JP2007237497A - Mold release film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold release film suppressed in its peeling charge and friction charge without separately providing an antistatic layer and a mold release layer and excellent in mold releasability even if used as a carrier sheet for molding a ceramic capacitor enhanced in capacity. <P>SOLUTION: One surface (A) of a polyester film has a surface center line average roughness (Ra) on the surface (A) of 1-20 nm, has not more than one piece/m<SP>2</SP>of projections with a height of 1 μm or above, and has a coefficient of friction between the surface end back of the film of 0.5 or below. A mold release layer containing a conductive substance to set the surface resistivity value of the mold release layer to 1×10<SP>4</SP>to below 1×10<SP>13</SP>Ω/SQARE is provided on the surface (A). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a release film in which peeling charging and frictional charging are suppressed. More specifically, it has a release layer that has both antistatic properties and releasability, and it is suitable for use as a high performance ceramic capacitor, that is, as a carrier sheet when molding green sheets. It is related with the film.

  Conventionally, as a release film, a polyester film coated with a silicone resin has excellent properties such as cost, strength, elastic modulus, chemical resistance, etc., for example, for resin sheet molding, adhesive release, Used for medical and electrical / electronic parts manufacturing applications.

  The mold release film is usually produced by providing a polyester film with a resin layer having a releasability, for example, a silicone resin layer. In the polyester film used here, usually particles are blended in order to improve processability, for example, slipperiness, winding characteristics and the like. In general, if particles are added, the handleability of the film is improved, but the surface of the film becomes rough. Avoiding this, if you stop blending the particles to create a flat surface, the resulting film will be extremely slippery and air bleed, will not wrinkle during processing or roll up It becomes.

  Conventionally, a molded body or a molded sheet molded from a release film is not so demanding for its surface characteristics, and has no problem in quality even if it is in a certain degree of rough surface state. In recent years, however, the demands on the surface properties of molded sheets have become very strict. For example, a sheet of vinyl chloride resin or urethane resin is formed by casting a solution of these resins on a release film, and high glossiness is particularly required on the molding surface. Moreover, in the release film for adhesive tape, since the unevenness | corrugation on the surface of a release film is shape-transferred to the surface of the adhesive layer of an adhesive tape, for example in the recessed part shape-transferred when sticking an adhesive tape on the glass surface Air enters and it is impossible to obtain a clean appearance. Therefore, surface flatness is required.

  Furthermore, in the film for release used for the process material of an electronic component, especially the request | requirement to surface flatness is high. For example, in order to improve performance such as downsizing and increasing the capacity of ceramic capacitors, green sheets of process materials used when manufacturing ceramic capacitors are being made thinner. When creating a ceramic capacitor thin layer sheet, a ceramic slurry in which ceramic powder and a binder are dispersed in a liquid medium is applied on a release film, and a very thin green sheet of 3 μm or less or 2 μm or less is formed. create. As the green sheet becomes thinner, the surface irregularities of the release film that becomes the base material of the green sheet greatly affect the increase in the defective rate and quality characteristics of the green sheet. Further, as the green sheet becomes thinner, further light release properties of the release film have become necessary.

  On the other hand, the silicone resin coating film has a drawback that it does not leak electric charge as shown by its silicone main chain bond and side chain structure, and is very easily charged. Therefore, for example, when the surface of the release film is charged, application spots are likely to occur on the resin coated on the surface of the release layer, and the release characteristics may deteriorate due to the release discharge of the release film. . In particular, since the film surface tends to be flattened as described above, peeling and frictional charging have become a problem.

  In order to obtain satisfactory antistatic properties in the conventional method of incorporating an antistatic agent into the release layer, in particular, an addition reaction type silicone resin using a platinum catalyst has been proposed. In some cases, since the curing is insufficient, an antistatic layer and a release layer are separately formed on the film to develop antistatic properties and release properties. However, such a configuration increases costs due to an increase in the number of processing steps, and is not sufficiently competitive in the market.

