JP2001049000A - Continuous production of epoxy-based resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously producing an epoxy-based resin sheet having excellent heat resistance stably in excellent mass productivity. SOLUTION: A coating solution comprising at least an alicyclic epoxy-based resin and 1.1 to 1.4 equivalents of a curing agent as components is cast 71 in a sheetlike state directly or through a different superimposed layer 6 to a readily peelable resin layer 5 formed on a continuous substrate 1. The cast layer 72 is heated and cured 4 to form a cured sheet 7 stuck directly or through the different superimposed layer to the resin layer. The cured sheet is peeled and recovered together with the resin layer from the continuous substrate. Consequently the occurrence of low crosslinked part can be prevented by making up for the deficiency of the curing agent by evaporation, the heating and curing treatment can be carried out at the boiling point of the curing agent or higher than it and a highly heat-resistant cured sheet is readily peeled and recovered through the resin layer from the continuous substrate. An epoxy-based resin sheet can be stably and efficiently obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous method for producing an epoxy resin sheet excellent in heat resistance and excellent in mass productivity.

[0002]

BACKGROUND OF THE INVENTION In the production of epoxy resin sheets by the casting thermosetting method, complicated processes such as injection and mold opening are required, and mass production of the sheets is poor. Therefore, an endless belt similar to a thermoplastic resin sheet is used. It is desired to develop a continuous production method using a cast heat-curing method, etc., for which it is necessary to overcome the problem of adhesion of the formed cured sheet to the continuous support and enable peeling and recovery. Become.

It is also necessary to overcome the problem of evaporation of the curing agent from the surface layer when an epoxy resin is cast on a continuous support. That is, if the heat curing temperature is lowered for the purpose of suppressing evaporation of the curing agent, a sheet having excellent heat resistance cannot be obtained, and when the curing treatment is performed at a high temperature, the curing agent evaporates and the curing reaction in the evaporated portion stops. As a result, a portion having a low degree of crosslinking is partially generated, and also in this case, the overall heat resistance is reduced.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to develop a method for stably and continuously producing an epoxy resin sheet having excellent heat resistance with good mass productivity.

[0005]

According to the present invention, there is provided a method for manufacturing a semiconductor device, comprising:
A coating liquid containing at least an alicyclic epoxy resin and 1.1 to 1.4 equivalents of a curing agent is developed in the form of a sheet, and the developed layer is heat-cured and directly or separately formed on the resin layer. And a method for continuously producing an epoxy-based resin sheet, comprising: forming a cured sheet that is in intimate contact with an intervening layer, and peeling and collecting the cured sheet together with the resin layer from a continuous support.

[0006]

According to the present invention, even if the curing agent evaporates and scatters during the heat-curing treatment, the shortage can be compensated for and the low crosslinking degree portion having low heat resistance can be compensated by setting the mixing ratio of the above-mentioned curing agent. Can be prevented, and can be heat-cured at a temperature equal to or higher than the boiling point of the curing agent to increase heat resistance, and the cured sheet is peeled from the interface with the continuous support through the easily peelable resin layer. The epoxy resin sheet can be easily recovered without breaking, and the epoxy resin sheet can be stably and efficiently obtained.

Further, the mass production speed can be easily controlled by adjusting the moving speed of the spreading layer through the continuous support, and the sheet thickness can be easily controlled by adjusting the moving speed and the coating liquid spreading amount. The surface state can be transferred and reflected favorably through the resin layer, and a sheet excellent in optical properties through a mirror surface or an uneven surface can be continuously and efficiently manufactured through a simple series of operations. .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The production method according to the present invention relates to a method in which an alicyclic epoxy resin is mixed with an alicyclic epoxy resin directly or via a separate superimposed layer on an easily peelable resin layer provided on a continuous support. 1.4
After developing a coating liquid containing at least an equivalent amount of a curing agent as a component and forming a cured sheet in close contact with the resin layer directly or via a separate superimposed layer by heating and curing the spread layer, The cured sheet is peeled and collected together with the resin layer from the continuous support to continuously obtain an epoxy resin sheet.

