JP6364663B2 - 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 for liquid crystal displays, plasma displays, organic EL, etc. used as display devices for electronic and electrical equipment, this information display screen is made of a hard transparent protection made of glass or the like. The present invention relates to a double-sided pressure-sensitive 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 pressure-sensitive adhesive film.

For example, for the purpose of improving the visibility of a display screen such as a liquid crystal, a silicone gel pressure-sensitive adhesive sheet laminated in the order of a separator, a pressure-sensitive adhesive layer, a base sheet, a silicone gel layer, and a separator is used as a peripheral part of a liquid crystal cell of a liquid crystal display device. There is known a method of sandwiching between a peripheral portion of a diffusion plate and / or a holding frame. (Patent Document 1). In the surface protective member laminated by laminating the pressure-sensitive adhesive layer of the silicone gel pressure-sensitive adhesive sheet and a conventional transparent member that is a hard plate such as glass or acrylic, when pasting on the information display screen of the display panel, Air bubbles were easily entangled in the sticking surface along the unevenness of the surface of the silicone gel layer.

In addition, for the purpose of protecting the display screen of liquid crystal or the like and improving the visibility, a method of bringing a transparent member into close contact with the information display screen of the display panel through a transparent gel is known. (Patent Document 2). 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 3). 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.

Japanese Patent Laid-Open No. 2001-200221 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 present inventor showed that when an information display screen of a display panel and a protective member obtained by bonding a transparent protective cover made of a glass plate and a double-sided adhesive film are bonded, A pressure-sensitive adhesive comprising an acrylic pressure-sensitive adhesive containing a polymer containing a (meth) acrylic copolymer as a main component and a cross-linking agent on the other side of which an adsorption layer mainly composed of a silicone resin is laminated. The complex viscosity was defined in the dynamic viscoelasticity measurement of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive film formed by laminating the layers. By setting the complex viscosity of the pressure-sensitive adhesive layer to a specific value, in the protective member, the pressure-sensitive adhesive layer absorbs irregularities on the glass surface of the transparent protective cover, and the pressure-sensitive adhesive layer is plastically deformed. Then, by absorbing the irregularities on the surface of the adsorption layer through the base film, it has been found that it has an effect of increasing the smoothness of the adsorption layer when finally adhering to an adherend. . Thereby, using the double-sided adhesive film, even when a transparent protective cover made of a glass plate is adhered to the display screen of the display panel, it is difficult to cause entrainment of bubbles at the time of attachment, and the visibility is also good. The present inventors have found that a protective member for an information display screen can be realized and have completed the present invention.

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, On the other side, a pressure-sensitive adhesive layer composed of a polymer mainly composed of a (meth) acrylic copolymer and an acrylic pressure-sensitive adhesive containing a crosslinking agent is laminated. The double-sided pressure-sensitive adhesive film is characterized in that a complex viscosity η ^{* at} 23 ° C. measured by measurement is 2.0 × 10 ² to 10 ⁴ Pa · s.

A second invention is the double-sided pressure-sensitive adhesive film according to the first invention, wherein the crosslinking agent is an aziridine-based crosslinking agent.

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

4th invention bonds a transparent protective cover and the adhesive layer of the double-sided adhesive film in any one of 1st invention-3rd invention, and affixes 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 is a glass plate having a thickness of 100 to 1000 μm and a light transmittance of 85% or more.

The double-sided pressure-sensitive adhesive film of the present invention comprises a polymer film mainly comprising a (meth) acrylic copolymer as a main component on one surface of a base film, wherein an adsorption layer mainly comprising a silicone resin is laminated on the other surface. By laminating a pressure-sensitive adhesive layer comprising an acrylic pressure-sensitive adhesive containing a cross-linking agent, and defining the complex viscosity in a specific numerical range in the viscoelasticity measurement of the pressure-sensitive adhesive layer, the both sides of the transparent protective cover In the state where the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film is bonded, the pressure-sensitive adhesive layer absorbs irregularities on the glass surface of the transparent protective cover, and the pressure-sensitive adhesive layer is plastically deformed, via the base film, By absorbing irregularities on the surface of the adsorption layer, the surface smoothness of the adsorption layer when finally adhering to the adherend is increased. As a result, when a protective member made of a glass plate is pasted on the information display screen of the display panel, the protective member made by pasting the transparent protective cover with the double-sided pressure-sensitive adhesive film is in contact with the surface and stuck at the sticking interface. It is easy to stick while releasing air, and it is difficult to cause entrainment of bubbles when 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 an information display screen of the present invention has a transparent protective cover and an adsorption layer mainly composed of a silicone resin laminated on one surface of a base film, and a (meth) acrylic copolymer on the other surface. A double-sided pressure-sensitive adhesive film comprising a separator formed by laminating a pressure-sensitive adhesive layer composed of a polymer having a polymer as a main component and an acrylic pressure-sensitive adhesive containing a crosslinking agent, and the pressure-sensitive adhesive layer It is provided in a state where it is stuck through.