JP 2002-79575 A Japanese Patent Laid-Open No. 10-16163 JP 2004-142179 A

  The present invention was made in order to solve the problems of the conventional release film, and the object of the invention is to provide a release film without separately providing an antistatic layer and a release layer. It is an object of the present invention to provide a release film that is excellent in releasability even if it is used as a carrier sheet when molding a high-performance ceramic capacitor.

According to the study by the present inventor, the above-mentioned problem is “the number of protrusions having a surface centerline average roughness (Ra) of one surface (A) of 1 to 20 nm and a height of 1 μm or more is 1 piece / m ^2. The base film is a polyester film having a friction coefficient of 0.5 or less between the front and back of the film, and the surface specific resistance value of the surface of the release layer on the surface (A) is 1 × 10 ⁴ Ω / □. As described above, it has been found that a release film characterized by being provided with a release layer containing a conductive substance that is less than 1 × 10 ¹³ Ω / □.

  The release film of the present invention has good releasability even when used for molding a thin ceramic sheet because the number of coarse protrusions on the release layer coating surface of the polyester film used is defined. In addition, since the release layer has a conductive material, it has excellent antistatic properties and stable release performance for a long period of time. The trouble of this can also be suppressed.

Hereinafter, the configuration of the present invention will be described in detail.
[Polyester film]
First, the polyester constituting the polyester film used in the present invention is mainly a polyester having an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. This polyester is substantially linear and may be any film-forming material, particularly any film-forming material by melt molding. Examples of aromatic dicarboxylic acids include terephthalic acid, 2,6-naphthalenedicarboxylic acid, Examples thereof include isophthalic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, anthracene dicarboxylic acid and the like. Examples of the aliphatic glycol include ethylene glycol, diethylene glycol, Polymethylene glycol having 1 to 10 carbon atoms such as trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, etc. Such as b-hexane dimethanol alicyclic diol, and the like.

  Among these polyesters, polyalkylene terephthalate, polyalkylene-2,6-naphthalate, particularly polyethylene terephthalate and polyethylene-2,6-naphthalate are preferable, and these are copolymer components of 20 mol% or less based on the total acid component. May be contained. For example, a copolymer in which 80 mol% or more of all dicarboxylic acid components are terephthalic acid and / or 2,6-naphthalenedicarboxylic acid and 80 mol% or more of all glycol components is ethylene glycol may be used. In this case, 20 mol% or less of the total acid component can be the above aromatic dicarboxylic acid other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid. An alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid. Further, 20 mol% or less of the total glycol component may be the above-mentioned glycol other than ethylene glycol, and aromatic diols such as hydroquinone, resorcin, 2,2-bis (4-hydroxyphenyl) propane, etc .; 1,4 -An aliphatic diol having an aromatic ring such as bis (hydroxymethyl) benzene; a polyalkylene glycol (polyoxyalkylene glycol) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like.

  Further, for example, a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid or an aliphatic oxyacid such as ω-hydroxycaproic acid is used in an amount of 20 mol% based on the total amount of the dicarboxylic acid component and the oxycarboxylic acid component. You may copolymerize below.

  Further, the polyester has an amount in a substantially linear range, for example, an amount of 2 mol% or less based on the total acid component, and a tri- or higher functional polycarboxylic acid or polyhydroxy compound such as trimellitic acid, pentane. Those obtained by copolymerizing erythritol and the like are also included.

  The polyester is known per se and can be produced by a method known per se. The polyester preferably has an intrinsic viscosity of 0.4 to 0.9 determined as a solution in o-chlorophenol at 35 ° C., more preferably 0.5 to 0.7, and The thing of 55-0.65 is especially preferable.

  In order to improve the slipping property of the film, the polyester film can contain inert fine particles. The inert fine particles to be contained preferably have an average particle size of less than 1 μm, particularly in the range of 0.01 μm or more and less than 1 μm. The mixing ratio is suitably 0.005 to 2% by weight, preferably 0.05 to 0.5% by weight.

