JPH09150585A - Thermal transfer receptor sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a print having fidelity to image information and uniform density by a method wherein the surface of a film layer being in contact with a receptor layer and/or the surface of the receptor layer is subjected to a smoothing treatment by a clearance calender and the surface roughness of the receptor layer based on JIS B 0601 is made a specific value or below. SOLUTION: A surface-side film layer 3 constituted mainly of polyolefin resin and an inorganic pigment is laminated on the surface of a sheetlike core material layer 1 with an adhesive layer 2 interlaid. An image receptor layer 6 containing dyeable resin as a main constituent is formed on the surface of the surface-side film layer 3. The surface roughness of the surface of the receptor layer 6 needs only to be made 1.0μm finally by a smoothing treatment by a clearance calender, and this treatment may be applied to either the surface of a sheetlike substrate 8 before formation of the receptor layer 6 or the surface of the receptor layer 6 after formation thereof. In this clearance calender, a nip pressure is applied with a prescribed clearance maintained and a decrease in a sheet pressure is smaller therein than in general calenders.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer receiving sheet (hereinafter simply referred to as a receiving sheet).
More specifically, the present invention, when used in a thermal printer, in particular, a dye thermal transfer printer, is capable of sharply receiving a thermally transferred dye image without causing curling, and having high resolution and density uniformity. The present invention relates to a receiving sheet capable of forming a full-color image excellent in color.

[0002]

2. Description of the Related Art In recent years, a thermal printer, especially a dye thermal transfer printer capable of printing a clear full-color image has attracted attention. In a dye thermal transfer printer, a receiving layer containing a dye-dyeing resin of a receiving sheet is superposed on a dye ink sheet, and heat supplied from a thermal head or the like causes a predetermined concentration of a dye at a predetermined position of the dye layer to be placed on the receiving layer. The image is formed by transferring to. The ink sheet is composed of three colors of yellow, magenta and cyan, or four colors of black and black. Full-color images are obtained by sequentially and repeatedly transferring dyes of each color of an ink sheet to a receiving sheet.

In such a printer with a thermal head, a receiving sheet in which an image receiving layer containing a dye-dyeable resin as a main component is formed on one surface of a substrate made of various films in order to obtain a good printed image. Is used. For example, a uniaxially or biaxially stretched film containing an inorganic pigment and a polyolefin resin as main components, or on one surface of a substrate made of synthetic paper, an image receiving layer containing a dyeing resin such as polyester as a main component is provided, It is known to be used as a receiving sheet. The sheet-like substrate as described above,
There are advantages such as uniform thickness, flexibility, and low thermal conductivity compared to paper made of cellulose fiber, and therefore, there is an advantage that a uniform and high-density transfer image can be obtained.

However, when thermal transfer is applied to a receiving sheet using the above-mentioned film or synthetic paper as a sheet-like substrate, the stretching stress of the film is released by heat and the film shrinks due to heat, and as a result, the receiving sheet is curled or curled. There are drawbacks such as wrinkles that make running in the printer difficult, and the commercial value of the obtained print is significantly reduced.

In order to improve the problems derived from such a sheet-like substrate, the uniaxially or biaxially stretched film may be laminated and adhered on both sides of a substrate having a small heat shrinkability such as paper. Being tried. But in this case,
The unevenness of the surface of the paper used as the core material affects the surface characteristics of the receiving sheet laminated on the paper, and therefore, during transfer, between the thermal head and the ink sheet and between the ink sheet and the image receiving layer. There is a drawback that unevenness in adhesion occurs, image quality is deteriorated, and halftone reproducibility is deteriorated.

Particularly in the full-color printer of the dye thermal transfer system, there is a severe demand for improvement of image quality, and as the dot density of the thermal head is improved, the adhesion between the thermal head and the ink sheet and between the ink sheet and the receiving sheet is improved. There is a strong need for improvements and for improved transfer accuracy and for being unaffected by the large amount of heat applied. However, these requests have not yet been sufficiently achieved.

[0007]

The present invention is suitable for thermal printers, particularly dye thermal transfer printers, eliminates the drawbacks of various conventional image receiving sheets, has good surface smoothness, and is free from thermal deformation and curling. Another object of the present invention is to provide a thermal transfer receiving sheet which is clear, faithful to image information, and capable of obtaining a print with good density uniformity. The receiving sheet of the present invention is applicable not only to a dye thermal transfer printer but also to various thermal printers such as a molten ink transfer system.

