JP7489911B2 - Liquid crystal sealant for liquid crystal dripping method - Google Patents

Description

The present invention relates to a liquid crystal sealant for the liquid crystal dropping method, and a liquid crystal display cell sealed with the cured product.

In recent years, the liquid crystal dropping method, which is highly mass-productive, has become widely used as a method for manufacturing liquid crystal display cells. In the liquid crystal dropping method, liquid crystal is dropped onto the inside of a liquid crystal sealant formed on one substrate, the other substrate is bonded under vacuum, and then the liquid crystal sealant is compressed to a specified gap (distance between the substrates) by atmospheric pressure by releasing the liquid crystal into the atmosphere, and then the liquid crystal sealant is cured by ultraviolet light or heat to produce a liquid crystal display cell.

However, in recent years, as liquid crystal display cells have become larger and the gaps have become narrower, problems have arisen in which the liquid crystal sealant does not collapse to the specified gap. This causes the gap to differ between the center and periphery of the liquid crystal display, making it impossible to achieve the desired display characteristics.

Recently, displays with curved shapes and highly flexible displays have been developed and commercialized, and the substrates used in these displays are flexible, such as plastic films, instead of the conventional rigid substrates such as glass (Patent Document 1). With such flexible substrates, uniform atmospheric pressure is not applied across the entire substrate when the gap is formed, which is one of the causes of gap defects.

In addition, with the introduction of flexible substrates, liquid crystal sealants are now required to have the ability to follow the bending of substrates, i.e., remain flexible even after curing. Liquid crystal sealants with excellent flexibility are also advantageous in terms of adhesive strength. For example, they can reduce peeling and damage to equipment caused by impact. From this perspective, there is an increasing demand for liquid crystal sealants to be flexible.

On the other hand, reducing the crosslink density of the cured product is an effective way to increase its flexibility. However, reducing the crosslink density usually also reduces its moisture permeability. This is thought to be because moisture penetrates through loose parts of the network. Therefore, in order to ensure low moisture permeability, it is necessary to achieve the contradictory properties of either increasing flexibility without reducing the crosslink density, or reducing the crosslink density without reducing moisture permeability.

JP 2012-238005 A

The present invention relates to a liquid crystal sealant that can be used in flexible displays and curved displays. More specifically, the object is to provide a liquid crystal sealant for the liquid crystal dropping method that has excellent crush resistance, and a liquid crystal display cell sealed with the cured product.

As a result of extensive investigations, the present inventors have found that a specific liquid crystal sealant for the liquid crystal dropping method has excellent crush resistance, and have arrived at the present invention.
In this specification, "(meth)acrylate" means "acrylate" and/or "methacrylate".

That is, the present invention relates to the following [1] to [10].
[1]
A liquid crystal sealant for a liquid crystal dropping method, comprising a curable compound, a filler, and a heat curing agent,
The average specific surface area of the filler is 10.0 m ² /g or more;
A liquid crystal sealant for use in a liquid crystal dropping method, having a viscosity of less than 500 Pa·s as measured at 25° C. and 5 rpm using an E-type viscometer.
[2]
The liquid crystal sealant for the liquid crystal dropping method according to the above item [1], wherein the elastic modulus of the cured product at 25° C. as measured by a Tensilon universal testing machine is 2500 MPa or less.
[3]
The liquid crystal sealant for the liquid crystal dropping method according to any one of the preceding items [1] to [3], wherein the moisture permeability of the cured product at a film thickness of 300 μm, measured at 60° C. and 90%, is 100 g/m ² ·24 h or less.
[4]
The liquid crystal sealant for a liquid crystal dropping process according to any one of the above items [1] to [3], wherein the content of the filler is 5 parts by mass or more and less than 50 parts by mass with respect to 100 parts by mass of the curable compound.
[5]
The liquid crystal sealant for a liquid crystal dropping process according to any one of the above items [1] to [4], wherein the filler comprises an organic filler and an inorganic filler, and the inorganic filler has been subjected to a hydrophobic surface treatment.
[6]
The liquid crystal sealant for a liquid crystal dropping process according to any one of the above items [1] to [5], wherein the curable compound contains urethane (meth)acrylate.
[7]
The liquid crystal sealant for liquid crystal dropping method according to the above item [6], wherein the urethane (meth)acrylate is obtained by reacting (a) a polyol having an aromatic ring, (b) an organic polyisocyanate, and (c) a hydroxyl group-containing (meth)acrylate.
[8]
The liquid crystal sealant for a liquid crystal dropping method according to any one of the above items [1] to [7], further comprising a thermal radical polymerization initiator.
[9]
The liquid crystal sealant for a liquid crystal dropping process according to any one of the above items [1] to [8], further comprising a photoradical polymerization initiator.
[10]
A liquid crystal display cell sealed with the liquid crystal sealant for a liquid crystal dropping method according to any one of items [1] to [9] above.

The present invention can provide a liquid crystal sealant that has excellent crush resistance when used in the liquid crystal dropping method, and a liquid crystal display cell sealed with the cured product.

1 is a graph showing the relationship between the dark interference fringes and the average specific surface area of liquid crystal sealants of Examples and Comparative Examples.

The liquid crystal sealing material for the liquid crystal dropping method of the present invention contains a curable compound, a filler, and a heat curing agent, and the filler has an average specific surface area of 10.0 ^m2 /g or more and a viscosity measured using an E-type viscometer at 25°C and 5 rpm of less than 500 Pa·s.

