JPH04270649A - Release film - Google Patents

Abstract

PURPOSE:To provide a release film which exhibits singnificantly low peel-off strength and can maintain this low peel-off strength, if thermally treated for a long time. CONSTITUTION:This release film consists of a porous layer which contains fluorine oil provided at least, on one surface of a film support. The film is best suited as a release film for pressure sensitive adhesive.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a release film,
In particular, the present invention relates to a release film that is optimal for use as a release film for an adhesive layer.

0002

BACKGROUND OF THE INVENTION Various types of release films (release films for adhesives) have been known. For example, a film support coated or laminated with release silicone or fluorine resin, a film support coated with fluorine vinyl/
Products coated or laminated with a specific silicone vinyl/vinyl copolymer (Japanese Unexamined Patent Publication No. 61-228078),
Fluorine resin/Specific silicone resin/
Products coated or laminated with a mixture of specific siloxanes (Japanese Unexamined Patent Publication No. 58-21491), and adhesive structures made of specific fluorosilicone coated or laminated on a film support (Japanese Patent Laid-open No. 1-154740) etc. are known.

0003

[Problems to be Solved by the Invention] However, in the conventional release film as described above, the peeling force when peeling the release film from the adhesive layer etc. may be too high depending on the application. A release film with strong peeling strength is desired. Further, when a pressure-sensitive adhesive layer is provided on a coating layer on a film support as described above and heat-treated for a long time, there is also a problem that the peeling force of the release film may become too high. For example, silicone rubber is sometimes laminated on an adhesive tape and then subjected to crosslinking heat treatment, but in such a case, the peeling force of the release film may become too high.

The present invention solves these problems and provides a release film that exhibits excellent low peeling force and can maintain this low peeling force even when subjected to long-term heat treatment. The purpose is to

[0005]

[Means for Solving the Problems] The release film of the present invention that meets this objective has a film support having at least one side of the film support.
It consists of a porous layer and a fluorine-based oil encapsulated in the porous layer.

The material of the film support of the present invention is not particularly limited, and various known plastic films can be used. Typical examples include polyester film,
Polycarbonate film, triacetyl cellulose film, cellophane film, polyamide film, polyimide film, polyphenylene sulfide film,
Examples include polyetherimide film, polyether sulfone film, aromatic polyamide film, polysulfone film, and polyolefin film. However, from the viewpoint of mechanical properties, thermal properties, cost, etc., it is preferable to use polyester film, polycarbonate film, and polyphenylene sulfide film.
Among these, polyester film is particularly preferred.

[0007] Polyester film is a general term for polymer films having ester bonds as the main bond chains in the main chain, and particularly preferred polyesters include polyethylene terephthalate, polyethylene 2,6-naphthalate, and polyethylene α,β-bis(2). -chlorophenoxy)ethane 4,4'-dicarboxylate, polybutylene terephthalate, etc. Among these, polyethylene terephthalate (hereinafter sometimes abbreviated as PET) is selected from comprehensive consideration of quality, economy, etc. is most preferred. PET also contains known additives, such as heat stabilizers, oxidation stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, and release agents. A molding agent, an antistatic agent, a nucleating agent, etc. may be added.

[0008] The above PET film is unoriented, uniaxially oriented,
Although any biaxially oriented PET film can be used, a biaxially oriented PET film is preferred because of its excellent mechanical strength. Biaxially oriented PET film is made by stretching an unstretched PET sheet or film by about 2.5 to 5 times in the so-called biaxial directions (longitudinal direction and width direction), and biaxially oriented by wide-angle X-ray diffraction. Refers to a pattern of orientation.

[0009] If the PET film has been subjected to a surface treatment using a known method, that is, a corona discharge treatment (in air, nitrogen, carbon dioxide, etc.) or an adhesion treatment,
It can be used more preferably because it improves adhesion with the porous layer, water resistance, solvent resistance, etc. Various known methods can be used for the adhesive treatment, and the above-mentioned treatment can be applied to films coated with various adhesive agents such as acrylic, urethane, and polyester during the film manufacturing process, or to films after uniaxial or biaxial stretching. Those coated with various easy-to-adhesive agents such as the following can be suitably used.

The thickness of the plastic film used as the film support is not particularly limited, and can be set to an appropriate thickness in the range of about 1 to 500 μm, depending on, for example, the stiffness required of the release film. .

