HK1010208B - Pressure-sensitive adhesive sheet and laminate of pressure-sensitive adhesive sheets - Google Patents

Description

Self-adhesive sheet and laminate of self-adhesive sheets

The present invention relates to a pressure-sensitive adhesive sheet and a laminate of pressure-sensitive adhesive sheets. More particularly, it relates to a pressure-sensitive adhesive sheet and a laminated product composed of a plurality of the above sheets laminated on each other. The sheet and laminate are both roll-up resistant and are preferably used as a home delivery label, merchandise display label, warning label and the like for attaching to merchandise, merchandise packaging, etc. on a home delivery.

Conventionally, a label is attached to a surface of a commodity or a commodity package to display the kind of the commodity, purchase, sale, or the like. Previously, display labels such as door-to-door labels, product display labels and warning labels have been used in a manner that the display label is laminated on a carrier sheet, the display label being composed of release paper and being in a sheet and tape form which is peeled off from a sheet-type carrier sheet or is peeled off therefrom after cutting a tape-type carrier sheet at a designated place.

However, such labels have the disadvantage that the release paper remains as waste, with the increase in the number of release papers used, the waste is correspondingly increased and with this environmentally undesirable consequences, and furthermore the worker is at risk of injury at the moment when cutting the carrier foil in the form of a tape.

In order to overcome the above-mentioned disadvantages, japanese utility model registration No. JP-3003840 proposes a laminate composed of a plurality of non-drying adhesive sheets laminated on each other, each of which comprises a backing sheet, a non-drying adhesive layer formed by applying a non-drying adhesive on one side of the backing sheet and leaving an uncoated portion at the edge (periphery) thereof, and an anti-sticking layer formed on the other side of the backing sheet, the above-mentioned non-drying adhesive layer and the above-mentioned anti-sticking layer being directly opposed to each other. The above-mentioned tack-free sheets have the advantage that the sheets can be peeled off one by one and adhered to an object in a relatively simple manner, with high working efficiency and safety, without causing waste such as release paper.

However, since a cured product obtained from a conventional heat-curable silicone resin is used in the release layer of the pressure-sensitive adhesive sheet constituting the aforementioned laminate and the silicone resin is cured at a high temperature of about 100 ℃ to 200 ℃ in the step of preparing the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet inevitably rolls up in terms of deformation of the liner sheet objectively due to heat and expansion and shrinkage of the liner sheet caused by release and absorption of moisture. In addition, a large-scale apparatus and a long working time are required. And most of the heat-curable silicone resins have problems of adversely affecting safety, sanitation and environment due to the use of a large amount of solvent in the preparation process. Fig. 1 is a perspective view showing a conventional sticker laminate rolled up at one edge thereof.

On the other hand, recently developed UV and EB curing systems respectively utilize ultraviolet rays (UV) and Electron Beams (EB) and are characterized in that they enable silicone resins to be cured under solvent-free conditions and at low temperatures, thus contributing to reduction of pollution, energy and labor saving, and furthermore making it possible to produce high-quality coatings. The above systems thus find wide application in many fields such as paints, inks, adhesives, coating agents, resists, photosensitive printing plates and dental filling materials.

Under such conditions, the present invention aims to provide a self-adhesive sheet and a laminate comprising a plurality of such sheets laminated on each other. The sheet and laminate can be efficiently produced by using a simple apparatus and are very suitable for display labels and the like.

In order to achieve the above object, as a result of extensive studies and developments accumulated by the present inventors, it has been found that the above object can be attained by using, as a release layer of a tack sheet, a layer containing a cured product obtained from a peelable resin which is curable at a low temperature by ionizing radiation of UV, EB or the like. The present invention has been accomplished using the above findings and information.

