JPH0712744B2 - Thermal transfer recording sheet - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording sheet useful for thermally transferring and recording a monochrome gradation image or a full-color image on a recording medium in continuous gradation using a thermal recording head or the like. It is a thing.

2. Description of the Related Art As a conventional thermal transfer recording sheet, a sheet-shaped heat-resistant substrate surface such as a polyethylene terephthalate (PET) film having a thickness of about 7 μm or a condenser paper is coated on the surface of a carnauba wax of 20% by weight and an ester wax.
A hot-melt material consisting of 40% by weight, mineral oil 10% by weight, and other auxiliary agents 10% by weight is used. An ink material layer in which 20% by weight of a pigment coloring material is mixed with this hot-melt binder material and has a thickness of 3 μm A thermal transfer recording sheet having a thermal transfer layer of about 60 ° C. formed by a hot melt coating method is known (for example, Y. Tokunaga and Kei Sugiyama, “Thermal Incoo Transfer Imaging”, IEE). Transactions on Electron Devices, ED-27, 21
8 to 222, 1980 (Y. Tokunaga and K. Sugiyama, “Therm
al Ink-Transfer Imaging ", IEEE Trans. on Electron
Devices, vol.ED-27, PP.218 to 222, 1980.)) Thermal transfer using this type of thermal transfer recording sheet is generally performed in a state where a recording medium such as recording paper and a thermal transfer recording sheet are pressed. A known thermal recording head is brought into pressure contact with the back surface of the base sheet, and the thermal transfer layer is selectively heated and controlled by the thermal recording head through the base sheet to melt transfer the ink material to the recording medium.

Problems to be Solved by the Invention In such a conventional thermal transfer recording seed, the ink material layer is not adhered to the recording medium until the binder material is completely melted from the base sheet side to the ink material layer surface. ， Transcribed. In this case, since the ink material melted in the thickness direction of the ink material layer adheres to and is transferred to the recording medium at one time, it is useful for binary density recording such as characters and figures, but images with halftones, etc. Since it cannot be used for applications requiring continuous gradation, digital gradation methods such as dither method and density pattern method are being studied.

However, according to the digital gradation method of this kind, not only is the apparatus expensive because complicated recording signal processing is required, but also high image quality cannot be expected, and the total resolution is the recording density of the thermal recording head. It was inevitable that it would drop significantly below.

The present invention has been made in view of the above points, and an object of the present invention is to provide a thermal transfer recording sheet capable of continuously controlling transfer recording density corresponding to temperature rising recording control.

Means for Solving the Problems In order to solve the above problems, the present invention provides a layer of an ink material in which the viscosity is controlled to be reduced by the temperature rising recording control and transferability to a recording medium is imparted. , A thermal transfer layer is prepared by mixing and dispersing a solvent adsorbent made of zeolite that adsorbs at least a solvent having a relationship that the solubility of at least one of a binder material and a coloring material constituting the ink material increases with temperature rise, This thermal transfer layer is installed on one surface side of a sheet-shaped heat-resistant substrate.

As the coloring material, dyes and pigments used in ordinary printing inks and paints, and mixtures thereof can be used. Further, the binder material is not limited to a single material and can be composed of a plurality of kinds of materials, and if necessary, a plasticizer, a softening agent, a surface active agent, a thixotropic agent, and other auxiliaries can be mixed. .

