JPH01221282A - Imaeg-receiving sheet for thermal transfer recording - Google Patents

Abstract

PURPOSE:To contrive improvements of recording sensitivity, resolution, clearness, color density, missing of dots or the like, by incorporating into an image-receiving layer a particulate pigment comprising fine particles having minute protrusions of an acicular, columnar, foil-like or other similar shape with a specified aspect ratio, in three-dimensional directions, and having a specified average particle diameter. CONSTITUTION:A pigment is selected and used which is formed through firm adhesion or agglomeration of fine primary particles having an acicular, columnar, foil-like or other similar shape with average sizes, recognized by observation under an electron microscope, of a minor axis size (W) of 0.005-0.5mum, a major axis size (L) of 0.1-10mum and an aspect ratio (L/W) of 2-1000, and comprises secondary particles having minute protrusions, preferably at least 50 protrusions, in three-dimensional directions and having an average particle diameter of 0.1-10mum as measured through observation by a light transmission method. When an intermediate layer comprising fine particles of a thermoplastic resin as a main constituent is provided between an image-receiving layer end a base, an excellent synergistic effect is produced by the intermediate layer and the image-receiving layer, which contributes to increase in sensitivity and is capable of imparting a recorded image with extremely high image quality.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to an image receiving sheet for thermal transfer recording, and in particular to improvement of an image receiving sheet for thermal transfer recording using heat-melting solid ink. The present invention provides an image-receiving sheet with significantly improved image quality.

``Prior art'' The thermal recording method, which can obtain a recorded image at the same time as a human input signal, is relatively simple and inexpensive, and has low noise, so it is used in a variety of applications, such as facsimile-1 computer terminal printers and measuring equipment printers. It is used for.

The most commonly used recording medium for these thermal recording systems is so-called color-forming type thermal recording paper, which is provided with a recording layer that develops color by causing a physical or chemical change when heated. However, color-forming type thermal recording paper tends to develop unnecessary color during the manufacturing process and storage, and the storage stability of recorded images is also poor, causing discoloration due to contact with organic solvents and chemicals. I wake up.

Therefore, a recording method using a recording medium using colored coloring material itself has been proposed as a recording medium to replace the color-forming type thermal recording paper.
In the publication, a coloring material that is solid or semi-solid at room temperature is coated on a support such as paper or a polymer film, and the coloring material on the support is brought into contact with recording paper, and then a thermal recording head is applied to the coloring material. A method has been proposed in which a recorded image is obtained by heating a coloring material on a support and selectively transferring the coloring material to a recording paper.

In this recording method, the coloring material on the support is melted by heat, transferred to the recording paper, and a recorded image is obtained by adhesion, adsorption, and dyeing, and it is said to have the characteristic that plain paper can be used as the recording paper. ing.

``Problem to be solved by the invention'' However, when plain paper is used as recording paper, the image quality is particularly poor. and various other methods (Japanese Unexamined Patent Publication No. 55-42824).

No. 60-110488, No. 60-110490, No. 60-110491, No. 60-192690) have been proposed, but nothing satisfactory has been obtained yet.

In addition, as the demand for color printing has increased in recent years, for example, a method of performing full-color recording by using a color material transfer sheet coated in at least three primary colors and performing overlapping printing with gradation control as necessary (Japanese Patent Application Laid-open No. 138685/1983, 61
~63495 No. 9 Proceedings of the 74th Research Meeting of the Society of Image Electronics Engineers 8
3-02-2) has also been proposed, but since full-color applications require particularly excellent ink receptivity and high image quality,
Further improvements in image-receiving sheets are desired.

In view of the current situation, the inventors of the present invention have conducted extensive research into improving image-receiving sheets for thermal transfer recording, which are useful for use in recording systems that thermally transfer colored coloring materials, particularly heat-melting solid ink layers. Extremely high resolution, clarity,
We have completed an image-receiving sheet that provides recorded images of extremely high quality with excellent color density, dot removal, etc.

"Means for Solving the Problems" The present invention provides an image-receiving sheet for thermal transfer recording comprising an image-receiving layer for receiving a transferred image from a color material transfer sheet on a support. It has needle-like, columnar, flake-like, etc. fine protrusions in the three-dimensional direction with a dimension (L)/minor axis dimension (W) of 2 to 1000, and an average particle diameter of 0.1 to 10 μm. This is an image-receiving sheet for thermal transfer recording characterized by containing a fine particle pigment.

