JPH03199090A - Image receiving sheet for thermal transfer recording - Google Patents

Abstract

PURPOSE:To obtain excellent image quality and highly developed color density by adding polyethylene glycol having a specific MR to an image receiving layer. CONSTITUTION:A barrier layer 2 and an image receiving layer 3 are successively provided on a base material 1 and, as the base material 1, art paper or coated paper is used and the barrier layer 2 is provided in a thickness of 3g/m<2> or more, desirably, 8-30g/m<2> as a dry wt. using either one of an aqueous solution of inorg. pigment and a water-soluble synthetic resin, an aqueous emulsion of a synthetic resin and an aqueous suspension of a synthetic resin or combination thereof. The image receiving layer 3 has function receiving the dye transferred from a thermal transfer sheet and is constituted using a polyester resin or polyarylate resin. Polyethylene glycol with a mean MW of 500-10000 is contained in the image receiving layer 3 and the compounding amount thereof is controlled within the range of 1-20%, pref. 3-10% by wt., of the solid component of the image receiving layer.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to an image receiving sheet for thermal transfer recording, in which a dye on a thermal transfer sheet is transferred by heat from a thermal head or the like in accordance with an image signal to perform recording, particularly a thermal sublimation type image receiving sheet. This invention relates to improvements in image-receiving sheets for thermal transfer recording using dyes.

``Prior art'' The thermal recording method, which allows a recorded image to be obtained at the same time as a human input signal, is relatively simple, inexpensive, and has low noise. It is used in various directions.

As the recording medium used in these thermal recording methods, 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, has been most commonly used. However, color-forming type thermal recording paper has poor storage stability of recorded images, and the color fading occurs when it comes into contact with organic solvents, chemicals, and the like.

Therefore, a recording method using a recording medium that utilizes colored coloring material itself has been proposed as a recording medium that replaces color-forming type thermal recording paper.
No. 6 discloses that 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
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 recording paper.

In this recording method, the coloring material on the support is melted, evaporated, and sublimated by heat, and transferred to the recording paper, and a recorded image is obtained by adhesion, adsorption, and dyeing, and the feature is that plain paper can be used as the recording paper. Since images with excellent gradation can be obtained by recording methods that use sublimable dyes as coloring materials, attempts have been made to apply them to full-color recording applications.

However, when plain paper is used as recording paper, dyeing is particularly difficult to occur, and the color density of the recorded image is not only low, but also
This causes significant fading over time, which is why JP-A-57-107885 and JP-A-59-1
As described in JP-A No. 65688, US Pat. No. 3,601,484, and the like, image-receiving sheets are used in which an image-receiving layer containing a thermoplastic resin as a main component is formed.

In addition, for recording images particularly rich in gradation, Japanese Patent Laid-Open Nos. 59-133092 and 187892-1982
There have also been proposals to improve the transfer efficiency by increasing the smoothness of the surface of the image-receiving layer, as in Japanese Patent Application Laid-Open No. 144394/1984, and to provide a cushion layer as in Japanese Patent Application Laid-open No. 144394/1983.

``Problem to be solved by the invention'' In general, dye-sublimation transfer methods can produce images with excellent gradation rich in gradation compared to melt-type transfer methods, but in order to obtain transferred images with high color density, a large amount of heat is required. It is said that energy is required, and in order to solve this problem, increasing the transfer efficiency has been a challenge for this method.

"Means for Solving the Problems" The present invention provides an image-receiving sheet for thermal transfer recording comprising an image-receiving layer on a support that receives a transferred image from a color material transfer sheet. 500-10000
An image-receiving sheet for thermal transfer recording characterized by containing polyethylene glycol.

"Function" As an image-receiving sheet for thermal transfer recording, a smooth barrier layer rich in cushioning and heat insulation properties is provided in advance on a base material such as paper, and the image-receiving layer is formed on this to improve adhesion with the thermal transfer sheet. Attempts have been made to improve the color density after transfer by increasing the efficiency of the heat signal provided from the heat head.

In this case, it has been proposed to smear an emulsion of polyurethane, polybutadiene, SBR, MBR, etc. as a barrier layer, but it is actually quite difficult to smear such a synthetic resin layer onto a paper-based surface. It is.

