JPH0369393A - Recording sheet for dye thermal transfer printer - Google Patents

Abstract

PURPOSE:To obtain a recording sheet excellent in clearness, gradation properties and uniformity of images, by specifying the Young's moduli, bulk densities and thicknesses of multilayer films provided respectively on one side, on which is provided dyeable coat film, and on the opposite side, and of a sheet form base. CONSTITUTION:The Young's modulus E1, bulk density D1 and thickness T1 of a multilayer film provided on one side, on which is provided a dyeable coat film of a recording sheet, the Young's modulus E2, bulk density D2 and thickness T2 of a multilayer film provided on the opposite side, and the Young's modulus E3, bulk density D3 and thickness T3 of a sheet form support are so set s to fulfil the relationships of formulas [I], [II] and [III]. The relationship of E3 >= E1 >= E2 ensures that the recording sheet obtained has sufficient stiffness and resistance to curling. The relationship of 2T3 >= T1 enables the use of a sheet support having excellent resistance to curling due to printing. The relationship of D2 >= D1 >= D3, particularly the bulk density of the face layer being lower than that of the back layer, enables formation of images with high thermal efficiency and ensures that the face polyolefin film layer is capable of compressive deformation, thereby enhancing deformability according to a thermal head.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording sheet for a dye thermal transfer printer. More specifically, the present invention provides a dye that can be used in a thermal printer, particularly a dye thermal transfer printer, to uniformly and sharply accept transferred dye without curling due to heat, and to record high-resolution full-color images. This invention relates to a recording sheet for thermal transfer printers.

[Prior Art and Problems to be Solved by the Invention] Recently, attention has been paid to the practical use of compact thermal printers, particularly (sublimation) dye thermal transfer printers capable of printing clear full-color images.

Dye thermal transfer printers overlap the dye-dyeable resin coating layer of a recording sheet onto the ink layer surface of an ink sheet, which has an ink layer made of a sublimation dye and a binder on a film, and print the image from a thermal head in response to an electrical signal. The supplied heat transfers the sublimation dye from the ink sheet to the recording sheet in the required area in the required density and dyes it to form and record an image.

In order to obtain good prints and prints on a recording sheet using a printer using such a thermal head, a multilayer structure mainly composed of a mixture of an inorganic pigment and a polyolefin is used.
It is known to use a biaxially stretched film as a base material for a recording sheet. A recording sheet for a dye thermal transfer printer is one in which a dye dyeing layer containing a dyeable resin such as polyester as a main component is provided on the base material. Such a recording sheet has the advantage of being able to produce uniform and high-density prints, probably because it has a uniform thickness, is flexible, and has lower thermal conductivity than paper made of cellulose fibers.

However, when a dye image is transferred using a thermal head to an image recording sheet using a multilayer structure film mainly composed of polypropylene or biaxially stretched as a base material,
The stretching stress of the multilayered stretched film is alleviated by heat, causing it to shrink. As a result, curls and wrinkles occur on the recording sheet, causing trouble in the running of the recording sheet during recording operations, and the resulting prints. There were drawbacks such as a significant decrease in the commercial value of the product.

In order to improve these problems, it is possible to create a composite substrate by laminating and pasting the above-mentioned multilayered or biaxially stretched films on both sides of a substrate with low heat shrinkability, such as paper. is being attempted. However, due to the use of paper containing wood pulp as the core, fibrous noise and unevenness may appear in the formed image, or unevenness may occur due to uneven lamination. There was a problem in that the reproducibility of images deteriorated.

Furthermore, in the dye thermal transfer method, since the amount of heat applied to the image recording sheet is large, it has been difficult to eliminate curling caused by heating in the case of a composite sheet in which sheets with different thermal shrinkage rates are laminated together.

Compact full-color printers using the dye thermal transfer method are expected to become widely used as electronic camera printers and video printers. , the emergence of a recording sheet that faithfully represents image information has been desired.

The present invention seeks to provide a recording sheet that is suitable for dye thermal transfer printers and eliminates the drawbacks associated with the use of multilayer films as described above.

It goes without saying that the use of the recording sheet of the present invention is not limited to dye transfer printers, but can be applied to various thermal printers including melt ink type printers.

