WO2008042681A1

WO2008042681A1 - Laser marking label and article with the label

Info

Publication number: WO2008042681A1
Application number: PCT/US2007/079634
Authority: WO
Inventors: Shunsuke Takano; Hajime Chisaka
Original assignee: 3M Innovative Properties Company
Priority date: 2006-10-03
Filing date: 2007-09-27
Publication date: 2008-04-10
Also published as: JP2008090063A; TW200828199A

Abstract

A laser marking label has, on an adhesive layer, a label layer capable of writing a pattern by laser. The label layer includes at least a first label layer and a second label layer. The first label layer is selectively removed in a laser write region at the time of laser writing, and the second label layer is exposed in the laser write region as a result of the removal of the first label layer. The second label layer has greater brittleness than that of the first label layer.

Description

LASER MARKING LABEL AND ARTICLE WITH THE LABEL

FIELD

The present disclosure relates to a laser marking label. More particularly, the present disclosure relates to a laser marking label which, once bonded to an article to be bonded, resists or prevents peeling from the article for forgery, re-use, and other purposes. The disclosure also relates to an article equipped with such a laser marking label.

BACKGROUND Laser marking labels and other labels have been used for labels of automobile components, for example. Recently, the removal of a label from an automobile component for forgery and bonding it again to other automobile components has occurred. The labels of the prior art have the drawback that bonding strength to the article to be bonded is low in comparison with the strength (resistance to collapse) of a label substrate. Therefore, when a sharp cutting edge such as a razor is carefully inserted between the article to be bonded and the label, the label can be peeled off from the bonded article without breaking the label substrate. For this reason, there is a strong demand at present for the counter-measure against the re-use and forgery of the labels.

Various counter-measures have been proposed in the past to prevent peel and re- use and forgery of laser marking labels and other labels.

For example, Japanese Unexamined Patent Publication (Kokai) No. 64-13579 describes a forgery prevention label including a self-supporting film substrate having UV transmissivity, a printing portion of characters, etc., printed by a UV absorbing ink and applied to at least one of the surfaces of the substrate, and a fluorescent dye-containing adhesive layer and a peel sheet that are serially bonded to the label bonding side of the substrate.

Japanese Unexamined Patent Publication (Kokai) No. 9-277423 describes a forgery prevention label or sheet including a transparent substrate cutting off at least ultraviolet rays and an adhesive layer containing a coloring agent that is dispersed in the adhesive layer and generates a color by the ultraviolet rays, wherein information is applied to the surface and this information is coated with a transparent protection layer. Japanese Unexamined Patent Publication (Kokai) No. 2000-305963 describes a label which is a sheet provided at least partially with a tackifier layer and having a re-use inhibition portion which is broken or undergoes deformation upon peeling after it is bonded to the article to be bonded, preferably a mechanically weak portion such as slits or a reduced thickness portion, arranged in the tackifier layer.

Japanese Unexamined Patent Publication (Kokai) No. 2002-40946 describes a re- bonding/illegal use prevention label including a label substrate formed of a transparent film, a peel layer formed below the label substrate into a pattern containing characters and/or figures, a printing layer formed in such a fashion as to be capable of being seen through the label substrate and/or the peel layer, and an adhesive layer formed below the printing layer.

Further, Japanese Unexamined Patent Publication (Kokai) No. 2003-316271 describes a forgery prevention adhesive label including a label substrate (A), an easy-peel layer (B) partially laminated on the label substrate (A) and having easy peelability, an ink layer (C) laminated on these layers and formed of ink, and a re-peelable follow-up adhesive layer (D) laminated on the ink layer (C), having re -peelability from a bonded article and capable of peeling on an interface with the bonded article to follow up the label substrate (A), wherein the re-peelable follow-up adhesive layer (D) is composed of an adhesive layer substrate (D-a), a urethane type adhesive layer (D-b), and a re-peelable type adhesive layer (D-c).

Japanese Unexamined Patent Publication (Kokai) No. 2003-345255 describes a forgery prevention label formed by printing a peel layer having peelability on the back of a transparent film, forming a printing layer in such a manner as to cover the back of the transparent film and the peel layer, forming a cushion layer having cushion property and peelability on the printing layer and forming an adhesive layer on the cushion layer.

Japanese Unexamined Patent Publication (Kokai) No. 2004-125927 describes a laminate label having an upper layer label and a lower layer label that are provisionally bonded, wherein a knob piece is formed on the upper layer label, an end line extending along the upper layer is printed on the lower layer label and slits are formed at a suitable position of the upper layer label.

