JP5130494B2 - Optical member - Google Patents

Description

  The present invention relates to surface protection of a synthetic resin plate and the like, in particular, a biaxially stretched polymer film suitably used as a protective film or a separator for constituent members of a liquid crystal display device such as a polarizing plate and a retardation plate, and surface protection using the same. Related to film.

  The liquid crystal display device is generally configured by laminating a polarizing plate, a liquid crystal cell, and a polarizing plate from the backlight side. Furthermore, various compensation plates such as a phase difference plate are inserted for the purpose of improving the display mode and the viewing angle. The lamination of the polarizing plate and the retardation plate is usually performed by bonding a polarizing plate with an adhesive layer or a retardation plate with an adhesive layer to an object.

  The polarizing plate has a structure in which a polarizing film is sandwiched with triacetyl cellulose, and usually has a pressure-sensitive adhesive layer for bonding on one side. In addition, since triacetyl cellulose in the polarizing plate is inferior in scratch resistance and moisture resistance, a surface protective film is provided on both sides to prevent damage, moisture, or adhesion of dust during handling or the manufacturing process of the liquid crystal display device. It is done. A surface protective film having a pressure-sensitive adhesive layer laminated on the surface opposite to the pressure-sensitive adhesive layer side of the polarizing plate, and a surface protective film having a release layer laminated on the pressure-sensitive adhesive layer side are used.

  In addition, various compensators such as a retardation plate are usually provided with a pressure-sensitive adhesive layer on one side, and for the purpose of preventing damage during the handling and manufacturing process of the liquid crystal display device, and adhesion of dust. As with the polarizing plate, a surface protective film (a surface protective film having a pressure-sensitive adhesive layer laminated on the side opposite to the pressure-sensitive adhesive layer side) and a release layer on the pressure-sensitive adhesive layer side were laminated on both sides of various compensation plates. Surface protection film) is used.

  And when sticking a polarizing plate, a phase difference plate, etc. to a liquid crystal cell, a surface protection film is peeled off and used.

  Conventionally, as the surface protective film on which the pressure-sensitive adhesive layer is laminated, a pressure-sensitive adhesive type such as a thermocompression bonding type such as a polyethylene film or an ethylene-vinyl acetate copolymer film, or a polyester film provided with a pressure-sensitive adhesive layer. Is used.

  Moreover, as a surface protective film in which a conventional release layer is laminated, a film in which a release agent such as silicone is applied to at least one surface of a biaxially stretched film such as polyester or polypropylene is used.

Japanese Patent Laid-Open No. 4-30120 Japanese Patent Laid-Open No. 6-148431 Japanese Unexamined Patent Publication No. 7-101026

  In general, components of the manufactured liquid crystal display device are inspected in a timely manner for evaluation of display capability, hue, contrast, and the like. However, conventionally used surface protection films have anisotropy in their base materials, so that the structural members to which such surface protection films are attached are hindered in inspections involving optical evaluation. Therefore, the surface protective film is peeled and removed once before the inspection, and a new surface protective film is attached again after the inspection is completed. The reason why the surface protective film is re-applied is that, even if the surface protective film can be re-applied, the beauty is lost if it is re-applied.

  In the above-described inspection, peeling and re-sticking of the surface protective film requires two steps in the process, which is a major obstacle in this field where cost reduction is pursued to the limit.

  As an attempt to inspect the polarizing plate or the retardation plate provided with the pressure-sensitive adhesive layer while solving the above-mentioned conventional problems and covering the surface protective film, for example, in JP-A-4-30120, A surface protective film or the like provided with an adhesive resin layer on one side of an optically isotropic substrate such as polycarbonate or polyarylate, and JP-A-6-148431 discloses a substrate made of a non-oriented film such as polyester or polypropylene. The surface protective film provided with a release layer on at least one side of the film is substantially the same as the direction of the orientation axis of the polarizing plate or the retardation plate in the orientation axis of the biaxially oriented polyester film in JP-A-7-101026. In general, a method of stacking layers so as to be the same or to be positioned at 90 ° has been proposed.

  Since such a non-oriented film has optical isotropy, it has a great advantage that it does not require peeling at the time of inspection. However, since it is difficult to suppress orientation in a normal melt extrusion method, Since it is necessary to use such a manufacturing method and the base film itself becomes expensive, the surface protection film finally peeled and removed is rarely used. In addition, the method using a biaxially oriented polyester film has a problem that the yield deteriorates because it is difficult to strictly control the direction of the orientation main axis.

  Accordingly, the present invention is intended to solve the above-mentioned drawbacks, and the purpose of the present invention is to use an optical device that does not require peeling at the time of inspection and is inspectable when used on a component member of a liquid crystal display device. A member is provided.

  As a result of diligent studies to solve the above problems, the present inventors have used a biaxially stretched polymer film having the maximum strain of the orientation main axis and the MOR value measured with a specific microwave transmission type molecular orientation meter. As a result, it has been found that defects can be easily seen at the time of inspection and that the cost can be reduced, and the present invention has been achieved.

That is, the present invention is as follows.
1. An optical member to which a surface protective film having a layer configuration of at least an adhesive layer / biaxially stretched polymer film is attached, wherein the optical member is a polarizing plate or a retardation plate, The molecular film is a polyester film, the maximum strain of the orientation main axis measured by the microwave transmission type molecular orientation meter of the biaxially stretched polymer film is 7 degrees or less, and the maximum / minimum ratio of microwave transmission intensity (MOR) The minimum value of (value) is greater than 1.8.
2. The optical member, wherein the biaxially stretched polymer film has a haze of 10% or less.
3. The biaxially stretched polymer film has a thermal shrinkage rate at 120 ° C. of 4% or less.
4). The optical member, wherein the biaxially stretched polymer film is composed of polyethylene terephthalate or polyester mainly composed thereof.
5). The optical member according to claim 1, wherein an antistatic layer is laminated on the surface opposite to the pressure-sensitive adhesive layer.
6). The optical member according to claim 1, wherein an antistatic layer is laminated between the pressure-sensitive adhesive layer and the biaxially stretched polymer film in the surface protective film.
7). The optical member, wherein a release layer is laminated on one side of the biaxially stretched polymer film.
8). An optical member, wherein the release layer is a release layer mainly composed of a silicone resin and / or a fluororesin.
9. The optical member, wherein the silicone resin is a thermosetting silicone resin or a radiation curable silicone resin.
10. A surface protective film used for the optical member.

