JP2007269860A - Pressure-sensitive adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent pressure-sensitive adhesive sheet in which protrusion of a pressure-sensitive adhesive does not occur at processing as a pressure-sensitive adhesive sheet for an electronic display. <P>SOLUTION: In the pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer formed at least one surface of the substrate, the pressure-sensitive adhesive layer contains an acrylic polymer as a main component, and the pressure-sensitive adhesive layers of a pair of pressure-sensitive adhesive sheets are stuck to each other such that they become a sticking area of 25 mm square under a condition of a temperature of 23°C and humidity of 50%. A relative movement amount of the sticking surface generated after a load of 1 kg is added in a parallel direction of the sticking surface relative to one pressure-sensitive adhesive sheet for 900 seconds is 0.10 mm or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed on the surface of a substrate, and particularly to a pressure-sensitive adhesive sheet used as an optical film for an electronic display.

  In recent years, an electronic display such as a plasma display panel (PDP), a liquid crystal display (LCD), a cathode ray tube (CRT), or an organic EL display is in the form of an adhesive sheet having an adhesive layer in order to achieve high functionality and light weight. Various optical films to be supplied are laminated. For example, PDP generates electromagnetic waves that are harmful to the human body and other devices, near infrared rays that cause wireless devices such as remote controls to malfunction, and orange neon light that reduces red density. Various optical films having a function of cutting light are supplied in the form of an adhesive sheet, and are laminated via an adhesive layer. Furthermore, in order to prevent external light from being reflected on the screen, an antireflection (AR) optical film, which is an adhesive sheet, is attached to the outermost surface.

  The various optical films formed into pressure-sensitive adhesive sheets are incorporated into an electronic display through processing steps such as slitting, punching, and sheet cutting. At this time, if the pressure-sensitive adhesive protrudes from the cut surface, the pressure-sensitive adhesive that protrudes from the cut surface adheres to the surface of the pressure-sensitive adhesive sheet when the pressure-sensitive adhesive sheets are stacked. Furthermore, there is a possibility that the product function is deteriorated due to adhesion of the adhesive to the electronic display internal components. Moreover, since there exists a possibility that an adhesive may adhere also to the cutting blade in a process, it needs to remove and productivity also falls by removal work.

Typical practical properties of the pressure-sensitive adhesive sheet include 1) adhesive strength, 2) tack (adhesiveness), and 3) holding power. As a method for measuring the holding force of the pressure-sensitive adhesive sheet, generally, a measurement method according to the method specified in JIS Z 0237-13 is mentioned. As a method for measuring the tack of the pressure-sensitive adhesive sheet, generally, JIS Z 0237-14 is used. And a measuring method using an inclined ball tack specified in the above. Patent Document 1 discloses a method for measuring the holding force of the pressure-sensitive adhesive sheet, which is different from the method for measuring the holding force defined in JIS Z 0237-13.
JP 2004-212757 A

  The present inventor aims to provide a pressure-sensitive adhesive sheet which does not protrude from the pressure-sensitive adhesive in various processing steps and is particularly useful as a component of an electronic display. However, even a conventional measurement method for measuring the characteristics of the pressure-sensitive adhesive sheet does not provide a sufficiently useful index for determining whether or not the pressure-sensitive adhesive is not protruded in the pressure-sensitive adhesive sheet for electronic displays. That is, even if the pressure-sensitive adhesive sheet is determined to have excellent characteristics by the conventional measurement method, the pressure-sensitive adhesive sometimes protrudes when applied to an electronic display. Therefore, since the conventional adhesive sheet was determined based on the conventional index, it was not sufficiently excellent as an adhesive sheet for electronic displays.

