JP4376610B2 - Surface protective film and surface protective film using the same - Google Patents

Description

  The present invention relates to a surface protective film having a releasability and a surface protective film, and in particular, a surface suitably used for the surface of a manuscript (photomask) when exposing an adhesive photoresist in a printed circuit board manufacturing process or the like. The present invention relates to a protective film and a surface protective film.

  Usually, a printed wiring board or a resin relief plate is produced by closely exposing a photomask (exposure original) to an adhesive photoresist such as a liquid photoresist. For this reason, if the surface of the photomask is not subjected to any treatment, when the photomask is removed from the photoresist after completion of exposure, a part of the photoresist adheres to the photomask surface and remains on the photomask even after wiping. As a result, there arises a problem that the exposure accuracy is lowered. Under such circumstances, conventionally, a surface protective film having releasability is provided on the surface of the photomask facing the photoresist to prevent the photoresist from adhering to the photomask.

  As such a surface protective film for a photomask, a film having a surface protective film having releasability on one surface of a plastic film and an adhesive layer on the other surface has been proposed (Patent Document). 1). However, even in such a surface protective film, adhesion of the photoresist to the surface protective film cannot be completely prevented, and in order to remove the photoresist remaining in these surface protective films, other dust, etc., The surface of the surface protection film is regularly cleaned (wiping operation) with a cleaning solvent. For this reason, it is required for such a surface protective film to maintain releasability so as to prevent resist adhesion even after cleaning.

For these reasons, surface protective films that have been maintained with a release property even after cleaning with a cleaning solvent have been proposed. Certainly, such surface protective films are cleaned with a cleaning solvent such as a lower alcohol. As for, sufficient releasability could be maintained (see Patent Document 2). However, as a recent photoresist coating method, a spray coating method or a curtain coating method has been used instead of the conventional screen printing in order to increase mass productivity. Therefore, the components and contents of the solvent contained in the photoresist have changed, and the surface protective film has been gradually attacked by the solvent comprising polyhydric alcohol or its derivative contained in the photoresist. Sufficient mold releasability for can not be sustained.
JP-A-11-7121 (paragraph number 0002) Japanese Patent Laid-Open No. 2000-273412 (paragraph number 0008)

  Therefore, the present invention does not attack the surface protective film by cleaning with a cleaning solvent, and is not affected by a solvent made of a polyhydric alcohol or a derivative thereof contained in the photoresist. It is an object to provide a surface protective film that maintains releasability and a surface protective film using the same.

  The surface protective film of the present invention has releasability and is formed from an ionizing radiation curable resin composition and an isocyanate prepolymer.

  The surface protective film of the present invention is formed from an ionizing radiation curable resin composition, an isocyanate prepolymer, and a release agent.

  Preferably, the release agent is a silicone compound.

  Preferably, the silicone compound is a silicone acrylate.

  Preferably, the silicone acrylate has a silicone content of 50% by weight to 90% by weight, a number average molecular weight of 5000 to 20000, and an acrylate functional group number of 3 or more.

  The surface protective film of the present invention is characterized by having the above-mentioned surface protective film on one surface of a plastic film and an adhesive layer on the other surface.

  In addition, the silicone content rate as used in the field of this invention means the ratio for which the polyalkylsiloxane skeleton in silicone acrylate accounts.

  The surface protective film and the surface protective film of the present invention may be attacked by a solvent comprising a polyhydric alcohol or a derivative thereof contained in the photoresist without the surface protective film being attacked by cleaning with a cleaning solvent. And extremely high releasability with respect to the photoresist can be maintained.

  The surface protective film of the present invention has releasability and is formed from an ionizing radiation curable resin composition and an isocyanate prepolymer. The surface protective film of the present invention is formed from an ionizing radiation curable resin composition, an isocyanate prepolymer, and a release agent. Hereinafter, embodiments of each component will be described.

  Since the surface protection film used on the surface of the photomask has unevenness due to through-holes etc. on the base substrate such as a printed wiring board, the convex part is applied with higher pressure than the smooth part when closely exposed, There is a problem that the surface protective film is scraped off little by little as exposure is repeated.

