JP4069625B2 - Pressure-sensitive adhesive sheet with separator, optical member assembly, and method for assembling the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a pressure-sensitive adhesive sheet with a separator, an optical member assembly, and an assembling method thereof, and is particularly used when laminating a plate-like or sheet-like optical member. The present invention relates to a pressure-sensitive adhesive sheet that is less prone to appearance defects such as traces and streaks, and has excellent pasting workability.
[0002]
[Prior art]
A variety of plate-like and sheet-like optical members are used in display products such as a liquid crystal display (LCD), a plasma display (PDP), a projection screen (PJ), and a cathode ray tube (CRT). These optical members are bonded to each other with a transparent adhesive for the purpose of reducing light loss due to light scattering between the optical members, increasing the efficiency during product assembly, and maintaining the strength of the product. . For example, for LCD, adhesion of polarizing plate and liquid crystal cell, adhesion of anti-reflective (AR) film and polarizing plate, adhesion of AR film, electromagnetic shield film, near infrared absorption (NIR) film, etc. for PDP, AR film for CRT And anti-glare (AG) film and CRT are bonded.
[0003]
As such adhesives, pressure-sensitive adhesives, heat-sensitive adhesives, ultraviolet (UV) curable adhesives, and the like have been developed. However, pressure-sensitive adhesives that require relatively little capital investment when being applied. Most widely used.
[0004]
In addition, as a method of forming an adhesive layer on the surface of the optical member, a method in which a liquid adhesive is directly applied to the surface of the optical member and an adhesive sheet previously formed on a separator film are laminated and transferred to the surface of the optical member. There is a way. The method of directly applying a liquid adhesive, although the adhesive itself is inexpensive, contaminates the work environment during the application work (especially when applying an organic solvent type adhesive, an organic solvent countermeasure is required) There are problems that it is difficult to form an adhesive layer with good thickness accuracy and that the optical member is easily damaged due to the application of a liquid adhesive. On the other hand, the method of laminate transfer of the adhesive sheet is relatively expensive, and the cost is likely to be higher than the method of direct application, but there is less contamination of the work environment and a large facility is required for bonding. There is also a feature that there is no, it is used properly according to the features of the two methods.
[0005]
As a pressure-sensitive adhesive sheet used for such an application, an adhesive sheet in which a pressure-sensitive adhesive layer is formed between two plastic separators is used. However, due to recent improvements in display accuracy, transparency has been improved, and the required accuracy for appearance defects such as bubbles and streaks mixed during pasting has increased, and in order to reduce costs, the pasting workability has been improved. An excellent adhesive sheet is required.
[0006]
[Problems to be solved by the invention]
The present invention eliminates such drawbacks as described in the prior art, has excellent transparency, hardly causes appearance defects such as air bubbles and streak marks at the time of pasting, and has a separator with excellent pasting workability. An object is to provide a pressure-sensitive adhesive sheet, an optical member assembly, and an assembly method thereof.
[0007]
[Means for Solving the Problems]
The present invention relates to a pressure-sensitive adhesive sheet with a separator comprising a pressure-sensitive adhesive layer to which an optical member is bonded, and a plastic separator provided on both sides, and the surface roughness Ra of the surface in contact with the pressure-sensitive adhesive layer of the plastic separator. Are both 0.1 μm or less, and the difference in peel force from the pressure-sensitive adhesive layer of the plastic separator on both sides is 10 mN / 25 mm or more, and the peel force from the adhesive layer of the plastic separator is both 200 mN / 25 mm. less and, then, the total light transmittance of the pressure-sensitive adhesive layer is a separator with pressure sensitive adhesive sheet is 80% or more.
[0009]
And this invention is a pressure sensitive adhesive sheet with a separator whose adhesive force to the acrylic board of the said pressure sensitive adhesive layer is 1 N / 25mm or more.
[0010]
Furthermore, the present invention is a pressure-sensitive adhesive sheet with a separator, wherein the adhesive layer is made of a cross-linked acrylic adhesive.
[0011]
Further, the present invention is an optical member assembly in which an optical member is bonded and assembled, and is bonded by a pressure-sensitive adhesive layer from which the plastic separators on both sides of the pressure-sensitive adhesive sheet with the separator are peeled off. It is an assembly.
[0012]
And this invention is a method of assembling the optical member assembly which affixed the optical member, Comprising: The pressure sensitive adhesive layer which peeled the plastic separator with weak peeling force of said pressure sensitive adhesive sheet with a separator, and 1st This is an assembling method of an optical member assembly in which an optical member is bonded and then a pressure-sensitive adhesive layer from which another plastic separator is peeled off and a second optical member are bonded.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described.
