JP7346808B2 - laminated sheet - Google Patents

Description

The present invention relates to a laminated sheet. Specifically, the present invention relates to a laminated sheet in which a film base material, an adhesive layer, and a release film are laminated in this order.

In recent years, electronic devices such as mobile phones, portable game consoles, and digital cameras have rapidly become popular. Adhesive sheets are used to fix parts that make up electronic devices and various devices. In addition, display devices such as liquid crystal displays (LCDs) usually have an anti-reflection film to prevent reflections from external light sources, a protective film to prevent scratches on the surface of the display device, and protective film to prevent scratches on the surface of the display device. Various films with adhesive sheets are used depending on the purpose, such as anti-scattering films that prevent optical components from scattering. In this way, adhesive sheets are used to fix various optical components, and adhesive sheets in which an adhesive layer is provided on one or both sides of a base material are often used.

For example, Patent Document 1 discloses a protective adhesive film in which a film base material is provided with an adhesive layer, and a release sheet is laminated on the adhesive layer, and the release sheet has a surface roughness Ra of 10 to 100 nm. A protective adhesive film in which the adhesive layer has a storage modulus G' of 2.0×10 ⁵ Pa or more at 23° C. is disclosed.

By the way, the above-mentioned pressure-sensitive adhesive sheet is manufactured by coating a release film with a pressure-sensitive adhesive to form a pressure-sensitive adhesive layer, and further laminating a film base material, a release film, etc. on the pressure-sensitive adhesive layer. . Such adhesive sheets are stored and transported by being wound up into rolls. In such a roll of a pressure-sensitive adhesive sheet, many minute irregularities may occur in the pressure-sensitive adhesive layer due to tightening during manufacturing or storage, resulting in so-called orange skin.

Patent Document 2 discloses a double-sided pressure-sensitive adhesive sheet that includes a pressure-sensitive adhesive layer having a first surface and a second surface, a first release film, and a second release film. Furthermore, in Patent Document 2, the arithmetic mean roughness Ra of the surfaces of the first release film and the second release film opposite to the surfaces in contact with the adhesive layer is set to 5 to 35 nm, and the maximum protrusion height Rp is set to 50 nm. It is being considered to suppress the occurrence of orange skin by adjusting the wavelength to 400 nm.

Japanese Patent Application Publication No. 2014-84336 International Publication No. 2014/157445

As mentioned above, pressure-sensitive adhesive sheets having a release film and a pressure-sensitive adhesive layer are known, and the occurrence of orange skin has been studied. However, even in conventional pressure-sensitive adhesive sheets, orange skin may occur in some cases, and improvement of this problem has been desired.

Therefore, in order to solve the problems of the prior art, the present inventors conducted studies with the aim of providing a pressure-sensitive adhesive sheet that suppresses the occurrence of orange skin and has good surface properties.

As a result of intensive studies to solve the above problems, the present inventors discovered that in a laminated sheet in which a film base material, an adhesive layer, and a release film are laminated in this order, the adhesive that forms the adhesive layer It has been found that by incorporating a chelate crosslinking agent into the composition, the surface of the laminated sheet is prevented from becoming orange skin-like.
Specifically, the present invention has the following configuration.

[1] A laminate sheet in which a film base material, an adhesive layer, and a release film are laminated in this order,
The thickness of the film base material is 38 μm or less,
When the reflection intensity (Wb) of the exposed surface of the release film is measured in a wavelength range of 0.3 to 1.0 mm using a wave scanning device, the reflection intensity (Wb) is 10 or more,
The adhesive layer is a laminated sheet containing a structure derived from at least a (meth)acrylic copolymer and a chelate crosslinking agent.
[2] The laminate sheet according to [1], wherein the adhesive layer further includes a structure derived from an epoxy crosslinking agent.
[3] The laminate sheet according to [1] or [2], wherein the content of the structure derived from the chelate crosslinking agent is 0.1 to 5.0 parts by mass relative to parts by mass of the (meth)acrylic copolymer. .
[4] The content of the structure derived from the epoxy crosslinking agent is 0.01 to 1.0 parts by mass based on 100 parts by mass of the (meth)acrylic copolymer according to [2] or [3]. Laminated sheet.
[5] The laminate sheet according to any one of [1] to [4], wherein the adhesive layer has a gel fraction of 40% or more.
[6] The laminate sheet according to any one of [1] to [5], wherein the arithmetic mean roughness of the exposed surface of the release film is 35 nm or more.

According to the present invention, it is possible to obtain a pressure-sensitive adhesive sheet and a laminated sheet in which the occurrence of orange skin is suppressed and the surface properties are good.