"Function" In the image-receiving sheet of the present invention, the structured fine particle pigment having protrusions in three-dimensional directions as described above constituting the image-receiving layer is as follows:
It means a fine particle pigment having a unique structure such as a sea urchin shape or a marimo shape with many protruding minute protrusions such as acicular, columnar, or flaky protrusions, for example, in the presence of at least one of phosphoric acid and its water-soluble salt. , a method of reacting a calcium hydroxide suspension with a specific concentration with a gas containing carbon dioxide (Japanese Patent Publication No. 57-30815
No.), a method of reacting in the presence of at least one specific carboxylic acid and its water-soluble salt (Japanese Patent Publication No. 57-315
No. 30), a carbonic acid gas is introduced into an aqueous suspension containing specific needle-shaped crystal nuclei calcium carbonate and calcium hydroxide at a specific temperature to perform a carbonation reaction to obtain a bundle of needle-shaped calcium carbonate. Method (Japanese Unexamined Patent Publication No. 59-232916)
Manufactured by etc.

The average size of these pigments observed by electron microscopy is the short axis dimension (W > 0.005 to 0.51' m
s major axis dimension (L) 0.1=10pm, aspect ratio (L)
/W) A pigment formed by tightly binding or bundling fine primary particles such as acicular, columnar, flaky, etc. with a particle size of 2 to 1000, and secondary particles having fine protrusions in three-dimensional directions. Preferably, those having 50 or more protrusions are selected and used.

Note that the average particle diameter observed when observing the above-mentioned specific structured fine particle pigment having minute protrusions using a light transmission method is 0.1μ.
If it is less than 1 m, the resulting image-receiving layer will lack oil absorption;
If it exceeds 0 μm, not only will the coating suitability of the image-receiving layer coating liquid be poor, but also a homogeneous image-receiving layer surface will not be obtained, resulting in a decrease in the quality of the recorded image.
A pigment having an average particle size of 1 to 5 μm is selected and used.

These pigments are present in the coating liquid medium, such as modified starch, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, casein, gelatin, natural or semi-synthetic polymers such as natural rubber, polyvinyl alcohol, isoprene, neoprene, etc. Polydienes such as polybutadiene, polybutene, polyisobutylene,
Polyalkenes such as polypropylene and polyethylene, vinyl polymers and copolymers such as vinyl halide, vinyl acetate, styrene, (meth)acrylic acid, (meth)acrylic acid ester, (meth)acrylamide, methyl vinyl ether, and polyesters. , polyurethanes, polyamides, styrene-butadiene systems, methyl methacrylate-butadiene-maleic acid systems, and other synthetic rubber latexes.

Among these, synthetic rubber latex is preferable because it has strong adhesive strength, is rich in rubber elasticity, and provides an image-receiving layer with excellent ink receptivity.For example, styrene-butadiene latex, (
meth)acrylic acid ester/butadiene latex,
Acrylonitrile/butadiene latex, styrene/(meth)acrylate/butadiene latex, styrene/(meth)acrylate/acrylonitrile/butadiene latex, etc. are particularly preferably used.

These synthetic rubber latexes are manufactured by adding crosslinking agents such as divinylbenzene as necessary to control melting point, rubber elasticity, solvent resistance, etc., and to modify the surface properties of resin particles. It is also possible to add α,β-ethylenically unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, and fumaric acid, and to modify the composition by copolymerization, polymer reaction, or the like. moreover,
It is also possible to modify it into a so-called ionomer resin by metal crosslinking.

In the present invention, if these so-called coating binders are used in an amount less than the same amount as the pigment, the excellent oil absorption properties brought about by the unique shape of the pigment will be impaired. It is used in a range of 50% by weight or less.

The above-mentioned coating composition constituting the image-receiving layer may further contain anionic, nonionic, cationic or amphoteric surfactants, pi regulators, viscosity regulators, softeners, and gloss imparters, if necessary. Various auxiliary agents such as agents, waxes, stabilizers, antistatic agents, crosslinking agents, optical brighteners, dyes, pigments, fragrances, antifoaming agents, and preservatives may be added. In addition, ordinary coating pigments such as plate-like, granular, columnar, acicular, spherical, and irregularly shaped pigments can be used in combination without losing the characteristics of the present invention.

Typical coating pigments include inorganic and organic pigments such as calcium carbonate, talc, kaolin, natural or synthetic silicates, titanium oxide, aluminum hydroxide, zinc oxide, and fine particles of urea/formaldehyde resin. It is desirable that the amount of these pigments is equal to or less than the amount of the specific structured fine particle pigment.

