JP6307078B2 - Release film - Google Patents

Description

  The present invention relates to a release film, particularly a polystyrene-based release film excellent in transferability.

  When manufacturing printed circuit boards, ceramic electronic parts, semiconductor packages, lens parts, thermosetting resin products, thermoplastic resin products, decorative boards, etc. In some cases, a plastic film is interposed as a release film. In addition, in the process of forming a thin film layer such as a thermosetting resin, thermoplastic resin, ceramic, metal, etc., and in a predetermined processing step, the thin film layer is laminated on a plastic film for the purpose of supporting and protecting the thin film layer In some cases, a plastic film may be peeled and removed as a release film. As described above, the plastic film is used for various purposes.

  In general, heat is often applied to a plastic film, and the case where a higher temperature is applied is increasing. Furthermore, with the recent demand for higher performance, the heat resistance required for plastic films has become severe. Specifically, for example, when a plastic film is used as a release film and interposed between a mold and a molding material to prevent fusion during press molding, the plastic film is usually stretched. Therefore, when dimensional variation (heat shrinkage) occurs in the plastic film due to heat, the film does not sufficiently follow the unevenness of the mold molding surface, and good shaping by the mold molding surface is not performed. For this reason, particularly good heat-resistant dimensional stability is required for the film.

  As an example of a plastic film excellent in dimensional stability, a syndiotactic polystyrene film is known. For example, Patent Document 1 discloses that mechanical strength and heat shrinkage in the longitudinal direction and the transverse direction are performed by performing specific sequential biaxial stretching on an unstretched amorphous film made of a syndiotactic polystyrene film. A technique for producing a syndiotactic polystyrene film having an excellent balance of rates is disclosed.

  On the other hand, the release film is required to be subjected to surface treatment such as matte treatment in order to further improve the releasability and / or to impart a matte property to the molded body. The mat processing is a processing for forming fine irregularities on the film surface by applying heat and pressure with a mold made of metal or rubber having a desired surface shape while applying tension to the film. By using a release film that has been matted when molding the material to be molded, the fine unevenness of the release film on the surface can be transferred to the molded body, resulting in matte properties in the molded body. Can be granted.

Japanese Patent Laid-Open No. 9-201873

  However, when mat processing is performed on the above-mentioned syndiotactic polystyrene film, a curl phenomenon occurs in the obtained release film in which the film is wound from the end alone. In particular, a release film having a large curl, in other words, a release film having a high curl rate, not only causes inconvenience in production when installed between the mold and the molding material, but also sufficiently extends the curl. However, it was difficult to interpose the release film, and the end portion was bent. For this reason, a streak-like pattern resulting from the end portion breakage of the release film is generated in the molded product, and as a result, a transfer defect of fine irregularities on the film surface occurs. In addition, if the release film is inferior in heat-resistant dimensional stability, the fine uneven shape on the film surface cannot be accurately transferred to the molded product, and a thick thin film can be formed where there is sufficient transfer and sweet transfer. So-called unevenness occurs.

  An object of the present invention is to provide a polystyrene-based release film that is sufficiently excellent in heat-resistant dimensional stability and curl resistance. That is, the present invention sufficiently follows the unevenness of the molding surface of the mold, and sufficiently prevents the occurrence of curling due to the mat processing, so that the molding surface of the molded body and the surface of the release film can be obtained. An object of the present invention is to provide a polystyrene-based release film that accurately achieves transfer to a molded product.

  The present invention is a release film composed of a biaxially oriented polystyrene film containing a syndiotactic polystyrene resin, wherein at least one surface is matted, and the curl rate of the release film is 80% or less. The present invention relates to a release film.

In the present specification, heat-resistant dimensional stability means a film characteristic that sufficiently prevents film shrinkage even when the film is heated.
The curl resistance means a film characteristic that sufficiently prevents the occurrence of a curling phenomenon even if the film is matted.

The release film of the present invention is sufficiently excellent in heat-resistant dimensional stability.
The release film of the present invention is further excellent in curl resistance.
The release film of the present invention can achieve the transfer onto the finely concavo-convex shaped molded body with sufficient accuracy.

