JP4768099B2 - Film roll - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a film roll obtained by winding a surface protective film, and more specifically, a surface protective film that can be wound into a roll without sticking a release paper to the pressure-sensitive adhesive layer of the surface protective film. Even if the pressure-sensitive adhesive layer surface is bonded to the mating base material, it can be lightly peeled off as necessary, and the peel strength does not increase even after aging. It is related with the film roll which wound up the surface protection film which does not impair the testability of.
[0002]
[Prior art]
The surface protective film generally has a configuration in which a plastic film is used as a base material and an adhesive layer is provided on one surface of the film. In recent years, the use for protecting the surface of optical components has been increasing. For example, it is used for surface protection when manufacturing various displays such as TVs, computers, word processors, car navigation systems, etc. Among them, surface protection of liquid crystal display panels, etc., which are currently growing rapidly, and further polarizing plates during the manufacturing process It is used to protect the surface of optical components and optical laminates such as retardation plates and viewing angle widening films. In general, transparent olefin-based films such as polyethylene and polypropylene are used as the base material of the surface protective film, and these surface protective films are used after the production and assembly of a liquid crystal display or the like is completed or in actual use. The film is removed by peeling.
[0003]
In recent years, a liquid crystal display using a TFT method (thin film transistor method) has attracted particular attention due to its high definition, high responsiveness, and the like, and the demand for a surface protective film during its manufacture has become strict. For example, when manufacturing polarizing plates, liquid crystal displays, etc., product defects are often inspected with the surface protective film attached, and the substrate is transparent for olefin-based films such as polyethylene films as in the past. Inferior properties, and many gels such as fisheye, it becomes a foreign matter defect in the defect inspection, and it has become difficult to inspect the product itself with high accuracy. Moreover, once a surface protective film is affixed on a polarizing plate, a liquid crystal display, etc., it often remains affixed for a long time until the next manufacturing process. And after completion of inspection etc., if peeling becomes heavy when peeling off, workability will be worsened, and part of the adhesive of the film will remain, and defects such as foreign matter and distortion will occur in display inspection etc. There was a problem.
[0004]
On the other hand, a release paper is generally used in the production process for forming the pressure-sensitive adhesive layer on the surface of the pressure-sensitive adhesive layer of the surface protective film before use, and it is wound up as it is to obtain a product. However, when the surface protective film is used, the release paper is simply peeled off and discarded, which is a problem in terms of generation of waste and cost.
[0005]
[Problems to be solved by the invention]
The object of the present invention is to solve such problems of the prior art, and can be wound into a roll without sticking release paper to the adhesive layer of the surface protective film, and the adhesive of the surface protective film unwound from the roll. Even if the surface of the adhesive layer is bonded to the mating substrate, it can be peeled lightly as necessary, and the peel strength does not increase even after aging. It is providing the film roll which wound up the surface protection film which does not impair property.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventor used a pressure-sensitive adhesive having specific physical properties as a pressure-sensitive adhesive layer, and was suitable for this pressure-sensitive adhesive layer on the surface protective layer formed on the opposite surface. The present inventors have found that an improved film roll of a surface protective film can be obtained by combining with a biaxially oriented polyester film provided with a release layer and further provided with additional performance.
[0007]
That is, in the present invention, a surface protective film in which a pressure-sensitive adhesive layer (B) is provided on one side of the biaxially oriented polyester film (A) and a protective layer (C) is provided on the opposite side is referred to as a pressure-sensitive adhesive layer (B). A film roll obtained by bringing the protective layer (C) into contact with the film roll, A comonomer in which the pressure-sensitive adhesive layer (B) has a function of improving at least one cohesive force selected from the group consisting of vinyl acetate, acrylonitrile, styrene, and methyl methacrylate; and methacrylic acid, acrylic acid, itaconic acid, hydroxyethyl methacrylate, Consists of an acrylic pressure-sensitive adhesive containing, as a copolymerization component, at least one functional group-containing monomer having a function of promoting high crosslinking selected from the group consisting of glycidyl methacrylate, and from a hydroxyl group, a carboxyl group, an epoxy group, an amine group, and an isocyanate group. A wax component having at least one reactive functional group selected from the group consisting of: It is a film roll characterized by satisfying all the following conditions (1) to (6).
(1) The biaxially oriented polyester film (A) has a side length of 210 mm and a width of a side length of 148 mm (area 310.8 cm). ² ) There is no foreign matter with a size of 25 μm or more per contact.