The average specific surface area of the filler may be measured by mixing all the fillers contained in the liquid crystal sealant and measuring them by the BET method or the like, or may be calculated from the specific surface area of each filler contained in the liquid crystal sealant. In the examples of the present invention described later, the average specific surface area was calculated based on the following formula (1).
Average specific surface area (m ² /g)=[(specific surface area (m ² /g) of each filler)×(content of each filler)]/(total content of fillers) (1)

There is no particular limitation on the method for measuring the specific surface area of the filler, but it can generally be measured by the BET method. In addition, if it is a commercially available product, the value specified in each company's catalog can be used instead of the above method.

To explain the above formula (1) in more detail, for example, the average specific surface area of a liquid crystal sealing material consisting of 100 parts by mass of curable compound, 5 parts by mass of filler A (specific surface area: 7.0 ^m2 /g), and 10 parts by mass of filler B (specific surface area: 2.0 ^m2 /g) is [(7.0 x 5) + (2.0 x 10)]/15 = 3.0 ( ^m2 /g).

The liquid crystal sealant of the present invention has excellent crush resistance. In other words, the liquid crystal sealant of the present invention is easily crushed to the desired gap when the upper and lower substrates are bonded together under vacuum and then released to the atmosphere.

The present inventors conducted lamination tests on various liquid crystal sealants and found that there is a certain relationship between the crushability of the liquid crystal sealant and the average specific surface area of the filler. This is because a filler with a small specific surface area tends to have a large particle diameter and is less likely to be crushed to a predetermined gap. Therefore, the average specific surface area of the filler is preferably 10.0 m ² /g or more, more preferably 14.0 m ² /g or more, and particularly preferably 17.0 m ² /g or more. There is no particular upper limit, but considering kneading with the liquid crystal sealant, it is preferably 200.0 m ² /g or less, and more preferably 100.0 m ² /g or less.

The inventors have also found that the crushability is also affected by the viscosity of the liquid crystal sealant. This is thought to be because a liquid crystal sealant with a high viscosity has a stronger resistance to atmospheric pressure when forming a gap. The viscosity measured using an E-type viscometer at 25°C and 5 rpm is preferably less than 500 Pa·s, more preferably less than 450 Pa·s, and particularly preferably less than 400 Pa·s. There is no particular preferred lower limit, but taking into account resistance to liquid crystal insertion, it is preferably 100 Pa·s or more, and more preferably 200 Pa·s or more.

In the present invention, the viscosity measurement was carried out under the following conditions.
0.15 mL of the liquid crystal sealant was added to the measuring cup of an E-type viscometer (RE105 manufactured by Toki Sangyo Co., Ltd.). After leaving it for 120 seconds as preheating under the conditions of a temperature of 25° C. and a cone of 3°×R7.7, the value after 180 seconds at a rotation speed of 5 rpm was measured.
For those exceeding the measurement limit at 5 rpm (600 Pa·s), the viscosity was measured at 0.5 rpm. The results are shown in Tables 1 and 2.

The gap measurement after laminating the substrates can be performed using an optical device or a step gauge, but in the present invention, the interference fringe dark lines after lamination of the substrates were observed as follows. The obtained liquid crystal sealant was applied in a square shape to a glass substrate with an alignment film, and liquid crystal was dropped inside the square. Another glass substrate with an alignment film was sprayed with 5 μm in-plane spacers, thermally fixed, and laminated to both substrates in a vacuum using a lamination device. After 3 minutes of exposure to the atmosphere, the liquid crystal sealant was cured by ultraviolet light or heat to prepare a liquid crystal cell for evaluation. Next, the evaluation liquid crystal cell was observed with an interference fringe inspection lamp, and the number of interference fringe dark lines on the outside of the liquid crystal sealant was counted. At this time, it is preferable that the number of interference fringe dark lines is two or less. A liquid crystal sealant with excellent crushability is crushed to the height of the in-plane spacer by atmospheric pressure, so the glass substrate becomes flat and the interference fringe dark lines are two or less. However, liquid crystal sealant with poor crushability does not crush to the height of the in-plane spacer, resulting in a difference in the gap between the liquid crystal sealant and its surroundings, and many dark interference fringes are observed.

The liquid crystal sealant of the present invention preferably has high flexibility and low moisture permeability. The flexibility can be evaluated by the elastic modulus. The elastic modulus of a 100 μm thick cured product cured at 120° C. for 60 minutes after irradiation with 3000 mJ/cm ² ultraviolet light (measurement wavelength: 365 nm) is preferably 100 MPa or more and 3000 MPa or less, more preferably 300 MPa or more and 2500 MPa or less, and particularly preferably 400 MPa or more and 2000 MPa or less at room temperature (25° C.) when measured with a universal testing machine (Shimadzu Corporation: Autograph AG-Xplus 500N). A liquid crystal sealant in the above range can be said to be preferable because it can follow the stress applied to the display.

In terms of moisture permeability, in a 300 μm thick cured product cured under conditions of 120°C for 60 minutes after irradiation with 3000 mJ/ ^cm2 UV rays (measurement wavelength: 365 nm), the moisture permeability under conditions of 60°C and 90% is preferably 100 g/ ^m2 ·24 h or less, more preferably 80 g/ ^m2 ·24 h or less, and particularly preferably 70 g/ ^m2 ·24 h or less.

