Cover film

Abstract

The present invention addresses the problem of providing a cover film that is less likely to generate cutting chips when being cut. A cover film according to the present invention is used to cover a test piece on a substrate. The cover film includes a support and an adhesion layer. The adhesion layer is formed by layering at least two polymer layers having different compositions. The elastic modulus of each of the at least two polymer layers is less than the elastic modulus of the support. The elastic moduli of the at least two polymer layers sequentially become smaller from the support side toward the opposite side from the support side.

Description

Cover film

[0001] The present invention relates to a cover film.

[0002] In the medical field of cytology and histology, a method for observing a microscopic specimen under a microscope is known. One example of a method for preparing such a microscopic specimen involves automatically placing a cover film having a polymer (e.g., an adhesive or a compound capable of acting as an adhesive) on a support, and then placing the cover film on a substrate (e.g., a glass slide) on which a few drops of a solvent capable of swelling and / or dissolving the polymer (hereinafter also referred to as a "mounting liquid," e.g., xylene) have been dropped, and on which a specimen is placed, using an automatic mounting device to bond the cover film to the substrate (hereinafter also referred to as "mounting"). This method allows for the preparation of a microscopic specimen in which the specimen is fixed between the substrate and the cover film.

[0003] For example, Patent Document 1 discloses an invention relating to a transparent film including a support film containing cellulose triacetate or a mixture of cellulose ester and cellulose triacetate as a main component.

[0004] U.S. Patent Application Publication No. 2018 / 0194913

[0005] When a cover film is used for encapsulation, the cover film is often cut before use. However, cutting the cover film can generate chips, and if the chips get mixed into the encapsulated sample, it may affect visibility during observation. Therefore, there is a need to reduce the chips generated when the cover film is cut. The present inventors studied the cover film with reference to Patent Document 1 and found that there is room for further improvement in the generation of chips during cutting.

[0006] Therefore, an object of the present invention is to provide a cover film that does not generate chips when cut.

[0007] As a result of extensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by the following configuration.

[0008] [1] A cover film used to cover an object on a substrate, the cover film comprising a support and an adhesive layer, the adhesive layer being a layer formed by laminating two or more polymer layers having different compositions, the moduli of elasticity of each of the two or more polymer layers being smaller than the moduli of elasticity of the support, and the moduli of elasticity of each of the two or more polymer layers being successively smaller from the support side toward the opposite side from the support side. [2] In the cover film, the average difference ΔE between the moduli of elasticity of the polymer layers contacting each other ａｖｅ and the maximum difference ΔE between the moduli of elasticity between the polymer layers in contact with each other. ｍａｘand satisfy the relationship of formula (1) described below. [3] A cover film used to cover an object on a substrate, the cover film comprising a support and an adhesion layer containing a polymer, wherein a cross section of the adhesion layer is exposed, and when the elastic modulus is measured in the thickness direction of the adhesion layer from one surface to the other surface at positions 20%, 40%, 60%, and 80% of the total thickness of the adhesion layer from the one surface, the elastic modulus at each position is smaller than the elastic modulus of the support and gradually decreases from the support side to the opposite side of the support side. [4] The cover film according to [2], wherein the elastic modulus of the adhesion layer changes continuously along the thickness direction. [5] The cover film according to any of [1] to [4], wherein the main component of the adhesion layer is a copolymer containing two or more repeating units derived from a monomer selected from the group consisting of (meth)acrylate, styrene, and acrylamide. [6] The cover film according to any one of [1] to [5], wherein the adhesive layer is a copolymer containing two or more repeating units derived from a monomer selected from the group consisting of ethyl acrylate, n-butyl acrylate, methyl acrylate, cyclohexyl acrylate, benzyl acrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, methyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, acetoacetoxyalkyl methacrylate, styrene, and dimethylacrylamide. [7] The cover film according to [6], wherein the copolymer has a weight-average molecular weight of 80,000 or more. [8] The cover film according to any one of [1] to [7], wherein the adhesive layer has a thickness of 5 to 30 μm.

[0009] According to the present invention, a cover film that is less likely to produce chips when cut can be provided.

[0010] The present invention will be described in detail below. The following description of the components may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

[0011] In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the upper and lower limits. In numerical ranges described in stages in this specification, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described in this specification, the upper or lower limit described in a certain numerical range may be replaced with a value shown in the Examples. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. In this specification, when a composition contains multiple substances corresponding to each component, the amount of each component in a composition or layer means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0012] In this specification, "(meth)acrylic" is a general term for acrylic and methacrylic, and means "one or more of acrylic and methacrylic." Similarly, "(meth)acrylate" means "one or more of acrylate and methacrylate." In this specification, unless otherwise specified, the refractive index refers to the refractive index for light with a wavelength of 550 nm, measured using an Abbe refractometer ("NAR-2T" manufactured by Atago Co., Ltd.).

[0013] In this specification, unless otherwise specified, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are molecular weights determined by gel permeation chromatography (GPC) using a column of TSKgel GMHxL, TSKgel G4000HxL, TSKgel G2000HxL, and / or TSKgel Super HZM-N (all of which are trade names manufactured by Tosoh Corporation), using THF (tetrahydrofuran) as a solvent, detecting with a differential refractometer, and converting the molecular weight using polystyrene as a standard substance.

[0014] In this specification, the term "process" includes not only an independent process but also a process that achieves its intended purpose even if it cannot be clearly distinguished from other processes. In this specification, "conveyance direction" refers to the longitudinal direction of a film-like or sheet-like member during production, and is synonymous with "longitudinal direction" and "MD (Machine Direction)." In this specification, "width direction" refers to the direction perpendicular to the conveyance direction, and is synonymous with "TD (Transverse Direction)." Regarding angles, "perpendicular" or "vertical" refers to a range of 90°±5°, and "parallel" refers to a range of 0°±5°. Similarly, unless otherwise specified, angles refer to a difference of within 5 degrees from the exact angle. The difference in the above angle is preferably within 4 degrees, and more preferably within 3 degrees. In this specification, a better effect of suppressing the generation of chips when cutting the cover film is also referred to as "a better effect of the present invention."

[0015] A first embodiment of the cover film of the present invention is a cover film used to cover an object on a substrate, comprising a support and an adhesive layer, wherein the adhesive layer is a layer formed by laminating two or more polymer layers having different compositions, wherein the modulus of elasticity of each of the two or more polymer layers is smaller than the modulus of elasticity of the support, and the modulus of elasticity of each of the two or more polymer layers gradually decreases from the support side to the opposite side of the support. A second embodiment of the cover film of the present invention is a cover film used to cover an object on a substrate, comprising a support and an adhesive layer containing a polymer, wherein a cross-section of the adhesive layer is exposed, and when the modulus of elasticity is measured along the thickness direction of the adhesive layer from the surface of the adhesive layer facing the support to the surface opposite the support at positions 20%, 40%, 60%, and 80% of the total thickness of the adhesive layer from the surface of the support side, the modulus of elasticity at each position is smaller than the modulus of elasticity of the support and gradually decreases from the support side to the opposite side of the support. Each embodiment is described in detail below.

[0016] [First embodiment] The first embodiment of the cover film of the present invention is a laminate in which an adhesive layer is formed by laminating two or more polymer layers having different compositions, and the elastic modulus of each of the two or more polymer layers is smaller than the elastic modulus of the support, and the elastic modulus of each of the two or more polymer layers gradually decreases from the support side toward the opposite side of the support side. Hereinafter, the cover film according to this embodiment will be described in detail.

[0017] <Support> The support of the cover film is not particularly limited, and any known support can be used.

[0018] Examples of materials constituting the support include polymers selected from the group consisting of cellulose acetates (cellulose-based polymers) such as cellulose triacetate (TAC), cellulose diacetate, cellulose acetate propionate, and cellulose acetate butyrate; polyester-based polymers such as polyethylene terephthalate (PET) and aliphatic polyesters; polyolefin-based polymers such as cycloolefin polymers (COP), polyethylene, and polypropylene; acrylic resins; polycarbonate (PC); and polystyrene. Cellulose acetate or polyethylene terephthalate is preferred, and cellulose triacetate (TAC) is more preferred.

[0019] When the support contains the above polymer, the weight average molecular weight (Mw) of the polymer is, for example, 10,000 to 1,000,000, and preferably 30,000 to 300,000. When the support contains cellulose acetate (more preferably TAC), the degree of substitution of the cellulose acetate is preferably 2.00 to 3.00, more preferably 2.40 to 2.95, and even more preferably 2.85 to 2.95. Examples of methods for measuring the degree of substitution include known measurement methods such as FT-IR and titration.

[0020] The support may use one type of the above polymer alone, or two or more types may be used. The content of the above polymer in the support is preferably 50% by mass or more, more preferably 80% by mass or more, based on the total mass of the support. The upper limit is not particularly limited, and may be 100% by mass or less, based on the total mass of the support. In particular, the support preferably contains cellulose acetate (more preferably TAC) in an amount of 50% by mass or more, more preferably 80% by mass or more, based on the total mass of the support. The upper limit is not particularly limited, and is preferably less than 100% by mass.

[0021] (Additives) The support may contain other components different from the polymer. Examples of other components include at least one additive selected from the group consisting of sugars, polyesters, organic acids represented by the general formula (1) described below, and compounds represented by the general formula (2) described below (hereinafter also referred to as "additive A"). When the support contains cellulose acetate (more preferably TAC) in an amount of 50% by mass or more relative to the total mass of the support, it is preferable that the support further contains additive A, more preferably contains one or more selected from the group consisting of polyesters and compounds represented by the general formula (2), and even more preferably contains polyester.

[0022] It is also preferable that the additive A has an average molecular weight of 500 or more. The average molecular weight of additive A of 500 or more means that when the support contains one type of additive A, the molecular weight of the one type of additive A is 500 or more. The molecular weight of the one type of additive A is preferably 700 or more, more preferably 800 or more. The upper limit is preferably 5000 or less, more preferably 1000 or less. For example, when the support contains one type of additive A, the molecular weight of the one type of additive A is 500 or more, and additive A does not contain one type of additive having a molecular weight of less than 500. In other words, when one type of additive A is contained, the molecular weight of the additive A is limited to 500 or more.