  The present inventor examined the causes that are not useful for determining the characteristics of the pressure-sensitive adhesive sheet for electronic displays using the index obtained by the conventional measurement method, and general pressure-sensitive adhesive sheets, pressure-sensitive adhesive labels, etc. While the molecular weight of the component is about tens of thousands, the pressure-sensitive adhesive sheet for electronic displays has a molecular weight of 300,000 to 2,000,000 as the main component of the pressure-sensitive adhesive. Compared to general pressure-sensitive adhesive sheets and pressure-sensitive adhesive labels It is a hard and non-sticky structure, and it is understood that the conventional measurement method is unlikely to cause a difference. Further, the extent of the pressure-sensitive adhesive is different from the adhesive strength, tack, and holding power, which are the practical properties of the pressure-sensitive adhesive sheet described above, and in order to obtain a useful index for judging the degree of pressure-sensitive adhesive, We thought that it was necessary to develop another measurement method different from the conventional one. Based on the above considerations, various measurement methods were examined. As a result, a measurement method capable of obtaining a new index having a high correlation with the protrusion of the adhesive during processing was found. Therefore, an excellent pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive does not protrude at the time of processing can be provided as a pressure-sensitive adhesive sheet for electronic displays.

  In addition, in patent document 1, although the characteristic of the adhesive sheet for electronic displays is measured, the glass plate is used as a to-be-adhered body which affixes an adhesive sheet at the time of a measurement, and it changes with compatibility with this to-be-adhered body. Therefore, it is difficult to say that it is sufficient as a measurement method for obtaining an index for judging the protrusion of the pressure-sensitive adhesive in the pressure-sensitive adhesive sheet.

  That is, the present invention is a pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer formed on at least one surface of the base material, wherein the pressure-sensitive adhesive layer contains an acrylic polymer as a main component and has a temperature of 23 ° C. The pressure-sensitive adhesive layers of the pair of pressure-sensitive adhesive sheets are bonded to each other so as to have a bonding area of 25 mm square under a condition of 50% humidity, and 1 kg in the direction parallel to the bonding surface with respect to one of the pressure-sensitive adhesive sheets. This is a pressure-sensitive adhesive sheet in which the relative movement amount of the bonding surface generated after applying the load of 900 seconds is 0.10 mm or less.

  The acrylic polymer is preferably a copolymer composed of at least a first monomer unit and a second monomer unit, and the first monomer unit is selected from the group consisting of acrylic acid esters, methacrylic acid esters, and combinations thereof. And the second monomer unit is selected from the group consisting of hydroxyalkyl acrylates, hydroxyalkyl methacrylates, unsaturated aliphatic carboxylic acids, and combinations thereof. Note that the cohesiveness of the pressure-sensitive adhesive layer is preferably adjusted with a crosslinking agent. In this case, when the acrylic polymer contained in the adhesive layer is 100 parts by weight in terms of solid content, it is preferable that 0.05 to 15 parts by weight of the crosslinking agent is contained in terms of solid content.

  One form of the pressure-sensitive adhesive sheet is an optical film for an electronic display.

  Further, the present invention is a processability evaluation method for an adhesive sheet comprising a base material and an adhesive layer formed on at least one surface of the base material, wherein the adhesive layer contains an acrylic polymer as a main component. Then, under the conditions of a temperature of 23 ° C. and a humidity of 50%, the pressure-sensitive adhesive layers of the pair of pressure-sensitive adhesive sheets are bonded to each other so as to have a bonding area of 25 mm square, and are bonded to the one pressure-sensitive adhesive sheet. Adhesive which measures the relative movement amount of the bonding surface generated after applying a load of 1 kg in the plane parallel direction for 900 seconds, and evaluates that it has excellent processability when the relative movement amount is 0.10 mm or less. This is a method for evaluating the processability of a sheet.

  According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that is sufficiently prevented from sticking out in processing steps such as slitting, punching, and sheet cutting, and that has excellent processability. Moreover, according to this invention, the evaluation method useful for evaluating the characteristic of the adhesive sheet for electronic displays can be provided.

  The pressure-sensitive adhesive sheet of the present invention comprises a base material and a pressure-sensitive adhesive layer formed on at least one surface of the base material. The pressure-sensitive adhesive layer contains an acrylic polymer as a main component, and has a temperature of 23 ° C. and a humidity of 50%. The adhesive layers of the pair of adhesive sheets are bonded to each other so as to have a 25 mm square bonding area, and a load of 1 kg is applied to the one adhesive sheet in a direction parallel to the bonding surface. The relative movement amount of the bonding surface produced after adding for a second is 0.10 mm or less.