  In the present invention, by using an ionizing radiation curable resin composition as a resin component constituting the surface protective film, the surface protective film can be made difficult to be scraped off even if exposure is repeated. As a result, it is possible to prevent a decrease in the releasability of the surface protective film due to physical scraping of the surface protective film, suppress an increase in haze, and prevent a decrease in resolution. Further, since the surface protective film is hardly damaged, the durability of the surface protective film is improved and the number of exposures can be greatly increased.

  The hardness of the surface protective film varies depending on the laminate, but the difference in haze before and after the Taber abrasion hardness test in JIS K5400: 1990 (ie, the haze before the Taber abrasion hardness test from the haze after the Taber abrasion hardness test) The value obtained by subtracting (hereinafter abbreviated as “ΔH”) is preferably less than 25, more preferably less than 20.

  As such an ionizing radiation curable resin composition, a photopolymerizable prepolymer that can be crosslinked and cured by irradiation with ionizing radiation (ultraviolet rays or electron beams) can be used. An acrylic prepolymer having two or more acryloyl groups in the molecule and having a three-dimensional network structure by crosslinking and curing is particularly preferably used. As the acrylic prepolymer, urethane acrylate, polyester acrylate, epoxy acrylate, melamine acrylate, polyfluoroalkyl acrylate, silicone acrylate and the like can be used. Furthermore, these acrylic prepolymers can be used alone, but it is preferable to add a photopolymerizable monomer in order to improve the cross-linking curability and further improve the hardness of the surface protective film.

  As photopolymerizable monomers, monofunctional acrylic monomers such as 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, butoxyethyl acrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol One kind of bifunctional acrylic monomer such as diacrylate, polyethylene glycol diacrylate, hydroxypivalate ester neopentyl glycol diacrylate, etc., or polyfunctional acrylic monomer such as dipentaerythritol hexaacrylate, trimethylpropane triacrylate, pentaerythritol triacrylate or the like Two or more are used.

  In addition to the above-mentioned photopolymerizable prepolymer and photopolymerizable monomer, the surface protective film preferably uses additives such as a photopolymerization initiator and a photopolymerization accelerator when cured by ultraviolet irradiation.

  Examples of the photopolymerization initiator include acetophenone, benzophenone, Michler's ketone, benzoin, benzylmethyl ketal, benzoylbenzoate, α-acyloxime ester, thioxanthone and the like.

  Further, the photopolymerization accelerator can reduce the polymerization obstacle due to air at the time of curing and increase the curing speed. For example, p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester, and the like. can give.

  Here, when the above-mentioned polyfluoroalkyl acrylate and silicone acrylate are used alone, it is possible to impart releasability to the surface protective film without using a mold release agent. Considering adhesiveness to the laminate, surface hardness, etc., it is preferable to use it together with the above-mentioned other ionizing radiation curable resin composition as a release agent rather than using it alone.

  Next, the release agent is not particularly limited, and a release agent using a fluorine-based compound or a silicone-based compound can be used. In consideration of the initial release property from the photoresist, the silicone-based compound It is preferable that Examples of such silicone compounds include silicone oils, silicone resins, organosilsesquioxane ladder polymers, silicone comb graft polymers, silicone acrylates, and the like. It is preferable to use silicone acrylate because it can be cross-linked with the product.

  Here, the silicone acrylate is contained in the ionizing radiation curable resin composition as described above. However, the adhesiveness to the laminate, the surface hardness, and the initial release property when the surface protective film is formed. From the viewpoint of sustaining releasability after repeated exposure and cleaning, it is desirable to use it as a release agent. Thus, when silicone acrylate is used as a release agent, the surface hardness is increased by another ionizing radiation curable resin composition, and the silicone content is increased so that sufficient release properties can be obtained even when a small amount of silicone acrylate is added. It is preferable to make the number average molecular weight and the number of acrylate functional groups specific from the viewpoint of making them specific and maintaining releasability after repeated exposure and cleaning.

  That is, such a silicone acrylate has a silicone content of 50% by weight or more, preferably 60% by weight or more as a lower limit, and an upper limit of 90% by weight or less, preferably 80% by weight or less. When the silicone content is 50% by weight or more, excellent release properties can be imparted, and when it is 90% by weight or less, effective acrylate functional group numbers can be imparted and the release properties can be maintained. .