The coating amount of the coating liquid constituting the image-receiving layer on the support is appropriately selected depending on the purpose of use of the image-receiving sheet, etc.; Ru. Note that plain paper, synthetic paper, synthetic resin film, etc. are appropriately selected and used as the support, and plain paper is preferably used because it has excellent thermal properties.

Specific examples of plain paper include, for example, paper made by ordinary paper making with cellulose pulp as the main component and the addition of paper strength enhancers, sizing agents, fixing agents, inorganic/organic fillers, etc.; For example, there are papers such as art paper, coated paper, and cast coated paper that have improved surface properties by size pressing or by providing a precoat layer mainly composed of pigments such as clay.

In the image-receiving sheet of the present invention, image quality is improved by providing an intermediate layer such as a rubber elastic layer typified by synthetic rubber latex, a microporous layer using hollow capsules or a foaming agent, etc. between the image-receiving layer and the support. In particular, if an intermediate layer containing thermoplastic resin fine particles as a main component is provided, an excellent effect can be achieved through a synergistic effect with the above-mentioned specific image-receiving layer of the present invention, and the sensitivity can be improved. This is one of the preferred embodiments of the present invention because it not only contributes to improvement but also provides recorded images of extremely high quality.

As the thermoplastic resin fine particles, condensation resin particles represented by nylon resin particles, polymerized resin particles represented by vinyl resin particles, etc. are preferably used. After the resin is manufactured by direct manufacturing method when manufacturing resin legally, submerged granulation method in non-solvent, mechanical granulation method such as freeze pulverization method, wet pulverization method, etc. Manufactured through processing, etc.

Among the resin fine particles mentioned above, vinyl resin particles are
It is particularly preferably used because physical property values can be easily controlled by selecting monomers, and fine particles can also be easily produced.

The vinyl resin particles are synthesized by selecting one or more suitable resin particles by a so-called polymerization method, preferably in the form of an aqueous dispersion by an emulsion polymerization method, a suspension polymerization method, or the like. Specific examples of the main ingredients are styrene, α-methylstyrene, 4-methylstyrene, 2-methylstyrene,
Methylstyrene, 4-methoxystyrene, vinyl chloride,
Examples include vinyl monomers such as vinylidene chloride, ethylene, vinylcyclohexane, methyl methacrylate, hexyl acrylate, vinyl acetate, and acrylonitrile, and rubber threads such as 1,3-butadiene, isoprene, and 2-chloro-1,3-butadiene. Adding upper additives lowers the melting point, softening point, and glass transition point of resin particles,
Conversely, the melting point, softening point, and glass transition point of the resin particles can be increased by adding a crosslinking agent such as divinylbenzene.

In addition, in order to modify the surface properties of resin particles, α, β-ethylenically unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, and fumaric acid are added, resulting in copolymerization and polymerization. It can also be modified by reaction or the like. Furthermore, it is also possible to modify it into a so-called ionomer resin by metal crosslinking.

The above-mentioned thermoplastic resin fine particles need to maintain their fine particle state even after coating and drying on a support, so those with a softening point (glass transition point) of at least room temperature or higher, preferably 40°C or higher are selected for use. be done. Since many of these resin particles have self-adhesive ability, they can be held and adhered to a support by heat treatment if necessary, but one or more types of so-called coating binders can be used as an adhesive. Among them, synthetic rubber latexes are preferably used because they are flexible and form a coating liquid with excellent adhesive strength.

Inorganic or organic pigments, various auxiliary agents, etc. may be further added to the above-mentioned composition constituting the intermediate layer, if necessary. Note that if the thickness of the intermediate layer is less than 1 .mu.m, no significant effect can be expected, so it is desirable that the intermediate layer has a thickness of 1 .mu.m or more, more preferably about 3 to 20 .mu.m.

When the intermediate layer thus formed is subjected to smoothing treatment before or after forming the image-receiving layer, due to the unique effect of the thermoplastic resin fine particles, a homogeneous surface with excellent smoothness is provided, which makes it particularly difficult to contact with a thermal head, etc. Adhesion efficiency during heating can be increased.

Smoothing treatment is appropriately carried out by heating and pressure treatment using, for example, a super calender, gloss calender, cast drum, etc. However, if the average particle diameter of the thermoplastic resin fine particles constituting the intermediate layer is less than 0.1 μm, the effect of the smoothing treatment will be reduced. On the other hand, if the thickness exceeds 20 μm, not only coating suitability but also the effect of smoothing treatment cannot be expected.
It is desirable to adjust within a range of approximately μm.

