JP4625436B2 - Adhesive sheet - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer containing an acrylic polymer as a main component, and particularly to a pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is formed on an optical film, and a pressure-sensitive adhesive sheet used by being bonded to the optical film.

  In an electronic display such as a plasma display panel (PDP), a liquid crystal display (LCD), a cathode ray tube (CRT), and an organic EL display, various optical films 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. Alternatively, various optical films having a function of cutting neon light are laminated. Furthermore, in order to prevent reflection of external light on the screen, an optical film for antireflection (AR) is bonded to the outermost surface.

  In recent years, as such an optical film, the use of a pressure-sensitive adhesive sheet having an adhesive layer, or by sticking and using an adhesive sheet having an adhesive layer on an optical film, it is possible to increase the functionality and weight. I'm trying.

In this case, when peeling off the release sheet on the light release side of the so-called non-carrier type pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer between the release sheets in the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, and bonding them to various functional films Defects having a lens effect due to the occurrence of air entrapment (occurrence of bubbles) cause image distortion in the electronic display, partial thinning of the color tone, and the like, which significantly deteriorates the image quality of the electronic display. For example, Patent Document 1 discloses a method for manufacturing a pressure-sensitive adhesive sheet that suppresses the generation of bubbles.
JP 2003-263726 A

  However, for example, when a non-carrier type pressure-sensitive adhesive sheet is bonded onto the grid forming surface of the electromagnetic wave shielding film on which the grid-like copper plating is applied on the film, air easily enters the grid. An object of this invention is to provide the adhesive sheet in which air does not enter easily at the time of bonding, even if a to-be-adhered surface is an uneven surface like the case where it bonds to an electromagnetic wave shield film.

  The inventors of the present invention first advanced the research on the idea that air cohesion during bonding could be prevented by increasing the cohesiveness of the pressure-sensitive adhesive in the pressure-sensitive adhesive layer. I didn't find it. And when cohesion property was too high, when bonding an adhesive sheet to a to-be-adhered body, it turned out that there existed a problem that it took time, ie, a problem that adaptability was bad. As a result of further diligent research, the present inventors have found that pressure-sensitive adhesive sheets have good conformability by containing methyl methacrylate and a styrene tackifier in the pressure-sensitive adhesive layer so that air is less likely to bite during bonding. It was found that can be obtained.

  That is, the present invention is a pressure-sensitive adhesive sheet in which a support and a pressure-sensitive adhesive layer containing an acrylic polymer as a main component are laminated, and the acrylic polymer contains methyl methacrylate as a kind of constituent monomer, The pressure-sensitive adhesive layer is a pressure-sensitive adhesive sheet further containing a styrene tack fire.

  Preferably, the acrylic polymer contains 5 to 15 parts by weight of the methyl methacrylate in 100 parts by weight. Preferably, the adhesive layer contains 0.5 to 3.0 parts by weight of the styrene tackifier with respect to 100 parts by weight of the acrylic polymer.

  The pressure-sensitive adhesive sheet according to the present invention is less susceptible to air entrainment during bonding to an adherend such as an optical film, and has good conformability.

  The present invention is a pressure-sensitive adhesive sheet in which a support and a pressure-sensitive adhesive layer containing an acrylic polymer as a main component are laminated, wherein the acrylic polymer contains methyl methacrylate as a kind of constituent monomer, The layer further contains a styrenic tackifier.

  The pressure-sensitive adhesive used for forming the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present invention contains, as a main component, an acrylic polymer containing methyl methacrylate as a constituent monomer. Methyl methacrylate gives a cohesive effect to the pressure-sensitive adhesive, and by mixing with a styrene tackifier, which will be described later, suppresses air entrainment when bonding the pressure-sensitive adhesive sheet to the adherend, and has good compatibility. It contributes to. Therefore, for example, when the pressure-sensitive adhesive sheet according to the present invention is provided as a non-carrier type pressure-sensitive adhesive sheet and the light-peeling side release sheet is peeled off and bonded to an optical film, air entrapment hardly occurs. In particular, when the optical film is attached to an uneven electromagnetic wave shield film, the effect that air entrapment hardly occurs can be remarkably confirmed. This is because the occurrence of air entrapment has been a problem particularly when the adherend surface is uneven.

  The content of methyl methacrylate, which is one of the constituent monomers of the acrylic polymer in the adhesive layer, is preferably 5 to 15 parts by weight per 100 parts by weight of the acrylic polymer, and is less than 5 parts by weight or more than 15 parts by weight. In addition, the balance between adhesiveness and cohesiveness is poor and the effect of suppressing the occurrence of air entrapment is poor. In particular, when the amount exceeds 15 parts by weight, the adhesive is too cohesive, and it takes time to fit the adherend.

