JP2015098580A - Resin sheet, and use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base material that is a resin sheet having curved shape, and having good optical performance and thermomechanical property and capable of satisfying the needs such as reduction in weight and thickness, safety improvement, a curved surface display, and a face body for a protection face.SOLUTION: This invention provides a transparent resin sheet with thickness of 0.1-10 mm obtained by curing a photocurable composition (A), the resin sheet characterized by being curved, in at least one direction in a plane, in the range of 0.1-5 m of a curvature radius.

Description

  The present invention is a resin sheet obtained by photocuring a photocurable composition and having a curved shape, which is excellent in optical characteristics and thermomechanical characteristics, and useful as a base material for display, and a display It is related with uses, such as a protection board for screens, a screen, a touch-panel board | substrate, and a face body for protective surfaces.

  Conventionally, a flat glass plate has been often used as a substrate for a display. For example, a flat glass substrate is used for a protective plate (cover) which is the forefront of the display, a liquid crystal display, an organic EL display, a touch panel, and the like.

In recent years, the progress of portable information terminals such as mobile phones and smartphones has been remarkable. These portable displays are required to be light and thin, and the glass plates used are also becoming thin.
However, the present situation is that the ease of cracking has become conspicuous as the thickness is reduced.

  Furthermore, flexible displays, curved displays, irregular displays, head-up displays, head-mounted displays, and the like have been proposed as next-generation displays. In particular, curved displays are a hot topic in television and in-vehicle applications from the viewpoint of design and visibility. However, the use of a glass plate is more difficult in a curved display. The ease of breaking when thin glass is bent is a big problem from the viewpoint of safety both in the manufacturing process and in the end product. Generally, a glass plate is manufactured by a casting method or a float method, but it is difficult to manufacture a glass plate having a curvature in the first place. For example, even if a flat glass plate is bent by heating, the susceptibility to cracking increases due to the stress strain remaining inside. Further, since in-mold molding is expensive, it is not suitable for mass production, and polishing a flat glass plate requires a lot of time.

  On the other hand, various transparent resin sheets have been proposed in order to meet demands such as light weight and thinness, safety, flexibility, curved surface, and irregular shape. However, these resin sheets have not only optical performance such as light transmittance and birefringence, but also thermomechanical properties such as heat resistance and hardness, and processing suitability such as solvent resistance. It is difficult to replace glass as a quality substrate.

  In order to satisfy these performances, a resin sheet obtained by photocuring has been proposed (for example, see Patent Document 1). Moreover, the cover glass which improved the ease of a crack by chemical strengthening is proposed (for example, refer patent document 2).

JP 2006-193596 A JP2013-125118A

  However, with the disclosed technique of Patent Document 1, although a high-performance and flat resin sheet can be obtained, a resin sheet having a curvature cannot be obtained. In particular, when cured sufficiently, since it is a crosslinked resin, it is difficult to bend it by a technique such as heating. In addition, although the disclosure technique disclosed in Patent Document 2 can improve the fragility by chemical strengthening, small-sized parts are manufactured by hand, which is inferior in productivity and is not practical. In general, chemical strengthening is performed by exchanging metal ions in glass at a high temperature. However, in the case of thin glass, there is a problem that it is deformed by a high temperature chemical strengthening process, and a thin film having a certain curvature. Chemical strengthening of glass is even more difficult.

  Therefore, the present invention is a resin sheet having a curved shape under such a background, and is excellent in optical performance and thermomechanical characteristics, and is required for lighter and thinner, improved safety, curved surface display, protective surface, and the like. The object is to provide a substrate that can be used.

  However, as a result of intensive studies in view of such circumstances, the present inventors have made a resin sheet photocured using the photocurable composition (A) having a curvature radius of 0.1 to at least one direction in the plane. It discovered that the resin sheet which has the curve of a predetermined shape was obtained by curving and curving in the range of 5 m, and completed this invention. The curvature radius (m) is the reciprocal of the curvature.

  That is, the gist of the present invention is a transparent resin sheet having a thickness of 0.1 to 10 mm obtained by curing the photocurable composition (A), and has a radius of curvature of 0.1 in at least one direction in the plane. The present invention relates to a resin sheet that is curved in a range of 1 to 5 m.

Furthermore, in the present invention, after the photocurable composition (A) is photocured, it is heated while being fixed with a fixing jig so that the radius of curvature is in the range of 0.1 to 5 m in at least one direction in the plane. It is preferable to obtain a resin sheet by curing.
This is to obtain a resin sheet having a curved shape while completing the curing by curving the resin sheet photocured in a semi-cured state to a desired curvature radius and thermally curing. This utilizes the fact that the shape of the crosslinked resin by curing is determined at the final stage of curing (polymerization). By this method, it is not necessary to prepare a curved mold and it is not necessary to cut the resin sheet, and a resin sheet having a desired curved shape can be manufactured.

  ADVANTAGE OF THE INVENTION According to this invention, the resin sheet which has the curved shape which is excellent in an optical characteristic and a thermomechanical characteristic can be manufactured with sufficient productivity. The resin sheet having a desired curved shape of the present invention is suitable as a protective plate for a display, a screen, a touch panel substrate, and a protective surface.

