JP2016000774A - Pressure sensitive adhesive sheet and bonded body using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensitive adhesive sheet capable of, even if an adherend has irregularity such as height difference, following the irregularity without including air bubbles, the pressure sensitive adhesive sheet also having excellent processing suitability in such as sheet punching processing.SOLUTION: A pressure sensitive adhesive sheet includes an adhesive layer and a release sheet disposed at least on one side of the adhesive layer. The adhesive layer consists of an acrylic pressure sensitive adhesive including isostearyl acrylate and alkyl acrylate having 8-13 carbon atoms as a monomer unit. In the adhesive layer, at 25°C, a storage modulus is 1.5×10-6.0×10Pa and a loss tangent is 0.50 or more, and at 50°C, a storage modulus is 1.5×10Pa or less and a loss tangent is 0.30 or more.

Description

  The present invention relates to a pressure-sensitive adhesive sheet, and more particularly to a pressure-sensitive adhesive sheet having excellent followability and excellent processability even when the surface of an adherend has irregularities such as steps. Moreover, this invention relates to the optical member which bonded together the several member using the said adhesive sheet.

  Display elements such as liquid crystal displays and organic EL displays are used in a wide range of fields including personal computers. Among these fields, information portable terminals such as mobile phones and tablet PCs, portable audio players, and the like are required to be further reduced in size and weight, and studies are being made to reduce the thickness of the display element itself. . In recent years, these display elements have adopted touch panels capable of intuitively operating electronic devices, and are incorporated in information equipment terminals as liquid crystal modules or organic EL modules having a transparent conductive film such as ITO. .

  The liquid crystal module and the organic EL module described above are bonded to a transparent protective member (for example, a glass substrate or a transparent resin substrate) that protects the surface of the display element and incorporated into an information device terminal or the like. At that time, if there is an air layer between each layer, the refractive index will be lowered and the display performance will be adversely affected. Therefore, each member or module must be connected via a liquid adhesive or adhesive sheet so that no air layer is formed between each layer. Are pasted together. In particular, the pressure-sensitive adhesive sheet is advantageous in terms of production cost because it does not require an application process or a drying process as compared with an adhesive.

  The transparent protective member arranged on the surface of such a display element has a peripheral portion on the surface side (ie, the inner surface side of the transparent protective member) on which the liquid crystal module and the organic EL module are attached in order to impart designability and distinguishability. May be decorated by printing or the like. Therefore, there is a step at the boundary between the part that is decorated with printing, etc., and the part that is not decorated on the surface of the surface protection substrate, and in some cases bubbles are generated near the step, resulting in improved display performance. It may have an adverse effect or the aesthetics may be impaired.

In order to solve the above problems, Japanese Patent Application Laid-Open No. 2010-189545 (Patent Document 1) has a gel fraction of 10 to 70%, a storage elastic modulus at 23 ° C. of 1 × 10 Pa ⁵ or less, and predetermined conditions. It has been proposed that an optical pressure-sensitive adhesive sheet having good followability to a level difference can be obtained by using a sheet having a pressure-sensitive adhesive layer having a residual stress below 3.0 N / cm ² or less. . However, if a low-elastic modulus (ie, soft) adhesive that can follow unevenness such as a step is used, when the adhesive sheet is cut into a predetermined size, secondary processing such as slit processing or half-cut processing is performed. At that time, a phenomenon that a part of the pressure-sensitive adhesive adheres to the blade (referred to as paste removal) occurred, and there was a problem of workability.

  Proposals have also been made in consideration of the punching workability described above. For example, in Japanese Patent Application Laid-Open No. 2012-062351 (Patent Document 2), the breaking strength and thickness of a separator (release sheet) provided on the surface of an adhesive layer are controlled within a specific range, and a high-speed peeling force for the adhesive layer is specified. It is described that by controlling to the above range, a pressure-sensitive adhesive sheet excellent in punching workability can be obtained even when a pressure-sensitive adhesive having a low storage elastic modulus at room temperature is used.

  JP-A-2008-308633 (Patent Document 3) has an alkyl group having 8 to 30 carbon atoms as an adhesive sheet that can prevent bubbles and peeling at the adhesive interface and is excellent in punching processability. A pressure-sensitive adhesive is an acrylic polymer obtained by copolymerizing a (meth) acrylic acid alkyl ester and a vinyl monomer mainly composed of a (meth) acrylic acid alkyl ester having an alkyl group having less than 8 carbon atoms at a specific weight ratio. An adhesive sheet used as a component is disclosed.

