JP5541552B2 - Adhesive tape - Google Patents

Description

  The present invention relates to an adhesive tape for fixing an optical film used in an image display device such as a liquid crystal display or an organic EL (Electro Luminescence) display.

  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, a reflector, a light guide plate, a diffusion sheet, etc. are generally laminated, an optical film such as a prism sheet is provided on the surface layer, and a lamp reflector is provided on the side of the light guide plate. In addition, a backlight module in which a light source such as an LED (Light Emitting Diode) or a cold cathode tube is disposed, and an LCD panel are stacked. 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 a problem in the past due to the high performance of electronic devices used, in particular, the thinning and multifunctionality of mobile phones. Yes. 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. Such a problem occurs particularly conspicuously with the increase in the screen size of portable electronic terminals such as smartphones and tablet terminals. On the other hand, the adhesive tape which suppresses distortion of an optical film is proposed, and the trial which suppresses distortion of an optical film while fixing between components satisfactorily is made | formed (refer patent documents 2-3).

  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 materials having reduced VOC (volatile organic compounds), and in particular in the field of these electronic devices, there is a demand. 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 adhesive tape using the water-based adhesive which can fix between components satisfactorily and can suppress distortion of an optical film suitably is desired. In addition, with the increase in the screen size of portable electronic terminals, it is also desired to improve the fixability of components, particularly the rebound resistance, in order to suppress the peeling of the adhesive tape due to the twisting of the terminals.

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

  The subject of this invention is the adhesive tape which can fix a member suitably and can suppress the distortion of an optical film, even when using the water-based adhesive which reduced VOC in the adhesive tape which fixes the optical film which produces distortion easily. Is to provide.

  In the present invention, the pressure-sensitive adhesive tape used for fixing the optical film, the pressure-sensitive adhesive layer in contact with the optical film is a pressure-sensitive adhesive layer made of a water-dispersed acrylic pressure-sensitive adhesive composition, and the glass transition of the pressure-sensitive adhesive layer The above problem can be solved by an adhesive tape having a temperature of −5 ° C. or lower and a gel fraction of 25 to 45%.

  The pressure-sensitive adhesive tape of the present invention has a glass transition temperature of −5 ° C. or lower and a gel fraction of 25 to 45 as a pressure-sensitive adhesive layer to be attached to an optical film while using a water-based pressure-sensitive adhesive layer with reduced VOC. % Of the pressure-sensitive adhesive layer can be used to fix the parts satisfactorily, have good repulsion resistance, and suitably suppress the distortion of the optical film. For this reason, while having excellent environmental compatibility, even when an optical film is an object to be adhered, it is possible to suppress a decrease in visibility due to distortion of the optical film and peeling of the adhesive tape due to deformation such as twisting of the housing Therefore, it is suitable for fixing between parts of an image display device to which an optical film is to be attached, particularly for fixing an optical film and a transparent panel.

It is a conceptual diagram which shows the measuring method of the distortion prevention property of the optical film in an Example. It is a conceptual diagram which shows the measuring method of the resilience resistance in an Example.

  The pressure-sensitive adhesive tape of the present invention is a pressure-sensitive adhesive tape used for fixing an optical film, the pressure-sensitive adhesive layer in contact with the optical film is a pressure-sensitive adhesive layer made of a water-dispersed acrylic pressure-sensitive adhesive composition, and the glass of the pressure-sensitive adhesive layer The transition temperature is −5 ° C. or lower, and the gel fraction is 25 to 45%.

[Adhesive layer]
In the pressure-sensitive adhesive tape of the present invention, 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. . In the present invention, the glass transition temperature (Tg) of the pressure-sensitive adhesive layer is −5 ° C. or lower, preferably −10 ° C. or lower, and more preferably −15 ° C. or lower, thereby sufficiently ensuring the flexibility of the pressure-sensitive adhesive. To do. Thereby, even when distortion arises in an optical film, distortion can be controlled, following the distortion suitably. Further, when the pressure sensitive adhesive is sufficiently wetted with the adherend, adhesion between the adherend and the pressure sensitive adhesive is ensured, and suitable rebound resistance can be realized.

