JP2002187367A - Thermal transfer image receiving sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer image receiving sheet having an ink acceptive layer provided on a base sheet and suppressing occurrence of a white paper part staining. SOLUTION: The thermal transfer image receiving sheet comprises the base sheet of a single layer structure or a multilayer structure, and the ink acceptive layer provided on the sheet. When the base sheet has the single layer structure, its thermal conductivity is set higher than 0.25 W/m.K. When the base sheet has the multilayer structure, thermal conductivity of the layer adjacent to the acceptive layer is set higher than 0.25 W/m.K.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer image-receiving sheet, and more particularly, to a thermal transfer image-receiving sheet used in a thermal transfer recording system in which an ink receiving layer is provided on a base sheet, and in particular, the occurrence of white paper stains is suppressed. And a thermal transfer image receiving sheet.

[0002]

2. Description of the Related Art In recent years, the demand for printers has been increasing year by year,
The recording methods of this printer include the electrophotographic method, the ink jet method, and the thermal transfer method. Among them, the operation and maintenance are easy, the device can be reduced in size and cost, and there is no noise. For this reason, the thermal transfer method has been attracting attention.

In this thermal transfer method, a thermal transfer member having an ink layer in which a coloring agent is dispersed in a heat-fusible material is superimposed on an image receiving sheet, and the ink layer is thermally melted by applying heat to the thermal transfer member in an image-like manner. Thermal transfer system in which the image is transferred to and recorded on an image receiving sheet, and a heat transfer body having an ink layer containing a heat sublimable dye or a heat transferable dye (hereinafter simply referred to as a sublimable dye) is superimposed on the image receiving sheet. There is a sublimation type thermal transfer system in which a sublimable dye in an ink layer is sublimated or transferred onto an image receiving sheet by applying heat to the thermal transfer body in an image form.

An image receiving sheet used in such a thermal transfer recording system is generally provided with an ink receiving layer on a base sheet in order to cope with full color, high resolution, high definition, and high printing speed. A thermal transfer image receiving sheet is used. Further, in order to achieve the above full color, high resolution, high definition, and high printing speed, it is necessary to increase the temperature (printing energy) and printing pressure of the thermal head of the printer. However, when the temperature and printing pressure of the thermal head are increased, there is a problem that the transfer and permeation of ink to a non-image area (white paper stain) is likely to occur. Especially at the boundary between the image part and the non-image part,
White paper stains easily occur.

Various thermal transfer image receiving sheets have been proposed so far. For example, (1) the thermal conductivity is 0.
A melt transfer type ink image-receiving sheet comprising a bubble-containing layer formed on a sheet-like support of 25 W / m · K or less and an ink-receiving layer provided thereon directly or via an undercoat layer (Japanese Patent Laid-Open No. 7-1995). JP-A-228065), (2) a thermal transfer image-receiving sheet containing a water-retaining surfactant in an ink-receiving layer (JP-A-11-129636);
(3) A thermal transfer image-receiving sheet (Japanese Patent Laid-Open No. 2000-15943) in which a water-retaining surfactant and an organic filler and / or an inorganic filler having a Mohs hardness of 2 or less are contained in an ink receiving layer has been proposed. I have.

However, the image receiving sheet of (1) is intended to obtain a print ink image having excellent dot reproducibility as well as recording density. However, if the temperature and the printing pressure of the thermal head are increased, a problem arises that white paper stains cannot be avoided. Further, the image receiving sheets of (2) and (3) have a high reflection density value (OD value) at high energy, have excellent dot reproducibility at low energy, and generate print stains even in a high temperature environment. Although difficult to use, if a highly heat-insulating base sheet (for example, having a thermal conductivity of 0.25 W / m · K or less) is used, when the temperature of the thermal head or the printing pressure is increased, the white paper portion stains. Can not always be sufficiently suppressed.

