TWI790340B - surface protection film - Google Patents

Abstract

The present invention provides a surface protection film capable of forming a roll without using a separator. The surface protection film of embodiment of this invention has a base material and an adhesive layer. The adhesive layer has a thickness of 5 μm or less and a surface roughness Sa of 3 nm˜10 nm. In one embodiment, the surface protection film does not include a separator and can be wound into a roll. In one embodiment, the width of the surface protection film is 1 m or more.

Description

surface protection film

field of invention The present invention relates to surface protection films.

Background of the invention For the optical layered body (for example, a polarizing plate, a layered body including a polarizing plate), in order to protect the optical layered body (ultimately an image display device) before the actual use of the image display device to which the optical layered body is applied, ), releasably bonded with a surface protection film. In actual use, the laminated body of the optical laminate/surface protection film is bonded to a display unit to produce an image display device, and then the surface protection film is peeled off and removed at an appropriate time. A typical surface protection film has a resin film and an adhesive layer as a base material. When the surface protection film is stored in a roll form in actual use, sticking occurs due to the adhesive layer. Therefore, when the roll is formed, a separator is temporarily attached to the surface of the adhesive layer in order to prevent sticking. However, from both viewpoints of cost and operability, it is strongly desired that there is no need to use a surface protection film for the separator. prior art literature patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2017-165983

Summary of the invention The problem to be solved by the invention The present invention was made to solve the above-mentioned conventional problems, and its main object is to provide a surface protection film that can be formed into a roll without using a separator. way of solving the problem

The surface protection film according to the embodiment of the present invention has a substrate and an adhesive layer, wherein the thickness of the adhesive layer is 5 μm or less, and the surface roughness Sa is 3 nm to 10 nm. In one embodiment, the above-mentioned surface protection film does not include a separator, and can be wound into a roll. In one embodiment, the width of the surface protection film is 1 m or more. In one embodiment, the storage elastic modulus of the adhesive layer is 1.0×10 ⁴ Pa to 1.0×10 ⁷ Pa. Invention effect

According to an embodiment of the present invention, by setting the thickness of the adhesive layer to 5 μm or less and setting the surface roughness Sa of the adhesive layer to 3 nm to 10 nm, a surface protection film capable of forming a coil without using a separator can be realized. .

form for carrying out the invention Hereinafter, preferred embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

A. Outline of surface protection film Fig. 1 is a schematic cross-sectional view of a surface protection film according to an embodiment of the present invention. The surface protection film 100 of this embodiment has a base material 10 and an adhesive layer 20 . Any appropriate treatment layer (not shown) may be provided as necessary on the side of the substrate 10 opposite to the adhesive layer 20 . In an embodiment of the present invention, the thickness of the adhesive layer is 5 μm or less, and the surface roughness Sa is 3 nm˜10 nm. By thus setting the thickness of the adhesive layer to be very thin, and thus setting the surface roughness Sa of the adhesive layer to a small value within a predetermined range, blocking at the time of forming a roll can be significantly suppressed. As a result, a surface protection film capable of forming a roll without using a separator can be realized. Therefore, the surface protection film according to the embodiment of the present invention is very useful from both viewpoints of cost and handleability. Furthermore, according to the embodiment of the present invention, it is possible to realize a surface protection film capable of maintaining an excellent appearance even when it is formed into a roll. Specifically, it is possible to prevent the generation of indentation when forming a coil and the generation of air bubbles when bonding to an optical layered body. In actual use, the laminated body of the optical laminate/surface protection film is bonded to the display unit to make an image display device, and when the surface protection film is peeled off at an appropriate time later, if there are indentations or bubbles in the surface protection film, Then, even if there is no problem with the display unit itself bonded with the optical laminate, the image display device may be judged to be defective in the pre-shipment inspection due to the indentation or air bubbles of the surface protection film. As a result, there is a problem in that the efficiency from manufacture to shipment of the image display device decreases. The surface protection film according to the embodiment of the present invention can eliminate such a problem, and therefore is extremely valuable industrially.

A typical surface protection film 100 is long and can be wound into a roll. As described above, the surface protection film 100 may be wound in a roll without using a separator. The width of the surface protection film 100 is preferably 1 m or more, more preferably 1.2 m or more, and still more preferably 1.5 m or more. According to the embodiment of the present invention, blocking can be remarkably suppressed even in such a wide film. In addition, it is needless to say that the film with a width of less than 1 m can also acquire the effect of this invention.

