cover film

Abstract

The present application provides a cover film which is not easy to generate cutting chips when cutting, and further, is not easy to generate voids when using an encapsulation liquid to adhere to a substrate, and has excellent adhesion to the substrate. The cover film of the present application is a cover film for covering a test object on a substrate, and has a support and a polymer layer containing a polymer, the polymer layer having a fracture toughness value of 0.2 MPa·m 0.5 The support has an in-plane retardation of 1000 nm or less at a wavelength of 590 nm, and satisfies necessary conditions relating to a dissolution rate of the polymer layer into xylene, and a viscosity of a xylene solution of the polymer layer.

Description

Technical Field

[0001] This invention relates to a covering film. Background Technology

[0002] A known method involves automatically overlapping a cover film pre-formed with a polymer layer on a support onto a substrate (slide, etc.) containing a few drops of a solvent (referred to as a "sealing solution," such as xylene) that swells and / or dissolves the polymer layer, thereby bonding the cover film to the substrate (hereinafter also referred to as "sealing"). This method enables the preparation of microscopic specimens in which the specimen is fixed between the substrate and the cover film.

[0003] For example, Patent Document 1 discloses a microscope cover film, characterized in that the microscope cover film, which is made by providing a polymer adhesive layer with a glass transition temperature of 50°C or higher on a transparent support, contains a silane coupling agent on the surface of the polymer adhesive layer and / or in the polymer adhesive layer.

[0004] Previous technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 11-101943 Summary of the Invention

[0007] The technical problem to be solved by the invention

[0008] In the aforementioned automatic sealing device, the cover film is mostly used by cutting, so it is required that no chips are generated when cutting the cover film.

[0009] Furthermore, when using an encapsulating liquid to adhere the cover film to a substrate on which the test subject is placed, it is also required from an observational point of view that it is not easy to create gaps.

[0010] In addition, from an operability perspective, the cover film must also have excellent adhesion to the substrate after sealing.

[0011] The inventors, after studying the covering film described in Patent Document 1, found that it could not meet the above requirements. In particular, the covering film described in Patent Document 1 has voids.

[0012] Therefore, the objective of this invention is to provide a covering film that does not easily generate chips during cutting, and furthermore, does not easily generate gaps when bonded to a substrate using an encapsulating liquid, thus exhibiting excellent adhesion to the substrate.

[0013] means for solving technical problems

[0014] The present invention is the result of in-depth research conducted by the inventors to solve the aforementioned problems. Specifically, it was discovered that the above-mentioned problems can be solved according to the following structure.

[0015] [1] A covering film for covering an object to be examined on a substrate.

[0016] The aforementioned covering film has a support and a polymer layer containing a polymer.

[0017] The fracture toughness value of the polymer layer is 0.2 MPa·m. 0.5 above,

[0018] The aforementioned support exhibits an in-plane retardation of less than 1000 nm at a wavelength of 590 nm.

[0019] Both requirements 1 and 2 are met.

[0020] Requirement 1: The dissolution rate of the above polymer layer to xylene is 0.01–0.25 g·m⁻¹. -2 ·s -1 ,

[0021] Requirement 2: When the viscosity of a xylene solution with a solid content of 20% obtained by dissolving the above polymer layer in xylene is set as X, 1 / X is 0.005~0.060 cP. -1 .

[0022] [2] According to the covering film described in [1], the dissolution rate of the xylene is 0.01 to 0.15 g·m⁻¹. -2 ·s -1 The above 1 / X is 0.010 to 0.060 cP. -1 .

[0023] [3] The covering film according to [1] or [2], wherein the weight-average molecular weight of the polymer is 50,000 to 140,000.

[0024] [4] The covering film according to any one of [1] to [3], wherein the glass transition temperature of the polymer layer is 60°C or higher.

[0025] [5] The covering film according to any one of [1] to [4], wherein the polymer is a polymer comprising at least two repeating units derived from monomers selected from the group consisting of acrylate monomers and methacrylate monomers.

[0026] [6] The covering film according to any one of [1] to [5], wherein the polymer is a polymer comprising at least two repeating units derived from monomers selected from the group consisting of methyl methacrylate, ethyl acrylate, ethyl methacrylate, 2-methoxyethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, benzyl acrylate, 2-ethylhexyl methacrylate and lauryl methacrylate.

[0027] [7] The covering film according to any one of [1] to [6], wherein the polymer comprises repeating units derived from ethyl acrylate and repeating units derived from ethyl methacrylate.

[0028] Invention Effects

[0029] According to the present invention, a covering film is provided that does not easily generate chips during cutting, and furthermore, does not easily generate gaps when bonded to a substrate using an encapsulating liquid, and exhibits excellent adhesion to the substrate. Detailed Implementation

[0030] The present invention will now be described in detail.

[0031] The following description of the necessary conditions is sometimes based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

[0032] The following explains the meaning of each statement in this specification.

[0033] In this specification, the numerical range indicated by "~" refers to the range encompassed by the values ​​recorded before and after "~" as the lower and upper limits. Within the numerical ranges described in stages in this specification, the upper or lower limit recorded as a certain numerical range can be replaced with the upper or lower limit of other numerical ranges described in stages. Furthermore, within the numerical ranges described in this specification, the upper or lower limit recorded as a certain numerical range can also be replaced with the values ​​shown in the embodiments.

[0034] In this specification, a combination of two or more preferred methods is a more preferred method.

[0035] In this specification, when multiple substances equivalent to each component are present in the composition, the amount of each component in the composition or layer, unless otherwise specified, refers to the total amount of the multiple substances present in the composition.

[0036] In this specification, "(meth)acrylic acid" is a general term encompassing acrylic acid and methacrylic acid, and specifically refers to "at least one of acrylic acid and methacrylic acid". Similarly, "(meth)acrylate" refers to "at least one of acrylate and methacrylate".

[0037] In this specification, unless otherwise stated, the refractive index refers to the refractive index relative to light with a wavelength of 550 nm, as measured using a NAR-2T manufactured by ATAGO CO.,LTD.

[0038] In this specification, the acid dissociation constant (pKa) refers to the pKa in aqueous solution, specifically the value obtained by calculation using the software package described below, based on a database of Hammett substituent constants and known literature values.

[0039] Software package 1: Advanced Chemistry Development (ACD / Labs) Software V8.14 for Solaris (1994-2007ACD / Labs).

[0040] On the other hand, pKa can also be determined using molecular orbital calculations. A more specific method is to calculate the H+ in an aqueous solution based on thermodynamic cycles. + The method of calculating H is based on the dissociation free energy. + Methods for calculating the dissociation free energy include, for example, DFT (density functional theory), but various other methods have been reported in the literature and are not limited to this. Furthermore, several software programs exist capable of performing DFT, such as Gaussian16.

[0041] As mentioned above, pKa in this specification refers to the value obtained by using software package 1 to calculate a database of substituent constants based on Hammett and known literature values. However, when pKa cannot be calculated by this method, the value obtained by Gaussian16 based on DFT (density functional theory) is used.

[0042] Furthermore, as mentioned above, pKa in this specification refers to "pKa in aqueous solution," but when pKa in aqueous solution cannot be calculated, "pKa in dimethyl sulfoxide (DMSO) solution" is used.

[0043] <Covering film>

[0044] The cover film of the present invention is used to cover the test subject on a substrate.

[0045] Furthermore, the covering film of the present invention has a support and a polymer layer containing a polymer, the polymer layer having a fracture toughness value of 0.2 MPa·m. 0.5 The support has an in-plane delay of less than 1000 nm at a wavelength of 590 nm, and satisfies requirements 1 and 2 below.

[0046] Requirement 1: The dissolution rate of the polymer layer into xylene is 0.01–0.25 g·m⁻¹. -2 ·s -1 .

[0047] Requirement 2: When the viscosity of a xylene solution with a solid content of 20% obtained by dissolving the polymer layer in xylene at 25°C is set as X, 1 / X is 0.005~0.060cP. -1 .

[0048] The mechanism by which the cover film of the present invention does not easily generate chips during cutting, and thus does not easily generate gaps when bonded to the substrate using the sealing liquid, and has excellent adhesion to the substrate may not be clear, but the inventors speculate as follows.

[0049] The fracture toughness of the covering membrane of the present invention is 0.2 MPa·m. 0.5 The ability to track deformations that may occur during cutting without breaking suggests that the film is less prone to chipping during cutting.

[0050] Furthermore, in order to prevent gaps from forming when the cover film is bonded to the substrate using an encapsulation liquid and to ensure excellent adhesion to the substrate, it is considered necessary to move the polymer into the gaps and ensure polymer-based adhesion.

[0051] Here, the dissolution rate is 0.25 g·m⁻¹. -2 ·s -1 The appropriate penetration rate of the encapsulating liquid into the polymer layer ensures sufficient time for the polymer to move from the polymer layer into the pores. On the other hand, the dissolution rate is 0.01 g·m⁻¹. -2 ·s -1 In the above, before the sealing liquid disappears through drying, a sufficient amount of polymer is supplied between the cover film and the substrate to ensure a tight seal.