[0007] By the way, there are various types of thermal transfer type printers.
White paper stains easily occur. For example, by increasing the pressure at which the thermal head is brought into contact with the surface of the image receiving sheet via the thermal transfer member (ink ribbon), the transfer performance of the ink image dots to the image receiving sheet is improved, and the printing density, 2. Description of the Related Art A printer of a type that improves the reproducibility of a tone is known. In such a printer,
The contact pressure (printing pressure) of the thermal head may reach several N / mm ² . If the contact pressure of the thermal head is not less than about 0.5 N / mm ² , white paper stains are liable to occur. Further, even when the temperature of the thermal head (printing energy) is increased, white paper stains are likely to occur. Therefore, there is a demand for an image receiving sheet which is unlikely to cause white paper stains even when printing is performed by a printer having a high temperature or contact pressure of the thermal head.
As a method of increasing the contact pressure of the thermal head, there is a method called a micro dry (registered trademark) method.
As a model of the printer, brand names MD-1000, MD-5000, MD-500 manufactured by Alps Electric Co., Ltd.
0J etc.

[0008] Furthermore, white paper stains tend to occur in an environment where the temperature is relatively high. Since thermal transfer printers are often used in places where high temperatures can occur, such as in factories and warehouses, there is a need for a printer that does not easily cause white paper stains even in a high-temperature environment.

[0009]

In the present invention, under such circumstances, an ink receiving layer is provided on a base sheet, and the temperature (printing energy) and contact pressure (printing pressure) of a thermal head are particularly high. It is an object of the present invention to provide a thermal transfer image receiving sheet in which white paper stains are less likely to occur in a case or under a high temperature environment.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a thermal transfer image-receiving sheet in which white paper stains are unlikely to occur, and as a result, a base sheet having a single-layer structure having a thermal conductivity higher than a certain value. Alternatively, it has been found that the object can be achieved by using a base sheet having a multilayer structure in which the thermal conductivity of a layer adjacent to the ink receiving layer is higher than a certain value. The present invention has been completed based on such findings.

That is, the present invention provides: (1) In a thermal transfer image-receiving sheet having a single-layered base sheet and an ink receiving layer provided thereon, the base sheet has a thermal conductivity of 0.25 W / m.K, and (2) a multi-layered base sheet and a heat transfer image receiving sheet having an ink receiving layer provided thereon, wherein the ink receiving in the base sheet is performed. A thermal transfer image-receiving sheet, wherein the thermal conductivity of a layer adjacent to the layer is higher than 0.25 W / m · K.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The thermal transfer image-receiving sheet of the present invention has a base sheet and an ink receiving layer provided thereon, and the base sheet has a single-layer structure. And may have a multilayer structure. In the present invention, when a base sheet having a single layer structure is used, its thermal conductivity needs to be higher than 0.25 W / m · K. If the thermal conductivity is 0.25 W / m · K or less, the effect of suppressing the generation of white paper stains, particularly when the temperature and contact pressure of the thermal head is high or in a high-temperature environment, cannot be sufficiently exhibited. The white paper stain is a phenomenon in which ink transfers and penetrates into a non-image part, and is mainly caused by excessive heat storage of the ink and the thermal head. When the thermal conductivity of the base sheet is higher than 0.25 W / m · K, this excessive heat storage can be avoided, and the ink and the thermal head are cooled by heat radiation, so that white paper stains are generated. Is suppressed. The preferred thermal conductivity is 0.28 W / m · K
That is all.

On the other hand, when a base sheet having a multilayer structure is used, the thermal conductivity of the layer adjacent to the ink receiving layer needs to be higher than 0.25 W / m · K for the same reason as described above. , Preferably 0.28 W / m · K or more. The substrate sheet having the multilayer structure can be obtained by a method such as laminating or co-extrusion. By using such a multilayer structure, the physical properties of layers other than the layer adjacent to the ink receiving layer can be freely controlled. Therefore, additional functions can be provided. For example, when a base sheet having a three-layer structure is used and an ink receiving layer is provided on the uppermost layer, a sheet having a thermal conductivity higher than 0.25 W / m · K is used for the uppermost layer, and an intermediate layer is used. May have high concealing properties, and the lowermost layer may have an appropriate coefficient of friction so as to enhance transportability in the printer.

