JP2009227826A

JP2009227826A - Double coated self-adhesive tape and image display module

Info

Publication number: JP2009227826A
Application number: JP2008075372A
Authority: JP
Inventors: Yusuke Takahashi; Daisuke Yamakawa; 大輔山川; 佑輔高橋
Original assignee: Dic Corp; Ｄｉｃ株式会社
Priority date: 2008-03-24
Filing date: 2008-03-24
Publication date: 2009-10-08

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double coated self-adhesive tape which is used when an image display panel is stuck/fixed to a surface panel on the whole surface, allows the surface panel to be hardly dropped during the use of a small-sized electronic terminal device and can allow the surface panel to be exfoliated from the image display panel without developing a defect in the image display panel when the small-sized electronic terminal device is used for a long period of time and repaired. <P>SOLUTION: The double coated self-adhesive tape has an adhesive layer for sticking/fixing the image display panel and another self-adhesive layer for sticking/fixing the surface panel so that there is a specific ratio between the adhesion of one of these self-adhesive layers and that of the other of them. Even after the small-sized electronic terminal device, which is obtained by sticking/fixing the image display panel to the surface panel on the whole surface while interposing the double coated self-adhesive tape between them, is used for a long period of time, the surface panel can be exfoliated from the side of the image display panel without developing the defect in the image display panel. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a double-sided pressure-sensitive adhesive tape used when an image display panel and a surface panel of an image display module suitably used for a small electronic terminal are adhered and fixed to the entire surface.

In recent years, small electronic terminals such as mobile phones and PHS have formed a large market and have been rapidly developed. In particular, in mobile phone terminals, multifunction, thinning, lightening, high definition, high brightness, and the like are important requirements for securing competitiveness in the market.

Increasing light transmittance is effective for increasing the brightness and definition of small electronic terminals. As an example, a touch panel configuration with a touch panel unit and a display unit corresponding to a display device, such as a liquid crystal display, is attached. It is disclosed (see Patent Document 1). The touch panel of the said structure is a touch panel which reduced the fall of the transmittance | permeability by not interposing an air layer between a touch panel part and a display part. Such a structure has begun to be adopted in a mobile phone for which thinning and high definition are remarkably required.

As a double-sided pressure-sensitive adhesive sheet used for a touch panel having such a structure, a double-sided pressure-sensitive adhesive sheet having a 180 ° peel-off adhesive strength of the touch panel side pressure-sensitive adhesive layer of 3.5 N / 20 mm or more and a display device side of 0.1 to 3.0 N / 20 mm. Is disclosed (see Patent Document 2). The double-sided pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet in which the adhesive force on the display device side is reduced, and the touch panel is once pasted and fixed on the display surface of the display device, and then easy to be pasted again. However, the double-sided pressure-sensitive adhesive sheet disclosed here can be re-applied immediately after sticking, but when peeled off after long-term use, the double-sided pressure-sensitive adhesive sheet will adhere firmly and display as a touch panel when repairing etc. When the device is peeled off, an optical film such as a polarizing film used for the surface layer of the display device may be deformed.

A pressure-sensitive adhesive composition for optical members has been disclosed (see Patent Document 3), in which adhesive strength hardly increases after storage for a long period of time, and adhesive residue does not easily occur on glass during peeling. The pressure-sensitive adhesive composition does not cause adhesive residue when it is peeled off from glass, but when used for fixing the front panel and the display device, problems similar to those of the double-sided pressure-sensitive adhesive sheet occur.

JP-A-10-222305 JP2003-238915 JP 2004-263165 A

Accordingly, an object of the present invention is a double-sided adhesive tape used for sticking and fixing an image display panel and a surface panel to the entire surface, and the surface panel is unlikely to fall off during use of a small electronic terminal, and after long-term use. It is an object of the present invention to provide a double-sided pressure-sensitive adhesive tape that can peel off a surface panel from an image display panel without causing any trouble in the image display panel during repair.

As a result of intensive studies to achieve the above-mentioned object, the present inventor fixed and fixed an image display panel as a double-sided adhesive tape used for fixing and fixing an image display panel and a surface panel of a small electronic terminal to the entire surface. The pressure-sensitive adhesive layer has a specific adhesiveness, and a pressure-sensitive adhesive layer for fixing to the surface panel is formed, and these pressure-sensitive adhesive layers have a specific ratio of adhesiveness. If the double-sided adhesive tape is used, the image display panel and the surface panel can be seen from the image display panel side even after a long period of use of a small electronic terminal in which the image display panel and the surface panel are adhered and fixed over the entire surface. The present invention has been completed by finding that it can be easily peeled off and does not cause defects in the image display panel.

That is, the present invention is a double-sided pressure-sensitive adhesive tape that fixes a surface panel and an image display panel of an image display device including an image display panel and a surface panel, and the double-sided pressure-sensitive adhesive tape is attached to the image display panel. Triacetyl cellulose having a pressure-sensitive adhesive layer and a pressure-sensitive adhesive layer attached to the front panel, and having an adhesive force on the side of the pressure-sensitive adhesive layer attached to the image display panel in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH On the other hand, using a 2 kg roller, the pressure is reduced by one reciprocation, and after leaving at rest for 1 hour, the peeling at a peeling speed of 300 mm / min is 180 ° and the adhesive strength (F _A1 ) is ₁ to 5 N / 20 mm. Yes, after pressure-bonding under the same conditions and leaving for 240 hours in an atmosphere at a temperature of 60 ° C. and a relative humidity of 90%, the 180 ° peel adhesion at a peeling speed of 300 mm / min (F _A2 ) Is 1 to 5 N / 20 mm, and the adhesive strength on the pressure-sensitive adhesive layer side to be attached to the front panel is a 2 kg roller for a smooth acrylic plate in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH. Then, the adhesive force (F _B1 ) is 180 ° peel-off adhesive force (F _B1 ) at a peeling speed of 300 mm / min after one-time reciprocation and left standing for 1 hour.
F _B1 ≧ 2F _A1 (1)
The double-sided pressure-sensitive adhesive tape is characterized by the following.

The double-sided pressure-sensitive adhesive tape of the present invention can suitably fix the image display panel and the surface panel, and the double-sided pressure-sensitive adhesive tape is separated from the image display panel and the double-sided pressure-sensitive adhesive layer when peeled after long-term use. It can be peeled off cleanly without leaving any adhesive residue. Therefore, the double-sided pressure-sensitive adhesive tape of the present invention is difficult to deform the optical film provided on the surface layer of the image display panel at the time of peeling after long-term use, and when performing repair etc., when there is no failure in the image display panel, The image display device can be repaired at low cost without requiring replacement of an expensive image display panel.

