JP2001066430A - Surface protective film, optical member and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface protective film which satisfies the required characteristics that the film does not peel from an optical member by environmental changes such as temperature and humidity, and which can be easily peeled from the optical member when the film is to be peeled. SOLUTION: The protective film 1 is adhered to cover the surface of the optical material 2 with an adhesive layer 12. In this case, the adhesive layer 12 of the surface protective film 1 contains a surfactant, and the optical member is prepared by adhering and covering the surface of the optical material 2 with the film 1. The liquid crystal display device has the optical member on at least one side of the liquid crystal cell. Thereby, an adhesive layer which is easily peelable with the adhesion strength hardly increasing with time can be formed, and the layer can be peeled without giving any damages to the liquid crystal cell.

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 can be easily peeled off from an optical member adhered to a liquid crystal cell.

[0002]

BACKGROUND OF THE INVENTION Optical materials such as a polarizing plate used for forming a liquid crystal display device and an elliptically polarizing plate obtained by laminating the polarizing plate and a retardation plate are adhesively coated with a surface protective film so that the surface is not damaged or contaminated. After being subjected to an assembling step or the like of bonding the optical member in a liquid crystal cell in a state where the surface protection film has been made, the surface protection film is peeled off from the optical member when the surface protection becomes unnecessary.

However, the conventional surface protective film has a large adhesive strength when peeled off from an optical member after assembly due to an increase in the size of a liquid crystal display device or the like, resulting in poor work efficiency. And the display quality deteriorates, and the device is damaged.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to develop a surface protection film which can be easily peeled off from an optical member at the time of peeling while satisfying the property of not peeling off from the optical member due to environmental changes such as temperature and humidity.

[0005]

The present invention relates to a protective film for adhesively covering the surface of an optical material via an adhesive layer, wherein the adhesive layer contains a surfactant and a surface protective film. It is an object of the present invention to provide an optical member characterized in that a surface of an optical material is adhesively coated with a protective film, and a liquid crystal display device having the optical member on at least one side of a liquid crystal cell.

[0006]

According to the present invention, it is possible to form an easily peelable pressure-sensitive adhesive layer in which the adhesive force is hardly increased with time by containing a surfactant,
Even after maintaining a long-term adhesive state while satisfying the property of not peeling off from the optical member due to environmental changes such as temperature and humidity, it can be easily peeled off from the optical member adhered to the liquid crystal cell via hand or machine, and A surface protection film that can be peeled off without giving damage such as a change in cell gap can be obtained.

[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 an optical material via an adhesive layer, wherein the adhesive layer contains a surfactant. Is adhered and coated.
FIG. 1 shows an example of the optical member. 1 is a surface protective film, 11 is a protective substrate, 12 is an adhesive layer, 2 is an optical material, and 21 is an adhesive layer.

The surface protective film is formed such that a surfactant-containing 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.

In general, from the viewpoint of inspection and controllability of optical materials by transparency, for example, polyester resins, acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefins A protective substrate made of a film or rubber sheet made of a transparent polymer such as a resin or an acrylic resin, or a laminate thereof is used.

[0010] The thickness of the protective substrate can be appropriately determined according to the strength and the like, and is generally 500 µm or less, especially 5 to 300 µm.
m, especially 10 to 200 μm. An antistatic layer may be provided on one or both sides of the protective substrate for the purpose of preventing static charge during peeling. 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 surface protective film can be formed by attaching an adhesive layer to a protective substrate, and the attachment can be performed by an appropriate method. Incidentally, as an example, for example, a base polymer or the like is dissolved or dispersed in a suitable solvent to prepare a pressure-sensitive adhesive liquid, which is directly applied on a protective substrate by a suitable development method such as a casting method or a coating method. Or a method in which an adhesive layer is formed on a separator and transferred to a protective substrate according to the method described above.

In forming the above-mentioned pressure-sensitive adhesive layer, an appropriate pressure-sensitive adhesive or pressure-sensitive adhesive can be used, and the type thereof is not particularly limited. Incidentally, examples thereof include those having an appropriate polymer such as an acrylic polymer, a silicone polymer, a polyester or a polyurethane, a polyamide or a polyether, a fluorine or a rubber as a base polymer, and the like.

At the time of preparing the above-mentioned pressure-sensitive adhesive liquid, a surfactant is blended, whereby a pressure-sensitive adhesive layer containing a surfactant is formed, thereby achieving the object of the present invention. As the surfactant, for example, one or more appropriate ones such as a phosphate ester type, an alkyl ether sulfate type, a polyoxyethylene alkyl ether type, sodium laurate, and lauryl betaine can be used.