Hereinafter, the pressure-sensitive adhesive sheet with a separator of the present invention will be specifically described.
[0014]
The pressure-sensitive adhesive sheet with a separator of the present invention has high transparency and a total light transmittance of 80% or more. More preferably, it is 90% or more. When the total light transmittance is lower than 80%, the light transmittance when the optical member is bonded is poor, and there arises a problem that the display becomes dark or the contrast is lowered. Here, the total light transmittance was measured with an integrating sphere turbidimeter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.) according to JIS-K7105, with the two separators peeled off and only the adhesive layer.
[0015]
The adhesive layer in the pressure-sensitive adhesive sheet with a separator of the present invention is a pressure-sensitive adhesive, and has an adhesive force of 1 N / 25 mm or more when attached to an acrylic plate. If it is less than 1 N / 25 mm, sufficient adhesion to the optical member cannot be obtained, causing problems such as peeling. The adhesive strength with respect to the acrylic plate here is 2 m / min using an adhesive sheet from which one separator is peeled off using a rubber roll in which a pressure of 5880 N / m is applied to an acrylic plate (Sumipec E000 manufactured by Sumitomo Chemical Co., Ltd., thickness 1.5 mm flat plate). And the other separator is peeled off, and a 25 μm PET film (S-25 manufactured by Unitika) is pasted under the same conditions to produce a test piece, which is further left at room temperature for 30 minutes, and then the peel angle This is a value obtained by measuring the adhesive strength at 180 degrees, a peeling rate of 0.3 m / min, and room temperature.
[0016]
As this pressure-sensitive adhesive, a commonly used acrylic adhesive obtained by copolymerizing various acrylic monomers, natural rubber adhesive, polyisobutylene, butyl rubber, styrene-butylene-styrene copolymer (SBS), etc. Synthetic rubber adhesives, ethylene-vinyl acetate copolymer (EVA) adhesives, and the like, and mixed adhesives thereof can be used. Among these, a cross-linked acrylic adhesive is preferably used because, for example, it is easy to obtain a highly transparent adhesive such that the total light transmittance of the adhesive sheet is 80% or more.
[0017]
This cross-linked acrylic adhesive is mainly composed of a low Tg monomer such as butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylamide, acrylonitrile, etc. It can be obtained by crosslinking an acrylic copolymer obtained by copolymerization with a functional group monomer with a crosslinking agent.
[0018]
As this acrylic copolymer, those having a weight average molecular weight in the range of 100,000 to 1,500,000 are preferably used. If the weight average molecular weight is less than 100,000, the amount of low molecular weight substances in the adhesive increases, so the cohesive force of the adhesive tends to be low, and problems such as peeling are likely to occur when the optical member is bonded. Further, when the weight average molecular weight exceeds 1,500,000, there is a problem that the viscosity when dissolved in a solvent is high, and it is difficult to obtain a smooth adhesive coating appearance when formed into an adhesive sheet. The glass transition point (Tg) of this acrylic copolymer is preferably -20 ° C or lower. If the Tg is higher than −20 ° C., the adhesive becomes hard, and an appropriate adhesive force to the optical member cannot be obtained even if it is pressure-bonded at room temperature.
[0019]
As this crosslinking agent, known crosslinking agents such as isocyanate, melamine, and epoxy can be used. In addition, as this crosslinking agent, a polyfunctional crosslinking agent such as trifunctional or tetrafunctional is more preferably used in order to form a network structure that gently spreads in the adhesive.
[0020]
In addition, an appropriate amount of a tackifier, an antioxidant, an ultraviolet absorber, a softener, a filler and the like may be added to the adhesive layer as necessary.
[0021]
As for the thickness of the adhesive bond layer in this invention, 5-100 micrometers is preferable normally. More preferably, it is 10-50 micrometers. When the thickness is less than 5 μm, it is impossible to follow the irregularities on the surface of the optical member, and a sufficient adhesive force cannot be obtained. On the other hand, if the thickness is greater than 100 μm, the price per unit area increases, and the transparency causes a decrease in thickness.
[0022]
The difference in peel force from the adhesive layer between the double-sided plastic separator (1) and the plastic separator (2) used in the present invention is 10 mN / 25 mm or more. When it is less than 10 mN / 25 mm, when one separator is peeled off when an adhesive sheet is attached to an optical member, an adhesive layer adheres to the peeled separator, and adhesion with a smooth and good appearance on the other separator The phenomenon that the drug layer does not remain (crying separation phenomenon) occurs. When this tear-off phenomenon occurs, the adhesive layer cannot be applied smoothly to the optical member, and the optical member cannot be attached with good appearance.
