JP6251111B2 - Double-sided adhesive film and protective member for information display screen using the same - Google Patents

Description

The present invention relates to a double-sided adhesive film that can be attached to or detached from an adherend such as an information display screen of a display panel and a protective member for an information display screen using the same.・ For the purpose of protecting and improving the visibility of information display screens such as liquid crystal displays, plasma displays, and organic EL displays used as display devices for electrical equipment, this information display screen has a hard transparent protection made of glass or resin plate. The present invention relates to a double-sided adhesive film for attaching a cover, and a protective member for an information display screen comprising a laminate of the transparent protective cover and the double-sided adhesive film.

For example, for the purpose of protecting the display screen of liquid crystal or the like and improving the visibility, a method in which a transparent member is closely attached to the information display screen of the display panel via a transparent gel is known. (Patent Document 1). According to the above method, the glass substrate of the display panel and the conventional transparent member that is a hard plate such as glass or acrylic are bonded together because the glass substrate and the transparent member of the hard plate are bonded in surface contact. Not only was it easy to entrain bubbles, but once they were pasted together, it was difficult to escape the entrained bubbles. When bubbles are entrained, the brightness, brightness, and color of the display become nonuniform due to the bubbles and display unevenness occurs. Therefore, operations such as re-sticking and extruding bubbles are required. In order to extrude the entrained bubbles, the appearance of the display surface may be impaired while the bubbles are strongly pushed out from the surface of the transparent member with a finger or repeatedly applied. .

Further, a stress relaxation layer mainly composed of an acrylic or urethane resin is disposed on the adherend surface constituting the display body, and is formed of glass or a resin plate via a hydrophilic liquid layer on one side of the stress relaxation layer. 2. Description of the Related Art A display device protector that attaches a transparent protector to the adherend surface is known. (Patent Document 2). The protective body requires a process of laminating the stress relaxation layer, the hydrophilic liquid layer, and the transparent protective body on the adherend surface that forms the display body. Therefore, an expensive manufacturing apparatus is required, and the process is also performed. Since it becomes complicated, there is a drawback that it becomes expensive as a result.

JP 2003-295780 A JP 2011-167862 A

The present invention can be attached to or detached from an adherend such as an information display screen of a display panel, and even when a hard protective member is attached, entrainment of bubbles occurs at the time of attachment. An object of the present invention is to provide a double-sided pressure-sensitive adhesive film that is difficult and excellent in visibility, and a protective member for an information display screen using the same.

As a result of intensive studies, the inventor has found that the information display screen of the display panel, the transparent protective cover made of a hard plate such as glass or acrylic, and the protective member bonded with the double-sided adhesive film are attached. A separator formed by laminating an adsorption layer mainly composed of a silicone resin on one surface of the material film and laminating an adhesive layer made of an acrylic adhesive on the other surface, It has been found that a double-sided pressure-sensitive adhesive film having a high smoothness on the surface of the adsorption layer can be obtained by using a plastic film substrate and having a high smoothness on the separator surface. As a result, even when a transparent protective cover made of a hard plate such as glass or acrylic is attached to the display screen of the display panel using the double-sided adhesive film, it is difficult to cause entrainment of bubbles at the time of attachment, and visibility The present invention has been completed by finding that a protective member for an information display screen can be realized.

1st invention is the double-sided adhesive film for sticking a transparent protective cover to the information display screen of a display panel, Comprising: The adsorption layer which has a silicone resin as a main component is laminated | stacked on one side of a base film, A separator layer made of an acrylic pressure-sensitive adhesive layer is laminated on the other surface, the separator to be bonded to the adsorption layer is made of a plastic film base material, and the surface smoothness of the adsorption layer bonding surface of the separator is The double-sided pressure-sensitive adhesive film has a center line surface roughness Ra of 0.20 μm or less.

A second invention is the double-sided pressure-sensitive adhesive film according to the first invention, wherein the separator has a thickness of 25 to 200 μm.

A third invention is the double-sided pressure-sensitive adhesive film according to the first invention or the second invention, wherein the separator has a Young's modulus of 3.0 to 4.2 GPa.

In a fourth aspect of the present invention, the adsorption layer is formed by curing a silicone composition comprising a diorganopolysiloxane having two or more alkenyl groups in one molecule and an organohydrogenpolysiloxane by an addition reaction. The first invention is characterized in that the adsorption layer has an Asker FP hardness of 20 or more, an Asker CSC2 hardness of 60 or less, and a gel fraction of the adsorption layer of 60 to 98%. It is a double-sided adhesive film in any one of-3rd invention.

5th invention is the double-sided adhesive film in any one of 1st invention-4th invention, wherein the thickness of the said adsorption layer is 10-100 micrometers.

According to a sixth invention, the diorganopolysiloxane is a linear diorganopolysiloxane having vinyl groups only at both ends, a linear diorganopolysiloxane having vinyl groups at both ends and side chains, and vinyl only at the ends. One of the first to fifth inventions, which is at least one selected from a branched diorganopolysiloxane having a group and a branched diorganopolysiloxane having a vinyl group at the terminal and side chain. It is a double-sided adhesive film of description.