[0052] Furthermore, the above 1 / X is 0.060cP. -1 The polymer exhibits excellent diffusivity, allowing it to migrate into the pores. Furthermore, the aforementioned 1 / X is 0.005 cP. -1 The above indicates that the polymer itself has a specified molecular chain length, and by using this polymer, the cover film can be made to adhere tightly to the substrate.

[0053] That is, by satisfying the above requirements 1 and 2, it can be considered that when the cover film is bonded to the substrate using the sealing liquid, gaps are not easily generated, and the adhesion between the cover film and the substrate is excellent.

[0054] The following section describes the structure of the covering membrane. The fracture toughness value, requirement 1, and requirement 2 will be detailed later.

[0055] In addition, the following will refer to the fact that it is not easy to generate chips during cutting as "chip resistance", the fact that it is not easy to generate gaps when using an encapsulating liquid to bond the cover film to the substrate as "gap suppression", and the fact that the cover film and the substrate have excellent adhesion as "adhesion".

[0056] [Support]

[0057] From a microscopic point of view, a transparent support is preferred as the support for the covering film. Furthermore, in this specification, "transparent" means that the transmittance of visible light (wavelength: 380–780 nm) is 60% or more. Transmittance is the ratio of transmitted light to incident light on the support.

[0058] (Material of the support structure)

[0059] As a transparent support, it is not subject to any special restrictions and can use known transparent supports.

[0060] The transparent support is preferably a material in which the content of the specific ester compound described later is less than 1% by mass relative to the total mass of the support.

[0061] Materials constituting the support include, for example, cellulose polymers such as cellulose triacetate (TAC), cellulose diacetate, cellulose acetate propionate, and cellulose acetate butyrate; polyester polymers such as aliphatic polyesters; polyolefin polymers such as cyclic olefin polymers (COP), polyethylene, and polypropylene; acrylic resins; polycarbonate (PC); and polystyrene, preferably cellulose polymers, acrylic resins, or cyclic olefin polymers (COP), and more preferably cellulose triacetate (TAC).

[0062] When the material constituting the support is a polymer, its weight-average molecular weight (Mw) is, for example, 10,000 to 1,000,000, preferably 30,000 to 300,000.

[0063] The support can use one of the above materials alone, or two or more materials.

[0064] The content of the aforementioned material in the support is preferably greater than 50% by mass relative to the total mass of the support, more preferably 80% by mass or more. The upper limit is not particularly limited; if the support does not contain a specific ester compound, it may be less than 100% by mass relative to the total mass of the support; if the support contains a specific ester compound, it may be the remainder.

[0065] (Specific ester compounds)

[0066] The support of the cover film of the present invention is preferably such that the content of a specific ester compound is 1% by mass or less relative to the total mass of the support.

[0067] That is, the support, whether it contains a specific ester compound or not, preferably contains less than 1% by mass relative to the total mass of the support.

[0068] A specific ester compound is an ester compound obtained by the condensation reaction of an oxyacid of an organic acid or inorganic acid with a hydroxyl-containing compound, wherein the pKa of at least one of the hydrolysate, namely the oxyacid of an organic acid or inorganic acid and a compound having a hydroxyl group, is 2.5 or less.

[0069] In addition, when multiple ester compounds have pKa values, any one of the multiple pKa values ​​can be below 2.5.

[0070] Examples of specific ester compounds include, for example, phosphate esters, phosphites, sulfonates, and nitrates.

[0071] Examples of hydrolysates of specific ester compounds with a pKa of 2.5 or less include phosphoric acid generated by the hydrolysis of phosphate ester compounds, phosphorous acid generated by the hydrolysis of phosphite ester compounds, sulfonic acids such as methanesulfonic acid and benzenesulfonic acid generated by the hydrolysis of sulfonate ester compounds, and nitric acid generated by the hydrolysis of nitrate ester compounds.

[0072] Examples of phosphate ester compounds include, for example, triphenyl phosphate, biphenyl diphenyl phosphate, bisphenol A bis-(diphenyl phosphate), trimethyl phosphate, triethyl phosphate, diphenyl-2-methylacryloyl ethyl phosphate, tricresyl phosphate, tri(xyl) phosphate and toluene diphenyl phosphate.

[0073] Examples of phosphite compounds include, for example, triphenyl phosphite, biphenyl diphenyl phosphite, bisphenol A bis-(diphenyl phosphite), trimethyl phosphite, triethyl phosphite, diphenyl-2-methylacryloyl ethyl phosphite, tricresyl phosphite, tri(xyl) phosphite, and toluene diphenyl phosphite.

[0074] Examples of sulfonate compounds include, for example, methyl benzenesulfonate, ethyl benzenesulfonate, methyl toluenesulfonate, and ethyl toluenesulfonate.

[0075] The preferred ester compound is a phosphate ester compound, more preferably a triphenyl phosphate, a biphenyl diphenyl phosphate or a tricresyl phosphate, and even more preferably a triphenyl phosphate or a biphenyl diphenyl phosphate.

[0076] When the support contains a specific ester compound, the specific ester compound may be a single compound or two or more compounds. When two or more specific ester compounds are present, the total content of the specific ester compounds relative to the total mass of the support is preferably less than 1% by mass.

[0077] When the support contains a specific ester compound, the content of that specific ester compound is preferably 0.6% by mass or less, more preferably 0.4% by mass or less, relative to the total mass of the support. The support is particularly preferably free of the specific ester compound.

[0078] The content of specific ester compounds contained in the support can be determined by the following assay method.

[0079] For example, the types and amounts of ester compounds contained in the support are determined using known methods such as gas chromatography-mass spectrometry (GC / MS). Based on the structural formulas of the ester compounds, the pKa of the hydrolysates formed by the hydrolysis of each ester compound contained in the support is calculated. In the presence of hydrolysates with a pKa of 2.5 or lower, the content of the ester compounds formed from these hydrolysates (or the total content if two or more exist) is the content of the specific ester compound. In the absence of hydrolysates with a pKa of 2.5 or lower, the support does not contain the specific ester compound.

[0080] (Second ester compound)

[0081] The support may contain a second ester compound in addition to a specific ester compound.

[0082] As the second ester compound, there are no particular restrictions if the pKa of the hydrolysate is greater than 2.5. For example, carboxylic acid esters composed of carboxylic acids and hydroxyl-containing compounds can be cited.

[0083] Examples of carboxylic acid ester compounds include, for instance, sugar ester compounds.

[0084] -glycoester compounds-

[0085] Sugar esters are compounds made by replacing some or all of the hydrogen atoms in the hydroxyl groups of sugars with acyl groups.

[0086] Examples of sugars include monosaccharides, disaccharides, and polysaccharides, with disaccharides being preferred.

[0087] Examples of monosaccharides include pentoses such as ribose, deoxyribose, arabinose, and xylose; hexoses such as glucose, galactose, and fructose; and triose, tetroose, and heptose.

[0088] Examples of disaccharides include sucrose, lactose, maltose, trehalose, maltodextrose, and cellobiose, with sucrose being preferred.

[0089] Examples of polysaccharides include glycogen and starch.

[0090] Sugars can have either a chain-like or a cyclic structure. Examples of cyclic structures found in sugars include furanose rings and pyranose rings.

[0091] Examples of 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-furanylcarbonyl.

[0092] The number of carbon atoms in the acyl group is preferably 1 to 10.

[0093] As a sugar ester compound, it is more preferably a sugar ester compound represented by the following general formulas (I) to (III).

[0094] (I)(HO)mG-(LR 1 )n

[0095] (II)(HO)pG-(LR 1 )q

[0096] (III)(HO)t-G'-(L'-R 2 )r

[0097] (In general formulas (I) to (III), G and G' independently represent monosaccharide residues or disaccharide residues, respectively. R 1 Each group can be independently represented by an aliphatic group or an aromatic group, with at least one group representing an aromatic group. R 2 Each of these groups independently represents an aliphatic group. L and L' independently represent divalent linking groups. m represents an integer greater than or equal to 0, n, p, and q independently represent integers greater than or equal to 1, r represents an integer greater than or equal to 3, and t represents an integer greater than or equal to 0. However, m+n≥4, p+q≥4, m>p, n<q. Furthermore, m+n and p+q are equal in number to the hydroxyl counts of unsubstituted sugars with a cyclic acetal structure having the same backbone as the aforementioned G, which is not a residue, and r+t is equal in number to the hydroxyl counts of unsubstituted sugars with a cyclic acetal structure having the same backbone as the aforementioned G', which is not a residue.

[0098] As sugar ester compounds, more preferably are aromatic sugar ester compounds represented by the above general formula (I), ester compounds represented by the above general formula (II) with a different degree of substitution than aromatic sugar ester compounds represented by the above general formula (I), and sugar ester compound mixtures formed by mixing aliphatic sugar ester compounds represented by the above general formula (III).

[0099] Hereinafter, preferred ranges that are common to all sugar ester compounds and preferred ranges specific to each sugar ester compound that satisfy general formulas (I) to (III) will be described.

[0100] Each sugar ester compound used in the above-mentioned sugar ester compound mixture uses monosaccharide residues or disaccharide residues as its backbone. That is, in the above general formulas (I) to (III), G and G' independently represent monosaccharide residues or disaccharide residues, respectively.