  The inert fine particles may be either organic particles or inorganic particles, or may be mixed particles of organic particles and inorganic particles. The inert fine particles may be formed of two or more components. The ratio of the major axis to the minor axis (major axis / minor axis) of the inert fine particles of each component is preferably 1.0 to 1.2. By blending these inert fine particles, very fine irregularities can be formed on the film surface. Specific examples of such inert fine particles include inorganic particles such as calcium carbonate, kaolin, silicon oxide, barium sulfate, titanium oxide, and alumina oxide; crosslinked polystyrene resin particles, crosslinked silicone resin particles, crosslinked acrylic resin particles, and crosslinked polystyrene resin particles. Organic resin particles such as the above may be used, and the inorganic material and the organic material may be particles having a shell core structure. Furthermore, fine unevenness may be formed on the film surface by precipitating fine particles from the catalyst residue used in the polyester synthesis reaction, and the film may have good sliding properties.

  In the present invention, these fine particles are preferably subjected to particle size adjustment and coarse particle removal using a purification process before being added to the polyester. Examples of the industrial means of the purification process include a dry or wet centrifugal method and an air classification method. In addition, it is particularly preferable that these means are used in combination of two or more and purified stepwise.

  The film made of the polyester used in the present invention needs to have a surface centerline average roughness (Ra) of one surface (A) of 1 nm or more and less than 20 nm, preferably 5 nm or more and less than 18 nm. When Ra is 20 nm or more, the smoothness of the surface becomes insufficient for using the obtained release sheet as a carrier sheet for thin layer molding, while when Ra is less than 1 nm, The processing suitability of the film deteriorates.

Further, the polyester film used in the present invention needs to have a protrusion having a height of 1 μm or more on one side (A) of less than 1 / m ² . If this requirement is not satisfied, for example, a silicone resin may be applied to the surface to form a release layer, which may cause the silicone resin to be uncoated and cause molding defects during green sheet molding. In particular, the number of protrusions having a height of 0.5 μm or more is preferably 1 or less per 1 m ^{2, and the} number of protrusions having a height of 0.25 μm or more is preferably 1 or less per 1 m ² .

  Furthermore, the polyester film used in the present invention needs to have a coefficient of friction between the front and back of the film of 0.5 or less, preferably 0.4 or less. When the friction coefficient exceeds 0.5, handling properties in the transport process of the release layer coating such as silicone resin and the subsequent processing process are deteriorated, wrinkles are generated in the transport system, or the product is wound in a roll shape. This is not preferable because wrinkles and protrusions are transferred to the product. If the friction coefficient is too small, it becomes difficult to maintain the shape of the film roll spread in a roll shape, and the handleability tends to be lowered, so 0.07 or more is preferable.

  The polyester film may be a single layer film or a laminated film. In the case of a laminated film, it can be composed of at least two layers, and is preferably produced by coextrusion. In this case, the polyester constituting each layer may be the same or different, but the same is preferable.

  In the case of a laminated film, if the type of polyester constituting the film is expressed as A, B, C, for example, a laminated structure of A / B, A / B / A, A / B / C can be taken. In addition, since it is not economically preferable when there are too many layers, it is desirable to have three layers or less.

  The total thickness of the polyester film is preferably in the range of 10 to 100 μm, particularly preferably in the range of 15 to 50 μm, whether it is a single layer film or a laminated film.

  The film of the present invention can be produced according to a conventionally known method or a method accumulated in the art. However, in order to cut coarse particles in the film and to form a smooth surface, special attention must be paid to melt filtration. It is necessary to melt-extrude the polyester to which the predetermined particles have been added with an extruder, and remove impurities contained in the melted polyester by filtration. In the present invention, in order to obtain the above-mentioned film, it is preferable to use a filter having an absolute filtration accuracy of 1 to 20 μm. In order to suppress the filtration life and the generation of coarse protrusions, it is more preferable to use a filter having an absolute filtration accuracy of 3 to 10 μm.

