JP2012201736A - Double-sided pressure-sensitive adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive tape for fixing an optical film to another member, particularly a double-sided pressure-sensitive adhesive tape capable of suitably fixing members to each other and suppressing distortion in an optical film, even when the amount of VOC (volatile organic compounds) is reduced and a peeling stress in a low speed region generates.SOLUTION: The double-sided pressure-sensitive adhesive tape includes a pressure-sensitive adhesive layer disposed on both surfaces of a support, in which the pressure-sensitive adhesive layer to be stuck to an optical film comprises a water dispersion type acrylic pressure-sensitive adhesive composition. The composition includes an acrylic copolymer containing 50 to 98 mass% of (meth)acrylate having alkyl groups having 4 to 8 carbon atoms, 1 to 10 mass% of (meth)acrylate having alkyl groups having 2 or less carbon atoms, and 1 to 10 mass% of a carboxyl group-containing monomer. The pressure-sensitive adhesive layer has a gel fraction of 10 to 50%. The obtained tape achieves suitable fixing property between members and distortion preventing property.

Description

  The present invention relates to a double-sided pressure-sensitive adhesive tape that fixes an optical film used in an image display device such as a liquid crystal display or an organic EL (Electro Luminescence) display to another member.

  Image display devices such as liquid crystal displays are used in a wide range of fields including word processors and personal computers, and in particular, electronic notebooks, mobile phones, PHS, smartphones, game machines, electronic books, and the like have become increasingly smaller. It has come to be used as a display device for electronic equipment. In these image display devices, in an image display module such as an LCD module, a configuration in which a backlight module and a display panel such as an LCD panel provided on the surface are fixed with an adhesive tape is widely used. An optical film such as a prism sheet is often provided on the surface layer fixed to the display panel.

  For example, in a sidelight type backlight type liquid crystal display (schematic diagrams shown in FIGS. 1 and 2), generally, a reflector, a light guide plate, a diffusion sheet, etc. are laminated, and an optical film such as a prism sheet is provided on the surface layer, A backlight module provided with a light reflector such as an LED (Light Emitting Diode), a cold cathode tube, etc., provided with a lamp reflector on the side of the light guide plate, and an LCD panel are laminated. A double-sided adhesive tape (usually punched into a frame shape, the width of which is usually about 0.5 mm to about 10 mm) is sandwiched between the LCD panel and the backlight module. The double-sided adhesive tape may be in contact with only the prism sheet on the surface of the backlight module, or it may be in contact with the prism sheet on the surface of the backlight module and the casing containing the backlight module. It also has a role of fixing a diffusion sheet or the like installed on the lower side of the sheet and a role of preventing the entry of dust and a cushioning property to prevent the above-described parts from cracking due to an impact.

  Further, the adhesive tape is strongly required to have both light shielding properties and light reflection properties in order to block light leaked from the light source and effectively use light. Such an adhesive tape has been studied for improving the characteristics, and an adhesive tape for an LCD module that is thin and has both light-shielding properties and light-reflecting properties is disclosed (see Patent Document 1).

  However, in recent years, the adhesive tape used for the part has been exposed to problems that have not been regarded as problems in the past due to the high performance of electronic devices used, in particular, the thinning and multifunctionality of mobile phones. ing. As one of them, the internal members have been made thinner along with the thinning of multi-function mobile phones. However, due to the thinning of the optical film, the optical film whose periphery is fixed with double-sided adhesive tape has been tested in the reliability test. There is a problem that the optical film is distorted when left at a high temperature. When illuminated with light passing through such a distorted portion, the image in the LCD panel lacks sharpness. In addition, such an image display device needs to have good adhesion to peeling at a low speed so as not to cause peeling between members fixed by twisting or the like. For such a problem, an adhesive tape that suppresses the distortion of the optical film has been proposed, and attempts have been made to suppress the distortion of the optical film while fixing the parts satisfactorily (see Patent Documents 2 to 3). .

  On the other hand, in consideration of the environment, in recent years, it has been desired that the peripheral materials of these image display devices are shifted to VOC (volatile organic compound) -free materials, and the demand is particularly high in these electronic device fields. Therefore, conversion from a solvent-based pressure-sensitive adhesive to a water-based pressure-sensitive adhesive was also expected in the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape. For this reason, realization of the double-sided adhesive tape using the water-based adhesive which can fix between components satisfactorily and can suppress distortion of an optical film suitably was desired.

JP 2004-156015 A JP 2008-248226 A JP 2010-168437 A

  An object of the present invention is to provide an adhesive tape for fixing a distortion-prone optical film to another member, and when using a water-based adhesive with reduced VOC, even when peeling stress occurs in a low speed region, It is providing the double-sided adhesive tape which can fix suitably and can suppress distortion of an optical film.

  Furthermore, the halogen content is 0.3%, which makes it difficult to obtain anchoring with the adhesive layer, particularly good reworkability that can be removed when removing a part once bonded at the time of manufacturing failure or repair and performing repair work or the like. An object of the present invention is to provide a double-sided pressure-sensitive adhesive tape capable of realizing suitable reworkability even when a support provided with a colored ink layer of less than mass% is used.

  In the present invention, a double-sided pressure-sensitive adhesive tape for fixing an optical film and another member, wherein a pressure-sensitive adhesive layer is provided on both sides of a support, and at least the pressure-sensitive adhesive layer attached to the optical film is in an aqueous medium. A pressure-sensitive adhesive layer formed from a water-dispersed acrylic pressure-sensitive adhesive composition in which acrylic copolymer emulsion particles are dispersed. The acrylic copolymer forming the acrylic copolymer emulsion particles has a carbon number of 4 A monomer that contains (meth) acrylate having an alkyl group of ˜8, (meth) acrylate having an alkyl group having 2 or less carbon atoms, and a carboxyl group-containing monomer as monomer components to form the acrylic copolymer. The content of (meth) acrylate having an alkyl group having 4 to 8 carbon atoms in the component is 50 to 98 mass%, and the number of carbon atoms is 2 or less. Double-sided pressure-sensitive adhesive in which the content of the (meth) acrylate having a ru group is 1 to 10% by mass, the content of the carboxyl group-containing monomer is 1 to 10% by mass, and the gel fraction of the pressure-sensitive adhesive layer is 10 to 50% The tape can solve the above problems.

  The double-sided pressure-sensitive adhesive tape according to the present invention uses a water-based pressure-sensitive adhesive layer with reduced VOC, but uses a pressure-sensitive adhesive layer with a specific composition as the pressure-sensitive adhesive layer on the side to be attached to the optical film. And distortion of the optical film can be suitably suppressed. For this reason, it is possible to suppress a decrease in visibility due to distortion of the optical film even when the optical film is an object to be adhered while having excellent environmental compatibility. It is suitable for fixing between parts, particularly for fixing an optical film and a transparent panel.

It is sectional drawing which shows schematic structure of the LCD module unit which provided the adhesive tape between the LCD panel and the backlight housing | casing. It is an exploded view which shows schematic structure of the LCD module unit which provided the adhesive tape between the LCD panel and the backlight housing | casing. It is a conceptual diagram which shows the measuring method of the distortion prevention property of the optical film in an Example.

  The double-sided pressure-sensitive adhesive tape of the present invention is a double-sided pressure-sensitive adhesive tape that has pressure-sensitive adhesive layers on both sides of a support and is used for fixing an optical film to another member. At least the pressure-sensitive adhesive layer attached to the optical film is a pressure-sensitive adhesive layer formed from a water-dispersed acrylic pressure-sensitive adhesive composition in which acrylic copolymer emulsion particles are dispersed in an aqueous medium. (Meth) acrylate having an alkyl group having 4 to 8 carbon atoms, (meth) acrylate having an alkyl group having 2 or less carbon atoms, and a carboxyl group-containing monomer. Is contained as a monomer component in a predetermined amount, and the gel fraction of the pressure-sensitive adhesive layer is 10 to 50%.

