JP6791138B2 - Adhesive sheet and laminate and their manufacturing method - Google Patents

Description

The present invention relates to an adhesive sheet and a laminate suitable for adhering a pair of optical members, and a method for producing the same.

In recent years, display device modules such as liquid crystal displays (LCDs) and input device modules such as touch panels have come to be widely used in various fields. In the manufacturing process of these display device modules and input device modules, a transparent double-sided adhesive sheet is used for bonding optical members.

A cold cathode fluorescent lamp (CCFL), a light emitting diode (LED), or the like is used as a backlight source for a display device module such as a liquid crystal display (LCD). However, when such a light source is used, the transmitted light is not uniform, so a light diffusing sheet (light diffusing adhesive sheet) that uniformly diffuses the light emitted from the light source is used in combination. For example, Patent Document 1 discloses a light diffusing pressure-sensitive adhesive composition containing a predetermined acrylic copolymer and a cross-linking agent. Further, Patent Document 2 discloses a light diffusing pressure-sensitive adhesive composition containing an acrylic polymer having a predetermined molecular weight and spherical fine particles. In Patent Documents 1 and 2, a pressure-sensitive adhesive composition is applied and heat-dried to form a pressure-sensitive adhesive layer having a high haze value.

By the way, in recent years, the LCD has been made smaller and thinner, and it has been studied to make the optical film constituting the LCD thinner. Further, as the LCD becomes thinner, the double-sided adhesive sheet used for bonding the optical films constituting the LCD is required to be thinner, and naturally, the light diffusing adhesive sheet is also required to be thinner.

Japanese Unexamined Patent Publication No. 2010-159333 Japanese Unexamined Patent Publication No. 2013-1745

As described above, in order to increase the haze value of the light diffusing pressure-sensitive adhesive sheet, fine particles are added to the pressure-sensitive adhesive sheet. However, when fine particles are added to the light diffusing sheet and the light diffusing pressure-sensitive adhesive sheet is thinned, the dispersibility of the fine particles deteriorates and the haze value varies, or the adhesiveness of the pressure-sensitive adhesive sheet becomes uneven. There was a problem that it got worse.

Therefore, in order to solve the problems of the prior art, the present inventors have proceeded with studies for the purpose of providing a thin-film adhesive sheet having a high haze having light diffusivity. It was. Furthermore, the present inventors have proceeded with studies so that such a thin-film pressure-sensitive adhesive sheet can exhibit uniform light diffusivity and excellent adhesiveness.

As a result of diligent studies to solve the above problems, the present inventors have achieved a thin film of the pressure-sensitive adhesive sheet by forming a pressure-sensitive adhesive sheet using a dual-cure type pressure-sensitive adhesive containing a specific component. I found that it could be done. Furthermore, the present inventors have achieved good adhesiveness and durability with little variation in the haze value even when the haze value of the thinned adhesive sheet is increased by using the dual-cure type adhesive. We have found that it can be maintained and have completed the present invention.
Specifically, the present invention has the following configuration.

[1] A base polymer (A) containing a non-crosslinkable (meth) acrylic acid ester unit (a1) and an acrylic monomer unit (a2) having a crosslinkable functional group, and at least one polymerizable unsaturated group. The monomer (B), the cross-linking agent (C) that reacts with the base polymer (A) by heat, and the polymerization initiator (D) that initiates the polymerization reaction of the monomer (B) by irradiation with active energy rays. A pressure-sensitive adhesive sheet containing a pressure-sensitive adhesive composition containing the solvent (E) and the solvent (E) semi-cured by heating or irradiation with active energy rays, and having a haze of 35 to 60%.
[2] The adhesive sheet according to [1], which has a thickness of 7 to 30 μm.
[3] The pressure-sensitive adhesive sheet according to [1] or [2], wherein the pressure-sensitive adhesive contains fine particles.
[4] The pressure-sensitive adhesive sheet according to [3], wherein the average particle size of the fine particles is 3 to 15 μm.
[5] The adhesive sheet according to any one of [1] to [4], wherein the deviation distance after 60 minutes measured according to the holding force measuring method of JIS Z0237 by crimping to a SUS plate is 10 mm or more.
[6] The distance of deviation after 60 minutes measured according to the holding force measurement method of JIS Z0237 after being pressure-bonded to a SUS plate and further cured by heating or irradiating with active energy rays is less than 10 mm [1]. ] To the adhesive sheet according to any one of [5].
[7] The adhesive sheet according to any one of [1] to [6], which is a double-sided adhesive sheet.
[8] A method for producing a laminate, which comprises a step of bringing the adhesive sheet according to any one of [1] to [7] into contact with the surface of an adherend and heating in that state, or a step of irradiating an active energy ray.
[9] A laminate produced by the method according to [8].
[10] The laminate according to [9], which has optical members on both surfaces of the adhesive sheet.

According to the present invention, the pressure-sensitive adhesive sheet can be thinned by forming the pressure-sensitive adhesive sheet from a dual-cure type pressure-sensitive adhesive containing a specific component. Further, according to the present invention, even when the haze value of the thinned adhesive sheet is increased, the haze value does not vary much and uniform light diffusivity can be exhibited. Further, the pressure-sensitive adhesive sheet of the present invention can exhibit good adhesiveness and durability even when it is thinned.

FIG. 1 is a cross-sectional view showing a laminated body according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be based on typical embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.

(Adhesive sheet)
The pressure-sensitive adhesive sheet of the present invention contains a base polymer (A) containing a non-crosslinkable (meth) acrylic acid ester unit (a1) and an acrylic monomer unit (a2) having a crosslinkable functional group, and a polymerizable unsaturated group. Initiation of polymerization that initiates the polymerization reaction of the monomer (B) having at least one of the above, the cross-linking agent (C) that reacts with the base polymer (A) by heat, and the monomer (B) by irradiation with active energy rays. The pressure-sensitive adhesive composition containing the agent (D) and the solvent (E) is semi-cured by heating or irradiation with active energy rays. The haze of the pressure-sensitive adhesive sheet of the present invention is 35 to 60%.

The pressure-sensitive adhesive sheet of the present invention contains a base polymer (A) containing a non-crosslinkable (meth) acrylic acid ester unit (a1) and an acrylic monomer unit (a2) having a crosslinkable functional group, and a polymerizable unsaturated group. A monomer (B) having at least one, a cross-linking agent (C) that reacts with the base polymer (A) by heat, and a polymerization initiator that initiates a polymerization reaction of the monomer (B) by irradiation with active energy rays. The pressure-sensitive adhesive composition containing (D) and the solvent (E) is semi-cured by heating or irradiation with active energy rays, and the pressure-sensitive adhesive sheet exhibits a soft semi-cured state. ing. Here, the semi-cured state means that the gel fraction is less than 20%, and the gel fraction may be less than 15% or less than 10%.