The double-sided pressure-sensitive adhesive tape of the present invention is a double-sided pressure-sensitive adhesive tape that fixes a surface panel and an image display panel of an image display device including an image display panel and a surface panel, and displays an image as an adhesive layer provided on each surface. It has the adhesive layer stuck on a panel, and the adhesive layer stuck on a surface panel. The adhesive layer attached to the image display panel has a 180 ° peel adhesive strength (F _A1 ) of ₁ to 5 N / 20 mm (temperature 23 ° C., relative humidity 50% RH) with respect to triacetyl cellulose. Using a 2 kg roller, the pressure is applied by one reciprocation, and after leaving for 1 hour, the adhesive is peeled at 180 ° at a peeling speed of 300 mm / min. The same adhesive force (F _A2 ) after standing for 240 hours in an atmosphere of 90% humidity is 1 to 5 N / 20 mm. Also, 180 ° peel adhesive strength (F _B1 ) on the pressure-sensitive adhesive layer side to be attached to the front panel (temperature 23 ° C., relative humidity 50% RH) using a 2 kg roller against a smooth acrylic plate The number of times of pressure bonding is one reciprocation, and after leaving at rest for 1 hour, 180 ° peeling adhesive force at a peeling speed of 300 mm / min) is expressed by the formula (1)
F _B1 ≧ 2F _A1 (1)
It has the adhesive force represented by.

[Adhesive layer affixed to the image display panel]
As an adhesive which forms the adhesive layer stuck on an image display panel, what has transparency of the grade which does not reduce the visibility of an image display apparatus can be used preferably. For example, known acrylic, rubber-based, vinyl ether-based, and silicone-based pressure-sensitive adhesives can be used, and among them, acrylic pressure-sensitive adhesives are preferable. In particular, an acrylic copolymer containing a (meth) acrylic acid ester having an alkyl group having 2 to 14 carbon atoms as a monomer component is preferable. For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) Examples thereof include acrylate and n-lauryl (meth) acrylate, which can be used alone or in combination of two or more. Among these, n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, or a monomer using them in combination is preferably a main component, and the amount used is in the monomer component constituting the acrylic copolymer. It is preferable that it is 50-99 mass%, and it is more preferable that it is 85-99 mass%. By using the above-mentioned types and amounts as the main monomer, it becomes easy to adjust the adhesive strength to a low range.

Furthermore, a vinyl monomer having a functional group such as a hydroxyl group, a carboxyl group or an amino group in the side chain is added in a range of 0.01 to 15% by mass in the monomer component constituting the acrylic copolymer. Is preferred. For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, crotonic acid, fumaric acid , Carboxypropyl acrylate maleate, dimethylaminoethyl acrylamide, N-vinyl pyrrolidone, acrylonitrile, N-vinyl caprolactam, acrylamide, styrene, vinyl acetate, N-methylol acrylamide, glycidyl methacrylate, etc. The above can be used in combination. Among these, it is preferable to use a vinyl monomer containing a carboxyl group, more preferably acrylic acid, methacrylic acid, or a monomer using a combination thereof, and the amount used is acrylic. It is preferable that it is 0.1-1.0 mass% in the monomer component which comprises a copolymer. By using the above-mentioned types and amounts of the carboxyl group-containing monomer, it becomes easy to reduce the rate of increase in adhesive strength over time.

The acrylic copolymer can be obtained by copolymerization by a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, an ultraviolet irradiation method, or an electron beam irradiation method.

Weight average molecular weight measured by standard polystyrene conversion measured by gel permeation chromatography (GPC) of acrylic copolymer (gel permeation chromatography, SC-8020 manufactured by Tosoh Corporation, high molecular weight column TSKgelGMHHR-H, The solvent (tetrahydrofuran) is preferably 1 million to 2 million, and more preferably 1.3 to 1.8 million. By adjusting the molecular weight to the above range, it becomes easy to adjust the adhesive strength to a low range, and excellent in heat resistance, weather resistance, and moisture resistance.

Moreover, in order to raise the cohesion force of an adhesive layer, it is preferable to add a crosslinking agent. Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, a chelate crosslinking agent, and an aziridine crosslinking agent. The amount of the crosslinking agent added is preferably such that the gel fraction of the pressure-sensitive adhesive layer is 50 to 95%. A more preferable gel fraction is 70 to 90%. The gel fraction is expressed as a percentage with respect to the original mass by immersing the cured adhesive layer in toluene, measuring the mass after drying of the insoluble matter left after standing for 24 hours, and measuring the mass.

Further, in order to adjust the adhesive strength of the pressure-sensitive adhesive layer, a tackifier resin may be added within a range where the transparency is not lowered, specifically, within a range where the total light transmittance does not fall below 85%. The tackifier resin to be added to the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of the present invention is a rosin resin such as rosin or an esterified product of rosin; a terpene resin such as a diterpene polymer or an α-pinene-phenol copolymer; (C5-based) and aromatic (C9-based) petroleum resins; other examples include styrene-based resins, phenol-based resins, and xylene resins. In consideration of transparency, in order to make the b * value of the pressure-sensitive adhesive layer after standing at 100 ° C. for 14 days (the higher the yellowness is, the stronger the yellowishness), the hydrogenated rosin or the unevenness with less unsaturated double bonds. It is preferable to add an esterified rosin, an aliphatic or aromatic petroleum resin, a high Tg acrylic resin, or the like to the pressure-sensitive adhesive layer. As addition amount of tackifying resin, when an adhesive resin is an acrylic copolymer, it is preferable to add 1-10 mass parts with respect to 100 mass parts of acrylic copolymers.

In addition to the above, known and commonly used additives can be added to the pressure-sensitive adhesive used in the double-sided pressure-sensitive adhesive tape of the present invention. For example, plasticizers, softeners, fillers, pigments, flame retardants and the like can be added.

The adhesive layer attached to the image display panel preferably has a storage elastic modulus of 5.0 × 10 ⁴ Pa or more at 80 ° C. at a frequency of 1 Hz from the viewpoint of heat resistance and durability. Further, the pressure-sensitive adhesive layer preferably has a temperature showing a convex peak of its loss tangent curve at a frequency of 1 Hz, preferably −50 ° C. to −10 ° C., more preferably −40 ° C. to −20 ° C. . By adjusting the convex peak of the loss tangent curve within this range, it is possible to maintain the adhesiveness to the impact when the small portable terminal is dropped.

The dynamic viscoelasticity of the pressure-sensitive adhesive layer in the present invention is obtained by sandwiching a test piece between parallel disks, which are measuring parts of the tester, using a viscoelasticity tester (manufactured by Rheometrics, trade name: Ares 2KSTD). Then, the storage elastic modulus (G ′) and the loss elastic modulus (G ″) at a frequency of 1 Hz are measured, and the loss tangent is calculated by an expression represented by 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, the thickness of the pressure-sensitive adhesive alone is adjusted to be in the above range. When the thickness of the pressure-sensitive adhesive is adjusted to the above range, the dynamic viscoelastic spectrum of the pressure-sensitive adhesive can be measured in the same manner as when there is no base material even if the base material is sandwiched between them.

The thickness of the pressure-sensitive adhesive layer attached to the image display panel is preferably 1 to 50 μm, and more preferably 10 to 30 μm. If it is 10 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 or the like that is becoming lighter and thinner.

Moreover, it is preferable that the adhesive layer stuck on an image display panel has high transparency. For example, the total light transmittance (JIS K 7361) is preferably 85% or more, more preferably 90% or more, and still more preferably 95% or more.

