JP2011089113A - Self-adhesive tape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a self-adhesive tape which has excellent holding power and constant load peeling resistance to various adherends even under moist and hot environment, and can suitably be peeled even when being attached to the adherend for a long period of time. <P>SOLUTION: The self-adhesive tape having suitable adhesiveness, holding power, and resistance to constant load peeling, and further having excellent anchoring to a resin film base material and excellent repeelability is materialized by using a water-dispersible acrylic self-adhesive composition which includes: 2-ethylhexyl acrylate; a (meth)acrylate with a 4-8C alkyl group; a carboxy group-containing monomer; and a nitrogen-containing vinyl monomer as monomer components, wherein an acrylic copolymer formed by using both acrylic acid and methacrylic acid as the carboxy group-containing monomers is included, and using a self-adhesive layer formed by using a carbodiimide-based cross-linking agent with a molar ratio of 0.03-1 with respect to the carboxy group in the acrylic copolymer as a cross-linking agent for cross-linking with the carboxy group. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pressure-sensitive adhesive tape in which a resin film substrate is provided with a pressure-sensitive adhesive layer made of a water-dispersed acrylic pressure-sensitive adhesive composition in which acrylic copolymer emulsion particles are dispersed in an aqueous medium.

  Adhesive tape is used as a bonding means with excellent workability and high bonding reliability in parts such as office automation equipment, home appliances, and automobiles for parts fixing and labeling for displaying product information. On the other hand, from the viewpoint of protecting the global environment, assembly products such as OA equipment are often disassembled after use and recycled and reused. At this time, when the parts are joined with the adhesive tape or when the label is attached, an operation for peeling the adhesive tape or the label is required, and the adhesive can be removed without breaking the residue or the supporting substrate. Characteristics (so-called removability) are required. Further, in recent years, suppression of emission of volatile organic compounds (so-called VOC) has been strongly demanded. In the pressure-sensitive adhesive tape, a solventless type pressure-sensitive adhesive has attracted attention, and replacement of a solvent-type pressure-sensitive adhesive with a water-dispersed pressure-sensitive adhesive has been desired.

  As the water-dispersed pressure-sensitive adhesive, for example, a pressure-sensitive adhesive composition excellent in rough surface adhesion and removability is disclosed as an acrylic copolymer water-dispersed pressure-sensitive adhesive (see Patent Document 1). However, in the case of preparing a double-sided pressure-sensitive adhesive tape having higher adhesive strength, it is difficult for the pressure-sensitive adhesive composition to ensure sufficient removability. In addition, when an inexpensive resin film, particularly polyethylene terephthalate (PET), is used as the base material, the adhesive may fall off at the time of re-peeling in a state of high adhesion to the object to be deposited.

  Moreover, a water-dispersed acrylic pressure-sensitive adhesive using acrylic acid and methacrylic acid in combination is disclosed as a water-dispersed pressure-sensitive adhesive having excellent adhesion to a film substrate. However, the pressure-sensitive adhesive composition has not been examined for removability, and when the acrylic pressure-sensitive adhesive disclosed in this patent document is used as a constituent component, it is stuck. It was difficult to ensure removability due to a large increase in adhesive strength over time. In particular, there has been a problem that the increase in adhesion to a metal surface such as stainless steel is large.

  Moreover, as a double-sided adhesive tape having removability, a (meth) acrylic acid alkyl ester having a C 1-12 alkyl group and a nitrogen-containing vinyl monomer are used as a monomer, and carbodiimide is used as a crosslinking agent. An acrylic pressure-sensitive adhesive composition using a system cross-linking agent is disclosed (see Patent Document 3). However, when the acrylic pressure-sensitive adhesive composition of the present technology is used, it has been difficult to develop strong adhesion and removability. In addition, as a releasable pressure-sensitive adhesive tape excellent in low-temperature adhesiveness and heat-resistant adhesiveness, a pressure-sensitive adhesive tape using acrylic acid and methacrylic acid and using a carbodiimide compound as a crosslinking agent is disclosed (see Patent Document 4). ). However, when the acrylic pressure-sensitive adhesive composition of the present technology is used and an inexpensive resin film, particularly polyethylene terephthalate (PET) is used as a base material, it has been difficult to ensure sufficient removability.

JP 2006-265537 A JP-A-2005-248059 JP2007-177003 JP 2007-39607 A

  The problem to be solved by the present invention is that it has good adhesion and holding power to the adherend, is suitable for constant load peelability, and is excessively adhesive even when stuck for a long time. Water-dispersed emulsion type that can form an adhesive tape that does not easily cause adhesive residue when peeled off even when using a general-purpose resin film, especially PET film, as a substrate It is to provide an adhesive.

  In the present invention, by using methacrylic acid and acrylic acid in combination as a water-dispersed pressure-sensitive adhesive composition, stable and strong adhesion is secured from a highly polar metal-based adherend to a low-polar olefin-based adherend. In addition, by using a nitrogen-containing vinyl monomer in combination with these acid components, an acrylic having not only the surface of the emulsion particles but also acid groups, specifically, carboxyl groups, on the inside of the particles is present at the same level or higher. Copolymer emulsion particles can be prepared. As a result, the cohesive force between the emulsion particles can be secured by the acid groups present on the particle surface, and the cohesive force inside the emulsion particles can be improved by the acid groups present inside the particles, so that the pressure-sensitive adhesive layer can be used at the time of re-peeling. It is possible to form a pressure-sensitive adhesive layer that is less liable to drop off or leave adhesive residue. Normally, if the adhesive layer has a portion with low cohesive strength, the portion with low cohesive strength has high fluidity, so that the adhesion of the adhesive to the adherend easily progresses over time, and is stuck for a long time. In this case, the adhesive strength is excessively increased, and re-peeling becomes difficult. According to the pressure-sensitive adhesive composition containing the acrylic copolymer emulsion having the above-described configuration, a portion having a low cohesive force in the pressure-sensitive adhesive layer can be reduced, and deterioration of removability over time can be suitably suppressed. Moreover, the impregnation property of the adhesive to the nonwoven fabric is improved by 2-ethylhexyl acrylate, the removability can be greatly improved, and a (meth) acrylate having a C 4-8 alkyl group is used in combination. Thereby, strong adhesiveness can be improved significantly, maintaining re-peelability. The pressure-sensitive adhesive tape of the present invention uses a carbodiimide-based crosslinking agent as a crosslinking agent in the water-dispersed acrylic pressure-sensitive adhesive composition in a molar ratio of 0.03 to 1 with respect to the carboxyl group in the acrylic copolymer. By doing, suitable adhesiveness is realizable with respect to the resin film base material with which the adhesiveness of a water-dispersed adhesive is not favorable. For this reason, even if it is the structure by which the adhesive layer which has strong adhesiveness was provided in the resin film base material, it is hard to produce the peeling of an adhesive layer at the time of peeling, and suitable removability can be implement | achieved.

  According to the water-dispersed acrylic pressure-sensitive adhesive composition of the present invention, it is formed from a water-dispersed pressure-sensitive adhesive that can significantly reduce discharge of volatile organic compounds (so-called VOC) and organic solvent odors, It adheres firmly to adherends such as metal, has a suitable holding force and constant load peelability, and as a substrate without excessively increasing the adhesive force even when stuck for a long time Even when a PET base material is used, an adhesive tape that does not easily cause a so-called adhesive residue or a support base material can be realized without performing a special treatment such as heating when peeling.

  Furthermore, according to the pressure-sensitive adhesive tape comprising the water-dispersed acrylic pressure-sensitive adhesive composition, even when used in a high-humidity environment, the adhesive strength does not increase excessively even when applied for a long period of time, as a base material. Even when a PET substrate is used, it is possible to obtain excellent moisture resistance without causing a so-called adhesive residue or destruction of the support substrate without performing a special treatment such as heating when peeling. .

It is a conceptual diagram of a titration curve obtained by potentiometric titration with a basic solution of an acrylic copolymer emulsion. It is a conceptual diagram of a differential curve based on a titration curve obtained by potentiometric titration with a basic solution of an acrylic copolymer emulsion. It is a conceptual diagram of a titration curve obtained by potentiometric titration with an acidic solution of an acrylic copolymer emulsion. It is a conceptual diagram of a differential curve based on a titration curve obtained by potentiometric titration with an acidic solution of an acrylic copolymer emulsion.

<Water-dispersed acrylic pressure-sensitive adhesive composition>
(Acrylic copolymer)
In the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention, the acrylic copolymer forming the acrylic copolymer emulsion particles has 2-ethylhexyl acrylate and an alkyl group having 4 to 8 carbon atoms ( An acrylic copolymer containing a meth) acrylate, acrylic acid, methacrylic acid and a nitrogen-containing vinyl monomer as monomer components is used.

  In the present invention, by using 2-ethylhexyl acrylate as a monomer component, suitable removability can be imparted to the adhesive tape. As content of 2-ethylhexyl acrylate, it is preferable that it is 10-90 mass%, and it is more preferable that it is 20-80 mass%. By keeping the content of 2-ethylhexyl acrylate within this range, it is easy to suppress the adhesion between the pressure-sensitive adhesive and the adherend over time, and the adhesive strength is hardly increased excessively. it can.

  Moreover, by using together with 2-ethylhexyl acrylate and using the (meth) acrylate which has a C4-C8 alkyl group, strong adhesiveness can be improved greatly, maintaining removability. Examples of the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms include n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, isooctyl (meth) acrylate, and n-octyl (meta ) (Meth) acrylates such as acrylates can be used. Among them, acrylate monomers having an alkyl group having 4 to 8 carbon atoms are preferably used, and n-butyl acrylate can be particularly preferably used. It is also preferable to use n-butyl acrylate and t-butyl methacrylate in combination. The amount of (meth) acrylate having an alkyl group having 4 to 8 carbon atoms is preferably 10 to 80% by mass, and more preferably 20 to 70% by mass.

