JP2005200498A - Removable double-coated adhesive tape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a removable double-coated adhesive tape for an LCD module, which, when a removal of a LCD panel from a back light enclosure is conducted, does not cause the panel to separate with the adhesive tape being stuck on the LCD panel or slipped out of place and which, during the assembly process or delivery work, prevents the LCD panel from slipping out of place or coming off. <P>SOLUTION: The removable double-coated adhesive tape for the LCD module is used, which, being one used by being attached between the LCD panel and back light enclosure of the LCD module, is constituted by a substrate, an adhesive agent layer A provided on one surface of the substrate, and an adhesive agent layer B provided on the other side of it. Herein, (1) the adhesive strength (a) of the adhesive agent layer A for the LCD panel is 0.05-1 N/20 mm, (2) the adhesive strength (b) of the adhesive agent layer B for the back light enclosure is 5-25 N/20 mm, and (3) the abrasive resistance parameter α of the adhesive agent layer A is ≤0.05. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a re-peelable double-sided pressure-sensitive adhesive tape that is used by being stuck between an LCD panel of an LCD module and a backlight housing.

  LCD modules (liquid crystal display devices) are used in a wide range of fields such as word processors and personal computers. Especially, electronic notebooks, mobile phones, PHS, etc. are used as display devices for increasingly smaller electronic devices. It has become. Among such LCD modules, for example, a sidelight type backlight type LCD module (schematically shown in FIG. 5) generally includes a reflector 11, a light guide plate 10, a diffusion plate in a backlight housing 13. 9, a prism sheet 8 (increasing brightness) and an LCD panel 7 are laminated in order, and an LED 12 (Light Emitting Diode) provided with a lamp reflector on the side of the light guide plate is disposed.

  Further, a double-sided adhesive tape 1 (usually punched into a frame shape, and its width is usually about 0.5 mm to about 10 mm) is sandwiched between the LCD panel 7 and the backlight housing 13. The double-sided adhesive tape 1 is in contact with not only the LCD panel 7 and the backlight housing 13 but also the prism sheet 4, and also has a role of fixing the diffusion plate 9 installed on the lower side of the prism sheet 4. Yes.

  The LCD module is subjected to a lighting inspection for performance confirmation after assembly. If a defect in the LCD panel or backlight housing is found by the inspection, the backlight housing and the LCD panel are separated, parts are replaced or cleaned, then reassembled, and the lighting inspection is performed again. It has been repeated. This series of work is called repair work. During repair work, the process of separating the backlight housing and the LCD panel is usually performed by the operator manually deforming the LCD module by twisting, and separating the entire backlight housing by distorting it. The LCD panel is separated from the backlight housing by pulling parts such as a flexible printed circuit board connected to the LCD panel. In this case, if the adhesive force of the double-sided adhesive tape is too strong, the LCD panel will be damaged during separation. Therefore, it is necessary that the adhesive strength of the double-sided pressure-sensitive adhesive tape exhibits an appropriate adhesive strength so as not to damage the LCD panel.

  In the repair work, only the LCD panel is separated from the backlight housing, and the double-sided adhesive tape is still attached to the backlight housing. is important. If the double-sided pressure-sensitive adhesive tape is separated on the LCD panel side, a new double-sided pressure-sensitive adhesive tape must be attached to the backlight housing again. In addition, if the double-sided adhesive tape breaks or a part of the adhesive is dropped or missing, the broken double-sided adhesive tape is removed from the backlight housing during reassembly, or the missing or missing piece of adhesive is removed. Therefore, the inside of the backlight housing must be cleaned, and work efficiency is greatly reduced. Actually, when the LCD module is deformed to separate the LCD panel, there is a problem that the edge part of the LCD panel rubs the surface of the adhesive, causing a part of the adhesive layer to drop off or to be lost. .

  As a double-sided adhesive tape for performing repair work without damaging the LCD panel, the adhesive force of the adhesive layer that adheres to the LCD panel side is reduced from the adhesive force of the adhesive layer that adheres to the backlight housing side, and A re-peelable double-sided pressure-sensitive adhesive tape has been proposed in which the loss tangent value and peak temperature of the pressure-sensitive adhesive layer have a specific range (see Patent Document 1).

  However, in reality, if the re-peelable double-sided adhesive tape proposed in this technology is used, the LCD panel will not be destroyed during repair work, but the double-sided adhesive tape may be peeled off from the backlight housing, or the prism sheet. There was a problem that would shift. If the tape is removed from the backlight housing, reassembly work cannot be performed smoothly.

  In order to solve this, it is necessary to further reduce the adhesive force of the pressure-sensitive adhesive layer on the LCD panel side and increase the difference from the adhesive force of the pressure-sensitive adhesive layer on the backlight housing side. In order to reduce the adhesive strength of the pressure-sensitive adhesive layer, means for increasing the degree of crosslinking of the pressure-sensitive adhesive is generally used. However, simply curing the adhesive excessively and lowering the adhesive strength makes the adhesive too brittle, causing the adhesive to drop off or breakage during repair work, causing adhesive fragments to appear on the backlight housing. It will remain. Double-sided pressure-sensitive adhesive tapes that use such an excessively cured pressure-sensitive adhesive are punched into a frame shape, and the pressure-sensitive adhesive may drop off or be damaged when processed into a re-peelable double-sided pressure-sensitive adhesive tape for LCD panels. The pieces of adhesive that fall off get mixed in.