The above method is carried out by using at least a resin coating liquid and an epoxy resin coating liquid, for example, a roll coating method, a spin coating method, a wire bar coating method, an extrusion coating method, a curtain coating method, It can be performed by applying an appropriate method such as a spray coating method, a dip coating method, a doctor blade method or the like, which can flow and develop an epoxy resin coating liquid or the like to form a sheet.
In particular, a casting method, particularly an extrusion coating method in which an epoxy-based resin coating solution is flow-developed through a die can be preferably applied from the viewpoint of coating efficiency and production efficiency.

FIG. 1 shows an example of a process of a continuous production system by the above-mentioned extrusion coating method. In this method, first, a continuous support made of an endless belt 1 is moved in a direction indicated by an arrow through a driving drum 2 and a driven drum 3 by, for example, 0.1 to 5 mm.
While rotating and running at a constant speed of 0 m / min, especially 0.2 to 5 m / min, a coating liquid of resin is continuously applied thereon in the form of a sheet via a die 51, and the spread layer 52 is formed. The resin layer 5 is dried or cured by heating or light irradiation as necessary to form an easily peelable resin layer 5 composed of a film. In the illustrated example, an ultraviolet irradiation device 53 is provided.

Next, an easily peelable resin layer 5 is sequentially formed on the continuous support 1 as described above, and a superposed layer provided on the resin layer or separately provided as necessary according to the resin layer. 6
On top of this, an epoxy-based resin coating liquid is sequentially applied through a die 71 arranged on the upper part of the continuous support and developed into a sheet,
The spread layer 72 is heat-cured through the heating device 4 to form a cured sheet 7 in close contact with the resin layer 5 and the like, and collects the cured sheet 7 together with the resin layer 5 and the like from the continuous support 1. Thus, the desired epoxy resin sheet is continuously manufactured.

According to the above-mentioned method, an epoxy resin sheet can be continuously manufactured through a simple series of operations, is excellent in mass productivity, and has an easily peelable resin layer formed first on the continuous support 1. 5 enables the obtained epoxy resin sheet to be easily and efficiently peeled and collected from the continuous support. In addition, the mass production speed can be easily controlled by adjusting the moving speed of the spreading layer through the continuous support, and the thickness of the epoxy resin sheet obtained by adjusting the moving speed and the coating liquid spreading amount can be easily controlled. it can.

In the process of forming the resin layer and the like or the cured sheet, it is preferable to keep the surface of the continuous support as horizontal as possible from the viewpoint of making the thickness uniform. By the way, by maintaining the horizontal level of the continuous support at the time of the curing treatment at 5 mm per 5 times the intended effective width of the cured sheet to be formed, particularly per 20 times the volume, particularly at 1 mm per 40 times the volume,
± 15% thickness accuracy of the formed epoxy resin sheet
Hereinafter, it can be set to ± 10% or less.

In the above, as the continuous support, an epoxy resin coating liquid such as a belt-like object such as an endless belt, a plate-like object, a drum, or the like can be successively spread, and the spread layer is supported to form a sheet. Any suitable one that can be maintained can be used. The material forming the continuous support may be any material that can withstand the heat-curing treatment of the epoxy resin, and therefore may be a suitable material such as a metal such as stainless steel, copper or aluminum, glass or plastic. In particular, a continuous support made of stainless steel is preferable from the viewpoint of durability and the like.
The thickness of the continuous support is appropriately determined according to the strength and the like,
Generally, it is 0.1 to 10 mm, especially 0.5 to 2 mm.

Further, according to the above-mentioned method, the surface morphology of the continuous support can be favorably transferred and reflected via the resin layer. Therefore, the surface of the continuous support is, for example, a flat surface, a prism surface, a lens surface, or the like, depending on the surface form of the epoxy resin sheet to be formed when used as a liquid crystal cell substrate, an antireflection sheet, a prism sheet, a diffusion sheet, or the like. An appropriate form such as a fine uneven surface can be used.
When a smooth surface is used, it is also possible to obtain an epoxy resin sheet having a mirror-like surface by using a continuous support having a surface roughness Ra of 0.02 μm or less.

In the present invention, the easily peelable resin layer provided first on the continuous support is intended to enable the obtained epoxy resin sheet to be integrally and easily peeled off from the continuous support. Therefore, in forming the resin layer, a resin layer that does not adhere to the continuous support or that can be easily peeled off even if it adheres is used.