  In the present invention, the 2-ethylhexyl acrylate and the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms can be expressed more suitably in the monomer component forming the acrylic copolymer. The sum of the contents of ethylhexyl acrylate and (meth) acrylate having an alkyl group having 4 to 8 carbon atoms is preferably 50 to 98% by mass, and particularly preferably 80 to 98% by mass. The ratio of the content of 2-ethylhexyl acrylate in the monomer component forming the acrylic copolymer and the (meth) acrylate having a C 4-8 alkyl group is (2-ethylhexyl acrylate / C 4 -C The mass ratio represented by (meth) acrylate having 8 alkyl groups is preferably 9/1 to 2/8, and particularly preferably 75/25 to 25/75.

  In the present invention, (meth) acrylate monomers other than those described above may be used in combination as the (meth) acrylate monomer that forms the acrylic copolymer. Examples of other (meth) acrylate monomers include (meth) acrylate monomers such as methyl (meth) acrylate and ethyl (meth) acrylate, and one or more of these may be used in combination. . Especially, it is preferable to use together (meth) acrylate which has a C2-C2 alkyl group, such as methyl (meth) acrylate and ethyl (meth) acrylate, and it is preferable that it is 1-10 mass% as usage-amount. .

  In the present invention, acrylic acid and methacrylic acid are used in combination as a monomer having an acid group in order to introduce an acid group into the surface and inside of the acrylic copolymer emulsion. The carboxyl group of acrylic acid and methacrylic acid is easy to ensure cohesive force by interaction between carboxyl groups, there are many means for increasing cohesive force with many reactive crosslinking agents, and interaction with the nitrogen-containing vinyl monomer described later. It has the advantage that it can be expressed. Furthermore, in the present invention, acrylic acid tends to be oriented in the vicinity of the particle surface and methacrylic acid is oriented inside the particle by using acrylic acid having relatively high hydrophilicity and methacrylic acid that is more hydrophobic than acrylic acid. The acid groups can be arranged in a well-balanced manner on the surface and inside of the acrylic copolymer emulsion particles. The presence of acid groups in the vicinity of the particle surface can ensure cohesion between emulsion particles, and the presence of acid groups present in the particles can improve cohesion within emulsion particles. Thereby, since the obtained adhesive layer can reduce a part with low cohesive force and can suppress the deterioration of removability with time, it is difficult for the adhesive layer to fall off or have adhesive residue at the time of re-exfoliation. Moreover, the combined use of methacrylic acid and acrylic acid has the effect of greatly improving the constant load performance necessary for strong adhesion.

  As for the contents of acrylic acid and methacrylic acid, the sum of the contents of methacrylic acid and acrylic acid in the monomer component forming the acrylic copolymer is 0.5 to 10% by mass, preferably 0.5 to 5% by mass. %, More preferably 1.5 to 3.5% by mass. By setting it within this range, the crosslinking reaction with the crosslinking agent easily proceeds well. Further, when the pressure-sensitive adhesive layer is formed, a cohesive force suitable for the pressure-sensitive adhesive layer is ensured, and the holding power and the removability are easily compatible. Furthermore, the cohesive force necessary for ensuring moisture resistance and the hydrophobicity of the pressure-sensitive adhesive layer surface can be ensured.

  The combined ratio of methacrylic acid and acrylic acid is preferably such that the molar equivalent ratio of methacrylic acid / acrylic acid is 0.2 or more, more preferably 1.3 or more, and even more preferably 2 or more. More preferably, it is more preferably 4 or more, and still more preferably 6 or more. By setting the combined ratio within the above range, the amount of surface acid groups and the amount of internal acid groups in the acrylic copolymer emulsion particles can be suitably controlled.

  In addition, other carboxyl group-containing monomers may be used in combination as the monomer having an acid group as long as the acid group distribution in the acrylic copolymer emulsion particles is not inhibited. As other carboxyl group-containing monomers, for example, one or more selected from carboxyl group-containing vinyl monomers such as itaconic acid, maleic acid, maleic anhydride, phthalic acid, phthalic anhydride, and crotonic acid can be used. When these carboxyl group-containing monomers are used in combination, it is preferable that the total amount of the carboxyl group-containing monomers including acrylic acid and methacrylic acid is in the range of 0.5 to 10% by mass.

  In the present invention, a nitrogen-containing vinyl monomer is further used as the monomer component of the acrylic copolymer. The nitrogen-containing vinyl monomer is presumed to produce an effect of drawing a carboxyl group that is easily oriented on the particle surface into the particle by interacting with an acid group, particularly a carboxyl group, in the acrylic copolymer emulsion particles. In order to produce this effect, the content of the nitrogen-containing vinyl monomer is preferably set to the above lower limit or more. On the other hand, when the content is increased, the reactivity with the crosslinking agent described later tends to decrease, but by setting the content to the upper limit or less, necessary reactivity can be ensured. When the content is within this range, the acid group distribution in the acrylic copolymer emulsion particles can be easily converged to a suitable distribution range.

  Examples of the nitrogen-containing vinyl monomer include N-vinylpyrrolidone, N-vinylcaprolactam, N-cyclohexylmaleimide, N-phenylmaleimide, acryloylmorpholine, acrylonitrile, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N , N-diethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N-methylenebis (meth) acrylamide, N-isopropylacrylamide, 1 selected from N, N-dimethylaminopropylacrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and t-butylaminoethyl (meth) acrylate Species or two or more can be used. Among them, it is preferable to use at least one selected from N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylonitrile, acrylamide, N, N-dimethylacrylamide and dimethylaminoethyl (meth) acrylate, and N-vinylpyrrolidone It is particularly preferred to use

  The content of the nitrogen-containing vinyl monomer in the monomer component forming the acrylic copolymer is 0.1 to 4.5% by mass, preferably 0.5 to 4% by mass, more preferably 0.5 to By adjusting in the range of 3.5% by mass, the effect of the present invention can be suitably expressed.

  The ratio of the nitrogen-containing vinyl monomer and the vinyl monomer having a carboxyl group in the acrylic copolymer is not particularly limited, but the number of moles of the nitrogen-containing vinyl monomer in the monomer component constituting the acrylic copolymer. Is X, and the molar ratio X / Y is preferably from 1/1 to 1/20, more preferably from 1/1 to 1/5, where Y is the number of moles of the vinyl monomer having a carboxyl group. 1-1 / 3 is more preferable. If it is in the said range, reaction with the vinyl monomer which has a carboxyl group, and the crosslinking agent mentioned later will advance easily. Furthermore, it becomes easy to converge the distribution of carboxyl groups in the acrylic copolymer emulsion to a range described later.

  In the acrylic copolymer used in the present invention, monomers other than those described above can be used as necessary. Examples of such monomers include a hydroxyl group-containing monomer, (meth) acrylic acid 2-hydroxy Alcoholic hydroxyl group-containing monomers such as ethyl, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and the like can be used as appropriate. As keto group or aldehyde group-containing monomer, diacetone acrylamide, diacetone methacrylamide, acrolein, formyl styrene, vinyl methyl ketone, vinyl ethyl ketone, vinyl isobutyl ketone, diacetone acrylate, diacetone methacrylate, acetonitrile acrylate, 2-hydroxypropyl Examples include acrylate acetoacetate and butanediol acrylate acetate. As the silane monomer, 3-methacryloxypropylmethyldimethoxysilane [for example, KBM-502 manufactured by Shin-Etsu Chemical Co., Ltd.], 3-methacryloxypropyltrimethoxysilane [for example, KBM-503 manufactured by Shin-Etsu Chemical Co., Ltd.], 3 -Methacryloxypropylmethyldiethoxysilane [for example, KBE-502 manufactured by Shin-Etsu Chemical Co., Ltd.], 3-methacryloxypropyltriethoxysilane [for example, KBE-503 manufactured by Shin-Etsu Chemical Co., Ltd.], 3-acryloxypropyltri And methoxysilane [for example, KBM-5103 manufactured by Shin-Etsu Chemical Co., Ltd.]. Moreover, N methylol acrylamide etc. are mentioned as a methylol group containing monomer. Examples of the phosphoric acid group-containing monomer include Sipomer PAM-100, PAM-200, and PAM-300 manufactured by Rhodia Nikka Co., Ltd., and 20% by mass or less in the monomer component forming the acrylic copolymer. It can be used at a ratio of 1 type or 2 types or more.

  The weight average molecular weight of the acrylic copolymer used in the present invention is preferably 500 to 1,200,000, more preferably 60 to 1,000,000. By setting it within the range, it is possible to balance both the flexibility when the pressure-sensitive adhesive impregnates the nonwoven fabric and the cohesive force necessary for removability. The said weight average molecular weight is standard polystyrene conversion by a gel permeation chromatography (GPC). As an example of measurement conditions, HLC-8220GPC (manufactured by Tosoh Corporation) is used, the column is TSKgel GMHXL (manufactured by Tosoh Corporation), the column temperature is 40 ° C., the eluent is tetrahydrofuran, the flow rate is 1.0 mL / min, and standard polystyrene. Can be measured by using TSK standard polystyrene.

  In order to adjust the molecular weight, a chain transfer agent may be used in the polymerization. Examples of the chain transfer agent include known chain transfer agents such as lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimethylcapto-1-propanol. Can be used.