It is a schematic sectional drawing for demonstrating the usage method when using the release film of this invention.

  The polystyrene-based release film (hereinafter simply referred to as “PS-based release film”) according to the present invention is a biaxially oriented film containing a syndiotactic polystyrene-based resin. Biaxial orientation means that the polymer molecules constituting the film are oriented mainly in two directions different from each other in the in-plane direction of the film, preferably in two directions substantially perpendicular to each other. For example, it can be achieved by simultaneous biaxial stretching described later.

<Syndiotactic polystyrene resin>
The syndiotactic polystyrene resin (hereinafter simply referred to as “SPS resin”) contained in the PS release film of the present invention is a styrene polymer having a so-called syndiotactic structure. The syndiotactic structure is a syndiotactic structure, that is, a three-dimensional structure in which phenyl groups or substituted phenyl groups that are side chains with respect to the main chain formed from carbon-carbon bonds are alternately located in opposite directions. It means structure.

The tacticity (stereoregularity) of the SPS resin can be quantified by an isotope carbon nuclear magnetic resonance method ( ¹³ C-NMR method). The tacticity of the SPS resin measured by the ¹³ C-NMR method is the ratio of the presence of a plurality of consecutive structural units, for example, a dyad for two, a triad for three, a pentad for five. Can be indicated by The SPS resin in the present invention is usually 75% or more, preferably 85% or more, racemic triad, 60% or more, preferably 75% or more, or 30% or more, preferably 50%, racemic pentad. It is a styrenic polymer having the above syndiotacticity.

  Styrenic polymers as SPS resins include polystyrene, poly (alkyl styrene), poly (aryl styrene), poly (halogenated styrene), poly (halogenated alkyl styrene), poly (alkoxy styrene), poly (alkoxy styrene). Vinyl benzoate ester), hydrogenated polymers thereof and the like, and mixtures thereof, or copolymers based on these.

Examples of poly (alkyl styrene) include poly (methyl styrene), poly (ethyl styrene), poly (isopropyl styrene), poly (tertiary butyl styrene), poly (vinyl styrene), and the like.
Examples of poly (aryl styrene) include poly (phenyl styrene) and poly (vinyl naphthalene). )
Examples of poly (halogenated styrene) include poly (chlorostyrene), poly (bromostyrene), poly (fluorostyrene), and the like.
Examples of poly (halogenated alkylstyrene) include poly (chloromethylstyrene).
Examples of poly (alkoxystyrene) include poly (methoxystyrene) and poly (ethoxystyrene).

  The weight average molecular weight of the SPS resin constituting the PS release film according to the present invention is 10,000 to 3,000,000, preferably 30,000 to 1,500,000, particularly preferably 50,000 to. 500,000. The glass transition temperature of the SPS resin is 60 to 140 ° C, preferably 70 to 130 ° C. The melting point of the SPS resin is 200 to 320 ° C, preferably 220 to 280 ° C.

The SPS resin can be obtained as a commercial product or can be produced by a known method.
For example, it can be obtained as “Zarek” (142ZE, 300ZC, 130ZC, 90ZC) manufactured by Idemitsu Kosan Co., Ltd.

  In the PS release film, the SPS resin has two or more SPS resins having different tacticity (racemic dyad, racemic triad or racemic pentad), type, glass transition temperature and / or melting point within the above-mentioned range. It may be contained.

  The PS-type release film of the present invention is not limited to the above SPS-based resin, as long as it does not adversely affect the heat-resistant dimensional stability, curl resistance, heat-resistant deformation, film-forming property, heat-resistant strength stability, etc. It may contain.

  Specific examples of other polymers include, for example, polystyrene resins other than the SPS resins, polystyrene resins such as styrene-butadiene block copolymers (SBR), hydrogenated styrene-butadiene-styrene block copolymers (SEBS), and the like. Synthetic rubber; Polyester resin such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polytrimethylene terephthalate; polyphenylene sulfite; polyarylate; polyether sulfone; polyphenylene ether .