Specifically, the present invention provides a pressure-sensitive adhesive sheet comprising a backing sheet, a pressure-sensitive adhesive sheet formed at least in a part of one side of the backing sheet, and a release layer comprising a cured product obtained from an ionizing radiation-curable releasable resin formed at least in a part of the other side of the backing sheet; and providing a laminate comprising a plurality of release sheets laminated to each other so that the pressure-sensitive adhesive sheet and the release layer are directly opposed to each other and the entire surface of the pressure-sensitive adhesive sheet is covered with the release layer.

Brief description of the drawings: fig. 1 is a perspective view showing an example of a conventional tack sheet laminate, fig. 2 is a sectional view showing an example of a tack sheet laminate of the present invention, fig. 3 is a sectional view showing another example of a tack sheet of the present invention, and fig. 4 is a sectional view showing an example of a tack sheet of the present invention, in which symbols are described below. 1: liner sheet 2: adhesive sticker thin layer 3: and (4) an anti-sticking layer: sealing layer 5: sealing layer 6: printing layer 7: release sheet 10: self-adhesive sheet 11: tack-free sheet 12: self-adhesive sheet 20: release sheet a: end B: end tip

First, a laminate of a self-adhesive sheet and the sheet is explained with reference to the drawings according to the present invention.

Fig. 2 and 3 show cross-sectional views of examples of laminates of a self-adhesive sheet of the present invention, which are distinguished from each other.

FIG. 2 is a cross-sectional view of a laminate in which a plurality of release sheets laminated each have a pressure-sensitive adhesive sheet in the same place relative to each backing sheet. Fig. 2 shows a structure in which a pressure-sensitive adhesive sheet 10 of the present invention having an underlying sheet 1 is attached with a pressure-sensitive adhesive sheet 2 on one side thereof and provided with a release layer 3 on the other side thereof to occupy at least an area opposite to the pressure-sensitive adhesive sheet 2, that is, a back face right at a place where the pressure-sensitive adhesive sheet 2 is formed, the pressure-sensitive adhesive sheets 10 are laminated one by one in a plurality so that the pressure-sensitive adhesive sheet 2 and the release layer 3 are directly opposite to each other and the surface of the pressure-sensitive adhesive sheet 2 which is in contact with the release layer 3 is completely covered therewith.

On the other hand, FIG. 3 is a sectional view of a laminate in which a plurality of laminated release sheets each have a pressure-sensitive adhesive sheet at mutually different positions with respect to each liner sheet. Fig. 3 also shows a structure in which a pressure-sensitive adhesive sheet 11 of the present invention having an under sheet 1 is attached with a pressure-sensitive adhesive sheet 2 at one side end a thereof and with a release layer 3 at the other side end B thereof, and a plurality of pressure-sensitive adhesive sheets 11 are laminated one on another so that the pressure-sensitive adhesive sheet 2 and the release layer 3 are directly opposed to each other and the surface of the pressure-sensitive adhesive sheet 2 in contact with the release layer 3 is completely covered therewith.

In fig. 2 and 3, 20 denotes a release sheet.

Fig. 4 shows a cross-sectional view of an example of a self-adhesive sheet according to the present invention which is different from the aforementioned sheets 10, 11, and indicates a structure in which a backing sheet 1 is provided on one side thereof with a sealing layer 4 and a pressure-sensitive adhesive sheet 2 in order, and on the other side thereof with a sealing layer 5, a printing layer 6 and a release layer 3 in order. In a release sheet 12 having such a sealing layer, the pressure-sensitive adhesive sheet 2 and the release layer 3 may each be located on one side and the other side of the backing sheet 1, respectively as shown in fig. 2, on the same end associated with the sheet 1 or as shown in fig. 3, on ends different from each other associated with the sheet 1.

The backing sheet used in the inventive release sheet is not particularly limited, but a sheet previously used as a display label in general may be selectively used. Examples of backing sheets include (the term "including" is intended to include but not be limited to) paper such as wood-free paper, cellophane and coated paper, and plastic sheets such as polyester sheets, polyolefin sheets and polystyrene sheets. The thickness of the backing sheet is not particularly limited but may be suitably selected depending on the case, and is often in the range of 10 to 300. mu.m, preferably 50 to 150. mu.m.