Action In the thermal transfer recording sheet of the present invention, thermal transfer recording is performed in the same manner as in the past. At this time, the thermal energy applied from the sheet-shaped heat-resistant substrate side by a thermal recording head or the like reduces the viscosity of the ink material from the sheet-shaped heat-resistant substrate side, and it is contained in the solvent adsorbent made of zeolite. The ink exudates the solvent and is adjacent to the surface of the solvent adsorbent, and thermal energy is applied not only to the sheet-shaped heat-resistant substrate side but also to the solvent adsorbent, and the ink material exudes to the exuded solvent. Since a part of it melts by heat, the viscosity easily decreases. Then, the ink material whose viscosity has decreased penetrates the surface of the solvent adsorbent due to its thermal expansion and fluidity, and seeps out to the surface of the thermal transfer layer by the contact pressing force applied to the recording medium and the thermal transfer recording sheet. Also,
At this time, in the thermal transfer layer portion where the solvent adsorbent does not exist, in the case where the viscosity of the ink material does not decrease enough to cause transferability on the surface (that is, the low applied heat amount region),
Only the ink material having a reduced viscosity that has exuded through the solvent adsorbent contributes to thermal transfer. The exudation amount of the ink material whose viscosity has decreased is proportional to the amount of heat dissolution and viscosity of the surface of the solvent adsorbent, and the amount of ink material whose viscosity has decreased from the sheet-shaped heat-resistant substrate side. In proportion to the heat energy supplied from the heat resistant substrate side, that is,
Continuous gradation recording can be performed directly by performing temperature increase recording control.

Practical Example FIG. 1 shows a sectional structural view of an example of a thermal transfer recording sheet according to the present invention.

In FIG. 1, reference numeral 100 is a thermal transfer recording sheet, 200 is a recording medium such as recording paper, 300 is a thermal recording head, and 400 is a pressing force for pressing the thermal transfer recording sheet 100 and the recording medium 200 to each other. It is properly adjusted to obtain good and good transfer recording.

The thermal transfer recording sheet 100 includes a binder material 122, such as a hot melt binder material, on one side of a sheet-shaped heat-resistant substrate 110, which has a relationship with a coloring agent 121 containing at least one of a pigment and a dye, the viscosity of which is reduced by a temperature rise. The thermal transfer layer 140 is formed by mixing and dispersing a solvent adsorbent 130 that adsorbs at least a solvent whose solubility in at least one of the colorant 121 and the binder material 122 increases with temperature rise into the ink material 120 Stratified.

In this example, the solvent adsorbent 130 is considered as a particle having a spherical particle diameter φ, and the particle diameter φ is illustrated as being smaller than the thickness t of the layer of the ink material 120.

The pulse width of the voltage applied to the heating resistor 310 of the thermal recording head 300 is varied to perform temperature rise control, and the thermal transfer layer 140 is heated from the back surface 140b side via the sheet-shaped heat resistant substrate 110, When the melting point or softening point of the binder material 120 is reached and thermal energy is still applied, the ink material 120a with substantially reduced viscosity is produced.

Further, in the temperature rising state, the solvent adsorbed to the solvent adsorbent 130 begins to seep out, and at least a part of the ink material 120 adjacent to the solvent adsorbent 130 is dissolved in proportion to the temperature rise, and the solvent Ink material whose viscosity has been substantially reduced by
Generates 0b.

On the other hand, in the solvent adsorbent 130, the amount of solvent that exudes increases as the temperature rises, the amount of the ink material 120 that dissolves at the surface 130a of the solvent adsorbent increases, and the viscosity decreases. The ink material 120a, 120b whose viscosity has been lowered follows the arrow 150 through the arrow 130a and begins to permeate.

This permeation reaches the front side 140a of the thermal transfer layer, and is transferred to the recording medium 200 that is in contact and pressed with the thermal transfer layer 140 by the pressing force 400, and is solidified. The amount of the ink material 120 that is thermally transferred is proportional to the viscosity and the amount of the ink material 120a, 120b whose viscosity has decreased in the vicinity of the surface 130a of the solvent adsorbent. It is possible to directly perform gradation recording by separating from the medium 200.

This temperature increase recording control can also be performed by changing the power applied to the heating resistor 310 or the number of times of heat generation.

In the figure, the case where the solvent adsorbent 130 has the same particle size is illustrated, but the particle size can have a distribution.

The sheet-shaped heat resistant substrate 110 has, for example, a thickness of 3.5 to
About 15 μm polyethylene terephthalate, polyimide, cellophane, polycarbonate, triacetyl cellulose, resin film such as nylon, or fine paper,
Heat-resistant paper such as glassine paper, tracing paper, and condenser paper can be used.