[0008]

A thermal transfer receiving sheet of the present invention is formed on at least one surface of a sheet-shaped core material layer and the sheet-shaped core material layer, and contains a polyolefin resin and an inorganic pigment as main components, And a biaxially stretched film layer having a multilayer structure, and a receptive layer formed on at least one layer of the film layer and containing a dye-dyeable resin as a main component, wherein the film layer comprises: The surface in contact with the receiving layer and / or the surface of the receiving layer is smoothed by a clearance calendar, and the surface roughness (Ra value) of the receiving layer based on JIS B 0601 is 1.0 μm or less. To do.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of intensive studies on the smoothing treatment of the surface of a receiving layer of a receiving sheet or the surface of a support on which the receiving layer is formed, the present inventors have found that clearance between rolls can be adjusted. It has been found that the use of possible clearance calendars most effectively overcomes the drawbacks of the prior art, leading to the completion of the invention. In the present invention,
A clearance calendar is a calendar in which the clearance between rolls is set in advance to a sheet thickness or less, and an appropriate nip pressure is applied to smooth the calender (eg, horizontal super calender, Yuri Roll Machine Co., Ltd.).
Made).

An example of the constitution of the receiving sheet of the present invention is shown in FIG. In FIG. 1, on the surface of the sheet-shaped core material layer 1,
The front-side film layer 3 containing a polyolefin resin and an inorganic pigment as main components is laminated via an adhesive layer 2. Similarly, the back side film layer 5 may be laminated on the opposite side of the sheet-shaped core material layer 1 with the adhesive layer 4 interposed therebetween. An image receiving layer 6 containing a dye-dyeing resin as a main component is formed on the surface of the surface side film layer 3. Further, the back surface coating layer 7 may be provided on the front surface of the back surface side film 5 (the back surface side of the receiving sheet).

If a conventional calender is used to obtain the required smoothness, the nip pressure is uniformly applied in the thickness direction of the sheet, so that the inside of the sheet is compressed more than necessary and the elasticity of the sheet is lost. I will be destroyed. Good adhesion between the thermal head and the ink sheet and between the ink sheet and the receiving sheet is indispensable in order to obtain a print that is true to the image information and has good density uniformity. If it is lost, the adhesion between the layers will decrease.
Further, the sheet-shaped core material layer is a cellulose sheet, or
In the case of the pigment-coated article, the formation unevenness of the cellulose sheet may be transferred to the surface film by applying the nip pressure, and the visual smoothness may be impaired. However,
The clearance calendar according to the present invention can apply a nip pressure while maintaining a constant clearance, and a receiving sheet having a smaller decrease in sheet thickness and a smaller decrease in sheet elasticity as compared with a general calendar can be obtained. To be Further, the surface roughness (Ra
The value) tends to be smaller than that when treated with an ordinary calendar.

The surface roughness (Ra value) of the receptive layer is one of the indicators of the adhesion between the ink sheet and the receptive sheet, that is, whether or not a print faithful to image information and having good density uniformity can be obtained. However, the Ra value on the surface of the receiving layer is 1.
It was found that when the thickness is 0 μm or less, a print faithful to desired image information and having good density uniformity can be obtained. Preferably, the Ra value is 0.01 to 1.0 μm, and the Ra value is 0.
If it is less than 01 μm, slippage between the receiving sheets may be insufficient, and overrun of the receiving sheets may occur during printing by the printer. The surface roughness (Ra value) in the present invention means the center line average roughness and is based on JIS B 0601.

In the present invention, as the material of the roll of the clearance calendar, any combination of metal roll / metal roll, metal roll / elastic roll and elastic roll / elastic roll can be used, and a desired receiving sheet. Is obtained. Although not particularly limited,
As the elastic roll, the hardness (Shore D) is 78 to 95.
The one with a degree of around 0 is preferably used, and during the smoothing process,
The Ra value on the surface of the sheet-shaped support on which the receiving layer is provided or on the roll surface in contact with the receiving layer surface is preferably 1 μm or less. Further, the clearance to be set is preferably set to 10 to 99% of the sheet thickness, and if the clearance is set to less than 10%, the elasticity of the sheet is lost and the visual smoothness is deteriorated. come.