(Distribution of acid groups)
The water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention is a composition comprising an acrylic copolymer emulsion in which emulsion particles of the acrylic copolymer are dispersed in an aqueous medium. The acrylic copolymer emulsion particles in the water-dispersed acrylic pressure-sensitive adhesive composition include the acid group amount (AN _SUR ) on the surface of the acrylic copolymer emulsion particles and the acid group amount inside the acrylic copolymer emulsion particles. _{(aN iN)} and the ratio _{of, (aN iN) / (aN} SUR) is desirably 1 or more acrylic copolymer emulsion particles. In the present invention, by using an acrylic copolymer in which the amount of acid groups inside is equal to or greater than the amount of acid groups on the surface, adhesive residue can be reduced and excessive increase in adhesive strength over time can be suppressed. Thus, an adhesive tape having suitable removability can be realized. According to the water-dispersed acrylic pressure-sensitive adhesive composition using such acrylic copolymer emulsion particles, excellent removability is achieved even when a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer is used. Therefore, it is possible to realize a pressure-sensitive adhesive tape excellent in both characteristics of conflicting strong adhesion and re-peeling. Furthermore, adhesive tapes with excellent water resistance can be obtained by securing cohesive force by acid group orientation both between and within the particles and reducing the hydrophilicity of the pressure-sensitive adhesive layer surface by improving the amount of acid groups on the particle surface (improving hydrophobicity). be able to. The acid group amount ratio (AN _IN ) / (AN _SUR ) is preferably 1.3 or more, more preferably 1.5 or more, and further preferably 2.0 or more. On the other hand, the upper limit is not particularly limited as long as there is a surface acid group amount (A _SUR ) that can ensure cohesion between the acrylic copolymer emulsion particles, but the ratio is preferably 10 or less, and preferably 5 or less. Is more preferable. When it is within the above-mentioned upper limit range, the interaction between the particles easily proceeds, the cohesive force between the particles is easily increased, and the removability and water resistance are improved.

(Measurement method of acid group distribution)
The distribution of acid groups in the acrylic copolymer emulsion particles used in the present invention is measured by the following method. The method for measuring the distribution of acid groups of the acrylic copolymer emulsion particles in the present invention is preferably a potentiometric titration because it is a simple operation with little measurement error. The acid group can be measured by potentiometric titration according to the method disclosed in Japanese Patent Application Laid-Open No. 2007-003454, and is measured in detail by the following method.

  In the present invention, a method for measuring the distribution of acid groups in the acrylic copolymer emulsion particles using potentiometric titration is shown below.

  The acidic sample dispersion used for potentiometric titration can be prepared by mixing acrylic copolymer emulsion particles (solid content) and ion-exchanged water at a mass ratio represented by (acrylic copolymer emulsion / ion-exchanged water). Adjust to / 100. Extraction of the acrylic copolymer emulsion particles from the water-dispersed acrylic pressure-sensitive adhesive composition may be performed in a state of being dispersed in an aqueous medium or in a state of being separated from the aqueous medium. In addition, extraction is easy if the acrylic copolymer emulsion is prepared and then extracted before the additives are added. The acidic sample dispersion to be adjusted is preferably an acidic sample dispersion having a pH of 4 or less. From the water-dispersed acrylic pressure-sensitive adhesive composition neutralized with ammonia water or the like, acrylic acid is dispersed in an aqueous medium. When extracting the copolymer emulsion, it is preferable to adjust the pH to 4 or less by adding a weak acid such as formic acid or butyric acid to the sample dispersion as necessary.

  For titration, an automatic potentiometric titrator can be used. Examples of the automatic potentiometric titrator include AT-610, AT-420N-WIN manufactured by Kyoto Electronics Co., Ltd.

Calculation of the acid group amount (AN _SUR ) and the internal acid group amount (AN _IN ) on the surface of the acrylic copolymer emulsion particles is calculated based on a titration curve obtained by potentiometric titration. When potentiometric titration is performed with the X-axis as the base dropping amount and the Y-axis as the pH, between the titration start point P ₀ and the titration end point P ₃ , the minimum point P ₁ and the minimum point P at which the pH becomes minimum after the base titration starts. titration curve having an inflection point P ₂ appearing next to ₁ (FIG. 1) is obtained. The local minimum point P ₁ and the inflection point P ₂ are more clearly converted to a differential curve (FIG. 2) of a titration curve in which the X-axis is a base dropping amount (mL) and the Y-axis is ΔE / mL. easily read the ₁ and _{P 2.}

The region of P _{0 to} P ₁ in the titration curve is a region where the free acid in the aqueous phase of the sample dispersion is neutralized, and the pH value decreases as the free acid in the aqueous phase is neutralized. shows the minimum value P ₁ that the pH value becomes minimum when neutralized. Therefore, the amount of base dripped in this region is the titration amount required to neutralize the acid in the aqueous phase. From the base titration and the base concentration of the inorganic base solution used for the titration, the acid group amount (AN _AQUA ) [meq / g] in the aqueous phase in the sample dispersion is calculated.

In the water-dispersed acrylic pressure-sensitive adhesive composition, since the acid used for polymerizing the acrylic copolymer generally remains, the acrylic copolymer emulsion particles are extracted in a state dispersed in an aqueous medium. Free acid is present in the aqueous phase of the sample dispersion. On the other hand, when only the acrylic copolymer emulsion particles are separated and dispersed in ion-exchanged water, there is a possibility that P ₀ = P ₁ because there is theoretically no acid in the aqueous phase. .

When the acid in the aqueous phase is neutralized, the acid groups on the surface of the acrylic copolymer emulsion particles that are easily neutralized are then neutralized. Since this becomes the region of P _{1 to} P ₂ of the titration curve, the amount of base dripped in this region is the titration amount required to neutralize the acid groups on the surface of the acrylic copolymer emulsion particles. The acid group amount (AN _SUR ) [meq / g] on the surface of the acrylic copolymer emulsion particles is calculated from the base titration and the base concentration of the inorganic base solution used for the titration.

When the acid groups on the surface of the acrylic copolymer emulsion particles are neutralized, neutralization of the acid groups inside the acrylic copolymer emulsion particles, which are difficult to neutralize, begins. This is the inflection point P ₂ in the titration curve. Appears as The amount of acid groups (AN _IN ) inside the acrylic copolymer emulsion particles is determined by titration of the total amount of acid groups present inside the emulsion particles when the emulsion particles form particles stably. Therefore, it is preferable to calculate from the above calculation result and the total acid group amount (AN _TOTAL ) in the sample dispersion by the following formula.
AN _IN = AN _TOTAL- (AN _SUR + AN _AQUA )

  In the inorganic base solution used for the titration, potassium hydroxide or sodium hydroxide can be preferably used as the inorganic base used for titration, and potassium hydroxide is particularly preferably used. The concentration of the inorganic base used for titration is preferably adjusted in the range of 0.1 to 2 mol / L.

  As other titration conditions, it is preferable to perform titration by intermittent constant rate titration, the intermittent time is 10 seconds, the maximum dripping amount is 20 mL, the single injection amount at the intermittent injection is preferably 0.16 mL / time, and the injection speed Is preferably 5 seconds / mL, the potential for collecting data is 4 mL, and the titration for detecting pH is preferably performed every 0.16 mL.

  To illustrate a specific measurement method, a water-dispersed acrylic pressure-sensitive adhesive composition containing 3 g of acrylic copolymer emulsion particles (solid content) was weighed into a 300 mL polyethylene beaker with a dropper, Ion exchange water is poured into the polyethylene beaker until the total amount of the test sample reaches 100 g and stirred. Then, the electrode and the temperature assurance electrode are immersed. The tip of the titration nozzle is higher than the liquid level, and is 2 cm away from the electrode so that the titration reagent does not reach the electrode. Under the above conditions, automatic potentiometric titration is started with stirring. After the measurement is completed, meq / g is calculated from the titration amount at the equivalent point automatically printed on the obtained titration curve.

The total acid group amount (AN _TOTAL ) in the acidic sample dispersion can be obtained by a measurement method based on potentiometric titration with an inorganic acid solution as shown below, even when calculated from the theoretical amount of acid groups calculated from the charged amount. The obtained value may be used. A method for measuring the total amount of acid groups (AN _TOTAL ) in the sample dispersion by potentiometric titration is described below.

  For the preparation of the sample dispersion, potassium hydroxide is added to a sample dispersion equivalent to the acidic sample dispersion used above until pH 13 and all acid groups including the inside of the particles are neutralized. When the dispersion of acrylic copolymer emulsion particles is a basic sample dispersion having a pH of 13, all acid groups inside are drawn out to the surface of the emulsion particles by electrostatic interaction. Therefore, by performing back titration of the basic sample dispersion with an inorganic acid solution, the acid groups on the surface of the acrylic copolymer emulsion particles and the acid groups on the inside can be titrated equally, and the total amount of acid groups in the sample dispersion Can be calculated.

  The acid used for the titration is preferably sulfuric acid, and the concentration is preferably 0.1 mol / L. As the potentiometric titration apparatus, an apparatus similar to the above can be preferably used.

When potentiometric titration is performed with the X-axis being the acid dropping amount and the Y-axis being the pH, the inflection points Q ₁ , Q ₂ , Q _{3 are in the} order of the acid titration from the titration start point Q ₀ to the titration end point Q _4. A titration curve is obtained (FIG. 3). By converting these inflection points into differential curves (FIG. 4) of titration curves in which the X axis is the acid drop amount (mL) and the Y axis is ΔE / mL, the inflection points can be read more clearly. X-coordinate at these inflection points _{Q1, Q} 2, _{Q 3} is an acid dropped quantity at each _point, acid dropping amount in Q 0 to Q ₁ neutralizing the residue of potassium hydroxide used in adjusting to pH13 This is the titration amount required to do this. The acid dripping amount in Q _{1 to} Q ₂ is a titration amount required to neutralize all acid groups present in the acrylic copolymer emulsion particles, and the acid dripping amount in Q _{2 to} Q ₃ is the water phase. This is a titration amount required to neutralize the acid groups therein. Therefore, the total amount of acid groups in the acidic sample dispersion is converted into meq / g based on the amount of acid dropped in Q _{1 to} Q ₃ and the concentration of acid used for titration. (AN _TOTAL ) is calculated.

  As a specific measurement method, a water-dispersed acrylic pressure-sensitive adhesive composition containing 3 g of acrylic copolymer emulsion particles (solid content) was weighed into a 300 mL polyethylene beaker with a dropper, and then Ion exchange water is poured into a polyethylene beaker until the total amount of the test sample reaches 100 g and stirred. Subsequently, 1N potassium hydroxide is added and stirred until the test sample reaches pH 13. Then, the electrode and the temperature assurance electrode are immersed. The potentiometric automatic titration is started in the same manner as the titration conditions described above. After the measurement is completed, meq / g is calculated from the titration amount at the equivalent point automatically printed on the obtained titration curve.