In the image-receiving sheet of the present invention, the image-receiving layer can have a multilayer structure as long as at least one layer of the image-receiving layer contains as a main component a structured fine particle pigment having the above-mentioned unique shape as defined in the present invention. If necessary, a synthetic resin layer, a coating layer consisting of a pigment and a binder, an antistatic layer, etc. are provided on the back side of the support to prevent curling, provide printability,
It is also possible to add aptitude for wandering.

The image-receiving sheet for thermal transfer recording of the present invention thus obtained is:
In particular, it exhibits extremely excellent performance as an image receiving sheet when a heat-melting solid ink layer is used as a color material transfer sheet, and has excellent recording sensitivity, resolution, sharpness, and
High-quality recorded images with excellent color density, dot removal, etc. can be obtained.

The reason why such excellent effects are obtained is not necessarily clear, but due to the unique three-dimensional structure of structured fine particle pigments having protrusions in three-dimensional directions, a bulky image-receiving layer with rich porosity is formed, resulting in the formation of a highly porous and bulky image-receiving layer. It is speculated that this is because it has excellent ink receptivity and provides a uniform and dense coating surface.

The heat-melting solid ink layer used in the present invention is mainly composed of one or more heat-melting materials such as waxes and low softening point resins and a coloring material, and is solid at room temperature, but when heat is applied during recording. This is an ink layer that melts and transfers when heated, and various types are known and commercially available.

Both pigments and dyes can be used as coloring materials, but
In particular, in full-color applications, so-called oil-soluble dyes are preferably used because they have excellent meltability in the heat-melting materials used.

In addition, the image receiving sheet for thermal transfer recording of the present invention can be used not only by a thermal recording method in which contact heating is performed using a hot plate or a thermal head of a thermal printing unit, but also by heat radiation such as an infrared lamp, a YAG laser, a carbon dioxide laser, etc. Thermal recording using a non-contact heating method is also useful.

"Example" The present invention will be explained in more detail by referring to an example below, but it is of course not limited to such an example. Unless otherwise specified, parts and percentages in a layer are respectively "by weight". "parts" and "wt%".

Example 1 Marimo-like light calcium carbonate (trade name: Karrai) -
S A, average particle size 3.3 μm, Shiroishi Chuo Research Fracture) 1
00 parts of sodium polyacrylate (trade name: Nearon T-
40. A carboxy-modified styrene-butadiene latex (trade name: T-
038, solid content 48% 2 manufactured by Nippon Gosei Rubber Co., Ltd.) and 10 parts of a 20% aqueous solution of polyvinyl alcohol (product name: PVA205. manufactured by Kuraray Co., Ltd.) were added, and an antifoaming agent was further added to form a coating liquid for the image-receiving layer. Prepared. After confirming by microscopic observation that the pigment in the coating liquid maintained its marimo-like shape, a dry weight of 20% was applied to the felt side of a high-quality paper weighing 53g/rd.
g/rd, coated and dried with a wire bar, and then smoothed with a super calender consisting of a mirror-finished metal roll and an elastic roll (linear pressure 200 kg/cm).
) An image receiving sheet for thermal transfer recording was obtained.

Comparative Examples 1 to 3 In place of the marimo-like light calcium carbonate of Example 1, granular calcium carbonate (product name: Brilliant 5-15. manufactured by Shiroishi Kogyo Co., Ltd.) (comparative example 2), columnar calcium carbonate (product name: Albagros) An image receiving sheet was obtained in the same manner as in Example 1, except that acicular calcium carbonate (trade name: Tamavar TP-123, manufactured by Okutama Kogyo Co., Ltd.) (Comparative Example 4) was used. Ta.

Comparative Example 4 The marimo-like light calcium carbonate dispersion used in Example 1 was pulverized with a sand mill to destroy the marimo-like bundles,
An image receiving sheet was obtained in the same manner as in Example 1 except that primary particles were used.

Examples 2-3 Marimo-like light calcium carbonate (trade name: Karurai)-A as a pigment 7. Average particle size 1.5 μm, Shiraishi Chuo Research Fracture) (Example 2), sea urchin-like light calcium carbonate (product name: Unibur 70, average particle size 2°5 μm)
An image-receiving sheet was obtained in the same manner as in Example 1, except that Example 3) (manufactured by Shiraishi Kogyo Co., Ltd.) was used.

Example 4 Gyrolite-type calcium silicate-based highly oil-absorbing pigment (
Product name: Fluorei 1-RF, manufactured by Tokuyama Soda Co., Ltd.) and 11 parts of sodium polyacrylate (product name: Nearon T-40..
After dispersing the mixture in 90 parts of a 0.2% aqueous solution of Toagosei Co., Ltd.), 5 parts (solid content) of carboxy-modified styrene-butadiene latex (trade name: 5N-307° manufactured by Naugatuck Co., Ltd.) were added and further 10% aqueous solution of oxidized starch 10
and an antifoaming agent to prepare a coating solution.