In the present invention, the control of the surface roughness of the receiving sheet by the clearance calendar cannot be generally stated depending on the material of the receiving layer, the material of the sheet-shaped substrate, the thickness thereof, etc. It can be easily performed by appropriately adjusting the nip pressure. In the present invention, the smoothing treatment with a clearance calendar may be such that the Ra value on the surface of the receiving layer finally becomes 1.0 μm or less. For example, the surface of the sheet-shaped support before the formation of the receiving layer or the receiving surface after the formation of the receiving layer. It may be on any surface of the layers, or may be subjected to appropriate smoothing treatment after the formation of the back surface layer, and may be performed twice or more during the process.

As the sheet-shaped core material used in the present invention, paper containing cellulose pulp as a main component, coated paper, art paper, cast paper, laminated paper having a thermoplastic resin layer provided on at least one thereof, or the like, or A film or sheet of polyester, polyamide, polyolefin, polystyrene, polycarbonate, polyvinyl alcohol, polyvinyl chloride or the like containing a synthetic resin as a main component is used. The thickness of the sheet-shaped core material layer is generally 4 to 2
It is 50 μm, preferably 10 to 200 μm.

In the present invention, a multilayer structure film containing a thermoplastic resin such as a polyolefin resin used for the front and back of the sheet-shaped core material layer and an inorganic pigment as main components is preferably used, and a representative example thereof is synthetic paper. To be Such a synthetic paper has a structure in which a biaxially stretched thermoplastic resin film is used as a substrate film and a uniaxially stretched thermoplastic resin paper-like layer film is laminated on the surface thereof.

The base film resin may contain stabilizers, plasticizers, fillers, pigments, and other auxiliary materials in a stretchable range, if necessary. It is desirable that the base film contains a filler in a proportion of 0 to 3% by weight. When the filler material is more than 3% by weight, the mechanical strength of the obtained receiving sheet may be insufficient. Further, the paper-like layer film contains filler particles, and microvoids are formed in the vicinity of the filler particles by stretching, so that the paper-like film has good writing properties and a feeling close to that of natural paper. The inorganic pigment used as the filler for the paper-like layer film is selected from, for example, clay, talc, gypsum, barium sulfate, diatomaceous earth, silicon oxide, and other white pigments, and they are used alone or in combination. Generally, the paper-like layer film contains a filler in a proportion of 5 to 60% by weight.

The sheet-like support used in the present invention is 2
It is desirable to have a thickness of 0 to 300 μm. When the thickness is less than 20 μm, the mechanical strength of the obtained receiving sheet is insufficient, and its hardness and repulsion against deformation are insufficient, so that the curling of the receiving sheet which occurs at the time of printing is sufficiently prevented. In some cases, it may not be possible. On the other hand, if the thickness exceeds 300 μm, the thickness of the receiving sheet obtained may be excessive. In a printer with a predetermined volume, there is a limit to the capacity of the receiving sheet,
An increase in the thickness of the receiving sheet naturally leads to a decrease in the number of receiving sheets contained in the printer. In this case, in order to accommodate a predetermined number of receiving sheets, the volume of the printer must be increased, which makes it difficult to make the printer compact.

In the film layer of the receiving sheet of the present invention, a receiving layer is provided on at least one surface of the film-shaped substrate for receiving the dye of the ink ribbon. The receiving layer is composed of a resin having a high dye-dyeability, a cross-linking agent, an anti-fusion agent, an ultraviolet absorber and the like. Acetate butyrate-based resins, polyester-based resins, and the like are used as the resin having high dye-dyeability. Further, the crosslinking agent is an isocyanate compound or an epoxy compound, the ultraviolet absorber is a benzotriazole-based, benzophenone-based, phenylsalicylate-based or cyanoacrylate-based ultraviolet absorber, etc., and the anti-fusion agent is an acrylic silicone resin, a lubricant or a release agent. A mold agent or the like is used.