[0011] The surface roughness and haze of the film support are also not particularly limited, and depend on the thickness of the porous layer, the adhesion strength and separation required between the porous layer and the film support, which will be described later. It may be set appropriately to a desired value, taking into consideration the transparency required for the mold film.

In the release film of the present invention, a porous layer is provided on at least one side of the film support. The porous layer as used in the present invention has a layer structure with a large number of voids inside and on the surface of the layer. It is particularly preferable that the voids be so-called through holes that communicate with the outside in the porous layer from the viewpoint of absorption of fluorine-based oil, which will be described later.

In the present invention, the peak pore size in the pore size distribution curve of the porous layer is 0.06 to 2.0 μm, preferably 0.08 to 1.0 μm, more preferably 0.10 μm.
~0.5 μm. The peak pore size of the pore size distribution curve is 0.
If it is less than 0.06 μm, the absorption of fluorine-based oil is insufficient, and the peak pore diameter in the pore size distribution curve is 2.0 μm.
If it exceeds 0 μm, the surface smoothness will be reduced and the adhesion to the adhesive layer etc. will be reduced.

[0012] Also, it is desirable that the pore area ratio is in the range of 20 to 85%, preferably 30 to 75%, and more preferably 35 to 65%. If the pore area ratio is less than 20%, the fluorinated oil The absorbency tends to decrease, and if it exceeds 85%, the pores tend to be partially connected, which tends to cause bleeding and the like.

When observed from the surface of the porous layer, the pores are independent, and their circularity r (=b/a,
It is particularly preferable that the diameter (a: long axis diameter of the hole, b: short axis diameter of the hole) is from 1 to 5, since there is little bleeding of the fluorine-based oil. This roundness is an average value of 1000 or more measurement points, and is usually determined using an image analyzer.

[0014] Furthermore, it is desirable that the spread of the pore size distribution in the pore size distribution curve is small, that is, a sharp pore size distribution, which accounts for at least 50%, preferably at least 60%, of the number of pores.
More preferably, 70% or more of the pore size is within ±30% of the peak pore diameter.

Next, in the present invention, when the center line average roughness of the porous layer is 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.1 μm or less, the impregnability of fluorine oil is improved. preferable.

Furthermore, the surface of the porous layer in the present invention has 5/40 μm or more, preferably 7/40 μm or more undulations with a height of 0.2 μm or more, preferably 0.3 μm or more, more preferably 0.4 μm or more. 40μm or more, more preferably 1
It is desirable to have 0 pieces/40 μm or more. Height is 0.
If the number of undulations of 2 μm or more is less than 5/40 μm, the absorption rate of fluorine-based oil is slow and workability is reduced.

Furthermore, the waviness index of the surface of the porous layer is 0.0.
35-0.3 μm, preferably 0.045-0.2 μm
, more preferably from 0.055 to 0.13, since the absorption rate of fluorine-based oil is improved.

As described above, the porous layer of the film support having a porous layer is impregnated with and encapsulated in the fluorine oil. Examples of solvents for fluorine-based oils include alcohols, carboxylic acid esters, ketones, aliphatic hydrocarbons, alicyclic or aromatic hydrocarbons, halogenated hydrocarbons, fluorine-based solvents, and mixtures thereof. It will be done. Among these, fluorine-based solvents are the best in terms of solubility of fluorine-based oils, and are also the best in terms of obtaining the low peeling force aimed at in the present invention.

Typical fluorinated oils include perfluoropolyether fully fluorinated oils, and specifically, for example, the following compounds 1, 2, 3, and 4.
The main component is a compound represented by the formula 5 or the like.

[0020]

[Chemical formula 1]

[0021]

[Case 2]

[0022]

[Chemical formula 3]

[0023]

[C4]

[0024]

[Chemical formula 5] (The values of n and m in the above chemical formulas 2, 3, 4, and 5 are 1
~500).

Among these, compounds represented by the following formula 6 are preferred in the present invention from the viewpoint of release properties.

[0026]

[C6]

The fluorine-based oil-containing porous layer of the release film of the present invention may contain known additives, such as antifoaming agents, coating properties improvers, thickeners, and antistatic agents, to the extent that they do not impede the purpose of the present invention. , an antioxidant, an ultraviolet absorber, a curing agent, a dye, etc., or fine particles made of an inorganic or organic compound as a lubricant.

