JPH0548754B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a thermal transfer method useful for thermal transfer recording of monochromatic gradation images, full-color images, etc. in continuous gradation onto a recording medium using a thermal recording head, laser light, etc. This relates to record sheets.

Conventional technology Conventional thermal transfer recording sheets have a thickness of 7 μm.
Carnauba wax is applied as a binder material to the surface of a sheet-like heat-resistant substrate such as polyethylene terephthalate (PET) film or capacitor paper.
20% by weight, ester wax 40% by weight, mineral oil 10%
A thermal transfer layer with a thickness of about 4 μm consisting of an ink material layer made by mixing 20% by weight of a pigment coloring material with this hot-melt binder material is hot melted. Formed by coating method, melt transfer temperature is 60
A thermal transfer recording sheet with a temperature of about °C is known.
~222 pages, 1980 (Y. Tokunaga and K.
Sugiyama, “Thermal Ink-Transfer
Imaging”, IEEE Trans.on Electron Devices,
vol. ED-27, pp. 218-222, 1980.)) In general, thermal transfer using this type of thermal transfer recording sheet is performed by pressing the base sheet against the recording medium such as recording paper and the thermal transfer recording sheet. A known thermal recording head is pressed against the back surface, and the temperature of the thermal transfer layer is selectively heated and recorded by the thermal recording head via the base sheet to melt and transfer the ink material to the recording medium.

Problems to be Solved by the Invention In such conventional thermal transfer recording sheets, the ink material layer extends from the base sheet side to the surface of the ink material layer, and the ink material does not adhere to the recording medium until the binder material has completely melted. , transcribed. In this case, since the ink material melted in the thickness direction of the ink material layer is attached and transferred to the recording medium at once,
Although it is useful for binary density recording such as characters and figures, it cannot be used for applications that require continuous gradation, such as images with halftones, and digital gradation methods such as the dither method and density pattern method cannot be used. Preparation methods are being considered.

However, according to this kind of digital gradation method,
Not only is the equipment expensive because it requires complex recording signal processing, but high image quality cannot be expected, and in addition, it is inevitable that the overall resolution and recording density will be significantly lower than that of the thermal recording head. .

The present invention has been made in view of the above, and an object of the present invention is to provide a thermal transfer recording sheet that can continuously control the transfer recording density in response to temperature-rising recording control.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a relationship in which the viscosity of the thermal transfer recording sheet is controlled to decrease through temperature increase recording control, thereby imparting transferability to the recording medium. A hot melt that has an ink material and has a lower melting point (softening point) or pour point than the binder material that is a constituent of the ink material, is not completely compatible with the binder material at room temperature, and is solid at room temperature. A thermal transfer layer in which auxiliary particles made of the material are mixed and dispersed in the ink material in the form of particles,
It is arranged on one side of a sheet-like heat-resistant substrate.

The term "ink material" herein collectively refers to recording materials containing the intended material to be transferred and recorded onto a recording medium, and it does not matter whether they are colored or non-colored. In normal color transfer recording, the ink material includes a binder material and a coloring material made of pigments, dyes, or mixtures thereof used in conventional printing inks and paints, for example.

Furthermore, the term binder material collectively refers to materials whose viscosity decreases as the temperature rises, imparting transferability to recording media, and these materials are not limited to a single material, but may be composed of multiple types of materials. The binder material also includes plasticizers, softeners, surfactants, thixotropic agents, and other auxiliary agents added as necessary.

Further, although the particle size of the auxiliary particles is preferably spherical, the particle size may not matter. Further, the particle size of the auxiliary particles may be the same particle size, or may have an appropriate particle size distribution from a small particle size to a large particle size.

The auxiliary particles are preferably non-colored, white, or transparent materials, but colored or opaque materials can be used as required. The auxiliary particles are also preferably compatible or partially compatible with the binder material when melted, but may be incompatible.

