MXPA97004290A - Articles in retrorreflexi layers - Google Patents

Abstract

The present invention relates to transparent heat-sensitive adhesive, characterized in that it comprises an acrylic polymer and a phenolic resin, the heat-sensitive adhesive has a coefficient of elasticity ranging from about 1 × 10 5 to about 1 × 10 6 pascals (5 × 10 5 - 1 x 107 dynes / cm2) at 70 ° C, wherein the adhesive exhibits a transparency of at least 85%, and contains from about 15 to about 50 parts by weight of phenolic resin per 100 parts by weight of acrylic polymer. A retroreflective article, characterized in that it comprises a retroreflective laminate having a substantially flat surface and a structured surface, the structured surface is made up of a plurality of geometric concavities and corresponding peaks, a layer with color placed on the geometric concavities and adhered thereto a plurality of separate positions and a layer of heat sensitive adhesive placed on the color layer, wherein the layer of heat sensitive adhesive comprises an acrylic polymer and a phenolic resin, wherein the layer of heat sensitive adhesive has a coefficient of elasticity ranging from about 1 x 105 to about 1 x 107 pascals (1 x 108 dynes / cm2) at 30 ° C, which shows a transparency of at least 85% and containing from about 15 to about 50 parts by weight of phenolic resin per 100 parts by weight of acrylic polymer

Description

ARTICLES IN RETRORREFLEXIVE LAYERS Background of the Invention 1. Brief Description of the Invention This invention relates to retroreflective or retroreflective articles with the backside with adhesive wherein the adhesive has a low heat transfer temperature, adequate tack, does not come off during use, and the adhesive does not detrimentally affect the appearance of the articles. 2. Related Technique Retroreflective or retroreflective layers have gained wide application in signaling and similar banners because they have high capacity. to be recognized at night and use the so-called retroreflective property of light such that they efficiently reflect the received light in a direction substantially opposite to the incident direction of light. The retroreflective layers of the type of enclosed lenses and retroreflective layers REF: 24848 of the type of encapsulated lenses are examples of known retroreflective layers. Retroreflective layers of the cube corner type, such as described in Japanese Unexamined Patent Publication (Ko ai) No. 60-100103, have caused an increase in attention because they have remarkably high retroreflectivity. The particular characteristic of this type of retroreflective layer is that it reflects efficiently and at a wide angle the incident light through its structured surface portion, generally equipped with a large number of pyramidal projections. However, although its retroreflectivity is extremely high, a layer of this kind consists of a thick plastic film and has a high coefficient of elasticity. Accordingly, when attached to a substrate article such as an aluminum foil when using a pressure sensitive adhesive, it is likely to come off the foil. In the case of some signage banners, in particular those used in Japan, the periphery of metal signage banners, they are typically bent or curved at their edges, for example, to prevent danger. Accordingly, an effort is concentrated in such a curved portion of the retroreflectively layered article adhered thereto and the adhesive will likely allow the retroreflective sheeting to come off the metal substrate. In this way, if a heat-sensitive pressure sensitive adhesive is used, it is necessary that it has a high tack value. On the other hand, pressure sensitive adhesives possessing various other properties are required, including some pressure sensitive adhesiveness, at room temperature in addition to heat activated adhesiveness. Pressure-sensitive adhesion at ambient temperature (sometimes referred to as "pre-adhesion" for heat-activated adhesives) is desired so that a retroreflective layered article assembly and support panel will adhere together and will be handled conveniently and effective before heat activation of the adhesive. To go ahead with the aforementioned problem of the detachment of the retroreflective layer of the substrates, as well as to provide a prior adhesion at room temperature, a heat-sensitive adhesive comprising an acrylic polymer and a tackifying resin, as well as optionally a Phenolic resin is known, as described in Japanese Examined Patent Publication (Kokoku) No. 63-56274 and U.S. Patent No. 4,248,748 (McGrath et al.). While the adhesive described in this patent shows great utility in general, it has certain limitations. The adhesive does not contain a crosslinking agent, nor does it have adequate flexibility or transparency. In addition, the cohesion of the adhesive is low, and the adhesive is likely to come off. The activation temperature (defined herein as the temperature necessary for the adhesive to exhibit sufficient tack to adhere to an aluminum substrate) of this adhesive (82 ° C) is high, on the contrary, and the problem remains that when the Adhesive is used to adhere the retroreflective article of the cube corner type to a substrate, the cube corner elements for the article in retroreflective layers can be subjected to thermal distortion, with consequent decrease in retroreflectivity.

It would be advantageous if an adhesive were available having high cohesiveness and adequate tack and adhesion at low temperature such that when the retroreflective layer is bonded to a substrate, the retroreflective layer can be repositioned. Furthermore, it would be advantageous if the color of the adhesive was adequately transparent or white so that the ability to be recognized from the retroreflective layer is not reduced by the light or reflection of the adhesive. It would also be advantageous if the adhesive had a low heat activation temperature. An adhesive comprising the combination of nitrile-butadiene rubber (NBR) with a phenolic resin or NBR with an epoxy resin has hitherto been known as a heat-sensitive adhesive having high cohesion, but is generally difficult to give stickiness to an adhesive of this - - class, furthermore, due to the color of the adhesive, there remains the problem that the capacity to be recognized of the retroreflective layer is low. These adhesives also have the problem that they require a high heat activation temperature, and used for a retroreflective layer of cube corner or other type of structure, the retroreflective elements are thermally deformed resulting in the remarkable decrein retroreflectivity.

Brief Summary of the Invention In accordance with the present invention, the retroreflective layer article having a structured surface comprised of a plurality of accurately formed projections is provided with a smooth surface supersize adhesive such that the article can be heat bonded to an article of substrate at a low temperature such as not to cause deformation of the projections in a precisely formed manner. At about 70 ° C, the adhesive has high cohesion and the article does not detach from the substrate during use, and the articles have a high capacity to be recognized, even at normal handling temperatures the adhesive has adequate tackiness to allow the articles be repositioned The present invention provides, in one embodiment, a retroreflective article comprising a retroreflective, transparent, layered article having a first substantially planar surface and a second structured surface, the second structured surface comprised of a plurality of corresponding geometric concavities and peaks, a layer of colored sealing film disposed on and attached to a first portion of the geometric concavities, a second portion of the geometric concavities excluded from contact with the colored, sealing film layer, and a layer of transparent, heat-sensitive adhesive, disposed on the sealing film layer, colored. A feature of the invention, the heat sensitive adhesive (another aspect of the invention) comprises an acrylic polymer and a phenolic resin, the heat sensitive adhesive has a coefficient of elasticity ranging from about 10 to about 1000 kg / cm2 (approximately 1 x 106 to approximately 1 x 108 dynes / cm2) at 30 ° C. Preferably, either the phenolic resin and / or the acrylic resin are crosslinked, the phenolic resin is crosslinked in an application of sufficient heat (approximately 150 ° C), while the acrylic resins can be crosslinked using selected crosslinking agents. of the group consisting of polyisocyanate compounds, epoxide compounds, polyglycidylamines, ethylene imine derivatives (for example aziridines such as bisamides), and acetylacetone compounds (for example aluminum acetylacetonates, zirconium, titanium oxide, chromium, zinc, iron, manganese, cobalt and the like). Although the phenolic resins used herein contribute to the tack of the heat sensitive adhesive, the heat sensitive adhesive also preferably comprises a non-phenolic tackifier, also described herein. As the phr"geometric concavity" is used, it means a concavity defined by shaped protrusions having at least two planar facets, such as prisms, pyramidal protrusions, cube corner protrusions and the like. The phrase does not include concavities defined by protrusions that does not include planar facets, such as protrusions present in holographic films. The term "transparent retroreflective layered article" means a plastic layered article that transmits at least 90% of the incident light in the visible spectrum (approximately 400-700 nanometers wavelength), as determined by a standard spectrophotometer. The term "transparent heat sensitive adhesive layer" means the heat sensitive adhesives found suitable for use in the present invention exhibiting transparency of at least 85% in terms of the value measured by the method that will be described in the Methods section. Test in the present. This is because if the transparency of the heat sensitive adhesive is less than 85%, the color of the adhesive is reflected in the sealed portion and the geometric concavity portion of the retroreflective layer, and the ability to be recognized from the retroreflective layer falls off. A further understanding of the invention will become apparent upon review of the brief description of the drawings and description of the illustrative embodiments that follow.