The release film of the present invention is particularly effective as a release film for adhesives that is peeled off from the adhesive layer. The target adhesive layer is not particularly limited, but (1)
Polymers such as natural rubber, styrene-butadiene rubber, polyisobutylene, polychloroprene, polyacrylate rubber, polyvinyl ether rubber, (2) polyvinyl chloride, copolymer of vinyl chloride and vinyl acetate, polyvinyl butyral, Mixtures of polymeric substances and plasticizers such as chlorinated rubber and hydrochloric acid rubber; (3) Tackifiers such as rosin, rosin esters, coumaron resins, terpene resins, hydrocarbon resins, and oil-soluble phenolic resins; (4) Fillers. agent,
Various additives such as pigments, anti-aging agents, stabilizers, etc.
Typical examples include various combinations of 1) to (4) and silicone pressure-sensitive adhesives obtained by combining silicone resin and silicone rubber to impart special properties.

Next, the method for manufacturing the release film of the present invention will be described, but the method is not necessarily limited thereto.

First, the porous layer of the present invention is obtained by mixing a water-dispersible polymer and a specific colloidal silica in a specific range, and applying and drying the mixed solution. Here, water-dispersible polymers can be water dispersions of various polymers, but specific examples include acrylic polymers, ester polymers, urethane polymers, olefin polymers, vinylidene chloride polymers, and epoxy polymers. , amide polymers, and modified products and copolymers thereof. Acrylic polymers and urethane polymers are preferably used because they have a sharp pore size distribution and a large pore area, and acrylic polymers are particularly preferred from the viewpoint of mechanical stability and strength of the coating film.

The above-mentioned polymer used in the present invention is preferably dispersed in water and has a particle shape. If the polymer does not have a particle shape, that is, if it is a water-soluble polymer or a polymer dissolved in an organic solvent, it is difficult to make it porous. Although the particles are preferably dispersed as primary particles, they do not necessarily have to be dispersed as primary particles, and may include secondary agglomerated particles.

Acrylic polymers suitable as the porous layer-forming polymer of the present invention include at least 40 mol% of acrylic monomers and/or methacrylic monomers and their ester-forming monomers, and acrylic monomers having various functional groups, such as acrylic monomers. acid, methacrylic acid,
Alkyl acrylate, alkyl methacrylate (alkyl groups include methyl group, ethyl group, n-propyl group,
isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, lauryl group, stearyl group, cyclohexyl group, phenyl group, benzyl group, etc.), and 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate , 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylolmethacrylamide, N-methylolacrylamide, N,N-di Amide group-containing monomers such as methylol acrylamide, N-methoxymethylmethacrylamide, and N-phenylacrylamide; amino group-containing monomers such as N,N-diethylaminoethyl methacrylate and N,N-diethylaminoethyl acrylate; and epoxies such as glycidyl acrylate and glycidyl methacrylate. Group-containing monomers, salts of acrylic acid, methacrylic acid (sodium salts, potassium salts,
ammonium salts, etc.), and these can also be used in combination with various monomers. Examples of various monomers include epoxy group-containing monomers such as allyl glycidyl ether, styrene sulfonic acid, vinyl sulfonic acid, and their salts (sodium salt, potassium salt,
Monomers containing sulfonic acid groups or their salts such as ammonium salts), monomers containing carboxyl groups or their salts such as crotonic acid, itaconic acid, maleic acid, fumaric acid, and their salts, maleic anhydride, anhydride Monomers containing acid anhydrides such as itaconic acid, vinyl isocyanate, allyl isocyanate, styrene, vinyl methyl ether, vinyl ethyl ether, vinyl tris alkoxysilane, alkyl maleic acid monoester,
Alkyl fumaric acid monoester, acrylonitrile,
Examples include methacrylonitrile, alkyl itaconic acid monoester, vinyl chloride, vinyl acetate, and vinylidene chloride. The above-mentioned monomers are copolymerized using one type or two or more types.

Water dispersion 20 of the above-mentioned water-dispersible polymer
The colloidal silica to be mixed with 90 parts by weight is preferably the following silica because it causes waviness in the porous layer. In other words, spherical colloidal silica is connected like beads (
Porous membranes with a undulating structure on the surface when using a long-chain structure in which multiple spherical colloidal silicas are connected in a chain, or when connected silicas are branched and/or bent. can be obtained. The above-mentioned colloidal silica is made by connecting primary particles of spherical silica with metal ions of divalent or higher valence intervening, and at least 3 or more particles, preferably 5 or more particles, and more preferably 7 or more particles. It also includes particles connected in a bead shape that are branched and/or bent.