[Curable compound]
The liquid crystal sealant of the present invention contains a curable compound. The curable compound is not particularly limited as long as it is a compound that is cured by light, heat, or the like, but is preferably a compound having a (meth)acrylic group or an epoxy group, and particularly preferably an epoxy (meth)acrylate, a urethane (meth)acrylate, or a polybutadiene compound.

[(Meth)acrylate]
Specific examples of (meth)acrylates include N-acryloyloxyethylhexahydrophthalimide, acryloylmorpholine, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, cyclohexane-1,4-dimethanol mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, phenoxyethyl (meth)acrylate, phenylpolyethoxy (meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate, o-phenylphenol monoether, and the like. ethoxy (meth)acrylate, o-phenylphenol polyethoxy (meth)acrylate, p-cumylphenoxyethyl (meth)acrylate, isobornyl (meth)acrylate, tribromophenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate acrylate, tricyclodecane dimethanol (meth)acrylate, bisphenol A polyethoxy di(meth)acrylate, bisphenol A polypropoxy di(meth)acrylate, bisphenol F polyethoxy di(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tris(acryloxyethyl)isocyanurate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate )acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxy tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ester diacrylate of neopentyl glycol and hydroxypivalic acid, diacrylate of an ε-caprolactone adduct of an ester of neopentyl glycol and hydroxypivalic acid, etc. Preferred examples include o-phenylphenol monoethoxy(meth)acrylate and o-phenylphenol polyethoxy(meth)acrylate.

[Epoxy (meth)acrylate]
Epoxy (meth)acrylate is obtained by a known method by reacting epoxy resin with (meth)acrylic acid. The epoxy resin as the raw material is not particularly limited, but is preferably a bifunctional or higher epoxy resin, such as dimer acid modified epoxy resin, resorcinol diglycidyl ether, 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 novolac type epoxy resin, bisphenol F novolac 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 a triphenolmethane skeleton, and other diglycidyl ethers of bifunctional phenols such as catechol and resorcinol, diglycidyl ethers of bifunctional alcohols, and their halides and hydrogenated products. Among these, bisphenol A type epoxy resin and resorcinol diglycidyl ether are preferred from the viewpoint of liquid crystal contamination. The ratio of epoxy groups to (meth)acryloyl groups is not limited, and is appropriately selected from the viewpoint of process suitability.
Partial epoxy (meth)acrylates in which a portion of the epoxy groups is acrylic esterified are preferably used, with the acrylic ester content being preferably about 30 to 70%.

[Urethane (meth)acrylate]
Urethane (meth)acrylates have a flexible skeleton specific to the urethane structure, and therefore the cured product has flexibility and low moisture permeability and can conform to bending in flexible displays. For this reason, it is preferable to use urethane (meth)acrylates as the curable compound, and it is even more preferable to use those having a polyester structure.
The urethane (meth)acrylate can be obtained by reacting (a) a polyol, (b) an organic polyisocyanate, and (c) a hydroxyl group-containing (meth)acrylate in a conventional manner, and a catalyst such as a tin compound may be used as necessary.
In the synthesis of the urethane (meth)acrylate, it is preferable to react 1.1 to 2.0 equivalents, and particularly preferably 1.3 to 2.0 equivalents, of the isocyanate group of the component (b) with 1 equivalent of the hydroxyl group of the component (a). The reaction temperature is preferably room temperature (25°C) to 100°C.
It is preferable to react 0.95 to 1.1 equivalents of hydroxyl groups in component (c) per equivalent of isocyanate groups in the reaction product of components (a) and (b). The reaction temperature is preferably room temperature (25°C) to 100°C.

Specific examples of (a) polyols include tricyclodecane dimethanol, hydrogenated polybutadiene polyol, dimer diol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,18-octadecanediol, 1,20-icosanediol, and 1-methyl-1,8-octanediol. , 2-methyl-1,8-octanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, cyclohexane-1,4-dimethanol, polyethylene glycol, polypropylene glycol, bisphenol A poly(n≒2-20)ethoxydiol, bisphenol A poly(n≒2-20)propoxydiol, and other diols (a-1), and polyester polyols (a-2) which are reaction products of these diols (a-1) with dibasic acids or their anhydrides (e.g. succinic acid, adipic acid, azelaic acid, sebacic acid, dimer acid, isophthalic acid, terephthalic acid, phthalic acid, or their anhydrides). Preferred are polyester polyols and polyols having an aromatic ring, and particularly preferred are polyester polyols having an aromatic ring. Examples of the aromatic ring include aromatic hydrocarbon rings such as a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthroline ring; and aromatic heterocycles such as a furan ring, a pyrrole ring, a thiophene ring, a pyridine ring, a thiazole ring, and a benzothiazole ring; and preferably a benzene ring or a naphthalene ring.
The component (a) may be used alone or in a mixture of two or more kinds.

(b) Specific examples of organic polyisocyanates include tolylene diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-cyclohexylmethane diisocyanate, xylylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, trimethylhexamethylene diisocyanate, dimeryl diisocyanate, 1,5-naphthalene diisocyanate, 3,3'-dimethyl-4,4'-diphenylene diisocyanate, etc. Preferred examples include tolylene diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate.

(c) Specific examples of hydroxyl group-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 1,4-butanediol (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, pentaerythritol tri(meth)acrylate, ε-caprolactone adduct of 2-hydroxyethyl (meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate, etc. Preferred examples include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and polyethylene glycol mono(meth)acrylate.