The type of the above-mentioned resin is not particularly limited, and an appropriate resin can be used. Incidentally, examples thereof include urethane resins and acrylic resins, polyester resins and polyvinyl alcohol, polyvinyl alcohol resins such as ethylene vinyl alcohol copolymer, vinyl chloride resins and vinylidene chloride resins, polyarylate resins and sulfone resins. Resin, amide resin or imide resin,
Examples include polyethersulfone-based resins, polyetherimide-based resins, polycarbonate-based resins and silicone-based resins, fluorine-based resins and polyolefin-based resins, styrene-based resins and vinylpyrrolidone-based resins, cellulose-based resins and acrylonitrile-based resins. For forming the easily peelable resin layer, a blend of two or more kinds of appropriate resins may be used.

The easily peelable resin layer adheres to the epoxy-based cured sheet or the like, and is peeled and recovered from the continuous support together with the epoxy-based cured sheet to form a one-sided surface layer of the epoxy-based resin sheet. Is preferably excellent in optical characteristics. Further, it is preferable that the surface of the epoxy resin sheet is coated so as not to be easily damaged. A urethane resin is preferably used for forming the resin layer in view of such easy peelability, optical properties, hard coat properties, and particularly easy peelability for a stainless steel continuous support.

The resin layer is formed by, for example, forming a solution of the resin in an appropriate solvent such as an organic solvent or water as required, coating the solution on a predetermined surface of the continuous support by an appropriate method such as described above, and applying the solution as necessary. After drying, a film can be formed by an appropriate method such as a method of curing treatment by a method according to the resin such as heat treatment or light irradiation. In this case, the viscosity of the coating solution can be determined as appropriate, but is generally 1 to 100 cP from the viewpoint of coating efficiency and uniform application, and particularly when the extrusion coating method is used, the viscosity is particularly 1 to 10 centipoise. The prepared resin liquid can be preferably used.

The thickness of the resin layer to be formed can be appropriately determined, but is generally 1 to 10 μm, especially 8 μm or less, from the viewpoint of easy peelability and prevention of generation of cracks during peeling. The thickness is preferably 2 to 5 μm. When the coating layer of a urethane resin or the like is cured by light irradiation, it is preferable to use a high-pressure or low-pressure ultraviolet lamp having a center wavelength of 365 nm or 254 nm from the viewpoint of processing efficiency and the like.

When the easily peelable resin layer is formed, the coating liquid is added with, for example, ethylene oxide to improve the peelability from the continuous support.
An appropriate drug such as an ethylene polymer of No. 00 or a linear saturated hydrocarbon such as paraffin can be blended.

When forming the epoxy resin sheet as exemplified by the temporary wire in FIG. 1, a separate superposed layer 6 is provided on the easily peelable resin layer 5 as necessary, and the epoxy resin is cured thereon. A sheet 7 can be provided. In the illustrated example, the coating liquid for superimposition is sequentially spread on the resin layer in the form of a sheet via the die 61 in accordance with the formation of the resin layer described above, and the spread layer 62 is formed into a film via the curing device 63 and superimposed. A layer 6 is formed.

Resin layer 5 and cured sheet 7 of epoxy resin
The superimposed layer provided as needed between, for example, chemical resistance and optical anisotropy, low water absorption and low moisture permeability, with the purpose of imparting appropriate functions such as gas barrier properties such as low oxygen permeability. It may be. Therefore, the superimposed layer provided separately,
One or two or more layers may be used.

In the liquid crystal cell, when moisture or oxygen permeates the cell substrate and enters the cell, the appearance of the liquid crystal may be deteriorated due to deterioration of the liquid crystal or the formation of bubbles, or the transparent conductive film pattern may be broken. Therefore, in the case of a liquid crystal cell, it is important to prevent permeation of water vapor and oxygen gas, and a cell substrate provided with a gas barrier layer capable of preventing the permeation of such gas is preferably used.