[0034] In addition, colloidal silica and other inorganic particles,
For example, they may be composite or mixed particles with alumina, ceria, titania, etc., or they may be connected with these particles interposed therebetween. The intervening metal ion is preferably a divalent or higher metal ion, such as Ca2+, Zn2+
, Mg2+, Ba2+, Al3+, Ti4+, etc. In particular, when Ca2+ is used, it is suitable for creating colloidal silica connected and branched in a bead shape. In addition, the primary particle size of colloidal silica is 5 nm to 100 nm.
, preferably 7 nm to 50 nm, more preferably 8 nm
When it is 30 nm, it is preferable in terms of increasing the pore-forming property and the pore area ratio. Furthermore, the waviness of the porous layer occurs when silica particles are connected and branched in a beaded pattern, and the more primary particles of connected silica, the better, but usually 3 or more and less than 100, preferably 3 to 100. 5 or more 5
It is desirable that the number is less than 0, more preferably 7 or more and less than 30. If the number is less than 2, the expression of waviness is insufficient, and if the number is 100 or more, the content of connected and/or branched silica particles in the form of beads in the porous coating film is 3 to 80.
The amount is preferably 10 to 70 parts by weight, more preferably 20 to 60 parts by weight. If the content is less than 3 parts by weight, there is no porosity forming property and no waviness occurs, so the absorption rate of the fluorine-based oil tends to be slow. If it is contained in an amount exceeding 80 parts by weight, the pore formation property decreases, the pore diameter decreases, and the pore area ratio decreases, resulting in a decrease in the absorption rate of the fluorinated oil and the strength of the coating film. Therefore, disadvantages such as dust generation during cutting are likely to occur.

The porosity changes depending on the ratio of the average particle diameter of the water-dispersible polymer and the colloidal silica, and the average particle diameter of the colloidal silica needs to be smaller than the average particle diameter of the water-dispersible polymer. It cannot be made porous. In the case of the colloidal silica connected in the form of beads, the length in the minor axis direction of the connected particles observed with an electron microscope is defined as the particle diameter, and the average value of 100 measurement lengths is defined as the average particle diameter.

The average particle diameter ratio of water-dispersible polymer/colloidal silica is 2/1 to 1000/1, preferably 5/1.
The ratio is particularly preferably from 10/1 to 200/1, more preferably from 10/1 to 200/1, from the viewpoint of forming pores in the porous layer. In particular, in the relationship between the average particle diameter (a1) of colloidal silica and the average particle diameter (a2) of the water-dispersible polymer, the average particle diameter ratio is within the above range, and the water-dispersible polymer particles 1
The minimum number of colloidal silica particles required to completely cover the surface of
31/2 ・a1 2 )], the amount per water-dispersible polymer particle is in the range of 0.3α to 10α, preferably 0.5α to 6α, more preferably 0.7α to 3α. It is preferable that the effects of the present invention are more clearly expressed when the blending ratio is adjusted.

[0037] Any known coating method can be used, such as gravure coating, reverse coating, bar coating, kiss coating, and die coating.

The thickness of the porous layer is not particularly limited, but is usually 0.
．． The thickness is preferably about 1 to 50 μm, preferably about 1 to 30 μm, and more preferably about 3 to 20 μm. If the thickness is too thin, the ability to absorb fluorine-based oil will be insufficient, and if it is too thick, the strength of the coating film will tend to be insufficient.

The porous layer of the surface-porous film thus obtained as a film support is impregnated with a fluorine oil having the composition as described above. The amount of impregnation is preferably 20% by volume or more of the voids in the porous layer. This impregnation method is not particularly limited, and any known method can be used.

[0040]

[Effects of the Invention] In the release film of the present invention, the porous layer formed on the film support is impregnated with fluorine oil, so the following properties can be achieved without deteriorating the properties of the film support. We were able to obtain excellent results.

First, the release film of the present invention has excellent adhesion between the film support and the porous layer, and the porous layer has excellent release properties. In particular, it has excellent mold releasability against adhesives.

Furthermore, the release film of the present invention is capable of maintaining excellent mold release properties even when subjected to heat treatment for a long time, and has excellent handling properties during post-processing. There is.