However, even when the slits or other security marks are incorporated in the label as described above, the label substrate can be peeled off from the bonded article by using a sharp cutting edge, although the time required and the difficulty of the operation becomes higher. When the slits are formed in the label, printing defects are likely to occur when the label surface is printed and the breakage of the label is likely to occur owing to the existence of the slits as a trigger during the time in which the label is peeled from the liner and is bonded to the bonded article. In the case of the forgery prevention labels according to the prior art, the label has a form of a multi-layered film having a complicated structure, so that not only is its production difficult, but these labels cannot be easily applied to the laser marking labels that have been drawing attention in recent years.

SUMMARY

In some embodiments, the present disclosure provides a forgery prevention label that eliminates the problems with the forgery prevention labels of the prior art and cannot be used again by peeling the label from a bonded article once it is bonded to the article even when a deliberate operation is carried out. In some embodiments, the present disclosure provides a forgery prevention label that does not need to incorporate a security mark such as a slit for preventing re-use and forgery that may result in destruction of the label. In some embodiments, the label has a simple construction and is moreover adaptable to a laser marking label.

In some embodiments, the present disclosure provides a forgery prevention label that can accomplish improved design and graphic features by using laser marking and kiss cutting by laser.

In some embodiments, the present disclosure provides a forgery prevention label that is excellent in weatherability and a curve follow-up property and does not cause cracks and wrinkles when it is applied to a curve portion of a bonded article, in addition to the improved design and graphic features.

Furthermore, in some embodiments, the present disclosure provides an article equipped with the forgery prevention label described above.

These and other features will be readily appreciated from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a sectional view showing a laser marking label according to one embodiment of the present invention.

Fig. 2 is a sectional view showing the state after laser marking is applied to the laser marking label shown in Fig. 1.

DESCRIPTION OF REFERENCE NUMERALS

1 : first label layer

2: second label layer

3: adhesive layer

4: liner layer

10: laser marking label

DETAILED DESCRIPTION As a result of intensive studies for accomplishing the features described above, the inventors have found that it is effective to constitute a label substrate of a forgery prevention label in such a fashion as to possess at least two layers of a label layer. Specifically, the substrate of the forgery prevention layer comprises a main layer having brittleness and a sub-layer having higher toughness than the main layer. The present disclosure provides a laser marking label having, on an adhesive layer, a label layer capable of accepting a writing pattern by laser, wherein the label layer includes at least a first label layer as a sub-layer and a second label layer as a main layer serially from above. The first label layer (the sub-layer) is selectively removed in its laser write region at the time of laser writing, and the second label layer (the main layer) is exposed in the laser write region as a result of the removal of the first label layer. The second label layer has greater brittleness than the first label layer.

The present disclosure also provides an article with a forgery prevention label on a surface thereof, wherein the forgery prevention label is the one that is obtained by conducting laser writing on the laser marking label according to the present disclosure and then bonding the laser marking label to the surface of the article through the adhesive layer. In some embodiments, the forgery prevention labels of the present disclosure cannot be peeled from an article to which they were bonded and cannot be used again after it is bonded to the article, by constituting a label substrate by a combination of specific first and second label layers as will be understood from the following detailed description. This forgery prevention label contains a brittle label layer in the label substrate.

Therefore, even when a peeling operation is carefully conducted by using a razor, etc., the label layer cannot be peeled without inviting breakage and damage of the marking pattern owing to the existence of the brittle label layer. On the other hand, because the forgery prevention label contains the label layer having low brittleness (e.g., not brittle), the label substrate is not broken when it is bonded to the bonded article, thus satisfying both of the requirements.

The forgery prevention label according to the disclosure does not need incorporation of a security function such as slits. Therefore, the forgery prevention label is free from the occurrence of breakage resulting from the existence of such slits. Further, because the forgery prevention label has a simple construction, its production is easy and damage does not occur during the production and transportation. What is important is that the forgery prevention label can be used as a laser marking label, the demand for which has increased in recent years, as its delicate and high quality marking cannot be accomplished by other printing can be executed. In the forgery prevention label according to the disclosure, improved design and graphic features can be accomplished by conjointly using kiss cutting with laser marking while accomplishing the reduction of the size of a system construction.

In some embodiments, the forgery prevention label can accomplish excellent weatherability and curve following properties in addition to the improved design and graphic features. As a matter of fact, in some embodiments, the forgery prevention label is free from the occurrence of cracks and wrinkles even when it is bonded to a curve portion of a bonded article or a portion of other complicated shape.