[0023]
Moreover, the peeling force from the adhesive layer of the plastic separators (1) and (2) used in the present invention is both 200 mN / 25 mm or less. When the peeling force is higher than 200 mN / 25 mm, the peeling workability of the separator is deteriorated, the separator cannot be smoothly peeled off, the adhesive layer is folded, wrinkles or a step is generated on the surface of the adhesive layer, and is attached to the optical member. Occasionally, the deformation remains, resulting in a defect in appearance, and air bubbles are likely to be mixed during bonding. The peeling force here is a value measured at room temperature at a peeling angle of 180 degrees, a peeling speed of 1 m / min.
[0024]
The plastic separators (1) and (2) have a surface roughness of 0.1 μm or less in contact with the adhesive layer surface. When the surface roughness is larger than 0.1 [mu] m, and transferred to roughness adhesive layer of the separator surface, the adhesive layer surface is a problem bubbles on attachment is crude is easily mixed is generated. The surface roughness here is the centerline average roughness (Ra) or JIS B measured with a contact type surface roughness meter (for example, measuring device SE-3C, analysis device AY-22, manufactured by Kosaka Laboratory Ltd.). It means arithmetic mean roughness (Ra) defined by 0601 (1994) or JIS B 0601 (2001).
[0025]
Examples of the base material of the plastic separators (1) and (2) include polyester film, polypropylene film, polyethylene film, polycarbonate film, polystyrene film, and triacetyl cellulose film. Among these, a biaxially stretched polyester film which can easily obtain a smoother surface and is excellent in productivity can be preferably used.
[0026]
Further, the surface of the plastic separators (1) and (2) that is in contact with the adhesive layer is subjected to a release agent treatment. Examples of the releasing agent include simple substances such as silicone resins, fluororesins, polyvinyl alcohol resins, and resins having an alkyl group, modified products, and mixtures. Among them, a silicone resin that can easily be easily peeled off from the adhesive layer can be preferably used. Particularly, a silicone resin cured by heat, ultraviolet rays, electron beams, etc. can transfer the silicone resin to the adhesive layer. It can be more preferably used for the reason of few.
[0027]
The thickness of the plastic separators (1) and (2) is preferably 10 to 200 μm. More preferably, it is 20-75 micrometers. If the thickness is less than 10 μm, the film strength is insufficient, and problems such as tearing of the film during the production of the adhesive sheet, and easy wrinkling occur. On the other hand, if it is thicker than 200 μm, the film itself becomes expensive.
[0028]
As a method of forming the adhesive layer here, a known method such as a method of applying an adhesive whose viscosity is adjusted by dissolving in an organic solvent, a method of melting and applying the adhesive, or a method of dispersing and applying in water is used. Although it can be used, as a method for forming a cross-linked acrylic adhesive, a method of applying an adhesive having a viscosity adjusted by dissolving in an organic solvent is common.
[0029]
Further, the plastic separators (1) and (2) include surface treatment such as corona treatment and plasma treatment and primer (primer) in order to improve adhesion to the release agent layer on the surface of the plastic film as necessary. ) May be applied. Moreover, you may apply | coat an antistatic agent in order to prevent static electricity generation as needed. Examples of the antistatic agent here include various cationic antistatic agents having a cationic group such as a quaternary ammonium salt, a pyridinium salt, and a primary to tertiary amino group, a sulfonate group, a sulfate ester base, and phosphorus. Anionic antistatic agents having an anionic group such as acid ester base and sulfonate group, amphoteric antistatic agents such as amino acid and aminosulfate ester, nonionic antistatic agents such as amino alcohol, glycerin and polyethylene glycol Examples thereof include various antistatic agents, and polymer antistatic agents obtained by increasing the molecular weight of these antistatic agents.
[0030]
Hereinafter, although the Example demonstrates the pressure sensitive adhesive sheet with a separator concretely by an Example, this invention is not limited to this.