  As a base material, what is used for formation of electronic displays, such as PDP, LCD, CRT, an organic electroluminescent display, is used, for example, The kind in particular is not restrict | limited. As the substrate, for example, an optical film comprising a substrate layer and one or more optical functional layers is used. Examples of the optical functional layer include an antireflection layer, an electromagnetic wave shielding layer, a near infrared cut layer, a neon light cut layer, a polarizing layer, a retardation layer, an optical compensation layer, a brightness enhancement layer, and an antiglare layer.

  As the base material layer, a known transparent resin film such as polyethylene terephthalate (PET), triacetyl cellulose (TAC), polyarylate, polyimide, polyether, polycarbonate, cycloolefin resin, norbornene resin is preferably used. Can do. When the pressure-sensitive adhesive sheet is used as an optical film for an electronic display, PET and TAC excellent in transparency are particularly preferably used for the substrate. The base material layer is preferably subjected to surface treatment such as corona treatment, alkali treatment, plasma treatment, and easy adhesion resin layer coating treatment in order to improve adhesion with other layers such as an optical functional layer.

  For example, a polarizing film can be used as the optical functional layer. As a polarizing film, what has a transparent protective film on the single side | surface or both surfaces of a polarizer can be used, for example. The polarizer here is not particularly limited, and various types can be used. Examples of the polarizer include hydrophilic polymers such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. Examples thereof include polyene-based oriented films such as those obtained by adsorbing volatile substances and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. As the transparent protective film, a cellulose-based polymer such as triacetyl cellulose is preferable from the viewpoints of polarization characteristics and durability. For the adhesion treatment between the polarizer and the transparent protective film, an isocyanate-based adhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive, a vinyl-based latex, a water-based polyester, or the like is used.

  As the pressure-sensitive adhesive used for forming the pressure-sensitive adhesive layer, a material containing an acrylic polymer and a crosslinking agent is preferably used. As the acrylic polymer, a polymer having a skeleton as a main component of a monomer unit (also referred to as “first monomer unit”) selected from the group consisting of acrylic acid esters, methacrylic acid esters, and combinations thereof is used. The first monomer unit is, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, methyl methacrylate, ethyl It is selected from the group consisting of methacrylate, n-butyl acrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, and combinations thereof. In particular, n-butyl acrylate (Tg = −55 ° C.) and 2-ethylhexyl acrylate (Tg = −70 ° C.) having a low glass transition point (Tg) having adhesive force even at low temperatures are preferable.

  The acrylic polymer is preferably a copolymer of a monomer unit that is a main component of the skeleton and a monomer unit having a functional group capable of reacting with a crosslinking agent (also referred to as “second monomer unit”).

  The monomer unit having a functional group is preferably selected from the group consisting of hydroxyalkyl esters of acrylic acid, hydroxyalkyl esters of methacrylic acid, unsaturated aliphatic carboxylic acids, and combinations thereof. The second monomer unit includes, for example, 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate which are hydroxyalkyl acrylate esters, 2-hydroxybutyl acrylate and 2-hydroxyethyl methacrylate and 2-hydroxyethyl methacrylate which are hydroxyalkyl esters. It is selected from the group consisting of propyl methacrylate and 4-hydroxybutyl methacrylate, unsaturated aliphatic carboxylic acids acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, and combinations thereof. In particular, it is preferable to use one or more of 2-hydroxyethyl acrylate, acrylic acid, and methacrylic acid because the aggregation effect by polymerization with n-butyl acrylate and 2-ethylhexyl acrylate is high.

  When the acrylic polymer is a copolymer, it is preferable that the monomer unit of the copolymer is 90 to 99.5% by weight of the first monomer unit and 0.5 to 10% by weight of the second monomer unit. If the total amount of the second monomer unit is less than 0.5% by weight, the cohesiveness of the pressure-sensitive adhesive is low, and if it exceeds 10% by weight, the cohesion is strong and it is difficult to form an adhesive layer.

