JPH0713175A - 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, and especially, storage stability and productivity of a liquid crystal display panel can be improved, by incorporating isobornyl (meth)acrylate, epoxyacrylate, photopolynm. initiator, epoxy resin, and latent thermosetting agent. CONSTITUTION:This sealing agent contains isobornyl (meth)acrylate, epoxyacrylate, photopolymn. initiator, compd. having polymerizable glycidyl groups in the molecule, and latent thermosetting agent as the essential component. When this sealing agent for liquid crystal is used for the production of a liquid crystal display panel, the sealing agent is interposed between two substrates having electrodes and irradiated with light (UV rays) in the laminated state for first hardening of the sealing agent. Then a liquid crystal is sealed between the two electrode substrates and the sealing agent is completely hardened by isotropic heat treatment. Thereby, long-time heating to harden the sealing agent is not necessary so that the productivity is improved.

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, the epoxy acrylate-based ones that have been used in the past are not sufficiently satisfactory in adhesive strength, and the polyether-based urethane acrylate and polyester-modified urethane acrylates are the main components. In a reliability test such as humidity resistance, the orientation was deteriorated, which was not satisfactory.

For this reason, a sealing agent having both a light (ultraviolet) curable functional group and a thermosetting functional group has been proposed.
The storage stability is poor, or when manufacturing a liquid crystal display panel, it adopts a process of encapsulating the liquid crystal by heat curing after irradiation with ultraviolet rays, so productivity is improved even when compared with a one-component epoxy resin. It didn't reach.

[0010]

[Means for Solving the Problems] In order to solve the above problems, in the present invention, (A) isobornyl (meth) acrylate, (B) epoxy acrylate, (C) photopolymerization initiator, (D) intramolecular A liquid crystal sealant containing at least one compound having a polymerizable glycidyl group and (E) a latent thermosetting agent as an essential component.
It is a plan.

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

The isobornyl (meth) acrylate of the item (A) is a compound represented by the following general formula (1) or (2).

[0013]

[Chemical 1]

The epoxy (meth) acrylate in the item (B) is a substance obtained by reacting an epoxy resin with (meth) acrylic acid in an amount approximately equivalent to the epoxy groups of the epoxy resin, or an epoxy resin. It is a substance obtained by reacting a mixture of a (meth) acrylate having an epoxy group and an equivalent amount of a carboxyl group with a polybasic acid.

Examples of the epoxy (meth) acrylate include bisphenol A type diglycidyl ether type,
Addition reaction products of epoxy resins such as glycerin diglycidyl ether type, polyalkylene glycol diglycidyl ether type, polybasic acid diglycidyl ester type, cyclohexene oxide type with (meth) acrylic acid or (meth) acrylate having a carboxyl group Can be mentioned.

Examples of the photopolymerization initiator of the item (C) 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 that generate radicals upon irradiation with ultraviolet rays such as the above can be used in the present invention.

The compound having at least one polymerizable glycidyl group in the molecule of the item (D) includes an epoxy resin having one or more glycidyl groups in one molecule, and ring-opening polymerization of the glycidyl group. Although the epoxy resin etc. which generate | occur | produce can be mentioned, it is not specifically limited in this invention.

Here, as the epoxy resin, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin or the like, or an epoxy resin obtained by adding them in water, novolac type epoxy resin, (mono) glycidyl ester type epoxy resin. Examples thereof include resins, urethane-modified epoxy resins, nitrogen-containing epoxy resins obtained by epoxidizing meta-xylenediamine, and rubber-modified epoxy resins containing polybutadiene, NBR, etc., but are not limited to these, and It can be used in any form, liquid or liquid.

Further, as the latent heat curing agent of the item (E),
Generally used latent thermosetting agents such as dicyandiamide, dibasic acid hydrazides, imidazoles, imidazole / epoxy adducts, boron trifluoride amine complex can be used.

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]
Add phosphorus compounds such as acid phosphates, coloring agents such as dyes and pigments, polymerization inhibitors, antioxidants, leveling agents, inorganic fillers for adjusting viscosity, spacer agents for adjusting gaps, etc. It is also possible.

Further, according to the present invention, when manufacturing a liquid crystal display panel, light (ultraviolet rays) is irradiated on the two electrode-attached substrates with the liquid crystal sealant sandwiched therebetween to cause primary curing of the sealant. Since the sealing agent can be completely cured by isotropic heat treatment after enclosing the liquid crystal between the two electrode substrates in 1st, there is no need to heat for a long time to cure the sealing agent. The productivity can be improved as compared with the epoxy resin.

[0022]

EXAMPLES Examples and comparative examples of the present invention are shown in Table 1 below. In Examples 1 and 2, the thermosetting component isobornyl methacrylate was blended in addition to the light (ultraviolet) curing component,
The storage stability, adhesiveness, orientation, etc. were confirmed.

In Comparative Examples 1 and 2, 2-hydroxyethyl methacrylate was blended in place of isobornyl methacrylate, and storage stability, adhesiveness, orientation and the like were confirmed.

[0024]

[Table 1]

According to this, in Examples 1 and 2, the mixing ratio of the light (ultraviolet) curing component and the thermosetting component was changed, but since isobornyl methacrylate was used as the monomer component, the storage stability was It can be stored at room temperature for 3 months or more, is at a practically sufficient level, and has good heat resistance and humidity resistance as a panel after curing.

On the other hand, in the case of Comparative Examples 1 and 2, the storage stability becomes extremely poor, and when a process of encapsulating liquid crystal after light (ultraviolet) curing and heat curing during the isotropic treatment is adopted. Orientation deteriorates when heat is applied.

[0027]

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, and also has excellent storage stability.

Further, according to the liquid crystal sealant of the present invention, it is possible to perform primary curing with ultraviolet rays in the production of a liquid crystal display panel and completely cure it with heat such as isotropic treatment after encapsulating the liquid crystal. Compared with one-pack epoxy resin,
Since the productivity can be improved and the positional deviation between the substrates and the gap defect can be eliminated, a highly reliable liquid crystal display panel can be obtained.

Claims (1)

[Claims] 1. An (A) isobornyl (meth) acrylate, (B) an epoxy acrylate, (C) a photopolymerization initiator,
(D) An epoxy resin having at least one polymerizable glycidyl group in the molecule, and (E) a latent thermosetting agent as an essential component, which is a liquid crystal sealant.