JP6310271B2 - Optical pressure-sensitive adhesive composition, optical pressure-sensitive adhesive sheet, and image display device - Google Patents

Description

  The present invention relates to an optical pressure-sensitive adhesive composition, an optical pressure-sensitive adhesive sheet, and an image display device.

  In recent years, an image display device such as a liquid crystal display device and an input / output device such as a touch panel used in combination with the image display device have been widely used. In the production of these image display devices and input / output devices, a pressure-sensitive adhesive composition is used when bonding constituent members (Patent Document 1).

  In recent years, in order to impart design properties, a printing unit may be provided at the peripheral portion of a touch panel type input / output device or an image display device, and this printing unit has a printing step of several μm to several tens of μm. . Therefore, when bonding such a printing surface with an adhesive sheet, the adhesive cannot follow a printing level | step difference, but the bubble enters into a level | step difference part and the problem that designability is impaired has arisen.

  Therefore, in order to improve the performance (step following capability) to fill the level difference between the members and / or the level difference existing in the member, there is a demand for a flexible adhesive that is less likely to generate bubbles and that can follow the level difference. It has been.

JP 2002-327160 A

  The present invention provides an optical pressure-sensitive adhesive composition capable of obtaining a pressure-sensitive adhesive layer in which the generation of delay bubbles is reduced and has excellent step following ability and adhesive strength, and is obtained using the optical pressure-sensitive adhesive composition. An optical pressure-sensitive adhesive sheet and an image display device including the optical pressure-sensitive adhesive sheet are provided.

  As a result of intensive studies to solve such problems, the present inventors have found a copolymer obtained from a monomer mixture containing a monomer having a branched alkyl group having 10 to 24 carbon atoms in a predetermined ratio. It has been found that by using the adhesive sheet, it is possible to obtain a pressure-sensitive adhesive sheet in which the generation of delay bubbles is reduced and which has excellent step following ability and adhesive force.

1. The optical pressure-sensitive adhesive composition according to one embodiment of the present invention includes (a1) 3 to 18% by mass of a (meth) acrylic acid alkyl ester monomer having a branched alkyl group having 10 to 24 carbon atoms, (A2) 42 to 95% by mass of a (meth) acrylic acid alkyl ester monomer having a straight chain and / or branched alkyl group having 1 to 9 carbon atoms, and (a3) a hydroxyl group-containing monomer 2% % To 40% by mass, and (a4) a monomer mixture containing 0.1% by mass to 5% by mass of the nitrogen atom-containing monomer (wherein the component (a1) in the monomer mixture) The total of the component (a2) and the component (a3) is 75% by mass or more and 100% by mass or less.) (0) with respect to 100 parts by mass of the copolymer (A) and the copolymer (A) .01 parts by mass or more and 20 parts by mass or less (B) a crosslinking agent.

  2. In the optical pressure-sensitive adhesive composition as described in 1 above, the (A) copolymer may have a weight average molecular weight of 50,000 to 700,000.

3. In the optical pressure-sensitive adhesive composition according to 1 or 2, the total of monomers having an acryloyl group in the monomer mixture may be 20% by mass or more and 100% by mass or less.

4 . In the optical pressure-sensitive adhesive composition according to any one of 1 to 3 , the acid value of the (A) copolymer may be 1.0 or less.

5 . The optical adhesive sheet which concerns on 1 aspect of this invention has an adhesive layer formed from the optical adhesive composition in any one of said 1 thru | or 4 .

6 . The optical pressure-sensitive adhesive sheet described in 5 above can be used for bonding members constituting a touch panel type input / output device or an image display device.

7 . The image display apparatus which concerns on 1 aspect of this invention contains the adhesive sheet for optics as described in said 5 or 6 .

  The optical pressure-sensitive adhesive composition has (a1) 3 to 18% by mass of a (meth) acrylic acid alkyl ester monomer having a branched alkyl group having 10 to 24 carbon atoms, and (a2) 1 carbon atom. (Meth) acrylic acid alkyl ester monomer having a straight chain and / or branched alkyl group of 9 or less and 42% by mass or more and 95% by mass or less, and (a3) a hydroxyl group-containing monomer of 2% by mass or more and 40% by mass or less. (Here, the total of the component (a1), the component (a2) and the component (a3) in the monomer mixture is 75% by mass or more and 100% by mass or less). (A) the copolymer, and (B) a crosslinking agent that is 0.01 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the copolymer (A). Using the agent composition, Generation of bubbles is reduced, and it is possible to obtain a pressure-sensitive adhesive layer excellent in conformability to irregularities and adhesion.

  Moreover, since this adhesive layer is excellent in transparency, it can be used suitably for an image display apparatus and an input / output device, for example.

FIG. 1 is a cross-sectional view schematically showing a configuration of a first input / output device (touch panel type input / output device) according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a configuration of a second input / output device (touch panel type input / output device) according to an embodiment of the present invention. FIG. 3A is a cross-sectional view illustrating the step-following property of a known pressure-sensitive adhesive sheet, and FIG. 3B is a pressure-sensitive adhesive sheet included in the image display device (touch panel type input / output device) shown in FIG. It is sectional drawing explaining the level | step difference followability of this.

  Hereinafter, the present invention will be described in detail with reference to the drawings. In the present invention, “parts” means “parts by mass” and “%” means “mass%” unless otherwise specified.

1.1. Optical pressure-sensitive adhesive composition An optical pressure-sensitive adhesive composition according to an embodiment of the present invention is (a1) a (meth) acrylic acid alkyl ester monomer having a branched alkyl group having 10 to 24 carbon atoms (this specification). In the text, it may be simply described as “component (a1).) 3% by mass to 18% by mass and (a2) having a linear and / or branched alkyl group having 1 to 9 carbon atoms (meta ) 42% by mass or more and 95% by mass or less of an acrylic acid alkyl ester monomer (in this specification, it may be simply referred to as “component (a2)”), and (a3) 2% by mass of a hydroxyl group-containing monomer. 40 mass% or less (in this specification, it may be simply referred to as “component (a3)”), and a monomer mixture (wherein the component (a1) in the monomer mixture, The component (a2) and (A) copolymer of (a3) component is 75% by mass or more and 100% by mass or less) and 0.01 part by mass or more and 20 parts by mass with respect to 100 parts by mass of (A) copolymer. And (B) a crosslinking agent which is not more than part.

  By using the optical pressure-sensitive adhesive composition according to this embodiment, it is possible to obtain a pressure-sensitive adhesive layer in which the generation of delay bubbles is reduced and the step following ability and the adhesive force are excellent.

  In the present invention, “delay bubble” refers to bubbles generated over time in an adhesive layer after the adhesive layer is formed. The generation of the delay bubble is one of the causes for reducing the transparency of the pressure-sensitive adhesive layer. This delay bubble often occurs when heat is applied to the adhesive layer (for example, when a device including the adhesive layer is driven). The reduction in the generation of delay bubbles will be described in detail in the section of action and effect described later. Further, the step following ability will also be described in detail in the section of the effect described later.

1.1. (A) Copolymer The component (A) preferably has a functional group from the viewpoint of enhancing moisture and heat whitening resistance. In the present invention, moist heat whitening is a phenomenon in which the pressure-sensitive adhesive film is whitened (white turbid) when it is returned to room temperature after being exposed to high temperature and high humidity conditions (for example, 60 ° C. and 95% RH). Moreover, a functional group is a crosslinkable functional group which can react with the below-mentioned (B) crosslinking agent and can build a crosslinked structure, for example, a hydroxyl group, an amino group, etc. are mentioned.