The glass transition temperature of the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive tape of the present invention is the peak temperature of the loss tangent (tan δ) of the dynamic viscoelastic spectrum. The measurement of dynamic viscoelasticity is performed by, for example, using a viscoelasticity tester (Rheometrics, trade name: Ares 2KFRTN1), inserting a test piece between parallel disks as measurement units of the tester, and a frequency of 1 Hz. Then, the storage elastic modulus (G ′) and loss elastic modulus (G ″) from −50 ° C. to 150 ° C. are measured at a temperature rising rate of 2 ° C./min. Tan δ is calculated from the following calculation formula.
tan δ = G ″ / G ′
In the test piece, an adhesive having a thickness of 0.5 to 2.5 mm may be sandwiched between parallel disks alone, or a laminate of a base material and an adhesive may be stacked in layers and sandwiched between parallel disks. In the latter case, even if the base material is sandwiched in the middle, the peak temperature of the loss tangent of the dynamic viscoelastic spectrum of the adhesive is not affected.

  The pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of the present invention is a pressure-sensitive adhesive layer having a gel fraction of 25 to 45%. By setting the gel fraction of the pressure-sensitive adhesive layer within the above range at the above glass transition temperature, it is possible to ensure sufficient wettability and adherence to the adherend, while at the same time agglomerating to withstand stress. By securing the force, it is possible to satisfactorily suppress the distortion of the optical film and realize suitable rebound resistance. In addition, the said gel fraction is a gel fraction represented by the mass fraction ratio before and behind immersion after measuring the insoluble matter after immersing an adhesive layer in toluene for 24 hours.

  The pressure-sensitive adhesive tape of the present invention has a pressure-sensitive adhesive layer having the above glass transition temperature and gel fraction. The glass transition temperature of the pressure-sensitive adhesive layer is the glass transition of the acrylic copolymer used in the pressure-sensitive adhesive composition. It is appropriately adjusted depending on the temperature, the glass transition temperature of the tackifying resin, the softening point, the blending amount, and the like. Further, the gel fraction can be appropriately adjusted depending on the amount of the crosslinking agent and the crosslinking agent added to the pressure-sensitive adhesive composition, and the functional group monomer and the amount of the functional group monomer introduced into the acrylic copolymer that reacts with the crosslinking agent.

(Acrylic copolymer)
As the water-dispersed acrylic pressure-sensitive adhesive composition used for the pressure-sensitive adhesive layer, a composition in which emulsion particles of an acrylic copolymer are dispersed in an aqueous medium can be used. The acrylic copolymer preferably has a glass transition temperature measured by a dynamic viscoelastic spectrum of −45 ° C. to −25 ° C., more preferably −40 ° C. to −30 ° C. By setting the glass transition temperature of the acrylic copolymer within the range, it becomes easy to sufficiently secure the flexibility of the pressure-sensitive adhesive. Thereby, even when distortion occurs in the optical film, it becomes easy to suppress the distortion while suitably following the distortion. In addition, when the pressure-sensitive adhesive is sufficiently wetted with the adherend, it is easy to ensure adhesion between the adherend and the pressure-sensitive adhesive, and it is easy to realize suitable repulsion resistance.

  The glass transition temperature of the acrylic copolymer constituting the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of the present invention is the peak temperature of the loss tangent (tan δ) of the dynamic viscoelastic spectrum. In the measurement of dynamic viscoelasticity, a sheet composed only of an acrylic copolymer is prepared and can be measured in the same manner as the pressure-sensitive adhesive layer.

  As the (meth) acrylate monomer used for the acrylic copolymer, a (meth) acrylate monomer used for the pressure-sensitive adhesive can be used as appropriate, and in particular, a (meth) acrylate monomer having an alkyl group having 4 to 8 carbon atoms. Can be preferably used as the main monomer component. Examples of the (meth) acrylate monomer having 4 to 8 carbon atoms include n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isooctyl (meth). (Meth) acrylates such as acrylate and n-octyl (meth) acrylate can be used. Among these, n-butyl acrylate and / or 2-ethylhexyl acrylate can be preferably used, and 2-ethylhexyl acrylate is particularly preferable because the glass transition temperature of the resulting pressure-sensitive adhesive layer can be easily controlled to be low. Further, the compatibility with the tackifier resin is easily improved, and the adhesion with the substrate or the adherend is easily improved.

  The content of the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms is preferably 50 to 98% by mass, and preferably 80 to 98% by mass in the monomer component used for the acrylic copolymer. Particularly preferred. By making content of the (meth) acrylate which has a C4-C8 alkyl group into the said range, it becomes easy to ensure the softness | flexibility of an adhesive sufficiently. Thereby, even when distortion occurs in the optical film, it becomes easy to suppress the distortion while suitably following the distortion. In addition, when the pressure-sensitive adhesive is sufficiently wetted with the adherend, it is easy to ensure adhesion between the adherend and the pressure-sensitive adhesive, and it is easy to realize suitable repulsion resistance.