Furthermore, in some embodiments, the present disclosure provides an article equipped with a label that makes the most of the features of the forgery prevention label described above. The forgery prevention label can be used especially advantageously for automobile components. The present disclosure provides a laser marking label having a label layer capable of generating a written pattern by laser, that is, a label capable of being laser marked. In some embodiments, the labels are laminated on a peelable liner layer through an adhesive layer. The present disclosure also provides an article having bonded to a predetermined portion the laser marking label after laser marking is applied to the label. Here, the term "pattern" means various kinds of patterns to which writing is possible by laser marking and includes lines, characters, numerals, symbols, marks, logos, bar codes, lines, patterns, etc., and their combinations, although they are not particularly restrictive.

The laser marking label can typically have a layer construction as schematically shown in Fig. 1. In other words, a label layer 5 is laminated on a peelable liner layer 4 through an adhesive layer 3 in the laser marking label 10. The label layer 5 includes a first label layer 1 as a sub-layer and a second label layer 2 as a main layer from above. Incidentally, the laser marking label 10 shown in the drawing represents an example and may arbitrarily have an additional layer or layers, whenever necessary. In this laser marking label 10, the first label layer 1 is selectively removed in a predetermined pattern by laser writing indicated by an arrow Ll shown in Fig. 2. In other words, when the first label layer 1 is scanned with the laser Ll having a predetermined intensity and writing is executed, the first label layer 1 is burnt off (hereinafter called also "etched") in only the laser write region and is selectively removed. Since only the first label layer 1 is removed in its entire thickness in this selective removing step, the second label layer 2 as the foundation is as such exposed without being etched. Consequently, when the laser marking label 10 is checked by eye after laser writing, the first label layer 1 and the second label layer 2 that is exposed in a predetermined pattern in its part can be observed, and the written marking pattern can be recognized by the difference of contrast between the first label layer 1 and the second label layer 2. The marking pattern can also be recognized by utilizing the difference of characteristics other than the contrast by changing the construction of the first label layer 1 and the second label layer 2, whenever necessary.

The difference of contrast for recognizing the marking pattern can be confirmed by various means but recommended is a method that colors the first label layer 1 and the second label layer 2 into mutually different colors and utilizes the difference of colors between the first label layer 1 and the second label layer 2 for the recognition of the marking pattern after the selective removal of the first label layer 1. The difference of their colors is not particularly limited as long as an excellent marking effect can be acquired owing to the excellent contrast. Therefore, the first and second label layers can be colored into arbitrary colors. When the first label layer 1 is colored to black and the second layer 2, to white, for example, the white marking pattern floats on the black foundation and the recognition effect becomes remarkable.

In the laser marking label 10, coloration of the first label layer 1 and the second label layer 2 can be executed by various means but can be generally and advantageously executed by using colorants. The colorants can be advantageously used in the form in which the colorants in the required amounts are blended with the raw materials used for forming the first label layer 1 and the second label layer 2.

Pigments and dyes can be used either singly or in combination as the colorants. To uniformly disperse the pigment and the dye, they are used in the form of powder or fine particles. Examples of the pigments and dyes that can be suitably used for executing the present invention include carbon black, ivory black, titanium oxide, zinc oxide, basic lead carbonate and strontium titanate though they are in no way restrictive. When it is desired to color into black, for example, the pigment such as carbon black can be used as the colorant. Carbon black, in particular, is susceptible to the heat of laser used for writing and is easily burnt off. Therefore, it can be used advantageously for coloring the first label layer 1. When it is desired to color into white, the pigment such as titanium oxide can be used as the colorant.

A coloring assistant can be used in combination with the colorant to achieve a peculiar recognition effect for the marking pattern in the laser marking label 10. For example, it is possible to use aluminum powder, mica powder, pearl mica powder, mica powder, etc., as the coloring assistant. When these coloring assistants are used in combination, the color tone such as metallic tone, pearl mica tone, etc., can be imparted to the marking pattern.

In the laser marking label 10, the second label layer 2 has its feature in that when its brittleness is compared with that of the first label layer 1, the second label layer 2 has greater brittleness than the first label layer 1. When the laser marking label 10 is bonded to the bonded article through the adhesive layer 3, the bonding strength between the bonded article and the adhesive layer 3 is strong. When one attempts to forcedly peel the label 10 by using the razor, the second label layer 2 that is intentionally so formed as to be brittle is damaged. Consequently, the attempt of peeling becomes obvious and the label 10 cannot be used again for forgery, etc., because the label 10 peeled is damaged.

