Heat-sensitive recording material and process for producing same

Abstract

A heat-sensitive recording material comprising support (A) having provided thereon transfer layer (B) and support (C) in order, these supports having the property that before heating the adhesion strength between transfer layer (B) and support (C) is smaller than the adhesion strength between transfer layer (B) and support (A) and larger than 0.1 g/cm but, after heating to a temperature higher than the heat sensitive temperature of transfer layer (B), the adhesion strength between transfer layer (B) and support (C) becomes greater than the adhesion strength between support (A) and transfer layer (B), and the transfer layer (B) comprising, at least on the side to be in contact with support (C), a heat-sensitive composition containing as a major component a mixture of a heat-sensitive substance which is fluidized at the heat sensitive temperature of the heat-sensitive substance and an adhesiveness-imparting agent which can adhere to support (C) at a temperature not higher than the heat sensitive temperature of the heat-sensitive agent; and a process for producing same. An embodiment includes the transfer layer (B) comprising two layers: one being a colored layer adhering to support (A); and the other being a heat-sensitive layer adhering to support (C).

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat-sensitive recording material and a process for producing the same.

2. Description of the Prior Art

Heretofore, a so-called transfer-type heat-sensitive copying method is known in which a transfer sheet having a heat-sensitive transfer layer and a receiving sheet are superposed on each other and heat is imagewise applied to the heat-sensitive layer of the heat-sensitive transfer sheet to imagewise soften and melt this layer, thus imagewise transferring the transfer layer onto the receiving layer to obtain a copy, as disclosed, for example, in U.S. Pat. No. 2,769,391. The heat-sensitive copying material to be used therefor comprises two independent sheets, i.e., a receiving sheet and a transfer sheet. These two sheets are superposed over each other for use in duplication.

Therefore, in the conventional method, insufficient contact between the receiving sheet and the transfer sheet results in an insufficient and non-uniform transfer of the transfer layer to the receiving sheet upon application of heat. If the transfer layer is increased in thickness than is necessary to achieve duplication so as to improve the above defect, the transfer layer spreads too widely in lateral direction upon transfer, which results in obtaining discontinuous, broad or distorted images only.

Also, in the conventional method using two separate sheets, a slight deviation can occur between the two sheets or one of the sheets can wrinkle upon duplication. Therefore, it has the defect in that transfer is not achieved at all in some areas, in that seriously distorted copied images result, and in that the material transfer is so difficult to handle that copying cannot be conducted with stability.

Furthermore, in the conventional method, the transfer layer must possess additional properties such as coloring properties when used for copying documents, or an affinity for an ink when used for producing a master for offset printing, as well as the heat-sensitive property, depending upon the end use to which the assembly is put. Since a conventional transfer layer has had to possess a plurality of properties as described above, it has been difficult to obtain a transfer layer capable of satisfying all of these requirements.

SUMMARY OF THE INVENTION

An object of the present invention is to obtain a novel heat-sensitive recording material without the defects which have been encountered with the above-described conventional heat recording materials.

Another object of the present invention is to provide a heat-sensitive recording material which can be handled with ease and stably provide a sharp and distinct copied image with no distortion, no broadened areas and discontinuous areas, and to provide a process for producing the same. The material of the present invention can be applied to various heat-sensitive copying or recording methods.

The above-described objects of the invention can be attained by using the heat-sensitive recording material of the present invention.

The heat-sensitive recording material of the present invention comprises support A having thereon transfer layer B and support C in order, these sheets having the property that before heating the adhesion strength between transfer layer B and support C is less than the adhesion strength between transfer layer B and support A and is larger than 0.1 g/cm but, after heating to a temperature higher than the heat sensitive temperature of transfer layer B, the adhesion strength between transfer layer B and support C becomes greater than the adhesion strength between support A and transfer layer B, with the transfer B comprising, at least at the side thereof in contact with support C, a heat-sensitive composition containing as a major component a mixture of a heat-sensitive substance which becomes fluid at the heat-sensitive temperature of the heat-sensitive substance and an adhesiveness-imparting agent which can adhere to support C at a temperature not higher than the heat-sensitive temperature of the heat-sensitive substance. In this invention, the recording material can be handled integrally as one sheet by adhering the transfer layer B on support A to the receiving support C with an appropriate degree of strength.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 is a cross-sectional view showing one embodiment of the heat-sensitive recording material of the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the heat-sensitive recording material of the present invention in which transfer layer B comprises a colored layer or an ink-receptive layer B-1 and a heat-sensitive layer B-2.

FIF. 3 shows the condition of duplication using reflection exposure method with the heat-sensitive recording material 1 of the present invention, in which numeral 2 denotes an original and 3 an image area.

FIG. 4 shows the condition of the material after copying, in which delamination occurs between transfer layer B and support C at the non-image area B and, at image area B', delamination occurs between support A and transfer layer B'.

FIG. 5 shows the relationship between the press-contacting temperature and the peel strength required between the transfer layer B and support C, in one example of the heat-sensitive recording material of the present invention, in the case of press-contacting support C onto transfer B formed on support A.

DETAILED DESCRIPTION OF THE INVENTION

The transfer layer B of the present invention must comprise, at least at one side thereof which is in contact with support C, a heat-sensitive composition containing as a major component a mixture of a heat-sensitive substance and an adhesiveness-imparting agent. As long as this condition is satisfied, the number of layers forming the transfer layer B is not particularly limited.