Function In the present invention, by controlling temperature increase by a thermal recording head or the like via a heat-resistant substrate,
First, the auxiliary particles are melted, and the binder material located around them is melted by heat conduction through the auxiliary melting particles. Therefore, when temperature raising recording is controlled by pulse width modulation with a recording medium in pressure contact with the surface of the thermal transfer layer, the melted auxiliary particles first penetrate and adhesively transfer to the recording medium in accordance with the pulse width. Along with this penetration and adhesive transfer, the ink material that is melted adjacent to the auxiliary particles and whose viscosity has been substantially reduced together with the binder material penetrates into the recording medium and is adhesively transferred.

In addition, when the auxiliary particles and the binder material are selected to be partially compatible or compatible, the auxiliary particles and the binder material first become compatible along the surface of the auxiliary particles corresponding to the pulse width, and the viscosity decreases. do. Therefore, to the recording medium through the contact interface between the auxiliary particles and the ink material,
infiltration of the auxiliary particulate material and the substantially reduced viscosity ink material containing the binder material compatible therewith;
Adhesive transfer.

Penetration of the above-mentioned substantial ink material into the recording medium, adhesive transfer, thermal energy of temperature-raising recording control,
It therefore increases with pulse width.

In this way, after the pulse width modulated recording signal is applied to the thermal recording head etc., before the above-mentioned auxiliary particles and the ink material whose viscosity has been reduced substantially return to the original solid state, and before the adhesion to the recording medium When the thermal transfer sheet and the recording medium are separated in a low viscosity state that allows transfer, a transfer recording such as a monochrome image having continuous tone characteristics can be obtained in response to a pulse width modulation recording signal. In this case, if cyan, magenta, yellow, and even black are added to the thermal transfer recording sheet, a full-color image can be recorded by sequentially overlapping recording using pulse width modulated primary color recording signals using the primary color method or the four primary color method.

In this type of thermal transfer sheet, the particle diameter of at least some of the auxiliary particles is
If t is selected to be larger than the thickness t of the ink material layer (thickness of the ink material layer in the part where the auxiliary particles are not located), the above-mentioned melting auxiliary particles and even lower viscosity ink material can be applied to the recording medium. It has the advantage of being able to effectively perform penetration and adhesive transfer.

The formation of a thermal transfer layer having such protruding auxiliary particles is achieved by using the solvent coating method as described above.The mixed amount of the solvent material is appropriately selected, the mixed material is applied to the surface of the heat-resistant substrate, and after layering, the solvent material is coated. By evaporating and removing the auxiliary particles, the thickness of the ink material layer can be easily achieved by reducing the particle size of at least some of the auxiliary particles.

Embodiment FIG. 1 is a partial cross-sectional structural diagram of an embodiment of a thermal transfer recording sheet according to the present invention.

In the figure, 100 is a thermal transfer recording sheet, 100
120 is a sheet-like heat-resistant substrate, and 120 is a layer made of an ink material having a thickness of t, which is a binder material 121 made of a hot melt material mixed with a coloring material 122 made of a pigment, a dye, or both.
This ink material layer 120 has a binder material 121.
The auxiliary particles 123 are solid at room temperature (for example, 0° C. to 35° C.) and have a lower melting point (softening point) or pour point than the binder material 121 and are not completely compatible with the binder material 121.
are mixed and dispersed to form the thermal transfer layer 130. In this embodiment, the particle diameter φ of the auxiliary particles 123 is selected to be larger than the thickness t of the ink material layer 120,
The particles 123 cross the thickness direction of the layer 120, and a portion thereof protrudes from the ink material layer surface 120a. Note that the auxiliary particles 123 do not necessarily need to be in complete contact with the base surface 110a.

Furthermore, the protruding surfaces 123b of the auxiliary particles 123 may be thinly coated with the binder material 121 or even the coloring material 122.

For example, the heat-resistant base 110 has a thickness of 4 to 4.
Use 10 μm polyethylene terephthalate (PET), polyimide film, or capacitor paper.

