JP2001033776A - Surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a surface protective film, which is not released from an optical member due to such a change as of ambient temperature or humidity and which is stably released and separated from it with either low or high speed via a hand or a machine without any damage to the optical member or without being released from a liquid crystal cell, while satisfying basic performance of being released and separated from the optical member without residual glue in the case of releasing. SOLUTION: The protective film 1 adheres to and coats a surface of an optical member 2. Its adhesive power to the optical member with 10 m/min release speed is <=2.5 times that with 0.3 m/min release speed based on 180 deg. peel at normal temperature. Therefore, the release speed dependency of the adhesive power is little so as to make it stably be released and separated from the optical member with either low or high speed and to make it efficiently be released with high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface protective film which has a small dependency on the peeling speed of an adhesive force and can be easily peeled off from an optical member, and is suitable for manufacturing a liquid crystal panel.

[0002]

BACKGROUND OF THE INVENTION Optical members such as a polarizing plate and a retardation plate used for forming a liquid crystal panel and an elliptically polarizing plate obtained by laminating them are usually bonded and covered with a surface protective film so that the surface is not damaged. It is used for panel assembly and the like, and the protective film is peeled off after bonding the optical member and the liquid crystal cell.

[0003] However, in the conventional surface protective film, the adhesive force depends on the peeling speed. Generally, the adhesive force increases with an increase in the peeling speed, and the protective film is not damaged without damaging the optical member or peeling off from the liquid crystal cell. There is a limitation on the peeling speed at the time of separation and removal from the optical member, and there is a problem that high-speed peeling is difficult.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to satisfy the basic performance of separating from an optical member without peeling off from an optical member due to environmental changes such as temperature and humidity, and at the time of peeling without leaving any adhesive, from a low speed to a high speed. An object of the present invention is to develop a surface protective film that can be stably separated by hand or machine without damaging an optical member or separating from a liquid crystal cell.

[0005]

The present invention relates to a protective film for adhesively covering the surface of an optical member. The adhesive film has an adhesive force based on a 180 degree peel at room temperature at an ordinary temperature of 0.3 m at a peeling speed of 10 m / min. The surface protection film is characterized in that the surface protection film is within 2.5 times that of the peeling rate per minute.

[0006]

According to the present invention, the adhesive force has a small dependence on the peeling speed and can be stably separated by hand or machine without causing damage to the optical member or peeling from the liquid crystal cell from a low speed to a high speed. It is possible to obtain a surface protective film that does not peel off from the optical member due to environmental changes such as temperature and humidity, and can be peeled off from the optical member without any adhesive residue at the time of peeling, and can be peeled efficiently at high speed.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The surface protective film according to the present invention comprises:
A protective film that adhesively covers the surface of the optical member, and has an adhesive force based on a 180-degree peel at room temperature at an ordinary temperature of 0.3 m with a peeling speed of 10 m / min.
/ Min within 2.5 times that of the peel rate. An example is shown in FIG. 1 is a surface protective film, 11 is a protective substrate, 12 is an adhesive layer, 2 is an optical member, 21 is an optical material, and 22 is an adhesive layer.

The surface protective film is formed such that an adhesive layer 12 is provided on a protective substrate 11 as shown in the figure and the protective substrate can be peeled off from the optical member together with the adhesive layer. As the protective substrate, an appropriate thin leaf body according to the related art can be used, and there is no particular limitation.

Generally, from the viewpoint of management of optical members based on transparency, for example, polyester resins, acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, acrylic resins, etc. A protective substrate made of a film or rubber sheet made of a transparent polymer such as a system resin or a laminate thereof is used. The thickness of the protective substrate is
It can be appropriately determined according to the strength and the like, and is generally 500 μm or less, preferably 5 to 300 μm, particularly 10 to 200 μm.

In forming the adhesive layer, an appropriate adhesive substance or adhesive can be used. By the way, as an example,
Examples of the base polymer include an appropriate polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, and a fluorine or a rubber.

The adhesive layer in the surface protective film has an adhesive force of 0.3 m / min at a peeling speed of 10 m / min in the adhesive force at the time of peeling and separating the one adhered to the surface of the optical member.
Formed within 2.5 times that of a minute peel rate. Accordingly, the separation and separation can be stably performed through a hand or a machine without causing damage to the optical member or separation from the liquid crystal cell from a low speed to a high speed. The above-mentioned adhesive force depends on a predetermined peeling rate at normal temperature to the optical member.
Based on 0 degree peel.

Suppression of the above-mentioned dependence of the adhesive force on the peeling speed,
An adhesive layer that is preferable from the viewpoint of preventing change in adhesive force due to environmental changes such as temperature and humidity, preventing peeling from an optical member, and peeling and separating from an optical member having no adhesive residue at the time of peeling is an acrylic-based adhesive layer. It is excellent in transparency, weather resistance, heat resistance and the like like an adhesive, and has a peeling speed dependency of the adhesive strength of 2.0 times or less, especially 1.5 times or less.

