JP2001059016A - Epoxy resin composition for flow casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition capable of providing a resin board having a good accuracy of thickness, and a transparent resin board for a liquid crystal display element by a flow casting method by including a specific epoxy resin and an acid anhydride-based hardening agent. SOLUTION: This epoxy resin composition comprises (A) an epoxy resin preferably containing 25-70 wt.% epoxy resin solid at normal temperature, [preferably an epoxy resin of formula I (R1 is an organic compound residue having y active hydrogens; n1, n2.ny are each 0-100 with the proviso that the total thereof is 1-100; y is 1-100; A is a group having a substituent and represented by formula II, Z is a group of formula III or the like, and the formula I includes one or more groups of formula III)], and (B) an acid anhydride- based hardening agent, preferably in an amount regulated so that the amount of the acid anhydride group of the component B may be 0.7-1.2 eq. based on 1 eq. epoxy group of the component A. For example, a compound obtained by partially esterifying 4-methylhexahydrophthalic anhydride with a cyclic alcohol of formula IV can be used as the component B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an epoxy resin composition for producing a resin plate by a casting method, a resin plate comprising a cured product obtained by curing the same, a transparent resin plate for a liquid crystal display element, and Relates to a liquid crystal display device.

[0002]

2. Description of the Related Art A transparent resin plate is used for a liquid crystal cell of a liquid crystal display device. As a transparent resin plate for a liquid crystal display element, a plate made of a thermoplastic resin or a thermosetting resin is used, but as a substitute for a glass plate, heat resistance,
From the viewpoint of optical isotropy and the like, thermosetting resins are more preferably used. A liquid epoxy resin is mainly used as the thermosetting resin, and the above-described plate is manufactured by a casting method.

[0003]

However, in the casting method, since the production efficiency is low and mass production is difficult, it is desired to improve the production efficiency by the casting method. The casting method is, for example, a production method in which a liquid resin is spread in a sheet shape on a rotating smooth stainless steel endless belt and is continuously formed, but the conventional liquid method used in the above casting method is used. When an epoxy resin is used in this casting method, the resin has a low viscosity, so that the resin flows unnecessarily on the stainless steel belt, and the thickness of the obtained plate varies greatly. When a resin plate having a thickness variation is used for a transparent resin plate for a liquid crystal display element, fatal defects such as color unevenness and luminous intensity unevenness are given to a display function of a liquid crystal display device obtained by using the resin plate.

[0004] The casting method is a method of molding a thermoplastic resin sheet, and no example of molding a thermosetting epoxy resin sheet by the casting method has been reported in the past. Conventionally, as an epoxy resin composition, a low-viscosity liquid used for casting or potting as described above, printing, and the like, and a solid material having no fluidity at room temperature as a transfer molding material for sealing semiconductor elements and the like. However, there is no known epoxy resin composition suitable for producing a resin plate by a casting method.

An object of the present invention is to provide an epoxy resin composition capable of producing a resin plate having good thickness accuracy and a transparent resin plate for a liquid crystal display element by a casting method. further,
An object of the present invention is to provide a resin plate manufactured using the epoxy resin composition, a transparent resin plate for a liquid crystal display element, and a liquid crystal display device obtained using the transparent resin plate for a liquid crystal display element. .

[0006]

Means for Solving the Problems In order to achieve the above object, the epoxy resin composition of the present invention is characterized by containing the following components (A) and (B). (A) An epoxy resin containing 25 to 70% by weight of a solid epoxy resin at normal temperature. (B) an acid anhydride-based curing agent;

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Since the epoxy resin composition of the present invention is formed into a resin plate by a casting method, it is usually in a liquid state at ordinary temperature, but may be in a solid state. Can be used. Here, normal temperature is usually
Means 25 ° C. When the epoxy resin composition is liquid at normal temperature, the viscosity at 25 ° C. is preferably 50 to 400 poise, and more preferably 75 to 150 poise. Also,
When the epoxy resin composition is solid at room temperature, it is heated and melted to have a viscosity of 50 to 400 poise, and more preferably 75 to 150 poise.
It is preferable to adjust the poise to use. When the viscosity is less than 50 poise, the resin flows unnecessarily on the stainless steel belt during casting, and the thickness of the obtained plate tends to vary widely. On the other hand, when the viscosity is more than 400 poise, there is a tendency that casting workability is deteriorated, and that bubbles are present and defects in appearance are caused. This viscosity can usually be measured with a rotary E-type viscometer.