7th invention bonds a transparent protective cover and the adhesive layer of the double-sided adhesive film in any one of 1st invention-6th invention, and affixes it on the information display screen of a display panel through the said adsorption layer. In the protective member to be worn, the transparent protective cover has a thickness of 100 to 1000 μm, a light transmittance of 85% or more, and is a hard resin plate or glass plate selected from a polyester resin, an acrylic resin, and a polycarbonate resin This is a protective member for an information display screen.

The double-sided pressure-sensitive adhesive film of the present invention is formed by laminating an adsorption layer mainly composed of a silicone resin on one surface of a base film, and laminating an adhesive layer made of an acrylic pressure-sensitive adhesive on the other surface, By setting the surface smoothness of the separator to be bonded to the adsorption layer to a specific centerline surface roughness, the surface smoothness of the adsorption layer becomes very high, and the information display screen of the display panel and glass or acrylic When sticking a transparent protective cover made of a hard plate such as a double-sided adhesive film, it is easy to stick while releasing air at the sticking interface, even though it is in the condition of sticking by surface contact. Sometimes it is difficult to cause entrainment of bubbles.

Below, the double-sided pressure-sensitive adhesive film of the present invention and the protective member for an information display screen using the same will be described in more detail based on the components.

(overall structure)
The protective member for an information display screen of the present invention comprises a transparent protective cover and an adhesive layer composed mainly of a silicone resin on one surface of a base film, and an acrylic adhesive on the other surface. A double-sided pressure-sensitive adhesive film formed by laminating a pressure-sensitive adhesive layer and made of a separator bonded to the adsorption layer is provided in a state of being bonded via the pressure-sensitive adhesive layer.

(Transparent protective cover)
Among the constituent members of the protective member for the information display screen of the present invention, the transparent protective cover may be a hard resin plate or a glass plate selected from a polyester resin, an acrylic resin, and a polycarbonate resin.

As the transparent protective cover, it is preferable to select one having a refractive index close to the refractive index of the glass substrate that is the surface member of the information display screen, more preferably one having a refractive index of 1.2 to 1.6. It is preferable to use it. This is because the light reflected at the interface can be reduced by bringing materials having similar refractive indexes into close contact with each other.

The transparent protective cover preferably has a visible light total light transmittance of 85% or more in a wavelength range of 380 to 780 nm. This is because, when the transmittance is less than 85%, the light emitted from the screen is difficult to transmit through the transparent member, so that the visibility is lowered.

(Measurement method of total light transmittance)
The total light transmittance here was measured with an integrating sphere turbidimeter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.) according to JIS-K7105.

The thickness of the transparent protective cover is preferably in the range of 100 to 1000 μm from the viewpoints of hardness and cutting processability. When the thickness of the transparent protective cover is smaller than 100 μm, workability when the transparent protective cover is stuck on the information display screen may be deteriorated. On the other hand, when the thickness of the transparent protective cover exceeds 1000 μm, the cost increases, the transmittance may decrease, and the visibility may decrease.

The transparent protective cover preferably further has a center line surface roughness Ra of 5.0 μm or less. This is because when the center line surface roughness Ra is larger than 5.0 μm, bubbles are likely to be involved when the transparent protective cover is attached to the information display screen.

In some cases, the transparent protective cover may be provided with a light reflection preventing layer, and a film of a metal oxide such as ITO, SiO ₂ , TiO ₂ , ZnO ₂ or the like is formed on one side of the transparent protective cover as a light reflection preventing agent. . Such a film may be formed, for example, by sputtering ITO or the like. When the light reflection preventing layer is formed by this method, a highly reliable material such as transparency can be obtained.

In addition, the formation of the light reflection preventing layer is preferably performed in terms of cost. For example, an acrylic or acrylic resin binder is added to a fine powder of metal oxide such as ITO, SiO ₂ , TiO ₂ , or ZnO ₂ to form a solution or It may be formed by a wet method in which it is emulsified and applied with a gravure coater, spin coater or the like. The particle diameter of the metal oxide fine powder used as an antireflection agent in the wet method is preferably as fine as possible from the viewpoint of transparency, and is preferably 10 to 500 nm. Since the yield deteriorates due to poor dispersibility and secondary aggregation, those having a particle size of up to 1.0 μm are preferable.

(Double-sided adhesive film)
The double-sided pressure-sensitive adhesive film used for the protective member for the information display screen of the present invention is formed by laminating an adsorption layer mainly composed of a silicone resin on one surface of a base film and an acrylic pressure-sensitive adhesive on the other surface. A pressure-sensitive adhesive layer is laminated, and a separator made of a plastic film with a centerline surface roughness Ra specified is attached to the adsorption layer. Further, a polyester resin film and a silicone resin film are bonded to the pressure-sensitive adhesive layer. The cover film that has been subjected to mold processing is provided in a state of being bonded.