(Transparent protective cover)
Of the constituent members of the protective member for the information display screen of the present invention, the transparent protective cover preferably uses a glass plate. 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 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-K7105.

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 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 an information display screen of the present invention has an adsorption layer composed mainly of a silicone resin laminated on one side of a base film, and a (meth) acrylic copolymer on the other side. A pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive containing a polymer as a main component and a crosslinking agent is laminated, and a separator made of a plastic film is bonded to the adsorption layer. The layer is provided in a state in which a cover film obtained by subjecting a polyester resin film to a silicone release treatment is bonded to the layer.

(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)
In the pressure-sensitive adhesive layer of the present invention, a (meth) acrylic acid ester copolymer is the main component because it is easy to obtain a highly transparent pressure-sensitive adhesive having a total light transmittance of 80% or more. An acrylic pressure-sensitive adhesive comprising a polymer and a crosslinking agent can be suitably used.

Examples of the acrylic pressure-sensitive adhesive include acrylic acid alkyl esters such as butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, amyl acrylate, cyclohexyl acrylate, and benzyl acrylate, and methacrylic acid. Methacrylic acid alkyl esters such as methyl, butyl methacrylate, methacrylic acid-2-ethylhexyl, cyclohexyl methacrylate, and benzyl methacrylate, acrylic acid 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, Le propylene glycol, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, those obtained by copolymerizing methacrylic acid -tert- butyl aminoethyl used.

As the (meth) acrylic acid ester 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 (meth) acrylic acid ester 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 crosslinking agent used in the acrylic pressure-sensitive adhesive include an isocyanate-based crosslinking agent, an aziridine-based crosslinking agent, and an epoxy-based crosslinking agent, and metal chelate-type crosslinking agents. In the present invention, an aziridine-based crosslinking agent is preferably used because the initial curing rate is high and a smoother surface can be obtained. When the initial curing rate is slow, the adhesive surface tends to become so-called crushed skin during aging of the double-sided adhesive film after heating and drying, and gaps are generated or transparency is reduced when pasting to the protective cover. Or other problems occur.

By using the above-mentioned aziridine-based crosslinking agent, the initial curing rate of the pressure-sensitive adhesive is increased, and curing and aging of the pressure-sensitive adhesive layer are completed while maintaining a smoother surface state. When the adhesive layer of the double-sided adhesive film is bonded to the transparent protective cover, the adhesive layer absorbs irregularities on the glass surface of the transparent protective cover by increasing the smoothness of the surface of the adhesive layer. The adhesive layer is finally adhered to the adherend by improving the effect and the effect of absorbing the irregularities on the surface of the adsorption layer of the adhesive film through the base film by plastic deformation of the adhesive layer. In this case, the smoothness of the surface of the adsorption layer is increased. As a result, when the adsorption layer of the protective member is attached to the information display screen of the display panel, entrainment of bubbles can be further suppressed.

The aziridine-based crosslinking agent is a compound having at least two aziridinyl groups or substituted aziridinyl groups in one molecule. For example, N, N′-hexamethylene-1,6-bis (1-aziridinecarboxamide) , Trimethylolpropane-tri-β-aziridinylpropionate, bisisophthaloyl-1- (2-methylaziridine), tri-1-aziridinylphosphine oxide, N, N′-diphenylmethane-4,4 '-Bis (1-aziridinecarboxamide), N, N'-toluene-2,4-bis (1-aziridinecarboxamide), tris-1- (2-methylaziridine) phosphine, trimethylolpropane-tri-β -(2-methylaziridine) propionate and the like. You may use together these 2 or more types of aziridine type crosslinking agents.

The crosslinking agent may be added in an amount of 0.005 to 10 parts by weight, particularly 0.01 to 5 parts by weight, based on 100 parts by weight of the acrylic pressure-sensitive adhesive. When the addition amount of the crosslinking agent is less than 0.005 parts by weight, the pressure-sensitive adhesive is not sufficiently cured, and a cohesive force cannot be obtained. On the other hand, when the addition amount of the crosslinking agent exceeds 10 parts by weight, the curing of the pressure-sensitive adhesive proceeds excessively, and the pressure-sensitive adhesive strength is extremely reduced.