Brief Description of the Drawings FIGURE 1 is a cross-sectional (elongated) view of a retroreflective layered article made in accordance with the present invention; and FIGURE 2 is a perspective view of a signal article made in accordance with the present invention, also illustrates the rounded edge test. These figures, which are idealized, are not to scale and are proposed to be only illustrative and not limiting.

Detailed Description of the Illustrative Modalities A retroreflective article according to the present invention is illustrated in Figure 1. A coating portion (cover film) 1 is preferably placed on a smooth, flat surface of a layer 2, the combination of the coating 1 and the layer 2 are referred to as a structured layered article 7. A layer of colored sealing film 3 is placed on the structured surface of the layer 2, and the concavities 10. are defined between the cavities of the layer 2 and the layer of sealing film, colored 3 to give retroreflectivity to the article. In the drawing, the reference numeral 4 represents a chemical priming layer or a corona treatment layer placed on the surface of the colored sealing film layer 3. Chemical and / or physical priming is preferred but not necessary for the invention. The combination of the layers consists of the structured layered article 7, the colored sealing layer 3, and the priming layer or the corona treatment layer 4 and is designated as a retroreflective layered article 8. A layer 5 of a The heat-sensitive adhesive of the invention is placed on the surface of the primer layer or the corona treatment layer 4. A removable protective coating 6 is preferably placed on the surface of this layer of heat-sensitive adhesive 5 to protect its surface. A sheet having members 1 to 6 described above will be referred to as a "retroreflective, heat-sensitive layered article" 9.

The inventive adhesive and the component layers of the articles of the invention are now described in more detail.

I. Heat Sensitive Adhesive A. Elasticity Coefficient The heat sensitive adhesives of the invention have a coefficient of elasticity ranging from about 10 to about 1000 kg / cm2 (about 1 x 106 to about 1 x ? dynes / cm2) at 30 ° C. The coefficient of elasticity is a dynamic viscoelasticity measurement, which can be measured using a commercially available dynamic, mechanical, thermal analyzer used in the compression mode condition, at a frequency of 6.28 rad / sec, such as an available RSAII Model analyzer. of Rheometrics Co. A cylindrical sample shape is used _ has an outside diameter equal to 3 to 3.5 millimeters (mm) and a length equal to 6 to 8 mm. When the coefficient of elasticity of the inventive adhesive is less than 10 kg / cm 2 (1 x 106 dynes / cm 2), the cohesion decreases, so that the retroreflective layer article of the invention will probably come off the curved edge (rounded edge) of the invention. substrate article after joining (pressure with heat). In addition, because the tack (sometimes referred to as "pre-adhesion") is too high, air will likely be trapped between the adhesive and the substrate article when the retroreflective sheet is temporarily attached to the substrate article, and the repositioning satisfactory. It becomes difficult. When the coefficient of elasticity exceeds 1000 kg / cm2 (1 x 108 dynes / cm2), or on the other hand, the final connection at a heat-pressure temperature of around 70 ° C becomes difficult and on the other hand, because the tack is too low, the positioning at the time of the provisional union becomes difficult. In addition, when the pressure temperature with heat becomes high, the retroreflective sheet is heated by a high temperature at the time of final bonding, possibly damaging the geometry of the cube corner. Accordingly, the constituent materials comprising plastics, such as the article in structural layers are subjected to thermal deformation and the retroreflectivity of the reflective sheet decreases. Therefore, a coefficient of elasticity equal to or less than the upper limit mentioned above is preferable. The coefficient of elasticity of the inventive adhesive is preferably in the range of 70 to 800 kg / cm2 (7 x 106 to 8 x 107 dynes / cm2) and particularly preferably in the range of 80 to 500 kg. / cm2 (8 x 106 to 5 x 107 dynes / cm2). When the coefficient of elasticity is within the ranges described herein, the final connection to the pressure temperature with low heat becomes easier, higher cohesion can be obtained and the problems at the time of the provisional connection described above they can be easily solved. The reason why the coefficient of elasticity of the inventive adhesive is reported at 30 ° C is because the capacity for pressure with heat at 70 ° C is required and that it still has adequate pre-adhesion tack at room temperature (approximately 25 ° C) for the adhesive of the present invention. Furthermore, according to the present invention, from the data of Tables 1 and 3, the elasticity coefficient of the inventive adhesive at 70 ° C is preferably 5 to 100 kg / cm2 (5 x 105 to 1 x 107). dynes / cm2), and more preferably 10 to 50 kg / cm2 (1 x 10 to 5 x 10E dynes / cm2). The term "pressure temperature with heat" represents a value of the surface temperature of the retroreflective sheet measured by using a thermocouple.

B. Glass transition temperature The glass transition temperature of the adhesives of the present invention is preferably within the range of 0 to 40 ° C. When the vitreous transition temperature is less than 0 ° C, the tackiness of the previous adhesion tends to become excessively high and when it exceeds 40 ° C, on the contrary, the tackiness of the previous adhesion tends to become excessively low and in addition, the temperature of pressure with heat tends to become high. The glass transition temperature of the adhesive is preferably within the range of 10 to 35 ° C and preferably in particular within the range of 15 to 30 ° C. When the vitreous transition temperature is within such ranges, the final bond at a lower heat pressure temperature becomes easier and at the same time, a tack can be obtained within a suitable range.

Here, the term "vitreous transition temperature" means a measurement value obtained by using a viscoelastometer of the rigid body pendulum type known under the. commercial designation RHEOVIBRON Rigid-Body Pendulum Type Viscoelastometer DDV-OPAIII, a product of Tohoku Electronic Industrial Co. The detail of the measuring method will be described in the section of the Test Methods in the present. The tack value of the adhesive of the present invention is preferably within the range of 19 to 393 gf / cm (50 to 1,000 gf / pg) in terms of the value of the "pre-adhesion test" which is also described in the Test Methods section, and preferably particularly within the range of 196 to 374 gf / cm (500 to 950 gf / pg).

C. Transparency As previously mentioned, the heat sensitive adhesives of the present invention exhibit transparency of at least 85% in terms of the value measured by the method that will be described in the Test Methods section herein. If the transparency of the adhesive is less than 85%, the color of the adhesive is reflected in the seal portion and the portion of the structured surface of the reflective sheet, and the ability to be recognized from the reflective sheet decreases. The preferred range is approximately 88% and preferably additionally, at least 90%, to improve the ability to be recognized from the reflective sheet. Although the phenolic resin and the non-phenolic tackifier have a high coloring power, the transparency value of the adhesive described above can be obtained by adding a predetermined amount of a non-phenolic tackifier such or by adding the acrylic polymer.