[Adhesive layer affixed to the front panel]
As the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer applied to the front panel, a known acrylic, rubber-based, or silicone-based pressure-sensitive adhesive resin should be used in the same manner as the pressure-sensitive adhesive layer applied to the image display panel. Can do. Among them, a pressure-sensitive adhesive containing an acrylic copolymer containing a repeating unit derived from an acrylate ester having an alkyl group having 2 to 14 carbon atoms as a repeating unit is in view of light resistance, heat resistance, and cost. preferable.

As the monomer component used for the acrylic copolymer, the same monomer component as that of the pressure-sensitive adhesive layer attached to the image display panel can be used. Especially, it is preferable to make n-butyl acrylate into a main component, and it is preferable that the usage-amount is 50-99 mass% in the monomer component which comprises an acrylic copolymer, and is 80-90 mass%. More preferably. By using the above-mentioned types and amounts as the main monomer, the durability is excellent.

Furthermore, a vinyl monomer having a functional group such as a hydroxyl group, a carboxyl group or an amino group in the side chain is added in a range of 0.01 to 15% by mass in the monomer component constituting the acrylic copolymer. Is preferred. As these vinyl monomers, the same monomers as those used for the pressure-sensitive adhesive layer attached to the image display panel can be used. Especially, it is preferable to use the vinyl-type monomer containing a carboxyl group, It is more preferable to use the monomer which used acrylic acid, methacrylic acid, or it together, Furthermore, the usage-amount is 1. It is preferable that it is 0-5.0 mass%. As the carboxyl group-containing monomer, it is easy to adjust the adhesive strength within a high range by using the above-mentioned types and amounts. Two or more kinds of acrylic copolymers may be mixed and used.

The weight average molecular weight measured in terms of standard polystyrene measured by gel permeation chromatograph (GPC) of the acrylic copolymer is preferably 800,000 to 1,500,000, more preferably 1,000,000 to 1,200,000. By adjusting the molecular weight to the above range, durability is excellent and it is easy to adjust the adhesive strength to a high range.

Moreover, in order to raise the cohesion force of an adhesive layer, it is preferable to add a crosslinking agent. As the cross-linking agent, the same cross-linking agent as the pressure-sensitive adhesive layer attached to the image display panel can be used. The amount of the crosslinking agent added is preferably such that the gel fraction of the pressure-sensitive adhesive layer is 25 to 95%. A more preferable gel fraction is 50 to 90%.

Furthermore, in order to improve the adhesive strength of the pressure-sensitive adhesive layer, the same as the pressure-sensitive adhesive layer applied to the image display panel as long as the transparency is not lowered, specifically, the total light transmittance does not fall below 85%. The tackifying resin may be added. As addition amount of tackifying resin, when an adhesive resin is an acrylic copolymer, it is preferable to add 5-60 mass parts with respect to 100 mass parts of acrylic copolymers.

In addition, in the adhesive used for the adhesive layer attached to the front panel, addition of a plasticizer, a softener, a filler, a pigment, a flame retardant, etc., similar to the adhesive layer attached to the image display panel. An agent may be added.

The pressure-sensitive adhesive layer attached to the front panel preferably has a convex peak of the loss tangent curve at a frequency of 1 Hz, preferably −50 ° C. to −10 ° C., and −40 ° C. to −20 ° C. Is more preferable. By adjusting the convex peak of the loss tangent curve within this range, it becomes easy to ensure adhesion to the impact when the small portable terminal is dropped.

The adhesive layer preferably has a storage elastic modulus of 5.0 × 10 ⁴ Pa or more at 80 ° C. at a frequency of 1 Hz from the viewpoint of foam resistance.

As for the thickness of the adhesive layer affixed on a surface panel, 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 or the like that is becoming lighter and thinner.

Moreover, it is preferable that the adhesive layer stuck on the front panel also has high transparency, for example, the total light transmittance (JIS K 7361) is preferably 85% or more, and 90% or more. Is more preferably 95% or more.

[Double-sided adhesive tape]
The double-sided pressure-sensitive adhesive tape of the present invention is used for fixing the front panel and the image display panel of the image display module, and has a pressure-sensitive adhesive layer attached to the image display panel and a pressure-sensitive adhesive layer attached to the surface panel. .

The adhesive strength on the side of the pressure-sensitive adhesive layer applied to the image display panel of the double-sided pressure-sensitive adhesive tape of the present invention is a 180 ° peel-off adhesive strength (F _A1 ) is ₁ to 5 N / 20 mm, and after sticking, it is left for 240 hours in an atmosphere with a temperature of 60 ° C. and a relative humidity of 90%, and then 180 ° peel adhesion (F _A2 ) is 1 to 5 N / 20 mm. Double-sided adhesive tape.

Also, the adhesive force on the pressure-sensitive adhesive layer side applied to the front panel of the double-sided pressure-sensitive adhesive tape of the present invention is a 180 ° peel-off adhesive force after leaving a smooth acrylic plate to be attached and left for 1 hour after application ( F _B1 ) is the formula (1)
F _B1 ≧ 2F _A1 (1)
It has the adhesive force represented by.
In the measurement of the adhesive force, the sticking to the object to be attached is a sticking by one-time reciprocation using a 2 kg roller in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH, The peeling speed at the time of peeling is 300 mm / min.

According to the double-sided pressure-sensitive adhesive tape of the present invention, the image display panel and the front panel can be suitably fixed by the configuration, and the double-sided pressure-sensitive adhesive tape is used as an image display of the image display panel and the double-sided pressure-sensitive adhesive tape when peeling after long-term use. It can be peeled off cleanly without leaving adhesive residue from the interface of the side pressure-sensitive adhesive layer. Therefore, the double-sided pressure-sensitive adhesive tape of the present invention is difficult to deform the optical film provided on the surface layer of the image display panel at the time of peeling after long-term use, and when performing repair etc., when there is no failure in the image display panel, The image display device can be repaired at low cost without requiring replacement of an expensive image display panel.

The adhesive strength of the pressure-sensitive adhesive layer attached to the image display panel by peeling off by 180 ° is the adhesive strength after standing for 1 hour after application to the triacetyl cellulose film, and after application, the temperature is 60 ° C. and the relative humidity is 90 °. It is particularly preferable from the viewpoints of durability and adhesion reliability that the adhesive strength after standing for 240 hours in a% atmosphere is 3 to 5 N / 20 mm.

Further, the relational expression between the 180 ° peel adhesive strength (F _A1 ) of the pressure-sensitive adhesive layer attached to the image display panel and the 180 ° peel adhesive strength (F _B1 ) of the pressure sensitive adhesive layer attached to the display panel is 7F _A1 ≧ F _B1 ≧ 2.5F _A1 is preferable.

The adhesive strength of each pressure-sensitive adhesive layer may be adjusted as appropriate within the preferred range of the pressure-sensitive adhesive used for each pressure-sensitive adhesive layer. For example, the adhesive strength is adjusted by the acrylic monomer or gel fraction used for the pressure-sensitive adhesive. Easy to do. For example, the adhesive force can be easily increased by increasing the content of the carboxyl group-containing monomer. Further, the adhesive strength can be adjusted by adjusting the thickness of the pressure-sensitive adhesive layer and the thickness of the base material. When the pressure-sensitive adhesive layer is thickened, the adhesive strength is easily increased.