  The introduction of acid groups into the acrylic copolymer emulsion particles can be controlled by appropriately selecting the monomer composition and polymerization method. As the monomer composition, acid groups can be introduced into the particles by increasing the hydrophobicity of the acid monomer. Moreover, an acid group can also be introduce | transduced inside a particle | grain by copolymerizing the nitrogen-containing monomer which interacts with an acid group. On the other hand, as the polymerization method, a so-called dropping polymerization method can be selected and controlled by changing the composition of the emulsion to be dropped in the first half and the second half of the dropping. Specifically, the acid monomer can be introduced into the particles by increasing the ratio of the acid monomer in the first half of the dropping and decreasing the ratio of the monomer having an acid group in the second half of the dropping.

  In addition, the average particle diameter of the acrylic copolymer emulsion particles in the present invention is not particularly limited, but since it may be difficult to introduce acid groups into the emulsion particles if it is 150 nm or less, the lower limit is The particle diameter is preferably more than 150 nm, more preferably 200 nm or more, and even more preferably 300 nm or more. Moreover, as an upper limit, it is preferable that it is 1000 nm or less, It is more preferable that it is 800 nm or less, It is more preferable that it is 600 nm or less, It is still more preferable that it is 400 nm or less.

  Here, the average particle diameter of the particles means a 50% median diameter of the emulsion particles on the volume basis, and the numerical values are based on values obtained by measurement by a dynamic light scattering method. If the average particle size becomes too small, the surface area of the particles increases and the proportion of the particle surface in contact with water increases. As a result, for example, when a carboxyl group is used as the acid group, the carboxyl group is easily ionized into a carboxylate anion, and the tendency of the carboxyl group to localize on the particle surface is increased.

For this reason, the ratio (AN _IN ) / (AN _SUR ) between the amount of acid groups on the surface of the resulting acrylic copolymer emulsion and the amount of acid groups inside (AN _SUR ) may not be within the desired range as described above. . Accordingly, the average particle diameter is preferably more than 150 nm. On the other hand, when the average particle size becomes too large, an excessively large average particle size is not preferable in order to promote fusion between the emulsion particles after forming the pressure-sensitive adhesive layer, and it is preferable to suppress the average particle size to 1000 nm or less.

(Production method)
An acrylic copolymer emulsion in which acrylic copolymer emulsion particles are dispersed in an aqueous medium can be produced by an emulsion polymerization method for obtaining an emulsion-type pressure-sensitive adhesive. In the emulsion polymerization, an appropriate amount of an anionic or nonionic emulsifier or other dispersion stabilizer is used in order to ensure polymerization stability. Especially an emulsifier is not restrict | limited, A well-known emulsifier can be used. Examples of the anionic emulsifier include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate and the like. Examples thereof include ethylene alkyl ether and polyoxyethylene alkyl phenyl ether.
Furthermore, it is preferable to use an emulsifier having a polymerizable unsaturated group in the molecule, which is known as a “reactive emulsifier”. Specifically, Latemul S-180 [manufactured by Kao Corporation], Latemu PD-104 [manufactured by Kao Corporation], Aqualon HS-10 [manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], Aqualon HS-20 [No. Ichi Kogyo Seiyaku Co., Ltd.], Aqualon KH-10 [Daiichi Kogyo Seiyaku Co., Ltd.], Aqualon KH-1025 [Daiichi Kogyo Seiyaku Co., Ltd.], Aqualon KH-05 [Daiichi Kogyo Seiyaku Co., Ltd. )], Aqualon RN-10 [Daiichi Kogyo Seiyaku Co., Ltd.], Aqualon RN-20 [Daiichi Kogyo Seiyaku Co., Ltd.], Aqualon ER-10 [Daiichi Kogyo Seiyaku Co., Ltd.], Aqualon ER-20 [Daiichi Kogyo Seiyaku Co., Ltd.], New Frontier A-229E [Daiichi Kogyo Seiyaku Co., Ltd.], Adeka Soap SE-10 [Asahi Denka Kogyo Co., Ltd.], Adeka Soap SE -20 [Asahi Denka Kogyo Co., Ltd.], Adeka Asopu SR-10 N [Asahi Denka Co., Ltd.], ADEKAREASOAP SR-20 N [Asahi Denka Co., Ltd.], and the like. It is preferable to use a reactive emulsifier because the water resistance of the coating is improved in addition to the polymerization stability.

  Among the emulsion polymerization methods, it is preferable to use a dropping polymerization method. Moreover, in order to make it easy to introduce an acid group into the particle, a dropping polymerization method may be selected and controlled by changing the composition of the emulsion to be dropped in the first half and the second half of the dropping. Specifically, the acid monomer can be introduced into the particles by increasing the ratio of the acid monomer in the first half of the dropping and decreasing the ratio of the acid monomer in the second half of the dropping.

  The polymerization initiator used in the emulsion polymerization is not limited, and a known polymerization initiator can be used. Specifically, 2,2 ′,-azobis (2-methylpropionamidine) dihydrochloride, 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2′-azobis (2-amidinopropane) ) Dihydrochloride, 2,2′-azobis [N- (2-arboxyethyl) -2-methylpropionamidine] hydrate, 2,2′-azobis (N, N′-dimethyleneisobutylamidine) Azo initiators such as hydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, persulfate initiators such as potassium persulfate, ammonium persulfate, sodium persulfate Agents, benzoyl peroxide, t-butyl hydroperoxide, peroxide initiators such as hydrogen peroxide, carbonyl initiators such as aromatic carbonyl compounds, persulfate and sodium hydrogensulfite Combination with helium, and the like redox initiators such as a combination of a peroxide and sodium ascorbate.

(Aqueous medium)
The aqueous medium used in the present invention may be water alone or a mixed solvent of water and a water-soluble solvent. The above-mentioned “mixed solvent of water and water-soluble solvent” usable in the present invention is a mixed solvent of a water-soluble solvent mainly composed of water, and the water-soluble solvent with respect to the total amount of the mixed solvent. The content of is preferably 10% by weight or less, more preferably 5% by weight or less. Examples of the water-soluble solvent include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl carbitol, ethyl cellosolve, butyl cellosolve, or polar solvents such as N-methylpyrrolidone, which may be used alone. Two or more kinds may be used in combination.

(Crosslinking agent)
In the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention, the cohesive force of the pressure-sensitive adhesive layer can be suitably used by using a carbodiimide-based cross-linking agent as a cross-linking agent, and a resin film, particularly PET, can be used as a base material. Even when the base material is used, the pressure-sensitive adhesive layer is preferably in close contact with the base material, and even if the pressure-sensitive adhesive layer is a strong pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer is unlikely to drop off during re-peeling. As the carbodiimide-based crosslinking agent, carbodilite SV-02 [Nisshinbo Co., Ltd .; water-soluble type], carbodilite V-02 [Nisshinbo Co., Ltd .; water-soluble type], carbodilite V-02-L2 [Nisshinbo Co., Ltd .; water-soluble type] Carbodilite V-04 [Nisshinbo Co., Ltd .; water-soluble type], Carbodilite E-01 [Nisshinbo Co., Ltd .; emulsion type], Carbodilite E-02 [Nisshinbo Co., Ltd .; emulsion type], Carbodilite E-03A [Nisshinbo Co., Ltd .; Emulsion type], Carbodilite E-03 [Nisshinbo Co., Ltd .; emulsion type] and the like. Among these, a water-soluble type can be preferably used.

  The content of the carbodiimide-based crosslinking agent is 0.03 to 1, preferably 0.08 to 0.5, more preferably 0.08 to 0.5, based on the carboxyl group in the acrylic copolymer contained in the water-dispersed acrylic pressure-sensitive adhesive composition. Preferably, when used at a molar ratio of 0.15 to 0.3, the adhesion to the substrate is good, and suitable removability can be realized even with strong adhesion.

(Tackifying resin)
In the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention, it is preferable to use a tackifying resin in order to adjust the strong adhesiveness of the resulting pressure-sensitive adhesive layer. As the tackifier resin used in the present invention, an emulsion type tackifier resin can be preferably used from the viewpoint of use in an aqueous dispersion type pressure-sensitive adhesive composition. Examples of the emulsion type tackifying resin include rosin, polymerized rosin, polymerized rosin ester, rosin phenol, stabilized rosin ester, disproportionated rosin ester, terpene, terpene phenol, petroleum resin, etc. Can be illustrated.

  Among these, a polymerized rosin ester-based tackifier resin and a rosin phenol-based tackifier resin are preferable, and it is particularly preferable to blend these in combination. Specifically, polymerized rosin ester-based tackifier resins are Superester E-650 [Arakawa Chemical Industries, Ltd.], Superester E-788 [Arakawa Chemical Industries, Ltd.], Superester E-786. 60 [Arakawa Chemical Industries, Ltd.], Super Ester E-865 [Arakawa Chemical Industries, Ltd.], Super Ester E-865NT [Arakawa Chemical Industries, Ltd.], Harrier Star SK-508 [Harima Chemicals ( Co., Ltd.] Harrier Star SK-508H [Harima Kasei Co., Ltd.], Harrier Star SK-816E [Harima Kasei Co., Ltd.], Harrier Star SK-822E [Harima Kasei Co., Ltd.], Harrier Star SK- 323NS [manufactured by Harima Chemicals Co., Ltd.] and the like, and rosin phenolic tackifying resins are Tamanoru E-100 [manufactured by Arakawa Chemical Industries, Ltd.], Tamanoru E 200 [(manufactured by Arakawa Chemical Industry Ltd.), Tamanol E-200NT Arakawa Chemical Industries, Ltd.], and the like.

  When these are used in combination, the ratio of the polymerized rosin ester-based tackifier resin (A) to the rosin phenol-based tackifier resin (B) is 5 / in a mass ratio represented by (A) / (B). 1 to 1/5 is preferable, and 3/1 to 1/3 is more preferable. If it is in the said range, heat resistance and removability can be improved with sufficient balance.

