WO2016158827A1 - Layered body - Google Patents

Abstract

The purpose of the present invention is to provide a novel layered body, which is a layered body that has an adhesive sheet and a front panel comprising a polycarbonate-based resin layer and a thermoplastic resin different from this polycarbonate-based resin, and that also has outstanding shape stability in a high-temperature and high-humidity environment. Provided is a layered body having a front panel and an adhesive sheet, the layered body being characterized in that: the front panel comprises a B layer having a polycarbonate-based resin as a principal constituent resin and an A layer having a thermoplastic resin different from the polycarbonate-based resin as a principal constituent; the total thickness of the A layer is 10-250 µm, and the ratio ((A)/(T)) of the thickness (A) of one A layer to the total thickness (T) of the A layer and the B layer is 0.05-0.40; and the internal stress (σ) of the front panel and the adhesive sheet when the layered body of the front panel and the adhesive sheet is exposed for 120 hours to an environment with a temperature of 85°C and a humidity of 85% RH is 0.47 MPa or less.

Description

Laminated body

The present invention relates to a laminate. Specifically, the present invention relates to a laminate that is used as a substrate material or a protective material, and can be suitably used as a cover material for a surface protection panel of an image display device, a mobile phone, a smartphone, a tablet device, a wearable terminal, or the like.

Conventionally, glass has been mainly used as a cover material for image display devices. However, since glass is easily broken by an impact and is heavy, substitution with a resin material has been studied.

The resin material as such a glass substitute material is mainly required to have impact resistance, surface hardness, and shape stability in a high temperature and high humidity environment.
Polycarbonate resin plates have transparency and are excellent in impact resistance and heat resistance, and thus are used for soundproof partitions, carports, signboards, glazing materials, lighting fixtures, and the like. However, since the surface hardness is low, it has a drawback of being easily scratched.

In order to improve this defect, for example, Patent Document 1 discloses a resin laminate obtained by subjecting a laminate obtained by coextruding a polycarbonate resin and an acrylic resin to a hard coat treatment.

As a method for suppressing the warpage of the polycarbonate resin plate, for example, Patent Document 2 discloses a resin laminate in which a methyl methacrylate-styrene copolymer resin (MS resin) is laminated on a polycarbonate resin.

Similarly, as a method for suppressing the warpage of the polycarbonate resin plate, Patent Document 3 discloses a resin laminate in which the glass transition temperature difference and the water absorption difference of each layer in which a polycarbonate resin is laminated are defined.

JP 2006-103169 A JP 2010-167659 A WO2014 / 061817

As described above, a front plate having a polycarbonate resin layer and a layer made of a thermoplastic resin different from the polycarbonate resin is laminated on a base material via an adhesive sheet, for example, It is used as a surface protection panel and cover material. However, since the front plate having such a structure has a different coefficient of thermal expansion or moisture absorption between a polycarbonate resin and a thermoplastic resin different from the polycarbonate resin, for example, when placed in a high temperature and high humidity environment, one resin There was a problem that it was difficult to maintain the shape stability of the front plate, such as the layer absorbing moisture and changing dimensions.

Therefore, the present invention relates to a laminate comprising a polycarbonate resin layer, a front plate having a thermoplastic resin layer different from the polycarbonate resin, and an adhesive sheet, and has excellent shape stability in a high temperature and high humidity environment. A new laminate will be provided.

The present invention is a laminate including a front plate and an adhesive sheet, wherein the front plate includes a B layer mainly composed of a polycarbonate resin and a thermoplastic resin different from the polycarbonate resin as a main component. The total thickness of the A layer is 10 to 250 μm, and the ratio of the thickness (A) of the one A layer to the total thickness (T) of the A layer and the B layer is ((A) / (T)) is 0.05 to 0.40, and is determined by the formulas (1) and (2) described below, and the temperature is 85 ° C. and the humidity is 85% RH for 120 hours. Proposed is a laminate in which the internal stress (σ) of the front plate and the pressure-sensitive adhesive sheet is 0.47 MPa or less when the laminate is exposed.

The laminate proposed by the present invention includes a total thickness of a thermoplastic resin A layer mainly composed of a thermoplastic resin different from a polycarbonate resin in the configuration of the front plate, and A with respect to the total layer thickness of the A layer and the B layer. By defining the thickness ratio ((A) / (T)) for one layer and by defining the internal stress (σ) within a predetermined range, it has excellent shape stability in a high-temperature and high-humidity environment. Can be demonstrated.
Therefore, the laminate proposed by the present invention can be suitably used as various substrate materials, protective materials, and the like, for example, by bonding them to a base material. For example, in addition to various substrate materials and protective materials as constituent materials for portable display devices such as mobile phone terminals, smartphones, portable electronic playground equipment, portable information terminals, tablet devices, mobile personal computers, wearable terminals, liquid crystal televisions, liquid crystal monitors, It can be suitably used as various substrate materials and protective materials as constituent materials for stationary display devices such as desktop personal computers, car navigation systems, and automobile meters.

It is a schematic diagram of a model for calculating internal stress.

Hereinafter, an example of the embodiment of the present invention will be described in detail.

In the present specification, “the“ main component ”for each layer” means a resin component having the highest content (mass%) in the resin composition forming each layer. Although not specified, as a guideline, a resin that occupies 50% by mass or more, particularly 80% by mass or more, particularly 90% by mass (including 100% by mass) of the resin contained in the resin composition forming each layer. In addition, when there are two or more types of main components, the total amount thereof corresponds to the content.
Further, “the“ main component ”of the polymer and its derivative” means a monomer having the highest ratio among the monomer units constituting the polymer and its derivative.

<This laminate>
A laminate according to an example of an embodiment of the present invention (hereinafter referred to as “the present laminate”) is a laminate including a front plate and an adhesive sheet. As described later, in a predetermined exposure test, the laminate and the front plate are adhered. The laminate is characterized in that the internal stress of the sheet is within a predetermined range.

<Front plate>
The front plate of this laminated body should just be provided with the B layer which has a polycarbonate-type resin as a main component, and the thermoplastic resin A layer which has a thermoplastic resin different from this polycarbonate-type resin as a main component. As an example, there may be mentioned those provided with an A layer containing an acrylic resin as a main component resin and a B layer containing a polycarbonate resin as a main component resin.

Moreover, for example, a front plate having a configuration in which an A layer is formed on one side or both sides of the B layer can be given.
Here, the front plate preferably has characteristics such as transparency, rigidity, impact resistance, secondary workability, and high surface hardness.

<A layer>
The A layer is a layer mainly composed of a thermoplastic resin different from the polycarbonate resin.
Here, “different” means that the types or composition ratios of the monomers constituting the polymer are not the same.

The thermoplastic resin as the main component of the A layer is not particularly limited as long as it is different from the polycarbonate resin as the main component of the B layer described later. For example, polyethylene terephthalate, polyethylene naphthalate, polypropylene terephthalate, polybutylene terephthalate. Polyester resins typified by aromatic polyesters such as poly-1,4-cyclohexylenedimethylene terephthalate, and aliphatic polyesters such as polylactic acid polymers, polyolefin resins such as polyethylene, polypropylene, and cycloolefin resins , Polycarbonate resin, acrylic resin, polystyrene resin, polyamide resin, polyether resin, polyurethane resin, polyphenylene sulfide resin, polyesteramide resin, polyether Steal resin, vinyl chloride resin, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, modified polyphenylene ether resin, polyarylate resin, polysulfone resin, polyetherimide resin, polyamideimide resin , Polyimide resins and copolymers containing these as main components, or mixtures of these resins. These may be one kind or a mixture of two or more kinds.

Moreover, as said polycarbonate resin as a main component of A layer, what is necessary is just different from the polycarbonate-type resin used as the main component of B layer mentioned later, for example, aliphatic polycarbonate, alicyclic polycarbonate, and bisphenol C are contained. And aromatic polycarbonate.

Here, although not particularly limited in the present invention, for example, when the A layer is a surface layer, it is preferable to select a resin having a higher hardness than the B layer. Specifically, an acrylic resin (a1) described later or a polycarbonate resin (a3) having a specific structure can be used.

<Preferable specific configuration example of layer A>
As a preferred example of the A layer, a layer containing an acrylic resin (a1) as a main component resin can be exemplified. Preferably, the A layer comprises an acrylic resin (a1), a copolymer having an aromatic vinyl monomer unit, a (meth) acrylic acid ester monomer unit, and an unsaturated dicarboxylic anhydride monomer unit. a2).
As another preferred example of the A layer, a layer containing a polycarbonate resin (a3) containing a structural unit derived from a dihydroxy compound in a part of the structure as a main component resin can also be mentioned.
Next, each of these component resins (a1) to (a3) will be described.

(Acrylic resin (a1))
The acrylic resin (a1) is a (co) polymer obtained by polymerizing a (meth) acrylic acid ester monomer unit as a main component and a derivative thereof.

Here, the “(meth) acrylic acid ester monomer unit” is meant to include an acrylic acid ester monomer unit or a methacrylic acid ester monomer unit.

Examples of the (meth) acrylic acid ester monomer unit include, for example, methyl methacrylate, methacrylic acid, acrylic acid, benzyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, and t-butyl. (Meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, glycidyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-methoxyethyl (meth) ) Acrylate, 2-ethoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, norbornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, disic Pentanyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, acrylic (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2- (meth) acryloyloxyethyl succinate 2- (meth) acryloyloxyethyl maleate, 2- (meth) acryloyloxyethyl phthalate, 2- (meth) acryloyloxyethyl hexahydrophthalate, pentamethylpiperidyl (meth) acrylate, tetramethylpiperidyl (Meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, etc. can be mentioned. These can be used alone or in combination of two or more. Examples of other monomer units that can be polymerized with these acrylic monomer units include olefin monomer units and vinyl monomer units.

