JP4886969B2 - Adhesive sheet - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive sheet, and particularly relates to a pressure-sensitive adhesive sheet for adhering onto a coated steel plate surface of an automobile.

Various adhesive tapes such as a chipping-resistant sheet, a marking sheet, or a surface protection sheet are attached to the surface of a coated steel plate of an automobile.
On the other hand, the surface of a coated steel plate of an automobile has not only a flat surface but also a tertiary concave curved surface, a tertiary convex curved surface, and the like, and, for example, a belt-like groove or protrusion is provided. In particular, a relatively large number of thin strip-shaped grooves and strip-shaped protrusions are provided at the part where the chipping-resistant sheet is adhered. In other words, chipping is a phenomenon in which pebbles and small objects on the road surface are thrown up by the wheels and collide with the vehicle body when the vehicle is running, and damage the painted surface of the vehicle body. Chipping with sand, gravel, or rock salt sprayed for safe driving on a damaged road will significantly damage the painted surface of the vehicle body. Such chipping causes peeling of the overcoat layer, intermediate coat layer, or undercoat layer, and rusting of the base metal, so the side sill of the automobile body, the lower part of the door, the lower part of the wheel arch part of the front fender and rear fender For example, a chipping-resistant coating film is provided or a chipping-resistant adhesive sheet is attached. Many narrow belt-like grooves and belt-like projections are provided in these parts in view of the structure and design of the vehicle body.

For example, when a strip-like groove exists on the surface of the coated steel plate to which the adhesive tape is attached, it is necessary to attach the adhesive tape to the surface inside the groove. For example, as shown in FIG. 1 (a), when the adhesive tape 10 is stuck on the surface of the vehicle body 1, if the belt-like groove 2 exists on the adherend surface, the adhesive tape is applied to the inner surface 2 a of the belt-like groove 2. Since it is necessary to also stick the 10 tip part 10t, the worker pushes the part of the tip part 10t of the adhesive tape 10 with a finger and sticks it. However, if the adhesive strength is insufficient or the base material has high rigidity, the tip 10t of the adhesive tape 10 peels off from the inner surface 2a of the strip-shaped groove 2 and rises as shown in FIG. , It will be a subject of complaints because it detracts from aesthetics.
In addition, as shown in FIG. 2A, after the adhesive tape 10 is pasted across the belt-like groove 2 on the surface of the vehicle body 1 in the first step, the inside of the belt-like groove 2 in the next step. An operation in which an operator pushes the intermediate portion 10b not in contact with the surface 2a with a finger and attaches the intermediate portion 10b to the inner surface 2a as shown in FIG. 2B is often used. However, even in such a case, if the adhesive force is insufficient or the rigidity of the substrate is high, the intermediate portion 10b of the adhesive tape 10 is separated from the inner surface 2a of the belt-like groove 2 as shown in FIG. Since it peels off and floats, it loses its beauty and becomes a subject of complaints.

Conventionally, as an anti-chipping sheet to be adhered to the surface of an automobile-coated steel sheet, for example, an anti-chipping protection film in which an adhesive layer is provided on a polyurethane film substrate or a polyvinyl chloride film substrate is known (Patent Document 1). . However, this chipping-resistant pressure-sensitive adhesive sheet has a problem in that it floats and tunnels when it is attached to a tertiary concave curved surface. Further, as a chipping-resistant adhesive sheet, a sheet in which an acrylic adhesive layer is provided on a base material of a polyurethane film, an ionomer film, a polyester film, an ultrahigh molecular weight polyethylene film, or a fluorine resin film is also known (patent) Reference 2). However, the chipping-resistant adhesive sheet has a problem that, as described above, floating and tunneling occur when it is attached to a tertiary concave curved surface.
JP 59-41376 Utility Model Registration No. 3069550

  Therefore, the object of the present invention is to maintain the physical properties required as an adhesive tape, particularly as an adhesive tape (for example, a chipping-resistant sheet, a marking sheet, or a surface protection sheet) for automobile coated steel sheets while maintaining the physical properties required as an adhesive tape. It is still another object of the present invention to provide a pressure-sensitive adhesive sheet that is less likely to float and tunnel even when attached to a tertiary concave curved surface.

According to the present invention, the subject is a pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer formed on at least one surface of the base material,
(A) Young's modulus of the substrate is 20 to 110 MPa,
(B) When the entire pressure-sensitive adhesive sheet is gradually stretched in a certain direction at a speed of 200 mm / min, the rate of change in elongation stress between the stress in the 10% stretched state and the stress in the 40% stretched state is -50% to + 60%, and
(C) said to extend the entire pressure-sensitive adhesive sheet to 40% elongation state in a certain one direction state, and are stress relaxation ratio 30% or more after a lapse of three minutes from the stop of the stretched in this state,
(D) the substrate is
(1) One hard layer made of polycarbonate-based polyurethane having a Young's modulus of 850 to 2000 MPa and a thickness of 1 to 30 μm
(2) including a single soft layer made of polyester-based polyurethane having a Young's modulus of 5 to 20 MPa and a thickness of 70 to 300 μm,
(E) The pressure-sensitive adhesive of the pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive containing a copolymer of an acrylate ester-based monomer, a carboxyl group-containing ethylenically unsaturated monomer, and a polymerizable acid anhydride monomer or vinyl acetate. ,And,
(F) that you form the adhesive layer on the surface of the soft layer can be solved by the adhesive sheet according to claim.