  The softening point of the tackifying resin is preferably 120 to 180 ° C, more preferably 140 to 180 ° C. Heat resistance improves by mix | blending a tackifying resin with a high softening point.

  In the blend ratio of the acrylic copolymer / tackifying resin, the acrylic copolymer / tackifying resin = 100/10 to 100/40 is preferable, and the acrylic copolymer / tackifying resin = 100 is more preferable. / 15 to 100/35. If it is in the said range, heat resistance and removability can be improved with sufficient balance.

(Additive)
In the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention, as an additive, a base (such as aqueous ammonia) for adjusting the pH within a range that does not impair the desired effect of the present invention, if necessary, Acids, plasticizers, softeners, antioxidants, fillers such as glass and plastic fibers, balloons, beads, and metal powders, colorants such as pigments and dyes, pH adjusters, film formation aids, leveling agents, Known materials such as thickeners, water repellents, and antifoaming agents can be optionally added to the pressure-sensitive adhesive composition.

(Solid content concentration)
In addition, the solid content concentration of the water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention is not particularly limited, but in terms of manufacturing costs and transportation costs, and when used after drying. From the viewpoint of excellent drying properties, the solid content concentration is preferably 40 to 70% by weight.

(Initial gel fraction)
The water-dispersed acrylic pressure-sensitive adhesive composition used in the present invention has a gel fraction of the uncrosslinked solid matter when the aqueous medium is removed from the composition so that the crosslinking reaction does not proceed and only the solid content is obtained. (Hereinafter referred to as initial gel fraction) is preferably 15% by mass or less, more preferably 10% by mass or less, further preferably 5% by mass or less, and 3% by mass or less. Is even more preferable. In the present invention, by setting the initial gel fraction of the water-dispersed acrylic pressure-sensitive adhesive composition within this range, the anchoring property to a resin film substrate, particularly a PET substrate, becomes extremely suitable, and good removability It becomes easy to realize. Also, using a water-dispersed acrylic pressure-sensitive adhesive composition having an initial gel fraction within the range, after removing the aqueous medium so as not to proceed with the crosslinking reaction, the crosslinking reaction is allowed to proceed to form a pressure-sensitive adhesive layer. By doing so, an adhesive tape excellent in anchoring property to a resin film substrate, particularly PET can be formed.

  The initial gel fraction can be adjusted by the polymerization temperature at the time of preparing the water-dispersed acrylic pressure-sensitive adhesive composition, the kind of initiator, and the amount used. When the initial gel fraction is 15% by mass or less, it is preferable to use, for example, an azo initiator, a persulfate initiator, and a peroxide initiator as the initiator. Of these, azo initiators and persulfate initiators such as ammonium persulfate can be preferably used.

  The initial gel fraction is measured by removing the aqueous medium from the water-dispersed acrylic pressure-sensitive adhesive composition containing no crosslinking agent to obtain a solid content, and then measuring the insoluble content by immersing the solid content in toluene for 24 hours. be able to.

  The polymerization temperature at the time of emulsion polymerization may be appropriately adjusted according to the polymerization initiator used. For example, when ammonium persulfate is used, when the initial gel fraction is 15% by mass or less, the polymerization temperature Is preferably less than 70 ° C and more preferably less than 65 ° C.

<Adhesive tape>
The pressure-sensitive adhesive tape of the present invention is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed by drying and crosslinking the above water-dispersed acrylic pressure-sensitive adhesive composition on at least one surface of the base material. . Crosslinking of the water-dispersed acrylic pressure-sensitive adhesive composition is a carbodiimide that is contained at a molar ratio of 0.03 to 4 with respect to the carboxyl group in the acrylic copolymer contained in the water-dispersed acrylic pressure-sensitive adhesive composition. Crosslinking is performed with a system crosslinking agent. In the present invention, the above water-dispersed acrylic pressure-sensitive adhesive composition makes it possible to cause cross-linking points between and inside the acrylic copolymer emulsion particles, and to crosslink them with a carbodiimide-based cross-linking agent. Even when a PET base material is used as a base material, the pressure-sensitive adhesive layer adheres favorably to the base material, and even if it is a strong pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer falls off during re-peeling hard.

(Base material)
Examples of the resin film substrate used for the pressure-sensitive adhesive tape of the present invention include polyethylene terephthalate (hereinafter referred to as PET), triacetyl cellulose (hereinafter referred to as TAC), polyacrylate, polyimide, polyether, polycarbonate, polysulfone, polyethersulfone, cellophane, Aromatic polyamide, polyethylene, polypropylene, polyvinyl alcohol and the like can be mentioned. Especially, in this invention, when a PET base material is used as the resin film base material, excellent removability can be realized by suitable anchoring with the pressure-sensitive adhesive layer.

  These resin film base materials are preferably subjected to easy adhesion treatment for the purpose of improving the adhesion to the pressure-sensitive adhesive layer. As easy adhesion treatment, surface concavo-convex treatment by sandblasting method or solvent treatment method, or surface oxidation treatment such as corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment, Examples include primer coatings such as polyester resins and acrylic resins. For example, as PET films subjected to easy adhesion treatment, EMBLET PTM (primer coating) manufactured by Unitika Ltd., EMBLET SG (corona discharge treatment) manufactured by Unitika Ltd., Teijin Tetron Film G2, HS, manufactured by Teijin Ltd. O3, HSL, U2 (primer coating), Toray Industries, Inc. Lumirror S105 (corona discharge treatment), Mitsubishi Chemical Polyester Film Corporation T100E, and the like. Although the thickness of a polyethylene terephthalate film is not specifically limited, As thickness which does not impair a softness | flexibility, the range of 1-200 micrometers is preferable and the range of 1-100 micrometers is more preferable. By using a polyethylene terephthalate film having a thickness in the range of 1 to 200 μm, suitable resilience resistance can be realized.

(Adhesive layer)
The pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of the present invention is a pressure-sensitive adhesive layer formed by crosslinking the water-dispersed acrylic pressure-sensitive adhesive composition, and the pressure-sensitive adhesive layer is made of toluene as an index of the degree of crosslinking of the pressure-sensitive adhesive layer. The gel fraction for measuring the insoluble matter after immersion for 24 hours is preferably 20 to 75%, more preferably 25 to 65%, and particularly preferably 35 to 60%. By making a gel fraction into the said range, re-peelability and strong adhesiveness can be ensured with sufficient balance.

  The pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape of the present invention is a layer obtained by removing the solvent from the water-dispersed acrylic pressure-sensitive adhesive composition. The preferable thickness of the pressure-sensitive adhesive layer added to both sides when the double-sided pressure-sensitive adhesive tape is formed is 30 to 300 μm, more preferably 50 to 200 μm.

  The pressure-sensitive adhesive layer in the present invention preferably has a temperature having a convex peak value on the tangent loss in the dynamic viscoelastic spectrum, which is −60 ° C. to −5 ° C., and is −30 ° C. to −10 ° C. It is more preferable. When it exists in this range, it becomes easy to balance re-peelability and strong adhesiveness in a well-balanced manner.

  The above-mentioned dynamic viscoelastic characteristics are measured between the parallel disks that are the measuring unit of the test machine using a viscoelasticity tester (manufactured by Rheometrics, trade name: Ares 2KSTD) in the measurement of dynamic viscoelasticity. A test piece is sandwiched in between and a storage elastic modulus (G ′) and a loss elastic modulus (G ″) from −50 ° C. to 150 ° C. are measured at a frequency of 1 Hz. The test piece is an adhesive having a thickness of 0.5 to 2.5 mm. May be sandwiched between the parallel disks alone, but the laminate of the base material and the adhesive may be stacked in layers and sandwiched between the parallel disks. When the thickness of the pressure-sensitive adhesive is adjusted to the above range, the present inventors have no influence on the dynamic viscoelastic spectrum of the pressure-sensitive adhesive even if the substrate is sandwiched between them. Has confirmed.

(Manufacturing process of adhesive tape)
In order to laminate the pressure-sensitive adhesive layer on the nonwoven fabric, the pressure-sensitive adhesive solution is directly applied to the resin substrate using a roll coater, die coater, etc., and then a drying step is performed to bond the separator (hereinafter referred to as direct coating method). ), Or a method in which a pressure-sensitive adhesive solution is once coated on a separator, followed by a drying step, and then transferred to a resin substrate (hereinafter referred to as a transfer method).

  The 180 degree peel adhesive strength of the adhesive tape is determined by JIS-Z-0237, and a stainless steel plate is used as the adherend. [A] A sample left for 1 hour in an environment of 23 ° C. and 50%, and [B] 1 day in an environment of 23 ° C. and 50% after being left for 10 days in an environment of 60 ° C. and 0 to 5%. When preparing samples that were allowed to stand for a period of time and measuring the adhesive strength ([A] and [B]) when the adhesive tape samples [A] and [B] were peeled off at a speed of 1000 m / min in the direction of 180 degrees The adhesive strength of [A] is preferably 10 to 25 N / 20 mm, more preferably 15 to 25 N / 20 mm, and the difference in adhesive strength of [B]-[A] is preferably within 10 N / 20 mm. . In the case of the adhesive strength in this range, it becomes easy to achieve both re-peelability and strong adhesiveness in a balanced manner. In addition, the adhesive tape at the time of evaluation adjusts an adhesive tape sample by cut | disconnecting to 20 mm width x 100 mm length, and in the case of a double-sided adhesive tape, a double-sided adhesive tape is lined with a 25-micrometer-thick PET film, and 20-mm width A double-sided adhesive tape sample is prepared by cutting to a length of × 100 mm.

  In the pressure-sensitive adhesive tape of the present invention, direct printing or a separately created decorative layer is laminated on the surface of the single-sided pressure-sensitive adhesive tape provided with the pressure-sensitive adhesive layer on one side of the resin film substrate. Thereby, it can be set as the adhesive label which has an information display surface. Moreover, when it has the printing and decoration layer which make these information displays, in order to protect the said printing and decoration layer, the coating layer may be provided.