As described above, the pressure-sensitive adhesive sheet of the present invention is semi-curable, but the pressure-sensitive adhesive sheet is completely cured by heating or irradiating the surface of the adherend with heat or active energy rays after the pressure-sensitive adhesive sheet is attached to the surface of the adherend. That is, the pressure-sensitive adhesive sheet of the present invention is in a semi-cured state only by heating or irradiation with active energy rays before bonding, but is completely cured by heating or active energy rays after bonding. The curing method in the semi-curing step and the complete curing step may be the same, but it is preferable to cure by different methods. Specifically, when thermosetting is performed in the semi-curing step, it is preferable to irradiate the active energy ray in the complete curing step, and when the active energy ray is irradiated in the semi-curing step, the complete curing step is performed. It is preferable to perform thermosetting. In the present specification, such a two-step curing adhesive sheet may be referred to as a dual cure type adhesive sheet.
In the present specification, the "semi-cured state" means a soft state after curing by either heat or active energy rays and before curing in the second stage. In addition, the "fully cured state" is an adhesive sheet in a semi-cured state. It means a state of being cured by heating or irradiating with active energy rays. Specifically, when the "semi-cured state" is changed to the "completely cured state", the storage elastic modulus of dynamic viscoelasticity measured by shear stress or tensile stress at a frequency of 1 Hz is at least Tg (glass transition point). ) In the range from higher temperature to 60 ° C, it becomes 1.5 times or more. At the time of complete curing, the dynamic viscoelasticity is preferably 1.5 to 1000 times, more preferably 2 to 100 times. Further, the storage elastic modulus of dynamic viscoelasticity measured by shear stress or tensile stress at a frequency of 1 Hz of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive sheet in the semi-cured state in the present invention is in a temperature region higher than Tg (glass transition point) or 50. In the region of ° C. or higher, it is preferably 1.0 × 10 ⁶ Pa or less, more preferably 8.0 × 10 ⁵ Pa or less, and further preferably 5.0 × 10 ⁵ Pa or less.

The thickness of the pressure-sensitive adhesive sheet is preferably 7 to 30 μm, more preferably 7 to 20 μm, and even more preferably 7 to 15 μm. The pressure-sensitive adhesive sheet of the present invention can maintain uniform light diffusivity, adhesiveness, and durability for a long period of time even when the pressure-sensitive adhesive sheet is thinned to be within the above range.

The pressure-sensitive adhesive contained in the pressure-sensitive adhesive sheet of the present invention preferably contains fine particles. The fine particles may be any fine particles having a function of diffusing the light incident on the pressure-sensitive adhesive sheet, and may be organic fine particles or inorganic fine particles.
Examples of the inorganic fine particles include fine particles made of silica, calcium carbonate, aluminum hydroxide, magnesium hydroxide, clay, talc, aluminum oxide, titanium oxide and the like.
Examples of the organic fine particles include polystyrene resin, polyolefin resin such as polyethylene and polypropylene, (meth) acrylic resin such as polymethacrylate resin and polyacrylate resin, epoxy resin, and silicone resin, and a crosslinked structure is formed on these resins. Resin particles made of a copolymerized resin or the like in which two or more monomers selected from the formed crosslinked polymer, ethylene, propylene, styrene, methyl methacrylate, benzoguanamine, formaldehyde, melamine, butadiene and the like are copolymerized. Can be used.
Further, fine particles made of a silicon-containing compound having an intermediate structure between inorganic and organic (for example, Tospearl series manufactured by Momentive Performance Materials Japan) can also be used as fine particles.
One type of these fine particles may be used alone, or two or more types may be used in combination. It is also possible to use a combination of organic fine particles, inorganic fine particles, and fine particles having an intermediate structure between inorganic and organic.
Among them, as the fine particles used in the present invention, it is preferable that the adhesive sheet does not excessively reduce the total light transmittance, and acrylic beads and silica beads having high transparency are preferable.

The shape of the fine particles is not particularly limited, but is preferably spherical because light can be diffused uniformly.
The average particle size of the fine particles is preferably 0.1 to 20 μm, more preferably 1 to 20 μm, and even more preferably 3 to 15 μm. Here, in the present specification, the "average particle size" means the maximum length of a particle image of fine particles (Dmax: the maximum length at two points on the contour of the particle image) using a transmission electron microscope or a scanning electron microscope. And the maximum vertical length (DV-max: the shortest length between these two straight lines when the particle image is sandwiched between two straight lines parallel to the maximum length), and the synergistic average thereof. The value (Dmax × DV-max) ^1/2 is set as the particle size, and the particle size is measured for any 100 light-diffusing particles by this method, and the arithmetic average value thereof. If the average particle size of the fine particles is equal to or less than the above upper limit value, it tends to be difficult to feel graininess or foreign body sensation when the adhesive sheet is visually recognized with the naked eye. It tends to be easy to adjust the haze to the desired value.

The content of the fine particles in the pressure-sensitive adhesive composition can be 1 to 15 parts by mass with respect to 100 parts by mass of the pressure-sensitive adhesive. When the content of the fine particles is within the above range, it tends to be easy to suppress a decrease in the total light transmittance, and it tends to be easy to adjust to a desired haze.

The haze of the adhesive sheet is 35-60%. Here, the haze value of the adhesive sheet is determined by sticking a slide glass (product number: S9112) manufactured by Matsunami Glass Co., Ltd. on one surface of the adhesive sheet and a transparent PET film (manufactured by New Tac Kasei Co., Ltd.) on the other surface. It is a value when CPET75H) is pasted and measured. When measuring the haze of such a bonded product, in order to eliminate the influence of fine air and the like mixed during the bonding, the laminated sample is charged at 0.5 MPa and 40 ° C. for 30 minutes. Perform autoclave (pressure defoaming) treatment. Then, NDH4000 manufactured by Nippon Denshoku Kogyo Co., Ltd. can be used for the haze measurement.

In the present invention, the adhesive sheet is pressure-bonded to the SUS plate, and the deviation distance after 60 minutes measured according to the holding force measuring method of JIS Z0237 is preferably 10 mm or more, more preferably 20 mm or more. .. The above-mentioned deviation distance is a measured value of the adhesive sheet in a state before irradiating the adhesive sheet with active energy rays and in a semi-cured state.

Further, in the present invention, the distance of the deviation after 60 minutes measured according to the holding force measurement method of JIS Z0237 after the pressure-sensitive adhesive sheet is pressure-bonded to the SUS plate and further cured by heating or irradiating with active energy rays. It is preferably less than 10 mm. In the present invention, the adhesive has a certain degree of fluidity in the semi-cured state, but after the second stage of curing, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive sheet aggregates and exhibits strong adhesiveness. With such a configuration, the pressure-sensitive adhesive sheet can be made into a thin film, and further, good adhesiveness and durability are exhibited after complete curing. Further, in the present invention, the haze variation after the pressure-sensitive adhesive sheet is completely cured is small, and uniform light diffusivity is exhibited.

Young's modulus of the adhesive sheet (semi-cured state) may be a 0.01~0.30N / mm ^2, may be 0.03~0.20N / mm ^2. When Young's modulus is within the above range, the semi-cured adhesive sheet tends to have a desired hardness. The Young's modulus can be set within a desired range by adjusting the amount of the monomer added, which will be described later. The Young's modulus in the present specification is a value obtained from a stress-strain diagram measured at a tensile speed of 10 (mm / min) using an Autograph AGS-X manufactured by Shimadzu Corporation.

