JPH0713174A - Sealing agent for liquid crystal - Google Patents

Abstract

PURPOSE:To obtain a sealing agent for liquid crystal excellent in heat resistance, moisture resistance, adhesion strength, etc., with which misalignment of substrates and gap defect can be prevented, especially, diffusion of monomers after screen printing can be prevented, by incorporating polycarbonate-modified urethane acrylate, glycerol monoacrylate, monomers having ethylenic unsatd. groups, and photopolymn. initiator. CONSTITUTION:This sealing agent contains polycarbonate-modified urethane acrylate, glycerol monoacrylate, monomers having polymerizable ethylenic unsatd. groups in the molecule, and photopolymn. initiator as the essential component, and consists of an electron beam-or UV-curing resin. The polycarbonate modified urethane acrylate is synthesized by compounding polycarbonate polyols, diisocyanate, and hydroxyl group-contg. (meth)acrylates properly selected according to the purpose such as hardening property, viscosity, flexibility. As for the photopolymn. initiator, any compd. can be used as far as it produces free radicals by irradiation of electron beams or UV rays.

Description

Detailed Description of the Invention

[0001]

This invention relates to a liquid crystal sealant.

[0002]

2. Description of the Related Art A conventional liquid crystal display panel having a structure in which liquid crystal is sealed between two substrates with electrodes is manufactured as follows.

That is, one substrate with electrodes is coated with a sealant by screen printing or a dispenser, the other substrate with electrodes is superposed with a bead-shaped or rod-shaped spacer agent interposed therebetween, and both are sealed under pressure. The agent is cured and liquid crystal is sealed between the two substrates with electrodes.

Conventionally, as a sealant, a thermosetting type one-component epoxy resin having excellent adhesiveness and moisture resistance has been used.

It has also been proposed to use a light (ultraviolet) curable adhesive containing epoxy acrylate as a main component (Japanese Patent Laid-Open No. 1-243029).

[0006]

However, when a thermosetting adhesive is used as the sealant, it is excellent in reliability such as moisture resistance, but in the manufacturing process, the curing method requires about 2 hours or more for heat curing. This requires a long time, which hinders work efficiency.

Further, a lateral shift occurs between two pre-aligned substrates, and a gap varies.

On the other hand, when a light (ultraviolet) curable resin is used, the curing can be carried out at room temperature in a short time, so that a lateral shift occurs between the two substrates during the curing of the sealant, and a gap variation. However, after screen printing, the monomer component was volatilized, so the resin was in a solidified state, and the gap could not be sufficiently removed even when pressure was applied, and the adhesive strength was not sufficiently expressed. .

[0009]

[Means for Solving the Problems] In order to solve the above problems, in the present invention, (A) polycarbonate modified urethane acrylate, (B) glycerol monomethacrylate, (C) at least one or more polymerizable compounds in the molecule The present invention proposes a liquid crystal sealant composed of a monomer having an ethylenically unsaturated bond, (D) an electron beam and a UV curable resin containing a photopolymerization initiator as an essential component.

In addition to the above components, a coupling agent for improving adhesiveness, an inorganic filler for adjusting viscosity, and a spacer agent for adjusting gap are added to the sealant composition of the present invention. You may.

Further, the polycarbonate-modified urethane acrylate of the item (A) comprises a polycarbonate polyol represented by the following general formula (1), a diisocyanate and a hydroxyl group-containing (meth) acrylate for the purpose of curability, viscosity, flexibility and the like. It is possible to use the one which is selected and blended according to the necessity and synthesized.

[0012]

[Chemical 1]

(In the formula, R ₁ and R ₂ are the same or different divalent hydrocarbon groups, or the same or different divalent groups consisting of the same or different hydrocarbon groups connected to each other by an ether bond or an ester bond. , N represents an average number of 1 to 60.)

The glycerol monomethacrylate of the item (B) is represented by the following structural formula.