In the laser marking label 10, brittleness of the first label layer 1 and the second label layer 2 can be expressed by a fracture point load and elongation after fracture. When the elongation after fracture is as small as possible and the load at that time is appropriate, the value represents suitable brittleness. Both fracture point load and elongation after fracture can be measured by the fracture point load measurement method stipulated in JIS B7721 (tensile/compressive tester). In the laser marking label 10, the fracture point load of the second label layer 2 is ordinarily about 30 N/25 mm or below and preferably within the range of about 10 to about 30 N /25 mm. The elongation after fracture of the label layer 2 is ordinarily about 5% or below and preferably 3% or below. The first label layer 1 preferably has elongation at break of 15% or more to support the label layer 2 before bonding. In some embodiments, it may be preferred to add a brittleness imparting agent to only the second label layer 2 in order to create the difference of brittleness between the first label layer 1 and the second label layer 2. The brittleness imparting agent imparts physical and mechanical brittleness to the second label layer and provides a peel prevention function to the resulting label owing to this brittleness. The brittleness imparting agent may be an organic material or an inorganic material as long as such functions can be acquired. Generally, the inorganic material can be advantageously used as the brittleness imparting agent in consideration of compatibility with other components of the label layer. Examples of the organic material suitable as the brittleness imparting agent include talc, silicon dioxide, calcium carbonate, aluminum borate and titanium oxide though they are not restrictive. Further, the brittleness imparting agent may be formed from a metal material such as stainless steel, nickel, and the like. These brittleness imparting agents may be employed either singly or in combination of two or more kinds. Preferred among them is talc.

The brittleness imparting agent can be used in various forms but is used generally and preferably in the form of powder or fine particles. The size (diameter) of the brittleness imparting agent can be varied over a broad range but is generally within the range of about 1 to about 30 μm. The brittleness imparting agent can be advantageously used in the form in which a necessary amount of the brittleness imparting agent is blended in the raw materials used for forming the second label layer in the same way as the case of the colorant described above.

Subsequently, the construction of the laser marking label according to the present invention and its use will be explained in further detail.

In the laser marking label according to the invention, the first label layer can be formed of a resin material generally called "binder" for example an acrylic resin, a urethane resin or their mixture as a main component. In some embodiments, the acrylic resin is most preferred as the main component of the first label layer. For example, an acryl-polyol resin can be advantageously used.

The first label layer is colored to a color different from the second label layer to create the contrast between the first and second label layers. Coloring of the first label layer is generally carried out by using the colorant described above. The blend amount of the colorant can be changed over a broad range. In the case of the black color, the blend amount is generally within the range of about 1 to about 10 wt% on the basis of the total amount of the raw materials of the label layer.

Formation of the first label layer can be executed by arbitrary film forming methods. General-purpose film formation methods such as a knife coating method, a calendar roll method, a T-die method, a blow molding method, an inflation molding method, etc., can be employed. For example, film formation can be conducted by coating a solution of the formation raw materials of the first label layer onto a support that is subjected to peel treatment. To prepare the coating solution, ethyl acetate, methyl ethyl ketone, toluene, methanol, ethanol and isopropyl alcohol can be used. The second label layer and the adhesive layer are serially laminated on the resulting first label layer. According to another method, it is also possible to simultaneously form and laminate the first label layer, the second label layer and the adhesive layer.

The first label layer can have a variety of thickness depending on the detail of the label and its application. The thickness of the first label layer is generally within the range of about 5 to about 15 μm. When the thickness of the first label layer exceeds 15 μm, adverse influences are exerted on the appearance characteristics of the resulting label, its printing characteristics, and its brittleness characteristics. When defined from another aspect, the first label layer can satisfy the following requirements (1) and (2).

(1) The first label layer can be burnt out (etched) at a predetermined laser beam writing intensity. However, the second label layer is merely exposed, and even when it is etched, etching should remain at only a negligible level.

(2) The first label layer can stably hold the brittle second label layer in combination with the adhesive layer and does not break the second label layer during the ordinary label bonding operation.

The second label layer can be formed of the resin material generally called "binder" in the same way as the first label layer. For example, an acryl resin, a urethane resin or their mixture can be used as a main component. In some embodiments, the acryl resin is most preferred as the main component of the second label layer. An acryl-polyol resin, for example, can be advantageously used.

The second label layer is colored to a different color from the first label layer to create the contrast between the first and second label layers. Coloring of the second label layer is generally carried out by using the colorants described above. The blend amount of the colorant can be changed over a broad range. In the case of the white color, the blend amount is generally within the range of about 20 to about 60 wt% on the basis of the total amount of the raw materials of the label layer. The second label layer further contains the brittleness imparting agent described above. Various organic and inorganic materials can be used as the brittleness imparting agent but the organic materials are particularly useful. Among them, talc is most preferred. Though the blend amount of talc and other brittleness imparting agent can be changed over a broad range, it is generally within the range of about 20 to about 75 wt%, preferably within the range of about 20 to about 40 wt%, on the basis of the total amount of the raw materials of the label layer. When the blend amount of the brittleness imparting agent is below 20 wt%, the resulting second label layer does not have brittleness and the peel prevention function cannot be obtained in this label layer. For example, the laser marking label can be smoothly peeled from the bonded article without breakage by putting a razor into the adhesive layer. When the blend amount of the brittleness imparting layer exceeds 75 wt%, on the contrary, the second label layer becomes so brittle that the label substrate will be broken when the laser making label is peeled from the liner layer or the label is bonded to the bonded article.