FIG. 1 is a sectional view illustrating the structure of the laminated sheet of the present invention.

In the following, the present invention will be explained in detail. Although the constituent elements described below may be explained based on typical embodiments and specific examples, the present invention is not limited to such embodiments. In this specification, a numerical range expressed using "~" means a range that includes the numerical values written before and after the "~" as lower and upper limits.

(Laminated sheet)
The present invention relates to a laminated sheet 100 in which a film base material 10, an adhesive layer 20, and a release film 30 are laminated in this order, as shown in FIG. That is, the film base material 10 and the release film 30 are bonded together with the adhesive layer 20 interposed therebetween. Here, the adhesive layer includes a structure derived from at least a (meth)acrylic copolymer and a chelate crosslinking agent. In addition, the thickness of the film base material is 38 μm or less, and the exposed surface of the release film (the surface opposite to the surface in contact with the adhesive layer) is scanned with a wavelength of 0.3 to 1.0 mm using a wave scanning device. When the reflection intensity (Wb) of the area is measured, the reflection intensity (Wb) is 10 or more. Note that the present invention may also relate to a wound body obtained by winding up a laminated sheet into a roll shape.

The adhesive layer included in the laminate sheet of the present invention includes a structure derived from at least a (meth)acrylic copolymer and a chelate crosslinking agent. Since the laminate sheet of the present invention is a sheet in which the adhesive layer has the above structure, even when the laminate sheet is wound, a fine uneven structure is not formed in the adhesive layer of the laminate sheet. As a result, it is possible to prevent the surface of the film base material from becoming orange skin-like. The surface quality of the film base material surface can be visually evaluated. For example, when observing fluorescent light reflected on the surface of a film base material, if the image of the fluorescent light reflected on the film base material appears undistorted or slightly distorted, this indicates the occurrence of orange skin. It can be determined that the appearance (surface quality) is good. In the present invention, the laminated sheet was wound around a 3-inch paper tube for 100 m at a tension of 60 N to form a rolled body, and the rolled body was stored for one week under conditions of 23°C and 50% relative humidity. However, the occurrence of orange skin on the surface of the film base material is suppressed.

Note that the occurrence of orange skin on the surface of the film base material can be evaluated not only by visual evaluation but also by the value of the reflection intensity (Wb) or the reflection strength (Wc) of the surface of the film base material. Specifically, after peeling off the release film of the laminated sheet and laminating the exposed adhesive layer to a black acrylic board, the amount of reflected light on the film base material surface was measured using Wave-Scan Dual Wave Scan manufactured by BYK Gardner. Measure using a device. In a wave scan device, the diffuse reflection of light due to undulations and undulations on the sheet surface is measured as a wavelength pattern in bright and dark regions. Specifically, the sheet surface is irradiated with a laser (point light source) at an angle of 60° to the sheet surface, and the amount of reflected light is read by a sensor. Such reflected light is measured at predetermined intervals to detect the optical profile of the surface. After classifying the obtained optical profile using filter function conversion, the reflection intensity (Wb) in the wavelength range of 0.3 to 1.0 mm and the reflection intensity Wc in the wavelength range of 1.0 to 3.0 mm are determined. get. The reflection intensity (Wb) of the film base material surface is preferably less than 4.0, more preferably 3.0 or less, even more preferably 2.0 or less, and 1.0 or less. It is particularly preferable. Further, the reflection intensity (Wc) of the surface of the film base material is preferably less than 2.4, more preferably 2.0 or less, even more preferably 1.5 or less, and 1.3 or less. It is particularly preferable that

In the laminated sheet of the present invention, the thickness of the film base material is 38 μm or less, and the exposed surface of the release film (the surface opposite to the surface in contact with the adhesive layer) is scanned using a wave scanning device at a wavelength of 0.5 μm. The reflection intensity (Wb) when measuring the reflection intensity (Wb) in the wavelength range of 3 to 1.0 mm is 10 or more. In the present invention, even if the thickness of the film base material is thin and the reflection intensity (Wb) of the exposed surface of the release film (the surface opposite to the surface in contact with the adhesive layer) is high, the The occurrence can be suppressed.

(Adhesive layer)
The adhesive composition forming the adhesive layer contains at least a (meth)acrylic copolymer and a chelate crosslinking agent. It is preferable that the adhesive composition further contains a crosslinking agent other than a chelate crosslinking agent. Moreover, the adhesive composition may further contain a crosslinking accelerator. In addition, in this specification, "(meth)acrylic" represents both acrylic and methacryl, or either one.