The transfer layer B can be formed as one layer comprising a composition containing as a major component a mixture of a heat-sensitive substance and an adhesiveness-imparting agent. It can further contain a coloring agent such as an oil-soluble dye, a water-soluble dye, an alcohol-soluble dye or a disperse dye, or an organic or inorganic pigment if it is to have end-use applications for copying documents, a spirit dye if it is to have end-use applications for preparing a spirit master, or an ink-receptive agent if it is to have end-use applications for producing a master for general printing and, if desired, various polymers, low molecular weight compounds, fillers and the like for the purpose of adjusting the cohesive force of the transfer layer. A suitable amount of these addenda can range from about 2 to 80, preferably 5 to 60, percent by weight of the layer.

Also, as a preferred improved embodiment, the transfer layer can comprise two layers: one layer being a colored or ink-receptive layer B-1 in contact with support A; and the other layer being a heat-sensitive layer B-2 in contact with support C, containing as a major component a mixture of a heat-sensitive substance and an adhesiveness-imparting agent.

Where, for example, a reflection exposure method is used, the transfer layer B must substantially transmit the ligth used for exposure, while where a stencil transmission method is used, the transfer layer B must possess a component which absorbs the light used for exposure to generate heat.

The heat-sensitive substance must become fluid at the heat-sensitive temperature employed upon heat-sensitive duplication. Usually, the heat-sensitive temperature is preferably not less than about 40.degree.C and not higher than about 200.degree.C, most preferably 50.degree. to 150.degree.C. As the heat-sensitive substance, those which exhibit almost no fluidity at a temperature lower than the heat-sensitive temperature but become fluid very quickly at the heat-sensitive temperature, that is, those substances which exhibit the characteristics as graphically shown, e.g., by XY'Z, in FIG. 5 are preferable.

Suitable examples of such heat-sensitive substances are paraffins having a variety of melting points, e.g. (50.degree. to 75.degree.C); waxes such as candelilla wax (m.p. 60.degree. - 80.degree.C), bees wax (m.p. 60.degree. - 66.degree.C), montan wax (m.p. 65.degree. - 105.degree.C), ceresine wax (m.p. 65.degree. - 85.degree.C), carnauba wax (m.p. 75.degree. - 86.degree.C), etc.; wax analogs such as stearic acid, stearyl alcohol, etc.; synthetic resins such as coumarone-indene resins, phenolic resins, e.g., novalac (m.p. 50.degree. - 150.degree.C), alkylphenolic resins (m.p. 70.degree. - 150.degree.C), petroleum resins, comparatively low molecular weight polystyrene (e.g., having a number mean molecular weight about 300 to 200,000, having a melting point of about 50.degree. to 150.degree.C), aliphatic hydrocarbon polymers (e.g., having an number mean molecular weight of about 500 to 2,000 and a melting point of about 50.degree. to 130.degree.C), etc.; natural resins and modified ones thereof such as rosin, ester gum, hydrogenated rosin, etc., these materials can be used either alone or in combination.

The adhesiveness-imparting agent must impart adhesivity to the mixture of the adhesiveness-imparting agent and the heat-sensitive substance upon mixing such that the mixture can adhere to support C at a temperature less than the heat-sensitive temperature of the heat-sensitive substance.

Suitable examples of adhesiviness-imparting agent which can be used and which satisfy the above-described requirement are a variety of rubbers and resins having a glass transition point or a softening point less than the heat-sensitive temperature of the heat-sensitive substance, preferably a softening point or glass transition point of more than 5.degree. less than the heat-sensitive temperature from a practical standpoint. To illustrate some specific examples, there are rubbers such as natural rubber, polyisobutylene, butadiene rubber, styrene-butadiene rubber, nitrile rubber, etc.; polyvinyl chloride and the copolymers thereof (e.g., vinyl chloride-vinyl acetate, vinyl chloride-vinyl propionate, vinyl chloride-vinylidene chloride, vinyl chloride-vinyl acetate-maleic anhydride, etc.); polyvinylidene chloride and copolymers thereof (e.g., vinylidene chloride-methyl acetate, vinylidene chloride-ethyl acetate, vinylidene chloride-acrylonitrile, vinylidene chloride-vinyl chloride, etc.); polyvinyl acetate and the copolymers thereof (e.g., vinyl acetate-methyl acrylate, vinyl acetate-ethyl acrylate, etc.); polymethacrylates and the copolymers thereof (e.g., methyl methacrylate-methyl acrylate, methyl methacrylate-ethyl acrylate, methyl methacrylate-2-ethyl hexyl acrylate, etc.); polyacrylates and the copolymers thereof; polystyrene and the copolymers thereof (e.g., styrene-butadiene, etc.); ethylene copolymers such as ethylene-vinyl acetate, ethylene-acrylate, etc.; other polyolefins; polyvinyl ethers; polyvinyl butyral; polyesters; nylon, a variety of plasticizers (e.g., dicyclohexyl phthalate, di(2-ethyl hexyl)phthalate, etc.) or low molecular weight compounds capable of exhibiting analogous effects; and the like. These materials have a glass transition points or softening point up to 180.degree.C, preferably up to 140.degree.C and can be suitably selected so as to have the appropriate relationship to the heat-sensitive temperature of the heat-sensitive substance with which they are used.

The amount of the adhesiveness-imparting agent employed can be appropriately selected depending upon the combination of the heat-sensitive substance and the adhesiveness-imparting agent used or the desired degree of adhesion strength between, e.g., the transfer layer B and support C. Generally, the proportion of the adhesiveness-imparting agent in the heat-sensitive layer is about 1 to 90 percent by weight, preferably 5 to 70 percent by weight and, more preferably, 20 to 50 percent by weight.