  Moreover, when using 2-ethylhexyl acrylate which can be used especially preferably, it is preferable to set it as 40 mass% or more in the monomer component used for an acrylic copolymer, and it is more preferable to set it as 60 mass% or more, 80 It is more preferable to set it as mass% or more, and it is still more preferable to set it as 90 mass% or more. By setting it as the said range, it becomes easy to ensure the softness | flexibility of an adhesive sufficiently. Thereby, even when distortion occurs in the optical film, it becomes easy to suppress the distortion while suitably following the distortion.

  In the present invention, (meth) acrylate monomers other than those described above may be used in combination as the (meth) acrylate monomer that forms the acrylic copolymer. Examples of other (meth) acrylate monomers include (meth) acrylate monomers such as methyl (meth) acrylate and ethyl (meth) acrylate, and one or more of these may be used in combination. . Especially, it is preferable to use together (meth) acrylate which has a C2-C2 alkyl group, such as methyl (meth) acrylate and ethyl (meth) acrylate, and it is preferable that it is 1-10 mass% as usage-amount. .

  In the present invention, it is preferable to use a carboxyl group-containing monomer 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. And the like.

  The content of the carboxyl group-containing monomer is 0.5 to 10% by mass, preferably 0.5 to 5% by mass, more preferably 1.5 to 3.5% by mass in the monomer component forming the acrylic copolymer. % Is preferred. By setting it within this range, the crosslinking reaction with the crosslinking agent easily proceeds well. Furthermore, it becomes easy to secure a cohesive force capable of withstanding stress, it is possible to satisfactorily suppress the distortion of the optical film, and it is easy to realize suitable repulsion resistance.

  In the present invention, it is preferable to further use a nitrogen-containing vinyl monomer as the monomer component of the acrylic copolymer. The nitrogen-containing vinyl monomer is presumed to produce an effect of drawing a carboxyl group that is easily oriented on the particle surface into the particle by interacting with an acid group, particularly a carboxyl group, in the acrylic copolymer emulsion particles. Content of a nitrogen-containing vinyl monomer is 0.1-4.5 mass%, Preferably, it is 0.5-4 mass%, More preferably, it is 0.5-3.5 mass%.

  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.

  The ratio of the nitrogen-containing vinyl monomer and the vinyl monomer having a carboxyl group in the acrylic copolymer is not particularly limited, but the number of moles of the nitrogen-containing vinyl monomer in the monomer component constituting the acrylic copolymer. Is X, and the molar ratio X / Y is preferably from 1/1 to 1/20, more preferably from 1/1 to 1/5, where Y is the number of moles of the vinyl monomer having a carboxyl group. 1-1 / 3 is more preferable. If it is in the said range, reaction with the vinyl monomer which has a carboxyl group, and the crosslinking agent mentioned later will advance easily.

  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 making it within this range, the flexibility to develop sufficient wettability and adhesion to the adherend is improved, while the cohesive force that can withstand stress is improved, thereby improving the distortion of the optical film. It can be suppressed and it is easy to realize suitable repulsion resistance. 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.

(Tackifying resin)
In the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention, a tackifying resin should be used to develop sufficient wettability and adhesion to an adherend and to improve cohesive strength to withstand stress. Is preferred. The glass transition temperature of the tackifying resin is preferably 30 to 120 ° C, more preferably 40 to 100 ° C, still more preferably 45 to 80 ° C, and still more preferably 50 to 60 ° C. By adding a tackifier resin having a glass transition temperature higher than that of the acrylic copolymer, the strong adhesiveness is improved.

  The glass transition temperature of the tackifying resin used for the pressure-sensitive adhesive constituting the pressure-sensitive adhesive tape of the present invention is the midpoint glass transition in JIS K 7121 at the step-like change portion of the glass transition of the DSC curve measured using a DSC measuring device. It is a temperature defined as a temperature. A specific measurement method is, for example, a value obtained by analyzing a DSC curve measured using a DSC measurement apparatus (trade name: DSC822, manufactured by METTLER TOLEDO Co., Ltd.) using software attached to the apparatus. The sample is dried at 60 ° C. for 2 days or more under vacuum using a vacuum dryer. The range from −50 ° C. to 200 ° C. is measured twice continuously at a temperature increase rate of 2 ° C./min, and the glass transition temperature is calculated by analyzing the second measurement data.

