JPH0558917B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a thermal transfer recording sheet and a thermal transfer recording sheet 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 or the like. The present invention relates to a manufacturing method thereof.

Conventional technology Conventional thermal transfer recording sheets have a thickness of 7 μm.
m polyethylene terephthalate (PET)
Apply 20% by weight of carnauba wax, 40% by weight of ester wax, and mineral oil as binder materials to the surface of a sheet-like heat-resistant substrate such as film or capacitor paper.
A thermal transfer layer with a thickness of about 4 μm is formed by using a hot melt material consisting of 10% by weight of 10% by weight and 10% by weight of other auxiliaries, and an ink material layer of 20% by weight of a pigment coloring material mixed with this hotmelt binder material. A thermal transfer recording sheet formed by a melt coding method and having a melt transfer temperature of about 60°C is known (for example, Wai Tokunaga and Kei Sugiyama,
“Thermal Ink-Transfer Imaging, IEE Transactions
On Electron Devices, ED-27 volume,
pp. 218-222, 1980 (Y. Tokunaga and K.
Sugiyama, “Thermal Ink-Transfer
Imaging”，IEEE Trans.on Electron Devices，
vol.ED-27, PP.218-222, 1980.)) Thermal transfer using this type of thermal transfer recording sheet is generally carried out in a state in which a recording medium (image receptor) such as recording paper and the thermal transfer recording sheet are brought into pressure contact. Then, a known thermal recording head is pressed against the back surface of the base sheet, and the temperature of the thermal transfer layer is selectively heated and recorded by the thermal recording head through 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 is applied to the recording medium (image receptor) only after the binder material has completely melted from the base sheet side to the surface of the ink material layer. The ink material is adhered and transferred. 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, it is useful for binary density recording such as characters and figures, but it is useful for recording images with halftones, etc. , it cannot be used for applications that require continuous gradation, and the dither method,
Digital gradation methods such as the density pattern method 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 will be significantly lower than the recording density 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, and a method for manufacturing the same. There is.

Means for Solving the Problems In order to solve the above problems, the present invention provides a heat-transferable ink material layer whose viscosity is controlled to be reduced by temperature-raising recording control on a sheet-like heat-resistant substrate. A thermal transfer recording sheet is constructed by further disposing on the surface of this ink material layer a porous solid particle layer through which the ink material whose viscosity and reduction is controlled can penetrate.

In addition, the above thermal transfer recording sheet is produced by applying a liquid mixture material containing solid particles, a hot melt binder material, and a solvent for this binder material to the surface of the ink material layer, and by evaporating and removing the solvent. It is manufactured using a manufacturing method using so-called solvent coating, which is characterized by forming a porous solid particle layer.

Function: Due to the presence of the solid particle layer in such a thermal transfer recording sheet, the solid particles act as a spacer, and even if the binder material, so-called ink material, is thermally melted to the surface of the ink material layer, the ink material does not reach the surface of the ink material layer. This prevents the particles from being attached and transferred to the recording medium all at once. This molten ink material is further heated,
When the solid particles are heated to a temperature higher than the melting point (or softening point) of the binder material that makes up the ink material, the so-called molten ink material travels through the gaps between the solid particle layers, that is, the surface of the solid particles, and forms the recording medium. It penetrates to the side, is extruded, and is transferred to the recording medium.
The amount of penetration and extrusion corresponds to the temperature of the molten ink material and its viscosity reduction, ie, the amount of heat from the thermal recording head. When the thermal transfer recording sheet and the recording medium are peeled off after this temperature increase recording control has been completed and before the ink material remaining in the ink material layer has cooled down to its original solid state, a portion of the molten ink material will appear on the surface. The solid particles adhered to are also adhered and transferred to the recording medium.