The lower limit of the weight average molecular weight of the urethane (meth)acrylate in terms of polystyrene in GPC is preferably 1000 or more, more preferably 2000 or more, particularly preferably 3000 or more, and most preferably 4000 or more. The upper limit is preferably 10000 or less, more preferably 8000 or less, particularly preferably 7000 or less, and most preferably 6000 or less. By being in the above range, the viscosity of the liquid crystal sealant is in an appropriate range while maintaining good flexibility and moisture permeability.

[Epoxy resin]
In a preferred embodiment of the present invention, the curable compound contains an epoxy resin.
The epoxy resin is not particularly limited, but is preferably a bifunctional or higher epoxy resin, for example, dimer acid modified epoxy resin, resorcinol diglycidyl ether, 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 novolac type epoxy resin, bisphenol F novolac 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 a triphenolmethane skeleton, diglycidyl ethers of bifunctional phenols such as catechol and resorcinol, diglycidyl ethers of bifunctional alcohols, and their halides and hydrogenated products. Among these, bisphenol A type epoxy resin and resorcinol diglycidyl ether are preferred from the viewpoint of liquid crystal contamination.

[Polybutadiene compound]
In addition, it is also a preferred embodiment of the present invention to use a polybutadiene compound having an epoxy group or a (meth)acrylic group in the curable compound. Polybutadiene compounds having an epoxy group are available on the market, for example, as JP-100 and JP-200 manufactured by Nippon Soda Co., Ltd. Polybutadiene compounds having a (meth)acrylic group are available on the market, for example, as TEAI-1000 and TE-2000 manufactured by Nippon Soda Co., Ltd.
From the viewpoint of reducing the contamination of liquid crystal, the lower limit of the number average molecular weight of these polybutadiene compounds is preferably 500, more preferably 750, and particularly preferably 1000. From the viewpoint of handling properties, the upper limit of the number average molecular weight is preferably 10000, more preferably 8000, and particularly preferably 6000.

The curable compound may be one of the above materials or a mixture of two or more types. When a curable compound is used in the liquid crystal sealant of the present invention, it is preferably 10 to 95 mass % of the total amount of the liquid crystal sealant, and more preferably 20 to 90 mass %.

[Filler]
The liquid crystal sealant of the present invention contains a filler. From the viewpoint of the crushability of the liquid crystal sealant, the specific surface area of the filler is preferably 10.0 m ² /g or more, more preferably 15.0 m ² /g or more, and particularly preferably 18.0 m ² /g or more. The shape of the filler is preferably spherical. The liquid crystal sealant is improved in fluidity by the filler being spherical, so that the crushability is improved. In addition, the surface of the filler is preferably subjected to a hydrophobic surface treatment. By subjecting the filler to a hydrophobic surface treatment, the filler becomes more compatible with the curable compound, and the liquid crystal sealant is improved in fluidity, so that the crushability is improved. Examples of the hydrophobic surface treatment include methylation treatment and various coupling treatments.

The particle size of the filler is preferably 0.01 to 1.0 μm, more preferably 0.05 to 0.7 μm, and particularly preferably 0.05 to 0.3 μm. The filler content is preferably 1 part by mass or more and less than 60 parts by mass, more preferably 5 parts by mass or more and less than 50 parts by mass, particularly preferably 10 parts by mass or more and less than 30 parts by mass, and most preferably 10 parts by mass or more and less than 20 parts by mass, relative to 100 parts by mass of the curable compound. In addition, the amount of filler having a particle size of 0.5 μm or more is preferably less than 20 parts by mass, and more preferably less than 10 parts by mass, relative to 100 parts by mass of the curable compound.

The filler contained in the liquid crystal sealing material of the present invention may be either an organic filler or an inorganic filler, or may contain both.
Examples of the organic filler include urethane fine particles, acrylic fine particles, styrene fine particles, styrene olefin fine particles, and silicone fine particles. The silicone fine particles are preferably KMP-594, KMP-597, KMP-598 (manufactured by Shin-Etsu Chemical Co., Ltd.), Trefil ^RTM E-5500, 9701, EP-2001 (manufactured by Toray Dow Corning Co., Ltd.), the urethane fine particles are preferably JB-800T, HB-800BK (manufactured by Negami Chemical Industries, Ltd.), the styrene fine particles are preferably Rabalon ^RTM T320C, T331C, SJ4400, SJ5400, SJ6400, SJ4300C, SJ5300C, SJ6300C (manufactured by Mitsubishi Chemical), and the styrene olefin fine particles are preferably Septon ^RTM SEPS2004, SEPS2063.
These organic fillers may be used alone or in combination of two or more. Also, two or more may be used to form a core-shell structure. Among these, urethane fine particles, acrylic fine particles, styrene fine particles, and styrene olefin fine particles are preferred, and acrylic fine particles are particularly preferred.
When the above acrylic fine particles are used, it is preferable that the acrylic fine particles are of a core-shell structure consisting of two kinds of acrylic rubber, and it is particularly preferable that the core layer is made of n-butyl acrylate and the shell layer is made of methyl methacrylate. This is sold by Aica Kogyo Co., Ltd. as Zefiac ^RTM F-351S.
The silicone fine particles include organopolysiloxane crosslinked powder, linear dimethylpolysiloxane crosslinked powder, etc. The composite silicone rubber includes the silicone rubber whose surface is coated with silicone resin (e.g., polyorganosilsesquioxane resin). Among these fine particles, particularly preferred are linear dimethylpolysiloxane crosslinked powder silicone rubber or silicone resin-coated linear dimethylpolysiloxane crosslinked powder composite silicone rubber fine particles. These organic fillers may be used alone or in combination of two or more.