[Adhesive layer]
In the double-sided pressure-sensitive adhesive tape of the present invention, the pressure-sensitive adhesive layer attached to the optical film is formed by crosslinking a water-dispersed acrylic pressure-sensitive adhesive composition in which acrylic copolymer emulsion particles are dispersed in an aqueous medium. It is an agent layer. The acrylic copolymer forming the acrylic copolymer emulsion particles is a (meth) acrylate having a C 4-8 alkyl group, a (meth) acrylate having a C 2 or less alkyl group, carboxyl A predetermined amount of a group-containing monomer is contained as a monomer component. In the present invention, by using the pressure-sensitive adhesive layer at least as the pressure-sensitive adhesive layer on the optical film side, even when the pressure-sensitive adhesive layer is a water-based pressure-sensitive adhesive layer, the optical film and other members are satisfactorily separated. While being able to fix, distortion of an optical film can be controlled suitably.

  In the present invention, by using (meth) acrylate having an alkyl group having 4 to 8 carbon atoms as the monomer component of the acrylic copolymer, it becomes easy to obtain adhesion to the adherend and reworkability. Examples of the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms include n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl ( (Meth) acrylates such as (meth) acrylate and n-octyl (meth) acrylate can be used, and n-butyl acrylate can be preferably used.

  In order to more suitably express the effect of (meth) acrylate having an alkyl group having 4 to 8 carbon atoms, (meth) having an alkyl group having 4 to 8 carbon atoms in the monomer component forming the acrylic copolymer The acrylate content is 50 to 98% by mass, preferably 80 to 98% by mass.

  In the present invention, as the (meth) acrylate monomer forming the acrylic copolymer, in addition to the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms, the (meth) having an alkyl group having 2 or less carbon atoms. By using acrylate together, distortion of the optical film can be suitably suppressed. Examples of the (meth) acrylate having an alkyl group having 2 or less carbon atoms include methyl (meth) acrylate and ethyl (meth) acrylate, and one or more of these can be used in combination. Of these, it is preferable to use methyl methacrylate.

  The amount of (meth) acrylate having an alkyl group having 2 or less carbon atoms in the monomer component forming the acrylic copolymer is 1 to 10% by mass, preferably 1 to 5% by mass.

  In the present invention, a carboxyl group-containing monomer is used in order to increase the cohesive force within and between the acrylic copolymer emulsion particles. As the carboxyl group-containing monomer, one or more selected from carboxyl group-containing vinyl monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, phthalic acid, phthalic anhydride, and crotonic acid are used. it can. Among them, acrylic acid and methacrylic acid are easy to ensure cohesive force by interaction between carboxyl groups, and there are many means for increasing cohesive force with many reactive crosslinking agents, and can express interaction with nitrogen-containing vinyl monomer described later. The acrylic acid can be used particularly preferably.

  Content of a carboxyl group-containing monomer is 0.5-10 mass% in the monomer component which forms an acryl-type copolymer, Preferably, it is 0.5-5 mass%. By setting it within this range, the crosslinking reaction with the crosslinking agent easily proceeds well. Furthermore, when the pressure-sensitive adhesive layer is formed, a cohesive force suitable for the pressure-sensitive adhesive layer is ensured, and it is easy to achieve both reworkability and strong adhesiveness.

  In the present invention, a nitrogen-containing vinyl monomer may be further used as the monomer component of the acrylic copolymer. As the nitrogen-containing vinyl monomer, a nitrogen-containing monomer having an amide group can be preferably used. Compared with amine-based nitrogen-containing monomer groups, nitrogen-containing monomers having an amide group do not have too strong interaction with acid groups, and can suitably maintain cohesive force in emulsion particles and interaction between particles, Since cohesive force as a pressure-sensitive adhesive is easily obtained, suitable adhesiveness and reworkability are easily obtained. As the nitrogen-containing monomer having an amide group, for example, one or more selected from N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylonitrile, acrylamide, and N, N-dimethylacrylamide can be used.

  In the acrylic copolymer used in the present invention, monomers other than those described above can be used as necessary. Examples of such monomers include a hydroxyl group-containing monomer, (meth) acrylic acid 2-hydroxy Alcoholic hydroxyl group-containing monomers such as ethyl, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and the like can be used as appropriate. As keto group or aldehyde group-containing monomer, diacetone acrylamide, diacetone methacrylamide, acrolein, formyl styrene, vinyl methyl ketone, vinyl ethyl ketone, vinyl isobutyl ketone, diacetone acrylate, diacetone methacrylate, acetonitrile acrylate, 2-hydroxypropyl Examples include acrylate acetoacetate and butanediol acrylate acetate. As the silane monomer, 3-methacryloxypropylmethyldimethoxysilane [for example, KBM-502 manufactured by Shin-Etsu Chemical Co., Ltd.], 3-methacryloxypropyltrimethoxysilane [for example, KBM-503 manufactured by Shin-Etsu Chemical Co., Ltd.], 3 -Methacryloxypropylmethyldiethoxysilane [for example, KBE-502 manufactured by Shin-Etsu Chemical Co., Ltd.], 3-methacryloxypropyltriethoxysilane [for example, KBE-503 manufactured by Shin-Etsu Chemical Co., Ltd.], 3-acryloxypropyltri And methoxysilane [for example, KBM-5103 manufactured by Shin-Etsu Chemical Co., Ltd.]. Moreover, N methylol acrylamide etc. are mentioned as a methylol group containing monomer. Examples of the phosphoric acid group-containing monomer include Sipomer PAM-100, PAM-200, and PAM-300 manufactured by Rhodia Nikka Co., Ltd., and 20% by mass or less in the monomer component forming the acrylic copolymer. It can be used at a ratio of 1 type or 2 types or more.

  The weight average molecular weight of the acrylic copolymer used in the present invention is preferably 500 to 1,200,000, more preferably 60 to 1,000,000. By setting it as the said range, the softness | flexibility at the time of an adhesive impregnating a nonwoven fabric and cohesion force required for rework property can be reconciled in balance. The said weight average molecular weight is standard polystyrene conversion by a gel permeation chromatography (GPC). As measurement conditions, TSKgel GMHXL [manufactured by Tosoh] is used as the column, the column temperature is 40 ° C., the eluent is tetrahydrofuran, the flow rate is 1.0 mL / min, and the standard polystyrene is TSK standard polystyrene.

  In order to adjust the molecular weight, a chain transfer agent may be used in the polymerization. Examples of the chain transfer agent include known chain transfer agents such as lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimethylcapto-1-propanol. Can be used.

(Type of tackifying resin)
In the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention, it is preferable to use a tackifying resin in order to adjust the strong adhesiveness of the resulting pressure-sensitive adhesive layer. As the tackifier resin used in the present invention, an emulsion type tackifier resin can be preferably used from the viewpoint of use in an aqueous dispersion type pressure-sensitive adhesive composition. Examples of the emulsion-type tackifying resin include rosin, polymerized rosin, polymerized rosin ester, rosin phenol, stabilized rosin ester, disproportionated rosin ester, terpene, terpene phenol, petroleum resin, etc. Can be illustrated.

  Among these, a polymerized rosin ester-based tackifier resin and a rosin phenol-based tackifier resin are preferable, and it is particularly preferable to blend these in combination. Specifically, polymerized rosin ester-based tackifier resins are Superester E-650 [Arakawa Chemical Industries, Ltd.], Superester E-788 [Arakawa Chemical Industries, Ltd.], Superester E-786. 60 [Arakawa Chemical Industries, Ltd.], Super Ester E-865 [Arakawa Chemical Industries, Ltd.], Super Ester E-865NT [Arakawa Chemical Industries, Ltd.], Harrier Star SK-508 [Harima Chemicals ( Co., Ltd.] Harrier Star SK-508H [Harima Kasei Co., Ltd.], Harrier Star SK-816E [Harima Kasei Co., Ltd.], Harrier Star SK-822E [Harima Kasei Co., Ltd.], Harrier Star SK- 323NS [manufactured by Harima Chemicals Co., Ltd.] and the like, and rosin phenolic tackifying resins are Tamanoru E-100 [manufactured by Arakawa Chemical Industries, Ltd.], Tamanoru E 200 [(manufactured by Arakawa Chemical Industry Ltd.), Tamanol E-200NT Arakawa Chemical Industries, Ltd.], and the like.

  When these are used in combination, the ratio of the polymerized rosin ester-based tackifier resin (A) to the rosin phenol-based tackifier resin (B) is 5 / in a mass ratio represented by (A) / (B). It is preferably 1 to 1/5, more preferably 3/1 to 1/3, and still more preferably 1/1 to 1/3. If it is in the said range, rework property and strong adhesiveness can be improved with good balance.