  The optical member of the present invention uses a biaxially stretched polymer film having the maximum strain of a specific orientation main axis and the minimum value of the maximum / minimum ratio (MOR value) of the microwave transmission intensity, so that optical evaluation (for example, , Display ability, hue, contrast, optical defects, etc.) can be easily observed without peeling off the surface protective film. Moreover, the cost can be reduced by using an inexpensive resin having excellent overall performance such as polyethylene terephthalate.

It is sectional drawing which showed typically an example of the surface protection film of this invention. It is sectional drawing which showed typically an example of the surface protection film of this invention. It is sectional drawing which showed typically an example of the surface protection film of this invention. It is sectional drawing which showed typically an example of the surface protection film of this invention. It is sectional drawing which showed typically an example of the surface protection film of this invention. It is sectional drawing which showed typically an example of the surface protection film of this invention. It is sectional drawing which showed typically the example which bonded together the surface protection film of FIG. 1, FIG. 4 to the polarizing plate as an optical member. It is the schematic of the sampling method in evaluation of <the maximum distortion of an orientation main axis | shaft, and the minimum value of a MOR value>.

  Hereinafter, the present invention will be described in detail. The biaxially stretched polymer film of the present invention is characterized in that the maximum strain of the orientation main axis measured with a microwave transmission type molecular orientation meter is 7 degrees or less and the minimum value of the MOR value is larger than 1.8. It is a biaxially stretched polymer film and can be produced by the following method. However, it is not limited to this method.

  The biaxially stretched polymer film in the present invention is a film obtained by subjecting an organic polymer to melt extrusion or solution extrusion, stretching in the longitudinal direction and width direction, cooling, and heat setting. Polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polyethylene-2,6-naphthalate, and polypropylene terephthalate, polyamides such as nylon 6, nylon 4, nylon 6, 6, and nylon 12, polyimide, polyamideimide, and polyethersulfone , Polysulfone, polyetheretherketone, polycarbonate, polyarylate, polyacryl, cellulose propionate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyetherimide, polyphenylenesulfur De, polyphenylene oxide, polystyrene, syndiotactic tick polystyrene, and norbornene-based polymer. These organic polymers may be copolymerized or blended with a small amount of other organic polymers. Of these, aromatic polyesters such as polyethylene terephthalate, polyethylene-2,6-naphthalate, and polypropylene terephthalate, and aliphatic polyesters such as polylactic acid are preferably used.

  Among these, in particular, polyethylene terephthalate has few impurities, and is most suitably used from the comprehensive performance such as transparency, mechanical properties, surface smoothness, solvent resistance, scratch resistance, moisture permeability, and cost.

  In addition, the surface protective film of the present invention is peeled and removed when the polarizing plate has been subjected to inspection for optical evaluation such as display capability, hue, contrast, and optical defects, and incorporated into a liquid crystal display device. That is, it becomes unnecessary after the inspection is completed. Therefore, the main repeating unit, which has biodegradability that decomposes in nature, has a low environmental impact, such as low heat and does not damage the incinerator, and excellent transparency and mechanical strength, is represented by the general formula: − An aliphatic polyester film composed of units represented by O—CHR—CO— (R is H or an alkyl group having 1 to 3 carbon atoms) is also suitable as the base film of the surface protective film of the present invention.

  Examples of the aliphatic polyester having a repeating unit include polylactic acid, polyglycolic acid, poly (2-oxybutyric acid), and the like, and one or more of these are selected and used. When using 2 or more types, a mixture and a copolymer may be sufficient. In addition, in the polymer having an asymmetric carbon, there are optical isomers such as L-form, DL-form, and D-form, any of which may be present, and two or more isomers are mixed. It may be a thing. The aliphatic polyester can be produced by a known method such as ring-opening polymerization using a corresponding dehydrated cyclic ester compound of an α-oxy acid. Among these aliphatic polyesters, polylactic acid is particularly preferable.

  The biaxially stretched polymer film of the present invention can be formed by a conventional method. In particular, a melt or solution of a homopolymer or copolymer is formed into a film by an extrusion method, a calendering method, a casting method, etc. An axial stretching method is preferred.

  In the present invention, the maximum strain of the orientation main axis of the biaxially stretched polymer film is a numerical expression of a phenomenon in which the direction of the orientation main axis is bent in the film width direction due to heat shrinkage. In the optical inspection of the polarizing plate, when the maximum distortion of the alignment main axis increases, a phenomenon occurs in which light is out of phase due to the birefringence effect and light leaks to the analyzer side. As a result, it is unclear whether the polarizing plate is inspected or the attached polymer film is inspected, which is not preferable.

  In the present invention, the biaxially stretched polymer film needs to have a maximum strain of the orientation main axis measured by a microwave transmission type molecular orientation meter of 7 degrees or less. More preferably, the maximum strain of the orientation main axis is 6 degrees or less, and particularly preferably, the maximum strain of the orientation main axis is 5 degrees or less. When the maximum strain of the orientation main axis is larger than 7 degrees, it is not preferable because it may hinder the discovery of foreign matters in the specimen and the confirmation of display capability at the time of examination.

  In addition, the biaxially stretched polymer film needs to have a minimum value of the maximum / minimum ratio (MOR value) of microwave transmission intensity measured with a microwave transmission type molecular orientation meter greater than 1.8. The MOR value is an index of anisotropy, and the larger the MOR value, the greater the anisotropy of molecular orientation. The minimum value of the MOR value is preferably 2.0 or more, and particularly preferably, the minimum value of the MOR value is 2.2 or more. When the minimum value of the MOR value is 1.8 or less, when the biaxially stretched polymer film is produced, the unevenness of the orientation axis becomes large at the center and the end in the film width direction, which is not preferable.