The thermal conductivity in the present invention is measured by a probe method. This probe method
The hot wire method is developed by the method described in Japanese Patent No. 1810084 (Japanese Patent Publication No. Hei 5-13461). As a measuring instrument using the probe method, for example, there is "QTM-500" (trade name) manufactured by Kyoto Electronics Industry Co., Ltd.

In the present invention, when a substrate sheet having a single-layer structure is used, its thickness is preferably at least 5 μm, more preferably at least 10 μm.
If the thickness is less than 5 μm, the occurrence of white paper stains may not be sufficiently suppressed. The upper limit of the thickness is not particularly limited and is appropriately selected depending on the situation.
It is not more than 00 μm. On the other hand, when a substrate sheet having a multilayer structure is used, the thickness of the layer adjacent to the ink receiving layer is preferably 5 μm or more, more preferably 10 μm or more. If the thickness is less than 5 μm, the occurrence of white paper stains may not be sufficiently suppressed. The upper limit of the thickness of the layer is not particularly limited and is appropriately selected depending on the situation, but is usually 300 μm or less. Further, the thickness of the entire base sheet having a multilayer structure is selected in a range of usually 10 to 500 μm, preferably 20 to 400 μm.

In the present invention, when a substrate sheet having a multilayer structure is used, at least one layer other than the layer adjacent to the ink receiving layer has voids and a density of 1.2 g.
/ Cm ³ or less. Thereby, flexibility and cushioning property can be provided, and a high-resolution thermal transfer image-receiving sheet can be obtained. More preferred density in the range of 0.6~1.0g / cm ^3.

The material of the substrate sheet in the thermal transfer image-receiving sheet of the present invention is not particularly limited, and may be selected from those conventionally used as the substrate of the thermal transfer image-receiving sheet, such as paper, synthetic paper, and plastic film. It can be appropriately selected and used depending on the situation. Here, as the paper, for example, high-quality paper, cast-coated paper, art paper, coated paper, finely coated paper, impregnated paper such as synthetic resin or emulsion, cellulose fiber paper such as backing paper for wallpaper, and synthetic fiber pulp, synthetic paper It can be selected from non-cellulose fiber paper such as wood pulp, mixed paper of cellulose fiber and non-cellulose fiber, or processed paper obtained by laminating at least one surface using the above-mentioned paper as a core material. In post-processing such as papermaking and coating, it is preferable to include components such as fillers having relatively high thermal conductivity.

The synthetic paper can be selected from a synthetic paper provided with a paper-like layer having fine pores, a synthetic paper having a sea-island structure, and the like. On the other hand, as plastic films, for example, polyolefin-based, polyvinyl chloride-based, polyethylene terephthalate-based, polystyrene-based,
The film can be selected from polymethacrylate-based and polycarbonate-based films.

When the substrate sheet is made of a plastic film, a surface treatment such as an oxidation method or a roughening method may be optionally carried out in order to improve the adhesion with a layer such as an ink receiving layer provided thereon. Can be applied. Examples of the oxidation method include corona discharge treatment, chromic acid treatment (wet method), flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment, and examples of the unevenness method include a sand blast method and a solvent treatment method. Is mentioned. These surface treatment methods are appropriately selected according to the type of the base sheet, but generally, the corona discharge treatment method is preferably used from the viewpoints of effects and operability.

In the thermal transfer image receiving sheet of the present invention, the ink receiving layer provided on the base sheet has a function of receiving the ink of the thermal transfer body, and may have a single layer structure. It may have a multilayer structure. The multilayer structure has a configuration in which a release layer (anti-blocking layer), an antistatic layer, and the like are laminated on a coating layer (in the case of a single layer, this is an ink receiving layer) as a main constituent layer,
And / or a configuration in which an easy adhesion treatment layer, an antistatic layer, a concealing layer, and the like are laminated below the coating layer.