(2) The biaxially oriented polyester film (A) has a side length of 210 mm and a width of a side length of 148 mm (area 310.8 cm). ² ) There are no more than 10 foreign matters having a size of 5 μm or more and less than 25 μm.
(3) The protective layer (C) contains a release agent and an antistatic agent.
(4) The peeling force when the protective layer (C) is peeled from the pressure-sensitive adhesive layer (B) is 10 mN / 25 mm or more and 1000 mN / 25 mm or less.
(5) The normal pressure-sensitive adhesive force of the pressure-sensitive adhesive layer (B) to the stainless steel plate is 30 mN / 25 mm or more and 500 mN / 25 mm or less, and the rate of change of the adhesive force after 60 ° C. and 1 week is 0.5 to 2 times. .
(6) The thickness of the pressure-sensitive adhesive layer (B) is 3 μm or more and 50 μm or less.
[0008]
Furthermore, the visible light transmittance of the surface protective film constituting the film roll is preferably 70% or more, and the haze is preferably 10% or less.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The surface protective film in this invention takes the structure which provided the adhesive layer on the single side | surface of the biaxially oriented polyester film used as a base material, and provided the protective layer on the opposite surface.
[0010]
[Polyester film]
As the base material of the surface protective film in the present invention, a biaxially oriented polyester film excellent in high transparency, productivity, and processability is used. The biaxially oriented polyester film is not particularly limited, but a biaxially oriented polyethylene terephthalate film or a biaxially oriented polyethylene-2,6-naphthalene dicarboxylate film is preferable. Moreover, in the structure, you may take the multilayered structure of arbitrary layers by coextrusion.
[0011]
The polyester constituting such a biaxially oriented polyester film is preferably a crystalline linear saturated polyester comprising an aromatic dibasic acid component and a diol component. For example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene- Examples include 2,6-naphthalenedicarboxylate. Further, a copolymer in which some of these are substituted with other components, a polyalkylene glycol, or a mixture with other resins may be used.
[0012]
The biaxially oriented polyester film can be produced by a conventionally known method such as a sequential biaxial stretching method or a simultaneous biaxial stretching method. For example, the sequential biaxial stretching method can be performed by the following method. After the polyester polymer is sufficiently dried, it is extruded from a die (for example, T-die, I-die, etc.) onto a cooling drum by a melt extrusion method, and rapidly cooled to obtain an unstretched film or a co-extruded unstretched film. Produced, and then stretched the unstretched film at a temperature of 60 to 140 ° C. in the range of 2 to 5 times in the machine direction, and then stretched at a temperature of 80 to 150 ° C. in the range of 2 to 5 times in the transverse direction. It can be manufactured by performing heat fixation at a temperature of 160 to 260 ° C. for 1 to 100 seconds. The heat setting may be performed under limited shrinkage. Moreover, it is preferable to use an electrostatic contact method at the time of melt extrusion.
[0013]
Further, the isotropic property of the biaxially oriented polyester film should be as good as possible in order not to cause breakage in a specific direction. For example, the above-described stretching ratios in the longitudinal direction and the transverse direction may be the same. preferable.
[0014]
Although there is no restriction | limiting in particular in the thickness of a film, 5-500 micrometers is preferable. More preferably, the thickness is preferably 10 to 200 μm in order to improve workability such as bonding and productivity.
[0015]
In such a biaxially oriented polyester film, in order to improve the slipping property at the time of winding the film and the handling at the time of processing such as adhesive coating, a lubricant such as calcium carbonate, alumina, kaolin, silica, Can contain inorganic fine particles such as titanium oxide, barium sulfate, zeolite, etc., and organic fine particles such as silicone resin, cross-linked polystyrene, acrylic resin, and other additives such as stabilizers, UV absorbers, flame retardants Further, an antistatic agent or the like can be contained. There are no particular restrictions on the timing of addition of fine particles, additives, etc., as long as it is a stage until a biaxially oriented polyester film is formed. For example, it may be added at the polymerization stage, or may be added during film formation. Good.
