JP6472044B2 - 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. To stick a hard transparent protective cover to this information display screen 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. 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 diligent study, the present inventor found that the information display screen of the display panel, the transparent protective cover made of a glass plate, and a protective member bonded with a double-sided adhesive film were attached to one surface of the base film. In the double-sided pressure-sensitive adhesive film formed by laminating an adhering layer that can be attached or removed, and laminating an acrylic pressure-sensitive adhesive layer containing an acrylic copolymer and an isocyanate-based crosslinking agent as essential components on the other surface, When the Martens hardness on the surface of the pressure-sensitive adhesive layer is 8 to 15 mN / mm ² and the gel fraction of the pressure-sensitive adhesive layer is 35 to 80%, the transparent protective cover and the pressure-sensitive adhesive layer are pasted to form a protective member Then, since the adhesive layer can be plastically deformed so as to cancel the irregularities on the surface of the transparent protective cover and the irregularities on the surface of the adsorption layer, the protective part in which the transparent protective cover is bonded to the adhesive layer The surface of the adsorbing layer can be kept smooth in the state of the material, and it is found that bubbles are less likely to occur when the adsorbing layer of the protective member is attached to the information display screen, and the present invention is completed. It came to.

1st invention is the double-sided adhesive film for sticking a transparent protective cover on 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 pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive having an acrylic copolymer and an isocyanate-based crosslinking agent as essential components is laminated on one surface, and the Martens hardness of the pressure-sensitive adhesive layer surface is 8 to 15 mN / mm ² . And a pressure-sensitive adhesive layer having a gel fraction of 35 to 80%.

The second invention is the double-sided pressure-sensitive adhesive film according to the first invention, wherein the amount of the isocyanate-based crosslinking agent added in the pressure-sensitive adhesive layer is 0.05 to 2.0% by weight.

3rd invention is a double-sided adhesive film as described in 1st invention or 2nd invention , wherein the thickness of the said adsorption layer is 10-50 micrometers, and the thickness of the said adhesive layer is 5-30 micrometers. .

In a fourth invention, the adsorption layer is obtained 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 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 the first to third inventions, characterized in that it is at least one selected from diorganopolysiloxane and branched diorganopolysiloxane having vinyl groups at the terminals and side chains. It is.

5th invention bonds a transparent protective cover and the adhesive layer of the double-sided adhesive film in any one of 1st invention- 4th invention, and affixes it on the information display screen of a display panel through the said adsorption layer. The protective member for an information display screen to be worn is characterized in that the transparent protective cover is a glass plate having a thickness of 100 to 1,000 μm and a total light transmittance of 85% or more. It is a member.

The double-sided pressure-sensitive adhesive film of the present invention is a pressure-sensitive adhesive composed of an acrylic pressure-sensitive adhesive having an adsorbing layer laminated on one surface of a base film and an acrylic copolymer and an isocyanate-based crosslinking agent as essential components on the other surface. When the layers are laminated and the Martens hardness and gel fraction on the surface of the pressure-sensitive adhesive layer are within a specific range, when the transparent protective cover and the pressure-sensitive adhesive layer are attached to form a protective member When the adhesive layer of the protective member and the information display screen of the display panel are attached, the adhesive layer can be plastically deformed so as to cancel the unevenness of the surface of the transparent protective cover and the unevenness of the surface of the adsorption layer. Although it is in the condition of contacting and sticking, it becomes easy to stick while releasing air at the sticking interface, and bubbles are less likely to be involved at the time of sticking.

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 the information display screen of the present invention is formed by laminating an adsorption layer on one side of a transparent protective cover and a base film, and laminating an adhesive layer made of an acrylic adhesive on the other side. The double-sided pressure-sensitive adhesive film composed of the 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 is a glass plate having a visible light total light transmittance of 85% or more in the region of a wavelength of 380 to 780 nm. Is preferred. This is because, when the total light 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 K 7105.

The thickness of the transparent protective cover is preferably in the range of 100 to 1,000 μm from the viewpoint 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 1,000 μm, the cost increases, and the transmittance may decrease and the visibility may decrease.

