JP2006010995A - Method for forming alignment film, and liquid crystal display device using alignment film, and method for manufacturing display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems associated with a display malfunction due to uneven film thickness, a high cost of a manufacturing device and so on with respect to an inkject printing method which uses a smaller amount of an alignment layer varnish than those of a relief printing method, a spin coat method and so on, though it is a method for forming an alignment layer hopeful in future. <P>SOLUTION: In the method for forming the alignment layer, the alignment layer varnish is applied to a substrate by using one inkjet head, wherein surface tension of the alignment layer varnish is 32 dyne/cm or less and further the varnish contains a solvent of which the boiling point is 175°C or more. Thereby the method for forming the alignment layer without any residual mark of linking between alignment layer varnish application is provided and the cost of the manufacturing device is reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an alignment film forming method for applying an alignment film varnish on a substrate, a liquid crystal display device using the alignment film varnish, and a method for manufacturing the same.

In the manufacturing method of a liquid crystal display device, several methods shown below are known as a method and apparatus for applying or printing an alignment film varnish on the entire surface of a limited region on a glass substrate.
(1) As shown in FIG. 1, an alignment film varnish is formed on a glass substrate 6 from a resin relief plate 5 which is composed of a doctor roll 1, an anix roll 3, a liquid discharge port 2, and a plate cylinder 4 and fixed to the plate cylinder. It is a letterpress printing method to apply.
(2) A spin coat coating method in which an alignment film varnish is dropped from a liquid discharge port onto a central portion of a glass substrate horizontally fixed on a turntable, and then the substrate is rotated to apply the alignment film varnish (Patent Document) 1).
(3) A spray coating method in which an alignment film varnish is sprayed from a liquid discharge port onto a glass substrate that is horizontally fixed on a transport table, and the alignment film varnish is applied to the glass substrate (Patent Document 2).
(4) An inkjet printing method in which an alignment film varnish is applied to a conveyed glass substrate using an inkjet head (Patent Document 3).

JP-A-6-21468 JP 2001-174819 A JP-A-9-105937

  The alignment film forming method by letterpress printing is the most commonly used coating method because of its high productivity, but it has many problems. First, the amount of alignment film varnish used is large. This is because the alignment film varnish is applied to an anix roll and a doctor roll in addition to the letterpress. Second, the yield is a problem that is peculiar to liquid crystal display devices. Since this is mainly contact coating with a relief printing plate, it is caused by contamination from the relief printing plate. The third point is that it takes too much time to handle various products. This is because when the size of the alignment film forming region on the substrate is changed, it is necessary to change the relief plate itself.

  Since the alignment film forming method by spin coating is non-contact application, it is an alignment film forming method that can avoid contamination and the like in letterpress printing. However, this is a method of forming an alignment film that has a problem that productivity is low with a large glass substrate and is not suitable for mass production. Further, a mask is required to apply to the alignment film forming region on the substrate, and therefore an unnecessary alignment film varnish must be used. Moreover, when a mask is not used, there exists a fault that an alignment film varnish will wrap around to the back side of a glass substrate.

  Since the alignment film forming method by spray coating is non-contact coating like spin coating, it is a coating method that can avoid contamination and the like in letterpress printing. However, in this case as well, a mask is required to apply to a limited alignment film forming region on the substrate, and therefore an unnecessary alignment film varnish must be used.

  The alignment film forming method by ink jet printing is a non-contact coating method similar to spray coating and spin coating coating, and is therefore a coating method that can avoid contamination and the like in letterpress printing. Further, only the necessary amount of the alignment film varnish is used, and the cost can be reduced as compared with letterpress printing. Furthermore, when the size of the alignment film forming region on the substrate is changed, it is only necessary to change the ejection pattern of the alignment film varnish, and it is possible to cope with various types in a shorter time than letterpress printing.

  As described above, the alignment film forming method by ink jet printing has many advantages, but it must be said that it has a very serious problem from the viewpoint of forming an alignment film for a large-sized substrate to be mass-produced. . In general, it is ideal to assemble two or more inkjet heads having a width smaller than the length of the short side of the large substrate and attach them to the coating device, and apply the alignment film varnish in one scan along the long side of the substrate. It is. However, many problems arise due to the huge number of heads. One is that the cost of the manufacturing apparatus increases. Another is that the control system of the ink jet head is complicated, and the flying variation between the ink jet heads is also increased. In addition to these, maintenance of the ink jet head becomes enormous, and if a problem occurs in one ink jet head, the entire apparatus becomes inoperable, and replacement work at the time of the trouble becomes large. Thus, the problem of reliability is highlighted from the viewpoint of forming an alignment film on a large substrate.

