JP2002258753A - Heat resistant label - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive heat resistant label having a substrate which hardly shrinks even when the label is stuck to a body particularly as a bar code label and used in a high temperature environment and capable of correctly imparting printed information. SOLUTION: The heat resistant label has a heat resistant adhesive layer having >=0.3 N/25 mm adhesive power at 150 deg.C on one face of a substrate comprising an unstretched film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant label, and more particularly to a bar code label, which hardly shrinks even when used in a high-temperature environment after being attached to an adherend. The present invention relates to an inexpensive heat-resistant label capable of transmitting printed information accurately.

[0002]

2. Description of the Related Art In recent years, bar codes have become indispensable to the information society as the simplest and familiar automatic recognition technology. In fields requiring a larger amount of information, two-dimensional barcodes having an overwhelming amount of information have begun to be used instead of one-dimensional barcodes. This bar code is not limited to displaying the code of the product obtained by the consumer in the final stage of distribution, the process just before that, and even retroactively, products and components from the manufacturing to the distribution stage,
Barcode printing is often used for recognition of members and the like. Bar codes are actively used for production management in production lines of automobiles and electric and electronic products, and product management in distribution facilities. By the way, in the production management in the production line of the above-mentioned automobiles and electric / electronic products, a bar code is directly printed on a component, or a bar code-labeled label is attached to the component. Yes, therefore, when a label is used, the label may be required to have heat resistance. Conventionally, polyimide films and polyetherimide films have been used for heat-resistant barcode labels, but these films are expensive and have the drawback that the resulting barcode labels are inevitably costly. is there. In addition, polyethylene terephthalate film or polyethylene film, which is generally used as a base material of a bar code label, is inexpensive, but has poor heat resistance. When used in an environment, there is a possibility that the base material shrinks, and as a result, unfavorable situations such as a case where printed information cannot be accurately recognized may be caused. Therefore,
Barcode labels that are excellent in heat resistance and inexpensive are desired. On the other hand, a film made of an oriented thermoplastic resin, the second transition point or more, at a temperature below the melting point, and stretched in two directions vertically and horizontally, a biaxially stretched film that has undergone plane orientation,
It is known that the tensile strength and the impact strength are remarkably improved, and the heat shrinkage is remarkably increased when the heat setting is not performed. As the biaxially stretched film, a polyethylene terephthalate film, a polyvinyl chloride film,
A film made of a highly crystalline resin such as a polyvinylidene chloride film, a polypropylene film, a polyethylene film, and a nylon film, or a film made of an amorphous resin such as a polystyrene film has been put to practical use. Further, as described above, a film which is not heat-set after biaxial stretching has a remarkably large heat shrinkage, and is therefore used as a heat shrinkable film for packaging. In the above-mentioned biaxially stretched film, in applications other than the heat shrinkable film application, generally, a treatment for suppressing an increase in heat shrinkage by performing heat setting treatment after biaxial stretching is provided. As the label base material, generally, the above-described biaxially stretched thermoplastic resin film, particularly, a biaxially stretched polyethylene terephthalate film or a biaxially stretched polyethylene film has been preferably used. However, although these films are heat-set after biaxial stretching, they are still inevitable to shrink when used in a high-temperature environment, making them suitable as base materials for barcode labels for heat-resistant applications. There was a problem that was not.

[0003]

SUMMARY OF THE INVENTION Under such circumstances, according to the present invention, the shrinkage of the base material hardly occurs even when the base material is used as a bar code label in a high-temperature environment when applied to an adherend. The purpose of the present invention is to provide an inexpensive heat-resistant label that does not occur and can transmit print information accurately.