D. Acrylic Polymer Acrylic polymers suitable for use in the formulation of adhesives of the present invention are polymers having tackiness to ^ normal temperature (approximately 25 ° C) and that can be attached to the substrate using minimum pressure. Acrylic polymers including those derived from α, β-unsaturated carboxylic acids and acrylic esters are preferred as monomer units because these can easily improve the binding power of the adhesive (through crosslinking) and can also improve the transparency of the adhesive same. Examples of α, β-unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and the like. Examples of acrylic esters include acrylic acid ethers having alkyl groups of 4 to 12 carbon atoms such as butyl acrylate, isobutyl acrylate, isooctyl acrylate, 2-methylbutyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate and Similar. Examples of other useful polymerizable monomers include esters of acrylic acid having up to three carbon atoms in an alkyl group such as methyl acrylate, ethyl acrylate, isopropyl acrylate and the like. In addition, esters of methacrylic acid having 1 to 20 carbon atoms in an alkyl group such as ethyl methacrylate, isopropyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, cyclohexyl methacrylate and similar; esters of acrylic or methacrylic acid, the alkyl group of which is either one of 2-hydroxyethyl, 2-hydroxypropyl, 3-chloro-2-hydropropyl, hydroxyethoxyethyl, methoxyethyl, methoxyethyl, ethoxyethyl, dimethylaminoethyl, diethylaminoethyl, glycidyl and the like, as also styrene, chlorostyrene, α-methylstyrene, vinyltoluene, acrylamide, methacrylamide, N-methylollamide, N-methoxymethyl acrylamide, vinyl chloride, vinyl acetate, vinyl propionate, acrylonitrile, vinylpyridine, and acrylic acid esters having up to 3 carbon atoms in an alkyl group, and the like. Particularly preferred examples of the acrylic polymers described above include terpolymer of acrylic acid-methyl isooctyl-methacrylate acrylate, and copolymer of acrylic acid-isooctyl acrylate. The weight average molecular weight of the acrylic polymer is preferably within the range of 10,000 to 5,000,000 and preferably particularly within the range of 500,000 to In addition, the proportion of the acrylic polymer to the total adhesive is preferably within the range of 50 to 75 weight percent and preferably particularly within the range of 65 to 73 weight percent. If the ratio is less than 50 percent, the stickiness of the adhesive's previous adhesion tends to fall remarkably and the heat pressure temperature tends to become high. When the proportion exceeds 75 weight percent, on the other hand, the stickiness of the adhesive tends to become high and the cohesive strength of the adhesive itself tends to fall.

E. Crosslinking Agent The adhesives of the present invention can be crosslinked before or after the attachment of the retroreflective sheet to a substrate. There are two crosslinking mechanisms for the acrylic polymers useful in the invention: through the crosslinking of free radical polymerization of ethylenically unsaturated groups in the monomers, and through covalent or ionic crosslinking through chemical groups pending the structures of acrylic polymer, for example, -COOH, and epoxy groups. As previously established, the phenolic resin useful in the invention can be cured by exposure to heat. To initiate the crosslinking of the acrylic polymers through free radical polymerization, the crosslinking method can be any of the known methods such as the addition of a crosslinking agent, heat crosslinking, crosslinking with ultraviolet radiation, beams of electrons and the like. Preferably, the acrylic polymers useful in the adhesives of the invention can be crosslinked through pendant groups by means of a chemical which is referred to herein as a crosslinking agent. In other words, it is preferred that the acrylic polymer be subjected to one or both types of crosslinking reaction. This is because this improves the cohesion of the adhesive and easily improves the bond strength. In addition, it becomes easier to control the aforementioned elasticity coefficient to a predetermined range and to control the pressure temperature with heat as well as the tackiness -of the previous adhesion to the respective desired ranges. Acrylic polymers having a functional group or groups that can be reacted with the crosslinking agent, such as a carboxyl group, a hydroxyl group, an epoxy group and the like, can be used as the crosslinkable acrylic polymer described above . More precisely, examples of crosslinkable acrylic polymers are already described carboxyl group-containing acrylic copolymers such as the terpolymer of acrylic acid-isooctyl acrylate-methyl acrylate, and the copolymer of acrylic acid-isooctyl acrylate. The crosslinking agents that can be used in the present invention can be selected from the group consisting of polyisocyanate compounds, epoxide compounds, polyglycidylamines, ethylene imine derivatives, metal salts of organic acids and metal chelates of organic compounds. Preferably, one or at least two kinds of members selected from the group consisting of the ethylene imine derivatives and the metal salts of organic acids are used in combination. Suitable ethyleneimine derivatives are those within general formula (I): (I) wherein R1 and R3 are the same or different and are independently selected from the group consisting of H and C..H2 +2, wherein n is an integer ranging from 1 to about 5, and R 'is a divalent radical selected from the group consisting of benzene (-CÉH4-), substituted benzene, triazine and CrH2rr, where m is an integer ranging from 1 to about 10. A particularly preferred bisamide used in the Examples has the following structural formula (Formula II): (ID Preferred metal salts of organic acids include acetylacetonates within the general formula (III): (III) wherein: M is a positively charged ion selected from the group consisting of TiO, Cr, Al, Zr, Fe, Ni, Zn, Co, and Mn; n is an integer ranging from about 2 to about 4; and R4 and R5 are the same or different and are independently selected from the group consisting of H and CyH2 > +2, where y is an integer ranging from 1 to about 5. R4 and R5 are preferably both methyl groups. Particularly in the case of adhesives containing the preferred crosslinking agents of acrylic polymers containing carboxyl group, mentioned above, are derivatives of ethylene imine, ethylene imine and the acetylacetonate compounds. This is because they have a high crosslinking reaction rate and can substantially complete the crosslinking reaction in a relatively rapid step after the adhesive layer was placed on the retroreflective sheet. Accordingly, the changes in the coefficient of elasticity, the hot pressure temperature and the tackiness value described above with the time step can be reduced. More specifically, a preferred example of the ethyleneimine derivative is an aziridine compound such as a bisamide. This is because the crosslinking reaction easily occurs even when the amount of the ethyleneimide derivative is very small, and the crosslinking reaction can be extremely easily completed in a relatively fast stage. Preferred examples of metal salts of organic acids are acetylacetonates of aluminum metal, zirconium, titanium, chromium and the like. Even though the amount of a metal acetylacetonate of this kind is very small, the crosslinking reaction occurs easily, so that the crosslinking reaction can be completed in a particularly easy way in a relatively fast stage. Particularly preferred among them is aluminum acetylacetonate. This is because the combination with the acrylic polymer containing carboxyl group described above, the crosslinking proceeds at a suitable reaction rate, and the problem of gelation of the adhesive solution does not occur. The amount of addition of the crosslinking agent in the present invention is within the range of 0.05 to 3 parts by weight, preferably particularly within the range of 0.1 to 2 parts by weight, based on 100 parts by weight of the component of resin in the adhesive. When the crosslinking agent is the ethyleneimine derivative, the addition amount is preferably within the range of 0.05 to 0.5 parts by weight, and preferably particularly within the range of 0.1 to 0.3 parts by weight. - weight, based on 100 parts by weight of the resin component in the adhesive. If the amount is smaller than 0.05 parts by weight, the cohesion of the adhesive can not be sufficiently increased and if this exceeds 0.5 parts by weight, on the contrary, the stickiness of the adhesive drops and the detachment is likely to occur on the interface between the retroreflective sheet and the attached article. When the crosslinking agent is a metal salt of an organic acid, the addition amount is preferably within the range of 0.1 to 3 parts by weight, and particularly particularly within the range of 0.5 to 1.6 parts by weight. weight, based on 100 parts by weight of the resin component of the adhesive. If the amount is smaller than 0.1 parts by weight, the cohesion of the adhesive can not be sufficiently increased and if it exceeds 3 parts by weight, on the contrary, the stickiness of the adhesive drops and the detachment is likely to occur on the interface between the retroreflective sheet and the attached article.

