JP2007090849A - Releasing film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a releasing film comprising a biaxial stretched polypropylene film having an excellent processing suitability and heat resistance, in which a resin layer for releasing is formed at least on one surface. <P>SOLUTION: The mold releasing film is characterized in that the resin layer for releasing, preferably, a silicone resin layer is formed at least one surface of the biaxial stretched polypropylene film in which an elastic modulus in a longitudinal direction (E<SB>MD</SB>) and an elastic modulus in a lateral direction (E<SB>TD</SB>) are both 2,500 MPa or more, and a ratio (E<SB>MD</SB>/E<SB>TD</SB>) of the elastic modulus in the longitudinal direction (E<SB>MD</SB>) to the elastic modulus in the lateral direction (E<SB>TD</SB>) is in the range of 0.8-1.2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a release film composed of a biaxially stretched polypropylene film having a release resin, preferably a silicone resin layer formed on at least one surface excellent in processability and heat resistance.

Biaxially stretched polypropylene film (hereinafter sometimes referred to as OPP film) is based on its excellent transparency, mechanical strength, moisture resistance, rigidity, etc., as well as packaging materials, labels, adhesive tapes, and release film bases. It is used in a wide range of fields such as material films.
As an example of using an OPP film as a release film, for example, it has been proposed to apply silicone to a film formed by biaxially stretching a polypropylene added with a specific phenolic antioxidant and a lactone antioxidant ( Patent Document 1). However, shrinkage is caused by heat when a silicone resin is applied and crosslinked to a sequential biaxially stretched polypropylene film having a longitudinal draw ratio of 4.6 times and a transverse draw ratio of 9.2 times described in Examples, There is a risk of curling.

JP 2003-82177 A

  Therefore, the present invention has variously studied the development of a biaxially stretched polypropylene film with little thermal shrinkage even when a release resin is applied and crosslinked, and as a result, the ratio of the elastic modulus in the machine direction and the transverse direction is high. By using a biaxially stretched polypropylene film in the same range, a release film composed of a biaxially stretched polypropylene film having a release resin layer formed on at least one surface excellent in processability and heat resistance can be obtained. As a result, the present invention has been completed.

In the present invention, the longitudinal elastic modulus (E _MD ) and the transverse elastic modulus (E _TD ) are both 2500 MPa or more, and the longitudinal elastic modulus (E _MD ) and the transverse elastic modulus (E _TD ) A release resin layer, preferably a silicone resin layer, is formed on at least one surface of a biaxially stretched polypropylene film having a ratio (E _MD / E _TD ) in the range of 0.8 to 1.2. It is a release film.

  The release film of the present invention has a high modulus of elasticity in both the longitudinal direction and the transverse direction, and has a high modulus of elasticity and a ratio of the modulus of elasticity in the longitudinal direction and the transverse direction in the same range. Can be obtained.

Polypropylene , which is a raw material for the biaxially oriented polypropylene film according to the present invention, is a polymer mainly composed of propylene which is generally produced and sold under the name of polypropylene, and usually has a density of 0.890 to 0.930 g / A homopolymer of propylene having a cm ³ , MFR (ASTM D1238 load 2160 g, temperature 230 ° C.) of 0.5 to 60 g / 10 minutes, preferably 0.5 to 10 g / 10 minutes, more preferably 1 to 5 g / 10 minutes. Alternatively, it is a copolymer of propylene and another small amount, for example, 1% by weight or less of an α-olefin, such as ethylene, butene, hexene-1, or the like, or a composition of a homopolymer and a copolymer.
Among these, a homopolymer of propylene, or a polymer having a high isotacticity with a random copolymer of 1% by weight or less or a composition thereof is excellent in elastic modulus and heat resistance of the obtained biaxially stretched polypropylene film. Therefore, it is preferable.
The polypropylene according to the present invention is not limited to a Ziegler-Natta catalyst, and may be one polymerized using various known catalysts including a single site catalyst (metallocene catalyst).
Polypropylene includes heat stabilizers, weather stabilizers, UV absorbers, lubricants, slip agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, pigments, dyes, inorganic or organic fillers, etc. Usually, various additives used for polyolefin may be added within a range not impairing the object of the present invention.