[0101] The aforementioned sugar ester compounds refer to compounds in which at least one substituted group (e.g., hydroxyl, carboxyl) in the sugar backbone structure constituting the compound is bonded to at least one substituent ester. That is, the sugar ester compounds described herein also include sugar derivatives in a broader sense, such as compounds containing sugar residues like gluconic acid as structural components. Specifically, the aforementioned sugar ester compounds also include ester bodies of glucose and carboxylic acids, as well as ester bodies of gluconic acid and alcohols.

[0102] The aforementioned sugar ester compounds preferably have a furanose structure or a pyranose structure. When a furanose structure or a pyranose structure is used as the sugar backbone, the following conditions are satisfied in the above general formulas (I) to (III): m+n≥4, p+q≥4, and r is 3 or more.

[0103] Furthermore, when the sugar backbone has a furanose or pyranose structure, the following conditions are also met: the number of hydroxyl groups in m+n and p+q is equal to the number of hydroxyl groups in unsubstituted sugars with a cyclic acetal structure that is assumed to have the same backbone as the above-mentioned G, which is not a residue; and the number of hydroxyl groups in r+t is equal to the number of hydroxyl groups in unsubstituted sugars with a cyclic acetal structure that is assumed to have the same backbone as the above-mentioned G', which is not a residue.

[0104] In addition, the upper limits of m+n, p+q and r+t can be determined according to the type of G or G' mentioned above. If G or G' is a monosaccharide residue, it becomes 5, and if it is a disaccharide residue, it becomes 8.

[0105] The sugar ester compounds represented by the above general formulas (I) to (III) are preferably esterified compounds formed by esterifying all or part of the OH groups of the above-mentioned compounds (A) in which G or G' is a monosaccharide residue having a furanose structure or a pyranose structure, or in the above-mentioned compounds (B) in which at least one furanose structure or a pyranose structure is bonded together with two disaccharide residues.

[0106] Examples of compounds (A) include glucose, galactose, mannose, fructose, xylose, and arabinose, but are not limited to these.

[0107] Examples of compound (B) include lactose, sucrose, fructotetraose, 1F-fructopentose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, metriose, and fructotriose. In addition, examples include gentiobiose, gentiotriose, gentiotetraose, xylitol, and galactosylsucrose, but the list is not limited to these.

[0108] Among these compounds (A) and (B), compounds having both furanose and pyranose structures are particularly preferred. For example, sucrose, fructotriose, fructotetraose, 1F-fructopentose, or stachyose are preferred, with sucrose being more preferred. Furthermore, in compound (B), compounds formed by bonding at least one furanose structure or two pyranose structures are also a preferred embodiment.

[0109] The substituent used for esterifying all or part of the OH groups in compounds (A) and (B) is not particularly limited. A monocarboxylic acid is preferred. That is, the R group in general formula (I) and general formula (II) described above... 1 and the R mentioned in the above general formula (III) 2 It is preferable to represent the acyl group separately and independently.

[0110] There are no particular limitations on the aforementioned monocarboxylic acids; known aliphatic, alicyclic, and aromatic monocarboxylic acids can be used. The carboxylic acid used can be one type or a mixture of two or more. In the presence of multiple R... 1 Or the above R 2 In this case, they can be the same as each other, or they can be different.

[0111] On the other hand, the L in general formula (I) and general formula (II) and the L' in general formula (III) preferably represent single bonds, -O-, -CO-, and -NR, respectively. 11 -(R 11 (representing any one of the substituents with a valence of 1), and in the presence of multiple of the above L... 1 In the case of L' mentioned above, they can be the same as each other or different. Among them, from the above R... 1 and R 2 Based on the view that it can be easily substituted by an acyl group, the above L 1 Or the above L' is preferably represented as -O-.

[0112] Next, preferred embodiments of aromatic sugar ester compounds represented by the above general formulas (I) and (II) will be described.

[0113] In the above general formulas (I) and (II), the above R 1 Each group can independently represent an aliphatic group or an aromatic group, with at least one group representing an aromatic group. Wherein, the above R... 1 Preferably, each and every aromatic group is represented independently; more preferably, all of them are the same aromatic group.

[0114] Furthermore, in the above general formulas (I) and (II), m represents an integer greater than or equal to 0, n, p and q each independently represent an integer greater than or equal to 1, m > p, n < q.

[0115] In the aromatic sugar ester compounds represented by the above general formula (I) and the aromatic sugar ester compounds represented by the above general formula (II), when G is a disaccharide residue, n is preferably 3 or more, and more preferably 5 or more.

[0116] As the one being R 1 Examples of preferred aromatic monocarboxylic acids used in substitution include benzoic acid, methylbenzoic acid, and other aromatic monocarboxylic acids in which an alkyl or alkoxy group is introduced into the benzene ring of benzoic acid; cinnamic acid; benzyl acid, biphenyl carboxylic acid, naphtholic acid, tetrahydronaphtholic acid, and other aromatic monocarboxylic acids having two or more benzene rings; and their derivatives.

[0117] Next, a preferred embodiment of the aliphatic glycol ester compound represented by the above general formula (III) will be described. In the above general formula (III), the above R 2 Each aliphatic group can be represented independently.

[0118] As a result of R 2 Preferred aliphatic monocarboxylic acids used for substitution include saturated fatty acids such as acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, 2-ethylhexanecarboxylic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, hexacosanoic acid, mordanic acid, beeswax acid, and lacquer wax acid; and unsaturated fatty acids such as undecenoic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, and octenic acid.

[0119] Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, and cyclooctane carboxylic acid, as well as their derivatives.

[0120] The above R 2 Preferably, each R represents an acyclic aliphatic group independently. 2 Preferably, it represents a non-cyclic aliphatic group.

[0121] The above R 2 Preferably, it represents two or more aliphatic groups.

[0122] In aliphatic monocarboxylic acids, the aliphatic glycol ester compound represented by the above general formula (III) is preferably substituted with at least acetic acid. That is, the R in the above general formula (III) 2 At least one of them preferably represents an acetyl group.

[0123] On the other hand, the more preferred option is the aforementioned R. 2 At least one of the above-mentioned R represents a branched aliphatic group, particularly preferably in the R group. 2 When two or more aliphatic groups are represented, only one represents a branched aliphatic group. Preferably, the aliphatic sugar ester compound represented by the above general formula (III) is substituted with isobutyric acid in addition to acetic acid. That is, the R in the above general formula (III) is... 2 Preferably, it contains acetyl and isobutyryl groups.

[0124] From the viewpoint of improving the planar defects of the obtained cellulose ester film, the above-mentioned G' in general formula (III) preferably represents a disaccharide residue.

[0125] Methods for manufacturing aliphatic sugar ester compounds substituted with these aliphatic monocarboxylic acids are, for example, described in Japanese Patent Application Publication No. 8-245678.

[0126] When using a combination of sugar ester compounds represented by the above general formulas (I) to (III) as sugar ester compounds, the mixing ratio is not particularly limited, but the total content of aromatic sugar ester compounds / the content of aliphatic ester compounds (mass ratio) is preferably greater than 1, more preferably 2 to 10, and even more preferably 3 to 5.

[0127] Furthermore, when using a combination of sugar ester compounds represented by the above general formulas (I) to (III) as sugar ester compounds, the total content of the sugar ester compounds represented by the above general formulas (I) to (III) is preferably 1 to 30% by mass relative to the cellulose ester, more preferably 5 to 30% by mass, even more preferably 5 to 20% by mass, and particularly preferably 5 to 15% by mass.

[0128] Regarding the sugar ester compounds represented by the above general formulas (I) to (III), reference can also be made to the description in paragraphs

[0015] to

[0056] of Japanese Patent Application Publication No. 2012-031313, which is incorporated herein by reference.

[0129] (Properties of the support)

[0130] -thickness-

[0131] The thickness of the support is not particularly limited, but is preferably 50 to 250 μm, more preferably 50 to 150 μm, and even more preferably 100 to 150 μm.

[0132] -Refractive index-

[0133] The refractive index of the support is not particularly limited, for example, it can be 1.440 to 1.600, and from the point of view of microscopic inspection, it is preferably 1.460 to 1.560, which is close to that of the glass slide (refractive index 1.52 to 1.56).

[0134] -Delay-

[0135] The in-plane delay of the support is below 1000 nm.

[0136] From the viewpoint of being suitable for observation under a polarized light microscope, the in-plane retardation of the support is preferably 600 nm or less, more preferably 400 nm, and even more preferably 200 nm or less. Furthermore, the lower limit of the in-plane retardation can be exemplified as 0 nm.

[0137] From the viewpoint of observation suitable for polarized light microscopy, the thickness retardation of the support is preferably -300 to 300 nm, more preferably -100 to 100 nm, and even more preferably -50 to 50 nm.

[0138] In addition, in this specification, the in-plane retardation Re(λ) at wavelength λ and the thickness-direction retardation Rth(λ) at wavelength λ refer to the retardations measured by the following methods. Furthermore, unless otherwise specified, λ is set to 590 nm.