  In the present invention, the maximum strain of the orientation main axis and the minimum value of the MOR value measured by a microwave transmission type molecular orientation meter are measured by the following methods. First, when the film shape is a roll shape, a rectangle of 500 mm in the longitudinal direction and a full width in the width direction is cut out. Then, as shown in FIG. 8, a square of 100 mm square is cut out at three or more locations including two vertices of the rectangle and the center thereof in the width direction (tenter direction) including the same end side. In FIG. 8, 21 is a longitudinal direction, 22 is a width direction, 23 is an edge, 24 is a vertex, and 25 is the center of the vertex. Next, the orientation main axis and the MOR value are obtained by a microwave transmission type molecular orientation meter, and when the molecular orientation angle of the first measured point is 0 degree, the orientation angles of the other three points are the largest from the one with the largest difference. The value was obtained and used as the maximum strain of the orientation main axis. Similarly, the lowest value was obtained from the smallest MOR value, and was used as the lowest MOR value. As the microwave transmission type molecular orientation meter, a molecular orientation meter (MOA-2001A) manufactured by Kanzaki Paper Co., Ltd. was used.

  In the present invention, as a method for setting the maximum strain of the orientation main axis measured by a microwave transmission type molecular orientation meter of the biaxially stretched polymer film and the minimum value of the MOR value in the above range, as described later, Method of optimizing temperature and stretch ratio, temperature and stretch ratio in transverse stretching, and relaxing the film in the longitudinal direction before performing heat setting after transverse stretching, method of heat fixing at 130 to 250 ° C., etc. Is preferred. Here, the method of performing the next stretching by suppressing the orientation by stretching the first stretching at a high temperature is effective for suppressing the maximum strain of the orientation main axis low and increasing the MOR value.

  The biaxially stretched polymer film of the present invention preferably has a heat shrinkage rate at 120 ° C. of 4% or less. Particularly preferably, it is 1% or less. When the heat shrinkage rate at 120 ° C. exceeds 4%, it is not preferable because the flatness is disturbed when a process involving heating is performed when laminating the adhesive resin layer and the antistatic layer.

In the present invention, the thermal shrinkage at 120 ° C. is measured by the following method. First, a circle with a diameter of 50 mm is drawn around the intersection of diagonal lines of a film cut into a square with a side of 100 mm. Next, this is left for 30 minutes in a hot air dryer heated to 120 ° C. under no load. This is taken out, a dimensional change is read by a digitizer, and it is obtained by the following formula from the length (B) of the maximum position of contraction passing through the intersection of diagonal lines.
Thermal shrinkage at 120 ° C. (%) = (50−B) / 50 × 100

  In the present invention, as a method for setting the heat shrinkage rate of the biaxially stretched polymer film at 120 ° C. in the above range, the film is stretched in the longitudinal direction at 120 to 180 ° C. before the heat setting treatment after transverse stretching. A method of performing relaxation treatment of ˜5%, a method of setting the heat setting treatment temperature to 130 to 250 ° C., a method of performing relaxation treatment of 2 to 5% in the width direction after the heat setting treatment, or a combination of these methods. Is preferred.

  Further, the biaxially stretched polymer film of the present invention preferably has a haze of 10% or less, particularly preferably 5% or less. If the haze exceeds 10%, the scattered light when light passes through the biaxially stretched polymer film increases, which increases the amount of transmitted light and consequently decreases the inspection property, which is not preferable. The visible light transmittance of the biaxially stretched polymer film is preferably 75% or more.

  Although the manufacturing method of the biaxially stretched polymer film in this invention is not specifically limited as long as the film which has said film characteristic defined by this invention is obtained, it explains in detail by making a polyester film into a representative example.

  Examples include a method in which a non-oriented polyester obtained by melting polyester and extruding into a sheet is subjected to longitudinal stretching and lateral stretching at a temperature equal to or higher than the glass transition temperature, followed by heat setting treatment. The longitudinal stretching temperature is preferably 90 to 135 ° C, particularly preferably 100 to 130 ° C. The draw ratio is preferably 1.1 to 4.0 times, and particularly preferably 1.5 to 3.5 times. The transverse stretching temperature is preferably 80 to 130 ° C, particularly preferably 90 to 120 ° C. The draw ratio is preferably 2.5 to 6.0 times, particularly preferably 3.0 to 5.5 times.

  In the present invention, relaxing the film in the longitudinal direction before carrying out heat setting after transverse stretching is effective for reducing the maximum distortion of the orientation main axis and increasing the MOR value. The temperature during the longitudinal relaxation treatment is preferably in the range of 90 to 200 ° C, particularly preferably in the range of 120 to 180 ° C. The relaxation amount varies depending on the transverse stretching conditions, and it is preferable to set the relaxation amount and the relaxation temperature so that the thermal shrinkage rate at 120 ° C. of the film after the relaxation treatment is 4% or less.

  The heat setting treatment temperature is preferably in the range of 130 to 250 ° C, particularly preferably in the range of 180 to 245 ° C. In the heat setting treatment, first, the heat setting treatment is performed at a fixed length, and further the relaxation treatment in the width direction is set to 1 to 10%, preferably 2 to 5% in the cooling step after the heat setting treatment, so that the orientation main axis is maximized. This is effective for reducing the distortion and increasing the MOR value.

  The thickness of the biaxially stretched polymer film is not particularly limited, but it is appropriate to set it to 300 μm or less in consideration of use and workability. When the thickness exceeds 300 μm, the advantage of the thin polymer film is lost. Further, the biaxially stretched polymer film may be not only a single layer but also a multilayer.

  The biaxially stretched polymer film of the present invention can contain known additives as required. For example, a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistance agent, an impact resistance improver, and the like may be contained. However, since transparency is required in optical applications, it is preferable to keep the additive content to a minimum.

  In order to improve the adhesiveness, water resistance, chemical resistance, etc. of the biaxially stretched polymer film of the present invention with a layer laminated on the film such as an adhesive layer, a release layer, and an antistatic layer, A known surface treatment method, that is, corona discharge treatment (in air, nitrogen, carbon dioxide, etc.) or easy adhesion treatment may be performed. Various methods known in the art can be used for the easy adhesion treatment, and in the film production process, a method of applying aqueous coating solutions of various known easy adhesion resins to the film after biaxial stretching is preferably employed.