The gel fraction of the adhesive layer is preferably 20% or more, more preferably 30% or more, even more preferably 40% or more, and particularly preferably 50% or more. In addition, although the said gel fraction is the gel fraction immediately after forming an adhesive layer, it is preferable that the gel fraction of the adhesive layer after time is also more than the said lower limit. By setting the gel fraction immediately after forming the adhesive layer to the above lower limit value or more, the adhesive layer becomes difficult to deform, and the occurrence of orange skin during winding is easily suppressed.
When measuring the gel fraction, first, the adhesive layer that has been applied within 3 hours after applying the adhesive composition on a release film is immersed in ethyl acetate while wrapped in a metal mesh (150 mesh). Leave at ℃ for 24 hours. Then, the taken out adhesive layer is dried at 100° C. for 1 hour, the weight ratio before and after immersion in ethyl acetate is calculated, and the gel fraction is calculated from the following formula.
Gel fraction (%) = Weight of adhesive layer after immersion in ethyl acetate / Weight of adhesive layer before immersion in ethyl acetate x 100

The thickness of the adhesive layer is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 15 μm or more. Moreover, although the upper limit of the thickness of the adhesive layer is not particularly limited, in the present invention, for example, even if the thickness is 50 μm or less, the occurrence of orange skin can be suppressed. The thicker the adhesive layer is, the less the effect of citrus skin will appear, but in the present invention, even if the adhesive layer is a thin film, for example, 50 μm or less, the occurrence of citrus skin can be suppressed. be able to.

<(meth)acrylic copolymer>
The (meth)acrylic copolymer preferably contains units derived from (meth)acrylate having a crosslinkable functional group. In addition, in this specification and the claims, a "unit" is a repeating unit (monomeric unit) which comprises a polymer.

The crosslinkable functional group is preferably at least one selected from a carboxy group, a hydroxy group, an amino group, an amide group, an epoxy group, and an isocyanate group; It is more preferable that at least one of the above is used.
Examples of the carboxy group-containing monomer unit include acrylic acid and methacrylic acid.
The hydroxy group-containing monomer unit is a repeating unit derived from a hydroxy group-containing monomer. Examples of the hydroxy group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate; Examples include (meth)acrylic acid [(mono, di or poly)alkylene glycol] such as (meth)acrylic acid mono(diethylene glycol), and (meth)acrylic acid lactones such as (meth)acrylic acid monocaprolactone.
Examples of the amino group-containing monomer unit include repeating units derived from amino group-containing monomers such as (meth)acrylamide and allylamine.
Examples of the epoxy group-containing monomer unit include repeating units derived from glycidyl group-containing monomers such as glycidyl (meth)acrylate.

It is preferable that the (meth)acrylic copolymer further contains a non-crosslinkable (meth)acrylic acid ester unit. The non-crosslinkable (meth)acrylic acid ester unit is preferably a repeating unit derived from an alkyl (meth)acrylic acid ester. Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and (meth)acrylate. Isobutyl acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, ( Isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-undecyl (meth)acrylate, (meth) Examples include n-dodecyl acrylate, stearyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and the like. These may be used alone or in combination of two or more.

The (meth)acrylic copolymer may have other monomer units in addition to the above-mentioned monomer units, if necessary. Other monomers may be used as long as they are copolymerizable with the above-mentioned acrylic monomers, such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, and lauric acid. Examples include carboxylic acid vinyl esters such as vinyl, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl benzoate, and styrene.

The weight average molecular weight of the (meth)acrylic copolymer is preferably 100,000 to 2,000,000, more preferably 200,000 to 1,500,000. The weight average molecular weight is a value measured by size exclusion chromatography (SEC) and calculated based on polystyrene. As the (meth)acrylic copolymer, a commercially available one may be used, or one synthesized by a known method may be used.

<Crosslinking agent>
The adhesive composition forming the adhesive layer contains a chelate crosslinking agent. Therefore, the adhesive layer obtained by curing the adhesive composition includes a structure derived from the chelate crosslinking agent. The chelate crosslinking agent is preferably a metal chelate crosslinking agent, more preferably an acetylacetone metal chelate compound. Examples of metals that can be included in the acetylacetone metal chelate compound include nickel, chromium, iron, titanium, zinc, cobalt, manganese, copper, tin, and zirconium. Specific examples of acetylacetone metal chelate compounds include aluminum trisacetylacetonate, ferric trisacetylacetonate, zirconium trisacetylacetonate, titanium trisacetylacetonate, and the like.