Mold Release Resin The mold release resin according to the present invention is a resin generally used as a resin excellent in mold release properties such as silicone resin, acrylic silicone resin, fluororesin or melamine resin. Among these release resins, a silicone resin is preferable because the ceramic green sheet can be peeled relatively easily.
Examples of such a silicone resin include a thermal condensation reaction type: a product obtained by reacting silanol functional dimethylpolysiloxane at both ends with methylhydropolysiloxane or methylmethoxysiloxane in the presence of an organotin catalyst, and a thermal addition reaction type. : Molecular vinyl polysiloxane having vinyl groups at both ends or both ends and side chains and methylhydropolysiloxane reacted in the presence of a platinum-based catalyst, UV curable (radical addition type): alkenyl With a photopolymerization agent added to a siloxane containing a group and a mercapto group, UV curable (hydrosilyl type): using the same platinum catalyst as the thermal addition reaction type, UV curable (radical polymerization type): (meta ) Acrylic group-containing siloxane with photopolymerization agent, UV curable (cationic) Type): Epoxy group-containing siloxane with onium salt photoinitiator added, and electron beam curing type: Radical polymerizable group-containing siloxane (no functional group, no photoinitiator) Good). Moreover, the form of the silicone resin can be appropriately selected from a solvent type, an emulsion type, a solventless type, and the like.
Among these silicone resins, the heat addition reaction type is preferable.
Examples of the various siloxanes used as the raw material for the silicone resin include KS-778, KS-835, KS-847, KS-838, KS-770L, KS-776L, KS-3702, Shin-Etsu Chemical Co., Ltd. Manufactured and sold by Dow Corning Co., Ltd. under the trade names such as SRX357, BY24-384, SRX211, SD7220, SD7226 and GE Toshiba Silicone Co., Ltd. TPR6722, TPR6721, TPR6702, XS56-A8012, TPR6701, XS56-A3969. Yes.

Biaxially stretched polypropylene film (A)
The biaxially stretched polypropylene film used as the base material of the release film of the present invention has both a longitudinal elastic modulus (E _MD ) and a transverse elastic modulus (E _TD ) of 2500 MPa or more, preferably 2700 MPa or more, and The ratio of the elastic modulus in the direction (E _MD ) to the elastic modulus in the transverse direction (E _TD ) (E _MD / E _TD ) is in the range of 0.8 to 1.2, preferably 0.9 to 1.1. It is an axially stretched polypropylene film. A film having both a longitudinal elastic modulus (E _MD ) and a transverse elastic modulus (E _TD ) of less than 2500 MPa has low rigidity as a release film, resulting in poor processability when coating a release resin. There is a fear. Further, when the ratio (E _MD / E _TD ) of the elastic modulus in the vertical direction (E _MD ) and the elastic modulus in the horizontal direction (E _TD ) is outside the above range, the rigidity balance as a release film is poor, and the release resin When coating the film, the film may curl.
The biaxially stretched polypropylene film according to the present invention is usually 7 to 12 times, preferably 8 to 11 times, transverse direction (TD) in the machine direction (MD) using a known biaxially stretched film forming apparatus using the polypropylene. ) In the range of usually 7 to 12 times, preferably 8 to 11 times, can be produced by simultaneous biaxial stretching or sequential biaxial stretching. In the case of simultaneous biaxial stretching, the stretching temperature is usually in the range of 140 to 200 ° C, preferably 150 to 190 ° C. In the case of sequential biaxial stretching, the longitudinal stretching temperature is usually 100 to 150 ° C, preferably 110 to 140 ° C. The transverse stretching temperature is usually 140 to 200 ° C, preferably 150 to 190 ° C. Further, in the sequential biaxial stretching, the longitudinal stretching temperature may be 100 to 150 ° C., preferably 110 to 140 ° C., and 1.0 to 2.0 times, preferably 1.1 to 1.8 times. Among these, the simultaneous biaxial stretching method is a range in which the ratio (E _MD / E _TD ) of the longitudinal elastic modulus (E _MD ) and the transverse elastic modulus (E _TD ) of the biaxially stretched polypropylene film easily obtained is within the above range. This is preferable. In the case of simultaneous biaxial stretching, an excellent balance film can be easily obtained.
The biaxially stretched polypropylene film of the present invention is preferably subjected to surface treatment such as corona treatment, flame treatment, plasma treatment, etc. on the surface on which the release layer is laminated. When the surface treatment is not performed, the adhesion between the biaxially stretched polypropylene film and silicone may be reduced.