Examples of inorganic fillers include silica, silicon carbide, silicon nitride, boron nitride, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, mica, talc, clay, alumina, magnesium oxide, zirconium oxide, aluminum hydroxide, magnesium hydroxide, calcium silicate, aluminum silicate, lithium aluminum silicate, zirconium silicate, barium titanate, glass fiber, carbon fiber, molybdenum disulfide, asbestos, etc., and preferably fused silica, crystalline silica, silicon nitride, boron nitride, calcium carbonate, barium sulfate, calcium sulfate, mica, talc, clay, alumina, aluminum hydroxide, calcium silicate, aluminum silicate, but preferably silica, alumina, and talc. Two or more of these inorganic fillers may be mixed and used.

[Thermal hardener]
The liquid crystal sealing material of the present invention contains a heat curing agent.
Examples of the heat curing agent include compounds having a carboxy group bonded to an aromatic ring in the molecule, polyamines, polyphenols, organic acid hydrazides, etc. However, the present invention is not limited to these. Examples of the heat curing agent include aromatic hydrazides such as terephthalic acid dihydrazide, isophthalic acid dihydrazide, 2,6-naphthoic acid dihydrazide, 2,6-pyridine dihydrazide, 1,2,4-benzene trihydrazide, 1,4,5,8-naphthoic acid tetrahydrazide, and pyromellitic acid tetrahydrazide. In addition, examples of aliphatic hydrazides include formhydrazide, acetohydrazide, propionic acid hydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, sebacic 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 Examples of the hydrazidoamine derivatives include dihydrazides having a hydantoin skeleton such as 1-(1-hydrazinocarbonylmethyl)isocyanurate, tris(2-hydrazinocarbonylethyl)isocyanurate, tris(1-hydrazinocarbonylethyl)isocyanurate, tris(3-hydrazinocarbonylpropyl)isocyanurate, and bis(2-hydrazinocarbonylethyl)isocyanurate. In view of the balance between curing reactivity and latency, preferred are isophthalic acid dihydrazide, malonic acid dihydrazide, adipic acid dihydrazide, tris(1-hydrazinocarbonylmethyl)isocyanurate, tris(1-hydrazinocarbonylethyl)isocyanurate, tris(2-hydrazinocarbonylethyl)isocyanurate, and tris(3-hydrazinocarbonylpropyl)isocyanurate, and particularly preferred is tris(2-hydrazinocarbonylethyl)isocyanurate.

[Curing accelerator]
The liquid crystal sealing material of the present invention can further improve its reactivity by adding a curing accelerator, such as an organic acid or imidazole.
Examples of the organic acid include organic carboxylic acids and organic phosphoric acids, and organic carboxylic acids are preferred. Specific examples of the organic acid include aromatic carboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, benzophenonetetracarboxylic acid, and furandicarboxylic acid, succinic acid, adipic acid, dodecanedioic acid, sebacic acid, thiodipropionic acid, cyclohexanedicarboxylic acid, tris(2-carboxymethyl)isocyanurate, tris(2-carboxyethyl)isocyanurate, tris(2-carboxypropyl)isocyanurate, and bis(2-carboxyethyl)isocyanurate.
Examples of the imidazole compound include 2-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 2,4-diamino-6(2'-methylimidazole(1'))ethyl-s-triazine, 2,4-diamino-6(2'-undecylimidazole(1'))ethyl-s-triazine, and 2,4-diamino-6(2'-undecylimidazole(1')). 2,4-diamino-6(2'-ethyl-4-methylimidazole(1'))ethyl-s-triazine, 2,4-diamino-6(2'-ethyl-4-methylimidazole(1'))ethyl-s-triazine, 2,4-diamino-6(2'-methylimidazole(1'))ethyl-s-triazine·isocyanuric acid adduct, 2-methylimidazole isocyanuric acid 2:3 adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-3,5-dihydroxymethylimidazole, 2-phenyl-4-hydroxymethyl-5-methylimidazole, 1-cyanoethyl-2-phenyl-3,5-dicyanoethoxymethylimidazole, and the like.
When a curing accelerator is used in the liquid crystal sealing material of the present invention, its content is preferably 0.1 to 10 mass %, more preferably 1 to 5 mass %, of the total amount of the liquid crystal sealing material.

[Photoradical polymerization initiator]
The liquid crystal sealing material of the present invention may contain a photoradical polymerization initiator. The photoradical polymerization initiator is not particularly limited as long as it is a compound that generates radicals or acids and initiates a chain polymerization reaction by irradiation with ultraviolet light or visible light, and examples of the photoradical polymerization initiator include benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, diethylthioxanthone, benzophenone, 2-ethylanthraquinone, 2-hydroxy-2-methylpropiophenone, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propane, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, camphorquinone, 9-fluorenone, and diphenyl disulfide. Specific examples include IRGACURE ^RTM 651, 184, 2959, 127, 907, 369, 379EG, 819, 784, 754, 500, OXE01, OXE02, OXE03, OXE04, DAROCURE ^RTM 1173, LUCIRIN ^RTM TPO (all manufactured by BASF), Seikuol ^RTM Z, BZ, BEE, BIP, BBI (all manufactured by Seiko Chemical Co., Ltd.), etc. Among these, preferred are IRGACURE ^RTM OXE01, OXE02, OXE03, and OXE04, which are oxime ester initiators.
From the viewpoint of preventing liquid crystal contamination, it is preferable to use a compound having a (meth)acrylic group in the molecule, for example, a reaction product of 2-methacryloyloxyethyl isocyanate and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one is preferably used. This compound can be obtained by the method described in WO 2006/027982.
When a photoradical polymerization initiator is used in the liquid crystal sealing material of the present invention, its content is preferably 0.001 to 3 mass %, more preferably 0.002 to 2 mass %, of the total amount of the liquid crystal sealing material.

