JP4546340B2 - Manufacturing method of liquid crystal display element - Google Patents

Description

  The present invention relates to a method for manufacturing a liquid crystal display element.

  In recent years, in the field of flat panel display (FPD), liquid crystal display (LCD), plasma display (PDP), field emission display (FED), vacuum fluorescent display (VFD) and the like have been actively researched. Among these, liquid crystal display devices (hereinafter referred to as “LCD”) are currently in the limelight for reasons such as mass production technology, ease of driving means and high image quality. An LCD is a device that fills liquid crystal, which is a medium having an optical switch function, between a pair of substrates and displays information on a screen using the refractive index anisotropy of the liquid crystal.

  Conventionally, in a structure of a liquid crystal display element, there is always an alignment film called an alignment layer for aligning liquid crystal molecules. Usually, the alignment film aligns liquid crystal molecules in a uniaxial direction using a technique called rubbing method in which an organic alignment film made of polyimide (PI) is rubbed with a cloth or the like. Recently, as a non-contact alignment method, in addition to the rubbing method, a liquid crystal molecule alignment method using a UV irradiation method or an ion beam method has been proposed, and some of them have already been mass-produced.

  The rubbing method is excellent in that the process is simple and easy to manufacture, but on the other hand, scratches and streak-like defects are generated by rubbing with a cloth. As a result, the orientation becomes non-uniform and the problem of display failure occurs. On the other hand, the UV alignment method and ion beam method, which are non-contact alignment methods, can avoid the occurrence of scratches and streak-like defects as in the rubbing method, but the alignment force is inferior, so that stable performance during mass production is obtained. Needs further improvement.

  An example of a conventional liquid crystal panel cell manufacturing process using such a rubbing method or a non-contact alignment method will be described below.

  1A to 1F are cross-sectional views illustrating steps of manufacturing a conventional liquid crystal panel cell. One substrate 1 (FIG. 1A) of a pair of glass substrates (TFT or color filter is provided) is prepared, washed, and then coated with polyimide (PI) (FIG. 1B). The alignment film 3 is formed by performing an alignment process by a rubbing method (FIG. 1C) by rubbing the applied PI film 2 with a cloth or the like or a non-contact alignment method (FIG. 1D) by UV irradiation or ion beam irradiation. Next, as shown in FIG. 1E, the spacer balls 4 are sprayed and an adhesive is applied around the substrate to form a sealant 5. Next, as shown in FIG. 1F, the glass substrate is superposed on the other alignment-treated glass substrate, and after being pressure-fixed by a jig, it is bonded by heating or UV irradiation. Thereafter, liquid crystal is injected to form a polarizing plate to complete a liquid crystal panel cell.

  In such a conventional liquid crystal panel cell, problems caused by the rubbing method and the non-contact alignment method have been pointed out.

  The prior art has proposed a technique for solving the above problems.

Japanese Patent Application Laid-Open No. 05-243934 discloses a liquid crystal display device in which liquid crystal is sandwiched between substrates having a pair of transparent electrodes, and a liquid crystal is formed on at least one of the liquid crystal alignment film interfaces formed on the mutually facing surfaces of the substrate. Proposing a technology that aims to achieve uniform alignment of liquid crystal molecules in the vicinity of the alignment film by forming a layer (adsorption layer) made of liquid crystal molecules that do not undergo phase transition in the thickness of 100 to 800 nm. is doing. In the invention in this patent document, the liquid crystal molecule adsorption layer is formed by blending an adsorbent into the alignment film itself and by introducing molecules having a large polarity such as oxygen and sulfur into the molecular skeleton of the alignment film. It is adsorbed on the alignment film. However, in the former method in which the adsorbent is blended with the alignment film itself, there is a problem that components contained in the adsorbent penetrate into the liquid crystal as impurities. It is necessary to add a process for introduction of molecules. This patent document also proposes a technique for forming an adsorption layer of liquid crystal molecules by forming a film made of an adsorbent on an alignment film, but also by this technique, the components of the adsorbent are contained as impurities in the liquid crystal. There was a problem of penetration.
Japanese Patent Laid-Open No. 05-243934

  The object of the present invention has been made in view of the above-described problems in the prior art, and by applying a thin coating of a crystalline epoxy resin on the surface of the alignment film, liquid crystal is utilized by utilizing the characteristics having both crystallinity and adhesiveness. A method of manufacturing a liquid crystal display element capable of solving the above problem by supplementing the orientation of the liquid crystal display device is provided.

As a reference example, in a liquid crystal display element in which liquid crystal is sandwiched between a pair of substrates,
The pair of substrates has an alignment film and an alignment auxiliary film formed on the alignment film, and the substrates are arranged via liquid crystal so that the alignment auxiliary films face each other,
The alignment auxiliary film is made of a resin material having a mesogenic structure in the molecular skeleton and a reactive group that reacts with heat or ultraviolet rays at both ends.
Provided is a liquid crystal display element characterized by the above.

