JP2015093397A - Pigment type thermal transfer medium and image formation method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pigment type thermal transfer medium capable of forming an image with a reduced level-difference caused by layer thickness of a coloring ink layer and an adhesion layer formed on one surface of a base material, and with excellent adhesion to a transfer-target body.SOLUTION: A pigment type thermal transfer medium 10 includes: a coloring ink layer 2 for an image-screen; and an adhesion layer 3 having two or more partitioned areas, field-sequentially formed on one surface of a base material 1. The coloring ink layer 2 is composed of an ink composition including a pigment, a thermoplastic resin and a solvent. The adhesion layer 3 is composed of a thermoplastic resin with layer thickness of 1-5 μm.

Description

  The present invention relates to a pigment-type thermal transfer medium containing a pigment as a coloring material, and a method for forming an image on a transfer medium using the same.

  As an image forming system by thermal transfer using a thermal head, a sublimation dye type thermal transfer system and a pigment type thermal transfer system are known. In particular, the sublimation dye-type thermal transfer system that contains a sublimation dye as a colorant has a beautiful photographic color because the sublimation dye moves (transfers) to the transfer target on which the image receiving layer is formed in a continuous tone. It is excellent as an image forming method. In the case where the material to be transferred itself is a material capable of receiving and fixing a dye, an image can be formed without applying the image receiving layer to the material to be transferred.

However, an image obtained by the sublimation dye type thermal transfer system has the following drawbacks.
1) Since the image formation uses dye sublimation, the sharpness of the contour of the finished image is unsatisfactory, and the solid density of the thin line is insufficient compared to the thick line. That is, it becomes a problem to represent characters.
2) Since a dye is used as the colorant, the durability of the image is inferior, and the development in fields where heat resistance and light resistance are particularly required is limited.
3) The dye as the coloring material is limited, and the cost becomes high as the material.

  On the other hand, the pigment-type thermal transfer system was developed as a means for solving such drawbacks of the sublimation dye type (Patent Document 1). Specifically, a pigment is dispersed as a colorant in a binder resin, and is composed of a colored ink layer and an adhesive layer. The adhesive layer is first transferred to the transfer target, and the colored ink layer is transferred thereon to form an image. Is the method.

  As described above, the pigment-type thermal transfer method uses a thermal head having a plurality of minute dot shapes to form a colored ink layer containing a binder resin and a pigment in a minute dot shape on a transfer target to which an adhesive layer has been previously transferred. It is characterized by forming an image by transferring. Thus, since the pigment-type thermal transfer type pixel has a minute dot shape rather than continuous gradation, the outline of the image is clear and a thin line character can have a sufficient density. Furthermore, it is cheaper than the above sublimation dyes, and the cost can be greatly reduced as a whole.

  However, in order for the image formed by the pigment-type thermal transfer method to have sufficient resistance, the affinity (compatibility) of the adhesive layer that can firmly fix the colored ink layer and a sufficient layer thickness are required. There are problems with conventional pigment-type thermal transfer media. As a pigment-type thermal transfer medium, a case where a colored ink layer and an adhesive layer made of a pigment are formed on the same film base material will be described below as an example. For example, as a method for improving the affinity (compatibility) between the colored ink layer and the adhesive layer, a resin having the same component as the binder resin contained in the colored ink layer is used for the adhesive layer. On the other hand, in order to form the adhesive layer with a sufficient layer thickness, it is possible to make the adhesive layer thicker than the colored ink layer (see FIG. 4).

  As described above, when the thickness of the adhesive layer is made larger than the thickness of the colored ink layer, a difference in thickness occurs between the two, and in particular, a continuous pigment is formed by a winding method using a film substrate. When producing a mold thermal transfer medium, this step becomes a factor that causes a decrease in productivity and quality.

As a measure to eliminate such anxiety factors such as productivity and quality degradation due to such winding steps,
For example, although a method of forming a colored ink layer and an adhesive layer on separate substrates is also performed, the production process and the number of materials such as the substrate increase, resulting in a problem of reduced productivity and high cost.

JP 2002-234203 A

  The present invention relates to a pigment-type thermal transfer medium that can reduce the level difference between the color ink layer formed on one surface of the substrate and the adhesive layer and can form an image with excellent adhesion to the transfer target. For the purpose of provision.

According to the first aspect of the present invention, there is provided a pigment-type thermal transfer medium in which a colored ink layer and an adhesive layer having two or more partitioned regions are formed in one surface order on one surface of a substrate. Because
The colored ink layer is composed of an ink composition containing a pigment, a thermoplastic resin, and a solvent,
The adhesive layer is a pigment-type thermal transfer medium comprising a thermoplastic resin having a layer thickness of 1 to 5 μm.

