JPH10168401A - Printing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a printing sheet which is excellent in strength of adhesion to an adherend, can be easily peeled from the adherend when heated, and is suitable for labels, etc., by forming, on one side of a printing substrate, an adhesive layer contg. expandable microspheres and having a smooth surface together with an intermediate layer sandwiched between the substrate and the adhesive layer and by using a substrate of which the side to be brought into contact with the intermediate layer comprises a porous polymer layer having a specified density. SOLUTION: The printing substrate is a mono- or multilayer-structured sheet which has a porous polymer layer having an apparent density of 0.85g/cm<3> or lower and formed on the side to be brought into contact with the intermediate layer, thus enabling water, etc., in an adherend to evaporate through the substrate. The porous polymer layer is pref. a plastic film having a microvoid structure on the surface or a porous film. The intermediate layer can be formed from a natural rubber or a rubberlike synthetic resin having a Shore D hardness of 50 or lower, pref. 40 or lower, and usually has a thickness of 0.1-150μm. For instance, the expandable microspheres comprise shells and a suitable, easily volatile substance (e.g. isobutane) contained therein and have an average particle size of 1-50μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention has excellent adhesive strength and can be easily peeled off from an adherend by heating at any time, and is suitable for forming labels for adherends containing volatile components such as water. It relates to a sheet for printing.

[0002]

BACKGROUND OF THE INVENTION Heretofore, there has been known a printing sheet in which an adhesive layer containing heat-expandable microspheres is provided on a printing substrate made of a film. This is because the adhesive layer is heated to expand or expand the heat-expandable microspheres so that the adhesive strength can be reduced and the adhesive can be easily peeled off from the adherend. Are used for forming labels for various applications.

[0003] However, unevenness of the heat-expandable microspheres contained in the adhesive layer affects the printing substrate and reduces printability, and the heat-expandable microspheres are exposed on the outer surface of the adhesive layer. There was a problem that the adhesive strength to the adherend was poor. Further, when the adhesive is adhered to an adherend made of modified polyphenylene oxide, polycarbonate, or the like, there is a problem that floating or peeling occurs due to volatile components such as moisture in the adherend.

[0004]

DISCLOSURE OF THE INVENTION The present invention is excellent in both the adhesive strength to an adherend and the effect of lowering the adhesive strength by heat treatment, and hardly causes floating or peeling even when adhered to a volatile matter-containing adherend for a long time. Development of a printing sheet that maintains a good adhesion state.

[0005]

According to the present invention, there is provided a single-layer or multi-layer printing substrate having an adhesive layer containing a heat-expandable microsphere and having a smooth outer surface via an intermediate layer on one surface. At least the side of the printing substrate that contacts the intermediate layer has an apparent density of 0.85.
An object of the present invention is to provide a printing sheet comprising a porous polymer layer of g / cm ³ or less.

[0006]

According to the above-described structure in which the intermediate layer is interposed and the outer surface of the adhesive layer is smooth, excellent printing characteristics with respect to the printing base material, fine ink information can be accurately provided, and the thermal expansion Prevents the spheres from being exposed to the outer surface, secures an effective bonding area, and makes it possible to exhibit adhesive properties comparable to adhesives that do not contain thermally expandable microspheres. It can be easily controlled, can achieve the desired adhesive strength, can be firmly bonded to a rough adherend, and has a high density of thermally expandable microspheres near the adherend. It is also possible.