In a preferred embodiment of the pressure-sensitive adhesive sheet of the present invention, when the whole pressure-sensitive adhesive sheet is gradually stretched in a certain direction at a speed of 200 mm / min, the inflection point of the stress strain curve is 1% stretch point and 15%. It exists between the% extension point.
In another preferable aspect of the pressure-sensitive adhesive sheet of the present invention, the ratio (Th / Tw) of the thickness (Th) of the hard layer to the thickness (Tw) of the entire base material is 1/10 to 1 / 150.
Furthermore, in another preferable aspect of the pressure-sensitive adhesive sheet of the present invention, an intermediate hardness layer made of polycarbonate-based polyurethane is included between the pressure-sensitive adhesive layer and the soft layer.

In a further, in another preferred embodiment of the pressure-sensitive adhesive sheet of the present invention, a sticking of the coated steel sheet surface of an automobile.
Furthermore, in another preferable aspect of the pressure-sensitive adhesive sheet of the present invention, it is a chipping-resistant sheet, a marking sheet, or a surface protective sheet.

  According to the pressure-sensitive adhesive sheet of the present invention, for example, even when adhered to a tertiary concave curved surface while maintaining the physical properties as a pressure-sensitive adhesive tape for automobile coated steel sheets (for example, a chipping-resistant sheet, a marking sheet, or a surface protective sheet). , Floating and tunneling are less likely to occur.

  The pressure-sensitive adhesive sheet according to the present invention comprises a base material and a pressure-sensitive adhesive layer provided on one surface of the base material, and the base material has a Young's modulus of the whole base material of 20 to 110 MPa, preferably 30 to 110 MPa, more preferably 35 to 100 MPa. In the present specification, the Young's modulus is a value measured according to JIS K-7127. When the Young's modulus of the whole substrate is less than 20 MPa, the pressure-sensitive adhesive sheet becomes insufficient, and not only is the workability of sticking inferior, but also the apparent adhesive force is lowered and floating may occur. Moreover, since the flexibility is inferior when the Young's modulus of the whole substrate exceeds 110 MPa, it becomes a cause of floating and tunneling when it is stuck to a tertiary concave curved surface.

  The pressure-sensitive adhesive sheet according to the present invention is stretched by 10% (that is, 1.1 times the initial length) when the whole pressure-sensitive adhesive sheet is gradually stretched in a certain direction at a speed of 200 mm / min. The change rate of the extensional stress is −50% to + 60% with respect to the stress in the state of 40) and the stress in the 40% elongation state (that is, the state extended to 1.4 times the initial length). As shown in FIG. 3, when the sheet is gradually stretched in a certain direction at a speed of 200 mm / min, a stress is applied according to the degree of stretching until the yield point Y of the sheet is reached as shown by a curve S1. Ascending at a steep slope and past the yield point Y, the increase in stress is alleviated. When further expanded, the stress further increases according to the degree of expansion (curve S2), when the stress decreases according to the degree of expansion (curve S3), or when the stress does not change according to the degree of expansion (FIG. Not shown).

For example, when the pressure-sensitive adhesive sheet according to the present invention shows a locus similar to the curve S1 to the curve S2 in FIG. 3, the stress (S _B ) and the 40% elongation state in the 10% elongation state (point B in FIG. 3) ( it is necessary that the stress (the rate of change of S _H) and the tensile stress (U) is + 60% or less in terms H) in FIG. That is, Formula (1):
U = _{[(S H -S B) / S} B ] × 100 (1)
The rate of change (U) calculated from is required to be + 60% or less, preferably + 50% or less, and more preferably + 45% or less.

Further, the pressure-sensitive adhesive sheet according to the present invention, for example, indicating the same locus as the curve S1- curve S3 in FIG. 3, the stress in the state 10% elongation (in terms of Fig. 3 B) _{(S B)} and 40% elongation It is necessary that the rate of change (U) of the extension stress with the stress (S _L ) in the state (point L in FIG. 3) is −50% or more. That is, Formula (2):
U = [(S _L −S _B ) / S _B ] × 100 (2)
The rate of change (U) calculated from the above is required to be −50% or more, preferably −30% or more, and more preferably −10% or more.

  When the rate of change (U) of the extension stress exceeds + 60%, the stress of the pressure-sensitive adhesive sheet is high, and therefore, when sticking to a tertiary concave curved surface, it causes floating and tunneling. On the other hand, when the rate of change (U) of the elongation stress is less than −50%, the polymer constituting the base material is broken and causes deterioration.