The binder material 121 and the auxiliary particles 123 are, for example, solid at least at room temperature (0° C. to 35° C.), and of the material 121 and the particles 123, at least the material 12
The hot melt material 1 is made of one or more kinds of hot melt materials whose viscosity is reduced by temperature raising recording control and imparts adhesion and transfer adhesion to the recording medium (image receptor). Its melting point (softening point) or pour point is
The temperature is selected in the range of 50 to 170°C, preferably 60 to 150°C. If the melting point or pour point is less than 50°C, the ink material 120 and auxiliary particles 123 transferred and recorded on the recording medium are likely to soften or set off during storage, while if it exceeds 170°, the thermal recording head etc., making it difficult to control temperature rise records.

Examples of hot melt materials include non-aqueous solvent-soluble waxes such as carnauba wax, beeswax, solid paraffin, and microcrystalline wax, low molecular weight polyethylene, polyvinyl stearate, petroleum resin, polyamide resin, and rosin-modified resin. Non-aqueous solvent-soluble resins, water-soluble hot melt materials such as polyethylene glycol, hydroxyethyl cellulose, polyacrylamide, and polyvinylpyrrolidone are used. These hot melt materials can be used alone or in combination as required.

In order to impart flexibility to these hot melt materials, softeners such as polyvinyl acetate, cellulose esters, acrylic resins, stearic acid, and lanolin can be appropriately added.

When the hot melt material itself is highly flexible, for example, petroleum resin, low molecular weight polyethylene, etc., a softener may not be added. On the other hand, as the temperature rises, the viscosity decreases and the stickiness increases.
By adding to the hot melt material an adhesive material that is fluid at temperatures (°C), such as polybutyne, polyisobutylene, polybutadiene, silicone oil, etc., it is possible to reduce the viscosity against elevated temperatures and improve the transfer efficiency.

The binder material 121 and the auxiliary particles 123 are appropriately selected from, for example, the above-mentioned hot melt materials.
In this case, the auxiliary particles 123 are the binder material 12
has a melting point (softening point) or pour point lower than 1, is not completely compatible with material 121 at room temperature (for example, 0 ° C. to 35 ° C.), is solid at room temperature, and is mixed in particulate form with material 121 at room temperature, The material is selected to be dispersed. A valid choice is that when the binder material 121 is the non-aqueous solvent soluble hot melt material, the auxiliary particles 123 are the water soluble hot melt material, or vice versa. When both the binder material 121 and the auxiliary particles 123 are selected to be non-aqueous solvent soluble, it is effective to configure the auxiliary particles 123 with carnauba wax, for example.

As the coloring material 122 in colored transfer recording, organic or inorganic pigments, water-soluble dyes or oil-soluble dyes, or mixtures of multiple types of these coloring materials, which are used in commonly used printing inks and paints, can be used as appropriate. selected.

For example, in black transfer recording, carbon black and diamond black are used as pigments, and CI Solvent Black 3 (CI Solvent Black 3) is used as dye.
Solvent Black3) etc. are used.

In addition to the above, for full color transfer recording, C.I. Pigment Blue 15 is also available as a cyan color.
(CI Pigment Blue15) (pigment), CI Solvent Blue25 (dye),
C.I. Pigment Red 57 for magenta color
(CI Pigment Red57) (pigment), CI Solvent Red49 (dye),
C-I Pigment Yellow for yellow color
12 (CI Pigment Yellow12) (pigment), CI Pigment Yellow12
Pigment Yellow 17 (CI Pigment
Using an ink material 120 of four primary colors including black and three primary colors of pigments, dyes, or mixtures thereof, such as CI Solvent Yellow 16 (pigment) and CI Solvent Yellow 16 (dye),
Either the thermal transfer layers 130 are arranged in frame order on the same base sheet 110 and these are superimposed and transferred to a recording medium such as recording paper in frame order, or the primary color thermal transfer layers are placed on separate transfer sheets 100 for each primary color.
A known linear thermal recording head is arranged for each primary color transfer sheet, and pulse width modulated primary color recording signals of three to four primary colors are delayed in accordance with the arrangement position of each recording head. , full-color recording can be performed by line-sequential overlapping transfer.

Mixed weight % of binder material 121 and coloring material 122
For example, the coloring material 122 is selected to be 2 to 60%, and therefore the binder material 121 is selected to be 98 to 40%.