  In order to solve the above-mentioned problems, as a result of intensive studies on the volatile characteristics and wettability of the alignment varnish as a solution, it is possible to produce large substrates while maintaining the advantages such as contamination contamination avoidance by inkjet printing, cost reduction, and multi-product compatibility. The inventors have found a method for forming an alignment film that can be used, and have reached the present invention.

  The present invention is a method of forming an alignment film by applying an alignment film varnish on a substrate using a single inkjet head, wherein the alignment film varnish is one of solvents and has a surface tension of 32 dyne / cm or less, and , A method including a solvent having a boiling point of 175 ° C. or higher. By using such an alignment film forming method, not only the manufacturing apparatus cost can be reduced, but also the running cost can be reduced. Further, since only one inkjet head is used, there is no flying variation between the inkjet heads. In addition, replacement work in the event of a failure is also facilitated. In the present invention, the same alignment film varnish is used, and a method of forming an alignment film by applying an alignment film varnish on a substrate by scanning a single ink jet head twice or more, or scanning a substrate twice or more. Then, an alignment film varnish is applied to a substrate from one inkjet head to form an alignment film.

  The present invention also relates to a method for manufacturing a display device characterized in that an alignment film is formed by the above method, and a display device comprising the alignment film formed by the above method.

  The present invention also relates to a display device having an alignment film containing a solvent having a surface tension of 32 dyne / cm or less and a boiling point of 175 ° C. or higher. This not only provides products with excellent film display characteristics that are often observed when applying alignment film formation methods by conventional inkjet printing, but also improves cost performance by improving productivity and reducing equipment costs. Product can be provided.

  According to the present invention, there is provided a method for forming an alignment film by applying an alignment film varnish on a substrate using a single inkjet head, wherein the alignment film varnish has a surface tension of 32 dyne / cm or less and a boiling point. By including a solvent at 175 ° C. or higher, it is possible to provide a method for forming an alignment film without a joint mark between alignment film varnishes, and to reduce the manufacturing apparatus cost.

Example 1
Embodiments of an alignment film forming method and a liquid crystal display manufacturing method using the same according to the present invention will be described in detail with reference to the drawings.

  The alignment film varnish used for forming the alignment film is a polymer solution containing polyamic acid as a solute and an organic solvent as a solvent. Here, the polyamic acid which is the main material and the organic solvent will be described, but it is not particularly limited even if a soluble polyimide is included as a part of the solute.