These aqueous synthetic resin emulsions rapidly penetrate into the pores between fibers as large as 1 to 100 μm in the base paper within a few seconds immediately after being applied to the paper, making it impossible to obtain smoothness. Also,
When coated paper is used as the base material, the synthetic resin emulsion first forms a coating resin layer on the surface at the beginning of the drying process after coating, and then the water inside evaporates, and then drying ends. . In this case, since the synthetic resin is not an extender pigment, the volume changes greatly during drying, and the smoothness of the surface immediately after coating is lost due to evaporation of water.

Furthermore, it is possible to improve the smoothness by adding inorganic pigments such as calcium carbonate, kaolin, titanium oxide, aldanium hydroxide, barium sulfate, etc. as extender pigments. However, when such a barrier layer is provided, inorganic pigments generally have higher thermal conductivity than synthetic resins, so the heat applied from the print head tends to escape through the inorganic pigments in the barrier layer. However, only an image-receiving sheet for thermal transfer recording with poor thermal efficiency can be obtained, and the color density thereof is extremely low.

Note that known synthetic resins that can be used as extender pigments include polymers and copolymers of polyolefin, polystyrene, polytetrafluoroethylene, polyvinyl chloride, polyvinylidene chloride, polybenzoguanamine, silicone resins, and the like. When these resins are added to the barrier layer, a somewhat higher color density can be obtained than when inorganic pigments are added. If a higher color density is desired, it is possible to add a plasticizer to the image-receiving layer, but this method is not considered preferable because the dye tends to bleed, resulting in poor storage suitability.

However, as a result of intensive research, the present inventors found that
The present inventors have discovered that when the image-receiving layer contains polyethylene glycol having an average molecular weight in the range of 500 to 10,000, an image-receiving sheet for thermal transfer recording with excellent image quality and high color density can be obtained, and the present invention has finally been completed.

Here, the average molecular weight of polyethylene glycol is 500
~10,000, more preferably from 1,500 to 5,000; however, if the average molecular weight is less than 500, the effect of improving color density will be small; on the other hand, if it exceeds 10,000, the thermal transfer sheet and image receiving sheet for thermal transfer recording will deteriorate during printing. The image-receiving layer tends to be easily thermally fused, which is not preferable.

The amount of polyethylene glycol contained in the image-receiving layer is adjusted within the range of 1 to 20% by weight, more preferably 3 to 10% by weight of the solid content of the image-receiving layer.

Incidentally, if it is less than 1% by weight, the effect of improving the color density will be small, while if it exceeds 20% by weight, it tends to result in poor storage stability, which is not preferable.

The reason why an image-receiving sheet for thermal transfer recording with a high color density can be obtained by adding polyethylene glycol to the image-receiving layer is not clear, but it is because the dye transferred from the transfer sheet to the image-receiving sheet is easily dispersed in polyethylene glycol, or It is presumed that polyethylene glycol makes it easier for the dye to disperse into the resin of the image-receiving layer, thereby increasing the color density.

The basic structure of the image receiving sheet for thermal transfer recording of the present invention is as shown in FIG. That is, on top of the substrate 1, a barrier layer 2,
An image receiving layer 3 is sequentially provided.

Further explanation will be given based on this figure.

Base materials include art paper, coated paper, lightweight coated paper, lightly coated paper, coated paper such as glossy type, dull type, matte type, etc., as well as high quality paper, medium quality paper, super calendered paper, etc. uncoated paper is used. Of course,
Transparent, translucent, and opaque films may also be used depending on the purpose for which the image-receiving sheet for thermal transfer recording is used.

As the barrier layer, an inorganic pigment, an aqueous solution of a water-soluble synthetic resin, an aqueous emulsion of a synthetic resin, an aqueous suspension, or a combination thereof can be applied using a known blade coater, air knife coater, bar coater, or rondo blade coater roll. Using a coater, gravure coater, curtain coater, etc., the dry weight is 3g/
m or more, preferably 8 to 30 g/cd. The purpose of the barrier layer is: ■ To improve image quality by smoothing the surface of the base material or imparting cushioning properties and increasing adhesion with the transfer sheet; ■ The image-receiving layer provided on the barrier layer is the barrier layer. Improving the image quality by suppressing the penetration of the heat into the substrate, and increasing the thermal efficiency of the image receiving sheet by suppressing the heat applied from the thermal head from escaping into the substrate. Depending on the quality required for the sheet, it may not be provided at all, or it may have a structure of one layer or 2.3 layers.

