JPH1111030A - Melt thermal transfer ink receptive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a melt thermal transfer ink receptive sheet having excellent gradation reproducibility of an ink image and recording density and pencil writing properties for use in a melt thermal transfer printer using a thermal head. SOLUTION: The melt thermal transfer ink receptive sheet comprises a porous ink receptive layer formed by coating at least one surface of a sheet-like support with bubble-containing coating liquid obtained by mechanically agitating resin liquid and drying it and having a surface mean pore size of a range of 0.5 to 30 μm, and an overcoating layer further provided on the receptive layer and containing pigment particles and binder as main components in such a manner that its coating amount is 0.1 to 4.0 g/cm and as the pigment particles those having a BET specific surface area of 20 to 600 m<2> /g are used as needed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink receiving sheet used in a fusion heat transfer printer using a thermal head. To elaborate further,
The present invention is capable of recording an ink image having excellent gradation reproducibility and recording density, and also has an ink receiving sheet for melt thermal transfer (hereinafter, referred to as a receiving sheet) having pencil writing properties.
It is about.

[0002]

2. Description of the Related Art A fusion thermal transfer recording method for recording an ink image using a thermal transfer ink sheet and a thermal head is widely used in printers such as word processors and facsimile machines because of its simple mechanism and easy maintenance. Conventionally, high-quality paper has been used as a receiving sheet for such a recording system. However, in recent years, with the development of full-color thermal transfer recorded images, higher gradation reproducibility than before has been required for transfer ink images. For this reason, printers have shifted from the conventional method of obtaining gradation without changing the size of one dot to the dot variable method of changing the size of each dot. In addition, the receiving sheet has excellent dot reproducibility that the dot shape of the melt-transferred ink is faithfully reproduced in full-color recording from low applied energy to high applied energy, and a sufficient amount of ink is transferred. Therefore, high recording density is strongly required as an important quality of a recorded image.

[0003] In order to make the thermal transfer image full color as described above, it is necessary to appropriately adapt the characteristics of the receiving sheet. In other words, when using uncoated paper for normal printing in the full-color fusion thermal transfer method, a decrease in recording density, which is considered to be caused by low heat insulation, and poor dot reproducibility due to insufficient cushioning properties may occur. is there. In addition, if the surface of the receiving sheet is too rough, the portion where the ink is not transferred, that is, the ink is apt to be generated, and if the surface is too smooth, the ink is not anchored and the transferred image is not transferred. It is easy for the ink to be transferred to the ink ribbon in a reverse manner, thereby causing a drop. Any of these dropouts causes poor dot reproducibility.
In addition to the decrease in the recording density due to the above-described poor dot reproducibility, a recording density defect due to the low ink absorbency of the molten ink receiving layer may also occur.

As an attempt to solve these problems, it has been proposed to provide an undercoat layer containing hollow particles on a support in order to improve the cushioning properties of the receiving sheet (Japanese Patent Laid-Open No. 2-89690). And JP-A-64-
27996). However, even with this method, the cushioning properties and heat insulation properties of the obtained receiving sheet are still insufficient, and no satisfactory results have been obtained. Further, when the hollow particles are dissolved in an organic solvent or the like used for forming the receiving layer, a polymer having high resistance to the organic solvent is used as an adhesive for the hollow particles, or on a layer containing the hollow particles. It is necessary to provide an organic solvent resistant polymer layer. However, this necessity complicates the manufacturing process of the receiving sheet and raises the cost.