F. Phenolic Resin Phenolic resins have the tackifying effect of acrylic polymer, and can more readily give tackiness to the surface suitable for the adhesive of the present invention. The amount of addition of the phenolic resins is suitably from 5 to 100 parts by weight based on 100 parts by weight of the acrylic polymer.

If the amount is less than 5 parts by weight, the effect of improving the cohesion of the adhesive is not sufficient, and if it exceeds 100 parts by weight, on the other hand, the transparency of the heat-sensitive adhesive tends to fall below 85%. % due to the colorability of phenolic resins. In addition, because the amount of addition of the acrylic polymer decreases relatively, the tackiness of the surface as well as the bond strength tend to fall. The addition amount of the phenolic resin is also preferably from 10 to 75 and more optimally from 15 to 50 parts by weight. In this case, the effect of giving cohesion to the adhesive and the balance of colorability becomes satisfactory. Phenolic resins that can be used in the adhesives of the present invention include both novolac and resole phenolic resins. He - term "phenolic resin" is used herein broader to include resins such as phenol-aldehyde condensates, xylene-aldehyde condensates, cresol-aldehyde condensates, melamine-aldehyde condensates, resorcinol-aldehyde condensates, and its derivatives.

Resole phenolic resins having a molar ratio of aldehyde component to phenolic component ranging from about 1 to about 3 are preferred. When the molar ratio is much less than 1, the resins have low reactivity, and when the molar ratio is much greater than 3, the amount of the unreacted aldehyde component is high, which is not environmentally acceptable and the resins exhibit poor stability at room temperature. Molar ratios ranging from about 1.5 to about 2.5 are particularly preferred to obtain a good balance of reactivity and stability. Preferred novolac resins have a molar ratio of the aldehyde component to the phenol component ranging from about 0.6 to about 0.9 for similar reasons. Resole phenolic resins having a predetermined amount of self-crosslinking can also be used by means of reactive groups such as methylol groups, and the like, and novolac types which have a relatively high molecular weight but do not have self-crosslinking.

The type of resol is particularly suitable because the self-crosslinking reaction proceeds after the retroreflective sheet is bonded, and the cohesion of the adhesive can be remarkably improved. When the novolac type is used, a crosslinking agent such as hexamethylene tetramine is preferably used in combination, because the stability of the ambient temperature is high. In addition, among the phenolic resins, so-called, the oil-soluble phenols containing an alkyl group introduced into the benzene ring are particularly suitable for the present invention.

G. Non-phenolic tackifier The adhesives of the present invention preferably contain a non-phenolic tackifier wherein "non-phenolic" means that the tackifier is selected from tackifier of the type of rosins, terpenes and hydrocarbon resin. Certain tackifiers of the terpene type may have a minor portion of the phenolic comonomer.

Non-phenolic tackifiers are useful since they make it easy to control the coefficient of elasticity, the tackiness and the heat pressure temperature of the adhesive to the desired ranges. Suitable non-phenolic tackifiers include one or more types of abietic acid such as abietic acid, neoabietic acid, palustric acid, dihydroabietic acid, tetrahydroabietic acid, and dehydroabietic acid, esters of all these; and types of pimaric acid, such as pimaric acid and isopi aric acid, dehydrated versions thereof, and esters thereof. The esters of the abietic acid types and types of pimaric acid are typically and preferably made by reacting the acid with a polyol, such as pentaerythritol, glycerin, ethylene glycol, and the like. The examples Representative commercials include those known under the trade designations ESTER GUM 8D (an ester of rosin), HERCOFLEX 400 (an ester of rosin), HERCOLYN D (a hydrogenated methyl ester), FORAL 85 (a hydrogenated glycerol rosin ester), ESTER R-95 (an ester of rosin of pentaerythritol) and FORAL 105 (an ester of rosin of hydrogenated pentaerythritol), all available from Hercules Chemical Co. Suitable non-phenolic tackifiers, of the terpenom type, include monomers of polymerized versions such such as α-pinene, β-pinene and dipentene (limonene) and the like, with optional modification with monomers of 9 carbon atoms such as styrene monomer. The typical molecular weights of these tackifiers vary from about 300 to about 2000. The monomers are typically derived from turpentine and other natural sources, such as citrus peel, although the synthetic versions are equally operative. Commercially available non-phenolic, terpene-type tackifiers include those known under the trade designations ZONAREZ A-25 (based on a-pipe, Tg = -22 ° C), ZONAREZ A-100 (based on a- pipeno, Tg = 55 ° C), both available from Arizona Chemicals; PICCOLYTE S10 (based on β-pipe, Tg = -37 ° C), PICCOLYTE S115 (based on β-pipe, Tg = 64 ° C), PICCOLYTE A115 (based on a-pipe, Tg = 64 ° C ), PICCOFYN A-135 (phenolic polyterpene, Tg = 84 ° C), and PICCOLYTE HM-85 (styrenated terpene, Tg = 35 ° C), all available from Hercules Chemical.

Suitable non-phenolic, hydrocarbon-type tackifiers are low molecular weight polymers derived from either aliphatic or aromatic hydrocarbon monomers using a Lewis acid catalyst (cationic polymerization) or heat and pressure (radical initiated addition polymerization) free). Examples of suitable aliphatic resins include those derived from cis-piperylene, trans-piperylene, isoprene, 2-methylbutene-2, dicyclopentadiene and the like, which have molecular weights that vary preferentially from about 800 to about 1500. Commercially available versions include those known under the trade designations WINGTACK 10 (Tg = -28 ° C) and WINGTACK 95 (Tg = 50 ° C), both available from Goodyear Chemical Co .; ESCOREZ 1310 (Tg = 40 ° C) and ESCOREZ 5300 (Tg = 50 ° C), both from Exxon Chemical Co .; and PICCOTAC 95 (Tg = 41 ° C), available from Hercules Chemical Co. Examples of suitable aromatic resins include those derived from indene, styrene, methylidene (s), methylstyrene (s) and the like, preferably having a molecular weight which varies from about 300 to about 1200. 3 The aromatic resins can be hydrogenated to give better stability and / or compatibility. Commercially available versions include those known under the trade designations PICCOVAR AP-25 (type C9, Tg = -50 ° C) and REGALREZ 1094 (hydrogenated a-methyl styrene, Tg = 37 ° C), both available from Hercules Chemical Co.; ARKON P90 (hydrogenated type C9, Tg = 36 ° C), available from Arakawa Co .; and ESCOREZ 7105 (hydrogenated type C9, Tg = 52 ° C), available from Exxon Chemical Co. Colophony type tackifiers are optimal because they exhibit high compatibility with acrylic polymers and give high adhesion, and tack control It is done more easily. The content of the non-phenolic tackifier is preferably in the range of 1 to 35 parts by weight, and particularly particularly within the range of 10 to 30 parts by weight, on the basis of 100 parts by weight of the acrylic polymer When the content of the tackifier is within the range described above, the tack control of the adhesive becomes easy and the heat pressure temperature can be optimized, too.