In order to adjust the viscosity of the epoxy resin composition to the above-mentioned range, the epoxy resin of the component (A) and the acid anhydride-based curing agent of the component (B) which are specifically described below are appropriately used. It is possible by selecting and combining.

In the present invention, the epoxy resin as the component (A) is an epoxy resin containing 25 to 70% by weight of an epoxy resin which is solid at room temperature. The more preferable content of the epoxy resin which is solid at room temperature is 35 to 60% by weight. Here, normal temperature usually means 25 ° C. In addition, solid at room temperature means that it includes a semi-solid like a paste.

[0010] The content of epoxy resin solid at room temperature is 25
When the amount is less than 10% by weight, the viscosity of the epoxy resin composition becomes lower than the viscosity suitable for the casting method, and the resin plate and the resin for a liquid crystal display element are formed by curing the epoxy resin composition. There is a tendency that good plate thickness accuracy cannot be obtained. That is, by containing a predetermined amount of the epoxy resin which is solid at room temperature, a viscous effect is exhibited, and even when heat-cured at the time of casting and after casting, a sharp decrease in viscosity due to a temperature rise is unlikely to occur, and continuous precision is achieved. Thickness control can be performed. Further, when the content of the epoxy resin solid at room temperature is more than 70% by weight, the viscosity of the epoxy resin composition becomes higher than the viscosity suitable for the casting method, and the casting workability deteriorates, Bubbles tend to be present and cause defects in appearance.

As the epoxy resin which is solid at room temperature,
There is no particular limitation, conventionally known epoxy resins,
For example, nitrogen-containing epoxy resins such as bisphenol A epoxy resin, bisphenol F epoxy resin, phenol novolak epoxy resin, cresol novolak epoxy resin, alicyclic epoxy resin, triglycidyl isocyanurate, hydantoin epoxy resin, and water addition Bisphenol A type epoxy resin, aliphatic epoxy resin, glycidyl ether type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin which is the main type of low water absorption cured type, dicyclo ring type epoxy resin, naphthalene type epoxy resin, etc. These may be used alone or in combination. Among the above various epoxy resins, when transparency and discoloration resistance are required such as a transparent resin plate for a liquid crystal display element, bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, triglycidyl It is preferred to use isocyanurates. Among them, an alicyclic epoxy resin represented by the following general formula (1) is particularly preferable.

[0012]

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As the epoxy resin that is solid at room temperature as described above, an epoxy resin having an epoxy equivalent of 90 to 1000 and a softening point of 160 ° C. or less is preferably used. When the epoxy equivalent is less than 90, the cured product of the epoxy resin composition becomes brittle, and when the epoxy equivalent exceeds 1,000, the Tg of the cured product becomes low.

The epoxy resin of the above component (A) is
It contains a liquid epoxy resin at room temperature in addition to the epoxy resin solid at room temperature. The epoxy resin that is liquid at room temperature is not particularly limited, and conventionally known epoxy resins, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, water-containing bisphenol A type epoxy resin, Examples thereof include aliphatic epoxy resins, glycidyl ether type epoxy resins, and bisphenol S type epoxy resins, which may be used alone or in combination. Among the above various epoxy resins, as a transparent resin for a transparent resin plate for a liquid crystal display element, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, an alicyclic type It is preferable to use an epoxy resin. Among them, an alicyclic epoxy resin represented by the following general formula (2) is particularly preferable.

