JP2543702C - - Google Patents

Description

Description: TECHNICAL FIELD [Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

The present invention relates to a method for producing a high-quality heat-sensitive recording sheet having a remarkably improved image quality and sensitivity and an excellent or matte surface gloss having a uniform surface gloss.

0002.

[Conventional technology]

Generally, a heat-sensitive recording sheet is provided with a heat-sensitive color-developing layer containing a heat-coloring composition as a main component on a support such as paper or film, and a color-developed image is obtained by heating with a heat head, a heat pen, a laser, or the like. Is to record. Compared to other recording methods, the thermal recording method has the advantages of being able to record in a short time with a relatively simple device, generating less noise and polluting the environment, and being less costly, so it is a facsimile. , Recorders, printers, ticket vending machines, labels, etc. are widely used.

On the other hand, the demand for heat-sensitive recording sheets suitable for equipment is increasing due to the increasing variety and quality of equipment. For example, a printer for CRT screen copying that can output a gradation image, or a printer for measurement or a label printer that requires high contrast requires excellent image quality (dot reproducibility), and at the same time, a thermal recording sheet. Uniform luster tends to be preferred. On the other hand, for devices such as facsimiles or general printers that mainly use character images, the main focus is on the readability of characters, so a heat-sensitive recording sheet with low surface gloss and excellent image quality and sensitivity is required. Will be done. Furthermore, the power consumption and resolution of all devices are becoming lower and higher, and higher sensitivity and higher image quality are required to support these devices. Furthermore, the appearance is homogeneous and glossy. It has been desired to be able to select one having a toned or matte surface depending on the application.

In such a heat-sensitive recording sheet, a heat-sensitive color-developing layer is applied on a support such as conventional paper, and after drying, a smoothing treatment such as a super calendar is performed so as to improve the surface smoothness and the image quality and sensitivity. Manufactured.

0005

[Problems to be Solved by the Invention]

However, depending on such a manufacturing method, a heat-sensitive recording sheet having a satisfactory high image quality, high sensitivity and uniform surface gloss, or a heat-sensitive recording sheet having high image quality, high sensitivity and a uniform matte surface can be obtained. Was difficult.

Various measures have been proposed as measures for improving surface smoothness, improving contact with a thermal head, and improving image quality and sensitivity. For example, perform super calendar processing and Bekk
A method of setting the smoothness to 200 seconds to 1000 seconds (Tokuko Sho 52-20142), a heat-sensitive recording layer is provided on top of an undercoat layer containing wax, and the surface roughness Rz is reduced to 2 μm or less by super calendar processing. Method to do (Japanese Patent Laid-Open No. 59-204)
594), the heat-sensitive recording layer is formed by a method of performing a super calendar treatment using a heated metal roll to reduce the optical surface roughness Rp to 3.5 μm or less (Japanese Patent Laid-Open No. 61-237683), or a bend-type plaid coating method. There is a method of coating and drying to reduce the surface roughness Ra to 1.2 μm or less (Japanese Patent Laid-Open No. 55-156086). However, even if these measures are used, it is still not possible to obtain sufficient smoothness to give sufficient image quality and sensitivity, and further, the indexes for these smoothness have not yet sufficiently corresponded to the image quality.

In addition, many attempts have been made to improve the appearance of the thermal recording sheet. For example
Raw material formulation of heat-sensitive recording layer to prevent background stains and uneven gloss during calendar processing (Tokukosho 50-14531, Tokukousho 51-5497, JP-A 56-46786)
, Japanese Patent Application Laid-Open No. 60-64888, etc.), or calendar processing conditions (Japanese Patent Laid-Open No. 59-)
155094) etc. have been proposed, but it is difficult to eliminate uneven gloss due to uneven texture of the support or uneven coating of the thermal recording layer by smoothing treatment such as calendar processing, and therefore homogeneous. It was not possible to obtain a heat-sensitive recording sheet with excellent luster. On the contrary, in order to obtain a uniform matte surface, a process such as not performing a smoothing process such as a calendar or limiting it to the minimum necessary is used, but the heat-sensitive recording sheet obtained by these processes is used. On the contrary, the smoothness was lowered, and the image quality and sensitivity were inferior.