  The type of constituent monomer of the acrylic polymer is not particularly limited except that it contains methyl methacrylate. For example, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, And acrylic acid esters, methacrylic acid esters such as 2-ethylhexyl methacrylate; 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and 4-hydroxybutyl Acrylic acid hydroxyalkyl esters such as methacrylate, methacrylic acid hydroxy Alkyl esters; is selected from the group consisting of a combination thereof; acrylic acid, methacrylic acid, maleic acid, unsaturated aliphatic carboxylic acids such as fumaric acid, and itaconic acid. In particular, it is preferable to contain 60 to 80 parts by weight of n-butyl acrylate (Tg = −55 ° C.) having adhesive strength even at low temperatures and having a low glass transition point (Tg) in 100 parts by weight of the acrylic polymer. 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 pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present invention further contains a styrene tack fire. The styrene tackifier contributes to imparting appropriate adhesiveness and cohesion to the adhesive layer by mixing with the above-mentioned methyl methacrylate. Other tackifiers include rosin-based, terpene-based, aliphatic hydrocarbon-based, aromatic hydrocarbon-based, etc. Contributes to the suppression of air entrapment when The content of the styrene-based tackifier is preferably 0.5 to 3.0 parts by weight in terms of solid content with respect to 100 parts by weight of the solid content of the acrylic polymer solution contained in the adhesive layer, and less than 0.5 part by weight. Or, if it exceeds 3.0 parts by weight, the balance between adhesiveness and cohesiveness is poor and the effect of suppressing air entrainment is poor. It takes time. The weight average molecular weight (Mw) of the styrene tackifier is not particularly limited, but is preferably 10,000 to 60,000, particularly preferably 30,000 to 40,000. In the present specification, the weight average molecular weight (Mw) is a value in terms of polystyrene measured by gel permeation chromatography (GPC method).

  In addition to the above-described components, the pressure-sensitive adhesive solution for forming the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present invention includes a crosslinking agent, a plasticizer, a filler, a colorant, an antistatic agent, an antioxidant, You may add suitably additives, such as a ultraviolet absorber.

  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 support 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 support body.

  The adhesive layer may be provided only on one side of the support or on both sides. A release sheet may be provided on a surface different from the surface in contact with the support of the adhesive layer to protect the adhesive layer. When the support is a release sheet and the release sheet is provided on a surface different from the surface that contacts the support of the adhesive layer, a so-called non-carrier type adhesive sheet is formed. By laminating such a pressure-sensitive adhesive sheet on the one surface of the optical film by peeling off the release sheet having a stronger peelability (hereinafter also referred to as a light release sheet), the optical film can be easily laminated in the electronic display. Become. The optical film is used after being peeled off and laminated on a release sheet (hereinafter also referred to as a heavy release sheet) having a weaker peelability, which is bonded to the adhesive layer. In addition, in the heavy release sheet and the light release sheet, the peelability of the two release sheets was compared in the non-carrier type adhesive sheet in which each of the two release sheets was bonded to a different surface of the adhesive layer. The relative nature of the situation.

  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 and peeling are 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 a tendency for the pressure-sensitive adhesive to protrude during processing.

  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 peelability of the release sheet can be controlled by adjusting the type and / or coating amount of the drug used for the release treatment.

  As an optical film used as a support for an adhesive layer or as an adherend to which a non-carrier type adhesive sheet is adhered, for example, used for forming an electronic display such as a PDP, LCD, CRT, organic EL display, etc. Are used, and the type is not particularly limited. For example, an optical film composed of a base material 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. As an optical film for an electronic display, PET and TAC excellent in transparency are particularly preferably used. 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.

  The pressure-sensitive adhesive sheet of the present invention is suitable for the form of a non-carrier sheet used for applications such as an electromagnetic wave shield film that is copper-plated in a lattice shape and bonded to an optical film having an uneven surface. Yes. In such a form and use, the pressure-sensitive adhesive sheet of the present invention is excellent in the effect of preventing air entrapment in the lattice. Further, when the pressure-sensitive adhesive sheet of the present invention is in a form in which a pressure-sensitive adhesive layer is formed on an optical film, the pressure-sensitive adhesive laminated and laminated on a grid-shaped electromagnetic wave shielding film in an electronic display Especially suitable for sheets.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

1. Preparation of pressure-sensitive adhesive An acrylic polymer having a weight average molecular weight (Mw) of 1,000,000 (a copolymer of n-butyl acrylate, methyl acrylate, acrylic acid and methyl methacrylate, and the content of each monomer in the copolymer is The content of each monomer in Table 1 is shown in parts by weight when the acrylic polymer is 100 parts by weight.) 30 parts by weight of solvent (30 parts by weight of toluene and acetic acid) The solvent was mixed with 40 parts by weight of ethyl) to obtain an acrylic polymer solution having a solid content of 30% by weight. Adhered to this solution was a styrene tackifier having a weight average molecular weight (Mw) of 30,000 and a weight part shown in Table 1 in terms of solid content when the solid content of the acrylic polymer solution was 100 parts by weight. An agent solution was obtained. Instead of the styrene tackifier, Comparative Example 4 was added with 1.5 parts by weight of rosin tackifier, and Comparative Example 5 was added with 1.5 parts by weight of terpene tackifier.

