JP5026252B2 - Solvent-type re-peeling pressure-sensitive adhesive composition and re-peeling pressure-sensitive adhesive product - Google Patents

Description

  The present invention relates to a re-peeling adhesive product that is peeled off again after being attached to an adherend, and exhibits excellent peelability even at high-speed peeling, and a solvent mold for producing this pressure-sensitive adhesive product It is related with the adhesive composition. More specifically, the present invention relates to an adhesive product for re-peeling for protecting the surface of optical members such as an optical polarizing plate (TAC), a retardation plate, an EMI (electromagnetic wave) shield film, an antiglare film, and an antireflection film. It is.

  Liquid crystal displays, plasma displays, etc. are laminated with optical films having various functions, such as optical polarizing plates (TAC), retardation plates, EMI (electromagnetic wave) shield films, antiglare films, antireflection films, and the like. It is used. These optical films have a protective film affixed to the surface in order to prevent surface damage during the display manufacturing process and performance inspection stage. It is peeled off in the assembly process.

  As a surface protection film, it is necessary to have transparency that does not interfere with the performance inspection, and a sticking property that does not allow air bubbles and the like, and an increase in adhesive strength after sticking to the adherend and adherence to the adherend. There must be no body contamination. Furthermore, recently, as the size of the display has increased, the protective film has also increased in area, so that the peeling process has been mechanized, and as a result, it has become an important required characteristic that high-speed peeling by a machine is possible.

  However, as the peeling speed becomes higher, the peeling force (adhesive force) tends to increase, which places a greater load on the peeling machine. In addition, when peeling off, a part that peels off smoothly and a part that does not peel off easily occur, causing a phenomenon of peeling while making a buzzing sound (zipping peeling), and the optical film surface is damaged or broken. was there.

  For this reason, many attempts have been made to improve the high-speed peelability of the protective film. For example, Patent Document 1 discloses that by blending a high Tg (meth) acrylic polymer having no adhesiveness at room temperature and a low Tg (meth) acrylic polymer having sufficient adhesive strength, A pressure-sensitive adhesive for a protective film that does not peel off (has moderate tackiness) and has good high-speed peelability is disclosed.

  The adhesive product for the protective film as described above is designed to have a considerably lower adhesive force (slight adhesion) than a general adhesive product on the premise that it is peeled off. However, if the Tg of the high Tg polymer is too high, the adhesive strength is originally low, so that the adhesiveness at a low temperature is almost lost, or the crosslinking progresses with time and does not stick to the adherend. There was a problem.

  Therefore, the present inventors have found a solvent-type re-peeling pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer excellent in high-speed peelability for the purpose of applying to a surface protective film of an optical film, and has already filed an application. (Japanese Patent Application No. 2006-256312).

However, in the technique described in the above application, when peeling off under harsh conditions, adherend contamination in which part of the adhesive remains on the adherend may occur, improving re-peelability. Was demanded. In addition, there is room for improvement in terms of conformability (wetability) to the adherend.
JP 2005-146151 A

  Therefore, in the present invention, for the purpose of applying to a surface protective film of an optical film, a solvent-type re-peeling pressure-sensitive adhesive that can form a pressure-sensitive adhesive layer that is excellent in high-speed peelability and hardly causes troubles such as adherend contamination. An agent composition was found, and the problem was to provide an adhesive product for re-peeling with good characteristics.

  The solvent-type re-peeling pressure-sensitive adhesive composition of the present invention is a solvent-type re-peeling pressure-sensitive adhesive composition used by blending a crosslinking agent, and has a high Tg polymer having a glass transition temperature (Tg) of 0 ° C. or higher. (A) and a low Tg polymer (B) having a Tg lower than that of the high Tg polymer and exhibiting pressure-sensitive adhesion, and a solvent, both of the high Tg polymer (A) and the low Tg polymer (B) The pressure-sensitive adhesive layer containing a functional group capable of reacting with the cross-linking agent and obtained from the pressure-sensitive adhesive composition is compatible with the high Tg polymer (A) and the low Tg polymer (B). The high Tg polymer (A) is an island and the low Tg polymer (B) is a sea.

  The functional group of the high Tg polymer (A) and the low Tg polymer (B) is preferably a hydroxyl group. In this case, the high Tg polymer (A) and the low Tg polymer (B) each contain a hydroxyl group. It is preferable that it is comprised from the raw material monomer which contains (meth) acrylate 0.1 to 10 mass% in 100 mass% of raw material monomers.

  It is also a preferred embodiment of the present invention that the high Tg polymer is synthesized from a raw material monomer containing 70% by mass or more of vinyl acetate or methyl acrylate.

  The present invention also includes a re-peeling pressure-sensitive adhesive product in which a pressure-sensitive adhesive layer obtained from the solvent-based re-peeling pressure-sensitive adhesive composition of the present invention is formed on at least one surface of a support substrate. At this time, the 180 ° adhesive strength to the acrylic plate was measured in an atmosphere of 23 ° C. and 65% relative humidity using an adhesive product in which an adhesive layer having a thickness of 20 μm was formed on a polyethylene terephthalate film substrate having a thickness of 38 μm. In this case, 0.05 to 0.3 N / 25 mm for low-speed peeling at 0.3 m / min, 0.2 to 3 N / 25 mm for high-speed peeling at 30 m / min, and adhesive strength at high speed peeling at low speed peeling. When the value divided by the force is 15.0 or less, a re-peeling pressure-sensitive adhesive product that exhibits excellent high-speed peelability is obtained, which is a preferred embodiment of the present invention.

  The details of the optical confirmation method of the sea-island structure, the method of preparing the adhesive product sample, and the method of measuring the adhesive strength will be described later.

  In the present invention, since the high Tg polymer (A) and the low Tg polymer (B) have a sea-island structure, the pressure-sensitive adhesive has both the advantages of the high Tg polymer (A) and the advantages of the low Tg polymer (B). As a result, the high-speed peelability could be improved. In addition to the low Tg polymer (B), the functional group serving as a reaction point with the cross-linking agent was also introduced into the high Tg polymer (A), so that adherend contamination was not caused. Therefore, it was possible to provide a re-peeling pressure-sensitive adhesive product suitable for protecting the surface of an optical film.

  First, the solvent-based re-peeling pressure-sensitive adhesive composition according to the present invention will be described. However, the scope of the present invention is not limited to these descriptions, and the gist of the present invention is not impaired except for the following examples. Changes can be made as appropriate within the range. The solvent-type re-peeling pressure-sensitive adhesive composition of the present invention becomes a pressure-sensitive adhesive product by drying (removing the solvent). Refers to the case of 10 N / 25 mm or less. The “polymer” in the present invention includes not only a homopolymer but also a copolymer or a copolymer of three or more. The “monomer” of the present invention is an addition polymerization type monomer.

  First, the 1st essential component in the solvent-type re-peeling adhesive composition of this invention is a high Tg polymer (A) whose glass transition temperature (Tg) is 0 degreeC or more. The presence of the high Tg polymer (A) suppresses an increase in high speed peeling force.

Here, the Tg of the polymer can be determined by DSC (differential scanning calorimeter), DTA (differential thermal analyzer), and TMA (thermomechanical analyzer). In addition, since the Tg of the homopolymer is described in various documents (for example, the polymer handbook), the Tg of the copolymer can be calculated from the Tg _n (K) of the various homopolymers and the mass fraction (W _n ) of the monomer as follows. It can also be obtained by an expression.

Where W _n ; mass fraction of each monomer
Tg _n : Tg (K) of homopolymer of each monomer

  The Tg of the main homopolymer is 105.85 ° C. for polyacrylic acid, 9.85 ° C. for polymethyl acrylate, −24.15 ° C. for polyethyl acrylate, −54.15 ° C. for poly n-butyl acrylate, 2-ethylhexyl acrylate is -70.00 ° C, poly-2-hydroxyethyl acrylate is -15.00 ° C, poly-2-hydroxyethyl methacrylate is 84.85 ° C, poly-4-hydroxybutyl acrylate is -32.00 ° C, poly Methyl methacrylate is 104.85 ° C., polyvinyl acetate is 30.00 ° C., polybenzyl acrylate is 6.00 ° C., polyacrylonitrile is 125 ° C., and polystyrene is 100 ° C.