  In order to obtain the polyester film according to the present invention, for example, the polyester is melted, filtered and extruded (coextruded in some cases) at a temperature of melting point (Tm: ° C.) to (Tm + 70) ° C. An unstretched film (optionally laminated unstretched film) of .8 dl / g is obtained. Next, the unstretched film is uniaxially (longitudinal or transverse) at a temperature of (Tg-10) to (Tg + 70) ° C. (where Tg is the glass transition temperature of the polyester) 2.5 times or more, preferably 3 times or more. And then stretched in the direction perpendicular to the stretching direction at a temperature of Tg to (Tg + 70) ° C. at a rate of 2.5 times or more, preferably at a rate of 3 times or more. Further, if necessary, the film may be stretched again in the machine direction and / or the transverse direction. Thus, the total draw ratio is preferably 9 times or more, more preferably 12 to 35 times, and particularly preferably 15 to 25 times as the area draw ratio. Furthermore, the biaxially oriented film can be heat-set at a temperature of (Tg + 70) ° C. to (Tm−10) ° C. (where Tm is the melting point of polyester), and is preferably 180 to 250 ° C., for example. The heat setting time is preferably 1 to 60 seconds.

  In addition to the fine particles described above, the polyester fill includes colorants, antioxidants, ultraviolet absorbers, lubricants, catalysts, and other resins such as polyethylene, polypropylene, ethylene / propylene copolymers, and olefinic ionomers. Etc. can be arbitrarily contained within a range not impairing the object of the present invention.

[Release layer]
The release film of the present invention needs to have a release layer containing a conductive substance on the surface (A) satisfying the surface roughness and the number of protrusions of the polyester film. The release layer here refers to a silicone release layer formed of a curable silicone resin, and as the curable silicone resin, a material generally known as a release agent can be used. It can be used by selecting from known materials described in "Material Handbook" (Toray Dow Corning, 19933.8). Examples thereof include KS-847 (H) and KS-778 manufactured by Shin-Etsu Silicone Co., Ltd., TPR-6700 manufactured by Toshiba Silicone Co., Ltd., and the like. These curing methods are generally heat or radiation curing. For example, a thermosetting reaction in which methyl vinyl polysiloxane having vinyl groups at both ends of the molecular chain or both ends and side chains and methyl hydrogen polysiloxane are reacted in the presence of a platinum-based catalyst can be exemplified.

  That is, for example, a coating liquid containing a polydimethylsiloxane having a vinyl group represented by the following formula (A), a methyl hydrogen polysiloxane represented by the following formula (B) and a Pt-based compound is applied to a film, heated and dried. And can be formed by a curing reaction. The heating conditions are, for example, preferably 10 to 120 seconds at a temperature of 80 to 160 ° C., more preferably 15 to 60 seconds at a temperature of 100 to 150 ° C., in order to make the drying and curing reaction sufficient.

  In the above formula (A), m and n are numbers of 1 or more, but if m is in the range of 1 to 100, n is in the range of 20 to 5000, and m + n is in the range of 30 to 5000, the crosslinking reaction proceeds favorably and durability This is preferable because it is a layer with a thickness of about 10 nm.

  In the above formula (B), a and b are numbers of 1 or more, but when a is in the range of 3 to 200, b is in the range of 1 to 20, and 5 ≦ a + b ≦ 200, the crosslinking reaction proceeds appropriately. It is preferable because it becomes a durable layer.

  Note that the number of repeating units m, n, a, and b in the above formulas (A) and (B) does not mean a block bond, but these are simply the sum of the respective units m, n, a, b It should be understood that this is only an indication. Therefore, each unit in the above formulas (A) and (B) may be randomly bonded or may be block bonded.

The curable silicone resin is preferably added with a silane compound represented by the following formula.
(R ₁ ) ₃ —Si—R _{3
(R 1 -O) 3 -Si-} R 3
_{(R 1 -0-R 2)} 3 -Si-R 3
(However, R ₁ and R ₂ are each a chain alkyl group having 1 to 5 carbon atoms, and R ₃ is a vinyl group or a phenyl group.)
The amount of the silane compound added is preferably in the range of 1 to 5 parts by weight with respect to 100 parts by weight of the silicone resin.

