JP3386372B2 - Manufacturing method of epoxy optical sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an epoxy optical sheet having excellent optical properties, heat resistance, light weight, etc., which is excellent in mass productivity.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a sheet made of an epoxy resin, a casting method of injecting an epoxy resin into a gap of a casting mold to perform a curing treatment or cutting a cured epoxy resin plate into a sheet I knew how to do it. However, there has been a problem that sheet manufacturing efficiency is poor due to the need for complicated steps such as injection, mold opening, and cutting. In addition, the thickness is, for example, 500 μm in both casting method and cutting method.
When the thickness is thinner than the following, optical distortion is likely to occur, and there is a problem that it is difficult to obtain a sheet that can be used for optical applications.

With the spread of portable telephones and information devices, it is strongly desired to provide thin and lightweight liquid crystal cells. From the viewpoint of strength and heat resistance, an optical sheet made of epoxy resin serves as a cell substrate. Is expected. However, in that case, it is required to be thin and have excellent thickness accuracy, performance such as a small phase difference, and to be able to provide a large amount, but as described above, an epoxy-based optical sheet that can satisfy such requirements is required. The means of provision is unknown.

In accordance with the usual method for producing a resin sheet, an epoxy sheet can be continuously produced by a calendering method using rolling rolls, a melt extrusion method using a T die or the like, a resin solution casting method on a support, and the like. It is conceivable that the epoxy resin also has applications as an adhesive, so when the epoxy resin is molded into a sheet by such a method, the molded sheet cannot be peeled and collected by being adhered to a roll, a die, a support, or the like.
It will be damaged during peeling. In addition, there are drawbacks such that the surface tends to be uneven, and it is difficult to achieve the surface smoothness required for the optical sheet.

[0005]

DISCLOSURE OF THE INVENTION The present invention is excellent in thickness accuracy and optical characteristics and has a practical thickness of about 500 μm.
It is an object to develop a manufacturing method capable of efficiently obtaining a sheet made of the following epoxy resin.

[0006]

According to the present invention, the surface is smooth and moves sequentially.
On the support, while sequentially forming an easily peelable resin layer thereon, a liquid epoxy resin, on the resin layer,
A solid epoxy resin, a curing agent, and an epoxy resin coating liquid containing at least components of a leveling agent are sequentially spread in a sheet form and subjected to a curing treatment to form a cured sheet in close contact with the resin layer, and the cured sheet. The present invention provides a method for continuously producing an epoxy-based optical sheet, which comprises recovering from the support together with the resin layer.

[0007]

According to the production method of the present invention, an epoxy optical sheet having an easily peelable resin layer can be peeled and recovered from a support, and the surface state of the support can be adjusted by the resin layer. A sheet that can be satisfactorily transferred and reflected and that has excellent optical characteristics such as a mirror surface can be continuously and efficiently manufactured through a simple series of operations.

The mass production speed can be easily controlled by adjusting the moving speed of the spreading layer through the support, and the sheet thickness can be easily controlled by adjusting the moving speed and the spreading amount of the coating liquid. The strength and heat resistance can be easily controlled by using the resin in combination. As a result of the above, the thickness is, for example, 500 μm.
It is possible to obtain an epoxy-based optical sheet that is thin and has excellent thickness accuracy, excellent optical characteristics such as a small phase difference, and excellent heat resistance, with good mass productivity.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The production method of the present invention has a smooth surface.
While sequentially forming a resin layer that is easily peelable against it on a support that sequentially moves with , at least a liquid epoxy resin, a solid epoxy resin, a curing agent and a leveling agent are formed on the resin layer. Epoxy resin coating liquid as a component is sequentially spread in a sheet form and subjected to a curing treatment to form a cured sheet in close contact with the resin layer, and the cured sheet is collected from the support together with the resin layer to obtain an epoxy resin. The optical sheet is continuously manufactured.