  The surface protective film in the present invention is a film in which an adhesive layer is laminated on one side of a biaxially stretched polymer film, or a film in which a release layer is laminated on one side of a biaxially stretched polymer film.

  As the pressure-sensitive adhesive layer, a layer having adhesiveness to an optical member, for example, 1) a heat-sensitive adhesive resin layer such as polyester-based, polyolefin-based, polyamide-based, etc. 2) acrylic-based, polyester-based, urethane-based, polyether And a rubber-based pressure-sensitive adhesive resin layer, 3) or a saturated polyester resin, a polyurethane-based resin, a polybutadiene polyol, a polyolefin polyol, a functional group-containing acrylic copolymer, etc. Film formed and partially or incompletely cross-linked 4) Soft polyvinyl chloride film containing 20% by weight or more of plasticizer in polyvinyl chloride 5) Saturated polyester resin film 6) Acrylic copolymer Film, 7) Butyl rubber, urethane rubber, butadiene rubber (polybutadiene rubber, styrene- Tadiene rubber, styrene-butadiene-styrene block copolymer, etc.), films obtained by forming synthetic rubber such as styrene-isoprene-styrene rubber, 8) polyolefins such as low molecular weight polyethylene, atactic polypropylene, chlorinated polypropylene, etc. 9) Filming an ethylene copolymer such as an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, an ethylene-acrylic acid ester copolymer The obtained film etc. are mentioned.

  When the rework property is required, the pressure-sensitive adhesive layer should be peelable (easy to peel), and when permanent adhesion is required, the pressure-sensitive adhesive layer should have a strong adhesive force or adhesive force. select. The thickness of the pressure-sensitive adhesive layer is set to about 1 to 50 μm.

  The release layer is preferably composed mainly of a silicone resin and / or a fluororesin.

  As the silicone resin, those generally known as release agents can be used, and known release agents described in “Silicone Material Handbook” (Toray Dow Corning, 19933.8) are appropriately selected and used. can do. Generally, a thermosetting or radiation curable release agent is used. As the thermosetting type, for example, a condensation reaction type and an addition reaction type, and as the ionizing radiation curing type, any reaction type such as an ultraviolet ray or electron beam curing type can be used.

  As the condensation reaction type silicone resin, for example, polydimethylsiloxane having a terminal —OH group and polydimethylsiloxane having a terminal —H group (hydrogen silane) using an organic tin catalyst (for example, an organic tin acylate catalyst) are used. Examples include those that undergo a condensation reaction to form a three-dimensional crosslinked structure.

  Examples of the addition reaction type silicone resin include those in which polydimethylsiloxane having a vinyl group introduced at the terminal thereof and hydrogensilane are reacted using a platinum catalyst to form a three-dimensional crosslinked structure.

  Examples of ultraviolet (UV) curable silicone resins include those that use the same radical reaction as ordinary silicone rubber crosslinks as the most basic types, those that are photocured by introducing an acrylic group, and those that use onium salts with ultraviolet rays. Examples include those that decompose to generate a strong acid and thereby cleave the epoxy ring to crosslink, and those that crosslink by addition reaction of thiol to vinylsiloxane. Electron beams have stronger energy than ultraviolet rays, and a crosslinking reaction by radicals occurs without using an initiator as in the case of ultraviolet curing.

  The curable silicone resin has a degree of polymerization of about 500 to 200,000, preferably about 1,000 to 100,000, and specific examples thereof include KS-718 manufactured by Shin-Etsu Chemical Co., Ltd., − 774, −775, −778, −779H, −830, −835, −837, −838, −839, −841, −843, −847, −847H, X-62-2418, −2422, −2125, -2492, -2494, -5048, -470, -2366, -630, X-92-140, -128, KS-723A / B, -705F, -708A, -883, -709, -719, Toshiba Silicon TPR-6701, -6702, -6703, -3704, -6705, -6721, -6722, -6700, XSR-7029, YSR- 022, YR-3286, DK-Q3-202, -203, -204, -205, -210, -240, -3003, -3057, SFXF-2560, Toray Dow Corning Silicone manufactured by Dow Corning SD-7226, -7229, -7320, BY-24-900, -171, -312, -374, SRX-375, SYL-OFF23, SRX-244, SEX-290, manufactured by Co., Ltd. SILCOLEASE425 manufactured by I Japan Co., Ltd. can be exemplified. In addition, silicone resins described in JP-A-47-34447 and JP-B-52-40918 can also be used. Furthermore, these curable silicone resins may be used alone or in combination of two or more.

  As the fluororesin, a known release agent can be used. As such a fluororesin, for example, a polymer (including an oligomer) or a copolymer composed of a fluorine-containing vinyl polymerizable monomer, or an alkyl group substituted with a fluorine-containing vinyl polymerizable monomer and a fluorine atom, Examples thereof include a copolymer with at least one vinyl polymerizable monomer that does not contain a functional group or the like, or a mixture thereof having 5 to 80 mol% of fluorine atoms.

  Specific examples of the polymer comprising the fluorine-containing vinyl polymerizable monomer include poly [2- (perfluorononenyloxy) ethyl methacrylate] and poly [2- (perfluorononenyloxy) ethyl acrylate. ], Poly [2- (perfluorononenyloxybenzoyloxy) ethyl methacrylate], poly [2- (perfluorononenyloxybenzoyloxy) ethyl acrylate], poly [2,2,2-trifluoroethyl methacrylate], Poly [2,2,2-trifluoroethyl acrylate], poly [2,2,3,3,3-pentafluoropropyl methacrylate], poly [2,2,3,3,3-pentafluoropropyl acrylate], Poly [1-methyl-2,2,3,3,4,4-hexafluorobutyl methacrylate Rate], poly [1-methyl-2,2,3,3,4,4-hexafluorobutyl acrylate], poly [perfluoroheptylethyl methacrylate], poly [perfluoroheptylethyl acrylate], poly [perfluoroheptyl] Vinyl ether], poly [α, β, β-trifluorostyrene], polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene and the like.

  Examples of the vinyl polymerizable monomer that does not contain an alkyl group substituted with a fluorine atom or a functional group that can be copolymerized with the fluorine-containing vinyl polymerizable monomer include hydrocarbon-based vinyl polymerizable monomers and carbonized monomers. Examples thereof include compounds such as hydrogen-based non-conjugated divinyl polymerizable monomers and functional group-containing vinyl polymerizable monomers.