  The high Tg polymer (A) used in the present invention may have a Tg of 0 ° C. or higher, but in order to further improve the high-speed peelability, the Tg is preferably 10 ° C. or higher, more preferably 20 ° C. or higher, 30 More preferably, it is not lower than ° C. However, if the Tg of the high Tg polymer (A) is too high, although it may be a slightly adhesive type for re-peeling, the adhesive strength may be insufficient. Therefore, it is preferably less than 80 ° C, preferably 75 ° C or less, and 70 ° C. More preferred are:

  In the high Tg polymer (A), a functional group having reactivity with a crosslinking agent to be blended later must be introduced. By cross-linking the high Tg polymer (A), the high Tg polymer (A) having a relatively low molecular weight that causes adherend contamination is increased in molecular weight, and adherend contamination is suppressed. Examples of the functional group include a hydroxyl group, a carboxyl group, an amino group, an amide group, and an epoxy group.

  In order to introduce the functional group into the high Tg polymer (A), a functional group-containing monomer may be used as a raw material monomer of the high Tg polymer (A). As the functional group-containing monomer, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, caprolactone-modified hydroxy (meth) acrylate, α- (hydroxymethyl) methyl acrylate, Hydroxyl group-containing (meth) acrylates such as mono (meth) acrylate of polyester diol obtained from ethyl α- (hydroxymethyl) acrylate, phthalic acid and propylene glycol; (meth) acrylic acid, cinnamic acid and crotonic acid Unsaturated monocarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid and other unsaturated dicarboxylic acids; carboxyl group-containing monomers such as monoesters of these unsaturated dicarboxylic acids; amino groups, amide groups, epoxy groups, etc. Or (meth) acrylates having any of the above.

  Among the above, hydroxyl group-containing (meth) acrylates having a hydroxyl group as a functional group are preferable. In particular, a monomer having a hydroxyl group separated from a (meth) acryloyl group has better cross-linking reactivity and conformability. Therefore, when the amount of the cross-linking agent is desired to be reduced or the conformability to an adherend is regarded as important. In this case, a (meth) acrylate (for example, 4-hydroxybutyl (meth) acrylate) in which a hydroxyl group is bonded to an alkyl group (propyl group or higher) having a larger carbon number than 2-hydroxyethyl (meth) acrylate. Is preferably used.

  These functional group-containing monomers are preferably 0.1 to 10% by mass in 100% by mass of the raw material monomer of the high Tg polymer (A). If the amount of the functional group-containing monomer used is less than 0.1% by mass, the amount of the functional group in the high Tg polymer (A) decreases, and the effect of suppressing adherend contamination is not sufficiently exhibited, which is not preferable. On the other hand, if it exceeds 10% by mass, the adhesive strength increases with time after adhesion to an adherend (adhesion progress), which is not preferable. The use amount of the functional group-containing monomer is more preferably 0.3 to 8% by mass, and further preferably 0.5 to 6% by mass.

  As the copolymerization partner of the functional group-containing monomer, any known radical polymerizable monomer can be used. To reduce the haze of the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition of the present invention, vinyl acetate is used. Is preferably used. Since the refractive index of the vinyl acetate polymer is close to the refractive index of the (meth) acrylate polymer (particularly a polymer containing 2-ethylhexyl acrylate or butyl acrylate), which is the main component of the low Tg polymer (B), It is because a haze becomes small and it becomes suitable as a film for surface protection of an optical film. Therefore, the high Tg polymer (A) is preferably obtained from a raw material monomer essentially containing vinyl acetate and the functional group-containing monomer. At this time, 70-99.9 mass% of vinyl acetate is preferable, 80-99.9 mass% is more preferable, 90-99.9 mass% is further more preferable.

  Instead of vinyl acetate, methyl acrylate may be used as a copolymerization partner for the functional group-containing monomer. Adhesiveness and familiarity are improved. The methyl acrylate is preferably 70 to 99.9% by mass, more preferably 80 to 99.9% by mass, and still more preferably 90 to 99.9% by mass.

  When the methyl acrylate-based high Tg polymer (A) is used, it is preferable to use a monomer for controlling the refractive index as a raw material monomer for the low Tg polymer (B) described later. The haze of the obtained pressure-sensitive adhesive layer can be reduced. The monomer for controlling the refractive index is a monomer used to bring the refractive index of the low Tg polymer close to the refractive index of the high Tg polymer. For example, the high Tg polymer (A) is synthesized from methyl acrylate and a hydroxyl group-containing monomer. In this case, in addition to 2-ethylhexyl acrylate, butyl acrylate and 2-hydroxyethyl acrylate, benzyl acrylate is selected as a raw material monomer for the low Tg polymer (B), so that the high Tg polymer (A) and the low Tg polymer (B) are selected. Can be made close to each other, and the haze of the pressure-sensitive adhesive layer can be reduced to 3% or less.

  In addition to vinyl acetate, methyl acrylate and the above functional group-containing monomers, other monomers that can be used for the synthesis of high Tg polymer (A) include (meth) acrylic acid, methyl methacrylate, ethyl (meta) having a high Tg of homopolymer. ) Acrylate, acrylonitrile, styrene and the like are preferable. Moreover, the monomer which can be used as a raw material monomer of the low Tg polymer mentioned later can also be used if a kind and quantity are selected so that Tg of a high Tg polymer (A) may be 0 degreeC or more. A preferred embodiment of the high Tg polymer (A) is a polymer synthesized from vinyl acetate and 2-hydroxyethyl acrylate and / or 4-hydroxybutyl acrylate. This is because haze can be reduced to 3% or less while suppressing adherend contamination. Further, as described above, if a monomer for controlling the refractive index is used in the synthesis of the low Tg polymer (B), the high Tg polymer (A) synthesized from methyl acrylate and 2-hydroxyethyl acrylate and / or 4-hydroxybutyl acrylate. ) Can be preferably used because haze can be reduced to 3% or less while suppressing adherend contamination.

  The refractive index of a typical homopolymer is 1.5270 for polyacrylic acid, 1.4720 for polymethyl acrylate, 1.4685 for polyethyl acrylate, 1.4660 for poly n-butyl acrylate, 1.4900, poly-2-ethylhexyl acrylate 1.4650, poly 2-hydroxyethyl acrylate 1.4480, poly 2-hydroxyethyl methacrylate 1.5119, poly 4-hydroxybutyl acrylate 1.4520, polyvinyl acetate Is 1.4665 and polybenzyl acrylate is 1.5132.

  In addition, when importance is not attached to haze or adherend contamination, the above Tg range is satisfied mainly in (meth) acrylic acid, methyl methacrylate, ethyl (meth) acrylate, acrylonitrile, styrene, etc. having a high homopolymer Tg. The high Tg polymer (A) may be constituted.

  The molecular weight of the high Tg polymer (A) is preferably about 2000 to 100,000 in terms of mass average molecular weight (Mw). As will be described later, the high Tg polymer (A) becomes an island having a sea-island structure and has an action of suppressing an increase in adhesive force and a zipping phenomenon during high-speed peeling. If Mw is too large, it is difficult to form fine islands, so the above range is preferable. A more preferable range of Mw is about 20,000 to 90,000.

  The second essential component contained in the solvent-type re-peeling pressure-sensitive adhesive composition of the present invention is a low Tg polymer (B) exhibiting pressure-sensitive adhesiveness. The low Tg polymer (B) is required to be lower than the Tg (0 ° C. or higher) of the high Tg polymer (A), and in order to say “shows pressure-sensitive adhesiveness”, the Tg is less than 0 ° C. It is preferable that More preferably, it is -20 degrees C or less, More preferably, it is -35 degrees C or less. However, if the Tg of the low Tg polymer (B) is lower than −80 ° C., the cohesive force tends to decrease, and adherend contamination tends to occur, such being undesirable.

  In order to obtain this low Tg polymer (B), it is preferable to use a combination of an alkyl (meth) acrylate and the above functional group-containing monomer. The alkyl (meth) acrylate is necessary for ensuring adhesive strength, and the functional group-containing monomer is a monomer for introducing a functional group for reacting with a crosslinking agent described later into the low Tg polymer (B). As the functional group-containing monomer, any of the monomers exemplified for the high Tg polymer (A) can be used, and the hydroxyl group-containing (meth) acrylate is suitable as in the case of the high Tg polymer (A). . Moreover, the usage-amount is preferable 0.1-10 mass% similarly to the time of the high Tg polymer (A). When the amount of the functional group-containing monomer used is less than 0.1% by mass, the amount of the functional group in the low Tg polymer (B) decreases, the speed of the crosslinking reaction becomes slow, or the high-speed adhesive force becomes too large. If the content exceeds 10% by mass, the adhesive strength increases with time after adhesion to the adherend (adhesion progress), which is not preferable. The use amount of the functional group-containing monomer is more preferably 0.3 to 8% by mass, and further preferably 0.5 to 6% by mass.