  The softening point of the tackifying resin is preferably 120 to 180 ° C, more preferably 140 to 180 ° C. By adding a tackifying resin having a high softening point, strong adhesiveness is improved.

  In the blend ratio of the acrylic copolymer / tackifying resin, the acrylic copolymer / tackifying resin = 100/10 to 100/40 is preferable, and the acrylic copolymer / tackifying resin = 100 is more preferable. / 15 to 100/35. If it is in the said range, rework property and strong adhesiveness can be improved with good balance.

(Crosslinking agent)
In the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention, it is preferable to use a crosslinking agent for the purpose of improving the cohesive strength of the resulting pressure-sensitive adhesive layer. Examples of the crosslinking agent include known isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, polyvalent metal salt crosslinking agents, metal chelate crosslinking agents, keto-hydrazide crosslinking agents, oxazoline crosslinking agents, and carbodiimide crosslinking agents. A crosslinking agent, a silane crosslinking agent, a glycidyl (alkoxy) epoxysilane crosslinking agent, or the like can be used. Among them, a type of crosslinking agent that is added after the completion of polymerization and causes the crosslinking reaction to proceed is preferable. Examples thereof include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an oxazoline-based crosslinking agent, a carbodiimide-based crosslinking agent, and a glycidyl (alkoxy) epoxysilane-based crosslinking agent. Specifically, in the isocyanate-based cross-linking agent, Bernock DNW-5000 [manufactured by DIC Corporation], Bernock DNW-5010 [manufactured by DIC Corporation], Bernock DNW-5100 [manufactured by DIC Corporation], Bernock DNW- 5500 [manufactured by DIC Corporation], Aquanate 100 [manufactured by Nippon Polyurethane Industry Co., Ltd.], Aquanate 105 [manufactured by Nippon Polyurethane Industry Co., Ltd.], Aquanate 110 [manufactured by Nippon Polyurethane Industry Co., Ltd.], Aquanate 120 [manufactured by Nippon Polyurethane Industry Co., Ltd.], Aquanate 130 [manufactured by Nippon Polyurethane Industry Co., Ltd.], Aquanate 200 [manufactured by Nippon Polyurethane Industry Co., Ltd.], Aquanate 210 [manufactured by Nippon Polyurethane Industry Co., Ltd.], LS2319 [manufactured by Sumika Bayer Urethane Co., Ltd.], LS2336 [Sumika Bayer Ure Tanhydr Co., Ltd.], Bayhydur 3100 [manufactured by Sumika Bayer Urethane Co., Ltd.] and the like, and epoxy crosslinking agents include Denacol EX-832 [Nagase Kasei Kogyo Co., Ltd.], Denacol EX-841 [Nagase Kasei] Kogyo Co., Ltd.], Tetrad C [Mitsubishi Gas Chemical Co., Ltd.], Tetrad X [Mitsubishi Gas Chemical Co., Ltd.], etc. Catalyst manufactured], Epocross WS-700 [manufactured by Nippon Shokubai Co., Ltd.], Epocross K-2010E [manufactured by Nippon Shokubai Co., Ltd.], Epocross K-2020E [manufactured by Nippon Shokubai Co., Ltd.], Epocross K-2030E [(stock) ) Manufactured by Nippon Shokubai Co., Ltd., and carbodiimide-based crosslinking agents include Carbodilite SV-02 [Nisshinbo Co., Ltd.], Carbodilite V-02 [Nisshinbo ( )], Carbodilite V-02-L2 [Nisshinbo Co., Ltd.], Carbodilite V-04 [Nisshinbo Co., Ltd.], Carbodilite E-01 [Nisshinbo Co., Ltd.], Carbodilite E-02 [Nisshinbo Co., Ltd.] )], Carbodilite E-03A [Nisshinbo Co., Ltd.], Carbodilite E-04 [Nisshinbo Co., Ltd.], and glycidyl (alkoxy) epoxysilane crosslinking agents, 2- (3,4-epoxycyclohexylethyltrimethoxy) Silane [KBM-303; Shin-Etsu Silicone Co., Ltd.], γ-glycidoxypropyltrimethoxysilane [KBM-403; Shin-Etsu Silicone Co., Ltd.], γ-glycidoxypropylmethyldiethoxysilane [KBE-402 Manufactured by Shin-Etsu Silicone Co., Ltd.], γ-glycidoxypropyltriethoxysilane [KBE-403; Manufactured by Co., Ltd.] and the like.

  Especially, it is preferable to use the crosslinking agent which reacts with the vinyl monomer which has an acid group, and the above-mentioned isocyanate type crosslinking agent, an epoxy compound, an oxazoline compound, a carbodiimide type crosslinking agent, a glycidyl (alkoxy) epoxysilane compound, etc. are preferable. The present invention is a technique characterized by ensuring the cohesive force of the acrylic copolymer over the whole by orienting an appropriate amount of acid groups both on the emulsion particle surface and inside the particle. By using a cross-linking agent that reacts with an acid group, an improvement in cohesion can be suitably achieved.

  The pressure-sensitive adhesive layer used in the present invention is a pressure-sensitive adhesive layer obtained by crosslinking the water-dispersed acrylic pressure-sensitive adhesive composition, and has a gel fraction of 10 to 50%, preferably 15 to 45%. It is an agent layer. In the present invention, by using the composition having the above composition and using the pressure-sensitive adhesive layer having a gel fraction in the above range, it is possible to suitably fix the parts and to suppress the distortion of the optical film satisfactorily. What is necessary is just to adjust content suitably for the gel fraction of an adhesive layer according to the crosslinking agent to be used. Moreover, the gel fraction uses the value of the gel fraction for measuring the insoluble matter after the pressure-sensitive adhesive layer is immersed in toluene for 24 hours.

(Additive)
In the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention, as an additive, a base (such as aqueous ammonia) for adjusting the pH within a range that does not impair the desired effect of the present invention, if necessary, Acids, plasticizers, softeners, antioxidants, fillers such as glass and plastic fibers, balloons, beads, and metal powders, colorants such as pigments and dyes, pH adjusters, film formation aids, leveling agents, Known agents such as thickeners, water repellents and antifoaming agents can be optionally added to the adhesive composition.

  As for the thickness of an adhesive layer, 5-50 micrometers is preferable, More preferably, it is 10-30 micrometers. If it is 5 μm or more, sufficient adhesiveness can be obtained, and if it is 50 μm or less, it can be suitably applied to a display device and the like that are becoming lighter and thinner.

[Support]
The support used in the present invention is not particularly limited, and various supports used for fixing the image display device peripheral member can be used. The support may be, for example, a support made of only a resin film, or a support in which a colored layer is provided on the resin film. However, the optical film and other members are fixed, particularly the optical film and the transparent panel. Since the light-shielding performance and the light-reflecting performance are often required for fixing, it is easy to realize good light-shielding performance and light-reflecting performance, and therefore a support provided with a colored layer on the resin film can be preferably used. .

  As the resin film used for the support, a known and commonly used resin film can be used, and examples thereof include cellophane, polyethylene, polypropylene, nylon, polystyrene, polyimide, and polyester. Among these, polyester is preferably used because it is excellent in strength and insulation. Polyethylene terephthalate can be preferably used because it has good adhesion to an ink layer using a polyurethane resin.

  As thickness of the resin film used as a support body, 6-100 micrometers is preferable. When the thickness is 6 μm or more, the film is hardly cracked at the time of peeling, and when it is 100 μm or less, peeling is hardly generated at the time of application to the adherend. More preferably, it is 12-50 micrometers.

  Further, the resin film itself may be colored white or black, and when the resin film is a light-reflecting white resin film, the brightness of the image display can be reduced when used for the image display unit of the image display device. Since it can raise, it is preferable. Of these, white polyethylene terephthalate having insulating properties and light diffuse reflection properties is most preferred. Moreover, it is preferable in order to raise the contrast of an image display apparatus that a resin film is a black resin film which has light-shielding property. Among them, black polyethylene terephthalate is preferable because it can provide excellent light shielding properties.