  The polystyrene resin other than the SPS resin includes a so-called isotactic polystyrene resin and an atactic polystyrene resin.

  The content of the SPS resin relative to the total amount in the PS release film is preferably 60% by weight or more, more preferably 80% by weight or more, and most preferably 95% by weight from the viewpoint of further improving the heat-resistant dimensional stability. % Or more. When two or more kinds of SPS resins are contained, the total ratio thereof may be within the above range.

<Other additives>
The PS release film of the present invention may contain additives such as a lubricant, an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, an inorganic filler, a colorant, a crystal nucleating agent and a flame retardant. . In particular, the PS release film of the present invention preferably further contains a lubricant and an antioxidant.

  Examples of the lubricant include hydrocarbon resins, fatty acids, fatty acid amides, fatty acid esters, fatty alcohols, partial esters of fatty acids and polyhydric alcohols, and composite lubricants. By including a lubricant, the releasability of the release film of the present invention can be further improved.

  The content of the lubricant is preferably 0.01 to 3.0% by weight, particularly 0.02 to 1.0% by weight, based on the SPS resin in the PS film, from the viewpoint of the release property of the release film. . When two or more kinds of lubricants are contained, the total amount thereof may be within the above range.

  As the antioxidant, an antioxidant used for the purpose of preventing yellowing in the field of PS release film can be used. For example, a phenolic antioxidant, a phosphorus antioxidant, a sulfur antioxidant Agents and the like. From the viewpoint of further improving the heat-resistant dimensional stability and curling resistance, the antioxidant preferably contains at least a phenolic antioxidant. By containing an antioxidant, particularly a phenolic antioxidant, the heat-resistant dimensional stability and the curl resistance can be further improved.

A phenolic antioxidant is an organic compound containing a phenol skeleton, and a phenol skeleton-containing organic compound conventionally used as a phenolic antioxidant in the field of PS film can be used. The phenolic antioxidant can be obtained as a commercial product.
Commercially available phenolic antioxidants include, for example, Sumilizer GA-80 (manufactured by Sumitomo Chemical Co., Ltd.), ADK STAB AO-60, ADK STAB AO-80, ADK STAB AO-330 (both manufactured by ADEKA), and Irganox 245 (BASF). Product), Sianox 1790 (manufactured by CYTEC), and the like.

The phosphorus antioxidant is an organic compound containing a phosphorus atom, and a phosphorus atom-containing organic compound conventionally used as a phosphorus antioxidant in the field of PS film can be used. Phosphorous antioxidants can be obtained as commercial products.
Examples of commercially available phosphorus antioxidants include Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.), Adekastab PEP-36 (manufactured by ADEKA), Irgafos 38, Irgafos 168 (both manufactured by BASF), and the like.

The sulfur-based antioxidant is an organic compound containing a sulfur atom, and a sulfur atom-containing organic compound conventionally used as a sulfur-based antioxidant in the field of PS film can be used. The sulfur-based antioxidant can be obtained as a commercial product.
Examples of commercially available sulfur-based antioxidants include Sumilyzer MB (manufactured by Sumitomo Chemical Co., Ltd.), Adeka Stub AO-412S (manufactured by ADEKA), and the like.

  The content of the antioxidant is 0.01 to 3.0% by weight, particularly 0.02 to 1.0% by weight, based on the SPS resin in the PS film, from the viewpoint of heat-resistant dimensional stability and curl resistance. % Is preferred. When two or more kinds of antioxidants are contained, the total amount thereof may be within the above range. In particular, the content of the phenolic antioxidant is preferably within the above range from the viewpoint of further improving the heat-resistant dimensional stability and curling resistance.

<Method for producing PS release film>
The PS release film of the present invention can be produced by the following method.
For example, the SPS and other polymers and additives contained as desired are mixed in a predetermined ratio, melted and kneaded to produce a precursor film (unstretched film), and then the obtained precursor film is simultaneously used. Sequentially used for biaxial stretching and mat processing.