Among them, the acrylic resin (a1) has a methyl methacrylate monomer, a methacrylic acid monomer, an acrylic acid monomer, a maleic anhydride monomer, and an aromatic vinyl monomer from the viewpoint of reducing internal stress. A copolymer with at least one of a monomer and a vinyl cyanide monomer can be suitably used.

There is no restriction | limiting in particular about the stereoregularity of acrylic resin (a1). However, the three-dimensional structure of the (meth) acrylic acid ester monomer unit is preferred because the higher the proportion of the syndiotactic structure, the higher the glass transition temperature and the better the heat resistance. From this viewpoint, among the triad fractions of mm, mr, and rr, those having a three-dimensional structure having the highest molar ratio of rr can be preferably used. This triad fraction can be measured by a known method using a nuclear magnetic resonance measuring apparatus (1H-NMR).

(Copolymer (a2))
As described above, the A layer is preferably a layer containing the acrylic resin (a1) and the copolymer (a2). Among them, it is preferable to form the A layer by mixing the acrylic resin (a1) and the copolymer (a2).

The copolymer (a2) is a copolymer having an aromatic vinyl monomer unit, a (meth) acrylic acid ester monomer unit, and an unsaturated dicarboxylic anhydride monomer unit.

Examples of the “aromatic vinyl monomer unit” include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, α- Examples include units derived from styrene monomers such as methylstyrene and α-methyl-p-methylstyrene. These aromatic vinyl monomer units can be used alone or in combination of two or more.
Of these, styrene units and α-methylstyrene units are preferred. Styrene monomer units are preferred because they are easily available industrially and are economical, and α-methylstyrene monomer units are preferred because they can improve the glass transition temperature.

Examples of the “(meth) acrylic acid ester monomer unit” include methacrylic acid such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, dicyclopentanyl methacrylate, and isobornyl methacrylate. Mention may be made of units derived from ester monomers and acrylic ester monomers such as methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate and decyl acrylate. These (meth) acrylic acid ester monomer units can be used alone or in combination of two or more.
Among these, a methyl methacrylate monomer unit is preferable from the viewpoint of compatibility with the acrylic resin (a1) and appearance.

Examples of the “unsaturated dicarboxylic acid anhydride monomer unit” include units derived from respective anhydride monomers such as maleic acid anhydride, itaconic acid anhydride, citraconic acid anhydride, aconitic acid anhydride and the like. be able to. These unsaturated dicarboxylic acid anhydride monomer units can be used alone or in combination of two or more.
Among these, a maleic anhydride monomer unit is preferable from the viewpoint of compatibility with the acrylic resin (a1) and transparency.

The constituent unit of the copolymer (a2) is preferably 45 to 85% by mass of an aromatic vinyl monomer unit, 4 to 45% by mass of a (meth) acrylic acid ester monomer unit, an unsaturated dicarboxylic acid anhydride unit. 8 to 20% by mass of a monomer unit, more preferably 55 to 85% by mass of an aromatic vinyl monomer unit, 5 to 30% by mass of a (meth) acrylic acid ester monomer unit, an unsaturated dicarboxylic acid anhydride unit It is in the range of 10 to 18% by mass of the monomer unit.
The structural unit of the copolymer (a2) can be qualitatively and quantitatively analyzed by a known method, for example, a nuclear magnetic resonance (NMR) measuring device or other instrumental analyzer.

If the aromatic vinyl monomer unit occupies 45% by mass or more, particularly 55% by mass or more among all the structural units of the copolymer (a2), the thermal stability is improved, and the acrylic resin (a1) and When mixed, a good appearance can be obtained, and water absorption can be reduced, which is preferable.
Moreover, if a (meth) acrylic acid ester monomer unit occupies 4 mass% or more among all the structural units of a copolymer (a2), especially 5 mass% or more, it will be a phase with acrylic resin (a1). It is preferable because the solubility is improved and the transparency is improved.
Moreover, if unsaturated dicarboxylic anhydride monomer unit occupies 8 mass% or more among all the structural units of a copolymer (a2), especially 10 mass% or more, it is a phase with acrylic resin (a1). It is preferable because the solubility is improved and the transparency and heat resistance are improved.

On the other hand, if the ratio of the aromatic vinyl monomer unit is 85% by mass or less in the total constituent units of the copolymer (a2), the heat resistance is maintained while maintaining the miscibility with the acrylic resin (a1). This is preferable because it can improve water resistance and reduce water absorption.
Moreover, if the ratio of a (meth) acrylic acid ester monomer unit is 45 mass% or less among all the structural units of a copolymer (a2), especially if it is 30 mass% or less, with acrylic resin (a1) It is preferable because water absorption can be suppressed while ensuring compatibility.
If the proportion of the unsaturated dicarboxylic acid anhydride unit is 20% by mass or less, particularly 18% by mass or less among all the structural units of the copolymer (a2), the compatibility with the acrylic resin (a1) is improved. While ensuring, improvement in thermal stability and water absorption can be suppressed, which is preferable.

The copolymer (a2) includes the above three monomer units, that is, an aromatic vinyl monomer unit, a (meth) acrylic acid ester monomer unit, and an unsaturated dicarboxylic anhydride monomer unit. Other copolymerizable units "may be contained. However, the content is preferably 5% by mass or less.
Examples of the “other copolymerizable units” include vinyl cyanide monomers such as acrylonitrile and methacrylonitrile, vinyl carboxylic acid monomers such as acrylic acid and methacrylic acid, N-methylmaleimide, and N-ethyl. N-alkylmaleimide monomers such as maleimide, N-butylmaleimide, N-cyclohexylmaleimide, N-arylmaleimide monomers such as N-phenylmaleimide, N-methylphenylmaleimide, N-chlorophenylmaleimide, etc. Mention may be made of units derived from a monomer. These copolymerizable units can be used alone or in combination of two or more.

The copolymer (a2) preferably has a polystyrene-equivalent weight average molecular weight (Mw) of 100,000 to 200,000 as measured by gel permeation chromatography (GPC). Here, it is preferable that the weight average molecular weight (Mw) is in this range because the A layer obtained by mixing with the acrylic resin (a1) is excellent in moldability and appearance. From this viewpoint, a more preferable range of weight average molecular weight (Mw) is 110,000 to 180,000.

The production method of the copolymer (a2) can be produced by a known polymerization method and is not particularly limited. For example, solution polymerization, bulk polymerization, and the like can be applied, and batch, semi-batch, and continuous methods can be appropriately employed as the polymerization process. In this laminate, there are few by-products, and it is easy to control molecular weight adjustment and transparency, so that a batch polymerization process can be suitably used in solution polymerization.

((A1) / (a2))
In the layer A, the mixing mass ratio of the acrylic resin (a1) and the copolymer (a2) is preferably (a1) / (a2) = 80/20 to 20/80.
If the mixing ratio of the acrylic resin (a1) and the copolymer (a2) is in the above range, the interlayer adhesion with the B layer is excellent, while maintaining the surface hardness and transparency that are the characteristics of the acrylic resin. It is preferable because heat resistance and water absorption are suppressed.

In order to reduce the internal stress generated in the high temperature and high humidity environment of the present laminate, it is preferable that (a1) / (a2) = 70/30 to 40/60, particularly 70/30 to 60 / More preferably, it is 40.

(Polycarbonate resin (a3))
As described above, the A layer is also preferably composed mainly of a polycarbonate resin (a3) having a specific structure. Thereby, a high surface hardness can be imparted to the laminate.

Here, the polycarbonate resin (a3) is a polycarbonate resin containing a structural unit derived from a dihydroxy compound represented by the following (Chemical Formula 1) in a part of the structure.

Examples of the dihydroxy compound represented by the above (Chemical Formula 1) include isosorbide, isomannide and isoidet which are in a stereoisomeric relationship. These may be used alone or in combination of two or more.

The dihydroxy compound represented by the above (Chemical Formula 1) is an ether diol that can be produced from a saccharide using a biogenic material as a raw material. In particular, isosorbide can be produced at low cost by hydrogenating and dehydrating D-glucose obtained from starch, and can be obtained in abundant resources. For these reasons, isosorbide is most preferred.

In the polycarbonate resin (a3) as the main component of the A layer, the content ratio of the structural unit derived from the dihydroxy compound represented by the above (Chemical Formula 1) is preferably 50 mol% or more, and 60 mol% or more. More preferably, it is preferably 90 mol% or less, and more preferably 80 mol% or less.

In the polycarbonate resin (a3) as the main component of the A layer, the content ratio of the structural unit derived from the dihydroxy compound represented by (Chemical Formula 1) is in the above range, and thus the hardness of the polycarbonate resin (a3) is: The intermediate value between the aromatic polycarbonate resin and the acrylic resin is taken, and the punching workability is dramatically improved as compared with the display front plate in which the acrylic resin layer is arranged on the surface layer.
More specifically, when the content of the structural unit is 90 mol% or less, the surface hardness and heat resistance are excellent, and the impact resistance and the lowering of interlayer adhesion with the B layer described later can be suppressed. Therefore, it is possible to prevent various problems such as a decrease in yield at the time of punching and breakage when handling a product as a display front plate.
On the other hand, when the content ratio is 50 mol% or more, impact resistance and punching workability are excellent, and a decrease in surface hardness and heat resistance can be suppressed. Moreover, this laminated body can obtain further sufficient surface hardness by disposing a hard coat layer on at least one surface, and is suitable for any use of a display front plate and a transparent building material.

The polycarbonate resin (a3) may have a structural unit other than the structural unit. For example, a structural unit derived from an aliphatic dihydroxy compound described in International Publication No. 2004/111106 pamphlet, The structural unit derived from the alicyclic dihydroxy compound as described in 2007/148604 pamphlet can be mentioned.

Among structural units derived from the above aliphatic dihydroxy compounds, selected from the group consisting of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. It is preferable to have a structural unit derived from at least one dihydroxy compound.