In the present invention, a plasticizer may be further added to the acrylic pressure-sensitive adhesive. Examples of the plasticizer include hydrocarbon plasticizers such as process oil, liquid polybutadiene, liquid polyisobutylene, liquid polyisoprene, liquid paraffin, paraffin wax, copolymer oligomer of ethylene and α-olefin (Mw 5,000 to 100). , 000), propylene and α-olefin copolymer oligomers excluding ethylene (Mw 5,000-100,000); chlorinated paraffins; ester plasticizers such as phthalates (diethyl phthalate, dibutyl phthalate, dioctyl phthalate, Didecyl phthalate, dilauryl phthalate, distearyl phthalate, diisononyl phthalate, etc.), adipic acid ester (dioctyl adipate, etc.), sebacic acid ester (dioctyl sebacate, etc.) (Nolic acid, linolenic acid), and those having unsaturated double bonds that can be hydrogenated include hydrogenated products thereof. One plasticizer may be used, or two or more plasticizers may be used in combination.

In the protective member which bonded the transparent protective cover which consists of a glass plate, and a double-sided adhesive film by adding a plasticizer to the acrylic adhesive of the said adhesive layer further, the said adhesive layer is the glass surface of the said transparent protective cover. The adhesive layer is plastically deformed and absorbs the unevenness on the surface of the adsorption layer via the base film, so that the adhesive layer is finally adhered to the adherend. The effect of increasing the smoothness of the adsorption layer is further increased.

The plasticizer may be added in an amount of 0.05 to 10 parts by weight, particularly 0.1 to 5 parts by weight, based on 100 parts by weight of the acrylic pressure-sensitive adhesive. When the addition amount of the plasticizer is less than 0.05 parts by weight, the pressure-sensitive adhesive layer is plastically deformed, and the effect of absorbing irregularities on the surface of the adsorption layer is reduced via the base material film. As a result, the effect of preventing the introduction of fine bubbles when the protective member is adhered to the display screen is reduced. On the other hand, when the added amount of the plasticizer exceeds 10 parts by weight, there is a problem that the adhesive durability is lowered due to a decrease in cohesive force.

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 in addition, but the addition of the auxiliary material generates birefringence of light in the thickness direction of the obtained pressure-sensitive adhesive layer, thereby providing transparency. In particular, in the present invention in which the thickness of the pressure-sensitive adhesive layer is formed to be 10 to 50 μm, the transparency is remarkably lowered. Therefore, it is preferable not to add them or to keep them in a relatively small amount.

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.

The thickness of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive film in the present invention is 10 to 50 μm, preferably 10 to 30 μm. When the thickness of the pressure-sensitive adhesive layer is less than 10 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. On the other hand, when the thickness of the pressure-sensitive adhesive layer exceeds 50 μm, it becomes difficult to maintain the smoothness of the pressure-sensitive adhesive surface, and when the pressure-sensitive adhesive layer and the transparent protective cover are adhered, adsorption on the opposite side is difficult. The surface of the layer cannot be kept smooth, and bubbles are involved when the adsorption layer of the protective member is attached to the information display screen.

(Measurement method of complex viscosity of adhesive layer)
The dynamic viscoelastic property of the pressure-sensitive adhesive layer constituting the double-sided pressure-sensitive adhesive film of the present invention is defined by the storage elastic modulus and loss elastic modulus of the dynamic viscoelastic spectrum at a specific frequency and a specific temperature. In the measurement of dynamic viscoelasticity, using a viscoelasticity testing machine (trade name: MR-300, manufactured by Rheology Co., Ltd.), a test piece is sandwiched between parallel disks which are measuring parts of the testing machine, and the frequency The storage elastic modulus (G ′) and loss elastic modulus (G ″) from −50 ° C. to 150 ° C. are measured at 1 Hz. The complex viscosity η ^* is a value defined by the following equation (1). It is calculated based on the complex elastic modulus G ^* defined by (2), where ω represents the angular velocity.

In the present invention, the complex viscosity η ^{* at} 23 ° C. is preferably 10 ² to 10 ⁴ Pa · s by dynamic viscoelasticity measurement (frequency 1 Hz) of the pressure-sensitive adhesive layer. When the complex viscosity η ^* is less than 10 ² Pa · s, the surface of the adhesive layer is too soft to be easily deformed, and a protective member having a transparent protective cover adhered to the adhesive layer In the state, the pressure-sensitive adhesive layer protrudes from the end face. On the other hand, when the complex viscosity η ^* exceeds 10 ⁴ Pa · s, the pressure-sensitive adhesive becomes hard, and the pressure-sensitive 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. Disappear. As a result, it becomes impossible to keep the surface of the adsorption layer 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 adhesive layer of the protective member is pasted on the information display screen, Entrainment will occur.