An example of the manufacturing process by the above method is shown in FIG. This method shows a continuous manufacturing method by a casting method, in which a support composed of an endless belt 1 having a smooth surface is passed through a driving drum 11 and a driven drum 12 for, for example, 0.1 to 10 m / min. While running at a constant speed of 0.2 to 5 m / min, the resin liquid 3 is continuously applied onto it through the die 2 and dried, or if necessary, cured by heating or light irradiation. The film 31 is used. In the illustrated example, the ultraviolet irradiation device 4 is arranged.

Next, while the resin layer 31 is sequentially formed on the support as described above, the epoxy resin coating liquid 6 is sequentially applied on the resin layer through the die 5 and is spread in a sheet shape, and the spread is performed. The layer 61 is cured through an appropriate curing device 7 such as a heating system or a light irradiation system to sequentially form a cured sheet 62 that is in close contact with the resin layer 31, and the cured sheet 6 is formed.
2 is collected from the support 1 together with the resin layer 31 to continuously manufacture the epoxy optical sheet 8.

The recovery of the epoxy optical sheet from the support is preferably performed in a high temperature atmosphere such as a glass transition temperature or higher from the viewpoint of preventing cracking. Therefore, the recovery is such that the curing reaction of the epoxy resin through the epoxy group progresses by about 70% or more, and plastic deformation occurs even in a high temperature atmosphere such as the curing temperature atmosphere by the heat curing method or the temperature atmosphere near the glass transition temperature. It is preferable to carry out after the cured state is reached, from the viewpoint of preventing the occurrence of cracks and strains.

When collecting the epoxy optical sheet from the support, a peeling means can be used if necessary. Further, the formed continuous body of the epoxy-based optical sheet can be collected by cutting it into a suitable size through a suitable cutting means such as a laser beam, an ultrasonic cutter, dicing or a water jet, if necessary.

In the above method, the support may be a belt-like material such as an endless belt, a plate-like material, a drum, or the like.
An appropriate epoxy resin coating liquid can be used so that it can be continuously and successively spread and the spread layer can be supported and maintained in the form of a sheet. The material forming the support may be any material as long as it can withstand the curing treatment of the epoxy resin, and thus may be a suitable material such as metal such as stainless steel, copper or aluminum, glass or plastic. Above all, stainless steel is preferable in terms of durability.

The surface of the support is preferably as smooth as possible in terms of improving the thickness accuracy. Incidentally, it is also possible to obtain an epoxy optical sheet having a mirror-like surface by using a support having a surface roughness Ra of 0.02 μm or less.
Therefore, in the process of forming the resin layer and the cured sheet, it is preferable to keep the surface of the support as horizontal as possible. As a result, an epoxy-based optical sheet having a thickness accuracy of ± 10% or less can be easily obtained.

In order to form the resin layers sequentially provided on the support, a suitable transparent resin which is not adhered to the support or has a weak adhesive force even if adhered and can be easily peeled from the support is used. It can be used and is not particularly limited. Examples of such resins include urethane resins, acrylic resins, polyester resins, polyvinyl alcohol, polyvinyl alcohol resins such as ethylene vinyl alcohol copolymer, vinyl chloride resins and vinylidene chloride resins.

Further, polyarylate resin, sulfone resin, amide resin, imide resin, polyether sulfone resin, polyetherimide resin, polycarbonate resin, silicone resin, fluorine resin, polyolefin resin, Styrene-based resin, vinylpyrrolidone-based resin, cellulose-based resin, acrylonitrile-based resin and the like can also be used for forming the resin layer. In addition, a blend of two or more kinds of appropriate transparent resins may be used for forming the resin layer.

The resin layer is peeled off together with the forming sheet to form a surface layer on one side of the epoxy optical sheet,
It is preferably excellent in optical properties such as transparency. A urethane resin is preferably used for forming the resin layer from the viewpoints of such optical properties and the above-mentioned easy peeling property, particularly the easy peeling property with respect to the stainless support.

As described above, the resin layer can function as a surface coat layer of the epoxy optical sheet. From this point of view, the resin layer forming material is, for example, chemical resistance or surface hardness,
It can also be selected for the purpose of imparting functions such as optical anisotropy, low water absorption, gas barrier properties such as low moisture permeability and low oxygen permeability.