[0007] Further, by disposing the adhesive layer via the intermediate layer, the force for expanding and / or expanding the heat-expandable microspheres at the processing temperature for expanding and / or expanding the adhesive layer is reduced. The adhesive layer is three-dimensionally deformed into a wave structure or a corrugated structure overcoming the drag due to the elastic modulus. As a result, the reduction of the bonding area due to the heat treatment is efficiently achieved, the reduction of the bonding strength is surely realized, the bonding strength is excellent, and the separation operation can be easily performed. It can be performed reliably. Further, the printing substrate has an apparent density of 0.85 on at least the side in contact with the intermediate layer.
By having a polymer layer of g / cm ³ or less, volatile matter such as moisture in the adherend permeates and diffuses into the printing sheet and volatilizes from the side surface, etc. Stable and lasting.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The printing sheet of the present invention comprises a single-layer or multi-layer printing substrate having an adhesive layer containing heat-expandable microspheres and having a smooth outer surface on one side via an intermediate layer. At least the side of the printing substrate in contact with the intermediate layer comprises a porous polymer layer having an apparent density of 0.85 g / cm ³ or less. Examples thereof are shown in FIGS. 1 is a printing substrate, 2 is an intermediate layer, 3 is an adhesive layer,
Reference numerals 2 and 13 denote layers forming a printing substrate having a multilayer structure, and 31
Is the outer surface layer of the adhesive layer. Reference numeral 4 denotes a separator provided as needed. The figure shows a label obtained by adding ink information to a printing base material, and 5 is the ink information.

As the printing substrate, a single layer structure or a multilayer structure having a porous polymer layer having an apparent density of 0.85 g / cm ³ or less at least on the side in contact with the intermediate layer is used. Therefore, in the single-layer structure as illustrated in FIG. 1, the entire printing substrate is formed of the porous polymer layer having the apparent density, and in the multilayer structure as illustrated in FIG. At least the side in contact with the intermediate layer 2 is formed of the porous polymer layer 13 having the apparent density. By disposing such a porous polymer layer, it becomes possible to volatilize volatile components in the adherend through the printing substrate. The apparent density of the porous polymer layer, which is preferable from the viewpoint of its volatility, is 0.10 to 0.10.
0.83g / cm ^3, which is especially 0.15~0.80g / cm ^3.

The above-mentioned porous polymer layer only needs to exhibit a predetermined apparent density based on its porous structure, and therefore, the form of the printing substrate is not particularly limited. A porous polymer layer more preferable in terms of volatility and the like is a plastic film or a porous film having a microvoid structure on the surface. The thickness of the printing base material is generally 500 μm or less, particularly 5 to 250 μm, but is not limited thereto.

[0011] The printing substrate having a multilayer structure may be a porous substrate such as paper, cloth or non-woven fabric, and / or other conventional printing substrate and a porous polymer layer by a heat fusion method or an adhesive method. It can be obtained as a laminate of two layers or three or more layers composed of a laminate or the like by an appropriate method such as a method using an agent. Above all, it is preferable that the entire printing substrate is formed porous from the viewpoint of volatility and the like, and that the porous polymer layer is formed of a plastic film or a porous film having the microvoid structure described above. Is preferred. The thickness of each layer forming the multilayer substrate can be appropriately determined, but is generally 50
0 μm or less, especially 1 to 250 μm or less, especially 3 to 200 μm
m.

The plastic forming the porous polymer layer and other base material is not particularly limited, and any suitable plastic may be used according to the purpose of use of the printing sheet. In general, for example, olefin resins such as polyethylene and polypropylene, ethylene-propylene copolymer and ethylene-vinyl acetate copolymer, polystyrene and polyvinyl chloride, vinyl chloride-vinyl acetate copolymer and polyvinyl acetate, polyvinyl butyral and polyvinyl Vinyl resins such as formal, polyvinyl acetal and polyvinyl hydroxide, cellulose resins such as ethyl cellulose and cellulose acetate, and polyester resins such as polyethylene terephthalate and polyethylene naphthalate are used.

In addition, polyurethane resins, various polyamide resins such as aliphatic and aromatic resins, xylene resins,
Polycarbonate resin, acrylic resin such as polymethyl methacrylate or polyacrylate, acetal resin, polyarylate, polyvinylidene chloride, styrene / isoprene copolymer or styrene / butadiene rubber, rubber polymer such as nitrile rubber or polybutadiene, polyimide Polyether ether ketone, polyether sulfone, polyether imide, polysulfone, polyphenylene sulfide, polyamide imide, polyester imide, polyparabanic acid, silicone resin, and fluorine resin such as polytetrafluoroethylene are also generally used. In addition, two or more plastics can be blended and used.