Among the structural units derived from the above alicyclic dihydroxy compounds, those containing a 5-membered ring structure or a 6-membered ring structure are preferable. The six-membered ring structure may be fixed in a chair shape or a boat shape by a covalent bond. By including a structural unit derived from an alicyclic dihydroxy compound having a 5-membered ring structure or a 6-membered ring structure, the heat resistance of the obtained polycarbonate can be increased. The number of carbon atoms contained in the alicyclic dihydroxy compound is usually preferably 70 or less, more preferably 50 or less, and further preferably 30 or less.

Examples of the alicyclic dihydroxy compound containing the 5-membered ring structure or the 6-membered ring structure include those described in the above-mentioned International Publication No. 2007/148604. Among these, cyclohexanedimethanol, tricyclodecanedimethanol, adamantanediol and pentacyclopentadecanedimethanol can be preferably exemplified.
In view of industrial availability, cyclohexanedimethanol is preferably selected, and 1,4-cyclohexanedimethanol is particularly preferable. On the other hand, when importance is attached to heat resistance and interlayer adhesion with the B layer described later, it is preferable to select tricyclododecane secondary methanol.

The polycarbonate resin (a3) used for the A layer can be produced by a generally used polymerization method, and may be either a phosgene method or a transesterification method in which it reacts with a carbonic acid diester. Among them, in the presence of a polymerization catalyst, a dihydroxy compound represented by the above (Chemical Formula 1) in a part of the structure, an aliphatic and / or alicyclic hydroxy compound, and other dihydroxy compounds used as necessary And a transesterification method in which carbonic acid diester is reacted.

The transesterification method includes a dihydroxy compound represented by the above (Chemical Formula 1) as a part of the structure, an aliphatic and / or alicyclic hydroxy compound, other dihydroxy compounds used as necessary, and a carbonic acid diester. Is a basic catalyst, and further, an acidic substance that neutralizes the basic catalyst is added to perform a transesterification reaction.

Representative examples of carbonic acid diesters include diphenyl carbonate, ditolyl carbonate, bis (chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis (biphenyl) carbonate, diethyl carbonate, dimethyl carbonate, dibutyl carbonate, and dicyclohexyl carbonate. Is mentioned. Of these, diphenyl carbonate is particularly preferably used.

The molecular weight of the polycarbonate resin (a3) can be represented by a reduced viscosity. The lower limit of the reduced viscosity is preferably 0.20 dl / g or more, more preferably 0.30 dL / g or more, and 0.35 dL / g or more. The upper limit of the reduced viscosity is preferably 1.20 dL / g or less, more preferably 1.00 dL / g or less, and even more preferably 0.80 dL / g or less.
If the reduced viscosity of the polycarbonate resin is too low, the mechanical strength of the molded product may be small. If it is too large, the fluidity at the time of molding tends to decrease, and the productivity and moldability tend to decrease.

(Other ingredients)
The layer A can appropriately contain various additives, modifiers and the like as long as the effects of the present invention are not impaired. Here, examples of the additive include an antioxidant, an ultraviolet absorber, a light stabilizer, a lubricant, a flame retardant, and a colorant. Examples of the modifier include impact resistance improvers, compatibilizers and antistatic agents.

<B layer>
B layer is a layer which shares the function which expresses especially impact resistance, heat resistance, etc. among the functions of this laminated body.

In the B layer, the polycarbonate resin (b1) can be used alone as a main component resin, and various modifiers (b2) described later are mixed with the polycarbonate resin (b1) as the main component resin. It can also be used.

(Polycarbonate resin (b1))
Examples of the polycarbonate resin (b1) include aromatic polycarbonate resins and aliphatic polycarbonate resins.
The polycarbonate resin (b1) may be a homopolymer or a copolymer with another copolymerizable monomer.
Further, the structure of the polycarbonate resin (b1) may be a branched structure, a linear structure, or a mixture of a branched structure and a linear structure.
The polycarbonate resin (b1) may be obtained by any known production method such as a phosgene method, a transesterification method, or a pyridine method.

The weight-average molecular weight of the polycarbonate resin (b1) may be 10,000 to 100,000, particularly 20,000 or more and 40,000 or less, particularly 22,000 or more and 28,000 or less. Further preferred.
As the polycarbonate resin (b1), only one kind can be used alone, or two or more kinds having different weight average molecular weights can be used in combination.
If the weight average molecular weight of polycarbonate-type resin (b1) exists in the said range, since impact resistance is ensured and extrusion moldability is also favorable, it is preferable.

(Modifier (b2))
In order to adjust the melt viscosity and improve the hardness, the polycarbonate resin (b1) and the modifier (b2) are preferably mixed and used to form the B layer.

As the modifier (b2), a specific acrylic resin (b2) can be exemplified.

(Acrylic resin (b2))
The acrylic resin (b2) is preferably an acrylic copolymer composed of 5 to 80% by mass of aromatic (meth) acrylate monomer units and 95 to 20% by mass of methyl methacrylate monomer units.
In the acrylic resin (b2), if the content ratio of the aromatic (meth) acrylate monomer unit and the methyl methacrylate monomer unit is within the above range, the compatibility and the surface hardness with the polycarbonate resin (b1). Since the improvement effect can be expressed, it is preferable.
From this viewpoint, the aromatic (meth) acrylate monomer unit is preferably 10 to 70% by mass and the methyl methacrylate monomer unit 90 to 30% by mass, and the aromatic (meth) acrylate monomer unit 25 to More preferably, it is 60% by mass and 75 to 40% by mass of methyl methacrylate monomer units.

Examples of the aromatic (meth) acrylate monomer unit include phenyl (meth) acrylate and benzyl (meth) acrylate. These can be used alone or in combination of two or more.
Of these, phenyl methacrylate and benzyl methacrylate are preferred, and phenyl methacrylate is more preferred from the viewpoint of compatibility with the polycarbonate resin (b1).

The acrylic resin (b2) can contain other copolymerizable monomer units other than the aromatic (meth) acrylate monomer unit and the methyl methacrylate monomer unit, if necessary.
When other monomer units are contained, the content is preferably 0.1 to 10% by mass in the acrylic resin (b2).

The acrylic resin (b2) preferably has a polystyrene-reduced weight average molecular weight (Mw) of 5,000 to 30,000 as measured by gel permeation chromatography (GPC).
When the weight average molecular weight (Mw) of the acrylic resin (b2) is in the above range, the compatibility with the polycarbonate resin (b1) is good, and the moldability and surface hardness improvement effect and appearance of the obtained B layer are good. It is preferable because it is excellent.
From this viewpoint, the range of the weight average molecular weight (Mw) of the acrylic resin (b2) is more preferably 10,000 to 28,000.

The mixing mass ratio of the polycarbonate resin (b1) and the acrylic resin (b2) is not particularly limited, and is preferably (b1) / (b2) = 99 to 65/1 to 35. It is preferable if the mixing ratio of the two is within the above range because the obtained B layer is excellent in moldability, surface hardness improvement effect, appearance, and the like.
From this viewpoint, it is more preferable that (b1) / (b2) = 95/5 to 70/30.

(Preferred polycarbonate resin)
Among these, from the viewpoint of reducing the internal stress generated in the high temperature and high humidity environment of the laminate, the polycarbonate resin as the main component resin of the B layer is preferably as the glass transition temperature is higher. It is particularly preferable to use the homopolymer (b1). On the other hand, when importance is attached to the surface hardness of the laminate, those containing the polycarbonate resin (b1) and the modifier (b2) are preferable.

(Other ingredients)
The B layer can be blended with the above-described various additives and other resins as long as the effects of the present invention are not impaired.
Examples of the additive include an antioxidant, an ultraviolet absorber, a light stabilizer, a lubricant, a flame retardant, a colorant, and a hydrolysis inhibitor.

(Glass transition temperature of each layer)
The glass transition temperature of the A layer is preferably as small as the difference from the glass transition temperature of the B layer from the viewpoint of suppressing internal stress generated in a high-temperature and high-humidity environment, and is preferably 100 to 140 ° C. Above or 140 ° C. or less _, among them 115 ° C. or more, more preferably 120 ° C. or more.
On the other hand, the glass transition temperature of the B layer is preferably as high as possible from the viewpoint of suppressing internal stress generated in a high-temperature and high-humidity environment, preferably 100 ° C. to 160 ° C., and more preferably 120 ° C. or more or 155 ° C. or less. Further preferred.

Further, if the absolute value of the difference between the glass transition temperature of the A layer and the glass transition temperature of the B layer is 30 ° C. or less, the warpage of the front plate after the high temperature and high humidity environment test at a temperature of 85 ° C. and a humidity of 85% RH It is preferable because it can be further suppressed. From such a viewpoint, the absolute value of the difference is preferably 30 ° C. or less, more preferably 20 ° C. or less, more preferably 10 ° C. or less, and particularly preferably 5 ° C. or less. More preferably.
This is because, in a high-temperature and high-humidity environment, the A layer is susceptible to various strain relaxation phenomena due to a decrease in softening temperature due to water absorption, but if the absolute value of the difference is within the above range, This is because the dimensional change behaviors of both layers are close to each other, and as a result, warpage is considered to be suppressed.
The glass transition temperature is a value obtained by measuring at a heating rate of 10 ° C./min according to JIS K7121 using a differential scanning calorimeter. However, the glass transition temperature can also be measured by other known instrument analyzers such as a dynamic viscoelastic device.

<Hard coat layer (C layer)>
The front plate may further include a hard coat layer (C layer) as an outermost surface layer on one side or both sides. However, the hard coat layer (C layer) may not be provided.
The hard coat layer (C layer) is a layer that imparts excellent surface hardness and scratch resistance to the front plate.

For example, the hard coat layer (C layer) is cured by irradiating an energy beam such as an electron beam, radiation, or ultraviolet ray to cure the curable resin composition for forming the C layer, or curing for forming the C layer by heating. It can be formed by curing the functional resin composition.
Among these, from the viewpoint of molding time and productivity, it is preferable to form a hard coat layer (C layer) by irradiating ultraviolet rays to cure the C layer forming curable resin composition.