Therefore, the resin layer has an easily peelable property, for example, a laminated layer in which a polyvinyl alcohol resin layer for the purpose of providing a gas barrier property is provided on a urethane resin layer for the purpose of providing an easily peelable property. In addition to the single-layered product, it may be formed as a multi-layered product for the purpose of imparting other functions.

The resin layer is formed by, for example, dissolving the resin in an appropriate solvent such as an organic solvent or water, if necessary, and performing a roll coating method, a wire bar coating method, an extrusion coating method, a curtain coating method, or a spray coating method. To a predetermined surface of the support by a suitable method such as, and after drying it as necessary, a film is formed by an appropriate method such as a method of curing by a method depending on the resin such as heat treatment or light irradiation. This can be done by

In the case of the above-mentioned coating method, it is preferable to prepare the resin liquid at 1 to 100 centipoise from the viewpoint of uniform coating. Further, in the case of coating on the endless belt by the above-mentioned casting method, the method by the extrusion coating method is preferable from the viewpoint of coating efficiency and the like, and in that case, the resin liquid prepared to 1 to 10 centipoise can be preferably used. . When the coating layer of urethane resin or the like is cured by irradiation with light, it is preferable to use a high-pressure or low-pressure ultraviolet lamp having a central wavelength of 365 nm or 254 nm in terms of processing efficiency.

The thickness of the resin layer to be formed can be appropriately determined, but is generally based on each layer unit forming the resin layer from the standpoint of easy peelability and prevention of cracking during peeling. 1-10 μm, especially 8 μm or less, especially 2-5 μm
It is preferable that

To prepare the epoxy resin coating liquid that spreads on the resin layer, at least a liquid epoxy resin, a solid epoxy resin, a curing agent and a leveling agent are used. By using a solid epoxy resin together, strength and heat resistance can be improved, the viscosity of the coating liquid can be adjusted, and especially the viscosity of the coating liquid can be increased to control the thickness of the spreading layer. Can be facilitated.

The liquid or solid epoxy resin may be appropriately selected depending on the intended use of the optical sheet to be formed and is not particularly limited. By the way, for example, bisphenol A type and bisphenol F
Type, bisphenol type such as bisphenol S type and hydrogenated types thereof, novolak type such as phenol novolac type and cresol novolac type, nitrogen-containing ring type such as triglycidyl isocyanurate type and hydantoin type, alicyclic type and aliphatic type Examples thereof include aromatic type such as type and naphthalene type, glycidyl ether type, low water absorption type such as biphenyl type, dicyclo type, ester type and ether ester type, and modified types thereof.

A liquid or solid epoxy resin which can be preferably used in view of optical characteristics such as transparency does not contain a conjugated double bond such as a benzene ring like an alicyclic type resin and has good discoloration preventive property. It is something. The liquid or solid epoxy resin may be used alone or in combination of two or more.

The use ratio of the liquid epoxy resin and the solid epoxy resin may be appropriately determined depending on the desired strength, heat resistance, viscosity of the coating liquid, and the like. Generally, from the viewpoint of the expression of the combined effect of the solid epoxy resin, 1 to 300 parts by weight, particularly 5 to 200 parts by weight, particularly 10 to 150 parts by weight of the solid epoxy resin per 100 parts by weight of the liquid epoxy resin. A system resin is used.

As the liquid epoxy resin, a solid epoxy resin is used in combination to obtain an epoxy resin coating solution having excellent coatability and spreadability into a sheet form. Above all, a two-liquid mixed type which shows a liquid state at room temperature can be preferably used. In general, a liquid epoxy resin having an epoxy equivalent of 100 to 1000 and a softening point of 120 ° C. or lower can be preferably used in terms of physical properties such as rigidity and strength of the obtained optical sheet.