The coating liquid for forming the gas barrier layer can be prepared using an appropriate material capable of being liquefied so as to prevent the permeation of a desired gas. In general, it has excellent ability to inhibit the permeation of a target gas such as water vapor or oxygen gas, and especially has a small oxygen permeability coefficient, for example, polyvinyl alcohol and its partially saponified products, ethylene / vinyl alcohol copolymer, polyacrylonitrile, polyvinylidene chloride Polymers such as are used. In particular, a vinyl alcohol-based polymer can be preferably used from the viewpoint of gas barrier properties, water diffusibility, and uniformity of water absorption.

The coating liquid for forming a superposed layer such as a gas barrier layer provided on the resin layer may be, for example, a fluid such as a polymer solution prepared by using one or more kinds of forming materials in combination with a solvent as necessary. It can be prepared in a state where it can be developed. The thickness of the superposed layer to be formed can be appropriately determined and is not particularly limited. In general, the thickness is preferably 15 μm or less, particularly 13 μm or less, particularly 1 to 10 μm in terms of transparency and prevention of coloring, functionality such as gas barrier properties and thinness, and flexibility of the obtained epoxy resin sheet. preferable.

The preparation of the epoxy resin coating solution spread on the resin layer or the superimposed layer on the resin layer may be performed by appropriately using a thermosetting resin in order to obtain an epoxy resin sheet having excellent heat resistance and transparency. One or two or more alicyclic epoxy resins can be used, and the type is not particularly limited.
Rather than obtaining a coating liquid having excellent coating properties and spreadability into a sheet form, etc., a two-liquid mixed type liquid which shows a liquid state at a temperature lower than the temperature at the time of coating, especially at room temperature, can be preferably used. In this case, a solid alicyclic epoxy resin may be used in combination for the purpose of adjusting viscosity, improving strength, heat resistance, and the like. Increasing the viscosity of the coating liquid by using a combination of solid substances is also advantageous for facilitating the control of the thickness of the spreading layer.

A curing agent is added to the epoxy resin coating liquid for the purpose of imparting thermosetting properties. The curing agent used is not particularly limited, and one or more curing agents appropriate for the alicyclic epoxy resin used in combination can be used. Above all, an acid anhydride-based curing agent is preferably used from the viewpoint of improving the heat resistance of the epoxy resin sheet and preventing discoloration.

Examples of the acid anhydride-based curing agents include phthalic anhydride and maleic anhydride, trimellitic anhydride and pyromellitic anhydride, nadic anhydride and glutaric anhydride,
Tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, dodecenylsuccinic anhydride, dichlorosuccinic anhydride, benzophenonetetracarboxylic anhydride, chlorendic anhydride, etc. Is raised.

In particular, from the viewpoint of the above-mentioned discoloration prevention properties, it is colorless or pale yellow like phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride and methylhexahydrophthalic anhydride, and has a molecular weight of about 140 to About 200 are preferably used, and in particular, methylhexahydrophthalic anhydride is preferably used in view of transparency and liquidity at room temperature and workability of compounding.

The amount of the curing agent to be used should be 1.1 to 1.4 equivalents to 1 equivalent of the epoxy group of the alicyclic epoxy resin. Thereby, even if the curing agent evaporates and scatters from the surface layer of the coating layer during the heat curing treatment, it can be supplemented to obtain an epoxy resin sheet having excellent heat resistance.

In preparing the epoxy resin coating solution,
If necessary, appropriate additives such as a curing accelerator and a leveling agent can be blended. The hardening accelerator is blended for the purpose of shortening the required hardening treatment time by accelerating the hardening speed, and it is possible to shorten the distance required for hardening by the blending to about a fraction of that in the case of no blending. Therefore, it is preferable to add a curing accelerator from the viewpoint of improving mass productivity and downsizing of manufacturing equipment.

The curing accelerator to be used is not particularly limited, and includes, for example, tertiary amines, imidazoles, quaternary ammonium salts, organic metal salts, and the like, depending on the type of the alicyclic epoxy resin or the curing agent. Appropriate compounds such as phosphorus compounds and urea compounds can be used alone or in combination of two or more. The amount of the curing accelerator used can be appropriately determined according to the accelerating effect and the like.
-7 parts by weight, preferably 0.1-5 parts by weight, particularly 0.2-3 parts by weight.