The transparent protective cover preferably has a center line surface roughness Ra of 5.0 μm or less. When the center line surface roughness Ra is larger than 5.0 μm, it becomes difficult to cancel the irregularities on the surface of the transparent protective cover even if the pressure-sensitive adhesive layer is plastically deformed. This is because entrapment of bubbles is likely to occur when the information display screen is attached.

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 antireflection layer is preferably performed in terms of cost. For example, a binder of an acrylic resin is added to a fine powder of metal oxide such as ITO, SiO ₂ , TiO ₂ , ZnO ₂ to form a solution or an emulsion, You may form this by the wet method apply | coated with a gravure coater, a spin coater, etc. 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. Particles with a particle size smaller than 1.0 μm are preferred because of poor dispersibility and poor yield due to secondary aggregation.

(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 has an adsorption layer laminated on one side of the base film, and an acrylic pressure-sensitive adhesive and an isocyanate-based crosslinking agent as essential components on the other side. It is made by laminating a pressure-sensitive adhesive layer, a plastic film separator is pasted on the adsorption layer, and a polyester resin film with a silicone release treatment is further pasted on the pressure-sensitive adhesive layer. It is provided in a combined state.

(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., but are not limited thereto. Is not to be done. A polyester film and a polycarbonate film are preferable from the viewpoints of handling property and cost at the time of thermal crosslinking of the pressure-sensitive adhesive layer and the adsorption layer. 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)
The pressure-sensitive adhesive layer of the present invention is obtained by copolymerizing various acrylic monomers and / or oligomers for the reason that it is easy to obtain a highly transparent pressure-sensitive adhesive having a total light transmittance of 80% or more of the double-sided pressure-sensitive adhesive film. An acrylic pressure-sensitive adhesive containing an acrylic copolymer and an isocyanate-based crosslinking agent as essential components can be suitably used. Moreover, an isocyanate type crosslinking agent is suitable at the point which can anticipate the hydroxyl group which exists on the surface of the glass plate used as a transparent protective cover, and favorable adhesiveness.

Examples of the acrylic copolymer include acrylic acid compounds having hydroxyl groups in acrylates and / or methacrylic acid esters and methacrylic acid compounds having hydroxyl groups, as well as vinyl acetate, vinyl ether, styrene, acrylonitrile, methacrylonitrile, and other vinyls. A copolymer containing a group-containing compound or a compound such as acrylic acid, methacrylic acid, itaconic acid, propylene glycol acrylate, acrylamide, methacrylamide, dimethylaminoethyl methacrylate, or tert-butylaminoethyl methacrylate as required. Is used.

Examples of the acrylate ester include methyl acrylate, ethyl acrylate, butyl acrylate, -2-ethylhexyl acrylate, isobutyl acrylate, tert-butyl acrylate, isooctyl acrylate, isononyl acrylate, lauryl acrylate, Examples include, but are not limited to, stearyl acrylate, isostearyl acrylate, isobonyl acrylate, amyl acrylate, cyclohexyl acrylate, benzyl acrylate, and the like. These compounds may be used alone or in combination of two or more.

Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, and phenyl methacrylate. , Isobonyl methacrylate, glycidyl methacrylate, allyl methacrylate, and the like, but are not limited thereto. These compounds may be used alone or in combination of two or more.

Examples of the acrylic acid compound having a hydroxyl group include, but are not limited to, acrylic esters such as hydroxylethyl acrylate, hydroxybutyl acrylate, hydroxypropyl acrylate, and hydroxyhexyl acrylate. These compounds may be used alone or in combination of two or more.

Examples of the methacrylic acid compound having a hydroxyl group include methacrylate esters such as hydroxylethyl methacrylate, hydroxybutyl methacrylate, hydroxypropyl methacrylate, hydroxyhexyl methacrylate, methoxyethyl methacrylate, and ethoxyethyl methacrylate. However, it is not limited to these. These compounds may be used alone or in combination of two or more.

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. When the weight average molecular weight is less than 100,000, the adhesive strength is increased, which causes a problem that it is difficult to separate the adhesive layer from the bonded cover film. 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.