[0023] The average molecular weight of additive A is a weighted average of molecular weights, and is calculated by summing the values ​​obtained by multiplying the molecular weights of two or more additives A by the content of each of the two or more additives A relative to the total mass of additive A. More specifically, the average molecular weight of additive A is a value (X) calculated by the following formula 1. In particular, in formula 1, the molecular weight of the ith additive A (i represents an integer of 1 or more) contained in the support is substituted for Mi, and the mass ratio (content) of the ith additive A relative to the total mass of additives A is substituted for Wi, to calculate the average molecular weight. Formula 1 X = ΣMiWi / ΣWi Specifically, if additive A contains additive A-X (M1 having a number average molecular weight of 900) as the first additive and additive A-Y (M2 having a molecular weight of 400) as the second additive, and the content (W1) of additive A-X relative to the total mass of additive A is 0.8, and the content (W2) of additive A-Y relative to the total mass of additive A is 0.2, the calculation is "(900 × 0.8 + 400 × 0.2) / (0.8 + 0.2) = 800," and the average molecular weight (X) is "800." The total mass of additive A corresponds to the total mass of additives A-X and A-Y. As described above, when the support contains two or more additives A, as long as the average molecular weight is 500 or more, additive A having a molecular weight of less than 500 may be included. When two or more additives A are included, it is preferable to include at least one additive A having a molecular weight of less than 500. When the additive A has a molecular weight distribution, the molecular weight indicates a number average molecular weight, and the average molecular weight is calculated using the number average molecular weight.

[0024] The additive A will be described in detail below.

[0025] -Sugars- Examples of sugars include monosaccharides, disaccharides, and polysaccharides, with disaccharides being preferred. Examples of monosaccharides include pentoses such as ribose, deoxyribose, arabinose, and xylose, trioses, tetroses, hexoses, and heptoses. Examples of disaccharides include sucrose, lactose, maltose, trehalose, turanose, and cellobiose, with sucrose being preferred. Examples of polysaccharides include glycogen and starch. The sugars may be either linear or cyclic. Examples of the cyclic sugars include furanose rings and pyranose rings.

[0026] In some or all of the hydroxyl groups of the saccharide, the hydrogen atoms in the hydroxyl groups may be replaced with substituents. When hydroxyl groups in multiple hydroxyl groups are replaced with substituents, the multiple substituents may be the same or different. The substituent is preferably an acyl group. The acyl group preferably has 1 to 10 carbon atoms. Examples of the acyl group include aliphatic acyl groups such as formyl, acetyl, propionyl, 2-methylpropionyl, 2,2-dimethylpropionyl, and 2-ethylhexanoyl; and aromatic acyl groups such as benzoyl, 1-naphthylcarbonyl, 2-naphthylcarbonyl, and 2-furylcarbonyl.

[0027] -Polyester- As the polyester, known polyesters can be used, and polyesters containing a repeating unit represented by general formula (1A) and having capped ends are preferred.

[0028]

[0029] In general formula (1A), X represents a non-cyclic divalent linking group having 2 to 10 carbon atoms. R represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkynyl group having 2 to 8 carbon atoms, or an aryl group having 6 carbon atoms. m represents an integer of 0 to 4.

[0030] "Acyclic" means that it does not contain a cyclic structure. Examples of groups that do not contain a cyclic structure include linear or branched groups. Examples of the acyclic divalent linking group having 2 to 10 carbon atoms include alkylene groups having 2 to 10 carbon atoms, alkynylene groups having 2 to 10 carbon atoms, and the above alkylene groups and alkynylene groups having a heteroatom (e.g., oxygen atom, nitrogen atom, etc.). The number of carbon atoms in the acyclic divalent linking group represented by X is preferably 2 to 6, more preferably 2 to 4. The acyclic divalent linking group represented by X may have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, a hydroxyl group, a carboxy group, and groups combining these.

[0031] The group represented by R may have a substituent. Examples of the substituent include the substituents that X may have. The number of carbon atoms in the group represented by R does not include the number of carbon atoms in the substituents that the group represented by R may have. R may form a ring structure. Examples of the ring structure include a cyclohexyl group, a cyclooctyl group, a boronyl group, an isobornyl group, and a norbornyl group. The alkyl group having 1 to 8 carbon atoms represented by R is preferably an alkyl group having 1 to 4 carbon atoms, and more preferably a methyl group or an ethyl group. Examples of the aryl group having 6 carbon atoms include a phenyl group and a 4-methylphenyl group.

[0032] m represents an integer of 0 to 4. m is preferably an integer of 1 to 4, more preferably an integer of 1 or 2, and even more preferably 1 from the viewpoints of reactivity and availability of raw materials.

[0033] The terminally-capped polyester preferably has a terminal structure obtained by reacting the polyester terminal with a monoalcohol (or a monoalcohol derivative capable of forming an ester bond with the terminal carboxy group of the polyester) or a monocarboxylic acid (or a monocarboxylic acid derivative capable of forming an ester bond with the terminal hydroxyl group of the polyester). For example, when a polyester having a terminal carboxy group is obtained by reacting a dibasic acid with a diol, the terminal can be capped with a monoalcohol residue by reacting this with a monoalcohol. Furthermore, when a polyester having a terminal hydroxyl group is obtained, the terminal can be capped with a monocarboxylic acid residue by reacting this with a monocarboxylic acid. The term "residue" refers to a partial structure of the polyester, and represents a partial structure characteristic of the monomer forming the polyester. For example, a monocarboxylic acid residue formed from a monocarboxylic acid R-COOH is R-CO-, and a monoalcohol residue formed from a monoalcohol R-OH is R-O-. The terminals of the polyester are preferably capped with an acyl group, and more preferably have a terminal structure obtained by reacting with a monocarboxylic acid.

[0034] Examples of the polyester include the polyesters described in paragraphs

[0024] to

[0035] of JP-A-2015-227955, the contents of which are incorporated herein by reference.

[0035] —Organic Acid Represented by General Formula (1)— The support may contain an organic acid represented by the following general formula (1): X １１ -L-(R １１ ) ｎ (1) X １１ represents an acidic group having an acid dissociation constant of 5.5 or less. L represents a single bond or a divalent or higher linking group. R １１ represents an alkyl group having 6 to 30 carbon atoms, an alkenyl group having 6 to 30 carbon atoms, an alkynyl group having 6 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or a heterocyclic group having 6 to 30 ring members, which may further have a substituent. n is 1 when L is a single bond, and is (the valence of L - 1) when L is a divalent or higher linking group. In other words, L is a single bond or an (n+1) valent linking group.

[0036] The organic acid represented by the general formula (1) is preferably a partial derivative of a polyvalent organic acid. In this specification, the partial derivative of a polyvalent organic acid refers to a compound having a structure in which one molecule of a fatty acid and one molecule of a polyvalent organic acid are ester-bonded to one molecule of a polyhydric alcohol, and having at least one unsubstituted acidic group derived from a polycarboxylic acid. In this specification, the term "fatty acid" refers to an aliphatic monocarboxylic acid. In other words, the fatty acid in this specification is not limited to so-called higher fatty acids, but also includes lower fatty acids having 12 or less carbon atoms, such as acetic acid and propionic acid. The partial derivative of the polyvalent organic acid is preferably a partial derivative of a polycarboxylic acid. In other words, the organic acid represented by the general formula (1) has a structure in which one molecule of a fatty acid and one molecule of a polycarboxylic acid are ester-bonded to one molecule of a polyhydric alcohol, and preferably has at least one unsubstituted carboxyl group derived from a polycarboxylic acid. The polycarboxylic acid used in the partial derivative of the polycarboxylic acid is not particularly limited, but is preferably, for example, succinic acid, citric acid, tartaric acid, diacetyltartaric acid, malic acid, or adipic acid.

[0037] Examples of the polyhydric alcohol used in the partial derivative of the polyhydric organic acid include adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol, and glycerin, with glycerin being preferred. The organic acid represented by the general formula (1) is preferably a so-called organic acid glyceride.

[0038] Examples of the organic acid represented by general formula (1) include the organic acids described in paragraphs

[0046] to

[0049] of JP-A-2015-227955, the contents of which are incorporated herein by reference.

[0039] —Compound Represented by General Formula (2)— The support may contain a compound represented by the following general formula (2).

[0040]

[0041] In general formula (2), R １ , R ３ and R ５ each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, or an aromatic group. These alkyl groups, cycloalkyl groups, alkenyl groups, and aromatic groups may have a substituent. However, R １ , R ３ and R ５ is an alkyl group or a cycloalkyl group substituted with a group having a ring structure, and R １ , R ３ and R ５ The total number of ring structures present in the ring structure is three or more.

[0042] The above R １ , R ３ and R ５ The number of carbon atoms in the alkyl group in the above is preferably 1 to 20, more preferably 1 to 10, even more preferably 1 to 5, and particularly preferably 1 to 3. As the alkyl group, a methyl group or an ethyl group is preferable. However, in the case of an alkyl group substituted with a group having a ring structure, the number of carbon atoms is preferably 7 to 20, more preferably 7 to 12, and even more preferably 7 to 10. The ring structure in the alkyl group having a ring structure may be an aromatic ring (including an aromatic heterocycle) or an aliphatic ring, but is preferably an aromatic hydrocarbon group or an aliphatic ring. １ , R ３ and R ５ The number of carbon atoms in the cycloalkyl group in the above formula is preferably 3 to 20, more preferably 3 to 10, even more preferably 4 to 8, and particularly preferably 5 or 6. Examples of the cycloalkyl group include a cyclopropyl group, a cyclopentyl group, and a cyclohexyl group, and a cyclohexyl group is preferred. １ , R ３ and R ５The number of carbon atoms in the alkenyl group in the above R is preferably 2 to 20, more preferably 2 to 10, and even more preferably 2 to 5. Examples of the alkenyl group include a vinyl group and an allyl group. １ , R ３ and R ５ The aromatic group in may be either an aromatic hydrocarbon group or an aromatic heterocyclic group, but is preferably an aromatic hydrocarbon group. The number of carbon atoms in the aromatic group is preferably 6 to 20, more preferably 6 to 16, and even more preferably 6 to 12. The aromatic group is preferably a phenyl group or a naphthyl group, and more preferably a phenyl group.

[0043] R １ , R ３ and R ５ Each of the above groups may have a substituent. The substituent is not particularly limited and examples thereof include an alkyl group, an aryl group, an alkoxy group, an alkylthio group, an alkylsulfonyl group, a halogen atom, and an acyl group. An alkyl group, an aryl group, an alkoxy group, or an acyl group is preferred, and an alkyl group or an alkoxy group is more preferred.