  The alkyl (meth) acrylate that is the main constituent of the low Tg polymer (B) preferably has 4 to 12 carbon atoms in the alkyl group from the viewpoint of adhesive properties. This carbon number is preferably 4 to 10, more preferably 4 to 8. If the carbon number is less than 4 (3 or less) or more than 12 (13 or more), the adhesive strength may be reduced. Specifically, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, amyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) ) Acrylate, cyclohexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) ) Acrylate, dodecyl (meth) acrylate, etc., among which butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate and isooctyl acrylate are more preferable. These may be used alone or in combination of two or more, and is not limited.

  In 100% by mass of the raw material monomer of the low Tg polymer (B), the alkyl (meth) acrylate having 4 to 12 carbon atoms is preferably used in the range of 50 to 99.9% by mass. More preferably, it is 60-99.7 mass%, More preferably, it is 70-99.5 mass%. If the amount of alkyl (meth) acrylate used is within the above range, the resulting pressure-sensitive adhesive will exhibit sufficient adhesive strength and tackiness, but if it is less than 50% by mass, the adhesive strength and adhesion to the adherend will be shown. The wettability may be insufficient, and if it exceeds 99.9% by mass, the amount of the functional group-containing monomer serving as a crosslinking point is too small, and the high-speed adhesive force may be excessively increased.

  In synthesizing the low Tg polymer (B), other monomers may be copolymerized. The other monomer is a monomer that can be copolymerized with the alkyl (meth) acrylate and the functional group-containing monomer, and is other than these. For example, alkyl (meth) acrylates other than the alkyl (meth) acrylates; aromatic ring-containing (meth) acrylates such as benzyl (meth) acrylate; aliphatic unsaturated hydrocarbons such as ethylene and butadiene; and aliphatics such as vinyl chloride Halogen substitution products of unsaturated hydrocarbons; aromatic unsaturated hydrocarbons such as styrene and α-methylstyrene; vinyl esters such as vinyl acetate; vinyl ethers; esters of allyl alcohol and various organic acids; And ethers of various alcohols; unsaturated cyanide compounds such as acrylonitrile; and the like. These may be used alone or in combination of two or more, and is not limited. The other monomer is preferably 0 to 49.9% by mass in 100% by mass of the raw material monomer mixture. If it exceeds 49.9% by mass, the amount of the alkyl (meth) acrylate or the functional group-containing monomer will be reduced as a result, so that desired adhesive properties cannot be obtained. A more preferred upper limit is 40% by mass, and a still more preferred upper limit is 30% by mass.

  In the most preferable embodiment of the low Tg polymer (B), when the high Tg polymer (A) contains a vinyl acetate unit as a main component (70% by mass or more), 2-ethylhexyl acrylate, butyl acrylate, 2- It is a polymer obtained from a raw material monomer mixture containing hydroxyethyl acrylate and / or 4-hydroxybutyl acrylate. This polymer has good adhesive properties, and since it approximates the refractive index of the high Tg polymer (A) whose main component is vinyl acetate units, the haze of the resulting adhesive layer can be reduced. It is. When the total of 2-ethylhexyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate is 100% by mass, 2-ethylhexyl acrylate is 20-80% by mass, butyl acrylate is 20-80% by mass, The amount of 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate is preferably 0.5 to 6% by mass. Of course, monomers other than these can also be used in combination as described above, but when applied to applications in which haze is important, monomers other than 2-ethylhexyl acrylate, butyl acrylate, hydroxyethyl acrylate, and 4-hydroxybutyl acrylate are used. It is preferable to set it as 10 mass% or less.

  On the other hand, when the high Tg polymer (A) has, for example, a methyl acrylate unit as a main component, the most preferable embodiment of the low Tg polymer (B) is 2-ethylhexyl acrylate, butyl acrylate, 2-hydroxy A copolymer of ethyl acrylate and / or 4-hydroxybutyl acrylate and benzyl acrylate. As described above, the haze of the pressure-sensitive adhesive layer can be reduced to 3% or less by the combined use of benzyl acrylate. When the total of these monomers is 100% by mass, 2-ethylhexyl acrylate is 20 to 80% by mass, butyl acrylate is 20 to 80% by mass, and hydroxyethyl acrylate and 4-hydroxybutyl acrylate are 0.5 to 6 mass% and benzyl acrylate are preferably 5 to 20 mass%.

  The low Tg polymer (B) preferably has an Mw of 200,000 or more from the viewpoint of improving the adhesive properties. In addition, when the two-stage polymerization method described later is adopted, the molecular weight of only the low Tg polymer (B) cannot be measured, but a mixture of the high Tg polymer (A) and the low Tg polymer (B) (including graft products). The total Mw is preferably 100,000 to 700,000. A more preferable range of Mw is 150,000 to 650,000, and a more preferable range of Mw is 200,000 to 600,000.

  The high Tg polymer (A) and the low Tg polymer (B) are incompatible because of different Tg and different compositions. In the present invention, the high Tg polymer (A) and the low Tg polymer (B) must form a sea-island structure. The sea-island structure is in a microphase-separated state, and the larger one becomes the sea (continuous phase). In the present invention, the amount of the low Tg polymer (B) is increased to disperse the low Tg polymer (B) as sea (continuous phase) and the high Tg polymer (A) as islands. Due to the action of the high Tg polymer (A) dispersed in islands, an increase in adhesive force and a zipping phenomenon during high-speed peeling can be suppressed. In order to exert this effect, the high Tg polymer (A) needs to be 1% by mass or more (more preferably 4% by mass or more), and if it is small, the above effect becomes insufficient. However, if the amount is too large, adhesive strength and wettability to the adherend may be insufficient.

  Whether or not the sea-island structure is manifested is determined by applying an adhesive layer obtained by applying and drying the adhesive composition to an optical microscope, a transmission electron microscope, a scanning electron microscope, a phase contrast microscope, a polarizing microscope. The presence or absence of the sea-island structure can be determined by observing with a scanning tunneling microscope, microscopic Raman, or the like. The preferred form of the sea-island structure is such that the island-like portions are almost spherical and dispersed in the continuous phase (sea), and the average diameter of each island-like substance is about 0.1 to 10 μm. The presence or absence of such a sea-island structure can also be observed using an optical microscope, a phase contrast microscope, and a polarizing microscope.

  In order to confirm that the pressure-sensitive adhesive layer is obtained from a pressure-sensitive adhesive composition containing two types of polymers, for example, two Tg values are observed by measuring tan δ of dynamic viscoelasticity. You can check whether or not. The tan δ of the dynamic viscoelasticity is, for example, an angular vibration frequency of 6.28 rad / s by using a rheometer (manufactured by T.A. Instruments; “ARES”) by a shear mode, a paraplate method (8 mmφ), It may be measured at a measurement temperature range of −50 to 150 ° C.

  In the present invention, a high-Tg polymer (A) and a low-Tg polymer (B) having an approximate refractive index are used, and a sea-island structure in which both are phase-separated microscopically provides excellent transparency with a haze of 3% or less. A sticky product can be obtained. The haze is preferably as small as possible. If the high Tg polymer (A-1) is used or the refractive index controlling monomer is used during the synthesis of the low Tg polymer (B), the haze can be reduced to 2.5% or less. The haze can be measured, for example, with a turbidimeter. In addition, the haze of this invention employ | adopts the measured value in the state of the adhesive product which provided the adhesive layer in transparent films (support base material), such as a polyethylene terephthalate, for example.