Examples of the isocyanate-based crosslinking agent include aromatic diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, and 2,2,4-trimethyl. Aliphatic diisocyanates such as hexamethylene diisocyanate, or alicyclic diisocyanates such as 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, 1,2-bis (isocyanatomethyl) cyclohexane, norbornene diisocyanate Is mentioned. Of these, aliphatic diisocyanates are preferably used in that they are non-yellowing and that an appropriate hardness of the pressure-sensitive adhesive can be easily obtained. In addition, the kind of isocyanate type crosslinking agent is not necessarily limited to these.

The addition amount of the isocyanate-based crosslinking agent is preferably 0.05 to 2.0% by weight in 100% by weight of the pressure-sensitive adhesive, and more preferably 0.10 to 1.0% by weight. When the addition amount is less than 0.05% by weight, the curing becomes insufficient and the pressure-sensitive adhesive layer becomes too soft to maintain the surface smoothness. Therefore, a transparent protective cover is bonded to the pressure-sensitive adhesive layer. The surface of the adsorption layer cannot be kept smooth in the state of the protection member, and bubbles are involved when the adsorption layer of the protection member is attached to the information display screen. When the added amount exceeds 2.0% by weight, the pressure-sensitive adhesive layer of the present invention becomes too hard, and the pressure-sensitive adhesive layer is plastic so as to cancel out the irregularities on the surface of the transparent protective cover and the irregularities on the surface of the adsorption layer. Can not be deformed. As a result, the surface of the adsorption layer cannot be kept smooth in the state of the protective member in which the transparent protective cover is adhered to the pressure-sensitive adhesive layer, and when the adsorption layer of the protective member is attached to the information display screen, Entrainment will occur.

(Method for measuring the gel fraction of the adhesive layer)
The gel fraction of the pressure-sensitive adhesive layer constituting the double-sided pressure-sensitive adhesive film of the present invention is such that the pressure-sensitive adhesive film provided with only the pressure-sensitive adhesive layer on a base material cut to a predetermined size is immersed in toluene for 30 minutes, and then immersed 45 The weight of the pressure-sensitive adhesive layer after immersion is measured after drying for 24 hours at a temperature, and the weight ratio with the weight of the pressure-sensitive adhesive layer before immersion that has been measured in advance is obtained.

(Measurement method of Martens hardness of the adhesive layer surface)
The measurement of the Martens hardness on the surface of the pressure-sensitive adhesive layer constituting the double-sided pressure-sensitive adhesive film of the present invention was performed using an ultra-fine indentation hardness tester (ENT-2100 manufactured by Elionix Co., Ltd.) under the following conditions.
Working indenter: Spherical indenter (radius 200 μm)
Maximum load: 10μN
Loading time: 10 sec
Holding time: 5 sec
Unloading time: 10 sec

As physical properties of the pressure-sensitive adhesive, it is preferable that the Martens hardness of the surface of the pressure-sensitive adhesive layer is 8 to 15 mN / mm ² . When the Martens hardness is less than 8 mN / mm ² , the pressure-sensitive adhesive layer surface is too soft and can be easily deformed, and it becomes difficult to maintain the smoothness of the pressure-sensitive adhesive layer surface. The surface of the adsorbing layer cannot be kept smooth in the state of the protective member with the protective cover attached, and bubbles are involved when the adsorbing layer of the protective member is attached to the information display screen. When the Martens hardness is greater than 15 mN / mm ^2, the flexibility of the double-sided adhesive film itself is reduced, and the adhesive layer is plastically deformed so as to cancel the unevenness on the surface of the transparent protective cover and the unevenness on the surface of the adsorption layer. become unable. As a result, when the transparent protective cover is bonded to the pressure-sensitive adhesive layer, the surface of the adsorption layer cannot be kept smooth in the state of the protection member, and when the adsorption layer of the protection member is attached to the information display screen Bubble entrainment occurs.