[0044] R １ , R ３ and R ５ It is preferable that any one of R is an alkyl group substituted with a group having a ring structure. The ring of the group having a ring structure is preferably a benzene ring, a naphthalene ring, a cyclopentane ring, a cyclohexane ring, or a nitrogen-containing heteroaromatic ring (e.g., a pyrrole ring, a pyrazole ring, an imidazole ring, an oxazole ring, a thiazole ring, a pyridine ring, an indole ring, or an isoindole ring). In addition, the compound represented by general formula (2) can be obtained by adding R １ , R ３ and R ５ It is preferable that at least two of R are alkyl groups or cycloalkyl groups having a ring structure as a substituent. １ and R ３ are each independently an alkyl group which may have a substituent, an aromatic group which may have a substituent, or a cycloalkyl group which may have a substituent. １ , R ３ and R５ It is more preferred that the total number of ring structures present in the substituents is a maximum of four.

[0045] R ５ is preferably an alkyl group or a cycloalkyl group which may be substituted with a group having a ring structure or an acyl group, more preferably an alkyl group substituted with an aryl group, an alkyl group substituted with an acyl group (preferably an alkyl group substituted with an acyl group and an aryl group), or a cycloalkyl group, and still more preferably an alkyl group or cycloalkyl group substituted with an aryl group.

[0046] Among the compounds represented by general formula (2), preferred compounds are listed below. １ , R ３ and R ５ A compound in which any one of the above is an alkyl group substituted with an aromatic ring. As the alkyl group substituted with an aromatic ring, one in which one or two aryl groups are substituted on the alkyl group (when two aryl groups are substituted, it is preferable that they are substituted on the same carbon atom). Furthermore, one in which an aryl group and an acyl group (preferably an aryloyl group) are substituted on the alkyl group is also preferred. １ , R ３ and R ５ wherein any one of the above is a group containing a cycloalkyl group (preferably a cycloalkyl group).

[0047] The compound represented by general formula (2) is R １ , R ３ and R ５ is more preferably an alkyl group, an alkenyl group, or an aryl group. １ , R ３ and R ５ More preferably, each of these has one or more ring structures, and even more preferably, each has one ring structure.

[0048] The compound represented by general formula (2) and a synthesis method thereof are also described, for example, in paragraphs

[0072] to

[0078] of JP-A-2015-227955, the disclosures of which are incorporated herein by reference.

[0049] Additive A may be used alone or in combination of two or more. The content of Additive A may be, for example, 30 parts by mass or less per 100 parts by mass of the cellulose acetate content in the support, and is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, in terms of achieving better effects of the present invention. The lower limit is not particularly limited, and may be, for example, 1 part by mass or more, more preferably 3 parts by mass or more, per 100 parts by mass of the cellulose acetate content.

[0050] Furthermore, the support preferably contains a specific ester compound that satisfies the following requirement 1, with the content being 1 mass % or less relative to the total mass of the support: Requirement 1: At least one of the hydrolysates of the ester compound has an acid dissociation constant (pKa) of 2.5 or less. That is, the support preferably does not contain the specific ester compound, or, if it contains the specific ester compound, preferably contains the specific ester compound in an amount of 1 mass % or less relative to the total mass of the support.

[0051] The specific ester compound is a hydrolyzate of an ester compound obtained by a condensation reaction between an organic or inorganic oxo acid and a hydroxy group-containing compound, i.e., a compound in which at least one of the organic or inorganic oxo acid and the hydroxy group-containing compound has a pKa of 2.5 or less. When an ester compound has multiple pKas, the ester compound is considered to satisfy requirement 1 if any one of the multiple pKas is 2.5 or less.

[0052] As used herein, the acid dissociation constant (pKa) refers to the pKa in an aqueous solution, and specifically, is a value determined by calculation based on a database of Hammett's substituent constants and known literature values ​​using the following software package 1: Advanced Chemistry Development (ACD / Labs) Software V8.14 for Solaris (1994-2007 ACD / Labs).

[0053] Examples of specific ester compounds include phosphate ester compounds, phosphite ester compounds, sulfonate ester compounds, and nitrate ester compounds. Hydrolysates of specific ester compounds having a pKa of 2.5 or less include phosphoric acid produced by hydrolysis of phosphate ester compounds, phosphorous acid produced by hydrolysis of phosphite ester compounds, sulfonic acids such as methanesulfonic acid and benzenesulfonic acid produced by hydrolysis of sulfonate ester compounds, and nitric acid produced by hydrolysis of nitrate ester compounds.

[0054] When the support contains a specific ester compound, the specific ester compound may be one type alone or two or more types. When two or more types of specific ester compounds are present, the total content of the specific ester compounds is 1 mass% or less relative to the total mass of the support. When the support contains a specific ester compound, the content of the specific ester compound is preferably 0.6 mass% or less, more preferably 0.4 mass% or less, relative to the total mass of the support, in terms of better achieving the effects of the present invention. It is particularly preferable that the support does not contain a specific ester compound.

[0055] The content of the specific ester compound contained in the support can be measured by the following measurement method. For example, the type and content of each ester compound contained in the support are measured by a known measurement method such as gas chromatography-mass spectrometry (GC / MS). The pKa of the hydrolysate produced by hydrolysis of each ester compound contained in the support is calculated from the structural formula of the ester compound. When a hydrolysate having a pKa of 2.5 or less is present, the content of the ester compound produced by that hydrolysate (the total content when two or more types are present) is the content of the specific ester compound. When no hydrolysate having a pKa of 2.5 or less is present, the support does not contain the specific ester compound.

[0056] In addition to additive A, the support may contain known additives (for example, ultraviolet inhibitors, anti-degradation agents, fine particles, optical property adjusters, etc.).

[0057] (Physical Properties of Support) As will be described later, in this embodiment, the elastic modulus of the support is greater than the elastic modulus of any of the polymer layers of the adhesive layer. The elastic modulus of the support is the storage elastic modulus (unit: Pa = N / m ２ The storage modulus can be measured by cutting the cover film in a direction intersecting the main surface of the cover film in an environment of 25°C, and measuring the exposed cross section at a position within 20% of the total thickness from the surface of the adhesive layer side of the support (0% position of the total thickness) by a known method using a nanoindenter and a Berkovich indenter. A specific method for measuring the storage modulus of the support will be described in the Examples below.

[0058] The elastic modulus of the support may be, for example, 1 to 10 GPa, and preferably 3 to 6 GPa. The storage elastic modulus of the support can be adjusted, for example, by at least one of the composition of the support, the stretching conditions performed in the production of the support, and the heat treatment conditions.

[0059] The thickness of the support is preferably from 50 to 250 μm, more preferably from 50 to 145 μm, and even more preferably from 100 to 145 μm, in terms of better handling properties and optical properties.

[0060] The refractive index of the support is not particularly limited, but may be, for example, 1.440 to 1.600, and from the viewpoint of microscopic examination, it is preferably 1.460 to 1.560, which is close to that of a glass slide (refractive index 1.52 to 1.56).

[0061] The support is preferably transparent. In this specification, "transparent" means that the transmittance of visible light (wavelength: 380 to 780 nm) is 60% or more. The transmittance is the ratio of transmitted light to incident light through the support. The transmittance of the support is preferably 80% or more, more preferably 90% or more. There is no particular upper limit, and it may be 100% or less. The transmittance of the support is measured using a known measuring device in accordance with "Plastics - Determination of total luminous transmittance and total luminous reflectance" as defined in JIS K 7375:2008.

[0062] The support may be subjected to a surface treatment such as ultraviolet irradiation, corona discharge, glow discharge, etc. Furthermore, the surface of the support may be provided with an undercoat layer.

[0063] (Method for Producing Support) The method for producing the support is not particularly limited, and the support can be produced from raw materials containing a polymer constituting the support and any additives according to a known film-forming method such as solution film-forming or melt film-forming. Hereinafter, the method for producing the support will be described using as an example a method for producing a cellulose acetate support, which includes a film-forming step of forming a film from a composition containing cellulose acetate, and a stretching step of stretching the film obtained in the film-forming step.

[0064] -Film-forming process- In the film-forming process, a film is formed using a composition containing cellulose acetate as a main component. Examples of film-forming methods include solution film-forming and melt film-forming, with the solution film-forming method being preferred. In the solution film-forming method, a film is formed using a solution (hereinafter also referred to as "dope") containing cellulose acetate, a solvent, and optional additives.

[0065] The solvent contained in the dope can be any known solvent used in preparing a solution casting dope. From the viewpoint of reducing the haze of the support, at least one solvent selected from the group consisting of ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms is preferred. The ethers, ketones, and esters may have a cyclic structure. Compounds having two or more functional groups selected from the group consisting of an ether bond (—O—), a ketone group (—CO—), and an ester bond (—COO—) can also be used as the solvent. The solvent may also have other functional groups such as an alcoholic hydroxyl group. In the case of a solvent having two or more functional groups, the number of carbon atoms may be within the range specified for the compound having any of the functional groups. The dope may also contain a poor solvent. Examples of poor solvents include methanol, ethanol, propanol, butanol, and water, with methanol being preferred.

[0066] The dope can be prepared by a known method, for example, by a method and apparatus for preparing a dope in a normal solvent casting method. The dope can be prepared by stirring cellulose acetate and a solvent at 0 to 40°C. A high-concentration dope may be stirred under pressure and heat. The heating temperature is usually 40°C or higher, preferably 60 to 200°C. The components may be roughly mixed in advance and then placed in a container (such as a tank), or may be added sequentially to the container.

[0067] The film-forming conditions and equipment used are the same as those for conventional cellulose acylate film production. The prepared dope (cellulose acetate solution) is sent from a dope outlet to a pressure die and uniformly cast from the die (slit) onto the surface of an endless metal support (e.g., a metal drum, a metal band, or a metal belt). The resulting film is then peeled off from the endless metal support to obtain a film (hereinafter also referred to as a "web") mainly composed of cellulose acetate.

[0068] After casting the dope, the film may be pre-dried to remove at least a portion of the solvent contained in the dope. Pre-drying may be performed on either the film on the endless metal support or the film peeled off from the endless metal support. For example, the web peeled off from the endless metal support may be pre-dried by clamping both ends in the width direction with tenter clips and transporting the web with a tenter. Examples of pre-drying methods include air drying, in which air is blown onto the film (web) during transportation, heat drying using a heating means such as a microwave or an oven, and a combination of these.