The pressure-sensitive adhesive sheet of the present invention may be a single-sided pressure-sensitive adhesive sheet or a double-sided pressure-sensitive adhesive sheet, but is preferably a double-sided pressure-sensitive adhesive sheet. Examples of the single-sided adhesive sheet include a multi-layer sheet in which an adhesive layer is laminated on a support.
Examples of the double-sided adhesive sheet include a single-layer adhesive sheet composed of only an adhesive sheet, a multi-layer adhesive sheet in which a plurality of adhesive layers are laminated, and a multi-layer sheet in which adhesive layers are laminated on both sides of a support.

<Adhesive composition>
The pressure-sensitive adhesive composition contains a base polymer (A) containing a non-crosslinkable (meth) acrylic acid ester unit (a1) and an acrylic monomer unit (a2) having a crosslinkable functional group, and a polymerizable unsaturated group. A monomer (B) having at least one, a cross-linking agent (C) that reacts with the base polymer (A) by heat, and a polymerization initiator that initiates a polymerization reaction of the monomer (B) by irradiation with active energy rays. It contains (D) and a polymer (E).

Further, the monomer (B) in the pressure-sensitive adhesive composition may have a vapor pressure of 300 Pa or less at 25 ° C., and the surface tension of the solvent (E) at 25 ° C. shall be 20 mN / m or more and less than 40 mN / m. Can be done. As a result, the coating suitability when producing the pressure-sensitive adhesive sheet is improved, and when the pressure-sensitive adhesive composition is coated and heat-cured, a pressure-sensitive adhesive sheet having a smooth surface can be formed. This is considered to be due to the following reasons. First, by containing the solvent (E), the problem that the end portion becomes thick at the time of coating when the pressure-sensitive adhesive sheet is produced is less likely to occur. Further, as with the solvent (E), by containing the monomer (B) that functions as a liquid medium that lowers the viscosity of the coating material, the concentration of the solvent (E) that tends to cause popping is low. It can be suppressed. When heated, the solvent (E) selectively evaporates, but the inclusion of the monomer (B), which is difficult to volatilize, suppresses a rapid increase in the surface tension of the coating film. Further, the selective evaporation of the solvent (E) increases the viscosity as the solid content concentration in the pressure-sensitive adhesive sheet increases, and the flow of the substance in the pressure-sensitive adhesive sheet is suppressed. It is considered that these synergistic actions can suppress manufacturing problems such as the generation of thick-walled edges and sides, and can form an adhesive sheet with a smooth surface.

The monomer (B) and the solvent (E) in the pressure-sensitive adhesive composition may satisfy at least one or all of the following conditions (1) and (2).
(1) The melting point of the monomer (B) is 25 ° C. or lower.
(2) The solvent (E) does not have a polymerizable unsaturated group and has a higher vapor pressure at 25 ° C. than the monomer (B).

In the pressure-sensitive adhesive composition, the solvent (E) shall have a difference in solubility parameter between the solvent (E) and the monomer (B) within 2 [(cal / cm ³ ) ^1/2 ]. Can be done. As a result, the coating suitability when producing the pressure-sensitive adhesive sheet is improved, and when the pressure-sensitive adhesive composition is coated and heat-cured, a pressure-sensitive adhesive sheet having a smooth surface can be formed. This is considered to be due to the following reasons. First, by containing the solvent (E), it is less likely that a coating defect that the end portion becomes thick at the time of coating when the pressure-sensitive adhesive sheet is produced is less likely to occur. Further, when the pressure-sensitive adhesive composition is thermoset by keeping the difference in solubility parameter between the solvent (E) and the monomer (B) within 2 [(cal / cm ³ ) ^1/2 ]. In addition, it is possible to suppress the rapid evaporation of the solvent (E) due to the excessive disruption of gas-liquid equilibrium. As a result, the surface of the adhesive sheet is prevented from becoming a citron skin (orange peel). Further, similarly to the solvent (E), by containing the monomer (B) that functions as a liquid medium for reducing the viscosity of the coating agent, the concentration of the solvent (E) that easily causes coating defects is suppressed to a low level. Be done. Further, when heated, the viscosity increases as the solid content concentration in the pressure-sensitive adhesive sheet increases due to the evaporation of the solvent (E), and the flow of the substance in the pressure-sensitive adhesive sheet is suppressed. It is considered that these synergistic actions suppress manufacturing problems such as the generation of thick-walled edges and coating defects, and can form an adhesive sheet with a smooth surface.

The solvent (E) does not have a polymerizable unsaturated group, and the surface tension at 25 ° C. may be 20 mN / m or more and less than 40 mN / m. That is, in the pressure-sensitive adhesive composition, the monomer (B) has a vapor pressure of 300 Pa or less at 25 ° C., and the solvent (E) has a surface tension of 20 mN / m or more and less than 40 mN / m at 25 ° C. Further, the solvent (E) may be composed of a solvent having a solubility parameter difference of 2 [(cal / cm ³ ) ^1/2 ] or less from that of the monomer (B).

[Base polymer (A)]
The pressure-sensitive adhesive composition contains a non-crosslinkable (meth) acrylic acid ester unit (a1) and an acrylic monomer unit (a2) having a crosslinkable functional group as the base polymer (A). In the present specification and claims, a "unit" is a repeating unit (monomer unit) constituting a polymer.

The non-crosslinkable (meth) acrylic acid ester unit (a1) is derived from the (meth) acrylic acid alkyl ester. Examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylic acid, ethyl (meth) acrylic acid, propyl (meth) acrylic acid, isopropyl (meth) acrylic acid, n-butyl (meth) acrylic acid, and (meth). Isobutyl acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, ( Isooctyl acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, (meth) Examples thereof include n-dodecyl acrylate, stearyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, and benzyl (meth) acrylate. One of these may be used alone, or two or more thereof may be used in combination.
In the present invention, "(meth) acrylate" means containing both "acrylate" and "methacrylic acid", and "(meth) acrylic acid" means "acrylic acid" and "methacrylic acid". Means to include both.

Examples of the acrylic monomer unit (a2) having a crosslinkable functional group include a hydroxy group-containing monomer unit, an amino group-containing monomer unit, a glycidyl group-containing monomer unit, and a carboxy group-containing monomer unit. Be done. These monomer units may be one type or two or more types. The ratio of the carboxy group-containing monomer unit contained in the acrylic monomer unit (a2) may be 1% by mass or less with respect to the total mass of the acrylic monomer unit (a2), and is 0.1. It may be 0% by mass or less by mass% or less. By setting the ratio of the carboxy group-containing monomer unit contained in the acrylic monomer unit (a2) within the above range, corrosion of metal wiring or the like is suppressed when the surface of the adherend is provided with metal wiring or the like. Can be done.