  The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, but is preferably 300,000 to 2,000,000, particularly preferably 800,000 to 1,300,000. In the present specification, the weight average molecular weight (Mw) is a value in terms of polystyrene measured by gel permeation chromatography (GPC method).

  The acrylic polymer can be produced by various known methods. For example, a radical polymerization method such as a bulk polymerization method, a solution polymerization method, or a suspension polymerization method can be appropriately selected. As the radical polymerization initiator, various known azo and peroxide initiators can be used. Among the above production methods, the solution polymerization method is preferred, and the acrylic polymer produced by the above method is dissolved in a polar solvent such as toluene, ethyl acetate, methyl ethyl ketone, etc. to prepare an acrylic polymer solution.

  The crosslinking agent uses a crosslinking agent capable of crosslinking with the acrylic polymer, for example, isocyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, trimethylol propane tolylene diisocyanate, trimethylol propane tolylene diisocyanate, diphenylmethane triisocyanate, etc. Epoxy compounds such as bisphenol A, epichlorohydrin type epoxy resin, ethylene glycol glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane; hexamethylene Amine compounds such as diamine, triethyldiamine, polyethyleneimine; aluminum, iron, copper, zinc, tin, titanium, nickel A metal chelate compound in which a polyvalent metal such as acetylacetone or ethyl acetoacetate is coordinated; N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxide), N, N′-toluene-2,4 One or more of aziridine-based compounds such as -bis (1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1- (2-methylaziridine), tri-1-aziridinylphosphine oxide are preferably used Can be used. In particular, the use of one or more of trimethylolpropane tolylene diisocyanate, trimethylolpropane xylylene diisocyanate, glycerin diglycidyl ether, and 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane causes stickiness of the adhesive. It is preferable without suppressing color change and yellowing at high temperature. The cross-linking agent imparts adhesive performance by cross-linking the acrylic polymer between molecules. When the acrylic polymer is 100 parts by weight in terms of solid content, the crosslinking agent is added in an amount of 0.05 to 15 parts by weight, in particular 0.1 to 5 parts by weight, and further 0.2 to 3 parts by weight in terms of solids. It is preferable. If the amount is less than 0.05 part by weight, the adhesive is soft, and the adhesive is likely to protrude during processing. If the amount exceeds 15 parts by weight, unintentional peeling or peeling is likely to occur due to insufficient adhesive force, and discoloration easily occurs at high temperatures. Become. A crosslinking agent is added to, for example, an acrylic polymer solution to prepare an adhesive solution. In addition, about the solid component of an acryl-type polymer, and the solid component of a crosslinking agent, it can be considered that the added amount is contained in the adhesion layer as it is.

  Furthermore, you may add suitably additives, such as a tackifier, a plasticizer, a filler, a coloring agent, an antistatic agent, antioxidant, a ultraviolet absorber, to the said adhesive agent solution as needed.

  The method for forming the pressure-sensitive adhesive layer is not particularly limited. For example, the pressure-sensitive adhesive solution is applied to the surface of the substrate by a known method such as a gravure printing method, a spray method, a dipping method, a roll coater method, or a die coater method. Dry to form an adhesive layer. Or you may form an adhesion layer by the method of providing an adhesion layer in the peeling sheet mentioned later, and transferring this to a base material. In this case, the adhesive layer is protected by two release sheets, using a so-called non-carrier type adhesive layer sheet, and then peeling the one release sheet of this sheet and bonding the exposed surface to the surface of the substrate. An adhesive layer may be formed. Although the thickness of an adhesion layer is not specifically limited, Preferably it is 5-150 micrometers, More preferably, you may be 10-90 micrometers. If the thickness is less than 5 μm, unintentional peeling or peeling is likely to occur due to insufficient adhesive strength, and if it exceeds 150 μm, the pressure-sensitive adhesive becomes excessive, resulting in a decrease in light transmission and the pressure-sensitive adhesive protruding during processing.