B. Substrate The substrate may be composed of any appropriate resin film. Examples of the forming material of the resin film include ester-based resins such as polyethylene terephthalate-based resins, cycloolefin-based resins such as norcamphene-based resins, olefin-based resins such as polypropylene, polyamide-based resins, Polycarbonate-based resins, copolymer resins thereof, and the like. Ester-based resins (particularly polyethylene terephthalate-based resins) are preferred. In the case of such a material, the modulus of elasticity is sufficiently high, and there is an advantage that deformation does not easily occur even if tension is applied during transportation and/or bonding.

A typical substrate has a thickness of 10 μm to 100 μm, preferably 20 μm to 50 μm. With such a thickness, there is an advantage that deformation does not easily occur even if tension is applied during transportation and/or lamination. In the embodiment of the present invention, since the thickness of the adhesive layer is very thin, the thickness of the base material is dominant for the thickness of the surface protection film. In one embodiment, the thickness of the surface protection film may be, for example, 15 μm to 60 μm.

The modulus of elasticity of the substrate can typically be measured in accordance with JIS K 7127: 1999. The modulus of elasticity of the substrate is preferably 100 MPa to 350 MPa at a tensile speed of 100 mm/min. When the modulus of elasticity of the base material is in such a range, there is an advantage that deformation does not easily occur even if tension is applied during transportation and/or lamination.

C. Adhesive layer The thickness of the adhesive layer is, as described above, 5 μm or less, preferably 3 μm or less, more preferably 1 μm or less. The lower limit of the thickness is, for example, 0.1 μm. By setting the thickness of the adhesive layer so as to be very thin, and setting the surface roughness Sa of the adhesive layer to a small value within a predetermined range as described later, it is possible to remarkably suppress stickiness when forming a roll. even. As a result, a surface protection film capable of forming a roll without using a separator can be realized.

The surface roughness Sa of the adhesive layer is 3 nm to 10 nm as described above, preferably 3 nm to 8 nm, more preferably 4 nm to 6 nm. By setting the surface roughness Sa of the adhesive layer to such a range, and setting the thickness of the adhesive layer to be very thin as described above, blocking at the time of forming a roll can be significantly suppressed. As a result, a surface protection film capable of forming a roll without using a separator can be realized. Such surface roughness can be achieved, for example, by adjusting the drying conditions of the adhesive when the adhesive layer is formed. Drying conditions may vary depending on the composition of the binder and the like. The drying temperature may be, for example, 100° C. to 150° C., and the drying time may be, for example, 30 seconds to 180 seconds. In addition, surface roughness Sa can be measured according to ISO25178-6 (2010) or JISB 0681-6: 2014.

The storage elastic modulus of the adhesive layer is preferably 1.0×10 ⁴ Pa to 1.0×10 ⁷ Pa, more preferably 2.0×10 ⁴ Pa to 5.0×10 ⁶ Pa. When the storage elastic modulus of the pressure-sensitive adhesive layer is in such a range, blocking at the time of forming a roll can be further significantly suppressed. It should be noted that the storage elastic modulus can be obtained, for example, by dynamic viscoelasticity measurement at a temperature of 23° C. and an angular velocity of 0.1 rad/s.

吖化合物。黏合劑也可以含有例如矽烷偶合劑。黏合劑的摻合處方可以根據目的及希望的特性而適當設定。Any appropriate adhesive can be employed as the adhesive for forming the adhesive layer. Examples of the base resin of the adhesive include acrylic resins, styrene-based resins, silicone-based resins, urethane-based resins, and rubber-based resins. Such base resins are described in, for example, JP-A-2015-120337 or JP-A-2011-201983. The descriptions of these publications are incorporated herein by reference. From the viewpoints of chemical resistance, adhesiveness for preventing infiltration of the treatment liquid during immersion, degree of freedom with respect to an adherend, and the like, an acrylic resin is preferable. Examples of the crosslinking agent that can be contained in the adhesive include isocyanate compounds, epoxy compounds,

Acridine compounds. The adhesive may also contain, for example, a silane coupling agent. The blending recipe of the adhesive can be appropriately set according to the purpose and desired characteristics.

D. Processing layer As described above, any suitable treatment layer may be provided on the side of the substrate opposite the adhesive layer as desired. Specific examples of the treatment layer include an antistatic layer, a hydrophilic layer, and a hard coat layer.