Furthermore, in JP2011-074308A (Patent Document 4), (A) an alkyl group having 4 to 18 carbon atoms (meth) acrylic acid alkyl ester, (B) an amide group-containing monomer, In a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive containing a copolymer of a monomer component containing a (meth) acrylic acid ester having an alkoxy group, when a large amount of the component (B) is used, the storage elastic modulus increases, and (A) and ( When the amount of the component (C) is increased, the storage elastic modulus can be lowered. When the molecular weight of the copolymer is increased, the storage elastic modulus tends to be increased. The component (C) has a higher tan δ of the copolymer. It is taught that it has a function of suppressing foaming of the pressure-sensitive adhesive sheet, and that the tan δ of the copolymer can be adjusted by the amount of the crosslinking agent. When the tan δ at 140 ° C. and 1.0 Hz of the agent component is 0.13 or more and the storage elastic modulus at 25 ° C. and 1.0 Hz is 8.9 × 10 ⁴ Pa or less, generation of bubbles and peeling at the adhesive interface It is taught that a pressure-sensitive adhesive sheet can be obtained which is excellent in uneven follow-up property.

JP 2010-189545 A JP 2012-062351 A JP 2008-308633 A JP 2011-074308 A

  However, although the pressure-sensitive adhesive sheet proposed in Japanese Patent Application Laid-Open No. 2012-0623351 is excellent in punching workability, a specific separator is required, and thus a conventionally used general-purpose separator or release sheet cannot be applied. The material selection is limited.

  Japanese Patent Application Laid-Open No. 2008-308633 provides a pressure-sensitive adhesive sheet that can prevent generation of bubbles at the pressure-sensitive adhesive interface and is excellent in punching workability by using a specific acrylic polymer as described above as a pressure-sensitive adhesive component. However, the term “bubble” here means peeling or floating due to the durability of the pressure-sensitive adhesive when the pressure-sensitive adhesive sheet is applied to a non-adhesive adherend ( For example, [0007] and [0076] do not mean the generation of bubbles caused by inferior followability to unevenness such as a step on the adherend surface.

  Furthermore, Japanese Patent Application Laid-Open No. 2011-074308 teaches that loss tangent (tan δ) and storage elastic modulus affect the uneven followability of an adhesive, but has a low storage elastic modulus (that is, soft) acrylic system. No consideration has been given to the above-described problem of processability when an adhesive is used.

  In view of the above-mentioned situation, the present inventors have efficiently changed the energy of deformation of the adhesive to heat by increasing the loss tangent even if the acrylic adhesive has a certain degree of storage modulus (that is, hard). As a result, it has been found that it is possible to achieve both conformability to unevenness such as a level difference of the adhesive and processing suitability. Moreover, the knowledge that the adhesive which has the storage elastic modulus and loss tangent of a specific range was obtained by adding a specific acrylate monomer to an acrylic polymer after copolymerization was acquired. The present invention is based on such knowledge. Therefore, an object of the present invention is to provide a pressure-sensitive adhesive sheet that can follow irregularities without embedding bubbles even when the adherend has irregularities such as steps, and is excellent in processability such as sheet punching. That is.

The pressure-sensitive adhesive sheet according to the present invention is a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer and a release sheet provided on at least one surface side of the pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer is composed of an acrylic pressure-sensitive adhesive containing isostearyl acrylate and an alkyl (meth) acrylate having 8 to 13 carbon atoms as monomer units,
The pressure-sensitive adhesive layer has a storage elastic modulus at 25 ° C. of 1.5 × 10 ⁵ Pa or more, 6.0 × 10 ⁵ Pa or less, a loss tangent of 0.50 or more, and a storage elastic modulus at 50 ° C. of 1 .5 × 10 ⁵ Pa or less and loss tangent is 0.30 or more.

  According to the aspect of the present invention, the acrylic polymer may be a copolymer of a (meth) acrylic acid ester monomer and a hydroxyl group-containing (meth) acrylate monomer.

  According to the aspect of the present invention, the second release sheet may be provided on the surface of the pressure-sensitive adhesive layer opposite to the surface on which the release sheet is provided.

Moreover, the manufacturing method of the adhesive sheet by another aspect of this invention is a method of manufacturing the adhesive sheet provided with the adhesive layer and the release sheet provided in the at least one surface side of the said adhesive layer. There,
An adhesive composition comprising an acrylic polymer, an isostearyl acrylate monomer, and an alkyl (meth) acrylate monomer having 8 to 13 carbon atoms,
The pressure-sensitive adhesive composition is applied to one surface of the release sheet,
Polymerizing the applied adhesive composition to form an adhesive layer;
Including things.

  According to the aspect of the present invention, the isostearyl acrylate monomer may be contained in the pressure-sensitive adhesive composition in a range of 20% by mass to 50% by mass.

  According to the aspect of the present invention, the pressure-sensitive adhesive composition contains the alkyl (meth) acrylate monomer having 8 to 13 carbon atoms in a range of 7 to 40% by mass. Also good.

  According to the aspect of the present invention, the acrylic polymer may be a copolymer of a (meth) acrylic acid ester monomer and a hydroxyl group-containing (meth) acrylate monomer.