In the present invention, the thickness of the coating layer of the ink receiving layer is preferably in the range of 1 to 30 μm. If the thickness is less than 1 μm, the generation of white paper stains can be suppressed, but the ink receiving performance (ink absorption and anchor effect) may be insufficient. If the thickness exceeds 30 μm, the thermal conductivity of the coating layer itself may be reduced. When the value is too low, the heat radiation effect of the base sheet is hardly sufficiently exhibited, excessive heat storage in the coating layer occurs, and white paper stains are caused. Further, even when the thermal conductivity of the coating layer itself is high, if the thickness exceeds 30 μm, there is a possibility that the whiteness of the white paper portion may be caused due to a decrease in flatness of the coating layer. A more preferred coating layer thickness is in the range of 5 to 30 μm.

In the present invention, the Beck smoothness of the ink receiving layer is preferably 100 seconds or more. If the Beck smoothness is less than 100 seconds, white paper stains may occur due to a decrease in the flatness of the ink receiving layer, and the effect of the present invention may be impaired. More preferred Beck smoothness is 500 seconds or more.

Further, the coating layer in the ink receiving layer is
It is usually composed of a filler and a binder as main components. Here, as the filler, conventionally known fillers such as titanium oxide, talc, calcium carbonate, clay, silica,
Inorganic fillers such as aluminum hydroxide, granular represented by styrene-acrylic, hollow, through-hole, doughnut-shaped plastic pigments, urea-based,
Organic fillers such as cellulose-based fillers and the like can be mentioned. These fillers may be used alone or in combination of two or more.However, if a soft filler is used, the generation of white paper stains can be more effectively suppressed. It is advantageous to use organic fillers and inorganic fillers having a Mohs hardness of 2 or less.

The average particle size of these fillers is usually 0.1
10 μm, preferably 0.1 μm to 7 μm. When the average particle diameter of the filler is 0.1 to 7 μm, the Beck smoothness of the ink receiving layer is usually 100 seconds or more, and the above-mentioned effects can be obtained. On the other hand, as the binder, conventionally known binders, for example, acrylic resin, urethane resin, styrene resin, styrene-acrylic resin, polyester resin, etc., considering the compatibility with the thermal transfer member. Thus, one or more types can be appropriately selected and used.

The content ratio of the filler and the binder in the coating layer in the ink receiving layer is 0.5: 1 to 5: 1 by weight.
Is preferable. If the proportion of the filler is less than the above range, the ink receiving performance may be insufficient, and if it is more than the above range, the surface layer strength is reduced, and a part of the ink receiving layer is peeled off and transferred to a thermal transfer body at the time of printing. Symptoms may occur. For these reasons, a more preferable content ratio of the filler and the binder is in the range of 0.5: 1 to 4: 1 by weight.

In the present invention, in addition to the filler and binder described above, the coating layer in the ink receiving layer may contain, if necessary, a conventional ink receiving layer in a range that does not impair the object of the present invention. Various additives commonly used in coating layers, for example, a release agent for preventing fusion between a thermal transfer image receiving sheet and a thermal transfer body (thermal transfer ribbon) during thermal transfer recording, light resistance, dark fading resistance, and dyeing properties And the like, an ultraviolet absorber, a light stabilizer, an antioxidant, a surfactant, an antistatic agent, a fluorescent dye, a plasticizer, and the like.

Examples of the release agent include silicone oils such as silicone oils, fluorine silicone oils, modified silicone oils such as epoxy-modified, amine-modified, alcohol-modified, and polyether-modified silicone oils, petroleum-based liquid paraffins and the like, and paraffin wax. And a wax system such as polyethylene wax. Further, as an agent for improving light resistance, dark fading resistance, dyeing property and the like, for example, a copolymer of (meth) acrylamide and another copolymerizable monomer, specifically (meth) acrylamide / styrene / ( (Meth) acrylic acid copolymers, etc., furthermore, esters of aromatic polybasic acids, aliphatic polybasic acids, alicyclic polybasic acids, etc. with aliphatic alcohols, alicyclic alcohols, phenols, etc. Group urethane compounds, aromatic urethane compounds and the like.