  The pressure-sensitive adhesive layer may be provided only on one side of the substrate, or may be provided on both sides. A release sheet may be provided on the surface of the adhesive layer to protect the adhesive layer. Examples of release sheets include paper, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyethylene terephthalate and other synthetic resin films, rubber sheets, paper, cloth, nonwoven fabric, nets, foam sheets, and metals. An appropriate thin leaf body made of foil or a laminate of these can be used. The surface of the release sheet may be subjected to release treatment such as silicone treatment, long-chain alkyl treatment, fluorine treatment, etc., as necessary, in order to enhance the peelability from the adhesive layer.

  The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having a displacement amount of 0.10 mm or less according to the displacement amount measurement test described below.

(Displacement measurement test)
FIG. 1 is a front view (a) and a side view (b) schematically showing a state of a deviation amount measurement test. The pressure-sensitive adhesive sheet is cut to prepare a pressure-sensitive adhesive sheet 1 of 30 mm × 50 mm and a pressure-sensitive adhesive sheet 2 of 25 mm × 100 mm. As for the adhesive sheets 1 and 2, base material 1a, 2a and adhesive layer 1b, 2b are laminated | stacked, respectively. These pressure-sensitive adhesive sheets 1 and 2 are left under conditions of a temperature of 23 ° C. and a humidity of 50% for 2 hours. All the following steps are also performed under conditions of a temperature of 23 ° C. and a humidity of 50%. Then, the adhesive layers 1b and 2b of the adhesive sheets 1 and 2 are bonded to each other so that the bonding area is 25 mm × 25 mm, and the adhesive portion is reciprocated once by a rubber roller having a weight of 2 kg from the substrate 1a side of the adhesive sheet 1. Use a test piece. When the peeling sheet is stuck on the surface of the pressure-sensitive adhesive layers 1b and 2b, the two pressure-sensitive adhesive sheets 1 and 2 are bonded together after the peeling sheet is peeled off. After 30 minutes, the pressure-sensitive adhesive sheet 1 is fixed to a jig that hangs the test piece vertically so that the pressure-sensitive adhesive sheet 1 is on the upper side, and a weight 3 having a weight of 1 kg is hung on the end portion of the pressure-sensitive adhesive sheet 2 below, for 900 seconds. The relative movement amount (deviation amount) of the latter two adhesive sheets is measured to 1/100 mm with a laser dimension measuring device (trade name: LS-3036, manufactured by Keyence Corporation).

  Hereinafter, the present invention will be specifically described with reference to examples.

Example 1
1. Preparation of pressure-sensitive adhesive 30 parts by weight of an acrylic polymer (a copolymer of 99% by weight of n-butyl acrylate and 1% by weight of 2-hydroxyethyl acrylate) having a weight average molecular weight (Mw) of 1,000,000 was added to 70 parts by weight of a solvent (toluene 30 (A solvent in which parts by weight and 40 parts by weight of ethyl acetate are mixed) was dissolved to obtain an acrylic polymer solution having a solid content of 30% by weight. When the solid content of the acrylic polymer solution was 100 parts by weight, a solution obtained by adding 0.50 part by weight of trimethylolpropanxylylene diisocyanate as a crosslinking agent in terms of solid content to this solution was used as a pressure-sensitive adhesive solution.

2. Preparation of pressure-sensitive adhesive sheet The pressure-sensitive adhesive solution prepared above was applied on the silicone resin-coated surface of a release sheet consisting of a 75 μm thick PET film (trade name; MRF75, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) with a silicone resin coated on one side. The sheet was dried at 100 ° C. for 1 minute to obtain a sheet having an adhesive layer with a thickness of 25 μm after drying. After the antireflection (AR) treatment on the surface of a 100 μm thick PET film (trade name; A-4300, manufactured by Toyobo Co., Ltd.), the opposite surface of the treated surface and the sheet having the above adhesive layer are adhered to each other at room temperature. Aged for a week. In this way, an adhesive sheet of Example 1 was obtained.