  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 them, it is preferable to use a polymerized rosin ester tackifier resin and / or a rosin phenol tackifier resin. 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 the rosin ester tackifier resin is super ester NS-125A [manufactured by Arakawa Chemical Industries, Ltd.] -Perester NS-100H [Arakawa Chemical Industries, Ltd.], Harrier Star SK-90D-55 [Harima Kasei Co., Ltd.], Harrier Star SK-385NS [Harima Kasei Co., Ltd.], etc., and modified rosin Examples of the ester-based tackifier resin include Harrier Star SK-501NS [manufactured by Harima Kasei Co., Ltd.], Harrier Star SK-370N [manufactured by Harima Chemical Co., Ltd.], and the like. 120B [manufactured by Arakawa Chemical Industry Co., Ltd.], Superester NS-100A [manufactured by Arakawa Chemical Industry Co., Ltd.], and the like. ], Tamanol E-200 [manufactured by Arakawa Chemical Industries, Ltd.], Tamanol E-200NT [manufactured by Arakawa Chemical Industries, Ltd.] and the like.

  The blend ratio of acrylic copolymer / tackifying resin is preferably acrylic copolymer / tackifying resin = 100/10 to 100/40, more preferably acrylic copolymer, in the ratio by mass. / Tackifying resin = 100/15 to 100/35. If it is in the said range, sufficient wettability to a to-be-adhered body, expression of adhesiveness, and the cohesive force which can endure stress can be improved with sufficient 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. By using a crosslinking agent that reacts with these acid groups, an improvement in cohesive force can be suitably expressed.

(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. As the said support body, the support body in which the colored layer was provided in the support body which consists only of a resin film, for example may be sufficient. When fixing the optical film and other members, especially when fixing the optical film and the transparent panel, light shielding performance and light reflection performance are often required, so when realizing good light shielding performance and light reflection performance, A support in which a colored layer is provided on a 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.

  Aliphatic or alicyclic isocyanates 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.

  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.

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.

[Adhesive tape]
The pressure-sensitive adhesive tape of the present invention is a pressure-sensitive adhesive tape for fixing an optical film, and is a pressure-sensitive adhesive tape provided with the pressure-sensitive adhesive layer attached to the optical film on at least one surface of a support. With this configuration, it is possible to suitably fix an optical film that is likely to be distorted while having excellent environmental compatibility due to VOC reduction, and it is possible to suitably suppress distortion of the optical film while having good repulsion resistance.

  The form of the pressure-sensitive adhesive tape may be a single-sided pressure-sensitive adhesive tape provided with a pressure-sensitive adhesive layer on one side of the support, or a double-sided pressure-sensitive adhesive tape provided with pressure-sensitive adhesive layers on both sides of the support. A double-sided pressure-sensitive adhesive tape is preferable for fixing between the components for fixing the other members. The pressure-sensitive adhesive layer attached to the optical film has suitable adhesion to various adherends, particularly transparent panels such as glass panels. It is also preferable to use an adhesive layer. 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. In addition, when using single-sided adhesive tape for fixing between parts, it can also be applied to fixing between parts by using a separate double-sided adhesive tape on the surface that does not have an adhesive layer or by applying an adhesive. .

  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 tape. 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 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.

  7-15 N / 20mm is preferable and, as for the 180 degree | times peel adhesive force with respect to the optical film and glass of the adhesive tape of this invention, 8-13 N / 20mm is more preferable. 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 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. Particularly preferred are those that do not substantially contain. The adhesive tape with reduced halogen is suitable for suppressing malfunction of the image display device.

  As an embodiment of the 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 the pressure-sensitive adhesive layer to be attached to the optical film. The structure which has an adhesive layer affixed on an optical film in a colored layer surface 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, fixing an optical film and another member, and sticking an adhesive layer formed from the water-dispersed acrylic pressure-sensitive adhesive composition to the optical film. used. The 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 deformation occurs in the optical film after fixing the optical film to other members. It is suitable for an image display device that requires fixing of an optical film and another member. Moreover, it has good adhesiveness and is particularly excellent in resilience resistance. For this reason, the optical film is likely to be distorted, and the adhesive tape is likely to be peeled off due to deformation such as twisting of the housing. It can be suitably used as a component fixing tape used for fixing an optical film of a display device. In addition, as a light-shielding tape, light-reflecting tape, and light-shielding reflective tape for fixing the optical film and transparent panel of a thin image display device that requires suitable light-shielding / reflecting performance and requires reworkability at the time of defect or repair It can be suitably used.

  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. Distortion occurs especially when the rate of change is greater than ± 0.05% in the flow direction or width direction, especially when the rate of change is greater than + 0.06% in the flow direction and greater than -0.06% in the width direction. It's easy to do. The 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.