Release Film The release film of the present invention is a release film characterized in that a release resin layer, preferably a silicone resin layer, is formed on at least one side of the biaxially stretched polypropylene film (A). . The thickness of the release film is usually 10 to 100 μm, preferably 20 to 50 μm for the biaxially stretched polypropylene film, and the thickness of the resin layer for release is 0.01 to 5.0 μm, preferably 0.1 to 0.1 μm. It is in the range of 2.0 μm. For example, within this range, it is possible to adjust in terms of adhesion to the release film substrate, stability of peel strength during the release process, and non-migration of the silicone resin component. An excellent release film can be obtained.

The release film of the present invention is produced by applying the release resin to at least one surface of the biaxially stretched polypropylene film, and then drying and curing (crosslinking) with heat, ultraviolet rays, electron beam, or the like as necessary. Can do.
The method for applying the release resin is not particularly limited, and the release resin may be applied as it is or diluted with a solvent so that the release resin layer has a desired thickness. . When diluting the release resin with a solvent, for example, aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbons such as cyclohexane, n-hexane and n-heptane, and halogenated carbonization such as perchloroethylene Organic solvents such as hydrogen, lower alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol, and ethyl acetate and methyl ethyl ketone can be used.

Examples of the method for applying the release resin include an air knife coater, a direct gravure coater, a gravure offset, an arc gravure coater, a gravure reverse and jet nozzle type gravure coater, a top feed reverse coater, and a bottom feed reverse coater. Further, it may be applied to the biaxially stretched polypropylene film using various known coating machines such as a reverse roll coater such as a nozzle feed reverse coater, a 5-roll coater, a lip coater, a bar coater, a bar reverse coater, and a die coater.
The release resin can be dried and cured (thermal curing, ultraviolet curing, etc.) individually or simultaneously. When performed simultaneously, although it depends on the heat resistance (thermal dimensional stability) of the biaxially stretched polypropylene film (A), it is heated for 15 seconds or more in a temperature range of 80 ° C. to 120 ° C., preferably 90 ° C. to 110 ° C. It is preferable to do. When the drying temperature is less than 80 ° C., the thermosetting time becomes long and the productivity is lowered, and the release resin such as silicone is not sufficiently cured. Further, when the drying temperature is 120 ° C. or higher, the film may be wrinkled.

In the present invention, an antistatic agent is blended into the biaxially stretched polypropylene (A) to obtain an antistatic formulation, and an antistatic layer (B) is provided together with a release resin layer (C) to prevent static charge. Things are also done.
Such an antistatic layer (B) is preferably formed by laminating an antistatic layer (B) and a release resin layer (C) in this order on one side of the biaxially stretched polypropylene film (A). Of course, the antistatic layer (B) may be provided on one side of the biaxially oriented polypropylene film (A), and the release resin layer (C) may be provided on the other side.
By providing it, the antistatic layer (B) can be made of various materials having anti-static properties such that the surface has a specific resistance of 10 ¹² Ω / □, particularly 10 ¹² Ω / □ or less. . Examples thereof include an antistatic agent, a conductive filler, a binder resin containing a conductive polymer, a conductive polymer itself, a thermosetting resin containing an inorganic compound such as a metal, and a polymer type antistatic agent.
Antistatic agents used in the antistatic layer include anionic antistatic agents such as alkyl sulfate type and alkyl phosphate type, and cation type antistatic agents such as quaternary ammonium salt type, quaternary ammonium resin type and imidazoline type. Agents, sorbitan, ether type nonionic antistatic agents, betaine type amphoteric antistatic agents. The binder resin is not particularly limited, and polyolefin resin, polyvinyl alcohol resin, polybutyral resin, and the like can be used.