  The invention according to claim 2 is the pigment-type thermal transfer medium according to claim 1, wherein the adhesive layers having the two or more partitioned regions are made of different thermoplastic resins.

The invention according to claim 3 uses a thermal head having a plurality of minute dot shapes from the back surface of the pigment-type thermal transfer medium, in which the pigment-type thermal transfer medium according to claim 1 or 2 is in close contact with the transfer target. An image forming method for forming an image on a transfer medium by heating and pressing,
A step of transferring an adhesive layer in the form of a plurality of minute dots to the surface of the transfer object;
And a step of transferring the colored ink layer in a plurality of fine dot shapes.

According to a fourth aspect of the present invention, there is provided a thermal head having a plurality of minute dot shapes from the back surface of the pigment-type thermal transfer medium, wherein the pigment-type thermal transfer medium according to the first or second aspect is in close contact with the intermediate transfer medium. Using heat and pressure,
Transferring the adhesive layer to the surface of the intermediate transfer medium in a plurality of fine dot shapes;
A step of transferring the colored ink layer to the surface of the intermediate transfer medium in a plurality of fine dot shapes;
And a step of transferring the image formed on the intermediate transfer medium to the transfer medium by heating and pressurizing the intermediate medium by bringing the intermediate transfer medium and the transfer medium into close contact with each other. is there.

  According to the first and third aspects of the present invention, a colored ink layer and an adhesive layer having two or more partitioned regions are formed on one surface of the base material for one screen image, and the adhesion is further performed. By setting the thickness of the layer to 1 to 5 μm, it is possible to increase the thickness of the adhesive layer while suppressing a step difference in thickness between the colored ink layer and the adhesive layer. As a result, it is possible to form an image having excellent adhesion to a transfer target from a thermal transfer medium having a small thickness difference between the colored ink layer and the adhesive layer.

Further, according to the invention according to claim 2, by forming the adhesive layer having the two or more partitioned regions from different thermoplastic resins, different adhesiveness is utilized after image formation on the transfer target. Functions can be added. For example, if an adhesive layer with a partition area with strong adhesiveness and a partition area with low adhesiveness is formed in one screen of the image, the colored ink remains as it is when it is peeled off with an adhesive tape after the image is formed on the transfer target. A second image can be formed by the area that is peeled off and the area that peels off and disappears. By forming this second image as a latent image, it can be used to determine the authenticity of the transfer object.

  According to the fourth aspect of the present invention, instead of directly forming an image on a transfer medium, an image is temporarily formed on an intermediate transfer medium, whereby a surface having a complicated shape is formed. However, a highly accurate image can be easily formed.

1 is a schematic plan view showing an embodiment of a pigment-type thermal transfer medium of the present invention. 1 is a schematic cross-sectional view showing an embodiment of an image using a pigment-type thermal transfer medium of the present invention. FIG. 3 is a schematic plan view showing an embodiment of a latent image by the pigment-type thermal transfer medium of the present invention. FIG. 6 is a schematic plan view showing an embodiment of a conventional pigment-type thermal transfer medium.

Hereinafter, the present invention will be described in detail based on the drawings.
As shown in FIG. 1, a pigment-type thermal transfer medium 10 according to the present invention has a colored ink layer 2 and an adhesive layer 3 having two or more partitioned areas on one surface of a base material 1 for one image screen. It is characterized by being formed in a surface sequential manner.

  FIG. 1A shows a plan view of a pigment-type thermal transfer medium 10 according to the present invention. The colored layer 2 is composed of a yellow ink layer, a red ink layer, a blue ink layer, and a black ink layer, and the adhesive layer 3 is a first layer. One embodiment which consists of two division area of one adhesion layer 3a and the 2nd adhesion layer 3b is shown.

  FIG. 1B shows a cross-sectional view of the pigment-type thermal transfer medium 10 according to the present invention. The layer thickness of the colored ink layer 2 and the adhesive layer 3 is substantially the same on one surface of the substrate 1. It is characterized by the same thickness. Thereby, even if the base material 1 is a film base in a winding form, a step due to the layer thickness of the colored ink layer 2 and the adhesive layer 3 can be suppressed. Can prevent productivity and quality degradation.

  Further, by transferring the first adhesive layer 3a and the second adhesive layer 3b in an overlapping manner, it is possible to form the adhesive layer 3 having a thickness approximately double that of the colored ink layer 2 (see FIG. 2). . Thereby, the colored ink layer 2 transferred after that can be firmly fixed. That is, with respect to the conventional problem relating to the fixing of the step and the image, the adhesive layer 3 is divided into a plurality of sections (for example, two sections) and the layer thickness is equal to that of the colored ink layer 2. Can be resolved. At the same time, by transferring the first adhesive layer 3a and the second adhesive layer 3b in an overlapping manner, the thickness of the adhesive layer 3 can be sufficiently secured, and the colored ink layer 2 can be firmly fixed after transfer. can do.