  By the way, when the LCD panel and the backlight housing are fixed with a re-peelable double-sided adhesive tape that further reduces the adhesive strength of the pressure-sensitive adhesive layer on the LCD panel side, when the consumer uses the LCD panel in various situations, There is a risk that the panel peels off from the double-sided adhesive tape and comes off from the device body. In order to prevent this, means for combining physical fixing methods such as a gripping part such as a bezel may be employed (a schematic diagram is shown in FIG. 6). When such a means is used, it seems that an adhesive layer is unnecessary on the LCD panel side. However, in reality, if there is no adhesive layer on the LCD panel side, the LCD panel fitted in the backlight housing will be displaced during the assembly process or transportation operation of the LCD module, and fixed by the physical means. Work cannot be performed smoothly.

JP 2003-268325 A

  Accordingly, an object of the present invention is to prevent the adhesive tape from being peeled off or shifted while the adhesive tape is adhered to the LCD panel when the LCD panel is peeled off from the backlight housing in the repair work of the LCD module. Another object of the present invention is to provide a re-peelable double-sided pressure-sensitive adhesive tape for an LCD module, which is free from contamination by foreign matter, and in which an LCD panel is not displaced or easily peeled off during an assembly process or a transportation operation. Another object of the present invention is to provide a re-peelable double-sided pressure-sensitive adhesive tape for LCD modules which is excellent in processability.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that the pressure-sensitive adhesive layer has a specific range of adhesive strength with respect to the adherends of the LCD panel and the backlight housing, and the LCD panel. The use of a re-peelable double-sided pressure-sensitive adhesive tape in which the wear resistance parameter α of the pressure-sensitive adhesive layer adhered to the adhesive layer is in a specific range has found that the problems of the present invention can be solved, leading to the completion of the present invention. It was.

That is, the present invention is a re-peelable double-sided pressure-sensitive adhesive tape that is used by being stuck between an LCD panel of an LCD module and a backlight housing, wherein the re-peelable double-sided pressure-sensitive adhesive tape comprises a support and a support. It is composed of an adhesive layer A provided on one surface and an adhesive layer B provided on the other surface,
(1) The adhesive strength (a) of the pressure-sensitive adhesive layer A to the LCD panel is 0.05 to 1 N / 20 mm,
(2) The adhesive strength (b) of the pressure-sensitive adhesive layer B to the backlight housing is 5 to 25 N / 20 mm,
(3) Provided is a releasable double-sided pressure-sensitive adhesive tape for an LCD module, wherein the wear resistance parameter α of the pressure-sensitive adhesive layer A is 0.05 or less.

  The present invention also provides an LCD module in which the above-mentioned removable double-sided adhesive tape for an LCD module is adhered between an LCD panel and a backlight housing.

The wear resistance parameter α is in accordance with the following conditions using a wear tester (Taber type) manufactured by Tester Sangyo Co., Ltd. according to the wear resistance test (wear wheel method) of JIS K 5600-5-9. It is the value measured by.
Model number: AB-101
Abrasion wheel: HS-17
Load: 250g (arm only) * Arm is used on both sides.
Rotation speed: 60 rotations / minute rotation number: 5
Measurement atmosphere: 23 ° C., 50% RH
The wear resistance parameter α is
alpha = calculated by dropping amount of adhesive (g) / (pressure-sensitive adhesive coating weight ^{(g / m 2) × 0.0026m} 2).
* Area where wear ring rotates: 26cm ²
In the present invention, the effects of the invention described below can be obtained by setting the wear resistance parameter α to 0.05 or less and the adhesive strengths of the pressure-sensitive adhesive layers A and B to the above ranges.

  The re-peelable double-sided pressure-sensitive adhesive tape for LCD module of the present invention has two types with different adhesive properties, showing sufficient adhesive strength for backlight casing and relatively low adhesive strength for LCD panel. It has a pressure-sensitive adhesive layer. Therefore, by using the re-peelable double-sided adhesive tape for LCD module of the present invention so that the adhesive layer A is in contact with the LCD panel and the adhesive layer B is in contact with the backlight housing, Therefore, only the LCD panel can be easily separated from the backlight casing without peeling off the double-sided adhesive tape. Further, since the wear resistance parameter α is 0.05 or less, the pressure-sensitive adhesive layer is not broken or broken during the repair work, and the workability is excellent. Further, the trouble that the edge portion of the LCD panel rubs the surface of the adhesive and scrapes off the adhesive does not occur. Further, the double-sided pressure-sensitive adhesive tape is excellent in processability because there is no mixing of adhesive fragments when punching into a frame shape. Further, since the pressure-sensitive adhesive layer A has an appropriate adhesive strength, it does not shift during the assembling process or carrying of the LCD module, and the work of physically fixing can be performed smoothly.

  The re-peelable double-sided pressure-sensitive adhesive tape of the present invention comprises a support, a pressure-sensitive adhesive layer A provided on one side of the support and a pressure-sensitive adhesive layer B provided on the other side, and the pressure-sensitive adhesive for the LCD panel. The adhesive strength (a) of the layer A is 0.05 to 1 N / 20 mm (FIG. 1). The adhesive strength (a) is preferably from 0.1 to 0.8 N / 20 mm, particularly preferably from 0.2 to 0.6 N / 20 mm. If it is less than 0.05 N / 20 mm, the LCD panel and the backlight housing are bonded together, and the panel is peeled off or dropped in the process of carrying it for physical fixation. On the other hand, when the thickness exceeds 1 N / 20 mm, the LCD panel is easily cracked when the LCD panel is peeled off in the repair process.