Examples of the polymer type antistatic agent include a sulfonate group, a phosphate group, an acrylate group (as a base, an alkali metal base such as sodium, lithium, and potassium, an ammonium base, and the like).
These may be coated on the polypropylene film (A) biaxially stretched in-line, or may be biaxially stretched as a whole after coating on the polypropylene film before biaxial stretching.
The thickness of the antistatic layer (B) is not particularly limited, but is about 0.1 to 100 μm.
In order to laminate a binder resin containing an antistatic agent or the like on the biaxially stretched polypropylene film (A), various methods such as coextrusion and dry lamination can be used. When applying antistatic agent, air knife coater, direct gravure coater, gravure offset, arc gravure coater, gravure reverse and jet nozzle type gravure coater, top feed reverse coater, bottom feed reverse coater and nozzle feed reverse Various known coating machines such as a reverse roll coater such as a coater, a 5-roll coater, a lip coater, a bar coater, a bar reverse coater, and a die coater can be used.
The thickness of the antistatic layer (B) is usually from 0.01 to 100 micrometers (μm).
Among these antistatic layers (B), an antistatic layer (B ′) containing a polyester resin and tin oxide-based fine particles is preferable.

Antistatic layer (B ') containing polyester resin and tin oxide fine particles
In order to provide an antistatic layer (B ′) containing a polyester resin and tin oxide-based fine particles, it is generally desirable to use a coating liquid containing polyester fine particles and tin oxide-based fine particles.
The coating agent is a dispersion in which fine particles of polyester resin and tin oxide-based fine particles are dispersed, and in particular, an aqueous dispersion to form a uniform antistatic layer (B ′) coating by a simple operation. This is preferable.
This coating liquid contains tin oxide-based fine particles in a proportion of usually 50 to 1000 parts by mass with respect to 100 parts by mass of polyester resin fine particles.
When the ratio of the tin oxide-based fine particles is small, the antistatic property of the coating of the antistatic layer (B ′) may be insufficient. Moreover, when many, the adhesiveness of an antistatic layer (B ') and a biaxially stretched polypropylene film (A) may fall.

As the medium when the coating agent is a dispersion, water is suitable. If water is the main component, another organic solvent may be used in combination. Examples of such organic solvents include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-amyl alcohol, isoamyl alcohol, sec-amyl alcohol, tert-amyl. Alcohols such as alcohol, ketones such as methyl ethyl ketone, methyl isobutyl ketone, and ethyl butyl ketone, glycol derivatives such as ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and further 3-methoxy-3-methylbutanol, di- Examples include acetone alcohol and ethyl acetoacetate. These may be used alone or in combination of two or more.
The boiling point of the organic solvent used in combination is preferably one having a boiling point of 200 ° C. or lower and capable of azeotroping with water. Moreover, if the ratio of the organic solvent used together with water is 25% by mass or less of the total medium in the emulsion, the storage stability of the coating agent is good.

Examples of the polyester resin include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, hexahydroterephthalic acid, 4,4'-diphenyldicarboxylic acid and other dicarboxylic acids, among them terephthalic acid, 2,6-naphthalenedicarboxylic acid and the like. Polyester resins obtained from glycols such as ethylene glycol can be used. The polyester resin may be copolymerized with a tribasic or higher polybasic acid and / or a polyhydric alcohol as necessary in order to develop necessary physical properties.
The tribasic or higher polybasic acid includes trimellitic acid, pyromellitic acid, benzophenone tetracarboxylic acid, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, trimesic acid, ethylene glycol bis (anhydrotrimelli Tate), glycerol tris (anhydro trimellitate), 1,2,3,4-butanetetracarboxylic acid and the like.
Examples of the trifunctional or higher polyhydric alcohol include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol. However, when copolymerizing a tribasic or higher polybasic acid and a polyhydric alcohol, it is usually 10 mol% or less and 5 mol% or less with respect to the total acid component and the total alcohol component, respectively. If it exceeds 10 mol%, the film tends to be too hard and the processability tends to deteriorate.