On the other hand, the curing agent is also not particularly limited,
One or more appropriate curing agents can be used depending on the epoxy resin. Incidentally, examples thereof include organic acid compounds such as tetrahydrophthalic acid, methyltetrahydrophthalic acid, hexahydrophthalic acid and methylhexahydrophthalic acid, ethylenediamine and propylenediamine, diethylenetriamine and triethylenetetramine, and their amine adducts and metas. Examples thereof include amine compounds such as phenylenediamine, diaminodiphenylmethane and diaminodiphenylsulfone.

Amide compounds such as dicyandiamide and polyamide, hydrazide compounds such as dihydrazide, methylimidazole, 2-ethyl-4-methylimidazole, ethylimidazole, isopropylimidazole, 2,4-dimethylimidazole and phenylimidazole. Imidazole compounds such as undecyl imidazole, heptadecyl imidazole, and 2-phenyl-4-methyl imidazole are also examples of the curing agent.

Further, methyl imidazoline, 2-ethyl-4-methyl imidazoline, ethyl imidazoline, isopropyl imidazoline, 2,4-dimethyl imidazoline, phenyl imidazoline, undecyl imidazoline, heptadecyl imidazoline and 2-phenyl-4-methyl imidazoline. Such imidazoline compounds as well as phenol compounds, urea compounds, and polysulfide compounds are also mentioned as examples of the curing agent.

In addition, acid anhydride compounds and the like are also mentioned as examples of the above-mentioned curing agent, and in view of work environment property due to low irritation, high temperature durability due to improvement of heat resistance of the obtained sheet, discoloration prevention property, etc. As such an acid anhydride-based curing agent, it is preferable to use. Examples include phthalic anhydride and maleic anhydride, trimellitic anhydride and pyromellitic anhydride, nadic acid anhydride and glutaric anhydride, tetrahydrophthalic anhydride and methyltetrahydrophthalic anhydride, and hexahydrophthalic anhydride. Examples thereof include methyl hexahydrophthalic anhydride, methyl nadic acid anhydride, dodecenyl succinic anhydride, dichlorosuccinic anhydride, benzophenone tetracarboxylic acid anhydride and chlorendic acid anhydride.

Among them, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride and methylhexahydrophthalic anhydride are colorless or pale yellow,
An acid anhydride-based curing agent having a molecular weight of about 140 to about 200 can be preferably used.

The amount of the curing agent used can be appropriately determined according to the type and the epoxy equivalent of the liquid or solid epoxy resin, and can be the same as in the case of usual epoxy resin curing. By the way, in the acid anhydride curing agent, 0.5 to 1.5 equivalents, especially 0.6 to 1.
It is preferable to use the acid anhydride curing agent in a ratio of 4 equivalents, particularly 0.7 to 1.2 equivalents. When other curing agents are used alone or in combination of two or more, the amount used can be in accordance with the above equivalent ratio.

The leveling agent prevents the surface of the epoxy resin coating liquid from becoming a satin-like surface due to variations in surface tension due to scattering of the curing agent when the spreading layer of the epoxy resin coating solution is subjected to curing treatment in contact with air. Is added for the purpose of forming a smooth surface and the like, and one or two kinds of suitable ones capable of reducing the surface tension such as various surfactants such as silicone-based, acrylic-based and fluorine-based surfactants are used. More than one species can be used.
Above all, a silicone-based surfactant can be preferably used from the viewpoint of the surface smoothing effect and the like.

When preparing the epoxy resin coating solution, a curing accelerator may be added, if necessary. By blending the curing accelerator, the curing rate can be accelerated to shorten the required curing treatment time, and the required length of the support can be shortened to a fraction of that in the case of not blending. Therefore, it is preferable to add a curing accelerator from the viewpoints of improving mass productivity and downsizing of manufacturing equipment.

The curing accelerator to be used is not particularly limited, and depending on the type of liquid or solid epoxy resin or curing agent, for example, tertiary amines or imidazoles,
One or more suitable compounds such as quaternary ammonium salts, organic metal salts, phosphorus compounds and urea compounds can be used.

The amount of the curing accelerator used can be appropriately determined in view of the effect of accelerating the curing, etc. In general, the total epoxy resin 100 is used in order to prevent the cured product from discoloring.
The amount is preferably 0.05 to 7 parts by weight, more preferably 0.1 to 5 parts by weight, and particularly preferably 0.2 to 3 parts by weight.