  Next, the method for producing the solvent-type re-peeling pressure-sensitive adhesive composition of the present invention will be described. There are three types of suitable manufacturing methods. First, the blending method is a method in which a high Tg polymer (A) and a low Tg polymer (B) are separately polymerized, and then both are mixed (blended). The polymerization method is not particularly limited, but solution polymerization is simple. If the high Tg polymer (A) and the low Tg polymer (B) are polymerized with the same or compatible solvent, they can be blended in a solution state, and a solvent removal step is not required during blending. Convenient. In addition, when blending, in order to form a sea-island structure, it is preferable to stir at high speed with a disper or the like. When the pressure-sensitive adhesive composition of the present invention is prepared by a blend method, when the total nonvolatile content of the high Tg polymer (A) and the low Tg polymer (B) is 100% by mass, the high Tg polymer (A) The amount is preferably 4 to 20% by mass. In this method, when the high Tg polymer (A) is dispersed in the low Tg polymer, a clear sea-island structure is adopted, so that the amount of the high Tg polymer (A) can be reduced.

  The second method is a two-stage polymerization method. In this two-stage polymerization method, first, all the monomers for the high Tg polymer (A) (hereinafter referred to as “monomer (A)”) are polymerized by solution polymerization, and then the high Tg polymer (A) solution. In this method, a monomer for low Tg polymer (B) (hereinafter referred to as “monomer (B)”) is polymerized in the presence. The pressure-sensitive adhesive composition obtained by this two-stage polymerization method has storage stability (high Tg polymer (A) and low Tg polymer (B) are difficult to separate) compared to the pressure-sensitive adhesive composition obtained by the blend method. Are better. This is because a part of a polymer in which a low Tg polymer (B) is grafted to a high Tg polymer (A) is produced during the polymerization of the monomer (B), and this has an affinity for both the sea and the island. It is thought that this is to stabilize the island by exerting a surfactant-like action. In addition, in the adhesive layer which consists of an adhesive composition formed by the two-stage polymerization method, the diameter of an island will be about 0.3-10 micrometers. When the pressure-sensitive adhesive composition is prepared by a two-stage polymerization method, when the total amount of nonvolatile components of the high Tg polymer (A) and the low Tg polymer (B) is 100% by mass, the amount of the high Tg polymer (A) ( It is preferable that the content (including graft content) is 4 to 35% by mass.

  In the two-stage polymerization method, it is preferable to start adding the monomer (B) to the reaction vessel after the polymerization rate of the monomer (A) reaches about 70 to 95% by mass. This method makes it difficult to cause separation during storage of the composition. The polymerization rate (mass%) is a ratio of the mass of the monomer in the reaction vessel converted into a polymer (nonvolatile content), and can be easily obtained by measuring the nonvolatile content. The low Tg monomer (B) is preferably added dropwise to the reactor together with the polymerization initiator. The molecular weight can be increased.

  The separately polymerized high Tg polymer (A) may be added after the two-stage polymerization of the high Tg polymer (A) and the low Tg polymer (B) is completed. The composition of the post-added high Tg polymer (A) is preferably the same as the initially polymerized high Tg polymer (A) from the viewpoint of dispersion stability, but the molecular weight may be different. Furthermore, the effect of reducing the adhesive strength of high-speed peeling appears.

  The third method is a method in which a two-stage polymerization method and a post-addition of a high Tg polymer (A) are combined, and a high Tg polymer (A) and a high Tg polymer for post-addition (A ) Are polymerized together. And after charging a part of obtained high Tg polymer (A) to the reaction container for low Tg polymer (B) synthesis | combination, a monomer (B) is superposed | polymerized. It is a two-stage polymerization in a broad sense. Also in this case, it is considered that a graft product in which the low Tg polymer (B) is grafted to the high Tg polymer (A) is formed. This method has an advantage that the high Tg polymer (A) to be charged in the reaction vessel in advance when polymerizing the low Tg polymer (B) and the high Tg polymer (A) to be added later can be polymerized simultaneously.

  In this method, the amount of the high Tg polymer (A) charged during the polymerization of the low Tg polymer (B) is 1 to 10 mass with respect to 100 mass% of the total amount of the high Tg polymer (A) and the monomer (B). % Is preferable. Storage stability is improved. Then, after the polymerization of the monomer (B) is completed, the high Tg polymer (A) (including the graft) is included in 100% by mass of the total nonvolatile content of the high Tg polymer (A) and the low Tg polymer (B). It is preferable to post-add the high Tg polymer (A) so that the amount becomes 4 to 35% by mass. The timing of post-addition may be immediately after the polymerization of the low Tg polymer (B), but may be any time as long as the crosslinking agent is actually blended and applied. The same applies when post-added by the second-stage polymerization method of the second method described above.

  In any of the above production methods, specific examples of the solvent used in the solution polymerization include aromatic hydrocarbons such as toluene and xylene; aliphatic esters such as ethyl acetate and butyl acetate; and fats such as cyclohexane. Cyclic hydrocarbons; aliphatic hydrocarbons such as hexane and pentane, and the like can be mentioned, but are not particularly limited as long as the polymerization reaction is not inhibited. These solvents may be used alone or in combination of two or more. What is necessary is just to determine the usage-amount of a solvent suitably. Although the solvent type re-peeling pressure-sensitive adhesive composition of the present invention contains a solvent as an essential component, it is preferable to use the same solvent as the polymerization solvent. This is because the product obtained upon completion of the polymerization can be used as it is as a raw material for the solvent-type re-peeling pressure-sensitive adhesive composition.

  Reaction conditions such as polymerization reaction temperature and reaction time may be appropriately set according to, for example, the composition and amount of the monomer, and are not particularly limited. Further, the reaction pressure is not particularly limited, and may be any of normal pressure (atmospheric pressure), reduced pressure, and increased pressure. The polymerization reaction is desirably performed in an inert gas atmosphere such as nitrogen gas.

  The polymerization catalyst (polymerization initiator) is not limited, but for example, methyl ethyl ketone peroxide, benzoyl peroxide, dicumyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, lauroyl peroxide, t-butyl peroxide. Organic peroxides such as oxyoctoate, t-butylperoxybenzoate, lauroyl peroxide, trade name “Nyper BMT-K40” (manufactured by NOF Corporation; mixture of m-toluoyl peroxide and benzoyl peroxide), Known compounds such as azo compounds such as azobisisobutyronitrile, trade name “ABN-E” [Nippon Hydrazine Kogyo; 2,2′-azobis (2-methylbutyronitrile)] and the like can be used. . Further, for example, a known molecular weight regulator represented by mercaptans such as dodecyl mercaptan may be used.

  It is preferable to mix | blend a crosslinking agent with the adhesive composition of this invention. As the crosslinking agent, a compound having two or more functional groups capable of reacting with the functional groups of the high Tg polymer (A) and the low Tg polymer (B) is used.

  For example, if the high Tg polymer (A) and the low Tg polymer (B) have a hydroxyl group, an isocyanate compound is preferable, and if it has a carboxyl group, an isocyanate compound or an epoxy compound is preferable. In terms of reactivity, a combination of a hydroxyl group and an isocyanate compound is most preferable.

  Examples of the isocyanate compound include tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate, 1,5-naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate, Diisocyanate compounds such as hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, and isophorone diisocyanate; Burette polyisocyanate compounds such as “Sumijour N” (manufactured by Sumitomo Bayer Urethane Co., Ltd .; Sumijoule is a registered trademark); "Death Module HL" (both manufactured by Bayer AG; Death Module is a registered trademark), "Coronate EH" (Nippon Polyureta Manufactured by Kogyo Co., Ltd .; a polyisocyanate compound having an isocyanurate ring known as Coronate is a registered trademark; an adduct polyisocyanate compound such as “Sumijour L” (manufactured by Sumitomo Bayer Urethane Co., Ltd.); “Coronate L” (manufactured by Nippon Polyurethane Co., Ltd.) And polyisocyanate compounds such as “Duranate D201” (manufactured by Asahi Kasei Corporation; Duranate is a registered trademark). These can be used alone or in combination of two or more. In addition, so-called blocked isocyanates in which the isocyanate groups of these compounds are inactivated by reacting with a masking agent having active hydrogen can also be used.

  Examples of the epoxy compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A type epoxy resin, N, N, N ′, N′-tetraglycidyl-m-xylenediamine. 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N-diglycidylaniline, N, N-diglycidyltoluidine and the like.