[0016]
In this biaxially oriented polyester film, the center line average roughness (Ra) is preferably 2 nm or more and 500 nm or less. If the center line average roughness is less than 2 nm, there is a risk of hindering the transportability such as being difficult to slip during processing. If the center line average roughness is greater than 500 nm, the transparency deteriorates and the inspection property is lowered. When the pressure-sensitive adhesive layer is provided, particularly when the pressure-sensitive adhesive layer is applied on the surface of the protective layer and the pressure-sensitive adhesive layer is provided on the opposite surface by a transfer method, there is a concern that the biaxially oriented polyester film does not adhere uniformly due to the unevenness.
[0017]
Further, in the biaxially oriented polyester film, the width (area 310.8 cm) of one side length 210 mm and the side length 148 mm perpendicular to the side length 210 mm. ² It is preferable that no foreign matter having a size of 25 μm or more exists in the per film and that there are 10 or less foreign matters having a size of 5 μm or more and less than 25 μm. If there is a foreign material of 25 μm or more, a void or the like is generated at the time of application or transfer of the adhesive, and the adhesive is removed or swelled only by that part, so that the local area can be confirmed visually. May be a general appearance defect. Further, when there are more than 10 foreign matters having a size of 5 μm or more and less than 25 μm, the size of the foreign matter is difficult to visually confirm.
[0018]
[Adhesive layer]
The pressure-sensitive adhesive layer laminated on one side of the biaxially oriented polyester film is not only indoors but also for outdoor use, and because it can withstand various rays during inspection, it is particularly necessary to withstand ultraviolet rays. In order to prevent migration of components from the pressure-sensitive adhesive layer to the bonded base material, a layer made of an acrylic pressure-sensitive adhesive is particularly preferable.
[0019]
The thickness of the pressure-sensitive adhesive layer of the surface protective film is preferably 3 μm or more and 50 μm or less. When the thickness is less than 3 μm, it is governed by the hardness of the biaxially oriented polyester film that is the base material of the surface protective film when bonded to an uneven polarizing plate, etc., and the pressure-sensitive adhesive wets and spreads sufficiently on the polarizing plate surface. Absent. In addition, the necessary adhesive strength cannot be obtained, and when the films are bonded, there may be partial lifting. When the thickness is larger than 50 μm, the adhesive strength becomes higher than necessary, and when the adhesive is applied, there is a problem in terms of thickness control, curing control, and cost.
[0020]
The film roll of the present invention has a configuration in which a pressure-sensitive adhesive layer is provided on one side of a base material, and a surface protective film provided with a protective layer on the opposite side is brought into contact (bonded) with the pressure-sensitive adhesive layer and the protective layer. is there. The surface protective film is unwound from the film roll and bonded to a counterpart structure (polarizing plate, stainless steel plate, etc.) and used for protecting the surface of the counterpart structure. And when the other party structure is used for a process or an original use, the bonded surface protection film is peeled off.
[0021]
That is, the pressure-sensitive adhesive layer of the surface protective film needs to have a characteristic that it can be easily bonded to and peeled off from the other surface to be bonded (protective layer, polarizing plate, stainless steel plate, etc.). In order for the pressure-sensitive adhesive layer to exhibit such characteristics, it is preferable that the following range is satisfied.
(1) The peeling force when the protective layer (C) is peeled from the pressure-sensitive adhesive layer (B) is 10 mN / 25 mm or more and 1000 mN / 25 mm or less.
(2) The normal adhesive strength to the stainless steel plate is 30 mN / 25 mm or more and 500 mN / 25 mm or less, and the rate of change in adhesive strength after 1 week at 60 ° C. is 0.5 to 2 times.
[0022]
When the peeling force on the protective layer is less than 10 mN / 25 mm, winding roll deviation may occur, and when the peeling force is greater than 1000 mN / 25 mm, the film having a wide width when unrolled from the roll has a great tension. May be necessary due to the large amount of equipment, and the peeling charge may be increased, which may cause damage to the film surface. Moreover, it is not preferable that the normal state adhesive strength with respect to the stainless steel plate is less than 30 mN / 25 mm, because edge cracking may occur or the film may be easily peeled off by some contact. On the other hand, if it exceeds 500 mN / 25 mm, for example, in the step of peeling the surface protective film from the polarizing plate or the like, it is not easily peeled off, so that an inadvertent force is applied to the polarizing plate, which may cause deformation.
[0023]
Furthermore, it is necessary that the normal adhesion to the stainless steel plate does not change with time. Specifically, it is preferable that the change rate of the normal adhesion after 1 week at 60 ° C. is 0.5 to 2 times. If it is less than 0.5 times or more than 2 times, the fluctuation of the adhesive force becomes large, and when the surface protective layer is automatically peeled off, setting and management become complicated, and further, if the rate of change is large, peeling is difficult. Become.