The curable resin composition for forming the C layer for forming the hard coat layer (C layer) may be a resin composition containing the curable resin C1. As described above, when the C layer forming curable resin composition is cured by irradiating ultraviolet rays, the C layer forming curable resin composition starts photopolymerization in addition to the curable resin C1. A resin composition containing an agent is preferred.

Specific examples of the curable resin C1 include, for example, acrylate compounds, urethane acrylate compounds, epoxy acrylate compounds, carboxyl group-modified epoxy acrylate compounds, polyester acrylate compounds, copolymer acrylates, alicyclic epoxy resins, glycidyl ether epoxy resins. , Vinyl ether compounds, oxetane compounds and the like. These curable resins can be used alone or in combination of two or more.
As the curable resin C1 that imparts more excellent surface hardness, a polyfunctional acrylate compound, a polyfunctional urethane acrylate compound, a polyfunctional epoxy acrylate compound, or the like, a radical polymerization curable compound, an alkoxysilane, an alkylalkoxysilane, etc. A thermopolymerizable curable compound can be mentioned, and further, an organic / inorganic composite curable resin composition obtained by adding an inorganic component to the curable resin may be used.

An organic / inorganic hybrid curable resin composition may be mentioned as a curable resin composition for forming a C layer that gives particularly excellent surface hardness. Examples of the organic / inorganic hybrid curable resin composition include those composed of a curable resin composition containing an inorganic component having a reactive functional group in the curable resin.
Utilizing such an inorganic component having a reactive functional group, for example, an organic / inorganic composite in which this inorganic component is copolymerized and crosslinked with a radical polymerizable monomer, so that the organic binder simply contains the inorganic component. Compared to the system curable resin composition, it is preferable because curing shrinkage hardly occurs and high surface hardness can be expressed. Furthermore, from the viewpoint of reducing curing shrinkage, an organic / inorganic hybrid curable resin composition containing ultraviolet-reactive colloidal silica as an inorganic component having a reactive functional group can be mentioned as a more preferable example.

In order to give a particularly excellent surface hardness to the hard coat layer (C layer), it is preferable to adjust the concentration of the inorganic component contained in the hard coat layer (C layer), particularly the inorganic component having a reactive functional group.
From this viewpoint, the concentration of the inorganic component contained in the hard coat layer (C layer), particularly the inorganic component having a reactive functional group, is preferably 10 to 65% by mass. If the said density | concentration is 10 mass% or more, since the effect which provides the surface hardness excellent in the hard-coat layer (C layer) is acquired, it is preferable. On the other hand, if the concentration is 65% by mass or less, the hard coat layer (C layer) can be filled with an inorganic component, particularly an inorganic component having a reactive functional group, with excellent surface hardness. Can be effectively imparted.
From this viewpoint, the concentration is preferably 10 to 65% by mass, more preferably 20% by mass or more and 60% by mass or less, and particularly preferably 40% by mass or more and 55% by mass or less.

In addition, while improving adhesiveness with the adhesive sheet mentioned later, and reducing the internal stress which generate | occur | produces in the high-temperature, high-humidity environment of this laminated body, the main component resin of a hard-coat layer (C layer) is an adhesive sheet. The same resin as the main component resin is preferred. For example, when the main component resin of the pressure-sensitive adhesive sheet is an acrylic resin, the main component resin of the hard coat layer (C layer) is also preferably an acrylic resin.

The curable resin composition for forming the C layer contains a photopolymerization initiator, and the photopolymerization initiator absorbs ultraviolet rays to be excited and activated to cause a polymerization reaction, thereby curing the ultraviolet curable resin. Those where the reaction takes place are preferred.
Examples of the photopolymerization initiator include benzyl, benzophenone and derivatives thereof, thioxanthones, benzyldimethyl ketals, αhydroxyalkylphenones, α-hydroxyacetophenones, hydroxyketones, aminoalkylphenones, acylphosphine oxides, and the like. Can be mentioned. Of these, α-hydroxyalkylphenones are preferred because they hardly cause yellowing during curing and a transparent cured product is obtained. In addition, aminoalkylphenones are preferable because they have very high reactivity and a cured product having excellent hardness can be obtained. The said photoinitiator can be used individually by 1 type or in combination of 2 or more types.
The addition amount of the photopolymerization initiator is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the curable resin.

The curable resin composition for forming a C layer can contain a leveling agent as a surface adjustment component.
Examples of the leveling agent include silicone leveling agents and acrylic leveling agents. In particular, those having a reactive functional group at the terminal are preferable, and those having a reactive functional group having two or more functionalities are more preferable. preferable.
Specific examples include polyether-modified polydimethylsiloxane having an acrylic group having double bonds at both ends, and a polyester-modified polydimethylsiloxane having acrylic groups having two double bonds at the ends. be able to.
Among these, polyester-modified polydimethylsiloxane having an acrylic group that has a stable haze value and contributes to improvement of scratch resistance is particularly preferable.

In addition to the curable resin component, the curable resin composition for forming the C layer includes, for example, a lubricant such as a silicon compound, a fluorine compound, or a mixed compound thereof, an antioxidant, an ultraviolet absorber, and an antistatic agent. In addition, various additives such as a flame retardant such as a silicone compound, a filler, glass fiber, and an impact modifier can be contained within a range that does not impair the effects of the present invention.

The thickness of the hard coat layer (C layer) is not particularly limited. For example, the thickness is preferably 1 μm to 30 μm, more preferably 3 μm or more and 25 μm or less, especially 5 μm or more and 20 μm or less, and particularly preferably 7 μm or more and 15 μm or less.
Here, if the thickness of the hard coat layer (C layer) is in the above range, scratch resistance can be imparted and cracks due to stress are unlikely to occur, which is preferable.

When the hard coat layers (C layers) are provided on both sides, the thickness of each hard coat layer may be the same or different. In particular, the thickness of each hard coat layer is in the range of 7 μm to 15 μm, and the hard coat layer on the surface of the acrylic resin layer (A layer) is hard coat on the surface of the polycarbonate resin layer (B layer). The thickness is preferably equal to or greater than the thickness of the layer.

<Laminated structure of front plate>
The front plate may have a layer structure having a thermoplastic resin layer (A layer) different from the polycarbonate resin on one side or both sides of the polycarbonate resin layer (B layer), and includes other layers. May be. For example, it may be a laminate having an acrylic resin layer (A layer) on one side or both sides of a polycarbonate resin layer (B layer), and other layers may be provided.
Further, for example, as described above, a hard coat layer (C layer) may be provided on the single-sided outermost surface or the double-sided outermost surface.

As the layer structure of the front plate, (A) / (B), (A) / (B) / (A), (C) / (A) / (B), (C) / (A) / (B ) / (A), (C) / (A) / (B) / (C), and (C) / (A) / (B) / (A) / (C).
Here, when two or more of the same classification layers are included in the layer structure, the layers may have the same composition or different compositions.
Among these, (A) / (B), (A) / (B) / (A), (C) / (A) / (B), (C) / (A) / (B) / (C ), (C) / (A) / (B) / (A) / (C) configurations are preferred.
In the case of a display panel or the like, (viewing side) (C) / (A) / (B) / (C) (light source side) or (viewing side) (C) / (A) / (B) It is more preferable to arrange on the light source side.

<Thickness of front plate>
In the front plate, the thickness (a ₁ ) of the front plate is not particularly limited, and is preferably, for example, 0.1 mm to 3.0 mm, particularly 1.5 mm or less, of which 0.15 mm or more or 1 More preferably, it is 2 mm or less.

Further, the thickness (a ₁ ) of the front plate has a preferable range depending on the application application of the laminate. For example, when applied to the front cover material of various image display devices, it is preferably 0.1 to 2.0 mm, 0.15 mm or more or 1.5 mm or less, 0.2 mm or more or 0.8 mm or less, More preferably, it is 0.2 mm or more or 0.7 mm or less. If it is in this range, it is preferable because it is excellent in lightness and rigidity and shape stability in a high temperature and high humidity environment.

Also, when applying an adhesive layer etc. to the front plate to protect it from dirt or scratches on the surface of glass, etc., or to prevent scattering of broken pieces, the thickness of the front plate ( a ₁ ) is preferably from 0.1 mm to 0.6 mm, more preferably from 0.15 mm to 0.5 mm.

In any case, it is preferable that the thickness (a ₁ ) of the front plate is thinner in terms of reducing the internal stress (σ) of the laminate. From this viewpoint, the thickness (a ₁ ) of the front plate is preferably 0.7 mm or less, more preferably 0.6 mm or less, and further preferably 0.5 mm or less.

In the present laminate, the total thickness of layer A is preferably as small as possible in order to suppress internal stress generated in the high temperature and high humidity environment of the laminate, and further shape stability. On the other hand, in order to improve surface hardness. The thickness is preferably a certain thickness or more, and is preferably adjusted within an appropriate range according to the intended physical properties.
From such a viewpoint, the total thickness of the A layer is preferably 10 μm to 250 μm, more preferably 30 μm or more and 200 μm or less, and particularly preferably 50 μm or more or 150 μm or less.
In addition, when this laminated body is provided with two layers as A layer, for example, the total thickness for the two layers is the total thickness of the A layer.

Further, from the viewpoint of reducing the internal stress of the laminate and enhancing the shape stability in a high temperature and high humidity environment, the thermoplastic resin relative to the total thickness (T) of the thermoplastic resin layer A and the polycarbonate resin layer B layer. The ratio (A) / (T) of the thickness (A) of layer A to layer 1 is preferably 0.05 to 0.40, more preferably 0.07 or more and 0.35 or less. More preferably, it is 10 or more or 0.30 or less.
In addition, when providing two A layers, since the difference of the expansion / contraction behavior of A layer and B layer can be canceled by the front and back, it is preferable that the thickness of each A layer is mutually the same thickness.