  Moreover, it is preferable that (A) component does not contain a carboxyl group substantially. In the present invention, “(A) component substantially does not contain a carboxyl group” means, for example, that the content of the carboxyl group-containing monomer in the monomer mixture is 0.1% by mass or less. More specifically, it means that no carboxyl group-containing monomer is used as the monomer constituting the monomer mixture.

1.1.1. Monomer mixture Using the optical pressure-sensitive adhesive composition according to this embodiment, generation of delay bubbles is further reduced, adhesion to an adherend (particularly glass) is excellent, and step followability is excellent. The component (A) is preferably a copolymer of a monomer composition containing the component (a1), the component (a2) and the component (a3) in that an adhesive layer can be obtained. More preferably, it is a copolymer of a monomer composition containing the component (a1), the component (a2), the component (a3) and the component (a4).

  In the present invention, the expression “(meth) acrylic” is a concept including both acrylic and methacrylic.

In the present invention, the component (A) includes a structural unit (—CH—CH—C (═O) —) and / or a methacryloyl group derived from an acryloyl group (CH ₂ ═CH—C (═O) —). _{(CH 2 = C (CH 3} ) -C (= O) -) structural units derived from _{(-CH-C (CH 3)} -C (= O) -) may have. When (A) component has the said structural unit derived from an acryloyl group, (A) component can be a copolymer of the monomer mixture containing the monomer which has an acryloyl group. Further, when the component (A) has the structural unit derived from a methacryloyl group, the component (A) can be a copolymer of a monomer mixture containing a monomer having a methacryloyl group.

  In the present invention, the “(meth) acrylic acid ester monomer” is a monomer having one or more (meth) acryloyl groups in the molecule. In the present invention, the (meth) acryloyl group is a concept including both an acryloyl group and a methacryloyl group. More specifically, the (meth) acrylic acid ester monomer is a concept including (meth) acrylic acid ester having a functional group such as a hydroxyl group and an amino group in addition to the (meth) acrylic acid alkyl ester.

1.1.1.1. Component (a1) The component (a1) can contribute to the reduction in the generation of delay bubbles in the pressure-sensitive adhesive layer obtained by using the optical pressure-sensitive adhesive composition according to the present embodiment, and good step following ability. That is, due to the branched alkyl group having 10 to 24 carbon atoms contained in the component (a1), it is possible to reduce the occurrence of delay bubbles in the pressure-sensitive adhesive layer, and to have flexibility, and Since a pressure-sensitive adhesive layer having high wettability with respect to the adherend can be obtained, good step following ability can be achieved.

  When the component (a1) exceeds 18% by mass of the monomer mixture, the glass transition temperature (Tg) of the component (A) becomes too high, and the component is obtained using the optical pressure-sensitive adhesive composition according to this embodiment. As a result of the pressure-sensitive adhesive layer becoming too hard, the step following ability may be deteriorated. On the other hand, when it is less than 3% by mass, the pressure-sensitive adhesive force of the pressure-sensitive adhesive layer to the adherend is lowered and sufficient reliability can be obtained. There may not be.

  The content of the component (a1) in the monomer mixture is preferably 3% by mass or more in that the generation of delay bubbles can be further reduced and the step following ability can be improved. It is more preferably 5% by mass or more, further preferably 6% by mass or more, and on the other hand, it is preferably 18% by mass or less.

  As the component (a1), for example, isodecyl (meth) acrylate, isolauryl (meth) acrylate, isotetradecyl (meth) acrylate, isopentadecyl (meth) acrylate, isohexadecyl (meth) acrylate, (Meth) acrylic acid alkyl ester having a branched alkyl group such as (meth) acrylic acid isoheptadecyl, (meth) acrylic acid isostearyl, (meth) acrylic acid isoarachidyl, (meth) acrylic acid isobehenyl, (meth) acrylic acid isolignoseryl Of these, one can be used alone or two or more can be used in combination.

  Especially, it is more preferable that carbon number of (a1) component is 10 or more and 18 or less by the point which can provide a high softness | flexibility with the adhesive layer obtained from the said monomer mixture.

  In addition, the component (a1) has a branched alkyl group having 10 to 24 carbon atoms and is homogenous in that the generation of delay bubbles can be further reduced and the step following ability can be improved. The polymer is preferably a (meth) acrylic acid alkyl ester having a Tg of −45 ° C. or higher (in this case, Tg is usually −5 ° C. or lower). The pressure-sensitive adhesive layer obtained using the component (A) obtained from the monomer mixture containing 3% by mass to 18% by mass of the component (a1) whose Tg of the homopolymer is −45 ° C. or higher has an appropriate adhesion Due to the power, the delay bubble is further reduced.

  Among these, the component (a1) is more preferably isostearyl acrylate and / or isodecyl methacrylate.

1.1.1-2. (A2) component (a2) A component can contribute to the adhesive force of the adhesive layer obtained using the optical adhesive composition which concerns on this embodiment.

  When the component (a2) exceeds 95% by mass of the monomer mixture, sufficient wettability to the adherend and delay in the pressure-sensitive adhesive layer obtained using the optical pressure-sensitive adhesive composition according to this embodiment. It is difficult to achieve compatibility with bubble resistance, which tends to cause poor appearance. On the other hand, if it is less than 42% by mass, the adhesive strength may be inferior.

  In view of having appropriate softness and adhesive strength, the content of the component (a2) in the monomer mixture is preferably 45% by mass or more, more preferably 52% by mass or more, It is preferably 95% by mass or less, more preferably 90% by mass or less, and further preferably 83% by mass or less.

More specifically, the component (a2) includes methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylate n. -(Meth) acrylic acid alkyl ester monomer having a linear alkyl group such as hexyl, n-octyl (meth) acrylate, n-nonyl (meth) acrylate;
Branched alkyl such as isopropyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate (Meth) acrylic acid alkyl ester monomer having a group; among these, one can be used alone, or two or more can be used in combination.

  The component (A2) is preferably such that the Tg of the homopolymer is 0 ° C. or less in that the Tg of the component (A) can be lowered (for example, the Tg of the component (A) can be 0 ° C. or less). It is more preferable that the temperature is −40 ° C. or lower.

  The component (a2) can be, for example, a (meth) acrylic acid alkyl ester monomer having a branched alkyl group, and is particularly excellent in compatibility with the component (a1). The component (a2) is preferably an acrylic acid alkyl ester monomer having a branched alkyl group (a monomer having an acryloyl group) in that the Tg of the adhesive and the adhesive strength of the resulting adhesive can be adjusted. It is more preferably an acrylic acid alkyl ester monomer having a branched alkyl group having 5 to 9 carbon atoms, and more preferably 2-ethylhexyl acrylate and isooctyl acrylate or any one of them.

  In the monomer mixture, the content of the component (a1) relative to the content of the component (a2) (the component (a1) of the component (a1) can be used to reduce the Tg of the copolymer or adjust the conformability to the adherend. (Content / content of component (a2)) is preferably 0.03 or more and 0.75 or less, and more preferably 0.10 or more and 0.6 or less. From the same viewpoint, the sum of the component (a1) and the component (a2) is usually 55% by mass or more and 98% by mass or less, and preferably 66% by mass or more and 95% by mass or less.