2. Preparation of pressure-sensitive adhesive sheet 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.) coated with a silicone resin so that it becomes a light release sheet on one side The prepared adhesive solution was applied and dried at 100 ° C. for 1 minute to obtain a sheet having an adhesive layer having a thickness of 25 μm after drying. A silicone resin-coated surface of a release sheet consisting of a 75 μm thick PET film (trade name; MRA75, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) coated with a silicone resin so as to be a heavy release sheet on one side, and the adhesive layer exposed The non-carrier type pressure-sensitive adhesive sheet was obtained (this sheet is referred to as “sheet A”).

  Further, the light release sheet of sheet A was peeled off to obtain an adhesive sheet bonded to a PET film (trade name: A-4300, manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm (this is referred to as sheet B).

3. Familiarity evaluation test A familiarity evaluation test method will be described. FIG. 1 is a diagram showing the procedure and state of a conformability evaluation test. First, after cutting the sheet B into 10 cm × 10 cm, the heavy release sheet is peeled off, and the central portion P1 is set as St1 so that the adhesive surface 5a of the adhesive sheet 5 which is the sheet B is downward as shown in FIG. Press against the surface of the glass plate 6 with a finger and hold both ends P2, P3 in a floating state. Next, both ends P2 and P3 of the adhesive sheet 5 are separated as St2, and the end portions P2 and P3 of the adhesive sheet 5 are bonded to the glass plate 6 as shown in FIG. ) Is measured.

Here, the suitability evaluation test was performed as described above, the number of seconds (T1) was measured, and the suitability was evaluated as follows. Table 1 shows the results.
(Double-circle): It bonded in less than 60 seconds and air has also come out neatly.
◯: Bonded in 60 seconds to 120 seconds, and air is also clearly removed.
X: It is not pasted even for 120 seconds, and an air residue is also seen between the film and the glass.

4). Peel off the light release sheet of the air biting evaluation test sheet A and manually roll it on the copper foil surface of a copper foil film (copper-plated in a grid shape with a width of 20 μm, a pitch of 300 μm and a thickness of 120 μm on a 100 μm thick PET film) Bonding was performed with a bonding machine (load: 2 kg / cm), and the presence or absence of air entrapment and transparency were evaluated visually and with a magnifying glass (50 times) as follows. Table 1 shows the results.
A: There is no air biting, and there is a uniform and highly transparent feeling.
◯: Transparent, but air was observed with a magnifying glass, but air could not be confirmed visually.
X: Air is seen visually.

5. Deviation amount measurement test A deviation amount measurement test method will be described. FIG. 2 is a front view (a) and a side view (b) schematically showing the state of the deviation amount measurement test. The sheet B is cut to prepare a 30 mm × 50 mm adhesive sheet 1 and a 25 mm × 100 mm adhesive sheet 2. 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. A test piece is obtained by strengthening the bonding. 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).

  As described above, the deviation amount of each test piece was measured. Table 1 shows the results.

表１に示す結果からわかるように、実施例１〜９の粘着シートは、銅箔フィルムとの貼合時のエアーかみ込みがなく、さらに、なじみ性が良いことが確認された。一方、比較例１〜５の粘着シートは、銅箔フィルムとの貼合時にエアーが多数含まれることが確認された。

As can be seen from the results shown in Table 1, it was confirmed that the pressure-sensitive adhesive sheets of Examples 1 to 9 had no air entrapment at the time of bonding with the copper foil film and had good conformability. On the other hand, it was confirmed that the pressure-sensitive adhesive sheets of Comparative Examples 1 to 5 contain a large amount of air when bonded to the copper foil film.

  The pressure-sensitive adhesive sheet of the present invention is used on a pressure-sensitive adhesive sheet that is bonded to an optical film of 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, or an optical film. It is useful as an adhesive sheet on which the adhesive layer is formed. It is particularly useful as a pressure-sensitive adhesive sheet that is used by being bonded to an electromagnetic wave shielding film having copper plating in a lattice shape.

The figure which shows the procedure and state of a conformability evaluation test. The front view (a) and side view (b) which show the mode of a gap amount measurement test typically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Adhesive sheet 1a, 2a Base material 1b, 2b Adhesive layer 3 Weight 5 Adhesive sheet 6 Glass plate

Claims (3)

A pressure-sensitive adhesive sheet in which a support and a pressure-sensitive adhesive layer containing an acrylic polymer as a main component are laminated,
The acrylic polymer contains methyl methacrylate and n-butyl acrylate as one of the constituent monomers,
The methyl methacrylate is contained in 5 to 15 parts by weight in 100 parts by weight of the acrylic polymer, and the n-butyl acrylate is contained in 60 to 80 parts by weight in 100 parts by weight of the acrylic polymer.
The pressure-sensitive adhesive layer is a pressure-sensitive adhesive sheet containing 0.5 to 3.0 parts by weight of a styrene tackifier with respect to 100 parts by weight of the acrylic polymer .   The pressure-sensitive adhesive sheet according to claim 1, wherein the acrylic polymer further contains methyl acrylate and acrylic acid in addition to the methyl methacrylate and the n-butyl acrylate.   The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the acrylic polymer has a weight average molecular weight of 300,000 to 2,000,000.

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