[Chemical 2]

Examples of the monomer having at least one polymerizable ethylenic unsaturated bond in the molecule of the item (C) include 2-hydroxyethyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate.
Hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, trimethylolpropane tri (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, Dicyclopentadienyl diacrylate, glycidyl methacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate,
1,2-propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate,
Diglycerol tetra (meth) acrylate, glycerin tri (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, 2-
Hydroxy-3-phenoxypropyl (meth) acrylate, glycidol dimethacrylate, pentaerythritol triacrylate, tetrahydrofluhir (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, neopentyl glycol di (meth) ) Acrylate, 1,6-
Hexanediol di (meth) acrylate, tri (meth) acryloxyethyl phosphate, allyl acrylate, N-vinylpyrrolidone, vinyl acetate and the like.

Examples of the photopolymerization initiator of the item (D) include 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone and 2-hydroxy-
2-Methyl-1-phenylpropan-1-one, diethoxyacetophenone, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, benzophenone, benzoinisopropyl ether, methylphenylglyoxylate Compounds which generate radicals upon irradiation with electron beams and ultraviolet rays such as can be used in the present invention.

In addition to the above-mentioned components, various additives may be added to the liquid crystal sealant according to the present invention as required. For example, a coupling agent or bis [(2- Hydroxyethyl) methacrylate]
It is also possible to add a phosphorus compound such as acid phosphate, a coloring agent such as a dye or a pigment, a polymerization inhibitor, an antioxidant, a leveling agent, and a spacer agent for adjusting a gap.

When a liquid crystal display panel is manufactured using the liquid crystal sealant according to the present invention, the sealant is screen-printed or dispenser coated on one surface of the two electrode-attached substrates to seal the liquid crystal. Then, the sealing agent is cured by irradiating electron beams or ultraviolet rays with the substrates stacked.

[0019]

EXAMPLES Examples and comparative examples of the present invention are shown in Table 1 below. In Examples 1 to 3, glycerol monomethacrylate was blended with the polycarbonate-modified urethane acrylate to evaporate the monomer after screen printing, the adhesiveness,
Orientation etc. were confirmed.

In Comparative Example 1, polyether-modified urethane acrylate was used as the base material, in Comparative Example 2, 2-hydroxyethyl methacrylate was used instead of glycerol monomethacrylate, and in Comparative Example 3, 2,2-
Using bis [4- (methacryloxyethoxy / diethoxy) phenyl] propane, the volatilization of the monomer after screen printing, the adhesiveness, the orientation, etc. were confirmed.

[0021]

[Table 1]

According to this, in the example in which glycerol monomethacrylate was blended with the polycarbonate-modified urethane acrylate, it was confirmed that the volatilization of the monomer after screen printing was suppressed even when the other monomer components were blended at the same time.

On the other hand, in Comparative Example 1, by using glycerol monomethacrylate, the volatilization of the monomer after screen printing can be suppressed, but problems occur in the heat resistance and the orientation after the humidity resistance test.

In Comparative Example 2, since 2-hydroxyethylmethacrylate, which is a monomer component, was volatilized after the screen printing, an attempt was made to bond 1 hour after printing, but the gap could not be sufficiently secured.

In Comparative Example 3, since the boiling point of 2,2-bis [4- (methacryloxyethoxy.diethoxy) phenyl] propane is high, the volatilization of the monomer can be suppressed. As a result, there is a problem.

[0026]

As described above in detail, the liquid crystal sealant according to the present invention has the adhesiveness originally required as a sealant,
It has excellent moisture resistance and heat resistance, and does not cause misalignment during high-temperature and high-humidity operation, etc., and can prevent volatilization of monomers after screen printing, so it is sufficient for alignment during bonding. It satisfies the characteristic of being able to obtain excellent time.

Further, since the liquid crystal sealant according to the present invention can be cured in a short time and without heating, it is possible to improve productivity, and further, it is possible to eliminate misalignment between substrates and a gap defect. Therefore, a highly reliable liquid crystal display panel can be obtained.

[Procedure amendment]

[Submission date] June 22, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

[0021]

[Table 1]

Claims (1)

[Claims] 1. (A) Polycarbonate-modified urethane acrylate, (B) Glycerol monomethacrylate, (C)
A liquid crystal sealant comprising a monomer having at least one polymerizable ethylenically unsaturated bond in the molecule and (D) a photopolymerization initiator as essential components.