Formation of the second label layer can be executed by arbitrary film forming methods. Preferably, general-purpose film formation methods such as a knife coating method, a calendar roll method, a T-die method, a blow molding method, an inflation molding method, etc., can be employed. For example, film formation can be conducted by coating a solution of the formation raw materials of the second label layer onto a support that is subjected to peel treatment. To prepare the coating solution, ethyl acetate, methyl ethyl ketone, toluene, methanol, ethanol and isopropyl alcohol can be used. The resulting second label layer is laminated on the first label layer that has already been formed or is under formation. Subsequently, the adhesive layer is laminated in succession to the second label layer. According to another method, it is also possible to simultaneously form and laminate the first label layer, the second label layer and the adhesive layer.

The second label layer can have a variety of thickness depending on the detail of the label and its application. The thickness of the second label layer is generally within the range of about 40 to about 120 μm. When the thickness of the second label layer is below 40 μm, stiffness disappears, a working factor is adversely affected and the possibility that the laser penetrates through the second label layer during printing occurs. On the contrary, when the thickness exceeds 120 μm, the label becomes so thick that brittleness drops and the curve follow-up property gets deteriorated.

When defined from another aspect, the second label layer satisfies the following requirements (1) and (2).

(1) The second label layer can be etched at a predetermined laser beam writing intensity to an intermediate part of its label layer. (2) The label layer can be etched to its lower surface at improved laser beam intensity (laser kiss cut intensity) higher than the laser beam write intensity.

(3) The label should not be broken by an ordinary label bonding work.

The first and second label layers may further contain additives other than the colorant. Examples of the additives that can be arbitrarily used include an anti-oxidant, a UV absorber, a photo stabilizer, an antistatic agent, a flame retardant, a dispersant, and so forth. The blend amounts of these additives are not particularly limited. The laser marking label further includes the adhesive layer for bonding the label layer to the bonded article. The adhesive layer can be formed by using a heat-sensitive adhesive or a pressure-sensitive adhesive that is ordinarily used in the field of labels. Examples of suitable adhesives include an acryl type adhesive, an olefin type adhesive, an epoxy type adhesive and a urethane type adhesive, though they are not particularly restrictive. When a suitable bonding strength to the bonded article is taken into consideration, the acryl type adhesive can be used particularly advantageously.

The adhesive layer can be used at various bonding strength and various thickness. The bonding strength of the adhesive layer is preferably at least about 20 N/25 mm to the bonded article. The adhesive layer can be used at a variety of thickness. The thickness of the adhesive layer is generally within the range of about 10 to about 40 μm and preferably within the range of about 10 to about 30 μm. When the thickness of the adhesive layer is below 10 μm, the bonding strength is likely to drop and when the thickness is 40 μm or above, on the contrary, there is the possibility that a sharp edge tool such as a razor can be inserted (aggregation breakage) without destroying the second label layer. Incidentally, the adhesive layer bears also the role of stably holding the brittle second label layer in combination with the first label layer.

In some embodiments, the laser marking label further contains a liner layer that can be easily peeled before the use to protect the adhesive layer. The liner layer may be the one that is ordinarily used in the field of labels and includes, for example, a sheet of paper subjected to a peel treatment by a mold release agent such as a silicone resin, a sheet and a film. Incidentally, when the application of kiss cutting to the laser marking label is scheduled, the liner layer must be formed of a material that is not burnt out to its lower surface at the laser kiss cutting strength or must have a thickness sufficient to prevent burn-out. When peel treatment paper is used as the liner layer, peel treatment paper having a thickness of at least about 100 μm is preferably used.

Laser marking or kiss cutting treatment may have already been applied to the first label layer of the laser marking label according to the invention by the means described below in detail. Alternatively, the laser marking label may be designed so that such a treatment is not applied but is first applied before the use. In either construction, the laser marking label preferably has a large size that provides a large number of discrete labels. The laser marking label generally and preferably has a rectangular sheet form or a form analogous to the former. The laser marking label may well be constituted into an elongated product and taken up on a roll. The roll of the laser marking label is convenient for storage, transportation and handling.