H. Other Adhesive Additives A UV light absorber, an antioxidant, an agent that increases viscosity, inorganic particles, etc., can be suitably added to the adhesives of the invention to the extent that they do not severely reduce transparency or substantially adversely affect the vitreous transition temperature or the coefficient of elasticity of the inventive adhesives.

II. Structured Layered Article The structured layered article 7 may be any of the articles in cube corner layers described in Japanese Unexamined Patent Publication (Kokai) No. 60-100, 103, and U.S. Patent Nos. 4,588,258; 4,775,219; and 5,138,488. The structural layered article 7 may also comprise a substantially internal, fully reflective film comprising a plurality of parallel prisms, such as described in U.S. Patent Nos. 4,805,984; 4.9C6.070; 5,056,892; 5,175,030; ,183,597. Those skilled in the art will understand that these and other articles in structured layers can be used in the present invention. The structured layered article 7 preferably comprises a planar covering portion 1 in which the light is incident, and a layer 2 consisting of a large number of precisely formed elements (preferably pyramidal or a series of parallel prisms) which reflect substantially and totally the light in a direction opposite to the incident direction. The precisely formed elements define a plurality of concavities 10, filled with air or others with fluid. "Substantial and totally internal reflection" belongs to an optical quality of the film, and means that the film has a Test Value T of 5% or less, where the Test _ T is described as follows. The optical quality of a retroreflective film can be evaluated with an apparatus that includes a laser beam (such as a Spectra-Physics Inc. Model 117A) with a spatial filter, a beam spacer mechanism, and a collimator. Two diaphragms or irises of 18 and 38 cm of the laser beam are placed, and an annular sample holder with an opening of 6.35 cm in diameter is placed 84 cm from the laser beam. Directly behind the sample holder is an integrating sphere (with an opening diameter of 3 cm) and a LABSPHERE ML-400 radiometer. Using the diaphragms or iris, the laser beam is focused through the aperture to obtain a perfect circle of light of approximately 3 mm in diameter on a black surface mounted on a sample holder. A 100% source intensity measurement is taken without sample in its proper place. The TIRF to be tested is then mounted on the sample holder with its flat surface facing the laser beam and its indentations that extend vertically. Unless reported otherwise, the T-Test Values are measured at room temperature. The readings are then made in 12 to 15 different points in the TIRF within a _ 5 cm diameter of area while ensuring that none of the light hits the structure of the sample holder. The readings are averaged and multiplied by 100 to give the percent transmission that is the T-Test Value of the TIRF sample. The Value of the T Test is a criterion of the response fidelity of the TIRF sample. The smaller T Test Value percentages indicate better response fidelity than the larger percentages, and a T Test Value of 5% or less indicates that the film is substantial and totally internal reflection. The coating portion 1 preferably comprises an acrylic material having excellent durability, such as poly (methyl) methacrylate, polyester (such as poleitylene terephthalate) polyamide, polycarbonate, poly (vinyl chloride), poly (vinylidine chloride) , cellulose acetate butyrate, cellulose acetate propionate, poly (ether sulfone), polyurethane, ionomer resins (such as metal ion / acrylic acid crosslinked polyethylene ionomers known for the trade designation SURLYN) and the like, and in the form Preferred also comprises a UV light absorber. From the aspects of mechanical strength and light reflectivity, layer 2 preferably has a refractive index of about 1.6, which is possible if the layer is made of a polycarbonate resin, an ionomeric resin such as that just described , or an acrylic resin. The length of the base of the pyramid element preferably varies from about 0.1 to about 3.0 millimeters (mm), and more preferably ranges from about 0.2 to about 1.0 mm, in order to ensure good retroreflectivity and a wide angle property. For flexible articles of the invention, the length of up to 0.625 mm is preferable. The structured layered article 7 may be made of an integral material for example, by embossing a preformed sheet with a described arrangement of cube corner elements, or by emptying a fluid material in a mold; or these can be made as a layered or laminated product, for example, by emptying the elements against a preformed film as taught in US Pat. No. 3,684,384, or by laminating a preformed film on the front face of individual molded elements. Polycarbonates and ionomers are preferred, integral sheet materials. The thickness of the structured layered article 7 preferably ranges from about 50 to about 500 micrometers in terms of the height of the apex of the pyramid or A? prism to the base of the base portion. If the thickness is less than 50 micrometers, the mechanical strength is not sufficient and it is difficult to obtain a predetermined height for the pyramids or prisms, so that retroreflectivity decreases. If the thickness exceeds 500 micrometers, on the other hand, the total thickness of the retroreflective sheet becomes so thick that handling becomes difficult and the amount of adhesive required increases.

III. Colored Sealant Film Layer In the present invention, the colored sealant film layer 3 is involved in the retroreflectivity display by forming an air layer 10 between the colored, sealing film layer 3 and layer 2. In other words, In order for layer 2 to exhibit retroreflectivity, there must be an air layer just below the formed elements to produce a change in the refractive index. The colored, sealing film layer 3 is laminated to the structured surface of the layer 2, and the colored, sealing film layer 3 is bonded thereto with heat and / or radiation at a plurality of locations, thereby forming a plurality of sealed airbags. It is understood that "air" is used only as an example and that other fluids may be used, depending on the atmosphere in which the articles of the invention are produced, and conditioned that the fluid used is significantly different in the refractive index of the layer 2 (a difference in refractive indexes of 0.5 is preferred). The processes of US Pat. No. 4,025,159 can be used to effect the union of the colored layer 3 to the second structured surface of layer 2. If water, oil or the like enter between layer 2 and the sealing film layer, colored 3, the refractive index changes and retroreflectivity decreases. Accordingly, the preferentially colored layer has a seal effect for water and the like. The colored sealing film layer 3 - is preferably a plastic film-like article comprising a plastic resin such as a polyester containing a predetermined amount of one or more pigments such as titanium oxide, silica, red oxide and similar, added to the resin. You can use white, gri-3, red, yellow, as the color, and the pigments to be added (and their quantity) are selected appropriately in configuration with the application, ability to be recognized, etc. In particular, white and gray are suitable for the present invention because the ability to be recognized of the retroreflective articles of the invention is high.