In the case where a plastic sheet is used as the backing sheet, in order to improve the adhesiveness between the plastic sheet and the thin layer placed thereon, the plastic sheet can be subjected to roughening treatment such as sandblasting or solvent treatment, such as oxidation treatment with corona discharge, ozone ultraviolet irradiation, flame, chromic acid or hot air treatment, as required, on either one side or both sides thereof.

In the present invention, a pressure-sensitive adhesive sheet is placed on one side of the backing sheet and an anti-sticking layer is placed on the other side thereof. In the case where the backing sheet is composed of paper or nonwoven fabric, a sealant layer may be interposed between the backing sheet and the pressure-sensitive adhesive sheet as required. Further, either one or both of the sealing layer and the printed layer may be interposed therebetween in order as necessary.

The above-mentioned sealing layer is used for the purpose of preventing the permeation of the releasing agent, the pressure-sensitive adhesive and/or the ink into the backing sheet, for the purpose of improving the concealing property of the backing sheet, for the purpose of improving the adhesiveness between the backing sheet and the pressure-sensitive adhesive sheet, the releasing layer or the printed layer, or for the purpose of improving the printing property. In the case where the liner sheet is made of paper and is excessively soft, the seal layer serves the purpose of imparting rigidity to the sheet. The sealing layer is exemplified by a layer generally composed of a styrene-butadiene copolymer, an acrylic-based resin, a polyester-based resin, a polyurethane-based resin, or the like as a main component, and, as needed, a filler such as clay, silica, calcium carbonate, titanium oxide, and zinc oxide, which is impregnated into the main component. The thickness of the sealing layer is typically in the range of 0.1-30 μm.

In the present invention, the provided printed layer can be formed by a general printing method, when necessary, for example, by using a binder such as an acrylic-based resin, a polyurethane-based resin, a butyral-based resin, a nitrocellulose-based resin, an acetylcellulose-based resin, a polyester-based resin, a polyvinyl chloride-based resin, and a vinyl chloride/vinyl acetate-based copolymer resin, and gravure printing, screen printing, offset printing, and flexographic printing containing a colorant such as a pigment and a dye, an extender pigment, a solvent, and the like.

The release layer can be placed directly on the print layer, but can be placed on a protective layer positioned to protect the print layer as desired. The protective layer is exemplified by a layer composed of a polyvinyl resin, polyvinyl alcohol, acrylic-based resin, starch, alkyd resin, etc. The thickness of the protective layer is typically in the range of 0.1-30 μm.

The release layer used in the present invention is a thin layer containing a cured article obtained from an ionizing radiation-curable release resin. The ionizing radiation-curable release resin needs only to be cured with ionizing radiation at low temperatures and shows no particular limitation on the release properties of the adhesive sheet layer.

The ionizing radiation is exemplified by ultraviolet rays and electron beams, preferably ultraviolet rays. Ultraviolet rays are obtained by a high-pressure mercury vapor lamp, a fusion hydrogen lamp, a xenon lamp, etc., and electron beams are obtained by an electron beam accelerator. The ionizing radiation-curable release resin is exemplified by a resin which is curable with, for example, ultraviolet rays and is of the radical addition type, radical polymerization type, platinum addition type, cation curing type, etc. The curing characteristics of the ultraviolet curing type and the conventional heating curing type are collected in table 1.

TABLE 1

	Ultraviolet curing				Heat curing
						Free radical addition molding	Free radical polymerization	Platinum addition type	Cation curing type	Addition condensation type
	Curing temperature (. degree.C.)	0～80	0～80	0～80	0～80						100～200
Curing time (seconds)						1≥	1≥	3～5	1≥	10～30
	Curing Properties	Good taste	Good taste	Not good	Good taste						Good taste
Curing device						Small	Small	Small	Small	Big (a)
	Processing workability	Is easy to use	Is easy to use	Is easy to use	Is easy to use						Difficulty in

As can be seen from table 1, the curing temperature of any ultraviolet curable resin is lowered, the curing time is shortened, the curing apparatus is reduced and the process workability becomes easy as compared with the conventional heat curable resin. Such a lowered curing temperature is effective for preventing the final sticker sheet from being rolled up due to deformation thereof or absorption/release of moisture.