[0139] Re(λ) and Rth(λ) can be calculated using a phase difference measuring device (KOBRA-21WR, manufactured by Oji Scientific Instruments) based on the measured values ​​of the average refractive index ((nx+ny+nz) / 3) and film thickness (d(μm)) at wavelength λ.

[0140] A base coating, well-known in the photographic materials industry, can be applied to the surface of the support. The support can be subjected to surface treatments such as ultraviolet irradiation, corona discharge, or glow discharge.

[0141] [Polymer Layer]

[0142] The polymer layer of the covering membrane contains polymer and has a fracture toughness of 0.2 MPa·m. 0.5 The above conditions must be met, and requirements 1 and 2 must also be satisfied.

[0143] The following will describe the polymers and any components contained in the polymer layer, as well as the necessary conditions that the polymer layer must meet.

[0144] (polymer)

[0145] If the polymer contained in the polymer layer has a fracture toughness value of 0.2 MPa·m 0.5If both requirements 1 and 2 are met, then there are no special restrictions.

[0146] The polymer contained in the polymer layer is preferably swollen in an organic solvent used as a sealing liquid in the automatic sealing device, and more preferably dissolved in the aforementioned organic solvent. Examples of organic solvents used in the automatic sealing device include xylene, toluene, mesitylene (1,3,5-trimethylbenzene), pseudocumene (1,2,4-trimethylbenzene), thiobenzene (1,2,3-trimethylbenzene), dulene (1,2,4,5-tetramethylbenzene), anisole, ethyl propionate, amyl acetate, propyl acetate, isopropyl acetate, butyl acetate, methyl lactate, dimethyl carbonate, 1-butanol, and 1-propanol. The polymer is swollen or dissolved in any one of the following organic solvents: 2-butanol, 1-pentanol, 2-pentanol, isopentanol, tert-pentanol, neopentanol, cyclopentanol, 2-hexanol, 4-methyl-2-pentanol, methyl isobutyl ketone, acetylacetone, cyclopentanone, n-butyl ether, 1,2-dimethoxyethane, dioxane, cyclocyclopentylmethyl ether, 1-methoxy-2-propanol, propylene glycol methyl ether acetate, ethyl acetate, methyl acetate, acetone, and methyl ethyl ketone, or a mixture of two or more thereof. The polymer is swollen or dissolved in the aforementioned organic solvents, thereby bonding the cover film to the substrate and sealing the test subject.

[0147] From the viewpoint of excellent solubility in the aforementioned organic solvents, acrylic resins are preferred as polymers.

[0148] In this specification, acrylic resin refers to a polymer having repeating units derived from acrylate monomers and / or methacrylate monomers.

[0149] As an acrylic resin, it is not particularly limited if it has repeating units derived from acrylate monomers and / or methacrylate monomers. It can also be a homopolymer containing repeating units derived from a monomer selected from the group consisting of acrylate monomers and methacrylate monomers, or a polymer (polymer) containing at least two or more repeating units derived from monomers selected from the group consisting of acrylate monomers and methacrylate monomers.

[0150] Furthermore, the acrylic resin can be a copolymer comprising repeating units derived from at least one monomer selected from the group consisting of acrylate monomers and methacrylate monomers, and at least one monomer other than acrylate monomers and methacrylate monomers (e.g., acrylamide monomers such as dimethacrylamide and isopropylacrylamide, and vinyl monomers such as styrene).

[0151] In acrylic resins, the content of repeating units derived from acrylate monomers and / or methacrylate monomers is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, relative to all repeating units of the acrylic resin. The upper limit of the content of repeating units derived from acrylate monomers and / or methacrylate monomers is not particularly limited and can be 100% by mass relative to all repeating units of the acrylic resin.

[0152] As an acrylic resin, it is particularly preferred to have only repeating units derived from acrylate monomers and / or methacrylate monomers.

[0153] Acrylic resins can be prepared by known methods, for example, by recombination of at least one monomer selected from the group consisting of acrylate monomers and methacrylate monomers.

[0154] Examples of acrylate monomers and methacrylate monomers mentioned above include alkyl acrylates and alkyl methacrylates.

[0155] The alkyl groups in alkyl acrylates and alkyl methacrylates can be either straight-chain or branched.

[0156] Furthermore, the aforementioned alkyl group may also have substituents. Examples of substituents include aryl and hydroxyl groups, preferably aryl, and more preferably phenyl. The number of carbon atoms of the alkyl group that may have substituents in the alkyl acrylate and alkyl methacrylate is preferably 1 to 15, more preferably 1 to 8, further preferably 1 to 5, and particularly preferably 1 to 3.

[0157] A portion of the methylene group constituting the aforementioned alkyl group may be replaced by a divalent substituent. Examples of divalent substituents include -O- and -CO-.

[0158] Specific examples of the aforementioned acrylate monomers include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, lauryl acrylate, phenyl acrylate, benzyl acrylate, 2-methoxyethyl methacrylate, hydroxyethyl acrylate, and acetylacetoxyalkyl acrylate.

[0159] Specific examples of the aforementioned methacrylate monomers include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, lauryl methacrylate, 2-methoxyethyl methacrylate, hydroxyethyl methacrylate, and 2-acetylacetoxyethyl methacrylate.

[0160] The polymer preferably comprises a repeating unit derived from at least one monomer selected from the group consisting of ethyl acrylate, n-butyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, lauryl methacrylate, 2-methoxyethyl methacrylate, 2-acetylacetoxyethyl methacrylate, phenyl acrylate, phenyl methacrylate, styrene, and dimethacrylamide, more preferably comprising a repeating unit derived from at least one monomer selected from the group consisting of ethyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, benzyl methacrylate, lauryl methacrylate, and 2-methoxyethyl methacrylate.

[0161] One of the preferred ways to construct the polymer layer is to use a polymer X that comprises repeating units derived from alkyl acrylates and repeating units derived from alkyl methacrylates.

[0162] As a repeating unit derived from the alkyl acrylate contained in polymer X, it is preferably a repeating unit derived from an alkyl acrylate having 1 to 7 carbon atoms (preferably 1 to 5 carbon atoms, more preferably 1 to 3 carbon atoms), and from the viewpoint of fracture toughness value, it is more preferably a repeating unit derived from ethyl acrylate.

[0163] In polymer X, the content of repeating units derived from alkyl acrylates is preferably 5 to 40% by mass relative to all repeating units of polymer X, more preferably 20 to 30% by mass.

[0164] As a repeating unit derived from the alkyl methacrylate contained in polymer X, it is preferably a repeating unit derived from an alkyl methacrylate having 1 to 15 carbon atoms (preferably 1 to 5 carbon atoms, more preferably 1 to 3 carbon atoms).

[0165] Examples of alkyl methacrylates constituting repeating units derived from alkyl methacrylates include methyl methacrylate, ethyl methacrylate, 2-methoxyethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, benzyl acrylate, 2-ethylhexyl methacrylate, and lauryl methacrylate. From the viewpoint of dissolution rate and fracture toughness, polymer X preferably contains repeating units derived from ethyl methacrylate, tert-butyl methacrylate, or benzyl acrylate, and more preferably contains repeating units derived from ethyl methacrylate.

[0166] In polymer X, the repeating unit derived from alkyl methacrylate can be of only one type or more than two types.

[0167] In polymer X, the content of repeating units derived from alkyl methacrylates is preferably 60 to 95% by mass relative to all repeating units of polymer X, more preferably 70 to 90% by mass.

[0168] As a preferred embodiment of polymer X, polymer Y is preferably a polymer comprising repeating units derived from ethyl acrylate, repeating units derived from methyl methacrylate, and repeating units derived from other alkyl methacrylates besides methyl methacrylate. As mentioned above, ethyl methacrylate can be cited as an example of other alkyl methacrylates.

[0169] In polymer Y, the content of repeating units derived from ethyl acrylate is preferably 5 to 40% by mass relative to all repeating units of polymer Y, more preferably 10 to 30% by mass, and even more preferably 15 to 25% by mass.

[0170] In polymer Y, the content of repeating units derived from methyl methacrylate is preferably 20 to 80% by mass relative to all repeating units of polymer Y, more preferably 50 to 70% by mass.

[0171] Furthermore, in polymer Y, the content of repeating units derived from alkyl methacrylates (preferably ethyl methacrylate) other than methyl methacrylate is preferably 5 to 50% by mass relative to all repeating units of polymer Y, more preferably 10 to 40% by mass, and even more preferably 15 to 25% by mass.

[0172] The weight-average molecular weight (Mw) of the polymer is preferably 10,000 to 500,000, more preferably 50,000 to 140,000, and even more preferably 80,000 to 120,000.

[0173] In this specification, unless otherwise stated, the weight-average molecular weight (Mw) is the molecular weight obtained as follows: using a gel permeation chromatography (GPC) analysis apparatus with TSKgel GMHxL, TSKgel G4000HxL, TSKgel G2000HxL and / or TSKgel Super HZM-N (all trade names manufactured by Tosoh Corporation) columns, with THF (tetrahydrofuran) as solvent, detected by differential refractometer, and with polystyrene as a standard substance.