The present invention is a method for manufacturing a liquid crystal display element in which a liquid crystal is sandwiched between a pair of substrates,
(I) a step of forming an alignment film on one of the pair of substrates;
(II) A solution obtained by diluting a crystalline epoxy resin having a mesogenic structure in the molecular skeleton and a reactive group that reacts with heat or ultraviolet rays at both ends with an organic solvent on the alignment film , wherein the crystalline epoxy resin is Applying a solution contained at a concentration of 0.01% to 0.1% in the solution ;
(III) a step of evaporating the organic solvent from the applied solution to form an alignment auxiliary film, and (IV) the other substrate on which the alignment film and the alignment auxiliary film are formed by the same process as above. Including a step of superposing and adhering both of the alignment assisting films so that the alignment assisting films face each other.

Examples to which the present invention is applied will be described below.
It should be noted that the present invention is not limited to the following examples, and it is obvious that various modifications and changes can be made within the scope defined by the claims.

  FIG. 2 is a cross-sectional view of a liquid crystal display element according to an embodiment of the present invention. In the present invention, as shown in FIG. 2, a crystalline epoxy is formed on an alignment film 3 formed on one glass substrate 1 of a pair of glass substrates (having TFTs or color filters) at least one of which is transparent. An alignment auxiliary film 6 made of resin is formed, spacer balls 4 are dispersed on the alignment auxiliary film 6, and an adhesive is applied to the periphery of the substrate to form a sealant 5. Next, in the same manner as described above, the other glass substrate on which the alignment auxiliary film 6 is formed is superposed and bonded, and the liquid crystal is sandwiched between the substrates.

  Hereafter, the manufacturing process of the liquid crystal display element of this invention is demonstrated.

  3A to 3G are cross-sectional views illustrating steps of manufacturing a liquid crystal panel cell according to an embodiment of the present invention. One substrate 1 (FIG. 3A) of a pair of glass substrates (TFT or color filter is provided) is prepared, washed, and then a polyimide (PI) film 2 which is a polymer material is formed on the substrate. Apply (Figure 3B). Next, after baking at 200 ° C. for 30 minutes, alignment is performed by a rubbing method (FIG. 3C) by rubbing the applied PI film 2 with a cloth or the like, or a non-contact alignment method by UV irradiation or ion beam irradiation (FIG. 3D). Processing is performed to form an alignment film 3 having a thickness of about 1000 mm. Note that the film thickness of the alignment film can be in the range of about 500 mm to about 1000 mm.

Next, as shown in FIG. 3E, a crystalline epoxy resin solution in which a crystalline epoxy resin is dissolved in an organic solvent in advance is applied on the alignment film after the alignment treatment. In this example, methyl ethyl ketone (hereinafter abbreviated as “MEK”) is used as an organic solvent, and a crystalline epoxy resin YX4000 (registered trademark) manufactured by Japan Epoxy Resin Co., Ltd. is dissolved therein to a concentration of 20%. After preparing a saturated solution, a crystalline epoxy resin solution diluted with ethyl alcohol (C ₂ H ₅ OH) was used.

  Next, the organic solvent is evaporated by being left in a heat chamber at 160 ° C. for 6 hours. Thereby, the crystalline epoxy resin is deposited, and the alignment auxiliary film 6 coated on the alignment film is formed.

  Note that the concentration of the crystalline epoxy resin in the organic solvent and the thickness of the alignment auxiliary film to be formed are important factors in terms of uniformity of alignment and an effect on rubbing scratches, which will be described later.

  Next, spacer balls 4 are dispersed by the same process as in the prior art, and an adhesive is applied around the substrate to form a sealant 5 (FIG. 3F). Next, as shown in FIG. 3G, by the same process as described above, the other glass substrate on which the alignment auxiliary film 6 is formed on the alignment film subjected to the alignment treatment is overlapped so that both alignment auxiliary films face each other. After pressing and fixing with a jig, it is bonded by heating or UV irradiation. Thereafter, liquid crystal is injected to form a polarizing plate to complete a liquid crystal panel cell.

In this example, a crystalline epoxy resin was used as the material for the alignment auxiliary film 6. As a result, the problem of uniform orientation of the liquid crystal was solved or improved. The general formula of the molecular structure of a crystalline epoxy resin that is a biphenyl type epoxy is shown below.

  In this example, YX4000 (registered trademark) manufactured by Japan Epoxy Resin Co., Ltd., which is a crystalline epoxy resin represented by the general formula of the above biphenyl type epoxy, was used, but various resins represented by the above general formula, For example, YX4000H, YL6121H (registered trademark) manufactured by the same company can be used in the present invention. In addition to crystalline epoxy resins, acrylate resins, allyl resins, and the like can also be used.