IV. Primer layer A particularly preferred resin for forming the colored, sealing film layer is a polyester resin, in most cases because the pigment can be easily added to the resin. However, the bonding of the polyester films to the adhesive layers is not easy and further, when a pigment such as titanium oxide is added, the bonding becomes more difficult. Since the pigments in general They contain impurities such as acids and alkalis, these impurities migrate to the adhesive and promote the cure of the phenolic resin, for example causing the problem of the reduction of open time (period of time between the application of the adhesive and the cure of the adhesive). When the colored, sealing film layer is printed either physically or chemically, however, these problems can be effectively separated. In the present invention, a chemical priming layer or a corona treatment layer is preferably placed between the colored sealing film layer 3 and the heat sensitive adhesive layer 5. When a chemical priming layer is used and / or corona treatment, the adhesion between layers between the colored sealing layer film and the heat sensitive adhesive layer 5 can be improved, and in this way a high adhesion of the articles of the invention to the substrate is possible. Suitable chemical primer coatings can be selected from urethanes, silicones, epoxy resins, vinyl acetate resins, ethylene imines and the like. Urethane and silicone types are chemical priming coatings _ particularly effective for colored, sealing film layers. Among the type of silicone, the primer layer having a gelled, continuous network structure of inorganic particles, which is described in Japanese Unexamined Patent Publication (Kokai) No. 2-200476, is suitable for the present invention. This is because it has a particularly remarkable affinity for polyester resin and polyolefin resins. Examples of chemical primer layers for vinyl films and polyethylene terephthalate include crosslinked acrylic ester / acrylic acid copolymers described in U.S. Patent No. 3,578,622. The thickness of the chemical primer layer is suitably within the range of 10 to 3,000 nanometers (nm). If the thickness is less than 10 nm, the effect of the primer layer is minimal and if it exceeds 3,000 n, on the other hand, the inter-layer detachment will probably occur in the primer layer. The corona treatment is a preferred physical primer that can be applied in an appropriate manner to the surface of the colored, sealing film layer, on which the adhesive of the present invention is then coated. The corona treatment not only improves the adhesion between layers between the adhesive layer and the colored, sealing film layer, but also provides the advantage in the production process in that it can be applied separately after the structured layered article is applied. and the sealing film layer, colored 3, are sealed. The corona treatment in the present invention can be carried out suitably in a nitrogen atmosphere because the duration of the effect of the improvement of the adhesion between layers is high. Corona treatment of films is a well-known technique, and is generally described in Cramm, R.H., and Bibee, D.V., The Theory and Practice of Corona Treatment for Improving Adhesion, TAPPI, Vol. 65, No. 8, pp. 75- "3 (August 1982).

Examples and Test Methods The invention will be described more concretely with reference to the following illustrative examples and test methods. All -parts and percentages are by weight unless otherwise specified. The bisamide used in these Examples was that known in formula (II) above.

Test Methods Coefficient of Elasticity The test procedure of the coefficient of elasticity at 30 ° C and 70 ° C was previously described.

Transparency A 50 gm thick "A1200" polyester film, (a Toyo Boseki KK product) was laminated onto the coating surface which was formed on an exfoliating polyethylene laminate paper so that the coating amount became of 87.2 g +/- 3.2 g, and then the coating film was transferred to the polyester film by removing the peelable paper. Subsequently, the polyester film was laminated on the exposed surface side of the coating film thus transferred, and a coating sample was obtained under the state where it was interposed between the two polyester films. The transparency was measured using this coating film sample according to the method stipulated in 5.5 of JIS K 7105 (Testing Methods for Optical Properties of "Lastics).

Pre-Adhesion A commercially available 50 micron thick sheet or foil was laminated to the surface of the coating film prepared as described above, and the coating film equipped with peelable paper was bonded to the surface of the foil. at approximately 70 ° C. This film was cut to a width of 2.54 cm (1 inch) and a laminate sample was obtained. The laminate sample was allowed to stand for 24 hours at 20 ± 2 ° C and an RH (Relative Humidity) of 65 ± 5%. After the laminate sample was allowed to stand, the peelable paper was removed and the sample was attached to a 3 mm thick polycarbonate plate used as the substrate article, previously cleaned with isopropyl alcohol. Then, immediately afterwards, the 90 ° detachment test of the laminate sample was carried out. In this detachment test, the other operations were carried out according to the method stipulated in JIS Z 0237 (Testing Methods of Pressure Sensitive Adhesive Tapes and Sheets), 8, and the peel strength at a release rate of 300 m. / min and a peel angle of 90 ° C. The previous adhesion value used an average value of three measurement values of this peel strength.

Subsequent Adhesion The measurement was carried out in the same manner as in the "previous adhesion measurement method" described above except that the thickness of the aluminum sheet was changed to 80 microns, the substrate article was a flat aluminum plate 1 m thick, the laminate sample was bonded to the substrate article when using a heat lamp vacuum applicator (referred to later as "HLVA") and that the detachment operation in the detachment test was carried out after that a safety tape was bonded to the surface of the aluminum foil of the laminate sample.

Glass transition temperature by the rigid body pendulum viscoelastic measurement method A flat aluminum plate, 1 mm thick, was placed on the surface of the film formed in the same manner as described above, and the coating films were they transferred with heat to the aluminum plate at the binding temperatures shown in the Table, as the samples. A RHEOVIBRON DDV-OPAIII Rigid Body Pendulum Type Viscoelastometer, a product of Tohoku Electronic Industrial Co., was used as the measuring equipment. A knife edge R-06 was fitted to a pendulum structure FT-2 having a moment of inertia of 1.450 g / cm2 was placed on the sample and vibrated at the temperature start rate of 3 ° C / min. , a measurement interval of 10 seconds and a measurement temperature range of -30 to 100 ° C to measure a logarithmic decrease. The temperature corresponding to the peak point of the diagram for the temperature of this logarithmic decrease was used as the glass transition temperature by means of the viscoelastic measurement method, of the pendulum type. A retroreflective sheet of the prism type equipped with an adhesive layer was produced using the coating solution of this embodiment. When the adhesive layer was placed, the surface of the colored layer of the retroreflective sheet was treated with a urethane-type primer layer, and the coating solution was then applied to the surface and dried. The thickness of the adhesive layer was adjusted to 60 micrometers. The characteristics of the retroreflective sheet of the prism type thus produced are shown in Table 2. The method of evaluating each of the features was as follows.

Y Reflectivity Value The Y value of reflectivity was measured by using a reflector etro S80, a product of Nippon Denshoku Kogyo K.K. A D65 lamp was used as the light source and the angle of view was 2 °. The higher the Y value of reflectivity above 40, the sheet could be recognized whiter or with whiteness.

Interim Bonding Performance The ease of positioning to a predetermined binding position was evaluated when the prism-type retroreflective sheet produced in this embodiment was attached to an aluminum substrate for a signaling banner. The case where the positioning could be easily done was evaluated as "excellent", the case where the retroreflective sheet could be strongly joined but slid and the positioning could not be done was evaluated as "leaf slip", and the case where The reflective sheet was joined very strongly that this could not be easily detached by the hand was evaluated as "impossible blade positioning".

Binding temperature (pressure temperature with heat) The temperature at which the pressure with heat can be carried out when the prism-type retroreflective sheet was bonded to the aluminum substrate for a signaling banner using HLVA mentioned above was measured at put a thermocouple in contact with the surface of the reflective sheet.

Retroreflectivity drop after bonding The rate of retroreflectivity drop was measured after the retroreflective sheet of the prism type was bound to the aluminum substrate for the signaling banner as described above was evaluated using retroreflectivity before bonding as 100%.

Article adhesion test in retroreflective layers The 90 ° detachment test was carried out on retroreflective sheets after application to a substrate according to JIS Z0237. The case where the measurement is .590 kgf / cm (1.5 kgf / pg) or more, the result was evaluated as "excellent", and the case where the detachment between layers occurs, the result was evaluated as "detachment between layers".