  The pressure-sensitive adhesive tape of the present invention has a suitable holding force and excellent re-peelability that can be suitably peeled even for a large area of various adherends. In addition to glass surfaces such as display screens and window glass, various types of adherends such as flat surfaces, curved surfaces, and uneven surfaces made of materials such as plastic and metal are used to protect or shield light from impacts and scratches. As a protective label to be used or a POP advertisement, an adhesive label that is repeatedly attached and peeled off from the back surface can be used.

[Method for preparing water-dispersed acrylic pressure-sensitive adhesive composition]
Example 1
<Preparation of emulsion>
In a container, 75 g of ion-exchange water and surfactant Aqualon KH-1025 [Daiichi Kogyo Seiyaku Co., Ltd .; active ingredient 25%] 20 g and surfactant Latemul PD-104 [Kao Corporation; active ingredient 20%] 37.5 g was added and dissolved uniformly. Emulsified by adding 318.5 g of n-butyl acrylate, 136.5 g of 2-ethylhexyl acrylate, 25 g of methyl methacrylate, 7.5 g of N-vinylpyrrolidone, 1.5 g of acrylic acid, 11 g of methacrylic acid, and 0.2 g of lauryl mercaptan. As a result, 632.7 g of an emulsion was obtained.

<Manufacture of acrylic copolymer emulsion>
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, 342.5 g of ion-exchanged water was added, and the temperature was raised to 60 ° C. while blowing nitrogen. While stirring, a part of the emulsion [3.2 g], 5 g of ammonium persulfate aqueous solution [3% active ingredient], and 5 g of sodium hydrogen sulfite aqueous solution [3% active ingredient] were added and polymerized in 1 hour while maintaining 60 ° C. It was. Subsequently, the remaining emulsion (629.5 g) and ammonium persulfate aqueous solution (40 g [active ingredient: 1.25%]) were dropped and polymerized over 8 hours using a separate funnel while keeping the reaction vessel at 60 ° C. After completion of the dropping, the reaction vessel was stirred for 2 hours while maintaining the temperature at 60 ° C., and then the contents were cooled, and subsequently adjusted with ammonia water (active ingredient 10%) so that the pH became 7.5. This was filtered through a 200-mesh wire mesh to obtain 1025.9 g of an acrylic copolymer emulsion. Here, the obtained water-dispersed acrylic polymer had a solid content concentration of 50% and an average particle size of 367 nm.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
To the acrylic copolymer emulsion 1000 g [dry; 500 g], Surfynol PSA-336 [produced by Air Products Japan Co., Ltd .; active ingredient 100%] 2.5 g as a leveling agent, Surfynol as an antifoaming agent DF-110D [manufactured by Air Products Japan Co., Ltd .; active ingredient 100%] 2.5 g, emulsion type polymerized rosin ester tackifier resin superester E-865NT [made by Arakawa Chemical Industries, Ltd.] as a tackifier resin; Softening point 160 ° C.] 50 g in solid content, emulsion type rosin phenol-based tackifier resin Tamanol E-200NT [manufactured by Arakawa Chemical Industries, Ltd .; softening point 150 ° C.] 75 g in solid content, carbodiimide crosslinking agent Carbodilite V-04 [ Nisshinbo Co., Ltd .; water-soluble type] 6.25 g (0.5 mass in solids) ) Was added, and filtered through a 200 mesh screen, to obtain aqueous acrylic PSA composition.

(Example 2)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 1.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition in the same manner as in Example 1 except that 6.25 g of the carbodiimide-based crosslinking agent Carbodilite V-04 was changed to 12.5 g (1.0 part by mass in solid content). Manufactured.

(Example 3)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 1 except that 318.5 g of n-butyl acrylate was changed to 227.5 g and 136.5 g of 2-ethylhexyl acrylate was changed to 227.5 g.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1 except that the emulsion obtained above was used. Here, the obtained acrylic copolymer emulsion had a solid content concentration of 50% and an average particle size of 341 nm.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
Example 1 except that 6.25 g of the carbodiimide-based crosslinking agent Carbodilite V-04 was changed to 16.25 g (1.3 parts by mass in solid content) using the acrylic copolymer emulsion obtained above. A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as described above.

Example 4
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 1.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition in the same manner as in Example 1 except that 6.25 g of the carbodiimide-based crosslinking agent Carbodilite V-04 was changed to 23.75 g (1.9 parts by mass in solid content). Manufactured.

(Example 5)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 1.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that 6.25 g of the carbodiimide-based crosslinking agent Carbodilite V-04 was changed to 35 g (2.8 parts by mass in solid content). did.

(Example 6)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 5 except that the acrylic copolymer emulsion obtained above was used.

(Example 7)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 1 except that 318.5 g of n-butyl acrylate was changed to 136.5 g and 136.5 g of 2-ethylhexyl acrylate was changed to 318.5 g.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1 except that the emulsion obtained above was used. Here, the obtained acrylic copolymer emulsion had a solid concentration of 50% and an average particle size of 324 nm.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
An acrylic copolymer emulsion was produced in the same manner as in Example 5 except that the acrylic copolymer emulsion obtained above was used.

(Example 8)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 3 except that 16.25 g of the carbodiimide-based crosslinking agent Carbodilite V-04 was changed to 50 g (4 parts by mass in solid content).

Example 9
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 3, except that 16.25 g of the carbodiimide-based crosslinking agent Carbodilite V-04 was changed to 62.5 g (5 parts by mass in solid content). did.

(Example 10)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
The same method as in Example 3 except that 16.25 g of the carbodiimide-based crosslinking agent Carbodilite V-04 was changed to 12.5 g (Emulsion type) of Carbodilite E-04 [Nisshinbo Co., Ltd .; 1 part by mass in solid content]. A water-dispersed acrylic pressure-sensitive adhesive composition was produced.

(Example 11)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 10, except that 12.5 g of the carbodiimide-based crosslinking agent Carbodilite E-04 was changed to 25 g (2 parts by mass in solid content).

(Example 12)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 3, except that 16.25 g of the carbodiimide-based crosslinking agent Carbodilite V-04 was changed to 125 g (10 parts by mass in solid content).

(Example 13)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
Except for changing 16.25 g of the carbodiimide-based crosslinking agent carbodilite V-04 to 42.5 g of carbodilite V-02 [Nisshinbo Co., Ltd .; water-soluble type] (3.4 parts by mass in solid content), the same as in Example 3. The water-dispersed acrylic pressure-sensitive adhesive composition was produced by the method described above.

(Example 14)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition in the same manner as in Example 13, except that 42.5 g of the carbodiimide-based crosslinking agent Carbodilite V-02 was changed to 63.75 g (5.1 parts by mass in solid content). Manufactured.

(Example 15)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
The same method as in Example 3 except that 16.25 g of the carbodiimide-based crosslinking agent carbodilite V-04 was changed to 30 g of carbodilite SV-02 [Nisshinbo Co., Ltd .; water-soluble type] (2.4 parts by mass in solid content). Thus, a water-dispersed acrylic pressure-sensitive adhesive composition was produced.

(Example 16)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 15 except that 30 g of the carbodiimide-based crosslinking agent Carbodilite SV-02 was changed to 45 g (3.6 parts by mass in solid content).

(Example 17)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 15 except that 30 g of the carbodiimide-based crosslinking agent Carbodilite SV-02 was changed to 125 g (10 parts by mass in solid content).

(Example 18)
<Preparation of emulsion>
In a container, 75 g of ion-exchange water and surfactant Aqualon KH-1025 [Daiichi Kogyo Seiyaku Co., Ltd .; active ingredient 25%] 20 g and surfactant Latemul PD-104 [Kao Corporation; active ingredient 20%] 37.5 g was added and dissolved uniformly. Emulsified by adding 230.5 g of n-butyl acrylate, 230.5 g of 2-ethylhexyl acrylate, 25 g of methyl methacrylate, 1.5 g of N-vinylpyrrolidone, 1.5 g of acrylic acid, 11 g of methacrylic acid, and 0.2 g of lauryl mercaptan. As a result, 632.7 g of an emulsion was obtained.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1 except that the emulsion obtained above was used. Here, the obtained acrylic copolymer emulsion had a solid content concentration of 50%, an average particle size of 330 nm, and a weight average molecular weight of 800,000.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 5 except that the acrylic copolymer emulsion obtained above was used.

(Example 19)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3 except that 1.5 g of acrylic acid was changed to 7.5 g and 11 g of methacrylic acid was changed to 5 g.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1 except that the emulsion obtained above was used. Here, the obtained acrylic copolymer emulsion had a solid content concentration of 50%, an average particle size of 302 nm, and a weight average molecular weight of 770,000.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
The same as Example 3 except that 16.25 g of the carbodiimide-based crosslinking agent Carbodilite V-04 was changed to 37.5 g (3 parts by mass in solid content) using the acrylic copolymer emulsion obtained above. The water-dispersed acrylic pressure-sensitive adhesive composition was produced by the method described above.

(Example 20)
An emulsion was prepared in the same manner as in Example 5 except that 1.5 g of acrylic acid was changed to 5 g and 11 g of methacrylic acid was changed to 7.5 g.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1 except that the emulsion obtained above was used. Here, the obtained acrylic copolymer emulsion had a solid content concentration of 50%, an average particle size of 300 nm, and a weight average molecular weight of 750,000.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
Example 3 except that 16.25 g of the carbodiimide crosslinking agent Carbodilite V-04 was changed to 36.25 g (2.9 parts by mass in solid content) using the acrylic copolymer emulsion obtained above. A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as described above.

(Comparative Example 1)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 3 except that 16.25 g of the carbodiimide-based crosslinking agent Carbodilite V-04 was changed to 0 g.

(Comparative Example 2)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 3.

<Manufacture of acrylic copolymer emulsion>
In the same manner as in Example 3, an acrylic copolymer emulsion was produced.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition in the same manner as in Example 3 except that 16.25 g of the carbodiimide-based crosslinking agent Carbodilite V-04 was changed to 1.25 g (0.1 part by mass in solid content). Manufactured.