It is a figure of the specific example of the fixing jig used by the thermosetting of this invention. It is a figure of the specific example of the fixing jig used by the thermosetting of this invention. It is a figure of the specific example of the fixing jig used by the thermosetting of this invention.

Hereinafter, the present invention will be described in detail.
In the present invention, “(meth) acrylate” is a generic term for acrylate and methacrylate, and “(meth) acryloyl” is a generic term for acryloyl and methacryloyl. Moreover, polyfunctional here means having two or more (meth) acryloyl groups in a molecule | numerator.

The photocurable composition (A) used in the present invention may be any composition as long as it can be cured by light irradiation, and in particular, it is a composition containing a (meth) acryloyl group in terms of the productivity of the resin sheet. Is preferred.
Specifically, for example, the photocurable composition (A) preferably contains the following components (A1) and (A2) from the viewpoint of the heat resistance of the resin sheet.
(A1) Multifunctional (meth) acrylate compound (A2) Photopolymerization initiator

Examples of the polyfunctional (meth) acrylate compound (A1) include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, Propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate 1,6-hexanediol di (meth) acrylate, nonanediol di (meth) acrylate, glycerin di (meth) acrylate, pentaerythritol di (meth) ) Acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether di (meth) acrylate, hydroxypivalic acid modified neopentyl glycol di (meth) acrylate, isocyanuric acid ethylene oxide modified di (meth) acrylate, 2- Aliphatic compounds such as (meth) acryloyloxyethyl acid phosphate diester, bis (hydroxy) tricyclo [5.2.1.0 ^2,6 ] decane = di (meth) acrylate, bis (hydroxymethyl) tricyclo [5. 2.1.0 ^2,6] decane = di (meth) acrylate, bis (hydroxymethyl) pentacyclo [6.5.1.1 ^{3, 6.} 0 ^2,7 . 0 ^9,13 ] pentadecane = di (meth) acrylate, bis (hydroxymethyl) pentacyclo [6.5.1.1 ^3,6 . 0 ^2,7 . 0 ^9,13 ] pentadecane = di (meth) acrylate, 2,2-bis [4- (β- (meth) acryloyloxyethoxy) cyclohexyl] propane, 1,3-bis ((meth) acryloyloxymethyl) cyclohexane, 1,3-bis ((meth) acryloyloxyethyloxymethyl) cyclohexane, 1,4-bis ((meth) acryloyloxymethyl) cyclohexane, 1,4-bis ((meth) acryloyloxyethyloxymethyl) cyclohexane, etc. Alicyclic compound, diglycidyl phthalate di (meth) acrylate, ethylene oxide modified bisphenol A (2,2'-diphenylpropane) type di (meth) acrylate, propylene oxide modified bisphenol A (2,2'-diphenyl) Propane) type di (meth) acryle Bifunctional (meth) acrylates such as aromatic compounds such as carbonate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate , Dipentaerythritol hexa (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, tri (meth) acryloyloxyethoxytrimethylolpropane, glycerin polyglycidyl ether poly (meth) acrylate, isocyanuric acid ethylene oxide modified tri (meth) acrylate , Ethylene oxide modified dipentaerythritol penta (meth) acrylate, ethylene oxide modified dipentaerythritol hexa (meth) acrylate , Aliphatic compounds such as ethylene oxide-modified pentaerythritol tri (meth) acrylate, ethylene oxide-modified pentaerythritol tetra (meth) acrylate, 1,3,5-tris ((meth) acryloyloxymethyl) cyclohexane, 1,3 , 5-tris ((meth) acryloyloxyethyloxymethyl) cyclohexane and other trifunctional or higher functional (meth) acrylates. Other examples include urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, and polyether (meth) acrylate.

In the present invention, as the polyfunctional (meth) acrylate compound (A1), those containing an alicyclic structure are preferable in terms of rigidity and little heat discoloration. Moreover, it is preferable to contain polyfunctional (meth) acrylate and urethane (meth) acrylate in terms of surface hardness, and in particular, in terms of heat resistance, bis (hydroxy) tricyclo [5.2.1.0]. ^2,6 ] decane = di (meth) acrylate, bis (hydroxymethyl) tricyclo [5.2.1.0 ^2,6 ] decane = di (meth) acrylate, pentaerythritol tetra (meth) acrylate, trimethylolpropane tri It is preferable to contain polyfunctional (meth) acrylates such as (meth) acrylate and urethane (meth) acrylate.

  The urethane (meth) acrylate suitably used in the present invention is obtained, for example, by reacting polyisocyanate and a hydroxyl group-containing (meth) acrylate using a catalyst such as dibutyltin dilaurate as necessary. It is preferable.

Specific examples of the polyisocyanate include aliphatic polyisocyanates such as ethylene diisocyanate and hexamethylene diisocyanate, isophorone diisocyanate, bis (isocyanatomethyl) tricyclo [5.2.1.0 ^2,6 ] decane, and norbornene diisocyanate. 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, bis (4-isocyanatocyclohexyl) methane, 2,2-bis (4-isocyanatocyclohexyl) propane, water Polyisocyanates having an alicyclic structure such as a trimer compound of added xylylene diisocyanate and isophorone diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, tolylene diisocyanate, Such polyisocyanates having an aromatic ring such as lid diisocyanate. Of these, isophorone diisocyanate and norbornene diisocyanate are preferable in terms of low curing shrinkage.