  The adhesive strength (b) of the pressure-sensitive adhesive layer B to the backlight housing of the re-peelable double-sided pressure-sensitive adhesive tape of the present invention is 5 to 25 N / 20 mm. The adhesive strength (b) is preferably 8 to 22 N / 20 mm, and particularly preferably 11 to 20 N / 20 mm. When it is less than 5 N / 20 mm, the case where it peels from the backlight housing | casing side at the time of peeling will generate | occur | produce. On the other hand, if it exceeds 25 N / 20 mm, the peel adhesive strength is too strong, so that it becomes difficult to peel off when it is necessary to peel from the backlight housing side.

  The abrasion resistance parameter α of the re-peelable double-sided pressure-sensitive adhesive tape of the present invention is 0.05 or less, preferably 0.001 to 0.05. Moreover, it is more preferable that it is 0.001-0.04, and it is especially preferable that it is 0.001-0.03. If it exceeds 0.05, the adhesive drops off during repair, and the backlight is contaminated.

  The re-peelable double-sided pressure-sensitive adhesive tape of the present invention is preferably used as a means for fixing the LCD panel to the backlight housing in combination with a physical fixing method. As the physical fixing means, there is a fixing means using a gripping component or the like. FIG. 6 shows an example of a fixing method using a gripping part and a double-sided adhesive tape in combination.

  As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layers A and B used in the re-peelable double-sided pressure-sensitive adhesive tape of the present invention, known acrylic, silicone-based or rubber-based pressure-sensitive resins can be used.

  As the rubber-based adhesive, block copolymer systems such as styrene-isoprene-styrene, synthetic rubber-based adhesives such as polybutadiene and polybutylene, natural rubber, and the like can be used. When natural rubber is used, it is preferable not to contain sulfur. If it contains sulfur, it may cause contact failure.

  In addition, as the silicone-based pressure-sensitive adhesive, a peroxide crosslinking type or an addition condensation type may be used alone or as a mixture. Furthermore, it can also be used by mixing with an acrylic or rubber adhesive, or an adhesive having a silicone component pendant on the polymer main chain or side chain of the acrylic adhesive may be used.

When an acrylic resin is used as the adhesive, it is preferable to use a resin obtained by reacting a radical polymerizable monomer containing an acrylate ester having an alkyl side chain having 1 to 14 carbon atoms as a monomer component. As an acrylate ester having an alkyl side chain having 1 to 14 carbon atoms, for example,
(Group 1) methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sce-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate, lauryl acrylate methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sce-butyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, cyclohexyl Methacrylate, n-octyl methacrylate, isooctyl meta Relate, 2-ethylhexyl methacrylate, isononyl methacrylate, isodecyl methacrylate, lauryl methacrylate and the like. Among them, it is preferable to use a methacrylic acid alkyl ester having an alkyl side chain having 4 to 9 carbon atoms or an acrylic acid alkyl ester having an alkyl side chain having 4 to 9 carbon atoms. Among them, it is more preferable to use an acrylic acid alkyl ester having an alkyl side chain having 4 to 9 carbon atoms.

  As the monomer component, it is preferable to add an acrylic ester or other vinyl monomer having a polar group such as a hydroxyl group, a carboxyl group or an amino group in the side chain.

As a monomer containing a hydroxyl group,
(Group 2) 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, hydroxypropyl (meth) acrylate, caprolactone-modified (meth) acrylate, polyethylene glycol mono (meth) ) Acrylate, polypropylene glycol (meth) acrylate, and the like. Preferred examples include 4-hydroxybutyl (meth) acrylate and 6-hydroxyhexyl (meth) acrylate.

In addition, as a monomer having a polar group other than a hydroxyl group,
(Group 3) A monomer having a carboxyl group such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, acrylic acid dimer, ethylene oxide-modified succinic acid acrylate, N-vinyl-2-pyrrolidone, n-vinylcaprolactam, Examples thereof include monomers having an amide group such as acryloylmorpholine, acrylamide, N, N-dimethylacrylamide, 2- (perhydrophthalimido-N-yl) ethyl acrylate, acrylonitrile, maleic anhydride, itaconic anhydride and the like.

  In particular, as the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer A used in the re-peelable double-sided pressure-sensitive adhesive tape of the present invention, in addition to the monomer (group 1),

（式中、Ｘは水素原子又はメチル基、Ｒ_１は分岐鎖を有していてもよい炭素数１〜１２のアルキレン基、Ｒ_２は分岐鎖を有していてもよい炭素数１〜１２のアルキル基を表す。）で表される化合物、式(II)

(In the formula, X is a hydrogen atom or a methyl group, R ₁ is an alkylene group having 1 to 12 carbon atoms that may have a branched chain, and R ₂ is an alkyl group having 1 to 12 carbon atoms that may have a branched chain. A compound represented by the formula (II):

（式中、Ｘは水素原子又はメチル基、Ｒ_１は分岐鎖を有していてもよい炭素数１〜１２のアルキレン基を表す。）で表される化合物及び式(III)

(Wherein, X represents a hydrogen atom or a methyl group, R ₁ represents an alkylene group having 1 to 12 carbon atoms which may have a branched chain) and the formula (III)

（式中、Ｘは水素原子又はメチル基を表す。）で表される化合物を含有する重合性モノマーを反応して得られる粘着性樹脂を用いることが好ましい。

It is preferable to use an adhesive resin obtained by reacting a polymerizable monomer containing a compound represented by the formula (wherein X represents a hydrogen atom or a methyl group).

  The Tg of the adhesive resin is preferably -60 to -10 ° C. Among these, -50 to -20 ° C is more preferable, and -40 to -20 ° C is particularly preferable. When the temperature is lower than −60 ° C., the cohesive force of the pressure-sensitive adhesive is lowered, and the heat resistance is easily lowered. If it exceeds −10 ° C., it will be easy to peel off or crack the LCD.