The release film of the present invention contains a conductive substance in the silicone release layer, and the surface resistance value of the release layer surface is 1 × 10 ⁴ Ω / □ or more, and 1 × 10 ¹³ Ω / □. Less than, preferably 1 × 10 ⁸ Ω / □ or more and 1 × 10 ¹² Ω / □ or less. When the surface resistance value is 1 × 10 ¹³ Ω / □ or more, the antistatic effect is insufficient and the object of the present invention cannot be achieved. On the other hand, if it is less than 1 × 10 ⁴ Ω / □, it is necessary to increase the content of the conductive material, and the transparency of the release film becomes insufficient, such being undesirable.

  Further, the release film of the present invention has an initial residual adhesion rate of 80% or more, particularly 85% or more, and a residual adhesion rate with time of 80% or more after being held at a temperature of 60 ° C. and a humidity of 90% for 3 months. In particular, it is preferably 85% or more. When the initial residual adhesive rate and the residual adhesive rate over time after holding for 3 months at a temperature of 60 ° C. and a humidity of 90% are less than 80%, for example, as a release film for protecting an adhesive, or for a resin film or a ceramic sheet When used as a molding carrier sheet, a part of the release layer is easily transferred to the surface of the pressure-sensitive adhesive or to the surface of the resin film or ceramic sheet.

  Conventionally, the addition of an antistatic agent has been studied in order to impart an antistatic function to the silicone release layer. However, the cationic or anionic surfactant type antistatic agent has an ionic component, and this ionic component becomes a catalyst poison of the platinum catalyst used in the crosslinking reaction of the silicone resin. The residual adhesion rate was insufficient. Therefore, in the present invention, a conductive substance that does not inhibit the curing reaction of the silicone resin is used, that is, a conductive substance that does not contain an amine, phosphorus, sulfur, lead, ionic substance or the like that inhibits the curing reaction is used. It is desirable that these catalyst poisons are not present in the release layer.

  Examples of the conductive material preferably used include carbon nanomaterials such as fullerenes, single-walled carbon nanotubes, carbon nanohorns, multi-walled carbon nanotubes, and carbon nanofibers, and these include arc discharge method, laser evaporation method, CVD, Manufactured by vapor phase synthesis. Among them, since it is relatively easily entangled, the number of contact portions can be increased, and excellent conductivity performance can be easily obtained. Therefore, carbon nanotubes or carbon nanofibers, for example, a diameter of 10 to 100 nm, preferably 15 to 50 nm, more preferably 20 to 20 nm. Those having a structure of 30 nm and a length of 100 to 1000 nm, preferably 300 to 800 nm are preferable. By using such a conductive substance, it is possible to obtain a release film having an antistatic function capable of suppressing peeling charge and frictional charging and having excellent peelability and coating film durability.

The carbon nanomaterial content is suitably in the range of 0.2 to 50 parts by weight, particularly 0.8 to 30 parts by weight per 100 parts by weight of the silicone resin component. When the content is less than 0.2 parts by weight, the surface resistance value tends to exceed 10 ¹³ Ω / □, and when the content exceeds 50 parts by weight, the transmittance of the release film is 50%. Transparency tends to be reduced.

  In addition, as a coating method of the coating liquid for providing the silicone release layer, any known coating method can be employed. For example, a roll coater method, a blade coater method, and the like can be given. In double-sided coating, simultaneous or single-sided coating may be applied, and the method is not limited to these methods. The coating solution may be a coating solution using an organic solvent or an aqueous coating solution, but is preferably a solution in which polydimethylsiloxane or a hydrogenpolysiloxane compound is dissolved, such as toluene. The coating liquid using the organic solvent is preferable.

  The thickness of the release layer is preferably 30 nm to 300 nm, particularly 50 nm to 200 nm. When the release layer thickness is less than 30 nm, the peeling characteristics are not stabilized, and peeling may become heavy. Conversely, when it exceeds 300 nm, blocking tends to occur.