[0015]

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As the epoxy resin liquid at room temperature as described above, an epoxy resin having an epoxy equivalent of 90 to 950 is generally used.

In the present invention, as the acid anhydride-based curing agent as the component (B), those having a molecular weight of about 140 to 200 are preferably used. For example, phthalic anhydride, maleic anhydride, trimellitic anhydride, Pyromellitic acid, hexahydrophthalic anhydride, tetrahydrophthalic anhydride,
Colorless or pale yellow acid anhydrides such as methylnadic anhydride, nadic anhydride, glutaric anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride and the like can be mentioned. These may be used alone or in combination of two or more. And, among the above-mentioned acid anhydride-based curing agents, it is preferable to use phthalic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, and methylhexahydrophthalic anhydride.

Furthermore, in addition to the above-mentioned acid anhydride-based curing agents, conventionally known amine-based curing agents, phenol-based curing agents, those obtained by partially esterifying the above-mentioned acid-anhydride-based curing agents with alcohol, and hexahydrophthalic acid , A curing agent such as carboxylic acid such as tetrahydrophthalic acid and methylhexahydrophthalic acid may be used alone or in combination. When a carboxylic acid is used in combination, the curing speed can be increased and the productivity of the resin plate can be improved.

The mixing ratio of the epoxy resin ((A) component) and the acid anhydride-based curing agent ((B) component) is based on 1 equivalent of the epoxy group in the epoxy resin, and It is preferable that the acid anhydride group is set to be 0.5 to 1.5 equivalents. Particularly preferably 0.7 to 1.2
Is equivalent. That is, in the above mixing ratio, when the acid anhydride group is less than 0.5 equivalent, the hue after curing of the obtained epoxy resin composition becomes worse, and conversely, when it exceeds 1.5 equivalents,
This is because the moisture resistance tends to decrease.

As the curing agent, in addition to the acid anhydride-based curing agent, the above-mentioned amine-based curing agent, phenol-based curing agent, acid anhydride-based curing agent partially esterified with alcohol, or hexahydrophthalic acid, tetrahydro- Even when a curing agent such as a carboxylic acid such as phthalic acid or methylhexahydrophthalic acid is used in combination, the compounding ratio is based on the compounding ratio (equivalent ratio) using the acid anhydride-based curing agent.

The above-mentioned acid anhydride-based curing agent partially esterified with an alcohol is obtained by esterifying a part of the acid anhydride groups of the acid anhydride-based curing agent with an alcohol by a reaction represented by the following chemical reaction formula. Things.

[0022]

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The epoxy resin composition for casting further increases the reaction rate, and the time of the low melt viscosity state during curing is appropriately shortened to form a uniform resin plate. For this purpose, it is usually preferable to react 0.1 to 0.6 equivalent of the hydroxyl group of the alcohol with respect to 1 equivalent of the acid anhydride group. At this time, when the hydroxyl group of the alcohol is more than 0.6 equivalent, good heat resistance of the resin plate and the resin plate for a liquid crystal display element cannot be obtained.

The alcohol may be a monohydric or dihydric or higher polyhydric alcohol, and is not particularly limited. Polyhydric alcohols do not sublime during heating and lower the heat resistance of the cured epoxy resin composition. Not preferred. For example, monohydric alcohols include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, phenol, benzyl alcohol, allyl alcohol, cyclobutanol, cyclopentanol, cyclohexanol, etc., and dihydric alcohols include ethylene glycol, triethylene Glycol, propylene glycol, dipropylene glycol, hydroquinone,
Catechol, resorcin and the like, and trihydric or higher polyhydric alcohols include glycerin, pyrogallol, pentit and hexit.