  The number average molecular weight is preferably 5,000 to 20,000, and more preferably 10,000 to 15,000. By setting the number average molecular weight to 5000 or more, it is possible to prevent the release agent from being transferred to the photoresist side during exposure. By setting the number average molecular weight to 20000 or less, the ionizing radiation curable resin composition described above can be prevented. The compatibility can be prevented from lowering, the transparency of the coating can be maintained, and the releasability of the surface protective film can be maintained.

  The number of acrylate functional groups is preferably 3 or more, and more preferably 3 or more and 8 or less. By setting the number of acrylate functional groups to 3 or more, the reactivity with the ionizing radiation curable resin composition described above can be made sufficient, and the releasability can be maintained. Further, even if the number of acrylate functional groups is 8 or more, it is not possible to maintain the releasability by improving the reactivity with the ionizing radiation curable resin composition described above.

  The amount of such a release agent added varies depending on the type of release agent used, such as a fluorine-based compound or a silicone-based compound, but in the case of a silicone-based compound, generally, the total amount of resin solids constituting the surface protective film About 0.1 wt% to 20 wt%. Further, when silicone acrylate is used, it varies depending on the silicone content, but in the above range, it is preferably 0.5 wt% to 10 wt%, more preferably about 0.5 wt% to 5 wt%.

  Next, the isocyanate prepolymer which comprises the surface protective film of this invention with the ionizing radiation curable resin composition mentioned above is demonstrated. The isocyanate prepolymer here refers to an isocyanate prepolymer that is usually used in a room temperature curing system together with a polyol resin. Isocyanate prepolymers include tolylene diisocyanate type, diphenylmethane diisocyanate type, xylylene diisocyanate type, isophorone diisocyanate type, hexamethylene diisocyanate type, etc., depending on the raw material isocyanate. Isophorone diisocyanate and hexamethylene diisocyanate are preferably used.

  By releasing and curing such an isocyanate prepolymer together with the ionizing radiation curable resin composition, the mold release property can be maintained in the surface protective film. The reason why the releasability can be maintained when the isocyanate prepolymer is contained together with the ionizing radiation curable resin composition in this way is not necessarily clear, but on the surface of the coating, it is difficult to cure due to oxygen in the air or a release agent. It seems that there are not a few curing obstacles due to this, and it seems that the solvent resistance is lowered due to this, and when the isocyanate prepolymer is included in the surface protective film, the isocyanate prepolymer crosslinks on the surface of the coating, and the curing obstacle This is considered to be because the shortage of crosslinking caused slightly by the above can be compensated. Thus, it is considered that the surface protective film has improved solvent resistance and can maintain releasability as compared with the case where the isocyanate prepolymer is not contained. By irradiating with ionizing radiation in an atmosphere of inert gas or the like here, it is possible to prevent such a curing failure due to oxygen in the air. In addition, it is impossible to prevent the curing failure caused by the release agent.

  The content of such an isocyanate prepolymer is not particularly limited, and it cannot be generally stated because it varies depending on the isocyanate group content, the thickness of the surface protective film, and the amount of release agent added. The lower limit of the total resin solids constituting the membrane is 1% by weight or more, preferably 5% by weight or more, more preferably 10% by weight or more, and the upper limit is 50% by weight or less, preferably 30% by weight or less. . When the amount is 1% by weight or more, the isocyanate prepolymer undergoes a cross-linking reaction on the surface of the surface protective film, and the shortage of crosslinking caused by a curing failure can be compensated. By setting the amount to 50% by weight or less, ionizing radiation curable resin By using the composition, physical properties such as film hardness can be prevented from being impaired.