The laser marking label can be bonded and used to various bonded articles depending on its construction and features. Particularly, the laser marking label can not only depict a miniature and high quality pattern by laser marking but also has high weatherability and curve follow-up property and can be easily bonded without inviting defects such as cracks and wrinkles when it is bonded to bonded articles having complicated shapes. Therefore, the laser marking label can be advantageously used for automobile components and motorcycle components, for example.

When the laser marking label is used, a pattern is first written to the first label layer by using laser. The pattern to be written can be versatile depending on the construction of the label and its application and a desired pattern can be obtained by arbitrarily combining characters, numerals, logos and lines. When the pattern is decided, it is recommended to take the colors of the first and second label layers into consideration and to provide a marking pattern having excellent appearance, contrast and recognizability.

Write by laser, that is, laser marking, can be carried out in a customary manner. CO₂ laser (wavelength = 10.6 μm) and YAG laser (wavelength = 1.064 μm) can be used as marking laser. The resulting pattern can be made miniature or large by contracting or expanding the beam of these lasers. The intensity of the laser can be varied over a broad range at the time of marking but is generally within the range of about 10 to about 100 W. In addition to laser marking, it is advantageous to apply cutting treatment by using the laser, that is, kiss cutting, to the laser marking label in addition to laser marking. In other words, the first label layer 1, the second label layer 2, and the adhesive layer 3 can be cleanly removed in a predetermined pattern (kiss cutting line) without leaving paste by using a laser beam L2 having a higher intensity than the laser beam Ll used for laser writing of the first label layer 1. The discrete laser marking labels 10 separated can be separated for use from the liner layer 4 whenever they are used.

When carrying out kiss cutting by laser, CO₂ laser and YAG laser can be used as the laser for kiss cutting in the same way as the marking laser. Since both marking and kiss cutting can be executed by using the same laser system, the system is convenient from the aspects of the working factor, the space and the cost. In the case of kiss cutting, however, it is necessary to simultaneously remove the first label layer, the second label layer and the adhesive layer and for this reason, the laser having a higher intensity than the marking laser must be used. The laser intensity can be changed over the broad range when conducting kiss cutting, and is generally within the range of about 100 to about 200 W. After marking and kiss cutting by the laser are completed, the label substrate of the laser marking label is peeled from the liner layer and the label is bonded to the bonded article through the exposed adhesive layer. A jig may be used during the bonding work to prevent air entrapment, whenever necessary. The laser marking label can be firmly bonded to the bonded article and because the second label layer is so constituted as to be brittle, the second label as the brittle layer is destroyed when one attempts to peel the label for illegal purposes. In other words, the label cannot be peeled while keeping its original shape and appearance. Owing to this function, it is possible to prevent peel and re-use of the label. Incidentally, the second label layer as the brittle layer is sandwiched between the upper first label layer and the lower adhesive layer and is stably held. Therefore, the label is not destroyed during the ordinary bonding work.

In another aspect, the present disclosure provides also an article equipped with the laser marking label described above on its surface. In the case of this article, the laser marking label is used after laser writing is made and the liner layer is peeled, and is bonded to a predetermined position of the article through the adhesive layer. Generally, the kind of the article equipped with the label is not particularly limited.

The article is preferably vehicle components such as car components and motorcycle components in which illegal use and forgery of the label are often found. Needless to say, other articles are also embraced within the range of the invention and examples include electronic and electric products such as an ink cartridge, a toner case and a personal computer.

EXAMPLE

Subsequently, the invention will be explained with reference to examples thereof. Incidentally, the invention is not limited to these examples.

Example 1

Production of laser marking label: A laser marking label having a layer construction shown in Fig. 1 is produced by using a brittleness imparting agent or using talc, calcium carbonate or silica as the brittleness imparting agent as listed in the following Table 1.

To begin with, a PET film subjected to a mold release treatment with silicone is prepared and a second label layer (white color) is bar coated to a film thickness of 50 μm from an acryl resin solution to form a film. The composition of the second label layer is as follows.

White color acryl resin: trade name "TX-6013A-T26"; product of Nippon Yushi K.K.,

66 part by weight Curing agent: trade name "VESTANT T1890E", product of Degussa Co.,

4 parts by weight Brittleness imparting agent: talc Mg₃Si₄Oi₀(OH)₂, product of Kanto Kagaku K.K.,

30 parts by weight calcium carbonate CaCO₂, product of Kanto Kagaku K.K.,

30 parts by weight or silica SiO₂, product of Kanto Kagaku K.K.,

6 parts by weight

After the second label layer is cured, a first label layer (black color) is further formed on the former and a label substrate is completed. The first label layer is film- formed by bar coating to a film thickness of 10 μm from an acryl resin solution. The composition of the first label layer is as follows.