The content of the structure derived from the chelate crosslinking agent in the adhesive layer is preferably 0.1 parts by mass or more, and 0.2 parts by mass or more based on 100 parts by mass of the (meth)acrylic copolymer. It is more preferable that the amount is 0.3 parts by mass or more, and even more preferably 0.3 parts by mass or more. Further, the content of the structure derived from the chelate crosslinking agent in the adhesive layer is preferably 5.0 parts by mass or less, and 3.0 parts by mass based on 100 parts by mass of the (meth)acrylic copolymer. It is more preferably at most 2.0 parts by mass, and even more preferably at most 2.0 parts by mass. By setting the content of the structure derived from the chelate crosslinking agent within the above range, it is possible to more effectively prevent the surface of the film base material from becoming orange skin-like. Note that the content of the structure derived from the chelate crosslinking agent in the adhesive layer is the same as the content of the chelate crosslinking agent in the adhesive composition.

It is preferable that the adhesive composition forming the adhesive layer further contains another crosslinking agent in addition to the chelate crosslinking agent, and examples of such crosslinking agents include epoxy crosslinking agents. That is, the adhesive layer formed by curing the adhesive composition preferably includes a structure derived from an epoxy crosslinking agent. Examples of the epoxy crosslinking agent include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, and 1,6-hexane. Diol diglycidyl ether, tetraglycidyl xylene diamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether etc.

The content of the structure derived from the epoxy crosslinking agent in the adhesive layer is preferably 0.01 parts by mass or more, and 0.02 parts by mass or more based on 100 parts by mass of the (meth)acrylic copolymer. More preferably, the amount is 0.03 parts by mass or more. Further, the content of the structure derived from the epoxy crosslinking agent in the adhesive layer is preferably 1.0 parts by mass or less, and 0.5 parts by mass based on 100 parts by mass of the (meth)acrylic copolymer. It is more preferably at most 0.2 parts by mass, and even more preferably at most 0.2 parts by mass. By setting the content of the structure derived from the epoxy crosslinking agent within the above range, it is possible to more effectively prevent the surface of the film base material from becoming orange skin-like. Note that the content of the structure derived from the epoxy crosslinking agent in the adhesive layer is the same as the content of the epoxy crosslinking agent in the adhesive composition.

Further, the adhesive composition may contain other crosslinking agents such as an isocyanate crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, and a butylated melamine crosslinking agent.

<Solvent>
The adhesive composition forming the adhesive layer may contain a solvent. In this case, the solvent is used to improve the coating suitability of the pressure-sensitive adhesive composition. Examples of solvents include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene, and dichloropropane; methanol, ethanol, Alcohols such as propanol, isopropyl alcohol, butanol, isobutyl alcohol, and diacetone alcohol; Ethers such as diethyl ether, diisopropyl ether, dioxane, and tetrahydrofuran; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, and cyclohexanone; Methyl acetate , ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, ethyl butyrate and other esters; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene Examples include polyols such as glycol monomethyl ether acetate and derivatives thereof.

One type of solvent may be used alone, or two or more types may be used in combination. The content of the solvent in the adhesive composition is not particularly limited, but it is preferably 25 parts by mass or more and 500 parts by mass or less, and 30 parts by mass or more and 400 parts by mass, based on 100 parts by mass of the (meth)acrylic copolymer. It is more preferable to set it to less than 1 part.

<Other ingredients>
The adhesive layer may contain other components other than those mentioned above as long as the effects of the present invention are not impaired. Other components include components known as additives for adhesives. For example, select from among crosslinking accelerators, crosslinking retarders, plasticizers, antioxidants, metal corrosion inhibitors, tackifiers, silane coupling agents, ultraviolet absorbers, light stabilizers such as hindered amine compounds, etc. You can choose. Furthermore, dyes and pigments may be added for the purpose of coloring.
Examples of the crosslinking accelerator include organic tin compounds; amino compounds such as N,N,N',N'-tetramethylhexanediamine, triethylamine, and imidazole; metal complexes such as aluminum complexes; para-toluenesulfonic acid, phosphoric acid, Examples include hydrochloric acid and ammonium chloride.
Examples of crosslinking retarders include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, stearyl acetoacetate, acetylacetone, 2,4-hexanedione, benzoylacetone, etc. can be mentioned.
Examples of plasticizers include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, and benzoate. Examples include carboxylic acid vinyl esters such as vinyl acid, styrene, and the like.
Examples of the antioxidant include phenolic antioxidants, amine antioxidants, lactone antioxidants, phosphorus antioxidants, sulfur antioxidants, and the like. These antioxidants may be used alone or in combination of two or more.
Preferred examples of metal corrosion inhibitors include benzoliazole resins because of their compatibility with adhesives and their high effectiveness.
Examples of the tackifier include rosin resins, terpene resins, terpene phenol resins, coumaron indene resins, styrene resins, xylene resins, phenol resins, and petroleum resins.
Examples of the silane coupling agent include mercaptoalkoxysilane compounds (eg, mercapto group-substituted alkoxy oligomers, etc.).
Examples of the ultraviolet absorber include benzotriazole compounds and benzophenone compounds. However, when ultraviolet rays are used as active energy rays during post-curing, it is preferable to add them within a range that does not inhibit the polymerization reaction.