The acid value of the polyester resin blended in the coating agent is usually about 10 to 40 mgKOH / g.
The polyester resin is generally used in the form of a water-dispersible polyester resin emulsion as fine particles imparted with water-dispersibility. The fine particles of the water-dispersible polyester resin usually have a number average particle diameter of 0.001 to 0.1 μm (dynamic light scattering method).
An emulsion composed of fine particles of a polyester resin is prepared by, for example, mixing and stirring a polyester resin powder or granular material in water and an organic solvent to which a basic compound is added at a temperature near room temperature of 40 ° C. or less, and then stirring. There is a method of heating by heating to a temperature, stirring at a temperature not lower than the glass transition temperature of the polyester resin and not higher than 90 ° C. to make the polyester resin fine particles and cooling.
The fine particles of the polyester resin generally have a number average particle diameter of usually about 0.001 to 0.1 μm and are used in the state of an emulsion stably dispersed in a solvent.
When producing a water-dispersible polyester resin emulsion, it is desirable to add an organic amine in order to neutralize the carboxyl group of the polyester resin.
Examples of the organic amine include triethylamine, N, N-diethylethanolamine, N, N-dimethylethanolamine, morpholine, N-methylmorpholine, N-ethylmorpholine and the like. 1.5 equivalents are preferable, and 0.4 to 1.3 equivalents are more preferable.

When the amount is less than 0.2 times equivalent, neutralization may be incomplete and an emulsion with good dispersion stability may not be obtained. When the amount exceeds 1.5 times equivalent, the emulsion becomes thick and difficult to handle. There is.
Moreover, it is desirable to select those organic amines that volatilize in the drying step when forming the antistatic layer (B), and organic amines having a boiling point of 200 ° C. or lower are suitable. Thereby, it can be set as the antistatic layer (B) which does not have a bad influence on hardening of the mold release resin layer (C) formed on it. Although the density | concentration of the polyester resin in a water dispersible polyester resin emulsion is not specifically limited, In order to show favorable storage stability, maintaining moderate viscosity, 10-50 mass% is preferable.
The tin oxide-based fine particles in the coating agent generally have a number average particle diameter of usually 50 nanometers (nm) or less, and above all, the number average particle diameter is 50 nanometers (nm) or less and the volume average particle diameter is 200 nanometers ( nm) or less.
The tin oxide-based fine particles are preferably dispersed while maintaining the above-mentioned number average particle diameter.
If the tin oxide fine particles aggregate in the dispersion and the volume average particle diameter (dynamic light scattering method) exceeds 200 nm, the transparency of the coating tends to decrease.

Examples of the tin oxide fine particles include tin oxide, antimony-doped tin oxide, indium-doped tin oxide, aluminum-doped tin oxide, tungsten-doped tin oxide, titanium oxide-cerium oxide-tin oxide composite, and titanium oxide-tin oxide composite. Among them, tin oxide, antimony-doped tin oxide, and indium-doped tin oxide, which are excellent in performance such as conductivity and well-balanced in cost, are preferable.
The coating agent is prepared, for example, by mixing the water-dispersible polyester resin emulsion and the tin oxide-based fine particle aqueous dispersion. At that time, the tin oxide fine particle dispersion may be added to and mixed with the water-dispersible polyester resin emulsion, and conversely, the above emulsion may be added to and mixed with the tin oxide fine particle dispersion. Is optional.
In addition, when mixing both, in order to maintain the dispersion stability of a water-dispersible polyester resin emulsion, adjusting pH so that the pH of a liquid mixture may be 8-12 is performed as needed.
The coating agent can be prepared by mixing a water-dispersible polyester resin emulsion and a tin oxide-based fine particle dispersion.