  In the pressure-sensitive adhesive sheet according to the present invention, the whole pressure-sensitive adhesive sheet is stretched to 40% (that is, 1.4 times the initial length) in a certain direction, and after the extension is stopped in that state, 3 minutes have elapsed. The stress relaxation rate is 40% or more. As shown in FIG. 3 described above, when the sheet having the same trajectory as the curves S1 to S2 is stopped in the 40% stretched state (point H in FIG. 3), stress relaxation occurs, and the curve S4 is shown. As shown, the stress drops rapidly. Although not shown in FIG. 3, for the sheet showing the same locus as the curves S <b> 1 to S <b> 3, when the extension is stopped in the 40% extension state (point L in FIG. 3), stress relaxation occurs, and the same The stress drops rapidly.

A pressure-sensitive adhesive sheet according to the present invention, for example, indicating the same locus as the curve S2- curve S4 in FIG. 3, a stress (S _H) in a state elongation 40% (H point in Fig. 3), the extension stop 3 Ratio [(S _H −S _R ) / S _H ] × 100 with stress (S _R ) after elapse of minutes (point R in FIG. 3)
That is, the stress relaxation rate is 30% or more, preferably 40% or more, and more preferably 45% or more. For example, when the pressure-sensitive adhesive sheet according to the present invention shows a locus similar to that of the curve S3 in FIG. 3, the stress relaxation rate calculated in the same manner is 30% or more, preferably 40% or more, more preferably 45%. That's it. When the stress relaxation rate is less than 30%, it causes floating and tunneling when affixed to a tertiary concave curved surface.

  The pressure-sensitive adhesive sheet of the present invention has a residual stress of preferably 10 N / cm or less, more preferably 10 N / cm or less after elapse of 3 minutes after the entire pressure-sensitive adhesive sheet is stretched by 40% in a certain direction. Is 8 N / cm or less, more preferably 6.5 N / cm or less. If the residual stress after 3 minutes passes exceeds 10 N / cm, it will cause floating and tunneling when affixed to a tertiary concave curved surface.

  In addition, the adhesive sheet of the present invention preferably has an inflection point (point Y in FIG. 3) of the stress strain curve when the entire adhesive sheet is gradually stretched in a certain direction at a speed of 200 mm / min. Exists between the 1% and 15% extension points, more preferably between the 3% and 10% extension points.

Although the base material of the pressure-sensitive adhesive sheet according to the present invention can be composed of a single layer, the pressure-sensitive adhesive sheet has a base material satisfying the condition (a) and satisfies the conditions (b) and (c). In order to facilitate the preparation, in particular,
It is preferable that (1) at least one hard layer made of a resin having a Young's modulus of 500 MPa or more and (2) at least one soft layer made of a polyurethane having a Young's modulus of 50 MPa or less.

  In the present specification, the “hard layer” is a layer made of a resin having a Young's modulus of 500 MPa or more, and similarly, the “soft layer” is a layer made of polyurethane having a Young's modulus of 50 Ma or less. Further, the base material of the pressure-sensitive adhesive sheet according to the present invention is a layer that does not belong to either the hard layer or the soft layer (hereinafter referred to as an intermediate hardness layer), that is, a resin having a Young's modulus of more than 50 MPa and less than 500 MPa. Can be included.

  Examples of the resin constituting the hard layer include a polyurethane resin, an acrylic resin, a silicone resin, a fluorine resin, or a blend of these resins. From these resins, Young's modulus is 500 MPa or more (preferably 700 MPa). As described above, the hard layer can be formed by selecting a resin of 850 to 2000 MPa. A pressure-sensitive adhesive sheet that does not contain a hard layer having a Young's modulus of 500 MPa or more cannot exhibit a sufficient pressure-sensitive adhesive force. In addition, although the upper limit of the Young's modulus of the said hard layer is not specifically limited, when it exceeds 2000 MPa, it is inferior to a softness | flexibility.

  The base material in the pressure-sensitive adhesive sheet of the present invention may include the hard layer alone or a plurality of layers belonging to the hard layer. The thickness of the hard layer is not particularly limited, but the thickness (Th) of a single layer alone or the total thickness (Th) of a plurality of layers is the thickness of the entire substrate. The ratio (Th / Tw) to the thickness (Tw) is preferably 1/5 or less, more preferably 1/8 or less, and most preferably 1/10 to 1/150. Further, the thickness of the hard layer is, in the case of a single layer alone, the thickness thereof, or in the case of being composed of a plurality of layers, the total thickness thereof is preferably 60 μm or less, more preferably 40 μm or less, Most preferably, it is 1-30 micrometers. If the thickness ratio (Th / Tw) exceeds 1/5, or the thickness of the hard layer exceeds 60 μm, flexibility may be inferior. In addition, when there are a plurality of layers belonging to the hard layer, they may be adjacent to each other, or another layer (that is, the soft layer and / or intermediate hardness layer) 1 or more may be present between the hard layers. It may be interposed.

  The base material in the pressure-sensitive adhesive sheet of the present invention preferably includes a contamination-preventing coating layer provided on the surface as a layer belonging to the hard layer. As the anti-contamination coating layer, polyurethane, polyacrylic resin, silicone resin, fluorine resin, or a blend thereof can be used, and chemical resistance, abrasion resistance, and / or contamination resistance, etc. The characteristics of can be imparted.