[0174] Regarding the covering film of the present invention, when used as a covering film for stained specimens, the staining pigment spreads within the polymer layer, thereby sometimes reducing observability. To prevent this, it is also preferable to reduce the compatibility between the polymer and the staining pigment.

[0175] The compatibility between the polymer and the dyeing pigment (e.g., eosin) can be determined based on the Hansen solubility parameter distance. For example, the preferred Hansen solubility parameter distance between the polymer and the dyeing pigment is 12.00 MPa. 0.5 The above, more preferably 12.50 MPa 0.5 The above is further preferred to be 13.00 MPa. 0.5 The above applies. There is no upper limit to the distance for the Hansen solubility parameter; for example, the above Hansen solubility parameter distance is 40.00 MPa. 0.5 the following.

[0176] The polymer content in the polymer layer is not particularly limited, but is preferably 85% by mass or more, more preferably 90% by mass or more, relative to the total mass of the polymer layer. The upper limit can be 100% by mass or less, preferably 99.99% by mass or less, more preferably 99.95% by mass or less.

[0177] The polymer can be used alone or in combination with two or more polymers. When using two or more polymers, it is preferable to use a ratio that does not produce turbidity in the dried film formed by mixing the two or more polymers.

[0178] (Silane coupling agents)

[0179] The polymer layer may contain at least one selected from the group consisting of silane coupling agents, their hydrolysates, and their hydrolysates (hereinafter also collectively referred to as "silane coupling agents").

[0180] If the polymer layer contains a silane coupling agent, then even if the cover film of the present invention is stored in roll form, it is less likely to stick between the polymer layer and the back side of the support (the side of the support opposite to the side on which the polymer layer is formed), and its shelf life is better.

[0181] The type of silane coupling agent is not particularly limited, but is preferably a silane coupling agent having two or more different reactive groups in the molecule, at least one of which is a reactive group chemically bonded to an inorganic substance, and at least one of which is a reactive group chemically bonded to an organic material.

[0182] Regarding silane coupling agents, examples include silane coupling agents represented by the following general formula.

[0183] X-Si(R 1 )3

[0184] X represents a group having a reactive group. Examples of reactive groups include vinyl, epoxy, amino, (meth)acrylate, and mercapto groups. More specifically, X can be denoted as R... 2 -L- indicates a group. R 2 The symbol represents a reactive group, and L represents a divalent linking group (preferably an alkylene group that may contain heteroatoms (e.g., oxygen atoms).

[0185] R 1 This indicates a hydrolyzable group. A hydrolyzable group is a group that is directly bonded to Si (silicon atoms) and can undergo hydrolysis and / or condensation reactions. Examples of hydrolyzable groups include alkoxy, halogen, acyloxy, alkenyloxy, and isocyanate groups.

[0186] Silane coupling agents are preferably selected from vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-(methacryloyloxypropyl)trimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl- The silane is selected from one or more of the group consisting of γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-chloropropyltrimethoxysilane, more preferably from one or more of the group consisting of γ-glycidoxypropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-aminopropyltriethoxysilane, further preferably from one or more of the group consisting of γ-glycidoxypropyltrimethoxysilane and N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and particularly preferably from γ-glycidoxypropyltrimethoxysilane.

[0187] Hydrolysates of silane coupling agents refer to compounds obtained by hydrolyzing the hydrolyzable groups in the silane coupling agent. Furthermore, the aforementioned hydrolysates can be those in which all hydrolyzable groups are hydrolyzed (complete hydrolysates) or those in which only a portion of the hydrolyzable groups are hydrolyzed (partial hydrolysates). That is, the aforementioned hydrolysates can be complete hydrolysates, partial hydrolysates, or mixtures thereof.

[0188] Furthermore, the hydrolysis condensate of the silane coupling agent refers to a compound obtained by hydrolyzing the hydrolyzable groups in the silane coupling agent and condensing the resulting hydrolysate. Additionally, the aforementioned hydrolysis condensate can be a complete hydrolysis condensate (where all hydrolyzable groups are hydrolyzed and all hydrolysates are condensed) or a partially hydrolysis condensate (where some hydrolyzable groups are hydrolyzed and some hydrolysates are condensed). That is, the aforementioned hydrolysis condensate can be a complete hydrolysis condensate, a partially hydrolysis condensate, or a mixture thereof.

[0189] Furthermore, those skilled in the art will readily understand that the type of silane coupling agent used in the polymer layer is selected based on the type of organic material to be bonded to the glass, i.e., the type of polymer constituting the polymer layer.

[0190] The content of silane coupling agents in the polymer layer is preferably 0.1 mg / m² relative to the area of ​​the polymer layer. 2 The above, more preferably 5-25 mg / m² 2 .

[0191] Silane coupling agents can be used alone or in combination with two or more.

[0192] The silane coupling agent in the polymer layer can be uniformly distributed throughout the entire polymer layer or non-uniformly distributed on any surface of the polymer layer. In the case where the silane coupling agent is non-uniformly distributed on any surface of the polymer layer, this surface can be the surface of the polymer layer on the side opposite to the support, or the surface of the polymer layer on the side opposite to the support.

[0193] (Plasticizer)

[0194] The polymer layer of the present invention may contain a plasticizer.

[0195] By including plasticizers, it is possible to improve the compatibility of the polymer layer with solvents (such as xylene), increase the dissolution rate of the polymer layer when it comes into contact with the solvent, or improve the brittleness of the polymer layer.

[0196] The type of plasticizer is not particularly limited, but a plasticizer with high compatibility with the polymer used is preferred. For example, a plasticizer with a small difference between its Hansen solubility parameter and that of the polymer is preferred.

[0197] As a plasticizer, preferably, for example, is a plasticizer selected from the group consisting of phosphates such as triphenyl phosphate, bisphenol A bis-(diphenyl phosphate), trimethyl phosphate, triethyl phosphate and diphenyl-2-methylacryloyl ethyl phosphate; adipates such as dioctyl adipate, dibutyl adipate and diisobutyl adipate, and adipates such as ADEKASIZER LV-808 (manufactured by ADEKA CORPORATION) and POLYSIZER W-242, W-230-H, W-1020-EL and W-1430-EL; sebacate such as dioctyl sebacate; tri(2-ethylhexyl) trimellitate; dibutyl maleate; and glyceryl triacetate.

[0198] Furthermore, preferred plasticizers include phthalate esters such as diisononyl phthalate, bis(2-ethylhexyl) phthalate, and isodecanyl phthalate; trimellitic esters such as ADEKASIZER C series (e.g., C-8, manufactured by ADEKACORPORATION) and MONOSIZER W-705 (manufactured by DIC Corporation); pyromellitic esters such as ADEKASIZER UL-80 and UL-100 (manufactured by ADEKA CORPORATION); dipentaerythritol esters such as ADEKASIZER UL-8 (manufactured by ADEKACORPORATION); carboxylic acid esters with epoxy groups such as MONOSIZER W-150 (manufactured by DIC Corporation); and benzoate esters such as MONOSIZER PB-3A (manufactured by DIC Corporation).

[0199] Furthermore, polyethylene glycol compounds such as polyethylene glycol, triethylene glycol bis(2-hexyl acetate), and diethylene glycol dibenzoate are preferred as plasticizers.

[0200] Additionally, plasticizers can be deep eutectic solvents (DES). Deep eutectic solvents are solvents containing hydrogen bond acceptor compounds and hydrogen bond donor compounds, and are solvents that cause a decrease in the eutectic melting point and a significant decrease in the melting point by mixing hydrogen bond acceptor compounds and hydrogen bond donor compounds.

[0201] 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 alcohols, sugars, carboxylic acids, and amines.

[0202] As a deep eutectic solvent, examples include paragraphs 0025 to 0048 of US 2018 / 0194913 and Japanese Patent Application Publication No. 2020-105336.

[0203] (Thickener)

[0204] The polymer layer may contain a thickener.

[0205] The type of thickener is not particularly limited, and examples include polymers such as polysaccharides, cellulose, acrylic acid, polyvinyl alcohol, glycols and terpenes, inorganic particles such as silica particles and titanium dioxide particles, and organic particles such as polymers such as PMMA. Cellulose acetate (more preferably cellulose acetate butyrate or cellulose acetate phthalate) or silica particles are preferred.

[0206] From the viewpoint of being able to suppress the seepage (migration) of hydrophilic materials from components in contact with polymer layers, the surface of inorganic particles is preferably subjected to hydrophobic treatment.

[0207] The size of inorganic and organic particles is not particularly limited. However, if they are too large, scattering is more likely to occur, and microscopic properties may deteriorate. Therefore, the average secondary particle size (the average particle size of the aggregate of inorganic and organic particles) is preferably 1 μm or less. The lower limit is not particularly limited and can be 1 nm or more. Furthermore, the average secondary particle size of inorganic and organic particles can be measured using dynamic light scattering and a particle size measuring device (manufactured by OTSUKA ELECTRONICS CO.,LTD, "nanoSAQLA").