  The double-sided pressure-sensitive adhesive tape for fixing a glass panel optical film of the present invention can suppress malfunction of peripheral devices and gives a highly reliable product. Therefore, various electronic devices, particularly electronic notebooks, mobile phones, smartphones (high function Mobile phone), PHS, game device, electronic book, multi-function data terminal, mobile personal computer, etc., can be suitably used for fixing a glass panel of a display device of a miniaturized portable electronic device.

[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.

[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.

[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).

[Preparation method of acrylic copolymer emulsion]
(Preparation 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. There, 227.5 g of n-butyl acrylate, 227.5 g of 2-ethylhexyl acrylate, 25.0 g of methyl methacrylate, 7.5 g of N-vinylpyrrolidone, 1.5 g of acrylic acid, 11.0 g of methacrylic acid, 0.2 g of lauryl mercaptan Was added and emulsified to obtain 632.7 g of an emulsified liquid (1).

<Preparation 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 60 ° 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 dropwise addition, the reaction vessel was stirred for 2 hours while maintaining the temperature at 60 ° C., and then the contents were cooled, and subsequently prepared with ammonia water (active ingredient 10%) so that the pH was 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 341 nm.

(Preparation 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. There, 227.5 g of n-butyl acrylate, 227.5 g of 2-ethylhexyl acrylate, 25.0 g of methyl methacrylate, 7.5 g of N-vinylpyrrolidone, 12.5 g of acrylic acid, 0.20 g of lauryl mercaptan were added and emulsified, Emulsion (2) 632.7 g was obtained.

<Preparation 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 dropwise addition, the reaction vessel was stirred for 2 hours while maintaining the temperature at 60 ° C., and then the contents were cooled, and subsequently prepared with ammonia water (active ingredient 10%) so that the pH was 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 338 nm.

(Preparation 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. Then, 50.0 g of n-butyl acrylate, 405.0 g of 2-ethylhexyl acrylate, 25.0 g of methyl methacrylate, 7.5 g of N-vinylpyrrolidone, 12.5 g of acrylic acid and 0.20 g of lauryl mercaptan were added and emulsified, Emulsion (3) 632.7 g was obtained.

<Preparation 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 60 ° 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, 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 dropwise addition, the reaction vessel was stirred for 2 hours while maintaining the temperature at 60 ° C., and then the contents were cooled, and subsequently prepared with ammonia water (active ingredient 10%) so that the pH was 7.5. This was filtered through a 200-mesh wire mesh to obtain 1013.5 g of an acrylic copolymer (3) emulsion. Here, the emulsion of the obtained acrylic copolymer (3) had a solid content concentration of 50% and an average particle size of 330 nm.

(Adjustment Example 4)
<Preparation of emulsion (4)>
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. Emulsified by adding 231.25 g of n-butyl acrylate, 231.25 g of 2-ethylhexyl acrylate, 25.0 g of methyl methacrylate, 1.5 g of acrylic acid, 11.0 g of methacrylic acid and 0.2 g of lauryl mercaptan, (4) 632.7 g was obtained.

<Preparation of emulsion of acrylic copolymer (4)>
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 (4), 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, 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 dropwise addition, the reaction vessel was stirred for 2 hours while maintaining the temperature at 60 ° C., and then the contents were cooled, and subsequently prepared with ammonia water (active ingredient 10%) so that the pH was 7.5. This was filtered through a 200-mesh wire mesh to obtain 1013.5 g of an acrylic copolymer (4) emulsion. Here, the emulsion of the obtained acrylic copolymer (4) had a solid content concentration of 50% and an average particle size of 345 nm.

(Adjustment Example 5)
<Preparation of emulsion (5)>
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, 240 g of n-butyl acrylate, 240 g of 2-ethylhexyl acrylate, 7.5 g of N-vinylpyrrolidone, 1.5 g of acrylic acid, 11.0 g of methacrylic acid and 0.2 g of lauryl mercaptan were added to emulsify, and the emulsion (5 ) 632.7 g was obtained.

<Preparation of emulsion of acrylic copolymer (4)>
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 the emulsion (5), 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, 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 dropwise addition, the reaction vessel was stirred for 2 hours while maintaining the temperature at 60 ° C., and then the contents were cooled, and subsequently prepared with ammonia water (active ingredient 10%) so that the pH was 7.5. This was filtered through a 200 mesh wire net to obtain 1013.5 g of an acrylic copolymer (5) emulsion. Here, the emulsion of the obtained acrylic copolymer (5) had a solid content concentration of 50% and an average particle size of 340 nm.