[0069] The casting and drying method in the solvent casting method is described in U.S. Pat. Nos. 2,336,310, 2,367,603, 2,492,078, 2,492,977, 2,492,978, 2,607,704, 2,739,069, and 2,739,070, British Patent Nos. 640,731, and 736,892, as well as Japanese Patent Publications 45-004,554, 49-005,614, JP-A 60-176,834, 60-203,430, and 62-115,035, the contents of which are incorporated herein by reference. Further, as a film-forming method, cellulose acylate film-forming techniques described in JP-A Nos. 2000-301555, 2000-301558, JP-A Nos. 7-032391, 3-193316, 5-086212, 62-037113, 2-276607, 55-014201, 2-111511, and 2-208650 can be applied, and the contents of these film-forming techniques are incorporated herein by reference.

[0070] -Stretching Step- In the stretching step, the film (web) obtained in the film-forming step is stretched. The direction of stretching in the stretching step may be either the conveying direction or the width direction, or both, and it is preferable to stretch the web in at least the width direction. When stretching the web in the width direction, either uniaxial stretching in which the web is stretched only in the width direction or biaxial stretching in which the web is stretched in both the width direction and the conveying direction may be used, with biaxial stretching being preferred. In the biaxial stretching process, stretching in the conveying direction and stretching in the width direction may be performed sequentially or simultaneously. When stretching in the conveying direction and stretching in the width direction are performed sequentially, the order is not particularly limited, but it is preferable to stretch the web in the conveying direction and then in the width direction.

[0071] The method for stretching the web in the width direction is not particularly limited, and known stretching methods can be applied. Examples include a method in which both widthwise ends of the web are fixed with clips or pins using a tenter apparatus and the distance between the clips or pins is widened in the width direction, and a method in which the distance is widened in both the width direction and the conveying direction using a tenter apparatus, thereby simultaneously stretching in both directions. As the widthwise stretching process, stretching by a so-called tenter method, in which stretching is performed using a tenter apparatus, is preferred. This is because stretching by the tenter method can be performed smoothly by driving the clips using a linear drive system, thereby reducing the risk of breakage, etc.

[0072] The method for stretching the web in the conveying direction is not particularly limited, and known stretching methods can be applied. Examples include a method in which the web is conveyed between multiple rolls having different rotation speeds and stretched in the conveying direction by utilizing the difference in rotation speed, a method in which both ends of the web in the width direction are fixed with clips or pins using a tenter apparatus and the interval between the clips or pins is widened in the conveying direction, and a method in which the interval is widened in both the width direction and the conveying direction using a tenter apparatus, thereby simultaneously stretching the web in both directions.

[0073] The cellulose acetate support can be produced by the above-mentioned production method including the film-forming step and the stretching step, but the production method of the support is not limited to the above-mentioned production method.

[0074] <Adhesion Layer> In this embodiment, the adhesion layer is a layer formed by laminating two or more polymer layers, and these two or more polymer layers have different compositions. Here, the term "polymer layer" refers to a layer containing a polymer. Furthermore, "polymer layers with different compositions" refers to polymer layers with different types and / or contents of components contained therein.

[0075] In this embodiment, "two or more polymer layers are laminated" means that when a cross-sectional sample of the cover film is prepared using a known method such as a microtome and the composition distribution in the thickness direction of the cross-section is evaluated using known measurement methods such as infrared absorption spectroscopy (IR) and time-of-flight secondary ion mass spectrometry (TOF-SIMS), two or more sections with different compositions appear. The fact that the adhesive layer is a layer composed of two or more polymer layers laminated together and the number of polymer layers can be confirmed by cutting the cover film in a direction intersecting the main surface of the cover film and analyzing the cross-section exposed by the cutting using the above-mentioned analytical method or by observing it using an optical microscope. Furthermore, the composition of the polymer layer can be confirmed by separating each polymer layer from the adhesive layer as necessary, taking a sample from the polymer layer, and analyzing the obtained sample using a known measurement method such as gas chromatography-mass spectrometry (GC / MS).

[0076] In this embodiment, the two or more polymer layers constituting the adhesive layer satisfy the following requirements 1A and 1B. (Requirement 1A) The modulus of elasticity of each of the two or more polymer layers is smaller than the modulus of elasticity of the support. (Requirement 1B) The modulus of elasticity of each of the two or more polymer layers decreases successively from the support side toward the opposite side of the support side. For example, if the adhesive layer has n (n≧2) polymer layers and the modulus of elasticity of the kth polymer layer counting from the support side is E ｋ and the elastic modulus of the support is E Ｓ Then, requirements 1A and 1B are expressed by the following formula: (Requirement 1A) E ｓ >E ｋ (k=1, 2,..., n) (Requirement 1B)E ｋ >E ｋ＋１ (k=1, 2,..., n-1)

[0077] Although the mechanism by which cutting a cover film having a support and an adhesive layer formed by laminating two or more polymer layers satisfies the above requirements 1A and 1B is less likely to generate chips, the inventors speculate as follows: The cover film is cut to a predetermined size for use in encapsulation. When cutting the cover film, a blade penetrates the film and separates it, causing "shearing," followed by "fracture," in which the film is pulled and destroyed. In conventional cover films, the large difference in elastic modulus between the two main surfaces of the cover film causes stress concentration near the interface between the support and the adhesive layer when the cover film is cut, resulting in non-uniform fracture and the generation of chips. In contrast, the cover film according to the present embodiment satisfies requirements 1A and 1B, and therefore the elastic modulus between the two main surfaces of the cover film changes stepwise so that the closer the polymer layer is to the support, the closer the elastic modulus of the polymer layer is to the elastic modulus of the support. As a result, it is presumed that when the cover film is cut, stress concentration near the interface between the support and the adhesive layer is suppressed, the shape of the cut surface becomes more uniform, and the generation of cutting chips is suppressed.

[0078] The elastic modulus of the polymer layer in this embodiment is the storage elastic modulus (unit: Pa=N / m ２ ) and can be measured by a known method using a nanoindenter and a Berkovich indenter in an environment of 25°C. More specifically, in an environment of 25°C, the cover film is cut in a direction intersecting the main surface of the cover film, and the storage modulus of each polymer layer is measured at a position corresponding to 50% of the total thickness of the cross section exposed by the cutting using a nanoindenter and a Berkovich indenter, thereby obtaining the elastic modulus of each polymer layer. A specific method for measuring the storage modulus of each polymer layer will be described in the Examples below.

[0079] The elastic modulus of the polymer layer can be adjusted, for example, during the production of the cover film, by adjusting the chemical structure of the polymer contained in the polymer layer, adding additives and / or fillers to the polymer layer-forming solution, and by stretching the solution after application.

[0080] In the present embodiment, it is preferable that the adhesive layer further satisfies the following requirement 1C: (Requirement 1C) Average difference in elastic modulus between polymer layers in contact with each other ΔE ａｖｅ and the maximum difference ΔE between the moduli of elasticity between the polymer layers in contact with each other. ｍａｘ The relationship between these is expressed by the formula (1). Formula (1) 0%≦(|ΔE ｍａｘ -ΔE ａｖｅ |) / ΔE ａｖｅ Requirement 1C will be explained in more detail. The adhesive layer has n (n≧2) polymer layers, and the elastic modulus of the polymer layer arranged at the kth position counting from the support side is E ｋ and the elastic modulus of the support is E Ｓ In this case, the difference in modulus of elasticity between these two polymer layers in contact with each other, ΔE ｋ Is (E ｋ -E ｋ＋１ ) The average difference in modulus of elasticity between the two polymer layers, ΔE ａｖｅ is (ΔE １ , E ２ , ..., ΔE ｎ－１ ) / (n-1)=(E １－ E ｎ ) / (n-1). The difference in elastic modulus between adjacent polymer layers, ΔE ｋ The maximum value of ΔE ｍａｘ The ΔE calculated in this way is ａｖｅ and ΔE ｍａｘ satisfies the above formula (1), the effects of the present invention are more excellent, and therefore it is preferable. ａｖｅ and ΔE ｍａｘ More preferably, the relationship of the following formula (1a) is satisfied: 0%≦(|ΔE ｍａｘ -ΔE ａｖｅ |) / ΔE ａｖｅ ×100≦75%

[0081] When the adhesive layer has n (n≧2) polymer layers, the elastic modulus E of the first polymer layer arranged closest to the support １ The elastic modulus E of the first polymer layer is preferably 1 to 5 GPa, and more preferably 2 to 4 GPa. １ and the elastic modulus E of the supportｓ The difference between ｓ -E １ The lower limit of the elastic modulus is preferably 4 GPa or less, and more preferably 2 GPa or less, in that the effects of the present invention are more excellent. Although the lower limit is not particularly limited, it is preferably 0.1 GPa or more in that the effects of the present invention can be obtained with a small number of layers.

[0082] When the adhesive layer has n (n≧2) polymer layers, the elastic modulus E of the nth polymer layer located at the position farthest from the support is ｎ The elastic modulus E of the first polymer layer is preferably 0.1 to 3 GPa, and more preferably 1 to 3 GPa. １ and the elastic modulus E of the nth polymer layer ｎ The difference between １ -E ｎ ) is preferably 0.5 GPa or more, more preferably 1 GPa or more, in terms of more excellent effects of the present invention. The upper limit is not particularly limited, but is preferably 5 GPa or less.

[0083] The number of polymer layers in the adhesive layer is not particularly limited as long as it is two or more and satisfies the above requirements 1A and 1B, and may be, for example, 2 to 100, 2 to 10, or 2 to 5. In addition, the number of polymer layers in the adhesive layer may be 10 to 1,000, or 100 to 500, depending on the case.

[0084] The thickness of the adhesive layer is not particularly limited and may be, for example, 100 μm or less. In terms of providing better effects of the present invention, the thickness is preferably 40 μm or less, and more preferably 30 μm or less. In terms of providing better adhesion to a substrate (e.g., a glass plate), the thickness is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more.

[0085] (Polymer Layer) In this embodiment, each polymer layer included in the adhesive layer will be described in more detail.

[0086] -Polymer- The polymer contained in the polymer layer (i.e., the polymer contained in the adhesion layer) is not particularly limited, and known polymers can be used. Among these, polymers that dissolve or swell in organic solvents used as the sealing liquid in automatic sealing devices are preferred, and polymers that dissolve in the above organic solvents are more preferred. Examples of organic solvents used as the sealing liquid in automatic sealing devices include a single solvent selected from toluene, xylene, mesitylene (1,3,5-trimethylbenzene), pseudocumene (1,2,4-trimethylbenzene), hemimellitene (1,2,3-trimethylbenzene), durene (1,2,4,5-tetramethylbenzene), ethyl acetate, methyl acetate, acetone, and methyl ethyl ketone, as well as a mixed solvent of two or more of these. When the polymer swells in or dissolves in the above organic solvent, the cover film and the substrate adhere to each other, allowing the analyte to be sealed.