[0208] Furthermore, from the viewpoint of preventing scattering, the refractive index of the inorganic and organic particles is preferably close to that of the polymer layer. More specifically, the refractive index of the inorganic and organic particles is preferably 1.40 to 1.60.

[0209] When the polymer layer contains the aforementioned thickener and / or plasticizer, the content of each is not particularly limited. However, from the viewpoint of further maximizing the effect of each additive, the content relative to the total mass of the polymer layer is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 3% by mass or more. From the viewpoint of further suppressing chipping during cutting, the content of the thickener selected from the aforementioned inorganic and organic particle composition group contained in the polymer layer is particularly preferably within the above-mentioned range.

[0210] The upper limit of the above-mentioned additive content is not particularly limited. From the viewpoint of the adhesion of the polymer layer, it is preferably 20% by mass or less relative to the total mass of the polymer, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0211] (Properties of the polymer layer)

[0212] - Fracture toughness value-

[0213] The fracture toughness of the polymer layer is 0.2 MPa·m. 0.5 above.

[0214] From the perspective of chip resistance, the fracture toughness of the polymer layer is further preferably 1.0 MPa·m. 0.5 The above applies. The upper limit of the fracture toughness value of the polymer layer is not particularly limited, and in most cases is 5.0 MPa·m. 0.5 the following.

[0215] The method for determining the fracture toughness value of the polymer layer is as follows.

[0216] The fracture toughness of the polymer layer was determined using the indenter indentation method (IF method). More specifically, a cubic corner indenter was pressed into the polymer layer with a load of 20 mN using a nanoindenter (iNano, G200 manufactured by TOYO Corporation). The fracture toughness value (K) was calculated based on the length of the crack generated at the corner of the indentation using the following formula. IC Unit: MPa·m 0.5 ).

[0217] K IC =α(E / H) 0.5 ·(P / C 1.5 )

[0218] In addition, in the above formula, α is a constant of 0.032, which represents E as Young's modulus, H as Vickers hardness, P as indentation load, and C as crack length, respectively.

[0219] The fracture toughness of the polymer layer can be controlled by adjusting the type of repeating units in the polymer contained in the polymer layer and the weight-average molecular weight.

[0220] -Requirement 1-

[0221] The following is a requirement related to the polymer layer mentioned above.

[0222] Requirement 1: The dissolution rate of the polymer layer into xylene is 0.01–0.25 g·m⁻¹. -2 ·s -1 .

[0223] The above dissolution rate (g·m -2 ·s -1 The measurements should be performed in the following order.

[0224] A cover film containing a support and a polymer layer is cut to a specified size (24 mm long × 120 mm wide) to obtain a test sample, and its mass (mass before immersion) is determined. The test sample is immersed in xylene (1200 mL) in a container for a constant time. After immersion, the cover film is gently removed from the container, and the xylene is thoroughly dried. The mass after drying (mass after immersion) is determined, and the difference between the mass before and after immersion is calculated. This difference is then calculated by dividing the mass difference by the area (m²) of the test sample. 2 The dissolution rate (g·m) was calculated from the immersion time (s). -2 ·s -1 ).

[0225] The impregnation time can be set appropriately to allow the polymer layer to remain in place without bending or dissolving, preferably 30 to 300 seconds, for example, 60 seconds. The drying temperature and time for the xylene can also be set appropriately, for example, 60 minutes at 150°C.

[0226] From the viewpoint of superior void suppression and sealing properties, the above-mentioned dissolution rate is preferably 0.03 to 0.25 g·m⁻¹. -2 ·s -1 More preferably, it is 0.05–0.20 g·m -2 ·s -1 More preferably, it is 0.05–0.15 g·m -2 ·s -1 .

[0227] The dissolution rate of the polymer layer can be controlled by adjusting the type of repeating units and weight-average molecular weight of the polymer contained in the polymer layer.

[0228] -Requirement 2-

[0229] The following is the requirement 2 related to the polymer layer mentioned above.

[0230] Requirement 2: When the viscosity of a xylene solution with a solid content of 20% obtained by dissolving the polymer layer in xylene at 25°C is set as X, 1 / X is 0.005~0.060cP. -1 .

[0231] The above 1 / X(cP) -1 The measurements should be performed in the following order.

[0232] The polymer layer is peeled off from a cover film containing a support and a polymer layer, and the mass of the resulting polymer layer is measured. The resulting polymer layer is dissolved in xylene to prepare a xylene solution with a solid content concentration of 20%. That is, the xylene solution contains a specified amount of the components constituting the polymer layer as solid components.

[0233] The viscosity X (cP) of the above xylene solution was measured using an E-type viscometer (VISCOMETER RE-85L, manufactured by Toki Sangyo Co., Ltd.). The measurement temperature was set to 25°C. The reciprocal of the measured viscosity X (cP) was taken to calculate 1 / X (cP). -1 ).

[0234] From the perspective of superior void suppression and tightness, the above 1 / X(cP) -1 The preferred value is 0.007–0.060 cP. -1 More preferably, it is 0.010 to 0.060 cP. -1More preferably, it is 0.015–0.050 cP. -1 .

[0235] The above 1 / X(cP) -1 It can be controlled by adjusting the type of repeating units in the polymer contained in the polymer layer and the weight-average molecular weight.

[0236] -Glass transition temperature-

[0237] The glass transition temperature of the polymer layer is not particularly limited, but is preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 65°C or higher. The upper limit is not particularly limited, and examples include 100°C, but is preferably 90°C or lower, and more preferably 80°C or lower.

[0238] The glass transition temperature of the polymer layer was obtained by peeling the polymer layer off the cover film and heating the polymer layer from -50°C to 100°C at a rate of 10°C / min using a differential scanning calorimeter (DSC).

[0239] The glass transition temperature can be adjusted, for example, according to the type and content of repeating units contained in the polymer.

[0240] -thickness-

[0241] The thickness of the polymer layer is not particularly limited, but is preferably 1 to 100 μm, more preferably 10 to 40 μm, and even more preferably 10 to 30 μm.

[0242] -Refractive index-

[0243] From an optical point of view when observed under a microscope, the refractive index of the polymer layer is preferably close to that of glass (refractive index 1.52 to 1.56), which is 1.45 to 1.56, more preferably 1.46 to 1.56, and even more preferably 1.47 to 1.56.

[0244] [Other layers]

[0245] The cover film can have layers other than the support and polymer layer.

[0246] As another example of a layer, a backing layer can be cited.

[0247] The backing layer can be placed on the back of the support (the side opposite to the side where the polymer layer is placed) for purposes such as preventing scratches on the surface of the cover film, more reliably preventing adhesion during storage at extremely high temperatures, or maintaining the curl balance of the cover film.

[0248] Examples of materials that can be used as backing layers include, for example, synthetic polymers with high glass transition temperatures such as polystyrene and polymethyl methacrylate, as well as gelatin.

[0249] The total thickness of the polymer layer and the support in the cover film is not particularly limited, but is preferably 250 μm or less, more preferably 200 μm or less, and from the viewpoint of operability and microscopic inspection, is even more preferably 150 μm or less. Regarding the lower limit, from the viewpoint of operability and sealing, such as being less prone to bending, it is preferably 50 μm or more.

[0250] <Manufacturing Method of Covering Film>

[0251] The method of applying the polymer layer to the support is not particularly limited, and examples include coating, casting, and transfer by a coating machine or sprayer. Among these, it is preferable to coat the support with a coating liquid prepared by dissolving the polymer in a solvent and then dry the coating film to form the polymer layer.

[0252] The solvent used in the coating solution is preferably a wettable type that can dissolve the polymer and does not repel it on the support. Examples of such solvents include toluene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, and xylene.

[0253] If a material capable of dissolving the surface of the support or a material containing plasticizers that can dissolve low molecular weight components is used as a solvent in the coating liquid, the polymer can penetrate into the surface layer of the support, thereby improving the adhesion between the polymer layer and the support, preventing the polymer layer from peeling off, and further suppressing the generation of chips during cutting.

[0254] Based on the above viewpoint, the coating liquid used in the formation of the polymer layer preferably contains a solvent selected from the group consisting of ethyl acetate and butyl acetate, and more preferably contains ethyl acetate.

[0255] The content of solvents selected from the group consisting of ethyl acetate and butyl acetate in the coating solution is not particularly limited. However, from the viewpoint of further suppressing the generation of chips when the cover film is cut, it is preferably 40% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, relative to the total mass of solvents contained in the coating solution. The upper limit is not particularly limited and may be 100% by mass or less, but from the viewpoint of further suppressing substrate deformation, it is preferably 90% by mass or less.

[0256] After forming a coating film by coating a coating liquid containing the above-mentioned polymer onto a support, it is preferable to dry the obtained coating film to remove the solvent from the coating film.

[0257] Examples of drying processes performed in the drying step include placing the coating film at room temperature (23°C) for a specified time (e.g., natural drying), air drying by blowing gas onto the coating film, and heated drying by heating the coating film using a heating element such as an oven, as well as combinations thereof. Preferably, at least one of air drying and heated drying is performed as the drying process, and more preferably, air drying and heated drying are combined.