  Examples of hydrocarbon-based vinyl polymerizable monomers include methyl acrylate, propyl acrylate, butyl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, octadecyl acrylate, lauryl acrylate, and cesyl acrylate. , N, N-diethylaminoethyl acrylate, methyl methacrylate, propyl methacrylate, butyl methacrylate, isoamyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, octadecyl methacrylate, lauryl methacrylate, cesyl methacrylate, methacrylic acid N, N-diethylaminoethyl, vinyl acetate, vinyl propionate, vinyl caprate, vinyl laurate, vinyl stearate, styrene, α-methylstyrene, p-methylstyrene, chloride Nyl, vinyl bromide, vinylidene chloride, allyl heptanoate, allyl acetate, allyl caprate, allyl caproate, vinyl methyl ketone, vinyl ethyl ketone, 1,3-butadiene, 2-chloro-1,3-butadiene, 2, Examples include 3-dichloro-1,3-butadiene, isoprene and the like.

  Examples of the hydrocarbon-based non-conjugated divinyl polymerizable monomer include ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, polyethylene glycol diacrylate, and polyethylene. Examples include glycol dimethacrylate, divinylbenzene, vinyl acrylate, and dibromoneopentyl glycol dimethacrylate.

  Examples of the functional group-containing vinyl polymerizable monomer include acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methylol acrylamide, N-butoxymethyl acrylamide, diacetone acrylamide, methylol diacetone acrylamide, and 2-hydroxyethyl acrylate. , 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, 3-chloro-2-hydroxypropyl methacrylate and the like, and are selected from these, but are not particularly limited.

  Although the thickness of a mold release layer is not specifically limited, The range of 0.05-5 micrometers is preferable. When the thickness of the coating film is thinner than this range, the mold release performance is lowered and satisfactory performance cannot be obtained. On the other hand, if the thickness of the coating film is thicker than this range, it takes time for curing, which is not preferable for production.

  For the release layer, known additives such as an antifoaming agent, a coating property improving agent, a thickening agent, an antistatic agent, an antioxidant, an ultraviolet absorber, and a curing agent are used as long as the object of the present invention is not impaired. Further, a dye or the like may be contained.

  The method for laminating the pressure-sensitive adhesive layer and the release layer on the biaxially stretched polymer film as the base film is not particularly limited, but a coating method is preferably used. For example, the coating method includes air doctor coating method, knife coating method, rod coating method, forward rotation roll coating method, reverse roll coating method, gravure coating method, kiss coating method, bead coating method, slit orifice coating method, cast coating method. Etc.

  Moreover, drying and / or curing (thermal curing, ionizing radiation curing, etc.) of the coating film of the pressure-sensitive adhesive layer or the release layer can be performed independently or simultaneously. When performing simultaneously, it is preferable to carry out at the temperature of 80 degreeC or more. The drying and curing conditions are preferably 80 ° C. or higher and 10 seconds or longer. If the drying temperature is less than 80 ° C. or the curing time is less than 10 seconds, the coating film is not completely cured, and the coating film tends to fall off, which is not preferable.

  Furthermore, the surface protective film of the present invention is preferably provided with an antistatic layer for the purpose of suppressing the generation of static electricity. The antistatic layer is laminated by applying an antistatic resin composition. Examples of the antistatic agent contained in the antistatic resin composition include various cationic antistatic agents having a cationic group such as a quaternary ammonium salt, a pyridinium salt, and a primary to tertiary amino group, sulfone. Anionic antistatic agents having anionic groups such as acid bases, sulfate ester bases, phosphate ester bases, phosphonate bases, amphoteric antistatic agents such as amino acids and aminosulfates, amino alcohols, glycerols, polyethylenes Various surfactant type antistatic agents such as nonionic antistatic agents such as glycol type, and further, high molecular weight antistatic agents obtained by increasing the molecular weight of the above antistatic agents, etc. Monomers and oligomers having a secondary amino group or a quaternary ammonium group and capable of being polymerized by ionizing radiation, such as N, N-dialkylaminoalkyl ( Data) acrylate monomer, also polymerizable antistatic agents such as those quaternary compounds can be used.

  In the antistatic layer, in addition to the antistatic resin composition, the coating strength of the antistatic layer, adhesion to the biaxially stretched polymer film, water resistance, solvent resistance, blocking properties, etc. are improved. Therefore, as a binder, a thermoplastic compound such as a thermoplastic polyester resin, an acrylic resin, or a polyvinyl resin and / or a high molecular compound such as a thermosetting resin such as a thermosetting acrylic resin, a urethane resin, a melamine resin, or an epoxy resin is used. It is preferable to contain. Furthermore, it is particularly preferable to contain at least one or more of methylolated or alkylolized melamine-based, urea-based, glyoxal-based, acrylamide-based compounds, epoxy compounds, and polyisocyanates as a crosslinking agent.

The surface resistivity value of the antistatic layer can be arbitrarily set according to the purpose of use. For example, the surface specific resistance value at which ordinary dust does not adhere is about 1 × 10 ¹¹ Ω / □.

  The method for forming the antistatic layer on the surface of the biaxially stretched polymer film is not particularly limited, but a coating method is preferably used. For example, coating methods include air doctor coating, knife coating, rod coating, forward rotation roll coating, reverse roll coating, gravure coating, kiss coating, bead coating, slit orifice coating, cast coating, etc. Is mentioned.

  The drying temperature of the antistatic layer is preferably in the range of 60 to 150 ° C, particularly preferably in the range of 80 to 130 ° C. When the drying temperature is less than 60 ° C., the curing time becomes long and the productivity is lowered, which is not preferable.

  Although the antistatic layer is laminated on the surface of the biaxially stretched polymer film, the pressure-sensitive adhesive layer and the release layer may be laminated on the antistatic layer, but the antistatic layer side of the biaxially stretched polymer film It may be laminated on the opposite surface.