[0031]
Example 1 will be described. An acrylic copolymer using butyl acrylate as the main monomer and acrylic acid and methacrylic acid as the functional group monomers was synthesized by a solution polymerization method. The synthesized acrylic copolymer had a weight average molecular weight of 400,000. An adhesive solution in which 0.1 part by weight of an epoxy-based crosslinking agent is blended with 100 parts by weight of this acrylic copolymer is prepared, and a thermosetting silicone resin-based release agent is applied to one side of a 25 μm thick biaxially stretched polyester film. The separator coated with the mold was coated and dried so that the thickness of the adhesive when dried was 40 μm. Further, a separator coated with a thermosetting silicone resin release agent having a different release property from that of a separator coated with an adhesive on one surface of a 25 μm thick biaxially stretched polyester film was laminated on the adhesive layer surface. This adhesive sheet was allowed to stand at room temperature for 1 week and sufficiently aged, and then used for the test.
[0032]
In this adhesive sheet, the peel force from the adhesive layer of the separator coated with the adhesive was 68 mN / 25 mm, and the peel force from the adhesive layer of the laminated separator was 44 mN / 25 mm. Moreover, the result of measuring the surface roughness of the separator was both 0.05 μm.
[0033]
A second embodiment will be described. An adhesive sheet was prepared in the same manner as in Example 1 except that a 25 μm biaxially stretched polypropylene film separator having a slightly heavy release property was used for the separator coated with the adhesive. The peeling force from the adhesive layer of the separator coated with the adhesive in this adhesive sheet was 130 mN / 25 mm.
[0034]
Comparative Example 1 will be described. An adhesive sheet was produced in the same manner as in Example 1 except that the same separator as that applied with the adhesive was laminated on the adhesive layer surface.
[0035]
Comparative example 2 will be described. An adhesive sheet was prepared in the same manner as in Example 1 except that a 25 μm biaxially oriented polypropylene film separator having a slightly lighter release property was used for the separator coated with the adhesive. The peeling force from the adhesive layer of the separator coated with the adhesive in this adhesive sheet was 51 mN / 25 mm.
[0036]
Comparative Example 3 will be described. An adhesive sheet was prepared in the same manner as in Example 1 except that a 25 μm biaxially stretched polypropylene film separator having a high release property was used as the separator coated with the adhesive. The peeling force from the adhesive layer of the separator coated with the adhesive in this adhesive sheet was 450 mN / 25 mm.
[0037]
Comparative example 4 will be described. An adhesive sheet was prepared in the same manner as in Example 1 except that a separator coated with a thermosetting silicone resin release agent on one side of a 40 μm thick unstretched polypropylene film was used for the separator coated with the adhesive. . The peeling force from the adhesive layer of the separator coated with the adhesive in this adhesive sheet was 110 mN / 25 mm. Moreover, the result of measuring the surface roughness Ra of the separator was 0.3 μm.
[0038]
The characteristic values of the adhesive sheets of the above examples and comparative examples were measured by the following methods. The results are summarized in FIG.
(1) Total light transmittance The total light transmittance is measured according to JIS using an integrating sphere turbidimeter (NDH2000 model, manufactured by Nippon Denshoku Industries Co., Ltd.) with only two adhesive layers peeled off. -Measured according to -K7105.
(2) Adhesive strength against acrylic plate Using an adhesive sheet from which one separator was peeled off, a rubber roll in which a pressure of 5880 N / m was applied to an acrylic plate (Sumipec E000 manufactured by Sumitomo Chemical Co., Ltd., thickness 1.5 mm flat plate), 2 m / min A test piece was prepared by applying a 25 μm PET film (S-25 manufactured by Unitika) under the same conditions as those applied at a speed, and the other separator was peeled off. The adhesion strength (N / 25 mm) was measured at room temperature and a peeling speed of 0.3 m / min.
(3) Surface roughness of the separator The surface roughness of the separator in contact with the adhesive layer surface was measured with a contact-type surface roughness meter (manufactured by Kosaka Laboratory Ltd., measuring device SE-3C, analyzing device AY-22). The centerline average roughness (Ra) value was used.
(4) Separation force of the separator The adhesive sheet was cut to a width of 25 mm, and the separation force (mN / 25 mm) when peeling the separator from the adhesive layer at a peeling angle of 180 degrees, a peeling speed of 1 m / min in a room temperature atmosphere was measured. .
(5) Bonding workability An adhesive sheet from which one separator is peeled off is a rubber roll in which a pressure of 5880 N / m is applied to an acrylic plate (Sumitek Chemical Co., Ltd. Sumipec E000, thickness 1.5 mm flat plate) having a size of 100 mm × 200 mm. Used and pasted at a speed of 2 m / min. The other separator was peeled off, and a 50 μm PET film (S-50 manufactured by Unitika) was laminated under the same conditions. The bonding workability at this time was evaluated according to the following criteria.