  Specific examples of the hydroxyl group-containing (meth) acrylate include, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-hydroxy-3- (meth). Examples include acryloyloxypropyl (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, and dipentaerythritol tri (meth) acrylate. Of these, pentaerythritol tri (meth) acrylate and dipentaerythritol tri (meth) acrylate are preferable in terms of the pencil hardness of the resin sheet.

  Two or more urethane (meth) acrylates obtained by the reaction of polyisocyanate and hydroxyl group-containing (meth) acrylate may be used in combination. Among these reactants, acrylate compounds are preferable from the viewpoint of curing speed, and 2-9 functions, particularly 2-6 functions, are particularly preferable from the viewpoint of surface hardness and bending elastic modulus.

  When polyfunctional (meth) acrylate and urethane (meth) acrylate are contained as the photocurable composition (A), the content ratio (weight ratio) is multifunctional in terms of thermomechanical properties of the resin sheet. (Meth) acrylate / urethane (meth) acrylate is preferably 95/5 to 50/50, more preferably 92/8 to 60/40, and particularly preferably 90/10 to 70/30. If the urethane (meth) acrylate content is too small, the pencil hardness tends to decrease, and if it is too large, the water absorption tends to increase.

  In addition, the photocurable composition (A) used in the present invention may contain a monofunctional (meth) acrylate. Examples of the monofunctional (meth) acrylate include methyl (meth) acrylate and ethyl. (Meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, Tetrahydrofurfuryl (meth) acrylate, 2-ethylhexyl (meth) acrylate, glycidyl (meth) acrylate, cyclohexyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, tricyclodecyl (meth) acrylate, tricyclo Siloxymethyl (meth) acrylate, tricyclodecyloxyethyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxymethyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, isobornyl (meth) Acrylate, norbornyl (meth) acrylate, adamantyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate, 3-hydroxy-1-adamantyl (meth) acrylate, Examples include benzyl (meth) acrylate. Among these, alicyclic skeletons such as cyclohexyl (meth) acrylate, tricyclodecyl (meth) acrylate, tricyclodecyloxymethyl (meth) acrylate, isobornyl (meth) acrylate, norbornyl (meth) acrylate, and adamantyl (meth) acrylate (Meth) acrylate is preferred in terms of low cure shrinkage.

  When the monofunctional (meth) acrylate is contained as the photocurable composition (A), its content is 50 in terms of heat resistance with respect to 100 parts by weight of the polyfunctional (meth) acrylate compound. The amount is preferably not more than parts by weight, more preferably not more than 30 parts by weight, particularly preferably not more than 10 parts by weight. If the content is too large, the heat resistance tends to decrease. In addition, the minimum of content in the case of containing monofunctional (meth) acrylate is 0.001 weight part normally.

  The photopolymerization initiator (A2) used in the present invention is not particularly limited as long as it can generate radicals by irradiation with active energy rays, and various photopolymerization initiators can be used. For example, benzophenone, benzoin methyl ether, benzoin propyl ether, diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2,6-dimethylbenzoyl diphenylphosphine oxide, 2,4,6-trimethylbenzoyl diphenylphosphine oxide and the like can be mentioned. Among these, photopolymerization initiators such as 1-hydroxycyclohexyl phenyl ketone and 2,4,6-trimethylbenzoyldiphenylphosphine oxide are particularly preferable. These photopolymerization initiators may be used alone or in combination of two or more.

  These photopolymerization initiators (A2) are polyfunctional (meth) acrylate compounds (A1) (when monofunctional (meth) acrylates are contained, polyfunctional (meth) acrylate compounds (A1) and monofunctional ( It is preferably used at a ratio of usually 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, particularly 0.2 to 3 parts by weight, based on 100 parts by weight of the total of (meth) acrylate. Is preferred. If the amount used is too small, the polymerization rate tends to decrease and polymerization does not proceed sufficiently. If the amount is too large, the light transmittance of the resulting resin sheet tends to decrease (yellowing).

  Moreover, you may use a thermal polymerization initiator together with a photoinitiator. As the thermal polymerization initiator, known compounds can be used, such as hydroperoxide, t-butyl hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, and the like. Hydroperoxides, dialkyl peroxides such as di-t-butyl peroxide and dicumyl peroxide, t-butyl peroxybenzoates, peroxyesters such as t-butylperoxy (2-ethylhexanoate), benzoyl Examples include peroxides such as diacyl peroxides such as peroxides, peroxycarbonates such as diisopropylperoxycarbonate, peroxyketals, and ketone peroxides.

  In addition to the polyfunctional (meth) acrylate compound (A1) and the photopolymerization initiator (A2), the photocurable composition (A) used in the present invention includes a chain transfer agent, an oxidation agent, as appropriate. You may contain auxiliary components, such as an inhibitor, a ultraviolet absorber, a thickener, an antistatic agent, a flame retardant, an antifoamer, a coloring agent, and various fillers.