Examples of the liquid crystal that can be applied in the present invention include a fluorine-type TN liquid crystal, which is a mixture of a plurality of simple substances having the following structural formula. The structural formula of each single unit is shown below.

  The crystalline epoxy resin as described above is a material having a chemical structure having a glycidyl ether at both ends of a molecule while having a skeleton (mesogen) portion of a liquid crystal molecule, and has both properties of crystallinity and adhesiveness. In this embodiment, the crystalline epoxy resin deposited by the solvent evaporation process when forming the alignment auxiliary film 6 has a long and narrow molecular structure, so that it is aligned uniaxially on the alignment film at the time of deposition, and then bonded by heat. The epoxy group having a property undergoes a ring-opening reaction to improve the adhesion to the alignment film, and it is possible to fix the crystalline epoxy resin molecules by bonding with each other.

  The crystalline epoxy resin has an elongated molecular structure as described above, and is similar in shape and size to the liquid crystal constituent molecules described above. Therefore, by depositing these crystalline epoxy materials by evaporation, thinly coating the alignment film surface, and orienting the alignment film in a uniaxial direction, assisting the alignment of the alignment film with respect to the liquid crystal, while maintaining the alignment film surface. By having a fixed function, it can have a role of improving long-term reliability. Furthermore, when the coated crystalline epoxy resin is dissolved as an impurity in the liquid crystal, the crystalline epoxy resin and the liquid crystal are similar in shape and size as described above, so that the optical switch function of the liquid crystal is improved. There is no interference.

  As the liquid crystal, other liquid crystals can be used as long as they have a similar structure and size to the crystalline epoxy resin as described above.

In this embodiment, MEK was used as an organic solvent for dissolving the crystalline epoxy resin used in the present invention, except for a solvent that is so strong that it roughens the alignment film such as acetone (CH ₃ COCH ₃ ). Any material that dissolves the crystalline epoxy resin is applicable.

Table 1 shows data showing the relationship between the concentration of the crystalline epoxy resin in the organic solvent and the thickness of the alignment auxiliary film to be formed, and the effect on uniformity of alignment and rubbing scratches.

  Hereinafter, implementation conditions for obtaining the data will be described.

  A saturated solution of a crystalline epoxy resin (YX4000) with a concentration of 20% is prepared with an organic solvent (MEK). Thereafter, four types of crystalline epoxy resin solutions having concentrations of 1.0, 0.1, 0.01, and 0.001% were prepared by diluting with ethyl alcohol. This crystalline epoxy resin solution was applied on the alignment film on which the alignment treatment shown in FIG. 3E was performed. The liquid crystal panel cell was prepared according to the steps shown in FIGS. 3A to 3G as in the above example.

  In Table 1, the film thickness was calculated from the difference in film thickness between the sample coated with the crystalline epoxy resin solution and the sample not dropped. The rubbing scratches and orientation characteristics were visually observed with a polarizing microscope.

  When the concentration was 1.0%, rubbing scratches could not be confirmed because the alignment of the liquid crystal was disturbed. From the above results, it was confirmed that the rubbing scratches were reduced at a concentration of 0.01% to 0.1%, and problems such as poor alignment as a side effect were not confirmed. In the table, “◯” indicates the best result regarding the rubbing scratch and the orientation, and until “Δ”, the alignment can be sufficiently achieved. At a concentration of 0.001%, the alignment characteristics were good “◯”, but since the film thickness was too thin, many rubbing scratches “×” were observed.

  From the above results, the crystalline epoxy resin in the organic solvent applicable in the present invention has a concentration of more than 0.001% and a concentration of less than 1.0%, correspondingly a film thickness of more than 100%. And it turned out that an effect is acquired when it is a film thickness of 4000 mm or less. Preferably, it has been found that problems such as orientation defects and the like can be solved with a reduction in rubbing scratches at concentrations of 0.01% or more (film thickness of 300 mm or more) and 0.1% or less (film thickness of 4000 mm or less).

  The organic solvent was dried under vacuum using a reduced-pressure drying apparatus or the like, and then heated to form an alignment auxiliary film. A liquid crystal display element was produced according to the same process as in Example 1.

  As for the relationship between the concentration of the crystalline epoxy resin in the organic solvent and the film thickness of the alignment auxiliary film to be formed, and the effect on the uniformity of alignment and rubbing scratches, the same results as in Table 1 were obtained.

  In addition, by the said heating in this vacuum evaporation process, the effect similar to the case of the heat drying of Example 1, ie, the epoxy group which has the adhesiveness of crystalline epoxy resin by ring opening reaction by heating, and alignment assistance film | membrane It becomes possible to improve the adhesion with the alignment film and bond with the crystalline epoxy resin.