Thus, in the thermal transfer recording sheet according to the present invention, the amount of ink material that permeates through the solid particle surfaces forming the gaps, and further adheres to the solid particle surfaces and is transferred to the recording medium is small. , corresponds to the temperature increase recording control amount by the thermal recording head, that is, the amount of melted ink material based on the amount of heating, so the transfer recording optical density of the recording medium depends on the power applied to the heating resistor element of the thermal recording head, the pulse width, and the heat generated. It will be continuously controlled in accordance with the number of times, etc.

In addition, in the above-mentioned solvent coating method, the porous solid particle layer, which plays an important role in the present invention, is formed by evaporating the molten ink material by appropriately controlling the amount of mixed binder material and the amount of solvent dilution. It is possible to effectively create a high-density micro-gap through which water can penetrate.

Embodiment FIG. 1 shows a cross-sectional structure of an embodiment of a thermal transfer recording sheet according to the present invention.

100 is a thermal transfer recording sheet, and 110 is a sheet-like heat-resistant substrate such as capacitor paper or polyethylene terephthalate (PET) film having a thickness of 4 to 15 μm. Pigment,
A coloring material 122 made of a dye or both of these and a binder material 121 made of a hot melt material such as carnauba wax, for example, has a thickness of 1 to 1.
A thin layer 120 of ink material on the order of 3 μm is deposited. On the surface 120a of the ink material layer, heat-resistant solid particles 131 such as inorganic powder particles of alumina, titanium oxide, glass, etc. or organic resin powder particles of epoxy, polyimide, etc. are sprayed at high temperature, and the binder material 121 is used. Gap 13 by fusing
A porous solid particle layer 130 having a particle diameter of 5 is formed.

This thermal transfer recording sheet 100 has a recording medium (image receptor) 200 such as non-coated paper, coated paper, synthetic paper, plastic film, etc. on the front side of the solid particle layer 130, and a thermal recording medium (image receptor) 200 on the back side 110b of the base body 110. A recording head 300 is disposed, and a pressure 500 is applied by a recording platen 400 made of a rubber roller or the like, and the sheet 100 and the medium 200 are brought into contact with each other by the rotation 600 of the recording platen 400 as indicated by the arrow 60.
1,602, the paper is fed and recorded by thermal transfer.

Next, recording using this thermal transfer recording sheet is performed as follows. In the figure, the heating resistor 350 of the thermal recording head 300 is connected to the terminal 33.
When a recording signal 700 is applied between 1,341 and energized to generate heat, the ink material layer 12 is transferred through the base 110.
0 is heated. Depending on the amount of heating, the binder material 121, and therefore the so-called ink material layer 120, starts to melt from the base surface 110a side, but even if this melting reaches the ink material layer surface 120a, the solid particles 131 do not function as spacers. However, unlike conventional thermal melt transfer recording sheets, melt ink material 1
20' is not transferred to the recording medium surface 200a. This is because the solid particles 131 as a whole have not yet been heated to the melting point of the binder material 121.

The solid particles 131 are further heated by the molten ink material 120' until the temperature reaches the binder material 1.
Transfer to the surface 200a begins as indicated by A only when the melting point (or softening point) of 21 is exceeded. In this case, when the pressing force 500 is high, the solid particles 13 are transferred into the low-viscosity molten ink material 120'.
1 is pushed in, and the ink material 120' penetrates into the gaps 135 between the solid particles 131 and is forced out. The surface of ink material 120' thus rises within gap 135.

In this case, the wetting angle (contact angle) of the molten binder material 121, in other words the molten ink material 120'
, the solid particle surface 131a, and the recording medium surface 2
If the angle is selected to be as small as possible within 90 degrees with respect to 00a, that is, ink affinity, the surface tension of the molten ink material 120' (in other words, the molten binder material 121), Furthermore, due to the capillary phenomenon in the gap between the medium surface 200a and the particle surface 131a, the particle surface 131 flows through the gap 135.
a, causing ink penetration 123 along media surface 2
The molten ink material 120' is attached and transferred to 00a.