The gel fraction of the pressure-sensitive adhesive layer is 35% to 80%, and the surface of the adsorption layer is kept smooth in the state of a protective member in which a transparent protective cover is bonded to the pressure-sensitive adhesive layer, and the protective member is displayed on the information display screen. It is desirable in that it can prevent entrainment of bubbles when laminating. When the gel fraction is less than 35%, the cross-linking density of the pressure-sensitive adhesive layer becomes too low, and the cohesive force of the pressure-sensitive adhesive layer decreases, and in the state of the protective member bonded to the transparent protective cover, It becomes difficult to shift the double-sided adhesive film. When the gel fraction exceeds 80%, the crosslinking density becomes too high, the cohesive force of the pressure-sensitive adhesive layer is increased, and sufficient adhesive force to the transparent protective cover cannot be obtained.

The thickness of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive film in the present invention is suitably 5 to 30 μm. When the thickness of the pressure-sensitive adhesive layer is less than 5 μm, the pressure-sensitive adhesive force is lowered and an appropriate pressure-sensitive adhesive force cannot be obtained with respect to the transparent protective cover. In addition, when the thickness of the pressure-sensitive adhesive layer exceeds 30 μm, it becomes difficult to maintain the smoothness of the pressure-sensitive adhesive surface in a high state, and when the pressure-sensitive adhesive layer and the transparent protective cover are adhered to form a protective member In addition, the surface of the adsorption layer on the opposite side cannot be kept smooth, and bubbles are involved when the adsorption layer of the protective member is attached to the information display screen.

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 addition, it can use without a restriction | limiting especially as a diluent of the said adhesive. Examples include organic solvents such as acetone, methyl ethyl ketone, benzene, toluene, and ethyl acetate, 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. A die coater is preferable from the viewpoint of preventing air bubbles from mixing.

(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 center line surface roughness of the cover film is 0.10 μm or less. When the center line surface roughness is larger than 0.20 μm, the roughness of the cover film surface is transferred to the adhesive layer, and the unevenness on the surface of the adhesive layer formed by the transfer pastes the transparent protective cover and the adhesive layer. When the protective member is formed, the surface of the adsorbent layer is affected to cause unevenness on the surface of the adsorbent that cannot be canceled by the plastic deformation of the adhesive layer. When pasted, bubbles are likely to be mixed.

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 surface of the cover film to which the adhesive layer is attached.

(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. Furthermore, when peeling, it is required to be easily peelable with a small peeling force. In addition, in order to provide a crosslinked adsorption layer with a thickness of at least 10 μm and only by coating and heat treatment without using a basis weight processing method, 150 ° C. or less under a platinum catalyst or the like during the curing reaction of the silicone composition A polyorganosiloxane having two or more alkenyl groups in one molecule and SiH as a crosslinking agent, which is crosslinked to a deep portion in a short time at a low temperature, transparent, excellent in heat resistance, compression set, low viscosity and liquid type. It is preferable to use an addition reaction type liquid silicone composition which is thermally crosslinked by addition reaction with an organohydrogenpolysiloxane having a 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 crosslink density is insufficient, and the cohesive force and holding power may decrease accordingly. It becomes high, moderate adhesive force and tackiness cannot be obtained, and bubbles are likely to be mixed.

The addition reaction catalyst used for the cross-linking reaction is chloroplatinic acid, an alcohol solution of chloroplatinic acid, a reaction product of chloroplatinic acid and alcohol, a reaction product of chloroplatinic acid and an olefin compound, chloroplatinic acid and a 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, and 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 1,000 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 reduced and peeled off, and if it exceeds 1,000 parts by weight, the viscosity of the coating liquid of the silicone composition becomes too low. During the period after the curing, the coated adsorption layer partially flows, and the smoothness 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. 10-50 micrometers is preferable. In the case of the present invention, the thickness of the adsorption layer is more preferably 20 to 50 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 50 micrometers, the usage-amount of a silicone composition will increase and it will raise the manufacturing cost of a double-sided adhesive film.

(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, polyester resins or acrylic resins are preferable from the viewpoint of antistatic properties and coating properties.

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 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 the thickness is less than 25 μm, the film strength is insufficient, and sufficient protection performance cannot be obtained, and the film may be broken at the time of peeling. 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 0.20 μm, the roughness of the separator surface is transferred to the surface of the adsorption layer, and when the transparent protective cover and the adhesive layer are adhered to form a protective member, the plasticity of the adhesive layer There is a problem that irregularities that cannot be canceled out by deformation are generated on the surface of the adsorbent, and bubbles are likely to be mixed when the adsorbing layer surface of the protective member is attached to the information display screen of the display panel.