The hydroxy group-containing monomer unit is derived from the hydroxy group-containing monomer. Examples of the hydroxy group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate. Examples thereof include (meth) acrylic acid [(mono, di or poly) alkylene glycol] such as mono (meth) acrylic acid mono (diethylene glycol), and (meth) acrylic acid lactone such as (meth) acrylic acid monocaprolactone.
Examples of the amino group-containing monomer unit include those derived from amino group-containing monomers such as (meth) acrylamide and allylamine.
Examples of the glycidyl group-containing monomer unit include those derived from a glycidyl group-containing monomer such as glycidyl (meth) acrylate.
Examples of the carboxy group-containing monomer unit include those derived from acrylic acid and methacrylic acid.

The content of the crosslinkable acrylic monomer unit (a2) in the base polymer (A) may be 0.01 to 20% by mass, 0.5 to 15% by mass, or 0.5 to 0.5% by mass. It may be 10% by mass. When the content of the crosslinkable acrylic monomer unit (a2) is at least the above lower limit value, it has sufficient crosslinkability necessary for maintaining the semi-cured state, and when it is at least the above upper limit value, it is sufficient. The required adhesiveness can be maintained.

The base polymer (A) has, if necessary, a monomer unit other than the non-crosslinkable (meth) acrylic acid ester unit (a1) and the acrylic monomer unit (a2) having a crosslinkable functional group. You may. Other monomers may be copolymerizable with a non-crosslinkable (meth) acrylic acid ester and an acrylic monomer having a cross-linking functional group, for example, (meth) acrylonitrile, vinyl acetate, styrene, etc. Examples thereof include vinyl chloride, vinylpyrrolidone and vinylpyridine.
The content of the other monomer unit in the base polymer (A) may be 0 to 20% by mass or 0 to 15% by mass.

The weight average molecular weight of the base polymer (A) can be 100,000 to 2 million, and may be 300,000 to 1.5 million. The weight average molecular weight of the base polymer (A) is a value before being crosslinked with a crosslinking agent. The weight average molecular weight is a value measured by size exclusion chromatography (SEC) and determined based on polystyrene. As the base polymer (A), a commercially available polymer may be used, or a polymer synthesized by a known method may be used.

[Monomer (B)]
The monomer (B) contains at least one of a monofunctional monomer (B1) having at least one polymerizable unsaturated group and a polyfunctional monomer (B2) having two or more polymerizable unsaturated groups. You may. Examples of the polymerizable unsaturated group include a group containing an ethylenically double bond, and examples thereof include a (meth) acryloyl group and a vinyl group.
The monomer (B) may contain either a monofunctional monomer (B1) or a polyfunctional monomer (B2), and the monofunctional monomer (B1) and the polyfunctional monomer (B1) may be contained. Both of (B2) may be included. When the pressure-sensitive adhesive composition is heat-cured in the first step (semi-curing step) by containing the monomer (B), the pressure-sensitive adhesive sheet of the thermosetting product is in a semi-cured state and is inactive energy ray-cured. Can have sex. Further, when the pressure-sensitive adhesive composition is cured by irradiation with active energy rays in the first step, the pressure-sensitive adhesive sheet of the photocurable product is in a semi-cured state and has thermosetting property. In the present invention, it is also possible to heat-cure in the first step to bring it into a semi-cured state, and then to completely cure it by heat-curing in the second step again.

As the monomer (B), a monomer having a vapor pressure of 300 Pa or less at 25 ° C. may be used. As a result, the coating suitability is improved, and when the pressure-sensitive adhesive composition is coated and heat-cured, the solvent is selectively evaporated, and the pressure-sensitive adhesive sheet with few coating defects such as thick-walled edges and sides is produced. Can be formed.
The vapor pressure of the monomer (B) at 25 ° C. may be 200 Pa or less, or 100 Pa or less. The lower limit of the vapor pressure is not particularly limited in terms of coating suitability of the pressure-sensitive adhesive composition. The vapor pressure of the monomer (B) can be measured by JIS-K2258 "crude oil and fuel oil-vapor pressure test method-lead method" or the like, and for example, http: // www. chemsider. Predicted values can be obtained from websites such as com / and software such as ACD / PhysChem Suite. Further, the melting point of the monomer (B) may be 25 ° C. or lower. As a result, the transparency (haze, etc.) of the formed adhesive sheet is improved. Further, the melting point of the monomer (B) may be 20 ° C. or lower, or 15 ° C. or lower. The lower limit of the melting point is not particularly limited. The melting point of the monomer (B) can be measured by JIS K 0064: 1992 "Measuring method of melting point and melting range of chemical products" and the like.

If a monomer having an alkyl group having 10 or more chain length atoms or a monomer having a polycyclic structure is used as the monomer (B), it is possible to exert more excellent holding power after complete curing. Can be done. Usually, in order to polymerize a monomer as a higher molecular weight body, the shorter the number of chain length atoms, the easier it is for the monomers to bond with each other, resulting in more excellent curing. However, in the present invention, the use of the above-mentioned monomer promotes the entanglement of the monomer and the base polymer. As a result, it is considered that the pressure-sensitive adhesive composition is easily cured and can exhibit excellent holding power.
Examples of the monomer having an alkyl group having a chain length atom number of 10 or more include an alkyl acrylate having an alkyl group having a chain length atom number of 10 or more. As long as the number of chain length atoms of the alkyl group is 10 or more, it may have a side chain or a substituent. Alkyl groups can be mentioned as such side chains and substituents. The number of chain length atoms of the alkyl group may be 10 to 27, 10 to 25, or 15 to 22. Isostearyl acrylate can be mentioned as a particularly preferable alkyl acrylate from the viewpoint of holding power.
The monomer having a polycyclic structure may be a polycyclic aliphatic monomer or a polycyclic aromatic monomer. Examples of the polycyclic structure include a bicyclo structure and a tricyclo structure. Substituents such as alkyl groups may be bonded to these polycyclic structures. Specific examples of the polycyclic structure include a norbornene ring, an adamantane ring, and the like.

Specific examples of the monofunctional monomer (B1) that can be used in the present invention include pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, and n-octyl (meth) acrylate. , (Meta) isooctyl acrylate, (meth) n-nonyl acrylate, (meth) isononyl acrylate, (meth) n-decyl acrylate, (meth) isodecyl acrylate, (meth) n-undecyl acrylate, ( Examples thereof include lauryl acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, isobornyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and the like. Examples of the monofunctional monomer (B1) having a melting point of 25 ° C. or lower include pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, n-octyl (meth) acrylate, and (meth). ) Isooctyl acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, (meth) acrylic Examples thereof include lauryl acid acid, isostearyl (meth) acrylate, isobornyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Above all, the monofunctional monomer (B1) is preferably lauryl (meth) acrylate.

Examples of the polyfunctional monomer (B2) include ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, and di (meth) acrylic. Acid 1,4-butylene glycol, di (meth) acrylic acid 1,9-nonanediol, diacrylic acid 1,6-hexanediol, di (meth) acrylic acid polybutylene glycol, di (meth) acrylic acid neopentyl glycol, Tetraethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, trimethylol propane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, tetra (meth) Examples thereof include (meth) acrylic acid esters of polyhydric alcohols such as pentaerythritol acrylate, vinyl methacrylate and the like.
The monomer (B) may not have a functional group exhibiting reactivity with the functional group of the acrylic monomer unit (a2). For example, the monomer (B) may have the same functional group (for example, a hydroxy group) as the acrylic monomer unit (a2), or may have no functional group.