二唑系聚合物、聚苯胺系聚合物、聚氮化硫(polythiazyl)系聚合物、聚(伸苯伸乙烯)(poly(phenylene vinylene))系聚合物、聚(伸噻吩伸乙烯)(poly(thienylene vinylene))系聚合物、多并苯(polyacene)系聚合物、聚菲系聚合物、聚迫萘(polyperinaphthalene)系聚合物等。這些導電性聚合物可以單獨使用，或者組合使用2種以上。作為黏結劑樹脂，優選使用聚胺甲酸酯系樹脂。通過使用聚胺甲酸酯系樹脂，可以設置兼具柔軟性和對偏光板(實質上為保護層)的優異密合性的抗靜電層。A typical antistatic layer includes a conductive material and a binder resin. As the conductive material, any appropriate conductive material can be used, and a conductive polymer can be preferably used. Examples of conductive polymers include polythiophene-based polymers, polyacetylene-based polymers, polydiacetylene-based polymers, polyacetylene-based polymers, polyphenylene-based polymers, polynaphthalene-based polymers, poly Perylene-based polymers, polyanthracene-based polymers, polypyrene-based polymers, polyazulene-based polymers, polypyrrole-based polymers, polyfuran-based polymers, polyselenophene-based polymers, polyisothiadene-based polymers, get together

Oxadiazole-based polymers, polyaniline-based polymers, polythiazyl-based polymers, poly(phenylene vinylene)-based polymers, poly(poly(phenylene vinylene))-based (thienylene vinylene)-based polymers, polyacene-based polymers, polyphenanthrene-based polymers, polyperinaphthalene-based polymers, and the like. These conductive polymers may be used alone or in combination of two or more. As the binder resin, a polyurethane resin is preferably used. By using a polyurethane-based resin, it is possible to provide an antistatic layer having both flexibility and excellent adhesion to a polarizing plate (substantially a protective layer).

For the hydrophilic layer and the hard coat layer, since known structures in the art can be employed, detailed description thereof will be omitted.

E. Application of surface protection film Usually, in order to protect the optical layered body until the optical layered body (finally, an image display device) is actually used, the surface protection film according to the embodiment of the present invention is bonded and used in a detachable manner. Specific examples of optical laminates include polarizing plates, phase difference plates, conductive films for touch panels, surface treatment films, and laminates including polarizing plates and having an appropriate structure according to the purpose (for example, a circle for anti-reflection). Polarizing plate, Polarizing plate with conductive layer for touch panel, Polarizing plate with retardation layer, Polarizing plate integrated polarizing plate). Example

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. The measurement method of each characteristic in an Example is as follows. It should be noted that, unless otherwise specified, "parts" and "%" in the examples are based on weight.

(1) Thickness The thickness of the adhesive layer was measured by cutting out a cross section of the film on which the adhesive layer was formed, observing the cross section with a scanning electron microscope (SEM), and measuring the thickness of the layer. For the thickness of the antistatic layer, measurements were carried out as follows: the surface of the antistatic layer was dyed with RuO ₄ and embedded in epoxy resin. Then, the section prepared by the ultrathin section method was dyed with RuO ₄ , and the cross section of the coating layer was measured using TEM (H-7650 manufactured by Hitachi High-Tech Co., Ltd., accelerating voltage 100V). (2) Surface roughness Sa Measured in accordance with JIS B 0681-6: 2014. As a measuring device, a three-dimensional non-contact surface roughness measuring instrument (manufactured by Zygo Corporation, product name: NewView7300) was used, and the arithmetic mean roughness was measured under the conditions of an objective lens magnification of 50 and a measurement area of 0.14 mm×0.11 mm. (3) Roll Formability The surface protection films obtained in Examples and Comparative Examples were wound to form a roll. The state at the time of coil formation was evaluated according to the following criteria. ○: There is no sticking or wrinkling, and the coil is formed well. △: Sticking and wrinkles occur and the appearance is poor, but the coil is still formed. ×: Sticking and wrinkles occur, and the coil cannot be formed (4) The indentation will be The coil formed in the same manner as in (3) above was stored for 24 hours, and then the coil was unrolled, and the number of indentations per 1 m ² was visually checked. (5) Bubbles While transporting the surface protection films obtained in Examples and Comparative Examples and the polarizing plate obtained in Reference Example 1, align their longitudinal directions with each other and bond them together with a roller, and visually confirm the bubbles per 1 m ² after bonding. number of bubbles.