The binder material 122 that constitutes the ink material 120 does not necessarily have to be solid at room temperature (for example, 25 ° C.) under the condition that its viscosity is reduced by the temperature increase recording control and transfer adhesion is imparted. A hot-melt material that is solid at room temperature is used because of the storability of the transferred recorded matter.

Examples of hot melt materials include waxes such as carnauba wax, beeswax, paraffin, and microcristan wax, low molecular weight polyethylene, low molecular weight polystyrene, polyvinyl stearate, petroleum resin, polyamide resin, alicyclic saturated hydrocarbon resin, rosin. Examples of the modified maleic acid resin include a melting point or a pour point of 50 to 170 ° C., preferably 60 to 120 ° C., in view of the transfer sensitivity and the fastness of the transferred recorded matter. Similarly, a softening agent to be mixed in order to impart flexibility to the binder material is also appropriately selected from, for example, polyvinyl acetate, cellulose esters, acrylic resins, stearic acid, lanolin, etc. based on their melting or softening temperatures. used. When a flexible material such as petroleum resin or low molecular weight polystyrene is used as the binder material,
In particular, the softener may not be added. Furthermore, by including in the binder agent a pressure-sensitive adhesive material which has a relationship of decreasing viscosity with increasing temperature and increasing adhesiveness, and further increasing viscosity decrease with increasing temperature and transfer efficiency. For example, an adhesive material such as polybutene, polyisobutylene, polybutadiene, or silicone oil can be mixed with the hot melt material to adjust the thermal characteristics and used as a binder material.

As the coloring material 121, organic or inorganic pigments and dyes used in ordinary printing inks, paints, and the like, and mixed color materials thereof can be appropriately selected and used in coloring recording.

For example, in black transfer recording, carbon black and diamond black are used as pigments and CI Solvent is used as dyes.
Use Black3 etc.

In addition to the above for full color transfer recording, cyan pigments such as CI Pigment Blue 15 (pigment) and CI Solvent Blue 2
5 (dye), CI Pigment Red 57 (pigment) for magenta, CI Solvent Red (dye) 49, CI Pig for yellow
ment Yellow 12 (pigment), CI Pigment Yellow 17 (pigment), CI Solvent Yellow (dye) 16, etc. Pigment, dye or a mixture of these three primary colors or black of four primary colors of ink material 120 and solvent adsorption With the agent 130, the thermal transfer layers 140 are sequentially arranged in the frame order on the same base sheet 110, and these are frame-sequentially overlaid or transferred, or the above-mentioned primary color thermal transfer layers are formed into different transfer sheets 100 for each primary color. A publicly known linear thermal recording head is arranged for each primary color transfer sheet, and primary color recording signals of 3 to 4 colors are delayed corresponding to the positions where the respective recording heads are arranged, and line-sequentially overlapped and transferred. Full color recording is achieved. These coloring materials 121
The mixed weight% of the binder material 122 and the binder material 122 is determined in consideration of the transfer recording characteristics. When, for example, a dye is used as the coloring material 121, the transfer recording density is insufficient when the weight% of the ink material 120 in the layer is 2% or less, while when the colorant 122 is a pigment, the weight% is 60%. Ink material beyond 120
The overall viscosity of the recording medium does not decrease when melted, and the recording medium surface
The transfer to 200 becomes difficult and the transfer recording density becomes insufficient.
Therefore, the weight% of the coloring material 121 is appropriately selected within the range of 2 to 60%, and therefore the binder material 122 is correspondingly 98 to 40%.
It is desirable to select within the range.

Especially, the coloring material 121 is 10 to 50%, and the binder material 122 is 90 to 50%.
The ink material 120 within the range is excellent in transfer recording density and continuous gradation, and is a recommended range. This range is particularly effective when a pigment is used as the coloring material 121.

Further, as the coloring material 121, it is possible to select a dye containing a dye and showing a good thermal solubility in a solvent exuding from the solvent adsorbent 130. For example, when an aromatic or aliphatic hydrocarbon solvent is used as the solvent to be adsorbed on the solvent adsorbent 130, for example, CI Solve is used as the black dye.
nt Black 3, cyan dyes include CI Solvent Blue 25, magenta dyes include CI Solvent Red 49, and yellow dyes include CI Solvent Yellow 16.