  These crosslinking agents are preferably added so as to be 0.1 to 5 equivalents when the total of the functional groups of the high Tg polymer (A) and the low Tg polymer (B) is 1 equivalent. When the amount of the crosslinking agent is too small, the cohesive force of the resulting pressure-sensitive adhesive may be insufficient and the adherend may be contaminated. However, when the amount is too large, the adhesive force is insufficient or the wettability with respect to the rough surface decreases. A more preferable amount of the crosslinking agent is 0.2 to 4 equivalents, and further preferably 0.3 to 2 equivalents.

  The non-volatile content of the pressure-sensitive adhesive composition for solvent-type re-peeling of the present invention is not particularly limited, but is preferably, for example, 10 to 80% by mass, more preferably 20 to 70% by mass, and still more preferably 25 to 25%. 60% by mass. In order to increase the storage stability of the pressure-sensitive adhesive composition before blending the cross-linking agent, it is better that the non-volatile content is 40% by mass or more, as in the case of applying immediately after preparing the pressure-sensitive adhesive composition, When it is not necessary to consider storage stability, the non-volatile content may be prepared so as to have a viscosity suitable for coating. When the non-volatile content is less than 10% by mass, drying after application or the like takes a long time, which may reduce productivity. Moreover, when it exceeds 80 mass%, the viscosity of the whole composition will become high, handling property and applicability | paintability may lack, and there exists a possibility that it may become impractical. As the solvent for the pressure-sensitive adhesive composition, any of the polymerization solvents described above can be used, and as described above, the same solvent as the polymerization solvent is preferable.

  Addition of known crosslinking accelerators, tackifiers, modifiers, pigments, colorants, fillers, anti-aging agents, UV absorbers, UV stabilizers, antistatic agents, etc. to the pressure-sensitive adhesive composition of the present invention An agent may be added as long as the object of the present invention is not impaired. From the viewpoint of charging performance, for example, “Eleique (registered trademark) SEI-52” (manufactured by Yoshimura Oil Chemical Co., Ltd .; cationic antistatic agent) is preferable.

  Further, a compatibilizing agent may be added as long as it does not destroy the sea-island structure. The compatibilizer is not particularly limited. For example, a block copolymer or graft copolymer of (meth) acrylate and vinyl acetate, or a compatibilizer (a compound or polymer having a specific functional group) by ionic interaction is used. be able to. The addition amount of the compatibilizer is preferably about 0 to 20 parts by mass per 100 parts by mass of the resin component (total amount of the polymer (A) and the polymer (B)) in the solvent-type re-peeling pressure-sensitive adhesive composition.

  The pressure-sensitive adhesive composition of the present invention is used for production of a re-peeling pressure-sensitive adhesive product. An adhesive product (adhesive tape or sheet) in which an adhesive layer is formed on one side of a substrate by applying the adhesive composition on the substrate or release paper and forming a dry coating film thereof, the substrate A pressure-sensitive adhesive product having a pressure-sensitive adhesive layer formed on both sides thereof, or a pressure-sensitive adhesive product having only a pressure-sensitive adhesive layer having no substrate can be obtained. In the case of producing a paper base adhesive product, it is also possible to employ a method in which an adhesive composition is applied on a release paper to form an adhesive layer and then transferred to a paper base material. In forming the pressure-sensitive adhesive layer, it is desirable to perform heat drying under conditions where the solvent scatters (for example, at about 50 to 120 ° C. for about 30 to 180 seconds).

  As the base material, conventionally known papers such as fine paper, kraft paper, crepe paper, glassine paper; plastics such as polyethylene, polypropylene, polyester, polystyrene, polyethylene terephthalate, polyvinyl chloride, cellophane; woven fabric, non-woven fabric, etc. Textile products: These laminates can be used. When used for protecting the surface of an optical film, the substrate is preferably a transparent film such as polyethylene terephthalate.

  The method for applying the pressure-sensitive adhesive composition to the substrate is not particularly limited, and a known method such as a roll coating method, a spray coating method, or a dipping method can be employed. In this case, any of a method for directly applying the pressure-sensitive adhesive composition to the substrate, a method for applying the pressure-sensitive adhesive composition to a release paper, and then transferring the coated material onto the substrate can be employed. After apply | coating an adhesive composition, an adhesive layer is formed on a base material by making it dry.

  For example, release paper may be attached to the surface of the pressure-sensitive adhesive formed on the substrate. The pressure-sensitive adhesive surface can be suitably protected and preserved. The release paper is peeled off from the pressure-sensitive adhesive surface when the pressure-sensitive adhesive product is used. In addition, when the pressure-sensitive adhesive surface is formed on one side of a base material such as a sheet or tape, a release agent layer may be formed by applying a known release agent to the back surface of the base material. By winding the pressure-sensitive adhesive sheet (tape) in a roll shape with the pressure-sensitive adhesive layer on the inside, the pressure-sensitive adhesive layer comes into contact with the release material layer on the back of the substrate, so that the pressure-sensitive adhesive surface is protected and preserved. The

  The adhesive product for re-peeling obtained from the pressure-sensitive adhesive composition of the present invention has a 180 ° adhesive strength of 0.05 to 0.3 N / 25 mm for low-speed peeling at 0.3 m / min and 0 for high-speed peeling at 30 m / min. It is preferable that it is 2-3N / 25mm. If the low-speed peel adhesive strength is in the above range, it is sufficient as a surface protective sheet for an optical member, and if the high-speed peel adhesive strength is in the above range, it can be smoothly peeled without causing inconvenience such as zipping. . A more preferable low-speed peel adhesive strength is 0.06 to 0.2 N / 25 mm, and further preferably 0.07 to 0.15 N / 25 mm. Moreover, a more preferable high-speed peeling adhesive force is 0.3 to 2 N / 25 mm, and more preferably 0.5 to 1.5 N / 25 mm. Moreover, it can be said that the increase in the adhesive force at the time of high speed peeling was able to be suppressed as the value which remove | divided high speed peeling adhesive force by the low speed peeling adhesive force is 15.0 or less. This 180 ° adhesive strength is a value obtained by measuring 180 ° adhesive strength against an acrylic plate at 23 ° C. using an adhesive product in which an adhesive layer having a thickness of 20 μm is formed on a polyethylene terephthalate film substrate having a thickness of 38 μm. Is adopted. In the unit “N / 25 mm”, the portion “/ 25 mm” means the width of the pressure-sensitive adhesive sheet bonded to the adherend.

  Further, the adhesive product for re-peeling obtained from the pressure-sensitive adhesive composition of the present invention does not cause adherend contamination even when it is peeled at a low speed of 0.3 m / min when a 180 ° peel test is performed on an acrylic plate. (See Examples).

  EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the scope of the present invention is not limited only to these examples. Unless otherwise specified, “%” indicates “mass%” and “part” indicates “part by mass”.

Synthesis Example 1 (two-stage polymerization + post-addition)
112.8 parts of vinyl acetate (VAC) and 263 parts of ethyl acetate as a solvent were added to a flask equipped with a thermometer, stirrer, inert gas introduction tube, reflux condenser and dropping funnel. While flowing nitrogen gas under stirring, the internal temperature of the flask was raised to 75 ° C. and diluted with 1.1 parts of ethyl acetate as a polymerization initiator (“Laurox” manufactured by Kayaku Akzo; Lauroyl peroxide). 12 parts were charged into the flask to initiate the polymerization.

  After 30 minutes from the start of the reaction, a mixture of 24 parts of VAC, 4.2 parts of 2-hydroxyethyl acrylate (HEA), 0.14 part of “Laurox” and 52 parts of ethyl acetate was added to the flask over 1 hour. It was dripped in. After completion of dropping, the dropping funnel was washed with 14 parts of ethyl acetate and added to the flask. Immediately after that, 0.7 part of “Laurox” diluted with 6.3 parts of ethyl acetate was added as a booster (post-addition initiator), and further aged at 76 ° C. for 2 hours, and synthesized from VAC and HEA. An ethyl acetate solution of a high Tg polymer having a nonvolatile content of 30% was obtained. The high Tg polymer had a Tg of 28 ° C. and an Mw of 69,000. A method for measuring Mw will be described later.