[0025] Among the alcohols, cyclic alcohols are preferable, and cyclic polyhydric alcohols are more preferable. For example, monohydric cyclic alcohols include phenol, benzyl alcohol, cyclobutanol, cyclopentanol, cyclohexanol, and the like, and divalent or higher-valent cyclic polyhydric alcohols include hydroquinone, catechol, resorcinol, pyrogallol, and hydroxyhydroquinone. , Phloroglucin, p-dihydroxycyclohexane, o-dihydroxycyclohexane, m-dihydroxycyclohexane, 1,2,3-trihydroxycyclohexane, 1,2,4-trihydroxycyclohexane, 1,3,5-trihydroxycyclohexane, phenol novolak , Cresol novolak, or
Examples include a cyclic alcohol represented by the following general formula (3).

[0026]

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The above alcohols are used alone or in combination of two or more. Among the alcohols, cyclic alcohols represented by the general formula (3) are particularly preferable in consideration of heat resistance and transparency required for the resin plate and the transparent resin plate for a liquid crystal display element.

In addition to the components (A) and (B), the epoxy resin composition of the present invention may further comprise, if necessary, a conventionally used curing accelerator, deterioration inhibitor, modifier, silane cup, etc. Conventionally known various additives such as a ring agent, a leveling agent, a release agent, a dye, and a pigment can be appropriately compounded.

The curing accelerator is not particularly restricted but includes, for example, 1,8-diaza-bicyclo (5,
(4,0) tertiary amines such as undecene-7 and triethylenediamine, 2-ethyl-4-methylimidazole, 2
Imidazoles such as -methylimidazole, triphenylphosphine, tetraphenylphosphonium tetraphenylborate, tetra-n-butylphosphonium-o,
Examples include phosphorus compounds such as o-diethyl phosphorodithioate, quaternary ammonium salts, organic metal salts, and derivatives thereof. These may be used alone or in combination of two or more. It is preferable to use tertiary amines, imidazoles, and phosphorus compounds among the curing accelerators. Among them, a phosphorus compound is particularly preferable in order to obtain a transparent and tough epoxy resin cured product having a low degree of coloring.

The curing accelerator may be encapsulated in microcapsules, if necessary. By doing so, the curing of the epoxy resin composition during casting is prevented from abruptly progressing, the increase in viscosity is suppressed, and the thickness of the resin plate is poor,
It can prevent poor appearance and the like, and is particularly suitable when the epoxy resin composition is used while being heated.
Examples of the wall film material of the microcapsules include a cured epoxy resin, polystyrene, polymethacrylic acid, an ethylene-vinyl acetate copolymer, a polyurea resin, and a polyurethane resin.

The content of the curing accelerator is preferably set in the range of 0.01 to 8.0% by weight, more preferably 0.1% by weight, based on the epoxy resin (component (A)).
~ 3.0% by weight. That is, when the amount of the curing accelerator is less than 0.01% by weight, a sufficient curing promoting effect cannot be obtained, and when the amount exceeds 8.0% by weight, discoloration may be observed in the cured product of the epoxy resin composition. Because there is.

Examples of the above-mentioned deterioration inhibitor include conventionally known compounds such as phenol compounds, amine compounds, organic sulfur compounds and phosphine compounds.

Examples of the modifier include conventionally known glycols, silicones, alcohols and the like.

Examples of the silane coupling agent include silane coupling agents and titanate coupling agents known in the art.

The epoxy resin composition of the present invention is, for example,
It can be manufactured as follows. That is, the components (A) and (B) and, if necessary, a conventionally known curing accelerator, a deterioration inhibitor, a modifier, a silane coupling agent, a leveling agent, a release agent, a dye, a pigment, Mix in proportions. Then, if necessary, this is heated and mixed or kneaded to obtain an epoxy resin composition.

In order to obtain good heat resistance, the resin plate or the transparent resin plate for a liquid crystal display element has a Tg of 150 ° C.
The above components (A) and (B) can be arbitrarily blended so that the temperature is preferably 180 ° C. or higher.

The resin plate of the present invention may or may not be transparent. The transparency of the resin plate and the transparent resin plate for a liquid crystal display element of the present invention means that, at a thickness of 0.4 mm, the light transmittance at a wavelength of 600 nm is 6 as measured by a spectrophotometer.
0% or more, preferably 80% or more.