When the coloring material 122 is a dye, the mixing weight % is 2
If it is less than %, the transfer recording density is insufficient and the color material 122
If the amount of the coloring material exceeds 60% when the ink material is a pigment, the viscosity of the ink material 120 as a whole will not be reduced sufficiently, making transfer recording onto a recording medium difficult.

In particular, coloring material 122 is 10 to 50%, binder material 12
Ink material 120 selected within the range of 90% to 50%
is recommended because it has excellent transfer recording density and continuous gradation. This range is particularly useful when using a pigment as the coloring material 122 in consideration of weather resistance. In addition,
Ink material layer 120 can also be configured to be porous. In particular, when the coloring material 122 made of pigment is used and the ink material layer 120 is formed by a solvent coating method, it is possible to easily form a porous layer by controlling the evaporation of a true solvent contained in the solvent for the binder material 121 and a highly advantageous non-solvent added in a small amount. It can be done sexually.

Although the auxiliary particles 123 are spherical in the figure, they do not necessarily have to be spherical and may be polygonal. Further, although the same particle size φ is shown in the figure, it may have a suitable particle size distribution. In this case, it does not necessarily matter if the grain size φ is smaller than the thickness t of the layer 130 and has a grain size distribution that partially includes grain sizes that can be buried in the layer 130. In this case, the particle diameter φ of the particles 123 is expressed as an average pore diameter of 4 m.

Particles 123 effective for continuous tone transfer recording are φ>t
Particles that satisfy φ<t often exhibit the same behavior as the binder material 121, and this tendency becomes larger as φ becomes smaller.

The particle diameter φ of the auxiliary particles 123 is the same as that of the ink material layer 12.
It is practically selected based on the correlation with the thickness t of 0.
If the particle size φ is less than φ _nio = 1.5 μm, the thickness t of the ink material layer 120 will be too small due to the requirement of t < φ, making it impossible to obtain a high transfer recording density to a recording medium (image receptor) such as recording paper, and manufacturing In other words, it becomes difficult to form effective auxiliary particles 123 with φ<t that protrude toward the layer surface 120a, making it difficult to perform good continuous tone transfer recording, resulting in binary transfer recording similar to conventional thermal transfer recording sheets. easy.

On the other hand, the particle diameter φ of the auxiliary particles 123 is φ _nax = 15 μm
If the temperature exceeds 100, the heat capacity of the particles 123 becomes excessive, making it difficult to raise the temperature and melt the particles as expected by the thermal recording head, resulting in lower sensitivity and lower maximum transfer recording density.

Therefore, the preferred range of average particle diameter φm is 1.5 μm to 15 μm.
It is m. In particular, if the average particle diameter φm is selected within the range of 2 μm to 10 μm, continuous gradation properties, recording sensitivity, etc. will be good and this is a recommended range.

The arrangement density of the auxiliary particles 123 that satisfies φ>t is selected in consideration of the transfer recording pixel density and the thermal transfer recording characteristics.

The lowest arrangement density is when a single number is located in each transfer recording pixel.

Normally, when performing gradation recording using a known linear type thermal recording head, the recording density, that is, the transfer recording pixel density d, is 4 dots/mm from the viewpoint of image quality.
More selected. Therefore, the minimum value of the concealment ratio S limited to the auxiliary particles 123 that satisfies φ>t (the area _ratio of the particles 123 to the unit area of the base surface 110a) is (πφ ² _nio d ² )/4
When expressed as a percentage, if d=4 dots/mm,
The result is 2.8×10 ^-3 %.

On the other hand, the maximum value of S is the auxiliary particle 123 with φ>t
A plurality of pieces are arranged on the base surface 110 without overlapping each other.
π/4 in the case of the densest arrangement in a, therefore
It becomes 78.5%. S is appropriately selected within the above range.