In addition, when providing a difference in adhesive force between the pressure-sensitive adhesive layer attached to the image display panel and the pressure-sensitive adhesive layer attached to the front panel, the gel fraction of the pressure-sensitive adhesive layer attached to the image display panel is determined by By making it higher than the panel side or making the molecular weight of the acrylic copolymer used for the pressure-sensitive adhesive layer attached to the image display panel larger than that of the surface panel side, it becomes easy to provide a difference in adhesive strength between the two layers. When pressure-sensitive adhesives having the same composition are used for both pressure-sensitive adhesive layers, it is preferable to provide a difference in adhesive strength by these methods. Moreover, by making the thickness of the pressure-sensitive adhesive layer to be attached to the image display panel thinner than the display panel side, it becomes easy to provide a difference in adhesive strength between the two layers.

The adhesive strength of the pressure-sensitive adhesive layer applied to the image display panel is within the above range, and the adhesive layer applied to the image display panel is peeled off by 180 ° (F _A1 ) and the adhesive applied to the display panel. When the double-sided pressure-sensitive adhesive tape represented by the above relational expression is 180 ° peeling adhesive strength (F _B1 ) of the agent layer, when the surface panel is peeled from the image display panel together with the double-sided pressure-sensitive adhesive tape, Further, it can be easily peeled off and can be peeled without causing defects such as distortion, peeling and cracking in optical members such as polarizing plates and retardation plates of the image display panel.

The double-sided pressure-sensitive adhesive tape of the present invention preferably has high transparency. For example, the total light transmittance (conforming to JIS K 7361) is 85% or more (preferably 90% or more, more preferably 95%). It is desirable that Further, the haze (based on JIS K 7136) is preferably 2.0% or less, more preferably 1.0% or less.

The double-sided pressure-sensitive adhesive tape of the present invention may have a structure (FIG. 1) in which the respective pressure-sensitive adhesive layers are directly laminated or a structure having a base material (FIG. 2). A double-sided pressure-sensitive adhesive tape having no base material is preferable because it can contribute to a reduction in thickness, and a double-sided pressure-sensitive adhesive tape provided with a transparent base material is preferable because of excellent punching workability when cutting into a predetermined size. In the case of having a substrate, the adhesive layer to be attached to the image display panel and the adhesive layer to be attached to the image display panel may be provided on each surface of the transparent substrate. preferable.

Examples of the transparent substrate include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, diacetyl cellulose film, triacetyl cellulose film, acetyl cellulose butyrate film, polyvinyl chloride film, and polyvinylidene chloride. Film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, polymethylpentene film, polysulfone film, polyetheretherketone film, polyethersulfone film, polyetherimide film, polyimide film, fluorine resin Film, nylon film, acrylic resin film, etc. Nene resin film (JSR Corporation, trade name: ARTON), cyclic olefin polymer (Co. Optes trade name: ZEONOR film), and a plastic material such as is. Plastic materials can be used alone or in combination of two or more. Accordingly, a film or sheet made of these plastic materials (sometimes collectively referred to as “plastic film”) is used as the transparent substrate. Among the plastic films, a plastic film having high transparency (total light transmittance of 85% or more) can be preferably used.

In addition, for the purpose of improving the adhesiveness with the pressure-sensitive adhesive layer, the film substrate is subjected to surface unevenness treatment by sandblasting method or solvent treatment method, or corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, Surface treatment such as surface oxidation treatment such as ozone / ultraviolet irradiation treatment can be performed.

Moreover, an antistatic agent can be added to a base material as other compounding materials, and an antistatic function can be provided. Nonionic polyoxyethylene alkyl ether, polyoxyethylene alkylphenol, polyoxyethylene alkylamine, polyoxyethylene alkylamide, fatty acid polyethylene glycol ester, fatty acid sorbitan ester, polyoxyethylene fatty acid sorbitan ester, fatty acid glycerin ester, alkyl polyethyleneimine, etc. Can be mentioned. Examples of the cationic system include alkylamine salts, alkyl quaternary ammonium salts, and alkyl imidazoline derivatives. An acrylate compound having ethylene oxide as a skeleton can also be used. Polyaniline, polypyrrole, polythiophene, poly3,4-ethylenedioxythiophene, and derivatives thereof can be used as the conductive polymer. As the metal oxide, antimony-doped tin oxide (ATO), tin-doped indium oxide (ITO), aluminum-doped zinc oxide, antimony suboxide, or the like can be used. In addition, an ion conduction type antistatic agent in which metal ions such as lithium ions are mixed can also be used.

About the thickness of a transparent base material, it does not specifically limit, For example, it can select from the range of about 2-150 micrometers. From the viewpoint of imparting workability and thinness of the double-sided pressure-sensitive adhesive tape, the transparent substrate is preferably 25 to 150 μm.

The pressure-sensitive adhesive tape of the present invention can be prepared by a generally used method. For example, it can be produced by forming an adhesive layer on a film substrate or a release sheet. Specifically, the pressure-sensitive adhesive composition is directly applied to the base film and dried or cured / polymerized, or once coated on the release sheet and dried / cured / polymerized to form a pressure-sensitive adhesive layer. Similarly, it can be produced by a method of bonding to an adhesive layer or a base film prepared on a release sheet.

Application of the adhesive to the transparent substrate or release sheet is performed using a conventional coater such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, etc. be able to.

The thickness of the double-sided pressure-sensitive adhesive tape of the present invention is preferably 10 to 200 μm, and more preferably 20 to 100 μm. Those having a thickness in the range can be suitably applied to display devices and the like that are becoming lighter and thinner.

[Image display module]
The image display module of the present invention has at least a front panel and an image display panel in its configuration. Then, the front panel and the image display panel are image display modules having a configuration in which the entire surface is attached via a double-sided adhesive tape, and the double-sided adhesive tape of the present invention can be suitably applied to the entire surface.

<Surface panel>
The surface panel used for the image display module differs depending on the type and application of the small electronic terminal, but a surface panel made of a transparent plate generally used for the image display module and a touch panel can be used.

As the surface panel made of a transparent plate, an acrylic plate, a polycarbonate plate, or a tempered glass plate is usually used. Acrylic plates and polycarbonate plates are flexible, and therefore are less likely to cause cracking due to impact, and even if cracking occurs due to impact, there is little risk of debris scattering, so that they can be preferably used from the viewpoint of impact resistance. On the other hand, a tempered glass plate is preferably used because it has high hardness and is excellent in scratch resistance even when it is thinned.

The thickness is preferably 0.2 mm to 3 mm, and particularly preferably 0.3 mm to 2 mm.

The surface panel may be a surface panel made of only a transparent plate, but may be one in which the transparent plate is decorated or processed by printing or vapor deposition. When the image display module is used for a mobile phone, etc., it is printed in a frame shape on a transparent panel as shown in FIG. 4 or on a transparent panel as shown in FIG. And a surface panel in which a step formed by printing is filled with a transparent printed layer is preferably used.

According to the surface panel having a printing layer on a part of the surface of the transparent plate and the side having the printing layer on the side in contact with the pressure-sensitive adhesive layer, the portion other than the image display unit can be decorated with the printing layer. This is preferable because it is possible.

The printing layer is preferably a multicolor printing layer formed by screen printing for imparting design properties to the front panel. Moreover, when the material of the transparent plate which provides a printing layer is glass, in order to raise the adhesiveness of the said printing layer, the glass which provided the primer layer can be used preferably.