1.1.1-3. (A3) Component From the viewpoint of enhancing the whitening resistance of the pressure-sensitive adhesive layer obtained by using the optical pressure-sensitive adhesive composition according to this embodiment, the monomer mixture (a3) is a hydroxyl group-containing monomer (simply “ (It is also referred to as “component (a3).”) 2 mass% or more and 40 mass% can further be included.

  The component (a3) is a component capable of constructing a crosslinked structure with a crosslinking agent (B) described later. When the component (a3) exceeds 40% by mass of the monomer mixture, the Tg of the component (A) tends to be too high, whereas when it is less than 2% by mass, the whitening resistance of the pressure-sensitive adhesive layer is increased. May be inferior. The content of the component (a3) in the monomer mixture is superior in terms of the whitening resistance of the pressure-sensitive adhesive layer, and can further improve the step followability by further increasing the wettability with the adherend. It is preferably 5% by mass or more and 30% by mass or less, and more preferably 11% by mass or more and 30% by mass or less.

  Examples of the component (a3) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, ( Hydroxyl group-containing (meth) acrylic acid ester monomers such as (meth) acrylic acid 2-hydroxy-3-chloropropyl and (meth) acrylic acid 2-hydroxy-3-phenoxypropyl; ethylene glycol (meth) acrylate, (meta ) Polyethylene glycol acrylate, propylene glycol (meth) acrylate, and (meth) acrylic acid alkylene glycol such as polypropylene glycol (meth) acrylate. Among these, one kind is used alone, or two or more kinds are used in combination. You can also. Among these, from the viewpoint of excellent compatibility with the components (a1) and (a2), the component (a3) is an acrylate monomer (a monomer having an acryloyl group) containing a hydroxyl group. It is preferable.

1.1.1-4. (A4) Component From the viewpoint of imparting the cohesive strength of the optical pressure-sensitive adhesive composition according to this embodiment, the monomer mixture is also referred to as (a4) a nitrogen atom-containing monomer (also simply referred to as “(a4) component”). .) 0.1 mass% or more and 5 mass% or less can further be included. (A4) Nitrogen atoms contained in the component are bonded to hydrogen atoms present in the pressure-sensitive adhesive composition, and the hydrogen atoms are involved in the formation of hydrogen bonds in the pressure-sensitive adhesive composition, thereby causing high aggregation. Can express force. From the viewpoint of expressing a higher cohesive force, the content of the component (a4) in the monomer composition is preferably 0.2% by mass or more and 4% by mass or less, and 0.3% by mass or more and 3% by mass. % Or less is more preferable.

  The component (a4) is preferably an amide group or amino group-containing monomer, for example. The component (a4) is an amide group or amino group-containing monomer, so that the reaction between the component (A) and the component (B) described later is promoted, and the nitrogen atom constituting the amide group or amino group A hydrogen atom to be bonded participates in the formation of a hydrogen bond in the pressure-sensitive adhesive composition, whereby a higher cohesive force can be expressed.

  When the component (a4) is a cyclic nitrogen atom-containing monomer, the content of the cyclic nitrogen atom-containing monomer is less than 0.5% by mass (for example, 0 Preferably, it is less than 0.1% by mass (for example, less than 0% by mass and less than 0.1% by mass).

  As the component (a4), as an amino group-containing monomer, for example, chain monomers such as N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, and N, N-diethylaminoethyl methacrylate Is mentioned.

  Examples of the amide group-containing monomer include N, N-dimethylaminopropylacrylamide, N, N′-dimethylacrylamide, N, N′-diethylacrylamide, N, N′-dimethylaminoethylacrylamide, and N, N′-dimethyl. Examples include chain monomers such as aminopropylacrylamide, N-isopropylacrylamide, t-octyl (meth) acrylamide, diacetone acrylamide, N-propyl (meth) acrylamide, N-hexyl (meth) acrylamide, and (meth) acrylamide. It is done.

  An example of the cyclic nitrogen atom-containing monomer is a nitrogen-based heterocyclic ring-containing monomer. Examples of the nitrogen-based heterocycle-containing monomer include pentamethylpiperidyl (meth) acrylate, vinylpyridine, vinylpyrrolidone, acryloylmorpholine, and vinylcaprolactam. Among these, it can also be used individually by 1 type or in combination of 2 or more types.

  From the viewpoint of excellent copolymerizability with the components (a1) to (a3), the component (a4) is preferably a chain monomer, and a monomer having a (meth) acryloyl group is preferable.

1.1.1-5. Component (a5) The monomer mixture may contain a copolymerizable monomer other than the components (a1) to (a4) which are the component (a5). Component (a5) is, for example, (meth) acrylic acid n-decyl, (meth) acrylic acid n-lauryl, (meth) acrylic acid n-tetradecyl, (meth) acrylic acid n-pentadecyl, (meth) acrylic acid n- Hexadecyl, n-heptadecyl (meth) acrylate, stearyl (meth) acrylate, n-arachidyl (meth) acrylate, n-behenyl (meth) acrylate, n-lignoseryl (meth) acrylate, etc. 10 or more carbon atoms Aromatic ring groups such as (meth) acrylic acid alkyl ester monomers having a linear alkyl group of 24 or less, benzyl (meth) acrylate, 2-naphthyl (meth) acrylate, phenoxyethyl (meth) acrylate, etc. (Meth) acrylic acid ester monomers having (meth) acrylic acid dicyclopentenyloxyethyl, (meth) acrylic Glycidyl, (meth) acrylates having an ether group such as tetrahydrofurfuryl (meth) acrylate, styrene monomers such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene; vinyl carboxylates such as vinyl acetate Examples include esters, (meth) acryloyl group-containing macromonomers: carboxyl group-containing monomers, etc. Among these, one or two or more can be used in combination. The content of the component (a5) in the monomer composition is preferably 0% by mass or more and 20% by mass or less, and more preferably 0% by mass or more and 10% by mass or less.

  Among them, since the (meth) acrylic acid alkyl ester monomer having a linear alkyl group having 10 to 24 carbon atoms has crystallinity, the pressure-sensitive adhesive layer becomes hard and air bubbles are easily involved. The content of the (meth) acrylic acid alkyl ester monomer having a linear alkyl group having 10 to 24 carbon atoms in the product is preferably 4% by mass or less.

  Examples of the carboxyl group-containing monomer include carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid, citraconic acid, and aconitic acid. The content of the carboxyl group-containing monomer in the monomer mixture for preparing the component (A) is 0.1% by mass in that the acid value of the component (A) can be adjusted to 1.0 or less. The following is preferable.

  For example, in the optical pressure-sensitive adhesive composition according to the present embodiment, the component (a1) in the monomer mixture can be further improved in step following ability and the delay bubble can be further reduced. The total of the component (a2) and the component (a3) is 75% by mass or more and 100% by mass or less. In this case, the component (a1), the component (a2), and the component (a3) can all be acrylic acid ester monomers (that is, monomers having an acryloyl group).