In the coating agent thus obtained, an organic solvent derived from the water-dispersible polyester resin emulsion is contained, and in order to improve the coating performance, for example, a low-boiling alcohol such as isopropanol is used. An organic solvent is also added. In this case, the content of the organic solvent is 50% by mass or less of the whole solvent, and 50% by mass or more is preferably water.
Among these coating agents, it is preferable that tin oxide-based fine particles are dispersed in a solvent while maintaining good dispersibility equivalent to that in a tin oxide-based fine particle dispersion together with fine particles of water-dispersible polyester resin. is there. That is, it is preferable that the tin oxide-based fine particles exist as primary particles having a number average particle size of 50 nm or less and a volume average particle size of 200 nm or less.
Further, the solid content concentration in this coating agent, that is, the total concentration of the water-dispersible polyester resin and the tin oxide-based fine particles is generally 1 to 40% by mass, and if the solid content concentration is lower than 1% by mass, the base film (A ) Tends to make it difficult to form a film having a sufficient thickness when applied with a uniform thickness. On the other hand, when it exceeds 40% by mass, the dispersibility of the tin oxide fine particles may be insufficient.

Further, this coating agent does not require a crosslinking agent. By forming the antistatic layer (B ′) from the coating agent only by heating without mixing the crosslinking agent, the adhesion with the release resin layer (C) formed thereon is improved. Can do. However, if necessary, a functional group possessed by the water-dispersible polyester resin, for example, a crosslinking agent having reactivity with a carboxyl group or a hydroxyl group is mixed to increase the hardness of the coating.
Furthermore, an antioxidant, a lubricant, a colorant and the like can be added to the coating agent as long as the characteristics are not impaired.
As a method for applying the coating agent to the surface of the biaxially oriented polypropylene film (A), a known coating machine similar to the above can be used.

As a drying method of the applied coating agent, there is usually a method of drying at 60 ° C. to 230 ° C., for example, for 2 seconds to 50 seconds using a hot air circulating oven, an infrared heater, etc., and a biaxially oriented polypropylene film (A) An antistatic layer (B ′) is formed thereon.
The thickness of the antistatic layer (B) is usually from 0.01 to 100 micrometers (μm), which can provide a film having a uniform thickness that is hard to be damaged and scratched.
In order to improve the adhesion of the antistatic layer (B ′) to the biaxially stretched polypropylene film (A), an adhesive layer such as a silane coupling agent is provided on the surface of the biaxially stretched polypropylene film (A). An antistatic layer (B ′) may be provided on the adhesive layer, but it is not usually necessary.

  EXAMPLES Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples unless it exceeds the gist.

The physical property values in Examples and Comparative Examples were determined by the following evaluation methods.
(1) Elastic modulus (MPa)
A strip-shaped film piece (length: 150 mm, width: 15 mm) is cut out from the biaxially stretched polypropylene film in the machine direction (MD) and the transverse direction (TD), and a tensile tester [Tensilon universal tester manufactured by Orientec Co., Ltd.] RTC-1225] was used, and a tensile test was performed under the conditions of a distance between chucks: 100 mm and a crosshead speed: 5 mm / min to obtain an elastic modulus (MPa).
(2) Thermal contraction rate (%)
Cut out a 100 mm x 100 mm test piece from a biaxially stretched polypropylene film, measure the length (initial dimension) of the test piece, and then sandwich it in a 90 ° C or 120 ° C oven so that the test pieces do not overlap. Left for 15 minutes. Then, it was left to stand for 30 minutes or more at room temperature, the dimension (shrinked dimension) of the vertical direction (MD) and the horizontal direction (TD) was measured, and the thermal shrinkage rate (%) was obtained from the following formula.
Thermal shrinkage rate (%) = [shrinked dimension (mm) / initial dimension (mm)] × 100