(Precursor film production)
A well-known method can be employ | adopted for the manufacturing method of a precursor film. For example, a mixture composed of desired components may be melted and kneaded with an extruder, the kneaded material is extruded from a T die, and then cooled.

  The thickness of the precursor film is not particularly limited, and is, for example, 20 to 2000 μm, and preferably 30 to 1000 μm.

(Biaxial stretching process)
In the biaxial stretching treatment step, the heat setting treatment is usually performed after simultaneous biaxial stretching treatment. By such a biaxial stretching treatment step, the glass transition temperature of the film can be increased, the thermal expansion coefficient can be decreased, or the absolute value of the thermal shrinkage ratio can be decreased.

  In the biaxial stretching process, stretching is performed in the MD direction and the TD direction. The stretching method includes a sequential biaxial stretching method and a simultaneous biaxial stretching method, and a simultaneous biaxial stretching method is performed. Instead of simultaneous biaxial stretching, after performing stretching in one of the MD and TD directions, and then performing sequential biaxial stretching in which stretching is performed in the other direction, thermal expansion in the direction in which stretching was performed first The rate of decrease in the rate becomes smaller, the thermal shrinkage rate becomes worse, and the heat-resistant dimensional stability is lowered. When uniaxial stretching is performed instead of biaxial stretching, the coefficient of thermal expansion in the non-stretched direction is not reduced, and the heat-resistant dimensional stability is lowered. In the present specification, the MD direction is a so-called flow direction, and means the direction (longitudinal direction) of the precursor film taken from the extruder. The TD direction is a so-called width direction and means a direction orthogonal to the MD direction.

  When biaxial stretching is performed, the stretching ratio, stretching temperature, and stretching speed are not particularly limited as long as the object of the present invention is achieved, but the following ranges are preferable. This is because the thermal shrinkage rate is further improved.

The draw ratio is within a range in which breakage of 2.0 times or more does not occur in both the MD direction and the TD direction, and is particularly preferably 2.0 to 5.0 times, more preferably 2.2 to 4.0 times. . The draw ratios in the MD direction and the TD direction are preferably approximated. Specifically, when the stretching ratio in the MD direction and _P MD, the stretching ratio in TD direction and _{P TD, "P} TD _{-P MD"} is preferably -0.6 + 0.6, more preferably -0 .3 to +0.3. In addition, the draw ratio of MD direction is a ratio based on MD direction length just before extending | stretching. The stretching ratio in the TD direction is a ratio based on the length in the TD direction immediately before stretching.

The stretching temperature is Tg _P or more and Tg _P + 30 ° C. or less, where Tg _P (° C.) is the glass transition temperature of the SPS resin constituting the film, and is preferably from the viewpoint of further improving the heat-resistant dimensional stability. Tg _P ° C or higher and Tg _P + 25 ° C or lower. If the stretching temperature is too low or too high, the heat-resistant dimensional stability is lowered. The stretching temperature is the atmospheric temperature at which stretching is performed. When the SPS resin is composed of two or more types of polymers, the Tg _{P of the} SPS resin is the sum of the values obtained by multiplying the glass transition temperature of each polymer by the content ratio of the polymer.

The stretching speed is 50 to 10,000% / min in both the MD direction and the TD direction, preferably 100 to 5000% / min, and more preferably 100 to 3000% / min.
The stretching speed is a value calculated by {(dimension after stretching / dimension before stretching) -1} × 100 (%) / stretching time.

The heat setting treatment is a treatment for fixing the orientation of the polymer molecules by holding the stretched film at a temperature equal to or higher than the stretching temperature. The heat setting treatment temperature is Tg _P + 70 ° C. or higher and Tm _P or lower when the glass transition temperature of the SPS resin constituting the film is Tg _P (° C.) and the melting point is Tm _P (° C.). From the viewpoint of further improving the stability, it is preferably Tg _P + 75 ° C. or higher and Tm _P −20 ° C. or lower. If the heat setting treatment temperature is too low or too high, the heat shrinkage rate becomes high and the heat-resistant dimensional stability is lowered. The heat setting treatment temperature is an atmospheric temperature for holding the film. When the SPS resin is composed of two or more kinds of polymers, the Tm _{P of the} SPS resin is the sum of values obtained by multiplying the melting point of each polymer by the content ratio of the polymer.