Before the application of the recording signal 700 ends and the molten ink material 120' on the particle surface 131a in the layer 120 returns to its original solid state, preferably in the molten state, an appropriate time constant is set as the paper feeds 601, 602. When the recording medium 200 and the thermal transfer recording sheet 100 are separated from each other with
binder material, colorant 122, and solid particles 131 that are transferred to a to form ink material 120'.
A transfer record 140 consisting of is produced.

The amount of ink penetration 123 through the particle surface 131a and thus the gap 135 is determined by the amount of ink material 120'
The viscosity decreases due to the melting of the particles, and the particle surface 131a
Since the transfer by adhering to the ink corresponds to melting of the ink, it depends on the electric power applied to the heating resistor element 350, the pulse width P _w of the recording signal 700, and the number of times of heat generation.
The optical density of the transfer record 140 is continuously controlled.

In this way, a known linear thermal recording head is used as the recording head 300, and a pulse width (P _w ) modulated recording signal 700 is applied to each heating resistor element line-sequentially in response to the rotation 600 of the recording platen 400. Then, a continuous-tone, single-color half-tone image is formed on the substrate 110 sequentially in cyan, magenta,
By disposing a yellow ink material layer 120 and controlling the recording temperature of these primary color ink materials one after another using a pulse width modulation signal 700 and overlapping transfer recording, a full color image can be transferred and recorded.

In this case, the presence of the solid particles 131 has the advantage of providing a spacer, which prevents back-transfer of the ink material previously transferred and recorded in the case of overlapping transfer, resulting in a good full-color image.

The melting point (or softening point) of the solid particles 131 may be lower than, the same level, or higher than the melting point (or softening point) of the binder material 121, but the solid particles 131 may function as spacer particles. From the point of view of giving the binder material 121 a higher melting point (softening point) than the binder material 121, more preferably the ink material 1
It is recommended to choose a high melting point material that will not melt during the thermal transfer of 20'. The particle size of the solid particles 131 can be freely selected within a range that does not increase the heat capacity. When a pigment is used as the coloring material 122 and cannot be completely embedded in the heat-melting ink material 120', the thickness of the particles 1 is smaller than the thickness of the ink material layer 120.
The particle size of the ink layer 31 can be made small, but because of its role as a spacer, it is generally selected to have an average particle size of 10 μm or less, 1.5 μm or more, and greater than the thickness of the ink material layer 120.
The solid particles 131 are preferably transparent, colorless, white, light-colored, or not significantly colored so that the color of the transfer record 140 does not change significantly compared to the ink material 120'.

As the thermal recording head 300, a so-called flat type head in which heating resistive elements are arranged at a density of 4 dots/mm to 16 dots/mm on a flat plate surface 301 such as an alumina substrate can also be used, but due to its flatness, the recording platen 400 When the radius of curvature of the thermal transfer sheet 100 and the recording medium 20 are large,
0 cannot be peeled off quickly after the temperature increase recording control, and therefore, _the molten ink material 1 cannot be peeled off quickly after the temperature increase recording control.
20' may solidify, resulting in poor continuous gradation.
Furthermore, due to the insufficient pressing force of 500, the solid particles 131 cannot be effectively pushed into the molten ink material 120'.
There may be cases where the desired transfer recording density cannot be secured.

This difficulty lies in the fact that, as illustrated in FIG.
This problem is solved by adopting a so-called edge type head in which heating resistive elements 350 are arranged on the edge surface 302, not on the edge surface 302, separated from each other in the normal direction of the drawing paper and arranged at about 4 dots/mm to 12 dots/mm. be done. According to this head, the pressure contact width by the recording head 300 corresponds to the thickness of the base 310, and the paper feed 60
It can be extremely narrow, for example, about 2 to 4 mm in the 1,602 direction. Therefore, sheet 100 after temperature increase recording control
Not only can the medium 200 be quickly peeled off as shown in the figure, but also the pressure strength per unit area can be increased by reducing the pressure width, and the ink penetration 123 can be effectively performed through the gap 135 to achieve the desired result. It has the advantage of being able to perform continuous tone transfer recording at high density. In the figure, 321 and 322 are mechanically strong reinforcing bodies that also serve as heat sinks.