[0004]

Means for Solving the Problems The present inventors have intensively studied a heat-resistant label which is particularly suitable as a bar code label for heat-resistant use. For example, rather than a biaxially stretched film, it is generally considered that a non-stretched film having a small heat shrinkage ratio is more advantageous, so that a cast film of polymethyl methacrylate is produced and, together with a commercially available biaxially stretched polyethylene terephthalate film, at 150 ° C. The heat shrinkage of the film itself under heating conditions for 30 minutes was measured. As a result, the heat shrinkage in the machine direction (MD) and cross direction (CD) was 9.96% and 9.33% for the polymethyl methacrylate cast film, and 1.78% for the biaxially stretched polyethylene terephthalate film. 0.4%, indicating that the cast film had a significantly higher heat shrinkage than the biaxially oriented polyethylene terephthalate film. It is considered that this is because the properties of the resin itself and the heat-setting treatment after stretching in the biaxially stretched polyethylene terephthalate film are performed. However, when a heat-resistant acrylic pressure-sensitive adhesive was applied to each of the above films, attached to an aluminum plate, and heated at 250 ° C. for 5 minutes, the polymethyl methacrylate cast film surprisingly hardly shrank, and the label was hardly shrunk. Although no change in appearance was observed, the shrinkage of the biaxially stretched polyethylene terephthalate film was as large as 3% or more regardless of the length and width, and the label appearance also had cracks and wavy edges. This is because, in the case of a polymethyl methacrylate cast film, the heat shrinkage of the film itself is larger than that of the biaxially stretched polyethylene terephthalate film, but the heat shrinkage is smaller than that of the biaxially stretched film, and the film is adhered through the adhesive layer. It is considered that the base material is held in the body, and its contraction is inhibited. This was unexpected. As a result of further research based on these findings, the present inventors have found that a non-stretched film, preferably a thermoplastic resin film produced by a casting method or a calender method, is used as a base material, and one surface thereof is coated. It has been found that a label provided with a heat-resistant pressure-sensitive adhesive layer having a certain value of adhesive strength to a body has excellent heat resistance and is particularly suitable as a barcode label for heat-resistant applications, and has completed the present invention. . That is, the present invention provides (1)
A heat-resistant label comprising a heat-resistant pressure-sensitive adhesive layer having an adhesive strength at a temperature of 150 ° C. of at least 0.3 N / 25 mm on one surface of a substrate made of a non-stretched film, (2) a non-stretched film, 2. The heat-resistant label according to claim 1, which is made of a thermoplastic resin film and is formed by a casting method or a calender method, (3) the thermoplastic resin film is an acrylic resin film, a polyurethane resin film, or an acrylic resin film. 4. The heat-resistant label according to item 2, which is a mixed resin film of a resin-based resin and a polyurethane-based resin, and (4) the heat resistance according to item 1, 2, or 3 used as a barcode label for heat-resistant use. label,
Is provided.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The heat-resistant label of the present invention has a heat-resistant pressure-sensitive adhesive layer on one side of a substrate, and it is necessary to use a non-stretched film as the substrate.
As the unstretched film, in the present invention, a thermoplastic resin film is preferable, and a method for forming the film is not particularly limited as long as a substantially unstretched film can be obtained. A casting method, a calendar method, and the like can be preferably employed. The casting method is also called a solution casting method, in which the raw resin is dissolved in a solvent such as an organic solvent, and a water-like viscous dope to which a plasticizer is added is further removed to remove dirt and bubbles, and then a rotating flat surface is used. This is a method of casting a film on a completely homogeneous metal support. The film formed by this method is almost completely a non-stretched film, has no directionality, is excellent in thickness uniformity, and is excellent in flatness, transparency, and gloss. On the other hand, the calendar method uses mixing rolls,
This is a method in which a resin molding material kneaded with a Banbury mixer, an extruder, or the like is supplied to a calender having two or more rolls and rolled between the rolls to form a film. As a calendar roll, 3 in series, 3 inclines
This type, four series type, four-roll inverted L type, four-roll Z type, inclined Z type, five-type type, and the like are used. The film formed by this calendering method is slightly stretched in the traveling direction, but is a substantially non-stretched film,
The thickness uniformity is also good. Among these methods, a film formed by a casting method, which is an almost completely unstretched film, is preferable.