In the present invention, any of the above-described ultraviolet-curable resins of radical addition type, radical polymerization type, platinum addition type and cation curing type may be used as the ionizing radiation-curable release resin. Among them, platinum addition type resins involve a problem that a long time is required for curing and thus curability is low, but this problem can be solved by increasing the amount of ultraviolet radiation.

On the other hand, although not shown in table 1, the cation curable resin is easily inhibited from curing by a basic substance. Accordingly, in the case of using a cationically curable resin in the release layer and when the alkaline substance is contained in a thin layer in contact with the release layer, it is preferable that a barrier layer is interposed between the thin layer and the release layer. For example, in the case where the alkali substance for inhibiting curing is contained in the backing sheet or the ink for printing, it is preferable that a barrier layer is placed between the backing sheet or the printed layer and the release layer so that the alkali substance does not cause a side effect on the release layer. Needless to say, the barrier layer may double as a protective layer for the above-mentioned protective printed layer.

The barrier layer need only be separated from the alkaline species and impart film-forming properties. The substance for the barrier layer may be appropriately selected from a so-called clear varnish and a resin for the above-mentioned protective layer, provided that the substance satisfies the above-mentioned requirements. In the case where the pressure-sensitive adhesive thin layer is composed of a general crosslinking type pressure-sensitive adhesive thin layer (crosslinked with an organic-based crosslinking agent), the thin layer is difficult to peel. However, this problem is solved by using a thin layer of non-crosslinked or crosslinked non-crosslinked sticker with a metal-based crosslinking agent.

As mentioned above, it is advantageous to actually use a uv-sensitive platinum addition type silicone resin or a uv-sensitive cationic curing type silicone resin as the above-mentioned four types of ionizing radiation curing type release resins, whereas a large-scale apparatus is not required in the present invention, and a uv-sensitive silicone resin is often used for the need of release properties.

Examples of UV-sensitive free-radical addition-type silicone resins include an alkenyl-containing silicone, a mercapto-containing silicone, and a photocatalyst mixture. The photocatalyst is not particularly limited, but exemplified by acetophenone, phenylethylketone, benzophenone, xanthone, benzaldehyde, anthraquinone and fluorenone.

The ultraviolet-sensitive, radical-polymerizable silicone resin is exemplified by a mixture of a silicone-based oligomer and/or monomer to which an acryloyl group is introduced, and a silicone-based oligomer and/or monomer (1), and at least one compound (2) of an acrylic-based oligomer and/or monomer, and a photopolymerization initiator (3). The photopolymerization initiator is not particularly limited, but may be suitably selected from known compounds which generate a radical under irradiation of ultraviolet rays and are exemplified by an organic peroxide, a carbonyl compound, an organic sulfur compound and an azo compound.

On the other hand, examples of the ultraviolet-sensitive platinum addition type silicone resin include a mixture of monomethylvinylpolysiloxane and methylhydrogenpolysiloxane (each of which introduces a polyfunctional vinyl group), and a platinum-based catalyst. The platinum-based catalyst used therein is not particularly limited as long as it shows photoactivity, and a photoactive catalyst such as bis (2, 4-glutaric acid) platinum, (1, 5-cyclooctadiene) diphenyl platinum and (2, 4-hexadiene) diphenyl platinum and a mixture of the above catalyst components with a photodegradation-controlling agent represented by ethyl azo carboxylate can be illustrated.

Examples of the ultraviolet-sensitive cationically curable silicone resin include a mixture of a siloxane-based oligomer and/or monomer having a vinyl ether group or epoxy group incorporated therein and a cationic photopolymerization catalyst. The cationic photopolymerization catalyst is not particularly limited, but is exemplified by known compounds of cationic photopolymerization catalysts such as triarylsulfonium salt, triaryliodonium salt, and bis (dodecylbenzene) hexafluoroantimonate.