FIG. 2 is a cross-sectional structural diagram of another embodiment of the thermal transfer recording sheet according to the present invention.

In this example, the solid particles 131 are fixed onto the ink material layer surface 120a by the binder material layer 132 to form a porous solid particle layer 130 having gaps 135.

The solid particles 131 are attached to the binder material layer surface 132.
a (Surface of part where solid particles 131 are not present)
More protruding, the solid particle layer 130 forms an uneven surface, and the protruding particles form gaps 135 for ink penetration 123 (see FIG. 1).

Although the binder material 132 can be made of a heat-resistant material such as polyester resin, polyvinyl butylar resin, or ethyl cellulose, it is recommended that it be made of a hot melt material. In this case, the melting point (or softening point) of the binder material 132 may be higher, lower, or about the same as that of the binder material 121; The melting point (or softening point) is chosen to be lower than the binder material 121. For example, when the binder material 121 is made of carnauba wax with a melting point of 83°C, solid paraffin with a melting point of 51°C or a softening point of 70°C is used.
Binder material with alicyclic saturated hydrocarbon resin at 13 °C
2.

When the binder material 132 is made of a hot melt material in this way, the binder material layer 132 is melted by the melted ink material 120' in FIG.
The viscosity is reduced, facilitating ink penetration 123 through the particle surfaces 131a and gaps 135.

Note that when the binder material layer 132 is made of a hot melt material, it may be compatible or incompatible with the binder material 121. When the binder material 132 is selected for compatibility, the binder material 132 forms a compatible state with the binder material 121 in the transfer record 140 and does not precipitate, resulting in a smooth transfer record 1.
40 is advantageous. At the same time, the binder material layer 132 is extremely easily compatible with the molten ink material 120' at low temperatures and has a low viscosity, allowing ink penetration 123, which has the advantage of enabling high-sensitivity transfer recording. As the binder material 132 that is compatible with the carnauba wax type binder material 121, it is recommended to use, for example, an aliphatic petroleum resin.

These porous solid particle layers 130 are formed by selecting a solvent that is insoluble in the binder material 121 and dissolving the binder material 132 at room temperature (for example, 25° C.), and using this solvent and the binder material 132.
A diluted mixed solution of solid particles 131 is prepared, and a thin layer is formed on the surface 120a of the ink material layer at room temperature by a solvent coating method, and the solvent is evaporated and removed to form a porous solid particle layer 13.
0 can be produced. The thickness of the binder material layer 132 can be easily adjusted by selecting a small amount of the binder material 132 mixed and increasing the amount of solvent mixed.
The layer 130 can be made thinner than the grain size of 1, efficiently forming gaps 135, and forming an uneven surface.

In this case, the binder material 132 is thinly applied to the solid particle surface 131a, and the wettability of the molten ink material 120' to the particle surface 131a is improved, so that there is an advantage that the ink permeation 123 can be made easier.

In addition, in FIG. 2, the solid particle layer 130 is configured such that the particle size of the solid particles 131 is distributed. Particles 131 with a small particle size have a small heat capacity, so they are easily heated by the molten ink material 120', causing ink penetration 123 through the particle surface 131a with a small amount of heating, while large particles 131 do not have ink penetration. 123 requires a large amount of heating. Therefore, by providing the particles 131 with a suitable particle size distribution, there is an excellent advantage that the continuous tone operation range of the transfer recording 140 can be expanded. in this case,
Since the surface 200a of a medium such as recording paper usually has fine irregularities on the order of μm to 10 μm, contact between the medium surface 200a and the particles 131 is ensured with a high probability even if the diameters of the particles 131 are different. It does not interfere with ink transfer recording.