In the above, if the arrangement density of the auxiliary particles 123 is too low, the continuous gradation property is likely to be impaired, and the transferred recorded image becomes rough especially in the low density region. To prevent these, the arrangement density of particles 123 is 16 pieces/mm.
(256 pieces/mm ² , S is 4.5×10 ^-2 % at φ _nio = 1.5 μm)
It is desirable to select more than one.

The auxiliary particles 123 can be colored with dyes, pigments, etc., or colored material particles can be used as needed, but if the color is different from the coloring material 122, the color will change depending on the transfer recording density. or
Alternatively, in the case of the same color, the transfer recording density may change discontinuously, which may cause problems depending on the application.

Therefore, in order to achieve good continuous gradation, the particles 123 are preferably colorless, white, or transparent, so as not to significantly affect the color brightness of the coloring material 122. It is desirable to choose materials.

In addition, if the auxiliary particles 123 are selected to have a lower fusion heat energy, a lower specific heat, and a higher thermal conductivity than the binder material 121, there is an advantage that higher sensitivity and continuous gradation can be improved. .

The thickness t of the ink material layer 120 is appropriately selected so as to satisfy t<φ. The coating amount of the thermal transfer layer 130 as a whole is desirably selected within the range of 0.8 g to 5 g per 1 m ² in consideration of transfer recording density, continuous gradation, recording sensitivity, etc.

FIG. 2 is a system configuration diagram of a thermal transfer recording apparatus using a thermal transfer recording sheet according to an embodiment of the present invention.

Reference numeral 510 denotes a linear type thermal recording head, and in the temperature increasing recording section 511, resistance heating elements are arranged at a density of, for example, 4 dots/mm. This temperature increase recording section 51
A recording medium 200 and a thermal transfer recording sheet 100 having a thermal transfer layer 130 are inserted and pressed between 1 and a metal or heat-resistant platen 610, and the paper is fed as indicated by arrows 612 and 613 by rotating the platen 610 as indicated by an arrow 611. . 621 and 622 are a recording medium roll and a take-up roll, respectively, and 631 and 632 are a transfer body roll and a take-up roll, respectively.

Reference numeral 520 denotes a modulation power supply device that converts and supplies a heat generation control electric signal 500A pulse-width modulated in correspondence with the input image signal 500B to each of the resistance heating elements of the recording head 510 line-sequentially in synchronization with paper feeds 612 and 613. It is. By the recording head 510,
The temperature of the thermal transfer layer 130A corresponding to the recording section 511 is controlled to increase the temperature in a line-sequential manner via the base 110. In this example, a large number of auxiliary particles 12 are included in each recording pixel.
3 is located, and the heat generation of the heating resistor element is controlled in accordance with the pulse width P _W of the electric signal 500A. By this temperature increase recording control, the auxiliary particles 123 are melted in accordance with _PW , and the molten auxiliary particles 12 have a lower viscosity.
3' is formed. On the other hand, the binder material 121 having a higher melting point than the auxiliary particles 123 forming the ink material 120 also melts and has a lower viscosity from the base surface 110a side, although it progresses at a slower rate than the particles 123, so-called molten ink material 120' having a lower viscosity. form.

Needless to say, the thermal energy added during melting of a solid material is dissipated as heat of fusion, and its temperature is fixed at the melting point. However, the temperature of the molten material starts to rise again in a continuous manner in response to the applied thermal energy according to its specific heat and thermal conductivity.
Thus, the unmelted binder material 121 in the ink material 120 in contact with the interface 123a' of the auxiliary melting particles 123' is supplied with heat of fusion by heat conduction via the auxiliary particles 123'.

Therefore, a so-called molten ink material 120' having a lower viscosity is generated along the particle interface 123a', and the range of the lowered viscosity expands to the periphery of the interface 123a' as the pulse width P _W increases.

In this way, when the recording medium surface 200a is configured to be ink-philic, the melting auxiliary particles 123' permeate and stick to the surface 200a, and the melted ink material 120' also permeates at the same time.
It will be sticky.

Therefore, after the signal 500A is applied and before the melting auxiliary particles 123' and the melted ink material 120' return to their original solid state,
Transfer sheet 100 as paper feeds 612 and 613
When the recording medium 200 is peeled off, the auxiliary particles 1
23 and the ink material 120 melted in accordance with the pulse width P _W are attached to the recording medium 200 and a transferred record 160 is obtained.