<Reference Example 1: Production of Polarizing Plate> As the resin substrate, a long amorphous isophthalic acid-copolyethylene terephthalate (IPA-copolyethylene PET) film (thickness: 100 μm) with a water absorption rate of 0.75% and a Tg of 75° C. was used. Corona treatment is performed on one side of the substrate, and the corona-treated surface is coated with polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mole%) and acetoacetate at a ratio of 9:1 at 25°C. Aqueous solution of modified PVA (polymerization degree 1200, acetyl acetyl modification degree 4.6%, saponification degree 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z200") and dried to form a thickness of 11 μm The PVA-based resin layer was used to produce a laminated body. The free end of the obtained laminate was uniaxially stretched to 2.0 times in the longitudinal direction (length direction) between rolls having different circumferential speeds in an oven at 120° C. (assisted stretching in the air). Next, the laminated body was immersed for 30 seconds in an insolubilization bath (an aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 30° C. (insolubilization treatment). Next, the polarizing plate was immersed in a dyeing bath having a liquid temperature of 30° C. and the iodine concentration and immersion time were adjusted so that the polarizing plate had a predetermined transmittance. In this example, 0.2 parts by weight of iodine and 1.5 parts by weight of potassium iodide were blended with 100 parts by weight of water to obtain an iodine aqueous solution, and dipped in this iodine aqueous solution for 60 seconds (dyeing treatment). Next, it was immersed for 30 seconds in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 30° C. (crosslinking treatment). Then, the laminated body was immersed in an aqueous solution of boric acid at a liquid temperature of 70° C. (an aqueous solution obtained by mixing 4 parts by weight of boric acid with respect to 100 parts by weight of water and 5 parts by weight of potassium iodide), and between rollers at different peripheral speeds. Uniaxial stretching was carried out in the longitudinal direction (length direction) so that the total stretching ratio became 5.5 times (stretching in water). Then, the laminated body was immersed in a cleaning bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 30° C. (washing treatment). Next, a UV-curable adhesive is applied on the surface of the PVA-based resin layer (polarizer) of the laminate so that the thickness of the adhesive layer after curing is 1.0 μm, and a methacrylic resin film (thickness : 40 μm), the methacrylic resin film was heated to 50° C. using an IR heater, and ultraviolet rays were irradiated to harden the adhesive. Thus, a polarizing plate having a structure of resin substrate (protective layer)/polarizer/protective layer was obtained. It should be noted that the thickness of the polarizer is 5 μm, and the single transmittance is 42.3%.

<Example 1> 1-1. Preparation of antistatic layer-forming composition (coating solution) An aqueous dispersion (manufactured by Toyobo Co., Ltd., trade name "VYLONAL MD-1480") containing 25% of a saturated copolyester resin as a binder (binder dispersion) was prepared. Furthermore, an aqueous dispersion (slip agent dispersion) of carnauba wax (wax ester) as a slip agent was prepared. In addition, a conductive polymer containing 0.5% of poly(3,4-ethylenedioxythiophene) (PEDOT) and 0.8% of polystyrene sulfonate (number average molecular weight: 150,000) (PSS) was prepared. Aqueous solution (trade name "Baytron P", product of H.C. Stark Co.) (conductive polymer aqueous solution). Add 100 parts (solid content) of the above-mentioned binder dispersion liquid, 30 parts (solid content) of the above-mentioned slip agent dispersion liquid, 50 parts (solid content) of the above-mentioned conductive polymer aqueous solution, and a melamine-based Cross-linking agent, stirred for about 20 minutes, thoroughly mixed. Thus, a coating solution for forming an antistatic layer having an NV of about 0.15% was prepared.

1-2. Formation of antistatic layer A transparent polyethylene terephthalate (PET) film having a thickness of 38 μm, a width of 30 cm, and a length of 40 cm in which one surface (first surface) was corona-treated was prepared. The above-mentioned coating solution was applied to the corona-treated surface of the PET film with a bar coater, and dried by heating at 130° C. for 2 minutes. Thus, a laminate of antistatic layer (10 nm)/PET film was produced.