(Base film)
The base film used in the present invention is not particularly limited as long as it is a film made of various plastics. Examples include films made of polyolefin, polyester, polyamide, polycarbonate, triacetyl cellulose, fluororesin, polyphenylene oxide, polyimide, polyamideimide, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, etc. It is not limited. A polyester film and a polycarbonate film are preferable from the viewpoints of handleability and cost at the time of thermal crosslinking of silicone rubber. From the viewpoint of transparency, a polyester film, particularly polyethylene terephthalate is preferable. The thickness of the substrate may be appropriately selected according to the use, but is usually in the range of 5 to 400 μm, particularly 20 to 250 μm.

The surface of the base film may be subjected to corona discharge treatment, ultraviolet irradiation treatment, plasma treatment, flame treatment, or may be provided with an anchor layer or the like as necessary. As a method for laminating the anchor layer or the like, either a so-called in-line method for laminating at the time of film formation or a so-called off-line method for laminating on the formed film may be used.

(Adhesive layer)
Various pressure-sensitive adhesives such as acrylic, urethane, polyester, silicone and rubber can be used for the pressure-sensitive adhesive layer of the present invention. Acrylic pressure-sensitive adhesives and acrylic high-polymers obtained by copolymerizing various acrylic monomers and / or oligomers for the reason that it is easy to obtain a highly transparent pressure-sensitive adhesive with a total light transmittance of 80% or more on the double-sided pressure-sensitive adhesive film. A molecular adhesive (emulsion type) or the like can be suitably used.

This acrylic pressure-sensitive adhesive is, for example, acrylic acid alkyl ester such as butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, amyl acrylate, cyclohexyl acrylate, benzyl acrylate, or methyl methacrylate. , Methacrylic acid alkyl esters such as butyl methacrylate, methacrylic acid-2-ethylhexyl, cyclohexyl methacrylate, benzyl methacrylate, and acrylic acrylic esters or methacrylic acid alkyl esters, vinyl acetate, vinyl ether, styrene, acrylonitrile, Vinyl group-containing compounds such as methacrylonitrile, acrylic acid, methacrylic acid, itaconic acid, hydroxylethyl acrylate, hydroxylethyl methacrylate, acrylic Propylene glycol, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, those obtained by copolymerizing methacrylic acid -tert- butyl aminoethyl used.

As the acrylic copolymer used for the acrylic pressure-sensitive adhesive, those having a weight average molecular weight in the range of 100,000 to 1,000,000 are preferably used. If the weight average molecular weight is less than 100,000, the adhesive strength becomes high, and problems such as difficulty in peeling the cover film occur. Moreover, when a weight average molecular weight exceeds 1 million, solution viscosity will become high and there exists a problem that it is difficult to obtain the smooth adhesive coating external appearance at the time of coating. The glass transition point (Tg) of this acrylic copolymer is preferably -20 ° C or lower. When Tg is higher than −20 ° C., the pressure-sensitive adhesive becomes hard, and an appropriate pressure-sensitive adhesive force cannot be obtained for the transparent protective cover.

As a crosslinking agent used for the acrylic pressure-sensitive adhesive, known crosslinking agents such as isocyanate, melamine, and epoxy can be used. Examples of the isocyanate-based crosslinking agent include polyisocyanate compounds of polyisocyanates, trimers of these polyisocyanate compounds, terminal isocyanate urethane prepolymers obtained by reacting the above polyisocyanate compounds and polyol compounds, and these polyisocyanate compounds. And trimers of these polyisocyanate compounds. Specific examples of the polyvalent isocyanate include 2,4-tolylene diisocyanate, 2,5-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4′-diisocyanate, Examples include 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, dicyclohexylmethane-2,4′-diisocyanate, and lysine isocyanate. Moreover, you may use metal chelate compounds, such as aluminum and titanium, a polyfunctional epoxy compound, a melamine resin, and an amide resin.

The amount of the crosslinking agent added is preferably 0.005 to 20 parts by weight, particularly 0.01 to 10 parts by weight, based on the acrylic pressure-sensitive adhesive.

The thickness of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive film in the present invention is usually 5 to 100 μm, preferably 10 to 50 μm. As the method for forming the pressure-sensitive adhesive layer, a known method such as a method of applying a pressure-sensitive adhesive dissolved in an organic solvent or a method of dispersing and applying in water can be used. As a method for forming a pressure-sensitive adhesive, a method of applying a pressure-sensitive adhesive dissolved in an organic solvent and adjusting the viscosity is generally used.

In the case of using an ultraviolet-polymerization type acrylic pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition includes a photopolymerization initiator, a UV-crosslinking accelerator (increase) in addition to the main monomer and / or oligomer of acrylic acid. Auxiliary materials such as sensitizers and diluents are blended.