  Examples of the chain transfer agent include polyfunctional mercaptan-based compounds such as pentaerythritol tetrakisthioglycolate and pentaerythritol tetrakisthiopropionate. These polyfunctional mercaptan-based compounds are preferably used at a ratio of usually 10 parts by weight or less, more preferably 5 parts by weight or less, particularly 100 parts by weight of the polyfunctional (meth) acrylate-based compound (A1). Is preferably 3 parts by weight or less. When there is too much this usage-amount, there exists a tendency for the heat resistance and rigidity of the resin sheet obtained to fall. The lower limit of the polyfunctional mercaptan compound is usually 0.0001 parts by weight.

  Examples of the antioxidant include 2,6-di-t-butylphenol, 2,6-di-t-butyl-p-cresol, 2,4,6-tri-t-butylphenol, 2,6-di- t-butyl-4-s-butylphenol, 2,6-di-t-butyl-4-hydroxymethylphenol, n-octadecyl-β- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) ) Propionate, 2,6-di-tert-butyl-4- (N, N-dimethylaminomethyl) phenol, 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, 2,4 -Bis (n-octylthio) -6- (4-hydroxy-3 ', 5'-di-t-butylanilino) -1,3,5-triazine, 4,4-methylene-bis (2,6-di-) t-Butylpheno ), 1,6-hexanediol bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], bis (3,5-di-tert-butyl-4-hydroxybenzyl) sulfide 4,4′-di-thiobis (2,6-di-t-butylphenol), 4,4′-tri-thiobis (2,6-di-t-butylphenol), 2,2-thiodiethylenebis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis- (3,5-di-t-butyl-4-hydroxyhydrocinnamide), N, N′-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine, calcium (3,5-di-tert-butyl-4-hydroxybenzyl) monoethyl phosphonate 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tris (3,5-di-tert-butyl-4-hydroxy) Phenyl) isocyanurate, tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris-2 [3 (3,5-di-tert-butyl-4-hydroxy) Phenyl) propionyloxy] ethyl isocyanate, tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4-hydroxyphenyl) propionate] methane, 3,5-di-t-butyl-4-hydroxybenzyl Examples of the compound include phosphite-diethyl ester, and these compounds may be used alone or in combination of two or more. Among these, 1,6-hexanediol bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,2-thiodiethylene bis [3- (3,5-di-) t-butyl-4-hydroxyphenyl) propionate], tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4-hydroxyphenyl) propionate] methane suppresses yellowing of the resin sheet To preferred.

  The ultraviolet absorber is not particularly limited as long as it is soluble in the photocurable composition (A), and various ultraviolet absorbers can be used. Specific examples include salicylic acid ester, benzophenone, triazole, hydroxybenzoate, and cyanoacrylate. These ultraviolet absorbers may be used in combination. Among these, from the viewpoint of compatibility with the photocurable composition (A), benzophenone or triazole, specifically, (2-hydroxy-4-octyloxy-phenyl) -phenyl-methanone, 2-benzo Ultraviolet absorbers such as triazol-2-yl-4-tert-octyl-phenol are preferred. It is preferable that the content rate of a ultraviolet absorber is 0.001-1 weight% normally with respect to a photocurable composition (A), Most preferably, it is 0.01-0.1 weight%. If the amount of the ultraviolet absorber is too small, the light resistance of the resin sheet tends to decrease, and if it is too large, the light transmittance of the resin sheet tends to decrease.

In the present invention, the photocurable composition (A) obtained above is cured to obtain a transparent resin sheet.
In curing, the photocurable composition (A) is preferably photocured and then thermally cured. First, photocuring will be described.
In addition, the curing degree in this specification means the reaction rate of the (meth) acryloyl group.

  First, the photocurable composition (A) is filled into a space of a mold composed of two flat plates at least one of which is transparent and a spacer for controlling the thickness. As the flat plate, a glass plate is particularly preferable.

  The glass plate preferably has a thickness of 1 to 10 mm from the viewpoint of the strength of the mold, and more preferably, from the viewpoint of the surface smoothness of the resin sheet, at least one glass surface in contact with the photocurable composition (A) is optical. It is preferably polished. In particular, the surface smoothness Ra is preferably 50 nm or less. When the glass plate is too thin, it cannot withstand the shrinkage stress generated when the photocurable composition (A) is cured, and the glass plate tends to be cracked or warped. The glass plate may be chemically strengthened from the viewpoint of such strength. If the glass plate is too thick, the weight of the glass increases and the load on the equipment increases. In order to improve the demoldability of the resin sheet, the surface of the glass plate may be treated with a release agent.

  Moreover, in order to give a lens function, an anti-glare function, an anti-Newton ring function, etc. to the surface of a resin sheet, you may form a fine unevenness | corrugation on the surface of the flat plate which a photocurable composition (A) touches. By transferring such fine irregularities to the resin sheet, a resin sheet having a lens function, an antiglare function, or an anti-Newton ring function, or a resin sheet having a curved shape in the present invention can be obtained. In such a case, it is possible to use a technique such as sandblasting or etching in order to form fine irregularities on the surface of the flat plate.

  The spacer controls the thickness of the resin sheet, but the material is not particularly limited, and a known material such as a resin is used. Among the resins, rubbery materials such as silicon resin are preferable.