As the solid particles 131, powder particles made of a hot melt binder material can be used as long as they have a suitably higher melting point (softening point) than the binder material 121 or even the binder material 132. As these hot melt type solid particles 131, for example, aromatic petroleum resin powder having a softening point of 145 to 165° C. can be used. Although the solid particles 131 are shown in a spherical shape in FIGS. 1 and 2,
The particle shape does not necessarily matter, such as a polygonal shape.

Examples of manufacturing a thermal transfer recording sheet according to the present invention will be described below.

[Example 1] In the ink material 120, the binder material 12
A hot melt composite of carnauba wax (melting point 83°C) and castor wax (melting point 85.5°C) was used as 1, and 40% by weight of carbon black, an inorganic pigment, was mixed therein as coloring material 122, and this mixed material was heated 3. This mill melts and kneads the hot melt composite material. This kneaded ink material has a thickness of 9 μm.
A black ink material layer 120 having a thickness of approximately 1 μm is layered on a heat-resistant substrate 110 made of a PET film by hot melt coating.

As a material for coating the porous solid particle layer 130,
75 parts by weight of solid particles 131 made of alumina powder particles with an average particle size of 3 μm, and a hot melt material made of an alicyclic saturated hydrocarbon resin (Alcon P-70 manufactured by Arakawa Forestry Chemical Co., Ltd., softening point 70°C) as the binder material 132. 25 parts by weight of xylene, which is a solvent insoluble at room temperature for the binder material 121 and soluble at room temperature for the binder material 132, are mixed and dissolved in a ball mill.

This mixed solution is solvent coated on the surface 120a of the ink material layer at room temperature using a commercially available #3 bar coater, and the solvent is evaporated and removed.

The obtained solid particle layer 130 has an uneven surface and is porous, and thus the thermal transfer recording sheet 100 can be manufactured.

[Example 2] In Example 1, a phthalocyanine organic pigment (CI Pigment Blue) was used instead of carbon black.
15) in an amount of 40% by weight and similarly hot-melt coated with a cyan ink material layer 120 having a thickness of approximately 1 μm.

The material for coating the porous solid particle layer 130 includes 40 parts by weight of solid powder particles 131 made of transparent quartz glass with an average particle size of 3 μm, a binder material 132, and an aliphatic hot melt material compatible with the binder material 121. 25 parts by weight of petroleum resin (Hiretz 100G manufactured by Mitsui Petrochemicals, softening point 100°C) and 150 parts by weight of xylene as a solvent were mixed, and solvent coating was applied in the same manner as in Example 1.

The obtained solid particle layer 130 has an uneven surface and is porous, so that the thermal transfer recording sheet 100 can be manufactured.

Note that in the configuration shown in FIG. 2, the solid particles 131
The average particle size of
10 μm or less in order to prevent a decrease in thermal transfer sensitivity due to excessive length, and from the perspective of a spacer.
It is desirable to select the particle size within the range of 1.5 μm or more, and at least some of the solid particles within the distribution particle size range13
1 in the ink material layer 120 and the solid particles 1
From the viewpoint of obtaining good continuous gradation, it is recommended that the binder material layer 132 be selected to be larger than the total thickness of the binder material layer 132 that fixes the layer 31 to the layer surface 120a.

Further, in the above embodiment, the binder material 121
described the structure mainly using a hot melt binder material that is solid at room temperature, but binder material 1
No. 21 has a melting point (softening point) below room temperature (for example, 25° C.), and so-called adhesive materials that are in a molten state at room temperature can also be used. In this case, since stickiness occurs if the viscosity at room temperature is low, use an adhesive such as polybutene that has a viscosity of 1000 poise or more at room temperature (for example, 25° C.).

The viscosity of the binder material 121 made of these adhesives is also reduced by the temperature increase recording control, and a transfer record 140 is effectively produced through the gap 135 and the solid particles 131.