  When providing a colored layer on these resin films, it is preferable to use colored ink. As the colored ink used for the colored layer, a colored ink used for a colored tape such as a light-shielding tape or a light reflecting tape used for fixing the peripheral member of the image display device can be appropriately used. Especially, the halogen content of a colored layer is 0.3 mass% or less, Preferably it is 0.05 mass% or less, and the thing which does not contain a halogen substantially is especially preferable. Such a colored layer with a reduced halogen content uses colored ink that does not use halogen- or sulfur-containing resins such as vinyl chloride resin as the binder resin, and therefore, anchoring of the adhesive layer is particularly obtained. However, when the adhesive strength of the pressure-sensitive adhesive layer is high, it is difficult to obtain reworkability, but the above-mentioned pressure-sensitive adhesive layer used in the present invention is suitable for adhesion and reworking even if it is a colored layer having a low halogen content. Can be realized. Here, the halogen content is a detection amount when analyzed by fluorescent X-rays. For example, as a fluorescent X-ray analyzer, “ZSX Primus”, “ZSX Primus II”, etc. manufactured by Rigaku are listed.

  As the colored ink having a reduced halogen content, a colored ink that does not use a halogen- or sulfur-containing resin such as a vinyl acetate resin as a binder resin can be preferably used. As such a binder resin, for example, polyurethane resin, polyester resin, polyamide resin, acrylic resin, nitrocellulose and the like can be used. Among them, a polyurethane resin can be preferably used, and a polyester urethane resin can be particularly preferably used from the viewpoint of the adhesiveness with the pressure-sensitive adhesive layer and the adhesiveness with the resin film on which the colored layer is laminated.

  When a polyester urethane resin is used as the binder resin, the polyester urethane resin preferably has a glass transition temperature of -30 ° C to 30 ° C, more preferably -20 ° C to 30 ° C, and -15 ° C. More preferably, it is -25 degreeC, and it is especially preferable that it is -10 degreeC-25 degreeC. When the tan δ peak temperature of the polyester urethane resin is within this range, the colored layer has suitable flexibility and hardness, so that it is particularly difficult to cause cracks in the colored layer during rework, and the ink flow at high temperatures. It is difficult for peeling to occur.

The glass transition temperature of the polyester urethane resin is defined as the glass transition temperature, which is the tan δ peak temperature of the dynamic viscoelastic spectrum at a frequency of 1 Hz measured as follows.
Polyester urethane resin is formed to a thickness of 50 μm with a bar coater. Next, from a specimen cut to a sample length of 20 mm (sample length of 20 mm, film thickness of 50 μm) using a viscoelasticity tester from −150 ° C. to 250 ° C. at a frequency of 1 Hz and a temperature increase time of 3 ° C./1 minute. The storage elastic modulus (G ′) and the loss elastic modulus (G ″) are measured. The loss tangent tan δ is calculated by the following calculation formula.
Loss tangent tan δ = G ″ / G ′
Examples of the viscoelasticity tester include DMS210, DMS220, and DMS6100 manufactured by Seiko Instruments Inc.

  The colored ink used in the colored layer contains a curing agent used in ordinary inks, but it is also preferable to contain an aliphatic or alicyclic isocyanate curing agent as the curing agent. By cross-linking polyester urethane having a glass transition temperature of −30 ° C. to 30 ° C. and aliphatic or alicyclic isocyanate forming a relatively flexible cross-linked structure, it is easy to control the elastic modulus, and the flow of ink at high temperature It becomes easy to suppress peeling of the ink interface and the pressure-sensitive adhesive interface caused by. Further, since it is easy to obtain a suitable elastic modulus, it is difficult to crack the ink layer at the time of reworking, and it is easy to obtain an effect that the occurrence of tape tearing hardly occurs.

  Examples of the aliphatic or alicyclic isocyanate include hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, trimethylhexamethylene isocyanate, 1,6,11-undecane triisocyanate, lysine diisocyanate, lysine ester triisocyanate, 1,8-diisocyanate-4. -Isocyanatomethyloctane, 1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate are used. Further, trimers of these isocyanates can be preferably used, and among them, diisocyanate adducts, biurets, and nurates are preferable. Among these, hexamethylene diisocyanate or isophorone diisocyanate adduct, biuret, or nurate is preferable because the elastic modulus is easily controlled, and biuret or nurate is particularly preferable. A hardening | curing agent may be added independently and may add 2 or more types.

  As the colorant for coloring the color ink, known and conventional pigments and dyes not containing halogen can be used. When black, carbon black, when white, titanium oxide, calcium carbonate, barium sulfate, yellow In the case of yellow iron oxide, red is red pepper, cyan is blue, blue is aluminum powder, and pearl is mica titanium powder from the viewpoint of weather resistance, heat resistance, and dispersibility in ink resins. When the colored layer is a light shielding layer, those capable of forming a black ink layer are preferred, and carbon black is preferred because of its excellent light shielding properties. Moreover, when making a colored layer into a light reflection layer, what can form a white ink layer is preferable, and a titanium oxide can be used preferably.

  What is necessary is just to adjust suitably according to a use etc. as addition amount of a coloring agent, and 10 to 70% in the ink solid content containing a coloring agent is preferable. More preferably, it is 40 to 50%. If it is 10% or more, it preferably shows light shielding properties, and if it is 70% or less, the dispersion is good.

  When making a colored layer into a light shielding layer, it is preferable to contain an antiblocking agent in the colored ink to be used. Generation | occurrence | production of the pinhole by blocking can be suppressed by containing an antiblocking agent. Antiblocking agents such as silica, calcium carbonate, calcium phosphate, talc, etc., and organic compound antiblocking agents such as polyethylene wax (PE wax), fatty acid amide, fatty acid ester, higher fatty acid should be used. Is preferred. The particle-based anti-blocking agent prevents the blocking by forming irregularities on the surface of the ink layer and reducing the contact area between the ink surface and the back surface. On the other hand, the organic compound-based antiblocking agent prevents blocking by bleeding out on the surface of the ink layer. Therefore, it is preferable to use a particle-based anti-blocking agent and an organic compound-based anti-blocking agent in combination. In particular, silica that improves the adhesion to the pressure-sensitive adhesive is preferred as the particle-based antiblocking agent. Further, as the organic compound-based anti-blocking agent, PE wax that does not significantly reduce the adhesion with the pressure-sensitive adhesive is particularly preferable.

  The addition amount of the particle size blocking inhibitor is preferably 0.5 to 10% by mass with respect to the ink solid content. Among these, 1-5 mass% is more preferable. If it is 0.5 mass% or more, the effect of blocking prevention is exhibited suitably, and if it is 10 mass% or less, the ink film becomes brittle, and the tape is likely to be scratched during rework. On the other hand, the addition amount of the organic blocking inhibitor is preferably 0.5 to 10% by mass with respect to the ink solid content. Among these, 2-7 mass% is more preferable. If it is 0.5 mass% or more, the effect of blocking prevention is acquired suitably, and the adhesiveness and rework property with an adhesive will become favorable in it being 10 mass% or less. Moreover, you may contain other various additives as needed.

  What is necessary is just to adjust the thickness of a colored layer suitably according to a desired characteristic. For example, when the colored layer is a light-shielding layer, 1 to 10 μm is preferable and 3 to 7 μm is more preferable from the viewpoint of light-shielding properties and workability at the time of tape punching. In addition, it is preferable to make an ink layer into a low elasticity modulus from a viewpoint of rework property, so that the thickness of ink is thick.

  The colored layer may be a single layer, but two or more layers may be laminated depending on the desired concealability, light reflectivity, and light shielding property. In particular, when the colored layer is a light shielding layer, it is preferable to provide two or more colored layers in order to improve the light shielding property and prevent light leakage due to pinholes.

  The support used in the present invention may have a structure having a colored layer on only one surface of the resin film or a structure having a colored layer on both surfaces of the resin film, and can be appropriately selected depending on the purpose of use. As an example of a preferred embodiment, when the double-sided pressure-sensitive adhesive tape of the present invention is used as a light-shielding reflective tape, a light-reflective white resin film is used as the resin film, and a black colored layer using black ink on the white resin film A structure provided with a light shielding layer made of is preferable because it easily combines excellent light reflectivity and light shielding properties.

  Commercially available light-reflective resin films include Reiko 37W01, 3M ESR, Toray E20 # 38, Mitsubishi Chemical Polyester Film W400 # 38, Teijin DuPont Teflex FW2 # 13, etc. However, it is preferable because the thickness is thin and the reflectivity is high.