As the solvent adsorbent 130, molecular sieving carbon zeolite (including synthetic zeolite) is used.

Further, the solvent adsorbent 130 is 62.5 μm × 62.5 μm when each recording pixel, for example, a 16-mm thermal recording head is used.
Must be arranged so that at least one of them exists in the temperature rising state so that the solvent adsorbent 130 can permeate the ink materials 120a and 120b with reduced viscosity. In addition, when the solvent adsorbent 130 becomes the most dense, the heat capacity becomes large, and the absolute amount of the ink material 120 to be thermally transferred is insufficient, so that a sufficient transfer recording density cannot be obtained. Therefore, the solvent adsorbent 130 is appropriately used during this period.

The recording medium 200 includes high-quality paper, coated paper, art paper,
Papers such as synthetic paper and plastic films such as polyethylene terephthalate, polypropylene and cellophane can be used.

The thermal transfer recording sheet 100 is heat-transferred to one side of a sheet-shaped heat-resistant substrate 110 by a solvent coating method or a hot melt coating method in a state where the temperature is increased together with the ink material 120 to such an extent that the solvent contained in the solvent adsorbent 130 does not seep out. It can be obtained by layering the layer 140.

Further, in the case of the solvent coating method, a solution in which at least a part of the ink material 120 is preliminarily dispersed in a solvent having a relationship of increasing thermal solubility with temperature rise is used in the solvent coating method. 120 and another solvent are added and dissolved and dispersed, and this is coated on a sheet-shaped heat resistant substrate 110 with a wire bar coater or the like and dried to form a thermal transfer layer 140. Then, since the solvent adsorbent 130 is always stored in the solvent, it is possible to obtain a stable amount of adsorbed solvent that is hardly affected by humidity.

FIG. 2 shows a sectional structural view of a thermal transfer recording sheet in another embodiment of the present invention.

The sheet-shaped heat resistant substrate 110, the coloring material 121, and the binder material 122 are the same as those in FIG.

As the solvent adsorbent 130, the same solvent adsorbent as in FIG. 1 can be used, but the particle diameter φ thereof is larger than the layer thickness t of the ink material 120.

In this case, the ink materials 120a and 120b whose viscosity has decreased in accordance with the thermal energy applied by the thermal recording head 300 permeate the surface 130a of the solvent adsorbent from the sheet-shaped heat resistant substrate 110 side. At this time, since the solvent adsorbent 130 has a portion protruding from the layer of the ink material 120,
The surface 200a of the recording medium 200 on the side of the thermal transfer layer hardly contacts the ink material 120 directly but contacts the solvent adsorbent 130.
Therefore, only the solvent adsorbent that has penetrated the surface 130a is thermally transferred, and there is no ink material that cannot be transferred unless the viscosity is reduced on the solvent adsorbent 130, so smoother gradation recording from the paper surface density can be performed. You can

If the particle diameter φ is less than 1.5 μm, the thickness t of the ink material layer 120 becomes too small, and the maximum density of the transfer recording 160 cannot be made large.
Further, it is difficult to manufacture the uniform thermal transfer layer 120. on the other hand,
When the particle diameter φ of the solvent adsorbent 130 exceeds 15 μm, the heat capacity of the solvent adsorbent 130 becomes excessive, which makes it difficult to raise the desired temperature, and the path of permeation and extrusion 150 becomes excessively long, resulting in low sensitivity. , The maximum recording density also decreases.

Therefore, the preferable range of the particle diameter φ is 1.5 μm to 15 μm.
At this time, it is recommended that the particle diameter φ be selected within the range of 2 μm to 10 μm because the continuous gradation and recording sensitivity can be improved. In this case, the distribution of the particle size φ is allowed, but it is desirable that the maximum particle size value in this particle size distribution does not exceed 15 μm.

The ink material 120 is a solvent adsorbent in a state where the rise of the transfer recording density from the paper surface density is about 0.05 or less.
Can exist over 130.