[0087] As the polymer, an acrylic resin is preferred because of its excellent solubility in the above-mentioned organic solvents. In this specification, the term "acrylic resin" refers to a polymer having a repeating unit derived from a (meth)acrylate monomer. The acrylic resin is not particularly limited as long as it has a repeating unit derived from a (meth)acrylate monomer, and may be a homopolymer of one type of (meth)acrylate monomer or a copolymer of two or more types of (meth)acrylate monomers. The acrylic resin may also be a copolymer of one or more types of (meth)acrylate monomers and one or more monomers other than the (meth)acrylate monomer (e.g., an acrylamide monomer, a vinyl monomer, etc.). In the acrylic resin, the content of the repeating unit derived from the (meth)acrylate monomer is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, based on the total repeating units of the acrylic resin. The upper limit of the content of the repeating unit derived from the (meth)acrylate monomer is not particularly limited, and may be 100% by mass based on the total repeating units of the acrylic resin. It is particularly preferable that the acrylic resin has only repeating units derived from a (meth)acrylate monomer. The acrylic resin can be prepared by a known method, for example, by polymerizing one or more (meth)acrylate monomers.

[0088] Examples of the (meth)acrylate monomer include alkyl(meth)acrylate. The alkyl group in the alkyl(meth)acrylate may further have a substituent. Examples of the substituent include an aryl group, and a phenyl group is preferred. The number of carbon atoms in the alkyl(meth)acrylate, which may have a substituent, is preferably 1 to 15, more preferably 1 to 8, even more preferably 1 to 5, and particularly preferably 1 to 3. Specific examples of alkyl(meth)acrylate include methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, t-butyl(meth)acrylate, cyclohexyl(meth)acrylate, lauryl(meth)acrylate, benzyl(meth)acrylate, and acetoacetoxyalkyl(meth)acrylate.

[0089] The polymer may be a polymer containing at least one repeating unit derived from a monomer selected from the group consisting of (meth)acrylate, styrene, and acrylamide, and is preferably a copolymer containing two or more repeating units derived from two or more monomers, each of which is selected from the group consisting of (meth)acrylate, styrene, and acrylamide. The (meth)acrylate may be the alkyl (meth)acrylate already described, including preferred embodiments thereof.

[0090] Specific examples of the above monomers include ethyl acrylate, n-butyl acrylate, methyl acrylate, cyclohexyl acrylate, benzyl acrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, methyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, styrene, lauryl methacrylate, lauryl acrylate, acetoacetoxyalkyl methacrylate, acetoacetoxyalkyl acrylate, dimethylacrylamide, and isopropylacrylamide. Among these, the polymer preferably contains one or more repeating units derived from a monomer selected from the group consisting of ethyl acrylate, n-butyl acrylate, methyl acrylate, cyclohexyl acrylate, benzyl acrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, methyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, acetoacetoxyalkyl methacrylate, styrene, and dimethylacrylamide, more preferably contains one or more repeating units derived from a monomer selected from the group consisting of ethyl acrylate, methyl methacrylate, benzyl acrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, and cyclohexyl methacrylate, and even more preferably contains one or more repeating units derived from a monomer selected from the group consisting of ethyl acrylate and ethyl methacrylate. Furthermore, a copolymer containing two or more repeating units derived from a monomer selected from any of the above groups is particularly preferred.

[0091] Furthermore, as the polymer, an acrylic resin composed of a combination of repeating units derived from an alkyl acrylate and repeating units derived from an alkyl methacrylate is preferred in terms of achieving the effects of the present invention. The content of repeating units derived from alkyl acrylate and repeating units derived from alkyl methacrylate in such an acrylic resin is preferably 20 to 80 mass%, and more preferably 30 to 70 mass%, based on the total repeating units of the acrylic resin. Among these, an acrylic resin in which the total of repeating units derived from alkyl acrylates having 1 to 5 carbon atoms in the alkyl group and alkyl methacrylates having 1 to 5 carbon atoms in the alkyl group is 60 to 100 mass%, and more preferably 75 to 100 mass%, based on the total repeating units of the acrylic resin, is preferred in terms of achieving the effects of the present invention.

[0092] The weight average molecular weight (Mw) of the polymer is preferably from 10,000 to 500,000, more preferably from 50,000 to 140,000, and even more preferably from 60,000 to 120,000.

[0093] The content of the polymer is not particularly limited, but is preferably 85% by mass or more, more preferably 90% by mass or more, based on the total mass of the polymer layer. The upper limit may be 100% by mass or less. The polymer may be used alone or in combination with two or more types. When two or more types of polymers are used, they are preferably used in a ratio that does not cause turbidity in the dried film obtained by mixing the two or more types of polymers.

[0094] (Additives) The polymer layer may contain additives different from the polymers described above. Examples of additives contained in the polymer layer include carboxylic acid esters, phosphate esters, glycol compounds, deep eutectic solvents, and sulfonic acid esters.

[0095] Carboxylic acid esters are ester compounds produced by the reaction of a carboxyl group with a hydroxyl group. Examples of carboxylic acid esters include phthalic acid esters, trimellitic acid esters, pyromellitic acid esters, citrate esters, dipentaerythritol esters, carboxylic acid esters having an epoxy group, polyether esters, pentaerythritol esters, adipic acid esters, benzoic acid esters, adipate polyesters, and sebacate esters such as dioctyl sebacate. Examples of phosphate esters include t-butylphenyl diphenyl phosphate, tricresyl phosphate, and isopropylphenyl diphenyl phosphate. Examples of glycol compounds include polyethylene glycol, triethylene glycol bis(2-ethylhexanoate), and diethylene glycol dibenzoate.

[0096] Deep eutectic solvents (DES) are solvents containing a hydrogen bond acceptor compound and a hydrogen bond donor compound. By mixing the hydrogen bond acceptor compound and the hydrogen bond donor compound, a eutectic melting point depression occurs, resulting in a significant drop in melting point. Examples of hydrogen bond acceptor compounds include quaternary ammonium compounds, phosphorus compounds, metal salts, amino acids, and polycarboxylic acids. Examples of hydrogen bond donor compounds include alcohol compounds, sugars, carboxylic acids, and amine compounds. Examples of deep eutectic solvents include those described in U.S. Patent Application Publication No. 2018 / 0194913 and Japanese Patent Application Laid-Open No. 2020-105336, paragraphs

[0025] to

[0048] .

[0097] Examples of additives contained in the polymer layer include the additives described in paragraphs

[0036] to

[0080] of JP-A No. 2015-227955. The polymer layer may also contain a silane coupling agent, which will be described later.

[0098] The additives may be used alone or in combination of two or more. When the polymer layer contains an additive, the content of the additive is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 3% by mass or more, based on the total mass of the polymer layer. The upper limit of the content of the additive is not particularly limited, but from the viewpoint of the adhesiveness of the polymer layer, it is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, based on the total mass of the polymer.

[0099] (Physical Properties of Polymer Layer) The thickness of each polymer layer included in the adhesion layer may be the same or different. The thickness of each polymer layer may be, for example, 0.1 to 30 μm, or 1 to 20 μm. The thickness of each polymer layer may be appropriately changed depending on the desired thickness of the adhesion layer and the number of polymer layers to be laminated.

[0100] The glass transition temperature of the polymer layer is, for example, 100°C or lower, preferably 80°C or lower, more preferably 70°C or lower, and even more preferably 60°C or lower. The glass transition temperature of the polymer layer is, for example, 20°C or higher, preferably 45°C or higher. The glass transition temperature of the polymer layer is obtained by peeling the polymer layer from the cover film and heating the obtained polymer layer using a differential scanning calorimeter (DSC) from -50°C to 100°C at a rate of 10°C / min. The glass transition temperature of the polymer layer can be adjusted, for example, by the type and content of repeating units contained in the polymer.

[0101] From an optical viewpoint when observed under a microscope, the refractive index of the polymer layer is preferably 1.45 to 1.56, which is close to that of glass (refractive index 1.52 to 1.56), more preferably 1.46 to 1.56, and even more preferably 1.47 to 1.56. In terms of ease of forming a polymer layer having the above refractive index, it is preferable that the polymer constituting the polymer layer contains repeating units derived from one or more monomers selected from the group consisting of alkyl acrylate, alkyl methacrylate, and styrene. From the above viewpoint, the number of carbon atoms in the alkyl group in the alkyl acrylate or alkyl methacrylate is preferably 1 to 5, more preferably 1 to 3. Furthermore, from an optical viewpoint when observed under a microscope, it is preferable that the polymer layer is optically isotropic. For example, if the in-plane retardation of the polymer layer in the visible light region is 5 nm or less, the polymer layer can be said to be optically isotropic.

[0102] <Other Layers> The cover film according to this embodiment may have layers other than the support and the adhesive layer. The cover film preferably has a silane coupling agent layer on the surface of the adhesive layer opposite the support side, in order to suppress blocking when the cover film is stored in a rolled or stacked state and to improve storage stability over time. The silane coupling agent layer may contain at least one selected from the group consisting of a silane coupling agent, its hydrolysate, and its hydrolysis condensate (hereinafter, these are also collectively referred to as "silane coupling agents").

[0103] The type of silane coupling agent is not particularly limited, but a silane coupling agent having two or more different reactive groups in the molecule, at least one of which is a reactive group that chemically bonds with an inorganic material, and at least one of which is a reactive group that chemically bonds with an organic material, is preferred. Preferred silane coupling agents include silane coupling agents represented by the following general formula: Y-R-Si(CH ３ ) ３－ｎ X ｎ(In the formula, Y represents a vinyl group, a methacryl group, an epoxy group, an amino group, a mercapto group, or a chloro group; R represents a single bond, a methylene group, a polymethylene group, or a polymethylene group in which at least one methylene group is replaced by O, S, or NH; X represents a chloro group, a methoxy group, an ethoxy group, a methoxyethoxy group, an acetoxy group, a methylvinyloxy group, or an amino group; and n is 2 or 3.)

[0104] Specific examples of silane coupling agents include vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-(methacryloxypropyl)trimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-chloropropyltrimethoxysilane.