[Means and effects for solving the problem] The recording sheet for a dye thermal transfer printer of the present invention has a thickness of 1
0 to 80- sheet-like substrate, front and back film layers laminated on both the front and back surfaces thereof, each having a mono- or biaxially stretched multilayer structure containing a mixture of a polyolefin resin and an inorganic pigment as a main component; Young's modulus (El) of a multilayer structure film having a dye-dyeable coating layer formed on at least one of the front and back film layers, and laminated on one side having the dye-dyeable coating layer. , the tension (Dl) and thickness (T3), the Young's modulus (E2) and tension (D2) of the multilayer structure film laminated on the opposite side, and the Young's modulus (E3) of the sheet-like substrate, The tension (D3) and the thickness (T3) are expressed by the following relational expressions [1], [2] and [3]: E3≧2E+ ≧2E2 [1]2T,
≧TI [2] D2≧D, ≧D
It is characterized by satisfying I (3).

In the recording sheet of the present invention, the sheet-like substrate preferably contains polyethylene terephthalate as a main component.

In the recording sheet of the present invention, by using a multilayer structure consisting of a sheet-like substrate, a front and back polyolefin film layer, and a dye-dyeable coating layer, thermal curling is small under a wide range of conditions, and the resulting image has no density unevenness. It is clear from low to high densities, with no noise or noise, and is clear from low to high densities.
Color printing with uniform density becomes possible.

The structure of the recording sheet of the present invention will be explained with reference to the accompanying drawings.

In FIG. 1, a multilayer structure polyolefin film N2 is laminated and pasted on the surface side of a sheet-like substrate, and
A multi-N structure polyolefin film layer 3 is also formed on the back side, and these layers 1 to 3 constitute a support 4. A dye-dyeable coating N5 is formed and fixed on the surface polyolefin film layer 2.

As shown in FIG. 2, in the recording sheet of the present invention, below the back polyolefin film N3,
A back coat layer 6 may be formed and fixed.

Recording by heating using a thermal head or the like forms an image by applying heat from one side of the recording sheet, whether it is by sublimation dye transfer or leuco coloring. Therefore, in the present invention, not only the heat shrinkage rate of the front polyolefin film layer on the heated side is reduced, but also the polyolefin film layer on the back side has a predetermined heat shrinkability. Curl can be controlled.

A mono- or biaxially stretched multilayer structure film containing a mixture of an inorganic pigment and a polyolefin resin as a main component is known as synthetic paper, and is used for printing, writing printers, and other applications. The disadvantages of this synthetic paper are its weak stiffness and large heat shrinkage, but in order to solve these disadvantages, it is necessary to bond this sheet with other films or paper, or to create a multilayer structure of two or more sheets. It is also known to laminate films together. On the other hand, it is also known that this synthetic paper can be used as a recording sheet for thermal transfer printers such as those using a sublimation thermal transfer method to obtain uniform and clear transferred images. but,
This paper does not have sufficient heat resistance required for thermal transfer printer paper, and there is a high risk of curling due to heat shrinkage during processing or printing.

The sheet-like substrate used in the present invention has a modulus of elasticity (Young's modulus) that is higher than that of the surface and back polyolefin film layers.
It is necessary to have a large size so that curling during printing due to heat can be prevented. The heat shrinkage rate of such a sheet-like substrate according to JIS K-6734 is preferably equal to or lower than that of the biaxially stretched multilayer structure film of the surface polyolefin film layer, and the heat shrinkage rate value is 0.1%. It is preferable that it is below. Further, the tension of the sheet-like substrate needs to be smaller than that of both the front and back polyolefin film layers.

As such a sheet-like substrate, a thermoplastic film,
It is preferable to use a material with relatively good heat resistance, and for example, it is most preferable to use a film of polyethylene terephthalate. In addition, various polyesters,
Synthetic resin films such as polyolefin and nylon can also be used as the sheet-like substrate.

Generally, the sheet-like substrate used in the present invention has a Young's modulus (E3) of 50 to 1000 kg/l11
11! , the thickness (T3) is preferably 10 to 500 tntr, and the tightness is preferably 0.5 to 2.0.

The multilayer stretched polyolefin film on the front and back sides used in the present invention is already known as a synthetic paper with a multilayer structure or biaxially stretched film of polyolefin containing an inorganic pigment. Examples of multilayer structures include a three-layer structure in which a paper-like layer of a biaxially stretched film is present on the front and back sides of a base material layer, and a three-layer structure in which a paper-like layer of a biaxially stretched film is present on the front and back sides of a base material layer, and a layer other than the paper-like layer and the base material layer (for example, a paper-like layer on It may have a structure of four or more layers in which a surface layer (not containing pigment) is present. The Young's modulus of both the front and back polyolefin film layers is significantly smaller than that of the sheet-like substrate serving as the core, and the tightness (density) of these layers is greater than that of the sheet-like substrate, which ensures uniform image quality. It has a positive effect on the performance and compatibility with the head.