  The layer structure of the surface protective film of the present invention is illustrated in the drawings. 1 to 3 show the layer structure of a surface protective film in which an adhesive layer is laminated on one side of a biaxially stretched polymer film. 4 to 6 show the layer structure of a surface protective film in which a release layer is laminated on one side of a biaxially stretched polymer film. Here, 1 and 2 are surface protective films, 11 is a biaxially stretched polymer film, 12 is an adhesive layer, 13 is an antistatic layer, and 14 is a release layer. The layer structure of the surface protective film shown here is: adhesive layer / biaxially stretched polymer film, adhesive layer / biaxially stretched polymer film / antistatic layer, adhesive layer / antistatic layer / biaxially stretched high Molecular film, release layer / biaxially stretched polymer film, release layer / biaxially stretched polymer film / antistatic layer, release layer / antistatic layer / biaxially stretched polymer film.

  Moreover, the state which affixed the surface protection film of this invention on the member for optics is shown in FIG. Here, 3 is an optical member, 15 is triacetyl cellulose (TAC), 16 is a polarizing film, and 17 is an adhesive layer of a polarizing plate. Here, two types of surfaces having different layer configurations, that is, a surface protective film having a layer configuration of pressure-sensitive adhesive layer / biaxially stretched polymer film and a surface protective film having a layer configuration of release layer / biaxially stretched polymer film A protective film is used.

  Next, the description will be further described with reference to examples. However, the present invention is not limited to the following examples without departing from the gist thereof. In addition, the evaluation method of the physical property in a following example and a comparative example is as follows.

<Maximum strain of orientation main axis and minimum value of MOR value>
When the film shape is a roll shape, a rectangle of 500 mm in the longitudinal direction and a full width in the width direction is cut out. Then, as shown in FIG. 8, a square of 100 mm square is cut out at three or more locations including two vertices of the rectangle and the center thereof in the width direction (tenter direction) including the same end side. In FIG. 8, 21 is a longitudinal direction, 22 is a width direction, 23 is an edge, 24 is a vertex, and 25 is the center of the vertex. Next, the orientation main axis and the MOR value are obtained by a microwave transmission type molecular orientation meter, and when the molecular orientation angle of the first measured point is 0 degree, the orientation angle of the other three points is the largest from the one with the largest difference. The value was obtained and used as the maximum strain of the orientation main axis. Similarly, the lowest value was obtained from the smallest MOR value, and was used as the lowest MOR value. As the microwave transmission type molecular orientation meter, a molecular orientation meter (MOA-2001A) manufactured by Kanzaki Paper Co., Ltd. was used.

<Heat shrinkage at 120 ° C.>
Draw a circle with a diameter of 50mm around the intersection of the diagonal lines of the film cut into a 100mm square, leave it in a hot air dryer heated to 120 ° C for 30 minutes without load, and read the dimensional change with a digitizer. From the length (B) of the maximum position of contraction passing through the intersection of the diagonal lines, it was obtained by the following equation.
Thermal shrinkage at 120 ° C. (%) = (50−B) / 50 × 100

<Haze and total light transmittance>
Using a turbidimeter (NDH-300) manufactured by Nippon Denshoku Industries Co., Ltd., samples were arbitrarily taken from five locations, and the average value was obtained.

Example 1
Extruded through a film-forming die onto a rotary quenching drum containing polyethylene terephthalate with 200 ppm of aggregate silica particles having an intrinsic viscosity of 0.62 dl / g and an average particle diameter of 1.5 μm to obtain an unstretched film It was. This unstretched film was stretched 2.5 times at 124 ° C. in the longitudinal direction and then stretched 4.0 times at 90 ° C. in the width direction, and then annealed at 120 ° C. for 10 seconds. After passing through the tenter, both ends of the film were trimmed at a position 20 mm from the end, and a portion having a small amount of heat shrinkage was excised. Subsequently, the film was heated to 100 ° C. with a ceramic roll, and further 3% relaxation treatment was performed in the vertical direction while heating using four infrared heaters having a surface temperature of 700 ° C. Subsequently, a 2% relaxation treatment was performed while heating the film to 160 ° C. with a ceramic roll. Thereafter, both ends of the film are gripped with clips, heat-set at 200 ° C., further cooled to 180 ° C. to 120 ° C., 4% relaxed in the width direction, and biaxially stretched polyethylene having a thickness of 38 μm. A terephthalate film was obtained. The obtained biaxially stretched polyethylene terephthalate film had a maximum orientation strain of 4 degrees, a minimum MOR value of 2.74, a heat shrinkage at 120 ° C. of 0.27%, a haze of 0.8%, The light transmittance was 90%.

  A coating solution obtained by adding 400 parts by weight of toluene as a solvent to 100 parts by weight of an ethylene-vinyl acetate adhesive is applied to the biaxially stretched polyethylene terephthalate film having a thickness of 38 μm so that the film thickness after drying becomes 10 μm. And solidified to obtain a surface protective film having a pressure-sensitive adhesive layer laminated on one side. The inspection property of the polarizing plate using the obtained surface protective film was good.

Example 2
Extruded through a film-forming die onto a rotary quenching drum containing polyethylene terephthalate with 200 ppm of aggregate silica particles having an intrinsic viscosity of 0.62 dl / g and an average particle diameter of 1.5 μm to obtain an unstretched film It was. This unstretched film was stretched 1.8 times at 111 ° C. in the machine direction, and then stretched 4.3 times at 90 ° C. in the width direction. Furthermore, the film was heat-set at 180 ° C. in the width direction, followed by a 4% relaxation treatment at 170 ° C. to obtain a biaxially stretched polyethylene terephthalate film having a thickness of 39 μm. The resulting biaxially stretched polyethylene terephthalate film has a maximum strain of 5 degrees in the orientation main axis, a minimum MOR value of 2.79, a heat shrinkage at 120 ° C. of 1.22%, a haze of 0.5%, The light transmittance was 90%. A surface protective film having a pressure-sensitive adhesive layer laminated on one side was obtained in the same manner as in Example 1 except that this biaxially stretched polyethylene terephthalate film was used. The inspection property of the polarizing plate using the obtained surface protective film was as good as in Example 1.