[Production of water-dispersed acrylic pressure-sensitive adhesive composition]
(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 [Air Products Japan Co., Ltd .; active ingredient 100%] 2.5 g as an agent; Superester NS-100H [Arakawa Chemical Industries, Ltd .; glass transition temperature 50 ° C. as a tackifier resin ] 125 g in solid content, 0.15 g (0.03 parts by mass) of epoxy compound tetrad C [manufactured by Mitsubishi Gas Chemical Co., Ltd.] as a cross-linking agent, filtered through a 200-mesh wire mesh, and water-dispersed acrylic adhesive An agent composition (1) was obtained.

(Production Example 2)
A water-dispersed acrylic pressure-sensitive adhesive similar to Production Example 1 except that the amount of the crosslinking agent 0.15 g (0.03 parts by mass) in Production Example 1 was changed to 0.2 g (0.04 parts by mass). Composition (2) was produced.

(Production Example 3)
A water-dispersed acrylic pressure-sensitive adhesive as in Production Example 1 except that the amount of the crosslinking agent 0.15 g (0.03 parts by mass) in Production Example 1 was changed to 0.25 g (0.05 parts by mass). A composition (3) was produced.

(Production Example 4)
In place of 125 g of the tackifier resin superester NS-100H solid content used in Production Example 1, 62.5 g of superester E-865NT (manufactured by Arakawa Chemical Industry Co., Ltd .; glass transition temperature 100 ° C.) in solid content was obtained. Esters E-200NT (produced by Arakawa Chemical Industries, Ltd .; glass transition temperature 90 ° C.) were used at a solid content of 62.5 g, and the crosslinking agent content 0.15 g (0.03 parts by mass) was 0.35 g ( A water-dispersed acrylic pressure-sensitive adhesive composition (4) was produced in the same manner as in Production Example 1 except that the amount was 0.07 parts by mass).

(Production Example 5)
Instead of the acrylic copolymer (1) emulsion 1000 g [dry; 500 g] used in Production Example 3, the same procedure as in Production Example 3 was used except that the acrylic copolymer (2) was used. A water-dispersed acrylic pressure-sensitive adhesive composition (5) was produced.

(Production Example 6)
Water-dispersed acrylic pressure-sensitive adhesive as in Production Example 5 except that the amount of the crosslinking agent in Production Example 5 was changed to 0.25 g (0.05 parts by mass) and 0.4 g (0.08 parts by mass). A composition (6) was produced.

(Production Example 7)
In the same manner as in Production Example 6 except that the acrylic copolymer (3) was used in place of the 1000 g [dry; 500 g] emulsion of the acrylic copolymer (2) used in Production Example 6, A water-dispersed acrylic pressure-sensitive adhesive composition (7) was produced.

(Production Example 8)
A water-dispersed acrylic pressure-sensitive adhesive as in Production Example 7, except that the amount of the crosslinking agent in Production Example 7 was changed to 0.4 g (0.08 parts by mass) from 0.5 g (0.1 parts by mass). A composition (8) was produced.

(Production Example 9)
Instead of 125 g of the tackifier resin superester NS-100H solid content used in Production Example 1, 125 g of superester E-200NT (manufactured by Arakawa Chemical Industries, Ltd .; glass transition temperature 90 ° C.) was used in the solid content to crosslink. A water-dispersed acrylic pressure-sensitive adhesive composition (9) in the same manner as in Production Example 1, except that 0.15 g (0.03 parts by mass) of the agent was changed to 0.35 g (0.07 parts by mass). Manufactured.

(Production Example 10)
Instead of 125 g of the tackifier resin superester NS-100H solid content used in Production Example 1, 125 g of superester E-865NT [manufactured by Arakawa Chemical Industries, Ltd .; Water-dispersed acrylic pressure-sensitive adhesive composition (10) in the same manner as in Production Example 1, except that 0.15 g (0.03 parts by mass) of the agent was changed to 0.35 g (0.07 parts by mass). Manufactured.

(Production Example 11)
In place of 125 g of the tackifier resin superester NS-100H solid content used in Production Example 1, 50 g was used, and 0.15 g (0.03 parts by mass) of the crosslinking agent was added to 0.35 g (0.07 parts by mass). A water-dispersed acrylic pressure-sensitive adhesive composition (11) was produced in the same manner as in Production Example 1 except that the composition was changed to (Part).