  The heat setting process may be a tension type heat setting process in which the heat setting process is performed while maintaining the tension during the biaxial stretching process, or the heat setting process is performed by relaxing the tension simultaneously with the process. The heat fixing process may be performed, or after performing the heat fixing process (first heat fixing process) while maintaining the tension, the tension is relaxed and the heat fixing process (second heat fixing process). You may implement the composite heat setting process which performs. Preferably, a relaxation heat setting process is performed. When the heat setting process is performed by any of the above methods, the heat setting temperature is set within the above range.

When the heat setting treatment is performed by the relaxation method or the composite method described above, the relaxation magnification is 0 in both the MD direction and the TD direction from the viewpoint of reducing the absolute value of the heat shrinkage rate, further improving the heat-resistant dimensional stability, and flatness of the film. 0.8 to 1.00 times is preferable, more preferably 0.85 to 1.00 times, and most preferably 0.90 to 0.98 times. The relaxation magnifications in the MD direction and the TD direction are preferably approximated. Specifically, when the MD relaxation factor is Q _MD and the TD relaxation factor is Q _TD , “Q _TD -Q _MD ” is preferably −0.1 to +0.1, more preferably −0. 0.05 to +0.05, and most preferably -0.02 to +0.02. In addition, the relaxation magnification in the MD direction is a magnification based on the MD direction length immediately after stretching. The relaxation magnification in the TD direction is a magnification based on the length in the TD direction immediately after stretching.

(Matte processing)
Matting refers to transferring the surface shape of a mold to the film surface by applying heat and pressure between a set of molds having a desired surface shape while applying tension to the film. This is a process for forming fine irregularities for matting. The film to be matted is a film that has undergone a biaxial stretching process by the method described above. In the present invention, by subjecting the release film to mat processing under specific conditions, the curling phenomenon can be sufficiently prevented, and the release property of the release film can be reduced during press molding using the release film. While further improving, it is possible to accurately transfer the fine concavo-convex shape on the surface of the release film to the molded body.

  As a method of applying heat and pressure between a pair of molds, a mold pressing method in which two heated flat plate upper and lower molds are pressed, and passing between two hot rolls while pressing. A roll press method or the like can be used. One set of molds can be used in combination with one flat mold and one roll. The mold may be made of any material as long as the surface shape of the mold can be transferred to the film. For example, the mold may be made of metal, rubber, or film. Only the surface portion having the contact surface may be made of metal or rubber. Hereinafter, embodiments for performing the above-described mold pressing method or roll pressing method will be described. Instead of heating the film with the mold or roll in the above-described mold pressing method or roll pressing method, immediately before pressing with the mold or roll. Alternatively, the film itself may be directly heated with an IR heater or the like.

  The mat processing is performed on at least one side of the film, and is preferably performed on both sides of the film from the viewpoint of curling resistance. The mat processing being performed on both sides of the film means that a mold having a matte property described later is used as both molds in a set of molds. Thereby, the matte property is provided to both surfaces of the film. Matting is performed on one side of the film when one of a set of molds has a matte type described below and the other has no matte type. It means to do. Thereby, matte property is provided only to one side of the film.

The following conditions are adopted as mat processing conditions.
A matte mold is used as at least one of the set of molds, preferably both molds. The mold having a matte property is a mold in which a surface roughness is given to the contact surface with the film so that the matted film surface has a surface roughness (Ra) described later. In such a mold, the surface roughness of the contact surface with the film is the same as or greater than the surface roughness (Ra) described later of the matted film surface.

  The temperature which a set of molds gives to both sides of the film is 100 ° C to 250 ° C, preferably 120 ° C to 220 ° C.

In the case of a die pressing method, the pressing pressure is 0.5 to 300 kgf / cm ² , preferably 1 to 200 kgf / cm ² . In the case of the roll press method, it is 0.1 to 500 kgf / cm, preferably 1 to 100 kgf / cm.