The amount of molten ink material 120' is determined by the signal 500A.
increases as the pulse width P _W increases. Therefore,
Recording medium 20 together with molten binder material 121
Color material 122 transferred to 0, that is, transfer record 1
The optical density of 60 increases continuously corresponding to P _W ,
A transfer record 160 with continuous gradation is obtained.
In this case, the maximum density of the transfer recording 160 corresponds to the case where the melting progresses to the entire surface of the ink material layer surface 120a.

In addition, in the above, if the auxiliary particles 123 and the binder material 121 are selected to be partially compatible or completely compatible when the temperature is increased, there is an advantage that the transfer recording 160 can be performed more effectively.

In these cases, the transfer sheet 100 and the recording medium 2
Peeling off of 00 will affect the quality of the recorded and transferred image, so care must be taken.

A good transferred image is obtained when the molten ink material 120' and the auxiliary melting particles 123' cool down after the recording signal pulse 500A is applied, and before returning to their original solid form, they maintain fluidity to some extent. particle 1
23' provides a means for quickly peeling off the recording medium 200 and the thermal transfer recording sheet 100 while maintaining transferability to the medium surface 200a, and this peeling is performed in order to prevent uneven peeling of the recorded image. This is always done after traveling a certain distance (for a certain period of time) from section 511.

In this example, the tension of the paper feeds 612 and 613 is increased, and the sheet 100 and the medium 200 are uniformly separated by, for example, a stripper 700 after passing the recording section 511, so that the above conditions are satisfied.

The recording medium 200 may include non-coated paper, coated paper,
Synthetic paper such as polypropylene material, plastic film such as PET, cellophane, etc. are used.

FIG. 3 shows a cross-sectional structure of another embodiment of the thermal transfer recording sheet according to the present invention.

In this example, a case is shown in which the particle diameter φ of the auxiliary particles 123 has a distribution. The auxiliary particles 123 having the relationship φ<t and embedded in the ink material layer 120 mainly exhibit the same behavior as the binder material 121.

The auxiliary particles 123 having a relationship of φt dominantly contribute to continuous tone transfer recording. In this case, the smaller φ is, the more the melting is completed in the narrower pulse width P _W of the signal 500A, resulting in the transfer record 160, and the larger φ is, the larger the heat capacity is, so a wider pulse width P _W is required.

Therefore, by giving an appropriate distribution to the particle diameters of the auxiliary particles 123 in the relationship of φt, the slope of the pulse width _PW vs. transfer recording density characteristic curve is made gentler, and a good halftone image can be obtained. There is.

Note that sometimes the base surface 11 of the thermal transfer layer 130
The adhesive strength of 0a may be insufficient. To improve this, the substrate surface 110a is made of a thin material (for example, ethyl cellulose or polyvinyl butyral resin).
This can be improved by providing a heat-resistant intermediate layer 124 (about 1 μm) and placing a thermal transfer layer 130 thereon. Further, when the temperature increase recording control is performed using a light beam such as a laser beam, a photothermal conversion material such as carbon black can be mixed into the intermediate layer and used as a photothermal conversion layer.

In addition, when temperature-rise recording control is performed using a thermal recording head, heat-resistant material such as polysulfon resin mixed with fine silica powder is used to prevent the back surface 110b of the substrate from melting and causing a sticking phenomenon, or to ensure smooth running. The lubricant layer 111 can be provided to have a thickness of about 1 μm, for example.

FIG. 4 is a cross-sectional structural diagram of still another embodiment of the thermal transfer recording sheet according to the present invention.

In this example, the first auxiliary particles 123 have a lower melting point (softening point) or pour point than the binder material 121, and the second auxiliary particles 123 have a higher melting point (softening point) or pour point than the binder material 121. Auxiliary particles 124
are dispersed and arranged in the ink material layer 120.