As a compound represented by the above formula (I), in the formula (I), X is a hydrogen atom, R ₁ is —CH ₂ CH ₂ —, R ₂ is —CH ₃ , —CH ₂ CH ₃ , —CH ₂ CH ₂ CH ₃ , —CH ₂ CH ₂ CH ₂ CH ₃ are preferred, X is a hydrogen atom, R ₁ is —CH ₂ CH ₂ —, and R ₂ is —CH ₃ . It is particularly preferred. The compound represented by the above-mentioned formula (II), wherein (II), X is a hydrogen atom, R ₁ is _{-CH 2 CH 2 -, - CH} 2 CH 2 CH 2 -, - CH 2 CH ₂ CH ₂ CH ₂ — is preferred, X is a hydrogen atom, and R ₁ is particularly preferably —CH ₂ CH ₂ —. Furthermore, in the formula (III), X is preferably a hydrogen atom.

  The compound represented by the above formula (I) is preferably used in an amount of 2 to 15% by mass, more preferably 5 to 10% by mass, based on all monomers. Moreover, it is preferable to use 0.5-15 mass% of compounds represented by the said Formula (II) with respect to all the monomers, and it is more preferable to use 2-10 mass%. Furthermore, the compound represented by the formula (III) is preferably used in an amount of 0.05 to 5% by mass, more preferably 0.1 to 3% by mass, based on the total monomers.

  As the resin used for the pressure-sensitive adhesive layer A used in the re-peelable double-sided pressure-sensitive adhesive tape of the present invention, when a resin obtained by reacting the monomers represented by the formulas (I) to (III) as described above is used, the pressure-sensitive adhesive layer A Even when the adhesive strength (a) is 0.05 to 1 N / 20 mm, the wear resistance parameter α is reduced, and it receives mechanical shares such as friction and scratches during repair and tape processing. However, it is difficult for the adhesive layer to drop off or be damaged.

  The acrylic copolymer can be obtained by copolymerization by a known polymerization method such as a solution polymerization method, a cage polymerization method, a suspension polymerization method, or an emulsion polymerization method. Polymerization can be initiated by peroxides such as benzoyl peroxide and lauroyl peroxide, thermal initiation using azo-based thermal polymerization initiators such as azobisisobutylnitrile, acetophenone, benzoin ether, benzyl A starting method by ultraviolet irradiation using a ketal-based, acylphosphine oxide-based, benzoin-based or benzophenone-based photopolymerization initiator, or a method by electron beam irradiation can be arbitrarily selected.

  Moreover, in order to raise the cohesion force of an adhesive layer, you may add a crosslinking agent to an adhesive. Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, a chelate crosslinking agent, and a photocurable crosslinking agent. As the addition amount of the crosslinking agent, the pressure-sensitive adhesive layer A is preferably adjusted to have a gel fraction of 70 to 99%, and most preferably 80 to 95%. On the other hand, the pressure-sensitive adhesive layer B is preferably adjusted to have a gel fraction of 10 to 50%, and most preferably 20 to 45%. The gel fraction is obtained by immersing the composition of the pressure-sensitive adhesive layer after curing in toluene, measuring the mass after drying of the unnecessary portion remaining after standing for 24 hours, and expressing it as a percentage of the original weight.

  Various additives such as tackifier resins, antioxidants, ultraviolet absorbers, fillers, pigments, thickeners, and the like may be added to the pressure-sensitive adhesive layer as necessary, as long as the performance is not impaired.

  The coating solution for the pressure-sensitive adhesive layer is prepared by dissolving the above pressure-sensitive adhesive and, if necessary, other additives in an organic solvent. The organic solvent is not particularly limited as long as the above-described blending components are dissolved, but a known and commonly used organic solvent such as ethyl acetate, toluene, xylene, methanol, isopropyl alcohol is used alone or in combination. be able to.

  To form a pressure-sensitive adhesive layer on a support, a method of directly applying a pressure-sensitive adhesive solution on a support with a roll coater or a die coater, or once forming a pressure-sensitive adhesive layer on a separator and then transferring it to the support Use the method. The preferable thickness of the pressure-sensitive adhesive layer after drying is 3 to 300 μm, preferably 5 to 50 μm.

  As the support used for the re-peelable double-sided pressure-sensitive adhesive tape of the present invention, a known film such as a plastic film such as a polyester film, a polypropylene film, a polyethylene film or a polyimide film, a non-woven fabric, a cloth, a metal foil or paper can be used.

  Moreover, it is preferable that the thickness of the support body of this invention is 5-50 micrometers. More preferably, it is 10-45 micrometers. Of these, 10 to 20 μm is most preferable. If the thickness exceeds 50 μm, the followability of the re-peelable double-sided pressure-sensitive adhesive tape to the unevenness of the backlight housing is lowered. On the other hand, when the thickness is less than 5 μm, the workability of the tape is lowered. In particular, small LCDs, which are becoming lighter and thinner, have a step between the backlight housing and the prism sheet as shown in FIG. 3, and the thinner the support, the easier it is to follow the step.

  When the support is a film, it is preferable to perform easy adhesion treatment such as primer treatment, corona treatment, plasma treatment, etc. in order to improve the adhesion to the pressure-sensitive adhesive. If the adhesion is poor, the adhesive will easily fall off during repair.