The amount of the surfactant can be appropriately determined according to the desired adhesive strength. In the present invention, the adhesive strength to an optical material is 130 gf / 10 mm or less based on a 180 degree peel at room temperature, preferably 10 to 120 gf.
An adhesive layer adjusted to gf / 10 mm, particularly 20 to 100 gf / 10 mm, is preferred. From this point, the surfactant is used in an amount of 15 parts by weight or less, preferably 1 to 10 parts by weight, particularly 2 to 8 parts by weight per 100 parts by weight of the base polymer. It is preferable to mix them.

The pressure-sensitive adhesive layer may contain, as necessary, appropriate additives such as natural or synthetic resins such as tackifying resins and antioxidants for the purpose of controlling the adhesive strength. Can also. The adhesive layer can also be provided on the protective substrate as a superimposed 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 material, and the like.
It is 200 μm, especially 10 to 100 μm.

The optical material to be coated with the surface protective film is, for example, a polarizing plate, a reflective polarizing plate, a semi-transmissive polarizing plate, a polarized light separating polarizing plate, an elliptically polarizing plate obtained by combining these and a retardation plate, or a reflective material. It may be an appropriate one used for forming a liquid crystal display device such as a spheroidal polarizing plate or a transflective elliptically polarizing plate, and the type is not particularly limited.

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 a polarizing film.

On the other hand, the above-mentioned reflective polarizer is provided with a reflective layer on the polarizer, and is used to form a liquid crystal display device of a type which reflects incident light from the viewing side (display side) to display. This has the advantage that the built-in light source such as a backlight can be omitted and the thickness of the liquid crystal display device can be easily reduced. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is provided on one surface of the polarizing plate via a transparent protective layer or the like as necessary.

Specific examples of the reflective polarizing plate include a transparent protective layer, which is matted as required, and a reflective layer formed by attaching a foil or a vapor-deposited film made of a reflective metal such as aluminum to one surface of the transparent protective layer. can give. Further, there may be mentioned, for example, those in which fine particles are contained in the transparent protective layer to form a fine surface uneven structure, and a reflective layer having a fine uneven structure is provided thereon. The reflective layer has a reflective surface covered with a transparent protective layer or a polarizing plate. Is more preferable.

The reflection layer having the above-mentioned fine uneven structure has an advantage that the incident light is diffused by irregular reflection, thereby preventing directivity and glare, and suppressing unevenness of brightness and darkness.
Further, the transparent protective layer containing fine particles also has an advantage that the incident light and the reflected light thereof are diffused when transmitting the light and the unevenness of light and darkness can be further suppressed.

The reflection layer having a fine uneven structure reflecting the fine uneven structure on the surface of the transparent protective layer is formed by an appropriate method such as an evaporation method such as a vacuum evaporation method, an ion plating method and a sputtering method, and a plating method. The method can be performed by directly attaching a metal to the surface of the transparent protective layer. The transflective polarizing plate can be obtained by forming the reflective layer as a transflective reflective layer such as a half mirror that reflects and transmits light.

For the formation of the transparent protective layer in the above-mentioned polarizing plate, a polymer or the like having excellent transparency, mechanical strength, heat stability, moisture shielding property and the like is preferably used. Examples thereof include polyester resins and acetate resins, polyethersulfone resins and polycarbonate resins, polyamide resins and polyimide resins, polyolefin resins and acrylic resins, or acrylic, urethane and acrylic urethane resins. And thermosetting resins such as epoxy resins and silicone resins, 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 fine particles to be contained in the formation of the transparent protective layer having the fine surface irregularity structure include, for example, an average particle size of 0.5 to 5
Transparent inorganic fine particles of 0 μm silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like, and organic fine particles of a crosslinked or uncrosslinked polymer, etc. Fine particles are used. The amount of fine particles used is 1
The amount is generally 2 to 50 parts by weight, preferably 5 to 25 parts by weight per 00 parts by weight, but is not limited thereto.

The above-mentioned polarized light separating type polarizing plate reflects a linearly polarized light having a predetermined polarization axis or a circularly polarized light having a predetermined direction when natural light is incident thereon, and a brightness enhancement plate having a characteristic of transmitting other light to the polarizing plate. Light from a light source such as a backlight is incident to obtain transmitted light in a predetermined polarization state, and reflected light is inverted through a reflective layer or the like to be re-incident on a brightness enhancement plate. Or, by increasing the amount of light transmitted through the brightness enhancement plate by transmitting the entirety as light in a predetermined polarization state, and by increasing the amount of light that can be used for a liquid crystal display or the like by supplying polarized light that is hardly absorbed by the polarizing plate. The brightness can be improved.

As the brightness enhancement plate in the above-mentioned polarization separation type polarizing plate, for example, a linearly polarized light having a predetermined polarization axis such as a multilayer thin film of a dielectric or a multilayer laminate of thin films having different refractive index anisotropies is transmitted. Other light, such as those exhibiting the property of reflecting other light, such as cholesteric liquid crystal layers, especially cholesteric liquid crystal polymer oriented films and those in which the oriented liquid crystal layer is supported on a film substrate, and which reflects left or right circularly polarized light. Any suitable light such as a light-transmitting light may be used.