Transfer layer B can comprise two layers, i.e., a colored or ink-receptive layer B-1 in contact with support A and a heat-sensitive layer B-2 in contact with support C. In this case, as such a colored layer B-1, those layers which are prepared by incorporating in the heat-sensitive composition a variety of dyes such as oil-soluble dyes (e.g., Oil Black, Oil Blue, Oil Red, Oil Yellow, etc.), water-soluble dyes (e.g., Methylene Blue, Congo Red, etc.), alcohol-soluble dyes (e.g., Rhodamine, Safranine, Victoria Green, Crystal Violet, etc.) and disperse dyes; various organic or inorganic pigments such as carbon black, titanium oxide, zinc oxide, red iron oxide, Phthalocyanide Blue and Phthalocyanine Green in a suitable amount, or those which are prepared by incorporating the coloring agent in thermoplastic resins such as polyvinyl chloride or a copolymer thereof, polyvinylidene chloride or a copolymer thereof, polyvinyl acetate or a copolymer thereof, polymethacrylate or a copolymer thereof, polyacrylate or a copolymer thereof, polystyrene or a copolymer thereof, polyethylene or a copolymer thereof, polyvinyl acetal, polyvinyl alcohol, an alkylphenol resin, a polyamide, a polyester, a petroleum resin, a coumarone-indene resin, etc., or in thermosetting resins such as a melamine resin, a urea resin, a polyurethane, a reactive acrylic resin, an epoxy resin, etc., a natural resin or a modified natural resin such as rosin, ester gum, hydrogenated rosin, etc., various waxes, paraffins, or the mixture thereof, can be used.

As the ink-receptive layer B-1, those ink-receptive layers prepared by appropriately selecting ink-receptive materials from among various waxes, the above described thermoplastic resins, thermosetting resins, natural resins and the modified natural resins and, if desired, incorporating a coloring agent and a filler therein can be used. For example, for preparing a master for use in offset printing using an oily ink, oleophilic substances such as waxes, polystyrene, polyethylene, etc. are used, while for preparing a master for printing using a water-color ink, hydrophilic substances such as water-insolubilized polyvinyl alcohol are used. Thus, the material is selected depending upon the end use purpose.

The use of a colored or ink-receptive layer B-1 which is heat-insensitive at a heat-sensitive temperature of the heat-sensitive layer B-2 has the advantage of providing better copied images, because an excessive fluidity of the transfer layer upon heat sensitization can be controlled and the adhesion strength between the support A and transfer layer B is made constant regardless of the temperature.

As the heat-sensitive substance which forms the conventional heat-sensitive transfer stratum comprising a transfer sheet and a receiving sheet, those heat-sensitive substances which do not exhibit any fluidity when the temperature is increased to a certain point but become fluid very quickly at the heat-sensitive temperature, such as carnauba wax, are preferable. However, if adherence of transfer layer B comprising such a substance to support C is attempted at a temperature less than the heat-sensitive temperature of the transfer layer B by heat-pressing support C onto the surface of transfer layer B, formed on support A, using the above-described heat-sensitive substance alone, layer B will not adhere to support C at all, while when the temperature is increased to or higher than the heat-sensitive temperature, layer B adheres to support C so strongly, due to the fluidity of the heat-sensitive layer B, that the relative relationship in adhesion strength between these sheets is not satisfactory. This results in completely destroying the duplication ability thereof. That is, it is extremely difficult to control the adhesion strength between transfer layer B and receiving support C.

On the other hand, when those heat-sensitive substances whose viscosity decreases and fluidity increases gradually with an increase in temperature, such as a high molecular weight polymer, are used, it becomes possible to control the adhesion strength between transfer layer B and receiving support C to some extent, even though not to a completely sufficient extent. However, the change in fluidity versus the change in temperature is so slow that it has the defects that the boundary of the copied image are blurred, resulting in a copied image which is not sharp, and that the adhesion strength between transfer layer B and receiving support C tends to undergo changes with the lapse of time.

As is described above, when those substances which are preferred as a heat-sensitive substance for transfer-type heat-sensitive recording material are used per se as a heat-sensitive substance, technical difficulties have occurred in that the adhesion strength between the transfer layer B and the support C becomes impossible to control, whereas when those substances in which the adhesion strength between the transfer layer B and the support C can be controlled to some extent are used as a heat-sensitive substance, the heat-sensitive copying property is degraded.

However, it is now extremely easy to control the adhesion strength between the transfer layer B and the receiving support C by adding an adhesiveness-imparting agent to the heat-sensitive substance as described in the present invention.

As support A, those supports which are not melted by the heat applied upon heat-sensitive duplication, such as paper, plastic films, and the like, can be used. The support A can be appropriately selected depending upon the end-use application and the copying method employed. For example, in using the reflection exposure method as the copying method, support A must substantially transmit the light used. An appropriate thickness of support A is a thickness of about 5 to 500 .mu., preferably 5 to 100 .mu..

Suitable examples of plastic films are plastic films of polypropylene, polyethylene, polyvinyl chloride; polyvinylidene chloride, polymethyl methacrylate, polyvinyl alcohol, polystyrene, polycarbonate, polyester, nylon, polyurethane, cellulose derivatives, and the like. The choice of such a film will be dependent upon the purpose for use. If desired, these sheets can be subjected to a surface treatment such as corona discharge, flame treatment, chemical treatment, etc. or a coating treatment to appropriately adjust the adhesivity of the support.

As support C, those examples suitable for support A, such as paper and plastic films can be selected depending upon the end use. In order to adjust the adhesion between support C and transfer layer B or to impart ink-repellent properties, hydrophilic properties or marking properties, support C can be also subjected to, if desired, a surface treatment or a coating treatment as described previously for support A to appropriately adjust the adhesivity to the support C.

The absolute values of the adhesion strength between these supports are not particularly limited so long as the above-described relative and the condition in which the adhesion strength between layer B and support C before heating is greater than zero are satisfied. However, in practice, the peel strength between support A and transfer layer B is about 1 to 150 g/cm, preferably 2 to 50 g/cm, and the peel strength between layer B and support C is about 0.1 to 50 g/cm before heating and, after heating, is not less than about 2 g/cm, preferably not less than 20 g/cm as measured as described hereinafter.