  After the photocurable composition (A) is filled in the space of the mold, light irradiation is performed. As a light source to be used, a general ultraviolet lamp can be used, but a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, a xenon lamp, an LED lamp, etc. are used because of the availability and price of the irradiation device. .

The irradiation dose is preferably 0.1~100J / cm ^2, more preferably, 1~50J / cm ^2, more preferably 2~30J / cm ^2, particularly preferably from 3~20J / cm ^2. If the amount of irradiation light is too small, undulation tends to occur in the subsequent thermosetting, and if too much, it tends to be difficult to form a curved shape in the subsequent thermosetting.

The illuminance is preferably 10~100000mW / cm ^2, more preferably, in terms of fast light cure, 50~10000mW / cm ^2, more preferably, from the viewpoint of curing the inside of the resin sheet, 100~1000mW / cm ² .
Light irradiation can be performed from one side or both sides. It is also possible to divide it into multiple times.

In the present invention, it is preferable to control the reaction rate of (meth) acryloyl groups by photocuring to 50 to 90%. More preferably, it is 60 to 85%, and particularly preferably 70 to 80%. If the reaction rate is too small, undulation is likely to occur in the subsequent thermosetting, and if it is too large, it tends to be difficult to form a curved shape in the subsequent thermosetting. The reaction rate of the (meth) acryloyl group can be measured by an analytical method such as solid-state NMR or IR.
Examples of a method for controlling the reaction rate within the above range include adjusting the type and amount of the polyfunctional (meth) acrylate compound (A1) and the photopolymerization initiator (A2), controlling the illuminance and the light amount, and adjusting the curing temperature. It is done.

  After photocuring so as to be within the above reaction rate range, the obtained resin sheet is removed from the mold and peeled off. The resin sheet obtained here is called a photocured sheet. Since the photocuring sheet at this stage is flat, various processes such as printing, coating, cutting, cutting, drilling, and C surface processing can be easily performed.

  Next, in the present invention, the photocured sheet after photocuring is fixed in a curved shape, and thermosetting is performed. Specifically, the light-curing sheet is heat-cured while being fixed to a fixing jig so that the radius of curvature is 0.1 to 5 m in at least one direction within the surface, and the (meth) acryloyl group after heat-curing It is preferable to perform thermosetting so that the reaction rate is 1 to 40%, particularly 5 to 30%, more preferably 10 to 20% higher than the reaction rate after photocuring. If the difference between the reaction rate after heat curing and the reaction rate after photocuring is too small, the curing tends to be insufficient, and if too large, the resin sheet tends to be easily deformed.

  As a heating device used for thermosetting, a normal oven can be used. In the case where the curing process is performed continuously, an infrared heater can be used. The atmosphere in the oven may be any of air, inert gas, and vacuum, but vacuum is preferred in order to complete the curing reaction. The heating temperature is usually 50 to 300 ° C, more preferably 100 to 250 ° C, and particularly preferably 150 to 200 ° C. If the temperature is too low, thermosetting does not complete and the physical properties of the resin sheet tend to become unstable. Conversely, if the temperature is too high, the hue of the resin sheet tends to decrease. The heating time is usually 10 minutes to 20 hours, more preferably 30 minutes to 10 hours, and particularly preferably 1 to 7 hours. If the heating time is too short, thermosetting is not completed and the physical properties of the resin sheet become unstable. On the contrary, if the length is too long, the hue of the resin sheet tends to decrease.

  Although it does not specifically limit as a fixing jig, For example, the vertical holder as shown in FIG. 1, and the horizontal holder as shown in FIG. 2 and FIG. 3 are mentioned.

  In the present invention, the reaction rate of the (meth) acryloyl group after thermosetting is preferably 70% or more from the viewpoint of stabilization of physical properties. More preferably, it is 70-99%, Most preferably, it is 75-95%, More preferably, it is 80-90%. When the reaction rate is too low, thermomechanical properties such as heat resistance and surface hardness tend to be lowered. In general, the upper limit of the reaction rate is 99.9%.

  As a method for controlling the reaction rate after such heat curing, adjusting the kind and amount of the polyfunctional (meth) acrylate compound (A1) and the photopolymerization initiator (A2), the heating temperature and the heating time can be mentioned. .

  After thermosetting, the resin sheet is removed from the fixing jig to obtain the resin sheet having the desired curved shape of the present invention. In addition, it is possible to further heat-treat such a resin sheet in order to improve the degree of curing and to remove stress strain.

  Although the thickness of the resin sheet of this invention changes with uses, it is 0.1-10 mm, Preferably it is 0.2-5 mm, Most preferably, it is 0.2-2 mm. If the thickness is too thin, the rigidity of the display substrate tends to decrease, and if it is too thick, it tends to be difficult to reduce the weight and thickness of the display.

  In general, the resin sheet of the present invention preferably has a total light transmittance of 85% or more, more preferably 88% or more, and particularly preferably 90% or more. If the total light transmittance is too small, the brightness of the display tends to decrease.