As an auxiliary material for the pressure-sensitive adhesive, a filler or the like may be included, and such a filler is added for the purpose of adjusting the hardness or adhesiveness, an inorganic metal filler as a light reflection preventing agent. Vinyl acetate, styrene, tackifier (tackifier) and the like may be blended. However, since the addition of the auxiliary material causes birefringence of light in the thickness direction of the obtained pressure-sensitive adhesive layer and lowers the transparency, particularly in the present invention in which the thickness of the pressure-sensitive adhesive layer is formed to 10 to 50 μm. In view of the remarkable decrease in transparency, it is preferable not to add them or to keep them relatively small.

A desired amount of the tackifier for the pressure-sensitive adhesive is added to the acrylic pressure-sensitive adhesive for the purpose of improving the tackiness, and examples thereof include rosin-based resins, terpene-based resins, xylene-based resins, and the like. 0 to 50 parts by weight is preferable, and 0 to 40 parts by weight is more preferable.

In addition, it can use without a restriction | limiting especially as a diluent of the said adhesive. In particular, an organic solvent is desirable as a diluent, for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, benzene, toluene, xylene, chlorobenzene, tetrahydrofuran, methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, ethyl acetate. 1,4-dioxane, 1,2-dichloroethane, dichloromethane, chloroform and the like, but are not limited thereto.

 Examples of the coating method for the pressure-sensitive adhesive layer of the present invention include a comma knife coater, a die coater, and a reverse coater for both solution type and solventless type. Extrusion methods and calendering methods may be used as long as they are solventless, but a die coater is preferred from the viewpoint of preventing bubbles from being mixed.

(Cover film)
In the double-sided pressure-sensitive adhesive film of the present invention, a polyester resin film is preferably bonded to the pressure-sensitive adhesive layer surface as a cover film. The centerline surface roughness of the cover film is preferably 0.20 μm or less. More preferably, the surface roughness of the cover film is 0.10 μm or less. When the center line surface roughness is greater than 0.20 μm, the roughness of the cover film surface is transferred to the adhesive layer, light scattering occurs due to the roughness of the adhesive layer, and a double-sided adhesive film is attached to the transparent protective cover, There may be a problem that visibility when used as a protective member for an information display screen is lowered.

The polyester resin film used as the cover film is preferably a biaxially stretched polyester film in terms of dimensional stability, transparency and hardness. The polyester resin film serving as the cover film preferably has a thickness in the range of 10 to 200 [mu] m, and in the range of 25 to 100 [mu] m in view of hardness and cutting processability. When the thickness is less than 10 μm, the film strength is insufficient, and problems such as tearing when the cover film is peeled off and wrinkling easily occur when pasting to a double-sided adhesive film. On the other hand, when the thickness is greater than 200 μm, problems such as an expensive film itself occur.

Moreover, when sticking the double-sided adhesive film of this invention to the said transparent protective cover through an adhesive layer, it peels and uses a cover film, and peels a cover film from the said adhesive layer. In order to adjust the peeling force at the time, it is preferable to apply a silicone release agent to the adhesive layer bonding surface of the cover film.

(Adsorption layer)
The properties of the silicone resin used in the adsorption layer of the present invention are high in transparency, have flexibility like rubber, and the surface of the adsorption layer is also along the adherend surface with respect to the adherend surface. Is required. Further, when peeling, it is required to be easily peeled with a small peeling force. Further, in order to provide a crosslinked adsorbing layer only by coating and heat treatment with a thickness of at least 10 μm and without using a basis weight processing method, at 150 ° C. under a platinum catalyst or the like during the curing reaction of the silicone composition. As a crosslinker and polyorganosiloxane having two or more alkenyl groups in one molecule, which crosslinks to the deep part in the following low temperature in a short time, is transparent, heat resistant, excellent in compression set, low viscosity and liquid type It is preferable to use an addition reaction type liquid silicone composition that is thermally crosslinked by an addition reaction with an organohydrogenpolysiloxane having a SiH group.

Diorganopolysiloxanes having two or more alkenyl groups in one molecule include linear diorganopolysiloxanes having vinyl groups only at both ends and linear diorganopolysiloxanes having vinyl groups at both ends and side chains. It is preferable to use at least one selected from organopolysiloxane, branched diorganopolysiloxane having a vinyl group only at the terminal, and branched diorganopolysiloxane having a vinyl group at the terminal and side chain.

One form of these diorganopolysiloxanes is a linear diorganopolysiloxane having vinyl groups only at both ends, and is a compound represented by the following general formula (Formula 1).

  (In the formula, R represents the following organic group, and n represents an integer.)

  (In the formula, R represents the following organic group, and n and m represent integers.)

The organic group (R) bonded to the silicon atom other than the vinyl group may be different or of the same type. Specific examples include alkyl groups such as methyl, ethyl and propyl groups, and aryl groups such as phenyl and tolyl groups. Or a monovalent hydrocarbon group excluding the same or different kinds of unsubstituted or substituted aliphatic unsaturated groups in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with halogen atoms, cyano groups, or the like Preferably, at least 50 mol% of them is a methyl group, and the diorganopolysiloxane may be used alone or in a mixture of two or more.