Next, a method for producing a resin plate and a transparent resin plate for a liquid crystal display element by a casting method using the epoxy resin composition of the present invention will be described with reference to the production process example of FIG. In the casting method illustrated in FIG. 1, the endless belt 1 made of stainless steel is divided into a driving drum 11 and a driven drum 12.
Through, for example, 0.1 to 10 m / min, preferably
The vehicle is driven at a constant speed such as 0.2 to 5 m / min.

While running the endless belt 1 made of stainless steel at the above-mentioned constant speed, first, an easily peelable resin liquid 3 is applied to the stainless steel through the die 2 and dried, or if necessary, heated or lighted. The resin layer 31 is cured by irradiation or the like. In FIG. 1, an ultraviolet irradiation device 4 is provided.

Examples of the resin easily peelable from stainless steel include urethane resins, acrylic resins, polyester resins, polyvinyl alcohol, ethylene vinyl alcohol copolymer, vinyl chloride resins, vinylidene chloride resins, and the like. Polynorbornene resin, polycarbonate resin, polyarylate resin and the like can be mentioned.

Next, the epoxy resin composition 6 of the present invention is applied on the resin layer 31 through the die 5 and is spread in a sheet shape. The spread layer 61 is appropriately heated by a heating method or a light irradiation method. After forming a cured sheet 62 in close contact with the resin layer 31 through a curing device 7, the cured sheet 62 is recovered together with the resin layer 31 from the endless belt 1 made of stainless steel, and the long resin is removed. The plate 8 can be manufactured continuously. Further, the formed long resin plate 8 is cut into an appropriate size through an appropriate cutting means such as a laser beam, an ultrasonic cutter, dicing, or a water jet, so that the transparent resin plate for a liquid crystal display element of the present invention is cut. Can be manufactured.

The thickness of the resin plate of the present invention and the transparent resin plate for a liquid crystal display element are 500 μm or less, preferably 100 μm, in order to reduce the thickness and weight of the liquid crystal display element and to maintain sufficient strength. ４００400 μm, more preferably 200-300 μm.

The thickness accuracy is ± 15 μm or less,
Further, it is preferably ± 10 μm or less. This thickness accuracy is the maximum value with respect to the average thickness when measuring the thickness of the long resin plate 8 manufactured by the casting method at 10 points at equal intervals in the width direction and at intervals of 60 mm in the length direction. And the minimum value.

Using the above transparent resin plate for a liquid crystal display element,
The method for manufacturing the liquid crystal display device may be the same as the method using a conventional glass plate. That is, a liquid crystal display device can be manufactured by sequentially installing a transparent conductive film, a color filter, a liquid crystal alignment film, and the like on the transparent resin plate for a liquid crystal display element, assembling a cell, and sealing liquid crystal in the cell. .

The use of the resin plate of the present invention is not limited, and can be used not only for the above-mentioned transparent resin plate for a liquid crystal display element, but also for a touch panel, an electromagnetic wave sealing material, a solar cell cover and the like. It is.

[0046]

EXAMPLES Next, examples will be described together with comparative examples.

First, the following epoxy resin, acid anhydride-based curing agent, and curing catalyst were prepared.

[Epoxy resin A] An alicyclic epoxy resin solid at normal temperature represented by the following general formula (4) (epoxy equivalent: 185)

[0049]

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[Epoxy resin B] An alicyclic epoxy resin which is liquid at normal temperature and represented by the following general formula (2) (epoxy equivalent: 145)

[0051]

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[Acid anhydride-based curing agent A] 4-methylhexahydrophthalic anhydride is a cyclic alcohol represented by the following general formula (3), wherein a hydroxyl group is added in an amount of 0.1 equivalent to an acid anhydride group.
One obtained by reacting 3 equivalents to partially esterify. (Specifically, 4-methylhexahydrophthalic anhydride and the above-mentioned cyclic alcohol were reacted in the composition shown in parentheses below the acid anhydride-based curing agent in Table 1.)