[0024]
The center line average roughness (Ra) of the pressure-sensitive adhesive layer is preferably 2 nm or more and 500 nm or less. There is no particular problem in the case where the center line average roughness is small, but when it is larger than 500 nm, the thickness, the adhesive force, and the peeling force of the pressure-sensitive adhesive layer satisfy the above ranges when bonded to a polarizing plate or the like. Even if it is, it may not adhere completely, distortion may occur, and air bubbles may be generated in the recessed part.
[0025]
The pressure-sensitive adhesive to be used is not particularly limited, but an acrylic pressure-sensitive adhesive described below is preferable in order to satisfy the above characteristics. Acrylic pressure-sensitive adhesives include solvent-based and emulsion-based ones, and solvent-based pressure-sensitive adhesives are particularly preferable for easily obtaining the above-mentioned pressure-sensitive adhesive properties. As the acrylic solvent-based pressure-sensitive adhesive, those obtained by solution polymerization are used in order to satisfy various characteristics. As a raw material, the well-known thing for solution polymerization of an acrylic adhesive can be used. For example, as the main monomer as a skeleton, acrylic acid esters such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and octyl acrylate, and as comonomers for improving cohesion, vinyl acetate, acrylonitrile, styrene, methyl methacrylate, and the like Furthermore, methacrylic acid, acrylic acid, itaconic acid, hydroxyethyl methacrylate, glycidyl methacrylate, etc. are mentioned as functional group-containing monomers for further promoting high crosslinking and imparting stable low adhesive strength, but low adhesiveness and tackiness. In order to achieve high crosslinking with an isocyanate-based curing agent, an aziridine-based curing agent, etc. in order to have a high cohesive force, those containing a large amount of hydroxyl groups are particularly preferable. Also, in order to make the pressure-sensitive adhesive layer soft to some extent when bubbles are bonded to an uneven mating base material, among the above components, the main monomer as a skeleton having a low glass transition temperature (Tg) It is preferable to use a large amount of components and, on the other hand, to use a small amount of a comonomer component having a high Tg and improving cohesive strength.
[0026]
The synthesis of the pressure-sensitive adhesive can be performed by a known method. For example, in the presence of an organic solvent such as ethyl acetate or toluene, the necessary raw materials are introduced into the reaction vessel, and heated using a peroxide system such as benzoyl peroxide or an azobis system such as azobisisobutyronitrile as a catalyst. Can be polymerized under. In order to increase the molecular weight, for example, ethyl acetate is preferably used because batches of monomers are initially charged, and in the organic solvent species used, toluene has a large chain transfer coefficient and thus suppresses polymer growth. At this time, the weight average molecular weight (Mw) is preferably 300,000 or more, more preferably 400,000 or more. If the molecular weight is less than 300,000, even if it is crosslinked with an isocyanate curing agent, a product with sufficient cohesive strength cannot be obtained, and even when it is evaluated for holding power under load, it can be dropped immediately, or a stainless steel plate or a polarizing adhesive layer The adhesive may remain on the stainless steel plate, polarizing plate, etc. when it is peeled off after lapse of time. In order to improve the molecular weight, it is important to control at the polymerization stage. However, in general, the solvent system does not increase the molecular weight even if sufficient adhesive strength is obtained. It is necessary to improve the rate.
[0027]
Although it does not specify as a hardening | curing agent of an adhesive, general isocyanate type, an epoxy type, an aziridine type hardening | curing agent etc. can be used especially in an acrylic solvent type | system | group. The adhesive may contain, for example, a stabilizer, an ultraviolet absorber, a flame retardant, an antistatic agent and the like as an additive. In addition, the additive is necessary to suppress the adhesive force that is increased by using an adhesive having a low glass transition temperature, and also to suppress the increase in the adhesive force over time. As additives, organic resins such as wax, silicone oil, fluorine-based resin, and the like can be used. However, it is preferable that these components are transferred to the mating base material to which the components are bonded, and inspection properties are not impaired. Therefore, it is preferable that the PSA component partially reacts. For example, in an organic resin such as wax, a higher fatty acid ester having a reactive functional group such as a hydroxyl group, a carboxyl group, an epoxy group, an amine group, or an isocyanate group is used. It is preferable to use it.