As was described above, in the heat-sensitive recording material of the present invention, the adhesion strength between layer B and support C is greater than zero. That is, transfer layer B adheres to support C with a certain degree of strength. Therefore, even when the thickness of the transfer layer is reduced, transfer can be effected in high yield and the material can be handled as one sheet. In addition, good copied images with no distortion and image broadening, which have been defects in conventional materials, can be obtained with stability.

In order to obtain good copied images, it is necessary that the cohesive strength of transfer layer (B) itself or the adhesion strength between the colored or ink-receptive layer B-1 and the heat-sensitive layer B-2 must be greater than both the adhesion strength between transfer layer B and support C before heat sensitizing and the adhesion strength between transfer layer B and support A after heat sensitizing, whereas the cohesion strength must be of such degree that, upon separating support A from support C after copying, transfer layer B can be severed in an imagewise manner. In order to adjust the cohesive force, means can be taken in which various polymer a or low molecular weight compounds as previously described, or fillers such as titanium oxide or silica are incorporated or the transfer layer B can be formed as a discontinuous layer comprising fine particles, e.g., having a particle size ranging from about 0.1 to 100 .mu..

The process for producing the heat-sensitive recording material of the present invention which comprises support A, transfer layer B and support C comprises press-contacting support C onto the surface of transfer layer B formed on support A, each support having the property such that 1 before heating, the adhesion strength between support A and layer B is greater than the adhesion strength between transfer layer B and support C is greater than 0, and 2 this relation is changed by heating to a temperature not less than the heat sensitive temperature of the transfer layer B so that the adhesion strength between transfer layer B and support C becomes greater than the adhesion strength between support A and transfer layer B.

The transfer layer B comprises, at least at one one side in contact with support C, a heat-sensitive composition containing a major component a mixture of a heat-sensitive substance and an adhesiveness-imparting agent, this heat-sensitive substance exhibiting fluidity at a heat-sensitive temperature upon duplication and this adhesiveness-imparting agent imparting sufficient adhesiveness so that adherence to support C at a temperature less than the heat-sensitive temperature of the heat-sensitive substance occurs. Support C is press-contacted onto the surface of heat-sensitive composition of the transfer layer B comprising the heat-sensitive composition at a temperature not higher than the heat-sensitive temperature of the heat-sensitive composition and at a temperature not lower than the adhesiveness-generating temperature thereof.

Various methods for forming transfer layer B on support A can be employed, e.g., a method of applying a solution in water or an organic solvent, a dispersion in water or an organic solvent or a melt of the heat-sensitive composition to support A, followed by drying, or a method of forming a heat-sensitive composition layer on a separate temporary support, bringing this heat-sensitive composition layer into contact with support A and then removing the temporary support. Suitable examples of organic solvents which can be used as described hereinbefore are alcohols such as methanol, ethanol, butanol and isopropyl alcohol, aromatic hydrocarbons such as toluene, benzene and xylene, esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone, etc. These solvents or water can be used alone or as a mixture using a concentration in the solvent of 2 to 60 percent by weight.

Also, as a method for forming transfer layer (B) comprising a colored or ink-receptive layer B-1 and a heat-sensitive layer B-2, various methods can be employed, for example, a method of forming on support A a colored or ink-receptive layer B-1 and a heat-sensitive layer B-2 in turn, a method of forming a heat-sensitive layer B-2 on a separate temporary support, bringing this layer into contact with a colored or ink-receptive layer B-1 on support A previously formed, and then removing the temporary support, or a method of forming on a separate temporary support a heat-sensitive layer B-2 and a colored or ink-receptive layer B-1 in turn, bringing it into contact with support A, and then removing the temporary support.

The thickness of transfer layer B can be appropriately selected depending upon the end use purpose. However, generally the thickness ranges from about 0.3 to 18 .mu., more preferably 0.5 to 5.mu.. In order to obtain good copied images, the transfer layer should be as thin as possible. Where the layer B comprises two layers, a suitable thickness for transfer layer B-1 ranges from about 0.5 to 17 .mu. and for B-2 ranges from about 0.5 to 15 .mu., preferably 0.5 to 5 .mu..

Where transfer layer B comprises two layers, i.e., a colored or ink-receptive layer B-1 and a heat-sensitive layer, it is easy to make the thickness of the heat-sensitive layer B-2 as thin as about 0.5 to 5 .mu.. With such a structure, there is the advantage that good copied images can be obtained even when the colored or ink-receptive layer B-1 is quite thick.

After forming transfer layer B on support A as described above, support C is press-contacted onto the surface of the transfer layer B comprising the heat-sensitive composition. The press-contacting temperature should not be higher than the heat-sensitive temperature of the heat-sensitive composition and should not be lower than the adhesiveness-generating temperature. A suitable press-contacting temperature can range from room temperature (about 20.degree. - 30.degree.C) to about 180.degree.C, preferably 50.degree.C to 140.degree.C.

If the press-contacting temperature is not higher than the adhesiveness-generating temperature, adherence of transfer layer B to support C is impossible, while if the press-contacting temperature is not lower than the heat-sensitive temperature, the heat-sensitive substance is converted to a heat-sensitized state and the adhesion strength between the transfer layer B and support C becomes so great that relative relationship in the adhesion strength between the supports is not satisfied, resulting in a destruction of copying ability.

As has already been described, the adhesion strength between transfer layer B and support C can usually be about 0.1 to 50 g/cm, which can be highly controlled by selecting the press-contacting temperature, the application pressure, the time, the kind of adhesiveness-imparting agent, the compounds amount, and the like.