Therefore, in the above-described brightness improving plate of a type that transmits linearly polarized light having a predetermined polarization axis, the transmitted light is incident on the polarizing plate as it is, with the polarization axis aligned, so that the absorption loss by the polarizing plate can be suppressed and efficiently. Can be transmitted. On the other hand, a brightness enhancement plate that transmits circularly polarized light, such as a cholesteric liquid crystal layer, can be directly incident on the polarizing plate.However, from the viewpoint of suppressing absorption loss, the transmitted circularly polarized light is converted to linearly polarized light through a retardation plate. It is preferable to make the light incident on the polarizing plate. Incidentally, by using a quarter-wave plate as the retardation plate, circularly polarized light can be converted into linearly polarized light.

A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region is, for example, a retardation layer that functions as a quarter-wave plate for monochromatic light such as light having a wavelength of 550 nm. , For example, a method of superimposing a retardation layer functioning as a half-wave plate with the retardation layer exhibiting the above retardation characteristic. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement plate may be composed of one or more retardation layers.

The cholesteric liquid crystal layer also has a structure in which two or three or more layers are overlapped by a combination of layers having different reflection wavelengths, so that a layer which reflects circularly polarized light in a wide wavelength range such as a visible light region can be obtained. Thus, it is possible to obtain circularly polarized light transmitted in a wide wavelength range.

The optical material may be formed by laminating two or three or more optical layers, such as a laminate of the above-mentioned elliptically polarizing plate, reflection type polarizing plate and retardation plate. Therefore, a reflective elliptically polarizing plate, a transflective elliptically polarizing plate, or a combination of a reflective polarizing plate, a transflective polarizing plate, and a retardation plate may be used.

An optical material in which two or three or more optical layers are laminated can be formed by a method in which the optical materials are laminated separately in the course of manufacturing a liquid crystal display device or the like. The method described above has an advantage in that it is excellent in quality stability, assembling workability, and the like, and can improve manufacturing efficiency of a liquid crystal display device and the like. For the lamination, an appropriate adhesive means such as an adhesive layer can be used.

As a specific example of the above-mentioned retardation plate, a multilayer film obtained by stretching a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefin, polyarylate or polyamide is used. Examples thereof include a refractive film, an alignment film of a liquid crystal polymer, and an alignment layer of a liquid crystal polymer supported by a film.

The retardation plate is used for various wavelength plates such as 1/2 or 1/4, for example, for compensating coloring due to birefringence of a liquid crystal layer and compensating for a viewing angle such as expansion of a viewing angle. The film may be of any purpose having an appropriate retardation, and may be an obliquely oriented film having a controlled refractive index in the thickness direction. Further, two or more retardation plates may be laminated to control optical characteristics such as retardation.

The above-mentioned obliquely oriented film can be formed, for example, by applying a heat-shrinkable film to a polymer film and applying a shrinkage force by heating to stretch or / and shrink the polymer film. It can be obtained by a method such as

The optical member according to the present invention is one in which one or both of the front and rear surfaces of the optical material is adhesively coated with a surface protective film for the purpose of preventing damage or the like. When the surface protective film 1 is provided only on one surface of the optical material 2 as shown in the figure, an adhesive layer 21 for adhering to another member such as a liquid crystal cell can be provided on the surface where the surface protective film 1 is not provided, if necessary.

The above-mentioned pressure-sensitive adhesive layer can be formed with an appropriate pressure-sensitive adhesive according to the related art. Above all, from the viewpoint of preventing 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 a high quality and durable liquid crystal display device, the moisture absorption rate It is preferable that the pressure-sensitive adhesive layer has low heat resistance and excellent heat resistance. In addition, an adhesive layer or the like which contains fine particles and exhibits light diffusibility can be used.

In the case where the adhesive layer provided on the optical material 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.

Each layer of the optical material and the adhesive layer forming the optical member is made of, for example, a UV-absorbing material such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, a nickel complex salt compound, or the like. It may have an ultraviolet absorbing ability by an appropriate method such as a method of treating with an agent.

The surface protective film according to the present invention is bonded to the surface of an optical material to form an optical member, which is bonded to another member such as a liquid crystal cell, and aging for stabilizing the bonded state if necessary. It can be preferably used for forming various devices such as a liquid crystal display device which needs to separate and separate the surface protective film from the optical member after the heat treatment.

The above-mentioned liquid crystal display device has an appropriate structure according to the prior art, such as a transmission type or reflection type, or a transmission / reflection type in which the optical member according to the present invention is disposed on one or both sides of a liquid crystal cell. It can be formed as one. Therefore, the liquid crystal cell forming the liquid crystal display device is arbitrary, and may be an appropriate type such as an active matrix driving type represented by a thin film transistor type, a simple matrix driving type represented by a twisted nematic type or a super twisted nematic type, and the like. A liquid crystal cell of a type may be used.