(3) Peeling force (N / 50mm)
The release film was placed on a horizontal table with the coating film facing up, and the adhesive film No. 1 manufactured by Nitto Denko Corporation was applied to the coating film. 31B was affixed, cut into a size of 200 mm × 50 mm, and a load was applied from the top of the adhesive film to 20 g / cm ² and left at 70 ° C. for 20 hours. Then, using a tensile tester [Tensilon Universal Tester RTC-1225 manufactured by Orientec Co., Ltd.], peeling was performed 180 degrees at a pulling speed of 300 m / min, and the average peel load in the region where peeling was stable was determined as the width of the adhesive tape. The value divided by was taken as the peel force.
(4) Residual adhesion rate (%)
The release film was placed on a horizontal table with the coating film facing up, and the adhesive film No. 1 manufactured by Nitto Denko Corporation was applied to the coating film. 31B was affixed, cut into a size of 200 mm × 50 mm, and a load was applied from the top of the adhesive film to 20 g / cm ² and left at 70 ° C. for 20 hours. Thereafter, the release film is peeled off, and the pressure-sensitive adhesive film is subjected to 3 reciprocating pressure bondings using a 2 Kg rubber roller on a stainless steel plate, followed by heat treatment at 70 ° C. for 2 hours. Subsequently, adhesive force: F is measured according to the method of JIS-C-2107 (adhesive strength to a stainless steel plate, 180 degree peeling method). Adhesive film No. The percentage (Formula 2) of F to the adhesive force F ₀ when 31B was directly adhered to and peeled from the stainless steel plate was determined as the residual adhesion rate.
Residual adhesion rate (%) = [Adhesive strength (F) / Adhesive strength (F ₀ )] × 100

(5) Processing suitability When making a release film and drying the release film at 90 ° C. for 15 seconds, the suitability was judged as ○ when the release film did not curl and x when curled. .
(6) Antistatic property Based on JIS-K6911, the surface resistivity of the release resin layer (C ′) of the release film is measured using a digital ultrahigh resistance / microammeter R83340 manufactured by Advantest Corporation. (Condition: Standard state (temperature 23 ° C., relative humidity 50%) voltage 560 V).

Example 1
<Manufacture of biaxially oriented polypropylene film>
As a propylene homopolymer, F113G [Density: 0.91, MFR: 3.0 g / 10 min (230 ° C.)] manufactured by Mitsui Chemicals, Inc. was used.
Using a simultaneous biaxially stretched film forming apparatus manufactured by Bruckner, a propylene homopolymer was melt-extruded with a screw extruder (temperature: 250 ° C.), quenched with a cooling roll (temperature: 30 ° C.), and a thickness of about 2.4 mm. A multilayer sheet was obtained. Then, the sheet was used in the machine direction (MD) using a tenter (preheating temperature: 185 ° C., stretching temperature: 160 ° C. and heat setting temperature: 180 ° C. and relaxation rate; machine direction: 5% and machine direction: 5%). The film was stretched 9 times and 9 times in the transverse direction (TD) to obtain a simultaneous biaxially stretched polypropylene film having a thickness of 30 μm. Next, a corona treatment was performed on one side (coating surface) of the simultaneous biaxially stretched polypropylene film.

<Manufacture of release film>
A toluene / methyl ethyl ketone = 70/30 (volume ratio) mixed solvent solution of silicone (KS-847 manufactured by Shin-Etsu Chemical Co., Ltd.) and catalyst (PL-50T manufactured by Shin-Etsu Chemical Co., Ltd.) was prepared. On the coated surface (corona-treated surface) of the axially stretched polypropylene film, Mayer Bar No. 4 and dried and cured in an oven at 90 ° C. for 30 seconds to form a coating film of 0.1 g / m ² , then left at 40 ° C. for several tens of hours to create a release film did. Evaluation of the obtained release film was measured by the method described above.
The evaluation results are shown in Table 1.

Example 2
In place of the propylene homopolymer used in Example 1, HA722J [density: 0.91, MFR: 3.5 g / 10 min (230 ° C.)] manufactured by Basel was used, and Example 1 was used. In the same manner as above, a release film was obtained.
The evaluation results are shown in Table 1.