The monomer (B) may be any one of a monofunctional monomer (B1) and a polyfunctional monomer (B2) alone, or a monofunctional monomer (B1) and / or a polyfunctional monomer (B1). B2) may be used in combination of two or more.
The content of the monomer (B) in the pressure-sensitive adhesive composition is appropriately selected according to the composition, molecular weight, cross-linking density, etc. of the base polymer (A), and is not particularly limited, but is 100 parts by mass of the base polymer (A). On the other hand, it can be 5 to 150 parts by mass, 10 to 120 parts by mass, or 15 to 90 parts by mass.
The content of the monomer (B) may be 1 to 60% by mass, 2 to 50% by mass, or 5 to 35% by mass with respect to the total mass of the pressure-sensitive adhesive composition. It may be.

In particular, when the monomer (B) contains both a monofunctional monomer (B1) and a polyfunctional monomer (B2), it is appropriately selected according to the composition, molecular weight, cross-linking density, etc. of the polymer (A). However, the amount of the monofunctional monomer (B1) can be 4 to 120 parts by mass, 8 to 100 parts by mass, and 12 parts by mass with respect to 100 parts by mass of the base polymer (A). It can be ~ 80 parts by mass. The polyfunctional monomer (B2) can be 1 to 30 parts by mass, 2 to 20 parts by mass, and 3 to 10 parts by mass. Further, the content mass ratio of the monofunctional monomer (B1) and the polyfunctional monomer (B2) can be 2: 1, can be 3: 1, and can be 5: 1.

[Crosslinking agent (C)]
The cross-linking agent (C) is a cross-linking functional group contained in the base polymer (A) from among known cross-linking agents such as isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, and butylated melamine compounds. It can be appropriately selected in consideration of the reactivity with. For example, when a hydroxy group is contained as the crosslinkable functional group, an isocyanate compound can be used because of the reactivity of the hydroxy group. From the viewpoint that the acrylic monomer unit (a2) having a crosslinkable functional group can be easily crosslinked, an isocyanate compound and an epoxy compound can be used.

Examples of the isocyanate compound include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and the like.
Examples of the epoxy compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, and 1,6-hexanediol di. Glycidyl ether, tetraglycidyl xylene diamine, 1,3-bis (N, N-diglycidyl aminomethyl) cyclohexane, trimethylolpropan polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, etc. Can be mentioned.

As the cross-linking agent (C), one type may be used alone or two or more types may be used in combination. The content of the cross-linking agent (C) in the pressure-sensitive adhesive composition is appropriately selected according to the desired adhesive properties and the like, and is not particularly limited, but is 0.01 to 5 with respect to 100 parts by mass of the base polymer (A). It can be parts by mass, and can be 0.03 to 3 parts by mass.
The content of the cross-linking agent (C) can be 0.01 to 5.0% by mass and 0.02 to 2.0% by mass with respect to the total mass of the pressure-sensitive adhesive composition. it can.

[Polymerization initiator (D)]
The polymerization initiator (D) may be any as long as it can initiate the polymerization reaction of the monomer (B) by irradiation with active energy rays, and known photopolymerization initiators and the like can be used.
Here, the "active energy ray" means an electromagnetic wave or a charged particle beam having an energy quantum, and examples thereof include ultraviolet rays, electron beams, visible rays, X-rays, and ion rays. Among them, from the viewpoint of versatility, ultraviolet rays or electron beams are preferable, and ultraviolet rays are particularly preferable.

Examples of the polymerization initiator (D) include acetophenone-based initiators, benzoin ether-based initiators, benzophenone-based initiators, hydroxyalkylphenone-based initiators, thioxanthone-based initiators, amine-based initiators and the like.
Specific examples of the acetophenone-based initiator include diethoxyacetophenone and benzyl dimethyl ketal.
Specific examples of the benzoin ether-based initiator include benzoin and benzoin methyl ether.
Specific examples of the benzophenone-based initiator include benzophenone, methyl o-benzoylbenzoate and the like.
Specific examples of the hydroxyalkylphenone-based initiator include 1-hydroxy-cyclohexyl-phenyl-ketone.
Specific examples of the thioxanthone-based initiator include 2-isopropylthioxanthone, 2,4-dimethylthioxanthone and the like.
Specific examples of the amine-based initiator include triethanolamine, ethyl 4-dimethylbenzoate and the like.

As the polymerization initiator (D), one type may be used alone or two or more types may be used in combination. The content of the polymerization initiator (D) in the pressure-sensitive adhesive composition is appropriately selected depending on the content of the monomer (B), the irradiation amount of active energy rays at the time of semi-curing or complete curing, and the like, and in particular. Although not limited, it can be 0.05 to 10% by mass and 0.1 to 5.0% by mass with respect to the total mass of the monomer (B).
Further, the content of the polymerization initiator (D) can be 0.1 to 10 parts by mass and 1 to 5 parts by mass with respect to 100 parts by mass of the base polymer (A).

[Solvent (E)]
The solvent (E) is used to improve the coating suitability of the pressure-sensitive adhesive composition.
Examples of such a solvent (E) include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane and methylcyclohexane; and halogenated hydrocarbons such as dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene and dichloropropane. Classes; alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, diacetone alcohol; ethers such as diethyl ether, diisopropyl ether, dioxane, tetrahydrofuran; acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone, etc. Ketones; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, ethyl butyrate; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene Examples thereof include polyols such as glycol monoethyl ether and propylene glycol monomethyl ether acetone, and derivatives thereof.

Examples of the solvent (E) include a solvent that does not have a polymerizable unsaturated group and has a higher vapor pressure at 25 ° C. than that of the monomer (B). The larger the difference in vapor pressure between the monomer (B) and the solvent (E), the fewer coating defects and the easier the production. Therefore, the vapor pressure of the solvent (E) can be 2000 Pa or more and 5000 Pa. It can be the above. The upper limit is not particularly limited, but is practically 50,000 Pa or less. The vapor pressure of the solvent (E) can be measured by JIS-K2258-2 "Crude oil and petroleum products-How to obtain the vapor pressure-Part 2: Three-fold expansion method", for example, http: // www. chemsider. It can be predicted by a website such as com / or software such as ACD / PhysChem Suite.

Solvents that do not have a polymerizable unsaturated group and have a higher vapor pressure at 25 ° C. than the monomer (B) include hexane, heptane, cyclohexane, benzene, toluene, ethanol, isopropyl alcohol, diisopropyl ether, tetrahydrofuran, and acetone. , Methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate and the like. The solvent can be appropriately selected depending on the type of the monomer (B).