[0028]
Application of the pressure-sensitive adhesive solution to the biaxially oriented polyester film can be performed at any stage. In addition, when applying the coating liquid to a biaxially oriented polyester film, flame treatment and corona discharge are applied to the surface of the biaxially oriented polyester film as a pretreatment for improving adhesion and coating properties as necessary. By performing physical surface treatment such as treatment, plasma discharge treatment, or chemical surface treatment by applying an organic resin or inorganic resin paint during or after film formation, The adhesion of the biaxially oriented polyester film can be strengthened.
[0029]
As the method for coating the pressure-sensitive adhesive, any known method can be used, for example, a die coater method, a gravure roll coater method, a blade coater method, a spray coater method, an air knife coating method, a dip coating method, and the like are preferable. They can be used alone or in combination.
[0030]
In addition, the order of forming the pressure-sensitive adhesive layer and the protective layer is not particularly limited, but the film roll of the present invention is characterized in that it is wound without using a release paper. It is preferable to provide an adhesive layer on the opposite surface. Moreover, an adhesive layer can also be provided on the protective layer surface provided in advance, and after the film of this layer structure is wound up to create a film roll, the surface protective film is unwound and the adhesive is applied to both sides of the base film. A surface protective film in which a layer and a protective layer are formed can be obtained. In order to remove the pressure-sensitive adhesive layer lightly from the protective layer surface, the surface of the pressure-sensitive adhesive layer is partially crosslinked / cured by drying before winding. However, the adhesive strength is reduced, which is preferable.
[0031]
The drying temperature when applying the pressure-sensitive adhesive is preferably such that the residual solvent is as low as possible. For this purpose, the drying temperature and time are not specified, but preferably at a temperature of 50 to 150 ° C. for 10 seconds to 5 minutes. It is good to have time.
[0032]
Because the adhesive has fluidity, and when using an isocyanate curing agent as a cross-linking agent, the reaction is not yet complete immediately after heating and drying, so that the reaction is completed and a stable adhesive force is obtained. Curing is also necessary. In general, when heated at room temperature for about one week or longer, for example, about 50 ° C. is preferably 3 days or longer. In the case of heating, if the temperature is raised too much, the flatness of the plastic film may be deteriorated.
[0033]
[Protective layer]
In the surface protective film in the present invention, a protective layer is provided on the surface opposite to the pressure-sensitive adhesive layer of the biaxially oriented polyester film. The protective layer preferably contains a release agent so that it can be easily peeled off from the pressure-sensitive adhesive layer. In addition, the protective layer prevents dust from being formed on the surface of the surface protective film by preventing the other member (TFT display plate, etc.) from being destroyed by the peeling charge generated when the pressure-sensitive adhesive layer is peeled from the member. In order to prevent adsorption or to easily remove adhering dust, an antistatic agent is preferably included. The release agent and antistatic agent may be mixed and provided as a single layer, or an antistatic layer containing an antistatic agent may be provided first, and a release layer containing a release agent may be provided thereon. . In this case, since the outermost surface layer needs to be releasable from the pressure-sensitive adhesive layer, the release layer needs to be provided so as to be the outermost surface layer. Furthermore, the antistatic agent may be mixed in the pressure-sensitive adhesive layer, or may be provided between the pressure-sensitive adhesive layer and the biaxially oriented polyester film.
[0034]
Release agents and antistatic agents are incorporated into binders to form layers to improve the strength of the layers and improve adhesion to biaxially oriented polyester films, water resistance, solvent resistance, blocking properties, etc. It is preferable to do this. Examples of the binder include thermoplastic compounds such as thermoplastic polyester resins and acrylic resins and / or polymer compounds such as thermosetting resins such as thermosetting acrylic resins, urethane resins, melamine resins, and epoxy resins. It is particularly preferable that the crosslinking agent used together with the resin contains at least one selected from methylolated or alkylolized melamine-based, urea-based, acrylamide-based compounds, epoxy compounds, and polyisocyanates. In addition, when providing an antistatic layer and a release layer separately, it is preferable that the binder component used for both is a similar main component, since both adhesiveness improves.