As the ultraviolet absorber, benzophenone type, benzotriazole type, cyanoacrylate type, salicylate type, oxalic acid anilide type and the like can be used. As the light stabilizer, hindered amine type compounds and the like can be used. However, high molecular ultraviolet absorbers and light stabilizers are preferred since they may cause problems such as blocking and bleed-out. As the antioxidant, hindered phenol-based, phosphorus-based, sulfur-based antioxidants and the like are used.

In order to form a coating layer in the ink receiving layer, first, the above-mentioned filler and binder are mixed in an appropriate organic solvent or an aqueous solvent comprising a mixture of an organic solvent miscible with water and water. A coating solution having a concentration of about 5 to 40% by weight is prepared by dissolving or dispersing the adhesive and various additives used as necessary. Next, this coating liquid is applied directly on the base sheet or through an easy-adhesion treatment layer, an antistatic layer, a concealing layer, or the like, so that the thickness after drying becomes a desired value, and a drying treatment is performed. I do. As a coating method, a known method such as a Meyer bar method, a reverse roll method, a gravure method, a blade method, and an air knife method can be used. In the thermal transfer image-receiving sheet of the present invention, at least one layer having a curl preventing function, an antistatic function, a slipperiness improving function, and the like is provided on the surface of the base sheet opposite to the ink receiving layer, if desired. be able to.

[0030]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Example 1 As a base sheet, a white polyethylene terephthalate film (manufactured by DuPont, trade name: Melinex 339) having a single layer structure with a thermal conductivity of 0.31 W / m · K was used. Urethane resin (manufactured by Dainippon Ink and Chemicals, Inc., trade name: Hydran AP-40, solid content 2)
330 parts by weight of a through-hole type organic filler composed of 100 parts by weight of an acrylic-styrene resin (manufactured by Mitsui Chemicals, Inc., trade name: Grossdale 2001TX, solid content concentration: 20% by weight)
3 parts by weight of polyethylene glycol (trade name: PEG # 600, manufactured by NOF CORPORATION) and 10 parts by weight of water were mixed and sufficiently dispersed by a sand grinder to prepare a coating liquid. Next, on one side of the base sheet, the coating liquid was applied by a reverse roll coater so that the dry thickness became 20 μm, and dried to form an ink receiving layer, thereby producing a thermal transfer image receiving sheet. did.

Example 2 140 parts by weight of a polyester resin (manufactured by Toyobo Co., Ltd., trade name: Vylonal MD1930, solid content concentration: 30% by weight)
100 parts by weight of talc having a Mohs hardness of 1 (manufactured by Takehara Chemical Co., trade name: High Micron HE-5), 4 parts by weight of polyethylene glycol (manufactured by NOF Corporation, trade name: PEG # 600) and 160 parts by weight of water were mixed. The mixture was sufficiently dispersed by a sand grinder to prepare a coating liquid. Next, on one side of the same base sheet as in Example 1, this coating liquid is applied by a reverse roll coater so that the thickness after drying becomes 15 μm, and dried to form an ink receiving layer. As a result, a thermal transfer image-receiving sheet was produced.

Example 3 Styrene-alkyl acrylate copolymer (BA
Product name: Acronal YJ, manufactured by SF Dispersion Co., Ltd.
752 parts by weight -2741D, solid content concentration 55.5% by weight), 100 parts by weight of calcined kaolin having Mohs hardness of 2 (manufactured by Georgia Kaolin Co., Ltd., trade name: Alt White TE),
Polyethylene glycol (manufactured by NOF Corporation, trade name: PE
G # 600) 3 parts by weight and 200 parts by weight of water were mixed and sufficiently dispersed by a sand grinder to prepare a coating liquid. Next, on one side of the same base sheet as in Example 1, this coating liquid is applied by a reverse roll coater so that the thickness after drying becomes 10 μm, and dried to form an ink receiving layer. As a result, a thermal transfer image-receiving sheet was produced.