Various press-contacting method can be employed, e.g., a method of passing two superposed supports through two press rollers maintained at an appropriate temperature, or a method of press-contacting the two supports to each other using parallel heating plates.

In addition, the order of press-contacting support A, transfer layer B and support C can be different from that described above. For example, formation of transfer layer B on a separate temporary support, press-contacting support C onto transfer layer B at a temperature higher than the heat sensitive temperature of the transfer layer and not lower than the adhesiveness-generating temperature, removal of the temporary support to prepare a configuration comprising support C/transfer layer B, bringing the transfer layer of this configuration into contact with the adhesive agent-coated surface of support A coated with the adhesive agent capable of adhering to the transfer layer at a temperature not higher than the heat-sensitive temperature of the transfer layer, and application of a pressure to the assembly at a temperature not higher than the heat-sensitive temperature of transfer layer B is within the scope of this invention.

The combination of support A, transfer layer B and support C in the present invention includes, for example, polyester-(montan wax (this first listed component in the parentheses here and in the examples hereinafter being a heat sensitive substance), polyisoprene (this second listed component in the parentheses here and in the examples hereinafter being an adhesiveness-imparting agent))-cellulose acetate, polypropylene-(carnauba wax, styrene-butadiene copolymer rubber)-polyvinyl chloride, nylon- (montan wax-polybutadiene)polypropylene, nylon-(montan wax, low molecular weight polyethylene + a non-crystalline polyester)-polystyrene, polypropylene-(montan wax, ethylene-vinyl acetate copolymer)-cellulose acetate, polyethylene terephthalate-(montan wax, polyvinyl butyral, ethylene-vinyl acetate copolymer)-cellulose acetate, polyethylene terephthalate-(carnauba wax, ethylene-vinyl acetate copolymer)-internally plasticized polyvinyl chloride film, nylon-(carnauba wax, + montan wax, ethylenevinyl acetate copolymer)-internally plasticized polyvinyl chloride film, polyethylene terephthalate-(montan wax, ethylene vinyl acetate copolymer)-cellulose acetate, polyethylene terephthalate-(montan wax + carnauba wax, ethylene vinyl acetate copolymer)-cellulose acetate, and the like.

FIG. 1 is an enlarged cross-sectional view showing configuration 1 of the heat-sensitive copying material in accordance with the present invention, wherein A, B and C represent support A, transfer layer B and support C, respectively.

FIG. 2 is an enlarged cross-sectional view showing another configuration 1' of the heat-sensitive copying material in accordance with the present invention, wherein B-1 represents a colored or ink-receptive layer B-1, and B-2 a heat-sensitive layer B-2.

FIG. 3 shows the condition of copying employing a reflection exposure method using the heat-sensitive copying material 1 of the present invention, wherein numeral 2 denotes an original and 3 denotes an image area. Upon irradiation with infrared rays, heat is generated in image area 3, which travels in the order of support A and transfer layer B, and thus the temperature of transfer layer B corresponding to the image area reaches the heat-sensitive temperature. Thus, in the B'-portion, as a result of increase in adhesion strength between portion B' and support C, the adhesion strength between portion B' and support C becomes greater than the adhesion strength between support A and portion B' after heating, the former having been less than the latter before heating.

In this case, since the adhesion strength between layer B and support C is greater than zero before copying, that is, transfer layer B adheres to support C with a certain degree of adhesion strength, layer B is in uniform contact with support C over the entire surface with substantially no inclusions such as air bubbles therebetween and the above-described change in the relative relationship of the adhesion strength takes place uniformly and completely over the entire heated portion B'.

Upon delaminating support C from support A as shown in FIG. 4, a positive copied image B' corresponding to the image area is formed on support C while a negative copied image is formed on support A. Because no heating occurred in the non-image area, delamination occurs between transfer layer B and support C since the adhesion strength between support A and the transfer layer B is greater than the adhesion strength between transfer layer B and support C, whereas in the image area B', delamination occurs between support A and transfer layer B' since the adhesion strength between transfer layer B' and support C is greater than the adhesion strength between support A and transfer layer B'.

FIG. 5 shows the relationship between the press-contacting temperature and the adhesion strength between transfer layer B and support C in conducting the press-contacting at a pressure of 3 kg/cm.sup.2 for 2 seconds, in which a heat-sensitive composition provided on a polyethylene terephthalate film [support A ] is brought into contact with a cellulose acetate film [support C ], with this composition containing montan wax as a heat-sensitive substance and ethylene-vinyl acetate copolymer (vinyl acetate content: 40 percent by weight) as an adhesiveness-imparting agent in a weight proportion of 70 : 30.

X represents the point at which adhesiveness appears, transfer layer B being capable of adhering to support C at a temperature higher than this temperature. Y represents the heat sensitive temperature, the adhesion strength of transfer layer B to support C sharply increasing at a temperature higher than this temperature.

When a heat-sensitive substance, montan wax, alone is used as the heat-sensitive composition, the adhesion strength between layer B and support C increases along the curve XY'Z (represented by a dotted line). From this, it is apparent that it is difficult to adhere transfer layer B to support C at a temperature less than the heat-sensitive temperature of the transfer layer (66.degree.C).

However, when a composition prepared by compounding the heat-sensitive substance (montan wax) with an adhesiveness-imparting agent (ethylene-vinyl acetate copolymer) suitable adhesion property as shown by XYZ in FIG. 5 can surprizingly be imparted to the transfer layer without destroying the heat-sensitive property at all. This adhesion property is characteristic of the heat-sensitive substance. The adhesion strength between transfer layer B and support C can be closely controlled by press-contacting support C onto transfer layer B at a temperature between X and Y as shown in FIG. 5.