[0005] As another attempt to solve the above problem, a sheet-like support mainly composed of plastic is provided on a sheet-like support.
There is also an example in which a resin layer containing a component eluted in water is formed, and a water-soluble component is eluted and removed from the resin layer, whereby the receiving sheet is made porous to improve its ink receiving ability (Japanese Patent Application Laid-Open No. HEI 2 (1998) -210, No. 2). In this case, a sufficient maximum image color density cannot be obtained, or there is a defect such as lack of gloss in the printed image. Not reached. In addition, since the receiving sheet is mainly composed of plastic, there still remain problems such as difficulty in recycling paper resources and lack of writability with a pencil or a mechanical pencil.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and, when used in a fusion heat transfer type color printer, has good tone reproducibility and recording density of a transferred image and a pencil An object of the present invention is to provide an ink receiving sheet for fusing heat transfer, which also has writability.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, formed a porous ink receiving layer on a sheet-like support, and further contained a pigment To control the average diameter of the pores distributed on the surface portion of the porous ink receiving layer to an appropriate value, and optimize the coating amount of the overcoat layer, and As a result, it has been found that the above problem can be solved by optimizing the specific surface area of the pigment in the overcoat layer, and the present invention has been completed. That is, the ink receiving sheet for fusion thermal transfer of the present invention has a sheet-like support and a porous ink receiving layer formed on at least one surface of the sheet receiving substrate, and the porous ink receiving layer is formed of a film-forming resin. A foamed resin coating liquid prepared by subjecting the liquid to a foaming treatment by mechanical stirring is applied on the surface of the sheet-like support, and is formed by drying. A large number of continuous pores having an average pore diameter of 30 μm are formed,
An overcoat layer of 0.1 to 4.0 g / m ² containing pigment particles and a binder resin is formed on the porous ink receiving layer. Further, in the receiving sheet of the present invention, the BET specific surface area of the pigment particles contained in the overcoat layer is 20.
~600m is preferably ² / g.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies to achieve the above object, and as a result, formed a porous ink receiving layer on a sheet-like support, and mainly provided pigment particles and a binder resin thereon. By providing an overcoat layer as a component, the amount of coating of this overcoat layer is optimized,
If necessary, by optimizing the specific surface area of the pigment particles in the overcoat layer, it is possible to obtain a fused heat transfer ink receiving sheet having good tone reproducibility of the transferred image and good recording density, and also having pencil writing properties. Successful.

In the present invention, the porous ink-receiving layer formed on the sheet-like support contains a film-forming resin as a main component. Such a porous ink-receiving layer is formed by dispersing a large number of microbubbles in a resin liquid containing a film-forming resin as a main component by mechanically stirring the resin liquid, and applying the bubble-containing resin coating liquid to a support. It can be formed by coating on top and drying.

The film-forming resins usable for forming the porous ink receiving layer of the present invention include, for example, polyvinyl alcohols having various molecular weights and saponification degrees, derivatives thereof, starches, derivatives thereof and, for example, oxidized starch. Various modified starches such as methoxycellulose,
Cellulose derivatives such as carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylate copolymer, acrylamide-acrylate-methacrylate copolymer, styrene-maleic anhydride Alkali salts of acid copolymers, polyacrylamide and derivatives thereof, water-soluble resins such as polyethylene glycol, polyvinyl acetate, polyurethane, styrene-butadiene copolymer (SBR latex), acrylonitrile-butadiene copolymer (NBR latex), Methyl methacrylate-butadiene copolymer (M
(BR latex), polyacrylate, polymethacrylate, acrylate-styrene copolymer, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene-acrylic Copolymers, urethane-acrylic copolymers, water-dispersible resins such as polyvinylidene chloride, and glue, casein, soy protein, gelatin, sodium alginate, and the like can be used, but are not limited thereto. . These resins can be used alone or as a mixture of two or more, if necessary.

In the film-forming resin liquid, before the foaming treatment,
If necessary, one or more selected from known viscosity modifiers, dispersants, dyes, water-proofing agents, lubricants, crosslinking agents, plasticizers, and the like can be added.

The coating amount of the porous ink receiving layer on the sheet-like support is preferably ² to 40 g / m ² . If the coating amount is less than 2 g / m ² , it may be difficult to sufficiently coat the surface roughness of the support, and a surface having appropriate smoothness may not be obtained, or Insulation properties and compressive deformation may not be obtained. On the other hand, when the coating amount exceeds 40 g / m ² , the thickness of the obtained porous ink receiving layer becomes excessively large, and the bonding strength of the porous ink receiving layer is reduced. Troubles such as peeling of the porous ink receiving layer from the support may occur, and a good image may not be formed. Therefore, the coating amount of the porous ink receiving layer may be appropriately set according to the composition of the coating solution.

In the present invention, the porous ink receiving layer is formed by allowing a coating liquid containing the above-mentioned resin as a main component to contain a large number of fine bubbles, coating the fine bubbles on a sheet-like support, and drying. Can form fine bubbles,
There is no particular limitation on the method, equipment and coating method to be contained. There is also no particular limitation on the bubble-containing state of the resin coating solution containing bubbles, but preferably the bubble-containing coating solution,
The volume ratio to the stock solution (hereinafter referred to as the expansion ratio) is preferably more than 1 and 10 or less, more preferably 1.1 or more and 5 or less. That is, the expansion ratio is
It is a scale showing the bubble content in the bubble-containing resin coating solution,
The higher the expansion ratio, the thinner the resin film (wall) surrounding the bubbles. In the case of the same expansion ratio, the lower the solid content concentration of the resin liquid before foaming, the thinner the resin film. As described above, when the thickness of the resin film is reduced, it may be difficult to maintain the strength of the obtained porous ink receiving layer at a sufficient level. In this regard, the expansion ratio is in balance with the composition of the resin coating solution. May be appropriately set in consideration of the above.