On the other hand, the leveling agent is used for curing the spread layer of the epoxy resin coating liquid in contact with air.
It is compounded for the purpose of forming a smooth surface by preventing a matte surface from being generated due to variations in surface tension due to scattering of a curing agent and the like, for example, a silicone type, an acrylic type, a fluorine type, etc. One or more kinds of appropriate surfactants such as various surfactants which can lower the surface tension can be used.

Also, for example, phenol-based, amine-based, organic sulfur-based, phosphine-based antioxidants, modifiers such as glycols, silicones and alcohols, dyes and pigments,
Additives such as discoloration inhibitors and UV absorbers can also be included.

The epoxy resin coating liquid can be prepared by mixing the components with a solvent if necessary so as to be able to flow and develop. The viscosity of the coating liquid can be determined as appropriate, but is generally 1 poise or more, especially 5 to 5 in terms of improvement in thickness accuracy and coating efficiency due to suppression of thickness unevenness and the like.
The viscosity is preferably 500 poise, especially 10 to 300 poise.

The heat-curing treatment of the spread layer of the epoxy resin coating liquid formed on the resin layer or the like can be performed at an appropriate temperature according to the curing agent or the like. Above 140 ° C, especially 145 to 250
C., particularly preferably at 150 to 200.degree. In that case, the heating temperature may be higher than the boiling point of the curing agent. As the heating means, one or more suitable means such as hot air or an infrared heater can be used.

In the above, it is customary to obtain a cured sheet having excellent optical properties, for example, for 5 to 60 minutes, especially 15 to 60 minutes.
It is preferable to perform the heat curing treatment in a relatively short time such as 30 minutes. In addition, it is preferable that the temperature difference in the width direction of the spread layer be suppressed as much as possible from the viewpoint of improving the thickness accuracy of the sheet. The temperature control can be performed by an appropriate method such as a method of dividing the heating device into a plurality of zones and controlling the temperature for each zone.

By the above-mentioned curing treatment, an easily peelable resin layer or the like and a cured sheet are usually tightly adhered and integrated to form an epoxy resin sheet which can be handled as an integral product. The thickness of the cured sheet to be formed can be appropriately determined according to the intended use of the epoxy resin sheet. In general, the thickness is 1 mm or less, preferably 50 to 800 μm, particularly 100 to 600 μm in view of rigidity or flexibility such as bending strength, surface smoothness, low phase difference, thinness and lightness. 200 to 500 μm for optical applications
Is often advantageous.

In the above continuous production method, the formed epoxy resin sheet is recovered from the continuous support in a high-temperature atmosphere near the glass transition temperature or under the action of shrinkage stress due to rapid cooling in order to prevent cracking. It is preferable to peel it off. In particular, from the point of achieving a balanced flexibility that can prevent the occurrence of cracks and cracks and the occurrence of plastic deformation and residual strain, the glass transition temperature of the epoxy resin cured layer is 20 ° C or lower, especially ± 10 ° C. It is preferable to peel in the temperature range. Therefore, it is preferable to recover the obtained resin sheet after it has been hardened so as not to be plastically deformed even in a high temperature atmosphere such as near the glass transition temperature, from the viewpoint of preventing the occurrence of cracks and distortion.

In recovering the epoxy resin sheet from the continuous support, a peeling means can be used if necessary. Incidentally, in the illustrated example, a heat-resistant tape is adhered to the end portion of the resin layer 5 and the like, and a cured sheet of an epoxy resin is formed thereon. The system resin sheet is peeled and collected more efficiently than the continuous support.

The continuum of the formed epoxy-based resin sheet can be cut to an appropriate size through an appropriate cutting means such as a laser beam, an ultrasonic cutter, dicing, or a water jet, as required, and collected. The obtained epoxy resin sheet can be preferably used for various purposes according to the related art, and can be preferably used for optical applications such as a cell substrate in various cells such as a liquid crystal cell.

In the above case, when it is required to withstand a high temperature atmosphere or the like in a liquid crystal cell manufacturing process as in the case of a liquid crystal cell substrate, the obtained epoxy resin sheet is subjected to post-heating treatment if necessary, or the like. The transition temperature can be raised to 140 ° C. or higher, especially 160 ° C. or higher, especially 180 ° C. or higher.