Additionally, although the adhesiveness-generating temperature of the heat-sensitive composition can be room temperature (about 20.degree.- 30.degree.C) or less than that, it is preferably higher than room temperature to stabilize the adhesion strength with the lapse of time.

As the heat-sensitive substance, those with which the temperature difference betweeen Y and Z in FIG. 5 is small are preferred, because such substances provide sharp copied images. This temperature difference is preferably less than about 20.degree.C, e.g., a difference of 0.degree.C to 20.degree.C with a smaller difference being preferred.

Additionally, the adhesion strength between support A and transfer layer B can be varied somewhat depending upon the temperature as long as the adhesion strength is intermediate in strength between the adhesion strengths corresponding to Y and Z at least in the heat-sensitive temperature range Y to Z.

The adhesion strength between support A and transfer layer B can be adjusted by an appropriate selection of the material of support A or transfer layer B, by using a support A which has been surface treated and by a selection of laminating conditions of transfer layer B onto support A.

The heat-sensitive recording material of the present invention can be employed in various heat-sensitive copying or recording methods.

That is, the heat-sensitive recording material of the present invention can be used in a reflection or transmission exposure method wherein an original having an image capable of absorbing infrared rays or visible light and generating heat is superposed on the heat-sensitive copying material and the assembly is irradiated with infrared rays or visible light; a stencil transmission copying method wherein a stencil bearing image areas capable of transmitting infrared rays or visible light and nonimage areas capable of reflecting infrared rays or visible light is superposed on the copying material containing a substance capable of absorbing infrared rays or visible light and generating heat, and infrared rays or visible light are applied thereto from the stencil side; or a heat-printing method using an imagewise heated plate or a heating pen. A suitable exposure can be radiation of a wave length ranging from about 400 to 10,000 m.mu., preferably 700 to 3,000 m.mu., for an exposure time of less than 1 second, generally 0.5 to 0.001 second.

For example, the heat-sensitive recording material of the invention can be used in the following applications.

1. It can be used for copying general documents or as a chart paper for recording data of measuring devices, by using paper as support C and incorporating a coloring agent in the transfer layer or providing a colored layer.

2. It can be used as an intermediate original for use in diazo copying, for photographing film, or as an intermediate original for preparing an original printing plate, by using transparent plastic films as support A and support C and incorporating a coloring agent in the transfer layer or providing a colored layer.

3. It can be used as a stencil duplicating master using a porous sheet as support A.

4. It is usable as a spirit master by incorporating a spirit dye in the transfer layer or providing a colored layer containing a spirit dye.

5. It is usable as a lithographic printing master by using an ink-receptive or oleophilic light-sensitive substance such as wax or providing an ink-receptive layer and using, as support C, a support which, on at least the surface, is inkrepellent or can be rendered hydrophilic.

6. It is usable as a printing master by providing a comparatively thick, ink-receptive layer in the transfer layer and producing a relief plate.

Of course various additional modifications of the present invention can be made in view of the disclosure herein.

The present invention will now be illustrated in greater detail by reference to the following non-limiting examples of preferred embodiments of the present invention. Unless otherwise indicated, all parts, percents, ratios and the like are by weight.

EXAMPLE 1

Configuration: Support A/Colored layer B-1/Heat-sensitive layer B-2/Support C

Support A: Surface-corona-treated, stretched polypropylene film (20 .mu. thick)

Support C: Cellulose acetate film (50 .mu. thick)

Composition of Colored Layer (B-1): Weight Parts of Solids ______________________________________ Oil Black 2HB (black, oil-soluble dye 40 Beckamine P-138 (butylated urea 35 formaldehyde resin, produced by Dai Nippon Ink & Chemicals, Inc.) Nissetsu PE-900 (reactive (OH group- 25 containing) acrylic resin, produced by Nissetsu Ltd.) Composition of Heat-sensitive Layer (B-2): Weight Parts of Solids Montan Wax (heat-sensitive substance 80 m.p. 78.degree.C) Adhesiveness-imparting Agent (as 20 shown in Table 1) ______________________________________

Process for Production

A 15% toluene/ethyl acetate mixed solvent solution of the colored layer composition was coated onto the corona-treated surface of support A in an amount of 1.5 g/m.sup.2 on a solids basis, and dried at 100.degree.C. Then, a 20% toluene solution (heated to 40.degree.C) of the heat-sensitive layer composition was coated onto the colored layer surface in an amount of 1.5 g/m.sup.2 on a solids basis, then dried at 100.degree.C.

The heat-sensitive layer-coated surface of the thus prepared configuration of support A/colored layer B-1/heat-sensitive layer B-2 was brought into contact with support C and passed through two press rollers heated to 60.degree.C to obtain a heat-sensitive copying material. Additionally, a comparative sample was prepared for comparison using montan wax alone as a heat-sensitive composition.

The peel strength between the layers as measured in a manner similar to ASTM D 1876-61T are as shown in Table 1, but using 2 cm wide test sample and a head speed of 100 mm/min.

TABLE 1 __________________________________________________________________________ Peel Between Layers Peel Strength Between Peel Strength Between Adhesiveness-imparting Agent Support A/ Layer (B-2)/ Layer (B-1) Support C __________________________________________________________________________ (g/cm) (g/cm) Dicyclohexyl Phthalate (Plasti- 20 2.0 cizer) Evaflex No. 150 (ethylene-vinyl 20 0.8 acetate copolymer; vinyl acetate 33 wt%; made by Mitsui Polychemicals Co., Ltd.) Vistanex MNL 80 (polyisobutylene, 20 1.2 made by Esso Standard Petroleum Co.) None (Comparative sample) 20 0 __________________________________________________________________________

As is shown in Table 1, the effects of the present invention are apparent.