As the inorganic pigment, calcium carbonate, kaolin, titanium oxide, aluminum hydroxide, barium sulfate, etc. can be used.

As the water-soluble synthetic resin, polyacrylamide, various resins containing carboxyl groups or hydroxyl groups, such as carboxyl group-containing polyethylene, polyvinyl acetate, polyvinyl alcohol, cellulose resin, etc. can be used.

The synthetic resins constituting the aqueous emulsion and aqueous suspension include alkali-soluble types such as polyacrylic ester, polymethacrylic ester, polyolefin, polybutadiene, polystyrene, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyurethane, and polyester. , alkali-swellable, non-alkali-swellable, and modified polymers and copolymers can be used.

Further, if necessary, starch, modified starch, binders such as protein adhesives, antioxidants, dyes, antifoaming agents, surfactants, and other auxiliary agents may be added.

The image receiving layer functions to receive the dye transferred from the thermal transfer sheet, and is specifically constructed using the following synthetic resin.

■Things with ester bonds.

Polyester resin, polyacrylic acid ester resin, polycarbonate resin, polyvinyl acetate resin, styrene acrylate resin, vinyl toluene acrylate resin, etc.

■Things with urethane bonds.

Polyurethane resin etc. ■ Items with amide bond Polyamide resin etc. ■ Those with urea bond Urea resin etc. is used.

The image receiving layer is made of any one of these resins, or
The combined use is performed using a known blade coater, air knife coater, bar coater, rondo blade coater, roll coater, gravure coater, curtain coater, etc., and the dry weight is 1 g/rd or more, preferably 2 to 10 g/rrr. establish.

In addition, the coating liquid for the image layer may contain antifoaming agents, lubricants, antistatic agents, mold release agents, ultraviolet absorbers, dyes, etc., as necessary, to the extent that they do not impair the effects of the image-receiving layer. It can be added as appropriate.

"Examples" Examples will be described below to more specifically explain the present invention, but the present invention is of course not limited to these. Further, "parts" and "%" in the text indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 A barrier layer was provided on the surface of a 64 g/rd high-quality paper by preparing a coating liquid consisting of the following components and then smearing it.

Titanium oxide (product name: FA-55) is produced using a Coles disperser.
Disperse 10 parts of W, Furukawa Mining Specialty Co., Ltd. into this, 30 parts of a polyolefin resin pigment (product name Nichemipearl A-100, manufactured by Mitsui Petrochemicals ■), and polystyrene resin pigment (product name Niro Bake 0P-84J, manufactured by Nippon Acrylic ■). ) 45 parts, polyvinyl alcohol (product name: PVA-205, manufactured by Kuraray ■) 5 parts, polystyrene/acrylic copolymer latex (product name: Cevian A-4720, manufactured by Daicel) 1
0 parts were added to obtain a coating liquid with a solid content concentration of 37%. This coating liquid was applied to the surface of 64 g/rd high-quality paper at a dry weight of 15 g/n? Smear dry. Furthermore, this coated paper was subjected to super calender treatment.

In addition, processing with a super calender requires a linear pressure of 60 kg.
/ am, the surface temperature of the chrome-plated metal roll was 25° C., the paper passing speed was 5 m/min, and the number of paper passes was 2.

An image-receiving layer coating liquid was applied to the surface of the barrier layer after the super-calender treatment to form an image-receiving layer. The coating solution for the image-receiving layer was prepared and formed as follows.

Alcohol-modified silicone oil (product name Nitore Silicone SF-8427/manufactured by Tore Silicone ■) 10
(Representative example No. 14) (Test product: BZ-33
5 parts of 0KN-16 parts (manufactured by Katsuta Kako ■) were added with stirring, and further colloidal silica (trade name: Nearply) A
T-30A/manufactured by Asahi Denka ■) 15 parts, water-based modified urethane resin (product name: Hydran A P-40 part manufactured by Dainippon Ink ■) 100 parts, epoxy modified silicone oil (product name: Poron MF-11B/Shin-Etsu Chemical) (manufactured by ■), a crosslinking catalyst (product name: Catalyst PA-20/Dainippon Ink ■), and further
0 (reagent: average molecular weight 1570-630/manufactured by Kishida Kagaku Specialty Co., Ltd.) and water were added to obtain a coating liquid for an image-receiving layer having a solid content concentration of 20%. The thus obtained coating liquid was applied onto the surface of the barrier layer using a wire bar and dried to a dry weight of 1g1rd, followed by supercalender treatment to obtain an image-receiving sheet for thermal transfer recording. In addition, the super calender processing at this time was performed under a linear pressure of 90 kg/c1.
1. The test was carried out under the following conditions: the surface temperature of the chrome-plated metal roll was 70° C., the paper passing speed was 5 m/min, and the paper was passed twice. Then,
A thermal transfer sheet was prepared as follows.