Example 3
In Example 1, it carried out similarly to Example 1 except having changed only the thickness of the biaxial stretching polyethylene terephthalate film from 38 micrometers to 25 micrometers, and obtained the 25-micrometer-thick biaxial stretching polyethylene terephthalate film. The obtained biaxially stretched polyethylene terephthalate film had a maximum orientation strain of 4 degrees, a minimum MOR value of 2.76, a heat shrinkage at 120 ° C. of 0.25%, a haze of 0.3%, The light transmittance was 90%. Using this biaxially stretched polyethylene terephthalate film, a surface protective film having a pressure-sensitive adhesive layer laminated on one side was obtained in the same manner as in Example 1. The inspection property of the polarizing plate using the obtained surface protective film was as good as in Example 1.

Example 4
This was carried out in the same manner as in Example 1 except that a biaxially stretched polyethylene-2,6-naphthalate film having a thickness of 38 μm was used instead of the biaxially stretched polyethylene terephthalate film, and a biaxially stretched polyethylene-2,6 having a thickness of 38 μm. -A naphthalate film was obtained. The obtained biaxially stretched polyethylene-2,6-naphthalate film has a maximum orientation strain of 5 degrees, a minimum MOR value of 2.83, a heat shrinkage at 120 ° C. of 0.29%, and a haze of 0. 0.7% and the total light transmittance was 89%. Using this biaxially stretched polyethylene-2,6-naphthalate film, a surface protective film having a pressure-sensitive adhesive layer laminated on one side was obtained in the same manner as in Example 1. The inspection property of the polarizing plate using the obtained surface protective film was good.

Example 5
Biaxially stretched polyethylene terephthalate film with a thickness of 38 μm obtained in Example 1 (maximum strain of orientation main axis: 4 degrees, minimum value of MOR value: 2.74, thermal shrinkage at 120 ° C .: 0.27%, haze: 0.8%, total light transmittance: 90%) on one side, quaternary ammonium salt type cationic polymer compound (manufactured by Nitto Boseki Co., Ltd., PAS10L) 35 parts by weight, copolymer polyester resin 50 parts by weight, A 10% by weight methylolated melamine resin (Sumitomo Chemical Co., Ltd., SUMIMALM-40W) and 5 parts by weight of epoxy-modified silicone (Shin-Etsu Chemical Co., Ltd., Poln MF-18) are mixed and charged by 2% by weight. A coating solution for the prevention layer was prepared. This coating solution was applied at a coating amount of 4 g / m ² (wet), and subjected to heat drying and curing reaction at 120 ° C. for 1 minute, and an antistatic layer was laminated on one side of the film. Subsequently, a pressure-sensitive adhesive layer was formed on the surface opposite to the antistatic layer side of this biaxially stretched polyethylene terephthalate film in the same manner as in Example 1 to obtain a surface protective film. The inspection property of the polarizing plate using this surface protective film was as good as in Example 1. Further, this surface protective film was good with no generation of static electricity when peeled off and almost no adhesion of dust.

Example 6
In Example 5, a surface protective film was obtained by laminating an adhesive layer on one side in the same manner as in Example 1 on the surface of the biaxially stretched polyethylene terephthalate film on which the antistatic layer was laminated. The inspection property of the polarizing plate using this surface protective film was good. Further, this surface protective film was good with no generation of static electricity when peeled off and almost no adhesion of dust.

Example 7
In Example 1, instead of an ethylene-vinyl acetate adhesive, an addition reaction type silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., KS-778, toluene solution having a solid content of 30% by weight) is used as a release agent. Part and 1 part by weight of a platinum catalyst (manufactured by Shin-Etsu Chemical Co., Ltd., PL-50T) are dissolved in toluene to prepare a toluene solution having a total solid content of 3 wt. did. This release layer coating solution was applied to one side of the film at a coating amount of 6 g / m ² (wet), and heat-dried at 120 ° C. for 1 minute and an addition polymerization reaction to obtain a surface protective film. The inspection property of the polarizing plate using this surface protective film was as good as in Example 1.

Example 8
In Example 7, a UV curable silicone resin (X-62-5048, manufactured by Shin-Etsu Chemical Co., Ltd.) was used in place of the addition reaction type silicone resin as a release agent. A release layer coating solution made of UV curable silicone resin is applied to one side of the film at a coating amount of 6 g / m ² (wet) and UV cured under the condition of 1.0 J / cm ² to obtain a surface protective film. It was. The inspection property of the polarizing plate using this surface protective film was good.

Example 9
In Example 7, in place of the addition reaction type silicone resin, a fluorine-based solvent (Fluorinert FC-77, manufactured by 3M Co., Ltd.) was used as a diluting solvent, and a fluorine-containing acrylic resin (Neos ( Co., Ltd., Flease RBX-725NF) and fluorinated oil (DuPont, Krytox 157FS-M) were uniformly dispersed in a composition with a weight solid content ratio of 20:80, and a coating solution having a concentration of 3.0% by weight. It apply | coated so that it might become 0.4 micrometer (thickness after drying), 120 degreeC was heat-dried for 1 minute, and the surface protection film was obtained. The inspection property of the polarizing plate using this surface protective film was good.

Example 10
On the opposite side of the antistatic layer side of the biaxially stretched polyethylene terephthalate film obtained by laminating the antistatic layer obtained in the same manner as in Example 5, a release layer made of the same addition reaction type silicone resin as in Example 7 was laminated. A surface protective film was obtained. The inspection property of the polarizing plate using this release film was good. Further, this release film was good with no generation of static electricity when peeled and almost no dust.

Example 11
In Example 10, a release layer made of the same addition reaction type silicone resin as in Example 7 was laminated on the surface of the biaxially stretched polyethylene terephthalate film on which the antistatic layer was laminated to obtain a surface protective film. The inspection property of the polarizing plate using this surface protective film was good. Further, this surface protective film was good with no generation of static electricity and almost no dust adhering when it was peeled off as in Example 10.