[0258] The temperature of the gas used in the air-assisted drying process is not particularly limited, but is preferably 50–160°C, more preferably 80–140°C. The airflow velocity (wind speed) in the air-assisted drying process is not particularly limited, but is preferably 3–15 m / s, more preferably 5–10 m / s. The processing time for the air-assisted drying process is preferably 0.5–5 minutes. Examples of gases used in the air-assisted drying process include, for example, air and nitrogen.

[0259] The heating and drying temperature is not particularly limited, but is preferably 50–160°C. Furthermore, the heating time is preferably 0.5–5 minutes.

[0260] The method for forming a polymer layer containing a silane coupling agent is not particularly limited. For example, the following methods can be described: a first method in which a silane coupling agent is pre-added to a coating liquid for forming a polymer layer, a coating liquid containing a polymer and a silane coupling agent is coated on a support, and the coating film is dried to form a polymer layer; a second method in which a coating liquid prepared by dissolving a silane coupling agent in a solvent is coated on the surface of a polymer-containing coating film formed on a support, and the coating film is dried to form a polymer layer; and a third method in which a coating liquid containing a polymer and a coating liquid prepared by dissolving a silane coupling agent in a solvent are simultaneously coated (multilayer coating) on ​​a support, and the coating film is dried to form a polymer layer.

[0261] In the first to third methods described above, when the silane coupling agent is used as a raw material, the hydrolysis and condensation reactions of the silane coupling agent can be carried out during its formation.

[0262] From the viewpoint of being able to utilize silane coupling agents in small quantities and efficiently, the second and third methods described above are preferred. In the polymer layers containing silane coupling agents formed by the second and third methods described above, the silane coupling agents tend to be unevenly distributed on the surface of the polymer layer on the side opposite to the support.

[0263] As a solvent for the coating liquid prepared by dissolving silane coupling agents in the solvents used in the second and third methods described above, there are no particular limitations as long as the solvent can dissolve the silane coupling agents. For example, solvents that can dissolve the polymers described above can be cited. Among these, ethyl acetate is preferred from the viewpoint of improving adhesion.

[0264] <Uses>

[0265] The covering film of the present invention can be used as a covering film for covering a subject on a substrate. It is preferably used for preparing specimens for microscopic observation, and is more preferably suitable for microscopes equipped with an automatic sealing device.

[0266] The substrate for laminating the cover film can be glass or a film-shaped substrate (such as resin).

[0267] Example

[0268] The present invention will now be described in more detail with reference to embodiments.

[0269] Regarding the materials, quantities, proportions, processing content, and processing order shown in the following embodiments, appropriate modifications can be made as long as they do not depart from the spirit of the invention. Therefore, the scope of the invention should not be limited by the embodiments shown below.

[0270] <Making of the Covering Film>

[0271] The cover film is made by coating a support with a coating liquid containing a polymer. The detailed process is explained below.

[0272] [Construction of Support 1]

[0273] The support 1 is made according to the following method.

[0274] (Preparation of concentrated cellulose acylate solution from the core layer)

[0275] The following components are placed in a mixing tank and the mixture is stirred to dissolve the components, thereby preparing a cellulose acetate solution A2a for use as a core layer cellulose acylation concentrate.

[0276] 100 parts by weight of cellulose acetate with a degree of acetyl substitution of 2.88

[0277] • A mixture comprising the aliphatic carboxylic acid ester oligomer (oligomer A1) described below and a compound represented by the following formula (A-3), wherein the mass ratio of oligomer A1 to the compound represented by formula (A-3) is 4:1.

[0278] 430 parts by weight of dichloromethane

[0279] ·Methanol 64 parts by weight

[0280] The amount of the above-mentioned mixture contained in the cellulose ester solution A2a is adjusted such that the total content of polyester A and the compound represented by formula (A-3) contained in the support 1 prepared by the following method using cellulose ester solution A2a and cellulose ester solution A2b described below is 12.3%.

[0281] [Chemical Formula 1]

[0282]

[0283] Oligomer A1 is an aliphatic carboxylic acid ester oligomer, a condensation product of 1,2-cyclohexyldicarboxylic acid and ethylene glycol, with a terminal structure in which the hydrogen atoms of the two terminal hydroxyl groups are replaced by cyclohexyl groups (terminal capping). The number average molecular weight of oligomer A1 is 850.

[0284] (Preparation of concentrated outer cellulose acylate solution)

[0285] To prepare cellulose acetate solution A2b, which can be used as an outer layer cellulose acylate concentrate, 10 parts by mass of a matting agent solution B2 having the following composition are added to 90 parts by mass of the above cellulose acetate solution A2a (core layer cellulose acylate concentrate).

[0286] -Composition of matting agent solution B2-

[0287] • 2 parts by mass of silica particles (AEROSIL R972, manufactured by NIPPON AEROSIL CO., LTD.) with an average particle size of 20 nm.

[0288] 76 parts by weight of dichloromethane

[0289] ·Methanol 11 parts by weight

[0290] · 1 part by mass of cellulose acetate solution A2a (concentrated cellulose acylate from the core layer)

[0291] (Construction of Support 1)

[0292] The above-mentioned core layer cellulose acylate concentrate and the above-mentioned outer layer cellulose acylate concentrate were filtered using 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 concentrate and the filtered outer layer cellulose acylate concentrate were then simultaneously cast from the casting port of a belt casting machine onto the surface of a roller with a surface temperature of 20°C, forming a laminated film in which the core layer is sandwiched between two outer layers.

[0293] Next, the laminated film is peeled off from the rollers, and the two ends of the laminated film in the width direction are fixed with tenter frame clamps. The laminated film, fixed with tenter frame clamps, is stretched along the width direction at an elongation ratio of 1.1 times while being dried. Then, the laminated film is further dried by conveying it between the rollers of a heat treatment device to produce support 1.

[0294] The thickness of support 1 is 118 μm, and support 1 is equivalent to a transparent support (Re < 200 nm, Rth: -50 ~ 50 nm).

[0295] Among the hydrolysates of the ester compounds contained in support 1, the lowest pKa is 4.0, which is possessed by at least one hydrolysate of the compound represented by formula (A-3) above. Therefore, support 1 does not contain any specific ester compound.

[0296] [Polymer Synthesis]

[0297] Polymer 1 used in Example 1 was synthesized in the following order.

[0298] A mixture of 38 parts by mass of toluene and 25 parts by mass of ethyl acetate was added to a solution containing 60 parts by mass of ethyl acrylate, 240 parts by mass of methyl methacrylate, 98 parts by mass of toluene, 66 parts by mass of ethyl acetate, and 0.7 parts by mass of azoisobutyronitrile (ARI) for 2 hours at 80°C under a nitrogen atmosphere. The resulting mixture was then reacted at 80°C for another 2 hours. Next, 1.2 parts by mass of ARI were added to the mixture, and polymerization was carried out at 90°C to produce a polymer with a specified weight-average molecular weight, yielding polymer solution 1 containing polymer 1. The weight-average molecular weight (Mw) of the obtained polymer 1 was 100,000.

[0299] The polymers used in each embodiment and comparative example are shown in the table below. The ratios of the monomers are by weight, and to achieve these ratios, the polymers were synthesized using the monomers in the order described above.

[0300] However, in Comparative Example 3, a polymer was used that was a mixture of ARON S-1017 and ARON S-1030C in a weight ratio of 2:3.

[0301] [Preparation of coating solution]

[0302] The polymer coating liquid 1 used in Example 1 was obtained in the following order.

[0303] The polymer solution 1 was prepared by mixing ethyl acetate and toluene with a polymer solids concentration of 23% by mass and a ratio of ethyl acetate to all solvents of 57% by mass to obtain polymer coating solution 1.

[0304] Furthermore, the silane coupling agent coating solution 1 used in Example 15 was obtained by mixing 0.11 parts by weight of silane coupling agent KBM403 (γ-glycidoxypropyltrimethoxysilane) (manufactured by Shin-Etsu Chemical Co., Ltd.) with 109.89 parts by weight of ethyl acetate.

[0305] In other embodiments and comparative examples, the polymer coating liquid was also obtained in the above order.

[0306] [Formation of the polymer layer]

[0307] The cover film 1 used in Example 1 was obtained by forming a polymer layer on a support in the following order.

[0308] A polymer coating liquid 1 is applied to the aforementioned support 1 using an applicator to form a coating film. The amount of polymer coating liquid 1 applied is adjusted so that the thickness of the polymer layer after drying is 19 μm. The formed coating film is then subjected to a drying process involving blowing hot air at 100°C at a speed of 3.2 m / s for 2 minutes, followed by oven drying to evaporate the solvent, thus producing a cover film 1 consisting of the support 1 and a polymer layer containing the polymer 1. The total film thickness of the cover film 1, including the support 1 and the polymer layer, is 137 μm.

[0309] The covering films used in other embodiments and comparative examples were also obtained in the order described above.

[0310] In addition, in the coating process of the polymer layer used in Example 15, a coating film was formed by coating polymer coating liquid 15 and silane coupling agent coating liquid 1 by extrusion multilayer coating. The coating amount of polymer coating liquid 15 was adjusted so that the thickness of the polymer layer after drying was 19 μm. The coating amount of silane coupling agent coating liquid 1 was adjusted so that the coating concentration of silane coupling agent relative to the surface area of ​​the transparent support was 13.5 mg / m². 2 The amount.