<Elastic modulus of front plate>
The elastic modulus (E ₁ ) of the front plate is preferably 1500 to 4500 (MPa) from the viewpoint of reducing the internal stress of the laminate in a high temperature and high humidity environment and improving the shape stability. 1800 or more or 4000 (MPa) or less, more preferably 2000 or more or 3500 (MPa) or less.

<War amount of front plate>
From the viewpoint of reducing the internal stress of the laminate and enhancing the shape stability in a high-temperature and high-humidity environment, the front plate is allowed to stand for 120 hours in a temperature 85 ° C. and humidity 85% RH environment, and then the temperature 23 ° C. The average value of the amount of warping at the four corners after leaving for 4 hours in a humidity 50% RH environment is preferably 1.5 mm or less, more preferably 1.0 mm or less, and most preferably 0.3 mm or less. Particularly preferred.
On the other hand, even when the amount of warpage (δ) is large to some extent, the internal stress (σ) of the laminate is kept within a predetermined range by reducing the thickness of the front plate, decreasing the elastic modulus of the adhesive sheet, and the like. The shape stability in a high temperature and high humidity environment can be improved.
From the viewpoint of industrial productivity and yield of the front plate, the lower limit value of the warpage amount (δ) is preferably 0.01 mm or more, and more preferably 0.05 mm or more.

In order to adjust the warpage amount (δ) of the front plate to the above range, the total thickness of the A layer is reduced and the thickness of one A layer with respect to the total layer thickness (T) of the A layer and the B layer (A ) Ratio ((A) / (T)) and a method of balancing the elastic modulus, cure shrinkage, and thickness of the hard coat layers on the front and back sides are preferably employed. However, it is not limited to that method.

<Method for manufacturing front plate>
As a film forming method for laminating the A layer and the B layer, a known method can be adopted. For example, an extrusion casting method using a T-die having a melt mixing facility such as a single-screw extruder, a multi-screw extruder, a Banbury mixer, a kneader, etc. can be suitably used from the viewpoints of handling properties and productivity.

As a lamination method, a method of co-extrusion molding of melt-kneaded resin with a T-die having a feed block or a multi-manifold can be suitably used.
In order to improve the appearance of the laminate, it is preferable to use a forming roll (such as a metal elastic roll or a polishing roll) whose surface is mirror-finished.
The molding temperature in the extrusion casting method using a T die is appropriately adjusted depending on the flow characteristics and film-forming properties of the resin composition used, but is generally 300 ° C. or less, preferably 230 to 260 ° C. The molding roll temperature is approximately 90 to 160 ° C., preferably 95 to 150 ° C.

Further, when each layer is extruded, a single screw extruder or a multi-screw extruder can be suitably used, and each layer extruder preferably has a vent function and a filter function. The vent function is preferable because it can be used for drying the resin composition used for each layer, removing a small amount of volatile components, and the like, and a laminate having few defects such as bubbles can be obtained. In addition, there are various types of filter functions, and specific examples include a leaf disk filter, a back disk filter, a cone filter, a candle filter, and a cylindrical filter. Among them, a leaf disk filter that can easily secure an effective filtration area is preferable. The filter function can remove foreign matters, minute gels, and the like, and a laminated body with few appearance defects can be obtained.

In addition, the resin composition for forming each layer may be used by mixing each component in advance with a mixer such as a tumbler, V-type blender, Banbury mixer, extruder, etc. The components may be supplied directly, or the components weighed separately may be supplied to each supply port of an extruder having two or more supply ports.
Furthermore, the mixing method of various additives can use a well-known method. For example, (a) a master batch in which various additives are mixed in a suitable base resin at a high concentration (typically about 3 to 60% by mass) is prepared separately, and the concentration is added to the resin used. And (b) a method of directly mixing various additives into the resin to be used.

After coating the surface of layer A or layer B (referred to as “resin layer surface”) laminated as described above as a paint in which the above-described curable resin composition for C layer formation is dissolved or dispersed in an organic solvent By using a cured film, a method of forming and laminating on the surface of the resin layer can be exemplified. However, it is not limited to this method.

As a method of laminating on the surface of the resin layer, a known method can be used. For example, laminating method using cover film, dip coating method, natural coating method, reverse coating method, comma coater method, roll coating method, spin coating method, wire bar method, extrusion method, curtain coating method, spray coating method, The gravure coat method etc. are mentioned. In addition, for example, a method of using a transfer sheet in which a hard coat layer (C layer) is formed on a release layer and laminating the hard coat layer (C layer) on the surface of the resin layer may be employed.
Moreover, for the purpose of improving the adhesion between the hard coat layer (C layer) and the resin layer surface, various surface treatments such as corona treatment, plasma treatment and primer treatment can be performed on the resin layer surface.

And after laminating the curable resin composition for forming the C layer on the surface of the resin layer, for example, the curable resin composition is cured by irradiating energy rays such as electron beam, radiation, and ultraviolet rays, or The curable resin composition is preferably cured by heating. Among these, from the viewpoint of molding time and productivity, curing by ultraviolet irradiation is preferable.
Here, as the light source that emits ultraviolet rays, for example, an electrodeless high-pressure mercury lamp, an electroded high-pressure mercury lamp, an electrodeless metal halide lamp, an electroded metal halide lamp, a xenon lamp, an ultrahigh-pressure mercury lamp, or a mercury xenon lamp can be used. Among these, an electrodeless high-pressure mercury lamp is preferable because it is easy to obtain ultraviolet rays with high illuminance and is advantageous for curing an ultraviolet curable resin.

When the C-layer-forming curable resin composition is made of an ultraviolet curable resin and cured by irradiating with ultraviolet rays, since the transparency to the ultraviolet rays is high, the internal curing of the curable resin composition proceeds quickly. In some cases, the curing of the surface of the curable resin composition is delayed due to the inhibition effect of oxygen (referred to as oxygen damage). For this oxygen disorder, it is preferable to irradiate the resin composition with a nitrogen gas atmosphere by supplying nitrogen gas and then irradiate with ultraviolet rays, since the curing of the surface can proceed rapidly together with the inside of the resin composition. .

After the thermoplastic resin layer (A layer) is laminated on one side or both sides of the polycarbonate resin layer (B layer) to form a resin laminate, the resin laminate may be heat treated.
As the heat treatment conditions, the resin laminate is heat-treated in a temperature range lower by 5 ° C. to 30 ° C. than the glass transition temperature of the A layer, particularly in a temperature range lower by 5 ° C. to 25 ° C., particularly in a temperature range lower by 5 ° C.-20 ° C. Is preferred.

Further, the outermost surface on one side or both sides of the front plate can be subjected to any one or more of antireflection treatment, antifouling treatment, antistatic treatment, weather resistance treatment and antiglare treatment.
Each processing method is not particularly limited, and a known method can be used. For example, a method of applying a reflection reducing coating, a method of depositing a dielectric thin film, a method of applying an antistatic coating, and the like can be exemplified.

<Adhesive sheet>
The composition of the pressure-sensitive adhesive sheet used in the laminate is not particularly limited. However, it is preferable to use a pressure-sensitive adhesive sheet obtained by crosslinking a pressure-sensitive adhesive composition containing an acrylic resin as a main component resin from the viewpoint of adhesiveness, transparency, weather resistance, and the like.

(Adhesive composition)
The pressure-sensitive adhesive composition preferably contains an acrylic resin, a crosslinking monomer, and, if necessary, a crosslinking initiator, a reaction catalyst, and the like.

As the acrylic resin as the main component resin, an acrylate polymer (including a copolymer) is preferable.
Acrylic acid ester polymers (including copolymers) have properties such as glass transition temperature (Tg) depending on the types and composition ratios of acrylic monomers and methacrylic monomers used to polymerize them, and polymerization conditions. It is possible to adjust appropriately.

Examples of the acrylic monomer and methacrylic monomer used for polymerizing the acrylate polymer include 2-ethylhexyl acrylate, n-octyl acrylate, n-butyl acrylate, ethyl acrylate, methyl methacrylate, and the like. Vinyl acetate, hydroxyethyl acrylate, acrylic acid, glycidyl acrylate, acrylamide, acrylonitrile, methacrylonitrile, fluorine acrylate, silicone acrylate, etc., which are copolymerized with a hydrophilic group or an organic functional group, can also be used.

Among the acrylic ester polymers, (meth) acrylic acid alkyl ester copolymers are particularly preferable.
As the (meth) acrylate used for forming the (meth) acrylic acid alkyl ester copolymer, that is, the alkyl acrylate or alkyl methacrylate component, the alkyl group is n-octyl, isooctyl, 2-ethylhexyl, n-butyl, One of alkyl acrylate or alkyl methacrylate which is any one of isobutyl, methyl, ethyl and isopropyl, or a mixture of two or more selected from these is preferable.

As other components, an acrylate or methacrylate having an organic functional group such as a carboxyl group, a hydroxyl group, or a glycidyl group may be copolymerized. Specifically, a monomer component obtained by appropriately and selectively combining the alkyl (meth) acrylate component and the (meth) acrylate component having an organic functional group as a starting material is subjected to heat polymerization to form a (meth) acrylate ester copolymer. A polymer polymer can be obtained.
Among them, preferably, one of alkyl acrylates such as iso-octyl acrylate, n-octyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, or a mixture of two or more selected from these, or iso-octyl acrylate, Examples include those obtained by copolymerizing at least one or more of n-octyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, and the like with acrylic acid.

Examples of crosslinking monomers (also referred to as “crosslinking agents”) include organic compounds such as polyfunctional (meth) acrylates having two or more (meth) acryloyl groups, isocyanate groups, epoxy groups, melamine groups, glycol groups, siloxane groups, and amino groups. A polyfunctional organic functional group resin having two or more functional groups, an organometallic compound having a metal complex such as zinc, aluminum, sodium, zirconium, or calcium can be used.
Examples of the above polyfunctional (meth) acrylates include, for example, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, trimethylolpropane triacrylate, and the like. be able to.