40 parts of sublimable disperse dye (trade name: KST-B-136/manufactured by Nippon Kayaku ■) and 60 parts of hydroxyethyl cellulose were added to methyl ethyl ketone/toluene (weight/l ratio 1:1) while stirring with a mixer to form a solid. An ink composition for forming a thermal transfer layer having a concentration of 10% was obtained. The ink composition obtained in this manner was applied to a 9 μm-thick sheet of paper with a heat-resistant treatment on the back side.
The ET film was smeared with a wire bar so that the dry weight was Ig/- and dried to obtain a thermal transfer sheet.

The thermal transfer sheet thus obtained was placed on an image receiving sheet for thermal transfer recording, and a thermal head was used to output IW/dot, pulse width 0.3 to 4.5 m5ec, and dot density 3.
Printing was performed under the condition of 7 mm (dose), and visual evaluation was performed. The results obtained are shown in Table-1.

Example 2 The polyethylene glycol 600 blended into the image-receiving layer in Example 1 was replaced with polyethylene glycol 1500 (
A thermal transfer sheet was produced in the same manner as in Example 1, except that the reagent was changed to an average molecular weight of 1,500 to 1,600 (manufactured by Kishida Kagaku ■), and evaluated in the same manner as in Example 1. The obtained results are shown in Table 1. Ta.

Example 3 The polyethylene glycol 600 blended into the image-receiving layer in Example 1 was replaced with polyethylene glycol 4000 (
A thermal transfer sheet was produced in the same manner as in Example 1, except that the reagent was changed to an average molecular weight of 2,700 to 3,400 (manufactured by Kishida Kagaku ■), and evaluated in the same manner as in Example 1. The obtained results are shown in Table 1. Ta.

Example 4 The polyethylene glycol 600 blended into the image-receiving layer in Example 1 was replaced with polyethylene glycol 6000 (
A thermal transfer sheet was produced in the same manner as in Example 1, except that the reagent was changed to a two-average molecular weight of 7,400 to 9,000 (manufactured by Kishida Chemical Co., Ltd.), and evaluated in the same manner as in Example 1. The obtained results are shown in Table 1. Ta.

Comparative Example 1 An image receiving sheet for thermal transfer recording was obtained in the same manner as in Example 1 except that polyethylene glycol 600 (reagent: average molecular weight 570-630/manufactured by Kishida Kagaku ■) was not blended in the image receiving layer. Evaluate in the same way and table the obtained results.
Shown in 1.

Comparative Example 2 An image-receiving sheet for thermal transfer recording obtained in the same manner as in Example 1 except that ethylene glycol was added instead of polyethylene glycol 600, which was added to the image-receiving layer in Example 1, was evaluated in the same manner as in Example 1. The results obtained are shown in Table-1.

Comparative Example 3 A thermal transfer sheet was prepared in the same manner as in Example 1, except that the polyethylene glycol 600 blended in the image-receiving layer in Example 1 was changed to polyethylene glycol 200 (reagent: average molecular weight 190-210/manufactured by Kishida Kagaku ■). It was manufactured and evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Comparative Example 4 A thermal transfer sheet was prepared in the same manner as in Example 1, except that polyethylene glycol 600W and polyethylene glycol 20M (reagent: average molecular weight 18,000 to 25,000/manufactured by Kishida Chemical Co., Ltd.) were used in the image-receiving layer in Example 1. It was manufactured and evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Table 1 (Notes) ◎: Extremely excellent ○: Slightly excellent △: Slightly inferior, but no practical problems ×: Inferior "effect" As is clear from the results in Table 1, the thermal transfer recording of the present invention Good recorded images were obtained from all of the image-receiving sheets.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic structure of an image receiving sheet for thermal transfer recording. Base material barrier layer image receiving layer

Claims (1)

[Claims] 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, characterized in that the image-receiving layer contains polyethylene glycol having an average molecular weight of 500 to 10,000. An image receiving sheet for thermal transfer recording.