The release layer in the present invention can be formed by the following steps: for example, a thin layer composed of the above ultraviolet-sensitive silicone resin is placed on any of the underlayer sheet, the sealing layer, the printing layer, the protective layer and the barrier layer and cured by irradiating the above thin layer with ultraviolet rays having a wavelength of preferably 200-400nm, more preferably 200-300nm (for the cation-curable silicone resin) and with ultraviolet rays having a wavelength of 300-400nm (for the platinum-addition-type silicone resin) at about 0 to 80 ℃. The release layer may contain an antioxidant, a heat stabilizer, etc., as needed. The thickness of the release layer cannot be specified too clearly, but it may be generally specified in the range of 0.1 to 10.0. mu.m, preferably in the range of 0.5 to 4.0. mu.m, depending on the case.

The release layer does not have to be provided on the entire surface of the backing sheet, but as already explained in the description of fig. 2 and 3, only has to be provided on at least a part of the surface of the backing sheet opposite to the pressure-sensitive adhesive sheet, often in a position corresponding to the pressure-sensitive adhesive sheet of another pressure-sensitive adhesive sheet laminated on the pressure-sensitive adhesive sheet of the present invention. By partially disposing the release layer in the above manner, it becomes possible to perform embossing and writing on the portion without the release layer. Any sealing, printing, protective and barrier layers which are placed between the backing sheet and the release layer as required are preferably placed in the region corresponding to or over a larger area than the above-mentioned release layer.

The pressure-sensitive adhesive sheet formed on the backing sheet opposite to the release layer or on the sealing layer placed as required is a pressure-sensitive adhesive-containing sheet. The above adhesive sticker is not particularly limited, but is exemplified by known compounds such as acrylic-based, rubber-based and silicone-based adhesive stickers. From the viewpoint of the releasing property between the non-adhesive thin layer and the releasing layer and the adhesiveness between the pressure-sensitive adhesive thin layer and the adherend, among them, non-crosslinked pressure-sensitive adhesives and pressure-sensitive adhesives crosslinked with any of a metal-based crosslinking agent and an organic-based crosslinking agent are preferable. The pressure-sensitive adhesive is preferably appropriately selected according to the type of the corresponding release layer.

For example, in the case of using a uv-sensitive, radical-polymerizable or platinum addition type silicone resin as the release layer, any non-crosslinked adhesive and adhesives crosslinked with any of a metal-based crosslinking agent and an organic-based crosslinking agent can be used.

In the case of using an ultraviolet-sensitive cationically curable silicone resin as the release layer, the application of a pressure-sensitive adhesive crosslinked with an organic-based crosslinking agent to the pressure-sensitive adhesive thin layer involves the previously mentioned fear of difficulty in releasing, and for this reason, it is preferable to use a pressure-sensitive adhesive which is not crosslinked or crosslinked with a metal-based crosslinking agent. Examples of the metal-based crosslinking agent include known chelating compounds such as titanium, aluminum and zirconium. Examples of the organic-based crosslinking agent include, but are not limited to, those known such as polyisocyanate compounds, epoxy compounds and melamine compounds.

As the aforementioned acrylic-based pressure-sensitive adhesive, a pressure-sensitive adhesive containing at least one compound selected from the group consisting of a homopolymer of acrylic ester, a copolymer containing at least two acrylic ester units, and a copolymer of a monoacrylate copolymer and another functional monomer as a main component is used.

Examples of the above-mentioned acrylic esters include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, ethylhexyl (meth) acrylate, nonyl (meth) acrylate, and decyl (meth) acrylate. Examples of the functional monomer include carboxyl group-containing monomers such as (meth) acrylic acid, itaconic acid and maleic anhydride acid, hydroxyl group-containing monomers such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate and amide group-containing monomers such as (meth) acrylamide and dimethyl (meth) acrylamide.