These heat-sensitive copying materials obtained by the process of the present invention can be handled as one sheet and, when copying was conducted superposing the material on an original using a reflection exposure method using a commercially available heat-sensitive copying machine, black, negative and positive copied sheets were obtained in a simple copying operation.

The resulting copied sheets were favorably used as transparencies for an overhead projector, as an intermediate original for preparing a printing original plate and as an intermediate original for use in diazo copying.

EXAMPLE 2

In a manner analogous to Example 1 except for changing the composition of the heat-sensitive layer B-2 in Example 1 to that shown in Table 2, heat-sensitive copying materials were obtained. The results thus obtained are shown in Table 2.

Table 2 __________________________________________________________________________ Peel Strength Between Layer (B-2) and Support (C) Composition of Heat- Peel Strength Between Layer (B-2) sensitive Layer and Support (C) __________________________________________________________________________ (g/cm) Montan Wax/Evaflex No. 40=80/20 0.6 " =60/40 0.8 " =50/50 3.0 __________________________________________________________________________

These heat-sensitive copying materials were easy to handle and showed good copying properties similar to those obtained in Example 1.

EXAMPLE 3

In a manner analogous to Example 1 except for changing the composition of the heat-sensitive layer B-2 in Example 1 to (50 parts of carnauba wax + 50 parts of Evaflex No. 40) and changing support C and the press roll temperature as shown in Table 3, heat-sensitive copying materials were obtained. The results thus obtained are shown in Table 3.

Table 3 __________________________________________________________________________ Peel Strength Between Layer (B-2)/Support (C) Press Roll Temperature Support (C) 50.degree.C 60.degree.C 65.degree.C 80.degree.C __________________________________________________________________________ (g/cm) (g/cm) (g/cm) (g/cm) Cellulose Acetate Film 0 0.7*.sup.3 0.8*.sup.3 not less than 20 Corona-treated, Stretched 0 0.8*.sup.3 1.2*.sup.3 not less than Polypropylene Film 20 Vinylidene Chloride Copoly- 0.2*.sup.3 1.2*.sup.3 1.5*.sup.3 not less than mer-coated Paper*.sup. 1 20 Cellulose Acetate Film*.sup.2 0 0 0 not less than 20 __________________________________________________________________________ *.sup.1 :Saran F239, made by Asahi-Dow Ltd. *.sup.2 :Comparative example using carnauba wax alone as the heat-sensitive layer *.sup.3 :According to this invention.

The resulting heat-sensitive copying materials obtained in the present invention were handled as one sheet and showed good copying properties. The sample in which vinylidene chloride copolymer-coated paper was used as support C was used as a document copy by conducting duplication according to a transmission exposure method.

EXAMPLE 4

Configuration: Support A/Spirit Dye Layer B-1/Heat-sensitive Layer B-2/Support C

Support A : Polyethylene terephthalate film (12 .mu. thick)

Support C : Cellulose acetate film (50 .mu. thick)

Composition of Spirit Dye Layer (B-1): ______________________________________ Aizen Spilon Blue E-2B (alcohol- 30 parts soluble dye, made by Hodogaya Chemical Co., Ltd.) Beckamine P-138 35 Nissetsu PE 900 25 Denka Butyral 3000-1 (polyvinyl 10 butyral, butyralation degree: 65 mol%, made by Electro Chemical Industry, Co., Ltd.) Composition of Heat-sensitive Layer (B-2): Montan Wax 70 parts Evaflex No. 40 30 ______________________________________

In a manner analogous to Example 1 except for the press-contacting temperature being 65.degree.C, a heat-sensitive copying material was obtained. With this sample, the peel strength between support A and layer B-1 was 5 g/cm and the peel strength layerB-2 and support C was 0.5 g/cm.

When printing papers, wet with alcohol, were printed using a commercially available spirit printing machine employing as a master a positive copied sheet obtained from the above-described heat-sensitive copying material by conducting duplication using a heat-sensitive copying machine, printing was well effected to obtain dark blue printed images.

EXAMPLE 5 ______________________________________ Configuration: Support (A)/Transfer Layer (B)/Support (C) Support (A): Polyethylene terephthalate film (12 .mu. thick) Support (C): Internally plasticized polyvinyl chloride film (50 .mu. in thickness) Composition of Transfer Layer (B): Carnauba Wax (m.p. 84.degree.C) 35 parts Evaflex No. 40 35 Oil Black 2HB 30 ______________________________________

A toluene solution (heated to 60.degree.C) of the transfer layer composition was coated onto support A in an amount of 2 g/m.sup.2 on a solid basis, and dried at 110.degree.C. Then, the transfer layer-coated surface was brought into contact with support C and pressure was applied thereto at 65.degree.C to obtain an integral heat-sensitive copying material.

With this heat-sensitive copying material, the peel strength between support A/layer B was 10 g/cm and the peel strength between layer B/support C was 1 g/cm. This heat-sensitive copying material was easy to handle, showed good copying properties and was advantageously used for projection and as an intermediate original.

EXAMPLE 6

Configuration: Support A/Transfer Layer B (ink-receptive heat-sensitive layer)/Support C (paper having a hydrophilic layer thereon)

In a manner analogous to Example 5 except for using as support C an offset master for direct drawing (made by Fuji Photo Film Co., Ltd.), a heat-sensitive copying material was obtained for use as an offset master. The peel strength between layer B and support C was 2 g/cm. After conducting heat-sensitizing copying using a transmission exposure method, the surface of the resulting offset master plate having an ink-receptive wax image was desensitized and mounted on an offset printer. Upon conducting printing, good impressions were obtained.