Apply this coating solution to commercially available double-sided coated paper (105 g/n ()
After coating and drying it to a dry weight of 4 g/rd, the image receiving layer paint used in Example 1 was applied to a dry weight of 6 g/rd.
/rd and dried. Next, smoothing treatment was performed using a super calender (linear pressure 150 kg/cm
(metal roll surface temperature: 65° C.) to obtain an image-receiving sheet having a two-layer image-receiving layer.

Example 5 Modified low density polyethylene aqueous dispersion (trade name: Chemipearl M-200, average particle diameter 5 μm, softening point 76°C, solid content concentration 40%, manufactured by Mitsui Petrochemicals) 100
1 part, 20 parts of carboxy-modified styrene-butadiene latex (trade name: 5N-307, solid content concentration 48%, manufactured by Jumanoga Tatsuta Co., Ltd.), polycarboxylic acid type dispersant (trade name: Polystar 5ll-1020M, manufactured by NOF Corporation) )
One part was mixed and water was added to prepare a coating liquid for an intermediate layer having a solid content concentration of 30%.

This coating liquid was applied to a dry weight of 1 on high-quality paper of 64 g/m2.
After coating and drying to form an intermediate layer so as to give 0 g/rd, smoothing treatment was performed using a super calender, and Example 1 was prepared.
The coating liquid for the image-receiving layer used in the above was applied and dried using an air knife coater so that the dry weight was 13 g/rrr. Next, the image receiving sheet was further smoothed by a casting process in which it was pressed against a metal surface having a mirror surface heated to 85°C.

The nine types of thermal transfer recording image-receiving sheets thus obtained were subjected to a quality comparison test as described below, and the results are listed in the table.

That is, saturated polyester resin (trade name: Vylon 200
．． (manufactured by Toyobo Co., Ltd.) 1 part methyl ethyl ketone 12.5
After dissolving 0.5 parts of oil-soluble blue dye and completely dissolving it, wax fine powder (trade name: Diamifud L) was added.
-200. (manufactured by Nippon Kasei Co., Ltd.) was added to a dispersion liquid for 1 hour in an attritor to obtain a wax dispersion dye ink.

A color material transfer sheet was prepared by gravure printing this dye ink onto the untreated surface of a heat-resistant treated polyester film having a thickness of 6 μm so that the coating amount after drying was 4 g/rd.

The transfer layer of the color material transfer sheet is superimposed on the image receiving layer of the above nine types of image receiving sheets, and heat is applied from the back side of the transfer sheet with a thermal head (12V, 4 to 8 m5ec) to obtain a thermally transferred recorded image on the image receiving layer. Ta.

The density of the obtained recorded image was measured using a Macbeth color densitometer, and the image quality (dot omission) of the recorded image was visually evaluated according to the following evaluation criteria.

A... B... C... D
...E Excellent Poor Bekk smoothness of the surface of the image receiving layer is JIS P-8
Measurement was made in accordance with the 119 method (seconds/10cc). In addition, in order to confirm the suitability for full-color recording, we separately prepared monochrome color material transfer sheets using an oil-soluble yellow dye and a red dye in the same manner as the blue dye described above. Overlapping printing was performed on the same location on the image-receiving sheet in this order to obtain a black recorded image. The black density of the obtained recorded image was measured using a Macbeth color densitometer, and the degree of transfer of the next color ink was visually evaluated from the recorded matter and the amount of ink remaining on the transfer sheet surface using the same evaluation criteria as above.

Patent applicant: Kanzaki Paper Co., Ltd.

Claims (3)

[Claims] (1) In an image-receiving sheet for thermal transfer recording in which an image-receiving layer for receiving a transferred image from a color material transfer sheet is provided on a support, the image-receiving layer has an aspect ratio [major axis dimension (L)/minor axis dimension ( W)] has needle-like, columnar, flake-like, etc. fine protrusions in the three-dimensional direction and has an average particle diameter of 0.
．． An image-receiving sheet for thermal transfer recording, characterized in that it contains pigment particles having a particle size of 1 to 10 μm. (2) The image-receiving sheet according to claim 1, further comprising an intermediate layer containing thermoplastic resin fine particles as a main component between the image-receiving layer and the support. (3) Claim (1) wherein the fine particle pigment is a secondary particle in which fine particles having an aspect ratio of 2 to 1000 are bound or bundled.
Image receiving sheet as described.