  Further, in the optical pressure-sensitive adhesive composition according to this embodiment, the pressure-sensitive adhesive layer obtained using the optical pressure-sensitive adhesive composition can further reduce delay bubbles, has excellent step following ability, and is covered. From the viewpoint of achieving good adhesion to the adherend (especially glass), the component (a1), component (a2), component (a3) and (a3) in the monomer mixture for obtaining the component (A) a4) The total amount of the components can be 80% by mass or more and 100% by mass or less, and preferably 90% by mass or more and 100% by mass or less.

  Furthermore, the optical pressure-sensitive adhesive composition according to this embodiment has an acryloyl group in the monomer mixture from the viewpoint of further improving the step following ability and further reducing delay bubbles. The total amount of monomers is preferably 20% by mass or more and 100% by mass or less, preferably 25% by mass or more, more preferably 50% by mass or more, and further preferably 60% by mass or more. On the other hand, 99.9 mass% or less may be sufficient.

  In addition, in the optical pressure-sensitive adhesive composition according to the present embodiment, the monomer mixture has a methacryloyl group from the viewpoint that the step following ability can be further improved and the delay bubble can be further reduced. The total amount of monomers is preferably 0% by mass or more and 20% by mass or less.

1.1.2. Tg
In the optical pressure-sensitive adhesive composition according to the present embodiment, the pressure-sensitive adhesive layer obtained by using the optical pressure-sensitive adhesive composition is excellent in step followability, and the adhesiveness between the pressure-sensitive adhesive layer and the adherend is excellent. From the viewpoint of being able to increase, the Tg of the component (A) is preferably 0 ° C. or less, more preferably less than 0 ° C., further preferably −70 ° C. or more and −10 ° C. or less, and −70 It is particularly preferable that the temperature is from ℃ to -30 ℃. In the present invention, the Tg of the component (A) is a value calculated by the following formula (1) (FOX formula).

1 / Tg _A = W _a1 / Tg _a1 + W _a2 / Tg _a2 + W _a3 / Tg _a3 + W _a4 / Tg _a4 + W _a5 / Tg _a5 (1)
(In the formula, Tg _A represents the glass transition temperature (K) of the component (A), and Tg _a1 , Tg _a2 , and Tg _a3 are the constituent monomers (a1) component, (a2) component, ( a3) shows the glass transition temperature (Tg (K)) of the homopolymer prepared from the component, (a4) component, and (a5) component, and W _a1 , W _a2 , W _a3 , W _a4 , and W _a5 are ( (A) Indicates the weight fraction of component (a1), component (a2), component (a3), component (a4), and component (a5), which are constituent monomers contained in the component.

In addition, since Tg _A is calculated as an absolute temperature (K) by the above formula (1), it is converted to a Celsius temperature (° C.) as necessary.

  The glass transition temperatures of homopolymers prepared from typical monomers are shown in Table 1 below. More specifically, for example, Polymer Handbook Third Edition, Wiley-Interscience, 2003) It is described in.

1.1.3. The weight average molecular weight (A) component has a weight average molecular weight (Mw) of 50,000 to 700,000. When the weight average molecular weight of the component (A) is less than 50,000, sufficient cohesive force as an adhesive cannot be obtained and the durability may be inferior. On the other hand, when it exceeds 700,000, From the viewpoint of poor workability, the weight average molecular weight of the component (A) is preferably 100,000 or more, more preferably 150,000, on the other hand, preferably 600,000 or less, and 400,000 or less. More preferably, it is more preferably less than 400,000.

  Moreover, it is preferable that molecular weight distribution (Mw / Mn) is larger than 4 at the point which improves level | step difference followability. Here, the weight average molecular weight of the component (A) is obtained by using GPC (gel permeation chromatography) and calculating the weight average molecular weight (Mw) in terms of standard polystyrene under the following conditions.

<GPC measurement conditions>
Measuring device: HLC-8120GPC (manufactured by Tosoh Corporation)
GPC column configuration: The following five columns (all manufactured by Tosoh Corporation)
(I) TSK-GEL HXL-H (guard column)
(Ii) TSK-GEL G7000HXL
(Iii) TSK-GEL GMHXL
(Iv) TSK-GEL GMHXL
(V) TSK-GEL G2500HXL
Diluted with tetrahydrofuran so that the sample concentration is 1.0 mg / cm ³ Mobile phase solvent: Tetrahydrofuran Flow rate: 1.0 cm ³ / min
Column temperature: 40 ° C

1.1.4. Hydroxyl value In the present invention, the hydroxyl value means the number of mg of potassium hydroxide (KOH) required for acetylating the hydroxyl group contained in 1 g of a sample. The hydroxyl value can be calculated by the following method.

In the present invention, the hydroxyl value of the polymer is calculated by the following formula (2) based on the molecular weight (M) of the hydroxyl group-containing monomer used for copolymerization and the blending amount (Y mass%) of the hydroxyl monomer. Value.
Hydroxyl value of polymer (mgKOH) = Y / M × 561 (2)

  (A) The hydroxyl value of the copolymer is preferably 8 or more and 172 or less, more preferably 10 or more and 150 or less, and further preferably 20 or more and 130 or less. When the hydroxyl value of the copolymer (A) exceeds 172, the step following property of the pressure-sensitive adhesive layer obtained by using the optical pressure-sensitive adhesive composition according to the present embodiment may be lowered. When it exists, it may be inferior to the whitening resistance of this adhesive layer.

1.1.5. Content in pressure-sensitive adhesive composition The content of the component (A) in the optical pressure-sensitive adhesive composition according to this embodiment can be 40% by mass or more and 95% by mass or less of the pressure-sensitive adhesive composition, and is 45% by mass. % Or more and 95% by mass or less is preferable.

1.1.6. Polymerization Method The polymerization method of the component (A) is not particularly limited, and can be polymerized by a known method such as solution polymerization, emulsion polymerization, suspension polymerization, etc., but using a mixture of copolymers obtained by polymerization. In producing the pressure-sensitive adhesive composition of the present invention, polymerization is preferably performed by solution polymerization from the viewpoint that the treatment process is relatively simple and can be performed in a short time.

  In solution polymerization, generally, a predetermined organic solvent, each monomer, a polymerization initiator, and a chain transfer agent used as necessary are charged in a polymerization tank, and under a nitrogen stream or the reflux temperature of the organic solvent, The reaction is carried out by heating for several hours with stirring.

  In this case, at least a part of the organic solvent, the monomer and / or the polymerization initiator may be added sequentially. Examples of the organic solvent include aromatic hydrocarbons such as benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, aromatic naphtha; For example, aliphatic or alicyclic hydrocarbons such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, turpentine oil; Esters such as n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, methyl benzoate; for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone, Ketones such as methylcyclohexanone; Glycol ethers such as tylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether; for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl And alcohols such as alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol. These organic solvents can be used alone or in admixture of two or more.

  Among these organic solvents for polymerization, in the polymerization of component (A), it is preferable to use organic solvents that are less likely to cause chain transfer during the polymerization reaction, such as esters and ketones. In view of solubility and ease of polymerization reaction, use of ethyl acetate, methyl ethyl ketone, acetone or the like is preferable.