(Release film)
The release film used in the laminate sheet of the present invention may be a laminate release film having a release film base material and a release agent layer, or may be a single layer release film made of synthetic resin or the like. In this case, examples of the single-layer release film include polyolefin films such as polyethylene films and polypropylene films as low polar base materials. Paper or resin film is used as the base material for the release film in the laminated release film. When the base material for the release film is a resin film, examples thereof include polyolefin films such as polyethylene film and polypropylene film. As the release agent constituting the release agent layer, for example, a general-purpose addition type or condensation type silicone release agent, a long-chain alkyl group-containing compound, or the like is used. In particular, addition-type silicone release agents with high reactivity are preferably used.

The arithmetic mean roughness (Ra) of the exposed surface of the release film (the surface opposite to the surface in contact with the adhesive layer) may be 10 nm or more, 20 nm or more, or 30 nm or more. The thickness may be 35 nm or more. Further, the maximum projection height (Rp) of the exposed surface of the release film (the surface opposite to the surface in contact with the adhesive layer) may be 50 nm or more, or 100 nm or more. As described above, in the present invention, even when the values of the arithmetic mean roughness (Ra) and the maximum protrusion height (Rp) are large to some extent, the occurrence of orange skin can be suppressed. Note that the arithmetic mean roughness (Ra) of the release film may be less than 10 nm, and the maximum protrusion height (Rp) of the release film may be less than 50 nm.
The arithmetic mean roughness Ra and maximum protrusion height Rp of the release film are measured in accordance with JIS B 0601-1994. When the release film has a release agent layer, the surface opposite to the surface provided with the release agent layer is measured. As the measuring device, a surface roughness measuring machine SV3200 (stylus type) manufactured by Mitutoyo Co., Ltd. or the like can be used.

In addition, when the reflection intensity (Wb) in the wavelength range of 0.3 to 1.0 mm was measured on the exposed surface of the release film (the surface opposite to the surface in contact with the adhesive layer) using a wave scanning device. , the reflection intensity (Wb) is 10 or more. The reflection intensity (Wb) of the exposed surface of the release film (the surface opposite to the surface in contact with the adhesive layer) may be 12 or more, or may be 15 or more. The present invention has the advantage that even if the reflection intensity (Wb) of the exposed surface of the release film (the surface opposite to the surface in contact with the adhesive layer) is high, the occurrence of orange skin can be suppressed. It has characteristics.

When measuring the reflection intensity of a release film, place the release film on a glass plate with the release-treated side (the side of the laminated sheet that is bonded to the adhesive layer) facing down, and then peel off the release film. The amount of reflected light from the surface opposite to the treated surface (the exposed surface of the laminated sheet opposite to the adhesive layer) is measured using Wave-Scan Dual manufactured by BYK Gardner. Then, after classifying the obtained optical profile using filter function conversion, the reflection intensity in the wavelength range of 0.3 to 1.0 mm is obtained. In addition, when measuring the reflection intensity (Wb) of a release film, it is preferable to measure the release film before lamination, but it is also possible to measure the release film after peeling the release film from the laminated sheet. The measurement may be performed on the exposed surface of the release film of the laminated sheet (the surface opposite to the surface in contact with the adhesive layer).

The thickness of the release film is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. Further, the thickness of the release film is preferably 150 μm or less, more preferably 120 μm or less, and even more preferably 100 μm or less.

(Film base material)
Examples of the film base material include various resin film base materials that are generally used as base materials for pressure-sensitive adhesive sheets. For example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, cellophane, diacetylcellulose, triacetylcellulose, acetylcellulose butyrate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl acetate copolymer, Examples of resin films include polystyrene, polycarbonate, polymethylpentene, polysulfone, polyetheretherketone, polyethersulfone, polyetherimide, polyimide, fluorocarbon resin, nylon, and acrylic resin.

The film base material may be a base material consisting only of the above resin film, but may also be a laminated film base material provided with other layers. In this case, other layers include, for example, a hard coat layer, an antireflection layer, a low refractive index layer, a high refractive index layer, an antiglare layer, an antistatic layer, an ultraviolet absorption layer, a gas barrier layer, an antiblocking layer, etc. be able to.