In the base material of the pressure-sensitive adhesive sheet of the present invention, it is preferable that the sum of the products of Young's modulus and thickness of each layer belonging to the hard layer is 2000 N / m or more for all the layers belonging to the hard layer. The sum is more preferably 3000 N / m or more, and most preferably 4000 to 30000 N / m. That is, the following relational expression (3):
(Yh1 × Th1) + (Yh2 × Th2) +... + (Yhn × Thn) ≧ 2000 (N / m) (3)
(Where Yh1 is the Young's modulus of the first hard layer, Yh2 is the Young's modulus of the second hard layer, Yhn is the Young's modulus of the nth hard layer, and Th1 is the thickness of the first hard layer. Yes, Th2 is the thickness of the second hard layer, and Thn is the thickness of the nth hard layer)
Is preferably satisfied. When the above sum is less than 2000 N / m, the Young's modulus decreases, the pressure-sensitive adhesive sheet becomes insufficient, not only is the workability of sticking inferior, but also the apparent adhesive force is reduced, and floating may occur. . On the other hand, when the sum exceeds 30000 N / m, the followability to the tertiary concave curved surface is deteriorated, and floating may occur.

  The soft layer is made of a polyurethane resin, and a resin having a Young's modulus of 50 MPa or less (preferably 30 MPa or less, more preferably 5 to 20 MPa) is selected from known polyurethane resins to form the soft layer. it can. When a pressure-sensitive adhesive sheet containing a soft layer having a Young's modulus of 50 MPa or less is used as a chipping-resistant pressure-sensitive adhesive sheet, good chipping resistance can be exhibited.

  The base material in the pressure-sensitive adhesive sheet of the present invention can include the soft layer alone or a plurality of layers belonging to the soft layer. The thickness of the soft layer is not particularly limited, but the thickness (Ts) of one layer alone or the total thickness (Ts) of a plurality of layers is the total thickness of the substrate. The ratio (Ts / Tw) to the thickness (Tw) is preferably ½ or more, more preferably 1 / 1.5 or more, and most preferably 1 / 1.3-1 to 1.01. In addition, the thickness of the soft layer is, in the case of a single layer alone, the thickness thereof, or in the case of a plurality of layers, the total thickness thereof is preferably 50 μm or more, more preferably 60 μm or more, Most preferably, it is 70-300 micrometers. When the thickness ratio (Ts / Tw) is less than 1/2 or the thickness of the soft layer is less than 50 μm, the Young's modulus of the whole substrate is increased and the followability to the third concave curved surface is increased. May drop and float may occur. When there are a plurality of layers belonging to the soft layer, even if they are adjacent to each other, another layer (that is, the hard layer and / or intermediate hardness layer) 1 or more is interposed between the soft layers. You may do it.

In the pressure-sensitive adhesive sheet of the present invention, the sum of the product of Young's modulus and thickness of each layer belonging to the soft layer for all layers belonging to the soft layer is preferably 15000 N / m or less, The sum is more preferably 10,000 N / m or less, and most preferably 1000 to 10,000 N / m or less. That is, relational expression (4):
(Ys1 × Ts1) + (Ys2 × Ts2) +... + (Ysn × Tsn) ≦ 15000 (N / m) (4)
(Where Ys1 is the Young's modulus of the first soft layer, Ys2 is the Young's modulus of the second soft layer, Ysn is the Young's modulus of the nth soft layer, and Ts1 is the thickness of the first soft layer. Yes, Ts2 is the thickness of the second soft layer, and Tsn is the thickness of the nth soft layer)
Is preferably satisfied. When the sum exceeds 15000 N / m, the Young's modulus of the entire substrate is increased, the followability to the third concave curved surface is lowered, and floating may occur.

  The base material in the adhesive sheet of this invention can also contain the intermediate | middle hardness layer which does not belong to any of the said hard layer and the said soft layer. In addition, when the Young's modulus of the resin constituting the layer having these functions is 500 MPa or more, it has the functions and belongs to the hard layer, and the Young's modulus of the resin constituting these layers is 50 MPa or less. In this case, it has the function and belongs to the soft layer.

  As for the base material in the adhesive sheet of this invention, it is preferable that each resin which comprises a base material consists of non-yellowing resin, and the whole base material is a non-yellowing base material. That is, it is preferable that all of the resins constituting the hard layer, the soft layer, and the intermediate hardness layer (if present) are made of a non-yellowing resin, and the entire base material is a non-yellowing base material.

The base material in the pressure-sensitive adhesive sheet of the present invention can be prepared by a usual method. For example, the film can be formed by a casting method, an extrusion method, an inflation method, or the like.
Although the thickness of the base material in the adhesive sheet of the present invention is not particularly limited, it is preferably 51 to 500 μm, more preferably 100 to 350 μm.

  The pressure-sensitive adhesive sheet according to the present invention has a pressure-sensitive adhesive layer to be applied to the painted surface of a vehicle body on one surface of the substrate. As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, a normal pressure-sensitive adhesive, for example, an acrylic pressure-sensitive adhesive can be used.