(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.

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 1-9, Comparative Examples 1-2)
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 μm was formed.
(Anchor layer coating solution)
20 parts of acrylic polyol resin (manufactured by Toray Fine Chemicals, Cotax (registered trademark) LH455, solid content: 50%)
27 parts of polythiophene (manufactured by Shin-Etsu Polymer, Sepulzida (registered trademark) OC-SC100, solid content: 3%)
MEK 40 parts Toluene 13 parts

(Examples 1-9, Comparative Examples 1-2)
On the anchor layer, the adsorption layer coating solution described below is applied by a die coater and then crosslinked in an oven at 150 ° C. for 100 seconds to form an adsorption layer having a thickness of 28 μm. did.
(Adsorption layer coating solution)
68.59 parts of linear diorganopolysiloxane having vinyl groups at the molecular terminals and side chains (weight average molecular weight Mw: 540,000) / solvent-free organohydrogensiloxane-diorganosiloxane copolymer 0.41 part (weight) Average molecular weight Mw: 2,000) / solvent-free platinum catalyst (manufactured by Shin-Etsu Polymer, PL-56) 1.00 parts Toluene 30.00 parts Total 100.00 parts

(Examples 1-9, Comparative Examples 1-2)
A 50 µm thick polyester film separator is sandwiched between two rolls (rubber roll and metal roll) on the adsorption layer surface of each adhesive film on which the adsorption layer is formed. A pressure-sensitive adhesive film in which an adsorption layer and a separator were laminated on one side of a treated 50 μm-thick polyethylene terephthalate film was obtained.

Example 1
The pressure-sensitive adhesive film is coated on the surface opposite to the surface on which the adsorption layer is formed with the following pressure-sensitive adhesive layer coating solution with a die coater, heated and dried at 100 ° C. for 2 minutes, and 20 μm. The pressure-sensitive adhesive layer was formed by adjusting so as to have a thickness of 2 mm.
(Adhesive layer coating solution)
Acrylic copolymer 100.0 parts (hydroxybutyl acrylate, butyl acrylate copolymer, weight average molecular weight Mw: about 500,000, solid content 37%)
Hexamethylene diisocyanate 0.05 parts (solid content 37.5%)
Total 100.05 parts

(Example 2)
The pressure-sensitive adhesive layer coating solution described below was applied and dried in the same steps as in Example 1 to form a pressure-sensitive adhesive layer having a thickness of 20 μm.
(Adhesive layer coating solution)
Acrylic copolymer 100.0 parts (hydroxybutyl acrylate, butyl acrylate copolymer, weight average molecular weight Mw: about 500,000, solid content 37%)
Hexamethylene diisocyanate 0.10 parts (solid content 37.5%)
Total 100.10 copies

(Example 3)
The pressure-sensitive adhesive layer coating solution described below was applied and dried in the same steps as in Example 1 to form a pressure-sensitive adhesive layer having a thickness of 20 μm.
(Adhesive layer coating solution)
Acrylic copolymer 100.0 parts (hydroxybutyl acrylate, butyl acrylate copolymer, weight average molecular weight Mw: about 500,000, solid content 37%)
Hexamethylene diisocyanate 0.20 parts (solid content 37.5%)
Total 100.20 copies

Example 4
The pressure-sensitive adhesive layer coating solution described below was applied and dried in the same steps as in Example 1 to form a pressure-sensitive adhesive layer having a thickness of 20 μm.
(Adhesive layer coating solution)
Acrylic copolymer 100.0 parts (hydroxybutyl acrylate, butyl acrylate copolymer, weight average molecular weight Mw: about 500,000, solid content 37%)
Hexamethylene diisocyanate 0.50 parts (solid content 37.5%)
Total 100.50 parts

(Example 5)
The pressure-sensitive adhesive layer coating solution described below was applied and dried in the same steps as in Example 1 to form a pressure-sensitive adhesive layer having a thickness of 20 μm.
(Adhesive layer coating solution)
Acrylic copolymer 100.0 parts (hydroxybutyl acrylate, butyl acrylate copolymer, weight average molecular weight Mw: about 500,000, solid content 37%)
Hexamethylene diisocyanate 1.60 parts (solid content 37.5%)
101.60 copies in total

(Example 6)
A pressure-sensitive adhesive layer coating solution having the same composition as in Example 4 was applied and dried in the same steps as in Example 1 to form a pressure-sensitive adhesive layer having a thickness of 6 μm.