Moreover, you may use the surface panel by which the film which improves the visibility of the image displayed, such as a scattering prevention adhesive film, an antireflection film, and an anti-glare film, was stuck to the surface of the transparent plate.

As the film provided on the surface of the transparent plate, the surface panel having the structure of FIG. 5 provided with the surface protective film can prevent the transparent plate from being damaged or cracked, and can also prevent scattering of fragments even when the crack occurs. preferable.

As such a surface protective film, the thing of the structure by which the adhesive layer was provided in the hard coat film which consists of a resin film which has a hard coat layer can be used preferably.

The surface protective film preferably has a total thickness of 150 μm or less, and particularly preferably a total thickness of 60 to 150 μm, from the viewpoint of appearance and the problem of peeling due to catching of the edge portion. Moreover, in order to have suitable surface protection characteristics at the thickness, the elastic modulus of the resin film is 3 to 7 GPa, the thickness is 38 to 100 μm, the thickness of the hard coat layer is 5 to 25 μm, The pencil hardness on the hard coat layer surface of the coat film is preferably 3H or more, and the thickness of the pressure-sensitive adhesive layer is preferably 5 to 20 μm.

The front panel may be a touch panel type front panel. Examples of the touch panel type surface panel include a surface panel in which a transparent conductive film such as conductive polyethylene terephthalate or conductive glass as shown in FIG. 6 is fixed via a frame-shaped adhesive layer or silver paste. Moreover, the surface panel etc. which combined the said touch panel type surface panel and the surface panel which consists of the above transparent plates can be used.

<Image display panel>
As the image display panel used in the image display module of the present invention, an LCD module or an organic EL panel having an optical film or the like on a surface used in a general image display device can be used, and the LCD module is easily available. Can be preferably used.

The double-sided pressure-sensitive adhesive tape of the present invention can be particularly suitably applied when the surface of the image display module is soft such as an optical film or easily stretched. Examples of the optical film include various optical films such as a polarizing film, a retardation film, and a light transmissive film for protecting these surfaces.

<Image display module>
The image display module of the present invention has at least the above surface panel and the image display panel in its configuration. And the surface display panel and the image display panel are the image display modules of the structure which affixed the whole surface via the double-sided adhesive tape.

Since the image display module of the present invention does not have a gap at the bottom of the front panel, the image display module is suitable for thinning. The image display module of the present invention can be suitably used when the thickness is small, and the total thickness of the image display module is preferably 1 mm to 5 mm, and particularly preferably 1.5 mm to 2 mm.

The image display module of this invention can be manufactured by sticking the whole surface of a transparent surface panel and an image display panel through a double-sided adhesive tape.
The affixing step is a step of adhering the double-sided adhesive tape to either the front panel or the image display panel, and then affixing the two. In this step, a vacuum is used to reduce air bubble mixing during affixing. It is preferable to use a pasting device. By using the vacuum bonding apparatus, even if two rigid panels are bonded with a double-sided adhesive tape, such as a front panel and an image display panel, bubbles are less likely to be mixed.

Since the image display module of the present invention is a module suitable for thinning, a mobile information terminal such as a mobile phone, a PDA (Personal Digital Assistant), an electronic dictionary, a digital music player, a digital video player, a portable game device, The present invention can be suitably applied to various small electronic terminals such as portable GPS, cameras, video handheld PCs, and small electronic terminals such as portable electronic terminals.

<Embodiment>
Representative examples of the configuration of the image display module of the present invention are shown in FIGS. The configuration of FIG. 7 is a configuration in which an image display panel and a front panel are adhered to the entire surface with the double-sided adhesive tape. In the said structure, a display image can be visually recognized through the said surface panel from the surface panel side provided in the outermost layer. Further, the configuration of FIG. 8 is a configuration in which a surface panel in which a touch panel type panel and a panel made of a transparent plate are integrated with a double-sided adhesive tape or the like is adhered to the entire surface of the image display module with the double-sided adhesive tape. In the said structure, a display image can be visually recognized through the said surface panel from the surface panel side provided in the outermost layer.

As an image display module using a touch panel type display panel, as shown in FIG. 9, a touch panel having a configuration (F / F type) composed of two transparent conductive plastic films in which conductive layer forming surfaces are arranged to face each other. Or a touch panel (F / G type) composed of a transparent conductive plastic film (such as conductive PET) and conductive glass as shown in FIG. 10 and conductive layer forming surfaces as shown in FIG. An image display module having a configuration (F / F / P type) composed of two transparent conductive plastic films (conductive PET or the like) and a transparent substrate, which are opposed to each other, can be exemplified.

Other components may be added to the image display module of the present invention as necessary. For example, a flexible printed circuit (FPC) board or the like is provided in the lower layer of the image display panel in FIGS. It may be a configured. When the image display module is a backlight type image display module, the backlight module is added to the structure of FIGS.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these.

<Acrylic copolymer (a)>
Preparation of acrylic copolymer In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 93.8 parts by weight of n-butyl acrylate, 5 parts by weight of benzyl acrylate, 4-hydroxybutyl acrylate 1 part by weight, 0.2 part by weight of acrylic acid and 0.2 part of 2,2′-azobisisobutyronitrile as a polymerization initiator are dissolved in 70 parts by weight of ethyl acetate, and the temperature is raised to 60 ° C. after substitution with nitrogen. The reaction was allowed to proceed for 3 hours after warming. Thereafter, while adding 20 parts by weight of ethyl acetate dropwise over 50 minutes, 0.2 part by weight of perhexyl PV was added, the temperature was raised to 80 ° C., and the reaction was performed for 5 hours. After completion of the reaction, the reaction mixture was diluted with ethyl acetate to obtain an acrylic copolymer (a) having a resin solid content of 15% and a weight average molecular weight of 1.8 million.

<Acrylic copolymer (b)>
Preparation of acrylic copolymer In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 96.5 parts by weight of n-butyl acrylate, 0.5 parts by weight of 2-hydroxyethyl acrylate, 3 parts by weight of acrylic acid and 0.2 part of 2,2′-azobisisobutyronitrile as a polymerization initiator were dissolved in 100 parts by weight of ethyl acetate, and after nitrogen substitution, a polymerization reaction was carried out at 80 ° C. for 8 hours. After completion of the reaction, the mixture was diluted with ethyl acetate to obtain an acrylic copolymer (b) having a resin solid content of 45% and a weight average molecular weight of 800,000.

<Acrylic copolymer (c)>
Preparation of acrylic copolymer In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 98.8 parts by weight of n-butyl acrylate, 1 part by weight of 4-hydroxybutyl acrylate, acrylic acid 0.2 parts by weight and 0.2 part of 2,2′-azobisisobutyronitrile as a polymerization initiator were dissolved in 70 parts by weight of ethyl acetate, and after nitrogen replacement, the temperature was raised to 60 ° C. Reacted for hours. Thereafter, 20 parts by weight of ethyl acetate was added dropwise over 50 minutes, 0.2 part by weight of perhexyl PV was added 30 minutes after the start of the addition, the temperature was raised to 80 ° C., and the mixture was reacted for 30 minutes. Next, 0.3 part by weight of perhexyl PV was added and reacted for 40 minutes, and further 1 part by weight of perhexyl PV was added and reacted for 3 hours. After completion of the reaction, the reaction mixture was diluted with ethyl acetate to obtain an acrylic copolymer (c) having a resin solid content of 15% and a weight average molecular weight of 1,640,000.