Moreover, the manufacturing method of the bonding body by another aspect of this invention is a method of manufacturing a bonding body using an adhesive sheet,
Adhering the adhesive layer of the adhesive sheet to an adherend,
The release sheet is peeled from the pressure-sensitive adhesive sheet, the exposed pressure-sensitive adhesive layer is bonded to the other adherend, and the adherends are bonded together via the pressure-sensitive adhesive layer to form a bonded body.
Including things.

  According to the aspect of the present invention, the adherend may be an optical member.

  Furthermore, according to another aspect of this invention, the bonding body obtained using the adhesive sheet is also provided.

According to the present invention, the pressure-sensitive adhesive layer is composed of an acrylic pressure-sensitive adhesive containing isostearyl acrylate and an alkyl (meth) acrylate having 8 or more and 13 or less carbon atoms as monomer units, and the pressure-sensitive adhesive layer is 25 ° C. Has a viscoelastic property with a storage elastic modulus of 1.5 × 10 ⁵ Pa or more, 6.0 × 10 ⁵ Pa or less, and a loss tangent of 0.50 or more at room temperature (25 ° C. Therefore, even if sheet punching or the like is performed, the adhesive does not adhere to the blade and is excellent in workability. In addition, since the adhesive layer has viscoelastic properties such that the storage elastic modulus at 50 ° C. is 1.5 × 10 ⁵ Pa or less and the loss tangent is 0.30 or more, it is printed on the adherend side to which the adhesive layer is attached. Even if there are irregularities such as steps, the adhesive layer follows the irregularities when heated (about 50 ° C) by autoclaving after the adhesive layer is provided on the adherend, and as a result, the adhesive Air bubbles are not embraced in the layer.

It is the cross-sectional schematic by one Embodiment of the adhesive sheet by this invention.

  The pressure-sensitive adhesive sheet according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an embodiment of the pressure-sensitive adhesive sheet according to the present invention. The pressure-sensitive adhesive sheet 1 according to the present invention includes a pressure-sensitive adhesive layer 10 and a release sheet 20 a provided on at least one surface side of the pressure-sensitive adhesive layer 10. The 2nd release sheet 20b may be provided in the surface side opposite to the surface in which the release sheet 20a of the adhesive layer 10 is provided. Hereinafter, in this specification, the release sheet 20a and the second release sheet 20b may be collectively referred to as “release sheet”. By providing the release sheets 20a and 20b, the adhesive sheet 1 is first peeled off from the pressure-sensitive adhesive sheet 1 to expose the pressure-sensitive adhesive layer when the adhesive sheet 1 is bonded to another member via the pressure-sensitive adhesive layer. Then, the pressure-sensitive adhesive sheet 1 is bonded to one adherend (not shown), the release sheet 20b is peeled off from the pressure-sensitive adhesive sheet 1, and the other adherend (not shown) is bonded to the pressure-sensitive adhesive layer. The adherends can be bonded to each other via the.

The pressure-sensitive adhesive layer 1 is composed of an acrylic pressure-sensitive adhesive containing isostearyl acrylate and an alkyl (meth) acrylate having 8 to 13 carbon atoms as monomer units. It can be obtained by adding an isostearyl acrylate monomer and an alkyl (meth) acrylate monomer having 8 or more and 13 or less carbon atoms to a polymer (polymer component) and mixing them, and copolymerizing these components. . Conventionally, an acrylic pressure-sensitive adhesive mainly composed of (meth) acrylic acid ester has been used. However, the present inventors have proposed an acrylic heavy polymer obtained by polymerizing or copolymerizing a (meth) acrylic acid ester monomer. As will be described later, an isostearyl acrylate monomer and an alkyl (meth) acrylate monomer having 8 or more and 13 or less carbon atoms are post-added to the coalescence, and these components are copolymerized and used as an acrylic pressure-sensitive adhesive. Thus, the storage elastic modulus at 25 ° C. is 1.5 × 10 ⁵ Pa or more, 6.0 × 10 ⁵ Pa or less, the loss tangent is 0.50 or more, and the storage elastic modulus at 50 ° C. is 1.5 × It was found that a pressure-sensitive adhesive layer having viscoelastic properties such that 10 ⁵ Pa or less and loss tangent is 0.30 or more can be obtained. And by making the pressure-sensitive adhesive layer have viscoelastic properties as described above, even if the adherend has irregularities such as steps, it can follow the irregularities without embedding bubbles, and sheet punching processing etc. An adhesive sheet with excellent processability can be realized.