  As the acrylic pressure-sensitive adhesive, for example, a known acrylic pressure-sensitive adhesive obtained by copolymerizing a monomer component mainly composed of an acrylate ester with a monomer component having a functional group such as a carboxyl group or a hydroxyl group can be used. (For example, refer to JP2003-73640A). In particular, an acrylic copolymer having an acrylic acid ester monomer and a carboxyl group-containing ethylenically unsaturated monomer as a copolymerization component (further, if necessary, a functional group-containing ethylenically unsaturated monomer other than a carboxyl group and / or other May be used as a copolymerization component.

  Examples of acrylic ester monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl ( (Meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, isooctyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, 2-methoxyethyl (meth) ) Acrylate, butoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, etc., among which the alkyl ester moiety has 1 to 12 carbon atoms. Meth) acrylic acid alkyl esters are preferred, for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, the use of 2-ethylhexyl (meth) acrylate preferred.

  Examples of the carboxyl group-containing ethylenically unsaturated monomer include (meth) acrylic acid, acrylic acid dimer, crotonic acid, maleic acid, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, acrylamide N-glycolic acid, and cinnamic acid. Among them, it is preferable to use (meth) acrylic acid.

  Functional group-containing ethylenically unsaturated monomers other than carboxyl groups include hydroxyl group-containing ethylenically unsaturated monomers, epoxy group-containing ethylenically unsaturated monomers, alkoxysilyl group-containing ethylenically unsaturated monomers, amide groups, methylol groups, aceto groups. Examples thereof include an ethylenically unsaturated monomer containing an acetyl group. Among them, a hydroxyl group-containing ethylenically unsaturated monomer is preferably used.

  Examples of the hydroxyl group-containing ethylenically unsaturated monomer include 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate, and examples of the epoxy group-containing ethylenically unsaturated monomer include , Glycidyl (meth) acrylate, or allyl glycidyl ether can be used. Examples of the alkoxysilyl group-containing ethylenically unsaturated monomer include γ- (meth) acryloxyethyltrimethoxysilane, or γ- (meth). Examples include acryloxyethyl triethoxysilane. Examples of the ethylenically unsaturated monomer containing an amide group, methylol group, or acetoacetyl group include acrylamide, methacrylamide, N-methylolacrylamide, butoxy N-methylolacrylamide, diacetone acrylamide, and 2- (acetoacetoxy). Examples thereof include ethyl (meth) acrylate and allyl acetoacetate.

  Other ethylenically unsaturated monomers include polymerizable anhydride monomers such as maleic anhydride and itaconic anhydride, styrene, vinyl acetate, (meth) acrylonitrile, vinyltoluene, dialkyl esters of itaconic acid, dialkyl esters of fumaric acid, allyl alcohol And acrylic chloride, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl pyridine, vinyl pyrrolidone, methyl vinyl ketone, and the like. Among them, a polymerizable acid anhydride monomer is preferably used, and maleic anhydride is particularly preferable.

  The content ratio (copolymerization ratio) of the acrylic acid ester monomer, carboxyl group-containing ethylenically unsaturated monomer, functional group-containing ethylenically unsaturated monomer other than carboxyl group and other ethylenically unsaturated monomers is not particularly limited, Acrylic acid ester monomer is 50 to 99% by weight (preferably 60 to 95% by weight, particularly preferably 70 to 95% by weight), and carboxyl group-containing ethylenically unsaturated monomer is 0.1 to 15% by weight (preferably 1). 10 to 10% by weight, particularly preferably 1 to 8% by weight), and the functional group-containing ethylenically unsaturated monomer other than the carboxyl group is 0 to 10% by weight (preferably 0.05 to 8% by weight, particularly preferably 0.1%). To 5% by weight), and other ethylenically unsaturated monomers are 0 to 39% by weight (preferably 2 to 20% by weight, particularly preferably Is preferably 3 to 10% by weight).

  If the acrylate monomer is less than 50% by weight, the adhesive strength is low, and if it exceeds 99% by weight, crosslinking is insufficient and the cohesive force is insufficient, which is not preferable, and the carboxyl group-containing ethylenically unsaturated monomer is less than 0.1% by weight. In this case, the crosslinking is insufficient, and if it exceeds 15% by weight, the crosslinking reaction rate is too high and the pot life is insufficient, or the tack is greatly reduced. Furthermore, if the functional group-containing ethylenically unsaturated monomer other than the carboxyl group exceeds 10% by weight, the adhesive strength is unfavorable, and if the other ethylenically unsaturated monomer exceeds 39% by weight, the adhesive strength decreases. Absent.

  In the acrylic copolymer, each monomer is mixed with an organic solvent (for example, aromatic hydrocarbons such as toluene or xylene, esters such as ethyl acetate, aliphatic alcohols such as n-propyl alcohol, acetone or methyl ethyl ketone). Etc.) and the like, etc.) can be easily produced by methods well known to those skilled in the art such as radical copolymerization. Examples of the polymerization catalyst used for radical copolymerization include azobisisobutyronitrile, benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, and the like. The weight average molecular weight of the acrylic copolymer is preferably 200,000 to 1,500,000 (more preferably 300,000 to 1,200,000), and the glass transition temperature is preferably −20 ° C. or less (more preferably −30 ° C.). The following).