  In addition, in order to improve visibility and appearance when the LCD module is turned on, in order to block unnecessary light from the backlight and reuse the light, the support has a light-shielding layer and a light-reflecting layer laminated. More preferably, the pressure-sensitive adhesive layer B is provided on the reflective layer, and the pressure-sensitive adhesive layer A is provided on the light shielding layer. A schematic diagram of this re-peelable reflective / light-shielding double-sided adhesive tape is shown in FIG. As the light shielding layer, a metal vapor deposition layer and various ink layers can be considered, and among them, a black ink layer is preferable. As a light reflection layer, an aluminum vapor deposition layer, a silver vapor deposition layer, a white ink layer, and a white polyester (PET) film are preferable. When using white PET, Toray Co., Ltd. E20 # 38 and Teijin DuPont Co., Ltd. Teflex FW2 # 13 are preferable.

  When a black ink layer is used for the light shielding layer, a copolymer resin and a urethane resin obtained by copolymerizing vinyl alcohol, vinyl chloride, and vinyl acetate as the resin component of the ink and having a hydroxyl value of 1 to 10 Is preferably used as a mixture from the viewpoint of adhesiveness to the pressure-sensitive adhesive. In particular, when a resin obtained by reacting the monomers represented by the above formulas (I) to (III) is used as the pressure-sensitive adhesive, the adhesiveness is further increased, and the pressure-sensitive adhesive does not easily fall off during repair work.

  As a material of the backlight casing, polycarbonate (PC) resin, ABS resin, or an alloy of polycarbonate (PC) resin and ABS resin is used. The LCD panel uses glass or resin, or surface-treated glass or resin (glass coated with resin, or glass having a resin film pasted on the surface) or the like.

  Next, examples and comparative examples of the re-peelable double-sided pressure-sensitive adhesive tape of the present invention will be described and specifically described. However, the re-peelable double-sided pressure-sensitive adhesive tape of the present invention is not limited to these examples. Absent. In addition, the part displayed below is a mass part.

(Example 1)
(Preparation of acrylic copolymer a for pressure-sensitive adhesive layer A)
In a reaction vessel equipped with a condenser, stirrer, thermometer, and dropping funnel, 85 parts of 2-ethylhexyl acrylate, 5 parts of β-hydroxyethyl acrylate, 9 parts of 2-methoxyethyl acrylate, 1 part of acrylic acid and 2 as a polymerization initiator , 2′-azobisisobutylnitrile (0.2 parts) was dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, the mixture was polymerized at 80 ° C. for 8 hours to obtain a resin solution of acrylic copolymer a having a weight average molecular weight of 900,000. Obtained. The calculated Tg of the acrylic copolymer a is -48 ° C.

(Preparation of acrylic copolymer b for adhesive layer B)
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 74.8 parts of n-butyl acrylate, 20 parts of 2-ethylhexyl acrylate, 5.0 parts of acrylic acid, 0.2 part of β-hydroxyethyl acrylate, Then, 0.2 part of 2,2′-azobisisobutylnitrile as a polymerization initiator is dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization is carried out at 80 ° C. for 8 hours to obtain an acrylic copolymer having a weight average molecular weight of 450,000. A resin solution of coalescence b was obtained. The calculated Tg of the acrylic copolymer b is −50 ° C.

(Adjustment of black ink)
Sumiink "Panacia CVL-SPR805 Sumi" manufactured by Dainippon Ink & Chemicals, Inc., which is a mixture of a copolymer resin having a hydroxyl value of 1 to 10 and a urethane resin, obtained by copolymerizing vinyl alcohol, vinyl chloride and vinyl acetate. ”(Vinyl chloride / vinyl acetate) 100 parts, Dainippon Ink & Chemicals Co., Ltd.“ CVL Hardener No. 10 ”, Dainippon Ink & Chemicals Co., Ltd.“ Direducer V No. 20 ”35 parts. The black ink was adjusted.

(Preparation of ink coat film for support)
Both sides of Teflex FW2 # 13 manufactured by Teijin DuPont Co., Ltd. were subjected to corona treatment so that the wetting tension was 50 dyn / cm, and the black ink prepared on one side was subjected to gravure coating twice so that the dry thickness was 2 μm. Further, the film was cured at 40 ° C. for 2 days to obtain an ink coat film for a support having a thickness of 15 μm.

(Preparation of re-peelable double-sided adhesive tape)
(Adhesive layer A: LCD panel side adhesive layer)
To 100 parts of the solid content of the acrylic copolymer a resin solution, an isocyanate crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: coronate L-45 / toluene 45 adduct of tolylene diisocyanate and trimethylolpropane) The resin solution for the pressure-sensitive adhesive layer A was adjusted so that the solid content of the mixed solution was 30% with ethyl acetate. Thereafter, the resin solution for the pressure-sensitive adhesive layer A was applied onto a polyester film having a thickness of 75 μm after the release treatment so that the thickness after drying was 16 μm, followed by drying at 100 ° C. for 2 minutes for adhesion. Agent layer A was prepared. Next, the pressure-sensitive adhesive layer A was transferred to the black ink surface of the ink coat film and laminated with a hot roll at 80 ° C. under a pressure of 4 kgf / cm to obtain a single-sided pressure-sensitive adhesive tape.