The reason is not clear, but it is thought as follows. That is, if the storage elastic modulus at 25 ° C. of the pressure-sensitive adhesive layer is 1.5 × 10 ⁵ Pa or more, the pressure-sensitive adhesive layer is reasonably hard, so that the pressure-sensitive adhesive adheres to the blade even if sheet punching is performed. The processability can be improved. On the other hand, when the storage elastic modulus exceeds 6.0 × 10 ⁵ Pa, not only the pressure-sensitive adhesive layer becomes too hard and the impact resistance is inferior, but also the cohesive force of the pressure-sensitive adhesive is lowered and may cause floating or peeling. is there. Even if the loss tangent is in the predetermined range, the followability of the pressure-sensitive adhesive layer is deteriorated. The storage elastic modulus means the equilibrium elastic modulus of the rubber-like elastic region and is an index of “hardness” of the pressure-sensitive adhesive layer. The loss tangent is a value calculated from the loss elastic modulus / storage elastic modulus. The loss elastic modulus represents the viscous property of the pressure-sensitive adhesive layer and is related to the amount of energy that the material being deformed dissipates as heat. Therefore, it becomes an index for relaxing vibration energy. When the loss tangent at 25 ° C. is less than 0.50, when stress acts on the pressure-sensitive adhesive layer (that is, when punching or the like is performed), the stress is not appropriately converted into heat, and the pressure-sensitive adhesive composition The object may be deformed by stress, and as a result, the adhesive may adhere to the blade. The preferable range of the storage elastic modulus at 25 ° C. of the pressure-sensitive adhesive layer is 1.6 × 10 ⁵ Pa or more and 5.5 × 10 ⁵ Pa or less. Moreover, the preferable range of the loss tangent at 25 degreeC of an adhesive layer is 0.5 or more and less than 0.9. The value of loss elastic modulus / storage elastic modulus can be measured by a conventional method using a dynamic viscoelasticity measuring apparatus.

On the other hand, an adhesive layer having a viscoelastic property at 25 ° C. in the above range is relatively “hard”. Therefore, when unevenness such as a printed step exists on the surface of the adherend, the adherend adheres to the adherend at the step portion. Bubbles may be generated between the agent layer. However, in the present invention, the pressure-sensitive adhesive layer has viscoelastic properties such that the storage elastic modulus at 50 ° C. is 1.5 × 10 ⁵ or less and the loss tangent is 0.30 or more. Can be efficiently converted into deformation energy. For this reason, the followability of the pressure-sensitive adhesive layer is improved by performing curing at about 50 ° C. after bonding the pressure-sensitive adhesive layer to the adherend. Thus, bubbles can be removed. The preferable range of the storage elastic modulus at 50 ° C. of the pressure-sensitive adhesive layer is 1.4 × 10 ⁵ Pa or more and 3.0 × 10 ⁵ Pa or less. Moreover, the preferable range of the loss tangent at 50 degreeC of an adhesive layer is 0.35 or more and less than 0.7.

  The pressure-sensitive adhesive layer having the above viscoelastic properties is obtained by adding an isostearyl acrylate monomer and an alkyl (meth) acrylate monomer (monomer component) having 8 to 13 carbon atoms to an acrylic polymer (polymer component). It can be obtained by adding and copolymerizing these components. As the acrylic polymer as the polymer component, a polymer obtained by polymerizing or copolymerizing a (meth) acrylic acid ester monomer can be used. In addition, in this specification, (meth) acrylic acid shall mean acrylic acid and / or methacrylic acid.

  Examples of (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, and n-octyl (meta ) Acrylate, i-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, i-nonyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate Stearyl (meth) acrylate and the like can be used. These acrylic acid esters may contain 1 type (s) or 2 or more types.

  As the acrylic polymer as the polymer component, it is preferable to use a copolymer obtained by copolymerizing a hydroxyl group-containing (meth) acrylate in addition to the above (meth) acrylic acid ester.

  Examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 3-methyl. -3-hydroxybutyl (meth) acrylate, 1,1-dimethyl-3-butyl (meth) acrylate, 1,3-dimethyl-3-hydroxybutyl (meth) acrylate, 2,2,4-trimethyl-3-hydroxy Pentyl (meth) acrylate, 2-ethyl-3-hydroxyhexyl (meth) acrylate, glycerin mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, poly (ethylene glycol) Propylene glycol) mono (meth) acrylate, N- methylol acrylamide, allyl alcohol, methallyl alcohol and the like. One or more of these hydroxyl group-containing (meth) acrylates may be contained. By including the hydroxyl group-containing (meth) acrylate as described above, the reworkability of the acrylic pressure-sensitive adhesive can be improved.

  A carboxyl group-containing (meth) acrylate can be used instead of the hydroxyl group-containing (meth) acrylate described above, but when an acrylic polymer copolymerized with a carboxyl group-containing (meth) acrylate is used as an adhesive component, When a module substrate on which a transparent electrode such as ITO is formed as an adherend is bonded, there is a risk of corroding ITO or the like.

  The above-mentioned hydroxyl group-containing (meth) acrylate can be appropriately adjusted with respect to the (meth) acrylic acid ester in consideration of the cohesive force of the acrylic pressure-sensitive adhesive. It is preferable to add 0.1 to 20% of a hydroxyl group-containing (meth) acrylate monomer on a mass basis with respect to the (meth) acrylic acid ester.