When optical members are provided on both sides of the liquid crystal cell, they may be the same or different. Further, in forming a liquid crystal display device,
For example, one or more layers of appropriate components such as a prism array sheet, a lens array sheet, a light diffusing plate, and a backlight can be arranged at appropriate positions.

[0041]

EXAMPLES Example 1 100 parts of isononyl acrylate (parts by weight, the same applies hereinafter) and 4 parts of 2-hydroxyethyl acrylate were added to 150 parts of ethyl acetate via 0.5 part of azobisisobutyronitrile.
The acrylic polymer solution obtained by reacting at about 60 ° C. for 8 hours was mixed with 3 parts of a phosphate ester surfactant (Phosphanol RL-210, manufactured by Toho Chemical Industry Co., Ltd.) per 100 parts of the solid content and 3 parts. An isocyanate-based crosslinking agent (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to form an adhesive syrup, which was coated on a 38 μm-thick polyester film and dried to form a 25 μm-thick acrylic adhesive layer. After obtaining the surface protective film, it was adhered to one surface of a polarizing plate (HEG1425DU, manufactured by Nitto Denko Corporation) to obtain an optical member. The polarizing plate used had an adhesive layer protected by a separator on the other surface.

Example 2 An acrylic polymer solution and a pressure-sensitive adhesive syrup were obtained in the same manner as in Example 1 except that 2-ethylhexyl acrylate was used instead of isononyl acrylate. I got

Comparative Example 1 A pressure-sensitive adhesive syrup containing no phosphate ester-based surfactant was obtained, and a surface protective film and an optical member were obtained in the same manner as in Example 1.

Comparative Example 2 A pressure-sensitive adhesive syrup containing no phosphate ester-based surfactant was obtained, and a surface protective film and an optical member were obtained using the same according to Example 2.

Evaluation Test Adhesive Strength The optical members obtained in Examples and Comparative Examples were cut into a test piece having a width of 10 mm, and the adhesive strength of the surface protective film was examined by a manual peeling operation using a spring balance. The adhesive strength is
Ten workers performed the peeling operation five times each, and the average value of each worker was obtained.

Peeling workability The optical member obtained in each of the examples and comparative examples was 300 mm long and 20 mm wide.
A test piece cut to a size of 0 mm was adhered to a glass plate via an adhesive layer provided on the polarizing plate, the glass plate was placed on a table with the lower side, and an adhesive tape was adhered to a corner of the surface protective film. Then, the peeling operation was performed by a pickup method via the tape, and the peeling workability in that case was examined. Evaluation,
The case where the adhesive force was strong and time was required for peeling, the case where the glass plate itself was lifted at the time of peeling, and the case where the glass plate itself could be smoothly peeled without lifting were evaluated as good.

The results are shown in the following table. Example 1 Example 2 Comparative Example 1 Comparative Example 2 Adhesive force (gf / 10 mm) 80-110 90-120 140-160 170-200 Peeling workability Good Good Good Good Poor (* 1) Poor (* 1) * 1: Difficult to peel without supporting the glass plate

From the table, it can be seen that in the examples, the surface protective film can be peeled off from the optical member adhered to the glass plate with good workability, and can be peeled off without damaging the liquid crystal cell such as a change in cell gap.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an optical member.

[Description of Signs] 1: Surface protective film 11: Protective substrate 12: Adhesive layer 2: Optical material 21: Adhesive layer 3: Separator

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Ning Takahashi 1-1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Inside Nitto Denko Corporation (72) Inventor Homori Mamoru 1-1-1 Shimohozumi, Ibaraki City, Osaka Prefecture No. 2 Nitto Denko Corporation F-term (reference) 2H042 AA04 AA26 2H049 BA04 BA05 BA06 BA43 BB54 BC22 2H091 FA08X FA08Z FA11X FA11Z FA14Z FA15Z GA16 GA17 LA04 LA05 LA12 4J004 AA05 AA06 AA10 AA01 CA02 AA03 DA02 DA04 DA05 DA06 DB02 FA04

Claims (4)

[Claims] 1. A surface protective film, which is a protective film for adhesively covering the surface of an optical material via an adhesive layer, wherein the adhesive layer contains a surfactant. 2. An optical member, wherein the surface of an optical material is adhesively coated with the surface protective film according to claim 1 via the adhesive layer. 3. The method according to claim 2, wherein the optical material is a polarizing plate,
An optical member which is a reflective polarizing plate, a transflective polarizing plate, a polarized light separating polarizing plate, or a laminate having a retardation plate thereof. 4. A liquid crystal display device comprising the optical member according to claim 2 on at least one side of a liquid crystal cell.