Further, it is considered that the mechanism for developing the excellent transfer performance of the molten ink in the present invention is related to the physical properties such as the structural properties, heat insulation properties and compression properties of the porous ink receiving layer and the receiving sheet. Can be In terms of structural characteristics, the porous ink receiving layer formed on the support has a high absorption of the molten ink due to the capillary phenomenon because a large number of fine holes are open outward. Further, since a large number of pores contained in the porous ink receiving layer communicate with each other (constituting open cells), the permeability of the molten ink into the porous ink receiving layer is good. Thus, it is considered that a high ink receiving ability is expressed as a whole. In this regard, the size of the pores distributed on the surface portion of the porous ink receiving layer formed on the receiving sheet is important. That is, when the molten ink is transferred, in order to form a good image on the receiving sheet of the present invention, the average pore diameter of the surface of the porous ink receiving layer is preferably in the range of 0.5 to 30 μm, A more preferable result is provided when it is in the range of 0.5 to 20 μm. The pore diameter is closely related to the ability to capture the molten ink by capillary action due to its size (size), and the smaller the pores, the greater the ability. If the size of the pores is excessive, the transfer ink is buried in the pores or hinders good contact between the ink ribbon and the surface of the porous ink receiving layer, thereby causing poor transfer or uneven transfer. A defective image cannot be formed due to defective dot reproduction. The pore diameter on the surface of the porous ink receiving layer can be measured using an optical microscope or a scanning electron microscope photograph and an image analyzer. The size of the pores is determined by the composition of the resin liquid before the bubble formation / dispersion treatment, that is, the types of components, the component mixing ratios,
Appropriate because it is often affected by various factors such as bubbles, coating, the amount remaining as a component directly related to the film thickness in the porous ink receiving layer after drying, or the above-mentioned expansion ratio, coating method, etc. Conditions must be set. Further, the size of the pores on the surface of the porous ink receiving layer in the present invention is deeply related to the size of the bubbles formed by mechanical stirring, and generally, the smaller the bubbles in the resin coating solution, the more the coating, The pores on the dried ink receiving layer surface are also reduced. Accordingly, there is no particular limitation on the state of bubbles contained in the resin coating solution, but the same size as the pores on the surface portion of the porous ink receiving layer, that is, the average diameter is 0.5.
Preferably, microbubbles of up to 30 μm are dispersed and mixed, and more preferably the average diameter of the bubbles is in the range of 0.5 to 20 μm. The size of bubbles in the resin coating solution is
A part of the image can be photographed with an optical microscope and measured with an image analyzer.

In the present invention, a method for forming, dispersing, and containing bubbles in a resin liquid (hereinafter referred to as a foaming method) is, for example, a so-called confectionery foaming machine having a stirring blade rotating while carrying out planetary motion, generally an emulsifier. A homogenizer used for dispersion and the like, a stirrer such as a Cowles dissolver, or a mixture of air and resin liquid is continuously fed into a closed system while mechanically stirring the air to finely disperse the air. A device for mixing the resin liquid while dispersing it into bubbles, for example, a continuous foaming machine manufactured by Gaston County of the United States or Stoke of the Netherlands can be used. However, the type of the foam stirrer is not limited. In addition, due to insufficient capacity of the equipment for performing mechanical stirring, when the desired bubble-containing state cannot be obtained, or when it is necessary to improve the stability of bubbles in the bubble-containing resin liquid. May be appropriately selected from surfactants called foam stabilizers and foaming agents and blended into the resin coating solution.

Examples of such surfactants include higher fatty acids, modified higher fatty acids, and alkali salts of higher fatty acids.
In particular, the effect of increasing the foaming property of the resin liquid and the effect of improving the stability of the dispersed and contained bubbles are high. There is no restriction on the selection of these, but it significantly impairs the fluidity of the resin solution,
Naturally, use of a material that may impair coating workability is avoided. The amount of the surfactant such as the foam stabilizer and the foaming agent is preferably 0 to 30 parts by weight of the solid content of the surfactant based on 100 parts by weight of the solid content of the resin coating solution. , More preferably 1 to 20 parts by weight. Even if the amount of the surfactant added is more than 30 parts by weight, the effect is saturated and the economical disadvantage is often caused.