  The resin sheet of the present invention preferably has a retardation of 10 nm or less, more preferably 5 nm or less, and particularly preferably 2 nm or less. If the phase difference is too large, the fineness of the image tends to decrease when used for a display. The lower limit value of the phase difference is usually 0.01 nm.

  The resin sheet of the present invention preferably has a glass transition temperature of 150 ° C. or higher from the viewpoint of heat resistance. When the glass transition temperature is too low, the curvature of the resin sheet having a curved shape tends not to be stabilized. The preferable range of the glass transition temperature is 170 to 400 ° C, more preferably 190 to 300 ° C, and still more preferably 200 to 250 ° C. In adjusting this glass transition temperature to the said range, the method of controlling suitably the kind of photocurable composition (A) mentioned above and content of a component is mentioned. For example, the technique of raising the functional group number of a polyfunctional (meth) acrylate type compound (A1) is mentioned.

  The resin sheet of the present invention preferably has a pencil hardness of 3H or more, more preferably 5H or more, and particularly preferably 7H or more. If the pencil hardness is too low, the surface hardness as the protective plate tends to decrease. In adjusting such a pencil within the above range, a method of appropriately controlling the type of the photocurable composition (A) and the content of the components described above can be used. For example, a polyfunctional (meth) acrylate compound (A1), particularly a urethane (meth) acrylate having 3 to 6 functional groups may be used.

  The resin sheet of the present invention can be cut into a desired size by a known technique such as NC processing, punching processing, or laser processing. In such a case, it is preferable to apply a curved resin sheet to a flat support or press the resin sheet to make it flat once before processing. In view of such workability, the flexural modulus of the resin sheet is preferably 3 to 5 GPa. More preferably, it is 3.5-4GPa. If the flexural modulus is too low, the curved shape is not stabilized, and the rigidity as a display substrate tends to be reduced. Conversely, if the flexural modulus is too high, cracks tend to occur during processing.

  In adjusting the flexural modulus to the above range, a method of appropriately controlling the type of the photocurable composition (A) and the content of the components can be used. For example, polyfunctional (meth) acrylate compounds (A1), in particular, those having 2 to 6 functionalities as urethane (meth) acrylate may be used.

  The resin sheet having a curved shape can be obtained by the method described in detail above, but the radius of curvature of the resin sheet of the present invention is 0.1 to 5 m with respect to at least one in-plane direction, and the preferable lower limit is 0. The upper limit is preferably 3 m, more preferably 2 m, especially 1 m, especially 0.9 m, more preferably 0.8 m. If the radius of curvature is too small, it tends to be difficult to design as a display. Conversely, if it is too large, the impression as a curved display tends to be lacking.

  The curvature radius of the resin sheet of the present invention preferably has an in-plane tolerance of 10% or less. More preferably, it is 7% or less, and particularly preferably 5% or less. If the in-plane tolerance is too large, it is difficult to design a display. The lower limit of the in-plane tolerance is usually 0.1%.

In the present invention, the radius of curvature is obtained by equally cutting out nine test pieces from the resin sheet, measuring the radius of curvature in the bending direction with a caliper, and setting the average value thereof. The maximum value and the minimum value in the radius of curvature are calculated according to the following formula.
In-plane tolerance (%) = 100 × (maximum value of curvature radius−minimum value of curvature radius) / (average value of curvature radius)

  An adhesive layer, a hard coat layer, a printing layer, a gas barrier film, and a transparent conductive film can be formed on the resin sheet having a curved shape of the present invention according to various applications.

  Examples of the transparent conductive film include inorganic films such as indium and tin oxide (ITO) and organic films such as poly (3,4-ethylenedioxythiophene) (PEDOT). Among these, an ITO film is preferable in terms of conductivity and transparency. The film thickness of such a transparent conductive film is usually 100 to 5000 mm, preferably 200 to 3000 mm, and more preferably 300 to 2000 mm. If the film thickness is too thick, the substrate tends to swell, and if it is too thin, the conductivity tends to be insufficient.

  In forming the transparent conductive film, the film formation temperature is preferably 50 ° C to 300 ° C, more preferably 100 to 250 ° C, and still more preferably 130 to 200 ° C. If the film forming temperature is too low, the conductivity tends to be insufficient. Conversely, if the film forming temperature is too high, the light transmittance of the resin sheet tends to decrease.

  The conductivity of the obtained resin sheet having a curved shape with a transparent conductive film is preferably 500 Ω / □ or less, more preferably 200 Ω / □ or less, and further preferably 100 Ω / □ or less. Tend to decrease.

  Thus, the resin sheet having the curved shape of the present invention can be produced with high productivity, and the obtained resin sheet has an excellent effect on optical characteristics and thermomechanical characteristics, and a protective plate for display and a touch panel substrate. Furthermore, it is suitable as a face body for a protective surface.