Similar to the particles 123, the auxiliary particles 124 are set so that at least some of the particles have a particle size larger than the thickness t of the ink material layer 120, and the preferable particle size range is also the same as that of the auxiliary particles 123 described above. shall be applied accordingly.

The second auxiliary particles 124 are, for example, alumina,
Inorganic powders such as glass, quartz, titanium oxide, and silica, and organic resin powders such as epoxy resins and phenol resins are used, and the average particle size is preferably the first.
The particles are selected to the same extent as the auxiliary particles 123.

The above-mentioned concealment rate S is selected within the above-mentioned range as a total value with the first auxiliary particles 123, and preferably the S value of the second auxiliary particles 1 is greater than the S value of the first auxiliary particles 123.
It is desirable to select the S value of 24 to be about the same level or lower.

According to the configuration shown in FIG. 1, when the pulse width P _W of the signal 500A increases beyond a certain level, melting reaches from the base surface 110a side to the ink material layer surface 120a, and the entire layer 130 is melted at once. The image may be transferred to the recording medium 200, and the gradation in the high transfer recording density area may be lost.

In such a case, the second auxiliary particles 124 have the role of a spacer and cover the ink material layer surface 120.
It has the role of preventing excessive pressure contact between the recording medium surface 200a and the recording medium surface 200a, thus preventing the above-mentioned excessive transfer recording, and has the advantage that the gradation in the high transfer recording density region is improved.

In the thermal transfer recording sheet according to the present invention, auxiliary particles 12 are used so that at least some of the particles satisfy φ>t.
3 must be partially embedded in the ink material layer 120.

A useful method for manufacturing the sheet 100 that satisfies this condition is to mix the ink material 120 and the auxiliary particles 123 with a solvent material that dissolves the binder material 121 at room temperature but does not completely dissolve the auxiliary particles 123 at room temperature. The material is heat-resistant substrate 110
After the ink material layer 120 is coated to a predetermined thickness on one surface side of the auxiliary particles 123, the solvent material is evaporated and removed to reduce the thickness of the ink material layer 120. The diameter of at least some of the particles is smaller than that of at least some of the particles.
In addition, in FIG. 1 etc., a pigment or the like is used as the coloring material 122, and an opening is formed on the ink material layer surface 120a side.
The ink material layer 120 can also be configured to be porous so as to have fine through holes penetrating the base surface 110a.

A configuration example will be described below.

Example 1 4.95 parts by weight of aromatic petroleum resin (Nisseki Neopolymer NP-120, Nippon Petrochemicals Co., Ltd.) with a softening point of 120°C was used as the binder material 121, and 1.8 parts by weight of cyan pigment (CI Pigment Blue 15) was used as the coloring material 122. The ink material 120 is composed of a binder material 121 which has a melting point lower than that of petroleum resin and has a melting point of 83.
℃, 1.5 parts by weight of carnauba wax powder particles with an average particle size of 5 μm, and xylene was selected as a solvent in which petroleum resin dissolves at room temperature (25℃), but carnauba wax does not dissolve, and 24 parts by weight of xylene was added. The mixed materials are well mixed and dispersed using a ball mill at room temperature. Using a commercially available bar coater #5, this mixed solution was layered at room temperature on a sheet-like substrate 110 made of a 9 μm thick PET film and having a heat-resistant lubricant layer 111 on the back surface, and the xylene was evaporated and removed. do.

The coating amount of the obtained thermal transfer layer 130 was 1.9 g/m ²
On the surface of the thermal transfer layer 130, carnauba particles serving as auxiliary particles 123 are dispersed and protruded to form an uneven surface.

Using this thermal transfer recording sheet 100 and a recording medium 200 made of polypropylene synthetic paper having a thickness of 150 μm, transfer recording was performed using a thermal recording head 510.

The recording head 510 is a linear type with a recording density of 4 dots/mm, the applied power per heating resistor element is 0.7 W, the main scanning recording speed is 16.7 ms/line, the sub-scanning recording density is 4 dots/mm, and the recording signal is 500 A. 6
The pulse width is modulated by bits, and the maximum pulse width is
It is 4ms.