(Adhesive layer B: Backlight side adhesive layer)
Next, an isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: coronate L-45 / tolylene diisocyanate and trimethylolpropane is added to 100 parts of the solid content of the acrylic copolymer b resin solution. 4.5 parts of toluene) and 20 parts of rosin-based tackifier resin (D-135, manufactured by Arakawa Chemical Co., Ltd.), and the pressure-sensitive adhesive layer so that the solid content of the mixed solution becomes 40% with ethyl acetate A resin solution for B was prepared. Thereafter, the resin solution for the pressure-sensitive adhesive layer B was applied on a 75 μm-thick polyester film subjected to a release treatment so that the thickness after drying was 20 μm, and then dried at 100 ° C. for 2 minutes to adhere. Agent layer B was prepared. Next, the pressure-sensitive adhesive layer B was transferred onto the polyester film surface of the single-sided pressure-sensitive adhesive tape, and laminated with a hot roll at 80 ° C. at a pressure of 4 kgf / cm to obtain a re-peelable double-sided pressure-sensitive adhesive tape of Example 1. The obtained re-peelable double-sided pressure-sensitive adhesive tape was used for a test after aging at 40 ° C. for 2 days.

(Example 2)
(Preparation of acrylic copolymer c for adhesive layer A)
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 89 parts of 2-ethylhexyl acrylate, 5 parts of β-hydroxyethyl acrylate, 5 parts of 2-methoxyethyl acrylate, 1 part of acrylic acid and 2 as a polymerization initiator , 2'-azobisisobutylnitrile (0.2 parts) is dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization is carried out at 80 ° C. for 8 hours to obtain a resin solution of acrylic copolymer c having a weight average molecular weight of 900,000. Obtained. The calculated Tg of the acrylic copolymer c is −48 ° C.

(Preparation of re-peelable double-sided adhesive tape)
A re-peelable double-sided pressure-sensitive adhesive tape of Example 2 was produced in the same manner as in Example 1 except that the resin solution of acrylic copolymer c was used instead of the resin solution of acrylic copolymer a.

(Example 3)
A re-peelable double-sided pressure-sensitive adhesive tape of Example 3 was prepared in the same manner as in Example 1 except that Toray Co., Ltd. E20 # 38 was used instead of Teijin DuPont's Teflex FW2 # 13.

(Comparative Example 1)
(Preparation of acrylic copolymer d for adhesive layer A)
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 99.0 parts of n-butyl acrylate, 1.0 part of acrylic acid and 0.2 part of 2,2′-azobisisobutylnitrile as a polymerization initiator Was dissolved in 100 parts of ethyl acetate, purged with nitrogen, and polymerized at 80 ° C. for 8 hours to obtain a resin solution of an acrylic copolymer d having a weight average molecular weight of 700,000. The calculated Tg of the acrylic copolymer d is -54 ° C.

(Preparation of double-sided adhesive tape)
For 100 parts of the solid content of the acrylic copolymer d resin solution, an isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: coronate L-45 / toluene 45 adduct of tolylene diisocyanate and trimethylolpropane) % Solution) 6.5 parts was mixed, and the resin solution for the pressure-sensitive adhesive layer A was adjusted with ethyl acetate so that the solid content of the mixed solution became 40%. Thereafter, the resin solution for the pressure-sensitive adhesive layer A was applied onto a polyester film having a thickness of 75 μm after the release treatment so that the thickness after drying was 16 μm, followed by drying at 100 ° C. for 2 minutes for adhesion. Agent layer A was prepared. Next, the pressure-sensitive adhesive layer A was transferred to the black ink surface of the support ink-coated film prepared in the same manner as in Example 1, and laminated at a pressure of 4 kgf / cm with a hot roll at 80 ° C. to obtain a single-sided pressure-sensitive adhesive tape. It was. Next, the pressure-sensitive adhesive layer B was provided on the polyester film surface of the single-sided pressure-sensitive adhesive tape in the same manner as in Example 1 to obtain a re-peelable double-sided pressure-sensitive adhesive tape of Comparative Example 1. Used for testing after aging at 40 ° C. for 2 days.

(Comparative Example 2)
(Preparation of acrylic copolymer e for adhesive layer A)
Polymerization started with 87.9 parts of 2-ethylhexyl acrylate, 10 parts of n-butyl acrylate, 2 parts of 4-hydroxybutyl acrylate and 0.1 part of acrylic acid in a reaction vessel equipped with a condenser, stirrer, thermometer and dropping funnel As an agent, 0.2 part of 2,2′-azobisisobutylnitrile is dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization is carried out at 80 ° C. for 8 hours to prepare an acrylic copolymer e having a weight average molecular weight of 700,000. A resin solution was obtained. The calculated Tg of the acrylic copolymer e is −50 ° C.

(Preparation of double-sided adhesive tape)
For 100 parts of the solid content of the acrylic copolymer solution e, 3.6 parts of an isocyanate cross-linking agent (Saiden Chemical's Cybinol K-200, NV = 100%), chelate-based cross-linking agent (Saiden Chemical's Cybinol M-2) , NV = 5%) was mixed, and the resin solution for the pressure-sensitive adhesive layer A was adjusted so that the solid content of the mixed solution became 40% with ethyl acetate. Thereafter, the resin solution for the pressure-sensitive adhesive layer A was applied onto a polyester film having a thickness of 75 μm after the release treatment so that the thickness after drying was 16 μm, followed by drying at 100 ° C. for 2 minutes for adhesion. Agent layer A was prepared. Next, the pressure-sensitive adhesive layer A was transferred to the black ink surface of the support ink-coated film prepared in the same manner as in Example 1, and laminated at a pressure of 4 kgf / cm with a hot roll at 80 ° C. to obtain a single-sided pressure-sensitive adhesive tape. It was. Next, the pressure-sensitive adhesive layer B was provided on the polyester film surface of the single-sided pressure-sensitive adhesive tape in the same manner as in Example 1 to obtain a re-peelable double-sided pressure-sensitive adhesive tape of Comparative Example 2. It was used for the test after aging at 40 ° C. for 2 days.