[0035]
The antistatic agent is not particularly limited, but examples thereof include various cationic antistatic agents having cationic properties such as quaternary ammonium salts, pyridinium salts, and primary to tertiary amino groups, sulfonate groups, and nitrate ester bases. Anionic antistatic agents having anionic properties such as phosphate ester bases, amphoteric antistatic agents such as amino acids and aminosulfate esters, nonionic antistatic agents such as amino alcohols, glycerols, and polyethylene glycols Various surfactant-type antistatic agents and the above polymerized ones can be used. Moreover, what disperse | distributed electroconductive polymers, such as polyaniline, polypyrrole, and polythiophene, and oxide type fillers, such as tin and antimony, can also be used. Furthermore, a metal layer such as silver or tin may be provided by a vapor deposition method, a vacuum deposition method, a sputtering method, a plasma CVD method, or the like.
[0036]
The release layer not only prevents the surface protection film surface from dirt and improves the wiping property of the dirt, but also is the surface on which the adhesive layer is applied, and when it is rolled up, Therefore, it is preferable that it has an appropriate peeling force and is durable. Examples of the release agent include silicone-based, fluorine-based and alkyl polymer-based release agents, and an alkyl polymer system having particularly low migration property is preferable in order to prevent contamination in the process. In particular, a polymer having a long alkyl side chain is preferable, and a copolymer of an alkyl acrylate having 12 or more carbon atoms, particularly an alkyl group having 16 to 20 carbon atoms, and acrylic acid is preferable. If the alkyl chain of the alkyl acrylate has less than 12 carbon atoms, sufficient peelability may not be obtained. Among these, a copolymer obtained by long-chain alkylating polyvinyl alcohol or polyethylene chlorinated with chlorinated alkyloyl or alkyl isocyanate is particularly preferable.
[0037]
When the protective layer is provided with a biaxially oriented polyester film, the protective layer can be applied before completion of crystal orientation during film formation or after film formation after completion of crystal orientation.
[0038]
As an application method to the biaxially oriented polyester film, any known method can be applied. For example, a roll coating method, a gravure coating method, a reverse coating method, a spray coating method, or the like can be used alone or in combination. Coating of the protective layer can be performed by applying a coating liquid containing components for forming each of the protective layers to the base film and drying by heating to form a coating film. The heating condition is preferably 80 to 160 ° C. for 10 to 120 seconds, particularly preferably 120 to 150 ° C. for 20 to 60 seconds.
[0039]
Also, when applying the coating liquid to the biaxially oriented polyester film, if necessary, as a pretreatment for improving the adhesion and coating properties, the biaxial orientation is the same as when applying the adhesive layer. Chemical surface treatment that applies physical surface treatments such as flame treatment, corona discharge treatment, plasma discharge treatment to the polyester film surface, or applies organic resin or inorganic resin paint during or after film formation By applying this, the adhesiveness between the pressure-sensitive adhesive and the biaxially oriented polyester film can be strengthened.
[0040]
The surface protective film in the present invention is required to have high transparency for easy inspection. Specifically, the visible light transmittance is preferably 70% or more, and the haze is preferably 10% or less. If the light transmittance is less than 70% and the haze is greater than 10%, the transparency is poor, so that, for example, in the defect inspection when the surface protective film is bonded to the polarizing plate, the foreign matter cannot be detected. There is concern.
[0041]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. In addition, each physical-property value in an Example and a comparative example was measured as follows.
[0042]
(1) Peeling force
The pressure-sensitive adhesive layer surface of the surface protective film is directly attached to the protective layer surface of the same surface protective film with a rubber roller, and then reciprocated once with a 2 kg rubber roller so as to adhere. It is allowed to stand for 30 minutes under the conditions of a temperature of 23 ° C. and a humidity of 55 ± 5% RH, and then cut into a 25 mm width strip. Using a tensile tester (Strograph manufactured by Toyo Seiki Co., Ltd.), the bonded protective film is pulled at 180 ° at 300 mm / min, and the strength is taken as the peel force.
[0043]
(2) Normal adhesive strength
The pressure-sensitive adhesive layer surface of the surface protective film is directly attached to the cleaned stainless steel plate with a rubber roller, and then reciprocated once with a 2 kg rubber roller so as to adhere. It is left as it is for one day under the conditions of a temperature of 23 ° C. and a humidity of 55 ± 5% RH, and then cut into a 25 mm width strip. This is attached to a tensile testing machine (Strograph made by Toyo Seiki Co., Ltd.), and a stainless steel plate is fixed. The laminated film is pulled at 180 ° at 300 mm / min, and the strength is used as normal adhesive strength.