The thermal transfer layer 140 is formed, for example, by controlling the amount of the solvent used by the solvent coating method, and the layer thickness t of the ink material 120 formed after the solvent is evaporated is determined by the solvent adsorbent 1
It can be appropriately adjusted so as to be smaller than the particle diameter φ of 30.

In addition, the ink material 120
When the porosity of the pinholes in the layer is over 20%, the transfer recording density becomes insufficient and the recording sensitivity decreases, so
Porosity is kept below 20%.

An example of manufacturing a thermal transfer recording sheet is shown below.

<Example 1> Petroleum resin (softening point 100 ° C Mitsui Petrochemical Industry Co., Ltd. Hilets): 50 parts by weight Solid paraffin (melting point 50 to 52 ° C): 20 parts by weight CI Pigment Blue 15:30 parts by weight Zeolite (average particle size) About 3 μm in diameter Mizusawa Chemicals Co., Ltd. Mizuka Sieves 13X): 50 parts by weight dissolved in 400 parts by weight of xylene and uniformly dispersed
Using a wire bar coater (No.3), apply it to polyethylene elephthalate (PET. Thickness 9 μm) and air dry at 25 ° C. and 1 atm to obtain a thermal transfer recording sheet with 120 layers of ink material with a thickness of about 1 μm. It was Using a thermal recording head with a density of 4 lines / mm, a main scanning speed of 33.3 mec / line and a sub-scanning line density of 4 lines / mn at 0.7 w / dot, pulse width modulation of the recording signal, and thermal transfer recording with a maximum pulse width of 8 mec The transfer recording density continuously increased with respect to this pulse width, and gradation recording could be performed directly by the temperature rise control by pulse width modulation.

As described above, the method for forming the thermal transfer layer is not subject to the above-mentioned restrictions, and the configurations can be appropriately combined and implemented.

The temperature increase recording control can be controlled in a thermal recording head or the like by pulse width modulation, amplitude modulation, the number of pulses of a single width, or the like of the input signal to be applied. In the embodiment, the thermal recording head has been described. Thermal transfer recording can also be performed by using a recording head or laser light that can supply other heat energy.

EFFECTS OF THE INVENTION As described above, the present invention provides a solvent adsorbent made of zeolite that adsorbs a solvent having a relationship in which an amount of at least a part of a binder or a colorant that constitutes an ink material is thermally dissolved with increasing temperature, This is a thermal transfer recording sheet with a thermal transfer layer formed by mixing it with this ink material. By using this thermal transfer recording sheet, it is possible to perform continuous gradation transfer recording especially with pigment color materials, which was difficult with conventional thermal transfer recording sheets. In addition, the effect is great as a monochrome or full-color printer in the field of OA new media and facsimiles.

[Brief description of drawings]

FIG. 1 is a diagram showing the constitution of a thermal transfer recording sheet in one embodiment of the present invention, and FIG. 2 is a diagram showing the constitution of another embodiment of the thermal transfer recording sheet in the other embodiment. 100: Thermal transfer recording sheet, 110: Sheet-shaped heat resistant substrate, 120: Ink material, 130: Solvent adsorbent, 140 ...
Thermal transfer layer, 200 ... Recording medium, 300 ... Thermal recording head, 400 ... Pressing force, φ ... Solvent adsorbent particle size, t ...
The thickness of the layer of ink material.

Claims (2)

[Claims] 1. An ink material having a relationship in which its viscosity is controlled to be reduced by temperature rising recording control and transferability to a recording medium is imparted to at least one of a binder material and a coloring material constituting the ink material. A solvent adsorbent made of zeolite that adsorbs at least a solvent whose solubility increases with increasing temperature is mixed and dispersed to form a thermal transfer layer, and this thermal transfer layer is installed on one surface side of a sheet-shaped heat-resistant substrate. A thermal transfer recording sheet characterized in that 2. The thermal transfer recording sheet according to claim 1, wherein a solvent adsorbent having a particle diameter larger than the thickness of the layer made of the ink material is dispersed and mixed in the ink material.