of 1 to 5 minutes. As a result, it was found that good orientation can be obtained when the irradiation time is 2 to 3 minutes.
[0033]
The reason why the orientation can be imparted by the orientation treatment method shown in FIG. 4 is considered as follows. Since the laser beam or the ultraviolet light is irradiated through the striped photomask, the striped region on the surface of the alignment film is modified. The surface energy of the striped region is considered to be different from the surface energy of other regions. For this reason, it is considered that the liquid crystal molecules are aligned as in the case of the first embodiment.
[0034]
If the irradiation time of the irradiation light is shorter than a suitable time, it is considered that the alignment film surface is not sufficiently modified, and thus good alignment cannot be obtained. Conversely, when the irradiation time is longer than a suitable time, the resolution of the striped pattern is lowered, and it is considered that good orientation cannot be obtained.
[0035]
In the second embodiment, the pitch of the striped pattern is 1 μm, but it is not necessarily 1 μm. From the size of the liquid crystal molecules, the pitch is preferably 3 μm or less.
[0036]
Although FIG. 4 illustrates the case of a mask pattern having a shape in which a linear pattern is periodically arranged in a certain direction, it is not always necessary to periodically arrange the pattern. For example, it is good also as a mask pattern shape which arrange | positioned the pattern which has a long shape in one direction so that the longitudinal direction of each shape may become mutually parallel.
[0037]
Next, a modification of the second embodiment will be described with reference to FIG.
FIG. 5A shows a plan view of the mask pattern of the photomask used in the second embodiment. As shown in the figure, linear patterns extending in the y-axis direction are arranged in the x-axis direction at a pitch of 1 μm. Since the linear pattern does not have directivity in the y-axis direction, it is considered that there is no action of tilting liquid crystal molecules aligned in parallel to the y-axis. On the other hand, when directivity is given to the linear pattern, it is expected that the action of tilting the liquid crystal molecules works.
[0038]
As shown in FIG. 5B, when a mask pattern having a shape in which isosceles triangles facing the negative direction of the y-axis are connected in parallel to the y-axis, each mask pattern has directivity in the y-axis direction. become. FIG. 5B shows the case where the positions on the y-axis of the isosceles triangles of each mask pattern are aligned. However, as shown in FIG. 5C, the positions on the y-axis are not aligned. Good. Further, even if the isosceles triangles are not arranged parallel to the y-axis, they may be randomly arranged as shown in FIG. 5D as long as the longitudinal direction of each isosceles triangle faces a certain direction.
[0039]
5B to 5D, an isosceles triangle has been described as an example of a directional shape, but other shapes may be used. It is good also as a shape which connected the shape whose width | variety changes monotonously regarding the longitudinal direction of a mask pattern.
[0040]
In the above-described embodiment, a case where a plurality of regions having a long shape in one direction are arranged almost in parallel on the entire surface of the substrate and light is irradiated on these regions is shown. In this case, the longitudinal direction may be directed in a messy direction. With such an arrangement, a multi-domain liquid crystal display panel can be easily manufactured.
[0041]
Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.
[0042]
【The invention's effect】
As described above, according to the present invention, alignment treatment can be performed without performing rubbing treatment on the alignment film. In the case where the alignment process is performed on the substrate on which the TFT is formed, the TFT can be prevented from being broken due to the generation of static electricity.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a liquid crystal display panel.
FIG. 2 is a schematic view of an alignment processing apparatus for performing alignment processing according to the first embodiment of the present invention.
FIG. 3 is a perspective view of a substrate for explaining a surface energy state of an alignment film that has been subjected to alignment treatment by the method according to the first embodiment of the present invention;
FIG. 4 is a cross-sectional view of a substrate and a photomask for explaining an alignment processing method according to a second embodiment of the present invention.
FIG. 5 is a plan view of a mask pattern of a photomask used in the second embodiment of the present invention.
[Explanation of symbols]
10, 20 Substrate 11 Glass substrate 12 Color filter 13 Transparent electrodes 14 and 24 Alignment film 21 TFT substrate 30 Liquid crystal layer 40 Polarizer 41 Beam attenuator 42 Excimer laser light source 43 Optical axis 44 Alignment film 45 Substrate 46 Regions with different surface energy 50 Transparent Substrate 51 Alignment film 52 Glass substrate 53 Mask pattern 54 Photomask

Claims (6)

Forming an alignment film whose surface energy is changed by light irradiation on the surface of the transparent substrate;
Irradiating the alignment film with linearly polarized light, thereby changing the surface energy of a region formed by arranging a plurality of parallel long shapes in a direction parallel to the polarization direction;
After the step of changing the surface energy, it has a a step of manufacturing a liquid crystal panel using the transparent substrate,
A method of manufacturing a liquid crystal display panel , wherein the amount of change in surface energy that changes in the step of changing the surface energy is such that the liquid crystal molecules in the liquid crystal panel receive a region in which the surface energy has changed and are oriented in a specific direction . Forming an alignment film whose surface energy is changed by light irradiation on the surface of the transparent substrate;
Of the surface of the alignment film, light is irradiated to a region having a shape in which a plurality of patterns that are long in one direction are arranged so that the longitudinal directions of the patterns are substantially parallel to each other. by varying the surface energy and the surface energy of the other regions have a a step of imparting orientation to the orientation film,
A liquid crystal display panel in which the difference between the surface energy of the region irradiated with light and the surface energy of another region is a level at which liquid crystal molecules in contact with the alignment film are aligned in a specific direction under the influence of the surface energy. Manufacturing method.   The method for manufacturing a liquid crystal display panel according to claim 2, wherein the long shape in one direction includes a portion whose width monotonously changes in the longitudinal direction.   The method for manufacturing a liquid crystal panel according to claim 3, wherein a part of the region where the surface energy of the surface of the alignment film is changed in which the width changes monotonously with respect to the longitudinal direction tilts the liquid crystal molecules in contact with the alignment film. A pair of transparent substrates arranged in parallel;
An alignment film that is formed on the opposite surface side of at least one of the pair of transparent substrates, and whose surface energy is changed by light irradiation,
A liquid crystal layer sandwiched between the pair of transparent substrates,
The surface of the alignment film is flat on the order of the size of the liquid crystal molecules of the liquid crystal layer, and a plurality of patterns that are long in one direction are arranged so that the longitudinal directions of the patterns are substantially parallel to each other. surface energy of the light illuminated areas have a shape that varies with the surface energy of the other regions,
The liquid crystal display panel in which the difference in surface energy is a level at which liquid crystal molecules in contact with the alignment film are aligned in a specific direction under the influence of different surface energy .   The liquid crystal display panel according to claim 5, wherein the shape that is long in one direction includes a portion whose width monotonously changes in the longitudinal direction.

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