[0105] The hydrolyzate of a silane coupling agent refers to a compound obtained by hydrolysis of the hydrolyzable groups in the silane coupling agent. The hydrolyzate may be one in which all of the hydrolyzable groups are hydrolyzed (complete hydrolyzate) or one in which only a portion of the hydrolyzable groups are hydrolyzed (partial hydrolyzate). In other words, the hydrolyzate may be a complete hydrolyzate, a partial hydrolyzate, or a mixture thereof. The hydrolyzed condensate of a silane coupling agent refers to a compound obtained by hydrolyzing the hydrolyzable groups in the silane coupling agent and condensing the resulting hydrolyzate. The hydrolyzed condensate may be one in which all of the hydrolyzable groups are hydrolyzed and the resulting hydrolyzate is condensed (complete hydrolyzed condensate), or one in which only a portion of the hydrolyzable groups are hydrolyzed and the resulting hydrolyzate is condensed (partial hydrolyzed condensate). In other words, the hydrolyzed condensate may be a complete hydrolyzed condensate, a partial hydrolyzed condensate, or a mixture thereof.

[0106] The silane coupling agents may be used alone or in combination of two or more. The content of the silane coupling agents in the cover film is 0.1 mg / m per unit area. ２ More than 5 mg / m is preferable, and 5 to 25 mg / m ２ is more preferred.

[0107] Other layers include a backing layer. The backing layer may be provided on the back surface of the support (the surface opposite to the surface on which the polymer layer is provided) for the purposes of preventing scratches on the surface of the cover film, more reliably preventing blocking when stored in a high-temperature environment, or improving the curling balance of the cover film. Examples of materials constituting the backing layer include synthetic polymers with high glass transition temperatures, such as polystyrene and polymethyl methacrylate, and gelatin.

[0108] <Physical properties of cover film> The total thickness of the adhesive layer and the support in the cover film is preferably 250 μm or less, more preferably 200 μm or less, and even more preferably 150 μm or less, from the viewpoints of operability and microscopic examination during microscopic observation. The lower limit is preferably 50 μm or more, from the viewpoints of handling properties such as resistance to folding and encapsulation properties.

[0109] <Method for manufacturing cover film> As a method for manufacturing the cover film according to the present embodiment, for example, a method of repeating a polymer layer formation step of forming a new polymer layer on the surface of a support or on the surface of a previously formed polymer layer according to the number of target polymer layers can be mentioned. In the polymer layer formation step, it is preferable to perform a drying treatment of drying the film formed on the surface of the support or on the surface of a previously formed polymer layer.

[0110] The method for providing the polymer layer on the support in the polymer layer formation process is not particularly limited, and examples include coating with a coater or spray, casting, and transfer. Among these, it is preferable to form the polymer layer by applying a coating liquid obtained by dissolving a polymer in a solvent onto the support and then drying the coating film in a drying process. The type of solvent used in the coating liquid is preferably one that can dissolve the polymer and has wettability that prevents repellency on the substrate. Examples of such solvents include toluene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, and xylene. Using a material that can dissolve the surface of the support or a material that can elute low-molecular-weight components such as plasticizers contained in the support as the solvent used in the coating liquid allows the polymer to penetrate the surface layer of the support, increasing the adhesion between the polymer layer and the support, preventing peeling of the polymer layer, and further suppressing the generation of chips during cutting. From the above perspective, the coating liquid used to form the polymer layer preferably contains a solvent selected from the group consisting of ethyl acetate and butyl acetate, and more preferably contains ethyl acetate. The content of the solvent selected from the group consisting of ethyl acetate and butyl acetate in the coating solution is preferably 40% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the total mass of the solvent contained in the coating solution. The upper limit is not particularly limited and may be 100% by mass or less, but is preferably 90% by mass or less in terms of being able to further suppress deformation of the substrate.

[0111] Drying treatments performed in the polymer layer formation step include air drying, in which gas is blown onto the coating film, heat drying, in which the coating film is heated using a heating means such as an oven, and a combination of these, with heat drying or a combination of heat drying and air drying being preferred.

[0112] When heat drying is performed as the drying treatment, the heating temperature is preferably (Tg-30°C) to (Tg+150°C), and more preferably (Tg-10°C) to (Tg+80°C).When heat drying is performed as the drying treatment, the heating time is preferably 0.5 to 60 minutes, and more preferably 1 to 20 minutes.

[0113] The method for forming silane coupling agent layer can be, for example, the method that the coating liquid that comprises silane coupling agent in solvent is coated on the surface of the coating film that comprises polymer formed on the surface of support, and the coating film is dried; and the method that the coating liquid that comprises polymer and the coating liquid that comprises silane coupling agent in solvent are simultaneously coated on support (multi-layer coating), and the coating film is dried.The solvent that comprises in above-mentioned coating liquid is not particularly limited as long as it can dissolve silane coupling agent, and for example, can be the solvent that can dissolve above-mentioned polymer.

[0114] [Second embodiment] A second embodiment of the cover film of the present invention is characterized in that the adhesive layer contains a polymer, and the elastic modulus measured at a predetermined position in the thickness direction of the adhesive layer is smaller than the elastic modulus of the support, and gradually decreases from the support side to the opposite side of the support side. Hereinafter, the cover film according to this embodiment will be described in detail.

[0115] <Support> The support of the cover film according to this embodiment is the same as that described for the support of the cover film according to the first embodiment, including preferred embodiments.

[0116] <Adhesion Layer> The adhesion layer of the cover film according to this embodiment contains a polymer and satisfies the following requirements 2A and 2B. (Requirement 2A) When a cross section of the adhesion layer is exposed and the elastic modulus is measured in the thickness direction of the adhesion layer from one surface to the other surface at positions 20%, 40%, 60%, and 80% of the total thickness of the adhesion layer from one surface, the elastic modulus at each position is smaller than the elastic modulus of the support. (Requirement 2B) The elastic modulus at each of the above positions gradually decreases from the support side toward the opposite side from the support side. Here, the elastic moduli of the adhesion layer at positions 20%, 40%, 60%, and 80% of the total thickness of the adhesion layer from the surface opposite the support side of the adhesion layer are respectively defined as E ２０ , E ４０ , E ６０ and E ８０ and the elastic modulus of the support is E ＳThen, requirements 2A and 2B are collectively expressed by the following formula (2): ２０ <E ４０ <E ６０ <E ８０ <E ｓ

[0117] Although the mechanism by which chips are less likely to be generated when a cover film having a support and an adhesive layer containing a polymer satisfies the above requirements 2A and 2B is not entirely clear, the inventors speculate as follows: As already explained in the first embodiment, in conventional cover films, the difference in elastic modulus between the two main surfaces of the cover film is large, and it is speculated that stress concentration occurs near the interface between the support and the adhesive layer when the cover film is cut, resulting in non-uniform fracture and chips being generated. In contrast, in the cover film according to the present embodiment, by satisfying requirements 2A and 2B, the elastic modulus of the adhesive layer changes so that the closer the thickness direction position in the adhesive layer is to the support, the closer the elastic modulus at that position is to the elastic modulus of the support. As a result, stress concentration near the interface between the support and the adhesive layer is suppressed when the cover film is cut, which is speculated to result in a more uniform shape of the cut surface and suppress the generation of chips.

[0118] The elastic modulus at each position of the adhesive layer in this embodiment is a storage elastic modulus (unit: Pa) measured by the following method. The elastic modulus is measured in an environment of 25°C by cutting the cover film in a direction intersecting the main surface of the cover film and measuring the elastic modulus at positions corresponding to 20%, 40%, 60%, and 80% of the total thickness of the adhesive layer on the cross section exposed by cutting using a nanoindenter and a Berkovich indenter. A specific method for measuring the storage elastic modulus at each position of the adhesive layer will be described in the Examples below.

[0119] The elastic modulus at each position of the adhesive layer can be adjusted, for example, in the manufacturing method of the cover film of this embodiment described below, by adjusting the chemical structure of the polymer contained in the adhesive layer, adding additives and / or fillers to the polymer solution used to form the adhesive layer, and performing a stretching process after application.

[0120] In this embodiment, the profile of the elastic modulus along the thickness direction of the adhesive layer is not particularly limited as long as it satisfies requirements 2A and 2B. In this embodiment, it is preferable that the elastic modulus of the adhesive layer changes continuously along the thickness direction. The term "the elastic modulus of the adhesive layer changes continuously along the thickness direction" means that a section of 10% of the total thickness of the adhesive layer is selected in the thickness direction of the adhesive layer, and the elastic modulus at the end position of the end closest to the support of both ends of the selected section is expressed as E ｘ , the elastic modulus at the end position opposite to the support side is E ｙ In this case, in the above-mentioned section arbitrarily selected in the adhesive layer, ｘ >E ｙ " means that the relationship

[0121] In the present embodiment, the adhesion layer may satisfy the above requirements 2A and 2B, and may have an elastic modulus profile in which the elastic modulus in the section from the surface of the adhesion layer opposite the support side to 20% of the total thickness of the adhesion layer (excluding the surface and the position at 20% of the total thickness) is greater than the elastic modulus at the position at 20% of the total thickness of the adhesion layer. In this case, it is preferable that the elastic modulus in the section from 20% to 100% of the total thickness of the adhesion layer (excluding the surface on the support side) changes continuously along the thickness direction, i.e., continuously decreases from the support side to the opposite side of the support side.

[0122] In this embodiment, as long as the above requirements 2A and 2B are satisfied, the elastic modulus of the adhesive layer at each position is not limited. Among the elastic moduli of the adhesive layer at each position, the elastic modulus E at the position closest to the support is ８０ is preferably 1 to 5 GPa, more preferably 2 to 4 GPa. ８０ and the elastic modulus E of the support ｓ The difference between ｓ -E ８０ ) is preferably 4 GPa or less, more preferably 2 GPa or less, in terms of achieving better effects of the present invention. The lower limit is not particularly limited, but is preferably 0.1 GPa or more.

[0123] Among the elastic moduli of the adhesive layer at each of the above positions, the elastic modulus E at the position farthest from the support is ２０ is preferably 0.1 to 3 GPa, more preferably 1 to 2 GPa. ８０ and the elastic modulus E ２０ The difference between ８０ -E ２０ ) is preferably 0.5 GPa or more, more preferably 1 GPa or more, in terms of more excellent effects of the present invention. The upper limit is not particularly limited, but is preferably 5 GPa or less.

[0124] The thickness of the adhesive layer of the cover film according to this embodiment, including the preferred range, may be the same as the thickness of the adhesive layer of the cover film according to Embodiment 1. Furthermore, the physical properties of the adhesive layer, such as the glass transition temperature, refractive index, and optical isotropy, may be the same as the physical properties of the polymer layer of the cover film according to Embodiment 1, including the preferred range.