The formation of a plastic film or a porous film having a microvoid structure on the surface for forming the porous polymer layer described above includes, for example, a method of casting a polymer dispersion such as an emulsion or a method of stretching a film. A method of removing the mixed fine particles from the film mixed with the fine particles for removal by elution treatment, a method of perforating the film by embossing, a sintering method of fusing the polymer powder under heating, a solvent of the polymer, While the coating layer contains a solvent and the coating layer contains a solvent and is in an undried state, the coating layer is sprayed with a coagulating solvent that is compatible with the solvent and does not dissolve the polymer. An appropriate method such as a method of solidifying a layer can be used.

As the paper that may be used for forming the printing base material, for example, any suitable paper such as high-quality paper, coated paper, art paper, glassine paper, kraft paper, or impregnated paper can be used. Further, as the cloth or nonwoven fabric, for example, those made of suitable fibers such as amide-based or polyester-based fibers can be used.

The printing substrate may contain various additives or chemicals. Examples thereof include a colorant such as a white pigment for the purpose of improving the contrast with the pattern to be provided and an antioxidant for the purpose of improving the durability. For the purpose of improving the fixing power of ink information and the adhesion of the intermediate layer, the printing base material may be subjected to chemical etching treatment such as chromic acid treatment, ionizing radiation treatment such as corona treatment or plasma treatment, ozone exposure or flame exposure. Or a surface treatment such as a chemical or physical treatment for oxidizing the surface by exposure to high voltage or high voltage electric shock. Further, a primer layer or the like can be provided for the purpose of improving the adhesion to the intermediate layer. A printing substrate made of a highly polar polymer such as polyester exhibits a strong adhesive force to the intermediate layer.

In the present invention, the intermediate layer and the adhesive layer containing the heat-expandable microspheres are a composite for achieving good adhesive strength and a sufficient decrease in adhesive strength by heat treatment. Such a purpose can be achieved by forming a laminated structure in which the adhesive layer 3 is arranged on the base material 1 for use with the intermediate layer 2 interposed therebetween.

When the printing sheet is adhered to the adherend, the surface of the intermediate layer follows the surface shape of the adherend satisfactorily to provide a large adhesive area, and the intermediate layer is peeled off from the adherend. The adhesive layer is heated to expand the heat-expandable microspheres and / or
Or the function of reducing the restraint of foaming and / or expansion in the plane direction of the printing sheet during expansion to promote the three-dimensional deformation of the adhesive layer into a undulating structure, and the effect of the heat-expandable microspheres And improves the ability to impart fine ink information to the printing substrate.

The intermediate layer may have a hardness of 50 or less based on Shore D hardness according to ASTM D-2240 D type Shore.
Preferably, it can be formed of 40 or less natural rubber or synthetic rubber, or a synthetic resin having rubber elasticity. The thickness is generally 0.1 to 150 μm.

Examples of the synthetic rubber or synthetic resin include synthetic rubbers such as nitrile, diene and acrylic, thermoplastic elastomers such as polyolefin and polyester, ethylene-vinyl acetate copolymer, polyurethane, polybutadiene, and the like. Synthetic resins having rubber elasticity, such as soft polyvinyl chloride. In the present invention, an essentially hard polymer, such as polyvinyl chloride, having rubber elasticity in combination with a compounding agent such as a plasticizer or a softening agent may be used.

The intermediate layer may be formed by a method such as applying a solution of a component composed of natural rubber, synthetic rubber or synthetic resin having rubber elasticity, or a method of bonding a film or the like composed of the component to a printing substrate. May be performed in any suitable manner. In the present invention, the intermediate layer may be formed of a pressure-sensitive adhesive substance containing natural rubber, synthetic rubber, or a synthetic resin having rubber elasticity as a main component, or may be formed of a foamed film or the like mainly containing such a component. May be.