Example 4 Polyurethane emulsion (manufactured by Takeda Pharmaceutical Company, trade name: Takelac W-7004, solid content concentration: 33% by weight)
An adhesive for dry lamination was prepared by mixing 60 parts by weight, 50 parts by weight of water and 10 parts by weight of a curing agent (trade name: Takenate AW-725, manufactured by Takeda Pharmaceutical Co., Ltd.). Next, thermal conductivity of 0.18 W / m · K, density of 1.0 g / cm
^On one side of a 100 μm-thick polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., Crispar K2323) containing fine voids, the above-mentioned adhesive for dry lamination is dried with a gravure coater to a dry coating amount of 3 g / m ² . And heat conductivity of 0.29 W / m
・ K white polyethylene terephthalate film with a thickness of 50 μm (manufactured by DuPont, trade name: Melinex 33)
9) was laminated by a dry lamination method to prepare a substrate sheet formed of a multilayer structure film. Next, an ink receiving layer was formed on the surface of the polyethylene terephthalate film having a thermal conductivity of 0.29 W / m · K on the substrate sheet in the same manner as in Example 1 to produce a thermal transfer image receiving sheet.

Comparative Example 1 In Example 1, the heat conductivity was 0.2
Example 1 except that a 100 μm-thick polyethylene terephthalate film having a single layer structure of 2 W / m · K (manufactured by Toyobo Co., Ltd., trade name: Crispar G2323) was used.
In the same manner as in the above, a thermal transfer image-receiving sheet was produced.

As described above, a thermal transfer color printer (trade name: MD50, manufactured by Alps Electric Co., Ltd.) was applied to the thermal transfer image receiving sheets prepared in Examples 1 to 5 and Comparative Example 1 at 40 ° C.
00J), cyan ink (cyan for paper, MDC-
FLCC), magenta ink (magenta for paper, MDC-
FLCM) and yellow ink (yellow for paper, MDC
-FLCY), and prints a test pattern composed of cyan, magenta, and yellow charts, which are arranged in ten gradations from level 1 to level 10 in order from the lowest heat energy, and has a low density transfer property, a maximum density, and blank paper. The stain on the part was evaluated according to the following criteria, and the printability was evaluated. Table 1 shows the results.

(1) Printability (a) Low-density transferability The reflection density of cyan level 1 is measured using a Macbeth densitometer (RD-
918) is ０．１, 0.06 to
0.10 was rated as ○, and 0.05 or less was rated as ×. (B) Maximum density The reflection density at level 10 of magenta is measured using a Macbeth densitometer (R
D-918) when the value measured was 1.60 or more.
5 to 1.59 were evaluated as O, and 1.44 or less as X.

(C) Smearing of blank paper part: No stain is observed.
も の indicates that the printability was not significantly impaired and had no practical problem, and X indicates that the printability was clearly impaired due to a clear streak or band-like stain.

[0038]

[Table 1]

(Note) The values in parentheses at the low density transfer property and the maximum density indicate the reflection density (OD value).

[0040]

According to the present invention, it is possible to easily form a thermal transfer image-receiving sheet in which white paper stains are less likely to occur particularly when the temperature (printing energy) or contact pressure (printing pressure) of the thermal head is high or in a high-temperature environment. Can be obtained.

Claims (5)

[Claims] 1. A thermal transfer image-receiving sheet having a single-layer substrate sheet and an ink-receiving layer provided thereon, wherein the thermal conductivity of the substrate sheet is higher than 0.25 W / m · K. A heat transfer image receiving sheet characterized by the above-mentioned. 2. In a thermal transfer image receiving sheet having a multi-layered base sheet and an ink receiving layer provided thereon, a layer adjacent to the ink receiving layer in the base sheet has a thermal conductivity of 0.25 W / m.K. 3. The thermal transfer image-receiving sheet according to claim 2, wherein in the base sheet having a multilayer structure, at least one layer other than the layer adjacent to the ink receiving layer has voids and has a density of 1.2 g / cm ³ or less. . 4. The coating layer thickness of the ink receiving layer is 1 to 30 μm.
The thermal transfer image-receiving sheet according to claim 1, wherein m is m. 5. The thermal transfer image-receiving sheet according to claim 1, wherein the ink receiving layer contains an organic filler and / or an inorganic filler having a Mohs hardness of 2 or less.