  In particular, when the resin sheet of the present invention is used as a face body for a protective surface, it is important to have excellent solvent resistance and chemical resistance. Solvents include alcohols such as methanol and isopropyl alcohol, aliphatic hydrocarbons such as hexane and octane, alicyclic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as toluene and xylene, methyl acetate, ethyl acetate Esters such as acetone, ketones such as methyl ethyl ketone and γ-butyl lactone, chlorinated hydrocarbons such as methylene chloride, chloroform and chlorobenzene, ethers such as ethyl ether and tetrahydrofuran, ethylene glycols, N, N-dimethylformamide , N-methylpyrrolidone, gasoline, oil and the like. Examples of the chemical include alkaline water and hydrochloric acid. In general, it is preferable that no abnormality occurs in appearance even when immersed in these solvents and chemicals. Furthermore, it is preferable that no abnormality occurs in appearance even when exposed to solvent vapor.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example, unless the summary is exceeded.
In the examples, “parts” and “%” mean weight basis.

(1) Reaction rate of (meth) acryloyl group (%)
A test piece of 50 mm × 50 mm was cut out from a 150 mm × 150 mm resin sheet, freeze-pulverized, and then “AVANCE DPX-400” manufactured by BRUKER BIOSPIN, using a solid NMR probe, the observation nucleus was 13 C, and the rotation speed was 5000 Hz. And measured at room temperature (25 ° C.). The carbonyl carbon in the unpolymerized (meth) acryloyl group is detected on the high magnetic field side (166 ppm), and the polymerized carbonyl carbon is detected on the low magnetic field side (176 ppm). The reaction rate (%) was calculated from the ratio of these peak areas.

(2) Radius of curvature (m) and in-plane tolerance of curvature radius (%)
Nine 50 mm × 50 mm test pieces were cut out from a 150 mm × 150 mm resin sheet, and the radius of curvature in the bending direction was determined by measurement with calipers. The average value of the nine pieces was used as the radius of curvature of the resin sheet, and the in-plane tolerance (%) was calculated from the maximum value and the minimum value among the nine pieces according to the following formula.
In-plane tolerance (%) = 100 × (maximum value of curvature radius−minimum value of curvature radius) / (average value of curvature radius)

(3) Total light transmittance (%)
A 50 mm x 50 mm test piece was cut out from a 150 mm x 150 mm resin sheet, attached to a metal frame so as to be flat, and then measured for total light transmittance (%) with a Nippon Denshoku haze meter "NDH-2000". did.

(4) Flexural modulus (GPa)
A test piece having a length of 25 mm and a width of 10 mm was cut out from a 150 mm × 150 mm resin sheet and pressed from the convex direction with an autograph “AG-5kNE” (20 mm distance between fulcrums, 0.5 mm / min) manufactured by Shimadzu Corporation. The flexural modulus was measured.

(5) Pencil hardness A test piece of 50 mm × 50 mm was cut out from a resin sheet of 150 mm × 150 mm, and the pencil hardness was measured according to JIS K-5600.

(6) Glass transition temperature (° C)
A test piece having a length of 20 mm and a width of 5 mm was cut out from a resin sheet of 150 mm × 150 mm, and using a tensile mode of a dynamic viscoelastic device “DVE-V4 type FT Rheospectr” manufactured by Rheology, a frequency of 10 Hz, a heating rate The measurement was performed at 3 ° C./min and a strain of 0.025%.
The ratio (tan δ) of the imaginary part (loss elastic modulus) to the real part (storage elastic modulus) of the obtained complex elastic modulus was determined, and the maximum peak temperature of tan δ was defined as the glass transition temperature (° C.).

(7) Phase difference (nm)
A test piece having a length of 50 mm and a width of 50 mm was cut out from a resin sheet of 150 mm × 150 mm, and a retardation (nm) at a wavelength of 550 nm was measured at 25 ° C. using RETS100A manufactured by Otsuka Electronics.

(8) Solvent resistance A test piece of 50 mm × 50 mm was cut out from a 150 mm × 150 mm resin sheet, immersed in N-methylpyrrolidone at 40 ° C. for 10 minutes, and then the appearance was visually observed. The evaluation criteria are as follows.
○ ・ ・ ・ There was no abnormality in the appearance. × ・ ・ ・ An abnormality such as cloudiness occurred in the appearance.

(9) Surface resistance (Ω / □)
Measurement was performed using a 4-terminal resistance measuring instrument (Lorestar MP) manufactured by Mitsubishi Chemical Corporation.

<Example 1>
Two optical polishing glass plates of 170 mm × 170 mm × 8 mm size are opposed to each other, and bis (hydroxymethyl) tricyclo [5.2. 1.0 ^2,6 ] decane diacrylate (“A-DCP” manufactured by Shin-Nakamura Chemical Co., Ltd.) 90 parts, alicyclic structure-containing hexafunctional urethane acrylate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 10 parts, 1-hydroxycyclohexyl A photocurable composition (A) consisting of 1 part of phenylketone (“Irgacure 184” manufactured by Ciba Specialty Chemicals) was injected at 23 ° C. The mold was placed horizontally and conveyed with a conveyor, and irradiated with ultraviolet rays at a light intensity of 10 J / cm ² using a metal halide lamp. The obtained photocured sheet was removed from the mold, and a 150 mm × 150 mm × 0.7 mm resin sheet (A-1) was obtained by laser cutting. Next, the obtained resin sheet (A-1) is attached to the fixing jig (see FIG. 2) so that the curvature radius is 0.4 m in one direction in the plane, and is mounted in a vacuum oven at 1000 Pa, Heat curing was performed by heating at 200 ° C. for 5 hours to obtain a resin sheet (B-1) having a curved shape. The average curvature radius of the obtained resin sheet having a curved shape was 0.4 m, and various properties were as shown in Tables 2 and 3.
When a transparent conductive film made of ITO having a thickness of 300 mm was formed at 180 ° C. on the concave surface of the obtained resin sheet (B-1) by sputtering, a substrate with a transparent conductive film was obtained. It was 100Ω / □ and good.