Generally, the Young's modulus (E
3) is preferably 20 to 500 kg/mm'', the thickness (T3) is 1O to 200μ, and the tightness (Dl) is 0.1 to 1.5.

In addition, the Young's modulus (Ex
) is 20 to 500 kg/mm”, thickness (T2) is 1
The 0-200 tmS tension (D2) is preferably 0.1-1.5.

JIS K-6734 for surface polyolefin film layer
The heat shrinkage rate is A of the back polyolefin film layer.
The heat shrinkage rate is preferably 0.1% or less. For this reason, the stress during stretching is relaxed by heating the polyolefin film by contacting it with a hot roll, etc.
Treatment is performed to reduce the heat shrinkage rate. Depending on the state of thermal curling, it may be preferable to perform a treatment to reduce the heat shrinkage rate of the back polyolefin film layer, but it goes without saying that the heat shrinkage rate must be greater than the heat shrinkage rate of the front polyolefin film layer.

The relationship between E3≧2E and ≧2E in [Formula 1] is that the back polyolefin film layer, the front polyolefin film layer,
In particular, Young's modulus increases in the order of sheet-like substrates.
It is necessary that the Young's modulus of the sheet-like substrate serving as the core is at least twice that of the other materials.

This ensures that the resulting recording sheet has sufficient rigidity and
It becomes possible to have resistance to curling.

In [Formula 2], 2T3≧T! The relationship is that the thickness of the sheet-like substrate is 3 times the thickness of the surface polyolefin film layer.
It stipulates that the above is the same.

This has made it possible to use sheet-like substrates that have excellent resistance to curling caused by printing.

[Formula 3] The relationship of glue ≧DI≧D3 means that the tightness (density) of the front polyolefin film layer is smaller than that of the back polyolefin film layer, thermal efficiency is high, images can be formed, and the front polyolefin film layer However, it can be compressed and deformed, making it possible to better fit the thermal head.

In the present invention, various methods can be used for laminating the sheet-like substrate and the front and back polyolefin film layers, one of which is dry lamination. As the adhesive for dry lamination, polyether adhesives, polyester adhesives, and the like can be used, but adhesives with high heat resistance are preferred.

In the recording sheet for printers of the present invention, a transfer dye-dyeable coating layer is provided on the front side (and the back side, if necessary). As such a dyeable coating layer, a resin (for example,
A material whose main component is polyester resin) is used.

As such polyester resin, from Toyobo Co., Ltd.
Some are commercially available under the trademark Byron 200. It is preferable to apply a solution of polyester resin in an organic solvent (for example, toluene) and dry it to form a dye-dyeable coating layer of 3 to 12 g/po (dry weight).

If necessary, the back side may be coated with a back coat layer mainly composed of acrylic resin, surface active polymer, low molecular weight surfactant, etc. for the purpose of improving running properties and preventing static electricity. This is a technique commonly used in synthetic paper.

The weight of the back coat layer is generally 0.3-1.5g/nf
It is.

〔Example〕

Next, the sheet for a dye thermal transfer printer of the present invention will be explained with reference to Examples.

Stretched film with multilayer structure (Commercial II:
Heat-treated Yubo FPG80 (thickness: 80-1 made by Oji Yuka Synthetic Paper) to make the MD (longitudinal direction) heat shrinkage rate 0.5% to 0.2% of that of untreated film. did. Polyethylene terephthalate film (trademark Nilmirror 338)
, Thickness: 38 pm (manufactured by Toshi ■) A heat-treated film is used as the surface layer and an untreated film is used as the back layer on both sides of the sheet-like substrate, and the laminated sheet is laminated using a polyester adhesive using the Dryra ξ Tonate method. It was created. On top of the surface polyolefin film layer, polyester resin (
A toluene solution of Byron 2001 Toyobo (Trademark: Byron 2001) was applied and dried to form a 5 g/M dye-stainable coating layer.
A recording sheet for dye thermal transfer printing was created. E, -E, ,D on this recording sheet.

The values of ~D3 and T1~T3 were as listed in Table 1.

The above recording sheet for a sublimation dye thermal transfer printer was printed using a sublimation video printer (trademark: VY-50 manufactured by Hitachi, Ltd.), and the image and curl were compared and evaluated. The results are shown in Table 2.