  Further, in addition to the above-mentioned monomers constituting the acrylic polymer as the polymer component, glycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, glycidyl vinyl ether, 3,4-epoxycyclohexyl vinyl ether are appropriately used. , Glycidyl group-containing (meth) acrylate monomers such as glycidyl (meth) allyl ether, 3,4-epoxycyclohexyl (meth) allyl ether, acrylamide, methacrylamide, N-methyl (meth) acrylamide, N-ethyl ( (Meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-tert- Chill acrylamide, N- octyl acrylamide, may contain an amide group-containing (meth) acrylate of diacetone acrylamide.

  The above acrylic polymer can be obtained by polymerizing the above monomer by a method such as ordinary solution polymerization, bulk polymerization, emulsion polymerization or suspension polymerization, but the above acrylic pressure-sensitive adhesive is a solution. It is preferable to produce by solution polymerization obtained.

  Examples of the solvent used for the solution polymerization include organic solvents such as ethyl acetate, toluene, n-hexane, acetone, and methyl ethyl ketone. Examples of the polymerization initiator used in the polymerization include peroxides such as benzoyl peroxide and lauryl peroxide, azobis compounds such as azobisisobutyronitrile and azobisvaleronitrile, and polymer azo polymerization initiators. These can be used alone or in combination. Moreover, in the said superposition | polymerization, in order to adjust the molecular weight of the acrylic polymer obtained, a conventionally well-known chain transfer agent can be used.

  The mass average molecular weight of the resulting acrylic polymer is preferably in the range of 250,000 to 1,500,000, more preferably in the range of 400,000 to 1,000,000. When the mass average molecular weight is less than 250,000, the adhesive property of the pressure-sensitive adhesive composition may be inferior, and when the mass average molecular weight exceeds 1,500,000, the coating property of the pressure-sensitive adhesive composition is deteriorated. The mass average molecular weight can be measured by GPC (gel permeation chromatography) using a polystyrene standard sample.

  The pressure-sensitive adhesive used in the present invention is obtained by adding an isostearyl acrylate monomer and an alkyl (meth) acrylate monomer (monomer component) having 8 to 13 carbon atoms to the acrylic polymer (polymer component) described above. It can be obtained by copolymerizing these components. Examples of the alkyl (meth) acrylate monomer having 8 or more and 13 or less include ethylhexyl acrylate, dimethylhexyl acrylate, octyl acrylate, butylhexyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, tridecyl acrylate, and the like.

  As the blending amount of the monomer component to be added later, the isostearyl acrylate monomer is 20% by mass with respect to the total amount of the polymerization component (that is, the total amount of the acrylic polymer as the polymer component and the monomer component to be added later). % Or more and 50% by mass or less, more preferably 30% by mass or more and 50% by mass or less. The isostearyl acrylate monomer has a high effect on both the storage elastic modulus and loss tangent of the resulting copolymer (adhesive).

  Further, the alkyl (meth) acrylate monomer having 8 or more and 13 or less carbon atoms is 7 with respect to the total amount of the polymerization components (that is, the total amount of the acrylic polymer as the polymer component and the monomer component added later). It is preferably contained in the range of not less than 40% by mass and not more than 40% by mass, more preferably in the range of not less than 7% by mass and not more than 30% by mass. These alkyl acrylate monomers have the effect of lowering the storage modulus and the pressure-sensitive adhesive viscosity at the time of coating.

  In this invention, an adhesive layer can be formed by copolymerizing the adhesive composition which consists of an above-described polymer component and a monomer component. Components other than those described above may be included in the pressure-sensitive adhesive composition. For example, an alkyl (meth) acrylate monomer having 13 or more carbon atoms may be included.

  Moreover, the adhesive composition may contain additives, such as a ultraviolet absorber and antioxidant. As the ultraviolet absorber, known compounds can be used, and examples thereof include organic ultraviolet absorbers such as benzotriazole, benzophenone, salicylate, benzoate, and triazine, and inorganic ultraviolet absorbers. . By including an antioxidant, color change in the visible light region and color change in the near-infrared region can be further suppressed, and transparency can be maintained. The pressure-sensitive adhesive composition (acrylic pressure-sensitive adhesive) may be deteriorated by ultraviolet rays or temperature, and the oxidation of the acrylic pressure-sensitive adhesive can be suppressed by the antioxidant, so that transparency can be maintained. . Examples of the antioxidant include phenol-based, amine-based, sulfur-based, and phosphorus-based antioxidants.

  In addition, the pressure-sensitive adhesive composition may include, for example, processability, heat resistance, weather resistance, mechanical properties, dimensional stability, antioxidant properties, slip properties, mold release properties, flame retardancy, antifungal properties. For the purpose of improving and modifying the properties, electrical properties, strength, corrosion resistance, etc., for example, lubricants, plasticizers, fillers, fillers, antistatic agents, antiblocking agents, crosslinking agents, light stabilizers, Colorants such as dyes and pigments, rust preventives, etc. may be added. Further, if necessary, a coupling agent such as silane, titanium, and aluminum can be further included.