The linear diorganopolysiloxane having vinyl groups at both ends and side chains is a compound in which a part of R in the above general formula (Formula 1) is a vinyl group. The branched polyorganosiloxane having a vinyl group only at the terminal is a compound represented by the above general formula (Formula 2). The branched polyorganosiloxane having vinyl groups at the terminals and side chains is a compound in which a part of R in the above general formula (Formula 2) is a vinyl group.

The diorganopolysiloxane having two or more alkenyl groups in one molecule preferably has a weight average molecular weight in the range of 20,000 to 700,000. When the weight average molecular weight of the diorganopolysiloxane is less than 20,000, the curability is lowered or the adhesive force to the adherend is lowered. Moreover, when it exceeds 700,000, the viscosity of a composition will become high too much and stirring at the time of manufacture will become difficult.

Here, an example of the crosslinking agent used for the crosslinking reaction is organohydrogenpolysiloxane. The organohydrogenpolysiloxane has at least three hydrogen atoms bonded to silicon atoms in one molecule, but from a practical point of view, it has a total amount of 50 having two ≡SiH bonds in the molecule. It is preferable that the content is up to wt%, and the remainder includes at least three ≡SiH bonds in the molecule. The molecular shape may be linear, branched or cyclic.

The molar ratio (A) / (B) of the SiH group (B) in the organohydrogenpolysiloxane to the alkenyl group (A) in the diorganopolysiloxane having the alkenyl group is in the range of 1.0 to 2.0. It is preferable to mix | blend so that it may become. If the molar ratio (A) / (B) is less than 1.0, the crosslinking density is insufficient, and the cohesive force and holding power may be lowered accordingly. The density increases, moderate adhesive strength and tackiness cannot be obtained, and air bubbles are likely to be mixed.

The addition reaction catalyst used for the crosslinking reaction is chloroplatinic acid, alcohol solution of chloroplatinic acid, a reaction product of chloroplatinic acid and alcohol, a reaction product of chloroplatinic acid and olefin compound, chloroplatinic acid and vinyl group-containing siloxane, Reaction products, platinum-olefin complexes, platinum-vinyl group-containing siloxane complexes, rhodium complexes, ruthenium complexes, and the like. Moreover, you may use what melt | dissolved and disperse | distributed these things to solvents, such as isopropanol and toluene, or silicone oil. The adsorption layer subjected to the crosslinking reaction has flexibility such as silicone rubber, and this flexibility facilitates the close contact with the adherend.

The addition amount is preferably 5 to 2,000 ppm, particularly preferably 10 to 500 ppm as a noble metal component with respect to a total of 100 parts by weight of the silicone composition. If it is less than 5 ppm, the curability is lowered, the crosslinking density is lowered, and the holding power may be lowered. If it exceeds 2,000 ppm, the usable time of the treatment bath may be shortened.

The shape of the commercially available silicone product according to the present invention includes a solventless type, a solvent type, and an emulsion type, but any type can be used. Especially, since the solventless type does not use a solvent, it is very advantageous in terms of safety, hygiene, and air pollution. However, even in the solventless type, if necessary, an aromatic hydrocarbon solvent such as toluene or xylene, or a fat such as hexane, heptane, octane or isoparaffin is used to adjust the viscosity to obtain a desired film thickness. Use of aromatic hydrocarbon solvents, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as ethyl acetate and isobutyl acetate, ether solvents such as diisopropyl ether and 1,4-dioxane, or mixed solvents thereof Is done.

The addition amount is preferably 20 to 1000 parts by weight, particularly 25 to 900 parts by weight, based on 100 parts by weight of the total silicone composition. If it is less than 20 parts by weight, the adhesion between the adsorbing layer and the substrate may be lowered. If it exceeds 1000 parts by weight, the viscosity of the coating liquid of the silicone composition becomes too low, so that it is cured after coating. In the meantime, a part of the applied adsorption layer flows, and the uniformity of the adsorption layer surface is lowered.

As described above, the properties of the adsorbing layer are required to have a softness like rubber and follow the irregularities on the surface of the adherend to ensure adhesion when adhered to the adherend. And, for example, when using a double-sided adhesive film as the protective member for the information display screen, the film thickness of the adsorption layer is at least 10 μm or more in order to ensure the shearing force in the adhesion surface direction of the adsorption layer with respect to the adherend. 10-100 micrometers is preferable. In the case of the present invention, the thickness of the adsorption layer is more preferably 20 to 100 μm in order to prevent air bubbles from being mixed and to ensure air bubble absorbability. When the thickness is less than 10 μm, the shearing force in the adhesion surface direction of the protective member with respect to the adherend cannot be secured, and the protective member is easily peeled off from the adherend, particularly when applied for a long time. Moreover, when the thickness of an adsorption layer exceeds 100 micrometers, the usage-amount of a silicone composition will increase and the raise of the manufacturing cost of a double-sided adhesive film will be caused.