  Lamination of the colored layer on the resin film can be performed by printing by a known and commonly used printing method. For example, letterpress printing, flexographic printing, dry offset printing, gravure printing, gravure offset printing, offset printing, screen printing, and the like can be employed. Among them, the gravure printing is suitable for the repeated coating. The film surface to be ink-coated is preferably subjected to a known and commonly used easy adhesion treatment. Of these, easy adhesion treatment selected from corona treatment, plasma treatment, and primer treatment is preferred.

When the colored tape shielding tape or shielding reflective tape of the present invention preferably has a light transmission amount of when irradiated with light of 10000 cd / ^{m 2} on the support is 1 cd / ^{m 2} or less, 0.1 cd / M ² or less is more preferable.

[Double-sided adhesive tape]
The double-sided pressure-sensitive adhesive tape of the present invention is a double-sided pressure-sensitive adhesive tape that fixes an optical film and another member, and is provided with a pressure-sensitive adhesive layer on both sides of a support, and at least the pressure-sensitive adhesive layer that is attached to the optical film has the above water dispersion. It is a double-sided adhesive tape of the adhesive layer which consists of a type acrylic adhesive composition. With this configuration, the optical film has excellent VOC-free environmental compatibility, and has an adhesive property suitable for low-speed peeling stress when fixing an optical film that is easily distorted to other members. Can be suppressed. Furthermore, when using a support provided with a colored ink layer having a halogen content of 0.3% by mass or less, in which anchoring with the adhesive layer is difficult to obtain, in addition to these excellent performances, In addition to improving environmental friendliness, it is possible to realize good reworkability that can be removed when a repair work or the like is performed by removing parts once bonded at the time of manufacturing failure or repair.

  The double-sided pressure-sensitive adhesive tape of the present invention is a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of a support, and at least the pressure-sensitive adhesive layer attached to the optical film is made of the water-dispersed acrylic pressure-sensitive adhesive composition. It is. The pressure-sensitive adhesive layer attached to the optical film may be the same pressure-sensitive adhesive layer or another pressure-sensitive adhesive layer. What is necessary is just to select suitably according to other members to fix the adhesive layer of the other side with the adhesive layer stuck on an optical film, and the adhesive layer which consists of various water dispersion type acrylic adhesive compositions is applied. it can. In addition, since the adhesive layer stuck on the said optical film has suitable adhesiveness also with respect to various adherends, especially transparent panels, such as a glass panel, both surfaces can also be made into the same adhesive layer. preferable. Each pressure-sensitive adhesive layer may be a single-layer pressure-sensitive adhesive layer or a plurality of pressure-sensitive adhesive layers laminated, or may be used in a form in which a plurality of pressure-sensitive adhesive tapes are laminated.

  The pressure-sensitive adhesive layer can be formed on a resin film or a light shielding layer by a method generally used for application of a pressure-sensitive adhesive sheet. Specifically, for example, the composition for forming the pressure-sensitive adhesive layer can be directly applied to the support and dried, or it can be applied on the separator, dried, and then bonded to the support.

  The thickness of the double-sided pressure-sensitive adhesive tape of the present invention is preferably 20 to 100 μm, and more preferably 30 to 75 μm. Especially, it is especially preferable that it is 40-65 micrometers. Those having a thickness in this range can be suitably used for fixing components of an image display device, particularly for an image display device of a small electronic device.

  6-15N / 20mm is preferable and, as for the 180 degree | times peel adhesive force with respect to the optical film of the double-sided adhesive tape of this invention, 7-13N / 10mm20mm is more preferable. Moreover, it is preferable that the adhesive force with respect to glass is also the said range. When the adhesive force is within the above range, the components can be suitably fixed when fixing the components of the image display device.

  The double-sided pressure-sensitive adhesive tape of the present invention preferably has a halogen (chlorine, bromine, fluorine, iodine) content of 0.3% by mass or less, more preferably 0.05% by mass or less, as a whole tape. Particularly preferred are those substantially free of halogen. The double-sided adhesive tape with reduced halogen is suitable for suppressing malfunction of the image display device.

  As an embodiment of the double-sided pressure-sensitive adhesive tape of the present invention, it is sufficient that the pressure-sensitive adhesive layer is provided on the support as at least a pressure-sensitive adhesive layer to be attached to the optical film. The structure which has an adhesive layer affixed on an optical film in the colored layer surface of can be used preferably. Preferred examples include a form having an adhesive layer on both sides of a support having a colored layer on one side of the resin film, a form having an adhesive layer on both sides of a support having a colored layer on both sides of the resin film, and the like. It can be illustrated. In these forms, if the colored layer is a light shielding layer made of black ink, it can be used as a light shielding tape, and if it is a light reflection layer made of white ink, it can be used as a light reflecting tape. In addition, use a combination of the two, or use a light-reflective white film or a light-shielding black film as the resin film to be used, in combination with a light-shielding layer made of black ink or a light-reflective layer made of white ink. Also, a light-shielding reflective tape can be used.

[Usage]
The double-sided pressure-sensitive adhesive tape of the present invention is used for fixing an optical film and another member, and is used by sticking an adhesive layer formed by crosslinking the water-dispersed acrylic pressure-sensitive adhesive composition to the optical film. The The double-sided pressure-sensitive adhesive tape of the present invention has a suitable adhesive force to the adherend, and can suppress distortion of the optical film even when the optical film is deformed after fixing the optical film to another member. It is suitable for an image display device that requires fixing between an optical film and another member. Therefore, a component fixing tape used for fixing an optical film of a thin image display device in which the optical film is likely to be distorted, and the component is fixed in a space-saving manner, in particular, a suitable light-shielding reflection performance is required and is defective. It can be suitably used as a light-shielding tape, light-reflecting tape, or light-shielding reflective tape that fixes an optical film and a transparent panel of a thin image display device that requires reworkability at the time of repair or repair.

  Examples of the optical film include a prism sheet, a diffusion film, a light shielding film, and a reflective film. Among them, an optical film that is particularly susceptible to distortion includes a prism sheet in which a prism layer is provided on a film having a polarization reflection function. Examples of such an optical film include BEF-RP2RC and BEF-RP3 manufactured by 3M.

  The double-sided pressure-sensitive adhesive tape of the present invention can suitably suppress distortion of an optical film, and is particularly suitable for an optical film having a size of about 2.5 to 7 inches (diagonal). There is a distortion suppression effect.

The greater the rate of change in the outer shape of the optical film, the more likely the distortion occurs, and the more the distortion occurs when the behavior changes in the flow direction and the width direction. In particular, distortion is likely to occur when it is + 0.06% or more in the flow direction and -0.06% or less in the width direction. The double-sided pressure-sensitive adhesive tape of the present invention can suppress distortion even with the optical film. In addition, the external shape change rate of an optical film is represented by the following formula before and behind standing at 85 degreeC for 5 minutes.
External form change rate = [(length after standing−length before standing) / (length before standing)] × 100 (%)

  When the optical film has a prism layer and the ridge line of the prism layer obliquely intersects the flow direction of the adhesive tape, distortion of the optical film is likely to occur. Can be suitably suppressed.

  Other members that are fixed to the optical film by the double-sided adhesive tape of the present invention may be various members that are fixed to the optical film in the image display device. For example, liquid crystal provided on the surface layer of the image display device ( LCD) panel, electroluminescence panel, plasma display panel, electronic paper display panel, and other display panels. These display panels are used alone with glass or plastic, or with a functional film such as a polarizing film attached thereto. In the double-sided pressure-sensitive adhesive tape of the present invention, when the pressure-sensitive adhesive layer using the above water-dispersed acrylic pressure-sensitive adhesive composition is used on both surfaces, the adhesiveness with a glass panel or a polarizing film is particularly excellent.

  The aspect of fixing the optical film and the other member is not particularly limited as long as the image display area of the image display device can be secured, but preferably a double-sided pressure-sensitive adhesive tape having a frame shape by punching or the like According to the aspect of fixing the rectangular optical film and other members, the aspect of fixing the edge peripheral area of two or more sides of the rectangular optical film with a rectangular double-sided adhesive tape, the edge peripheral area of the rectangular optical film A mode of fixing with a small piece of double-sided adhesive tape at an arbitrary gap can be exemplified.