  The acrylic copolymer is an isocyanate compound (for example, JP-A-7-324183 or JP-A-2003-73640) or an epoxy compound (for example, JP-A-56-166281) as a crosslinking agent. Or a functional group such as a carboxyl group or a hydroxyl group by using a metal chelate compound, a metal salt, a metal alcoside, an aldehyde group, a non-amino resin-based amino compound, a urea group, a melamine group, or an aziridine group. Crosslinking is used to control adhesive strength and cohesive strength.

  The pressure-sensitive adhesive used in the present invention can contain a crosslinking accelerator, a tackifier, and the like. Examples of the crosslinking accelerator include acid catalysts such as p-toluenesulfonic acid, phosphoric acid, hydrochloric acid, and ammonium chloride. Examples of the tackifier include terpene resins, phenol resins, and terpene phenols. Examples thereof include resins, silicone resins, coumarone resins, rosin compounds (rosin or rosin esters, hydrogenated rosin esters), petroleum resins, xylene resins, and styrene resins. The pressure-sensitive adhesive used in the present invention may further contain a conventionally known pressure-sensitive adhesive additive as necessary. Examples of such known additives include pigments, dyes, inorganic / organic fillers, plastics. Examples thereof include an agent, a stabilizer, metal powder, carbon black, a silane coupling agent, a softening agent, and an ultraviolet absorber.

The pressure-sensitive adhesive used in the present invention preferably has a specific creep behavior. For example, with respect to the bonding area of the square one side 10 mm, the deviation amount of up to 1000 seconds at creep behavior at 9.8N load at 40 ° C., and preferably 300μm or more. Shift amount of the is equal to or less than 300 [mu] m, dispersion stress component of the chipping adhesive sheet substrate and a pressure-sensitive adhesive layer becomes insufficient, sometimes floating occurs. The upper limit of the amount of deviation is not particularly limited, but if it falls in less than 100 seconds, it causes cold flow due to insufficient cohesive force.
Although the thickness of the adhesive layer in the adhesive sheet of this invention is not specifically limited, Preferably it is 25-200 micrometers, More preferably, it is 30-100 micrometers.

  The pressure-sensitive adhesive in the pressure-sensitive adhesive sheet of the present invention is preferably non-yellowing. In this case, it is preferable to form a non-yellowing pressure-sensitive adhesive sheet in combination with a non-yellowing base material in which the entire base material is non-yellowing.

In order to protect the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention and to store or transport the pressure-sensitive adhesive sheet, a release sheet can be laminated on the surface of the pressure-sensitive adhesive layer.
As the release sheet, any sheet known in the art can be used. For example, films made of various resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, or polyacrylate, polyethylene laminated paper, polypropylene Using various paper materials such as laminate paper, clay-coated paper, resin-coated paper, or glassine paper as a support, and using a surface that has been subjected to a release treatment on the adhesive layer of the support, if necessary. it can. In this case, representative examples of the release treatment include application and formation of a release agent layer made of a release agent such as a silicone resin, a long-chain alkyl resin, or a fluorine resin. The thickness of the release sheet is not particularly limited and may be appropriately selected. Moreover, it can also be set as the roll type which performed the peeling prescription | regulation on the single side | surface of a base material, gave an adhesive process to the opposite surface, and stuck the adhesive surface and the peeling prescription surface.
When the pressure-sensitive adhesive sheet of the present invention is accompanied by a release sheet, the thickness of the release sheet is preferably 10 μm to 300 μm.

  The pressure-sensitive adhesive sheet of the present invention is a method in which a pressure-sensitive adhesive is directly applied to one surface of a base material, or, for example, a pressure-sensitive adhesive layer side is coated on a release surface of a release sheet, and then the pressure-sensitive adhesive layer side is the base material. It can manufacture by the transfer coating method which pastes and transfers on one surface of. Application of the pressure-sensitive adhesive to the substrate surface or release sheet surface can be carried out, for example, with a knife coater, roll coater, roll knife coater, air knife coater, die coater, bar coater, gravure coater, or curtain coater.

  EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but these do not limit the scope of the present invention.

Example 1
Polycarbonate-based polyurethane (Young's modulus = 55 MPa) as a primer on the surface of polyester-based polyurethane, which is made of a polycarbonate-based polyurethane (Young's modulus = 1250 MPa) having a thickness of 7 μm and a polyester-based polyurethane having a thickness of 293 μm (Young's modulus = 15 MPa) Was applied by a microgravure method so that the coating thickness became 1 μm. The Young's modulus of the entire base material after primer application was 50 MPa.
Subsequently, as a monomer component, a copolymer (weight) formed from 2-ethylhexyl acrylate / methyl acrylate / vinyl acetate / acrylic acid (weight component ratio = 49.4 / 24.7 / 24.7 / 1.2) An adhesive obtained by adding 0.2 parts by weight of aluminum tris (acetylacetonate) (weight ratio after drying) to 100 parts by weight of average molecular weight = about 650,000) has a thickness after drying of 60 μm. Thus, an adhesive sheet was prepared by coating on a release paper and transferring it onto the primer layer by transfer coating.