The coating system for forming the porous ink receiving layer on the support includes a Meyer bar system, a gravure roll system, a roll system, a reverse roll system, a blade system, a knife system, an air knife system, an extrusion system, It can be arbitrarily selected from known methods such as a cast method.

In the receiving sheet of the present invention, an overcoat layer is formed on the porous ink receiving layer. The coating amount of this overcoat layer is 0.1 to 4.0 g / m ² , preferably 0.5 to 2.0 g / m ² . When the coating amount is less than 0.1 g / m ² , the pencil writing property is insufficient, and when it exceeds 4.0 g / m ² , the pencil writing property is sufficient. Since the fine pores on the surface of the porous ink receiving layer are closed by the overcoat layer, the penetration of the molten ink into the inside is hindered, so that the gradation recording of the image is deteriorated.

The pigment particles used in the overcoat layer preferably have a BET specific surface area of 20 to 600 m ² / g. Examples of the pigment particles having such a BET specific surface area include kaolin and light carbonic acid. calcium,
Pigment particles such as titanium oxide, silicic acid, silicate, magnesium carbonate, and magnesium hydroxide can be used, but are not limited thereto. These pigments can be used alone or as a mixture of two or more, if necessary. When an overcoat layer containing pigment particles and a binder resin as main components is provided on the porous ink receiving layer, pencil writing properties are improved. At this time, it is preferable to use pigment particles having a BET specific surface area of 20 to 600 m ² / g, more preferably 40 to 500 m ² / g. The reason for this is that the BET specific surface area is 20 m ^2.
If it is less than / g, the contact area between the pigment particles and the lead of the pencil is insufficient, and as a result, the pencil writing properties may be insufficient. If it exceeds 600 m ² / g, the overcoat layer In order to maintain sufficient adhesive strength, it is necessary to use a large amount of a binder resin, and this binder resin closes the fine pores on the surface of the porous ink receiving layer. Is impaired, and as a result, image quality deteriorates.

Known paints such as dispersants, defoamers, dyes, wetting agents, and lubricants can be added to the overcoat layer coating material, if necessary.

The sheet having the porous ink-receiving layer of the present invention is capable of applying a bubble-containing resin coating liquid on one surface of a sheet-like support and exhibiting a good molten heat transfer image even in a dry state. It is possible to use a machine calender composed of two or more metal rolls or a super calender composed of a metal roll and a resin roll, or a metal roll and a cotton roll appropriately combined. Finishing treatment is performed on the surface of the porous ink receiving layer, and the smoothness of the surface can be further improved. After coating, the surface of the porous ink receiving layer in a semi-dry state or a dry state is brought into contact with a mirror-finished cast drum or the like in a heated or non-heated state to improve the surface smoothness. May be improved. However, when the above-mentioned smooth finishing treatment is performed under excessive pressure, the resin wall surrounding the air bubbles in the porous ink receiving layer is broken, and the ink receiving layer is densified, and the heat insulating property and the cushioning property are reduced, or the ink receiving property is reduced. Due to the deformation and / or destruction of the pores on the surface of the receiving layer, the excellent molten ink transfer performance of the porous ink receiving layer may be reduced. Therefore, in the above-mentioned smooth finishing, the processing conditions may be set appropriately.

As the sheet-like support used in the present invention, paper such as paper containing cellulose as a main component, coated paper, laminated paper and the like, and cloth such as woven fabric and non-woven fabric can be used. it can. In addition, plastic films such as polyolefin, methacrylate, and cellulose acetate, and synthetic paper composed of polyolefin and pigment, and porous synthetic resin films such as expanded polyethylene terephthalate film and expanded polypropylene film can be used.
These supports show better dot reproducibility and tone reproducibility with the same applied energy as the heat insulating property is better, can achieve an increase in recording density, and have the same density and recording quality. Since the amount of energy required to obtain it is small, it is also effective for energy saving. When a paper containing pulp as a main component and a coated paper are used as a support, they also have an advantage that they can be recycled.