  As an example of the image display device, there is a backlight type LCD, etc., as a general configuration, a reflection plate, a light guide plate, a diffusion sheet, etc. are laminated, and an optical film such as a prism sheet is provided on the surface layer, A backlight module in which a light reflector such as an LED (Light Emitting Diode) and a cold-cathode tube, in which a lamp reflector is provided on the side of the light guide plate, and a display panel (LCD panel) are sequentially stacked. A preferable embodiment of the pressure-sensitive adhesive tape of the present invention is a mode in which the adhesive tape is punched out and sandwiched between the display panel and the optical film on the surface of the backlight module. Even if the optical film side pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape is in contact with only the optical film on the surface of the backlight module, the double-sided pressure-sensitive adhesive tape is attached to the optical film on the surface of the backlight module. The form which touches across the housing | casing in which the light module was accommodated may be sufficient.

  Since the colored adhesive tape for fixing a glass panel of the present invention can suppress malfunction of peripheral devices and provide a highly reliable product, various electronic devices, in particular, electronic notebooks, mobile phones, smartphones (high function mobile phones) ), Can be suitably used for fixing a glass panel of a display device of a miniaturized portable electronic device such as a PHS, a game device, an electronic book, a multi-function data terminal, and a mobile personal computer.

[Production example of polyester urethane]
(Polyester urethane resin (A))
Number average molecular weight obtained from acid component of adipic acid / terephthalic acid = 50/50 and trimethyl-1,5-pentanediol (below) in a four-flask equipped with stirrer, thermometer, reflux condenser and nitrogen gas introduction tube 256.3 parts of 2,000 polyester diol (referred to as Mn) and 36.5 parts of isophorone diisocyanate were charged and reacted at 90 ° C. for 15 hours under a nitrogen stream. Next, 5.0 parts of isophoronediamine, 2.2 parts of di-n-butylamine, 175 parts of toluene, 350 parts of methyl ethyl ketone, and 175 parts of isopropylene alcohol were added and reacted under a stirring frame at 40 ° C. for 3 hours to obtain a resin solid content. A polyester urethane resin (A) having a concentration of 30.0%, a Gardner viscosity UV (25 ° C.), an amine value of 0, and a mass average molecular weight (hereinafter referred to as Mw) of 67,000 was obtained. The obtained resin had a tan δ peak temperature of -8 ° C.

(Polyester urethane resin (B))
A four-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen gas inlet tube was charged with 223.1 parts of polyester diol of Mn = 1,000 obtained from adipic acid and neopentyl glycol and 64.4 parts of isophorone diisocyanate. The mixture was reacted at 90 ° C. for 15 hours under a nitrogen stream. Next, 11.3 parts of isophoronediamine, 1.2 parts of di-n-butylamine, 175 parts of toluene, 315 parts of ethyl acetate, and 210 parts of isopropylene alcohol were added and reacted at 40 ° C. for 3 hours under a stirring frame to obtain a resin solid. A polyester urethane resin (B) having a partial concentration of 30.0%, a Gardner viscosity ST (25 ° C), an amine value of 0.5, and Mw of 100,000 was obtained. The peak temperature of tan δ of the obtained resin was −20 ° C.

[Black ink production example]
(Black ink production example 1)
4 parts of “Carbon Degussa Special 4A” manufactured by Degussa, 6 parts of “Carbon Special 250P” manufactured by Degussa, 40 parts of polyester urethane resin (A) (tan δ peak temperature = −8 ° C.), 23 parts of methyl ethyl ketone, toluene 13 parts, 6 parts of ethyl acetate, 3 parts of N-propyl acetate, and 3 parts of isopropyl alcohol were added, and the mixture was wet-dispersed with a sand mill for about 1 hour, and then a curing agent “KR90” (hexamethylene didiisocyanate of DIC) was added. A black ink (A) was prepared by adding 4 parts of biuret body) and 35 parts of DIC Corporation diluent “Direducer V No. 20”. In addition, resin represents solid content ratio.

(Black ink production example 2)
In place of the polyester urethane resin (A) of Production Example 1, polyester urethane resin (B) (polyester urethane resin, tan δ peak temperature = −20 ° C.) is used, and black ink (B )created.

[Production of support]
(Ink coat film (A))
A Terajin DuPont Films Co., Ltd. Teflex FW2 # 13 (thickness: 13 μm, tensile strength 23 N / 20 mm) is subjected to corona treatment so that the surface state becomes 50 dynes or more, and then the black ink (A) is dried to a thickness. Was twice gravure coated so that the thickness of the film became 4 μm. The drying was left at room temperature for 2 minutes. Thereafter, the film was cured at 40 ° C. for 2 days to obtain an ink coat film (A).

(Ink coat film (B))
An ink coat film (B) was obtained in the same manner as the ink coat film (A) except that the black ink (B) was used.

[Preparation method of acrylic copolymer emulsion]
(Adjustment example 1)
<Preparation of emulsion (1)>
In a container, 75.0 g of ion-exchanged water and surfactant Aqualon KH-1025 [Daiichi Kogyo Seiyaku Co., Ltd .; active ingredient 25%] 20.0 g and surfactant Latemul PD-104 [manufactured by Kao Corp .; effective Ingredient 20%] 37.5 g was added and dissolved uniformly. Thereto, 457 g of n-butyl acrylate, 25.0 g of methyl methacrylate, 17.5 g of acrylic acid, 0.5 g of 2-hydroxyethyl acrylate and 0.2 g of lauryl mercaptan were added and emulsified to obtain 632.7 g of emulsion (1). Obtained.

<Manufacture of emulsion of acrylic copolymer (1)>
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, 340 g of ion-exchanged water was added, and the temperature was raised to 65 ° C. while blowing nitrogen. While stirring, a part [3.2 g] of the emulsion (1), 5.0 g ammonium persulfate aqueous solution [3% active ingredient], 5.0 g sodium hydrogen sulfite aqueous solution [3% active ingredient] were added, While maintaining, polymerization was carried out in 1 hour. Subsequently, the remaining emulsion (1) 629.5 g and ammonium persulfate aqueous solution 40 g [active ingredient 1.25%] were dropped and polymerized using a separate funnel over 8 hours while maintaining the reaction vessel at 60 ° C. . After completion of the dropping, the reaction vessel was stirred for 2 hours while maintaining the temperature at 60 ° C., and then the contents were cooled, and subsequently adjusted with ammonia water (active ingredient 10%) so that the pH became 7.5. This was filtered through a 200-mesh wire mesh to obtain 1013.5 g of an acrylic copolymer (1) emulsion. Here, the emulsion of the obtained acrylic copolymer (1) had a solid content concentration of 50% and an average particle size of 311 nm.

(Adjustment example 2)
<Preparation of emulsion (2)>
In a container, 75.0 g of ion-exchanged water and surfactant Aqualon KH-1025 [Daiichi Kogyo Seiyaku Co., Ltd .; active ingredient 25%] 20.0 g and surfactant Latemul PD-104 [manufactured by Kao Corp .; effective Ingredient 20%] 37.5 g was added and dissolved uniformly. 457 g of n-butyl acrylate, 25.0 g of methyl methacrylate, 17.5 g of acrylic acid, 0.5 g of 2-hydroxyethyl acrylate, and 0.2 g of lauryl mercaptan were added and emulsified to obtain 632.7 g of the emulsion (2). Obtained.

<Manufacture of emulsion of acrylic copolymer (2)>
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, 340 g of ion-exchanged water was added, and the temperature was raised to 60 ° C. while blowing nitrogen. While stirring, a part [3.2 g] of emulsion (2), 5.0 g ammonium persulfate aqueous solution [3% active ingredient] and 5.0 g sodium hydrogen sulfite aqueous solution [3% active ingredient] were added, While maintaining, polymerization was carried out in 1 hour. Subsequently, 629.5 g of the remaining emulsion (2) and 40 g of an aqueous ammonium persulfate solution (active ingredient 1.25%) were dropped and polymerized using a separate funnel over 8 hours while maintaining the reaction vessel at 60 ° C. . After completion of the dropping, the reaction vessel was stirred for 2 hours while maintaining the temperature at 60 ° C., and then the contents were cooled, and subsequently adjusted with ammonia water (active ingredient 10%) so that the pH became 7.5. This was filtered with a 200-mesh wire mesh to obtain 1013.5 g of an acrylic copolymer (2) emulsion. Here, the emulsion of the obtained acrylic copolymer (2) had a solid content concentration of 50% and an average particle size of 324 nm.