○: The separator was easily peeled off, and the bonding work was easy.
X: The phenomenon of tearing occurred when the separator was peeled off, and the bonding operation could not be performed.
(6) Bonding appearance The appearance of the test piece evaluated for bonding workability was confirmed and evaluated according to the following criteria.
◯: Appearance was good, and no bubbles were mixed in or no adhesive layer was deformed.
X: Appearance was poor, and defects such as air bubbles and traces of deformation of the adhesive layer were observed.
−: The pasting operation could not be performed and the appearance could not be confirmed.
[0039]
As is clear from FIG. 1, Examples 1 and 2 which are adhesive sheets of the present invention were excellent in bonding workability, and the appearance of the bonded test pieces was also good. On the other hand, Comparative Example 1 using a separator having the same peeling force on the adhesive coating side and the laminating side, and Comparative Example 2 having a small difference in peeling force between the adhesive coating side and the laminating side separator as 7 mN / 25 mm, When the separator was peeled off, a tearing phenomenon occurred, and it was not possible to bond them together. Further, in Comparative Example 3 where the separator peeling force on the adhesive coating side is as high as 450 mN / 25 mm, since the separator cannot be peeled smoothly, a step is generated on the surface of the adhesive layer, and the adhesive layer is also applied to the bonded test piece. Appearance abnormalities due to deformation of were observed. Moreover, in Comparative Example 4 where the surface roughness Ra of the separator on the adhesive coating side was as large as 0.3 μm, the roughness was transferred to the adhesive layer, and air bubbles were observed in the bonded test pieces.
[0040]
As described in the above examples, the adhesive sheet with a separator of the present invention is used when laminating a plate-like or sheet-like optical member, has excellent transparency, and has an appearance such as bubble mixing or streak marks during pasting. It is possible to obtain a pressure-sensitive adhesive sheet that hardly causes defects and has excellent workability for pasting.
[0041]
The present invention also relates to an optical member assembly in which optical members are bonded to each other, wherein the optical member assembly is bonded by a pressure-sensitive adhesive layer from which a plastic separator on both sides of a pressure-sensitive adhesive sheet with a separator is peeled off. A pressure-sensitive adhesive layer having a pressure-sensitive adhesive sheet with a separator and a first optical member bonded to the pressure-sensitive adhesive layer from which the weak plastic separator has been peeled; In this method, the layer and the second optical member are assembled and assembled. As a result, the optical member can be assembled without hindering the transparency.
[0042]
【The invention's effect】
According to the present invention, it is possible to obtain a pressure-sensitive adhesive sheet with a separator and an optical member assembly that is excellent in transparency, hardly causes appearance defects such as air bubbles and streak marks during pasting, and has excellent pasting workability. Can do.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a table for explaining measurement results and the like of a pressure-sensitive adhesive sheet with a separator according to an example.

Claims (5)

In a pressure-sensitive adhesive sheet with a separator comprising a pressure-sensitive adhesive layer to which an optical member is bonded, and a plastic separator provided on both sides,
The surface roughness Ra of the surface in contact with the pressure-sensitive adhesive layer of the plastic separator is 0.1 μm or less, and the difference in peeling force from the pressure-sensitive adhesive layer of the double-sided plastic separator is 10 mN / 25 mm or more. The pressure-sensitive adhesive sheet with a separator is characterized in that both of the peeling forces from the adhesive layer of the plastic separator are 200 mN / 25 mm or less, and the total light transmittance of the pressure-sensitive adhesive layer is 80% or more. . The pressure-sensitive adhesive sheet with a separator according to claim 1, wherein the adhesive force of the pressure-sensitive adhesive layer to the acrylic plate is 1 N / 25 mm or more . The pressure-sensitive adhesive sheet with a separator according to claim 1 or 2, wherein the adhesive layer is made of a cross-linked acrylic adhesive. An optical member assembly assembled by bonding optical members,
An optical member assembly which is bonded by a pressure-sensitive adhesive layer from which the plastic separators on both sides of the pressure-sensitive adhesive sheet with a separator according to any one of claims 1 to 3 are peeled off . A method of assembling an optical member assembly in which optical members are bonded together,
The pressure-sensitive adhesive layer from which the pressure-sensitive adhesive sheet with a separator according to any one of claims 1 to 3 has been peeled off and the first optical member are bonded, and then another A method of assembling an optical member assembly , comprising assembling a pressure-sensitive adhesive layer from which a plastic separator has been peeled off and a second optical member .

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