Further, when the cell-containing resin coating solution is coated on the sheet-like support to produce the receiving sheet of the present invention, the receiving sheet itself is subjected to coating, drying, winding and the like in steps such as coating and drying. Curling may occur with the coating surface inside or outside. In this case, if the receiving sheet is used after being cut into a receiving sheet for forming an image having a predetermined size, it may be difficult to feed the sheet to a thermal transfer printer, or trouble such as deterioration of running properties inside the printer may occur. May occur. Further, since the fusion transfer recording method is a method in which a heat source is brought into contact with an ink ribbon and a dye component in the ribbon is transferred onto a recording sheet, heating of a porous ink receiving layer which is an image forming surface and a support layer are performed. Due to the difference in contraction or the difference in expansion characteristics, the receiving sheet curls inside the apparatus, and the above-described trouble occurs. Due to such curling, an image is formed obliquely with respect to the normal paper surface direction, and the receiving sheet tends to wrinkle inside the apparatus,
For this reason, the contact between the ink ribbon and the receiving sheet is not performed normally, causing ink transfer failure, and as a result, image quality may be deteriorated.

In order to prevent various kinds of troubles caused by such curling, the difference in heat shrinkage characteristic or the difference in expansion characteristic between the porous ink receiving layer and the support layer must be minimized. It is desirable to make it smaller. For this purpose, an anti-curl layer may be applied or laminated on the back surface of the receiving sheet, that is, on the surface opposite to the porous ink receiving layer. There is no limitation on the material of the anti-curl layer, the forming method, the amount of coating, the amount of lamination, etc.
Optimization can be performed in consideration of various factors such as the type and thickness of the support and the properties of the porous ink receiving layer, that is, the material composition, the expansion ratio, and the coating amount.

Further, depending on the type of material constituting the sheet-shaped support, when the obtained receiving sheet travels inside the printer, it receives various frictional forces due to the mechanism of the apparatus, or the inside of the apparatus due to heating. The influence of a decrease in humidity or the like may cause the receiving sheet in the printer to be charged with static electricity either individually or in combination. When a large number of images are continuously formed in such a state, the image forming surface of the receiving sheet and the back surface of the next receiving sheet are electrostatically adhered to each other and are difficult to peel off. In particular, since various types of plastic sheets or synthetic paper have a property of being easily charged in nature, when using them as a sheet-like support, static electricity is generated in the sheeting process by cutting or during storage after processing. This will make it difficult for the front and back of the receiving sheet to peel off. Needless to say, the above-mentioned trouble can occur even when paper is used as the support.
It is extremely effective to form a so-called antistatic layer on the back surface of the receiving sheet in order to prevent such troubles caused by charging. The antistatic can be achieved by using an antistatic material or reducing the coefficient of friction between the back surface of the receiving sheet and the porous ink receiving layer. The antistatic layer can be formed by appropriately selecting from a wide range of materials and methods as in the case of forming the anti-curl layer. The anti-curl layer and the antistatic layer can be individually formed on the back surface of the sheet-shaped support to obtain the expected performance.However, the manufacturing process is simplified, the manufacturing cost is reduced, or the expected performance is reduced. By appropriately selecting the material and the forming method as needed, such as the functional level, the object can be achieved by forming a single layer. That is, it is possible to provide trouble prevention performance such as curling prevention and antistatic with a single layer. Therefore, there is no limitation on the number of layers formed on the back surface of the sheet-shaped support.

[0026]

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited by these. In the Examples and Comparative Examples, “parts” all represent “parts by weight”.

Example 1 An ink receiving sheet for fusion thermal transfer was prepared by the following method. [Coating composition of porous ink receiving layer] Aqueous polyurethane resin liquid (trademark: Adekabon Titer HUX-401, manufactured by Asahi Denka Kogyo) 100 parts Higher fatty acid-based foam stabilizer (trademark: SN foam 200, manufactured by San Nopco) 5 parts Thickening Agent: carboxymethylcellulose (trademark: AG gum, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) 5 parts To the above-mentioned porous ink receiving layer coating material (solid content concentration 35%),
Using a stirrer (trade name: KENMIX IKO PRO, manufactured by Aikosha Seisakusho), a foaming treatment was performed at a stirring speed of 490 rpm for 8 minutes to prepare a bubble-containing resin coating solution having a foaming ratio of 4.0, which was immediately weighed. The amount of coating (dry) is 1 using the applicator bar on the surface of high-quality paper of 75 g / m ^2.
The composition was applied to a concentration of 5 g / m ² and dried to form a porous ink receiving layer. [Coating composition of overcoat layer] Pigment: Silica (trade name: Mizukasil P-705, manufactured by Mizusawa Chemical Co., BET specific surface area: 300 m ² / g) 100 parts Binder: silanolized polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray) 20 Part Dispersant: polyoxyethylene derivative (trademark: Emulgen A-60, manufactured by Kao) 1 part Coating amount of the overcoat layer paint (solid content: 10%) on the porous ink receiving layer using a Mayer bar (Dry) was applied so as to be 1.0 g / m ² , and dried to form an overcoat layer, thereby producing an ink receiving sheet for fusion heat transfer.