  The tension of the film is usually 1 to 300N, preferably 10 to 200N. The tension is a tension applied to a 1 m wide film. In particular, when the roll press method is adopted, the film speed is usually 0.1 to 10 m / min, preferably 0.2 to 5 m / min.

The curling rate can be controlled by adjusting the mat processing conditions while adjusting the surface roughness of the mold, the processing temperature of the film, the pressing pressure, and the film tension within the above ranges.
For example, the curl rate can be reduced by reducing the difference in surface roughness and / or temperature difference that a set of molds imparts to the film. Specifically, by making the difference in surface roughness that a set of molds gives to the film, that is, the difference in surface roughness on both sides of the matted film, within the range described later, the curl rate is made more effective. Can be reduced. By setting a temperature difference between a pair of molds on both sides of the film, for example, a set temperature difference between the upper mold and the lower mold, particularly 30 ° C. or lower, preferably 20 ° C. or lower, more preferably 10 ° C. or lower, Can be more effectively reduced.
Further, for example, the curling rate can be reduced by reducing the press pressure and / or the film tension. Specifically, in the case of the mold pressing method, the curling rate can be further effectively reduced by setting the pressing pressure to 1 to 100 kgf / cm ² , preferably 1 to 50 kgf / cm ² . By setting the tension of the film to 10 to 100 N, preferably 10 to 50 N, the curl rate can be further effectively reduced.

<PS release film>
The curl rate of the PS release film of the present invention is 80% or less, preferably 60% or less, more preferably 30% or less. If the curl rate is too large, the end part will be bent during press molding, and a streak-like pattern will be generated in the molded product due to the end part bend, and the surface shape of the release film will be sufficiently transferred around it. Not.

  In the present specification, the curl rate is the ratio of the projected area that decreases due to the occurrence of curling when a test piece (200 mm × 200 mm) is allowed to stand for 30 minutes at an atmospheric temperature of 180 ° C. It is measured by the method. The higher the curl rate, the greater the warp of the film, and the lower the curl rate, the smaller the warp of the film. The projected area of the test piece can be calculated from an image obtained by taking a photograph from directly above the test piece.

  In the PS release film of the present invention, the absolute value of heat shrinkage at 180 ° C. is usually 8% or less, preferably 6% or less, more preferably 3% or less. The absolute value of the heat shrinkage rate is within the above range for both the MD direction and the TD direction. When the absolute value of the heat shrinkage rate is too large, the heat-resistant dimensional stability is lowered, and when used as a release film for press molding, the molding surface of the mold cannot be formed sufficiently.

  In the present specification, the heat shrinkage rate is a heat shrinkage rate in each of the MD direction and the TD direction when the test piece (200 mm × 200 mm) is left at an ambient temperature of 180 ° C. for 30 minutes, and will be described in detail later. Measured by the method. As for the value of the heat shrinkage rate, a positive value means shrinkage, and a negative value means expansion.

  The PS release film of the present invention has at least one surface matted, and as a result, has a surface roughness (Ra) of 0.5 μm to 8.0 μm, particularly 0.6 μm to 5.0 μm. preferable. The PS release film of the present invention is preferably matted on both sides from the viewpoint of curling resistance, and as a result, each surface independently has a surface roughness (Ra) within the above range. From the viewpoint of curling resistance, in the most preferred embodiment, the difference in surface roughness between both surfaces is 1.5 μm or less, preferably 1.0 μm or less, more preferably 0.5 μm or less. The surface roughness of the film in this invention has shown the value measured by JISB-0601: 1994.

  The thickness of the PS release film of the present invention is not particularly limited, and is, for example, 10 to 150 μm, preferably 25 to 75 μm, and particularly preferably 35 to 60 μm.

  The PS release film of the present invention is particularly useful as a release film (transfer film) that requires transferability.

  Specifically, when the PS release film of the present invention is used as a release film, the mold and the molding material are formed by interposing the film between the mold and the molding material during press molding. The surface shape of the film can be accurately transferred while preventing fusion with the film. Moreover, since the mold release film of the present invention is sufficiently prevented from changing in dimensions, for example, even when the mold forming surface has irregularities with a depth of 1 mm, the forming surface can be accurately shaped.

