JP2010286640A - Visible light-curable liquid crystal sealing agent and liquid crystal display cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal sealing agent having excellent display quality and reliability, which is composed of a sealing agent sufficiently photo-cured by visible light of 400 nm or longer, and to provide a liquid crystal display cell using the liquid crystal sealing agent. <P>SOLUTION: The visible light-curable liquid crystal sealing agent includes: (a) a photo-initiator having a carbazole skeleton; (b) a hydrogen abstraction type photosensitizer; and (c) a (meth)acrylated epoxy resin that serves as a curable resin. The visible light-curable liquid crystal sealing agent may additionally contains (d) an epoxy resin and (e) a thermosetting agent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid crystal sealant having sufficient photocurability with visible light of 400 nm or more and excellent in low liquid crystal contamination, and a liquid crystal display cell using the same.

  In recent years, liquid crystal display cells have been applied to large-sized display screens such as televisions, and demand for them is increasing. For this reason, a liquid crystal dropping method has become the mainstream in place of the liquid crystal injection method in order to further increase the mass productivity of the liquid crystal panel manufacturing (Patent Document 1).

  In the liquid crystal dropping method, first, a seal pattern made of a rectangular uncured sealant is formed on one of two transparent substrates with electrodes by dispensing. Next, with the sealant in an uncured state, liquid crystal microdrops are dropped onto the entire surface of the transparent substrate seal pattern, and the other transparent substrate is immediately bonded to produce a liquid crystal cell. Temporary curing is performed by irradiating with ultraviolet rays. Thereafter, heating is performed as necessary to perform main curing, and a liquid crystal display cell is manufactured.

  In this liquid crystal dropping method, since the uncured sealing agent and the liquid crystal are in direct contact with each other, when the curing of the sealing agent is slow, the sealing agent component is eluted in the liquid crystal and contaminates the liquid crystal. Therefore, fast sealing with ultraviolet rays is an essential process.

  However, in the production of a liquid crystal display element by the liquid crystal dropping method, the liquid crystal is irradiated with a considerable amount of ultraviolet rays irradiated to cure the sealant. Accordingly, there has been a problem that the liquid crystal is deteriorated by ultraviolet rays having a short wavelength and high energy, the display quality of the liquid crystal display element is remarkably lowered, and the reliability is lowered.

  On the other hand, various investigations have been made and proposals have been made on a sealant that is highly sensitive to ultraviolet rays (Patent Documents 2 and 3). However, even in these inventions, the energy of the irradiated ultraviolet rays is high, and it is not sufficient as a countermeasure against deterioration of the liquid crystal.

  In view of the above-mentioned present situation, the present invention makes it possible to use visible light having a low energy of 400 nm or more, instead of using ultraviolet light having a short wavelength, in the production of a liquid crystal display element by a liquid crystal dropping method. An object of the present invention is to provide a liquid crystal sealing agent that has sufficient photocurability with visible light of 400 nm or more and that is excellent in low liquid crystal contamination.

JP 2001-133794 A JP 2007-3911 A JP 2008-179797 A

  The present invention relates to a liquid crystal sealant and a liquid crystal display cell using the same, and more specifically, a liquid crystal sealant having sufficient photocurability by visible light of 400 nm or more and excellent in low liquid crystal contamination, and the same It aims at proposing the used liquid crystal display cell.

  As a result of intensive studies, the present inventors have found that the photoinitiator having a carbazole skeleton has a low liquid crystal contamination property, and further uses a hydrogen abstraction type photosensitizer in combination to improve curability and provide a visible wavelength of 400 nm or more. The present invention was completed by finding that it has sufficient photocurability by light.

That is, the present invention relates to the following (1) to (6).
(1) A visible light curing comprising (a) a photoinitiator having a carbazole skeleton, (b) a hydrogen abstraction type photosensitizer and (c) a (meth) acrylated epoxy resin as a curable resin Liquid crystal sealant.
(2) The liquid crystal sealant according to (1), wherein (a) the photoinitiator having a carbazole skeleton is an initiator having an oxime ester skeleton in its molecule.
(3) The liquid crystal sealing agent according to (1) or (2), wherein (c) (meth) acrylated epoxy resin is a (meth) acrylated epoxy resin of resorcin diglycidyl ether.
(4) The liquid crystal sealing agent according to any one of (1) to (3), further comprising (d) an epoxy resin and (e) a thermosetting agent.
(5) The liquid crystal sealant according to any one of (1) to (4), which has sufficient photocurability with visible light of 400 nm or more.
(6) A liquid crystal display cell sealed with a cured product obtained by curing the liquid crystal sealing agent according to any one of (1) to (5).