  The pressure-sensitive adhesive composition can be prepared by mixing the above-described components and kneading and dispersing as necessary. The mixing or dispersing method is not particularly limited, and a usual kneading and dispersing machine such as a two-roll mill, a three-roll mill, a pebble mill, a tron mill, a Szegvari attritor, a high-speed impeller disperser, a high-speed stone mill, A high speed impact mill, a desper, a high speed mixer, a ribbon blender, a kneader, an intensive mixer, a tumbler, a blender, a desperser, a homogenizer, an ultrasonic disperser, and the like can be applied. In addition, in order to adjust the viscosity of the pressure-sensitive adhesive coating solution, a diluent solvent may be added to mix each component.

  The pressure-sensitive adhesive composition can be copolymerized in the same manner as the acrylic polymer that is a polymer component, and the same polymerization initiator and solvent can be used. The pressure-sensitive adhesive layer can be formed by coating the pressure-sensitive adhesive composition on one surface of the release sheet, evaporating the solvent component by drying, and then copolymerizing the pressure-sensitive adhesive composition. The thickness of the pressure-sensitive adhesive layer can be adjusted by the application amount of the pressure-sensitive adhesive composition, and is preferably about 5 to 20 μm. If the thickness of the pressure-sensitive adhesive layer (the coating amount of the pressure-sensitive adhesive composition) is too thin, there is a possibility that floating or peeling may occur due to a decrease in the adhesive strength. On the other hand, if the pressure-sensitive adhesive layer is too thin, the decorative layer cannot absorb the step when the adherend is subjected to decorative printing or the like, and tunneling may occur on the mold release. On the other hand, when the thickness of the pressure-sensitive adhesive layer exceeds 20 μm, the adhesive strength and the like are improved, but it is not suitable for portable information terminals and the like that are required to be lightweight and thin, and the transparency of the pressure-sensitive adhesive layer tends to decrease. is there.

  As the release sheet to which the pressure-sensitive adhesive composition is applied, conventionally known ones such as a release film, a separate paper, a separate film, a separate paper, a release film, and a release paper can be suitably used. Moreover, you may use what formed the release layer in the single side | surface or both surfaces of base materials for release paper, such as quality paper, a coated paper, an impregnation paper, and a plastic film. The release layer is not particularly limited as long as it is a material having releasability. For example, silicone resin, organic resin-modified silicone resin, fluororesin, aminoalkyd resin, melamine resin, acrylic resin, polyester resin, etc. There is. These resins can be used in any of emulsion type, solvent type and solventless type.

  The release layer is formed by applying a coating liquid in which a release layer component is dispersed and / or dissolved on one side of a release paper base film, followed by heat drying and / or curing. As a coating method of the coating liquid, a known and arbitrary coating method can be applied, for example, roll coating, gravure coating, spray coating and the like. Moreover, you may form a release layer in the whole surface or a part of at least single side | surface of a base film as needed.

  Moreover, as shown in FIG. 1, when providing a 2nd release sheet, the same thing as the above-mentioned release sheet may be used, and a different thing may be used.

  Since the pressure-sensitive adhesive sheet of the present invention is made of an acrylic pressure-sensitive adhesive and has high transparency, it can be suitably used as an optical application. Moreover, since it has metal corrosion resistance, it can be suitably used as an adhesive sheet when a liquid crystal module or an organic EL module provided with a transparent conductive film such as ITO is bonded to a surface protective glass. Furthermore, the pressure-sensitive adhesive sheet of the present invention can follow the unevenness without embedding bubbles even when the adherend has unevenness such as a step, and is excellent in processing suitability such as sheet punching. Even when the above-described module or the like is bonded to the printed surface protective glass, a display device free from bubbles and having excellent display performance can be manufactured.

  Examples The present invention will be described in more detail with reference to examples, but the present invention is not limited to the contents of these examples.

Example 1
<Preparation of acrylic polymer (polymer component)>
Nitrogen gas was introduced into a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, and the air in the reaction apparatus was replaced with nitrogen gas. Thereafter, 95 parts by mass of 2-ethylhexyl acrylate, 1.0 part by mass of 2-hydroxyethyl acrylate, 4 parts by mass of 2-ethylhexyl methacrylate, and 60 parts by mass of ethyl acetate were added to the reactor. Thereafter, 0.1 part by mass of azobisisobutyronitrile was added as a polymerization initiator, and the mixture was stirred and reacted for 3 hours at a reflux temperature of ethyl acetate in a nitrogen gas stream. An acrylic polymer A having a content of 40% was obtained.