 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 center line 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 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 of the addition reaction catalyst 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 amount of the solvent added 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 the amount is less than 20 parts by weight, the adhesion between the adsorption layer and the substrate may be lowered. If the amount exceeds 1,000 parts by weight, the viscosity of the silicone composition coating solution becomes too low. Before the curing, a part of the applied adsorption layer flows, and the smoothness of the adsorption layer surface decreases.

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 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 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.

(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, a separator made of a plastic film is used by adhering to the surface of the adsorption layer in order to prevent the surface of the adsorption layer from adhering to the surface and to prevent foreign matter adhesion and improve the handling of the double-sided adhesive film.

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 0.20 μm, the separator surface roughness is transferred to the adsorption layer surface, 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 as a protective member laminated via a transparent protective cover such as a glass plate and the adhesive layer to an information display screen of a display panel, air bubbles are likely to be mixed. There's a problem.

(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 1-7, 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 2.0 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
Total 100 copies

(Examples 1-7, Comparative Examples 1-2)
On the anchor layer, the following adsorbing layer coating solution having the adsorbing layer thickness shown in Table 2 was applied by a die coater and then crosslinked in an oven at 150 ° C. for 100 seconds. Thus, the adsorption layer of each example and comparative example was formed.

(Adsorption layer coating solution)
68.59 parts (Mw: 540,000) linear diorganopolysiloxane having vinyl groups at the molecular terminals and side chains / 0.41 part (Mw: 2, solvent-free organohydrogensiloxane-diorganosiloxane copolymer) 000) / solvent-free platinum catalyst (manufactured by Shin-Etsu Polymer, PL-56) 1.00 parts Toluene 30.00 parts Total 100.00 parts

(Examples 1-7, Comparative Examples 1-2)
A 50 μm thick polyester film is put on the surface of each adhesive film on which the above-mentioned adsorption layer is formed, sandwiched between two rolls (rubber roll and metal roll), and both are bonded together while releasing air, and plasma treatment is performed. A pressure-sensitive adhesive film in which an anchor layer, an adsorption layer and a separator were laminated on one side of a 50 μm thick polyethylene terephthalate film was obtained.

(Examples 1-7, Comparative Examples 1-2)
On the surface of the pressure-sensitive adhesive film opposite to the surface on which the adsorption layer is formed, the pressure-sensitive adhesive layer coating liquid listed in Table 1 is applied with a die coater in combination with the thicknesses listed in Table 2. The mixture was heated and dried at 100 ° C. for 2 minutes to form the pressure-sensitive adhesive layers of the examples and comparative examples.

(Examples 1-7, Comparative Examples 1-2)
Two rolls (rubber rolls) are combined with the release surface of the cover film obtained by applying a silicone release agent to a polyethylene terephthalate film with a thickness of 38 μm on the pressure-sensitive adhesive surface of each pressure-sensitive adhesive film on which the pressure-sensitive adhesive layer is formed. And a metal roll) and bonded together while releasing air, 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 2, and each evaluation method is shown below.

(Evaluation method)
(Complex viscosity)
Adhesives 1 to 5 in Table 1 were applied to one side of a fluororesin sheet having a thickness of 50 μm, and an adhesive layer was applied at a coating thickness of 50 μm, respectively, and then in an oven at 150 ° C. for 100 seconds. Cross-linked. Each obtained adhesive layer was peeled off from the said fluororesin sheet | seat, and the test piece for a viscoelasticity measurement was produced. Next, using a viscoelasticity tester (trade name: MR-300, manufactured by Rheology Co., Ltd.), a test piece is sandwiched between parallel disks which are measurement parts of the tester, and stored at 23 ° C. at a frequency of 1 Hz. The elastic modulus (G ′) and the loss elastic modulus (G ″) were measured, and the complex elastic modulus (G ^* ) was calculated from G ^* = √ (G ′ ² + G ″ ² ). Subsequently, the complex viscosity (η ^* ) was calculated from η ^* = G ^* / ω. Note that ω represents an angular velocity.