Further, the solvent (E) may have a surface tension at 25 ° C. of 20 mN / m or more and less than 40 mN / m, or 22 mN / m or more and less than 36 N / m. If the surface tension is at least the above lower limit value, it is possible to suppress the formation of yuzu skin (orange peel), and if it is less than the above upper limit value, coating defects such as the occurrence of thick edge (framing) are unlikely to occur.

The difference in solubility parameter between the solvent (E) and the monomer (B) may be within 2 [(cal / cm ³ ) ^1/2 ], and 1.5 [(cal / cm ³ ) ^{1 / 2} ] may be within. As a result, coating defects such as the generation of citron skin (orange peel) due to the abnormally accelerated evaporation of the solvent (E) are unlikely to occur. The solubility parameter serves as a guideline for dissolution and has the meaning of the following equation.
δ = (ΔE / V) 1/2
Here, δ is a solubility parameter, ΔE is a molar evaporation energy (cal / mol), and V is a molar volume (cm ³ / mol). Those with similar solubility parameter δ values dissolve well. It is consistent with the rule of thumb that similar things melt well. The solubility parameter can be obtained by various methods, but in the present specification, it is calculated from the chemical composition by the method of Fedors.

One type of solvent (E) may be used alone, or two or more types may be used in combination. The content of the solvent (E) in the pressure-sensitive adhesive composition is not particularly limited, but may be 25 to 500 parts by mass and 30 to 400 parts by mass with respect to 100 parts by mass of the base polymer (A). Can be done.
The content of the solvent (E) can be 10 to 90% by mass and 20 to 80% by mass with respect to the total mass of the pressure-sensitive adhesive composition.

[Plasticizer]
In the present invention, the pressure-sensitive adhesive composition may contain a plasticizer. When a plasticizer is contained, the content of the plasticizer can be 50 parts by mass or less, 30 parts by mass or less, and 10 parts by mass or less with respect to 100 parts by mass of the base polymer (A). It can also be.

As the plasticizer, a non-functional acrylic polymer can be used. The non-functional acrylic polymer is a polymer consisting only of an acrylic monomer unit having no functional group other than an acrylate group, or an acrylic monomer unit having no functional group other than an acrylate group and having no functional group. It means a polymer composed of a non-acrylic monomer unit.
Examples of the acrylic monomer unit having no functional group other than the acrylate group include those similar to the non-crosslinkable (meth) acrylic acid ester unit (a1).
Examples of the non-acrylic monomer unit having no functional group include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, and stearerate. Examples thereof include vinyl carboxylic acid esters such as vinyl acetate, vinyl cyclohexanecarboxylate, vinyl benzoate, and styrene.

[Arbitrary component]
The pressure-sensitive adhesive composition may contain components other than the above as long as the effects of the present invention are not impaired. Other components include components known as additives for pressure-sensitive adhesives, such as antioxidants, metal corrosion inhibitors, tackifiers, silane coupling agents, ultraviolet absorbers, and light stabilizers such as hindered amine compounds. You can select from among them as needed.
Examples of the antioxidant include a phenol-based antioxidant, an amine-based antioxidant, a lactone-based antioxidant, a phosphorus-based antioxidant, a sulfur-based antioxidant, and the like. One of these antioxidants may be used alone, or two or more thereof may be used in combination.
Examples of the metal corrosion inhibitor include benzodiazole resins.
Examples of the tackifier include rosin-based resin, terpene-based resin, terpene phenol-based resin, Kumaron inden-based resin, styrene-based resin, xylene-based resin, phenol-based resin, and petroleum resin.
Examples of the silane coupling agent include a mercaptoalkoxysilane compound (for example, a mercapto group-substituted alkoxy oligomer) and the like.
Examples of the ultraviolet absorber include benzotriazole-based compounds and benzophenone-based compounds. However, when ultraviolet rays are used for the active energy rays at the time of complete curing, it is necessary to add them within a range that does not inhibit the polymerization reaction.

(Manufacturing method of adhesive sheet)
The pressure-sensitive adhesive sheet of the present invention is obtained by semi-curing the pressure-sensitive adhesive composition by heating or irradiation with active energy rays, containing at least a part of the monomer (B) in an unreacted state, and a cross-linking agent ( Of at least one selected from C) and the polymerization initiator (D), at least a part thereof is contained in an unreacted state. That is, the method for producing a pressure-sensitive adhesive sheet of the present invention includes a step of heating the pressure-sensitive adhesive composition or irradiating it with active energy rays.
Further, the method for producing an adhesive sheet of the present invention preferably includes a step of adding fine particles. The fine particles are preferably added to the pressure-sensitive adhesive composition prior to the semi-curing step by heating or irradiation with active energy rays.

The pressure-sensitive adhesive sheet of the present invention may be composed of a pressure-sensitive adhesive layer and another layer, but is preferably composed of only a pressure-sensitive adhesive layer. Examples of the other layer include a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition other than the above, a support, a release sheet, and the like. Examples of the support include plastic films such as polystyrene, styrene-acrylic copolymer, acrylic resin, polyethylene terephthalate, polycarbonate, polyether ether ketone, and triacetyl cellulose; optical films such as antireflection film and electromagnetic wave shielding film; etc. Can be mentioned.

The manufacturing process of the pressure-sensitive adhesive sheet of the present invention includes a step of applying a pressure-sensitive adhesive composition on a release sheet to form a coating film, a step of heating the coating film to make a semi-cured product, or an activity of the coating film. It includes a step of making a semi-cured product by irradiation with energy rays.

Hereinafter, a step of applying the pressure-sensitive adhesive composition on the release sheet to form a coating film and a step of heating the coating film to form a semi-cured product will be described as representatives.
By heating the coating film, the reaction between the base polymer (A) and the cross-linking agent (C) proceeds to form a semi-cured product (adhesive sheet). That is, during heating, the polymerization reaction of the monomer (B) by the polymerization initiator (D) does not proceed in the coating film, or even if it progresses, it is slight, so that the semi-cured product (adhesive sheet) obtained. The monomer (B) and the polymerization initiator (D) contained in the pressure-sensitive adhesive composition remain in the pressure-sensitive adhesive composition. Therefore, the pressure-sensitive adhesive sheet of the present invention has active energy ray curability. In order to bring the pressure-sensitive adhesive composition into a semi-cured state, an aging treatment may be performed in which the pressure-sensitive adhesive sheet is allowed to stand at a constant temperature for a certain period of time after the solvent is removed after coating. The aging treatment can be performed, for example, by allowing it to stand at 23 ° C. for 7 days.

The release sheet is a peelable laminated sheet having a release sheet base material and a release agent layer provided on one side of the release sheet base material, or a polyolefin film such as a polyethylene film or polypropylene film as a low polarity base material. Can be mentioned. Papers and polymer films are used as the base material for the release sheet in the releaseable laminated sheet. As the release agent constituting the release agent layer, for example, a general-purpose addition type or condensation type silicone type release agent or a long-chain alkyl group-containing compound is used.
Specific examples of the silicone-based release agent include BY24-4527 and SD-7220 manufactured by Toray Dow Corning Silicone, and KS-3600, KS-774, and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. Can be mentioned. Further, the silicone-based release agent contains a silicone resin which is an organic silicon compound having ₂ units of SiO and (CH ₃ ) ₃ SiO _1/2 units or CH ₂ = CH (CH ₃ ) SiO _1/2 units. May be good. Specific examples of the silicone resin include BY24-843, SD-7292, SHR-1404, etc. manufactured by Toray Dow Corning Silicone Co., Ltd., KS-3800, X92-183, etc. manufactured by Shin-Etsu Chemical Co., Ltd.