  In addition to the ionizing radiation curable resin composition, isocyanate prepolymer, and release agent added as necessary, the surface protective film may be blended with other resins as long as these effects are not impaired. Good. However, in the case of a resin that reacts with an isocyanate prepolymer, such as a polyol resin, it is necessary to increase the amount of the isocyanate prepolymer that is reacted. In addition, the surface protective film has a lubricant, fine particles, a fluorescent brightening agent, a pigment, an antistatic agent, a flame retardant, an antibacterial agent, an antifungal agent, an antioxidant, and a plasticizer as long as these effects are not impaired. Various additives such as a leveling agent, a flow modifier, an antifoaming agent, and a dispersing agent can be included.

  In particular, as a surface protective film for a photomask, from the viewpoint of facilitating evacuation during contact exposure, an inorganic pigment, fine particles such as resin beads are included in the surface protective film on the surface of the surface protective film. It is preferable to form fine irregularities. Examples of such fine particles include inorganic pigments such as calcium carbonate, magnesium carbonate, barium sulfate, silica, aluminum hydroxide, kaolin, clay, talc, acrylic resin particles, polystyrene resin particles, polyurethane resin particles, polyethylene resin particles, benzoguanamine. Resin beads such as resin particles and epoxy resin particles can be used. The amount of such fine particles to be added varies depending on the type of fine particles and the thickness of the surface protective film, and thus cannot be generally stated. Usually, however, 0.1 wt% to 10 wt% with respect to the total resin solid content constituting the surface protective film. It is about wt%. In addition, the average particle size of such fine particles varies depending on the thickness of the surface protective film, but cannot be generally stated, but is usually about 0.1 μm to 10 μm, preferably 0.5 μm to 5 μm. The

  The thickness of the surface protective film is not particularly limited, but is preferably as thin as possible from the viewpoint of not reducing the resolution of the photomask at the time of exposure, and the surface protective film by repeating the surface hardness of the surface protective film and contact exposure. Specifically, the thickness is set to about 0.5 μm to 5 μm, preferably about 1 μm to 3 μm from the viewpoints of chipping, initial releasability, and sustained releasability after cleaning.

  Such a surface protective film is made by mixing an ionizing radiation curable resin composition, an isocyanate prepolymer, and a release agent added as necessary, other resins, other additives, a diluting solvent, and the like to protect the surface. I want to protect the photomask etc. by adjusting the coating solution for film and using a conventionally known coating method such as bar coater, die coater, blade coater, spin coater, roll coater, gravure coater, flow coater, spray, screen printing, etc. It can be produced by directly applying to a product, drying as necessary, curing by irradiation with ionizing radiation, and further curing by heating as necessary.

  As a method of irradiating with ionizing radiation, ultraviolet rays in a wavelength region of 100 nm to 400 nm, preferably 200 nm to 400 nm, emitted from an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a metal halide lamp, etc. are irradiated or scanned. The irradiation can be performed by irradiating an electron beam having a wavelength region of 100 nm or less emitted from a type or curtain type electron beam accelerator.

  The surface protective film of the present invention can also be used by directly forming it on a photomask as described above. For example, the surface protective film is formed on the other surface of the plastic film having an adhesive layer on one surface. In the same manner as above, a surface protective film is formed to produce a surface protective film, and the surface of the surface protective film having the adhesive layer and the surface of the photomask can be used together.

  Although it does not specifically limit as such a plastic film, A thing with high transparency is preferable, and the thing with a high ultraviolet-ray transmittance especially used in the case of exposure is more preferable. As such a plastic film, a plastic film having excellent transparency such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polystyrene, triacetyl cellulose, acrylic, polyvinyl chloride, and the like is used. In particular, a biaxially stretched polyethylene terephthalate film is preferably used because of its excellent mechanical strength and dimensional stability, such as plasma treatment, corona discharge treatment, deep ultraviolet irradiation treatment, and formation of an easily subtractable adhesion treatment layer. It is preferable to use one that has been subjected to easy adhesion treatment.

  The thickness of such a plastic film is preferably as thin as possible from the viewpoint of not reducing the resolution of the photomask at the time of exposure. However, in consideration of handleability and mechanical strength, it is 1 μm to 100 μm, preferably 2 μm to 25 μm. More preferably, it is about 4 μm to 15 μm.