In a biaxially stretched film, a heat setting treatment is performed after the biaxial stretching, so that the heat shrinkage of the film itself may be smaller than that of an unstretched film.
The heat shrink force is much larger than that of an unstretched film. Therefore, when a label having the biaxially stretched film as a base material is attached to an adherend and used in a high temperature environment of about 120 to 300 ° C., the base material may shrink. In contrast, an unstretched film may have a higher heat shrinkage than the biaxially stretched film, but the heat shrinkage is much smaller than that of the biaxially stretched film. Affix a label to the adherend to
Even when used in a high-temperature environment of about 20 to 300 ° C., if the force of the substrate held on the adherend via the pressure-sensitive adhesive layer is larger, the contraction of the substrate is suppressed. The thermoplastic resin constituting the unstretched film is not particularly limited. For example, polyethylene terephthalate, polyester resin such as polybutylene terephthalate, polyethylene naphthalate, polypropylene, polyethylene, polyolefin resin such as polymethylpentene, polyvinyl chloride resin Resins, polyurethane resins, acrylic resins, polyamide resins, polycarbonate resins, polyvinyl alcohol resins, and the like can be given. These resins are 1
The seeds may be used alone, or two or more kinds may be used in combination. Among these, a non-stretched film made of an acrylic resin, a polyurethane resin, or a mixed resin thereof is particularly preferable from the viewpoint of heat resistance and printing performance when used as a base material of a label. Here, the acrylic resin is not particularly limited as long as it can form a film, and for example, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polyacrylonitrile, or (meth) acrylate unit; Copolymers having a styrene unit or a urethane structure can be exemplified. On the other hand, polyurethane resins include both thermosetting resins and thermoplastic resins. In the present invention, thermoplastic polyurethane resins are preferably used. In the heat-resistant label of the present invention,
The thickness of the unstretched film used as the base material is not particularly limited and is appropriately selected depending on various circumstances. However, considering appropriateness as a label, it is usually 10 to 300 μm.
, Preferably in the range of 15 to 150 μm.

The unstretched film may be provided on one or both surfaces thereof with an unevenness treatment by sand blasting or a solvent treatment, a corona discharge treatment, an ozone / ozone treatment, for the purpose of improving the adhesiveness to a layer provided thereon. An oxidation treatment such as an ultraviolet irradiation treatment, a flame treatment, a chromic acid treatment, and a hot air treatment can be performed. In the heat-resistant label of the present invention, the heat-resistant pressure-sensitive adhesive layer provided on one side of the base material needs to have an adhesive force at a temperature of 150 ° C. of 0.3 N / 25 mm or more. This adhesive strength is 0.3N / 2
If it is less than 5 mm, the label is attached to the adherend,
When used in a high temperature environment of about 00 ° C., the adhesive strength is so small that the base material cannot be prevented from shrinking, the label may be deformed, and the label appearance and the accuracy of printed information may be impaired. The preferred adhesive strength is 0.4 N / 25 mm or more, particularly preferably 0.5 N / 25 mm or more. The upper limit of the adhesive strength is not particularly limited, but is generally 5
N / 25 mm. In addition, the above-mentioned adhesive strength is affixed to a stainless steel plate with a label of 25 mm width and 250 mm length,
24 hours after the application, the sample was left in an atmosphere at 150 ° C. for 1 minute, and measured under the atmosphere in accordance with JIS Z 0237 180-degree peeling method.

The heat-resistant pressure-sensitive adhesive used in the present invention is not particularly limited as long as the pressure-sensitive adhesive layer having the above-mentioned pressure-sensitive adhesive is obtained, and is not particularly limited. It can be appropriately selected from among silicone-based, polyurethane-based and polyester-based adhesives. Among these, natural rubber / synthetic polyisoprene-based, acrylic-based and silicone-based pressure-sensitive adhesives are particularly preferable as the heat-resistant pressure-sensitive adhesive. One of these adhesives may be used alone, or two or more thereof may be used in combination. Among rubber-based adhesives, natural rubber / synthetic polyisoprene-based adhesives having excellent heat resistance are preferable, and the adhesive includes natural rubber or synthetic polyisoprene as a main component, and further includes a tackifier and an anti-aging agent as desired. Those containing agents, fillers, vulcanizing agents, vulcanization accelerators, softeners, ultraviolet absorbers, light stabilizers and the like are used. Acrylic adhesives with a weight average molecular weight of 300,000 or more as a resin component
It is preferable that a crosslinking agent be contained together with the (meth) acrylate-based copolymer. As the (meth) acrylic acid ester-based copolymer, a (meth) acrylic acid ester having 1 to 20 carbon atoms in the alkyl group of the ester portion, and a monomer having a functional group having active hydrogen, if desired, Copolymers with other monomers used can be preferably mentioned.
Here, the alkyl group of the ester moiety has 1 to 20 carbon atoms.
Examples of (meth) acrylates include (meth) methyl acrylate, (meth) ethyl acrylate, (meth) acrylate, propyl (meth) acrylate, (meth) pentyl acrylate, (meth) Hexyl acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, myristyl (meth) acrylate, ) Palmityl acrylate, (meth)
And stearyl acrylate. These may be used alone or in combination of two or more.