Acrylic-based pressure sensitive adhesives are roughly classified into solvent-based ones and emulsion-based ones, and the solvent-based ones are generally composed of the above acrylic-based polymer, a solvent and, if necessary, a crosslinking agent, a tackifier, etc. In this case, the above-mentioned metal-based crosslinking agent and organic-based crosslinking agent may be used as the crosslinking agent.

On the other hand, an emulsion type acrylic-based pressure-sensitive adhesive is generally composed of the above acrylic-based polymer, an emulsifier, an aqueous solvent, and, if necessary, a tackifier, etc.

As the above rubber-based adhesive sticker, a rubber-based adhesive sticker containing at least one compound selected from natural rubber, polyisoprene rubber, polyisobutylene, polybutadiene rubber, styrene/butadiene/styrene block copolymer, styrene/isoprene/styrene block copolymer and the like as a main component is used.

The rubber-based sticker may be mixed with a tackifier, a plasticizer, a filler or the like as needed and is preferably used in the form of a solvent type or an emulsion type containing the aforementioned rubber latex.

As the above silicone-based adhesive sticker, a compound containing polydimethylsiloxane, polydiphenylsiloxane and, if necessary, a tackifier, a plasticizer, a filler and the like in the form of a solvent as main components is preferably used.

Examples of the tackifier for blending with the pressure-sensitive adhesive include natural resins such as rosin-based resin and polyterpene-based resin and resins such as aliphatic petroleum resin (C), if necessary₅Series), aromatic petroleum resin (C)₉Series), alicyclic petroleum resins (DCPD series), cumarone (cumarone) resins, alkylphenol resins, and xylene resins.

The adhesive sheet layer containing the adhesive can contain an antioxidant (anti-aging agent), a heat stabilizer, a light stabilizer and the like if necessary. The thickness of the above adhesive sticker thin layer may be appropriately determined within the range of usually 5 to 50 μm, preferably 10 to 30 μm.

The sticker sheet need not be placed over the entire surface of the backing sheet, but is placed with an edge section that is typically left free of the sticker sheet. This makes it easy to peel the self-adhesive sheets one by one from a laminate prepared from a large number of the above sheets.

The adhesive strength of the pressure-sensitive adhesive sheet in the present invention is not particularly limited, but is preferably at least 500gf/25 mm. When the adhesive strength is less than 500gf/25mm, there is a fear that the adhesive will peel off or peel off in relief when it is stuck to an adherend, and the function as a display label is lost. Under the aforementioned conditions, the adhesive strength is more preferably at least 1000gf/25 mm. The pressure-sensitive adhesive sheet according to the present invention can be peeled off from an adherend or permanently attached thereto, each depending on the kind of the adherend, and therefore the upper limit of the adhesive strength thereof is not specified. The adhesive strength was measured according to JIS Z0237 and 1980 using a cold-rolled stainless steel plate as the adherend.

The pressure-sensitive adhesive sheet according to the present invention can be produced with good workability by using a simple apparatus, and moreover, hardly causes curling unlike the conventional pressure-sensitive adhesive sheet. The laminate of the present invention comprising a plurality of the above self-adhesive sheets laminated to each other is not rolled up at the ends and edges thereof. Due to the above-described advantages, it becomes possible to peel off the above-described sheets one by one as display labels such as a label for a delivery door, a merchandise display label, a warning label and the like having good workability and goods, merchandise packages and the like also stuck to the delivery door. It also makes it possible to apply and/or write something to the place without the anti-sticking layer of the home delivery label and then cut the place to use it as a home delivery receipt as well.

Next, the present invention will be described in detail with reference to comparative examples and examples, but it is not intended to limit the present invention.