(Measurement method of rubber hardness of adsorption layer)
The rubber hardness of the adsorption layer constituting the double-sided double-sided pressure-sensitive adhesive film of the present invention is measured, for example, by using an Asker FP hardness meter (manufactured by Kobunshi Keiki Co., Ltd.). When 90-100 points are indicated by using an Asker FP type hardness tester, it is measured with an Asker CSC2 type hardness tester (manufactured by Kobunshi Keiki Co., Ltd.) that measures a material harder than the FP type.
.

The rubber hardness of the adsorption layer of the present invention is an ultra-soft composition that cannot be measured with a general rubber hardness meter Asker C type (based on JIS K 7312). That is, it is preferable that the Asker FP hardness is 20 or more and the Asker CSC2 hardness is 60 or less. When the Asker FP hardness of the adsorbing layer is less than 20, the adsorbing layer becomes too soft, and part of the adsorbing layer may remain on the adherend when peeled from the adherend. Moreover, when the Asker CSC2 hardness of the adsorption layer exceeds 60, the stress relaxation property is lowered, air bubbles are likely to be mixed, and the air bubble absorbability is lowered. When the rubber hardness of the adsorption layer is in the above range, the adsorption layer has an optimum cross-linking density, and it becomes possible to make it difficult for air bubbles to be entrained during pasting.

(Measurement method of gel fraction of adsorption layer)
The gel fraction of the adsorption layer constituting the double-sided pressure-sensitive adhesive film of the present invention was obtained by immersing the pressure-sensitive adhesive film, which was cut into a predetermined size and provided with only the adsorption layer on the substrate, in toluene for 24 hours. It is determined as the weight ratio of the adsorption layer.

The gel fraction of the adsorption layer of the present invention is preferably 60 to 98%. If the gel fraction of the adsorption layer is less than 60%, the crosslinking density of the adsorption layer is insufficient, the peel force becomes high and the re-peelability is lowered, or the adsorption layer is fixed to the display screen, so-called silicone fixing. Problems occur. When the gel fraction of the adsorbing layer exceeds 98%, the crosslink density becomes high, bubbles are likely to be mixed, and the bubble absorbability is lowered.

(Anchor layer)
In the present invention, when the protective member is peeled again after improving the adhesive force between the base film and the adsorbing layer and attaching the protective member to the adherend, between the adsorbing layer and the base film. An anchor layer may be provided between the base film and the adsorption layer for the purpose of smoothly peeling from the adherend without peeling.

Examples of the material for the anchor layer include polyester resins, acrylic resins, and urethane resins. Of these, acrylic resins are preferred, and acrylic polyol resins are particularly preferred from the viewpoint of antistatic properties and film properties.

In addition, an antistatic agent can be added to the anchor layer as an additional compounding material to impart an antistatic function. Nonionic polyoxyethylene alkyl ether, polyoxyethylene alkylphenol, polyoxyethylene alkylamine, polyoxyethylene alkylamide, fatty acid polyethylene glycol ester, fatty acid sorbitan ester, polyoxyethylene fatty acid sorbitan ester, fatty acid glycerin ester, alkyl polyethyleneimine, etc. Can be mentioned. An acrylate compound having ethylene oxide as a skeleton can also be used. Polyaniline, polypyrrole, polythiophene, poly3,4-ethylenedioxythiophene, and derivatives thereof can be used as the conductive polymer. As the metal oxide, antimony-doped tin oxide (ATO), tin-doped indium oxide (ITO), aluminum-doped zinc oxide, antimony suboxide, or the like can be used.

The thickness of the anchor layer is preferably in the range of 0.01 to 5.0 μm, more preferably in the range of 0.10 to 3.0 μm. When the thickness of the anchor layer is less than 0.01 μm, the thermally crosslinked adsorption layer is easily detached from the base film. Furthermore, the antistatic performance is not stable. On the other hand, when the thickness exceeds 5.0 μm, the anchor layer becomes inflexible and becomes a hard layer, resulting in poor adhesion to the base film.

As an application method of the anchor layer coating solution and the adsorption layer coating solution, known methods such as a multi-stage roll coater represented by a three-offset gravure coater and a five-roll coater, a direct gravure coater, a bar coater, and an air knife coater are available. Used as appropriate.

(Separator)
In the present invention, the surface of the adsorption layer is prevented from being stained and foreign matter adhered, and the handling of the double-sided pressure-sensitive adhesive film is improved. In particular, the double-sided pressure-sensitive adhesive film is bonded to a transparent protective cover and used as a protective member for an information display screen. In order to prevent air bubbles from being mixed, a separator made of a plastic film is attached to the surface of the adsorption layer.

A plastic film is used for the separator of the double-sided pressure-sensitive adhesive film of the present invention. For example, a polyester film, a polypropylene film, a polyethylene film, a polycarbonate film, a polystyrene film, etc. can be mentioned. Among these, a polyester film excellent in productivity and processability can be preferably used. Such polyester films include a biaxially stretched film, a uniaxially stretched film, and an unstretched film, and any of them can be used. In particular, a biaxially stretched film is generally used and can be preferably used. The thickness of the plastic film is preferably 25 to 200 μm. If it is thinner than 25 μm, the film strength is insufficient and sufficient protection performance cannot be obtained. Problems such as tearing of the film during peeling occur. On the other hand, if it is thicker than 200 μm, the film itself becomes expensive.