  The substrate 1 according to the present invention is not particularly limited as long as it has heat resistance and strength. For example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polypropylene (PP), polycarbonate (PC ) And a film or sheet of polyimide (PI). Among these, a PET film is preferable in terms of dimensional stability, surface smoothness, and cost.

  The colored ink layer 2 according to the present invention is made of a colored ink composition containing a pigment as a colored layer, a thermoplastic resin as a binder resin, a solvent for adjusting the ink, and an additive such as a dispersant.

The pigment that can be used in the present invention is preferably a pigment having a coloring density such as yellow, red, blue, black and the like that does not discolor or fade due to light, heat, temperature or the like. Moreover, it is also possible to use a pigment having a color tone other than the above-described colored pigments, or to use a mixture of two or more pigments.

  Examples of the thermoplastic resin used as the binder resin include butyral resins, polyamide resins, polyester resins, epoxy resins, acrylic resins, and vinyl resins such as vinyl chloride and vinyl acetate. These resins can be used alone or in combination of two or more.

  The colored ink composition contains a solvent for adjusting the viscosity of the ink, is selected according to the characteristics of the pigment and the binder resin, and can be used alone or in combination.

  The colored ink composition includes additives such as a dispersant for improving the dispersibility of the ink and a stabilizer for imparting storage stability to the ink, but is not particularly limited.

  The pigment content relative to the binder resin (thermoplastic resin) in the colored ink composition is preferably 15 to 40%, more preferably 20 to 30%. Within this range, the pigment can be well dispersed, and the image density after transfer can be satisfactory.

  Using the colored ink composition, the colored ink layer 2 can be formed by pattern-coating one surface of the substrate 1 by a gravure printing method or the like. The colored ink layer 2 thus obtained preferably has a thickness of 1 to 5 μm. If the thickness of the colored ink layer 2 is less than 1 μm, depending on the pigment content in the colored ink layer 2, the color density of the image after transfer may be insufficient. On the other hand, if the thickness exceeds 5 μm, there may be a problem in the fixing property of the image after transfer.

  The adhesive layer 3 according to the present invention comprises an adhesive layer forming composition containing a thermoplastic resin and a solvent. As the thermoplastic resin, a thermoplastic resin which is the binder resin forming the colored ink layer 2, for example, butyral resin, polyamide resin, polyester resin, epoxy resin, acrylic resin, vinyl resin such as vinyl chloride or vinyl acetate, etc. Is preferred. These resins may be used alone or in combination of two or more.

  As shown in FIG. 1B, the first adhesive layer 3a and the second adhesive layer 3b forming the adhesive layer 3 are characterized in that the colored ink layer 2 and the layer thickness are equal. . That is, in actual image formation, after the first adhesive layer 3a is transferred, the second adhesive layer 3b is transferred so as to be superposed on the first adhesive layer 3a. The layer 3 can be formed, and the image can be firmly fixed. Although the total thickness can be increased by increasing the number of sections of the adhesive layer 3, the number of sections needs to be adjusted in consideration of the composition of the colored ink layer 2 and the transfer target.

  The total thickness of the adhesive layer 3 necessary for firmly fixing the pixels is preferably 1 to 5 μm. For example, if the thickness of the colored ink layer 2 is 1 μm, the plurality of partitioned adhesive layers 3 formed with the same thickness can be formed with a total of at least 2 μm or more, thereby strengthening the pixel. It can be fixed. If it is less than 1 μm, the compatibility with the colored ink layer 2 is insufficient and fixing becomes insufficient. On the other hand, if the thickness exceeds 5 μm, the distance between the transfer target and the pixel increases, and physical strength due to friction or the like becomes a problem.

Further, in order to firmly fix the image formed by the transfer of the colored ink layer 2, it is preferable that the respective compositions forming the first adhesive layer 3a and the second adhesive layer 3b are the same. More preferably, by using the thermoplastic resin used for the colored ink layer 2, the content is 20% by mass or more based on the total thermoplastic resin contained in the pre-adhesion layer 3, thereby strengthening the image. It can be fixed. When the content is less than 20% by mass, the compatibility between the adhesive layer 3 and the colored ink layer 2 is poor, and the fixing of the image becomes insufficient.