Since the release film of the present invention has the above-mentioned excellent properties, it can be used in various applications where release properties are required, such as adhesive tapes, label separators, resin molded sheets, rubber molded sheets, etc. It can be applied to a wide range of applications, and is particularly suitable as a separator for adhesives for labels. Among adhesives, it is particularly suitable for silicone adhesives.

[Measurement and Evaluation Method] Characteristic values in the present invention are based on the following measurement method and evaluation criteria. (1) Mark the pores on an electron microscope surface photograph of the pore size distribution curve taken at 10,000 times magnification, and perform image processing using a QUant:met-720 image analyzer (manufactured by Image Analyzing Computer Co., Ltd.) to calculate each pore size. The area between the minimum pore diameter and the maximum pore diameter when converted into a perfect circle was divided into units of 10 mμ, and the number of holes in each divided portion was measured. From these measured values, a pore size distribution curve was drawn with the vertical axis as the number of pores per unit area and the horizontal axis as the pore diameter, and the pore diameter at the peak was determined.

(2) Pore area ratio The area occupied by the pores per unit area was calculated from the above pore size distribution curve using the following equation 1.

[0031]

[Math 1]

In Equation 1 above, each symbol represents the following. ai: Average pore diameter in each division when the pore diameter within the measurement area is divided into 10 mμ units ni: Number of pores in each division when the pore diameter within the measurement area is divided into 10 mμ units A: Measurement area

(3) Center line average roughness Cutoff 0.0 according to JIS-B-0601-1976.
Measured at 25mm.

(4) Scanning electron microscope ESM-32 with waviness height, waviness number, and waviness index cross-section measuring device PMS-1
00 (manufactured by Elionix Co., Ltd.) to measure the uneven shape of the surface observed at a magnification of 3000 times, and from the surface roughness curve, the nearest adjacent troughs and troughs of the peaks with a height of 0.2 μm or more were measured. When the sections were connected with a straight line, the number of peaks within a measurement length of 40 μm was measured, and the number was defined as the number of undulations with a undulation height of 0.2 μm or more. Also, from the above surface roughness curve, the cutoff is 10
The center line average roughness (Ra10) in μm and the center line average roughness (Ra1) at a cutoff of 1 μm were determined, and the waviness index was calculated using the following formula. Waviness index (μm)=Ra10−Ra1 The above-mentioned waviness index and waviness index were taken as average values of 50 measurement points.

(5) Porous layer coating strength: A 1 mm square crosscut was made on the surface of the porous layer, and a 90° peel test was performed using cellophane adhesive tape manufactured by Nichiban Co., Ltd., and the determination was made from the residual rate of the porous layer. did. Survival rate 80% or more: [○] Survival rate 80
Less than %: [×]

(6) Average particle diameter COULTER, N4 type, submicron particle analyzer (
(manufactured by Nikkaki Co., Ltd.), the particle diameter was determined by a laser light scattering method and was taken as the average value of 10 measurements. If measurement could not be performed by this method, it was determined from an electron micrograph at a magnification of 200,000 times.

(7) Average particle number From the average particle diameter a determined above and the particle specific gravity ρ determined by the density gradient method, the average number of particles contained in 1 ml of the V weight % aqueous dispersion is determined by the following equation 2. Ta.

[0038]

[Math 2]

(8) Peeling force Silicone adhesive tape with a width of 18 mm on the porous layer according to JIS-Z0237: T4080 (Sony Chemical Co., Ltd.
Co., Ltd.) and crimped it with a hand roller by reciprocating it with a load of 2 kg. Next, it was tested using a tensile tester at 25°C and 55RH% atmosphere at a peel angle of 180° and a tensile speed of 0. Peel force was determined by peeling the silicone adhesive tape from the coating layer at .05 m/min.

(9) Peeling force after heat treatment The sample obtained in (8) above was subjected to aging treatment at 100° C. for 120 hours, and then evaluated using the same method as in (8) above.

(10) Residual Peeling Force The sample from which the silicone adhesive tape was peeled from the porous layer in (8) above was re-applied once again to the same location with the same silicone adhesive tape using a hand roller under a load of 2 kg. After crimping, evaluation was performed using the same method as in (8) above.

(11) Oil filling rate The filling rate (volume %) of the fluorine-based oil is determined by [100-porosity (%)]. Here, the porosity of the porous layer is “
Pore distribution characteristics (cumulative pore curve, histogram, etc.) using Porosimeter 2000 (manufactured by CARLO, ERBA)
was measured and determined.