The thickness of the film base material may be 38 μm or less, and may be 25 μm or less. The thicker the film base material is, the less the effect of orange skin will appear, but in the present invention, even if the film base material is thin, for example, 38 μm or less or 25 μm or less, the occurrence of orange skin can be prevented. can be suppressed.

(Method for manufacturing laminated sheet)
The method for producing the laminated sheet is not particularly limited, but includes, for example, a step of coating an adhesive composition on a release film to form a coating film, and a step of forming an adhesive layer by heating this coating film. It is preferable to include the steps of: obtaining a pressure-sensitive adhesive layer; and laminating a film base material onto the pressure-sensitive adhesive layer. In the present invention, it is preferable to further include a step of winding the laminated sheet after the above-described step to obtain a rolled body of the laminated sheet.

In the step of forming a coating film, it is preferable to apply the adhesive composition using a known coating device. Examples of the coating device include a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a microgravure coater, a rod blade coater, a lip coater, a die coater, and a curtain coater.

The coating film can be heated using a known heating device such as a heating furnace or an infrared lamp. The heating temperature is preferably 60°C or higher and 200°C or lower.

When the laminated sheet thus obtained is made into a rolled body, the laminated sheet is wound around a tubular body such as a paper tube. The tension of the laminated sheet during winding is preferably 20N or more, more preferably 30N or more. The upper limit of the tension of the laminated sheet during winding is not particularly limited, but the higher the tension, the more likely it is that the occurrence of orange skin will be promoted. It is preferable that it is below.

When the laminated sheet is wound, the winding length may be 50 m or more, 60 m or more, or 100 m or more. The upper limit of the winding length is not particularly limited, and can be changed as appropriate depending on the use of the laminated sheet.

In the above-mentioned process, the reaction of the (meth)acrylic copolymer, the crosslinking agent, etc. proceeds by heating the coating film, and a cured product (adhesive layer) is formed. In order to bring the adhesive composition into a cured state, after the solvent is removed after coating, an aging treatment may be performed in which the adhesive sheet is left at a constant temperature for a certain period of time. The aging treatment may be performed after forming the rolled body, for example, by leaving it at 23° C. for 7 days.

(Application)
The laminated sheet of the present invention is preferably a laminated sheet for laminating optical members. When laminating the laminated sheet to an optical member, the release film is peeled off and the exposed adhesive layer is laminated to the optical member. The laminated sheet of the present invention can be used as, for example, an antireflection film, an anti-scattering film, a surface protection film, an oriented film, a polarizing film, a retardation film, and a brightness enhancement film by peeling off the release film.

EXAMPLES The features of the present invention will be explained in more detail below with reference to Examples and Comparative Examples. The materials, usage amounts, proportions, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. In addition, in the following, Examples 2 and 7 shall be read as Reference Examples 2 and 7, respectively.

(Example 1)
[Preparation of adhesive composition]
150 parts by mass of ethyl acetate and 0.75 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) were charged into a reaction apparatus equipped with a stirrer, a reflux condenser, a sequential dropping device, and a thermometer. Next, in another container, prepare 600 parts by mass of a monomer mixture consisting of 510 parts by mass of n-butyl acrylate (BA), 60 parts by mass of acrylic acid (AA), and 30 parts by mass of 2-ethylhexyl methacrylate (2EHMA). Of this, 150 parts by mass was charged into a reaction apparatus, heated, and refluxed at reflux temperature for 30 minutes. Next, under reflux temperature conditions, 35 parts by mass of ethyl acetate and 0.03 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) were sequentially added dropwise to the remaining 450 parts by mass of the monomer mixture over 120 minutes. After the completion of the dropwise addition, the polymerization reaction was further carried out for 120 minutes. Thereafter, a mixed solution of 15 parts by mass of ethyl acetate and 1.0 parts by mass of t-butyl peroxypivalate was sequentially added dropwise over 40 minutes, and the polymerization reaction was further carried out for 200 minutes. After the reaction was completed, the solution was diluted with ethyl acetate to a solid content of 50% by mass to obtain a solution of (meth)acrylic copolymer (X). The weight average molecular weight of the (meth)acrylic copolymer (X) was 500,000. The weight average molecular weight (Mw) of the (meth)acrylic acid ester copolymer was measured by GPC (gel permeation chromatography) on a sample dissolved in THF (tetrahydrofuran).
To 100 parts by mass of the solid content of the acrylic ester copolymer (A) obtained as described above, 1.0 parts by mass of a chelate crosslinking agent (manufactured by Kawaken Fine Chemical Co., Ltd.: Aluminum Chelate A (W)) was added, Adhesive composition A was prepared by diluting and stirring the solution with ethyl acetate to obtain a solution having a solid content concentration of 32% by mass.