Example 2
The operation described in Example 1 was performed except that the base material was a base material composed of a polycarbonate-based polyurethane having a thickness of 15 μm (Young's modulus = 1250 MPa) and a polyester-based polyurethane having a thickness of 285 μm (Young's modulus = 15 MPa). Was repeated to prepare an adhesive sheet. The Young's modulus of the entire base material after primer application was 80 MPa.

Example 3
The operation described in Example 1 except that the base material is a base material composed of a polycarbonate-based polyurethane having a thickness of 20 μm (Young's modulus = 1250 MPa) and a polyester-based polyurethane having a thickness of 280 μm (Young's modulus = 15 MPa). Was repeated to prepare an adhesive sheet. The Young's modulus of the entire base material after primer application was 100 MPa.

Example 4
Copolymer (weight average molecular weight = about 650,000) formed from 2-ethylhexyl acrylate / methyl acrylate / acrylic acid / maleic anhydride (weight component ratio = 75/25/5/5) as a monomer component. ) A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that 100 parts by weight of the pressure-sensitive adhesive was obtained by adding 0.2 parts by weight of aluminum tris (acetylacetonate) (weight ratio after drying). Created.

<< Comparative Example 1 >>
A pressure-sensitive adhesive sheet was prepared by repeating the operation described in Example 1 except that the base material was polyester-based polyurethane having a thickness of 300 μm (Young's modulus = 15 MPa). The Young's modulus of the whole base material after primer application was 15 MPa.

<< Comparative Example 2 >>
A pressure-sensitive adhesive sheet was prepared by repeating the operation described in Example 1 except that the base material was polyester-based polyurethane having a thickness of 300 μm (Young's modulus = 45 MPa). The Young's modulus of the entire substrate after primer application was 45 MPa.

<< Comparative Example 3 >>
The operation described in Example 1 was performed except that the base material was a base material composed of a polycarbonate-based polyurethane having a thickness of 7 μm (Young's modulus = 1250 MPa) and a polyester-based polyurethane having a thickness of 293 μm (Young's modulus = 80 MPa). Was repeated to prepare an adhesive sheet. The Young's modulus of the whole substrate after primer application was 120 MPa.

"Evaluation of the physical properties"
(1) Young's modulus The Young's modulus was measured at a test speed of 200 mm / min in accordance with JIS K-7127. The measurement direction was the resin flow direction during film formation.

(2) Adhesive strength A sample for measurement (width = 10 mm; length = 100 mm) is cut out from the pressure-sensitive adhesive sheet to be measured, and acid-resistant rain coating with an acid-resistant clear paint for automobiles (KINO 1200TW: Kansai Paint) applied. The steel sheet is crimped by reciprocating a 3 kg roll once. After crimping, after storing for 168 hours in an environment of 23 ° C. and 50% RH, using a universal tensile tester (TENSILON / RTA-100: Orientec Co., Ltd.), the adhesive strength (N / 10 mm).

(3) Holding force A measurement sample (width = 10 mm; length = 80 mm) is cut out from the pressure-sensitive adhesive sheet to be measured, and a pressure of 3 kg is applied to a melamine coated plate to which a primer (LX229G: manufactured by Lintec) is applied in advance. Using a holding force tester that can stick the measurement sample so that the sticking area becomes 10 mm square, backs it with aluminum for preventing elongation, and measures the amount of deviation in μm order over time. The holding force was measured under a load of 9.8 N under an environment of 40 ° C., and the amount of displacement (μm) after 1000 seconds or the time until dropping was measured.

(4) Stress relaxation A measurement sample (width = 10 mm; length = 150 mm) is cut out from the pressure-sensitive adhesive sheet to be measured, and the measurement sample is pulled by a tensile tester (TENSILON RTA) so that the distance between chucks becomes 100 mm. −100: manufactured by Orientec Co., Ltd.) (total length of fixing portion = 45 mm). Subsequently, while pulling at a speed of 200 mm / min, the stress change was continuously recorded, the distance between chucks was 140 mm, and the state was extended by 40% (extended state of 1.4 times the initial length), and then stopped. The load (residual stress) after 3 minutes from the stop was measured in N units.
Note that the anti-chipping adhesive sheet is frequently used in the rear fender of an automobile. As shown in FIG. 4, the rear fender is provided with a groove-like recess 2 in the vehicle body 1, and the angle (θ) of the R portion of the tertiary concave surface of the rear fender is generally within a range of 90 ° to 120 °. It is. When the angle (θ) of the R portion is 120 °, the expansion ratio is approximately 15% (2 / √3), and when the angle (θ) of the R portion is 90 °, the expansion ratio is approximately 40% ( 2 / √2) Therefore, assuming the case of 90 ° considered to be the maximum elongation rate, stress relaxation after 40% elongation was measured.