  As the polymerization initiator, it is possible to use organic peroxides, azo compounds and the like that can be used in ordinary solution polymerization. Examples of such organic peroxides include t-butyl hydroperoxide, cumene hydroxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, and di-i-propyl peroxydicarbonate. , Di-2-ethylhexyl peroxydicarbonate, t-butyl peroxybivalate, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 2,2-bis (4,4- Di-t-amylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-octylperoxycyclohexyl) propane, 2,2-bis (4,4-di-α-cumylperoxycyclohexyl) ) Propane, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) ) Butane, 2,2-bis (4,4-di-t-octylperoxycyclohexyl) butane and the like. Examples of the azo compound include 2,2′-azobis-i-butyronitrile and 2,2 ′. -Azobis-2,4-dimethylvaleronitrile, 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, etc. can be mentioned.

  Among these polymerization initiators, a polymerization initiator that does not cause a graft reaction during the polymerization reaction of the component (A) is preferable, and an azo type is particularly preferable. The amount used is usually 0.01 parts by mass or more and 2 parts by mass or less, and preferably 0.05 parts by mass or more and 1.0 parts by mass or less, with respect to 100 parts by mass of the total amount of monomers.

  Examples of the chain transfer agent include cyanoacetic acid; alkyl esters having 1 to 8 carbon atoms of cyanoacetic acid; bromoacetic acid; alkyl esters having 1 to 8 carbon atoms of bromoacetic acid; anthracene, phenanthrene, fluorene, 9-phenylfluorene. Aromatic compounds such as p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, p-nitrotoluene, etc .; benzoquinone, 2,3,5,6-tetra Benzoquinone derivatives such as methyl-p-benzoquinone; borane derivatives such as tributylborane; carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tri Bromomethane, 3-chloro-1-propene, etc. Halogenated hydrocarbons; Aldehydes such as chloral and furaldehyde; alkyl mercaptans having 1 to 18 carbon atoms; aromatic mercaptans such as thiophenol and toluene mercaptan; alkyl esters having 1 to 10 carbon atoms of mercaptoacetic acid and mercaptoacetic acid C1-C12 hydroxyalkyl mercaptans; Terpenes such as pinene and terpinolene;

  The polymerization temperature of the component (A) is generally about 30 to 180 ° C, preferably 40 to 150 ° C, and more preferably 50 to 90 ° C. When an unreacted monomer is contained in a polymer obtained by a solution polymerization method or the like, it can be purified by a reprecipitation method using methanol or the like in order to remove the monomer.

1.1.7. Acid value From the viewpoint of preventing corrosion of the adherend (for example, ITO), the acid value of the component (A) is preferably 1.0 or less, and more preferably 0 or more and 0.8 or less.

1.2. (B) Crosslinker In the optical pressure-sensitive adhesive composition according to this embodiment, the component (A) has a crosslinkable functional group, and may be described as (B) a crosslinker (simply referred to as “component (B)”. Further included). When the component (B) reacts with the component (A), a crosslinked structure is generated, and the pressure-sensitive adhesive layer containing the crosslinked structure is excellent in adhesion to an adherend (particularly glass).

  (B) A component can be an isocyanate type crosslinking agent. When component (B) is an isocyanate-based crosslinking agent, for example, it can react with a hydroxyl group contained in component (A) to form a crosslinked structure.

  In the optical pressure-sensitive adhesive composition according to this embodiment, the component (B) is not particularly limited as long as it is a cross-linking agent that can be cross-linked with the component (A) at room temperature or under heating. For example, xylylene diisocyanate, tolylene diene Isocyanate monomers such as isocyanate, chlorophenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate and hydrogenated diphenylmethane diisocyanate, and addition reaction of these with bivalent or higher alcohol compounds such as trimethylolpropane An isocyanate compound, an isocyanurate, a biuret thereof, and the like are exemplified.

  Moreover, the urethane prepolymer type isocyanate etc. which made the isocyanate compound addition reaction to well-known polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, polyisoprene polyol, etc. are mentioned. Of these, hexamethylene diisocyanate, tolylene diisocyanate, and derivatives thereof are preferably used.

  From the viewpoint that the pressure-sensitive adhesive layer obtained using the optical pressure-sensitive adhesive composition according to this embodiment can achieve better step following ability, the optical pressure-sensitive adhesive composition according to this embodiment includes the component (A). (B) component of 0.01 to 20 parts by mass (preferably 0.1 to 10 parts by mass) with respect to 100 parts by mass, It is preferable that B) component is included.

1.3. (C) Ketone-based organic solvent The optical pressure-sensitive adhesive composition according to this embodiment is (C) a ketone-based organic solvent having a mass of 40 to 120 parts by mass with respect to 100 parts by mass of the copolymer (A). (Hereinafter may be simply referred to as “component (C)”).

  Since the component (A) contained in the optical pressure-sensitive adhesive composition according to this embodiment is a copolymer of a monomer mixture containing 2% by mass or more and 40% by mass or less of the component (a3) containing a hydroxyl group, The component (A) has a relatively high polarity and tends to aggregate. For this reason, since the optical pressure-sensitive adhesive composition according to this embodiment further includes the component (C), aggregation of the component (A) can be suppressed, and thus the optical pressure-sensitive adhesive composition excellent in transparency. Can be obtained. Thereby, the adhesive layer excellent in transparency can be obtained using this optical adhesive composition.

  The content of the component (C) in the optical pressure-sensitive adhesive composition according to this embodiment is 60 parts by mass with respect to 100 parts by mass of the copolymer (A) in that the transparency can be further improved. Preferably, it is more than 80 parts by mass, more preferably 120 parts by mass or less.

  Examples of the component (C) include acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, and diacetone alcohol, and one or more of these can be used in combination.

  Moreover, another organic solvent can be used with (C) component. In this case, the mass ratio of the component (C) to the other organic solvent (component (C) / other organic solvent) is preferably 1/1 or more and 3/1 or less.

  Examples of other organic solvents include aromatic organic solvents (toluene, xylene, benzene), hydrocarbon organic solvents (pentane, hexane, isohexane, heptane, octane, decane), ester organic solvents (for example, ethyl acetate). , Methyl acetate, butyl acetate, methoxybutyl acetate, cellosolve acetate, amyl acetate, normal propyl acetate, isopropyl acetate, methyl lactate, ethyl lactate, butyl lactate), ether organic solvents (eg isopropyl ether, methyl cellosolve, cellosolve, butyl cellosolve) , Dioxane, methyl tertiary butyl ether, butyl carbitol), and one or more of these can be used in combination.

1.4. Other Components The optical pressure-sensitive adhesive composition according to the present embodiment can further contain components other than the (A) component, the (B) component, and the (C) component as necessary. For example, the optical pressure-sensitive adhesive composition according to this embodiment may be described as (D) a silane coupling agent (hereinafter, simply referred to as “component (D)”) within a range that does not impair the effects of the present invention. ), An ionic compound, an antioxidant, an ultraviolet absorber, a tackifier, a plasticizer, and the like may be blended.

1.4.1. (D) Silane coupling agent When the optical pressure-sensitive adhesive composition according to this embodiment includes the component (D), the surface of the adherend is subjected to pressure-sensitive adhesive using the optical pressure-sensitive adhesive composition according to this embodiment. When the layer is formed, the adhesion with the adherend can be kept good. Component (D) is, for example, polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyl Silicon compounds having an epoxy structure such as methyldimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropyltrimethoxysilane And an amino group-containing silicon compound such as N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane; and 3-chloropropyltrimethoxysilane; an oligomer type silane coupling agent, etc. A) Included in ingredients Silane coupling agents having a functional group which reacts with functional group is preferable because hardly cause peeling in wet heat environment.