The center line surface roughness Ra of the separator to be bonded to the adsorption layer surface is preferably 0.20 μm or less. More preferably, the center line surface roughness of the separator is 0.10 μm or less. When the center line surface roughness is greater than 0.2 μm, the roughness of the separator surface is transferred to the surface of the adsorption layer, light scattering due to the roughness of the adhesive layer occurs, and a double-sided adhesive film is attached to the transparent protective cover, There arises a problem that visibility when used as a protective member for an information display screen is lowered. In addition, when a double-sided adhesive film is used and a transparent protective cover made of a hard plate such as glass or acrylic and a protective member laminated through the adhesive layer, bubbles are mixed into the information display screen of the display panel. There is a problem that it is likely to occur.

(Measurement method of surface roughness)
The measurement of the centerline surface roughness in the present invention is performed using a contact type surface roughness meter (AY-22, manufactured by Kosaka Laboratory Ltd.), and the measured centerline average roughness Ra is used.

The Young's modulus of the plastic film used for the separator of the present invention is preferably 3.0 to 4.2 GPa. When the Young's modulus of the separator is less than 3.0 GPa, when pressure is applied to the double-sided adsorption film, local deformation occurs in the adsorption layer, and bubbles are likely to be mixed. On the other hand, when the Young's modulus of the separator exceeds 4.2 GPa, the separator becomes too hard, the handling property of the double-sided adsorption film is deteriorated, and the separation work of the separator becomes difficult.

(Measurement method of Young's modulus)
The Young's modulus of the plastic film used for the separator was measured according to JIS K7161 according to the Young's modulus (the sheet flow (MD) direction) of the separator. Specifically, in a 25 ° C. atmosphere, a separator film cut to a width of 25 mm was pulled with a tensile tester under conditions of a pulling speed of 300 mm / min and a chuck interval of 100 mm. The Young's modulus (tensile modulus) was determined from the tangent line.

Further, the peeling force of the separator from the adsorption layer is preferably 0.01 to 1.15 N / 25 mm. More preferably, it is 0.01-0.50 N / 25mm. If the peeling force of the separator is greater than 1.15 N / 25 mm, the separator peeling workability deteriorates, and the separator cannot be peeled smoothly, causing problems such as wrinkles on the adhesive film and steps on the adsorption layer surface. To do.

The peeling force of the separator from the adsorbing layer is such that the double-sided adhesive film is cut to a width of 25 mm, the adsorbing layer of the double-sided adhesive film is pressure-bonded to the separator by reciprocating a 2 kg roller, and left at room temperature for about 24 hours after the pressure-bonding. did. Next, using a tensile tester, the separator was peeled at a peeling angle of 180 ° and a peeling speed of 1200 mm / min, and the peeling force (N / 25 mm) of the separator of the double-sided pressure-sensitive adhesive film was measured.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated in detail, this invention is not restrict | limited to the following Example. In the examples, “parts” indicates parts by weight unless otherwise specified.

(Examples 1-8, Comparative Examples 1-3)
The following anchor layer coating solution was applied with a gravure coater on one side of a plasma-treated polyethylene terephthalate film having a thickness of 50 μm, and an anchor layer having a thickness of 2.0 μm was formed.

(Anchor layer coating solution)
20 parts of acrylic polyol resin (manufactured by Toray Fine Chemicals, Cotax LH455, solid content: 50%)
27 parts of polythiophene (manufactured by Shin-Etsu Polymer, Sepulzida OC-SC100, solid content: 3%)
MEK 40 parts Toluene 13 parts

(Examples 1-8, Comparative Examples 1-3)
On the anchor layer, the adsorbing layer coating solution shown in Table 1 was applied by a die coater in combination with the thickness of the adsorbing layer shown in Table 2, and then 150 ° C. in an oven. The film was crosslinked in 100 seconds to form the adsorption layers of the examples and comparative examples.

(Examples 1-8, Comparative Examples 1-3)
The separator shown in Table 2 is sandwiched between two rolls (rubber roll and metal roll) on the adsorption layer surface of each pressure-sensitive adhesive film on which the adsorption layer is formed. An adhesive film in which an adsorption layer and a separator were laminated on one side of the 50 μm thick polyethylene terephthalate film was obtained.

(Examples 1-8, Comparative Examples 1-3)
On the surface of the pressure-sensitive adhesive film opposite to the surface on which the adsorption layer is formed, the following pressure-sensitive adhesive layer coating solution is applied with a die coater, heated and dried at 100 ° C. for 2 minutes, and a thickness of 25 μm. An adhesive layer was formed.