[0044]
(3) Adhesive strength after 1 week at 60 ° C
A sample prepared in the same manner as the above normal adhesive strength was allowed to stand at 60 ° C. for 1 week, then returned to room temperature, and the adhesive strength after standing for 30 minutes was measured with a tensile tester to obtain the adhesive strength after 1 week. .
[0045]
(4) Light transmittance
The transmittance is measured at a wavelength of 550 nm (Nippon Seimitsu Optical Co., Ltd., Poic Haze Meter SEP-HS-D1 type).
[0046]
(5) Number of foreign matter in plastic film
A plastic film sample is 210 mm long x 148 mm wide (area 310.8 cm) ² ), And the entire range of the film was inspected by a visual inspection using the crossed Nicols method. Subsequently, the foreign matter in the detected sample film was observed with transmitted light using an optical microscope, and the maximum diameter of the portion observed as an optically abnormal range was defined as the size of the foreign matter. In addition, when the void (void) existing around the foreign particle is observed as an optically abnormal range, it is included in the size of the foreign particle. Then, the size of foreign particles was divided into 5 μm or more and less than 25 μm and 25 μm or more, respectively, and counted as the number of foreign particles.
[0047]
(6) Number of surface defects
The obtained surface protective film was bonded to a polarizing plate, and was 210 mm long × 148 mm wide (area 310.8 cm). ² ), And those having a level at which surface irregularities could be visually confirmed with the reflected light under a fluorescent lamp were counted.
[0048]
[Example 1]
As an acrylic adhesive, 2-ethylhexyl acrylate and n-butyl acrylate as main monomers, vinyl acetate as a comonomer, and hydroxyethyl methacrylate as a functional group-containing monomer in a ratio of 4: 3: 2: 1, and further added As an agent, 0.5 part of epoxy-modified stearyl acrylate is added to 10 parts of all the above monomers, and solution polymerization is performed using azobisisobutyronitrile as a reaction catalyst in a solvent of ethyl acetate to obtain a weight average molecular weight of about 45. Ten thousand adhesive polymers were prepared. Next, a rotating refrigeration is performed by melting polyethylene terephthalate polymer having an intrinsic viscosity of 0.62 containing 0.1% by weight of true spherical silica particles having an average particle size of 0.15 μm with an extruder and maintaining the temperature at 40 ° C. from the die. On the drum, the film was brought into close contact using an electrostatic contact method and quenched to obtain an unstretched film. Next, this unstretched film was stretched 3.5 times in the longitudinal direction and then 3.6 times in the transverse direction, and further heat-set at 220 ° C. to obtain a biaxially oriented polyethylene terephthalate film having a thickness of 50 μm. Furthermore, the corona treatment was performed on both surfaces of this film. Next, on one side of the film, an antistatic layer was provided as the first layer as a protective layer, and a release layer was provided as the second layer. As the antistatic layer, 30 parts of thiophene derivative polymer, 70 parts of copolyester (dicarboxylic acid component: 60 mol% terephthalic acid, isophthalic acid 35 mol%, adipic acid 5 mol%, glycol component: 95 mol% ethylene glycol 3% aqueous coating solution comprising 5 parts by weight of diethylene glycol and 5 parts of a nonionic surfactant was applied to form a coating film having a thickness of 0.15 μm after drying. As a release layer, 40 parts of polyethyleneimine octadecyl carbamate (manufactured by Nippon Shokubai Co., Ltd., RP-20), as a binder component, a polyester-based polyester resin (Espel 1510, manufactured by Hitachi Chemical Co., Ltd.) as well as an antistatic layer. A coating solution obtained by mixing 100 parts and 30 parts of melamine resin (manufactured by Sanwa Chemical Co., Ltd., Nicarac NS-11) was applied, dried and cured at 140 ° C. for 1 minute, and separated by 0.2 μm in thickness. A shape layer was formed. Next, a TDI-based isocyanate crosslinking agent is added to the above-mentioned pressure-sensitive adhesive polymer, applied to the surface opposite to the protective layer of the film so that the thickness after drying is 20 μm, dried at 100 ° C. for 2 minutes, wound up, 45 A sample was obtained after aging treatment at 1 ° C. for 1 week. The properties of this laminated film are shown in Table 1.
[0049]
[Comparative Example 1]
In Example 1, an adhesive was applied to the opposite surface of the antistatic layer without providing a release layer, and wound up.