In the receiving sheet of the present invention, on the surface (back surface) opposite to the receiving layer of the sheet-like support layer, the running property is improved, static electricity is prevented, and the image receiving layer is prevented from being damaged by rubbing between the receiving sheets. Further, when the printed receiving sheets are placed one on top of the other, a back coating layer may be formed for the purpose of preventing migration of the dye from the receiving layer to the back surface of the receiving sheet which is adjacent to the receiving layer. The back cover layer contains a resin effective as an adhesive, and this resin is also effective for the running property of the receiving sheet and the prevention of scratches on the receiving layer surface. As such a resin, an acrylic resin, an epoxy resin, a polyester resin, a phenol resin, an alkyd resin, a urethane resin, a melamine resin, or a reaction cured product of these resins can be used.

Various conductive agents can be added to the back surface coating layer for antistatic treatment. It is desirable to use a cationic polymer as the conductive agent. As the cationic polymer, polyethyleneimine, an acrylic polymer containing a cationic monomer, a cation-modified acrylamide polymer, a cationic starch and the like can be generally used. The coating amount of the back cover layer is 0.3
It is desirably within the range of 1.5 g / m ² . 0.
When it is less than 3 g / m ² , scratches on the receiving layer may not be sufficiently prevented when the receiving layer and the back surface rub against each other,
If it exceeds 1.5 g / m ² , the effect is saturated and it is uneconomical.

Instead of providing the back film layer, a thermoplastic resin coating layer may be provided on the back surface of the sheet support. Specific examples of the thermoplastic resin include homopolymers of α-olefins such as ethylene and propylene, or 2
Examples of the copolymer include a copolymer composed of more than one type of α-olefin, a copolymer of α-olefin as a main component with another monomer copolymerizable with the α-olefin, and a mixture thereof, but of course, the present invention is not limited thereto. Absent.
In addition, the resin contains pigments, stabilizers, antioxidants, antistatic agents,
A plasticizer, a dispersant, a lubricant, a fluorescent agent, etc. may be added. The thermoplastic resin coating layer is coated by a known method such as extrusion coating or solvent coating, and the coating amount is preferably in the range of 0.1 to 50.0 g / m ² .

In the present invention, known techniques such as wet laminating, extrusion laminating, dry laminating and wax laminating are used for laminating the sheet-shaped core material layer and the front surface side and back surface side film layers.
Generally, a dry lamination method is preferably used, and a polyether-based or polyester-based adhesive can be used as the adhesive. Moreover, the coating amount of the adhesive is 1.
It is preferably in the range of 0 to 50.0 g / m ² .

The receiving layer and other coating layers of the receiving sheet of the present invention can be formed by coating and drying using a coater such as a bar coater, a gravure coater, a blade coater, an air knife coater and a gate roll coater. it can.

[0025]

The present invention will be described in more detail with reference to the following examples, but of course the present invention is not limited thereto. In addition, "parts" and "%" in the examples all represent "parts by weight" and "% by weight". Example 1 A biaxially stretched multi-layered film (trademark: trademark) having a thickness of 80 μm as a core material, a polyolefin as a main component on its front and back surfaces, and calcium carbonate of about 30% as an inorganic pigment, and having a thickness of 60 μm. YUPO FPG60, made by Oji Oka Kasei Synthetic Paper, is laminated and laminated by a dry lamination method with a polyester adhesive to form a sheet-like support (thickness: 189μ).
m) was prepared. This sheet-shaped support was adjusted with a nip pressure of 100 kg / cm (linear pressure) using a clearance calendar (trademark: horizontal super calendar, Yuri Roll Machine, clearance: 100 μm), and surface roughness Ra = 0. Smoothing treatment was performed so that the thickness became 0.1 μm. On the surface of this sheet-shaped support, a paint having the following composition
1 was coated and dried so that the solid coating amount was 8 g / m ² to form a receptor layer. Further, on the back surface of this support, coating material-2 having the following composition was applied so that the solid coating amount was 1 g / m ^2, and dried to form a back surface layer (back surface coating layer). It was made. The surface roughness of the obtained receiving sheet on the receiving layer side was Ra = 0.2 μm. Paint-1 Polyester resin (trademark: Byron 200, manufactured by Toyobo Co., Ltd.) 100 parts Silicone oil (trademark: KF393, manufactured by Shin-Etsu Silicon Co., Ltd.) 3 parts Isocyanate (trademark: Takenate D-140N, manufactured by Takeda Pharmaceutical Co., Ltd.) 5 parts Toluene 300 parts Paint-2 Acrylic ester copolymer (Trademark: Primal WL-81, manufactured by Rohm and Haas) 100 parts Epoxy resin (Trademark: Epocoat DX-225, manufactured by Shell Chemical Co., Ltd.) 5 parts Conductive agent (Trademark: Saftomer ST1000) , Mitsubishi Yuka) 50 parts Denatured ethanol 1420 parts

