JP3092324B2 - Dye thermal transfer image receiving sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dye thermal transfer image receiving sheet (hereinafter, "receiving sheet").
More specifically, the present invention relates to a receiving sheet capable of obtaining a clear image without density unevenness when used in a dye thermal transfer printer.

[0002]

2. Description of the Related Art In recent years, the development of a thermal transfer type high-quality color hard copy, in particular, a dye thermal transfer type printer has been rapidly progressing. In this dye thermal transfer printer, the sublimable dye layers of the three colors (yellow, magenta, and cyan) of the ink sheet are heated by continuously controlling the heating energy of the thermal head, and the transfer amount of each color dye is controlled. And thereby, it is possible to form a full-color image of the density gradation on the receiving sheet.

[0003] With such a dye thermal transfer printer,
In order to form high-quality prints on a receiving sheet at high speed, a biaxially stretched film containing a thermoplastic resin such as polyolefin as a main component and having a large number of voids is used as a sheet-like base material of the receiving sheet. It is known. In such a receiving sheet, an image receiving layer containing a thermoplastic resin as a main component is provided on the sheet-like substrate. The receiving sheet using the above sheet-shaped substrate,
There are advantages such as uniform thickness, flexibility, and low thermal conductivity as compared with the use of paper or the like made of cellulose fibers, and therefore, there is an advantage that a uniform and high-density print can be obtained.

[0004] However, when such a biaxially stretched film is used as a sheet-like base material for a receiving sheet which requires image reproducibility, residual stress during stretching of the film is released by heat and heat during printing. However, the film thermally shrinks in the stretching direction, resulting in curling or wrinkling of the receiving sheet, which causes troubles such as paper jam of the receiving sheet running in the printer.

[0005] In order to improve the above-mentioned drawback of curling or wrinkling, a laminated sheet obtained by laminating and stretching a stretched film on both sides of a core material having relatively low heat shrinkage or a core material having a large elastic modulus. It is known to use as a sheet-like substrate. However, such a sheet-shaped substrate is obtained by laminating sheets having different heat shrinkage rates, so that curl occurs due to a difference in shrinkage rate due to heat or the like. Also, even if the difference in the shrinkage ratio of the stretched films laminated on the front and back is the same, heat is applied only to the front surface of the receiving sheet during printing, so a temperature difference occurs between the front surface and the back surface of the receiving sheet, For this reason, a difference occurs in the shrinkage ratio between the front and back sides, and curling occurs in the receiving sheet. Further, since the stretched films are laminated on the front and back surfaces of the core material, the production cost is greatly increased.

Further, Japanese Patent Application Laid-Open Nos. 2-106397 and 2-307786 disclose a method for improving curling prevention during printing and improving image uniformity. It has been proposed to use a sheet-like substrate laminated with a polyolefin resin of 35 μm and 5 to 25 g / m ^2. However, even when this is used as the sheet-like substrate of the receiving sheet, it is caused by unevenness of paper fibers. Print density unevenness is not prevented.

[0007]

SUMMARY OF THE INVENTION The present invention has good printing suitability for a dye thermal transfer printer and eliminates the drawback of density unevenness when a sheet-like substrate laminated with a polyolefin resin film is used. An object of the present invention is to provide a receiving sheet capable of forming a clear printed image and having excellent curl resistance.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned disadvantages of the conventional receiving sheet including a sheet-like substrate obtained by laminating a polyolefin resin film on base paper, By making the basis weight of the base paper and the amount of the polyolefin resin layer formed by extrusion coating on both sides of the base paper a specific ratio, a clear print image without density unevenness is obtained, and the curl resistance is It has been found that a receiving sheet excellent in the above can be obtained, and the present invention has been completed.

That is, the dye thermal transfer image receiving sheet of the present invention is an image receiving sheet formed on at least one surface of a sheet-like substrate and receiving a dye transferred from the ink sheet by heating. And the sheet-like substrate is formed by extrusion-coating a polyolefin resin layer on both front and back surfaces of a base paper containing cellulose as a main component, and the following formulas (1) to (3): 50 ≧ A ≧ 30 (1) B ≧ 0.65A (2) 0.65 ≧ (A + B) /C≧0.5 (3) [In the above formula, A represents the surface (where the image receiving layer is formed) represents the weight of the side) resin layer (g / m ^2), B represents the back surface (the weight of the opposite side) resin layer to the side where the image-receiving layer is formed (g / m ^2), C is Indicates the basis weight (g / m ² ) of the base paper. ] Is satisfied.