(Comparative Example 3)
The pressure-sensitive adhesive layer A was prepared in the same manner as in Example 1 except that the addition amount of the crosslinking agent was changed from 7 parts to 35 parts and the thickness after drying was changed from 16 μm to 2 μm.

  For the re-peelable double-sided adhesive tapes prepared in Examples and Comparative Examples, (1) Abrasion resistance parameter α, (2) Adhesive strength, (3) Selective removability during repair, (4 The contamination probability of the backlight housing, (5) LCD panel dropability during assembly work, and (6) punching suitability during tape processing were evaluated, and the results are shown in Tables 1 and 2.

(1) Abrasion resistance parameter α
The re-peelable double-sided pressure-sensitive adhesive tape produced in each example and comparative example is cut into a circular shape having a diameter of 120 mm, and a hole having a diameter of 10 mm is formed in the center. Furthermore, only the separator on the adhesive layer A side of the tape is cut out in a donut shape between the diameter of 60 mm and the diameter of 90 mm to obtain a test piece. The test piece is weighed with an electronic balance. Next, a wear test is performed according to JIS K 5600-5-9 using the following wear tester under the following conditions. After the abrasion test is completed, the removed or missing adhesive is removed using Dainippon Ink Chemical's single-sided tape PF-025H. Next, the weight of the test piece after the test is measured with an electronic balance, and the amount of the adhesive removed is calculated. The wear resistance parameter α was calculated by the following formula.
Model number: AB-101
Testing machine: Wear tester (Taber type) manufactured by Tester Sangyo Co., Ltd.
Abrasion wheel: HS-17
Load: 250g (arms only) * Arm used on both sides Rotating speed: 60 revolutions / minute revolution: 5
Measurement atmosphere: 23 ° C., 50% RH
Abrasive paper: No. 280 Abrasion resistance parameter α is
α = Amount of pressure-sensitive adhesive removed (g) / (pressure-sensitive adhesive coating amount (g / m ² ) × 0.0026 m ² )
* Area where wear wheel turns: 26cm ²

(2) Adhesive strength (Measurement of adhesive strength (a) of adhesive layer A)
The re-peelable double-sided pressure-sensitive adhesive tape produced in each Example and Comparative Example was cut into a width of 20 mm and a length of 100 mm, a polyester film having a thickness of 25 μm was stuck on the pressure-sensitive adhesive layer B of the tape, and the adhesive strength (a) was A sample for measurement was prepared. Subsequently, the surface of the pressure-sensitive adhesive layer A of each sample was attached to a glass LCD panel with a polarizing film (iodine polarizing film having a surface of triacetylcellulose: high luminance SR grade manufactured by Sumitomo Chemical Co., Ltd.), and 23 ° C. and 50%. The RH was pressurized by one reciprocating 2.0 kg roller. The adhesive strength (a) was measured by leaving at 23 ° C. and 50% RH for 1 hour and then peeling at 180 ° C. at a peeling speed of 300 mm / min at 23 ° C. and 50% RH.
(Measurement of adhesive strength (b) of adhesive layer B)
The re-peelable double-sided pressure-sensitive adhesive tapes prepared in each Example and Comparative Example were cut into a width of 20 mm and a length of 100 mm, a polyester film having a thickness of 25 μm was stuck on the pressure-sensitive adhesive layer A of the tape, and the adhesive strength (b) was A sample for measurement was prepared. Next, the surface of the pressure-sensitive adhesive layer B of each sample was attached to a PC (polycarbonate) resin plate, and pressurized with one reciprocating 2.0 kg roller at 23 ° C. and 50% RH. The adhesive strength (b) was measured by leaving at 23 ° C. and 50% RH for 1 hour and then peeling at 180 ° C. at a peeling rate of 300 mm / min at 23 ° C. and 50% RH. Furthermore, the same measurement was performed using an ABS (acrylonitrile / butadiene / styrene) resin plate.

(3) Selective removability during repair In the 2-inch LCD module of N503is (NEC's mobile phone), a polarizing film (iodinated polarizing film whose surface is triacetyl cellulose: high luminance SR grade manufactured by Sumitomo Chemical Co., Ltd.) The pasted glass LCD panel and PC (polycarbonate) backlight housing are bonded using the double-sided adhesive tapes of the examples and comparative examples punched into the shape shown in FIG. The panel and the backlight housing were physically fixed by the method shown in FIG.

Perform a 6-hour continuous lighting test (material temperature 70 ° C), leave it at 23 ° C for 24 hours, remove the stainless steel bezel, and place the flexible printed circuit board connected to the LCD panel vertically to the backlight housing The LCD panel was separated from the backlight housing by pulling. After the separation, it was observed whether the re-peelable double-sided adhesive tape produced in each Example and Comparative Example remained in the LCD panel or the PC backlight housing. (N = 100)
The selective removability was evaluated according to the following criteria.
A: Probability of tape remaining in the backlight housing = 100%
○: Probability of remaining tape in the backlight housing = 90% or more and less than 100% ×: Probability of remaining tape in the backlight housing = less than 90%

(4) Contamination probability of backlight casing After the test in (3) above, the presence or absence of contamination of the backlight casing due to the drop-off and loss of the adhesive was evaluated. (N = 100)
In addition, the contamination probability of the backlight housing was evaluated according to the following criteria.
A: Backlight contamination probability = 0%
○: Backlight contamination probability = 1% or more and less than 10% ×: Backlight contamination probability = 10% or more