When the printing sheet adhered to the adherend is peeled off from the adherend at any time, the adhesive layer forms the above-mentioned composite through foaming and / or expansion of the heat-expandable microspheres by heating. The object is to change the volume of the body to reduce the area of adhesion to the adherend, so that the printing sheet can be easily peeled off from the adherend. The formation of the adhesive layer can be generally performed using the heat-expandable microspheres and the adhesive.

As the heat-expandable microspheres, various microspheres capable of achieving the above object can be used. Examples thereof include those in which an appropriate substance that easily gasifies and exhibits thermal expansion properties, such as isobutane, propane, or pentane, is encapsulated in a shell-forming substance by a coacervation method, an interfacial polymerization method, or the like. . The average particle size of the thermally expandable microspheres used is generally 1 to 50 μm.

As the shell-forming substance forming the heat-expandable microspheres, for example, vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, polysulfone and the like are generally used. However, in the present invention, any material may be used as long as it is made of a heat-meltable substance or a substance which is destroyed by thermal expansion.

As the adhesive, polymers such as rubber or resin which allow expansion and / or expansion of the heat-expandable microspheres, preferably expansion and / or expansion of the heat-expandable microspheres are used as much as possible. An unrestricted one is used, and an appropriate adhesive can be usually selected and used according to the target adhesive strength of the printing sheet to the adherend. Commonly used ones include a low-temperature activation type heat-activatable adhesive, a water- or organic-solvent-activatable adhesive, or a pressure-sensitive adhesive. Among others, the function of the adhesive layer in the present invention A pressure-sensitive adhesive is preferably used from the viewpoints of simplicity and adhesion to an adherend.

Examples of the above-mentioned low-temperature activation type heat-activatable adhesive or water- or organic-solvent-activated adhesive include hot melt adhesives, silicone adhesives, fluorine adhesives, and the like.
An ultraviolet-curing adhesive, a hot pressure-sensitive adhesive containing a low melting point heat-fusible resin and exhibiting a strong adhesive strength by heating at room temperature with a low adhesive strength (Japanese Patent Application Laid-Open No. 56-13040, JP-B-56-13040, -50146) and the like.

Examples of the pressure-sensitive adhesive include a rubber-based pressure-sensitive adhesive having a base polymer of natural rubber or various synthetic rubbers, a polymer of an alkyl ester of acrylic acid or methacrylic acid, or another unsaturated monomer. Pressure-sensitive adhesive having a copolymer with a base as a base polymer, a polymer having a weight-average molecular weight of about 10,000 to 3,000,000 as a base polymer, and a polyisocyanate compound or an alkyl etherified melamine compound as required. Styrene-conjugated diene block copolymer-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, UV-curable pressure-sensitive adhesives, creep-improved pressure-sensitive adhesives, etc. (JP-A-56-61468, JP-A-61-174857, JP-A-63-174857).
17981, JP-B-56-13040).
The adhesive may contain appropriate additives such as a plasticizer, a filler, an antioxidant, and a tackifier in addition to the crosslinking agent.

The adhesive layer may be formed by, for example, mixing the heat-expandable microspheres and the adhesive with a solvent if necessary, and applying the mixture on the intermediate layer, or the adhesive layer on a separator. Can be formed by an appropriate method such as a method of transferring the film onto the intermediate layer.

The content ratio of the heat-expandable microspheres in the adhesive layer is generally 10% by weight or more, especially 15 to 95% by weight, in view of the initial adhesive strength and the adhesive strength decreasing property after heat treatment. , Preferably 20 to 80% by weight. The thickness of the adhesive layer and the expansion ratio are appropriately determined depending on the surface shape and material of the adherend, and are generally 500 μm or less, preferably 1 to 20 μm.
The thickness is 0 μm, especially 3 to 70 μm. The expansion ratio is
It is preferable to design so as to be about 1.5 to 100 times.

The distribution ratio of the heat-expandable microspheres in the adhesive layer is determined by the fact that the distance between the heat-expandable microspheres is equal to the maximum diameter due to the fact that the printing sheet is reliably separated from the adherend by heating. It is preferable that the microspheres are densely packed at a distance of 7 times or less, particularly 3 times or less the diameter of the microspheres having the following.