  Further, in the adhesive layer 3 according to the present invention, for example, when the first adhesive layer 3a and the second adhesive layer 3b are made of different thermoplastic resins, it becomes possible to form a latent image as shown in FIG. This can be used to determine the authenticity of the transfer target 4.

  Specifically, for example, a pigment-type thermal transfer medium having an adhesive layer 3 in which the first adhesive layer 3a is a thermoplastic resin having high adhesiveness and the second adhesive layer 3b is a thermoplastic resin having low adhesiveness is produced. . By using this pigment-type thermal transfer medium and transferring the first adhesive layer 3a to the transfer target 4 with a thermal head having a fine dot shape, a highly adhesive pattern shown in FIG. 3A can be formed. . Next, by transferring the second adhesive layer 3b in the same manner, a weakly adhesive pattern shown in FIG. 3B can be formed. By transferring the colored ink layer onto the adhesive layer 3 thus transferred, an image of the colored ink layer 2 shown in FIG. 3C is obtained. Thereafter, an adhesive tape having an intermediate adhesive property between the first adhesive layer 3a and the second adhesive layer 3b is applied and peeled off to fix the colored ink layer as shown in FIG. Latent image patterns can be obtained. The authenticity of the transfer object can be determined by the pigment-type thermal transfer medium and the peeling method as described above.

  The present invention can form an image indirectly as well as the method of directly forming an image on a transfer medium as described above. Hereinafter, an indirect image forming method on a transfer target will be described.

  Specifically, the adhesive layer 3 is thermally transferred to an intermediate transfer medium that is smooth and easily peelable, and further thermally transferred using the colored ink layer 2 thereon, thereby forming a desired image. Thereafter, the image surface side of the intermediate transfer medium and the transfer target 4 are brought into close contact with each other, and the image is transferred to the transfer target 4 through heat pressure, whereby a tightly bonded image can be formed. .

  The intermediate transfer medium is not particularly limited as long as it is a substrate having heat resistance, smoothness, strength, image acceptability, easy peelability and the like. For image receptivity and easy peelability, a layer having image receptivity and easy peelability may be provided on the surface of the substrate. By using such an indirect image forming method, it is possible to accurately form an image even on a transfer material made of a delicate material or a complicated shape, which cannot directly form an image with high accuracy. Here, the image acceptability is a property capable of holding an image, and the easy releasability is a property capable of being easily peeled off.

  The pigment-type thermal transfer medium according to the present invention uses a thermal head having a micro dod shape directly or indirectly to a transfer target for an IC card or a passport, and has excellent durability and density and contour. Can form clear fine lines, characters and images. In addition, a latent image can be formed based on the difference in adhesive strength of the adhesive layer. By using this latent image, the authenticity of the transfer body can be determined by peeling after the image formation.

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Colored ink layer 3 ... Adhesive layer 3a ... 1st adhesive layer 3b ... 2nd adhesive layer 4 ... Transfer object 5 ... Intermediate transfer Medium 6 ・ ・ ・ Image forming body 10 ・ ・ ・ Pigment type thermal transfer medium

Claims (4)

A pigment-type thermal transfer medium in which a colored ink layer and an adhesive layer having two or more partitioned regions are formed on one surface of a base material in order of image,
The colored ink layer is composed of an ink composition containing a pigment, a binder resin, and a solvent,
The pigment-type thermal transfer medium, wherein the adhesive layer is made of a thermoplastic resin having a layer thickness of 1 to 5 μm.   The pigment-type thermal transfer medium according to claim 1, wherein the adhesive layer having two or more partitioned regions is made of different thermoplastic resins. A pigment-type thermal transfer medium according to claim 1 or 2 and a transfer target are brought into close contact with each other, and the transfer target is heated and pressurized using a thermal head having a plurality of minute dot shapes from the back surface of the pigment-type thermal transfer medium. An image forming method for forming an image on
A step of transferring an adhesive layer in the form of a plurality of minute dots to the surface of the transfer object;
And a step of transferring the colored ink layer in the form of a plurality of minute dots. The pigment-type thermal transfer medium according to claim 1 or 2 and an intermediate transfer medium are brought into close contact with each other, and heated and pressurized from the back surface of the pigment-type thermal transfer medium using a thermal head having a plurality of minute dot shapes,
Transferring the adhesive layer to the surface of the intermediate transfer medium in a plurality of fine dot shapes;
A step of transferring the colored ink layer to the surface of the intermediate transfer medium in a plurality of fine dot shapes;
And a step of transferring the image formed on the intermediate transfer medium by transferring the image formed on the intermediate transfer medium by bringing the intermediate transfer medium and the transfer target into close contact with each other and heating and pressurizing the intermediate.