It should be noted that the epoxy resin coating liquid may be blended with the cured epoxy resin, if necessary. For example, phenol-based, amine-based, organic sulfur-based or phosphine-based antioxidants, glycols and Suitable additives such as modifiers such as silicones and alcohols, antifoaming agents and hydroxyl group-containing compounds, dyes and discoloration preventing agents, and ultraviolet absorbers can be added. The above-mentioned antifoaming agent is added for the purpose of preventing bubbles from being mixed in the obtained sheet, which causes deterioration of optical properties, and polyhydric alcohols such as glycerin can be preferably used.

The epoxy resin coating liquid can be prepared by bringing the components to be mixed together with a solvent, if necessary, so as to be in the state of fluid development. Therefore, in order to develop the epoxy resin coating liquid, an appropriate method that can be formed into a sheet by fluidizing the epoxy resin coating liquid according to the above-described resin layer forming method such as curtain coating method or roll coating method. Can be taken. In particular, the extrusion coating method can be preferably applied to the casting method from the viewpoint of coating efficiency.

The epoxy optical sheet according to the present invention is excellent in heat resistance because it is a cured sheet of epoxy resin, but it is more resistant to the high temperature atmosphere during the liquid crystal cell manufacturing process as a liquid crystal cell substrate. It is preferable that the cured sheet has a glass transition temperature of 170 ° C. or higher.
The thickness is 500 μm or less from the viewpoint of rigidity such as bending strength, surface smoothness, low phase difference, thinness and lightness, and especially 10
The thickness is preferably 0 to 400 μm, particularly preferably 200 to 300 μm, and the thickness accuracy is preferably ± 10% or less from the viewpoint of optical applications and the like.

Further, the retardation in the epoxy optical sheet is 20 nm or less from the viewpoint of preventing coloring due to birefringence when applied to a liquid crystal cell or the like.
It is preferably 10 nm or less, particularly preferably 5 nm or less.
The thickness accuracy is based on the difference between the maximum value and the minimum value with respect to the average thickness of the sheet.

The epoxy optical sheet according to the present invention can be preferably used for various optical applications such as a liquid crystal cell substrate and an antireflection sheet. In particular, because of its excellent optical properties, heat resistance, and smoothness of the surface, it is required to withstand high temperature treatment such as liquid crystal cell substrate, to have excellent bending strength, and to have a small phase difference and light weight. It can be preferably used for optical applications.

[0044]

Example 1 171 parts (parts by weight, the same applies hereinafter) of a liquid epoxy resin represented by the following formula (a), 209 parts of a solid epoxy resin represented by the formula (b), and hexahydrophthalic anhydride. 500
Parts, tetra-n-butylphosphonium o, o-diethylphosphorodithioate (formula c) 15 parts, glycerin 9 parts, and a silicone-based surfactant (leveling agent, Kusumoto Kasei Co., Disparlon LS-009) 1 part. An epoxy resin coating solution was prepared by mixing with stirring.

[0045]

[0046]

Next, according to the casting method illustrated in FIG. 1, a urethane type ultraviolet curable resin (NK Oligo UN-manufactured by Shin Nakamura Chemical Co., Ltd.) is used.
15% by weight toluene solution of 01) was discharged from a die and cast-coated on a stainless steel endless belt that rotates at a constant speed of 0.2 m / min. After toluene was volatilized and dried, 2000 mJ of ultraviolet light was passed through a low pressure mercury lamp. / Cm ² irradiation and curing treatment to form a urethane resin layer having a width of 500 mm and a thickness of 2 μm.

Then, while continuing the above operation, the above epoxy resin coating liquid was continuously discharged from the die onto the cured urethane resin layer and cast and spread in a sheet form, and the spread layer was heated by a heating device. After heating and curing at 120 ° C for 30 minutes through the resin, the cured sheet is peeled and collected from the endless belt together with the urethane resin layer adhered to it on the driven drum whose temperature is controlled to 150 ° C to continuously obtain an epoxy optical sheet. It was The sheet is cut into 300 mm squares, and the in-plane 36
When the thickness was measured with a laser thickness meter at points, the average thickness was 400 μm, the thickness accuracy was ± 10%, and the phase difference measured by the birefringence measuring device was 5 nm or less. The glass transition temperature of the sheet was 170 ° C or higher.