  The type of plastic constituting the molding material is not particularly limited. For example, epoxy resin, phenol resin, silicon resin, melamine resin, urea resin, alkyd resin, polyimide resin, polyester resin, polyurethane resin, acrylic resin, etc. can be used. It is.

Conditions known in the field of plastic molding can be used for the mold temperature, pressure, and processing time when press-molding using the PS release film of the present invention. For example, the mold temperature during pressing is usually 80 to 200 ° C. The press pressure is usually 1 to 150 kg / cm ² . The pressing time is usually 0.5 to 60 minutes.

Examples 1-5 / Comparative Examples 1-2
A mixture of the following components was melt extruded from a T die at a resin temperature of 280 ° C. with an extruder, and then cooled to obtain an unstretched film (precursor film). The unstretched film was subjected to a stretching process under the conditions described below. The stretching step consisted of stretching treatment and heat setting treatment, and the heat setting treatment was a relaxation type heat setting treatment at a predetermined temperature and a relaxation ratio. The stretching process is simultaneous biaxial stretching.

As a mixture component, syndiotactic polystyrene resin, antioxidant and lubricant were used in both Examples and Comparative Examples.
As the syndiotactic polystyrene resin, “Zarek 142ZE” (manufactured by Idemitsu Kosan Co., Ltd., glass transition temperature 95 ° C., melting point 247 ° C.) was used.
As the antioxidant, a phenolic antioxidant was used, and as the lubricant, an amide lubricant was used.
The blending ratio was 0.2 parts by weight of ADK STAB AO-60 and 0.2 parts by weight of lubricant with respect to 100 parts by weight of syndiotactic polystyrene resin.

The stretching conditions are as follows in both Examples and Comparative Examples.
The draw ratio is 3.3 x 3.4 times (MD x TD)
Stretching temperature: 115 ° C
Stretching speed: 500% / min Heat setting temperature: 215 ° C
Relaxation magnification: 0.92 × 0.92 (MD × TD)

  The stretched film obtained above was cut to a width of 1 m, and then subjected to mat processing by pressing with two flat molds to obtain a release film. The processing conditions (mold surface roughness, mold temperature, press pressure, film tension) are as shown in Table 1. Of the two molds, the upper mold uses the mold itself with a given surface roughness, and the lower mold gives a silicon rubber layer with a given surface roughness to the mold surface. We used what we did.

Evaluation The release film subjected to mat processing obtained in each example / comparative example was evaluated for the following items. The results are shown in Table 1. The specific evaluation method is as follows.

The curl rate 200mm × 200mm cut film is left in a hot air circulation oven set at 180 ° C in a hot air circulation oven for 30 minutes in a suspended state, then taken out and placed on a flat surface. The area (mm ² ) of the curled portion when viewed was measured. Based on this area, the curl rate (%) was calculated from the following formula.
Curling rate (%) = (Area of curled portion) / (Total area of film after heating) × 100
In addition, when the film curls, the total area of the film after heating is measured by stretching the curled film.

Surface Roughness The surface roughness of the film is an arithmetic average height (Ra) measured according to JIS B-0601: 1994. The upper surface is a film surface that comes into contact with the upper die during mat processing, and the lower surface is a fill surface that comes into contact with the lower die.

Thermal shrinkage rate First, two straight lines having a length of 150 mm were drawn on a test piece (film; 200 mm × 200 mm) so as to be parallel to the MD direction and the TD direction and cross each other at the midpoint. This test piece was left in a standard state (temperature 23 ° C. × humidity 50%) for 2 hours, and then the length of the straight line before the test was measured. Subsequently, the substrate was left standing in a suspended state with a corner supported in a hot air circulation oven set at 180 ° C. for 30 minutes, then taken out and allowed to cool in a standard state for 2 hours. Thereafter, the length of the straight line in each direction was measured, the amount of change from the length before the test was determined, and the thermal shrinkage rate was determined as the ratio of the amount of change to the length before the test. A positive value for heat shrinkage means shrinkage. It should be noted that if the absolute value of the heat shrinkage is 3% or less, a very preferable level (◎), a preferable level (◯) if it is 6% or less, a level (Δ) that causes no practical problem if it is 8% or less, If it exceeds 8%, it is a practically problematic level (x).