[Thermal radical polymerization initiator]
The liquid crystal sealing material of the present invention contains a thermal radical polymerization initiator, which can improve the curing speed and curability.
The thermal radical polymerization initiator is not particularly limited as long as it is a compound that generates radicals by heating and initiates a chain polymerization reaction. Examples of the thermal radical polymerization initiator include organic peroxides, azo compounds, benzoin compounds, benzoin ether compounds, acetophenone compounds, and benzopinacol, with benzopinacol being preferred. For example, organic peroxides include Kayamec ^RTM A, M, R, L, LH, SP-30C, Perkadox CH-50L, BC-FF, Kadox B-40ES, Perkadox 14, Trigonox ^RTM 22-70E, 23-C70, 121, 121-50E, 121-LS50E, 21-LS50E, 42, 42LS, Kayaester ^RTM P-70, TMPO-70, CND-C70, OO-50E, AN, Kayabutyl ^RTM B, Perkadox 16, Kayacarvone ^RTM BIC-75, AIC-75 (manufactured by Kayaku Akzo Co., Ltd.), Permec ^RTM N, H, S, F, D, G, and Perhexa ^RTM . H, HC, TMH, C, V, 22, MC, Percure ^RTM AH, AL, HB, Perbutyl ^RTM H, C, ND, L, Percumyl ^RTM H, D, Peroyl ^RTM IB, IPP, Perocta ^RTM ND (manufactured by NOF Corporation), and the like are commercially available products.

Azo compounds such as VA-044, 086, V-070, VPE-0201, and VSP-1001 (manufactured by Wako Pure Chemical Industries, Ltd.) are available commercially.

The content of the thermal radical polymerization initiator is preferably 0.0001 to 10 mass % of the total amount of the liquid crystal sealing agent of the present invention, more preferably 0.0005 to 5 mass %, and particularly preferably 0.001 to 3 mass %.

The liquid crystal sealant of the present invention may further contain additives such as a silane coupling agent, a radical polymerization inhibitor, a pigment, a leveling agent, an antifoaming agent, and a solvent, if necessary.

[Silane coupling agent]
Examples of the silane coupling agent include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)3-aminopropylmethyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, N-(2-(vinylbenzylamino)ethyl)3-aminopropyltrimethoxysilane hydrochloride, 3-methacryloxypropyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, etc. These silane coupling agents are sold by Shin-Etsu Chemical Co., Ltd. and the like as the KBM series, KBE series, etc., and are therefore easily available on the market. When a silane coupling agent is used in the liquid crystal sealant of the present invention, the amount of the silane coupling agent is preferably 0.05 to 3 mass % based on the total amount of the liquid crystal sealant.

[Radical Polymerization Inhibitor]
The radical polymerization inhibitor is not particularly limited as long as it is a compound that reacts with radicals generated from a photoradical polymerization initiator or a thermal radical polymerization initiator to prevent polymerization, and may be a quinone, piperidine, hindered phenol, nitroso, etc. Specifically, naphthoquinone, 2-hydroxynaphthoquinone, 2-methylnaphthoquinone, 2-methoxynaphthoquinone, 2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-methoxypiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-phenoxypiperidine-1-oxyl, or hydroquinone. , 2-methylhydroquinone, 2-methoxyhydroquinone, parabenzoquinone, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butylcresol, stearyl β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylpheno phenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl], 2,4,8,10-tetraoxaspiro[5,5]undecane, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenylpropionate)methane], 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-sec-triazine-2,4,6-(1H,3H,5H)trione, paramethoxyphenol, 4-methoxy-1-naphthol, thiodiphenylamine, aluminum salt of N-nitrosophenylhydroxyamine, trade name Adeka STAB LA-81, trade name Adeka STAB LA-82 (manufactured by ADEKA CORPORATION), and the like, but are not limited thereto. Among these, naphthoquinone-based, hydroquinone-based, nitroso-based, and piperazine-based radical polymerization inhibitors are preferred, naphthoquinone, 2-hydroxynaphthoquinone, hydroquinone, 2,6-di-tert-butyl-p-cresol, and Polystop 7300P (manufactured by Hakuto Co., Ltd.) are more preferred, and Polystop 7300P (manufactured by Hakuto Co., Ltd.) is most preferred.
The content of the radical polymerization inhibitor is preferably from 0.0001 to 1 mass %, more preferably from 0.001 to 0.5 mass %, particularly preferably from 0.01 to 0.2 mass %, based on the total amount of the liquid crystal sealing material of the present invention.

One example of a method for obtaining the liquid crystal sealant of the present invention is the following method. First, the curable compound, and if necessary, a photoradical polymerization initiator, a thermal radical polymerization initiator, and a radical polymerization inhibitor are heated and dissolved. Next, after cooling to room temperature, a thermal curing agent, a curing accelerator, a filler, and if necessary, a silane coupling agent, an antifoaming agent, a leveling agent, a solvent, etc. are added, and the mixture is mixed uniformly using a known mixing device such as a three-roll mill, a sand mill, a ball mill, etc., and filtered through a metal mesh to produce the liquid crystal sealant of the present invention.