  The present invention makes it possible to use visible light having a low energy of 400 nm or more in the production of a liquid crystal display device by a liquid crystal dropping method, to reduce the contamination and deterioration of the liquid crystal, and to produce a highly reliable liquid crystal display device. can do.

Hereinafter, the present invention will be described in detail.
The liquid crystal sealing material used in the present invention contains (a) a photoinitiator having a carbazole skeleton (the following general formula (1)). An initiator having this skeleton can generate radicals by light absorption, and can also generate radicals efficiently by energy from other photosensitizers. Moreover, since it has a nitrogen atom in the molecule, it has an effect on oxygen inhibition, which is generally a problem in radical curing, and curing can proceed efficiently. Furthermore, an initiator having a carbazole skeleton has low liquid crystal contamination, and dissolution of the initiator itself in the liquid crystal can be suppressed to a low level.

（式中、Ｒは炭素原子数１〜２０のアルキル基、水素原子、水酸基、炭素原子数１〜２０のアルコキシル基、（メタ）アクリル基、又はフェニル基を表す。）

(In the formula, R represents an alkyl group having 1 to 20 carbon atoms, a hydrogen atom, a hydroxyl group, an alkoxyl group having 1 to 20 carbon atoms, a (meth) acryl group, or a phenyl group.)

In the formula (1), the alkyl group having 1 to 20 carbon atoms as R may be linear or branched, for example, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl. Group, t-butyl group and the like. The alkoxyl group having 1 to 20 carbon atoms may be linear or branched. For example, methoxy group, ethoxy group, n-propoxy group, i-propoxy group, n-butoxy group, t-butoxy group, etc. Indicates.
Specifically, as this (a) initiator, N-1414 (carbazole skeleton-containing photoinitiator; 3,6-bis (2-methyl-2-morpholinopropionyl) -9-n-octylcarbazole; Asahi Denka Kogyo Co., Ltd. Manufactured by Co., Ltd.), N-1919 (carbazole oxime ester skeleton-containing photoinitiator; Adeka (registered trademark) Optomer N-1919; manufactured by Asahi Denka Kogyo Co., Ltd.) Irgacure OXE02 (carbazole oxime ester skeleton-containing Photoinitiator (ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (O-acetyloxime); Ciba Specialty Chemicals Co., Ltd. Manufactured) and the like.

From the viewpoint of reactivity, the component (a) preferably has an oxime ester skeleton in the molecule. Since the oxime ester skeleton is highly sensitive to light and supplements the photoreaction of the sealant, the amount added can be reduced. Specifically, N-1919 and Irgacure OXE02 described above are preferable.
Further, (a) the content of the photoinitiator in the liquid crystal sealant is preferably within the range of 0.01 to 3% by mass, more preferably about 0.1 to 0.5% by mass. is there. If the amount is less than 0.01% by mass, sufficient curing performance cannot be obtained and the liquid crystal is contaminated. If the amount is more than 3% by mass, the liquid crystal contamination of the initiator itself becomes a problem.

The liquid crystal sealant used in the present invention contains (b) a hydrogen abstraction type photosensitizer as an essential component. The above-described (a) carbazole skeleton photoinitiator alone does not enable a liquid crystal sealant that absorbs visible light of 400 nm or more. That is, in the present invention, (a) a carbazole skeleton photoinitiator and (b) a hydrogen abstraction type photosensitizer are used together for the first time in visible light of 400 nm or more, usually in the range of 400 to 600 nm. An absorbing liquid crystal sealant is possible. Therefore, the component (b) is essential for realizing sufficient visible light curability. This hydrogen abstraction type photosensitizer does not have sufficient visible light curability when used alone. Therefore, the present invention is realized only by the combined use of the component (a) and the component (b).
Specific examples of the component (b) include benzophenone, acridone, 2-ethylanthraquinone, 2-chlorothioxanthone, 2-isopropylanthraquinone, 2,4-diethylthioxanthone, and 2,4-diethylthioxanthone is particularly preferable. is there.
The content of the photosensitizer in the liquid crystal sealant is preferably in the range of 0.01 to 3% by mass, more preferably about 0.1 to 0.5% by mass. is there.