On the other hand, examples of the monomer having a functional group having active hydrogen include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and (meth) acrylate.
Hydroxyalkyl (meth) acrylates such as 3-hydroxypropyl acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate; acrylamide, methacryl Acrylamides such as amide, N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide; monomethylaminoethyl (meth) acrylate, monoethylaminoethyl (meth) acrylate,
Monoalkylaminoalkyl (meth) acrylates such as monomethylaminopropyl (meth) acrylate and monoethylaminopropyl (meth) acrylate; ethylene such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid and citraconic acid And unsaturated carboxylic acids. These monomers may be used alone or in combination of two or more. Examples of other optional monomers include vinyl esters such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; and styrene. Styrene-based monomers such as α-methylstyrene; diene-based monomers such as butadiene, isoprene and chloroprene; nitrile-based monomers such as acrylonitrile and methacrylonitrile; N, N-dimethylacrylamide;
And N, N-dialkyl-substituted acrylamides such as N-dimethylmethacrylamide. These may be used alone or in combination of two or more.

In the acrylic pressure-sensitive adhesive, the (meth) acrylate copolymer used as a resin component is not particularly limited in its copolymer form, and may be any of random, block, and graft copolymers. You may. Further, the molecular weight is preferably 300,000 or more in terms of weight average molecular weight, more preferably in the range of 500,000 to 2.5 million. If the weight average molecular weight is less than 300,000, the heat resistance is poor, and the adhesion to the adherend may be insufficient.
The weight average molecular weight is a value in terms of polystyrene measured by a gel permeation chromatography (GPC) method. In the present invention, the (meth) acrylate copolymer may be used alone or in combination of two or more. There is no particular limitation on the crosslinking agent in this acrylic pressure-sensitive adhesive,
Any one can be appropriately selected and used from those conventionally used as a crosslinking agent in an acrylic pressure-sensitive adhesive. Examples of such a crosslinking agent include a polyisocyanate compound, an epoxy resin, a melamine resin, a urea resin, a dialdehyde, a methylol polymer, a metal chelate compound, a metal alkoxide, and a metal salt, and a polyisocyanate compound is preferably used. Can be Here, as an example of the polyisocyanate compound,
Aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; isophorone diisocyanate; alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate; Nurates, and adducts, which are reactants with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil, may be mentioned.

In the present invention, one kind of the crosslinking agent may be used alone, or two or more kinds thereof may be used in combination. The amount used depends on the type of crosslinking agent,
Usually 0.01 to 20 parts by weight, preferably 0.1 parts by weight, based on 100 parts by weight of the (meth) acrylate-based copolymer.
It is selected in the range of 10 to 10 parts by weight. If desired, a tackifier, an antioxidant, an ultraviolet absorber, a light stabilizer, a softener, a silane coupling agent, a filler, and the like can be added to the acrylic pressure-sensitive adhesive. On the other hand, examples of the silicone-based pressure-sensitive adhesive include those containing, for example, polymethylsiloxane or polyphenylsiloxane as a main component, and optionally containing a crosslinking agent such as a peroxide, a tackifier, a plasticizer, a filler, and the like. Can be. In the heat-resistant label of the present invention, these pressure-sensitive adhesives may be directly applied to one side of the substrate to provide an adhesive layer, or provided with an adhesive on a release sheet to provide an adhesive layer. Thereafter, this may be adhered to one side of the base material, and the pressure-sensitive adhesive layer may be transferred. In this case, the release sheet may be adhered as it is, without being peeled off if desired, and peeled off when the label is used. The thickness of the pressure-sensitive adhesive layer provided on one side of the substrate is usually 5
To 100 μm, preferably about 10 to 60 μm.
Examples of the release sheet include paper substrates such as glassine paper, coated paper, and cast coated paper; laminated paper obtained by laminating a thermoplastic resin such as polyethylene on these paper substrates; or polyethylene terephthalate, polybutylene terephthalate, or polyethylene naphthalene. Examples thereof include those obtained by applying a release agent such as a silicone resin to a plastic film such as a polyester film such as phthalate or a polyolefin film such as polypropylene or polyethylene. The thickness of the release sheet is not particularly limited, but is usually about 20 to 150 μm.