<Acrylic copolymer (d)>
Preparation of acrylic copolymer In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 95 parts by weight of isooctyl acrylate, 5 parts by weight of acrylic acid and 2,2 ′ as a polymerization initiator -0.2 part of azobisisobutyronitrile was dissolved in 100 parts by weight of ethyl acetate, and after substitution with nitrogen, the temperature was raised to 60 ° C and reacted for 10 hours. After completion of the reaction, the mixture was diluted with ethyl acetate to obtain an acrylic copolymer (d) having a resin solid content of 30% and a weight average molecular weight of 900,000.

<Acrylic copolymer (e)>
Preparation of acrylic copolymer Polymerized with 60 parts by weight of ethyl acrylate, 35 parts by weight of n-butyl acrylate and 5 parts by weight of acrylic acid in a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet. As an initiator, 0.2 part of 2,2′-azobisisobutyronitrile was dissolved in 100 parts by weight of ethyl acetate, purged with nitrogen, heated to 60 ° C., and reacted for 10 hours. After completion of the reaction, the reaction mixture was diluted with ethyl acetate to obtain an acrylic copolymer (e) having a resin solid content of 30% and a weight average molecular weight of 800,000.

<Acrylic copolymer (f)>
Preparation of acrylic copolymer In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 86.3 parts by weight of n-butyl acrylate, 10 parts by weight of benzyl acrylate, 2-hydroxyethyl acrylate 3.5 parts by weight, 0.2 part by weight of acrylic acid and 0.2 part of 2,2′-azobisisobutyronitrile as a polymerization initiator were dissolved in 125 parts by weight of ethyl acetate, and after substitution with nitrogen, 60 ° C. And then reacted for 1.5 hours. Thereafter, 20 parts by weight of ethyl acetate was added dropwise over 50 minutes, 0.2 part by weight of perhexyl PV was added 30 minutes after the start of the addition, the temperature was raised to 80 ° C., and the mixture was reacted for 30 minutes. Next, 0.3 part by weight of perhexyl PV was added and reacted for 40 minutes, and further 1 part by weight of perhexyl PV was added and reacted for 3 hours. After completion of the reaction, the reaction mixture was diluted with ethyl acetate to obtain an acrylic copolymer (f) having a resin solid content of 15% and a weight average molecular weight of 1,000,000.

<Adhesive (A)>
0.23 parts by weight of an isocyanate-based crosslinking agent (TD-75 manufactured by Soken Chemical Co., Ltd., solid content: 75%) is added to 100 parts by weight of the acrylic copolymer (a), and the mixture is stirred with a stirrer for 20 minutes. (A) was obtained.

<Adhesive (B)>
0.7 parts by weight of an isocyanate-based crosslinking agent (Coronate L-45 manufactured by Nippon Polyurethane Co., Ltd., solid content: 45%) is added to 100 parts by weight of the acrylic copolymer (b), and the mixture is stirred with a stirrer for 20 minutes. Agent (B) was obtained.

<Adhesive (C)>
0.23 parts by weight of an isocyanate-based crosslinking agent (TD-75 manufactured by Soken Chemical Co., Ltd., solid content: 75%) is added to the acrylic copolymer (c) / 100 parts by weight, and the mixture is stirred with a stirrer for 20 minutes to give an adhesive. (C) was obtained.

<Adhesive (D)>
To the acrylic copolymer (d) / 100 parts by weight, 1.5 parts by weight of glycerin diglycidyl ether was added and stirred with a stirrer for 20 minutes to obtain an adhesive (D).

<Adhesive (E)>
To the acrylic copolymer (e) / 100 parts by weight, 0.5 part by weight of glycerin diglycidyl ether was added and stirred with a stirrer for 20 minutes to obtain an adhesive (E).

<Adhesive (F)>
0.23 parts by weight of an isocyanate-based crosslinking agent (TD-75 manufactured by Soken Chemical Co., Ltd., solid content 75%) and a silane coupling agent (A manufactured by Soken Chemical Co., Ltd.) per 100 parts by weight of the acrylic copolymer (a). −50) was added and stirred with a stirrer for 20 minutes to obtain a pressure-sensitive adhesive (F).

<Adhesive (G)>
0.2 parts by weight of an isocyanate-based crosslinking agent (TD-75 manufactured by Soken Chemical Co., Ltd., solid content: 75%) and a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd.) per 100 parts by weight of the acrylic copolymer (f). 0.06 part by weight of KBE-9007) was added and stirred with a stirrer for 20 minutes to obtain a pressure-sensitive adhesive (G).

Example 1
As the pressure sensitive adhesive for the image display panel side pressure sensitive adhesive layer, the pressure sensitive adhesive (A) is coated on a polyester film (hereinafter, peeled film) whose one side is peeled with a silicone compound so that the thickness after drying is 25 μm. And dried at 75 ° C. for 5 minutes. Next, the pressure-sensitive adhesive (B) was applied as a pressure-sensitive adhesive on the front panel side pressure-sensitive adhesive layer onto the release film so that the thickness after drying was 25 μm, and dried at 75 ° C. for 5 minutes. These were bonded to both sides of a 50 μm polyester film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.). Thereafter, aging was performed at 23 ° C. for 5 days to obtain an adhesive tape having a total thickness of 100 μm. The obtained adhesive tape had a total light transmittance of 91.1%.

Further, the pressure-sensitive adhesive (A) was coated on the release film so that the thickness after drying was 25 μm, and dried at 75 ° C. for 5 minutes. The obtained pressure-sensitive adhesive layer was laminated to prepare a pressure-sensitive adhesive layer having a thickness of 2 mm, and the dynamic viscoelasticity was measured with a viscoelasticity tester. As a result, the temperature showing the convex peak of the loss tangent curve of the pressure-sensitive adhesive (A) was −31 ° C., and the storage elastic modulus G ′ at 80 ° C. was 1.4 × 10 ⁵ Pa. When the dynamic viscoelasticity of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive (B) was measured in the same manner as the pressure-sensitive adhesive (A), the temperature showing the convex peak of the loss tangent curve of the pressure-sensitive adhesive (B) was −30 ° C. and 80 The storage elastic modulus G ′ at 1.3 ° C. was 1.3 × 10 ⁵ Pa.

(Example 2)
The pressure-sensitive adhesive (A) was applied as a pressure-sensitive adhesive for the image display panel side pressure-sensitive adhesive layer on the release film so that the thickness after drying was 25 μm, and dried at 75 ° C. for 5 minutes. Next, the pressure-sensitive adhesive (B) was applied as a pressure-sensitive adhesive on the front panel side pressure-sensitive adhesive layer onto the release film so that the thickness after drying was 25 μm, and dried at 75 ° C. for 5 minutes. These were bonded to both sides of a 100 μm cyclic olefin film (Zeonor film ZF-14 manufactured by Optes Co., Ltd.). Thereafter, aging was performed at 23 ° C. for 5 days to obtain an adhesive tape having a total thickness of 150 μm. The obtained adhesive tape had a total light transmittance of 90.5%.