The present invention contains a (meth) acrylated epoxy resin as the curable resin component (c). (Here, “(meth) acryl” means “acryl” and / or “methacryl”. The same shall apply hereinafter.)
The (meth) acryloylated epoxy resin is obtained by a known method by a reaction between the epoxy resin and (meth) acrylic acid. Although it does not specifically limit as an epoxy resin used as a raw material, An epoxy resin more than bifunctional is preferable, for example, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a bisphenol S type epoxy resin, a phenol novolac type epoxy resin , Cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, bisphenol F novolac type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin , Isocyanurate type epoxy resins, phenol novolac type epoxy resins having a triphenolmethane skeleton, and other difunctional phenolic diglycidyl esters such as catechol and resorcinol Ether compound, bi-functional alcohol diglycidyl ethers of, and their halides, and the like hydrogenated product. Among these, from the viewpoint of liquid crystal contamination, more preferred is resorcin diglycidyl ether. Further, the ratio of the epoxy group to the (meth) acryloyl group is not limited, and is appropriately selected from the viewpoint of process compatibility and liquid crystal contamination.
Moreover, it is preferable that it is in the range of 30-80 mass% as a content rate which occupies in the liquid-crystal sealing compound of (c) (meth) acrylated epoxy resin, More preferably, it is about 40-70 mass%.

In the liquid crystal sealant of the present invention, (d) an epoxy resin can be used to improve the adhesive strength. The epoxy resin (d) that can be used is not particularly limited, but is preferably a bifunctional or higher epoxy resin, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac. Type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolak type epoxy resin, bisphenol F novolak type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, hydantoin Type epoxy resin, isocyanurate type epoxy resin, phenol novolac type epoxy resin having triphenolmethane skeleton, other diglycidyl ethers of bifunctional phenols, bifunctional al Diglycidyl ethers of Lumpur acids, and their halides, and the like hydrogenated product. Among these, bisphenol type epoxy resin and novolac type epoxy resin are preferable from the viewpoint of liquid crystal contamination.
The content of the (d) epoxy resin in the liquid crystal sealant is about 5 to 50% by mass.

  The thermosetting agent as the component (e) that can be used in the liquid crystal sealant of the present invention is not particularly limited, and solid organic acid hydrazide is preferably used. For example, the aromatic hydrazide salicylic acid hydrazide, benzoic acid hydrazide, 1-naphthoic acid hydrazide, terephthalic acid dihydrazide, isophthalic acid dihydrazide, 2,6-naphthoic acid dihydrazide, 2,6-pyridinedihydrazide, 1,2,4-benzene Examples include trihydrazide, 1,4,5,8-naphthoic acid tetrahydrazide, pyromellitic acid tetrahydrazide and the like. Examples of aliphatic hydrazide compounds include form hydrazide, acetohydrazide, propionic acid hydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, 1,4- Cyclohexane dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, iminodiacetic acid dihydrazide, N, N'-hexamethylenebissemicarbazide, citric acid trihydrazide, nitriloacetic acid trihydrazide, cyclohexanetricarboxylic acid trihydrazide, 1,3-bis (hydrazinocarbono) Examples thereof include dihydrazides having a valine hydantoin skeleton such as ethyl) -5-isopropylhydantoin, which are preferable from the balance of curing reactivity and potential. Properly is a dihydrazide is a two-functional, particularly preferably can be exemplified isophthalic acid dihydrazide. The amount of the (e) thermosetting agent used is 0.5 to 2.0 equivalents, preferably 0 when the epoxy equivalent of the epoxy group of the epoxy resin of the component (d) is 1. .8 to 1.2 equivalents.