Black acryl resin: trade name "TX-6013A Black", product of Nippon Yushi K.K.

85 parts by weight Curing agent: trade name "VESTANT T1890E", product of Degussa Co.,

15 parts by weight

On the other hand, a PET film subjected to a mold release treatment with silicone and having a thickness of 100 μm is prepared and an acryl type adhesive (trade name "RD-

2904", product of 3M Company) is coated to the mold release treatment surface to a film thickness of 30 μm. Next, after the label substrate produced in the previous step is peeled from the PET film, the second label layer and the adhesive layer is laminated in close contact on the resulting adhesive layer. A laser marking label having a layer construction shown in Fig. 1 is acquired.

Evaluation of laser marking label:

The surface property (appearance), liner layer peelability, bonding work factor and self breaking property of the laser marking label produced in the manner described above are evaluated in the following procedures.

( 1 ) Surface property (appearance)

In this evaluation test, the difference of appearance resulting from the occurrence of eruptions and strings due to solidification in the solution of the brittleness imparting agent after drying of the coating is evaluated. Those labels in which eruptions and strings can be clearly observed on the film surface after drying are evaluated as "no good". Those labels in which the eruptions and strings are not so much noticeable though they occur are evaluated as "fair" and those in which the eruptions and strings are hardly observed are evaluated as "excellent". In this evaluation, the appearance is mat- like appearance in all the imparting agents. Therefore, the evaluation is made by uniformity of the mat base without considering the cloth property.

(2) Liner layer peelability:

In this evaluation test, whether or not the peeling operation of the label can be quickly peeled from the liner without problem is evaluated. One of the ends of the liner cut into a size of 1 cm x 5 cm, that is, a pasted film, is lifted up by fingers and the label is as a whole peeled from the liner for evaluation. Low peelability includes those labels which have low stiffness and coil round the finger, those which are partly broken during peeling, and so forth. Those labels in which peeling of the liner layer is extremely easy and no trouble occurs are evaluated as "fair". Those labels which can be peeled without trouble are evaluated as "excellent" and those in which breakage of the second label layer, etc., occurs during peeling are evaluated as "no good". (3) Bonding work factor:

In this bonding work factor, whether or not the bonding work can be quickly carried out without trouble when a film of 1 cm x 5 cm, having an adhesive and peeled from the liner is bonded to an aluminum flat sheet and a bonded article having a curve surface. Low peelability includes those labels which have low stiffness and wrinkles occur during the bonding work, those which are broken even partly during peeling, and so forth. Those labels in which the bonding work can be made without trouble are evaluated as "excellent". Those labels which have low stiffness and somewhat have difficulty in bonding are evaluated as "fair" and those in which wrinkles occur due to low stiffness and breakage of the second label layer, etc., occurs during peeling are evaluated as "no good".

(4) Self breaking property:

In this evaluation test, the label is bonded to a bonded article of an aluminum flat sheet and is aged for 24 hours at room temperature. While the label is heated by a dryer (at 7O⁰C or above), a cutting edge of a razor is deliberately inserted to evaluate the degree of difficulty of peeling. Those in which the second label layer invites remarkable breakage at the time of peeling from the bonded article are evaluated as "excellent", those in which the second label layer is broken, even slightly, are evaluated as "fair", and those in which breakage does not occur are evaluated as "no good".

In this example, commercially available labels A and B listed below are acquired and are also evaluated.

Label A product of T company thickness of first and second label layers: 145 μm thickness of adhesive layer: 30 μm thickness of liner layer: 140 μm

Label B product of 3M Company, model "#7847" thickness of first layer: 50 μm thickness of second layer: 10 μm thickness of adhesive layer: 30 μm thickness of liner layer: 120 μm

Table 1 given below altogether tabulates the evaluation results.

Table 1

As can be appreciated from the evaluation result tabulated in Table 1 above, the laser marking label that is effective for preventing peel and re-use can be acquired by employing the two-layered structure for the label substrate in accordance with the present invention and imparting brittleness to the second label layer by blending talc, or the like.

Example 2 Production of laser marking label:

The laser marking label is produced in accordance with the procedure of Example 1. However, to evaluate the change of the result depending on the blend amount of the brittleness imparting agent, this example uses talc as the brittleness imparting agent and its blend amount is set to nil (0 part by weight), 15 parts by weight and 30 or 50 parts by weight as tabulated in the following Table 2. Evaluation of laser marking label:

The surface property (appearance), bonding work factor and self breaking property of the laser marking label produced in the manner described above are evaluated in the same way as in Example 1 and other matters that come to be known are also checked.

Furthermore, the fracture point load of the second label layer of the entire label and its elongation at break are measured in the following way in accordance with the fracture point load measurement method stipulated by JIS B7721.