(Example 7)
A pressure-sensitive adhesive layer coating solution having the same composition as in Example 4 was applied and dried in the same steps as in Example 1 to form a pressure-sensitive adhesive layer having a thickness of 30 μm.

(Example 8)
The pressure-sensitive adhesive layer coating solution described below was applied and dried in the same steps as in Example 1 to form a pressure-sensitive adhesive layer having a thickness of 20 μm.
(Adhesive layer coating solution)
Acrylic copolymer 100.0 parts (hydroxybutyl acrylate, butyl acrylate copolymer, weight average molecular weight Mw: about 500,000, solid content 37%)
0.10 parts of xylylene diisocyanate (solid content 75%)
Total 100.10 copies

Example 9
The pressure-sensitive adhesive layer coating solution described below was applied and dried in the same steps as in Example 1 to form a pressure-sensitive adhesive layer having a thickness of 20 μm.
(Adhesive layer coating solution)
Acrylic copolymer 100.0 parts (hydroxyethyl acrylate, 2-ethylhexyl acrylate copolymer, weight average molecular weight Mw: about 600,000, solid content 40%)
Hexamethylene diisocyanate 0.50 parts (solid content 37.5%)
Total 100.50 parts

(Comparative Example 1)
The pressure-sensitive adhesive layer coating solution described below was applied and dried in the same steps as in Example 1 to form a pressure-sensitive adhesive layer having a thickness of 20 μm.
(Adhesive layer coating solution)
Acrylic copolymer 100.0 parts (hydroxybutyl acrylate, butyl acrylate copolymer, weight average molecular weight Mw: about 500,000, solid content 37%)
Hexamethylene diisocyanate 0.02 parts (solid content 37.5%)
Total 100.02 parts

(Comparative Example 2)
The pressure-sensitive adhesive layer coating solution described below was applied and dried in the same steps as in Example 1 to form a pressure-sensitive adhesive layer having a thickness of 20 μm.
(Adhesive layer coating solution)
Acrylic copolymer 100.0 parts (hydroxybutyl acrylate, butyl acrylate copolymer, weight average molecular weight Mw: about 500,000, solid content 37%)
Hexamethylene diisocyanate 2.50 parts (solid content 37.5%)
102.50 copies in total

(Examples 1-9, Comparative Examples 1-2)
The adhesive surface of each adhesive film on which the above-mentioned adhesive layer is formed has two release agent-coated surfaces of a cover film (made of polyethylene terephthalate) coated with a silicone release agent having a thickness of 25 μm. The film was sandwiched between rolls (rubber roll and metal roll) and bonded together while letting air escape, to obtain a double-sided pressure-sensitive adhesive film of the present invention.

The evaluation results of each example and comparative example are shown in Table 1, and each evaluation method is shown below.

(Evaluation method)
(Gel fraction of adhesive layer)
Using a polyethylene terephthalate film having a thickness of 50 μm as a base material, the adhesive layer coating liquids of Examples 1 to 9 and Comparative Examples 1 and 2 were applied to one side of the base material, and heated and dried at 100 ° C. for 2 minutes. Thus, pressure-sensitive adhesive layers having the thicknesses shown in Examples 1 to 9 and Comparative Examples 1 and 2 were formed. A film provided with only the pressure-sensitive adhesive layer was cut into a size of 100 mm × 100 mm to prepare a test piece, and the weight of the test piece was measured. Next, each test piece is immersed in toluene for 30 minutes, and then the residue obtained by filtering the test piece and the toluene solution is dried at 45 ° C. for 24 hours, and the weight after the drying of the test piece after immersion and the toluene solution are filtered. The dried residue was weighed after drying. Thereafter, the pressure-sensitive adhesive layer was removed from the test piece after drying, and the substrate weight was measured. The gel fraction was calculated by the following formula.
(Dry weight of test pieces and filtration residue after toluene immersion-base weight) / (Test piece weight before toluene immersion-base weight) (%)