[0050]
[Comparative Example 2]
In Example 1, as a base material for the surface protective film, the same content except that the polyethylene terephthalate polymer having an intrinsic viscosity of 0.61 contains 0.5% by weight of spherical silica particles having an average particle size of 0.5 μm. Thus, a plastic film was obtained and a laminated film was prepared. The characteristics are shown in Table 1.
[0051]
[Comparative Example 3]
In Example 1, a sample was prepared in the same manner except that the biaxially oriented polyethylene terephthalate film was changed to a polyethylene film as the base material of the surface protective film. The characteristics are shown in Table 1. The polyethylene film was used after corona treatment was applied to a 50 μm-thick film obtained by forming a polyethylene resin having a density of 0.925 and a melt index of 2.5 by inflation.
[0052]
[Table 1]
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Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3
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Plastic film PET PET PET PET PE
Peeling force (mN / 25mm) 150 1100 200 120
Normal adhesive strength (mN / 25mm) 120 600 110 110
後 After 1 week at 60 ° C 140 1000 120 130
Normal adhesive strength change rate 1.2 1.7 1.1 1.2
Number of surface protective film foreign matter
25μm or more (pieces) 0 0 5 15
<25 μm (pieces) 3 4 12 10
Light transmittance (%) 85 82 82 65
Haze (%) 6 7 7 12
Number of surface defects (pieces) 0 0 8 18
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[0053]
As is clear from Table 1, the surface protective film of the present invention shown in the examples forms a pressure-sensitive adhesive layer without using a release paper, and is easily peeled off at the time of use and bonded to a counterpart substrate. In addition, it can be peeled off lightly as needed, and does not become heavy even after aging. Furthermore, it is highly transparent and does not impair the inspection property of the bonded counterpart substrate.
[0054]
【The invention's effect】
The surface protective film in the present invention can form an adhesive without using a release paper, can be easily peeled off from a roll at the time of use, and can be used for manufacturing a liquid crystal display related part such as a polarizing plate. Since it is low and changes with time are small, productivity and yield can be improved, and by using a polyester film with few foreign substances as a base material, transparency is good and inspection properties can be improved. Furthermore, by providing the opposite surface of the pressure-sensitive adhesive layer with an antistatic treatment or a release treatment, it becomes easy to suppress charging during peeling and remove dust on the surface.

Claims (1)

A surface protective film in which a pressure-sensitive adhesive layer (B) is provided on one side of the biaxially oriented polyester film (A) and a protective layer (C) is provided on the opposite side, is a pressure-sensitive adhesive layer (B) and a protective layer (C). A co-monomer having a function of improving at least one cohesive force selected from the group consisting of vinyl acetate, acrylonitrile, styrene, and methyl methacrylate , wherein the pressure-sensitive adhesive layer (B) is a film roll obtained by contacting and rolling And an acrylic pressure-sensitive adhesive containing, as a copolymerization component, a functional group-containing monomer having a function of promoting high crosslinking selected from the group consisting of methacrylic acid, acrylic acid, itaconic acid, hydroxyethyl methacrylate, and glycidyl methacrylate. , a hydroxyl group, a carboxyl group, an epoxy group, an amine group, selected from the group consisting of isocyanate groups At least one wax component having a reactive functional group and contain a film roll, characterized by satisfying all the following conditions (1) to (6) are.
(1) In the biaxially oriented polyester film (A), there is no foreign matter having a size of 25 μm or more per area (area 310.8 cm ² ) having a side length of 210 mm and a side length of 148 mm.
(2) The biaxially oriented polyester film (A) has at most 10 foreign matters having a size of 5 μm or more and less than 25 μm per area (area 310.8 cm ² ) having a length of 210 mm on one side and a length of 148 mm on the right side. Only exists.
(3) The protective layer (C) contains a release agent and an antistatic agent.
(4) The peeling force when the protective layer (C) is peeled from the pressure-sensitive adhesive layer (B) is 10 mN / 25 mm or more and 1000 mN / 25 mm or less.
(5) The normal pressure-sensitive adhesive force of the pressure-sensitive adhesive layer (B) to the stainless steel plate is 30 mN / 25 mm or more and 500 mN / 25 mm or less, and the rate of change of the adhesive force after 60 ° C. and 1 week is 0.5 to 2 times. .
(6) The thickness of the pressure-sensitive adhesive layer (B) is 3 μm or more and 50 μm or less.