(Adjustment Example 3)
<Preparation of emulsion (3)>
In a container, 75.0 g of ion-exchanged water and surfactant Aqualon KH-1025 [Daiichi Kogyo Seiyaku Co., Ltd .; active ingredient 25%] 20.0 g and surfactant Latemul PD-104 [manufactured by Kao Corp .; effective Ingredient 20%] 37.5 g was added and dissolved uniformly. 457 g of n-butyl acrylate, 25.0 g of vinyl acetate, 17.5 g of acrylic acid, 0.5 g of 2-hydroxyethyl acrylate, and 0.2 g of lauryl mercaptan were added and emulsified to obtain 632.7 g of emulsion (3). Obtained.

<Manufacture of emulsion of acrylic copolymer (3)>
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, 340 g of ion-exchanged water was added, and the temperature was raised to 65 ° C. while blowing nitrogen. While stirring, a part [3.2 g] of emulsion (3), 5.0 g of ammonium persulfate aqueous solution [3% active ingredient] and 5.0 g of sodium hydrogen sulfite aqueous solution [3% active ingredient] were added, While maintaining, polymerization was carried out in 1 hour. Subsequently, 629.5 g of the remaining emulsion (3) and 40 g of an aqueous ammonium persulfate solution (active ingredient 1.25%) were dropped and polymerized over 8 hours using a separate funnel while keeping the reaction vessel at 60 ° C. . After completion of the dropping, the reaction vessel was stirred for 2 hours while maintaining the temperature at 60 ° C., and then the contents were cooled, and subsequently adjusted with ammonia water (active ingredient 10%) so that the pH became 7.5. This was filtered through a 200-mesh wire mesh to obtain 1013.5 g of an acrylic copolymer (3) emulsion. Here, the obtained emulsion of the acrylic copolymer (3) had a solid content concentration of 50% and an average particle size of 308 nm.

(Production Example 1)
To 1000 g [dry; 500 g] of the acrylic copolymer (1), Surfynol PSA-336 [manufactured by Air Products Japan Co., Ltd .; active ingredient 100%] 2.5 g as a leveling agent, defoaming Surfynol DF-110D [manufactured by Air Products Japan Co., Ltd .; active ingredient 100%] 2.5 g as an agent, emulsion type polymerized rosin ester-based tackifier resin super ester E-865NT [Arakawa Chemical Industries ( Co., Ltd .; softening point 160 ° C.] solid content 62.5 g, emulsion type rosin phenol-based tackifying resin Tamanol E-200NT [Arakawa Chemical Industries, Ltd .; softening point 150 ° C.] solid content 62.5 g, cross-linked Epoxy compound tetrad C [Mitsubishi Gas Chemical Co., Ltd.] 0.05 g (0.01 mass) ) Was added, and filtered through a 200 mesh screen to obtain aqueous acrylic PSA composition (1).

(Production Example 2)
In Production Example 1, a water-dispersed acrylic is the same as Production Example 1 except that 0.15 g (0.03 parts by mass) of an epoxy compound tetrad C [manufactured by Mitsubishi Gas Chemical Co., Ltd.] is added as a crosslinking agent. Type | system | group adhesive composition (2) was manufactured.

(Production Example 3)
To 1000 g [dry; 500 g] of the acrylic copolymer (2) emulsion, Surfynol PSA-336 [manufactured by Air Products Japan, Inc .; active ingredient 100%] 2.5 g as a leveling agent, defoaming Surfynol DF-110D [manufactured by Air Products Japan Co., Ltd .; active ingredient 100%] 2.5 g as an agent, emulsion-type polymerized rosin ester-based tackifier resin super ester E-865NT [Arakawa Chemical Industries ( Co., Ltd .; softening point 160 ° C.] solid content 62.5 g, emulsion type rosin phenol-based tackifying resin Tamanol E-200NT [Arakawa Chemical Industries, Ltd .; softening point 150 ° C.] solid content 62.5 g, cross-linked Epoxy compound tetrad C [Mitsubishi Gas Chemical Co., Ltd.] 0.05 g (0.01 mass) ) Was added, and filtered through a 200 mesh screen to obtain aqueous acrylic PSA composition (3).

(Comparative Production Example 1)
To 1000 g [dry; 500 g] of the acrylic copolymer (3) emulsion, Surfynol PSA-336 [manufactured by Air Products Japan Co., Ltd .; active ingredient 100%] 2.5 g as a leveling agent, defoaming Surfynol DF-110D [manufactured by Air Products Japan Co., Ltd .; active ingredient 100%] 2.5 g as an agent, emulsion type polymerized rosin ester-based tackifier resin super ester E-865NT [Arakawa Chemical Industries ( Co., Ltd .; softening point 160 ° C.] solid content 62.5 g, emulsion type rosin phenol-based tackifying resin Tamanol E-200NT [Arakawa Chemical Industries, Ltd .; softening point 150 ° C.] solid content 62.5 g, cross-linked Epoxy compound tetrad C [Mitsubishi Gas Chemical Co., Ltd.] 0.05 g (0.01 mass) ) Was added, and filtered through a 200 mesh screen to obtain aqueous acrylic PSA composition (1).

(Comparative Production Example 2)
In Comparative Production Example 1, water dispersion was performed in the same manner as Comparative Production Example 1 except that 0.15 g (0.03 parts by mass) of an epoxy compound tetrad C [manufactured by Mitsubishi Gas Chemical Co., Ltd.] was added as a crosslinking agent. Type acrylic pressure-sensitive adhesive composition (H2) was produced.

(Comparative Production Example 3)
In Comparative Production Example 1, water dispersion was carried out in the same manner as in Comparative Production Example 1, except that 0.25 g (0.05 parts by mass) of the epoxy compound Tetrad C [Mitsubishi Gas Chemical Co., Ltd.] was added as a crosslinking agent. Type acrylic pressure-sensitive adhesive composition (H3) was produced.

(Comparative Production Example 4)
In Production Example 1, a water-dispersed acrylic is the same as Production Example 1 except that 0.25 g (0.05 parts by mass) of an epoxy compound tetrad C [manufactured by Mitsubishi Gas Chemical Co., Ltd.] is added as a crosslinking agent. Type | system | group adhesive composition (H4) was manufactured.

[Production of solvent-based acrylic pressure-sensitive adhesive composition]
(Reference Production Example 1)
In a reaction vessel equipped with a condenser, stirrer, thermometer, and dropping funnel, 93 parts of n-butyl acrylate, 3.4 parts of vinyl acetate, 3.5 parts of acrylic acid, 0.1 part of β-hydroxy-ethyl acrylate, polymerization As an initiator, 0.2 part of 2,2′-azobisisobutylnitrile is dissolved in 100 parts of ethyl acetate, substituted with nitrogen, polymerized at 80 ° C. for 8 hours, and an acrylic copolymer having a mass average molecular weight of 800,000 ( S1) was obtained. 100 parts of the acrylic copolymer (S1), 10 parts of “Superester A100” manufactured by Arakawa Chemical Co., Ltd., and 10 parts by weight of “Pencel D135” manufactured by Arakawa Chemical Industries are diluted with toluene to a solid content of 40%. A solvent-based acrylic pressure-sensitive adhesive composition (S1) was obtained.

[Production of adhesive tape]
Example 1
The water-dispersed acrylic pressure-sensitive adhesive composition (1) obtained in Production Example 1 was coated on a 75 μm-thick polyester film subjected to a release treatment so that the thickness after drying was 20 μm, and 85 ° C. And dried for 2 minutes to obtain an adhesive layer. The obtained pressure-sensitive adhesive layer was transferred to both sides of the ink coat film (A), laminated with a heat roll of 80 ° C. at a pressure of 4 kgf / cm, and further cured at 40 ° C. for 2 days. A double-sided adhesive tape was obtained.

(Examples 2-3)
The double-sided pressure-sensitive adhesive tapes of Examples 2-3 were obtained in the same manner as in Example 1 except that the water-dispersed acrylic pressure-sensitive adhesive compositions (2)-(3) obtained in Production Examples 2-3 were used. .