(Example 3)
The pressure-sensitive adhesive (A) was applied as a pressure-sensitive adhesive on the image display panel on the release film so that the thickness after drying was 15 μm, and dried at 75 ° C. for 5 minutes. Next, the pressure-sensitive adhesive (B) is applied as a pressure-sensitive adhesive on the surface panel-side pressure-sensitive adhesive layer on the release film so that the thickness after drying is 50 μm, and dried at 75 ° C. for 5 minutes. did. These were bonded to both sides of a 75 μm polyester film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.). Thereafter, aging was performed at 23 ° C. for 5 days to obtain an adhesive tape having a total thickness of 140 μm. The obtained adhesive tape had a total light transmittance of 90.7%.

Example 4
The pressure-sensitive adhesive (C) was applied as a pressure-sensitive adhesive for the image display panel side pressure-sensitive adhesive layer on the release film so that the thickness after drying was 25 μm, and dried at 75 ° C. for 5 minutes. Next, the pressure-sensitive adhesive (B) was applied as a pressure-sensitive adhesive on the front panel side pressure-sensitive adhesive layer onto the release film so that the thickness after drying was 25 μm, and dried at 75 ° C. for 5 minutes. These were bonded to both sides of a 50 μm polyester film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.). Thereafter, aging was performed at 23 ° C. for 5 days to obtain an adhesive tape having a total thickness of 100 μm. The obtained adhesive tape had a total light transmittance of 91.0%.

Moreover, when the dynamic viscoelasticity of the said adhesive (C) was measured like Example 1, the temperature which shows the convex peak of the loss tangent curve of the adhesive layer of an adhesive (c) is -30 degreeC, and 80 The storage elastic modulus G ′ at 1.3 ° C. was 1.3 × 10 ⁵ Pa.

(Comparative Example 1)
The pressure-sensitive adhesive (D) was applied as a pressure-sensitive adhesive for the image display panel side pressure-sensitive adhesive layer on the release film so that the thickness after drying was 20 μm, and dried at 75 ° C. for 5 minutes. Next, the pressure-sensitive adhesive (E) was applied as a pressure-sensitive adhesive on the front panel side pressure-sensitive adhesive layer on the release film so that the thickness after drying was 20 μm, and dried at 75 ° C. for 5 minutes. These were bonded to both sides of a 12 μm polyester film (Lumirror S-10 manufactured by Toray Industries, Inc.). Thereafter, aging was performed at 23 ° C. for 5 days to obtain an adhesive tape having a total thickness of 52 μm.

(Comparative Example 2)
The pressure-sensitive adhesive (F) was applied as a pressure-sensitive adhesive on the image display panel side pressure-sensitive adhesive layer onto the release film so that the thickness after drying was 25 μm, and dried at 75 ° C. for 5 minutes. Next, the pressure-sensitive adhesive (B) was applied as a pressure-sensitive adhesive on the front panel side pressure-sensitive adhesive layer onto the release film so that the thickness after drying was 25 μm, and dried at 75 ° C. for 5 minutes. These were bonded to both sides of a 50 μm polyester film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.). Thereafter, aging was performed at 23 ° C. for 5 days to obtain an adhesive tape having a total thickness of 100 μm.

(Comparative Example 3)
The pressure-sensitive adhesive (A) was applied as a pressure-sensitive adhesive for the image display panel side pressure-sensitive adhesive layer on the release film so that the thickness after drying was 25 μm, and dried at 75 ° C. for 5 minutes. Next, the pressure-sensitive adhesive (A) was applied as a pressure-sensitive adhesive on the front panel side pressure-sensitive adhesive layer onto the release film so that the thickness after drying was 25 μm, and dried at 75 ° C. for 5 minutes. These were bonded to both sides of a 50 μm polyester film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.). Thereafter, aging was performed at 23 ° C. for 5 days to obtain an adhesive tape having a total thickness of 100 μm.

(Comparative Example 4)
The pressure-sensitive adhesive (G) was applied as a pressure-sensitive adhesive on the image display panel side pressure-sensitive adhesive layer onto the release film so that the thickness after drying was 25 μm, and dried at 75 ° C. for 5 minutes. Next, the pressure-sensitive adhesive (B) was applied as a pressure-sensitive adhesive on the front panel side pressure-sensitive adhesive layer onto the release film so that the thickness after drying was 25 μm, and dried at 75 ° C. for 5 minutes. These were bonded to both sides of a 50 μm polyester film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.). Thereafter, aging was performed at 23 ° C. for 5 days to obtain an adhesive tape having a total thickness of 100 μm.

(Comparative Example 5)
The pressure-sensitive adhesive (B) was applied as a pressure-sensitive adhesive for the image display panel side pressure-sensitive adhesive layer on the release film so that the thickness after drying was 25 μm, and dried at 75 ° C. for 5 minutes. Next, the pressure-sensitive adhesive (B) was applied as a pressure-sensitive adhesive on the front panel side pressure-sensitive adhesive layer onto the release film so that the thickness after drying was 25 μm, and dried at 75 ° C. for 5 minutes. These were bonded to both sides of a 50 μm polyester film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.). Thereafter, aging was performed at 23 ° C. for 5 days to obtain an adhesive tape having a total thickness of 100 μm.

(Measurement method of adhesive strength)
After sticking together with a polyethylene terephthalate film (Lumirror S-10 25 μm, manufactured by Toray Industries Inc.) without air bubbles on a surface different from the adhesive strength measuring surface of the double-sided adhesive tape, cut it to a size of 20 mm x 100 mm, Each adherend (image display panel side pressure-sensitive adhesive layer is triacetyl cellulose (TAC) film, front panel side pressure-sensitive adhesive layer is acrylic plate (AC)) is attached at 23 ° C and 50% RH in one reciprocating 2kg roller. Combined and left in an atmosphere of 23 ° C. and 50% RH for 1 hour. Thereafter, the peel adhesive strength in the 180 ° direction was measured at a peel speed of 300 mm / min with a Tensilon type peel tester. As the adherend, a triacetyl cellulose (TAC) film was a Sanlitz polarizing plate LLC2-9218, and an acrylic plate (AC) was an acrylic plate “Acrylite L” manufactured by Mitsubishi Rayon.

(Measurement method of adhesive strength after standing for 240 hours)
A test piece was prepared in the same manner as in the above “Adhesive strength measurement method”, and the adhesive strength measurement surface was bonded to each adherend in a reciprocating 2 kg roller at 23 ° C. and 50% RH atmosphere, and at 23 ° C. and 50% RH atmosphere. The sample was allowed to stand for 1 hour and then left in an environment of 60 ° C. and 90% RH for 240 hours. Thereafter, the film was allowed to stand in an atmosphere of 23 ° C. and 50% RH for 24 hours, and the peel adhesive force in the 180 ° direction was measured with a Tensilon-type peel tester at a peel speed of 300 mm / min.