  Next, the adhesive layer is formed from at least an adhesive component. The adhesive component is not particularly limited, and natural resin-based adhesives, synthetic resin-based adhesives, etc. are used, and synthetic resin-based adhesives such as acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, etc. Agents are preferably used. In addition, such an adhesive layer can contain various additives similar to the crosslinking agent and the surface protective film as long as the adhesiveness is not impaired.

  The thickness of the pressure-sensitive adhesive layer is not particularly limited, but 0.5 μm to 20 μm, preferably 1 μm to 10 μm, and more preferably 2 μm to 4 μm so that appropriate adhesiveness can be obtained without impairing transparency (resolution). To the extent. Moreover, it is good to stick the separator which performed the mold release process on the surfaces, such as a plastic film and paper, so that the handleability of a surface protection film may not fall by the adhesiveness.

  Such a pressure-sensitive adhesive layer is prepared by dissolving or dispersing a pressure-sensitive adhesive component and, if necessary, a crosslinking agent and other additives in a solvent to prepare a pressure-sensitive adhesive layer coating solution. It can be produced by applying and drying the surface of the plastic film opposite to the surface on which the surface protective film is formed by a conventionally known coating method. Alternatively, the adhesive layer coating solution can be applied to a separator or the like, dried, and laminated on the surface opposite to the surface of the plastic film on which the surface protective film is formed.

  As described above, according to the present invention, the ionizing radiation curable resin composition and the surface protective film having releasability formed from the isocyanate prepolymer are included in cleaning with a cleaning solvent and photoresist. Thus, a surface protective film and a surface protective film that maintain high releasability even after repeated exposure and cleaning without being attacked by the solvent to be obtained can be obtained.

  Hereinafter, the present invention will be described in more detail based on examples. In this example, “parts” and “%” are based on weight unless otherwise specified.

[Example 1]
A surface protective film coating solution of the following formulation is applied to one side of a 6 μm thick polyethylene terephthalate film (Lumirror: Toray Industries Inc.), and an adhesive layer coating solution of the following formulation is sequentially applied to the other side and dried. A surface protective film having a thickness of 2 μm was formed on the surface on which the protective film was formed by irradiating ultraviolet rays with a high-pressure mercury lamp. In addition, a separator having a thickness of 25 μm (MRB: Mitsubishi Chemical Polyester Film Co., Ltd.) was bonded to the surface having the adhesive layer in consideration of handling, and cured at 60 ° C. for 2 days to produce the surface protective film of Example 1. did. The silicone acrylate a used as the release agent had a silicone content of 70%, a number average molecular weight of about 12000, and a number of acrylate functional groups of 6.

<Prescription of Coating Solution for Surface Protective Film of Example 1>
・ Ionizing radiation curable resin composition 16 parts (polyester acrylate) (100% solids)
(Aronix M7100: Toa Gosei Co., Ltd.)
・ 5.5 parts of isocyanate prepolymer (solid content: 75%) (Bernock D750: Dainippon Ink & Chemicals, Inc.)
Release agent 0.2 parts (silicone acrylate a) (solid content 100%)
・ Photopolymerization initiator 1 part (Irgacure 184: Ciba Specialty Chemicals)
・ 77 parts of methyl ethyl ketone

<Prescription of coating solution for adhesive layer>
・ Acrylic adhesive (solid content 40%) 10 parts (Arontack SCL-200: Toagosei Co., Ltd.)
・ Toluene 10 parts ・ Ethyl acetate 10 parts

[Example 2]
A surface protective film of Example 2 was produced in the same manner as in Example 1 except that the coating liquid for surface protective film of Example 1 was changed to the coating liquid for surface protective film having the following formulation. The silicone acrylate b used as the release agent had a silicone content of 20%, a number average molecular weight of about 3000, and 2 acrylate functional groups.

<Prescription of Coating Solution for Surface Protective Film of Example 2>
・ Ionizing radiation curable resin composition 16 parts (epoxy acrylate) (solid content 100%)
(KAYARADR130: Nippon Kayaku Co., Ltd.)
・ 5.5 parts of isocyanate prepolymer (solid content: 75%) (Bernock D750: Dainippon Ink & Chemicals, Inc.)
Release agent 0.2 parts (silicone acrylate b) (solid content 100%)
・ Photopolymerization initiator 1 part (Irgacure 184: Ciba Specialty Chemicals)
・ 77 parts of methyl ethyl ketone

[Example 3]
A surface protective film of Example 3 was produced in the same manner as in Example 1 except that the coating liquid for surface protective film of Example 1 was changed to the coating liquid for surface protective film having the following formulation. The silicone oil used as the release agent was obtained by modifying one end of polysiloxane with an organic group.