The solute of the alignment film varnish used in this example is a polyamic acid starting from p-phenylenediamine as a diamine derivative and pyromellitic dianhydride as a carboxylic acid derivative. The same effect can be obtained by combining diamine derivatives and carboxylic acid derivatives as starting materials for polyamic acid in combinations other than this example. For example, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane as diamine derivatives 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 4,4'-diaminoterphenyl 1,1-metaxylylenediamine, 1,4-diaminocyclohexane, isophthalic acid dihydrazide, sebacic acid dihydrazide, succinic acid dihydrazide, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-dibutyl -4,4'-di Minodiphenylmethane, 3,3'-dibutoxy-4,4'-diaminodiphenylmethane, 2,4-diamino-1-octylbenzene, 2,4-diamino-1-octyloxybenzene, 2,4-diamino-1-methoxy Methylenebenzene, 2,4-diamino-1-butoxymethylenebenzene, 3,3'-dimethyl-4,4'-diaminodiphenyl ether, 1,6-diaminohexane, 1,8-diaminooctane, 1,10-diaminodecane 1,12-diaminododecane, 2,2-bis [4- (p-aminophenoxy) phenyl] propane, 2,2-bis [4- (p-aminophenoxy) phenyl] butane, 2,2-bis [ 4-
(P-aminophenoxy) phenyl] pentane, 2,2-bis [4- (p-aminophenoxy) phenyl] hexane, 2,2-bis [4- (p-aminophenoxy) phenyl] octane, 2,2- Bis [4- (p-aminophenoxy) phenyl] decane, 2,2-bis [4- (p-aminophenoxy) phenyl] tridecane, 2,2-bis [4- (p-aminophenoxy) phenyl] pentadecane, 2,2-bis [4- (p-aminophenoxy) phenyl] methane, 2,2-bis [4- (p-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (p-aminophenoxy) Phenyl] ketone, 2,2-bis [4-
(P-aminophenoxy) phenyl] biphenyl, 2,2-bis [4- (p-aminophenoxy) phenyl] cyclohexane, 2,2-bis [4- (p-aminophenoxy) phenyl] methylcyclohexane, 2,2 -Bis [4- (p-aminophenoxy) phenyl] propylcyclohexane, bis [4- (p-aminobenzoyloxy) benzoic acid] propane, bis [4- (m-aminobenzoyloxy) benzoic acid] propane, bis [ 4- (p-aminobenzoyloxy) benzoic acid] pentane, bis [4- (p-aminobenzoyloxy) benzoic acid] octane, bis [4- (p-aminobenzoyloxy) benzoic acid] ethane, bis [4- (P-aminobenzoyloxy) benzoic acid] decane, bis [4- (p-aminobenzoyloxy) benzoic acid ] Cyclohexane, bis [4- (p-aminobenzoyloxy) benzoic acid] methylcyclohexane, bis [4- (p-aminobenzoyloxy) benzoic acid] methane, bis [4- (p-aminobenzoyloxy) benzoic acid] Butane, bis [4- (m-aminobenzoyloxy) benzoic acid] butane, bis [4- (p-aminomethylbenzoyloxy) benzoic acid] propane, bis [4- (p-aminoethylbenzoyloxy) benzoic acid] Propane, bis [4- (p-aminobenzoyloxy) benzoic acid] octadecane, bis [4- (p-aminobenzoyloxy) benzoic acid] heptane, bis (p-aminobenzoyloxy) propane, bis (p-aminobenzoyl) Oxy) methane, bis (p-aminobenzoyloxy) ethane, bis (p-amino) Nzoyloxy) butane, bis (p-aminobenzoyloxy) pentane, bis (p-aminobenzoyloxy) hexane, bis (p-aminobenzoyloxy) heptane, bis (p-aminobenzoyloxy) octane, bis (p-amibenzoyl) Oxy) nonane, bis (p-aminobenzoyloxy) decane, bis (p-aminobenzoyloxy) dodecane, bis (p-aminobenzoyloxy) dodecane, bis (p-aminobenzoyloxy) tetradecane, bis (p-aminobenzoyl) Oxy) octadecane, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis [4- (3-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis [ 4- (2-Aminophenoxy) -3,5 Dimethylphenyl] hexafluoropropane, p-bis (4-amino-2-trifluoromethylphenoxy) benzene, 4,4'-bis (4-amino-2-trifluoromethylphenoxy) biphenyl, 4,4'-bis (4-amino-2-trifluoromethylphenoxy) diphenylsulfone, diaminosiloxane and the like can be mentioned.

Methyl pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride as carboxylic acid derivatives, 3, 3 ', 4,4'-diphenylmethane tetracarboxylic dianhydride, 3,3', 4,4'-diphenyl ether tetracarboxylic dianhydride, 3,3 ', 4,4'-diphenylsulfone tetracarboxylic dianhydride Anhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ', 4,4'-diphenylpropanetetracarboxylic dianhydride, 2,2-bis [4- (3,4 -Dicarboxyphenoxy) phenyl] propanetetracarboxylic dianhydride, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexafluoropropanetetracarbo Acid dianhydride, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] octyltetracarboxylic dianhydride, 2,2-bis [4- (3,4-dicarboxybenzoyloxy) Phenyl] propanetetracarboxylic dianhydride, 2,2-bis [4- (3,4-dicarboxybenzoyloxy) phenyl] tridecanetetracarboxylic dianhydride, 2,2-bis [4- (3 4-dicarboxyphenoxy) phenyl] tridecanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, butanetetracarboxylic dianhydride, 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid chloride, 4,
4'-diphenyl ether dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid chloride, 4,4'-diphenylmethane dicarboxylic acid, 4,4'-diphenylmethane dicarboxylic acid chloride, isophthalic acid, isophthalic acid chloride, adipic acid, adipic acid chloride, Examples include stearic acid and stearic acid chloride.

  The solvent of the alignment film varnish used in this example is a mixed organic solvent composed of 10 wt% octanol (2-ethylhexanol) and 90 wt% N-methyl-2-pyrrolidone. In this embodiment, the solvent for the alignment film varnish is selected from a solvent having a high solubility in polyamic acid and a solvent having a low surface tension and a high boiling point. The reason why the solvent having a small surface tension is mixed is to improve the wettability with respect to the substrate, and the reason why the solvent having a high boiling point is used is to maintain the wettability. In this example, N-methyl-2-pyrrolidone is selected as a solvent having high solubility in polyamic acid, and octanol is selected as a solvent having a low surface tension and a high boiling point. The surface tension of octanol is 30 dyne / cm and its boiling point is 184 ° C. In addition to N-methyl-2-pyrrolidone as a solvent with high solubility in polyamic acid, dimethylformamide, dimethylacetamide, dimethylsulfoxide, sulfolane, butyllactone, cresol, phenol, cyclohexanone, dioxane, tetrahydrofuran, butylcellosolve, butyl Cellsolve acetate, acetophenone, etc. can be used. In addition to octanol, decanol, nonanol, tridecanol, diethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monooctyl ether, dipropylene glycol are the solvents having a surface tension of 32 dyne / cm or less and a boiling point of 175 ° C. or higher. Monomethyl ether or the like can be used.