  4A to 4D are cross-sectional views illustrating steps of manufacturing a liquid crystal panel cell according to an embodiment of the present invention. In this embodiment, column spacers were used instead of the spacer balls used in Example 1. Hereinafter, the process will be described.

  A photosensitive resin is applied by spin coating on one substrate 1 (FIG. 4A) of a pair of glass substrates (TFTs or color filters are provided), and the solvent of the photosensitive resin is evaporated by prebaking. Next, ultraviolet rays are irradiated from above through a mask. The mask applied here has a pattern pattern of the column spacer 4. The photosensitive resin corresponding to the portion without the mask pattern is softened after irradiation with ultraviolet rays. Subsequently, the softened photosensitive resin is removed by processing with a developing solution. Finally, the remaining photosensitive resin is post-baked. Through the above steps, the column spacer 4 having a height of 3.5 μm was produced. In this embodiment, the height of the column spacer is 3.5 μm, but it can be set in the range of 2 to 10 μm depending on the application of the liquid crystal display device to be manufactured.

  Next, as shown in FIG. 4C, the alignment film 3 and the alignment auxiliary film 6 are formed on the substrate 1 and the column spacer 4 so as to cover the substrate 1 and the column spacer 4 by the same method as in the first embodiment.

  Next, as shown in FIG. 4D, an adhesive is applied on the alignment auxiliary film 6 around the substrate to form the sealant 5, and then the alignment film 3 and alignment film produced by the same method as in Example 1 are used. The other substrate having the auxiliary film 6 is overlapped so that the alignment auxiliary film faces, and after being pressure-fixed by a jig, it is bonded by heating or UV irradiation. Thereafter, liquid crystal is injected to form a polarizing plate to complete a liquid crystal panel cell.

  Also in the liquid crystal display device manufactured as described above, the same effects as those shown in Table 1 were obtained.

It is sectional drawing for demonstrating the manufacturing process of the conventional liquid crystal panel cell. It is sectional drawing for demonstrating the manufacturing process of the conventional liquid crystal panel cell. It is sectional drawing for demonstrating the manufacturing process of the conventional liquid crystal panel cell. It is sectional drawing for demonstrating the manufacturing process of the conventional liquid crystal panel cell. It is sectional drawing for demonstrating the manufacturing process of the conventional liquid crystal panel cell. It is sectional drawing for demonstrating the manufacturing process of the conventional liquid crystal panel cell. It is sectional drawing of the completed liquid crystal panel cell in one embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the liquid crystal panel cell of one embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the liquid crystal panel cell of one embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the liquid crystal panel cell of one embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the liquid crystal panel cell of one embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the liquid crystal panel cell of one embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the liquid crystal panel cell of one embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the liquid crystal panel cell of one embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the liquid crystal panel cell of one embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the liquid crystal panel cell of one embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the liquid crystal panel cell of one embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the liquid crystal panel cell of one embodiment of this invention.

Explanation of symbols

1 Glass substrate 2 PI film 3 Alignment film 4 Spacer ball 5 Wall 6 Alignment auxiliary film 7 Liquid crystal

Claims (6)

A method for manufacturing a liquid crystal display element in which a liquid crystal is sandwiched between a pair of substrates,
(I) a step of forming an alignment film on one of the pair of substrates;
(II) A solution obtained by diluting a crystalline epoxy resin having a mesogenic structure in the molecular skeleton and a reactive group that reacts with heat or ultraviolet rays at both ends with an organic solvent on the alignment film, wherein the crystalline epoxy resin is Applying a solution contained at a concentration of 0.01% to 0.1% in the solution ;
(III) a step of evaporating the organic solvent from the applied solution to form an alignment auxiliary film, and (IV) the other substrate on which the alignment film and the alignment auxiliary film are formed by the same process as above. Including a step of superimposing and adhering both of the alignment assisting films so that the alignment assisting films face each other.   The method for manufacturing a liquid crystal display element according to claim 1, wherein after step (III) of claim 1, ball spacers are dispersed on the alignment auxiliary film.   The method for manufacturing a liquid crystal display element according to claim 1, wherein an alignment film is formed on the one substrate via a column spacer in step (I) of claim 1.   The method for manufacturing a liquid crystal display element according to claim 1, wherein the crystalline epoxy resin is a biphenyl type epoxy.   The method of manufacturing a liquid crystal display element according to claim 1, wherein the step of evaporating the organic solvent is performed by heating or reduced pressure.   2. The liquid crystal display device according to claim 1, wherein after the step (I) of claim 1, the alignment film is aligned by using one of rubbing, UV irradiation, and ion beam. Method.

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