[0053]

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[Acid anhydride curing agent B] 4-methylhexahydrophthalic anhydride

[Curing accelerator] Tetra-n-butylphosphonium-o, o-diethylphosphorodithioate

The components shown in Tables 1 and 2 were blended in the proportions shown in the same table and melt-mixed to obtain the epoxy resin compositions of Examples 1 to 5 and Comparative Examples 1 and 2.

[0057]

[Table 1]

[0058]

[Table 2]

Further, the epoxy resin composition obtained
The viscosities at ° C. are shown in Tables 3 and 4. The viscosity was measured using a rotary E-type viscometer.

Then, these epoxy resin compositions are
Due to the production process of the casting method shown in FIG.
A transparent resin plate was prepared at a temperature of 5 ° C. and a belt traveling speed of 5 m / min, and cut into a predetermined size by a laser beam to obtain a transparent resin plate for a liquid crystal display element. As a result, as shown in Tables 3 and 4, both the transparent resin plates for liquid crystal display elements of Examples and Comparative Examples had good Tg (glass transition point) and light transmittance, and were determined by the above-mentioned method. The average thickness of each resin plate was 400 μm. Regarding the thickness accuracy, Examples 1 to 5 are superior to Comparative Example 1. Among them, Examples 2 to 4 have a particularly preferable thickness accuracy because the content of the epoxy resin solid at room temperature is in a particularly preferable range. It was good. In Comparative Example 2, although the thickness accuracy was good, visual inspection of the appearance revealed that the resin plate contained bubbles and the appearance was poor. (In Tables 3 and 4, good appearance was indicated by 、 and poor appearance was indicated by x.)

[0061]

[Table 3]

[0062]

[Table 4]

Using these transparent resin plates for a liquid crystal display element, a liquid crystal display device was manufactured in the same manner as in the conventional method using a glass plate. As a result, a clear display image with very little color unevenness and luminous intensity unevenness was obtained.

[0064]

As described above, the epoxy resin composition of the present invention contains, as an epoxy resin, an epoxy resin (component (A)) containing 25 to 70% by weight of an epoxy resin solid at room temperature. Therefore, it has a viscosity suitable for molding an epoxy resin sheet by the casting method, and the thickness accuracy of the resin plate obtained by the casting method and the transparent resin plate for the liquid crystal display element is remarkably compared to the conventional liquid epoxy resin. improves. Furthermore, a liquid crystal display device manufactured using the transparent resin plate for a liquid crystal display element has a very good display image.

[Brief description of the drawings]

FIG. 1 is an explanatory side view of an example of a production process of a casting method.

[Explanation of symbols]

 1: Endless belt made of stainless steel 31: Resin layer 61: Spread layer of epoxy resin composition 7: Curing device 62: Cured sheet 8: Resin plate

Continued on the front page F-term (reference) 2H090 JA09 JB03 JC01 JD15 4F071 AA42 AC09 AC10 AC12 AE02 AE03 AH12 BA02 BB02 BC01 4J036 AA01 AA05 AD01 AD21 AF27 AJ03 AJ05 AJ08 AJ09 AJ11 DB15 DC45 DD07 FA10 FA12 FA13

Claims (5)

[Claims] An epoxy resin composition for producing a resin plate by a casting method, comprising the following components (A) and (B): (A) An epoxy resin containing 25 to 70% by weight of a solid epoxy resin at normal temperature. (B) an acid anhydride-based curing agent; 2. The epoxy resin composition according to claim 1, wherein the epoxy resin solid at room temperature is represented by the following general formula (1). Embedded image 3. A resin plate comprising a cured product obtained by curing the epoxy resin composition according to claim 1 or 2. 4. A transparent resin plate for a liquid crystal display device, comprising a cured product obtained by curing the epoxy resin composition according to claim 1. 5. A liquid crystal display device using the transparent resin plate for a liquid crystal display element according to claim 4.