[Production of adhesive sheet with base material (laminated sheet)]
A release film (manufactured by Teijin Film Solutions Co., Ltd.: A38ST) with a thickness of 75 μm wound in a roll is rolled out, and the above-mentioned adhesive composition A is applied to the release-treated surface of the release film using a lip coater. It was dried at .degree. C. for 1.5 minutes to form an adhesive layer with a thickness of 15 .mu.m on the release film. Next, a film base material with a thickness of 23 μm (manufactured by Toray Industries, Inc.: U403) wound into a roll is rolled out, bonded onto the adhesive layer, and wound for 100 m around a 3-inch paper tube at a tension of 60 N to form the base material. A rolled body of the adhesive sheet (laminated sheet) was prepared. Next, after storing the above-mentioned rolled body at 23° C. and 50% relative humidity for one week, 5 m of the adhesive sheet with a base material was collected at a position where 80 m of the adhesive sheet was unwound.
Separately, a base material-less adhesive sheet was produced as a sample for measuring gel fraction and the like. In the production of the above-mentioned adhesive sheet with a base material, the release film (manufactured by Teijin Film Solutions Co., Ltd.: A38ST) was changed to a 75 μm thick (manufactured by Teijin Film Solutions Co., Ltd.: A71), and the film base material (manufactured by Toray Industries, Inc.: U403) was used. A rolled body of a base material-less pressure-sensitive adhesive sheet was obtained in the same manner as the above-mentioned base material-attached pressure-sensitive adhesive sheet except that a release film having a thickness of 75 μm (manufactured by Teijin Film Solutions Co., Ltd.: A38ST) was used.

(Example 2)
In the preparation of adhesive composition A, the adhesive sheet with a base material of Example 2 and the base material were prepared in the same manner as in Example 1, except that the number of parts of the chelate crosslinking agent added was changed from 1.0 parts by mass to 0.8 parts by mass. A material-less adhesive sheet was obtained.

(Example 3)
In the preparation of adhesive composition A, 0.058 parts by mass of a crosslinking agent (manufactured by Soken Kagaku Co., Ltd.: E-5XM) was further added, and the number of parts of the chelate crosslinking agent added was increased from 1.0 parts by mass to 0.1 parts by mass. A pressure-sensitive adhesive sheet with a base material and a pressure-sensitive adhesive sheet without a base material of Example 3 were obtained in the same manner as in Example 1 except for the following changes.

(Example 4)
A pressure-sensitive adhesive sheet with a base material and a pressure-sensitive adhesive sheet without a base material of Example 4 were obtained in the same manner as in Example 3 except that the number of parts of the chelate crosslinking agent added was changed from 0.1 part by mass to 0.5 part by mass.

(Example 5)
0.3 parts by mass of a chelate cross-linking agent (M-5A, manufactured by Soken Chemical Co., Ltd.) and a cross-linking agent (manufactured by Soken Chemical Co., Ltd.: Adhesive composition B was prepared by adding 0.04 parts by mass of E-AX) and diluting and stirring with ethyl acetate to obtain a solution with a solid content concentration of 32% by mass. Adhesive composition A was changed to adhesive composition B, and the number of parts of the chelate crosslinking agent added was changed from 1.0 parts by mass to 0.3 parts by mass, and the crosslinking agent (manufactured by Soken Kagaku Co., Ltd.: E-AM A pressure-sensitive adhesive sheet with a base material and a pressure-sensitive adhesive sheet without a base material of Example 5 were obtained in the same manner as in Example 1 except that 0.04 parts by mass of ) was added.

(Example 6)
Implemented except that the number of parts added of the chelate crosslinking agent was changed from 0.3 parts by mass to 0.5 parts by mass, and the release film (manufactured by Teijin Film Solutions Co., Ltd.: A38ST) was changed to a thickness of 75 μm (manufactured by Toyobo Co., Ltd.: E7002). A pressure-sensitive adhesive sheet with a base material and a pressure-sensitive adhesive sheet without a base material of Example 6 were obtained in the same manner as in Example 5.

(Example 7)
In the preparation of adhesive composition A, the number of parts of the chelate crosslinking agent added was changed from 1.0 parts by mass to 0.8 parts by mass, and the film base material with a thickness of 23 μm (manufactured by Toray Industries, Inc.: U403) was changed to the film base material with a thickness of 38 μm. A pressure-sensitive adhesive sheet with a base material and a pressure-sensitive adhesive sheet without a base material of Example 7 were obtained in the same manner as in Example 2 except that the adhesive sheet was changed to U403 (manufactured by Toray Industries, Inc.).