As the release sheet, two types of release sheets having different peelability can be used in order to facilitate the release. That is, if the peelability from one side and the peelability from the other side are different, it becomes easy to peel off only the release sheet having the higher peelability first. In that case, the peelability of each release sheet may be adjusted according to the bonding method and the bonding order.

The coating of the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive sheet can be carried out using a known coating device. Examples of the coating apparatus include a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a micro gravure coater, a rod blade coater, a lip coater, a die coater, a curtain coater and the like.

The coating liquid may contain a solvent. Examples of the solvent include methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, toluene, n-hexane, n-butyl alcohol, methyl isobutyl ketone, methyl butyl ketone, ethyl butyl ketone, cyclohexanone, ethyl acetate, butyl acetate, and propylene glycol monomethyl. Ether acetate, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, N-methyl-2-pyrrolidone and the like are used. One or more of these may be used alone, or two or more thereof may be mixed and used.

Further, the coating film can be heated by using a known heating device such as a heating furnace or an infrared lamp.

(How to use the adhesive sheet)
As a method of using the pressure-sensitive adhesive sheet of the present invention, when the pressure-sensitive adhesive sheet is in a semi-cured state, the first optical member and the second optical member are bonded together, and the pressure-sensitive adhesive sheet is completely cured by heating or irradiation with active energy rays. There is a way. As described above, the adherend is preferably an optical member. The first optical member may be a backlight, and the second optical member may be a polarizing plate.

In the present invention, the pressure-sensitive adhesive sheet is attached to the surface of the adherend in a semi-cured state and then completely cured by heating or irradiation with active energy rays, whereby the cohesive force of the pressure-sensitive adhesive sheet is increased and the adhesiveness is improved. Examples of the active energy ray include ultraviolet rays, electron beams, visible rays, X-rays, ion rays and the like, which can be appropriately selected depending on the polymerization initiator (D) contained in the pressure-sensitive adhesive sheet. Among them, from the viewpoint of versatility, ultraviolet rays or electron beams are preferable, and ultraviolet rays are particularly preferable.
As the light source of ultraviolet rays, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, a carbon arc, a xenon arc, an electrodeless ultraviolet lamp and the like can be used.
As the electron beam, for example, an electron beam emitted from various electron beam accelerators such as Cockloftwald type, Bandecliff type, resonance transformer type, insulated core transformer type, linear type, dynamistron type, and high frequency type can be used.

(Manufacturing method of laminated body and laminated body)
The present invention also relates to a method for producing a laminate, which comprises a step of bringing an adhesive sheet into contact with the surface of an adherend and heating in that state or a step of irradiating an active energy ray. The present invention also relates to a laminate produced by such a production method.
Here, the pressure-sensitive adhesive sheet is preferably brought into contact with the surface of a pair of adherends in a semi-cured state, and the pair of adherends is preferably a first optical member and a second optical member. That is, it is preferable to attach the optical members to both surfaces of the pressure-sensitive adhesive sheet.

In the method for producing a laminated body of the present invention, a roll-to-roll method can be used in the step of bringing the adhesive sheet into contact with the surface of the adherend. When the roll-to-roll method is applied, the production speed of the process of bringing the adhesive sheet into contact with the surface of the adherend can be increased, and the production efficiency of the laminated body can be increased.

FIG. 1 is a cross-sectional view illustrating an example of the structure of the laminated body of the present invention. As shown in FIG. 1, it is preferable that the laminate 100 of the present invention has the pressure-sensitive adhesive sheet 10 and has optical members 22 and 24 on both surfaces of the pressure-sensitive adhesive sheet 10.
Examples of the optical member include a backlight, a polarizing plate, a light guide plate, and a light diffusion sheet used in a liquid crystal display device. Since the pressure-sensitive adhesive sheet of the present invention has excellent light diffusivity, it is preferably used for bonding a backlight and a polarizing plate.

The features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the specific examples shown below. In the following, Example 2 shall be read as Reference Example 2.

(Example 1)
<Synthesis of base polymer (A)>
N-butyl acrylate monomer as a non-crosslinkable (meth) acrylic acid ester unit (a1) and 2-hydroxyethyl acrylate monomer as an acrylic monomer unit (a2) having a cross-linking functional group in a mass ratio of 9: 1 (a1). : A2) was blended. AIBN (azobisisobutyronitrile) was dissolved therein as a radical polymerization initiator. The solution was heated to 60 ° C. and randomly copolymerized to obtain a base polymer (A). The solution viscosity of the 35% by mass solution of the base polymer (A) at 23 ° C. was 5500 mPa · s. The polystyrene-equivalent weight average molecular weight measured using size exclusion chromatography (SEC) was 530,000.

<Preparation of adhesive solution>
Isostearyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., ISTA, vapor pressure: 0 Pa,) as a monomer (B1) having one polymerizable unsaturated group with respect to 100 parts by mass of the obtained base polymer (A). Trimethylol propaneethylene oxide-modified triacrylate (manufactured by Toa Synthetic Co., Ltd., Aronix M-360) as a polyfunctional monomer (B2) having a melting point of <-50 ° C.) of 15 parts by mass and having two or more polymerizable unsaturated groups. (EOTMPTA)) by 9 parts by mass, tolylene diisocyanate compound (Coronate L, manufactured by Toso Co., Ltd.) as a cross-linking agent (C) that reacts with the base polymer (A) by heat, 0.2 parts by mass, active energy ray. 1-Hydroxy-cyclohexyl-phenyl-ketone (BASF Japan Co., Ltd., IRGACURE184) as a polymerization initiator (D) that initiates a polymerization reaction with a monomer (B1) and a polyfunctional monomer (B2) by irradiation with 2 parts by mass, and 30 parts by mass of light diffusing particles (manufactured by Soken Kagaku Co., Ltd .: MX-1000 (average particle size: 10 μm)) were added, and the solid content concentration was 30% by mass with ethyl acetate of the solvent (E). Diluted to:

<Making an adhesive sheet>
A 38 μm-thick polyethylene terephthalate film (separator film) provided with a release agent layer treated with a silicone-based release agent from the pressure-sensitive adhesive solution prepared as described above (manufactured by Oji F-Tex Co., Ltd., 38RL-07 (2)). The surface of the film is uniformly coated with an applicator so that the coating amount after drying is 10 μm / m ² , dried in an air circulation type constant temperature oven at 100 ° C. for 3 minutes, and an adhesive layer is applied to the surface of the separator film. Formed. Next, a separator film having a thickness of 38 μm (38RL-07 (L) manufactured by Oji F-Tex Co., Ltd.) was attached to the surface of the pressure-sensitive adhesive layer. In this way, a double-sided pressure-sensitive adhesive sheet having a structure of a separator film / pressure-sensitive adhesive layer / separator film in which the pressure-sensitive adhesive layer is sandwiched between a pair of separator films having different peeling powers was obtained. The adhesive sheet was cured at 23 ° C. and a relative humidity of 50% for 7 days. The haze of the adhesive sheet was 36% and the thickness was 10 μm.