[0012] The heat-resistant label of the present invention has a thickness of 120 to 300.
Although it can be used as a label for articles used in a high temperature environment of about ° C, it is particularly suitable as a barcode label for heat resistance. There are (1) thermal transfer thermal method, (2) direct thermal method, (3) laser method, and (4) other methods (dot matrix method, ink jet method, etc.) as printing methods of the barcode label printer. In the present invention, the thermal transfer thermal method (1) is preferably used. In this thermal transfer thermal method, a thermal transfer ribbon having an ink layer in which a colorant is dispersed in a hot-melt material is superimposed on an image receiving sheet, and heat is applied to the thermal transfer ribbon by a thermal head, so that the ink layer is thermally melted. This is a system in which the image is transferred onto an image receiving sheet and barcode printing is recorded. In the present invention, as the image receiving sheet, a substrate made of the above-mentioned unstretched film is used, and may be directly printed and recorded on the surface of the substrate or, if desired, on the surface of the substrate by a conventional thermal transfer thermal method. A commonly used ink receiving layer may be provided, and printing and recording may be performed thereon. In addition, this printing is usually recorded on the surface of the substrate opposite to the pressure-sensitive adhesive layer, but if the unstretched film used as the substrate has transparency, it is recorded on one surface of the substrate. After that, an adhesive layer can be provided thereon.

In the heat-resistant label of the present invention, when printing is performed directly on the substrate or on the ink receiving layer on the surface of the substrate opposite to the pressure-sensitive adhesive layer, scratch resistance and scratch resistance are obtained. A protective layer can be provided on the print recording layer for the purpose of imparting water resistance, water resistance, weather resistance, stain resistance and the like. As this protective layer, an ionizing radiation-curable resin layer may be directly formed, or a transparent film of the same material as the base material of the heat-resistant label of the present invention may be provided via an adhesive layer. The thickness of this protective layer is usually in the range of 0.1 to 100 μm, preferably 0.3 to 50 μm. The adherend to which the heat-resistant label of the present invention is attached is not particularly limited,
For example, metals such as aluminum and stainless steel, glass, ceramics and the like can be mentioned.

[0014]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Example 1 Polyethylene terephthalate (PET) film [Toray
On one side of the product name "Lumirror # 38" manufactured by Co., Ltd., a silicone resin release agent [product name: "Silicone SYL OFF7198" manufactured by Toray Dow Corning Silicone Co., Ltd.] is applied by a Meyer bar coating method. Is 1μ thick
m and dried to prepare a release sheet. Next, acrylic acid 2- solution-polymerized at a concentration of 40% by weight in a toluene solvent was applied to the release-treated surface of the release sheet.
An acrylic adhesive having a molecular weight of 600,000 consisting of 50 parts by weight of ethylhexyl, 25 parts by weight of butyl acrylate, 21 parts by weight of vinyl acetate and 4 parts by weight of acrylic acid was dried with a roll knife coater to a thickness of 30 μm. And dried to form a uniform pressure-sensitive adhesive layer. Next, a 50-μm-thick polymethyl methacrylate (PMMA) film formed by a casting method was used as a base material, and the release sheet was bonded to one surface of the polymethyl methacrylate (PMMA) film via the pressure-sensitive adhesive layer to produce a pressure-sensitive adhesive sheet. Example 2 A thermoplastic polyurethane (TPU) resin film having a thickness of 50 μm was produced by a casting method, and an adhesive sheet was produced in the same manner as in Example 1 using this film as a base material. Example 3 A 50 μm-thick PMMA / TPU mixed resin film was prepared by a casting method using a mixed resin of PMMA resin and TPU resin at a weight ratio of 80:20, and this film was used as a substrate. In the same manner as in the above, an adhesive sheet was produced. Example 4 Weight ratio of methyl methacrylate unit to styrene unit was 8
Using a 5:15 methyl methacrylate-styrene copolymer, a 50-μm-thick methyl methacrylate-styrene copolymer film was prepared by a calendering method, and this film was used as a base material. A sheet was prepared.