Example 2 Polyolefin as a main component, about 30% as an inorganic pigment
On a biaxially stretched multi-layered film (trademark: YUPO FPG60, manufactured by Oji Yuka Synthetic Paper) having a thickness of 60 μm and containing calcium carbonate, the coating material-1 having the above composition (Example 1) was applied in a solid content amount. Of 8 g / m ² and then dried to prepare a sheet A having a receiving layer. Biaxially stretched multi-layered film having a thickness of 60 μm (trademark: YUPO FPG60, containing 30% calcium carbonate as another inorganic pigment).
A paint of the above-mentioned composition (Example 1) on Oji-Okaka Synthetic paper-
2 was coated and dried so that the solid coating amount was 1 g / m ^2, and thus a sheet B having a back surface coating layer was prepared. Thickness 80
Using the coated paper of μm as the core material, the receiving layer of the sheet A and the back coating layer of the sheet B are laminated and laminated on each surface by a dry lamination method using a polyester adhesive so that both are on the outside. The receiving sheet (thickness: 195
μm). This receiving sheet is smoothed so that the surface roughness Ra is 0.2 μm by adjusting the nip pressure using a clearance calendar (trademark: horizontal super calendar, Yuri Roll Machine, clearance: 100 μm). I did.

Example 3 A sheet C was prepared by extruding high-density polyethylene on one side of a coated paper having a thickness of 80 μm at a temperature of 320 ° C. to a thickness of 20 μm and pressing it against a cooling roll at 20 ° C. to provide a resin coating layer. Next, both sheets were laminated by a dry lamination method with a polyester-based adhesive so that the receiving layer of the sheet A prepared in Example 2 and the resin coating layer of the sheet C were on the outer side, respectively, and the sheets were received. A sheet (thickness: 162 μm) was produced. This receiving sheet is a clearance calendar (trademark:
Use a horizontal super calendar, Yuri Roll Machine, clearance: 80 μm) to adjust the nip pressure,
Smoothing treatment was performed so that the surface roughness Ra was 0.2 μm.

Example 4 Using the receiving sheet (thickness: 193 μm) having a surface roughness Ra = 0.2 μm obtained in Example 1, a clearance calendar (trademark: horizontal super calendar, Yuri Roll Machine, clearance) was used. : 100 μm) and the smoothing treatment was performed by adjusting the nip pressure to obtain a receiving sheet having a surface roughness Ra = 0.05 μm.

Example 5 A receiving sheet was prepared in the same manner as in Example 2 except that after the receiving sheet was prepared, the nip pressure was adjusted and smoothing treatment was performed so that the surface roughness Ra of the receiving sheet was 0.5 μm. Got the sheet.

Example 6 A receptor sheet was prepared in the same manner as in Example 2 except that the nip pressure was adjusted and the surface roughness of the receptor sheet was Ra = 0.9 μm. Got the sheet.

Comparative Example 1 A receiving sheet was prepared in the same manner as in Example 1 except that the smoothing treatment of the sheet-shaped support was omitted. The surface roughness of the obtained receiving sheet on the receiving layer side was Ra = 1.4 μm.

Comparative Example 2 A receiving sheet was prepared in the same manner as in Example 2 except that the smoothing treatment of the receiving sheet was omitted. The surface roughness of the obtained receiving sheet on the receiving layer side was Ra = 1.5 μm.

Comparative Example 3 A receiving sheet was prepared in the same manner as in Example 3 except that the smoothing treatment of the receiving sheet was omitted. The surface roughness of the obtained receiving sheet on the receiving layer side was Ra = 1.3 μm.