<Prescription of Coating Solution for Surface Protective Film of Example 3>
-Ionizing radiation curable resin composition 16 parts (urethane acrylate) (solid content 100%)
(NK Oligo U15HA: Shin-Nakamura Chemical Co., Ltd.)
・ 5.5 parts of isocyanate prepolymer (solid content: 75%) (Bernock D750: Dainippon Ink & Chemicals, Inc.)
・ Releasing agent 0.2 parts (silicone oil) (solid content 100%)
(X22-170DX: Shin-Etsu Chemical Co., Ltd.)
・ Photopolymerization initiator 1 part (Irgacure 184: Ciba Specialty Chemicals)
・ 77 parts of methyl ethyl ketone

[Comparative Example 1]
Comparative Example 1 was the same as Example 1 except that the surface protective film coating solution of Example 1 was changed to the surface protective film coating solution of the following formulation (without adding the isocyanate prepolymer). A surface protective film was produced.

<Prescription of Coating Solution for Surface Protective Film of Comparative Example 1>
・ Ionizing radiation curable resin composition 20 parts (polyester acrylate) (100% solids)
(Aronix M7100: Toa Gosei Co., Ltd.)
Release agent 0.2 parts (silicone acrylate a) (solid content 100%)
・ Photopolymerization initiator 1 part (Irgacure 184: Ciba Specialty Chemicals)
・ Methyl ethyl ketone 79 parts

[Comparative Example 2]
The surface of Comparative Example 2 was prepared in the same manner as in Example 2 except that the surface protective film coating solution of Example 2 was changed to a surface protective film coating solution having the following formulation (without addition of isocyanate prepolymer). A protective film was prepared.

<Prescription of Coating Solution for Surface Protective Film of Comparative Example 2>
・ Ionizing radiation curable resin composition 20 parts (epoxy acrylate) (solid content 100%)
(KAYARADR130: Nippon Kayaku Co., Ltd.)
Release agent 0.2 parts (silicone acrylate b) (solid content 100%)
・ Photopolymerization initiator 1 part (Irgacure 184: Ciba Specialty Chemicals)
・ Methyl ethyl ketone 79 parts

[Comparative Example 3]
The surface of Comparative Example 3 was prepared in the same manner as in Example 3 except that the surface protective film coating solution of Example 3 was changed to a surface protective film coating solution having the following formulation (without addition of isocyanate prepolymer). A protective film was prepared.

<Prescription of Coating Solution for Surface Protective Film of Comparative Example 3>
・ Ionizing radiation curable resin composition 20 parts (urethane acrylate) (solid content 100%)
(NK Oligo U15HA: Shin-Nakamura Chemical Co., Ltd.)
・ Releasing agent 0.2 parts (silicone oil) (solid content 100%)
(X22-170DX: Shin-Etsu Chemical Co., Ltd.)
・ Photopolymerization initiator 1 part (Irgacure 184: Ciba Specialty Chemicals)
・ Methyl ethyl ketone 79 parts

  With respect to the surface protective films obtained in the examples and comparative examples, the surface protective film is not affected by cleaning with a cleaning solvent or a solvent such as polyhydric alcohol contained in the photoresist. The following tests were conducted to evaluate whether or not formability persisted. Moreover, the abrasion resistance of the surface protective film by repeated exposure was evaluated. The evaluation results are shown in Table 1.

(1) Evaluation of initial releasability Adhesive tape (Nitto Polyester 31b: Nitto Denko Corporation) is attached to the surface having the surface protective film of the surface protective films of Examples 1 to 3 and Comparative Examples 1 to 3. The 180 ° peeling force at a peeling speed of 300 mm / min was measured and evaluated using a tensile tester (TENSILON HTM-100: Toyo Baldwin). The evaluation was “「 ”when the peel force was less than 20 g / 50 mm,“ ◯ ”when it was 20 g / 50 mm to 30 g / 50 mm, and“ x ”when it was uncured and had a tacky feeling. did.