[0311] <Measurement and Evaluation Methods>

[0312] [Glass transition temperature of the polymer layer]

[0313] The polymer layer was peeled off from the cover film, and the polymer layer was heated from -50°C to 100°C at a rate of 10°C / min using a differential scanning calorimeter (DSC) to determine the glass transition temperature (Tg (°C)) of the sample.

[0314] [Fracture toughness value]

[0315] A cubic indenter was pressed into the polymer layer with a load of 20 mN using a nanoindenter (iNano, G200 manufactured by TOYO Corporation), and the fracture toughness value K was calculated using the method described above. IC (MPa·m 0.5 In Table 1 described below, the fracture toughness values ​​K are listed according to the following categories. IC (MPa·m 0.5 ).

[0316] • A: Fracture toughness value K IC 1.0 MPa·m0.5 above

[0317] • B: Fracture toughness value K IC 0.2 MPa·m 0.5 Above and less than 1.0 MPa·m 0.5

[0318] • C: Fracture toughness value K IC Less than 0.2 MPa·m 0.5

[0319] [Dissolution speed]

[0320] The dissolution rate (g·m) was calculated according to the method described in part 1 of the above requirements. -2 ·s -1 ).

[0321] Specifically, the covering film was cut into pieces 24 mm long and 120 mm wide, and the cut pieces were immersed in 1200 mL of xylene in a stainless steel container for 60 seconds. The xylene was dried at 150°C for 60 minutes. The difference between the mass before and after immersion was divided by the area of ​​the covering film (m²). 2 The dissolution rate (g·m) was calculated from the immersion time (s). -2 ·s -1 ).

[0322] [1 / X (reciprocal of viscosity)]

[0323] Calculate 1 / X(cP) according to the method described in part 2 of the above requirements. -1 ).

[0324] [Dandruff-resistant]

[0325] After drying the covering film in an oven at 120°C for 30 minutes to ensure complete drying, a sensory evaluation was performed on its condition when cut with a push-cutting machine, based on the following criteria. For the evaluation of anti-shaving properties, a rating of B or higher is preferred in practical applications.

[0326] • A: Almost no chips were observed, and almost no peeling or lifting of the polymer layer was observed on the cut surface.

[0327] • B: Almost no chips were observed, but a slight lifting of the polymer layer was observed on the cut surface.

[0328] •C: There are a large number of chips, and a large amount of polymer layer peeling and lifting are present on the cut surface.

[0329] [Porosity suppression]

[0330] The SCA-Film-J0 automated sealing device (manufactured by SAKURA SEIKI Co., Ltd.) is used to bond and seal a substrate (glass slide) with a cover film to obtain a sealed substrate. Xylene is used as the sealing solution. The glass slide size is set to 26mm × 76mm, and the cover film size is set to 24mm × 50mm.

[0331] After the encapsulated substrate was left to stand for one day, visual inspection was performed to confirm the presence of encapsulation defects. If two or more defects larger than 1 mm in diameter (such as air bubbles or localized peeling) were found in the encapsulated substrate, it was determined that encapsulation defects had occurred in the encapsulated substrate. The encapsulation defect rate (%) was calculated by dividing the number of encapsulated substrates with encapsulation defects by the total number of encapsulated substrates.

[0332] The lower the rate of filling defects, the better the void suppression performance. In practical applications, the rate of filling defects is preferably less than 8.0%.

[0333] [Seamlessness]

[0334] The aforementioned encapsulated substrate was dried in an oven at 50°C for one week. After drying, the peeling of the cover film was visually observed within the encapsulated substrate. Adhesion was evaluated according to the following categories based on the area ratio of the peeled portions. A rating of B or higher is preferred for practical use.

[0335] • A: The area of ​​the stripped portion is less than 5%.

[0336] • B: The area affected by the peeling is more than 5% but less than 30%.

[0337] • C: The area of ​​the stripped portion is more than 30%.

[0338] <Results>

[0339] Table 1 shows the structure of the covering film used in each embodiment and comparative example, as well as the measurement and evaluation results.

[0340] In Table 1, the weight-average molecular weight column “Nk” represents N×1000, for example, “100k” means 100000.

[0341] Additionally, in the table, the following abbreviations are used for monomers.

[0342] ·EA: Ethyl acrylate

[0343] MMA: Methyl methacrylate

[0344] BMA: n-Butyl methacrylate

[0345] MEMA: 2-Methoxyethyl Methacrylate

[0346] EMA: Ethyl methacrylate

[0347] iBMA: Isobutyl methacrylate

[0348] ·tBMA: tert-butyl methacrylate

[0349] BnMA: Benzyl methacrylate

[0350] ·2EHMA: 2-Ethylhexyl methacrylate ·LMA: Lauryl methacrylate

[0351] ·2EHA: 2-Ethylhexyl acrylate

[0352] CHMA: Cyclohexyl methacrylate

[0353]

[0354] The results in Table 1 confirm that the covering film of the present invention achieves the desired effect.

[0355] Comparison of Examples 5 and 13 with other examples confirmed that the dissolution rate of xylene was 0.01–0.15 g·m⁻¹. -2 ·s -1 Furthermore, the aforementioned 1 / X ranges from 0.010 to 0.060 cP. -1 Under these conditions, it exhibits excellent void suppression and sealing properties.

[0356] A comparison of Example 4 with Examples 13 and 14 confirmed that, when the weight-average molecular weight of the polymer is 50,000 to 140,000, either the anti-chip properties or the void suppression properties are excellent.

[0357] A comparison of Examples 3, 5, and 12 with Examples 1, 2, 4, 6 to 11, and 16 confirms that when the glass transition temperature of the polymer layer is above 60°C, the void suppression and sealing properties are excellent.

[0358] Comparison of Examples 4, 6, 7 and 16 with other examples confirmed that when the polymer contains repeating units derived from ethyl acrylate and repeating units derived from ethyl methacrylate, the void suppression and anti-smear properties are excellent.

Claims

1. A covering film for covering an object to be examined on a substrate. The covering film has a support and a polymer layer containing a polymer. The fracture toughness of the polymer layer is 0.2 MPa·m. 0.5 above, The polymer is either polymer A or polymer B. Polymer A is an acrylic resin containing repeating units derived from ethyl acrylate and repeating units derived from methyl methacrylate. In polymer A, the total content of the repeating units derived from ethyl acrylate and the repeating units derived from methyl methacrylate is 90% or more by mass relative to the total repeating units of the acrylic resin, the content of the repeating units derived from ethyl acrylate is 15-25% by mass relative to the total repeating units of the acrylic resin, and the content of the repeating units derived from methyl methacrylate is 70-80% by mass relative to the total repeating units of the acrylic resin, excluding cases where the content of the repeating units derived from methyl methacrylate is 70% by mass relative to the total repeating units of the acrylic resin. The acrylic resin, which is polymer A, has a weight-average molecular weight of 50,000 to 140,000. Polymer B is an acrylic resin comprising repeating units derived from ethyl acrylate, repeating units derived from methyl methacrylate, and repeating units derived from a third monomer. In polymer B, the total content of the repeating units derived from ethyl acrylate, the repeating units derived from methyl methacrylate, and the repeating units derived from the third monomer is 90% by mass or more relative to the total repeating units of the acrylic resin; the content of the repeating units derived from ethyl acrylate is 15-25% by mass relative to the total repeating units of the acrylic resin; and the content of the repeating units derived from methyl methacrylate is 50-70% by mass relative to the total repeating units of the acrylic resin. The acrylic resin, which is polymer B, has a weight-average molecular weight of 45,000 to 145,000. The third monomer is n-butyl methacrylate or one selected from the group consisting of 2-methoxyethyl methacrylate, ethyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and lauryl methacrylate, and satisfies either (i) or (ii) below: (i) When the third monomer is n-butyl methacrylate, the content of the repeating unit derived from the third monomer is 10-25% by mass relative to the total repeating units of the acrylic resin; (ii) When the third monomer is selected from the group consisting of 2-methoxyethyl methacrylate, ethyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and lauryl methacrylate, the content of the repeating unit derived from the third monomer is 10-35% by mass relative to the total repeating units of the acrylic resin. The support has an in-plane retardation of less than 1000 nm at a wavelength of 590 nm. The covering film satisfies requirements 1 and 2. Requirement 1: The dissolution rate of the polymer layer to xylene is 0.01–0.20 g·m⁻¹. -2 ·s -1 , Requirement 2: The polymer layer is dissolved in xylene to obtain a xylene solution with a solid content concentration of 20%. When the viscosity of this xylene solution at 25°C is set as X, 1 / X is 0.005~0.060cP. -1 .

2. The covering film according to claim 1, wherein, The dissolution rate of the xylene is 0.01–0.15 g·m⁻¹. -2 ·s -1 The 1 / X is 0.010 to 0.060 cP. -1 .

3. The covering film according to claim 1 or 2, wherein, The glass transition temperature of the polymer layer is above 60°C.

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