The following is an example of a liquid crystal display cell according to the present invention.

The liquid crystal display cell of the present invention is a cell in which a pair of substrates, each having a predetermined electrode formed thereon, are arranged facing each other at a predetermined interval, the periphery is sealed with the liquid crystal sealant of the present invention, and liquid crystal is sealed in the gap. The type of liquid crystal to be sealed is not particularly limited. Here, the substrate is composed of a combination of substrates made of glass, quartz, plastic, silicon, etc., at least one of which is optically transparent. The manufacturing method thereof is to add a spacer (gap control material) such as glass fiber to the liquid crystal sealant of the present invention, apply the liquid crystal sealant to one of the pair of substrates using a dispenser or a screen printing device, etc., and then temporarily cure at 80 to 120°C as necessary. Thereafter, liquid crystal is dropped inside the dam of the liquid crystal sealant, and the other glass substrate is superimposed in a vacuum to form a gap. After the gap is formed, the liquid crystal display cell of the present invention can be obtained by curing at 90 to 130°C for 30 minutes to 2 hours. When used as a photothermal combined type, the liquid crystal sealant is irradiated with ultraviolet light by an ultraviolet irradiator to photocure it. The amount of ultraviolet irradiation is preferably 500 to 6000 mJ/cm ² , more preferably 1000 to 4000 mJ/cm ² (measurement wavelength: 365 nm). Thereafter, if necessary, the liquid crystal display cell of the present invention can be obtained by curing at 90 to 130° C. for 30 minutes to 2 hours. The liquid crystal display cell of the present invention thus obtained is free of display defects due to liquid crystal contamination and has excellent adhesion and moisture resistance reliability. Examples of spacers include glass fiber, silica beads, polymer beads, etc. The diameter of the spacer varies depending on the purpose, but is preferably 2 to 8 μm, more preferably 4 to 7 μm. The amount of the spacer used is preferably 0.1 to 4 parts by mass, more preferably 0.5 to 2 parts by mass, and particularly preferably about 0.9 to 1.5 parts by mass, relative to 100 parts by mass of the liquid crystal sealant of the present invention.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In addition, unless otherwise specified, "parts" and "%" in the text are based on mass.

[Synthesis Example 1]
A flask equipped with a thermometer, a cooling tube, and a stirrer was charged with 776.99 g of polyester polyol of methyl pentanediol, adipic acid, and isophthalic acid (P-2012 manufactured by Kuraray Co., Ltd., hydroxyl value 54.6 mg KOH / g) and 131.68 g of toluene diisocyanate (Coronate T-100 manufactured by Tosoh Corporation, molecular weight 174.2), and reacted at 80 ° C. The isocyanate content at this time was determined by adding an excess of amine and back titrating with hydrochloric acid, and it was confirmed that the value was within the range of plus or minus 2% of the residual amount of isocyanate determined from the calculated value. Next, 0.6 g of methoquinone (polymerization inhibitor), 90.43 g of 2-hydroxyethyl acrylate (molecular weight 116.1), and 0.3 g of dibutyltin dilaurate (catalyst) were added, and the mixture was stirred at 80°C and reacted until the absorption spectrum of the isocyanate group (2280 cm ^-1 ) disappeared in the infrared absorption spectrum, thereby obtaining a urethane acrylate oligomer with a weight average molecular weight of 6300.

[Synthesis Example 2]
100 parts (0.28 moles) of commercially available benzopinacol (Tokyo Chemical Industry Co., Ltd.) was dissolved in 350 parts of dimethylformaldehyde. 32 parts (0.4 moles) of pyridine as a base catalyst and 150 parts (0.58 moles) of BSTFA (Shin-Etsu Chemical Co., Ltd.) as a silylating agent were added to the mixture, which was then heated to 70°C and stirred for 2 hours. The resulting reaction solution was cooled and 200 parts of water was added while stirring to precipitate the product and deactivate the unreacted silylating agent. The precipitated product was separated by filtration and thoroughly washed with water. The resulting product was then dissolved in acetone, and water was added to recrystallize and refine the product. 105.6 parts (yield 88.3%) of the target 1,2-bis(trimethylsiloxy)-1,1,2,2-tetraphenylethane was obtained.

[Examples 1 to 16, Comparative Examples 1 to 10]
The curable compound, photoradical polymerization initiator, and radical polymerization inhibitor were dissolved by heating at 90°C in the ratios shown in Tables 1 to 3 below, then cooled to room temperature, and the thermal radical polymerization initiator, heat curing agent, curing accelerator, organic filler, inorganic filler, and silane coupling agent were added and stirred, then dispersed in a three-roll mill and filtered through a metal mesh (635 mesh) to prepare a liquid crystal sealant. The specific surface area of the filler was the value specified in the catalog of each company, and for F-351S, the value measured by the BET method was used.

[evaluation]
[viscosity]
In the present invention, the viscosity measurement was carried out under the following conditions.
0.15 mL of the liquid crystal sealant was added to the measuring cup of an E-type viscometer (RE105 manufactured by Toki Sangyo Co., Ltd.). After leaving it for 120 seconds as preheating under the conditions of a temperature of 25° C. and a cone of 3°×R7.7, the value after 180 seconds at a rotation speed of 5 rpm was measured.
For those exceeding the measurement limit at 5 rpm (600 Pa·s), the viscosity was measured at 0.5 rpm. The results are shown in Tables 1 to 3.