  Next, in the presence of the high Tg polymer, the monomer for the low Tg polymer was polymerized to synthesize a graft polymer. In a flask equipped with a thermometer, stirrer, inert gas introduction tube, reflux condenser and dropping funnel, 15 parts of the above-mentioned high Tg polymer (non-volatile content), n-butyl acrylate (BA) as a monomer for the low Tg polymer 27 parts, 6ethyl parts of 2-ethylhexyl acrylate (2EHA), 2.7 parts of HEA and 120 parts of ethyl acetate were charged and mixed well. While flowing nitrogen gas under stirring, the internal temperature of the flask was raised to 82 ° C., and “Niper (registered trademark) BMT-K40” (manufactured by NOF Corporation; m-toluoyl peroxide and benzoyl) as a polymerization initiator. 0.12 parts of a mixture with peroxide) was put into a flask to initiate polymerization.

  After 15 minutes from the start of the reaction, a mixture of 63 parts of BA, 140.7 parts of 2EHA, 6.3 parts of HEA, 0.26 parts of “Nyper BMT-K40” and 152.4 parts of ethyl acetate was added over 1 hour. It was dripped in the flask. 1. After the completion of dropping, 1.5 hours to 2.5 hours later, "ABN-E" (manufactured by Nippon Hydrazine Kogyo; 2,2'-azobis (2-methylbutyronitrile)) as a booster 1 part and 54.9 parts of ethyl acetate were added in 3 portions. Thereafter, the mixture was further aged at 78 ° C. for 1.5 hours.

  20 parts of the ethyl acetate solution of the high Tg polymer was added in a nonvolatile content to 100 parts of the nonvolatile content in the obtained graft polymer solution. About the adhesive layer obtained from this adhesive polymer solution, as a result of observing using SEM, it has confirmed that it was a sea-island structure (FIG. 1). In addition, in FIG. 1, the upper side is a polyethylene terephthalate (PET) of a base film. The lower side is an adhesive layer.

Synthesis example 2 (two-stage polymerization + post-addition)
A high Tg polymer was synthesized in the same manner as in Synthesis Example 1 except that the monomer composition for the high Tg polymer was changed as shown in Table 1.

  Next, in the presence of the high Tg polymer, the monomer for the low Tg polymer was polymerized to synthesize a graft polymer. In a flask equipped with a thermometer, stirrer, inert gas introduction tube, reflux condenser and dropping funnel, 15 parts of the above-mentioned high Tg polymer (non-volatile content), and 27 parts of BA, 2EHA 61.3 parts as a monomer for the low Tg polymer 4-hydroxybutyl acrylate (4HBA; homopolymer Tg = 241K), 1.7 parts of dodecyl mercaptan (DM) as a chain transfer agent and 105 parts of ethyl acetate were charged and mixed well. While the nitrogen gas was circulated under stirring, the internal temperature of the flask was raised to 82 ° C., and 0.12 part of the “Nyper BMT-K40” was charged into the flask to initiate polymerization.

  After 15 minutes from the start of the reaction, a mixture of 63 parts of BA, 23.1 parts of EHA14, 3.9 parts of 4HBA, 0.21 part of DM, 0.26 part of “Nyper BMT-K40” and 62.4 parts of ethyl acetate was added for 1 hour. Over a period of time. After completion of dropping, the dropping funnel was washed with 30 parts of ethyl acetate and added to the flask. From 1.5 hours to 2.5 hours after the completion of dropping, 1.1 parts of “ABN-E” and 9.9 parts of ethyl acetate were added in 3 portions as a booster. Thereafter, the mixture was further aged at 78 ° C. for 1.5 hours to obtain a graft polymer solution.

  Both ratios of the graft polymer and the high Tg polymer were mixed at a nonvolatile content of 100: 20 to obtain an adhesive polymer solution. Using this solution, a coating film was formed on the slide and observed with an optical microscope. As a result, it was confirmed that the structure was a sea-island structure.

Synthesis Examples 3 and 4 (two-stage polymerization + post-addition)
Synthesis Example 3 and Synthesis Example 4 are examples in which the mixing ratio of the high Tg polymer obtained in Synthesis Example 2 and the graft polymer was changed. Using the pressure-sensitive adhesive polymer solution obtained in each example, a coating film was formed on a preparation and observed with an optical microscope. As a result, it was confirmed that the structure was a sea-island structure.

Synthesis Example 5 (two-stage polymerization + post-addition)
A high Tg polymer solution and a graft polymer solution were obtained in the same manner as in Synthesis Example 2 except that the amount of DM used for synthesizing the graft polymer was reduced to 0.15 part. Both ratios of the graft polymer and the high Tg polymer were mixed at a nonvolatile content of 100: 20 to obtain an adhesive polymer solution. Using this solution, a coating film was formed on the slide and observed with an optical microscope. As a result, it was confirmed that the structure was a sea-island structure.

Synthesis Example 6 (two-stage polymerization + post-addition)
When synthesizing the graft polymer, a high Tg polymer solution and a graft polymer solution were obtained in the same manner as in Synthesis Example 2 except that the amount of the high Tg polymer (A) charged was reduced to 6 parts. Both ratios of the graft polymer and the high Tg polymer were mixed at a nonvolatile content of 100: 20 to obtain an adhesive polymer solution. Using this solution, a coating film was formed on the slide and observed with an optical microscope. As a result, it was confirmed that the structure was a sea-island structure.

Synthesis example 7 (blend)
A high Tg polymer solution was prepared in the same manner as in Synthesis Example 2. Next, the monomer for the low Tg polymer was separately polymerized. In a flask equipped with a thermometer, stirrer, inert gas introduction tube, reflux condenser and dropping funnel, 36 parts of BA, 2EHA 82.2 parts, HEA 1.8 parts, and 144 parts of ethyl acetate were added as monomers for the low Tg polymer. Charged and mixed well. While the nitrogen gas was circulated under stirring, the internal temperature of the flask was raised to 82 ° C., and 0.15 part of “Nyper (registered trademark) BMT-K40” was charged into the flask to initiate polymerization.

  After 15 minutes from the start of the reaction, a mixture of 54 parts of BA, 23.3 parts of EHA, 2.7 parts of HEA, 0.23 parts of “Nyper BMT-K40” and 92 parts of ethyl acetate was dropped into the flask over 1 hour. did. After completion of dropping, the dropping funnel was washed with 60 parts of ethyl acetate and added to the flask. From 1.5 hours to 2.5 hours after the completion of dropping, 1.1 parts of “ABN-E” and 69.9 parts of ethyl acetate were added in 3 portions as a booster. Thereafter, the mixture was further aged at 78 ° C. for 1.5 hours to obtain a low Tg polymer solution. The low Tg polymer solution and the high Tg polymer solution were mixed so that the nonvolatile content ratio was 100: 20 to obtain an adhesive polymer solution. Using this solution, a coating film was formed on the slide and observed with an optical microscope. As a result, it was confirmed that the structure was a sea-island structure.

Synthesis Example 8 (two-stage polymerization; for comparison)
Use 70 parts of VAC as the monomer for the first stage high Tg polymer and 210 parts of ethyl acetate as the solvent, mix well, and add to a flask equipped with a thermometer, stirrer, inert gas inlet tube, reflux condenser and dropping funnel did. While circulating nitrogen gas, the internal temperature of the flask was raised to 75 ° C., 0.09 part of “Niper BMT-K40” was charged into the flask, and polymerization was started.

  From 1.5 hours to 2.5 hours after the start of the reaction, 0.25 part of “ABN-E” and 2.3 parts of ethyl acetate were added in three portions as a booster. Thereafter, the mixture was further aged at 76 ° C. for 1.5 hours to obtain a polyvinyl acetate solution. At this time, the polymerization rate of vinyl acetate was 73%.

  Subsequently, in the same flask, as a monomer for the second stage low Tg polymer, 120 parts of BA, 2EHA 268 parts and 12 parts of HEA, 0.5 parts of “Nyper BMT-K40”, and 110 parts of ethyl acetate were mixed well to prepare a monomer solution. It was prepared and dropped evenly over 1 hour from the dropping funnel. From 1.5 hours to 2.5 hours after the completion of the dropwise addition, 1.4 parts of “ABN-E” and 212.6 parts of ethyl acetate were added in 3 portions as a booster, and further at 78 ° C. After aging for 1.5 hours, 200 parts of ethyl acetate was added. As a result of making a coating film on the preparation using the obtained pressure-sensitive adhesive solution and observing it using an optical microscope, it was confirmed that the structure was a sea-island structure.