(Production Example 12)
Instead of 125 g of the tackifier resin superester NS-100H solid content used in Production Example 1, 200 g was used, and 0.15 g (0.03 parts by mass) of the crosslinking agent was added to 0.5 g (0.1 mass). A water-dispersed acrylic pressure-sensitive adhesive composition (12) was produced in the same manner as in Production Example 1 except that the composition was changed to (Part).

(Production Example 13)
Instead of the acrylic copolymer (1) emulsion 1000 g [dry; 500 g] used in Production Example 4, the same procedure as in Production Example 4 was used, except that the acrylic copolymer (4) was used. A water-dispersed acrylic pressure-sensitive adhesive composition (13) was produced.

(Production Example 14)
Instead of the acrylic copolymer (1) emulsion 1000 g [dry; 500 g] used in Production Example 4, the same procedure as in Production Example 4 was used, except that the acrylic copolymer (5) was used. A water-dispersed acrylic pressure-sensitive adhesive composition (14) was produced.

(Comparative Production Example 1)
A water-dispersed acrylic pressure-sensitive adhesive as in Production Example 4 except that the amount of the crosslinking agent in Production Example 4 was changed to 0.35 g (0.07 parts by mass) and 0.15 g (0.03 parts by mass). A composition (H1) was produced.

(Comparative Production Example 2)
A water-dispersed acrylic pressure-sensitive adhesive as in Production Example 1 except that the amount of the crosslinking agent 0.15 g (0.03 parts by mass) in Production Example 1 was changed to 0.4 g (0.08 parts by mass). A composition (H2) was produced.

(Comparative Production Example 3)
A water-dispersed acrylic pressure-sensitive adhesive as in Production Example 5 except that the amount of the crosslinking agent in Production Example 5 was changed to 0.25 g (0.05 parts by mass) and 0.15 g (0.03 parts by mass). A composition (H3) was produced.

(Comparative Production Example 4)
A water-dispersed acrylic pressure-sensitive adhesive as in Production Example 5 except that the amount of the crosslinking agent in Production Example 5 was changed to 0.25 g (0.05 parts by mass). A composition (H4) was produced.

(Comparative Production Example 5)
A water-dispersed acrylic pressure-sensitive adhesive as in Production Example 5, except that the amount of the crosslinking agent in Production Example 5 was changed to 0.25 g (0.05 parts by mass) and 0.5 g (0.1 parts by mass). A composition (H5) was produced.

(Comparative Production Example 6)
A water-dispersed acrylic pressure-sensitive adhesive as in Production Example 7 except that the amount of the crosslinking agent in Production Example 7 was changed to 0.4 g (0.08 parts by mass) from 0.6 g (0.03 parts by mass). A composition (H6) was produced.

[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 to 14)
Except having used the water dispersion type acrylic adhesive composition (2)-(14) obtained by manufacture example 2-14, it carried out similarly to Example 1, and obtained the double-sided adhesive tape of Examples 2-14. .

(Comparative Examples 1-6)
The double-sided pressure-sensitive adhesive tapes of Comparative Examples 1 to 6 were used in the same manner as in Example 1 except that the water-dispersed acrylic pressure-sensitive adhesive compositions (H1) to (H6) obtained in Comparative Production Examples 1 to 6 were used. Obtained.

  The following evaluation was performed about the adhesive composition and adhesive tape obtained in the said Examples 1-8 and Comparative Examples 1-6. The obtained results are shown in the table.

(Measurement of glass transition temperature of acrylic copolymer)
Using an acrylic copolymer emulsion, a sheet was prepared in accordance with the production conditions of the adhesive tape, and a test piece was prepared by superimposing the sheet to a thickness of 5 mm. Using a viscoelasticity tester (trade name: Ares 2KFRTN1 manufactured by Rheometrix Co., Ltd.), a test piece was sandwiched between parallel disks as measurement parts of the tester, and the frequency was 1 Hz and the heating rate was 2 ° C./min. The storage elastic modulus (G ′) and loss elastic modulus (G ″) from 50 ° C. to 150 ° C. were measured, and tan δ was calculated based on the following formula to obtain the glass transition temperature.

(Measurement of glass transition temperature of tackifying resin)
The tackifying resin was dried at 60 ° C. for 2 days or more under vacuum using a vacuum dryer to obtain a test sample having a dry weight of 10 mg. Using the DSC measuring device (trade name: DSC822, manufactured by Mettler Toledo Co., Ltd.), the test sample was subjected to a DSC curve twice continuously at a temperature increase rate of 2 ° C / min in a temperature range of -50 ° C to 200 ° C. And the glass transition temperature was measured from the second measurement data.