[Preparation of a substrate with an alignment film by photo-alignment processing]
An alignment film liquid (NRB-U738, manufactured by Nissan Chemical Industries, Ltd.) was spin-coated onto a glass substrate, pre-baked on a hot plate at 80° C. for 3 minutes, and then baked in an oven at 230° C. for 30 minutes. The substrate with the alignment film was then irradiated with ultraviolet light at 500 mJ/cm ² (measured wavelength: 254 nm) using a UV irradiator, and further baked in an oven at 230° C. for 30 minutes.
[Preparation of Liquid Crystal Cell for Evaluation]
A main seal and a dummy seal were dispensed on the substrate with the alignment film of the photo-alignment type, so that the liquid crystal sealant was laminated to form a square with a line width of 0.6 mm, length 10 mm, and width 10 mm, and then a small drop of liquid crystal (JC-5015LA; manufactured by JNC Corporation) was dropped into the frame of the seal pattern. Furthermore, an in-plane spacer (Natco Spacer KSEB-525F; manufactured by Natco Corporation; gap width after lamination 5 μm) was sprayed on another photo-alignment substrate, which was then thermally fixed, and the substrate with the liquid crystal droplets was laminated in a vacuum using a lamination device. After 3 minutes of exposure to the atmosphere, a mask was placed only on the seal pattern frame, and UV light (measurement wavelength: 365 nm) was irradiated with 3000 mJ/cm ² ultraviolet light using a UV irradiator, and the substrate was then placed in an oven and thermally cured at 120 ° C for 60 minutes to prepare a liquid crystal cell for evaluation.
[Interference fringe observation]
The liquid crystal cell for evaluation was observed with an interference fringe inspection lamp (FNA-35; Funatec Corporation), and the number of dark interference fringes on the outside of the liquid crystal sealant was counted. The results are shown in Tables 1 to 3. The relationship between the average specific surface area and the number of dark interference fringes is shown in Figure 1.

[Moisture permeability]
The liquid crystal sealant produced in the examples and comparative examples was sandwiched between polyethylene terephthalate (PET) films to form a thin film with a thickness of 300 μm, which was then irradiated with ultraviolet light of 3000 mJ/cm ² (measurement wavelength: 365 nm) using a UV irradiator, placed in an oven and thermally cured at 120°C for 60 minutes, and after curing, the PET film was peeled off to obtain a sample. The moisture permeability of the sample at 60°C and 90% was measured using a moisture permeability measuring device (Lyssy: L80-5000). The results are shown in Tables 1 to 3.

[Elastic modulus]
The liquid crystal sealant produced in the examples and comparative examples was sandwiched between polyethylene terephthalate (PET) films to form a thin film with a thickness of 100 μm, which was then irradiated with ultraviolet light of 3000 mJ/cm ² (measurement wavelength: 365 nm) using a UV irradiator, placed in an oven and thermally cured at 120°C for 60 minutes, and after curing, the PET film was peeled off to obtain a sample. The sample was subjected to a tensile test at room temperature (25°C) and a test speed of 5 mm/min using a Tensilon universal testing machine (manufactured by A&D Co., Ltd., RTG-1210) to measure the strength. The results are shown in Tables 1 to 3.

The results in Tables 1 to 4 and Figure 1 confirm that the liquid crystal sealant of the present invention has excellent crush resistance. It was also confirmed that the liquid crystal sealant of the present invention has both flexibility and low moisture permeability.

The liquid crystal sealant of the present invention has excellent crush resistance and is both flexible and has low moisture permeability, making it particularly useful as a liquid crystal sealant for thin liquid crystal displays and curved liquid crystal displays.

Claims (8)

A liquid crystal sealant for a liquid crystal dropping method, comprising a curable compound, a filler, and a heat curing agent,
The filler contains an organic filler and an inorganic filler, and the inorganic filler is subjected to a hydrophobic surface treatment,
The average specific surface area of the filler is 10.0 m ² /g or more, and the particle size of the filler is 0.01 to 1.0 μm;
The viscosity measured using an E-type viscometer at 25° C. and 5 rpm is less than 500 Pa s,
A liquid crystal sealant for the liquid crystal dropping method, in which the moisture permeability of the cured product at a film thickness of 300 μm, measured at 60°C and 90%, is 100 g/ ^m2 ·24 h or less. The liquid crystal sealant for the liquid crystal dropping method according to claim 1, wherein the elastic modulus of the cured product at 25°C measured with a Tensilon universal testing machine is 2500 MPa or less. The liquid crystal sealant for the liquid crystal dropping method according to claim 1 or 2, wherein the content of the filler is 5 parts by mass or more and less than 50 parts by mass per 100 parts by mass of the curable compound. The liquid crystal sealant for a liquid crystal dropping process according to claim 1 , wherein the curable compound comprises a urethane (meth)acrylate. The liquid crystal sealant for the liquid crystal dropping method according to claim 4 , wherein the urethane (meth)acrylate is obtained by reacting (a) a polyol having an aromatic ring, (b) an organic polyisocyanate, and (c) a hydroxyl group-containing (meth)acrylate. The liquid crystal sealant for a liquid crystal dropping method according to claim 1 , further comprising a thermal radical polymerization initiator. The liquid crystal sealant for a liquid crystal dropping process according to claim 1 , further comprising a photoradical polymerization initiator. A liquid crystal display cell sealed with the liquid crystal sealant for a liquid crystal dropping process according to claim 1 .

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