Comparative Example 1
Extruded through a film-forming die onto a rotary quenching drum containing polyethylene terephthalate with 200 ppm of aggregate silica particles having an intrinsic viscosity of 0.62 dl / g and an average particle diameter of 1.5 μm to obtain an unstretched film It was. This unstretched film was stretched 3.0 times in the machine direction at 90 ° C., and then stretched 3.8 times in the width direction at 90 ° C. Further, the film was heat-fixed in the width direction at 200 ° C. and subsequently relaxed by 4% at 180 ° C. to obtain a biaxially stretched polyethylene terephthalate film having a thickness of 38 μm. The resulting biaxially stretched polyethylene terephthalate film has a maximum orientation strain of 17 degrees, a minimum MOR value of 1.36, a thermal shrinkage at 120 ° C. of 0.9%, a haze of 0.2%, The light transmittance was 90%. Except having used this biaxially-stretched polyethylene terephthalate film, it implemented similarly to Example 1 and obtained the surface protection film which laminated | stacked the adhesive layer on the single side | surface. The polarizing plate using this surface protective film had unevenness in contrast density in the width direction, and a rainbow due to light interference caused by the surface protective film was observed in the width direction, resulting in poor inspection.

Comparative Example 2
An unstretched film is produced by extruding a polyethylene terephthalate through a film-forming die onto a water quenching drum containing 200 ppm of aggregate silica particles having an intrinsic viscosity of 0.62 dl / g and an average particle diameter of 1.5 μm. The unstretched film was stretched 2.5 times at 90 ° C. in the machine direction and 3.8 times at 90 ° C. in the width direction, and then annealed at 120 ° C. for 10 seconds. After passing through the tenter, both ends of the film were trimmed at a position 20 mm from the end, and a portion having a small amount of heat shrinkage was excised. Subsequently, the film was heated to 100 ° C. with a ceramic roll, and further 3% relaxation treatment was performed in the vertical direction while heating using four infrared heaters having a surface temperature of 700 ° C. Subsequently, a 2% relaxation treatment was performed while heating the film to 160 ° C. with a ceramic roll. Thereafter, both ends of the film were gripped with clips, heat fixed at 200 ° C., and then relaxed by 4% at 180 ° C. to obtain a biaxially stretched polyethylene terephthalate film having a thickness of 38 μm. The obtained biaxially stretched polyethylene terephthalate film has a maximum orientation strain of 7 degrees, a minimum MOR value of 1.70, a heat shrinkage at 120 ° C. of 0.8%, a haze of 0.2%, The light transmittance was 90%. Except having used this biaxially-stretched polyethylene terephthalate film, it implemented similarly to Example 1 and obtained the surface protection film which laminated | stacked the adhesive layer on the single side | surface. In the polarizing plate using this surface protective film, a rainbow due to light interference caused by the surface protective film was observed in the width direction, and the inspection quality was poor.

Comparative Example 3
Extruded through a film-forming die onto a rotary quenching drum containing polyethylene terephthalate with 200 ppm of aggregate silica particles having an intrinsic viscosity of 0.62 dl / g and an average particle diameter of 1.5 μm to obtain an unstretched film It was. This unstretched film was stretched 2.0 times at 90 ° C. in the longitudinal direction, and then stretched 3.8 times at 90 ° C. in the width direction. The film was heat-set at 200 ° C. and subsequently relaxed by 4% at 180 ° C. to obtain a biaxially stretched polyethylene terephthalate film having a thickness of 38 μm. The resulting biaxially stretched polyethylene terephthalate film has a maximum orientation strain of 9 degrees, a minimum MOR value of 2.04, a heat shrinkage at 120 ° C. of 1.0%, a haze of 0.5%, and a total light beam. The transmittance was 90%. Except having used this biaxially-stretched polyethylene terephthalate film, it implemented similarly to Example 1 and obtained the surface protection film which laminated | stacked the adhesive layer on the single side | surface. The polarizing plate using this surface protective film had unevenness in contrast density in the width direction, and the inspection property was poor.

  The biaxially stretched polymer film of the present invention is optically obtained by using a biaxially stretched polymer film having a maximum strain of a specific orientation main axis and a minimum value of the maximum / minimum ratio (MOR value) of microwave transmission intensity. It is possible to make the defect easy to see without peeling off the surface protective film at the time of inspection of evaluation (for example, display ability, hue, contrast, optical defect, etc.). Moreover, the cost can be reduced by using an inexpensive resin having excellent overall performance such as polyethylene terephthalate. Therefore, it can be suitably used as a protective film or separator for surface protection of a synthetic resin plate, in particular, a constituent member of a liquid crystal display device such as a polarizing plate or a retardation plate.

DESCRIPTION OF SYMBOLS 1 Surface protective film 2 Surface protective film 3 Optical member 11 Biaxially stretched polymer film 12 Adhesive layer 13 Antistatic layer 14 Release layer 15 Triacetyl cellulose (TAC)
16 Polarizing film 17 Adhesive layer 21 of polarizing plate Longitudinal direction 22 Width direction 23 Edge 24 Vertex 25 Center of vertex

Claims (9)

An optical member to which a surface protective film having a layer structure of at least an adhesive layer / biaxially stretched polymer film is attached,
The optical member is a polarizing plate or a retardation plate;
The biaxially stretched polymer film is a polyester film,
The maximum strain of the orientation main axis measured by a microwave transmission type molecular orientation meter of the biaxially stretched polymer film is 7 degrees or less, and the minimum value of the maximum / minimum ratio (MOR value) of microwave transmission intensity is 1. An optical member characterized by being larger than 8.   The optical member according to claim 1, wherein the biaxially stretched polymer film has a haze of 10% or less.   3. The optical member according to claim 1, wherein the biaxially stretched polymer film has a heat shrinkage rate of 120% at 4 ° C. or less.   The optical member according to any one of claims 1 to 3, wherein the biaxially stretched polymer film is made of polyethylene terephthalate or polyester mainly composed thereof.   The optical member according to claim 1, wherein an antistatic layer is laminated on the surface of the surface protective film opposite to the pressure-sensitive adhesive layer.   The optical member according to claim 1, wherein an antistatic layer is laminated between the pressure-sensitive adhesive layer and the biaxially stretched polymer film in the surface protective film.   The optical member according to claim 1, wherein a release layer is laminated on one side of the biaxially stretched polymer film.   An optical member, wherein the release layer according to claim 7 is a release layer mainly composed of a silicone resin and / or a fluororesin. The optical member according to claim 8, wherein the silicone resin is a thermosetting silicone resin or a radiation curable silicone resin.