(Example 2)
1. Preparation of pressure-sensitive adhesive 30 parts by weight of an acrylic polymer having a weight average molecular weight (Mw) of 1,000,000 (a copolymer of 76.5% by weight of n-butyl acrylate, 20% by weight of methyl acrylate, and 3.5% by weight of acrylic acid) It was dissolved in 70 parts by weight of solvent (a solvent obtained by mixing 60 parts by weight of ethyl acetate and 10 parts by weight of methyl ethyl ketone) to obtain an acrylic polymer solution having a solid content of 30% by weight. When the solid content of the acrylic polymer solution is 100 parts by weight, 0.30 part by weight of trimethylolpropane tolylene diisocyanate as a crosslinking agent in terms of solid content and 1,3-bis (N, N-diglycidyl) are added to this solution. A pressure-sensitive adhesive solution was prepared by adding 0.10 parts by weight of aminomethyl) cyclohexane in terms of solid content.

2. Preparation of pressure-sensitive adhesive sheet A pressure-sensitive adhesive sheet of Example 2 was obtained in the same manner as Example 1 except that the pressure-sensitive adhesive solution was different.

(Example 3)
1. Preparation of pressure-sensitive adhesive 30 parts by weight of an acrylic polymer (a copolymer of 96% by weight of n-butyl acrylate, 1% by weight of 2-hydroxyethyl acrylate and 3% by weight of acrylic acid) having a weight average molecular weight (Mw) of 1,300,000 was used as a solvent It was dissolved in 70 parts by weight (a solvent obtained by mixing 40 parts by weight of toluene and 30 parts by weight of ethyl acetate) to obtain an acrylic polymer solution having a solid content of 30% by weight. When the solid content of the acrylic polymer solution was 100 parts by weight, a pressure-sensitive adhesive solution was obtained by adding 0.70 parts by weight of trimethylolpropane tolylene diisocyanate as a crosslinking agent in terms of solid content.

2. Preparation of pressure-sensitive adhesive sheet A pressure-sensitive adhesive sheet of Example 3 was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive solution was different.

Example 4
1. Preparation of pressure-sensitive adhesive 30 parts by weight of an acrylic polymer (a copolymer of 98% by weight of n-butyl acrylate and 2% by weight of 4-hydroxybutyl acrylate) having a weight average molecular weight (Mw) of 1,000,000 was added to 70 parts by weight of a solvent (toluene 50 (A solvent in which parts by weight and 20 parts by weight of ethyl acetate are mixed) was dissolved to obtain an acrylic polymer solution having a solid content of 30% by weight. When the solid content of the acrylic polymer solution was 100 parts by weight, a pressure-sensitive adhesive solution was obtained by adding 0.3 parts by weight of trimethylolpropane tolylene diisocyanate as a crosslinking agent in terms of solid content.

2. Preparation of pressure-sensitive adhesive sheet A pressure-sensitive adhesive sheet of Example 4 was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive solution was different.

(Comparative Example 1)
1. Preparation of pressure-sensitive adhesive Assuming that the solid content of the acrylic polymer solution prepared in the same manner as in Example 1 was 100 parts by weight, 0.125 parts by weight of trimethylolpropane xylylene diisocyanate as a crosslinking agent was added to this solution as a solid content. This was used as an adhesive solution.

2. Preparation of pressure-sensitive adhesive sheet A pressure-sensitive adhesive sheet of Comparative Example 1 was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive solution was different.

(Comparative Example 2)
The conventional AR film adhesive sheet was used as the adhesive sheet of Comparative Example 2.

  With respect to Examples 1 to 4 and Comparative Examples 1 and 2, the above-described deviation amount measurement test and the following tests were performed. The results are shown in Table 1.

(Slit processing aptitude evaluation test)
When the adhesive sheet is slit for 500 m with a slitter machine (trade name; AUTO SLITTER S-300, manufactured by Sanwa Giken Co., Ltd.), the adhesive is attached to the slit blade and the adhesive is not leaked from the end of the adhesive sheet. Was visually evaluated. The case where adhesion of an adhesive or the adhesion of an adhesive was not recognized was evaluated as “◯”, and the case where adhesion of an adhesive or an adhesive was observed was evaluated as “x”.