The surface protective film having the above-mentioned adhesive properties can be formed, for example, by a method of controlling the elastic modulus of the pressure-sensitive adhesive layer, particularly, the elastic modulus of the polymer forming the pressure-sensitive adhesive layer. In that case, the adhesive property described above can be imparted by using a pressure-sensitive adhesive layer having a higher elastic modulus than in the past.

The improvement in the elastic modulus of the pressure-sensitive adhesive layer can be realized by, for example, changing the kind of the polymer, increasing the molecular weight of the polymer, crosslinking treatment with a crosslinking agent or increasing the molecular weight. The adhesive layer may be blended with an appropriate additive such as a natural or synthetic resin such as a tackifier resin or an antioxidant, for the purpose of controlling the properties and adhesive strength, if necessary. it can.

The attachment of the pressure-sensitive adhesive layer to the protective substrate can be performed by an appropriate method. Incidentally, as an example, an adhesive substance or a composition thereof is dissolved or dispersed in a solvent composed of an appropriate solvent alone or a mixture such as toluene or ethyl acetate to prepare an adhesive liquid of about 10 to 40% by weight. Then, it is directly attached on the protective substrate by an appropriate developing method such as a casting method or a coating method, or an adhesive layer is formed on a separator according to the above and transferred to the protective substrate. And the like.

The adhesive layer may be provided on the protective substrate as a superposed layer of different compositions or types. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the adhesive strength, the surface roughness of the optical member, and the like, and is generally 1 to 500 μm, preferably 5 to 200 μm.
μm, especially 10 to 100 μm. The surface of the protective substrate on which the adhesive layer is provided may be subjected to an appropriate surface treatment such as a corona treatment for the purpose of improving the adhesion to the adhesive layer.

The optical member to be coated with the surface protective film is used for forming a liquid crystal panel such as a laminated body of a polarizing plate and a retardation plate such as a polarizing plate, a retardation plate and an elliptically polarizing plate, and an anti-glare sheet. It may be made of an appropriate optical material used. In the case of a lamination type optical material such as the elliptically polarizing plate, the lamination may be performed through an appropriate bonding means such as an adhesive layer.

Incidentally, specific examples of the above-mentioned polarizing plate include iodine and / or iodine on a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, and an ethylene / vinyl acetate copolymer-based partially saponified film. Examples thereof include a film obtained by adsorbing a dichroic dye and stretching, a polarizing film made of a polyene oriented film such as a dehydrated product of polyvinyl alcohol and a dehydrochlorinated product of polyvinyl chloride.

The polarizing plate may have a transparent protective layer on one or both sides of the polarizing film.
For the formation of the transparent protective layer, a polymer or the like having excellent transparency, mechanical strength, heat stability, moisture shielding property and the like is preferably used. Examples thereof include the polymers exemplified for the above-mentioned protective substrate, and thermosetting resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone, and ultraviolet-curing resins.

The transparent protective layer may be formed by an appropriate method such as a method of applying a polymer or a method of laminating a film, and the thickness may be appropriately determined. Generally 500 μm
Hereinafter, the thickness is preferably 1 to 300 μm, particularly 5 to 200 μm. The transparent protective layer may have a fine uneven structure on the surface by adding transparent particles to the transparent protective layer for the purpose of imparting diffusivity and anti-glare properties.

The transparent particles may be conductive, for example, made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 20 μm. In general, inorganic particles, organic particles composed of a crosslinked or uncrosslinked polymer, and the like are used. The amount of the transparent particles used is generally 1 to 50 parts by weight per 100 parts by weight of the transparent resin.

On the other hand, as a specific example of the above retardation plate, a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefin, polyarylate, or polyamide is stretched. Birefringent film or liquid crystal polymer oriented film,
Examples thereof include a film in which an alignment layer of a liquid crystal polymer is supported by a film.

The retardation plate may be any suitable wavelength depending on the purpose of use, such as various wavelength plates such as 1/2 or 1/4, or those for the purpose of compensating for coloring or viewing angle due to birefringence of the liquid crystal layer. The film may have a phase difference, and may be an obliquely oriented film in which the refractive index in the thickness direction is controlled. Further, two or more retardation plates may be laminated to control optical characteristics such as retardation.

The above-mentioned obliquely oriented film is formed, for example, by bonding a heat-shrinkable film to a polymer film and subjecting the polymer film to a stretching treatment and / or a shrinking treatment under the action of the shrinkage force caused by heating. It can be obtained by a method such as

The above-mentioned anti-glare sheet is usually provided on the viewing-side surface of the optical member for the purpose of preventing surface reflection and preventing deterioration of visibility due to reflection of external light. The anti-glare sheet is, for example, one according to the transparent protective layer containing transparent particles described above, one having a transparent resin layer containing transparent particles supported by a transparent substrate, and roughening the surface of the transparent substrate by buffing or the like. It may be formed by an appropriate method according to the related art, such as the one described above.