  The content of the component (D) in the optical pressure-sensitive adhesive composition according to this embodiment is based on the optical pressure-sensitive adhesive composition according to this embodiment from the viewpoint of maintaining good adhesion to the adherend. 0.01 mass% or more and 5 mass% or less, and preferably 0.1 mass% or more and 1 mass% or less.

1.5. Production of pressure-sensitive adhesive composition The pressure-sensitive adhesive composition for optics according to the present embodiment is usually prepared by mixing the components (A) and (B) and optional components at the same time or in any order. Prepared. Moreover, when mixing (A) component and (B) component, when preparing (A) component by solution polymerization, (B) component is added to the solution containing (A) component after the completion of polymerization. In addition, when the component (A) is prepared by bulk polymerization, uniform mixing becomes difficult after the completion of the polymerization. Therefore, it is preferable to add and mix the component (B) during the polymerization.

1.6. Applications The optical pressure-sensitive adhesive composition according to this embodiment can be used for bonding an optical member and an adherend.

  Examples of optical members to be bonded using the optical pressure-sensitive adhesive composition according to this embodiment include a polarizing film (polarizing plate), a retardation film, an elliptically polarizing film, an antireflection film, a brightness enhancement film, Examples thereof include an optical film selected from the group consisting of a light diffusion film and a hard coat film. Moreover, as a to-be-adhered body, the base material which consists of metal layers, such as an ITO layer, glass, or a plastics is mentioned, for example.

  Moreover, the adhesive layer obtained using the optical adhesive composition which concerns on this embodiment can be used suitably for bonding with glass at the point which is excellent in the adhesiveness with respect to glass.

  In addition, the pressure-sensitive adhesive layer obtained using the optical pressure-sensitive adhesive composition according to the present embodiment has reduced delay bubble generation, and is excellent in step followability and adhesive strength. It can be suitably used for bonding optical members constituting the image display device.

1.7. Adhesive sheet (adhesive layer)
The pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) according to one embodiment of the present invention has a pressure-sensitive adhesive layer formed by the optical pressure-sensitive adhesive composition according to the present embodiment. The pressure-sensitive adhesive layer can be produced, for example, by forming it into a film and removing the solvent.

  More specifically, the pressure-sensitive adhesive sheet according to the present embodiment is heated after being formed into a film by coating the optical pressure-sensitive adhesive composition according to the present embodiment on a separator (release film), for example. Can be obtained.

  More specifically, the optical pressure-sensitive adhesive composition according to the present embodiment is applied onto a substrate with a gravure coater, Mayer bar coater, air knife coater, roll coater, etc., and the applied pressure-sensitive adhesive composition is dried. Thus, the pressure-sensitive adhesive sheet according to this embodiment can be produced. By providing the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) according to this embodiment between the adherend and the optical member, the adherend and the optical member can be bonded to each other.

  The thickness of the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) according to this embodiment is usually about 1 μm to 250 μm, preferably about 10 μm to 180 μm. The adhesive strength of the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) according to this embodiment is usually 10 N / 25 mm or more and 40 N / 25 mm or less, and preferably 16 N / 25 mm or more and 24 N / 25 mm or less.

1.8. Effects The optical pressure-sensitive adhesive composition according to this embodiment comprises (a1) 3 to 18% by mass of a (meth) acrylic acid alkyl ester monomer having a branched alkyl group having 10 to 24 carbon atoms, (A2) 42 to 95% by mass of a (meth) acrylic acid alkyl ester monomer having a straight chain and / or branched alkyl group having 1 to 9 carbon atoms, and (a3) a hydroxyl group-containing monomer 2% % To 40% by mass of the monomer mixture (wherein the total of the component (a1), the component (a2) and the component (a3) in the monomer mixture is 75% by mass to 100% by mass). %) Or less.) (A) copolymer and (B) a crosslinking agent that is 0.01 part by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the copolymer (A). Due to the delay bubble A pressure-sensitive adhesive layer with reduced life and excellent step following ability and adhesive strength can be obtained.

  That is, by using the optical pressure-sensitive adhesive composition according to this embodiment, it is possible to obtain a pressure-sensitive adhesive layer in which the generation of delay bubbles is reduced and the step following ability and the adhesive force are combined. Therefore, the pressure-sensitive adhesive layer can be suitably used for, for example, an image display device or an input / output device.

1.8.1. Reduction of Delay Bubble Generation The present inventors have found that an adhesive layer obtained by using an adhesive composition containing the component (A) obtained from the monomer mixture containing the component (a1) can reduce the generation of delay bubbles. I found. Although it is not clear why the generation of the delay bubble can be reduced in the pressure-sensitive adhesive layer obtained from the composition containing the component (a1), the bulkiness of the branched alkyl group having 10 to 24 carbon atoms contained in the component (a1) As a result of some influence on the three-dimensional configuration of the component (A), it is presumed that the generation of delay bubbles can be reduced because gaps are hardly generated in the pressure-sensitive adhesive layer even under high temperature conditions, and bubbles are not easily generated. .

  That is, the optical pressure-sensitive adhesive composition according to this embodiment is obtained from a monomer mixture containing 3% by mass or more and 18% by mass or less of the component (a1) having a branched alkyl group having 10 to 24 carbon atoms. By including the component (A), the generation of delay bubbles in the pressure-sensitive adhesive layer can be reduced.

1.8.2. Step followability Further, the present inventors include 3% by mass or more and 18% by mass or less of the component (a1) having a branched alkyl group having 10 to 24 carbon atoms in the optical pressure-sensitive adhesive composition according to this embodiment. By including the component (A) obtained from the monomer mixture, the pressure-sensitive adhesive layer obtained by using the optical pressure-sensitive adhesive composition according to this embodiment has flexibility, and therefore has excellent step following ability. I found.

  In describing the excellent step following ability exhibited by the pressure-sensitive adhesive layer obtained by using the optical pressure-sensitive adhesive composition according to the present embodiment, the optical pressure-sensitive adhesive composition according to the present embodiment is used below. An image display device and an input / output device including the resulting adhesive layer will be described.

2. Image Display Device and Input / Output Device An image display device according to an embodiment of the present invention includes a pressure-sensitive adhesive layer obtained using the optical pressure-sensitive adhesive composition according to the present embodiment. An example of the image display device according to the present embodiment is a liquid crystal display device.

  Moreover, the input / output device according to an embodiment of the present invention includes a pressure-sensitive adhesive layer obtained by using the optical pressure-sensitive adhesive composition according to the present embodiment. In this case, examples of the input / output device include a capacitive touch panel type input / output device.

2.1. First Input / Output Device A touch panel type input / output device (first input / output device) 100 according to the present embodiment shown in FIG. 1 will be described in detail below.

  FIG. 1 is a cross-sectional view schematically showing a configuration of a first input / output device (touch panel type input / output device 100) according to an embodiment of the present invention. The touch panel type input / output device 100 according to the present embodiment includes a liquid crystal display device (LCD) 10, a touch panel unit 20, and an adhesive layer 30 provided between the LCD 10 and the touch panel unit 20. The pressure-sensitive adhesive layer 30 bonds the LCD 10 and the touch panel unit 20 together.