(Punching process aptitude evaluation test)
When 100 sheets of a pressure sensitive adhesive sheet were punched into a 17-inch screen size with a punching machine (trade name; S1600B, manufactured by Sakamoto Machine Co., Ltd.), adhesion of the adhesive to the punching blade and adhesion of the adhesive from the end of the pressure sensitive adhesive sheet The presence or absence was visually evaluated. The case where no adhesion of the adhesive or the adhesion of the adhesive was observed was evaluated as “◯”, and the case where the adhesion of the adhesive or the adhesion of the adhesive was observed was evaluated as “x”.

(Ball tack evaluation test)
In accordance with JIS Z 0237-14, an inclined ball tack with an inclination angle of 30 degrees was measured.

(Retention force evaluation test)
In accordance with JIS Z 0237-13, a 1 kg weight was attached and the deviation after 17 hours was measured. The presence or absence of deviation was evaluated visually, and the case where there was no deviation was designated as “NC”.

表１に示す結果からわかるように、ズレ量試験におけるズレ量が０．１０ｍｍ以下である実施例１〜４の粘着シートは、スリット加工時および打ち抜き加工時において粘着剤の付着および粘着剤のモレが認められず、電子ディスプレイ等に有用である。一方、ズレ量が０．１１ｍｍ以上である比較例１、２の粘着シートは、スリット加工時及び打ち抜き加工時における粘着剤の付着および粘着剤のモレが認められ、電子ディスプレイ等に適用した場合に、不都合が生じる場合がある。また、表１に示す結果からわかるように、このような実施例１〜４の特性と、比較例１，２の特性との差は、ボールタック評価試験や保持力評価試験から見出すことはできない。

As can be seen from the results shown in Table 1, the pressure-sensitive adhesive sheets of Examples 1 to 4 having a deviation amount of 0.10 mm or less in the deviation amount test were adhered to the adhesive and adhered to the adhesive during slitting and punching. This is useful for electronic displays and the like. On the other hand, the pressure-sensitive adhesive sheets of Comparative Examples 1 and 2 having a displacement amount of 0.11 mm or more were observed when the adhesive was adhered and the adhesive was leaked during slitting and punching, and applied to an electronic display or the like. Inconvenience may occur. Further, as can be seen from the results shown in Table 1, the difference between the characteristics of Examples 1 to 4 and the characteristics of Comparative Examples 1 and 2 cannot be found from the ball tack evaluation test or the holding power evaluation test. .

  The pressure-sensitive adhesive sheet of the present invention is useful as an optical film used in electronic displays such as a plasma display panel (PDP), a liquid crystal display (LCD), a cathode ray tube (CRT), and an organic EL display.

The front view (a) and side view (b) which show the mode of a gap amount measurement test typically.

Explanation of symbols

1, 2 Adhesive sheet 1a, 2a Base material 1b, 2b Adhesive layer 3 Weight

Claims (3)

A pressure-sensitive adhesive sheet comprising a base material and an adhesive layer formed on at least one surface of the base material,
The adhesive layer contains an acrylic polymer as a main component,
Under the conditions of a temperature of 23 ° C. and a humidity of 50%, the pressure-sensitive adhesive layers of the pair of pressure-sensitive adhesive sheets are bonded to each other so as to have a bonding area of 25 mm square, and the bonding surface is parallel to one of the pressure-sensitive adhesive sheets. The relative movement amount of the bonding surface that occurs after applying a load of 1 kg in the direction for 900 seconds is 0.10 mm or less,
Adhesive sheet. The acrylic polymer is a copolymer composed of at least a first monomer unit and a second monomer unit,
The first monomer unit is selected from the group consisting of acrylic esters, methacrylic esters, and combinations thereof;
The second monomer unit is selected from the group consisting of hydroxyalkyl acrylates, hydroxyalkyl methacrylates, unsaturated aliphatic carboxylic acids, and combinations thereof;
The pressure-sensitive adhesive sheet according to claim 1. The pressure-sensitive adhesive layer contains a crosslinking agent, and when the weight of the acrylic polymer is 100 parts by weight in terms of solid content, the crosslinking agent is contained in an amount of 0.05 to 15 parts by weight in terms of solid content. The adhesive sheet as described.

Images