(Measurement of glass transition temperature of adhesive layer)
A pressure-sensitive adhesive layer prepared according to the production conditions for the pressure-sensitive adhesive tape was laminated to a thickness of 5 mm to prepare a test piece. Using a viscoelasticity tester (trade name: Ares 2KFRTN1 manufactured by Rheometrix Co., Ltd.), a test piece was sandwiched between parallel disks as measurement parts of the tester, and the frequency was 1 Hz and the heating rate was 2 ° C./min. The storage elastic modulus (G ′) and loss elastic modulus (G ″) from 50 ° C. to 150 ° C. were measured, and tan δ was calculated based on the following formula to obtain the glass transition temperature.
tan δ = G ″ / G ′

(Measurement of gel fraction of adhesive layer)
According to the manufacturing conditions of the said adhesive tape, it provided on the polyester film (what was peel-processed) so that the thickness after drying might be set to 25 micrometers, and prepared the test piece. The test piece was cut into a size of 20 mm × 100 mm, the polyester film was peeled off, and the weight a before toluene extraction was measured. Next, after the same test piece was immersed in toluene for 24 hours, the gel was taken out and dried at 100 ° C. for 2 hours, and the weight b after toluene extraction was measured. The gel fraction was calculated from the following formula.
Gel fraction (%) = (b / a) × 100

(Waviness / distortion test of optical film)
The black ink side of the pressure-sensitive adhesive tape (outer shape: 32 mm × 42 mm, width: 2 mm) obtained by punching the pressure-sensitive adhesive tape prepared above into a frame shape as shown in FIG. Thin optical film “BEFRP2RC” (120 μm) manufactured by 3M Co., Ltd. (external shape: 30 mm × 40 mm, external shape change rate when left in an oven at 85 ° C. for 5 minutes / flow direction: + 0.08%, width direction: − 0.08%) (FIG. 1). 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

(Repulsion resistance test)
As shown in FIG. 2, a 100 μm PET film (Unite Emblet SA # 100) and a 2 mm thick polycarbonate (PC) plate are attached with a 3 mm wide tape. Then, pressurization is performed under the condition of one reciprocation of the 2 kg roller, and the floating peeling after observing at 60 ° C. and 90% RH for 72 hours is observed. When the float of 0.5 mm or more occurs, it is not suitable for a liquid crystal module fixing tape having a severe thickness difference.
○: Floating peeling is less than 0.5 mm ×: Floating peeling is 0.5 mm or more

  As apparent from Tables 1 to 3, the adhesive tapes of the present invention of Examples 1 to 14 can suitably suppress the waviness and distortion of the optical film while using the water-based adhesive with reduced VOC, and It had good resilience resistance. On the other hand, the pressure-sensitive adhesive tape of the comparative example cannot achieve both the suppression of the undulation and distortion of the optical film and the resilience resistance.

10: Double-sided adhesive tape 11: Optical film 12: Glass 20: Adhesive tape 21: PC board 22: PET film 23: Double-sided tape

Claims (4)

An adhesive tape used for fixing an optical film,
A water-dispersed acrylic in which the pressure-sensitive adhesive layer in contact with the optical film contains an acrylic copolymer having a glass transition temperature of −45 to −25 ° C., a tackifying resin having a glass transition temperature of 30 to 120 ° C., and a crosslinking agent. The water-dispersed acrylic pressure-sensitive adhesive composition is formed by dispersing emulsion particles of the acrylic copolymer in an aqueous medium. An acrylic copolymer is obtained by polymerizing a monomer component containing 40% by mass or more of 2-ethylhexyl acrylate in a monomer component used for the production of the acrylic copolymer, and the acrylic copolymer Content of the said tackifying resin with respect to 100 mass parts of union is 10-40 mass parts,
The pressure-sensitive adhesive tape, wherein the pressure-sensitive adhesive layer has a glass transition temperature of −5 ° C. or lower and a gel fraction of 25 to 45%. The said monomer component used for manufacture of the said acrylic copolymer contains 50-98 mass% in the said monomer component which has the C4-C8 alkyl group containing the said 2-ethylhexyl acrylate in the said monomer component. The pressure-sensitive adhesive tape according to claim 1. The acrylic copolymer polymerizes a monomer component that contains 40% by mass or more of 2-ethylhexyl acrylate in the monomer component used for the production of the acrylic copolymer and a nitrogen-containing monomer having an amide group. The pressure-sensitive adhesive tape according to claim 1 or 2 , wherein the pressure-sensitive adhesive tape is obtained. Pressure-sensitive adhesive tape according to any one of claims 1 to 3, wherein the optical film is a prism sheet.

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