[0010]

The sheet-like base material having a polyolefin resin layer used in the conventional receiving sheet has a basis weight of 180-2.
A polyolefin resin is laminated on both sides of a base paper of about 00 g / m ² at a total weight of 40 to 50 g / m ² . Therefore, the total weight of the polyolefin resin layers on both the front and back surfaces occupies only 20 to 30% of the total weight of the sheet-shaped substrate. For this reason, even if flexible polyethylene or the like is laminated on both sides of the base paper, the obtained sheet-like base material has insufficient flexibility as a whole, and therefore, the surface of the image receiving layer caused by minute irregularities on the base paper surface. There is a problem that the thermal head cannot follow the irregularities, resulting in poor image quality.

The present invention relates to a ratio ((A + B) / C) of the total weight of the front and back double-sided polyolefin resin layers formed on both sides of the base paper by extrusion coating to the basis weight of the base paper.
Is regulated to 0.5 to 0.65, the image quality of the obtained image on the receiving sheet can be greatly improved. If the ratio of the total weight of the front and back side resin layers to the basis weight of the base paper is less than 0.5, the image quality is not improved, and if it exceeds 0.65, the effect of improving the image quality is saturated, and This causes problems such as insufficient rigidity of the substrate.

Further, a great difference between the sheet-like substrate used for the receiving sheet of the present invention and the conventional one is that the sheet-like substrate obtained by the present invention has a surface resin layer weight of 3%.
0 g / m ² or more and 50 g / m ² or less, and the weight of the back resin layer is set to 0.65 times or more of the weight of the front resin layer, thereby reducing the density unevenness and the like due to the fibrous irregularities of the base paper. There is also a point that was able to be made. conventionally,
Although the density unevenness has been reduced by increasing the weight of the surface resin layer, a problem arises in that the increase in the weight of the surface resin layer causes curling to become more intense.
If the basis weight of the base paper is increased, the curl preventing property is improved, but there is a problem that the flexibility of the entire sheet-like base material is insufficient and that the print quality is deteriorated.

With a surface resin layer weight of less than 30 g / m ² ,
Unevenness on the surface of the base paper cannot be covered, resulting in poor image quality due to white spots and the like. Further, the image quality is also affected by the weight of the back surface resin layer, and the image quality is further improved by making the weight of the back surface resin layer 0.65 times or more the weight of the front surface resin layer.

In the present invention, the polyolefin resin which can be used for the sheet-like substrate includes homopolymers such as low-density polyethylene, high-density polyethylene, polypropylene, polybutene and polypentene which can be extrusion-coated.
Copolymers composed of two or more olefins, such as ethylene-polypropylene copolymers, linear low-density polyethylene composed of a copolymer of ethylene and α-olefin,
And mixtures thereof, and those having various densities and melt indexes can be used alone or as a mixture thereof. The polyolefin resin layer is formed by extrusion coating.

In the present invention, it is preferable to add a white pigment to the polyolefin resin in order to improve the whiteness of the receiving sheet. White pigments used for this purpose include titanium oxide, zinc oxide, talc, calcium carbonate and the like. Further, in the polyolefin resin in the present invention, resin metal salts such as stearic acid amide and zinc stearate, antioxidants such as hindered phenol, pigments such as cobalt blue and ultramarine blue, and dyes may be added. .

In the production of the base paper used in the present invention, the pulp forming the base paper is not particularly limited.
For example, it is possible to use wood pulp, waste paper pulp, non-wood natural pulp such as hemp or cotton, synthetic pulp made from polyethylene or polypropylene, or the like obtained by subjecting hardwood or softwood to chemical or mechanical treatment. it can. These pulp may be used alone or in combination of several kinds. Further, various fibers such as organic fibers such as acrylic fibers, rayon fibers, phenol fibers, polyamide fibers, and polyester fibers, and inorganic fibers such as glass fibers, carbon fibers, and alumina fibers may be mixed with the pulp. However, from the viewpoint of papermaking properties, it is preferable to mix cellulose pulp in an amount of 50% by weight or more.

In the base paper used in the present invention, various retention improvers, paper strength enhancers, sizing agents, fillers and the like can be appropriately selected and contained, and further, dyes, pH adjusters,
A slime control agent, an antifoaming agent and the like may be contained as necessary. In addition, a starch or polyvinyl alcohol, a surface sizing agent,
A pigment or the like may be applied.

The basis weight of the base paper used in the present invention is not particularly limited, but is preferably from 80 to 200 g / m ² .

The image-receiving resin used in the image-receiving layer of the present invention is preferably a thermoplastic saturated polyester resin, a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinyl propionate copolymer, or the like. However, other than the above, a polycarbonate resin, a polyvinyl acetal resin, a polyamide resin, a polyacrylate resin, an active energy ray-curable resin, or the like may be used.