[0125] The polymer contained in the adhesion layer is not particularly limited, and known polymers can be used. The adhesion layer may also contain additives of a different type from the polymer. The type, properties, and content of the polymer contained in the adhesion layer, as well as the type and content of the additives, may be the same as those of the polymer and additive contained in the polymer layer in the first embodiment, including preferred embodiments.

[0126] The cover film according to this embodiment may have other layers in addition to the support and the adhesive layer. Examples of the other layers include a silane coupling agent layer and a backing layer. When the cover film according to this embodiment has the silane coupling agent layer and / or the backing layer, the structure and formation method of each layer may be the same as the structure and formation method of each layer of the cover film according to the first embodiment, including preferred embodiments.

[0127] The preferred range of the total thickness of the adhesive layer and the support in the cover film according to this embodiment is the same as that described for the cover film according to the first embodiment.

[0128] <Cover film manufacturing method> As the cover film manufacturing method of this embodiment, for example, the method of preparing two or more kinds of polymer liquids that contain the polymer contained in adhesion layer and have different compositions, and then laminating the film that is made up of each polymer liquid on the surface of support, and then drying the formed laminated film.In the above-mentioned method, by adjusting the composition of each polymer liquid used (type and content of polymer, type and content of additive, and solid content concentration etc.), the amount of each polymer liquid, and the number of polymer liquids used etc., can form the adhesion layer that has the elastic modulus characteristics that is aimed.

[0129] In forming the above-mentioned adhesion layer, the method for providing a film of the polymer liquid on the surface of the support is not particularly limited, and examples thereof include coating by a coater or spray, casting, and transfer. As a method for forming the adhesion layer, a method is preferred in which a coating liquid is prepared by dissolving a polymer in a solvent, and a coating film is repeatedly formed by applying each coating liquid to form a laminate of coating films, and then the obtained laminate of coating films is dried to form the adhesion layer. In the above-mentioned formation method, it is more preferable to perform pre-drying to remove a portion of the solvent contained in the coating film every time a coating liquid is applied to form a coating film. By applying a new coating liquid to the surface of the pre-dried coating film to form a coating film, it is possible to prevent the coating films in contact with each other from completely mixing.

[0130] The composition of the coating liquid containing the polymer used to form the adhesion layer, including preferred embodiments, may be the same as the composition of the coating liquid used to form the polymer layer described in the first embodiment. The drying treatment performed in the adhesion layer forming step, including preferred embodiments, may be the same as the drying treatment performed in the polymer layer forming step described in the first embodiment. When the pre-drying is performed in the adhesion layer forming step, the pre-drying means and heating temperature may be the same as those in the drying treatment. Furthermore, when the pre-drying is performed, the drying time is preferably 0.05 to 10 minutes, more preferably 0.1 to 5 minutes.

[0131] <Uses> The cover film of the present invention, including the first and second embodiments, can be suitably used as a cover film used to cover a specimen on a substrate. In particular, it is more preferable to use it for preparing a specimen for microscopic observation, and even more preferable to use it in a microscope having an automatic sealing device. The uses of the cover film of the present invention are not limited to the above uses, and it can be used for, for example, sealing a thin film on a substrate and protecting an underlying layer by lamination. Furthermore, the substrate to which the cover film is attached may be glass or a film-shaped material (such as a resin).

[0132] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not deviate from the gist of the invention. Unless otherwise specified, "parts" and "%" are based on mass.

[0133] <Preparation of Polymer Solution> -Polymer Solution A1- To a mixture of 38 parts by mass of toluene and 25 parts by mass of ethyl acetate, at 80 ° C. under a nitrogen atmosphere, a mixed solution of 90 parts by mass of ethyl acrylate (EA), 210 parts by mass of methyl methacrylate (MMA), 98 parts by mass of toluene, 66 parts by mass of ethyl acetate, and 1.8 parts by mass of azoisobutyronitrile was added over 2 hours. Thereafter, the resulting mixture was reacted for 2 hours while maintaining the temperature at 80 ° C. Thereafter, 1.0 part by mass of azoisobutyronitrile was added to the above mixture, and the mixture was polymerized at 90 ° C. so that the weight average molecular weight of the resulting polymer was 80,000, to obtain a solution containing polymer A1 (EA / MMA = 3 / 7 (mass ratio)). 500 parts by mass of acetone was added to the obtained solution and mixed to obtain polymer solution A1 containing polymer A1.

[0134] —Polymer Solution A2— A polymer solution A2 containing polymer A2 (EA / MMA=15 / 85 (mass ratio), weight average molecular weight 100,000) was obtained by carrying out the same procedure as the method for producing polymer solution A1, except that 45 parts by mass of ethyl acrylate (EA) and 255 parts by mass of methyl methacrylate (MMA) were used instead of the 90 parts by mass of ethyl acrylate (EA) and 210 parts by mass of methyl methacrylate (MMA) used in the synthesis of polymer A1.

[0135] —Polymer Solution A3— A polymer solution A3 containing polymer A3 (EA / MMA / EMA=20 / 50 / 30 (mass ratio), weight average molecular weight 100,000) was obtained by carrying out the same procedure as the production method for polymer A1, except that 60 parts by mass of ethyl acrylate (EA), 150 parts by mass of methyl methacrylate (MMA), and 90 parts by mass of ethyl methacrylate (EMA) were used instead of the 90 parts by mass of ethyl acrylate (EA) and 210 parts by mass of methyl methacrylate (MMA) used in the synthesis of polymer A1.

[0136] —Polymer Solution A4— A polymer solution A4 containing polymer A4 (PMMA, weight-average molecular weight 100,000) was obtained by carrying out the same procedure as the preparation method for polymer solution A1, except that 300 parts by mass of methyl methacrylate (MMA) was used instead of 90 parts by mass of ethyl acrylate (EA) and 210 parts by mass of methyl methacrylate (MMA) used in the synthesis of polymer A1.

[0137] —Polymer Solution A5— A polymer solution A5 containing polymer A5 (EA / MMA / CHMA=25 / 50 / 25 (mass ratio), weight average molecular weight 70,000) was obtained by performing the same procedure as the method for producing polymer solution A1, except that 75 parts by mass of ethyl acrylate (EA), 150 parts by mass of methyl methacrylate (MMA), and 75 parts by mass of cyclohexyl methacrylate (CHMA) were used instead of the 90 parts by mass of ethyl acrylate (EA) and 210 parts by mass of methyl methacrylate (MMA) used in the synthesis of polymer solution A1.

[0138] <Preparation of Silane Coupling Agent Coating Liquid> A silane coupling agent coating liquid was obtained by adding 109.89 parts by mass of ethyl acetate to 0.11 parts by mass of a silane coupling agent KBM403 (γ-glycidoxypropyltrimethoxysilane) (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0139] <Preparation of Support> -Support A- (Preparation of Core Layer Cellulose Acylate Dope) The following components were placed in a mixing tank, and the mixture was stirred to dissolve the components, thereby preparing a cellulose ester solution A1 to be used as the core layer cellulose acylate dope. -100 parts by mass of cellulose acetate having an acetyl substitution degree of 2.88; -15 parts by mass of a mixture containing an aliphatic carboxylic acid ester oligomer (oligomer A1) described below and a compound represented by formula (A-3) below, the mass ratio of the content of oligomer A1 to the content of the compound represented by formula (A-3) being 4:1; -430 parts by mass of methylene chloride; -64 parts by mass of methanol. Oligomer A1 is an aliphatic carboxylic acid ester oligomer which is a condensate of 1,2-cyclohexyldicarboxylic acid and ethylene glycol, and has a terminal structure in which the hydrogen atoms of the hydroxyl groups at both terminals are substituted (capped) with cyclohexanoyl groups. The number average molecular weight of oligomer A1 was 850. The molecular weight of the compound represented by the following formula (A-3) was 384.

[0140]

[0141] (Preparation of Outer Layer Cellulose Acylate Dope) 10 parts by weight of a matting agent solution having the following composition was added to 90 parts by weight of the above cellulose ester solution A1 (core layer cellulose acylate dope) to prepare cellulose ester solution A2 to be used as the outer layer cellulose acylate dope.

[0142] (Composition of Matting Agent Solution) Silica particles having an average particle size of 20 nm (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.): 2 parts by mass Methylene chloride: 76 parts by mass Methanol: 11 parts by mass Cellulose ester solution A1 (core layer cellulose acylate dope): 1 part by mass

[0143] The core layer cellulose acylate dope and the outer layer cellulose acylate dope were filtered through a filter paper with an average pore size of 34 μm and a sintered metal filter with an average pore size of 10 μm, respectively. The filtered core layer cellulose acylate dope and the filtered outer layer cellulose acylate dope were simultaneously cast onto the surface of a stainless steel band from the casting nozzle of a band casting machine, forming a laminated substrate in which the core layer was sandwiched between two outer layers. The laminated substrate was then peeled off from the band, and both widthwise ends of the laminated substrate were fixed with tenter clips and dried while stretched in the width direction at a stretch ratio of 1.1. The laminated substrate was then transported between the rolls of a hot air drying device and further dried to produce a support A with a thickness of 120 μm.

[0144] -Support B- Support B was prepared in the same manner as Support A, except for the following changes. Cellulose ester solution A2 was prepared in the same manner as the preparation of cellulose ester solution A1, except that 12 parts by mass of triphenyl phosphate was used instead of the mixture of oligomer A1 and compound A-3. The obtained cellulose solution A2 was used as a core layer cellulose acylate dope and also used to prepare an outer layer cellulose acylate dope. Note that triphenyl phosphate corresponds to a specific ester compound because it generates phosphoric acid with a pKa of 2.0 upon hydrolysis. In addition, the molecular weight of triphenyl phosphate is 326. The content of the specific ester compound in Support B was more than 1% by mass relative to the total mass of Support B.

[0145] <Preparation of Cover Film> Cover films for each of Examples and Comparative Example 1 were prepared by the following method.