  The release layer of the present invention may contain fine inert particles. The fine inert particles give a lot of fine irregularities on the surface of the flat release layer, but the shape is so fine that it does not cause a problem even when transferred to a molded sheet. This is preferable because transfer (blocking) and process suitability are improved. In order to satisfy such requirements, the average particle diameter of the inert particles is preferably in the range of 3 to 80 nm, and particularly preferably in the range of 3 to 50 nm.

  As the inert particles, either organic particles or inorganic particles can be used, and mixed particles of organic particles and inorganic particles may be used. Specific examples of such inert particles include inorganic particles such as calcium carbonate, kaolin, silicon oxide, barium sulfate, titanium oxide, alumina oxide, magnesium oxide, zirconium oxide; crosslinked polystyrene resin particles, crosslinked silicone resin particles, crosslinked acrylic resin. Examples thereof include organic resin particles such as particles and crosslinked polystyrene resin particles, and may be particles in which an inorganic material and an organic material take the form of a shell core structure. In particular, in the case of fine particles, inorganic particles are preferred, and the ratio of the major axis to minor axis (major axis / minor axis) of the inert particles is preferably 1.0 to 1.2. By blending these inert particles, very fine irregularities can be formed on the surface of the release layer.

  The addition amount of the inert particles is preferably 0.05 to 25% by weight, more preferably 0.1 to 5% with respect to the weight of the release layer. When the addition amount is less than 0.05% by weight, the slipping property is lowered or the release layer is blocked, and the release property of the release layer becomes unstable. On the other hand, when it exceeds 25% by weight, not only the transparency is lowered, but also agglomeration is likely to occur and a coarse aggregate is generated.

  The release layer can be blended with various known additives as long as the object of the present invention is not hindered. Examples of the additive include an ultraviolet absorber, a pigment, an antifoaming agent, a lubricant (talc, clay, alumina, etc.) and the like. In addition to the release layer, another coating layer may be applied by combining such an additive and a resin.

[Anchor coat layer]
In the release film of the present invention, an anchor coat layer may be provided between the polyester film and the silicone release layer in order to improve the adhesion between the polyester film and the release layer. By providing the anchor coat layer, silicone transfer of the silicone release layer can be suppressed.

As such an anchor coat layer, a silane coupling agent can be preferably used. Examples of the silane coupling agent include those represented by the general formula Y—Si—X ₃ . Here, Y is an organic group having a functional group represented by an amino group, an epoxy group, a vinyl group, a methacryl group or a mercapto group, and X represents a hydrolyzable functional group represented by an alkoxy group. The thickness of the anchor coat layer is suitably 0.005 to 0.2 μm, particularly 0.01 to 0.1 μm.

  In forming such an anchor coat layer, it is necessary to apply the polyester film to the film surface before biaxial stretching in the film forming process of biaxial stretching, and then complete the biaxial stretching simultaneously with drying and heat treatment. preferable.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the examples, “part” means “part by weight”. The physical property values and characteristic values in the present invention were measured by the following methods.

(1) Coarse protrusion As for the height of the protrusion, polarizing films are provided above and below the polyester film, and the polyester film is visually observed by the crossed Nicols method. A foreign material portion that becomes a bright spot is sampled, and the height is measured using a non-contact surface roughness meter of WYKO CORPORATION NT-2000. The measurement conditions are as follows. A protrusion having a height of 1 μm or more is regarded as a coarse protrusion, and the number of coarse protrusions per 1 m ² is counted.
Measurement area: 462 μm × 607 μm
Measurement magnification: 10 times

(2) Surface centerline average roughness (surface roughness)
In accordance with JISB0601, the surface roughness is measured with a stylus type three-dimensional surface roughness meter manufactured by Kosaka Laboratory. The measurement conditions are as follows.
Stylus tip diameter: 2μ
Load: 10mg
Cut-off value: 0.25

(3) Friction coefficient Based on ASTM D1894, the friction coefficient when the polyester film is overlapped is measured.

(4) Peel strength (peel force)
A polyester adhesive tape (Nitto 31B) is bonded to the release layer surface of the polyester film, pressed with a 5 kg pressure roller and allowed to stand for 20 hours, and then the peeling force between the release layer and the adhesive tape is measured with a tensile tester.