As described above, a heat-transferable ink material layer containing a binder material whose viscosity is controlled to be reduced by temperature increase recording control is provided on a sheet-like heat-resistant substrate, and further on the surface of this ink material layer, Using the thermal transfer recording sheet according to the present invention, which is provided with a porous solid particle layer that is permeable to the ink material whose viscosity is controlled to be reduced, the thermal transfer recording sheet and the recording medium (image receptor) are connected to each other. is inserted between the thermal recording head and the recording platen facing it, and the thermal transfer recording sheet and the recording medium are fed in the same direction. Then, with the recording medium in pressure contact with the surface side of the solid particle layer, the thermal recording head controls and records the temperature of the ink material layer and the solid particle layer through the heat-resistant substrate, and this temperature increase is controlled by the thermal recording head. When the recording control is completed, the temperature-raising recording section passes through the recording section of the thermal recording head, and before the viscosity of the binder material returns to its original temperature state, the thermal transfer recording sheet and the recording medium are heated. According to a thermal transfer recording method and a thermal transfer recording device based on the principle of attaching and transferring the solid particles to the recording medium with the ink material attached to the surface of the solid particles after peeling off, it is possible to achieve good thermal transfer with continuous gradation. Can record. Particularly in this case, if the edge-type thermal recording head illustrated in FIG. It has the advantage that halftone images can be transferred and recorded.

Note that, as the solid particles 131, it is also possible to adjust the recording characteristics by using a mixture of a plurality of types of solid particles having different constituent materials or different specific heats.

Furthermore, the binder material 12 of the ink material layer 120
The material of layer 1, the mixing ratio of binder material 121 and coloring material 122, and the coating material of layer 120 may be changed.
The recording characteristics can be adjusted by changing the arrangement density, particle size, particle size distribution of the binder material 132, amount of the binder material 132, material quality, etc. These are applied to adjust the recording characteristics of each primary color thermal transfer recording sheet when performing full color overlapping transfer recording using the three primary color method or the like.

Effects of the Invention As described above, the present invention is a thermal transfer recording sheet provided with a porous solid particle layer, which enables thermal transfer recording in continuous gradations, which has been difficult with conventional heat-melting transfer recording sheets. Not only monochromatic half-tone images but also full-color images can be realized, and the industrial effects thereof are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of one embodiment of a thermal transfer recording sheet according to the present invention, and FIG. 2 is a sectional view of another embodiment of the thermal transfer recording sheet according to the present invention. 100...Thermal transfer recording sheet, 110...Heat-resistant substrate, 120...Ink material layer, 130...Porous solid particle layer, 140...Transfer recording, 200
... Recording medium, 300 ... Thermal recording head,
400...recording platen, 700...recording signal.

Claims (1)

[Scope of Claims] 1. A thermally transferable ink material layer whose viscosity is controlled to be reduced by temperature increase recording control is provided on a sheet-like heat-resistant substrate, and a layer of the ink material is further disposed on the surface of the heat-transferable ink material layer. 1. A thermal transfer recording sheet comprising a solid particle layer in which solid particles having a melting point or softening point higher than that of a binder material contained are arranged in a granular manner so as not to overlap in the thickness direction. 2. The thermal transfer recording sheet according to claim 1, wherein a solid particle layer is formed by fixing solid particles to the surface of the ink material layer using a hot melt material as a binder material. 3. A heat-transferable ink material layer whose viscosity is controlled to be reduced by controlling temperature is provided on the sheet-like heat-resistant substrate, and further has a melting point or softening point higher than that of the ink material layer on the surface of the heat-transferable ink material layer. When manufacturing a thermal transfer recording sheet with a solid particle layer in which solid particles are arranged in a granular manner so as not to overlap in the thickness direction, solid particles, a hot melt binder material, and a layer of this binder material are coated on the surface of the ink material layer. 1. A method for producing a thermal transfer recording sheet, comprising applying a mixed solution material containing a solvent, and forming a porous solid particle layer by evaporating and removing the solvent.