  The liquid crystal sealant according to the present invention may be blended with an inorganic filler and a coupling agent for the purpose of improving the adhesive strength and moisture resistance reliability, and further, if necessary, an organic filler, a pigment, a leveling agent, an erasing agent. Additives such as foaming agents and organic solvents can be blended.

  In the liquid crystal sealing agent of the present invention, the component (d) is first dissolved and mixed in the component (c) as necessary, and then the component (a) and the component (b) are dissolved in this mixture. A predetermined amount such as a ring agent, an inorganic filler, an organic filler, an antifoaming agent, and a leveling agent is added, and the component (e) is mixed as necessary, and a known mixing device such as a three-roll, sand mill, It is obtained by uniformly mixing with a ball mill or the like and filtering with a metal mesh.

The liquid crystal display cell of the present invention is a cell in which a pair of substrates having predetermined electrodes formed on a substrate are arranged opposite to each other at a predetermined interval, the periphery is sealed with the liquid crystal sealant of the present invention, and the liquid crystal is sealed in the gap. is there. The kind of liquid crystal to be sealed is not particularly limited. Here, the substrate is composed of a combination of substrates made of at least one of glass, quartz, plastic, silicon, etc. and having light transmission properties. For example, in the case of the liquid crystal dropping method, after adding a spacer (gap control material) such as glass fiber to the liquid crystal sealing agent of the present invention, a dispenser or a screen printing device is used on one of the pair of substrates. Then apply the liquid crystal sealant. Subsequently, the liquid crystal is dropped inside the liquid crystal sealing agent weir, and the other glass substrate is overlaid in a vacuum to create a gap. After forming the gap, the sealant is photocured. At this time, an ultraviolet cut filter is used to cut light of 400 nm or less. Amount of irradiation uses 405nm of the sensor, preferably ^{500mJ / cm 2 ~6000mJ / cm 2} , more preferably the dose of 1000mJ / cm ² ~4000mJ / cm ² is preferred. Then, the liquid crystal display cell of this invention can be obtained by hardening at 90-130 degreeC for 1-2 hours. The liquid crystal display cell of the present invention thus obtained has no display defects due to liquid crystal contamination, and has excellent adhesion and moisture resistance reliability. Examples of the spacer include glass fiber, silica beads, polymer beads and the like. The diameter varies depending on the purpose, but is usually 2 to 8 μm, preferably 4 to 7 μm. The amount used is usually 0.1 to 4 parts by weight, preferably 0.5 to 2 parts by weight, more preferably about 0.9 to 1.5 parts by weight, based on 100 parts by weight of the liquid crystal sealant of the present invention. is there.

Hereinafter, the present invention will be described in more detail with reference to examples. “Parts” in the table means parts by weight.
Examples 1 to 3, Comparative Examples 1 and 2
(Adjustment of sealant for liquid crystal dropping method)
Each resin component was mixed and stirred at the ratio shown in Table 1 below, and then the photopolymerization initiator was dissolved by heating. Then, after disperse | distributing a filler etc. with a 3 roll mill, it filtered with the metal mesh and adjusted the sealing compound for liquid crystal dropping methods.

(Evaluation)
The following evaluation was performed about the created sealing agents according to Examples 1 to 3 and Comparative Examples 1 and 2. Table 1 summarizes the results.

(1) Panel display unevenness Using the sealing agents of Examples 1 to 3 and Comparative Examples 1 and 2, a panel was prepared, a filter that cuts off light of 400 nm or less was used, and visible to 1000 mJ / cm ² with an ultraviolet irradiation device. Perform light irradiation. Thereafter, it was cured in a 120 ° C. heat oven for 1 hour, and the color unevenness generated in the liquid crystal around the seal portion was visually observed according to the following criteria.
◎ (No color unevenness)
○ (There is uneven color only in the corner)
Δ (color unevenness area is less than 1mm from the seal)
× (Color uneven area is 1mm or more from the seal)