The purpose of smoothing the outer surface of the adhesive layer is to prevent the effective adhesive area from being reduced due to the unevenness due to the exposure of the heat-expandable microspheres on the outer surface, thereby preventing the adhesive strength from being reduced.
Such smoothing is carried out by an appropriate method such as a method of forming an adhesive layer under pressure on a smooth surface as necessary, or a method of forming a printing sheet and then pressing through a smooth pressure roller or the like. be able to. Further, as shown in the figure, a method may be adopted in which an adhesive layer containing no heat-expandable microspheres is attached to the outer surface of the adhesive layer to form a smooth layer 31 on the outer surface.

Although the above-described separate adhesive layer provision method has the disadvantage of increasing the number of manufacturing steps of the printing sheet, it exhibits an adhesive property comparable to an adhesive containing no heat-expandable microspheres, and is applied to an adherend. There is an advantage that the adhesive strength can be easily controlled. In addition, the adhesive in the portion containing the heat-expandable microspheres does not need to consider the adhesive force to the adherend, and only needs to function as a simple binder of the heat-expandable microspheres that allows foaming and / or expansion. Therefore, there is an advantage that an adhesive (binder) that is different from the attached adhesive layer and that is advantageous for the expansion and / or expansion of the heat-expandable microspheres can be used.

The attached adhesive layer can be formed by an appropriate method such as a method of applying the adhesive layer on the thermally expandable microsphere-containing layer or a method of transferring the adhesive layer on the separator. From the point of adhesion to the adherend and releasability of the printing sheet due to heat treatment, etc., about 0.1 to 50 μm, preferably 0.5 to 50 μm
30 μm is preferred. The adhesive layer is preferably protected by, for example, bonding the separator 4 until it is put to practical use as shown in the figure, particularly in the case of a pressure-sensitive adhesive layer.

In the above, a high-polarity compound such as a water-absorbing resin or an emulsifier, a hydrophilic compound, or a water-absorbing compound may be added to the intermediate layer or the adhesive layer, if necessary, for the purpose of improving moisture permeability. it can. The moisture permeability can also be improved by forming the intermediate layer or the adhesive layer as a porous layer. The formation of the porous intermediate layer or the adhesive layer is, for example, a method of spreading the forming material of the intermediate layer or the adhesive layer into a fibrous form by a melt blow method or a curtain spray method, a method of applying a pattern in a dot form, and the like. It can be performed by an appropriate method.

The printing sheet of the present invention can also be formed by, for example, a method of separately forming a composite comprising an intermediate layer and an adhesive layer and bonding the composite to the printing substrate via the intermediate layer side. The printing sheet obtained can be firmly adhered to the adherend at the time of adhesion, and can be easily separated or separated from the adherend by heat treatment when it is desired to release the adhesion state. It can maintain a good adhesive state for a long time without floating or peeling off on an adherend containing volatile components such as.

Accordingly, the printing sheet of the present invention is adhered to a suitable adherend containing a polymer such as a modified polyphenylene oxide or a polycarbonate resin, or a volatile matter such as water such as a fiber molded product or wood for a predetermined period of time. It can be preferably used in various applications where it is required or desired to release the bonded state after achieving the bonding purpose, for example, a bar code label for a recycled product or a masking label.

The label can be obtained by adding necessary information such as ink information 5 or a pattern to the printing substrate 1 in the printing sheet as shown in the figure. Therefore, the label can be formed by a method according to the related art, the ink used, the pattern forming method such as the printing method, and the like are arbitrary, and the application information such as the pattern is also arbitrary.

The heat treatment conditions for allowing the printing sheet or label to be easily peeled off from the adherend include a decrease in the adhesive area due to the surface condition of the adherend, the type of the heat-expandable microspheres, and the like. It is determined by conditions such as the heat resistance of the printing substrate and the adherend.
~ 90 seconds. The heat treatment can be performed at an appropriate stage depending on the purpose of use.