Example 2 As an epoxy resin coating liquid, 266 parts of the liquid epoxy resin of the above formula (a) and the solid epoxy resin 11 of the above formula (b) were used.
After stirring 4 parts at 120 ° C. to dissolve and allowing it to cool to room temperature,
Curing agent 500 parts, tetra-n-butylphosphonium o,
O-diethyl phosphorodithioate (15 parts), glycerin (9 parts) and a silicone-based surfactant (1 part) were used by stirring and mixing. An epoxy type optical sheet having 10%, a phase difference of 5 nm or less and a glass transition temperature of 170 ° C. or more was continuously obtained.

The above-mentioned curing agent was prepared by stirring 100 parts of methylhexahydrophthalic anhydride and 15 parts of a modifier represented by the following formula (d) at 120 ° C. for esterification reaction and then at room temperature. It was obtained by allowing it to cool.

Comparative Example 1 An epoxy optical sheet was formed in the same manner as in Example 1 except that the epoxy resin coating solution was directly coated on the endless belt without providing a resin layer, but the adhesive strength with the belt was strong. As a result, cracks and cracks were generated during peeling and recovery, and it was not practical for an optical sheet.

Comparative Example 2 An epoxy-based optical sheet was formed in the same manner as in Example 1 except that a silicone-based surfactant was not added, but a satin-like pattern was generated on the surface, which was not practical as an optical sheet. .

[Brief description of drawings]

FIG. 1 is a side view illustrating a manufacturing process example.

[Explanation of symbols]

1: Endless belt (support) 31: Resin layer 61: Development layer of epoxy resin coating liquid 7: Curing device 62: Cured sheet 8: Epoxy optical sheet

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B29L 7:00 B29L 7:00 9:00 9:00 (72) Inventor Shinki Yagi 1-1-1 Shimohozumi, Ibaraki-shi, Osaka No. 2 Nitto Denko Corporation (72) Inventor Hiroshi Sugawa 1-1-2 Shimohozumi, Ibaraki-shi, Osaka No. 1-2 Nitto Denko Corporation (72) Inventor Toshishi Umehara 1-1-1, Shimohozumi, Ibaraki-shi, Osaka No. 2 within Nitto Denko Corporation (56) Reference JP-A-6-337408 (JP, A) JP-A-8-29763 (JP, A) JP-A-9-156051 (JP, A) JP-A-9 -234843 (JP, A) Japanese Patent Laid-Open No. 5-117412 (JP, A) Actual Development Sho 61-168908 (JP, U) Actual Public Inspection 2-39781 (JP, Y2) (58) Fields investigated (Int.Cl) . ⁷ , DB name) B29C 41/24 B29C 41/32 G02B 1/04 G02F 1/1333 500

Claims (4)

(57) [Claims] 1. A support having a smooth surface and sequentially moving ,
On the other hand , an epoxy resin coating liquid containing at least a liquid epoxy resin, a solid epoxy resin, a curing agent and a leveling agent is formed on the resin layer while sequentially forming an easily peelable resin layer. Epoxy optical sheet is continuously produced, which is characterized by recovering the cured sheet from the support together with the resin layer while forming a cured sheet in close contact with the resin layer by sequentially developing into a sheet shape and curing treatment. Method. 2. The epoxy optical sheet according to claim 1, wherein one or both of the liquid epoxy resin and the solid epoxy resin is an alicyclic resin, and the epoxy resin coating liquid also contains a curing accelerator. Production method. 3. The method for producing an epoxy optical sheet according to claim 1, wherein the curing agent is an acid anhydride compound. 4. The method for producing an epoxy optical sheet according to claim 3, wherein the acid anhydride compound is methylhexahydrophthalic anhydride.