<Preparation of pressure-sensitive adhesive composition>
The acrylic polymer A obtained above, isostearyl acrylate (carbon number 18), and 2-ethylhexyl acrylate (carbon number) were mixed according to the composition shown in Table 1 below, and further ethyl acetate 40 A pressure-sensitive adhesive composition 1 was prepared by mixing 0.3 part by mass of mass part and Lucirin (manufactured by BASF) as a polymerization initiator.

<Production of adhesive sheet>
The pressure-sensitive adhesive composition 1 obtained as described above was applied to an applicator so that the film thickness after drying was 175 g / m ² on a 50 μm-thick PET film (P502150, manufactured by Lintec Co., Ltd.) subjected to silicone release treatment. After coating and drying at 100 ° C. for 5 minutes, a 50 μm thick PET film (POL 501031, manufactured by Lintec), which has been subjected to silicone release treatment, is bonded to the surface of the pressure sensitive adhesive layer. The pressure-sensitive adhesive layer was irradiated with UV rays (VPS-6 (H valve used), manufactured by Fusion, irradiation conditions: 700 mJ / cm ² × 1 time) to produce a pressure-sensitive adhesive sheet 1.

<Examples 2-9, Comparative Examples 1-3>
Except having changed the composition of the adhesive composition according to the following Table 1, the adhesive composition was prepared like Example 1 and the adhesive sheet was produced.

<Comparative Example 4>
Nitrogen gas was introduced into a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, and the air in the reaction apparatus was replaced with nitrogen gas. Thereafter, in this reactor, 51.7 parts by mass of 2-ethylhexyl acrylate, 0.5 parts by mass of 2-hydroxyethyl acrylate, 1.87 parts by mass of 2-ethylhexyl methacrylate, 46 parts by mass of isostearyl acrylate, At the same time, 60 parts by mass of ethyl acetate was added. Thereafter, 0.1 parts by mass of azobisisobutyronitrile was added as a polymerization initiator, and the mixture was stirred and reacted for 3 hours at a reflux temperature of ethyl acetate in a nitrogen gas stream. A 40% acrylic polymer was obtained.

Next, the obtained acrylic polymer was applied to a PET film having a thickness of 50 μm (P502150, manufactured by Lintec) with a silicone peeling treatment using an applicator so that the film thickness after drying was 175 g / m ^2. To form a pressure-sensitive adhesive layer, followed by bonding a 50 μm thick PET film (POL 501031, manufactured by Lintec) with a silicone release treatment to the surface of the pressure-sensitive adhesive layer, normal temperature, normal humidity and normal pressure A pressure-sensitive adhesive sheet was obtained by performing aging for 1 week.

<Dynamic viscoelasticity measurement>
The obtained adhesive sheet was heat-treated in an autoclave apparatus under conditions of 0.5 MPa, 50 ° C. and 30 minutes, and then the carrier films on both sides were peeled off to obtain an adhesive. Measurement of storage elastic modulus E ′ and loss tangent tan δ of this pressure-sensitive adhesive at 25 ° C. and 85 ° C. was conducted in accordance with JIS K7244-1 using a solid viscoelasticity analyzer RSA-III manufactured by TA Instruments. The dynamic viscoelasticity measurement method (attachment mode: compression mode, frequency: 1 Hz, temperature: −50 to 150 ° C., temperature increase rate: 5 ° C./min) was performed. The results were as shown in Table 1 below.

<Evaluation of step following ability>
A glass having a thickness of 1.0 mm and a size of 60 mm × 120 mm was prepared, and decorative printing was performed on the peripheral portion of one surface thereof so that the width was 5 mm and the thickness was 50 μm (hereinafter, a step-formed glass plate). Say). Further, a glass having a thickness of 1.0 mm and a size of 60 mm × 120 mm for bonding to the step-formed glass plate was prepared (hereinafter referred to as a flat glass plate). Furthermore, what cut | judged the adhesive sheet obtained above as a pressure-sensitive adhesive sheet for bonding these two glass plates so that a size might be set to 60 mm x 120 mm was prepared.

The carrier film on one side of the pressure-sensitive adhesive sheet is peeled to expose the pressure-sensitive adhesive layer, and after bonding to the flat glass plate, the other carrier film of the pressure-sensitive adhesive sheet is peeled off, and the pressure-sensitive adhesive is exposed by an automatic bonding machine. By bonding the agent layer to the surface on which the decorative printing of the step-formed glass plate was performed, a bonded body of the flat glass plate and the step-formed glass plate was obtained. Subsequently, the obtained bonded body was heat-treated in an autoclave apparatus under conditions of 0.5 MPa, 50 ° C., and 30 minutes, and then the decorative print portion (peripheral edge of the bonded body) of the bonded body was visually observed. Then, it was confirmed whether or not the adhesive follows the step. The evaluation criteria were as follows.
O: No bubbles can be confirmed. X: Bubbles or air layers are observed at the stepped portions. The evaluation results are as shown in Table 1 below.