(2) Evaluation of releasability after wiping test As a wiping test, the surface having the surface protective film of Examples 1 to 3 and Comparative Examples 1 and 2 was treated with ethyl alcohol (EtOH) as a cleaning solvent. Was included in the gauze, and the releasability after 50 wiping operations was measured in the same manner as the initial releasability. Moreover, in order to evaluate the solvent resistance with respect to the polyhydric alcohol contained in a photoresist, the wiping test was done like the above using propylene glycol monomethyl ether (PGM) instead of ethyl alcohol (EtOH). The evaluation is “◎” when the peel force is less than twice the initial measurement value, “◯” when the peel force is 2 times or more and less than 10 times, and “×” when the peel force is 10 times or more. It was.

(3) Evaluation of abrasion resistance The separators of the surface protective films of Examples 1 to 3 and Comparative Examples 1 and 2 were peeled off and bonded to a transparent polyethylene terephthalate film (thickness: 188 μm), and then compliant with JIS K5400: 1990. Then, the Taber abrasion test was performed with the wear wheel CS-10F, the load 500 g, the rotation speed 70 rpm, and the rotation speed 100 times, and the value obtained by subtracting the haze before the test (initial haze) from the haze after the test was calculated as Taber abrasion hardness ΔH. It was. The haze was measured using a haze meter (NDH2000: Nippon Denka Co., Ltd.) based on JIS K7136: 2000. In the evaluation, a case where ΔH was less than 20 was evaluated as “◯”.

  As is clear from the results in Table 1, the surface protective films of Examples 1 to 3 are formed on the surface because the surface protective film is formed of an ionizing radiation curable resin composition, an isocyanate prepolymer, and a release agent. Not only has excellent solvent resistance to ethyl alcohol, which is a cleaning solvent used to clean the protective film, but also propylene glycol monomethyl ether, which is a polyhydric alcohol such as contained in a photoresist. However, it had excellent solvent resistance.

  In particular, since the surface protective film of Example 1 used a silicone acrylate having a silicone content of 70% by weight, a number average molecular weight of about 12000, and an acrylate functional group number of 6 as a release agent, the surface protective film was used after the wiping test. Also maintained extremely excellent release properties. On the other hand, since the surface protective film of Comparative Example 1 was formed without containing the isocyanate prepolymer, compared with Example 1, the release property after the wiping test was inferior. It was.

  Moreover, since the surface protective film of Example 2 used a silicone acrylate having a silicone content of 20% by weight, a number average molecular weight of about 3000, and an acrylate functional group number of 2 as a release agent, a wiping test was performed. Later, good release properties were maintained. On the other hand, since the surface protective film of Comparative Example 2 was formed without containing the isocyanate prepolymer, compared to Example 2, the release property after the wiping test was inferior. It was.

  In addition, the surface protective film of Example 3 was formed using an isocyanate prepolymer although the surface protective film was formed using silicone oil as a release agent, so that the initial release property was good, Even after the wiping test, good releasability was maintained. On the other hand, since the surface protective film of Comparative Example 3 was formed without containing an isocyanate prepolymer, the surface protective film was hardened by silicone oil and became uncured and tacky.

Claims (6)

  A surface protective film having releasability, which is formed from an ionizing radiation curable resin composition and an isocyanate prepolymer.   A surface protective film formed from an ionizing radiation curable resin composition, an isocyanate prepolymer, and a release agent.   The surface protective film according to claim 2, wherein the release agent is a silicone compound.   4. The surface protective film according to claim 3, wherein the silicone compound is silicone acrylate.   The surface protection film according to claim 4, wherein the silicone acrylate has a silicone content of 50 wt% or more and 90 wt% or less, a number average molecular weight of 5000 to 20000, and an acrylate functional group number of 3 or more.   A surface protective film comprising the surface protective film according to any one of claims 1 to 5 on one surface of a plastic film and an adhesive layer on the other surface.