(Example 2)
Next, alignment film formation by the ink jet printing method will be described. As shown in FIG. 2, the alignment film coating apparatus has a liquid discharge head 7 having a plurality of discharge ports through which the alignment film varnish flies, and a discharge drive control apparatus 9 that controls a discharge drive element that drives alignment film varnish flight from the discharge nozzle. , A liquid storage container 10 for storing the alignment film varnish, a supply pipe 8 for connecting the liquid storage container 10 and the liquid discharge head 7, and means for transporting the glass substrate 6 (not shown). Yes. Next, a coating method using this alignment film varnish coating apparatus will be described. The alignment film varnish is extruded from the liquid storage container 10, passes through the supply pipe 8, and is sent to the liquid discharge head 7. The alignment film varnish flies from the liquid discharge head 7 by controlling the discharge drive element by the discharge drive control device 9 and is applied to the alignment film forming region on the glass substrate 6 which is transferred by the transfer table. A process of applying the alignment film varnish on the substrate by this ink jet printing method will be described. Here, the application to the glass substrate on the color filter side will be described, but there is no particular change in the application to the glass substrate on the TFT (thin film transistor) side. The size of the glass substrate 6 shown in FIG. 2 is 280 mm (long side) × 200 mm (short side), and the thickness is 1 mm. The coating surface is an ITO transparent electrode, and it is important to remove surface contamination by ultraviolet irradiation before coating. In this example, a cleaning apparatus provided with an excimer lamp was used. In addition, a cleaning apparatus provided with a low-pressure mercury lamp as an ultraviolet irradiation light source can be used. The conveyance speed of the conveyance table is 250 mm / second. The gap between the liquid discharge head 7 and the glass substrate 6 is designed to be 1 mm. The discharge cycle of the alignment film varnish from the liquid discharge head 7 by the discharge drive control device 9 is 500 Hz. The alignment film varnish used here has a surface tension of 36 dyne / cm and a viscosity of 20 centipoise, but these values are not particularly limited because they depend on the driving voltage. FIG. 4 shows a method of applying the alignment film varnish to the alignment film formation region of the substrate using one liquid discharge head. FIG. 4 (a) is before coating, FIG. 4 (b) is during coating, and FIG. 4 (c) is after coating. Arrows indicate the direction of movement of the coated surface. In FIG. 4, since the glass substrate is scanned and folded, a joint is formed between the alignment film varnishes. However, by using octanol which is a solvent having a low surface tension and a high boiling point, the flying alignment film varnishes are connected to each other, and a joint cannot be observed after drying. Although the glass substrate is scanned and folded here, the liquid discharge head 7 may be scanned and folded. Also, a combination thereof may be used.

  In this embodiment, the color filter side glass substrate whose surface is the ITO transparent electrode 18 as shown in FIG. 5 has been described. However, the color filter side glass substrate whose surface is an organic protective film and the surface is an organic interlayer insulating film Alternatively, the alignment film may be printed on the TFT substrate side glass substrate of the inorganic interlayer insulating film by the method of this embodiment.

  In this example, it was stated that the seam could not be observed after drying, but since the application was performed in a container maintained at 60% humidity and 25 ° C., no cloudiness due to volatilization was observed. . Further, when the coated area was observed after drying, no pinholes were observed. The film thickness of the obtained alignment film was 91 nm, and the film thickness errors at the upper and lower end portions and the left and right end portions were all within 5%.

(Comparative Example 1)
An alignment film was prepared in the same manner as in Example except that a mixed organic solvent composed of 10 wt% ethylene glycol monobutyl ether and 90 wt% N-methyl-2-pyrrolidone was used as a solvent for the alignment film varnish. Although the surface tension of ethylene glycol monobutyl ether is as small as 27 dyne / cm, it is different from octanol in that it is a solvent having a boiling point as low as 171 degrees. When the joints were observed after coating and drying, the joints could be clearly confirmed. Similarly, when a butanol, pentanol, hexanol, propylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether having a boiling point of less than 175 ° C. is used as a solvent other than ethylene glycol monobutyl ether, it is clearly connected. Was observed. This is presumably because the area where the ink was first applied was dry when the ink-jet head turned back because the boiling point of the solvent was low.