(12) The porous layer encapsulating (impregnating) the slimy fluorine-based oil was rubbed back and forth three times with a finger, and the degree of staining of the porous layer by the fluorine-based oil was evaluated. ○: Good (almost no stains are seen) △:
Slightly inferior (slight stains occur.) ×: Poor (stains are noticeable.)

[0044]

[Examples] The present invention will be explained below using Examples and Comparative Examples, but the present invention is not limited thereto. Example 1 Center line average roughness of 0.053 μm as a film support,
The thickness of the following coating material after drying is 10 μm on one side of a biaxially stretched polyethylene terephthalate film with a thickness of 100 μm.
The porous layer film was obtained by coating and drying at 130° C. for 2 minutes. The coated surface of the polyethylene terephthalate film was subjected to corona discharge treatment in air. [Coating material composition] 70 parts by weight (solid content weight ratio) of an acrylic diameter polymer emulsion (methyl methacrylate/ethyl acrylate/acrylic acid (60/35/5% by weight) copolymer) with an average particle diameter of 0.2 μm and branched Beaded colloidal silica (for example, Snowtex UP manufactured by Nissan Chemical Co., Ltd.)
Average particle size: 0.015 μm) 30 parts by weight (solid content weight ratio) was diluted with water to obtain a 30% by weight coating material.

On the porous layer of the porous film thus obtained, a fluorinated solvent "Florinat" FC-77 (3
A coating material with a concentration of 3.5% by weight made by uniformly dissolving Krytox 157FS-M (manufactured by DuPont) as a fluorine-based oil was applied using a bar coat method using Krytox 157FS-M (manufactured by DuPont) as a diluting solvent. It was dried at ℃ for 1 minute to obtain a release film with a fluorine oil filling rate of 80%. As shown in Table 1, this release film had excellent release properties.

Comparative Examples 1 and 2 In the coating material forming the porous layer of Example 1, instead of the branched beaded colloidal silica, an average particle diameter of 0.015 μm was used.
Spherical colloidal silica (Comparative Example 1) with an average particle size of 0.
A porous film was prepared in the same manner except that 2 μm spherical colloidal silica (Comparative Example 2) was used, and then the same fluorine-based oil as in Example 1 was applied in the same manner to obtain a release film. As shown in Table 1, in Comparative Examples 1 and 2, the release properties and sliminess of the release film were poor due to poor properties of the porous layer.

Examples 2 to 4, Comparative Examples 3 and 4 In the coating material forming the porous layer of Example 1, the average particle diameter and solid proportion of the acrylic polymer emulsion and branched beaded colloidal silica were changed. A porous film was prepared in the same manner except for the above, and a release film was then prepared based on Example 1. As for the properties, as shown in Table 1, those whose porous layers are within the scope of the present invention (Examples 2 to 4) have excellent mold release properties, and those whose porous layers do not meet the scope of the present invention (Comparative Examples) 3, 4) It is found that the mold release properties are inferior.

[0048]

[Table 1]

Claims (8)

[Claims] Claim 1: On at least one side of the film support,
A release film comprising a porous layer and a fluorine-based oil encapsulated in the porous layer. 2. The porous layer has a peak pore diameter of 0.06 to 2.0 μm in a pore size distribution curve, and the porous layer surface has 5/40 μm of undulations with a height of 0.2 μm or more.
2. The release film according to claim 1, wherein the release film has a particle size of m or more. 3. The porous layer has a pore area ratio of 20 to 85.
%. The release film according to claim 1 or 2. 4. The waviness index of the surface of the porous layer is 0.
4. The release film according to claim 1, which has a particle diameter of 0.035 to 0.3 μm. 5. The release film according to claim 1, wherein the centerline average roughness of the surface of the porous layer is 0.5 μm or less. 6. The mold release according to claim 1, wherein the pores in the porous layer are through holes, and the circularity of the pores observed from the surface is in the range of 1 to 5. film. 7. The porous layer is a layer mainly composed of a mixture of a water-dispersible polymer and colloidal silica connected and/or branched in the form of beads.
The release film described in any of the above. 8. An adhesive layer is provided on the porous layer of the release film, and the porous layer allows separation between the porous layer and the adhesive layer. The release film described in any of the above.