(5) Process suitability Process suitability is determined qualitatively by visually observing wrinkles on a transport roll and wrinkles and misalignment during film winding as film handling properties in a film processing process for release.
○: Very good △: Wrinkles occur during film winding ×: Wrinkles during conveyance, wrinkles during winding, and misalignment occur

(6) Surface resistance value The surface resistance value was measured with a measuring instrument (R8340 / R12704) manufactured by Advantest Corporation. The measurement environment was measured with the above-described apparatus for a sample film aged for 24 hours in an atmosphere of a temperature of 23 ° C. and a humidity of 55%. The surface resistance value was evaluated according to the following criteria.
×: 10 ¹³ Ω / □ or more ○: 10 ⁴ Ω / □ or more, less than 10 ¹³ Ω / □

(7) Ceramic sheet moldability A ceramic powder dispersion slurry having the following composition is prepared.
(a) Ceramic slurry powder (barium titanate): 7 parts by weight
(b) Polyvinyl butyral: 3 parts by weight
(c) Dibutyl phthalate: 1 part by weight
(d) Toluene / ethanol: 20 parts by weight / 20 parts by weight The ceramic powder-dispersed slurry is adjusted by a ball mill so that the dispersion is 7 or more with a Hegman grind gauge. Next, this ceramic powder dispersion slurry is coated on the release film surface using a straight edge applicator having a gap of 1 mil, and dried at 110 ° C. for 2 minutes. Next, the release film and the ceramic sheet are peeled off at a speed of 0.5 m / second, and the ceramic sheet is observed for tearing.
○: The ceramic sheet is not broken during peeling.
X: The ceramic sheet is broken at the time of peeling.

[Example 1]
170 ° C. polyethylene terephthalate pellets containing 0.15% by weight of silicon oxide particles (average particle size 0.3 μm) as inert fine particles of the lubricant and having an intrinsic viscosity of 0.62 (o-chlorophenol solvent, measured at 35 ° C.) And dried at a melting temperature of 280 to 300 ° C., filtered through a filter having a filtration accuracy of 3 μm, and extruded on a rotary cooling drum having a surface finish of 0.3 s and a surface temperature of 20 ° C. using an extrusion die, An unstretched film having a thickness of 540 μm was obtained.

The obtained unstretched film is preheated to 75 ° C., then heated by an IR heater having a surface temperature of 900 ° C. from 15 mm above between low-speed and high-speed rolls, stretched 3.6 times in the longitudinal direction, and rapidly cooled. Subsequently, the film was supplied to a transverse stretching machine and stretched 3.9 times in the transverse direction at a temperature of 105 ° C. The obtained biaxially oriented film was heat-fixed at a temperature of 205 ° C. for 5 seconds to obtain a heat-fixed biaxially oriented polyester film having a thickness of 38 μm. In the film forming step, 3-glycidoxypropyltrimethoxysilane was used as an anchor coat layer of a release layer on one side of the polyester film at a position immediately before the uniaxially stretched film that had been longitudinally stretched entered lateral stretching. A 3 wt% aqueous solution (containing a surfactant) was applied in an amount of 5 g / m ² (wet) and dried.

Add platinum catalyst (3 parts by weight to 100 parts by weight of silicone resin) to the mixed solution of methyl vinyl polysiloxane and methyl hydrogen polysiloxane having vinyl groups on the polyester film surface to which the anchor coat layer has been applied. A silicone resin coating solution in which a curable silicone resin (KS778 manufactured by Shin-Etsu Chemical Co., Ltd.) to be reacted is dissolved in a mixed solvent of methyl ethyl ketone, methyl isobutyl ketone and toluene is applied, dried at 140 ° C. for 60 seconds, and separated. A release film having a mold layer thickness of 0.1 μm was obtained. In this coating liquid, carbon nanofibers (hereinafter referred to as CNF, average diameter 20 nm, length 0.1 to 10 μm) obtained by a gas phase catalyst synthesis method are used as conductive substances with respect to 100 parts by weight of silicon resin. And 20 parts by weight.
Table 1 shows the evaluation results of the obtained release film.