  The pressure-sensitive adhesive layer 30 is formed by, for example, applying the optical pressure-sensitive adhesive composition according to the present embodiment to the surface of a separator (not shown) and heating to peel off the obtained pressure-sensitive adhesive sheet from the separator. And the touch panel 20.

  As shown in FIG. 1, the LCD 10 is configured by laminating a polarizing plate 11, an adhesive layer 12, a liquid crystal panel 13, an adhesive layer 14, and a polarizing plate 15 in this order. The pressure-sensitive adhesive layer 12 bonds the polarizing plate 11 and the liquid crystal panel 13, and the pressure-sensitive adhesive layer 14 bonds the liquid crystal panel 13 and the polarizing plate 15.

  As shown in FIG. 1, the touch panel unit 20 includes a scattering prevention film 16, an adhesive layer 17, an ITO layer 18, and a glass panel 19 that are laminated in this order. The pressure-sensitive adhesive layer 17 bonds the scattering prevention film 16 and the ITO layer 18.

  The pressure-sensitive adhesive layers 12, 14, and 17 may be manufactured using the optical pressure-sensitive adhesive composition according to the present embodiment, similarly to the pressure-sensitive adhesive layer 30.

2.2. Second Input / Output Device Another example in which the optical pressure-sensitive adhesive composition according to the present embodiment is used for bonding members constituting the second input / output device (touch panel type input / output device). This will be described with reference to FIG. In the second input / output device 200 shown in FIG. 2, the optical pressure-sensitive adhesive composition according to this embodiment is used for bonding the constituent members, thereby eliminating the effect of eliminating the level difference between the members. Have.

  More specifically, the touch panel type input / output device 200 shown in FIG. 2 includes, for example, an image display device 22 configured by a liquid crystal display, a base material 26 such as glass or film having a sensor electrode 26a on the surface, Cover glass 28 provided with printing layer 28a on the surface, adhesive sheet 24a (24) for bonding image display device 22 and base material 26, and adhesive sheet 24b (24) for bonding cover glass 28 and base material 26 ,including.

  As shown in FIG. 2, the adhesive sheet 24a (24) is provided so as to fill a step formed between the sensor electrode 26a and the substrate 26, and the adhesive sheet 24b (24) It is provided so as to fill a step formed between the cover glass 28 and the cover glass 28. Since the pressure-sensitive adhesive sheets 24a and 24b manufactured using the optical pressure-sensitive adhesive composition according to the present embodiment are excellent in flexibility, the effect of filling a step formed between members constituting the touch panel type input / output device 200 ( Step following ability).

  FIGS. 3A and 3B are cross-sectional views illustrating the step following ability of the adhesive sheet 24 included in the image display device (touch panel type input / output device) shown in FIG.

  FIG. 3A is an example in which a gap 64 is generated because the known pressure-sensitive adhesive sheet 44 is inferior in step following ability. That is, as shown in FIG. 3A, the adhesive sheet 44 follows the step between the sensor electrode 26a and the substrate 26 due to the step generated between the sensor electrode 26a and the substrate 26. As a result, a gap 64 is generally easily generated between the adhesive sheet 44, the sensor electrode 26 a, and the base material 26. The presence of the air gap 64 may cause a problem that the visibility of the image display device is deteriorated.

  On the other hand, as shown in FIG. 3B, the pressure-sensitive adhesive sheet 24 according to the present embodiment does not generate a gap between the sensor electrode 26 a and the base material 26, and does not cause a gap between the sensor electrode 26 a and the base material 26. It follows the level difference. As the reason, since the adhesive sheet 24a according to the present embodiment is excellent in flexibility for the reasons described above, the adhesive sheet 24a includes the sensor electrode 26a, the base material 26, and the substrate 26 as shown in FIG. Therefore, it is difficult to generate a gap between the sensor electrode 26a and the base material 26.

  3B shows an example in which the adhesive sheet 24a is filled in the step between the sensor electrode 26a and the base material 26. As shown in FIG. 2, the adhesive sheet 24a is similar to the adhesive sheet 24a. The step between the printed layer 28a and the cover glass 28 may be filled with the sheet 24b.

  In addition, with reference to FIG. 3, although the level | step difference tracking property of the adhesive sheet in the touchscreen type input / output device 200 was described, also in image display devices other than a touchscreen type input / output device, it concerns on this embodiment in order to fill a level | step difference. An optical pressure-sensitive adhesive composition can also be used.

  By using the optical pressure-sensitive adhesive composition according to this embodiment, it is possible to obtain a pressure-sensitive adhesive layer in which the generation of delay bubbles is reduced and the step following ability is excellent. That is, the gap 64 in FIG. 3A can be filled with the optical pressure-sensitive adhesive composition according to this embodiment, and the gap 64 can be filled with the pressure-sensitive adhesive layer.

3. EXAMPLES Hereinafter, the present invention will be described based on the following examples, but the present invention is not limited to the examples.

3.1. Preparation of component (A) 3.1.1. Production of polymer 1 In a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer, a dropping funnel and a stirring device, 80 parts by mass of methyl ethyl ketone, 40 parts by mass of ethyl acetate, and 15 parts by mass of isostearyl acrylate as a monomer component Part, 2-ethylhexyl acrylate 74 parts by mass, hydroxyethyl acrylate 10 parts by mass, and acrylamide 1 part by mass, nitrogen reflux was performed at room temperature for 1 hour, and then the temperature of the monomer composition solution in the reaction vessel was adjusted. The temperature was raised to 80 ° C., and 0.1 part by mass of 2,2′-azobisisobutyronitrile was added as a polymerization initiator with stirring. Polymerization was carried out in a nitrogen stream for 10 hours to obtain a copolymer (polymer 1) solution having a weight average molecular weight of 300,000. The Tg and hydroxyl value of polymer 1 are shown together in Table 2.

3.1.2. Production of polymers 2 to 14 Polymers 2 to 14 were prepared by the method described in "3.1.1. Production of polymer 1" except that the solvent and monomer mixture having the composition shown in Table 2 were used. Each solution was obtained. The weight average molecular weight, Tg and hydroxyl value of the polymer polymers 2 to 14 are shown together in Table 2. In the production of polymer 8, 0.08 parts by mass of 2,2′-azobisisobutyronitrile was used as a polymerization initiator.

3.2. Preparation of pressure-sensitive adhesive composition (Examples 1 to 11 and Comparative Examples 1 to 4)
The compositions of Examples 1 to 11 and Comparative Examples 1 to 4 were obtained by mixing the polymers 1 to 14 shown in Table 2, the component (B) and the solvent in the ratios shown in Table 3.

3.3. Preparation of evaluation pressure-sensitive adhesive sheet The compositions of Examples 1 to 11 and Comparative Examples 1 to 4 were applied to the surface of the release-treated separator to remove the solvent, and then the separator was bonded to the pressure-sensitive adhesive surface. An adhesive sheet having a layer thickness of 50 μm was obtained. The separator on one side of the obtained pressure-sensitive adhesive sheet was peeled off, and a polyethylene terephthalate film having a thickness of 100 μm was bonded to obtain a pressure-sensitive adhesive sheet for evaluation.