Comparative Example 1
Using the sequential biaxially stretched film production apparatus used in Example 1, the propylene homopolymer used in Example 1 was melt-extruded with a screw extruder (temperature: 250 ° C.) and cooled with a cooling roll (temperature: 30 ° C.). The sheet was quenched and a sheet having a thickness of about 1.5 mm was obtained. Next, the sheet was stretched 5 times in the machine direction (MD) using a stretching roll (preheating temperature: 130 ° C., stretching temperature: 120 ° C., heat setting temperature: 130 ° C. and relaxation rate: 6.5%), and the tenter (Preheating temperature: 185 ° C., stretching temperature: 160 ° C., heat setting temperature: 180 ° C. and relaxation rate: 5%), 10-fold stretching in the transverse direction (TD) and sequential biaxial stretching with a thickness of 30 μm A polypropylene film was obtained. Subsequently, a corona treatment was performed on one side (coating surface) of the sequentially biaxially stretched polypropylene film. Next, a release film was prepared by the method described in Example 1 using a sequentially biaxially stretched polypropylene film.
The evaluation results are shown in Table 1.

Example 3
In Example 2, before the silicone was applied, the following coating agent was applied onto the coating surface (corona-treated surface) of the biaxially stretched polypropylene film with a Mayba-No. 3 was applied and dried in an oven at 100 ° C. for 20 seconds to obtain a biaxially stretched polypropylene film (A) on which an antistatic layer (B ′) was formed.
Content of coating agent
Water-based coating agent containing polyester fine particles and tin oxide fine particles · Product name ················································ SAS-U8135-20・ ・ ・ ・ ・ ・ 10-11 mass%
・ Isopropyl alcohol concentration: 20% by mass
・ Solvent ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Water, isopropyl alcohol

Next, on the side of the antistatic layer (B ′) of the biaxially oriented polypropylene film (A), the Mayor No. 4 and dried and cured in an oven at 90 ° C. for 30 seconds to form a coating film of 0.1 g / m ² , then left at 40 ° C. for several tens of hours to create a release film did. Evaluation of the obtained release film was measured by the method described above.
As a result, the specific resistance value on the surface of the release film was 1 × 10 ⁹ Ω / □.

  As is clear from the results in Table 1, the release film of the present invention has a high modulus of elasticity in both the longitudinal direction and the transverse direction, and has a high modulus of elasticity and a ratio of the modulus of elasticity in the longitudinal direction and the transverse direction. Since it is in the range, it is excellent in workability and heat resistance.

  The release film of the present invention has a high modulus of elasticity in both the longitudinal direction and the transverse direction, and has a high modulus of elasticity and a ratio of the modulus of elasticity in the longitudinal direction and the transverse direction in the same range. The process film used as a mount in the process of manufacturing ceramic capacitors and printed circuit board materials, process films for manufacturing thermosetting resin products, decorative boards, etc., release materials for adhesive tapes and various adhesive labels It can be used for various applications as a release film (release film).

Claims (5)

Both the longitudinal elastic modulus (E _MD ) and the transverse elastic modulus (E _TD ) are 2500 MPa or more, and the ratio of the longitudinal elastic modulus (E _MD ) to the transverse elastic modulus (E _TD ) (E _MD ). / E _TD ) having a release resin layer (C) formed on at least one surface of a biaxially stretched polypropylene film (A) having a range of 0.8 to 1.2.   It has an antistatic layer (B), The release film of Claim 1 characterized by the above-mentioned.   The release film according to claim 1 or 2, wherein an antistatic layer (B) and a release resin layer (C) are laminated in this order on one side of the biaxially stretched polypropylene film (A).   The release film according to any one of claims 1 to 3, wherein the biaxially stretched polypropylene film is a film obtained by simultaneous biaxial stretching. The release film according to any one of claims 1 to 4, wherein the biaxially stretched polypropylene film has a stretching ratio of at least 7 times in the machine direction and the transverse direction.