(Comparative example 1)
A pressure-sensitive adhesive sheet with a base material and a pressure-sensitive adhesive sheet without a base material of Comparative Example 1 were obtained in the same manner as in Example 3 except that the number of parts of the chelate crosslinking agent added was changed from 0.1 part by mass to 0 part by mass.

(Comparative example 2)
A pressure-sensitive adhesive sheet with a base material and a pressure-sensitive adhesive sheet without a base material of Comparative Example 2 were obtained in the same manner as in Example 6 except that the number of parts of the chelate crosslinking agent added was changed from 0.5 parts by mass to 0 parts by mass.

(Comparative example 3)
The adhesive sheet with base material of Comparative Example 3 was prepared in the same manner as Comparative Example 2 except that the 23 μm thick film base material (manufactured by Toray Industries, Inc.: U403) was changed to a 38 μm thick film base material (manufactured by Toray Industries, Inc.: U403). A base material-less adhesive sheet was obtained.

(measurement)
<Reflection intensity>
Dust was removed from the surface of a 30×40 cm glass plate using a dust-removing adhesive roller. Next, the release films of Examples and Comparative Examples were cut into 15 x 20 cm pieces, and then placed on a glass plate with the release-treated side facing down. The amount of reflected light on the opposite surface to the peeled surface was measured using Wave-Scan Dual (manufactured by BYK Gardner). Table 1 shows the values of reflection intensity Wb in the displayed wavelength range of 0.3 to 1.0 mm.

<Arithmetic mean roughness (Ra) and maximum protrusion height (Rp)>
For the release films used in Examples and Comparative Examples, the arithmetic mean roughness Ra and maximum protrusion height Rp of the surface opposite to the release-treated surface were measured using a surface roughness measuring device SV3200 (stylus type) manufactured by Mitutoyo. It was measured in accordance with JIS B 0601-1994.

<Gel fraction>
Immediately after coating and drying, the rolls of substrate-less adhesive sheets of Examples and Comparative Examples were cut into 60 x 100 mm pieces, the release films on both sides were peeled off, and the adhesive layer was covered with a metal mesh ( 150 mesh). The sample wrapped in mesh was immersed in ethyl acetate and left at 40°C for 24 hours. The taken out adhesive layer was dried at 100° C. for 1 hour, the weight ratio before and after immersion in ethyl acetate was calculated, and the gel fraction of the adhesive layer immediately after coating and drying was determined from the following formula.
Gel fraction (%) = Weight of adhesive layer after immersion in ethyl acetate / Weight of adhesive layer before immersion in ethyl acetate x 100

(evaluation)
<Yuzu skin evaluation>
The release films of the base-attached pressure-sensitive adhesive sheets of Examples and Comparative Examples were peeled off, and the exposed pressure-sensitive adhesive layers were bonded to a black acrylic board (manufactured by Mitsubishi Chemical Corporation). Thereafter, the light from the fluorescent lamp was reflected and observed, and the distortion of the image of the fluorescent lamp reflected on the film base material was evaluated based on the following criteria.
◎: There is no distortion in the image of the fluorescent light reflected on the film base material, and the occurrence of orange skin is completely suppressed.
○: The image of the fluorescent light reflected on the film base material appears slightly distorted, and there is some orange skin, but it is at a level that is not a problem.
×: The image of the fluorescent light reflected on the film base material appears distorted, and orange skin appears.

The laminated sheets obtained in the examples had good appearance and no so-called orange skin was observed. On the other hand, in the laminated sheet obtained in the comparative example, poor appearance occurred, and occurrence of orange skin was observed.

10 Film base material 20 Adhesive layer 30 Release film 100 Laminated sheet

Claims (3)

A laminated sheet in which a film base material, an adhesive layer and a release film are directly laminated in this order,
The thickness of the film base material is 25 μm or less,
When the reflection intensity (Wb) of the exposed surface of the release film is measured in a wavelength range of 0.3 to 1.0 mm using a wave scanning device, the reflection intensity (Wb) is 10 or more,
The adhesive layer includes at least a structure derived from a (meth)acrylic copolymer, a chelate crosslinking agent, and a structure derived from an epoxy crosslinking agent,
The content of the structure derived from the epoxy crosslinking agent is 0.01 to 1.0 parts by mass based on 100 parts by mass of the (meth)acrylic copolymer,
A laminated sheet in which the adhesive layer has a gel fraction of 50% or more . The laminated sheet according to claim 1, wherein the content of the structure derived from the chelate crosslinking agent is 0.1 to 5.0 parts by mass based on 100 parts by mass of the (meth)acrylic copolymer. The laminate sheet according to claim 1 or 2, wherein the exposed surface of the release film has an arithmetic mean roughness of 35 nm or more.

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