  Although it was also considered to suppress the volatilization of the solvent by lowering the substrate to room temperature or less when applying the alignment film, there are also drawbacks in that it is difficult to adjust the temperature uniformly within the substrate surface and the cost of the apparatus is increased. In addition, although the coating was carried out in a container maintained at a humidity of 60% and a temperature of 25 ° C., a white turbid region was observed on the alignment film surface because the substrate was brought to room temperature or lower. This is presumably because the substrate was condensed due to the temperature being lower than room temperature.

(Comparative Example 2)
As a solvent for the alignment film varnish, a mixed organic solvent composed of 10 wt% ethylene glycol monobutyl ether and 90 wt% N-methyl-2-pyrrolidone was used as in Comparative Example 1.

  In this comparative example, two or more inkjet heads having a width smaller than the length of the short side of the large substrate are assembled and attached to the coating apparatus, and the alignment film varnish is applied in one scan along the long side of the substrate. It was. FIG. 3 shows a method of applying the alignment film varnish to the alignment film formation region of the substrate using four liquid discharge heads 7. 3A is before coating, FIG. 3B is during coating, and FIG. 3C is after coating. The arrow indicates the scanning direction of the head. Since the coating is performed after modifying the substrate surface so that the alignment film varnish wets and spreads on the substrate as a conventional means, it is applied while forming the wet spreading region 11. Therefore, the joint between the alignment film varnishes does not occur due to the liquid discharge head 7 being folded back as shown in FIG.

  However, since two or more ink jet heads are assembled as in this comparative example, there is a drawback that the apparatus cost increases. In addition, there is a disadvantage that the entire apparatus does not function if one ink jet head is defective. In particular, in order to replace a defective inkjet head, it is necessary to remove and repair the entire inkjet head and drive device constructed by assembling two or more from the manufacturing apparatus, and the setup time must be greatly increased. It became clear.

It is the schematic for demonstrating alignment film varnish application | coating by a relief printing method. It is the schematic for demonstrating alignment film varnish application | coating by the alignment film formation method which concerns on this invention. It is the schematic for demonstrating alignment film formation by the conventional inkjet printing system. It is the schematic for demonstrating the wetting spread of the alignment film varnish in the alignment film formation method which concerns on this invention. It is the schematic for demonstrating the liquid crystal display device using alignment film formation which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Doctor roll, 2 ... Liquid discharge port, 3 ... Anix roll, 4 ... Plate cylinder, 5 ... Letterpress, 6 ... Glass substrate, 7 ... Liquid discharge head, 8 ... Liquid supply pipe, 9 ... Discharge drive control apparatus, 10 DESCRIPTION OF SYMBOLS ... Liquid storage container, 11 ... Wet spreading area, 12 ... Uncoated area, 13, 19 ... Orientation film, 14 ... Contact hole, 15 ... TFT drain electrode, 16 ... Inorganic protective film, 17 ... Organic protective film, 18 ... ITO transparent electrode, 20 ... overcoat film, 21 ... color filter film.

Claims (6)

  A method of forming an alignment film by applying an alignment film varnish on a substrate using a single inkjet head, wherein the alignment film varnish is one of solvents and has a surface tension of 32 dyne / cm or less and a boiling point of 175. An alignment film forming method comprising a solvent at a temperature of 0 ° C. or higher. In this method, a single inkjet head is turned back and forth twice to apply an alignment film varnish on the substrate to form an alignment film. The alignment film varnish is one of the solvents and the surface tension is 32.
An alignment film forming method comprising a solvent having a dyne / cm or less and a boiling point of 175 ° C. or more.   A method of forming an alignment film by applying an alignment film varnish onto a substrate from a single inkjet head by folding the substrate twice or more, wherein the alignment film varnish is one of solvents and has a surface tension of 32 dyne / cm or less. An alignment film forming method comprising a solvent having a boiling point of 175 ° C. or higher.   A method for manufacturing a display device, comprising forming an alignment film by the alignment film forming method according to claim 1.   A display device comprising an alignment film formed by the alignment film forming method according to claim 1. A display device having an alignment film,
The display device, wherein the alignment film contains a solvent having a surface tension of 32 dyne / cm or less and a boiling point of 175 ° C. or more.

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