<Examples 2 to 7>
A photocurable sheet, a resin sheet (A-1), and a resin having a curved shape in the same manner as in Example 1 except that the photocurable composition in Table 1 and the photocuring conditions and thermosetting conditions in Table 2 were used. A sheet (B-1) and a substrate with a transparent conductive film were obtained. Various characteristics were as shown in Tables 2 and 3.

<Comparative Example 1>
A photocurable sheet and a resin sheet having a curved shape were obtained in the same manner as in Example 1 except that the photocurable composition of Table 1 and the photocuring conditions and thermosetting conditions of Table 2 were used. However, the obtained resin sheet having a curved shape was wavy and the radius of curvature was not constant. Various characteristics were as shown in Tables 2 and 3.

<Comparative Example 2>
As shown in Table 1, a commercially available 0.7 mm thick polycarbonate sheet was cut into 150 mm × 150 mm and heat treated at 1000 Pa in a vacuum oven at 200 ° C. for 5 hours in the same manner as in Example 1. A resin sheet having a significantly curved shape and a desired curved shape could not be obtained. In addition, when the solvent resistance test of the base plate was performed, it became cloudy. Various characteristics were as shown in Tables 2 and 3.

<Comparative Example 3>
Using the photocurable composition of Table 1, the photocured sheet obtained under the photocuring conditions of Table 2 was mounted on a fixing jig (see FIG. 1) so as to have a radius of curvature of 0.4 m, and was not heated. The same procedure as in Example 1 was conducted except that the sample was left at room temperature for 5 hours. However, a resin sheet having a curved shape was not obtained. Various characteristics of the flat resin sheet were as shown in Tables 2 and 3.
A transparent conductive film made of ITO having a thickness of 300 mm at 180 ° C. was formed on one side of the obtained resin sheet by sputtering, and a substrate with a transparent conductive film was obtained. The surface resistance value was 100Ω / □. It was.

  As described above, in the examples, a resin sheet having a curved shape with a desired radius of curvature can be easily obtained, and the optical characteristics and mechanical characteristics of the obtained resin sheet are good, but compared. In any of the examples, a resin sheet having a desired curved shape could not be obtained and could not be put to practical use.

  The resin sheet having a curved shape obtained by the present invention can be advantageously used for various optical materials and electronic materials. For example, protective sheet, screen, touch panel, liquid crystal substrate, organic / inorganic EL substrate, PDP substrate, electronic paper substrate, light guide plate, retardation plate, optical filter, various display members, optical disk substrate, etc. It can be used for memory / recording applications, energy applications such as thin film battery substrates and solar cell substrates, optical communication applications such as optical waveguides, functional films / sheets, and various optical films / sheets. In addition to the optical material and the electronic material, for example, it can also be used for a mask for a protective surface, protective glasses, a lighting material, an automobile material, a building material, a medical material, a stationery, and the like.

Claims (12)

  It is a transparent resin sheet having a thickness of 0.1 to 10 mm obtained by curing the photocurable composition (A), and is curved in a range of curvature radius of 0.1 to 5 m in at least one direction in the plane. A resin sheet characterized by   After photocuring the photocurable composition (A), it is cured by fixing with a fixing jig so that the radius of curvature is in the range of 0.1 to 5 m in at least one direction within the surface. The resin sheet according to claim 1, wherein   The resin sheet according to claim 1 or 2, wherein an in-plane tolerance of the radius of curvature is within 10%.   The photocurable composition (A) is a composition containing a (meth) acryloyl group, the reaction rate of the (meth) acryloyl group after photocuring is 50 to 90%, and the (meth) acryloyl after thermosetting The resin sheet according to any one of claims 1 to 3, wherein the reaction rate of the group is 1 to 40% higher than the reaction rate after photocuring. A photocurable composition (A) contains the following component (A1) and (A2), The resin sheet as described in any one of Claims 1-4 characterized by the above-mentioned.
(A1) Multifunctional (meth) acrylate compound (A2) Photopolymerization initiator   The resin sheet according to claim 1, wherein the glass transition temperature is 150 ° C. or higher.   The resin sheet according to any one of claims 1 to 6, wherein the flexural modulus is 3 to 5 GPa.   Pencil hardness is 3H or more, The resin sheet as described in any one of Claims 1-7 characterized by the above-mentioned.   It is used for the protective plate for displays, The resin sheet as described in any one of Claims 1-8 characterized by the above-mentioned.   It is used for the screen of a display, The resin sheet as described in any one of Claims 1-8 characterized by the above-mentioned.   It is used for the face body for protective surfaces, The resin sheet as described in any one of Claims 1-8 characterized by the above-mentioned.   A touch panel substrate comprising a transparent conductive film formed on at least one surface of the resin sheet according to claim 1.

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