(5) Concave Surface Floating Test An experiment was performed in which a measurement sample (width = 15 mm; length = 70 mm) was cut out from the pressure-sensitive adhesive sheet to be measured and adhered to the groove-shaped concave portion of the rear fender of the automobile. That is, as shown in FIG. 4, both end portions 10 a and 10 a of the measurement sample 10 are pasted on the surface of the vehicle body 1 across the groove-shaped recess 2 (θ = 120 °), and an intermediate portion of the measurement sample 10 is attached. At 10b, the upper part of the groove-shaped recess 2 was closed. At this time, the intermediate portion 10 b of the measurement sample 10 is not in contact with the inner surface of the groove-shaped recess 2. Subsequently, when the intermediate portion 10b of the measurement sample 10 is pushed in the direction of arrow A toward the inner surface of the groove-shaped recess 2, the both end portions 10a and 10a of the measurement sample 10 are brought into contact with the surface of the vehicle body 1. Since it is fixed, the intermediate portion 10b is stretched and adhered to the inner surface of the groove-shaped recess 2 as shown in FIG. At this time, the intermediate portion 10b was pushed in with a finger, and was securely adhered to the inner surface of the groove-shaped recess 2. After 3 days from this sticking, the degree of adhesion between the inner surface of the groove-like recess 2 and the intermediate part 10b of the measurement sample 10 was visually evaluated in two stages. That is, the case where no float or tunneling occurred was evaluated as “◯”, and the case where float or tunneling occurred was evaluated as “X”.

(6) Convex surface float test A sample for measurement (width = 15 mm; length = 70 mm) was cut out from the pressure-sensitive adhesive sheet to be measured, and an experiment was performed in which the sample was attached to a belt-like convex portion of a rear fender of an automobile. That is, as shown in FIG. 6, the measurement sample 10 was attached to the belt-like convex portion 3 (θ = 120 °) provided on the surface of the vehicle body 1. At this time, the tip 10 t of the measurement sample 10 was stuck so as to reach the base 3 a of the belt-like convex portion 3. After 3 days from this sticking, the degree of adhesion between the surface of the belt-like convex portion 3 and the tip portion 10t of the measurement sample 10 was visually evaluated in two stages. That is, the case where no float or tunneling occurred was evaluated as “◯”, and the case where float or tunneling occurred was evaluated as “X”.

Tables 1 and 2 below show the physical properties measured by the above method.

  The pressure-sensitive adhesive sheet of the present invention can be used for sticking a painted surface of an automobile, and in particular, can be used as a chipping-resistant sheet, a marking sheet, or a surface protective sheet for an adherend having a cubic curved surface.

It is explanatory drawing which shows typically the aspect in the case of sticking an adhesive tape to the strip-shaped groove part of a to-be-adhered body. It is explanatory drawing which shows typically another aspect in the case of sticking an adhesive tape on the strip-shaped groove part of a to-be-adhered body. It is explanatory drawing which shows typically the behavior of the adhesive sheet in a stress strain curve. It is explanatory drawing which shows typically the state which stuck the both ends of the sample for a measurement to the vehicle body surface in the float test in the physical-property evaluation of an Example. It is explanatory drawing which shows typically the state which extended the intermediate part of the sample for a measurement, and was affixed on the internal surface of the groove-shaped recessed part in the float test in the physical-property evaluation of an Example. It is explanatory drawing which shows typically the state which stuck the sample for a measurement on the surface of a strip | belt-shaped convex part in the float test in the physical-property evaluation of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vehicle body; 2 ... Strip groove (groove-shaped recessed part);
3 ... strip-shaped convex part; 3a ... foot of convex part;
2a ... inner surface of the strip groove;
10 ... Adhesive tape (sample for measurement);
10a: both ends of the measurement sample;
10b: middle part of adhesive tape (sample for measurement);
10t: The tip of the adhesive tape.

Claims (6)

A pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer formed on at least one surface of the base material,
(A) Young's modulus of the substrate is 20 to 110 MPa,
(B) When the entire pressure-sensitive adhesive sheet is gradually stretched in a certain direction at a speed of 200 mm / min, the rate of change in elongation stress between the stress in the 10% stretched state and the stress in the 40% stretched state is -50% to + 60%,
(C) The entire pressure-sensitive adhesive sheet is stretched to a 40% stretched state in a certain direction, and the stress relaxation rate after elapse of 3 minutes after stopping the stretching in that state is 30% or more,
(D) the substrate is
(1) One hard layer made of polycarbonate polyurethane having a Young's modulus of 850 to 2000 MPa and a thickness of 1 to 30 μm, and (2) a Young's modulus of 5 to 20 MPa and a thickness. Including one soft layer made of polyester-based polyurethane,
(E) The pressure-sensitive adhesive of the pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive containing a copolymer of an acrylate ester-based monomer, a carboxyl group-containing ethylenically unsaturated monomer, and a polymerizable acid anhydride monomer or vinyl acetate. ,And,
(F) The pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer is formed on the surface of the soft layer.   The inflection point of the stress strain curve exists between a 1% extension point and a 15% extension point when the entire pressure-sensitive adhesive sheet is gradually extended in a certain direction at a speed of 200 mm / min. Item 2. The pressure-sensitive adhesive sheet according to item 1.   The ratio (Th / Tw) of the thickness (Th) of the hard layer to the thickness (Tw) of the entire base material is 1/10 to 1/150. Adhesive sheet.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, further comprising an intermediate hardness layer made of polycarbonate polyurethane between the pressure-sensitive adhesive layer and the soft layer. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, which is affixed to the surface of a coated steel plate of an automobile. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, which is a chipping-resistant sheet, a marking sheet, or a surface protective sheet.

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