[Example 2]
Polyethylene terephthalate pellet A containing 0.25% by weight of silicon oxide particles (average particle size 0.09 μm) as inert fine particles of the lubricant and having an intrinsic viscosity of 0.62 (o-chlorophenol solvent, measured at 35 ° C.) is obtained. It was. Further, 0.06% by weight of silicon oxide particles having an average particle diameter of 0.6 μm and 0.4% by weight of silicon oxide particles having an average particle diameter of 0.3 μm are contained as inert fine particles of the lubricant, and the intrinsic viscosity is 0.62. Polyethylene terephthalate pellets B (o-chlorophenol solvent, measured at 35 ° C.) were obtained. The obtained polyethylene terephthalate pellets A and polyethylene terephthalate pellets B were each dried at 170 ° C. for 3 hours, then supplied to two extruder hoppers and melted at a melting temperature of 280 to 300 ° C., and the filtration accuracy was 3 μm. The mixture was filtered and extruded on a rotary cooling drum having a surface finish of 0.3 s and a surface temperature of 20 ° C. using a two-layer extrusion die to obtain an unstretched film having a thickness of 540 μm. The thickness ratio of A and B is A / B = 1/9.

  Using the unstretched laminated film thus obtained, a biaxially stretched laminated film and a release film having an anchor coat layer provided on the polyethylene terephthalate A side were prepared in the same manner as in Example 1. The properties of this release film are shown in Table 1.

[Example 3]
In Example 2, instead of polyethylene terephthalate B, 0.01% by weight of silicon oxide particles having an average particle diameter of 1.2 μm and 0.2% by weight of calcium carbonate particles having an average particle diameter of 0.6 μm were used as inert particles of the lubricant. %, An unstretched laminated film, a biaxially stretched laminated film and A release film was prepared. The properties of this release film are shown in Table 1.

[Comparative Example 1]
In Example 1, an unstretched film, a biaxially stretched film, and a release film were prepared in the same manner as in Example 1 except that no lubricant was used. The properties of this release film are shown in Table 1.

[Comparative Example 2]
In Example 1, an unstretched film, a biaxially stretched film and a release film were prepared in the same manner as in Example 1, except that 0.1% by weight of kaolinite having an average particle diameter of 1 μm was contained as the inert particles of the lubricant. It was created. The properties of this release film are shown in Table 1.

[Comparative Example 3]
In Example 1, a release film was prepared in the same manner as in Example 1 except that carbon nanofibers were not added to the release layer. The properties of this release film are shown in Table 1.

  Since the release film of the present invention described above is provided with a release layer containing a conductive substance on the surface of the film on which the surface centerline average roughness and the number of coarse protrusions are specified, the release film is peeled off. In addition to suppressing charging and frictional charging, for example, it has good releasability when used as a carrier sheet for molding high-performance ceramic capacitors, and produces excellent quality molded products with high productivity. Can do.

Claims (5)

The surface center line average roughness (Ra) of one surface (A) is 1 nm or more and 20 nm or less, the number of protrusions having a height of 1 μm or more is 1 piece / m ² or less, and the coefficient of friction between the front and back of the film is The base film is a polyester film that is 0.5 or less, and the surface specific resistance value on the surface (A) of the release layer surface is 1 × 10 ⁴ Ω / □ or more and less than 1 × 10 ¹³ Ω / □, A release film characterized in that a release layer containing a conductive substance is provided.   The release film according to claim 1, wherein the conductive material is a carbon nanotube or a carbon nanofiber.   The release film according to claim 1 or 2, wherein the release layer is a thermosetting silicone layer subjected to a crosslinking reaction using a platinum catalyst.   The film for mold release according to claim 3, wherein the mold release layer does not contain an amine compound, a phosphorus compound, a sulfur compound, a lead compound and an ionic compound.   The release film according to any one of claims 1 to 4, wherein the release layer is laminated on the surface of the polyester film via an anchor layer formed from a silane coupling agent.