3.4. Test Method An evaluation test was performed on the compositions of Examples 1 to 11 and Comparative Examples 1 to 4 and the pressure-sensitive adhesive sheets obtained using the compositions by the following method. In Table 3, the blending amounts of the copolymer and the crosslinking agent are the masses of the copolymer and the crosslinking agent in a state in which no solvent is contained, respectively.

3.4.1. Haze value of the composition (Table 2)
About the polymers 1 thru | or 14, the haze value of the polymer varnish was measured using the turbidimeter COH-400 (made by Nippon Denshoku Industries Co., Ltd.). In terms of excellent transparency, the haze of the composition is preferably 5 or less, and more preferably 1 or less.

3.4.2. Haze value after wet heat test (moisture and heat whitening resistance) (Table 3)
The separator on one side of the evaluation pressure-sensitive adhesive sheet prepared in 3.3 above is peeled off, and a measurement sample is prepared by using a laminator roll so that the pressure-sensitive adhesive layer is in contact with the glass substrate. The sample was charged for 500 hours under 95% RH conditions, and then the haze was measured using a haze meter HM-150 (Murakami Color Research Laboratory) 10 minutes after being transferred to 23 ° C.-50% RH conditions ( Haze value after wet heat test). The haze value after the wet heat test is preferably 3 or less, more preferably 1.6 or less, and even more preferably 1.0 or less.

3.4.3 180 ° adhesive strength (Table 3)
The evaluation pressure-sensitive adhesive sheet prepared in 3.3 was cut into a size of 25 mm × 150 mm, and the separator of the pressure-sensitive adhesive sheet obtained in Examples and the like was peeled off on a glass plate at 23 ° C. and 50% RH. The glass plate was pressure-bonded to the exposed pressure-sensitive adhesive layer surface using a 2 kg roller. Twenty minutes after application, the pressure-sensitive adhesive sheet was peeled from the glass plate at 23 ° C. and a peeling angle of 180 ° at a peeling speed of 300 mm / minute, and the pressure-sensitive adhesive force (N / 25 mm) of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet was measured.

3.4.4. Step following and delay bubble (Table 3)
A PET pressure-sensitive adhesive tape adjusted to an arbitrary thickness was affixed on glass to prepare a step for evaluation, and the evaluation pressure-sensitive adhesive sheet prepared in 3.3 was pasted thereon. After autoclaving at 50 ° C. and 5 atm for 20 minutes, the step following ability was visually observed. The evaluation criteria are as follows.

(Evaluation criteria for step following ability)
○: A step of 35% or more of the thickness of the pressure-sensitive adhesive layer can be filled, and voids and bubbles are not visually recognized around the step.
(Triangle | delta): The level | step difference of 20% or more and less than 35% of adhesive layer thickness can be filled, and a space | gap and a bubble are not visually recognized around the level | step difference.
X: The level | step difference of 20% or more of adhesive layer thickness cannot be filled.

  Then, after leaving for 24 hours under the condition of 80 ° C., it was taken out and the delay bubble was visually observed. The evaluation criteria are as follows.

(Evaluation criteria for delay bubbles)
○: A step of 35% or more of the thickness of the pressure-sensitive adhesive layer can be filled, and voids and bubbles are not visually recognized around the step.
(Triangle | delta): The level | step difference of 20% or more and less than 35% of adhesive layer thickness can be filled, and a space | gap and a bubble are not visually recognized around the level | step difference.
X: The level | step difference of 20% or more of adhesive layer thickness cannot be filled.

Abbreviations in Table 2 and Table 3 have the following meanings.
AM: acrylamide 2EHA: 2-ethylhexyl acrylate EtAc: ethyl acetate 2HEA: 2-hydroxyethyl acrylate IDMA: isodecyl methacrylate IOA: isooctyl acrylate ISTA: isostearyl acrylate LA: n-lauryl acrylate MA: methyl acrylate MEK: Methyl ethyl ketone STA: n-stearyl acrylate VMA: n-behenyl methacrylate Coronate L: Tolylene diisocyanate crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd.)
Duranate 24A-100: Biuret of hexamethylene diisocyanate (Asahi Kasei Corporation)

  The compositions of Examples 1 to 11 are (a1) component 3% by mass to 18% by mass, (a2) component 42% by mass to 95% by mass, and (a3) component 2% by mass to 40% by mass. (A) a copolymer of a monomer mixture containing, and (B) a crosslinking agent that is 0.01 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the copolymer (A). Accordingly, it can be understood that the pressure-sensitive adhesive layer obtained by using the composition has reduced generation of delay bubbles and is excellent in step followability, adhesion (adhesive strength) and wet heat and whitening resistance.

  On the other hand, in the composition of Comparative Example 1, since the monomer mixture for preparing the component (A) does not contain the component (a1), in the pressure-sensitive adhesive layer obtained using the composition, It can be understood that the generation of delay bubbles could not be reduced.

  The compositions of Comparative Examples 2 to 4 have a linear alkyl group having 10 to 24 carbon atoms in place of the component (a1) in the monomer mixture for preparing the component (A) (meta ) It can be understood that the use of an acrylic acid alkyl ester monomer is inferior in the step following ability and the delay bubble generation cannot be reduced.

10 Liquid crystal display (LCD)
DESCRIPTION OF SYMBOLS 11,15 Polarizing plate 12,14,17 Adhesive layer 13 Liquid crystal panel 16 Anti-scattering film 18 ITO layer 19 Glass panel (touch panel)
DESCRIPTION OF SYMBOLS 20 Touch panel part 22 Image display apparatus 24, 24a, 24b Adhesive sheet 26 Base material 26a Sensor electrode 28 Cover glass 28a Print layer 30 Adhesive layer 44 Known adhesive sheet 64 Space | gap 100,200 Touch panel type input / output device

Claims (7)

(A1) 3 to 18% by mass of a (meth) acrylic acid alkyl ester monomer having a branched alkyl group having 10 to 24 carbon atoms;
(A2) a (meth) acrylic acid alkyl ester monomer having a straight chain and / or branched alkyl group having 1 to 9 carbon atoms in an amount of 42% by mass to 95% by mass;
(A3) 2% by mass to 40% by mass of a hydroxyl group-containing monomer,
(A4) 0.1% by mass or more and 5% by mass or less of a nitrogen atom-containing monomer,
(Wherein the total of the component (a1), the component (a2) and the component (a3) in the monomer mixture is 75% by mass or more and 100% by mass or less)). A) a copolymer;
(B) a crosslinking agent that is 0.01 parts by weight or more and 20 parts by weight or less based on 100 parts by weight of the copolymer (A);
An optical pressure-sensitive adhesive composition comprising:   The optical pressure-sensitive adhesive composition according to claim 1, wherein the (A) copolymer has a weight average molecular weight of 50,000 to 700,000. The optical pressure-sensitive adhesive composition according to claim 1 or 2 , wherein a total of monomers having an acryloyl group in the monomer mixture is 20% by mass or more and 100% by mass or less. The optical pressure-sensitive adhesive composition according to any one of claims 1 to 3 , wherein the acid value of the (A) copolymer is 1.0 or less. The optical adhesive sheet which has an adhesive layer formed from the optical adhesive composition of any one of Claims 1 thru | or 4 . The optical pressure-sensitive adhesive sheet according to claim 5 , which is used for bonding members constituting a touch panel type input / output device or an image display device. To claim 5 or 6 including the optical pressure-sensitive adhesive sheet according, the image display device.