<Evaluation of punching processability>
Using a punching machine (manufactured by Iwasaki Tekko Co., Ltd., model name: D250) from one side of the pressure-sensitive adhesive sheet, punching was performed at a rate of 100 shots / minute with a sealing blade. A sample in which the peripheral portion of the punched measurement sample did not float and the so-called glue was not removed when the carrier film was peeled by hand was designated as “◯”. On the other hand, a sample in which floating occurred in the peripheral portion of the punched measurement sample and degreasing occurred was designated as “x”. Note that “glue removal” is a phenomenon in which a part of the adhesive is drawn into a thread or a part of the adhesive layer is chipped between the pair of carrier films as the release sheet and the adhesive layer. Indicates. The evaluation results were as shown in Table 1 below.

As is clear from the evaluation results shown in Table 1, in the pressure-sensitive adhesive sheet (Comparative Examples 1 and 2) where the loss tangent at 25 ° C. of the pressure-sensitive adhesive layer is less than 0.5, there is a step in the adherend. In addition, the followability of the pressure-sensitive adhesive layer is poor and bubbles are generated. Moreover, in the adhesive sheet (comparative example 2) whose storage elastic modulus in 25 degreeC of an adhesive layer is less than 1.5 * 10 < ⁵ > Pa, in addition to level | step difference followability, workability also deteriorates. On the other hand, when the storage elastic modulus at 25 ° C. of the pressure-sensitive adhesive layer exceeds 6.0 × 10 ⁵ Pa, it is understood that the step following ability deteriorates although the processability is excellent.

  Moreover, compared with the adhesive (Example 1) which consists of the copolymer which added the isostearyl acrylate and 2-ethylhexyl acrylate post-added to the acrylic polymer A, it is a constituent monomer of the acrylic polymer A 2- The pressure-sensitive adhesive (Comparative Example 4) obtained by copolymerizing ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-ethylhexyl methacrylate and isostearyl acrylate has a high storage elastic modulus and has a step on the adherend. It can be seen that the followability of the agent layer is poor and bubbles are generated.

Claims (11)

A pressure-sensitive adhesive sheet comprising: a pressure-sensitive adhesive layer; and a release sheet provided on at least one surface side of the pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer is composed of an acrylic pressure-sensitive adhesive containing isostearyl acrylate and an alkyl (meth) acrylate having 8 to 13 carbon atoms as monomer units,
The pressure-sensitive adhesive layer has a storage elastic modulus at 25 ° C. of 1.5 × 10 ⁵ Pa or more, 6.0 × 10 ⁵ Pa or less, a loss tangent of 0.50 or more, and a storage elastic modulus at 50 ° C. of 1 A pressure-sensitive adhesive sheet characterized by having a loss tangent of 0.30 or more and 5 × 10 ⁵ Pa or less.   The pressure-sensitive adhesive sheet according to claim 1, wherein the acrylic pressure-sensitive adhesive is obtained by copolymerizing an acrylic polymer with an isostearyl acrylate monomer and an alkyl acrylate monomer having 8 to 13 carbon atoms. .   The pressure sensitive adhesive sheet according to claim 2 in which said acrylic polymer consists of a copolymer of a (meth) acrylic acid ester monomer and a hydroxyl-containing (meth) acrylate monomer.   The adhesive sheet as described in any one of Claims 1-3 with which the 2nd release sheet is provided in the surface side opposite to the surface in which the said release sheet of the said adhesive layer is provided. . A method for producing a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer and a release sheet provided on at least one surface side of the pressure-sensitive adhesive layer,
A pressure-sensitive adhesive composition comprising an acrylic polymer, an isostearyl acrylate monomer, and an alkyl acrylate monomer having 8 to 13 carbon atoms;
The pressure-sensitive adhesive composition is applied to one surface of the release sheet,
Polymerizing the applied adhesive composition to form an adhesive layer;
The manufacturing method of an adhesive sheet including this.   The method according to claim 5, wherein the pressure-sensitive adhesive composition contains the isostearyl acrylate monomer in a range of 20% by mass to 50% by mass.   The method according to claim 5 or 6, wherein the pressure-sensitive adhesive composition contains the alkyl acrylate monomer having 8 to 13 carbon atoms in a range of 7 to 40% by mass.   The method according to any one of claims 5 to 7, wherein the acrylic polymer comprises a copolymer of a (meth) acrylic acid ester monomer and a hydroxyl group-containing (meth) acrylate monomer. It is the method of manufacturing a bonding body using the adhesive sheet as described in any one of Claims 1-4,
Adhering the adhesive layer of the adhesive sheet to an adherend,
The release sheet is peeled from the pressure-sensitive adhesive sheet, the exposed pressure-sensitive adhesive layer is bonded to the other adherend, and the adherends are bonded together via the pressure-sensitive adhesive layer to form a bonded body.
Comprising a method.   The method according to claim 9, wherein the adherend is an optical member.   The bonding body obtained by the method of Claim 9 or 10.

Images