The content of the crosslinking monomer may be adjusted in combination with other factors so as to obtain a desired holding force, but is generally 0.01 to 40.0 parts by mass, preferably 100 parts by mass with respect to 100 parts by mass of the main component resin. Is preferably adjusted within a range of 0.1 to 30.0 parts by mass, particularly 0.5 to 30.0 parts by mass. However, this range may be exceeded in balance with other elements.

When cross-linking acrylate polymers, cross-linking initiators (peroxidation initiators, photoinitiators) and reaction catalysts (tertiary amine compounds, quaternary ammonium compounds, tin laurate compounds, etc.) are added as appropriate It is effective.

In the case of UV irradiation crosslinking (also referred to as “UV crosslinking”), it is preferable to add a photoinitiator.
As the photoinitiator, either a cleavage type photoinitiator or a hydrogen abstraction type photoinitiator may be used, but both may be used in combination.
Examples of the cleavage type photoinitiator include benzoin butyl ether, benzyl dimethyl ketal, and hydroxyacetophenone.
On the other hand, examples of the hydrogen abstraction type photoinitiator include benzophenone, Michler's ketone, dibenzosuberone, 2-ethylanthraquinone, and isobutylthioxanthone.
However, it is not limited to the substances listed above.

The addition amount of the photoinitiator may be adjusted as appropriate, but in general, the photoinitiator should be adjusted within a range of 0.05 to 5.0 parts by mass with respect to 100 parts by mass of the main component resin. It is preferable to use a mold and a cleavage type photoinitiator in a ratio of 1: 1. However, this range may be exceeded in balance with other elements.

(Other additives)
In addition to the above components, pigments such as pigments and dyes having near-infrared absorption characteristics, tackifiers, antioxidants, antioxidants, hygroscopic agents, ultraviolet absorbers, silane coupling agents, natural products, Various additives such as synthetic resins, glass fibers and glass beads can be appropriately blended.

The above pressure-sensitive adhesive sheet is mixed with an acrylic resin as a main component resin and, if necessary, a cross-linking agent and a reaction initiator or a reaction catalyst, and the mixture is stirred and mixed so that a desired thickness is obtained on the release film. The film can be formed into a pressure-sensitive adhesive sheet by crosslinking by heat drying or ultraviolet irradiation.

(Thickness)
The thickness (a ₂ ) of the pressure-sensitive adhesive sheet is preferably 10 μm to 300 μm from the viewpoint of reducing the internal stress of the laminate and increasing the shape stability in a high-temperature and high-humidity environment, and more preferably 30 μm or more or 250 μm or less. Among them, the thickness is particularly preferably 50 μm or more or 200 μm or less.

(Elastic modulus)
The elastic modulus (E ₂ ) of the pressure-sensitive adhesive sheet is preferably 0.001 MPa or more from the viewpoint of enhancing shape stability in a high temperature and high humidity environment. From this viewpoint, it is more preferably 0.01 MPa or more, and further preferably 0.1 MPa or more.
Further, from the viewpoint of improving tackiness, the elastic modulus (E ₂ ) is 30 MPa or less, preferably 20 MPa or less, more preferably 10 MPa or less.
Tack is defined as “representing the adhesive strength at the moment of bonding to an adherend”, and “is often judged qualitatively by fingers, etc.” (Mr. Kimura, Makoto Sunagawa et al., “ High-performance adhesives and adhesives "issued by Kyoritsu Publishing Co., Ltd. on February 20, 1989)
The elastic modulus (E ₂ ) of the pressure-sensitive adhesive sheet can be measured by performing a tensile test at a test speed of 300 mm / min in the length direction of the pressure-sensitive adhesive sheet cut out using a tensile tester.

(Tg)
Tg of the pressure-sensitive adhesive sheet is measured using a rheometer (“MARS” manufactured by Eihiro Seiki Co., Ltd.), pressure-sensitive adhesive jig: Φ25 mm parallel plate, strain: 0.5%, frequency: 1 Hz, temperature: −50 to 200 ° C. It can be measured by a loss tangent (tan δ) of dynamic viscoelasticity measurement by a shear method at a rate of 3 ° C./min.

<Characteristics of this laminate>
This laminate is obtained by the following formula (1) and formula (2), and the front plate when the laminate of the front plate and the pressure-sensitive adhesive sheet is exposed for 120 hours in an environment of temperature 85 ° C. and humidity 85% RH. The internal stress (σ) of the pressure-sensitive adhesive sheet is 0.47 MPa or less.

 

 

Here, the meaning of each character in the said Formula (1) and Formula (2) is as follows.
δ: When the front plate is exposed to a temperature of 85 ° C. and a humidity of 85% RH for 120 hours, the front plate is warped in a convex shape and the front plate end surface Lifting height from the stationary surface L: Sample length (10 cm)
θ: The front plate warp shape when only the front plate is exposed to a temperature of 85 ° C. and a humidity of 85% RH for 120 hours, and the front plate is left in a horizontal shape with a convex downward shape. of a perpendicular line drawn to the ground of the front plate from the center of curvature, the front plate warped shape of curvature center and the front plate straight angle [rho ₁ connecting the end points _of: the front plate only the temperature 85 ° C., 85% humidity RH environment Radius of curvature of the front plate warp when exposed for 120 hours a ₁ : thickness of the front plate a ₂ : thickness of the adhesive sheet b: sample width (10 cm)
E ₁ : Elastic modulus of front plate E ₂ : Elastic modulus of adhesive sheet I ₁ : Secondary moment of inertia of front plate I ₂ : Secondary moment of inertia of adhesive sheet h: a1 + a2
σ: Internal stress

From the test results conducted by the present inventors, this laminate is warped in a high-temperature and high-humidity environment as long as the internal stress (σ) determined by the above formulas (1) and (2) is 0.47 MPa or less. It has been confirmed that can be effectively suppressed.
From this point of view, the internal stress (σ) in the laminate is preferably 0.47 MPa or less, particularly 0.46 MPa or less, and particularly preferably 0.45 MPa or less. Furthermore, 0.40 MPa or less is preferable, and 0.30 MPa or less is more preferable.

The internal stress (σ) in this laminate is mainly the ratio of the thickness (A) of one layer (A layer) to the total thickness (T) of the A layer and the (A) layer and (B) layer ( (A) / (T)), the materials of the A layer and the B layer, the thickness and material of the pressure-sensitive adhesive sheet, and the like.

In the examples described later, as a warp evaluation method under a high temperature and high humidity environment, a temperature of 85 ° C. and a humidity of 85% RH are adopted as the high temperature and high humidity environment, but other environmental conditions such as a temperature of 60 ° C., Environmental conditions such as a humidity of 90% RH, a temperature of 70 ° C., and a humidity of 90% RH can also be adopted as the high temperature and high humidity environment.

<Use of this laminate>
As described above, the laminate is excellent in shape stability in a high temperature and high humidity environment, and can also improve transparency, impact resistance, surface hardness, and the like. Therefore, this laminated body can be suitably used as various substrate materials, protective materials, and the like by bonding them to various applications, for example, a base material. For example, in addition to various substrate materials and protective materials as constituent materials for image display devices such as mobile phone terminals, smartphones, portable electronic playground equipment, portable information terminals, tablet devices, mobile personal computers, wearable terminals, liquid crystal televisions, liquid crystal monitors, desktops It can be suitably used as various substrate materials and protective materials as constituent materials for stationary display devices such as personal computers, car navigation systems, and automobile meters.

This laminate can also be given a shape by various processing methods. For example, in addition to the method of heating and pressurizing using a mold, a pressure forming method, a vacuum forming method, a roll homing method and the like can be exemplified as the forming method. By imparting a shape to the laminate, it can be used for an image display device having a curved surface and various flexible devices.

<Explanation of phrases>
“Sheet” generally refers to a product that is thin by definition in JIS and has a thickness that is small and flat for the length and width. In general, “film” is thicker than the length and width. A thin flat product with an extremely small thickness and an arbitrarily limited maximum thickness, usually supplied in the form of a roll (Japanese Industrial Standard JISK6900). However, since the boundary between the sheet and the film is not clear and it is not necessary to distinguish the two in terms of the present invention, in the present invention, even when the term “film” is used, the term “sheet” is included and the term “sheet” is used. In some cases, “film” is included.
In addition, the expression “panel” such as an image display panel and a protection panel includes a plate, a sheet and a film, or a laminate thereof.

In the present specification, when “X to Y” (X and Y are arbitrary numbers) is described, it means “preferably greater than X” or “preferably,” with the meaning of “X to Y” unless otherwise specified. The meaning of “smaller than Y” is also included.
Further, when described as “X or more” (X is an arbitrary number), it means “preferably larger than X” unless otherwise specified, and described as “Y or less” (Y is an arbitrary number). In the case, unless otherwise specified, the meaning of “preferably smaller than Y” is included.

Examples will be described in more detail below. However, the present invention is not limited to the examples described below.
Various measured values and evaluations displayed in this specification were performed as follows.

(1) Thickness It measured using the commercially available thickness measuring device (made by MITUTOYO).

(2) modulus of elasticity _{(E 1, E} 2)
Regarding the elastic modulus (E1) of the front plate, a dynamic viscoelasticity measuring method “DVA-200” manufactured by IT Measurement Control Co., Ltd. was used according to the dynamic viscoelasticity measuring method described in JISK-7198A. In the transverse direction (TD), measured from −100 ° C. to 200 ° C. at a temperature rising rate of 1 ° C./min at a vibration frequency of 10 Hz and a strain of 0.1%, and from the obtained data, the storage elastic modulus at a temperature of 20 ° C. (E ′) was determined, and this storage elastic modulus (E ′) was used as E ₁ .
The elastic modulus (E ₂ ) of the pressure-sensitive adhesive sheet was measured by pulling the length direction of the pressure-sensitive adhesive sheet cut out using a tensile tester at a test speed of 300 mm / min.