Example 2 A porous ink receiving layer was formed on a support in the same manner as in Example 1. However, the porous ink receiving layer paint was subjected to a foaming treatment for 8 minutes by the stirrer to give a foaming ratio of 4.0.
After preparing a bubble-containing resin coating solution of and leaving it for 10 minutes,
This was hand painted. On the porous ink receiving layer, the same overcoat layer paint as in Example 1 was applied using a Meyer bar so that the coating amount (dry) was 1.0 g / m ² , and dried. An overcoat layer was formed, and an ink receiving sheet for heat transfer was prepared.

Example 3 In the same manner as in Example 1, an ink receiving sheet for heat transfer was prepared. However, the porous ink receiving layer paint was subjected to a foaming treatment for 25 minutes by the above-mentioned stirrer, and a foaming ratio of 6.
A bubble-containing resin coating solution of No. 0 was prepared and immediately applied by hand. On the porous ink receiving layer, the same overcoat layer paint as in Example 1 was applied using a Meyer bar so that the coating amount (dry) was 1.0 g / m ² , and dried. An overcoat layer was formed to obtain an ink receiving sheet for heat transfer for fusion.

Example 4 In the same manner as in Example 1, an ink receiving sheet for fusion heat transfer was prepared. However, the porous ink receiving layer paint was subjected to a foaming treatment for 8 minutes by the stirrer to give a foaming ratio of 4.0.
Was prepared and immediately applied by hand. [Coating composition of overcoat layer] Pigment: Silica (trade name: Mizukasil P-752, manufactured by Mizusawa Chemical Co., BET specific surface area: 450 m ² / g) 100 parts Binder: silanolized polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray) 20 Part Dispersant: polyoxyethylene derivative (trademark: Emulgen A-60, manufactured by Kao) 1 part Coating amount of the overcoat layer paint (solid content: 10%) on the porous ink receiving layer using a Mayer bar (Dry) was applied so as to be 1.0 g / m ² , and dried to form an overcoat layer, thereby obtaining an ink receiving sheet for melt thermal transfer.

Example 5 In the same manner as in Example 1, an ink receiving sheet for fusion heat transfer was prepared. However, the porous ink receiving layer coating material was subjected to foaming treatment for 8 minutes by the stirrer to prepare a bubble-containing resin coating solution having a foaming ratio of 4.0, which was immediately manually applied. [Overcoat layer coating composition] Pigment: Clay (trademark: HYDRAGLOSS90, manufactured by Nissei Kyoei, BET specific surface area: 22 m ² / g) 100 parts Binder: silanolized polyvinyl alcohol (trademark: R-1130, manufactured by Kuraray) 20 parts Dispersion Agent: polyoxyethylene derivative (trademark: Emulgen A-60, manufactured by Kao) 1 part The coating amount (drying) of the overcoat layer paint (solid content: 10%) on the porous ink receiving layer using a Mayer bar. ) Was applied so as to be 1.0 g / m ^2, and dried to form an overcoat layer, thereby obtaining an ink receiving sheet for melt thermal transfer.

Example 6 In the same manner as in Example 1, an ink receiving sheet for heat transfer by fusion was prepared. However, the porous ink receiving layer coating was subjected to foaming treatment for 8 minutes by the stirrer to prepare a bubble-containing resin coating solution having a foaming ratio of 4.0, which was immediately manually applied. [Overcoat layer coating composition] Pigment: Light calcium carbonate (trademark: Callite KT, manufactured by Mizusawa Chemical, BET specific surface area: 35 m ² / g) 100 parts Binder: silanolized polyvinyl alcohol (trademark: R-1130, manufactured by Kuraray) 20 Part Dispersant: polyoxyethylene derivative (trademark: Emulgen A-60, manufactured by Kao) 1 part Coating amount of the overcoat layer paint (solid content: 10%) on the porous ink receiving layer using a Mayer bar (Dry) was applied so as to be 1.0 g / m ² , and dried to form an overcoat layer, thereby obtaining an ink receiving sheet for melt thermal transfer.