(5) LCD panel drop resistance during assembly work In a 2-inch LCD module of N503is, a glass LCD panel with a polarizing film and a PC backlight housing are bonded together using the double-sided adhesive tapes of the examples and comparative examples. In this state, it was evaluated whether or not the LCD panel was peeled off from the backlight case when the LCD panel side was turned down and left for 1 minute. (N = 100)
The LCD panel drop resistance during assembly work was evaluated according to the following criteria.
A: LCD panel does not fall = 100%
○: LCD panel does not fall = 90% or more and less than 100% ×: LCD panel does not fall = less than 90%

(6) Punching suitability at the time of tape processing The presence or absence of adhesive drop-off and chipping when 1000 double-sided pressure-sensitive adhesive tapes of Examples and Comparative Examples were punched into the shape of FIG. 4 was evaluated.
The punching suitability during tape processing was evaluated according to the following criteria.
○: No dropout of adhesive on all punched samples ×: Occurrence of dropout of adhesive on one or more samples

※ＬＣＤパネルの割れは何れの粘着テープでも発生しなかった。

* The LCD panel did not crack with any adhesive tape.

  The double-sided pressure-sensitive adhesive tapes of Examples 1 to 3 are excellent in selective removability and contamination resistance during repair. In addition, it has excellent processability during tape processing. In particular, the double-sided pressure-sensitive adhesive tape of Example 1 is easy to follow even when there is a step between the backlight housing and the prism sheet because the support ink coat film is thin, and is excellent in selective removability at the time of repair.

Since the double-sided pressure-sensitive adhesive tape of Comparative Example 1 has a high adhesive strength of the pressure-sensitive adhesive layer A to the LCD panel, it is inferior in selective removability at the time of repair, and it is difficult to reuse the backlight after repair. Moreover, since the double-sided pressure-sensitive adhesive tape of Comparative Example 2 has a large wear resistance parameter α of the pressure-sensitive adhesive layer A, there are many contaminations of pressure-sensitive adhesive pieces during repair, and it is difficult to reuse the backlight after repair. Since the double-sided pressure-sensitive adhesive tape of Comparative Example 3 has a low adhesive strength of the pressure-sensitive adhesive layer A, the liquid crystal panel falls during assembly work, and the assembly workability is extremely poor.

It is a conceptual sectional view of a re-peeling type double-sided pressure-sensitive adhesive tape. It is a conceptual sectional view of a re-peeling type light-shielding / reflective double-sided adhesive tape. FIG. 3 is a schematic cross-sectional view of an LCD module in which a step is formed between a backlight housing and a prism sheet. It is a punched product of re-peelable double-sided adhesive tape. It is a conceptual sectional view of a sidelight type backlight type LCD module. It is a conceptual sectional view of an LCD module using a bezel.

Explanation of symbols

1: Double-sided adhesive tape 2: Support 3: Adhesive layer A
4: Adhesive layer B
5: Light shielding layer 6: Light reflecting layer 7: LCD panel 8: Prism sheet 9: Diffuser plate 10: Light guide plate 11: Reflector plate 12: LED
13: Backlight housing 14: Bezel

Claims (6)

A re-peelable double-sided pressure-sensitive adhesive tape that is used by sticking between an LCD panel of a LCD module and a backlight housing, wherein the re-peelable double-sided pressure-sensitive adhesive tape is provided on one side of the support and the support The pressure-sensitive adhesive layer A and the pressure-sensitive adhesive layer B provided on the other surface,
(1) The adhesive strength (a) of the pressure-sensitive adhesive layer A to the LCD panel is 0.05 to 1 N / 20 mm,
(2) The adhesive strength (b) of the pressure-sensitive adhesive layer B to the backlight housing is 5 to 25 N / 20 mm,
(3) A releasable double-sided pressure-sensitive adhesive tape for LCD module, wherein the pressure-sensitive adhesive layer A has an abrasion resistance parameter α of 0.05 or less. The pressure-sensitive adhesive layer A has the formula (I)

(In the formula, X is a hydrogen atom or a methyl group, R ₁ is an alkylene group having 1 to 12 carbon atoms that may have a branched chain, and R ₂ is an alkyl group having 1 to 12 carbon atoms that may have a branched chain. A compound represented by the formula (II):

(Wherein, X represents a hydrogen atom or a methyl group, R ₁ represents an alkylene group having 1 to 12 carbon atoms which may have a branched chain) and the formula (III)

2. The pressure-sensitive adhesive layer according to claim 1, wherein the pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive resin obtained by reacting a polymerizable monomer containing a compound represented by the formula (wherein X represents a hydrogen atom or a methyl group). Removable double-sided adhesive tape for LCD modules. The re-peelable double-sided pressure-sensitive adhesive tape for an LCD module according to claim 1, wherein the support has a thickness of 5 μm to 50 μm. The support is a resin film having a structure in which a light reflecting layer and a light shielding layer are laminated, the pressure-sensitive adhesive layer B is provided on the reflective layer, and the pressure-sensitive adhesive layer A is provided on the light-shielding layer. The re-peelable double-sided pressure-sensitive adhesive tape for an LCD module according to any one of claims 1, 2, and 3. The light shielding layer is a layer made of black ink, and the black ink is obtained by copolymerizing vinyl alcohol, vinyl chloride and vinyl acetate, and has a hydroxyl group value of 1 to 10 and a copolymer resin and a urethane resin. The re-peelable double-sided pressure-sensitive adhesive tape for an LCD module according to claim 4, which is contained. 6. An LCD module, wherein the re-peelable double-sided pressure-sensitive adhesive tape for an LCD module according to any one of claims 1, 2, 3, 4 and 5 is adhered between an LCD panel and a backlight housing.

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