(3) Warp evaluation by wet heat exposure test of front plate alone The resin laminates (front plates) obtained in the examples and comparative examples were cut into a size of 10 cm × 10 cm and set to a temperature of 85 ° C. and a humidity of 85% RH. The amount of warping at the four corners was evaluated immediately after being left in a constant temperature and humidity chamber for 120 hours, and then left in a constant temperature and humidity chamber set at a temperature of 23 ° C. and a humidity of 50% RH for 4 hours.
The amount of warpage was determined by placing the convex surface of the test piece, that is, the resin laminate (front plate) on a quartz surface plate, and visually measuring the floating height from the surface plate at the four corners using a height gauge. The average value of the corner curvature δ (mm) was calculated.

(4) Calculation of internal stress When the front plate obtained in Examples / Comparative Examples was cut into a size of 10 cm × 10 cm and exposed to a constant temperature and humidity chamber set at a temperature of 85 ° C. and a humidity of 85% RH for 120 hours. The resulting internal stress was calculated using the following formulas (1) and (2).

 

δ: When the front plate is exposed to a temperature of 85 ° C. and a humidity of 85% RH for 120 hours, the front plate is warped in a convex shape and the front plate end surface Lifting height from the stationary surface
L: Sample length (10cm)
θ: The front plate warp shape when only the front plate is exposed to a temperature of 85 ° C. and a humidity of 85% RH for 120 hours, and the front plate is left in a horizontal shape with a convex downward shape. of a perpendicular line drawn to the ground of the front plate from the center of curvature, the front plate warped shape of curvature center and the front plate straight angle [rho ₁ connecting the end points of: the front plate only the temperature 85 ° C., 85% humidity RH environment Curvature radius of front plate when exposed for 120 hours a ₁ : thickness of front plate a ₂ : thickness of adhesive sheet b: sample width (10 cm)
E ₁ : Elastic modulus of the front plate E ₂ : Elastic modulus of the adhesive sheet I ₁ : Cross-sectional second moment of the front plate
I ₂ : Cross-sectional secondary moment of adhesive sheet h: a ₁ + a ₂
σ: Internal stress

Here, a schematic diagram of the internal stress calculation model is shown in FIG.
As a calculation process, first, the warpage amount (δ) actually measured by the wet heat exposure test of the front plate alone is substituted into the equation (1), and only the front plate is placed in a temperature 85 ° C., humidity 85% RH environment for 120 hours. The curvature radius (ρ ₁ ) of the warp shape of the front plate when exposed was calculated.
Next, the sectional moments (I _{1 and} I ₂ ) of the front plate and the pressure-sensitive adhesive were calculated from the following formulas (3) and (4). Next, the calculated ρ ₁ and other physical property values were substituted into Equation (2) to calculate the internal stress (σ).

(5) Moist heat exposure test of front plate / adhesive sheet / glass laminate The front plate / adhesive sheet / glass laminate obtained in Examples and Comparative Examples was set to a temperature of 85 ° C. and a humidity of 85% RH. Immediately after being left in a humidity chamber for 120 hours and then left in a constant temperature and humidity chamber set at a temperature of 23 ° C. and a humidity of 50% RH for 4 hours, the appearance of the test piece was visually confirmed.

At this time, if the amount of warpage of the front plate due to wet heat exposure is large, peeling occurs at the interface between the front plate and the pressure-sensitive adhesive sheet, resulting in poor appearance due to air bubbles (air) mixing in the peeled portion. The size of the appearance defect portion was visually evaluated according to the following criteria.
○ (good): Area ratio of appearance defective part is less than 10% × (poor): Area ratio of appearance defective part is 10% or more

<Examples and comparative examples>
The main raw materials and materials used in Examples and Comparative Examples will be described.

(Thermoplastic resin (a1-1))
Acrylic resin (Mitsubishi Rayon Co., Ltd., trade name: Acrypet VH001, density: 1.19 g / cm ³ , methyl methacrylate / methyl acrylate = 99/1% by mass, stereoregularity (triad fraction): mm (9.2 mol%), mr (41.8 mol%), rr (49.0 mol%), Tg: 111 ° C., MFR (temperature: 230 ° C., load: 37.3 N): 2.0 g / 10 min)

(Thermoplastic resin (a2-1))
Copolymer (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name: Regisphi R-100, density: 1.14 g / cm ³ , styrene / methyl methacrylate / maleic anhydride = 75/15/10% by mass, Tg: 127 ° C., MFR (temperature: 230 ° C., load: 37.3 N): 4.2 g / 10 min)

(Thermoplastic resin (a3-1))
A molar ratio of a monomer unit derived from isosorbide, which is a dihydroxy compound, and a monomer unit derived from tricyclodecane dimethanol, obtained by a method according to Japanese Patent Application Laid-Open No. 2008-024919, is isosorbide / tricyclode Polycarbonate copolymer with candimethanol = 70/30 mol% (density: 1.36 g / cm ³ , Tg: 128 ° C., MFR (temperature: 230 ° C., load: 37.3 N): 9.6 g / 10 min)

(Polycarbonate resin (b1-1))
Product name: Caliber 301-15, density: 1.20 g / cm ³ , Tg: 149 ° C., MFR (temperature: 300 ° C., load: 11.8 N): 15.0 g / 10 min, manufactured by Sumika Stylon Polycarbonate Co., Ltd. )

(Curable resin composition (c))
(C-1) (Product name “UVHC7800G” manufactured by MOMENTIVE)
(C-2) (Product name “XRC39-6210” manufactured by MOMENTIVE)

(Adhesive sheet)
As the pressure-sensitive adhesive sheet, a pressure-sensitive adhesive resin composition comprising an acrylic acid ester copolymer, a crosslinking agent and a photopolymerization initiator is sandwiched between two peeled polyethylene terephthalate films, and is formed into a sheet shape having a thickness of 150 μm. The elastic modulus (E ₂ ): 0.30 MPa, Tg: −10 ° C. was used.

(Glass plate)
A commercially available soda lime glass (width: 100 mm × length: 100 mm × thickness: 0.5 mm) was used as the glass plate.

<Example 1>
100 parts by mass of a resin composition obtained by mixing 60 parts by mass of an acrylic resin (a1-1) and 40 parts by mass of a copolymer acrylic resin (a2-1), and a polycarbonate resin (b1-1) 100 The mass parts are respectively supplied to separate extruders having a vent function and a filter function, melt-kneaded at a resin temperature of 240 to 265 ° C., and a layered structure of (A layer) / (B layer) is formed by a feed block. In addition, after co-extrusion with a 260 ° C. T-die, the product is cooled by sequentially passing through a first cooling roll set to 100 ° C., a second cooling roll set to 110 ° C., and a third cooling roll set to 150 ° C. A front plate having a total thickness of 0.675 mm and a thickness of each layer (A layer) / (B layer) = 0.075 mm / 0.600 mm was obtained.

Next, the curable resin composition (cf) consisting of 60 parts by mass of the curable resin composition (c-1) and 40 parts by mass of the curable resin composition (c-2) is prepared using the bar coater. It was applied to the surface of the acrylic resin layer (A layer) of the face plate, dried in this state at 90 ° C. for 1 minute, and then exposed to ultraviolet rays at an exposure amount of 700 mJ / cm ² to obtain a curable resin composition (c). Was cured to form a hard coat layer (Cf).
Next, the curable resin composition (cb) consisting of 60 parts by mass of the curable resin composition (c-2) and 40 parts by mass of the curable resin composition (c-3) is mixed with the resin using a bar coater. It was applied to the surface of the polycarbonate-based resin layer (B layer) of the laminate, dried in this state at 90 ° C. for 1 minute, and then exposed to ultraviolet rays at an exposure amount of 700 mJ / cm ² to obtain a curable resin composition (c ) Was cured to form a hard coat layer (Cb) to prepare a front plate.

Next, the pressure-sensitive adhesive surface exposed by peeling off one release film of the pressure-sensitive adhesive sheet was superimposed on the surface of the hard coat layer (Cb) of the front plate and adhered with a hand roller. Next, the remaining peeled film was peeled off, soda lime glass (thickness: 0.5 mm) was stacked on the exposed adhesive surface, and press-bonded under reduced pressure (absolute pressure 5 kPa), followed by autoclave treatment (50 ° C., 0.00 mm). (2 MPa, 20 minutes) was applied and pasted to prepare a laminate. Further, the pressure-sensitive adhesive sheet was cured by irradiating the laminated body with ultraviolet rays so that 365 nm ultraviolet rays reached 2000 mJ / cm ² with a high pressure mercury lamp through soda lime glass, and the front plate / adhesive sheet / glass. A bonded body was prepared.

<Examples 2 and 3>
As shown in Table 1, in Example 1, the front plate and the front plate / adhesive sheet were the same as in Example 1 except that the thickness ratio and total thickness of each of the A layer and B layer of the front plate were changed. / A glass laminate was produced.

<Example 4>
100 parts by mass of thermoplastic resin (a3-1) and part by mass of polycarbonate resin (b1-1) are supplied to separate extruders having a vent function and a filter function, respectively, and are melt-kneaded at a resin temperature of 240 to 265 ° C. Then, after co-extrusion molding with a T die at 240 ° C. so as to have a laminated structure of two types and three layers of (Af layer) / (B layer) / (Ab layer) with a T die having a multi-manifold, The first cooling roll set to ° C, the second cooling roll set to 110 ° C, and the third cooling roll set to 120 ° C are sequentially passed through the cooling, the total thickness is 0.675 mm, and each layer thickness is (Af layer) / (B layer) / (Ab layer) = 0.075 mm / 0.525 mm / 0.075 mm After obtaining the front plate, a hard coat layer was applied in the same manner as in Example 1, and the front plate / adhesive sheet / A glass laminate was prepared. .