The optical member may be made of an optical material formed by laminating two or three or more optical layers, such as the above-mentioned laminate of an elliptically polarizing plate or a retardation plate. 2 layers or 3
An optical material obtained by laminating more than one optical layer can also be formed by a method of sequentially laminating layers in the manufacturing process of a liquid crystal panel or the like. There is an advantage that the manufacturing efficiency of a liquid crystal panel or the like can be improved due to its excellent performance and assembly workability.

Incidentally, in a wide wavelength range such as a visible light range, 1 /
A retardation plate functioning as a four-wavelength plate has, for example, a wavelength of 550.
A retardation layer that functions as a quarter-wave plate for monochromatic light such as nm light and a retardation layer that exhibits other retardation characteristics, such as 1 /
It can be obtained by a method in which a retardation layer functioning as a two-wavelength plate is superimposed.

As shown in the drawing, the surface of the optical member 2 on which the surface protection film 1 is not provided may be provided with an adhesive layer 22 for adhering to another member such as a liquid crystal cell, if necessary. Such an adhesive layer can be formed according to the above-mentioned surface protective film. Above all, from the viewpoint of prevention of foaming and peeling phenomena due to moisture absorption, deterioration of optical characteristics due to difference in thermal expansion, prevention of liquid crystal cell warpage, and formation of high quality and durable liquid crystal panel, moisture absorption rate It is preferable that the pressure-sensitive adhesive layer is low and has excellent heat resistance.

When the adhesive layer provided on the optical member is exposed on the surface, the adhesive layer may be temporarily attached with the separator 3 as shown in FIG. preferable. The separator is formed by, for example, providing a release coating with a suitable release agent such as a silicone-based or long-chain alkyl-based, fluorine-based or molybdenum sulfide on a suitable thin leaf according to the above-described protective substrate or the like. It can be carried out.

The respective layers such as a polarizing plate, a retardation plate, a transparent protective layer, an adhesive layer, and an antiglare sheet which form the optical member are formed of, for example, a salicylate-based compound, a benzophenol-based compound, a benzotriazole-based compound, and a cyano-based compound. A material having an ultraviolet absorbing ability by an appropriate method such as a method of treating with an ultraviolet absorbent such as an acrylate compound or a nickel complex salt compound may be used.

The surface protective film according to the present invention can be stably and easily peeled off from an optical member from a low speed to a high speed, and is adhered to an optical member, and the optical member is adhered to another member such as a liquid crystal cell. It can be preferably used in the production process of various devices such as a liquid crystal panel for separating and separating a film from an optical member.

[0032]

EXAMPLE 1 100 parts of 2-ethylhexyl acrylate (parts by weight, the same applies hereinafter), 70 parts of vinyl acetate, 8 parts of methyl acrylate and 5 parts of acrylic acid were added to 0.3 parts of benzoyl peroxide.
4 parts of a cross-linking agent (Tetrad C, manufactured by Mitsubishi Chemical Corporation) per 100 parts of the solid content was added to a polymer solution obtained by reacting at about 60 ° C. in toluene through the above-mentioned parts, and the mixture was placed on a 35 μm-thick polyester film. An acrylic adhesive layer having a thickness of 25 μm was formed by coating to obtain a surface protection film.

Comparative Example 1 An acrylic resin obtained by adding 3 parts of a crosslinking agent (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) per 100 parts of solid content to a solution of a polymer consisting of 100 parts of isononyl acrylate and 4 parts of 2-hydroxyethyl acrylate A surface protective film was obtained according to Example 1, except that an adhesive was used.

Evaluation Test The surface protective films obtained in Examples and Comparative Examples were adhered to a commercially available polarizing plate by a method of reciprocating a 2 kg rubber roll through the adhesive layer, and cut into a size of 50 mm × 150 mm. A test piece was formed, and a 180 ° peel value at a peeling rate of 10 m / min (at high speed) or 0.3 m / min (at low speed) was measured through a tensile tester to protect the surface of the polarizing plate at 23 ° C. The adhesion of the film was examined.

The results are shown in the following table.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view when applied to an optical member.

[Explanation of symbols]

 1: Surface protective film 11: Protective substrate 12: Adhesive layer 2: Optical member 21: Optical material 22: Adhesive layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuji Shiki 1-1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Inside Nitto Denko Corporation (72) Inventor Tomomori Masada 1-1-1, Shimohozumi, Ibaraki City, Osaka Prefecture No. 2 Nitto Denko Corporation F-term (reference) 2H042 AA07 AA26 BA02 BA03 BA20 2H049 BA02 BA06 BA25 BA26 BA27 BB12 BB13 BB22 BB24 BB25 BB28 BB30 BB51 BB54 BB63 BC22 BC24 2H091 FA08X FA08Z FA11ZFAZFA37

Claims (2)

[Claims] 1. A protective film for adhesively coating the surface of an optical member, wherein the peeling speed at an ordinary temperature of 180 ° peel based on a peeling speed of 10 m / min is 0.3 m / min. Surface protective film, wherein the surface protection film is within 2.5 times that of the above. 2. The optical device according to claim 1, wherein the optical member is a polarizing plate,
A surface protective film that is a retardation plate, a laminate thereof, or an antiglare sheet.