(Comparative Example 3)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 1.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
The same method as in Example 1 except that 6.25 g of the carbodiimide-based crosslinking agent Carbodilite V-04 was changed to 0.15 g (0.03 parts by mass) of the epoxy-based crosslinking agent Tetrad-C [Mitsubishi Gas Chemical Co., Ltd.]. Thus, a water-dispersed acrylic pressure-sensitive adhesive composition was produced.

(Comparative Example 4)
<Preparation of emulsion>
In a container, 75 g of ion-exchange water and surfactant Aqualon KH-1025 [Daiichi Kogyo Seiyaku Co., Ltd .; active ingredient 25%] 20 g and surfactant Latemul PD-104 [Kao Corporation; active ingredient 20%] 37.5 g was added and dissolved uniformly. Then, 227.5 g of n-butyl acrylate, 227.5 g of 2-ethylhexyl acrylate, 25 g of methyl methacrylate, 7.5 g of N-vinyl pyrrolidone, 12.5 g of acrylic acid and 0.2 g of lauryl mercaptan were added to emulsify, and an emulsion solution 632.7 g was obtained.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1 except that the emulsion obtained above was used. Here, the obtained acrylic copolymer emulsion had a solid content concentration of 50% and an average particle size of 338 nm.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 2 except that the acrylic copolymer emulsion obtained above was used.

(Comparative Example 5)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Comparative Example 4.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Comparative Example 4.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Comparative Example 4 except that 12.5 g of the carbodiimide-based crosslinking agent Carbodilite V-04 was changed to 37.5 g (3 parts by mass in solid content). did.

(Comparative Example 6)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Comparative Example 4.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Comparative Example 4.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Comparative Example 3 except that the acrylic copolymer emulsion obtained above was used.

(Comparative Example 7)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Comparative Example 4.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Comparative Example 4.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Comparative Example 6 except that 0.15 g of tetrad-C was changed to 1.5 g.

(Comparative Example 8)
<Preparation of emulsion>
In a container, 75 g of ion-exchange water and surfactant Aqualon KH-1025 [Daiichi Kogyo Seiyaku Co., Ltd .; active ingredient 25%] 20 g and surfactant Latemul PD-104 [Kao Corporation; active ingredient 20%] 37.5 g was added and dissolved uniformly. Thereto, 231.25 g of n-butyl acrylate, 231.25 g of 2-ethylhexyl acrylate, 25 g of methyl methacrylate, 12.5 g of acrylic acid, and 0.2 g of lauryl mercaptan were added and emulsified to obtain 632.7 g of an emulsion.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Example 1 except that the emulsion obtained above was used. Here, the obtained acrylic copolymer emulsion had a solid concentration of 50% and an average particle size of 326 nm.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Comparative Example 3 except that the acrylic copolymer emulsion obtained above was used.

(Comparative Example 9)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Comparative Example 8.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Comparative Example 8.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Comparative Example 8, except that 0.15 g of tetrad-C was changed to 1.5 g (0.3 parts by mass).

(Comparative Example 10)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 1.

<Manufacture of acrylic copolymer emulsion>
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, 342.5 g of ion-exchanged water was added, and the temperature was raised to 60 ° C. while blowing nitrogen. While stirring, a part [3.2 g] of the emulsion obtained above, 5 g of ammonium persulfate aqueous solution [3% active ingredient], and 5 g of sodium hydrogen sulfite aqueous solution [3% active ingredient] were added and maintained at 80 ° C. The polymerization was performed in 1 hour. Subsequently, 629.5 g of the remaining emulsion obtained above and 40 g of ammonium persulfate aqueous solution [active ingredient 1.25%] were used for 8 hours while maintaining the reaction vessel at 80 ° C. using separate funnels. Drop polymerization was performed. After completion of the dropping, the reaction vessel was stirred for 2 hours while maintaining the temperature at 80 ° C., and then the contents were cooled, and subsequently adjusted with ammonia water (active ingredient 10%) so that the pH became 7.5. This was filtered through a 200-mesh wire mesh to obtain 1025.9 g of an acrylic copolymer emulsion. Here, the obtained water-dispersed acrylic polymer had a solid content concentration of 50% and an average particle size of 354 nm.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Comparative Example 2 except that the acrylic copolymer emulsion obtained above was used.

(Comparative Example 11)
<Preparation of emulsion>
An emulsion was prepared in the same manner as in Example 1.

<Manufacture of acrylic copolymer emulsion>
An acrylic copolymer emulsion was produced in the same manner as in Comparative Example 10.

<Production of water-dispersed acrylic pressure-sensitive adhesive composition>
A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Comparative Example 10 except that 1.25 g of Carbodilite V-04 was changed to 12.5 g (1 part by mass).

[Method for preparing double-sided adhesive tape]
The water-dispersed acrylic pressure-sensitive adhesive composition containing the above-mentioned crosslinking agent was coated on a 75 μm-thick polyester film having been subjected to a release treatment so that the thickness after drying was 65 μm, and at 100 ° C. for 5 minutes. The pressure-sensitive adhesive sheet obtained by drying was transferred to both sides of a 16 μm thick PET base material (EMBLET PTM-16 manufactured by Unitika Co., Ltd.) that had been subjected to easy adhesion treatment by primer coating, and 4 kgf / cm with a 90 ° C. hot roll. Was laminated at a pressure of 2 to obtain a double-sided adhesive tape. In addition, this double-sided adhesive tape was used for the test after aging at 40 ° C. for 2 days.

  The following evaluation was performed about the adhesive composition and adhesive tape of the Example and comparative example which were obtained above. The obtained results are shown in Tables 1 to 4.

[Evaluation Method (Adhesive Composition)]
(Measurement method of carboxyl group distribution in acrylic copolymer emulsion)
Acrylic copolymer emulsion (A) obtained in Example 1 (solid content concentration 50.0%) 6.0 g (solid content 3 g) was weighed into a 300 mL polyethylene beaker with a dropper. Into a polyethylene beaker, 94 g of ion-exchanged water is poured and stirred (the total amount of the test sample is 100 g). Then, the electrode and the temperature assurance electrode are immersed. The tip of the titration nozzle was higher than the liquid level, and was placed 2 cm away from the electrode so that the titration reagent did not reach the electrode. The method file is set to intermittent titration at the titration mode, the intermittent time is 10 seconds, the maximum drop volume is 20 mL, the single injection volume at the time of intermittent injection is 0.16 mL / time, the injection speed is 5 seconds / mL, The potential for collecting data was designated as 4 mL, and the titer for collecting data was designated as 0.16 mL. While stirring, potentiometric automatic titration was performed. The amount of acid groups present on the surface of the acrylic copolymer emulsion particles calculated from the obtained titration curve was 0.097 meqv. / G, the amount of acid groups present inside the particles is 0.197 meqv. / G.

  The same measurement was performed for the acrylic copolymer emulsions of other examples and comparative examples, and the amount of acid groups present on the surface of the acrylic copolymer emulsion particles calculated from the titration curve, the amount of acid groups present inside the particles Was calculated. The obtained results are shown in Table 1.

(Average particle size of acrylic copolymer emulsion)
The value of the average particle diameter (50% median diameter on a volume basis) measured with a Nikkiso Co., Ltd. Microtrac UPA type particle size distribution analyzer was determined.

(Measurement of initial gel fraction of acrylic copolymer emulsion)
The pressure-sensitive adhesive sheet obtained by coating the obtained acrylic copolymer emulsion on a polyester film having a thickness of 75 μm after the release treatment so that the thickness after drying becomes 65 μm and drying at 100 ° C. for 5 minutes. Was transferred to both sides of a PET substrate, laminated with a 90 ° C. hot roll at a pressure of 4 kgf / cm, and immediately after obtaining a double-sided adhesive tape, a sample cut into a size of 40 mm × 50 mm was used as a sample. Next, the mass (G ₁ ′) of the sample before being immersed in toluene and the mass (G ₀ ′) of the nonwoven fabric substrate were measured in advance and immersed in a toluene solution at room temperature for 24 hours. And the toluene insoluble matter of the sample after immersion was separated by filtering with a 300 mesh wire mesh, the mass (G ₂ ′) of the residue after drying at 105 ° C. for 1 hour was measured, and the gel fraction was determined according to the following formula: Asked.
Initial gel fraction (mass%) = [(G ₂ ′ −G ₀ ′) / (G ₁ ′ −G ₀ ′)] × 100

[Evaluation method (adhesive tape)]
(Measurement of gel fraction)
The water-dispersed acrylic pressure-sensitive adhesive composition was applied onto a 75 μm-thick polyester film that had been peeled off so that the thickness after drying was 65 μm, and dried at 100 ° C. for 5 minutes. The pressure-sensitive adhesive sheet was transferred to both surfaces of the PET base material and laminated with a 90 ° C. hot roll at a pressure of 4 kgf / cm to obtain a double-sided pressure-sensitive adhesive tape. A sample cut into a size of 40 mm × 50 mm after aging in an environment of 40 ° C. for 2 days was used as a sample. Next, the mass (G ₁ ) of the sample before immersion in toluene and the mass (G ₀ ) of the PET substrate were measured in advance, and immersed in a toluene solution at room temperature for 24 hours. And the toluene insoluble matter of the sample after immersion is separated by filtering with a 300 mesh wire mesh, the mass (G ₂ ) of the residue after drying at 105 ° C. for 1 hour is measured, and the gel fraction is determined according to the following formula: Asked.
Gel fraction (% by mass) = [(G ₂ −G ₀ ) / (G ₁ −G ₀ )] × 100

(Evaluation of removability)
The double-sided pressure-sensitive adhesive tape sample was prepared by backing the double-sided pressure-sensitive adhesive tape with a PET film having a thickness of 25 μm and cutting it into a width of 20 mm × 100 mm. Next, stainless steel plate, acrylonitrile-butadiene-styrene (hereinafter referred to as ABS) plate, polycarbonate (hereinafter referred to as PC) plate, and PC / ABS composite resin plate are used as adherends. And then left to stand in an environment of 60 ° C. and 5% for 10 days. Then, it left still in 23 degreeC * 50% RH environment for 1 hour, and the removability at the time of peeling a double-sided adhesive tape sample at a speed | rate of 25 m / min in the direction of 135 degree | times was evaluated. The re-peelability was evaluated according to the following criteria.
A: The remaining area of the adhesive tape due to the adhesive residue on the adherend is less than 3% of the sticking area.
A to B: The remaining area of the adhesive tape due to the adhesive residue on the adherend is 3% or more and less than 10% of the sticking area.
○: The remaining area of the adhesive tape due to the adhesive residue on the adherend is 10% or more and less than 30% of the pasting area.
(Triangle | delta): The residual area of the adhesive tape by the adhesive residue on a to-be-adhered body is 30% or more and less than 80% of a sticking area.
X: The residual area of the adhesive tape due to the adhesive residue on the adherend is 80% or more of the sticking area.