Round edge test (see FIGURE 2) Frimero, a transverse side (23) of an aluminum substrate having a thickness (20) of 1.5 mm, a side (21) of 70 mm and a length (22) of 100 mm was bent in such a manner as to produce a sample substrate (25) having a curved surface having a radius of curvature of 3 to 10 mm as shown in FIGURE 2. In this case, the bending is made from a Such a way to provide a length of the curved surface corresponding to an arc having an arbitrary radius of curvature of 60. The sample substrates were produced by the radii of curvature in the unit of 1 mm. Next, the prism-type retroreflective sheet having the pressure-sensitive adhesive laminated thereon was cut to a width of 2.54 cm (one inch). After the peelable paper was peeled off, the surface was wiped with a surface treatment agent known under the trade designation FEYO180 (an aqueous solution of an alkylphenyl polyethylene glycol having a solids content of about 2% by weight), a product of Sumitomo 3M Co. , and two test samples (27) were bonded with heat to the sample substrates described above. The binding temperature shown in Tables 2 and 4 was used as the heat-binding condition. After each sample substrate having the samples attached thereto was cooled, the edges of the protruding test samples were adjusted or cut to exact measurement. In this way, the test samples were attached to the sample substrates having the radii of curvature of 3 to 10 mm, and the test of promotion or environmental stimulation,! was carried out in 14 cycles under the condition listed below to observe the precipitous removal of the retroreflective sheet from the curved surface. As a result, the minimum radius of curvature value of each sample substrate, in. which the precipitous removal of retroreflective sheet was not observed for the two samples, was used as the sample result. 1 cycle condition of the promotion or environmental stimulation test * 1. -30 ° C, 0% RH (2 hours) - (1 hour) - 2. 23 ° C, 65% RH (0.5 hours) - (0.5 hours) - 3. 40 ° C, 95% (2 hours) - (0.5 hours) - 4. 23 ° C, 65% RH (0.5 hours) - (0.5 h) - 5. -30 ° C, 0% RH (1.5 hours) - (1 h) - 6. 23 ° C, 65% RH (0.5 hours) - (1 hour) - 7. 80 ° C, 50% RH (1 hour) - (1 hour) ~ 8. 23 ° C, 65% RH (0.5 hours) * The conditions of the cycle were originally used in the automotive industry to provide a correlation to alterability at • interperience. The first time listed is the length of time the sample is allowed to stand at the indicated conditions. The time between the two different conditions, for example - (1 hour) -, is a range that changes to reach the next condition.

Example 1 A solution containing 26 weight percent of an acrylic copolymer (weight average molecular weight = about 1,400,000) containing 90% by weight of isooctyl acrylate and 10% by weight of acrylic acid as monomer units, a solution of methyl ethyl ketone containing 50 weight percent rosin ester ("ESTER GUM 8D, a product of Hercules Co.) as a non-phenolic tackifier and a methyl ethyl ketone solution containing 50 weight percent of a Phenolic resin ("BKR-2620", a product of Union Carbide) was mixed with a mixed solvent of ethyl acetate and toluene with stirring, to obtain a mixed solution The proportion of the content of each component in this mixed solution was adjusted so that 27 parts by weight of rosin ester and 27 parts by weight of the phenolic resin based on 100 parts by weight of the acrylic polymer, after this mixed solution was stirred continuously For 10 minutes, the bisamide expressed by the formula (I) given above was added as the crosslinking agent so that it was counted for 0.14 parts by weight based on 100 parts by weight of the resin component. In addition, methyl ethyl ketone was added to adjust the viscosity, and the mixed solution was stirred for about 10 minutes to thereby obtain a coating solution. This coating solution was applied to the polyethylene laminate paper and dried in an oven at room temperature for 4 minutes, 65 ° C for 5 minutes and at 95 ° C for 3 minutes. A color sensitive adhesive coating having a coating amount of 85 grams / square meter was obtained. The total transparency, pre-adhesion, vitreous transition temperature and subsequent adhesion of this coating were measured, and their measurement values were tabulated in Table 1. The coefficient of elasticity of the composition at 30 ° C and 70 ° C was also measured and it was reported in Table 1.

Example 2 The same procedures as those of Example 1 were carried out, except that the amounts of the components were charged to 30 parts by weight of the tackifier, 70 parts by weight of the phenolic resin and 0.13 parts by weight of bisamide.

Example 3 The same procedures as those of Example 1 were carried out, except that the amounts of the components were charged to 21 parts by weight of the tackifier and 21 parts by weight of the phenolic resin.

Example 4 The same procedures as those of Example 1 were carried out, except that the amounts of the components were charged to 19 parts by weight of the tackifier and 19 parts by weight of the phenolic resin.

Example 5 The same procedures were carried out as those of Example 1, except that the crosslinking agent was not added.

Example 6 The same procedures were carried out as those of Example 1, except that the crosslinking agent was charged to 1.1 parts by weight of aluminum acetylacetonate (aluminum acetylacetonate produced by Varitech Custo Specialties Co.), and 3.5 parts by weight, based on 100 parts by weight of the acrylic resin component, of acetylacetone (acetylacetone produced by Ardrich Chemical Co.) was added as a reaction inhibitor.

Example 7 The same procedures were carried out as those of Example 1, except that the acrylic copolymer was changed to 100 parts by weight of acrylic copolymer (having a weight average molecular weight of about 1,640,000) using 92% by weight of acrylate of butyl and 8% by weight of acrylic acid as the monomer units, and the amounts of the components were changed to 21 parts by weight of the tackifier and 21 parts of the phenolic resin.

Example 8 The same procedures as those of Example 1 were carried out, except that the tackifier was changed to 24 parts by weight of pentaerythritol rosin ester ("ESTER R-95", a product of Hercules Co.) and the amounts of the components were changed to 14 parts by weight of the phenolic resin and 0.15 parts by weight of bisamide.

Example 9 The same procedures were carried out as those of Example 1, except that the tackifier was not added, and the amounts of the other components were changed to 89 parts by weight of the phenolic resin and 0.13 parts by weight of bisamide .

Comparative Example 1 An example using BNR (butadiene-acrylonitrile rubber) instead of the acrylic copolymer in the adhesive component: The same procedures were carried out as those of Example 1, except that the coating solution was changed to the following solution . 100 parts by weight of a butadiene-acrylonitrile rubber ("Nipol N009", a product of Nippon Zeon) and 5.2 parts by weight of zinc oxide ("Protox 166", a product of New Jersey Zinc Co.) were vulcanized. a rubber mill and the mixture was transferred to a stirring tank, and 351 parts by weight of methyl ethyl ketone, and 90 parts by weight of a phenolic resin ("Varcum 861", product of Reichold Co.) were added with stirring and they were uniformly mixed to obtain a coating solution.

Comparative Example 2 The procedures of Example 1 were followed in the same manner, except that the coating solution was changed to the following solution. A mixture of 100 parts by weight of a solution containing an acrylic type copolymer using 90% by weight of isooctyl acrylate and 10% by weight of acrylic acid as the monomer unit, and 0.03 parts by weight of bisamide was mixed with a mixed solvent of ethyl acetate, methyl ethyl ketone and heptane to obtain a coating solution.

Comparative Example 3 The same procedures were carried out as those of Example 1, except that the amounts of the components were changed to parts by weight of the non-phenolic tackifier and 125 parts by weight of the phenolic resin.