1-3. Preparation of Adhesive Blending 92 parts by weight of 2-ethylhexyl acrylate, 4 parts by weight of acrylic acid, 4 parts by weight of methyl methacrylate, 3 parts by weight of a reactive surfactant (reactive surfactant that does not contain an oxyalkylene group), and 90 parts by weight of water were stirred and mixed with a homomixer to prepare a monomer emulsion. Next, 50 parts by weight of water, 0.01 part by weight of a polymerization initiator (ammonium persulfate), and 10% by weight of the monomer emulsion prepared above were added to a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer, and a stirrer. amount, and carried out emulsification polymerization at 75° C. for 1 hour while stirring. Then, 0.07 parts by weight of a polymerization initiator (ammonium persulfate) was further added, and the remaining whole monomer emulsion (an amount corresponding to 90% by weight) was added over 3 hours while stirring, and then reacted at 75° C. for 3 hours. Next, it was cooled to 30° C., ammonia water with a concentration of 10% by weight was added, and the pH was adjusted to 8 to prepare an aqueous dispersion of an acrylic emulsion polymer (concentration of an acrylic emulsion polymer: 41% by weight).

With respect to 244 parts by weight of the aqueous dispersion of the acrylic emulsion polymer obtained above (100 parts by weight of the acrylic emulsion polymer), stir and mix with a stirrer at 23° C., 2000 rpm, and 10 minutes under stirring conditions. Epoxy-based crosslinking agent [Mitsubishi Gas Chemical Co., Ltd., trade name "TETRAD-C", 1,3-bis(N,N-diecidylaminomethyl)cyclohexane, epoxy Equivalent weight: 110, number of functional bases: 4] 2.5 parts by weight, acetylene glycol-based compound (composition) with an HLB value of 4 [manufactured by Air Products, trade name "Surfynol 420", active ingredient 100% by weight] 1 part by weight ( The acetylene glycol-based compound is 1 part by weight), and polypropylene glycol [manufactured by ADEKA Co., Ltd., trade name "Adeka Pluronic 25R-1", Mn2800, PO content 90% by weight] 0.3 parts by weight, prepared an adhesive agent.

1-4. Preparation of surface protection film The adhesive obtained above was diluted with a liquid, and applied to the surface of the PET film of the above-mentioned laminate using an applicator manufactured by TESTER SANGYO Co., Ltd. so that the thickness after drying was 3 μm, and then dried in a hot air circulation oven at 130°C for 2 Minutes, and further aging (aging treatment) at 23°C for 5 days, an antistatic layer (10nm)/PET film (thickness: 38μm)/adhesive layer (thickness: 3μm, surface roughness Sa: 5nm) was obtained. Structured surface protection film. The obtained surface protection film was used for the evaluation of said (3)-(5). The results are shown in Table 1.

＜Comparative example 1＞ A surface protection film was produced in the same manner as in Example 1 except that the drying conditions of the adhesive were changed as shown in Table 1, and the surface roughness Sa of the adhesive layer was 1 nm. The obtained surface protection film was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 2 and Comparative Examples 2 to 10> A surface protection film was produced in the same manner as in Example 1 except that the thickness and/or surface roughness Sa of the adhesive layer were set as shown in Table 1. The obtained surface protection film was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Table 1]

＜Evaluation＞ From Table 1, it can be seen that the surface protection film of the Example of this invention can form a favorable roll material without using a separator. More specifically, rolls can be formed without blocking and without creasing. Moreover, the surface protection film of the Example of this invention can remarkably suppress generation|occurrence|production of bubbles at the time of lamination|stacking with an optical laminated body. Industrial availability

The surface protection film of the present invention is used to protect the optical layered body (eventually, an image display device) until the actual use of the optical layered body.

10‧‧‧Substrate 20‧‧‧adhesive layer 100‧‧‧Surface protection film

Fig. 1 is a schematic cross-sectional view of a surface protection film according to an embodiment of the present invention.

10‧‧‧Substrate

20‧‧‧adhesive layer

100‧‧‧Surface protection film

Claims (4)

A surface protection film, which has a base material and an adhesive layer, the thickness of the adhesive layer is not less than 1 μm and not more than 5 μm, and the surface roughness Sa is 4 nm to 6 nm. The surface protection film according to claim 1, which does not include a separator and can be wound into a roll. The surface protection film as claimed in claim 2, which has a width of 1 m or more. The surface protection film according to any one of claims 1 to 3, wherein the storage elastic modulus of the adhesive layer is 1.0×10 ⁴ Pa to 1.0×10 ⁷ Pa.

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