JP3898213B2 - Manufacturing method of liquid crystal display panel - Google Patents

Description

The present invention relates to a liquid crystal display panel and a manufacturing method thereof, a method of manufacturing a liquid crystal display panel, particularly to the parallel or nearly parallel orientation to the substrate surface at least one substrate surface.

  Conventionally, as a method for aligning liquid crystal molecules, a rubbing method, an oblique deposition method, and a diffraction grating method are known.

  The rubbing method is a method of rubbing (rubbing) a roll around which a nylon or vinyl 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.

  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.

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.
Japanese Patent Laid-Open No. 4-7520 JP-A-6-18885 JP-A-5-127164 Japanese Patent Laid-Open No. 1-210932

  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.

An object of the present invention is to provide a method for manufacturing a liquid crystal display panel using an alignment treatment technique which does not generate static electricity and is suitable for mass production.

In order to solve the above problems, a method for producing a liquid crystal display panel according to the present invention includes a step of forming an alignment film whose properties are changed by light irradiation on a transparent substrate, and a step of imparting alignment to the alignment film. And a step of creating a liquid crystal display panel in which liquid crystal molecules are sandwiched between the transparent substrates, and in the step of imparting orientation to the alignment film, the alignment film not subjected to alignment treatment is passed through a polarizer, A plurality of long patterns in one direction are irradiated with linearly polarized light on regions where the longitudinal directions of the patterns are substantially parallel to each other, thereby imparting alignment to the alignment film, thereby aligning the liquid crystal molecules along the longitudinal direction. It is characterized by being oriented .

In the method for producing a liquid crystal display panel of the present invention, it is preferable that the liquid crystal molecules are aligned in parallel with the direction of the linearly polarized light.

  According to the above invention, the alignment film can be imparted with alignment by irradiating the alignment film whose properties are changed by light irradiation. 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.

  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.

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 also be imparted to the liquid crystal molecules aligned along the longitudinal direction.

  According to the present invention, alignment treatment can be performed without subjecting the alignment film to rubbing treatment. 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.

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a partial cross-sectional view of the 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.

  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.

  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.

  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.

  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.

  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.

Using the above alignment treatment apparatus, the fluence on the surface of the alignment film 44 was set to 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.

  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.

  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.

  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.

  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.

  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.

  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.

  The first embodiment is particularly effective when performing alignment processing of the alignment film on the TFT substrate side. However, alignment processing of the alignment film formed on the substrate on which an active element such as a TFT is not formed. It is also applicable to. For example, the present invention can be applied to alignment processing of a simple matrix type liquid crystal display panel.

  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.

The surface of the alignment film 51 is irradiated with KrF excimer laser light through the photomask 54. Fluence of the laser light is 10mJ / cm ^2, was irradiated in 2000 shot at a repetition frequency 3Hz. The laser light used in the present embodiment is not linearly polarized light but includes various polarized light.

  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 embodiment was produced. 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.

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 was obtained when the irradiation time was 2 to 3 minutes.

  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.

  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.

  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.

  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.

  Next, a modified example 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.

  As shown in FIG. 5B, if the mask pattern has a shape in which isosceles triangles oriented in 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 a 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, the isosceles triangles may be randomly arranged as shown in FIG. 5D as long as the longitudinal direction of each isosceles triangle faces a certain direction.

  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.

  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 to these regions is shown. In the region, 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.

As described above, in the method for manufacturing a liquid crystal display panel, the transparent substrate is preferably a TFT substrate.

  Further, the liquid crystal display panel includes a pair of transparent substrates, an alignment film formed on an opposing surface side of at least one of the pair of transparent substrates, and a liquid crystal sandwiched between the pair of transparent substrates. A liquid crystal display panel having a layer, the surface of the alignment film is flat, and liquid crystal molecules in a region irradiated with light are aligned in a specific direction.

  In the liquid crystal display panel, the alignment film preferably has 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.

  As mentioned above, although this invention was demonstrated along embodiment, this invention is not restrict | limited to these. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

It is sectional drawing of a liquid crystal display panel. It is the schematic of the orientation processing apparatus for performing the orientation processing by the 1st Embodiment of this invention. It is a perspective view of the board | substrate for demonstrating the surface energy state of the orientation film which performed the orientation process by the method by the 1st Embodiment of this invention. It is sectional drawing of the board | substrate and photomask for demonstrating the orientation processing method by the 2nd Embodiment of this invention. It is a top view of the mask pattern of the photomask used in the 2nd Embodiment of this 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 (2)

Forming an alignment film whose properties are changed by light irradiation on a transparent substrate;
A step of imparting orientation to the alignment film;
Having a liquid crystal display panel that sandwiches liquid crystal molecules between the transparent substrates,
In the step of imparting orientation to the alignment film,
The alignment film is oriented by irradiating a plurality of long patterns in one direction on a non-aligned alignment film with linearly polarized light in a region where the longitudinal directions of the patterns are almost parallel to each other . By providing the above, the liquid crystal molecules are aligned along the longitudinal direction . 2. The method of manufacturing a liquid crystal display panel according to claim 1 , wherein the liquid crystal molecules are aligned in parallel with the direction of the linearly polarized light .

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