In the present invention, the image receiving layer may contain a low molecular weight organic compound such as a substituted phenol or terpene for the purpose of preventing oxidation, absorbing ultraviolet light, and / or sensitizing. In general, a white pigment used for improving the whiteness and opacity of a paint, a fluorescent dye for adjusting the color tone of the image receiving layer, and a dye such as blue or violet can be added to the image receiving layer as needed. Additives such as the above-mentioned white pigments, ultraviolet absorbers, and cross-linking agents are conveniently mixed with the image-receiving resin that is the main component of the image-receiving layer for coating. Above the receiving layer,
Alternatively, it may be applied as another coating layer below.

Further, a release agent can be used to enhance heat-resistant fusion during printing between the ink sheet and the image receiving layer. As such a release agent, waxes such as paraffin and polyethylene wax, metal soap, silicone oil, silicone-based resin, fluorine-based surfactant, and fluorine-based resin can be used.
It is preferable that the content be not more than weight%.

In order to prevent the occurrence of static electricity due to the running of the receiving sheet in the printer and the occurrence of running trouble, at least one surface of the receiving sheet may contain an antistatic agent. , May be added in the image receiving layer, or may be back coated. As the antistatic agent, a cationic hydrophilic polymer can be used.

[0023]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited by these examples.

Examples 1 to 3 and Comparative Examples 1 to 4 In Examples 1 to 3 and Comparative Examples 1 to 4,
A base paper having a basis weight shown in Table 1 was coated with a low-density polyethylene containing 10% (by weight) of anatase-type titanium oxide on the surface of the base paper (the side on which the image receiving layer was formed), and the coating amount shown in Table 1 Was extrusion-coated at a resin temperature of 340 ° C. Next, on the back surface of the base paper, a resin layer similar to the front surface resin layer was extrusion-coated at a resin temperature of 340 ° C. so that the coating amount shown in Table 1 was obtained. A sheet-like substrate was obtained. After performing a corona discharge treatment on the surface of the surface resin layer of the sheet-like base material, the coating composition for an image receiving layer having the following composition was applied to a solid content of 6 g / m ² using a wire bar. And then dried to form an image receiving layer, thereby producing a receiving sheet.

The image-receiving layer coating composition Ingredient weight polyester resin (trademark: Byron 200, 100 parts by Toyobo Co., Ltd.) silicone oil (trademark: KF393, manufactured by 3 parts by Shin-Etsu Silicone Co.) isocyanate (Trademark: Takenate D- 110N, 5 parts by weight, manufactured by Takeda Pharmaceutical) Toluene 300 parts by weight

A color bar signal generator (Shibazoku, C13A2) was applied to each of the receiving sheets obtained in Examples 1 to 3 and Comparative Examples 1 to 4 by a thermal transfer printer (Sony, trade name: UP5000). Step pattern was printed. Density unevenness of the obtained print image,
And the curl degree of the receiving sheet after printing was evaluated. Table 1 shows the results.

The evaluation of density unevenness and curl degree was performed as follows. 1. Density unevenness: Sensory evaluation was performed in three steps: 3 for print images having no or uneven density, or 3 for very small, 2 for small, and 1 for large.

2. Curl degree after printing: 14 cm x 10
Give a solid black print on the receiving sheet of cm size,
The printed receiving sheet is placed on a flat surface with its printed surface facing upward, the height of the four corners of the receiving sheet is measured from this flat surface, and the maximum height (mm) is used to determine the curl degree of the receiving sheet. did.

[0029]

[Table 1]

[0030]

The dye heat transfer image-receiving sheet of the present invention comprises:
A clear print image without density unevenness was obtained, and further, no or little curl was caused by heat during printing, which is extremely excellent in practical use.

Continuation of the front page (56) References JP-A-3-268998 (JP, A) JP-A-4-279391 (JP, A) JP-A-1-271289 (JP, A) JP-A-2-50891 (JP) JP-A-2-106397 (JP, A) JP-A-2-305688 (JP, A) JP-A-3-10890 (JP, A) JP-A-3-234588 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) B41M 5/38-5/40

Claims (1)

(57) [Claims] 1. A sheet-like substrate comprising: a sheet-like substrate; and an image-receiving layer formed on at least one surface of the sheet-like substrate and receiving a dye transferred from an ink sheet by heating. The material is formed by extrusion-coating a polyolefin resin layer on both sides of a base paper containing cellulose as a main component, and the following formula (1) to
(3): 50 ≧ A ≧ 30 (1) B ≧ 0.65A (2) 0.65 ≧ (A + B) /C≧0.5 (3) [where A is the surface (image) weight of the receptive layer is formed side) resin layer (g / m ^2), B stands, the back surface (the weight of the opposite side) resin layer to the side where the image-receiving layer is formed (g / m ²⁾ And C represents the basis weight (g / m ² ) of the base paper. ], Which is a dye thermal transfer image receiving sheet.