Example 7 In the same manner as in Example 1, an ink receiving sheet for fusing and transferring heat was prepared. However, the porous ink receiving layer coating was subjected to foaming treatment for 8 minutes by the stirrer to prepare a bubble-containing resin coating solution having a foaming ratio of 4.0, which was immediately manually applied.
On the porous ink receiving layer, the overcoat layer coating composition of Example 1 was applied using a Mayer bar so that the coating amount (dry) was 3.0 g / m ² , and dried to form an overcoat layer. Was formed to obtain an ink receiving sheet for fusion thermal transfer.

Example 8 In the same manner as in Example 1, an ink receiving sheet for fusion heat transfer was prepared. However, the porous ink receiving layer coating was subjected to foaming treatment for 8 minutes by the stirrer to prepare a bubble-containing resin coating solution having a foaming ratio of 4.0, which was immediately manually applied.
On the porous ink receiving layer, the overcoat layer paint of Example 1 was applied using a Meyer bar so that the coating amount (dry) was 0.3 g / m ² , and dried to form an overcoat layer. Was formed to obtain an ink receiving sheet for fusion thermal transfer.

Comparative Example 1 In the same manner as in Example 1, an ink receiving sheet for fusion heat transfer was prepared. However, the porous ink receiving layer paint was manually applied without performing a foaming treatment. Example 1 on the ink receiving layer
Overcoat layer (solid content: 10%) was applied using a Meyer bar so that the coating amount (drying) was 1.0 g / m ² , and dried to form an overcoat layer, and the melt heat transfer was performed. An ink receiving sheet for use was obtained.

Comparative Example 2 In the same manner as in Example 1, an ink receiving sheet for heat transfer was prepared. However, the porous ink receiving layer coating material was subjected to foaming treatment for 8 minutes by the stirrer to prepare a bubble-containing resin coating solution having a foaming ratio of 4.0, which was then manually applied after standing for 15 minutes. The overcoat layer paint of Example 1 (solid content concentration: 10%) was applied on the ink receiving layer using a Meyer bar so that the coating amount (dry) was 1.0 g / m ² , and dried. An overcoat layer was formed to obtain an ink receiving sheet for heat transfer for fusion.

COMPARATIVE EXAMPLE 3 In the same manner as in Example 1, an ink receiving sheet for heat transfer was prepared. However, the coating of the porous ink receiving layer was subjected to a foaming treatment for 8 minutes by the stirrer to prepare a bubble-containing mixed solution having a foaming ratio of 4.0, which was immediately manually applied. The overcoat layer was not coated.

Comparative Example 4 In the same manner as in Example 1, an ink receiving sheet for fusion heat transfer was prepared. However, the porous ink receiving layer coating was subjected to foaming treatment for 8 minutes by the stirrer to prepare a bubble-containing resin coating solution having a foaming ratio of 4.0, which was immediately manually applied.
The coating amount (dry) of the overcoat layer coating composition of Example 1 on the porous ink receiving layer using a Mayer bar was 5.
The composition was applied so as to be 0 g / m ² , and dried to form an overcoat layer, thereby obtaining an ink receiving sheet for heat transfer by fusion.

Comparative Example 5 In the same manner as in Example 1, an ink receiving sheet for fusing and thermal transfer was prepared. However, the porous ink receiving layer coating was subjected to foaming treatment for 8 minutes by the stirrer to prepare a bubble-containing resin coating solution having a foaming ratio of 4.0, which was immediately manually applied. [Coating composition of overcoat layer] Pigment: Silica (trademark: Sylysia 770, manufactured by Fuji Silysia Chemical Ltd., BET specific surface area: 700 m ² / g) 100 parts Binder: silanolized polyvinyl alcohol (trademark: R-1130, manufactured by Kuraray) 20 parts Dispersant: polyoxyethylene derivative (trademark: Emulgen A-60, manufactured by Kao) 1 part The coating amount of the overcoat layer paint (solid content concentration: 10%) on the porous ink receiving layer using a Mayer bar ( (Drying) was adjusted to 1.0 g / m ² , and dried to form an overcoat layer, thereby obtaining an ink receiving sheet for melt thermal transfer.