Example 1

An ultraviolet-sensitive cationically curable Silicone-based detackifier (manufactured by Toshiba Silicone Co., Ltd., under the trade name "TPR 6500") was applied to a substrate containing a unit weight of 90g/m with a trowel²The wood-free paper-based backing sheet of (1) was coated with clay to a thickness of 15 μm, and then the surface coated with the releasing agent was subjected to ultraviolet irradiation at room temperature by an ultraviolet radiator (120W) using two high-pressure mercury vapor lamps at an irradiation speed of 10m/min to cure the releasing agent and form a releasing layer having a thickness of 2.0 μm. Subsequently, the surface of the liner sheet opposite to the final release layer was coated with an acrylic solvent-based pressure-sensitive adhesive having high adhesive strength (manufactured by Toyo Ink mfg.co., ltd., under the trade name "BPS 4429-4") by means of a roll knife applicator without a crosslinking agent, and the thus-coated adhesive was dried to form a thin layer of pressure-sensitive adhesive having a thickness of 20 μm so as to form a pressure-sensitive adhesive sheet. The final sheet was then cut into a flat sheet of arbitrary size and 100 of the sheets were laminated so that any adhesive sheet was directly against any release layer. The laminate is then cut so that the areas coated with the adhesive make up 80% of each adhesive sheet to form a laminate of the above sheets.

The workability of the adhesive was examined on whether or not the roll-up occurred after the lamination and 14 days after the completion date of the laminate. The adhesive strength of the sheet before lamination was measured in accordance with JIS Z0237-1980 using a cold-rolled stainless steel plate (SUS306) as an adherend. And the adherend was also subjected to embossed peel and peel tests. The results are shown in Table 2.

Example 2

The processing method of example 1 was repeated to produce a pressure-sensitive adhesive sheet and a laminate thereof except that 100 parts by weight (in terms of solid content) of an acrylic solvent-based pressure-sensitive adhesive having high adhesive strength (BPS4429-4) was used as a pressure-sensitive adhesive and 0.5 part by weight of a metal-based crosslinking agent (manufactured by Toyo inkmfg.co., ltd., under the trade name "BXX 4805") was mixed. The evaluation results are shown in Table 2.

Example 3

A mixture of 100 parts by weight (in terms of solid content) of an ultraviolet-sensitive platinum addition type silicone-based releasing agent (manufactured by Shin-Etsu Chemical Co., Ltd., under the trade name "X-62-5413") and 5 parts by weight of a platinum catalyst (manufactured by the same manufacturer under the trade name "Cat-PL-5000") was applied to a coating roll containing a mixture having a unit weight of 90g/m²One side of an underlying sheet without wood paper, which had been coated with clay to a thickness of 15 μm, followed by heat treatment at 80 ℃ for 8 seconds, was then subjected to ultraviolet irradiation at room temperature by using an ultraviolet radiator (160W) of two high-pressure mercury vapor lamps at an irradiation speed of 10m/min to cure the above-mentioned releasing agent and form a releasing layer having a thickness of 2.0 μm. Subsequently, the surface of the liner sheet opposite to the final release layer was coated with an acrylic solvent-based pressure-sensitive adhesive having high adhesive strength (manufactured by Toyo Ink mfg.co., ltd., under the trade name "BPS 4429-4") by means of a roll knife applicator without a crosslinking agent, and the thus-coated adhesive was dried to form a thin layer of pressure-sensitive adhesive having a thickness of 25 μm so as to form a pressure-sensitive adhesive sheet. The final sheet is then cut into a flat sheet of arbitrary size, and it100 sheets were laminated so that any adhesive sheet was directly against any release layer. The laminate is then cut so that the areas coated with the adhesive make up 80% of each adhesive sheet to form a laminate of the above sheets.

The thus obtained pressure-sensitive adhesive sheet and a laminate formed therefrom were evaluated in the same manner as in example 1. The results are shown in Table 2.

Example 4

The processing method of example 3 was repeated to produce a pressure-sensitive adhesive sheet and a laminate thereof except that 100 parts by weight (in terms of solid content) of an acrylic solvent-based pressure-sensitive adhesive having high adhesive strength (BPS4429-4) was used as a pressure-sensitive adhesive and 0.5 part by weight of a metal-based crosslinking agent (manufactured by Toyo inkmfg.co., ltd., under the trade name "BXX 4805") was mixed. The evaluation results are shown in Table 2.