Comparative Example 1 Biaxially stretched PET film having a thickness of 50 μm [manufactured by Toray Industries, Inc.
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 using trade name "Lumirror # 50"] as a base material. Comparative Example 2 Biaxially stretched PMMA film having a thickness of 50 μm [Kanebuchi Chemical
A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 using "Sandulene 002AN" (trade name, manufactured by Co., Ltd.) as a substrate. Comparative Example 3 A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 using a polyethylene film having a thickness of 50 μm formed by an inflation method as a base material. Comparative Example 4 Solution-polymerized 2-ethylhexyl acrylate (59 parts by weight) and vinyl acetate (3) at a concentration of 40% by weight in a toluene solvent
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that an acrylic pressure-sensitive adhesive composed of 9 parts by weight and 2 parts by weight of acrylic acid and having a molecular weight of 250,000 was used. As described above, a printer [manufactured by Zebra Corp., trade name "140Xi"] and a thermal transfer ribbon [manufactured by Sony Corp., trade name "On the surface of the adhesive sheets obtained in Examples 1 to 4 and Comparative Examples 1 to 4" TR4070 "], barcode printing was recorded to produce labels, and the following heat resistance test was performed on each label to evaluate its heat resistance. <Heat resistance test of labels> Each label was slit into a square of 5 cm, the release film was peeled off, and the label was attached to an aluminum plate. The aluminum plate with the label is placed in an oven for 25
After heating at 0 ° C. for 5 minutes or at 300 ° C. for 1 minute, the shrinkage degree and appearance of the label taken out and affixed, and the state of barcode printing were evaluated according to the following criteria.
Further, the adhesive strength in an atmosphere at 150 ° C. was measured. The results are shown in Table 1.

(1) Degree of shrinkage of label ○: The maximum value of shrinkage is less than 1% regardless of the length and width of the label. Δ: The maximum value of the shrinkage ratio is 1% or more 3 regardless of the length and width of the label.
%Less than. X: The maximum value of the shrinkage ratio is 3% or more regardless of the length and width of the label. (2) Appearance of label ：: Label has no foaming, cracks or wavy edges. Δ: The label has some of foaming, cracks and wavy edges. ×: The label has any of foaming, cracks, and wavy edges. (3) Barcode printing state ：: No barcode waving or falling off. Δ: Some of the barcode was wavy or dropped. ×: The bar code is either wavy or missing.

[0017]

[Table 1]

From Table 1, it can be said that the labels of Examples 1 to 4 are excellent heat-resistant labels without any shrinkage of the label, no abnormality in appearance and no bar code printing even after heating. On the other hand, since the labels of Comparative Examples 1 to 3 use a stretched film, the label has a large shrinkage force upon heating, the label shrinks, the edges are wavy, and the barcode printing state is abnormal. Was seen. Also, in the label of Comparative Example 4, the label shrinks and the edge is wavy,
Barcode printing was also abnormal.

[0019]

The heat-resistant label of the present invention is inexpensive and excellent in heat resistance. In particular, even when used as a barcode label on an adherend and used in a high-temperature environment, shrinkage of the base material is suppressed. It hardly occurs, and print information can be transmitted accurately.

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Claims (4)

[Claims] 1. A heat-resistant label having a heat-resistant pressure-sensitive adhesive layer having an adhesive strength at a temperature of 150 ° C. of at least 0.3 N / 25 mm on one surface of a substrate made of an unstretched film. 2. The heat-resistant label according to claim 1, wherein the unstretched film is made of a thermoplastic resin film and formed by a casting method or a calendering method. 3. The heat-resistant label according to claim 2, wherein the thermoplastic resin film is an acrylic resin film, a polyurethane resin film, or a mixed resin film of an acrylic resin and a polyurethane resin. 4. The heat resistant label according to claim 1, which is used as a bar code label for heat resistant use.