(2) Measurement of specific resistance of sealing agent 0.1 g of the sealing agents of Examples 1 to 3 and Comparative Examples 1 and 2 were put in a sample bottle, irradiated with visible light of 1000 mJ / cm ² , cured, and then liquid crystal (Merck) , MLC-6866-100) 1 ml is added, placed in an oven at 120 ° C. for 1 hour, and then left at room temperature for 0.5 hour. Only the liquid crystal was taken out from the sample bottle after the treatment, put in the liquid electrode LE21 (manufactured by Ando Electric), and measured by measuring the specific resistance of the liquid crystal after 4 minutes at a measurement voltage of 10V with an electrometer R-8340 made by Advantest. . Judgment was made according to the following criteria.
◎ (3.00E + 12 or more)
○ (1.00E + 12 to 2.99E + 12)
Δ (5.00E + 11 to 9.99E + 12)
× (4.99E + 11 or less)
The specific resistance value “3.00E + 12” represents “3.00 × 10 ¹² ”, and the same description in Table 1 also has the same meaning.

Table 1
Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2
RGEAC 80 parts 80 parts 80 parts 80 parts
80 parts of R-93100
YD-8125 20 parts 20 parts 20 parts 20 parts 20 parts Irgacure OXE02 0.3 parts 0.3 parts 0.3 parts
N-1414 0.3 part
DETX 0.3 part 0.3 part 0.3 part Darocur TPO 0.3 part
S-510 1.5 parts 1.5 parts 1.5 parts 1.5 parts 1.5 parts
SEZ 50 parts 50 parts 50 parts 50 parts 50 parts (Evaluation items)
(1) Panel display unevenness ◎ ○ ◎ × ×
(2) Specific resistance ◎ ◎ ○ ○ ◎

RGEAC: reaction product of resorcin diglycidyl ether and acrylic acid R-93100: Bisphenol A type epoxy acrylate (reaction product of Epicoat 828 (Japan Epoxy Resin Co., Ltd.) and acrylic acid)
YD-8125: Bis phenol A type epoxy resin (product of Toto Kasei Co., Ltd.)
Irgacure OXE02: carbazole oxime ester skeleton-containing photoinitiator (ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (O-acetyloxime); Ciba Specialty Chemicals Co., Ltd.)
N-1414: carbazole skeleton-containing photoinitiator (3,6-bis (2-methyl-2-morpholinopropionyl) -9-n-octylcarbazole; manufactured by Asahi Denka Kogyo Co., Ltd.)
Darocur TPO: Photoinitiator (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide; manufactured by Ciba Specialty Chemicals)
DETX: Photosensitizer (2,4-diethylthioxanthone; manufactured by Sebel Hegner)
S-510: Silane coupling agent (manufactured by Chisso Corporation)
SEZ: Silica (manufactured by Admatechs Co., Ltd.)

 According to the results shown in Table 1 above, (a) a photoinitiator having a carbazole skeleton, (b) a hydrogen abstraction type photosensitizer and (c) (meth) acrylated epoxy of Examples 1 to 3 according to the present invention. The visible light curable liquid crystal sealing agent characterized by containing a resin as a curable resin has sufficient curability with visible light of 400 nm or more, and it is difficult to cause display unevenness of the panel. Further, the results of the panel display unevenness test of Examples 1 and 3 are particularly good, and it is shown that the carbazole skeleton and the oxime ester skeleton coexist in one molecule as the photoinitiator of (a). . Furthermore, by using resorcin diglycidyl ether as the acrylated epoxy resin of (c), it is possible to suppress a decrease in specific resistance value.

Claims (6)

A visible light curable liquid crystal seal comprising (a) a photoinitiator having a carbazole skeleton, (b) a hydrogen abstraction type photosensitizer and (c) a (meth) acrylated epoxy resin as a curable resin. Agent. 2. The liquid crystal sealant according to claim 1, wherein (a) the photoinitiator having a carbazole skeleton is an initiator having an oxime ester skeleton in its molecule. The liquid crystal sealant according to claim 1 or 2, wherein the (c) (meth) acrylated epoxy resin is a (meth) acrylated epoxy resin of resorcin diglycidyl ether. The liquid crystal sealing agent according to any one of claims 1 to 3, further comprising (d) an epoxy resin and (e) a thermosetting agent. The liquid crystal sealant according to any one of claims 1 to 4, wherein the liquid crystal sealant has sufficient photocurability by visible light of 400 nm or more. A liquid crystal display cell sealed with a cured product obtained by curing the liquid crystal sealing agent according to any one of claims 1 to 5.