Example 5

The processing method of example 3 was repeated to produce a pressure-sensitive adhesive sheet and a laminate thereof except that 100 parts by weight (in terms of solid content) of an acrylic solvent-based pressure-sensitive adhesive having high adhesive strength (BPS4429-4) was used as a pressure-sensitive adhesive and 0.5 part by weight of an isocyanate-based crosslinking agent (manufactured by ToyoInk mfg.co., ltd., under the trade name of "BHS 8515") was mixed. The evaluation results are shown in Table 2.

Comparative example 1

A mixture of 100 parts by weight (in terms of solid content) of a heat-curable Silicone resin (manufactured by Toray dow corning Silicone co., ltd., trade name "SRX 357") and 0.6 part by weight of a catalyst (manufactured by the same manufacturer, trade name "SRX 212") was applied to one side of the same underlying sheet used in example 1 with a puddle, and then the applied Silicone resin was subjected to a drying treatment of hot air at 130 ℃ for 1 minute to cure the above-mentioned releasing agent and form a releasing layer having a thickness of 2.0 μm. Subsequently, a self-adhesive sheet and a laminate thereof were prepared in the same manner as in example 1. The evaluation results are shown in Table 2.

TABLE 2

	Example 1	Example 2	Example 3	Example 4	Example 5	Comparative example 1
							Adhesive sticker	Acrylic-based, non-crosslinked	Acrylic-based, metal-crosslinking agents	Acrylic-based, non-crosslinked	Acrylic-based, metal-crosslinking agents	Acrylic-based, isocyanate-crosslinked	Acrylic-based, non-crosslinked
Antiblocking agent (Silicone resin)	Cation curing type	Cation curing type	Platinum addition type	Platinum addition type	Platinum addition type	Thermosetting type
							Rolled up after lamination	Not rolling up	Not rolling up	Not rolling up	Not rolling up	Not rolling up	Rolled up
Adhesive processability1)	Good taste	Good taste	Good taste	Good taste	Good taste	Not good (roll up)
							Adhesive strength2)(g/25mm)	1400	1500	1300	1450	1600	1450
Adhesive sticker sheet lifter	Is free of	Is free of	Is free of	Is free of	Is free of	Is free of

Note: 1) after 14 days of laminate formation

2) The adhesive strength was measured in accordance with JIS Z0237-1980 using a cold-rolled stainless steel plate as an adherend.

As can be seen from Table 2, examples 1 to 5 showed no curling up after lamination and had sufficient adhesive strength, whereas comparative example 1 showed a higher curing temperature (130 ℃ C.) after lamination and did not show good adhesive processability due to the use of a heat-curable silicone resin as a releasing agent.

Claims (5)

1. A pressure-sensitive adhesive sheet comprising a backing sheet, a pressure-sensitive adhesive sheet formed at least partially on one side of the backing sheet, and a release layer formed at least partially on the other side of the backing sheet and containing a cured product from an ionizing radiation-curable release resin formed from a silicone resin.

2. The pressure-sensitive adhesive sheet according to claim 1, wherein the ionizing radiation-curable release resin is an ultraviolet-sensitive silicone resin.

3. The self-adhesive sheet according to claim 2, wherein the ultraviolet-sensitive silicone resin is an ultraviolet-sensitive cationically curable silicone resin.

4. The self-adhesive sheet according to claim 2, wherein the ultraviolet-sensitive silicone resin is an ultraviolet-sensitive platinum addition type silicone resin.

5. A laminate comprising a plurality of pressure-sensitive adhesive sheets as claimed in any one of claims 1 to 4 laminated to each other so that the pressure-sensitive adhesive sheet and the release layer are directly opposed to each other and the entire surface of the pressure-sensitive adhesive sheet is covered with the release layer.