Measurement method of fracture point load and elongation at break:

As for the "entire label", the measurement is carried out by producing a two- layered film having a first label layer (black layer) and a second label (white layer), cutting the tape into a rectangular form having a width of 25 mm and a length of 15 cm, setting the sample to a tensile tester in such a fashion that the gap between sample grip chucks is 10 cm and conducting measurement in accordance with JIS B7721. As for the

"second label layer" alone, a white one layer film is produced and measurement is carried out similarly.

Table 2 given below altogether tabulates the evaluation results so obtained.

Table 2

Fracture point load: N/25 mm

No luster*: no luster, label is quickly fall to pieces after start of bonding work. As can be appreciated from the evaluation result tabulated in Table 2 above, the amount of 30 parts by weight for the brittleness imparting agent (talc) can keep the necessary brittleness and exhibits the most effective property with high working factor (not broken during the operation) among the four kinds of samples. As the addition amount of the brittleness imparting agent decreases, the brittleness performance drops, and as the addition amount increases, on the contrary, the working factor drops.

Example 3

Production of laser marking label: The laser marking label is produced in accordance with the procedure of Example

1. In this example, however, a mixture of white color urethane resins, that is, "Nippolan 983", trade name (product of Nippon Polyurethane Kogyo K. K.) and "Plaquce 205H", trade name (Daicell Kagaku Kogyo K. K.), in the same amount, is used in place of the acryl resin for the production of the second label layer (white layer). To evaluate the change of the result depending on the blend amount of the brittleness imparting agent, the blend amount of talc as the brittleness imparting agent is set to nil (0 parts by weight), 28 parts by weight or 50 parts by weight as tabulate in Table 3 below.

The surface property (appearance), bonding work factor and self breaking property of the laser marking label produced in the manner described above are evaluated in the same way as in Example 1 and other matters that come to be known are also checked. Furthermore, the fracture point load of the entire label and the second label layer are measured in the same way as in Example 2.

Table 3 altogether tabulates the evaluation results.

Table 3

Fracture point load: N/25 mm no luster**: no luster, not broken upon elongation no luster***: no luster, elongation

As can be appreciated from the evaluation result tabulated in Table 3, the amount of 50 parts by weight for the brittleness imparting agent (talc) exhibits the best brittleness among the three kinds of samples. When compared with the acryl resin used in Example 1 , however, the elongation at break is greater and the label is more difficult for breakage by the inserting test of the cutting edge. However, it can be used for the urethane resin, too, by finely adjusting the addition amount of the brittleness imparting agent.

Claims

What is claimed is:

1. A laser marking label comprising a label layer comprising at least a first label layer, a second label layer; and an adhesive layer; wherein when said first label layer is selectively removed in a laser write region at the time of laser writing, said second label layer is exposed in said laser write region as a result of the removal of said first label layer; and wherein said second label layer has greater brittleness than that of said first label layer.

2. The laser marking label according to claim 1, wherein the brittleness of said label layers can be expressed by a fracture point load (N/25 mm) stipulated by JIS B7721, and said second label layer has the fracture point load of not greater than 30 N/25 mm and an elongation after fracture of not more than 5%.

3. The laser marking label according to claim 1 or 2, wherein said first label layer and said second label layer are colored into mutually different colors, and a contrast difference between said first label layer and said second label layer provides a marking pattern after said first label layer is removed.

4. The laser marking label according to any one of claims 1 to 3, wherein said first and second label layers and said adhesive layer can be selectively removed by using a second laser having a higher intensity than a first laser used for laser writing of said first label layer.

5. A laser marking label according to any one of claims 1 to 4, wherein said second label layer comprises a brittleness imparting agent.

6. The laser marking label according to claim 5, wherein said brittleness imparting agent is selected from the group consisting of talc, silicon dioxide, calcium carbonate, aluminum borate, titanium oxide or a combination thereof.

7. The laser making label according to claim 5, wherein said brittleness imparting agent comprises at least one metal material selected from the group consisting of stainless steel and nickel.

8. The laser marking label according to claim 5 or 6, wherein said brittleness imparting agent is talc, and said talc is contained in an amount of 20 to 75 wt % on the basis of the total amount of said second label layer.

9. The laser marking label according to any one of claims 1 to 8, further comprising a peelable liner layer adjacent said adhesive layer.

10. An article comprising a surface and the forgery prevention label according to any one of claims 1 to 9 bonded to the surface of said article through said adhesive layer.

11. The article of claim 10, wherein a laser write region of the first label layer is selectively removed exposing the second label in said laser write region.

12. The article according to claim 10 or 11, wherein the article is an automobile component.