(Gel fraction)
Separately from the above, on the one side of a polyethylene terephthalate film having a thickness of 50 μm, the pressure-sensitive adhesives 1 to 5 in Table 1 were each provided with a pressure-sensitive adhesive layer with a coating thickness of 50 μm. Crosslinking was performed in 100 seconds. The pressure-sensitive adhesive film provided with 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 for 24 hours. The residue obtained by filtering the test piece and the toluene solution was dried at 45 ° C. for 24 hours, and the weight after drying of the test piece after immersion and the weight after drying of the residue obtained by filtering the toluene solution were measured. 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.
Gel fraction (%) = (weight of test piece and filtration residue after drying−base weight)
/ (Test piece weight before test-substrate weight)

(Image clarity of the adhesive layer)
(1) Adhesive layer after heating / crosslinking The adhesive layer of adhesive 1 to adhesive 5 in Table 1 is provided on one side of a 50 μm thick polyethylene terephthalate film with a coating thickness of 25 μm. Then, crosslinking was performed in an oven at 150 ° C. for 100 seconds. The pressure-sensitive adhesive film provided with the pressure-sensitive adhesive layer was cut into a size of 50 mm × 50 mm to prepare a test piece. Using the image clarity tester (ICM-1DP manufactured by Suga Test Instruments Co., Ltd.), measure the image clarity of each sample pressure-sensitive adhesive layer by the method according to JIS K 7374. Thus, the surface smoothness of the pressure-sensitive adhesive layer was evaluated.
(2) Image properties of the pressure-sensitive adhesive layer after curing and aging The mold release of the cover film in which a silicone release agent is coated on a 38 μm thick polyethylene terephthalate film on the pressure-sensitive adhesive surface of the above-mentioned pressure-sensitive adhesive film after heating and crosslinking The surfaces were pressed together by a method in which a 2 kg hand roller was reciprocated once, and after press bonding, aged at 45 ° C. for 96 hours and further allowed to stand at room temperature (23 ° C.) for 24 hours. The adhesive film after aging was cut into a size of 50 mm × 50 mm, and the cover film was peeled off to prepare a test piece. By measuring the image clarity of each sample pressure-sensitive adhesive layer by a method based on JIS K 7374, using the image clarity tester (ICM-1DP manufactured by Suga Test Instruments Co., Ltd.). The surface smoothness of the pressure-sensitive adhesive layer was evaluated.

(Adsorption performance evaluation)
The prepared double-sided pressure-sensitive adhesive film was cut into a width of 25 mm, and the separator of the adsorption layer was peeled off. Next, the adsorbing layer was pressure-bonded to a 3 mm thick soda-lime glass plate by reciprocating a 2 kg hand roller once and left at room temperature for 24 hours after pressure bonding. Next, using a tensile tester, peeling was performed at a peeling angle of 180 ° and a peeling speed: 1,200 mm / min, and the glass plate peeling force (mN / 25 mm) of the adsorption film was measured.
Evaluation standard of adsorption performance A: Glass plate peeling force is 25 mN / 25 mm or more and less than 150 mN / 25 mm ○: Glass plate peeling force is 150 mN / 25 mm or more and less than 400 mN / 25 mm X: Glass plate peeling force is less than 25 mN / 25 mm, 400 mN / 25mm or more

(Air release speed)
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 is bonded to a soda-lime glass plate having a thickness of 3 mm, and the time until the air is completely removed from the bonding interface and the bonding is completed is measured, and the speed per unit length in the length direction of the protective member. As calculated.

(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 drawing of the double-sided adhesive sheet 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 (4)

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 , Which is obtained by laminating a pressure-sensitive adhesive layer composed of a polymer mainly composed of a (meth) acrylic copolymer and an acrylic pressure-sensitive adhesive containing a crosslinking agent, and is measured by measuring the dynamic viscoelasticity of the pressure-sensitive adhesive layer. The double-sided pressure-sensitive adhesive film is characterized in that the complex viscosity η ^{* at} 23 ° C. is 2.0 × 10 ² to 10 ⁴ Pa · s. The double-sided pressure-sensitive adhesive film according to claim 1, wherein the crosslinking agent is an aziridine-based crosslinking agent. The double-sided pressure-sensitive adhesive film according to claim 1 or 2, wherein the pressure-sensitive adhesive layer has a thickness of 10 to 50 µm, and the adsorption layer has a thickness of 10 to 50 µm. In the protective member formed by bonding the transparent protective cover and the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive film according to any one of claims 1 to 3, and bonded to the information display screen of the display panel via the adsorption layer. The protective member, wherein the transparent protective cover is a glass plate having a thickness of 100 to 1,000 μm and a light transmittance of 85% or more.

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