Release Film Evaluation When the epoxy resin flakes were hot-press molded, the transfer films (release films having transfer properties) obtained in Examples 1 to 5, Comparative Example 1 and Comparative Example 2 were used. Specifically, as shown in FIG. 1, when the epoxy resin flake 1 is hot press-molded by the upper and lower molds 2, 3, the transfer film 4 is interposed between the flake 1 and the molds 2, 3. The transfer film 4 was held and fixed outside the mold. The transfer film 4 was arranged so that the surface to which the roughness was given by the silicon rubber layer was on the upper and lower molds 2 and 3 side. During pressing, the approach of the dies 2 and 3 was limited by the spacer 5. The press conditions were as follows. Temperature of molds 2 and 3; 180 ° C., press pressure; 100 kg / cm ² , spacer thickness 0.5 mm, press time; 10 minutes, depth of concave portion (height of convex portion): 1 mm.
After the press molding, the molded body was taken out and allowed to cool, and then the film 4 was peeled from the molded body. The transfer surface transferred to the surface of the molded body was visually observed and evaluated for transferability.
A: The transfer surface of the epoxy molding was free from streaks and unevenness, and the surface of the transfer film was transferred as it was;
○: The transfer surface of the epoxy molded body had almost no streak-like pattern or unevenness, and the surface of the transfer film was almost transferred;
Δ: The transfer surface of the epoxy molded product had a slight streak pattern and unevenness, and the transfer of the transfer film surface was slightly insufficient (no problem in practical use);
X: The transfer film bent on the transfer surface of the epoxy molding was transferred as a step, resulting in transferability having a practical problem.

  The release film of the present invention is sufficiently excellent in heat-resistant dimensional stability, has a good curl rate, is excellent in moldability (following property) and releasability, and imparts good matte properties to the molded product. I can do it. There are two methods for using the release film: a method of using the roll as it is (roll-to-roll method) and a method of cutting it in the longitudinal direction to use it as a single sheet (single-sheet method). In some cases, curling resistance becomes more problematic. The release film of the present invention is more useful as a release film used in such a single wafer system.

  The mold release film of the present invention is a mold such as a flat plate mold or a molding roll when manufacturing a printed circuit board, a ceramic electronic component, a semiconductor package, a lens component, a thermosetting resin product, a thermoplastic resin product, a decorative plate, and the like. It is useful as a release film interposed between the film and the molding material. The release film of the present invention is a so-called transfer film, and is useful as a film for transferring a matte tone provided on the surface of the film to the surface of a molding material. In addition, the release film of the present invention is laminated for the purpose of supporting and protecting the thin film layer in the process of forming a thin film layer such as a thermosetting resin, thermoplastic resin, ceramic, metal, or a predetermined processing process. It is useful as a process film to be peeled and removed.

Claims (5)

A release film comprising a biaxially oriented polystyrene film obtained by subjecting a precursor film containing a syndiotactic polystyrene resin and a phenolic antioxidant to simultaneous biaxial stretching and at least one-side mat processing ,
Ri der curl of not more than 80% of the release film,
The surface roughness of the matted surface is 0.5 μm or more and 8.0 μm or less,
The release film has a thickness of 10 to 150 μm.
A release film characterized by that.   The release film according to claim 1, wherein the curl rate is 60% or less.   The release film according to claim 1 or 2, wherein the syndiotactic polystyrene-based resin is syndiotactic polystyrene. The release film according to any one of claims 1 to 3, wherein a content ratio of the phenolic antioxidant is 0.01 to 3.0 wt% with respect to the syndiotactic polystyrene resin.   The release film according to claim 1, wherein the release film has a heat shrinkage rate of 8% or less.

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