Jitsue Group 2 Stretched film with multilayer structure (trademark: Yubo F) whose main components are inorganic pigment (calcium carbonate, 26%) and polyolefin
PG80, thickness: 80//Il, manufactured by Oji Yugosei, Ltd.) was heat-treated, and the heat shrinkage rate in MD (length direction) was 0.5% to 0.08% of that of the untreated film. did. Polyethylene terephthalate film (trademark Nilmirror S2)
5. Dry lamination method using a polyester adhesive with the heat-treated film described in Example 1 as the back layer and the heat-treated film described in Example 1 as the back layer on both sides of a sheet-like substrate made of 25-1 (manufactured by Toshi) (thickness: 25-1). laminated to form a laminated support,
A coating layer of 5 g/bot was formed on the surface layer in the same manner as in Example 1 to prepare a recording sheet for a dye thermal transfer printer.

Dl~D,,T,~T3. of each layer. The values of EI to E3 are the first
The test results are shown in Table 2.

The same operations as in Example 1 were carried out in the Fuju group. However, when a multilayer film (trademark: YUPO FPG60, thickness = 60-1 egg oil synthetic paper) is heat treated, the heat shrinkage rate in MD (length direction) is 0.5 of that of the untreated film. % to 0.2%.

A heat-treated film was used as the surface layer, an untreated film was used as the back layer to form a laminated sheet, and a coating layer of 5 g/rrT was formed on the surface layer in the same manner as in Example-1 to create a recording sheet for a dye thermal transfer printer. .

Table 1 shows the values of DI-Ds, E+'''Es, T1~T, and Table 2 shows the test results.

Comparative operation The same operation as in Example 1 was performed. However, instead of the polyethylene terephthalate film, a two-wheel stretched polypropylene film (trademark Nidorefan 80140° thickness: 40-1 manufactured by Toshi ■) was used*DI-D2 *E, ~E,
The values of and T I''' T s are shown in Table 1, and the test results are shown in Table 2.

Biaxially oriented polypropylene film (trademark: Nidorefan B)
O1160, thickness 60I! In the same manner as in Example 1, a dye-dyeable coating layer of 5 g/m was applied directly onto the surface of a sheet (manufactured by Toshi Corporation) to prepare a sheet for dye thermal transfer printing.

E s, D 3. The T 3 values are shown in Table 1 and the test results are shown in Table 2.

A multilayered structure whose main ingredients are inorganic pigments and polyolefins.
Or directly on the surface of the two-wheeled stretched film (trademark: YUPO FPG150, thickness: 150mm, made by Oji Yuka Synthetic Paper ■),
In the same manner as in Example 1, a dye-dyeable coating layer of 5 g/nf was applied to prepare a sheet for dye thermal transfer printing.

The values of E s, D s, T 3 are shown in Table 1, and the test results are shown in Table 2.

Table 1 [Note: E...Young's modulus in the longitudinal direction ()cg/mm")
T...martyrdom 2nd table

[Brief explanation of drawings]

1 and 2 are cross-sectional explanatory views of a recording sheet for a dye thermal transfer printer of the present invention, respectively. DESCRIPTION OF SYMBOLS 1... Sheet-like substrate, 2... Surface polyolefin film layer, 3... Back polyolefin film layer, 4... Support, 5... Dye-dyeable coating layer, 6... Back coat layer. [Effects of the Invention] The recording sheet for a dye thermal transfer printer of the present invention has excellent image clarity, gradation, and homogeneity;
In addition, curling after printing and during heating is significantly reduced, making it possible to create compact full-color printers using thermal transfer, including sublimation transfer, and is therefore of high practical value.

Claims (1)

[Scope of Claims] 1. A sheet-like substrate having a thickness of 10 to 80 μm, and 1 to 2 laminated and adhered on both the front and back surfaces thereof, each containing a mixture of a polyolefin resin and an inorganic pigment as a main component.
1, which has both front and back film layers of an axially stretched multilayer structure and a dye-dyeable coating layer formed on at least one of the front and back film layers, and has the dye-dyeable coating layer.
Young's modulus (E_1) of a multilayer structure film laminated on the surface side
), tension (D_1) and thickness (T_1), and Young's modulus (E_2) of the multilayer structure film laminated on the opposite side,
and tension (D_2), as well as Young's modulus (E_3), tension (D_3), and thickness (T_3) of the sheet-like substrate.
and satisfies the following relational expressions [1], [2] and [3]: E_3≧2E_1≧2E_2 [1] 2T_3≧T_1 [2] D_2≧D_1≧D_3 [3] Recording sheet for printers.