EXAMPLE 7

Configuration: Support A/Colored Layer B-1/Heat-sensitive Layer B-2/Support C

Support (A) : Stretched nylon film (15 .mu. thick)

Support (C) : Internally plasticized polyvinyl chloride film (100 .mu. thick)

Composition of Colored Layer (B-1): Weight Parts of Solids ______________________________________ Montan Wax 35 Carnauba Wax 20 Evaflex No. 40 (ethylene-vinyl acetate 15 copolymer) Oil Black HBB 30 Composition of Heat-sensitive Layer (B-2): Weight Parts of Solids Montan Wax 35 Carnauba Wax 20 Evaflex No. 40 15 ______________________________________

A toluene solution (heated to 60.degree.C) of the colored layer composition was coated onto support A in an amount of 1.5 g/m.sup.2 on a solid basis, and dried at 110.degree.C. Then, a toluene solution (heated to 60.degree.C) of the heat-sensitive layer composition was coated on the colored layer-coated surface in an amount of 2 g/m.sup.2 on a solid basis, and dried at 110.degree.C. The heat-sensitive layer-coated surface of the thus prepared constitution of support A/colored layer B-1/heat-sensitive layer B-2 was brought into contact with support C, pressure being applied thereto at 60.degree.C, to obtain an integral heat-sensitive copying material.

With this heat-sensitive copying material, the peel strength between support A and layer B-1 was 10 g/cm and the peel strength between layer B-2 and support C was 0.2 g/cm.

The resulting heat-sensitive copying material was easy to handle, showed good copying properties, and was advantageously used for projection and as an intermediate original.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

Claims

What is claimed is:

1. A heat-sensitive recording material comprising a support (A) having thereon a transfer layer (B) and a support (C) in turn, said supports having the property that before heating the adhesion strength between the transfer layer (B) and the support (C) is smaller than the adhesion strength between the transfer layer (B) and support (A) and larger than 0.1 g/cm but, after heating to a temperature higher than the heat-sensitive temperature of the transfer layer (B), the adhesion strength between the transfer layer (B) and support (C) becomes greater than the adhesion strength between support (A) and transfer layer (B), and said transfer layer (B) comprising, at least on the side thereof in contact with support (C), a heat-sensitive composition containing as a major component a mixture of a heat-sensitive substance which becomes fluid at the heat-sensitive temperature of the heat-sensitive substance and an adhesiveness-imparting agent which can adhere to support (C) at a temperature not higher than the heat-sensitive temperature of said heat-sensitive substance.

2. The heat-sensitive recording material as described in claim 1, wherein said transfer layer (B) comprises a colored layer in adhesive contact with support (A) and a heat-sensitive layer in adhesive contact with support (C).

3. The heat-sensitive recording material as described in claim 1, wherein said transfer layer (B) comprises an ink-receptive layer in contact with support (A) and a heat-sensitive layer in contact with support (C).

4. The heat-sensitive recording material as described in claim 1, wherein the proportion of said adhesiveness-imparting agent in said heat-sensitive layer (B) is about 1 to 90 percent by weight of the weight of said heat-sensitive layer (B).

5. The heat-sensitive recording material as described in claim 1, wherein said transfer layer (B) has a thickness ranging from about 0.3 to 18 .mu..

6. The heat-sensitive recording material as described in claim 1, wherein the peel strength between support (A) and layer (B) is about 1 to 150 g/cm and the peel strength between layer (B) and support (C) is about 0.1 to 50 g/cm before heating and not less than 2 g/cm after heating.

7. The heat-sensitive recording material as described in claim 1, wherein said heat-sensitive substance is a wax and said adhesiveness-imparting agent is an ethylene-vinyl acetate copolymer.

8. The heat-sensitive recording material as described in claim 7, wherein said wax is candelilla wax, bees wax, montan wax, ceresine wax, carnauba wax or a mixture thereof.

9. The heat-sensitive recording material as described in claim 8, wherein said wax is montan wax or a mixture of montan wax and carnauba wax.

10. A process for producing a heat-sensitive recording material, which comprises applying support (A) and support (C) onto opposite sides of transfer layer (B) at a temperature, for support (C), not higher than the heat-sensitive temperature of said heat-sensitive composition of layer (B) and not lower than the adhesiveness-generating temperature of layer (B), said support (A), transfer layer (B) and support (C) having the property that before heating the adhesion strength between layer (B) and support (C) is less than the adhesion strength between support (A) and layer (B) and greater than 0.1 g/cm but, after heating to a temperature higher than the heat-sensitive temperature of the transfer layer (B), the adhesion strength between layer (B) and support (C) becomes greater than the adhesion strength between support (A) and layer (B), and said transfer layer (B) comprising at least at the side thereof in contact with support (C) a heat-sensitive composition containing as a major component a mixture of a heat-sensitive substance which becomes fluid at the heat-sensitive temperature of the heat-sensitive sheet and an adhesiveness-imparting agent which can impart sufficient adhesiveness to adhere to support (C) at a temperature lower than the heat-sensitive temperature of said heat-sensitive substance.

11. The process for producing a heat-sensitive recording material as described in claim 10, including press-contacting support (C) onto the heat-sensitive layer of transfer layer (B) after forming transfer layer (B) on support (A).

12. The process for producing a heat-sensitive recording material as described in claim 10, including adhering support (A) to transfer layer (B) after forming transfer layer (B) on support (C).

13. The process as described in claim 11, including forming transfer layer (B) by first forming a colored layer on support (A) and then forming a heat-sensitive layer thereon, and press-contacting support (C) onto the heat-sensitive layer of transfer layer (B).

14. The process as described in claim 11, including forming transfer layer (B) by first forming an ink-receptive layer on support (A) and then forming a heat-sensitive layer on said ink-receptive layer and press-contacting support (C) onto the heat-sensitive layer of transfer layer (B).