[0039]

【Example】

Example 1 A mixture of a copolymer consisting of 50 parts of butyl acrylate (parts by weight, the same applies hereinafter), 50 parts of ethyl acrylate and 5 parts of acrylic acid to which 2 parts of a crosslinking agent was added was used to give an apparent density of a polymer material. Is coated on one side of 0.77 g / cm ³ YUPO paper (Oji Yuka Synthetic Paper Co., Ltd., FPG-80, the same applies hereinafter) and dried to provide a rubbery organic elastic layer (intermediate layer) having a thickness of 15 μm. A mixed solution containing the heat-expandable microspheres was applied thereon and dried at a low temperature to provide an adhesive layer having a smooth outer surface and a thickness of 40 μm to obtain a printing sheet.

The above-mentioned mixed solution is made of butyl acrylate 80
Parts, 15 parts of ethyl acrylate and 5 parts of acrylic acid having a weight average molecular weight of 250,000 and an average particle size of 15 μm.
m, a mixture of 60 parts of thermally expandable microspheres having a specific gravity of 1.01 and 2 parts of a polyisocyanate crosslinking agent.

Example 2 A blend of 94 parts of butyl acrylate, 3 parts of vinyl acetate, and 3 parts of acrylic acid to which 2 parts of a crosslinking agent had been added was coated on a Yupo paper laminated with a 30 μm-thick polypropylene film. It was applied and dried to provide a 30 μm thick intermediate layer, on which a 50 μm thick adhesive layer was provided according to Example 1 to obtain a printing sheet.

Example 3 An intermediate layer was provided on a nonwoven fabric (ELTAS N01020, manufactured by Asahi Kasei Kogyo Co., Ltd.) having an apparent density of 0.21 g / cm ³ made of a polymer material laminated with a polypropylene film having a thickness of 30 μm. A printing sheet was obtained according to Example 2.

Comparative Example 1 A printing sheet was obtained in the same manner as in Example 1 except that a 50 μm-thick polyester film (non-porous) was used as a printing substrate.

Comparative Example 2 A printing sheet was obtained in the same manner as in Example 2 except that a 50 μm-thick polyester film (non-porous) laminated with a 30 μm-thick polypropylene film was used as a printing substrate. Was.

Evaluation Test The following characteristics were examined for the printing sheets obtained in the examples and comparative examples. Adhesion Maintainability The printing sheet was adhered to the modified polyphenylene oxide plate via the adhesive layer, and heated at 50 ° C. for 24 hours to check for occurrence of floating.

Adhesive Strength A printing sheet having a width of 20 mm was adhered to a modified polyphenylene oxide plate, and its 180-degree peel adhesive force (peeling speed: 30)
0mm / min, 23 ° C) before heating (initial)
The adhesive strength and the adhesive strength after heat treatment at 170 ° C. for 45 seconds were examined.

The results are shown in the following table. The table also shows the apparent density of the printing substrate on the printing side and the contact side (inside) of the intermediate layer.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a label.

FIG. 2 is a cross-sectional view of another label example.

[Description of Code] 1: Printing substrate (11, 12, 13: substrate forming layer) 2: Intermediate layer 3: Adhesive layer (31: outer surface layer) 5: Ink information

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshiyuki Oshima 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation

Claims (4)

[Claims] 1. A printing substrate having a single-layer or multi-layer structure, comprising an adhesive layer containing heat-expandable microspheres and having a smooth outer surface via an intermediate layer on one surface of the printing substrate. A printing sheet, characterized in that at least the side of the material that contacts the intermediate layer is made of a porous polymer layer having an apparent density of 0.85 g / cm ³ or less. 2. The printing sheet according to claim 1, wherein the intermediate layer comprises a layer having rubber elasticity, and the adhesive of the adhesive layer comprises a pressure-sensitive adhesive substance. 3. The method according to claim 1, wherein the distance between the heat-expandable microspheres in the adhesive layer is not more than 7 times the diameter of the microsphere having the largest diameter. Printing sheet for bonding to an adherend containing volatile components. 4. A label obtained by adding ink information to a printing substrate in the printing sheet according to claim 1.