(Evaluation of removability, evaluation of moisture resistance)
The double-sided pressure-sensitive adhesive tape sample was prepared by backing the double-sided pressure-sensitive adhesive tape with a PET film having a thickness of 25 μm and cutting it into a width of 20 mm × 100 mm. Next, stainless steel plate, acrylonitrile-butadiene-styrene (hereinafter referred to as ABS) plate, polycarbonate (hereinafter referred to as PC) plate, and PC / ABS composite resin plate are used as adherends. Was applied, and allowed to stand in an environment of 60 ° C. and 90% for 10 days. Then, it left still in 23 degreeC * 50% RH environment for 1 hour, and the removability at the time of peeling a double-sided adhesive tape sample at a speed | rate of 25 m / min in the direction of 135 degree | times was evaluated. The re-peelability was evaluated according to the following criteria.
A: The remaining area of the adhesive tape due to the adhesive residue on the adherend is less than 3% of the sticking area.
A to B: The remaining area of the adhesive tape due to the adhesive residue on the adherend is 3% or more and less than 10% of the sticking area.
○: The remaining area of the adhesive tape due to the adhesive residue on the adherend is 10% or more and less than 30% of the pasting area.
(Triangle | delta): The residual area of the adhesive tape by the adhesive residue on a to-be-adhered body is 30% or more and less than 80% of a sticking area.
X: The residual area of the adhesive tape due to the adhesive residue on the adherend is 80% or more of the sticking area.

(Evaluation of strong adhesiveness and increase in adhesive strength over time after application of adherend)
The double-sided pressure-sensitive adhesive tape sample was prepared by backing the double-sided pressure-sensitive adhesive tape with a PET film having a thickness of 25 μm and cutting it into a width of 20 mm × 100 mm. Next, stainless steel plate, ABS plate, PC plate, PC / ABS plate are used as adherends, and one-way pressure sticking is performed with a 2 kg roller in an environment of 23 ° C./50%. [A] 23 ° C./50 A sample that was allowed to stand for 1 hour in an environment of 25% and a sample that was left for 10 days in an environment of [B] 60 ° C. and 0 to 5% and then left for 1 hour in an environment of 23 ° C. and 50% were prepared. On the other hand, [C] A sample was prepared which was allowed to stand in an environment of 60 ° C. and 90% for 10 days and then left in an environment of 23 ° C. and 50% for 1 hour.
Thereafter, the peeling force when the double-sided adhesive tape sample of [A] was peeled off at a speed of 300 mm / min in the direction of 180 degrees, and the double-sided adhesive tape samples of [A], [B], and [C] were 180 degrees. The adhesive strength ([A], [B], [C]) when peeled in the direction at a speed of 1000 mm / min was measured. Next, the increased adhesive force ([B]-[A]) or ([C]-[A]) was calculated. In addition, the measurement of adhesive force was implemented based on JIS-Z-0237.

(Evaluation of constant load peelability)
A 10 mm wide double-sided adhesive tape sample lined with a 25 μm thick polyester film is applied to a stainless steel plate (manufactured by Nippon Test Panel Co., Ltd.) so that the length is 50 mm, and a 2 kg roller is reciprocated once on the double-sided adhesive sheet. Was pressed and adhered. After being left for 1 hour in an atmosphere of 23 ° C. and 50% RH, a load of 300 g is applied so that the direction is 90 ° with respect to the peeling direction, and the time until a 50 mm long tape sample falls is measured. Evaluation was made according to the following criteria. The constant load peelability evaluation is a substitute evaluation method that assumes a case where deformation stress is applied to the double-sided pressure-sensitive adhesive tape for a long time from the outside, and the longer the time until dropping, the more the peel resistance, that is, the strong adhesiveness. Expresses superiority.
○: The falling time was 3 hours or more.
Δ: Dropped in less than 3 hours.
X: Dropped in less than 1 hour.

(Evaluation of holding power)
The double-sided pressure-sensitive adhesive tape was cut into a width of 20 mm × 100 mm, and pressed and pressed on a stainless steel plate at 23 ° C. and 50% in a reciprocating manner with a 2 kg roller so that the application area was 20 mm × 20 mm. . Next, a load of 0.5 kg was applied in a 40 ° C. environment, and the drop time was measured. In the case of holding for 24 hours (1440 minutes) or longer, “1440 <” is displayed in Table 1.

  As apparent from Tables 1 to 4, the pressure-sensitive adhesive tape of the present invention using the water-dispersed acrylic pressure-sensitive adhesive compositions of Examples 1 to 20 has good holding power and strong adhesiveness to the adherend. And excellent removability. On the other hand, as is clear from Tables 3 to 4 above, Comparative Examples 1-2 and 10 had a small amount of cross-linking agent, so that the anchoring property of PET was poor and the removability was poor. Moreover, the cohesive force was poor and the holding power was poor. Since the comparative example 3 uses the epoxy-type crosslinking agent, the anchoring property to a PET base material was inferior, and the re-peelability was poor. Since Comparative Examples 4 to 9 do not contain methacrylic acid and the amount of acid groups inside the acrylic copolymer emulsion particles is low, the adhesive force with time tends to increase, and adhesion to a plurality of adherends The force [B] was high and the removability was poor.

Claims (10)

An adhesive tape having an adhesive layer on at least one surface of a substrate made of a resin film,
The pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed by drying and crosslinking a water-dispersed acrylic pressure-sensitive adhesive composition in which acrylic copolymer emulsion particles are dispersed in an aqueous medium,
Water-dispersed acrylic pressure-sensitive adhesive composition The acrylic copolymer forming the acrylic copolymer emulsion particles is 2-ethylhexyl acrylate, a (meth) acrylate having 4 to 8 carbon atoms, a carboxyl group-containing Containing a monomer and a nitrogen-containing vinyl monomer as a monomer component, acrylic acid and methacrylic acid as the carboxyl group-containing monomer, 0.1 to 10% by mass in the monomer component forming the acrylic copolymer,
The cross-linking of the water-dispersed acrylic pressure-sensitive adhesive composition is a cross-linking with a carbodiimide-based cross-linking agent having a molar ratio of 0.03 to 1 with respect to the carboxyl group in the acrylic copolymer. tape. The ratio of the content of acrylic acid and methacrylic acid in the monomer component forming the acrylic copolymer is 2 or more in molar equivalent ratio represented by (methacrylic acid / acrylic acid). Adhesive tape. The sum of the contents of 2-ethylhexyl acrylate and (meth) acrylate having an alkyl group having 4 to 8 carbon atoms in the monomer component forming the acrylic copolymer is 50 to 98% by mass. The adhesive tape as described in. The sum of the contents of 2-ethylhexyl acrylate and (meth) acrylate having an alkyl group having 4 to 8 carbon atoms in the monomer component forming the acrylic copolymer is 50 to 98% by mass, the content of the nitrogen-containing vinyl monomer The pressure-sensitive adhesive tape according to any one of claims 1 to 3, wherein the amount is 0.15 to 4.5 mass%. The ratio of the content of 2-ethylhexyl acrylate in the monomer component forming the acrylic copolymer to the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms is (2-ethylhexyl acrylate / 4 to 8 carbon atoms). The pressure-sensitive adhesive tape according to any one of claims 1 to 4, which is 9/1 to 2/8 in a mass ratio represented by (meth) acrylate having an alkyl group of (5). The water-dispersed acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the acrylic copolymer emulsion particles have a particle size of 300 to 1000 nm. The acrylic copolymer emulsion particles are subjected to potentiometric titration by dropping an inorganic base solution into an acidic sample dispersion, and the titration start point P ₀ , the minimum point P _{1 at} which the pH becomes minimum after the start of titration, and the minimum point P ₁ titration curve having an inflection point P ₂ appearing next to (X-axis: a base dropping amount, Y axis: pH) when measuring the differential curve of
Acid group amount (AN _SUR ) on the surface of acrylic copolymer emulsion particles calculated from the amount of base dropped in P _{1 to} P ₂ ,
And inside the acrylic copolymer emulsion particles calculated by subtracting the amount of acid groups calculated from the amount of base dropped in P _{0 to} P ₂ from the total amount of acid groups (AN _TOTAL ) in the acidic sample dispersion The pressure-sensitive adhesive tape according to claim 1, which is an acrylic copolymer emulsion particle having a ratio (AN _IN ) / (AN _SUR ) of the acid group amount (AN _IN ) of 1 or more. The gel fraction of the solid content when the aqueous medium is removed so as not to allow the crosslinking reaction to proceed from the water-dispersed acrylic pressure-sensitive adhesive composition so that only the solid content is 15% by mass or less. The adhesive tape in any one. The pressure-sensitive adhesive tape according to any one of claims 1 to 8, wherein the pressure-sensitive adhesive layer has a gel fraction of 20 to 75%. In a temperature 23 ° C and relative humidity 50% RH environment, a stainless steel plate is crimped with a 2 kg roller with one round of crimping and left at rest for 1 hour, and then peeled 180 ° at a stripping rate of 1000 mm / min. The adhesive tape according to any one of claims 1 to 9, wherein the adhesive force (F _A1 ) is 10 to 25 N / 20 mm.

Images