<Example 5>
100 parts by mass of thermoplastic resin (a3-1) and part by mass of polycarbonate resin (b1-1) are supplied to separate extruders having a vent function and a filter function, respectively, and are melt-kneaded at a resin temperature of 240 to 265 ° C. Then, after co-extrusion molding with a T die at 240 ° C. so as to have a laminated structure of two types and three layers of (Af layer) / (B layer) / (Ab layer) with a T die having a multi-manifold, The first cooling roll set to ° C, the second cooling roll set to 110 ° C, and the third cooling roll set to 120 ° C are sequentially passed through the cooling, the total thickness is 0.275 mm, and each layer thickness is (Af layer) / (B layer) / (Ab layer) = 0.075 mm / 0.125 mm / 0.075 mm After obtaining the front plate, a hard coat layer was applied in the same manner as in Example 1, and the front plate / adhesive sheet / A glass laminate was prepared. .

<Comparative Examples 1 to 4>
As shown in Table 1, after obtaining the front plate in the same manner as in Example 1 except that the thickness ratio and total thickness of the A layer and B layer of the front plate were changed in Example 1, the front plate / adhesive A sheet / glass laminate was produced.

<Comparative Examples 5 and 6>
As shown in Table 1, after obtaining a front plate in the same manner as in Example 1 except that the thickness of the hard coat layer (Cb) was changed in Example 1, a front plate / adhesive sheet / glass laminate was obtained. Was made.

<Comparative Examples 7 and 8>
As shown in Table 1, after obtaining the front plate in the same manner as in Example 1 except that the third cooling roll temperature was changed during coextrusion molding of the front plate in Example 1, the front plate / adhesive sheet / A glass laminate was produced.

As shown in Tables 1 and 2, the configurations of Examples 1 to 5 showed good results with no peeling during the wet heat environment test, whereas Comparative Examples 1 to 8 caused peeling.
There is a correlation between the peeling behavior when subjected to the wet heat environment test and the internal stress σ calculated by the equations (1) and (2), and if the internal stress σ is below a certain level, It was confirmed that peeling during the test could be suppressed. This is considered that when the internal stress due to warpage generated when only the front plate is subjected to a wet heat exposure test is reduced below a certain level, the adhesion with the pressure-sensitive adhesive sheet is superior and peeling can be suppressed. It was confirmed that the internal stress: 0.47 MPa was a threshold value at which peeling occurred.

The factors of the front plate that affect the internal stress include elastic modulus, thickness, and warpage amount from the formulas (1) and (2). In particular, the internal stress can be reduced mainly by reducing the thickness or reducing the amount of warpage. Even if either is larger, the internal stress can be reduced and peeling can be suppressed by adjusting the other parameter to an appropriate range.

As means for reducing the amount of warpage, adjustments such as the layer configuration of the A layer and the B layer, the thickness ratio of the A layer and the B layer, the thickness ratio of the front and back coat layers, and the processing conditions such as the roll temperature condition during production Can be mentioned.

In particular, it is effective to make the layer configuration of the A layer and the B layer a 2-layer / 3-layer symmetrical configuration of A layer / B layer / A layer. By adopting a symmetric configuration, the difference between the expansion and contraction behaviors of the A layer and the B layer can be canceled on both sides, which is effective in reducing warpage.
From Examples 4 and 5, as for the front plate using the two-type / three-layer front / back symmetrical configuration, the amount of warpage of the front plate is compared with that using the two types / two-layer configuration of A layer / B layer. It can be confirmed that the internal stress can be kept small.

As another means for reducing the amount of warpage, the thickness of one layer (A layer) with respect to the total thickness (T) of the (A) layer and the (B) layer in a two-layer / two-layer configuration of A layer / B layer (A ) Ratio ((A) / (T)) is effective. The cause of warping is due to the difference in expansion and contraction behavior of the two layers. For example, if the A layer is made extremely thin and the thickness ratio is made non-uniform so as to approach the single layer body of the B layer, the influence of the A layer Since it becomes difficult to express, warping behavior can be suppressed.

As another means for reducing the amount of warpage, it is effective to bring the front and back hard coat layers (C layers) closer to the front and back objects. When the hard coat layer (C layer) is exposed to the moist heat test, the hard coat layer itself shrinks due to the progress of curing shrinkage, which causes warpage. It is preferable to balance the constitution of the coat layer, that is, the material and thickness.
When the material composition of the hard coat layer is the same on the front and back sides, it is preferable to make the thicknesses close to each other. In consideration of the above, it is preferable to adjust the thickness so that the front and back are balanced.

As another means of reducing the warpage amount, it is effective to reduce the thermal strain in the cooling process by adjusting the film forming conditions at the time of coextrusion. For example, by setting the third cooling roll to a high temperature within a range that does not cause poor appearance, the thermal distortion can be reduced by the annealing effect.

In Comparative Examples 1 to 8, peeling occurs due to a large internal stress.
In Comparative Example 1, even when the total thickness was as large as 1000 μm and the amount of warpage was small, the internal stress increased due to the large contribution of the thickness.
In Comparative Examples 2 to 4, since the thickness ratio of the A layer to the B layer was large, the amount of warpage of the front plate was large and the internal stress was large.
In Comparative Examples 5 to 6, the thickness of the back side hard coat layer (Cf) was thin and the front and back hard coat layers were not balanced, so the amount of warpage of the front plate was large and the internal stress was large.
In Comparative Examples 7 to 8, the third cooling roll temperature was not sufficiently high, the amount of thermal distortion of the front plate was large, the amount of warpage was large, and the internal stress was large.

δ: Lifting height of the front plate end surface from the stationary surface L: Sample length ρ: Radius of curvature of the front plate warp shape θ: Vertical line from the center of curvature of the front plate warp shape to the contact point of the front plate, and the front Angle formed by a straight line connecting the center of curvature of the face plate warp shape and the end point of the front plate 10: Front plate 20: Adhesive sheet

Claims (11)

1. A laminate including a front plate and an adhesive sheet,
   The front plate includes a B layer mainly composed of a polycarbonate resin and a thermoplastic resin A layer mainly composed of a thermoplastic resin different from the polycarbonate resin, and the total thickness of the A layer is 10 μm. The ratio of the thickness (A) of one A layer to the total thickness (T) of the A layer and the B layer ((A) / (T)) is 0.05 to 0.40. ,
   The internal stress of the front plate and the pressure-sensitive adhesive sheet obtained when the laminate of the front plate and the pressure-sensitive adhesive sheet is exposed for 120 hours in an environment of temperature 85 ° C. and humidity 85% RH, which is determined by the following formulas (1) and (2). A laminate having (σ) of 0.47 MPa or less.
   

   

   

   δ: When the front plate is exposed to a temperature of 85 ° C. and a humidity of 85% RH for 120 hours, the front plate is warped in a convex shape and the front plate end surface Lifting height from the stationary surface L: Sample length (10 cm)
   θ: The front plate warp shape when only the front plate is exposed to a temperature of 85 ° C. and a humidity of 85% RH for 120 hours, and the front plate is left in a horizontal shape with a convex downward shape. of a perpendicular line drawn to the ground of the front plate from the center of curvature, the front plate warped shape of curvature center and the front plate straight angle [rho ₁ connecting the end points _of: the front plate only the temperature 85 ° C., 85% humidity RH environment Radius of curvature of the front plate warp when exposed for 120 hours a ₁ : thickness of the front plate a ₂ : thickness of the adhesive sheet b: sample width (10 cm)
   E ₁ : Elastic modulus of the front plate E ₂ : Elastic modulus of the adhesive sheet I ₁ : Sectional moment of inertia of the front plate
   I ₂ : Cross-sectional secondary moment of the adhesive sheet h: a ₁ + a ₂
   σ: Internal stress
2. After the front plate was allowed to stand for 120 hours in an environment of temperature 85 ° C. and humidity 85% RH, and then left for 4 hours in an environment of temperature 23 ° C. and humidity 50% RH, The laminated body according to claim 1, wherein an average value is 1.5 mm or less.
3. The laminate according to claim 1 or 2, wherein the thermoplastic resin as the main component resin of the A layer is an acrylic resin.
4. The thermoplastic resin as the main component resin of layer A is composed of methyl methacrylate monomer, methacrylic acid monomer, acrylic acid monomer, maleic anhydride monomer, aromatic vinyl monomer, cyanide The laminate according to any one of claims 1 to 3, which is an acrylic resin (a1) made of a copolymer with at least one of vinyl monomers.
5. The thermoplastic resin as the main component resin of layer A is composed of methyl methacrylate monomer, methacrylic acid monomer, acrylic acid monomer, maleic anhydride monomer, aromatic vinyl monomer, cyanide Acrylic resin (a1) comprising a copolymer with one or more of vinyl monomers, an aromatic vinyl monomer unit, a (meth) acrylic acid ester monomer unit, and a maleic anhydride unit The laminate according to any one of claims 1 to 3, comprising a copolymer (a2) having a monomer.
6. The thermoplastic resin as a main component of the A layer is a polycarbonate resin (a3) containing a structural unit derived from a dihydroxy compound represented by the following (Chemical Formula 1) in a part of the structure. Or the laminated body of 2.
   

   
7. The polycarbonate-based resin as the main component resin of the B layer is composed of the polycarbonate-based resin (b1), 5 to 80% by mass of the aromatic (meth) acrylate monomer, and 95 to 20% by mass of the methyl methacrylate monomer unit. The laminate according to any one of claims 1 to 6, which comprises an acrylic copolymer (b2).
8. The laminate according to any one of claims 1 to 7, wherein the adhesive sheet has an elastic modulus (E ₂ ) of 0.001 to 30 MPa.
9. The laminate according to any one of claims 1 to 8, wherein the total thickness of the front plate is 0.7 mm or less.
10. In addition to the A layer and the B layer, the front plate includes a hard coat layer containing, as a main component, the same resin as the main component resin of the pressure sensitive adhesive sheet on the side laminated with the pressure sensitive adhesive sheet. The laminate according to any one of claims 1 to 9.
11. An image display device comprising the laminate according to any one of claims 1 to 10.
    

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