The optical density of the transfer record 160 is determined by the pulse width P _W =
At 0.77 ms, the optical density rises smoothly from the paper surface optical density of the recording medium 200, and the maximum transfer recording density is reached at P _W = 3.3 ms. During this period, the recording density changes continuously with respect to P _W , resulting in good continuous gradation. showed his sexuality.

Change coloring material 122 to cyan pigment, magenta color (CI Pigment Red.57), yellow color (CI
Pigment Yellow12), black (carbon black)
Good continuous tone transfer recording characteristics were obtained even when pigments were used.

Example 2 In Example 1, further second auxiliary particles 124
Thermal transfer recording sheet 1 was prepared by adding and dispersing 1.5 parts by weight of alumina powder particles with an average particle size of 5 μm.
According to 00, transfer record 1 for pulse width P _W
The optical density dependence of Example 60 was gentler than that of Example 1, and the highest transfer recording density was obtained at _PW of 4 ms, and even better continuous gradation characteristics were obtained. Similarly good continuous tone characteristics were obtained for the other pigment coloring materials of Example 1.

Thus, by using the thermal transfer recording sheets 100 according to Examples 1 and 2, it was possible to transfer and record not only single-color halftone images but also full-color images by overlapping the above-mentioned primary color sheets in a field-sequential manner.

Note that the following various methods are used to adjust the continuous tone characteristics. For example, a plurality of types of auxiliary particles 123 having different melting points (softening points) or pour points are mixed and used as the auxiliary particles 123. For example, Example 1,
In the second class, carnauba wax (melting point 83°C) and Lysol wax (softening point
(108℃) powder particles are mixed and used. Furthermore, the mixing ratio is changed. The second auxiliary particles 124 may also be a mixture of a plurality of different material powders, or may be used with a different mixing ratio.

In addition, the first and second auxiliary particles 123, 124
It is also effective to change the average particle diameter of one or both of the above, and even the particle size distribution.

The first auxiliary particles 123 may be material particles colored with dye or the like. In this case, the continuous gradation property is slightly degraded, but if the color material 122 is the same color, the optical density of the transfer record 160 is improved, and if the color material is a different color, the color of the transfer record 160 is changed in accordance with the pulse width. I can do it.

Effects of the Invention As described above, the present invention is a thermal transfer recording sheet in which auxiliary particles having a low melting point (softening point) or pouring point are arranged in an ink material layer, and the desired thermal transfer recording sheet can be easily manufactured. In addition, by using this thermal transfer recording sheet, it is possible to perform continuous tone transfer recording using pigment coloring materials, which was difficult with conventional melt transfer recording sheets.
As a monochrome or full color printer for OA, HA, new media, facsimile fields, etc., its industrial effects are extremely large.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional structural diagram of an embodiment of a thermal transfer recording sheet according to the present invention, and FIG. 2 is a system configuration diagram of a thermal transfer recording apparatus using an embodiment of a thermal transfer recording sheet according to the present invention. FIG. 3 is a cross-sectional structural diagram of another embodiment of the thermal transfer recording sheet according to the present invention;
The figure is a cross-sectional structural diagram of still another embodiment of the thermal transfer recording sheet according to the present invention.

Claims (1)

[Scope of Claims] 1. An ink material containing a binder material whose viscosity decreases upon heating and imparts transferability to a recording medium on one side of a sheet-like heat-resistant substrate; 1. A thermal transfer recording sheet comprising a thermal transfer layer in which auxiliary particles made of a hot-melt material solid at room temperature and having a melting point, softening point, or pouring point lower than that of the thermal transfer layer are dispersed in the form of particles. 2. The thermal transfer recording sheet according to claim 1, wherein the particle size of at least some of the auxiliary particles is set to be greater than or equal to the thickness of the layer made of the ink material. 3. The second auxiliary particles have a melting point, softening point, or pour point higher than that of the binder material, and at least some of the second auxiliary particles have a particle size larger than the thickness of the layer made of the ink material. 3. The thermal transfer recording sheet according to claim 2, further comprising: a.