Comparative Example 6 In the same manner as in Example 1, an ink receiving sheet for heat transfer by fusion was prepared. However, the porous ink receiving layer coating was subjected to foaming treatment for 8 minutes by the stirrer to prepare a bubble-containing resin coating solution having a foaming ratio of 4.0, which was immediately manually applied. [Coating composition of overcoat layer] Pigment: Light calcium carbonate (trademark: Callite SA, manufactured by Shiraishi calcium, BET specific surface area: 10 m ² / g) 100 parts Binder: silanolated polyvinyl alcohol (trademark: R-1130, manufactured by Kuraray) 20 Part Dispersant: polyoxyethylene derivative (trademark: Emulgen A-60, manufactured by Kao) 1 part Coating amount of the overcoat layer paint (solid content: 10%) on the porous ink receiving layer using a Mayer bar (Dry) was applied so as to be 1.0 g / m ² , and dried to form an overcoat layer, thereby obtaining an ink receiving sheet for melt thermal transfer.

Test Table 1 shows the structures of the porous ink receiving layer and the overcoat layer in each of the above Examples and Comparative Examples. Also,
The measurement of the pore size of the obtained porous ink receiving layer, the evaluation of the transferred ink image, and the evaluation of the pencil writing property were performed by the following methods. Table 2 shows the results of these measurements and evaluations. (1) Measurement method of pore diameter The pore diameter of the surface of the porous ink receiving layer is determined by taking a photograph of the surface of the receiving layer using a scanning electron microscope or an optical microscope, and then accurately defining the outline of the pores on the surface. Draw on a transparent film with a black pen or the like, and further read the outline information of the pores optically with a drum scanner (trademark: 2605 type drum scan densitometer, manufactured by Abe Design Co., Ltd.). (Trademark: Luzex
III, manufactured by Nireco). Since the shape of the pores formed on the surface of the porous ink receiving layer is not necessarily a perfect circle, the pore diameter is converted to a circle equivalent diameter based on the area within the contour of the pore obtained by image analysis. And displayed.

(2) Recording Performance With respect to the receiving sheet having the porous ink receiving layer obtained in each of Examples 1 to 7 and Comparative Examples 1 to 6, the receiving sheet was subjected to an environment at 20 ° C. and a relative humidity of 65%. After humidity control all day and night, a thermal transfer color printer (trade name: Trueprint)
t2200, manufactured by Victor Company of Japan, Ltd .: Originally an image forming apparatus of the sublimation transfer type, which was modified so as to be able to form an image of the melt transfer type, and melt-transfer-recorded the ink image on its surface. did. The reflection density of the obtained ink transfer image was measured with a Macbeth reflection densitometer and evaluated visually as described below. (A) Ink image formed at 17 gradations (black monochrome image)
About Macbeth reflection densitometer RD-914 (trademark)
The reflection density is measured for each applied energy using
The gradation reproducibility was evaluated. The gradation reproducibility was evaluated in three steps of ◎, 、, and × in order from the one reproduced well. (B) The peeling state of the ink receiving layer was evaluated by observing an image formed on the receiving layer, and evaluated in three stages of ◎, 、, and ×, in order from the one having no peeling of the ink receiving layer.

(3) Pencil Writability The image receiving sheet having the porous ink receiving layer obtained in each of Examples 1 to 7 and Comparative Examples 1 to 6 was subjected to an environment at 20 ° C. and a relative humidity of 65%. After conditioning for one day and night, handwriting was performed with a pencil (HB), and evaluation was performed in three stages of ◎, 、, and × in order of clear handwriting.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

According to the present invention, it is possible to obtain a recorded image having good tone reproducibility and recording density of a fused thermal transfer ink image.
At the same time, it becomes possible to practically use an ink image-receiving sheet for melting and thermal transfer having pencil writing properties, greatly contributing to the industry.

Claims (2)

[Claims] 1. A sheet-like support, and a porous ink receiving layer formed on at least one surface thereof, wherein the porous ink receiving layer is subjected to a foaming treatment by mechanically stirring a film-forming resin liquid. The foamed resin coating solution prepared by applying the above is coated on the surface of the sheet-like support, and dried to form a coating, at least a surface portion, 0.5
A large number of continuous pores having an average pore diameter of about 30 μm are formed, and an overcoat layer of 0.1 to 4.0 g / m ² containing pigment particles and a binder resin on the porous ink receiving layer. Wherein an ink receiving sheet for fusing heat transfer is formed. 2. The ink receiving sheet for melt thermal transfer according to claim 1, wherein the pigment particles contained in the overcoat layer have a BET specific surface area of 20 to 600 m ² / g.