[0044]

EXAMPLES Examples 1 to 4 A 17% by weight toluene solution of a urethane-based UV-curable resin (NK Oligo UN-01, manufactured by Shin-Nakamura Chemical Co., Ltd.) was discharged from a die by the casting method illustrated in FIG. The solution was cast on a stainless steel endless belt rotating at a constant speed of 0.2 m / min, and the toluene was evaporated and dried.
nm) and cured to form a urethane-based resin layer having a thickness of 2 μm.

Next, while continuing the above operation, the epoxy resin coating liquid is continuously discharged from the die at a rate of 100 g / min onto the cured urethane resin layer to develop the sheet into a sheet. After the layer was heated and cured at 165 ° C. for 25 minutes through a hot air heating device, the cured sheet was separated and recovered from the endless belt together with the urethane resin layer adhered thereto on a driven drum adjusted to 150 ° C., and the thickness was 400 μm. Was continuously obtained.

The above-mentioned epoxy resin coating liquid is alicyclic epoxy resin A (ERL-4, manufactured by Union Carbide Co., Ltd.).
221) 68.7 parts (parts by weight, the same applies hereinafter), alicyclic epoxy resin B (manufactured by Daicel Chemical Industries, EHPE-315)
0) 31.3 parts of an acid anhydride-based curing agent (manufactured by Hitachi Chemical Co., Ltd., NH-8210) and a curing accelerator (manufactured by Nippon Chemical Industry Co., Ltd., 2 parts of Hishicolin PX-4ET) prepared by stirring and mixing. In this case, the amount of the acid anhydride-based curing agent was changed to obtain the equivalent ratio as shown in the following table.

In the above-mentioned equivalent ratio, the epoxy equivalent of the alicyclic epoxy resin A was set to 135 and the epoxy equivalent of the alicyclic epoxy resin B was set to 185. Technology and evaluation / application of the curing agent)), the equivalent of the acid anhydride curing agent is 1
68 (published by Kobunshi Kanko Kai; by "Introductory Epoxy Resin")
And

Evaluation Test The epoxy resin sheet obtained above was further cured at 180 ° C. for 6 hours.
After heating for 0 minutes to allow the crosslinking to proceed sufficiently, the glass transition temperature (heat resistance) and the degree of curing were examined. The glass transition temperature was measured using a viscoelasticity measurement device (AREOME, ARE
The peak temperature of the loss modulus (G ") at a measurement frequency of 1 Hz using S) was used as a reference. The degree of curing was evaluated as x when the peak of tan δ was observed even at a temperature lower than the glass transition temperature. When there was no, it was evaluated as ○.

The results are shown in the following table. From the table, Examples 3 and 4 in which the equivalent ratio of the curing agent to the epoxy was 1.1 or more.
This indicates that the curing of the entire sheet has sufficiently proceeded. Example 1 Example 2 Example 3 Example 4 Epoxy / hardener equivalent ratio 1.0 / 0.9 1.0 / 1.0 1.0 / 1.12 1.0 / 1.25 Glass transition temperature (° C) 209 213 214 211 211 Degree of curing × × ○ ○

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an example of a manufacturing process.

[Explanation of symbols]

 1: Continuous support (endless belt) 2, 3: Driving / following drum 4: Heating device 5: Easily peelable resin layer 6: Overlapping layer 7: Cured sheet of alicyclic epoxy resin 51, 61, 71: Dies 52, 62, 72: development layer

Claims (4)

[Claims] 1. An alicyclic epoxy resin and 1.1 to 1.4 equivalents of a curing agent are directly or interposed on a readily peelable resin layer provided on a continuous support. The coating liquid as at least a component is developed into a sheet, and the spread layer is heat-cured to form a cured sheet directly or through a separate superposed layer on the resin layer, and then the cured sheet is formed. A continuous method for producing an epoxy resin sheet, wherein the resin layer is peeled and collected from a continuous support together with the resin layer. 2. The continuous production method of an epoxy resin sheet according to claim 1, wherein an acid anhydride curing agent is used as the curing agent. 3. The method for continuously producing an epoxy resin sheet according to claim 1, wherein the heat curing treatment is performed at 140 ° C. or higher. 4. The continuous production method according to claim 1, wherein an epoxy resin sheet having a glass transition temperature of 180 ° C. or higher is obtained.