(Durability test)
An adherend was prepared in which Sunlitz polarizing plates LLC2-9218 were pasted on the front and back surfaces of an acrylic glass plate so as to be orthogonal to each other. Next, a laminate in which an adhesive layer on the surface panel of a double-sided adhesive tape was attached to an acrylic board “Acrylite L” manufactured by Mitsubishi Rayon Co., Ltd. was attached to the adherend and autoclaved (50 degrees, 5 atmospheres, 20 minutes). ) To prepare a test piece.
Two similar test pieces were prepared and left for 240 hours under conditions of 85 ° C. and 60 ° C. and 90% RH, respectively. Thereafter, after standing at 23 ° C. and 50% RH for 1 hour, the occurrence of foaming, peeling, cracking, etc. was visually observed according to the following criteria. The evaluation results are as follows.
◯: Appearance defects such as foaming, peeling and cracking were not recognized.
Δ: Slight defects in appearance such as foaming, peeling and cracking were observed.
X: Appearance defects such as foaming, peeling and cracking were clearly recognized.

(Removability test)
An adherend was prepared by attaching a Sanritz polarizing plate to the front and back surfaces of an acrylic glass plate so as to be in a crossed Nicols position. Next, a laminate in which a surface panel side adhesive layer of a double-sided pressure-sensitive adhesive tape was pasted on an acrylic plate “Acrylite L” made by Mitsubishi Rayon Co., Ltd. having a thickness of 2 mm was adhered to the entire surface of the adherend, and autoclaved (50 °, 5 atmospheres, 20 minutes), and the test piece was created.
Two similar test pieces were prepared and left for 240 hours under conditions of 85 ° C. and 60 ° C. and 90% RH, respectively. Then, after leaving at 23 ° C. and 50% RH for 1 hour, the acrylic plate was peeled off at a peeling angle of about 10 ° to 80 °, and the peeling resistance at this time was evaluated according to the following criteria. Furthermore, the adherend (glass with a polarizing plate pasted on the front and back surfaces) after peeling off the acrylic plate is placed on a light box, and light leakage, adhesive residue, polarizing plate distortion, peeling, cracking, etc. are as follows. Visual evaluation was made.

[Removability evaluation criteria]
○: Peeling resistance was small, and it was easily peeled from the polarizing plate surface.
(Triangle | delta): Although peeling resistance was small, it peeled from the acrylic board surface.
*: Peeling resistance was large.

[Defect evaluation criteria for adherends]
◯: No defects such as light leakage, residual adhesive and adhesive tape, distortion of polarizing plate, peeling and cracking were observed.
Δ: Slight defects such as light leakage, residual adhesive and adhesive tape, distortion of the polarizing plate, peeling, and cracking were observed.
X: Problems such as light leakage, residual adhesive and adhesive tape, distortion of the polarizing plate, peeling and cracking were clearly observed.

As is apparent from Table 1, it was clear that the double-sided pressure-sensitive adhesive tape of the present invention can be suitably peeled off from the image display panel side not only immediately after application but also after a long period of time has elapsed.

It is sectional drawing which shows an example of the double-sided adhesive tape which does not have the base material of this invention. It is sectional drawing which shows an example of the double-sided adhesive tape which has a base material of this invention. It is sectional drawing which shows an example of the surface panel which has a frame-shaped printing layer in the transparent plate used for the image display module of this invention. It is sectional drawing which shows an example of the surface panel which has a frame-like printing layer and a transparent printing layer in the transparent plate used for the image display module of this invention. It is sectional drawing which shows an example of the surface panel which has a surface protection layer used for the image display module of this invention. It is sectional drawing which shows an example of the touchscreen type | mold surface panel used for the image display module of this invention. It is sectional drawing which shows an example of the image display module which has the surface panel which consists of a transparent board of this invention. It is sectional drawing which shows an example of the image display module which has a surface panel which consists of the panel which consists of a transparent board of this invention, and a touch panel. It is sectional drawing which shows an example of the image display module (F / F type) which has the touchscreen type surface panel of this invention. It is sectional drawing which shows an example of the image display module (F / G type) which has the touchscreen type surface panel of this invention. It is sectional drawing which shows an example of the image display module (F / F / P type) which has the touchscreen type surface panel of this invention.

Explanation of symbols

1: Adhesive layer affixed to the front panel 2: Adhesive layer affixed to the image display panel 3: Base material 4: Transparent plate 5: Frame printing layer 6: Transparent printing layer 7: Surface protective film 8: Transparent conductive Film 9: adhesive layer 10: silver paste 11: double-sided adhesive tape 12: image display panel 13: reinforcing plate 14: conductive glass

Claims

A double-sided pressure-sensitive adhesive tape for fixing the front panel and the image display panel of an image display module having an image display panel and a front panel,
The double-sided adhesive tape has an adhesive layer that is attached to the image display panel and an adhesive layer that is attached to the front panel,
As the adhesive strength on the adhesive layer side to be attached to the image display panel,
At a temperature of 23 ° C. and a relative humidity of 50% RH, the triacetyl cellulose film was crimped once with one reciprocation using a 2 kg roller and left at rest for 1 hour, and then 180 ° at a peeling speed of 300 mm / min. The peel adhesive strength (F _A1 ) is ₁ to 5 N / 20 mm,
Under the same conditions, 180 ° peeling adhesive strength (F _A2 ) at 1 to 5 N / 20 mm at a peeling speed of 300 mm / min after standing for 240 hours in an atmosphere of 60 ° C. and 90% relative humidity,
And as the adhesive force on the pressure-sensitive adhesive layer side to be attached to the front panel,
180 ° at a peeling speed of 300 mm / min after pressing and reciprocating once with a 2 kg roller against a smooth acrylic plate in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH. The peel adhesive strength (F _B1 ) is _expressed by the formula (1)
F _B1 ≧ 2F _A1 (1)
A double-sided adhesive tape characterized by
The double-sided pressure-sensitive adhesive tape according to claim 1, comprising a transparent resin film substrate as a core.
The double-sided pressure-sensitive adhesive tape according to claim 1 or 2, wherein the light transmittance in a visible light wavelength region is 85% or more.
The pressure-sensitive adhesive layer affixed to the image display panel and the pressure-sensitive adhesive layer affixed to the front panel are made of an acrylic pressure-sensitive adhesive containing an acrylic copolymer containing n-butyl acrylate as a main monomer component, and the image display The weight average molecular weight measured by gel permeation chromatography of the acrylic copolymer in the acrylic pressure-sensitive adhesive forming the pressure-sensitive adhesive layer attached to the panel is 1 to 2 million, and is attached to the surface panel. The double-sided pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the weight average molecular weight measured by gel permeation chromatography of the acrylic copolymer in the acrylic pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is 80 to 1,500,000. tape.
It is an image display module for small electronic terminals provided with the surface panel and the image display panel, Comprising: The said surface panel and an image display panel are interposed through the double-sided adhesive tape in any one of Claims 1-4 Image display module for small electronic terminals attached on the entire surface.
A method for producing an image display module for a small electronic terminal device, wherein the front panel and the image display panel are attached to each other via a double-sided adhesive tape,
After affixing the double-sided adhesive tape according to any one of claims 1 to 4 on the front panel or the image display panel, the entire surface panel and the image display panel are affixed via a double-sided adhesive tape by a vacuum application device. The manufacturing method of the image display module for small electronic terminals characterized by having the process to do.