(Martens hardness of the adhesive layer surface)
The above-prepared double-sided adhesive film was cut into a size of 10 mm × 10 mm to prepare a test piece, and each sample was subjected to the following conditions using an ultra-fine indentation hardness tester (ENTIONS manufactured by Elionix Co., Ltd.). The Martens hardness of the pressure-sensitive adhesive layer surface was measured.
Working indenter: Spherical indenter (radius 200 μm)
Maximum load: 10μN
Loading time: 10 sec
Holding time: 5 sec
Unloading time: 10 sec

(Image clarity of the adhesive layer)
The prepared double-sided adhesive film was cut into 100 mm × 100 mm, and the image clarity of each sample was measured using a image clarity tester (ICM-1DP manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS K 7374. .

(Adhesive force)
The prepared double-sided pressure-sensitive adhesive film was cut to a width of 25 mm, and the adhesive layer of the double-sided pressure-sensitive adhesive film was adhered to a stainless steel plate of SUS304 whose surface was polished. After leaving to stand, the peeling force at the time of peeling from the pressure-sensitive adhesive layer surface in the direction of 180 ° was measured.

(Bubble contamination evaluation)
The double-sided adhesive film created above is cut into 120 mm x 55 mm, and a 2 kg load roll is reciprocated twice from the adsorbing layer side where the separator of the double-sided adhesive film is laminated on a 300 μm thick transparent protective cover (glass plate). After pasting the agent layer, it was left at room temperature (25 ° C.) for 24 hours to obtain a protective member for an information display screen of the present invention. Thereafter, the separator of the protective member was peeled off, and the adsorbing layer was bonded to a soda-lime glass plate having a thickness of 3 mm.
Evaluation Criteria A: There is no mixing of bubbles. B: There is almost no mixing of bubbles, and there is no practical problem.
×: Air bubbles are mixed in and remain

It is sectional drawing of the double-sided adhesive film of this invention. It is sectional drawing of the protection member for information display screens of this 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 (glass plate)
8 Light reflection prevention layer

Claims (5)

A double-sided adhesive film for attaching a transparent protective cover to the information display screen of a display panel, in which an adsorption layer composed mainly of silicone resin is laminated on one side of the base film and acrylic on the other side A pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive having an acrylic copolymer and an isocyanate-based crosslinking agent as essential components is laminated, the Martens hardness of the pressure-sensitive adhesive layer surface is 8 to 15 mN / mm ² , and the pressure-sensitive adhesive A double-sided pressure-sensitive adhesive film, wherein the gel fraction of the agent layer is 35 to 80%. The double-sided pressure-sensitive adhesive film according to claim 1, wherein an addition amount of the isocyanate-based crosslinking agent in the pressure-sensitive adhesive layer is 0.05 to 2.0% by weight. The double-sided pressure-sensitive adhesive film according to claim 1 or 2 , wherein the adsorption layer has a thickness of 10 to 50 µm, and the pressure-sensitive adhesive layer has a thickness of 5 to 30 µm. The adsorption layer is obtained by curing a silicone composition comprising a diorganopolysiloxane having two or more alkenyl groups in one molecule and an organohydrogenpolysiloxane by an addition reaction, and the diorganopolysiloxane Are linear diorganopolysiloxanes having vinyl groups only at both ends, linear diorganopolysiloxanes having vinyl groups at both ends and side chains, branched diorganopolysiloxanes having vinyl groups only at the ends, The double-sided pressure-sensitive adhesive film according to any one of claims 1 to 3 , which is at least one selected from branched diorganopolysiloxanes having vinyl groups at 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 4 , and bonded to an information display screen of a display panel via the adsorption layer. A protective member for an information display screen, wherein the transparent protective cover is a glass plate having a thickness of 100 to 1,000 μm and a total light transmittance of 85% or more.

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