[0146] Example 1 Polymer solution A4 was applied by extrusion coating onto the surface of support A prepared by the above method. The amount of polymer solution A4 applied was adjusted so that the thickness of polymer layer C after drying would be the value shown in the table below. The coating film of polymer solution A4 was dried at 100°C for 5 minutes using a hot air dryer. Polymer solution A5 and the above silane coupling agent coating liquid were further applied onto the surface of the formed polymer layer C by extrusion multilayer coating. The amount of polymer solution A5 applied was adjusted so that the thickness of polymer layer A after drying would be the value shown in the table below. The amount of silane coupling agent coating liquid applied was 13.5 mg / m2, where the amount of silane coupling agent relative to the surface area of ​​the substrate was 13.5 mg / m2. ２ The coating film of polymer solution A5 and the coating film of the silane coupling agent coating solution were dried at 100°C for 5 minutes using a hot air dryer, to produce a cover film of Example 1 having, in this order, the support A, an adhesion layer composed of polymer layer A and polymer layer C, and a silane coupling agent layer.

[0147] Examples 2 and 4 to 6 Cover films of Examples 2 and 4 to 6 were each produced according to the same procedure as in Example 1, except that the type of polymer solution used to form polymer layer A was selected and / or the thickness of each polymer layer was adjusted to the value shown in the table below.

[0148] Example 3 Polymer solution A4 was applied to the surface of support A prepared by the above method using an extrusion coating method. The amount of polymer solution A4 applied was adjusted so that the thickness of polymer layer C after drying would be the value listed in the table below. The coating film of polymer solution A4 was dried using a hot air dryer at 100°C for 5 minutes. Polymer solution A2 was applied to the surface of the formed polymer layer C using an extrusion coating method. The amount of polymer solution A2 applied was adjusted so that the thickness of polymer layer B after drying would be the value listed in the table below. The coating film of polymer solution A2 was dried using a hot air dryer at 100°C for 5 minutes. Polymer solution A1 and the above silane coupling agent coating liquid were further applied to the surface of the formed polymer layer B using an extrusion multilayer coating method. The amount of polymer solution A1 applied was adjusted so that the thickness of polymer layer A after drying would be the value listed in the table below. The amount of the silane coupling agent coating solution applied was 13.5 mg / m2 relative to the surface area of ​​the substrate. ２ The coating film of polymer solution A1 and the coating film of the silane coupling agent coating solution were dried at 100°C for 5 minutes using a hot air dryer, to produce a cover film of Example 3 having, in this order, the support A, the polymer layer A, the adhesion layer composed of the polymer layer B and the polymer layer C, and the silane coupling agent layer.

[0149] Example 7 A cover film of Example 7 was produced in the same manner as in Example 4, except that support B was used instead of support A.

[0150] Example 8 Polymer solution A4 was applied to the surface of support A by extrusion coating. The amount of polymer solution A4 applied was adjusted so that, if only the coating film of polymer solution A4 was dried, the thickness of the polymer layer formed would be 8 μm. Next, the coating film of polymer solution A4 was dried at 100°C for 0.5 minutes, and then polymer solution A3 and the above-mentioned silane coupling agent coating liquid were further applied to the surface of the formed coating film of polymer solution A4 by extrusion multilayer coating. The amount of polymer solution A3 applied was adjusted so that, if only the coating film of polymer solution A3 was dried, the thickness of the formed polymer layer would be 12 μm. The amount of silane coupling agent coating liquid applied was 13.5 mg / m2, where the amount of silane coupling agent relative to the surface area of ​​the substrate was 13.5 mg / m2. ２ The film consisting of the coating film of polymer solution A4, the coating film of polymer solution A3, and the coating film of the silane coupling agent coating solution was dried at 100°C for 5 minutes using a hot air dryer, to produce a cover film of Example 8 having, in this order, the support A, an adhesive layer containing a polymer, and a silane coupling agent layer.

[0151] Comparative Example 1 Polymer solution A5 and the above-mentioned silane coupling agent coating solution were applied to the surface of support A prepared by the above-mentioned method by extrusion multilayer coating. The amount of polymer solution A5 applied was adjusted so that the thickness of polymer layer A after drying would be the value shown in the table below. The amount of silane coupling agent coating solution applied was adjusted so that the amount of silane coupling agent relative to the surface area of ​​the substrate was 13.5 mg / m ２ After the application of the polymer solution A5 and the silane coupling agent coating solution, the film was dried at 100°C for 5 minutes using a hot air dryer, thereby producing a cover film of Comparative Example 1 having, in this order, the support A, an adhesion layer made of the polymer layer A, and a silane coupling agent layer.

[0152] <Measurement> [Elastic Modulus] For the cover films of Examples 1 to 7 and Comparative Example 1, the elastic modulus of each polymer layer included in the adhesion layer was measured using the following method. First, the cover film was cut obliquely using a microtome to prepare a sample with an exposed obliquely cut surface. Each polymer layer was confirmed by observing the obliquely cut surface, and the storage modulus was measured at each position corresponding to 50% of the total thickness of each polymer layer using a nanoindenter (trade name "Triboindenter TI-950", manufactured by Hysitron) and a Berkovich indenter. The measurement conditions were a load of 500 μN, a loading time of 10 seconds, a holding time of 5 seconds, and an unloading time of 10 seconds. Ten points were measured at each position, and the arithmetic mean value of the 10 points was taken as the elastic modulus (unit: GPa) at each position.

[0153] In addition, on the obliquely cut surface of the sample, the storage modulus at a position corresponding to within 20% of the total thickness from the surface of the adhesive layer side of the support (0% position of the total thickness) was measured according to the above method, and the elastic modulus of the support (unit: GPa) was obtained. The measured elastic moduli of each polymer layer and the support are shown in the table below.

[0154] The elastic modulus of the adhesion layer of the cover films of Example 8 and Comparative Example 1 was measured using the following method. First, the cover film was cut obliquely using a microtome to prepare a sample with an exposed obliquely cut surface. Next, in an environment of 25°C, the storage modulus was measured on the obliquely cut surface from one surface of the adhesion layer toward the other surface at positions corresponding to 20%, 40%, 60%, and 80% of the total thickness of the adhesion layer using a nanoindenter (trade name "Triboindenter TI-950", manufactured by Hysitron) and a Berkovich indenter. The measurement conditions were a load of 500 μN, a loading time of 10 seconds, a holding time of 5 seconds, and an unloading time of 10 seconds. Ten points were measured at each position, and the arithmetic average of the 10 points was taken as the elastic modulus (unit: GPa) at each position. The table below shows the distribution of the measured elastic modulus in the thickness direction.

[0155] <Evaluation> [Adhesion] The cover film of each example was wrapped around a cylinder having a diameter of 8 mm and a cylinder having a diameter of 5 mm, respectively, with the polymer layer facing outward in an environment of 25°C and a relative humidity of 10%, and the presence or absence of peeling between the adhesion layer and the support was visually confirmed. Note that, in practice, an A rating or a B rating is preferable, with an A rating being more preferable. (Adhesion Evaluation Criteria) A: Peeling was observed on both the 8 mm diameter cylinder and the 5 mm diameter cylinder. B: No peeling was observed on the 8 mm diameter cylinder, but peeling was observed on the 5 mm diameter cylinder. C: Peeling was observed on both the 8 mm diameter cylinder and the 5 mm diameter cylinder.

[0156] [Cuttability] In an environment of 10 ° C and a relative humidity of 30%, the 25 mm wide long cover film produced in each Example and Comparative Example was unwound, the film was placed on a workbench, and the film was cut into chips every 50 mm using a cutter knife, with the cutting edge inserted from the support side of the cover film. After cutting, 3,000 sheets of chip-like film were produced, and the degree of chips adhering to the blade of the cutter knife and the cut surface of the cut film were visually observed. From the observation results, the cuttability of the cover film was evaluated according to the following evaluation criteria. In practical use, A rating, B rating, or C rating is preferred, A rating or B rating is more preferred, and A rating is even more preferred.

[0157] (Cuttability evaluation criteria) A: No chips are found to adhere to the blade, and no fuzz or lifting of the adhesive layer is found on the cut surface. B: No chips are found to adhere to the blade, but either fuzz or lifting of the adhesive layer is found on the cut surface. C: Chips are found to adhere to the blade, and either fuzz or lifting of the adhesive layer is found on the cut surface. D: A lot of chips are found to adhere to the blade, and a lot of fuzz and lifting of the adhesive layer is found on the cut surface.

[0158] <Results> The following table shows the configurations and properties of the cover films of the examples and comparative examples, as well as the evaluation results.

[0159]

[0160]

[0161] The results shown in the table confirm that the cover film of the present invention suppresses the generation of chips during cutting and is therefore excellent in the effects of the present invention. Furthermore, it was confirmed that the cover film of Comparative Example 1, whose adhesion layer does not satisfy the requirements of each embodiment of the present invention, was inferior in the above effects.

Claims

1. A cover film used to cover a test object on a substrate, comprising a support and an adhesive layer, wherein the adhesive layer is a layer formed by laminating two or more polymer layers having different compositions, the moduli of elasticity of each of the two or more polymer layers are smaller than the moduli of elasticity of the support, and the moduli of elasticity of each of the two or more polymer layers gradually decrease from the support side toward the opposite side from the support side.

2. The average difference in elastic modulus ΔE between the polymer layers in contact with each other in the cover film ａｖｅ and the maximum difference ΔE of the elastic modulus between the polymer layers in contact with each other. ｍａｘ and satisfy the relationship of formula (1). ｍａｘ -ΔE ａｖｅ |) / ΔE ａｖｅ ×100≦150% 3. A cover film used to cover a specimen on a substrate, comprising a support and an adhesive layer containing a polymer, wherein when a cross section of the adhesive layer is exposed and the elastic modulus is measured in the thickness direction of the adhesive layer from one surface to the other surface at positions 20%, 40%, 60% and 80% of the total thickness of the adhesive layer from the one surface, the elastic modulus at each position is smaller than the elastic modulus of the support and gradually decreases from the support side to the opposite side of the support side.

4. The cover film according to claim 2, wherein the modulus of elasticity of the adhesive layer changes continuously along the thickness direction.

5. A cover film according to any one of claims 1 to 4, wherein the main component of the adhesion layer is a copolymer containing two or more repeating units derived from a monomer selected from the group consisting of (meth)acrylate, styrene, and acrylamide.

6. A cover film according to any one of claims 1 to 4, wherein the main component of the adhesion layer is a copolymer containing two or more repeating units derived from monomers selected from the group consisting of ethyl acrylate, n-butyl acrylate, methyl acrylate, cyclohexyl acrylate, benzyl acrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, methyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, acetoacetoxyalkyl methacrylate, styrene, and dimethylacrylamide.

7. The cover film according to claim 6, wherein the weight average molecular weight of the copolymer is 80,000 or more.

8. The cover film according to any one of claims 1 to 4, wherein the adhesive layer has a thickness of 5 to 30 μm.

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