Comparative Example 4 In the smoothing treatment of the receiving sheet, a general calendar (trademark: mini super calendar, Yuri Roll Machine, clearance: 0 μm) was used in place of the clearance calendar, the nip pressure was adjusted, and the surface roughness was adjusted. A receiving sheet was obtained in the same manner as in Example 2 except that the smoothing treatment was performed so that Ra = 0.2 μm.

Comparative Example 5 The surface roughness Ra = 0.
A receiving sheet was obtained in the same manner as in Comparative Example 4 except that the smoothing treatment was performed so that the thickness became 9 μm.

Evaluation The receiving sheets obtained in each of the above Examples and Comparative Examples were measured and evaluated for quality by the following methods, and the results are shown in Table 1. [Sheet Thickness] The thickness of the receiving sheet (or sheet-shaped support) before and after the calendar treatment was measured with a paper thickness meter (trademark: digital paper thickness meter, manufactured by Toyo Seiki). [Surface Roughness] The center line average roughness (Ra) of the receiving sheet surface side of the receiving sheet was measured by a surface roughness analyzer (trademark: SP-11, manufactured by Kosaka Laboratory) based on JIS B0601. [Visual smoothness] Regarding the visual smoothness of the receiving sheet,
A sensory evaluation of swelling and swelling of the sheet was performed. [Image uniformity] A commercially available thermal transfer is performed by contacting each ink sheet of three colors of yellow, magenta, and cyan in which an ink layer containing a sublimable dye together with a binder is provided on a polyester film having a thickness of 6 μm with a receiving sheet. Using a video printer (trademark: VY-50, manufactured by Hitachi, Ltd.), a predetermined image was thermally transferred to a receiving sheet by heating it stepwise by a thermal head, and a halftone single color of each color and an image of color superposition were printed. . The image transferred onto the receiving sheet was visually evaluated for image uniformity (whether there is uneven density in the recording portion, white spots, etc.). As the evaluation criteria for the visual smoothness and the uniformity of the image, the evaluation result is 5, which is particularly excellent, 4 which is excellent, 3 which is ordinary, and 2 which is slightly defective.
The one with a remarkable defect was set as 1. It is necessary to be 3 or more for practical use, and not suitable for practical use if it is 2 or less.

[0037]

[Table 1]

As is clear from Table 1, in each of the examples, the surface smoothness and visual smoothness of the image were improved by smoothing the receiving sheet or the sheet-like support with a clearance calendar. A receiving sheet having excellent uniformity was obtained. On the other hand, as shown in Comparative Examples 1 to 3,
When the smoothing treatment by the clearance calendar was not performed, the surface smoothness was poor and the image was non-uniform. In Comparative Examples 4 and 5, the sheet-like support was subjected to a smoothing treatment using an ordinary calender, and although the surface smoothness was good, the swelling of the sheet-like core material layer was received due to the nip pressure. The layer surface was affected, the visual smoothness was lowered, the sheet thickness was greatly reduced, the elasticity of the sheet was lost, and the image uniformity was insufficient.

[0039]

EFFECT OF THE INVENTION The receiving sheet of the present invention has good surface smoothness, is free from thermal deformation and curling, is clear, is faithful to image information, and has good density uniformity. It enables full-color printing of thermal transfer methods including the sublimation thermal transfer method, and has a great contribution to the industrial world.

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory view showing the constitution of one embodiment of a receiving sheet of the present invention. Of course, the seat configuration is not limited to this specific example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sheet-shaped core material layer 2 ... Adhesive layer 3 ... Front-side film layer 4 ... Adhesive layer 5 ... Back-side film layer 6 ... Receiving layer 7 ... Back-covering layer 8 ... Sheet-like support layer

Claims (1)

[Claims] 1. A sheet-shaped core material layer, and a film layer formed on at least one surface of the sheet-shaped core material layer, containing a polyolefin resin and an inorganic pigment as main components, and having a biaxially stretched multilayer structure. And a receiving layer formed on at least one of the film layers and containing a dye-dyeable resin as a main component, in a thermal transfer receiving sheet, the surface of the film layer in contact with the receiving layer and / or the receiving layer Is subjected to a smoothing treatment by a clearance calendar, and the surface roughness (Ra value) of the above-mentioned receiving layer is 1.0 μm or less based on JIS B 0601.