(Adhesive layer coating solution)
Acrylic adhesive solution 100 parts (manufactured by Soken Chemical Co., Ltd. SK-1811L solid content: 23%)
Isocyanate-based crosslinking agent 0.2 part (TD-75 manufactured by Soken Chemical)
Silane coupling agent 0.1 part (A-50 made by Soken Chemical)
MEK 10 parts Toluene 10 parts

(Examples 1-8, Comparative Examples 1-3)
A cover film obtained by applying a silicone release agent to a polyethylene terephthalate film having a thickness of 38 μm on the pressure-sensitive adhesive surface of each pressure-sensitive adhesive film on which the above-mentioned pressure-sensitive adhesive layer is formed is formed with two rolls (rubber roll and metal roll). After sandwiching and adhering both while releasing air, the double-sided pressure-sensitive adhesive film of the present invention was obtained.

The evaluation results of each example and comparative example are shown in Table 2, and each evaluation method is shown below.

(Evaluation method)
(Rubber hardness)
Pour each coating solution for the adsorption layer shown in Table 1 into an aluminum cup with a diameter of 60 mm and crosslink it in a gear oven at 150 ° C. for 100 seconds to produce a test piece for measuring rubber hardness having a thickness of about 10 mm. did. Then, using an Asker FP hardness meter or an Asker CSC2 hardness meter (both manufactured by Kobunshi Keiki Co., Ltd.), a test piece was sandwiched in the measurement part of the hardness meter, and the rubber hardness of each sample was measured.

(Gel fraction)
The pressure-sensitive adhesive film before providing the pressure-sensitive adhesive layer was cut into a size of 50 mm × 50 mm to prepare a test piece, and the test piece was immersed in toluene in a container for 24 hours. Next, the weight of the test piece before and after the immersion was measured, and the weight of the adsorption layer before and after the immersion was calculated. The gel fraction was calculated by the weight of the adsorption layer before immersion / the weight (%) of the adsorption layer before immersion.

(Bubble contamination evaluation)
The double-sided adhesive film created above is cut into 120 mm x 55 mm, and the double-sided adhesive film is pasted to the transparent protective cover (glass plate) with a thickness of 300 μm on the surface through the adhesive layer. Then, after reciprocating a roll with a load of 2 kg from the surface side of the double-sided pressure-sensitive adhesive film, the roll was left at room temperature (25 ° C.) for 24 hours to obtain the protective member for the information display screen of the present invention. It was. The protective member was bonded to a soda-lime glass plate having a thickness of 3 mm, and the presence of bubbles was visually confirmed.
Evaluation criteria ◎: No bubbles are mixed ○: Bubbles are hardly mixed ×: Bubbles are mixed and remain

It is sectional explanatory drawing of the double-sided adhesive sheet of this invention. It is a section explanatory view of the protection member for information display screens of the present invention.

DESCRIPTION OF SYMBOLS 1 Base film 10 Double-sided adhesive film 2 Anchor layer 20 Transparent protective cover 3 Adsorption layer 30 Protection member for information display screens 4 Separator 5 Adhesive layer 6 Cover film 7 Transparent protective cover (hard resin plate or glass plate)
8 Light reflection prevention layer

Claims (6)

A double-sided adhesive film for attaching a transparent protective cover to an information display screen of a display panel, wherein an adsorption layer mainly composed of a silicone resin is laminated on one side of a base film, and the other side formed by laminating a pressure-sensitive adhesive layer including the acrylic pressure-sensitive adhesive, a separator bonded to the adsorption layer is made of a plastic film substrate, the surface smoothness of the adsorption layer lamination surface of separators is, the center line surface roughness der 0.10 [mu] m or less in Ra is, the Young's modulus of the separator 4.0～4.2GPa, and the gel fraction of the adsorption layer and wherein 60 to 77.1% der Rukoto Double-sided adhesive film. The double-sided pressure-sensitive adhesive film according to claim 1, wherein the separator has a thickness of 25 to 200 μm. The adsorption layer is formed by curing a silicone composition composed of a diorganopolysiloxane having two or more alkenyl groups in one molecule and an organohydrogenpolysiloxane by an addition reaction. wherein the FP hardness at 20 or more and an Asker CSC2 hardness in the range of 60 or less double-sided pressure-sensitive adhesive film according to claim 1 or 2. Wherein a thickness of the adsorption layer is 10 to 100 [mu] m, the double-sided pressure-sensitive adhesive film according to any one of claims 1-3. The diorganopolysiloxane is a linear diorganopolysiloxane having vinyl groups only at both ends, a linear diorganopolysiloxane having vinyl groups at both ends and side chains, and a branched form having vinyl groups only at the ends. The double-sided pressure-sensitive adhesive film according to any one of claims 1 to 4 , which is at least one selected from diorganopolysiloxane and a branched diorganopolysiloxane having vinyl groups at the terminals and side chains. For an information display screen comprising a transparent protective cover and an adhesive layer of the double-sided pressure-sensitive adhesive film according to any one of claims 1 to 5 , and bonded to an information display screen of a display panel via the adsorption layer In the protective member, the transparent protective cover is a hard resin plate or a glass plate having a thickness of 100 to 1000 μm, a light transmittance of 85% or more, and selected from a polyester resin, an acrylic resin, and a polycarbonate resin. A protective member for an information display screen.

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