Synthesis Example 9 (two-stage polymerization + post-addition)
A high Tg polymer was synthesized in the same manner as in Synthesis Example 1 except that the monomer composition for the high Tg polymer was changed as shown in Table 1. Next, in the presence of the high Tg polymer, the monomer for the low Tg polymer was polymerized to synthesize a graft polymer. In a flask equipped with a thermometer, stirrer, inert gas introduction tube, reflux condenser and dropping funnel, 15 parts of the above-mentioned high Tg polymer (non-volatile content), and 27 parts of BA, 2EHA 60.3 parts as a monomer for low Tg polymer , HEA 2.7 parts and ethyl acetate 120 parts were charged and mixed well. While the nitrogen gas was circulated under stirring, the internal temperature of the flask was raised to 82 ° C., and 0.12 part of “Niper BMT-K40” was charged into the flask to initiate polymerization.

  After 15 minutes from the start of the reaction, a mixture of 63 parts of BA, 140.7 parts of 2EHA, 6.3 parts of HEA, 0.26 parts of “Nyper BMT-K40” and 152.4 parts of ethyl acetate was added to the flask over 1 hour. It was dripped in. After completion of dropping, the dropping funnel was washed with 120 parts of ethyl acetate and added to the flask. From 1.5 hours to 2.5 hours after the completion of dropping, 1.1 parts of “ABN-E” and 9.9 parts of ethyl acetate were added in 3 portions as a booster. Thereafter, the mixture was further aged at 78 ° C. for 1.5 hours to obtain a graft polymer solution. Both ratios of the graft polymer and the high Tg polymer were mixed at a nonvolatile content of 100: 20 to obtain an adhesive polymer solution. Using this solution, a coating film was formed on the slide and observed with an optical microscope. As a result, it was confirmed that the structure was a sea-island structure.

Experimental example 1
The synthesis method in each synthesis example and the results of the property evaluation using the obtained pressure-sensitive adhesive polymer solution are also shown in Table 1. The characteristic evaluation method is as follows.

[Tg]
It is Tg calculated by the above formula.

[Mass average molecular weight (Mw)]
GPC measuring apparatus: Liquid Chromatography Model 510 (manufactured by Waters) was used under the following conditions.
Detector: M410 differential refractometer Column: Ultra Styragel Linear (7.8 mm × 30 cm)
Ultra Styragel 100Å (7.8mm × 30cm)
Ultra Styragel 500Å (7.8mm × 30cm)
Solvent: Tetrahydrofuran

  The sample concentration was 0.2%, the injection amount was 200 μl / time, and the polystyrene standard sample conversion value was Mw. In the case of two-stage polymerization with post-addition, the Mw of the graft polymer before post-addition was measured. In the case of two-stage polymerization without post-addition (Synthesis Example 8), Mw was not measured.

[Preparation of adhesive composition and production of adhesive product (test tape)]
About the adhesive polymer solution obtained by each synthesis example, the non volatile matter was prepared to 34% with ethyl acetate. For 100 parts of polymer, 250 parts by weight of dibutyltin dilaurate as a crosslinking accelerator and 10 parts of “Duranate (registered trademark) D-201” (hexamethylene diisocyanate; bifunctional; manufactured by Asahi Kasei Co., Ltd.) as a crosslinking agent The corresponding amount was added and stirred well to obtain an adhesive composition.

  A polyethylene terephthalate (PET) film (manufactured by Toray Industries, Inc .; thickness 38 μm) is used as a supporting substrate, and the pressure-sensitive adhesive composition is applied so that the thickness after drying is 20 μm, and then dried at 100 ° C. for 2 minutes. Thus, an adhesive film was prepared. After sticking and protecting the PET film which gave the mold release process on the adhesive surface, it was cured in an atmosphere of 40 ° C. for 3 days. The pressure-sensitive adhesive film after curing was conditioned for 24 hours in an atmosphere of 23 ° C. and a relative humidity of 65%, and then cut into an appropriate length with a width of 25 mm to prepare a test tape. The release film was peeled off during the test.

[Adherent contamination]
Using a 3 mm thick acrylic plate (standard test plate made by Nippon Test Panel Co., Ltd.) as an adherend, the test tape was reciprocated once with a 2 kg rubber roller in an atmosphere of 23 ° C. and 65% relative humidity. Crimp. After pressure bonding, the sample was left in an oven at 70 ° C. for 72 hours, and then temperature-controlled for 24 hours in an atmosphere at 23 ° C. and a relative humidity of 65%. The test tape was peeled off at a peeling speed of 0.3 m / min, and the surface state of the acrylic plate after peeling was visually observed. The case where no contamination was observed (no adhesive residue) was evaluated as ◯, and the case where there was a slight adhesive residue and was contaminated was evaluated as ×.

[Peeling adhesive strength]
The test tape is reciprocated once by a 2 kg rubber roller on a 3 mm thick acrylic plate having the same thickness as the adherend when the adherend is contaminated in an atmosphere of 23 ° C. and a relative humidity of 65%. After leaving for 25 minutes after pressure bonding, the peeling speed was 0.3 m / min for low speed peeling and 30 m / min for high speed peeling, and 180 ° peeling adhesive strength was measured in an atmosphere of 23 ° C. according to JIS K 6854. . In Tables 1 and 2, the low speed peel adhesive strength, the high speed peel adhesive strength, and the value obtained by dividing the high speed peel adhesive strength by the low speed peel adhesive strength (shown as “high speed / low speed”) are also shown.

[Haze (%)]
The haze (%) of the test tape was measured according to JIS K 7105 using a turbidimeter (manufactured by JEOL Ltd .; “NDH-2000”).

[Familiarity]
A test piece having a size of 4 cm × 4 cm is cut out from the test tape. A rough surface of a commercially available liquid crystal protective film (anti-glare) (manufactured by BUFFALO; BOF-H141S) is used as an adherend, and the anti-glare film is placed horizontally on a flat surface so that the rough surface is on top. The specimen is gently placed on the antiglare film in an atmosphere of 23 ° C. and 65% relative humidity. The time from when the test piece begins to get wet to the film until the entire test piece is fully adapted to the film is measured. The case where less than 120 seconds was evaluated as “◎”, the case where 120 seconds to less than 180 seconds were evaluated as “◯”, 180 seconds or more, or the case where the film was not completely wetted was evaluated as “x”.

In Table 1, each monomer and molecular weight modifier are abbreviated as follows. The numbers on the right are the Tg (K) values of homopolymers listed in the polymer handbook.
VAC: Vinyl acetate 305K
HEA: 2-hydroxyethyl acrylate 241K
4HBA: 4-hydroxybutyl acrylate 241K
2EHA: 2-ethylhexyl acrylate 203K
BA: n-butyl acrylate 219K
DM: Dodecyl mercaptan (molecular weight regulator)

  As is clear from Table 1, the pressure-sensitive adhesive compositions of Synthesis Examples 1 to 7 in which hydroxyl groups were introduced into both the high Tg polymer (A) and the low Tg polymer (B) had no adherend adherence at all. It became clear that it was useful as an adhesive for peeling. Also, it was found that the compatibility is very good when 4HBA is used rather than HEA. On the other hand, in Synthesis Examples 8 and 9, since no hydroxyl group was introduced into the high Tg polymer (A) and no crosslinking reaction occurred, some adherend contamination was observed. In each example, the high Tg polymer (A) and the low Tg polymer (B) are blended in a well-balanced manner and have a sea-island structure. Was 15.0 or less.

Synthesis Example 10 (blend)
[High Tg polymer]
155 parts of methyl acrylate (MA: homopolymer Tg = 283.00 K), 4.8 parts of HEA, 0.64 part of DM, 298.3 parts of ethyl acetate as a solvent, thermometer, stirrer, introduction of inert gas To a flask equipped with a tube, reflux condenser and dropping funnel. While flowing nitrogen gas under stirring, the internal temperature of the flask was raised to 78 ° C., and 0.4 parts of “Nyper BMT-K40” diluted with 3.6 parts of ethyl acetate was added to the flask as a polymerization initiator. Then, the polymerization was started.