(Example 2)
A double-sided pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that a pressure-sensitive adhesive sheet was prepared using the pressure-sensitive adhesive solution of Example 1 so that the coating amount was 25 μm / m ² . The adhesive sheet was cured at 23 ° C. and a relative humidity of 50% for 7 days. The haze of the adhesive sheet was 58% and the thickness was 25 μm.

(Comparative Example 1)
In <Preparation of Adhesive Solution> of Example 1, an isostearyl acrylate as a monomer (B1) having one polymerizable unsaturated group, and a trimethylolpropane ethylene oxide-modified triacrylate as a polyfunctional monomer (B2), An adhesive solution was prepared in the same manner as in Example 1 except that 1-hydroxy-cyclohexyl-phenyl-ketone was not blended as the polymerization initiator (D). A double-sided pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that a pressure-sensitive adhesive sheet was prepared using the pressure-sensitive adhesive solution so that the coating amount was 10 μm / m ² . The adhesive sheet was cured at 23 ° C. and a relative humidity of 50% for 7 days. The haze of the adhesive sheet was 37% and the thickness was 10 μm.

(Comparative Example 2)
A double-sided pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive solution of Comparative Example 1 was used to prepare the pressure-sensitive adhesive sheet so that the coating amount was 25 μm / m ² . The adhesive sheet was cured at 23 ° C. and a relative humidity of 50% for 7 days. The haze of the adhesive sheet was 59% and the thickness was 25 μm.

<Evaluation>
[Measurement of haze]
One adhesive surface of the double-sided adhesive sheet of Examples and Comparative Examples is bonded to a slide glass (product number: S9112) manufactured by Matsunami Glass Co., Ltd., and a transparent PET film (New Tac Kasei Co., Ltd., CPET75H) is attached to the other adhesive surface. Was pasted together. Subsequently, in order to eliminate the influence of fine air and the like mixed during bonding, the laminated samples were subjected to an autoclave (pressure defoaming) treatment at 0.5 MPa and 40 ° C. for 30 minutes. The haze of these bonded products was measured using NDH4000 manufactured by Nippon Denshoku Kogyo Co., Ltd.

[Measurement of holding power in semi-cured state]
The separator film on the lightly peeled side of the double-sided adhesive sheet obtained in Examples and Comparative Examples was peeled off, and a 100 μm PET film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.) was attached to the exposed adhesive layer surface to form an adhesive film. I got a sheet. After cutting out a test piece having a width of 25 mm × 100 mm from the adhesive film sheet, the separator on the heavy peeling side is peeled off, and the adhesive surface is attached to a SUS plate so that the area of the exposed bonded portion is 25 mm × 25 mm, and JIS According to the holding force measuring method of Z0237, a 1 kg weight was hung and the amount of deviation after 60 minutes was measured.

[Measurement of holding power after irradiation with active energy rays]
Attached to a 100 μm PET film in the same manner as in [Measurement of holding force in a semi-cured state], cut out a test piece having a width of 25 mm × 100 mm, and then peel off the separator on the heavy peeling side to expose the adhesive surface. It was affixed to a SUS plate so that the area of was 25 mm × 25 mm. Subsequently, after irradiating the integrated light amount of 1000 mJ / cm ² with an ultraviolet irradiator (ECS-301G1 manufactured by Eye Graphic Co., Ltd.) from the PET surface side, a 1 kg weight is hung for 60 minutes according to the holding force measurement method of JIS Z0237. The amount of deviation after that was measured.

[Durability evaluation]
The separator film on the lightly peeled side of the obtained double-sided adhesive sheet is peeled off, a polarizing plate (KN-18240T manufactured by Polatechno Co., Ltd.) is attached to the exposed pressure-sensitive adhesive layer surface, and then the separator film on the heavy peeled side is peeled off. It was affixed to non-alkali glass (Eagle XG manufactured by Corning Inc.). Next, the treatment was carried out in an autoclave under the conditions of 0.5 MPa and 40 ° C. for 30 minutes, and an integrated light amount of 1000 mJ / cm ² was irradiated from the non-alkali glass surface side with an ultraviolet irradiator (ECS-301G1 manufactured by Eye Graphic Co., Ltd.). Then, it was treated in a constant temperature and humidity chamber at 85 ° C. and a relative humidity of 85% for 240 hours, and evaluated according to the following criteria.
◯: No floating, peeling, or bubble generation.
Δ: Slight bubbles or floats were generated at the edge portion (within 0.5 mm from the edge of the polarizing plate).
X: Floating or peeling and air bubbles were generated in addition to the edge portion.

The pressure-sensitive adhesive sheet obtained in the examples was a high-haze pressure-sensitive adhesive sheet having uniform light diffusivity. In addition, the pressure-sensitive adhesive sheet obtained in the examples had a semi-cured state and an appropriate holding power after irradiation with active energy rays, and was also excellent in durability.

10 Adhesive sheet 22 Optical member 24 Optical member 100 Laminated body

Claims (6)

A base polymer (A) containing a non-crosslinkable (meth) acrylic acid ester unit (a1) and an acrylic monomer unit (a2) having a crosslinkable functional group,
A monomer (B) having at least one polymerizable unsaturated group and
A cross-linking agent (C) that reacts with the base polymer (A) by heat,
A polymerization initiator (D) that initiates a polymerization reaction of the monomer (B) by irradiation with active energy rays, and
A solvent (E), a pressure-sensitive adhesive composition containing, including the adhesive is semi-cured by irradiation with heat or active energy rays, a pressure-sensitive adhesive sheet,
The monomer (B) contains a monofunctional monomer (B1) and a polyfunctional monomer (B2).
The pressure-sensitive adhesive contains fine particles and contains
An adhesive sheet having a thickness of 7 to 20 μm and a haze of 35 to 60%. The pressure-sensitive adhesive sheet according to claim 1 , wherein the average particle size of the fine particles is 3 to 15 μm. The adhesive sheet according to claim 1 or 2 , wherein the deviation distance after 60 minutes measured by crimping to a SUS plate according to the holding force measuring method of JIS Z0237 is 10 mm or more. Claims 1 to 3 in which the deviation distance after 60 minutes, which is measured according to the holding force measurement method of JIS Z0237 after being pressure-bonded to a SUS plate and further cured by heating or irradiating with active energy rays, is less than 10 mm. The adhesive sheet according to any one of the above. The adhesive sheet according to any one of claims 1 to 4 , which is a double-sided adhesive sheet. A method for producing a laminate, which comprises a step of bringing the pressure-sensitive adhesive sheet according to any one of claims 1 to 5 into contact with the surface of an adherend and heating in that state, or a step of irradiating an active energy ray.

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