Example 4
The water-dispersed acrylic pressure-sensitive adhesive composition (1) obtained in Production Example 1 was coated on a 75 μm-thick polyester film subjected to a release treatment so that the thickness after drying was 20 μm, and 85 ° C. And dried for 2 minutes to obtain an adhesive layer. The obtained pressure-sensitive adhesive layer was transferred to both sides of the ink coat film (B), laminated with a heat roll of 80 ° C. at a pressure of 4 kgf / cm, and further cured at 40 ° C. for 2 days. A double-sided adhesive tape was obtained.

(Example 5)
A double-sided pressure-sensitive adhesive tape of Example 5 was obtained in the same manner as in Example 4 except that the water-dispersed acrylic pressure-sensitive adhesive composition (3) obtained in Production Example 3 was used.

(Comparative Examples 1-4)
The double-sided pressure-sensitive adhesive tapes of Comparative Examples 1 to 4 were used in the same manner as in Example 1 except that the water-dispersed acrylic pressure-sensitive adhesive compositions (H1) to (H4) obtained in Comparative Production Examples 1 to 4 were used. Obtained.

(Reference Example 1)
After 1.2 parts of “Coronate L-45” (isocyanate-based cross-linking agent) manufactured by Nippon Polyurethane Industry Co., Ltd. was blended in the solvent-based acrylic pressure-sensitive adhesive composition (S1) obtained in Reference Production Example 1, and sufficiently stirred Then, it was coated on a 75 μm-thick polyester film subjected to a release treatment so that the thickness after drying was 20 μm, and dried at 85 ° C. for 2 minutes to obtain an adhesive layer. This was transferred to both sides of the ink coat film (b), laminated with a heat roll at 80 ° C. at a pressure of 4 kgf / cm, and further cured at 40 ° C. for 2 days to obtain a double-sided pressure-sensitive adhesive tape of Reference Example 1. .

  Table 1 shows the monomer composition of the acrylic copolymer used in each composition obtained above. Moreover, about the adhesive layer and double-sided adhesive tape obtained by the said ink coat film, the Example, the comparative example, and the reference example, the following items were evaluated and the obtained result was shown to Tables 2-4.

[Measurement of elastic modulus, elongation, breaking strength, breaking elongation]
The black ink used for the ink coat film is processed into an ink coating with a width of 10 mm and a length of 150 mm, and under the conditions of an environmental temperature of 23 ° C. and a humidity of 50%, Tensilon Universal Tensile Tester (Orientec, RTA100) Was used to measure the elastic modulus, tensile strength, breaking strength, and breaking elongation when pulled at 300 mm / min when the chuck spacing was 100 mm.

[Adhesive strength]
The adhesive strength was determined by the following procedure in accordance with the JIS-Z0237 (2000) 180-degree peeling adhesive strength test method.
A stainless steel (SUS) plate, a glass plate, and an optical film (3M thin optical film “BEFRP2RC” (120 μm)) lined with a polyester film of 25 μm and a 20 mm width of the adhesive tapes of Examples and Comparative Examples were used at an environmental temperature of 23. Under the condition of 50 ° C. and humidity of 50%, press and reciprocate with a 2 kg roller, leave it for 1 hour, and use a Tensilon universal tensile tester (Orientec, RTA100) at 300 mm / min under the same temperature and humidity conditions. The film was pulled at a speed of 180 ° and peeled off by 180 ° to measure the adhesive force.
In addition, the thing with the adhesive force with respect to glass of 8 N / 20mm or more was judged to be favorable.

(Waviness / distortion test of optical film)
Attach the black ink side of the pressure-sensitive adhesive tape (external dimensions: 32 mm x 42 mm, width: 2 mm) obtained by punching the pressure-sensitive adhesive tape adjusted as described above into a frame shape at 23 ° C as shown in Fig. 3, and the white ink side. The thin optical film “BEFRP2RC” (120 μm) (outside: 30 mm × 40 mm) manufactured by 3M was attached (FIG. 3). In addition, the width | variety with which an adhesive tape and an optical film contact | connected was 1 mm on each side. This part was left to stand at 85 ° C. for 72 hours, and then left to stand at 23 ° C. for 1 hour.
○: No distortion occurred in the optical film Δ: Distortion occurred in the optical film ×: Large distortion occurred in the optical film

[Reworkability]
The adhesive tapes of Examples and Comparative Examples with a white surface lined on a stainless steel plate with a polyester film of 25 μm and a comparative example were pressure-applied once with a 2 kg roller under the conditions of an environmental temperature of 23 ° C. and a humidity of 50% RH. Leave in an environmental tester at 60 ° C. for 24 hours. Then, after leaving at 23 ° C. for 1 hour, it was peeled off at a speed of 300 mm / min in an oblique direction of 135 °, and it was evaluated whether or not the adhesive could be peeled off without leaving any adhesive.
○: It was possible to peel without adhesive residue.
X: Adhesive residue is generated.

[Light shielding]
The light box “Flat Illuminator HF-SL-A48LCG” manufactured by Dentsu Sangyo Co., Ltd. is adjusted to 10000 cd / m ² , and a light-shielding adhesive tape is placed on the light box. ) Measure with eye system luminance meter "eye scale 3"

  As is clear from Tables 3 to 4, the double-sided pressure-sensitive adhesive tapes of the present invention of Examples 1 to 5 have a suitable adhesiveness for low-speed peeling force while using a water-based pressure-sensitive adhesive with reduced VOC. And the wave | undulation and distortion of an optical film can be suppressed suitably. Moreover, it had suitable rework property by suitable anchoring property with respect to the support body which has a colored ink layer. On the other hand, the pressure-sensitive adhesive tape of the comparative example cannot suppress the undulation and distortion of the optical film. Moreover, it was inferior to the adhesiveness to an optical film or glass.

10: Adhesive tape 11: Prism sheet 12: Diffusion sheet 13: Light source 14: Light guide plate 15: Reflector plate 16: Backlight housing 17: LCD panel 18: Driver 20: Double-sided adhesive tape 21: Optical film 22: Glass

Claims (10)

A double-sided adhesive tape that fixes an optical film and another member,
A pressure-sensitive adhesive layer is provided on both surfaces of a support, and at least the pressure-sensitive adhesive layer attached to the optical film is made of a water-dispersed acrylic pressure-sensitive adhesive composition in which acrylic copolymer emulsion particles are dispersed in an aqueous medium. Agent layer,
The acrylic copolymer forming the acrylic copolymer emulsion particles is a (meth) acrylate having an alkyl group having 4 to 8 carbon atoms, a (meth) acrylate having an alkyl group having 2 or less carbon atoms, and Containing a carboxyl group-containing monomer as a monomer component,
The content of the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms in the monomer component forming the acrylic copolymer has an alkyl group having 50 to 98% by mass and an alkyl group having 2 or less carbon atoms (meth). The acrylate content is 1-10% by mass, the carboxyl group-containing monomer content is 1-10% by mass,
A double-sided pressure-sensitive adhesive tape, wherein the pressure-sensitive adhesive layer has a gel fraction of 10 to 50%. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the other member fixed to the optical film is a display panel of an image display device. The double-sided pressure-sensitive adhesive tape according to claim 2, wherein the display panel is a glass panel. The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 3, comprising n-butyl (meth) acrylate as the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms. OK The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the (meth) acrylate having an alkyl group having 2 or less carbon atoms is methyl (meth) acrylate. The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 5, comprising acrylic acid as the carboxyl group-containing monomer. The support is a support having a colored layer made of a colored ink having a halogen content of 0.3% by mass or less on at least one surface of a resin film, and is attached to an optical film on the colored layer side surface of the support. The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 6, wherein a pressure-sensitive adhesive layer to be attached is provided. The double-sided pressure-sensitive adhesive tape according to claim 7, wherein the colored ink comprises a polyurethane resin as a binder resin. The double-sided pressure-sensitive adhesive tape according to claim 8, wherein the polyurethane resin is a polyester polyurethane resin having a glass transition temperature of -30 to 30 ° C. The double-sided pressure-sensitive adhesive tape according to any one of claims 7 to 9, wherein the colored ink contains an anti-blocking agent.

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