Table 1: Heat Sensitive Adhesive of Examples 1 to 9 trapspa-adhesion coefficient temperature adhesion coefficient of elasticity prior to transition after elasticity a ° C (kg / cm2 (gf / cm vitrea ("C) (kgf / cm 70 ° C (kg / cm2 (dynes / cm)) (%) (gf / pg)) (kgf / pg) (dynes / cm2)) Example 1 100 9.02 303 24.3 .826 20 (1 x 107) (770) (2.1) (2 x 10) Example 2 400 88.3 27 32.5 .669 30 (4 x 107) (70) (1.7) (3 x 10c) Example 3 200 90.8 350 19.8 .944 20 (2 x 10") (890) (2.4) (2 x 10 *) Example 4 100 92.1 346 18.5 2.55 30 (1 x 107) (880) (6.5) (3 x 106 ) Example 5 75 (7.5 90.7 381 16.1.708 10 x 106) (970) (1.8) (1 x 106) Example 6 100 90.3 291 25.3 .787 20 (1 x 107) (740) (2.0) (2 x 106) Example 7 200 91.1 338 19.9 2.716 20 (2 x 107) (860) (6.9) (2 x 106) Example 8 100 89.9 326 18.9 2.322 30 (1 x 107) (830) (5.9) (3 x 106) Example 9 400 89.3 23 32.1.590 30 (4 x 107) (60) (1.5) (3 x 106) Table 2: Heat Receptive Retruereflective Articles of Examples 1 to 9 Cap and Tempera-Loss Test Proof of Bridging Bonding Test Adhesion Provisional Edge Rounding (%) HLVA Ce) * (%) do (mm) Example 1 45. 1 excellent 70 2 excellent 4 Example 2 46. 3 excellent 70 3 excellent 3 Example 3 47. 1 excellent 70 1 excellent 5 Example 4 46. 6 excellent 70 3 excellent 5 Ex empl o 5 45. 3 excel 70 70 excellent 6 Example 6 47.2 excellent 70 3 excellent 4 Example 7 46.3 excellent 70 2 excellent 5 Example 8 45.1 excellent 70 2 excellent 4 Example 9 43.1 excellent 70 2 excellent 3 * The baking time was 1.5 minutes at 70 ° C when using HLVA.

Table 3: Heat Sensitive Adhesives of Comparative Examples 1 to 3 coefficient of transparency - adhesion temperature adhesion coefficient of resistance before transition of elasticity to (gf / cm vitrea (° C) (kgf / cm elasticity a 30eC (kg / cm2 (gf / pg)) (kgf / pg) 70 (kg / cm2 (dynes / cm)) (%) (dynes / cm2)) Example 2000 40.5 0 42.0 .708 200 comparative 1 (2 x 10?) (1.8) (2 x 107) Example 9 92.1 799 -12.7 1.377 1 Comparative 2 (9 x 105) (2030) (3.5) (1 x 105) Example 3000 87.9 0 45.0. 157 200 Comparative 3 (3 x 10s) (0.4) (2 x 10 ') Table 4: Retruereflexive Layers of the Heat Sensitive Prism Type of Comparative Examples 1 to 3 Value and Test of Tempera- Calda of the Test Result of Union of retroreflexivi of the Provisional Union Test (° c) after Adhesion Edge (%) of the Rounded Union (mm) Example 39.3 slide93 30 Release > 10 Comparative 1 layer of dimienla layer to between layers Example 45.2 positions temp. exceeds > 10 Comparative 2 environmental ambient * impossible lens of the layer Example 46.1 deslizami 93 32 release > 10 Comparative 3 nd of dimienla layer to between layers The various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, property is claimed as contained in the following:

Claims (10)

1. A transparent heat sensitive adhesive comprising an acrylic polymer and a phenolic resin, characterized in that the heat sensitive adhesive has a coefficient of elasticity ranging from about 10 to about 1000 kg / cm2 (about 1 x 106 to about 1 x 108 dynes / cm2) at 30 ° C.

2. An adhesive according to claim 1, further characterized by at least one of the following. a) the phenolic resin is crosslinked by means of heat; or b) the acrylic polymer is crosslinked by means of a chemical crosslinking agent.

3. An adhesive according to claim 1, wherein the acrylic polymer is crosslinked by means of a chemical crosslinking agent, further characterized by at least one of the following: a) a chemical crosslinking agent is selected from the group consisting of polyisocyanate compounds, epoxide compounds, polyglycidylamines, ethylene imine derivatives, metal salts of organic acids, and metal chelates of organic compounds; or b) the chemical crosslinking agent is selected from the group consisting of an acetylacetonate of a positively charged ion selected from the group consisting of aluminum, zirconium, titanium oxide, chromium, iron, nickel, zinc, cobalt and manganese.

4. An adhesive according to claim 1, further characterized by at least one of the following: a) the adhesive comprises 1 to 35 parts by weight of a non-phenolic tackifier per 100 parts by weight of the acrylic polymer; or b) a non-phenolic tackifier; or c) the adhesive comprises 5 to 100 parts by weight of the phenolic resin per 100 parts by weight of the acrylic polymer.

5. An adhesive according to claim 1, further characterized by at least one of the following: a) it exhibits transparency of at least 85%; or b) it exhibits a vitreous transition temperature (by a measurement of the rigid body pendulum type) ranging from about 0 ° C to about 40 ° C.

6. An article comprising a layered article having a substantially planar surface and a structured surface, the structured surface comprising a plurality of precisely formed projections, a colored layer disposed on the structured surface and adhered thereto in a plurality of locations discrete, and a layer of heat sensitive adhesive disposed on the colored layer, characterized in that the layer of heat sensitive adhesive comprises an acrylic polymer and a phenolic resin, and has a coefficient of elasticity ranging from about 10 to about 1000 kg / cm2 (approximately 1 x 10 ° to approximately 1 x 103 dynes / cm2) at 30 ° C.

7. A retroreflectivity or retroreflective article according to claim 6, further characterized by at least one of the following: a) a vitreous transition temperature (by a rigid body pendulum type measurement) of the heat sensitive adhesive layer is from 0 ° C to 40 ° C; or b) the transparency of the heat-sensitive adhesive layer is at least 85%.

8. The retroreflective article according to claim 6, further characterized by at least one of the following: a) the acrylic polymer is crosslinked by a chemical crosslinking agent; or b) the acrylic polymer is crosslinked by a chemical crosslinking agent selected from the group consisting of polyisocyanate compounds, epoxide compounds, polyglycidylamines, ethylene imine derivatives, metal salts of organic acids, and metal chelates of organic compounds; or c) the acrylic polymer is crosslinked by a metal salt of an organic acid selected from the group consisting of an acetylacetonate of a positively charged ion selected from the group consisting of aluminum, zirconium, titanium oxide, chromium, iron, nickel, zinc , cobalt and manganese; or d) the adhesive comprises 5 to 100 parts by weight of the phenolic resin per 100 parts by weight of the acrylic polymer; or e) the adhesive comprises 1 to 35 parts by weight of a non-phenolic tackifier per 100 parts by weight of the acrylic polymer; or f) the adhesive comprises a non-phenolic tackifier of the rosin type.

9. A retroreflective article according to claim 6, characterized in that the article further comprises a primer layer between the colored layer and the adhesive layer.

10. An article according to claim 6, further characterized by at least one of the following: a) the plurality of accurately formed projections comprises a plurality of cube corners; or b) the plurality of accurately formed projections comprises a plurality of parallel cousins.