  After 15 minutes from the start of the reaction, a mixture consisting of 233 parts of MA, 7.2 parts of HEA, 0.96 parts of DM, 0.3 part of the “Nyper BMT-K40” and 279 parts of ethyl acetate was added over 1 hour. Was added dropwise to the flask. After completion of the dropping, the dropping funnel was washed with 20 parts of ethyl acetate and added to the flask. From 1.5 hours to 2.5 hours after the completion of the dropwise addition, a mixture of 0.8 part of the above-mentioned “ABN-E” and 7.2 parts of ethyl acetate was added in three portions as a booster. . Thereafter, the mixture was further aged at 78 ° C. for 1.5 hours. The non-volatile content of the obtained high Tg polymer solution was 38.6%. The high Tg polymer had a Tg of 9 ° C. and an Mw of 69,000.

[Low Tg polymer]
60 parts of BA, 134 parts of 2EHA, 6 parts of HEA, and 240 parts of ethyl acetate as a solvent were added to a flask equipped with a thermometer, a stirrer, an inert gas introduction tube, a reflux condenser and a dropping funnel. While flowing nitrogen gas under stirring, the internal temperature of the flask was raised to 87 ° C., and 0.25 part of “Nyper BMT-K40” diluted with 2.3 parts of ethyl acetate was added to the flask as a polymerization initiator. Then, the polymerization was started.

  After 15 minutes from the start of the reaction, a mixture of 90 parts of BA, 201 parts of 2EHA, 9 parts of HEA, 0.38 parts of the above-mentioned “Nyper BMT-K40”, and 153.4 parts of ethyl acetate was added to a flask over 1 hour. It was dripped in. After completion of the dropping, the dropping funnel was washed with 100 parts of ethyl acetate and added to the flask. From 1.5 hours to 2.5 hours after the completion of the dropwise addition, a mixture of 1.75 parts of “ABN-E” and 22 parts of ethyl acetate was added in three portions as a booster. In addition, 100 parts of ethyl acetate was added in a timely manner during the addition of the booster. Thereafter, the mixture was further aged at 78 ° C. for 1.5 hours. The non-volatile content of the obtained low Tg polymer solution was 45.5%. Moreover, Tg was -64 degreeC and Mw was 581,000.

  Both were mixed so that the non-volatile content of the high Tg polymer solution was 20 parts with respect to 100 parts of the non-volatile content of the low Tg polymer solution, and stirred well to obtain an adhesive polymer solution. As a result of observing the pressure-sensitive adhesive layer obtained from this pressure-sensitive adhesive polymer solution using an optical microscope, it was confirmed to have a sea-island structure.

Synthesis Example 11 (Blend)
[High Tg polymer]
A high Tg polymer was synthesized in the same manner as in Synthesis Example 10.

[Low Tg polymer]
The monomer composition of the initial charge was changed to 60 parts BA, 2EHA 114 parts, HEA 9 parts, benzyl acrylate (BZA: homopolymer Tg = 279.15K) 20 parts, and the dropping monomer composition was changed to BA 90 parts, 2EHA 171 parts, HEA 9 parts, A low Tg polymer was synthesized in the same manner as in Synthesis Example 10 except that BZA was changed to 30 parts. The non-volatile content of the obtained low Tg polymer solution was 45.5%. Moreover, Tg was -58 degreeC and Mw was 647,000.

  Both were mixed so that the non-volatile content of the high Tg polymer solution was 20 parts with respect to 100 parts of the non-volatile content of the low Tg polymer solution, and stirred well to obtain an adhesive polymer solution. As a result of observing the pressure-sensitive adhesive layer obtained from this pressure-sensitive adhesive polymer solution using an optical microscope, it was confirmed to have a sea-island structure.

Experimental example 2
For the pressure-sensitive adhesive polymer solutions obtained in Synthesis Examples 10 and 11, the values obtained by dividing Tg, Mw, low-speed peel adhesive strength, high-speed peel adhesive strength, and high-speed peel adhesive strength by the low-speed peel adhesive strength by the above-described methods (“high speed / Low speed "), haze, adherend contamination and conformability were measured and are shown in Table 2.

  As is clear from Table 2, even when a high Tg polymer was synthesized using methyl acrylate instead of vinyl acetate, adherend contamination was not observed and the adhesive properties were good. In Synthesis Example 10, the haze was 5.7%, which was larger than the target of 3%. This is considered to be because there was a difference between the refractive index of 1.4728 for the high Tg polymer and the refractive index of 1.4664 for the low Tg polymer. In Synthesis Example 11, benzyl acrylate, whose homopolymer has a high refractive index, was added to the copolymer component of the low Tg polymer, so the refractive index of the low Tg polymer increased to 1.4712, and the haze was significantly reduced to 2.1. .

  In the solvent-type re-peeling pressure-sensitive adhesive composition of the present invention, since the high Tg polymer (A) and the low Tg polymer (B) have a sea-island structure, the advantages of the high Tg polymer (A) and the low Tg polymer ( It was possible to obtain a pressure-sensitive adhesive having the advantages of B), and as a result, high-speed peelability could be improved. In addition to the low Tg polymer (B), the functional group serving as a reaction point with the cross-linking agent was also introduced into the high Tg polymer (A), so that adherend contamination was not caused.

  Accordingly, the pressure-sensitive adhesive product obtained using the pressure-sensitive adhesive composition has a surface of an optical member such as an optical polarizing plate (TAC), a retardation plate, an EMI (electromagnetic wave) shield film, an antiglare film, an antireflection film, or the like. It can be used as an adhesive product for re-peeling to protect. It can also be used as a protective film for the surface of other plastics and metal plates.

It is a SEM photograph (sea-island structure) of the coating film of the pressure-sensitive adhesive polymer solution obtained in Synthesis Example 1.

Claims (6)

A solvent-type re-peeling pressure-sensitive adhesive composition used by blending a cross-linking agent, wherein a glass transition temperature (Tg) synthesized from a raw material monomer containing 70% by mass or more of vinyl acetate or methyl acrylate is 0 ° C. or more and 70 A low Tg polymer (A) having a Tg lower than that of the high Tg polymer and a low Tg polymer (B) having a Tg lower than that of the high Tg polymer and exhibiting pressure-sensitive adhesiveness, and a solvent;
The pressure-sensitive adhesive composition separately polymerizes the high Tg polymer (A), and in the total amount of 100% by mass of the monomer (B) for the high Tg polymer (A) and the low Tg polymer (B), the high Tg polymer (A ) Is charged into the reaction vessel so that the content of the polymer becomes 1 to 10% by mass, the monomer (B) is polymerized in the reaction vessel, and the resulting polymer solution is mixed with the high Tg polymer (A). Is added later,
Both high Tg polymer (A) and low Tg polymer (B) contain a functional group capable of reacting with the crosslinking agent,
In addition, the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition has a high Tg polymer (A) and a low Tg polymer (B) without compatibility between the high Tg polymer (A) and the low Tg polymer (B). ) Forms a sea-island structure, which is the sea.   2. The solvent-type re-peeling pressure-sensitive adhesive according to claim 1, wherein the high Tg polymer (A) is 4 to 35% by mass out of 100% by mass of the nonvolatile content of the high Tg polymer (A) and the low Tg polymer (B). Composition.   The pressure-sensitive adhesive composition for solvent-type re-peeling according to claim 1 or 2, wherein the functional group of the high Tg polymer (A) and the low Tg polymer (B) is a hydroxyl group.   The high Tg polymer (A) and the low Tg polymer (B) are each composed of a raw material monomer containing 0.1 to 10% by mass of hydroxyl group-containing (meth) acrylate in 100% by mass of the raw material monomer. 2. The solvent-type re-peeling pressure-sensitive adhesive composition according to 1. A pressure-sensitive adhesive product for re-peeling, wherein a pressure-sensitive adhesive layer obtained from the solvent-type re-peelable pressure-sensitive adhesive composition according to any one of claims 1 to 4 is formed on at least one surface of a support substrate. When an adhesive product in which an adhesive layer having a thickness of 20 μm was formed on a polyethylene terephthalate film substrate having a thickness of 38 μm was used to measure 180 ° adhesive strength on an acrylic plate in an atmosphere of 23 ° C. and 65% relative humidity, It is 0.05 to 0.3 N / 25 mm for low speed peeling at 0.3 m / min, 0.2 to 3 N / 25 mm for high speed peeling at 30 m / min, and the adhesive force at high speed peeling is divided by the adhesive strength at low speed peeling. The peelable pressure-sensitive adhesive product according to claim 5 , wherein the measured value is 15.0 or less.