0008

[Means for solving problems]

The present inventors have arrived at the present invention as a result of diligent research in order to obtain a high-quality heat-sensitive recording sheet having such excellent image quality and sensitivity and having a uniform glossy or matte surface. The roughness curve and contact rate in the present invention are obtained by the following methods. Roughness curve: Based on JIS-B-0601, using a stylus tip curvature radius of 5 μm, measuring stylus pressure 4 mN (0.4 gf), scanning speed 0.3 mm / sec, measuring length 2.5 mm
, It was measured with a cutoff value of 0.8 mm and recorded on a chart, and Surfcom 1500A manufactured by Tokyo Seimitsu Co., Ltd. was used as the measuring device. Attachment 2 is shown as an example of the measurement. Contact rate: The ratio of the length of a straight line parallel to the center line drawn on the roughness curve (a line that equalizes the areas on both sides of the straight line) across the roughness curve, L1 in Attached Figure 2.
, L2, ..., Ln and L are expressed by the following equations.

According to the present invention, when forming the outermost surface layer of a heat-sensitive recording sheet provided with a heat-sensitive recording layer that develops color by heating on a support, the center line of the roughness curve based on the JIS-B-0601 method is used. A smooth body surface having a smooth surface having a contact rate of 20% or less with a straight line that is parallel and has a roughness curve and a contact rate of 90% and is drawn parallel to the center line at a position of 1.5 μm on the surface side. The outermost surface layer in a wet state (plastic state) is joined to the surface, dried in the joined state to make the outermost surface layer dry (non-plastic state), and then the outermost surface layer is a smooth surface. In the method for producing a high-quality heat-sensitive recording sheet that peels off from the surface, the outermost surface layer is in a semi-dry state, and a dry surface is coated with a solvent and re-wet.
Alternatively, it is a method for producing a high-quality thermal recording sheet, which is one of a state in which a heat-sensitive recording layer coating liquid or a protective layer coating liquid is further applied to a dried surface and re-wetted.

Examples of the support used for the heat-sensitive recording sheet of the present invention include papers such as high-quality paper, single-gloss paper, coated paper, and synthetic paper, and plastic films such as polyethylene terephthalate, polyethylene, and polypropylene.

The thermochromic materials used in the present invention include (1) leuco dyes such as fluorane-based, triphenylmethane-based, spiropirane-based, auramine-based, and phenothiazine-based, and coloring that reacts with these to develop color when heated. Combinations with agents, (2) those that form oxazine dyes such as combinations of resorcin and nitroso compounds, or those that form azo dyes, (3) those that form azo dyes with diazonium salts and couplers, (4) ) A compound containing a compound having a secondary alcoholic hydroxyl group and a combination of a metal inorganic salt or a metal acetate, (5) a combination of a carbohydrate and a dehydrating agent, (6) a long-chain fatty acid metal salt and a phenol. Combination with sex substances, (
7) Combination of organic acid heavy metal salt and alkaline earth metal sulfide, (8) Combination of organic acid heavy metal salt and organic chelating agent, (9) Combination of heavy metal oxalate and sulfur compound, (10) Fatty acid Combination of metal salt and aromatic polyhydroxy compound, (11)
Examples thereof include a combination of an organic acid noble metal salt and an organic polyhydroxy compound, (12) a combination of an organic acid noble metal salt and an aromatic organic reducing agent, and (13) a combination of a higher fatty acid heavy metal salt and zinc dialkyldithiocarbamate. However, the composition is not limited to these combinations, and any composition that develops color by heating may be used.

Examples of such leuco dyes include 3,3-bis (p-dimethylaminophenyl) phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylphthalide, and 3,3-. Bis (p-dimethylaminophenyl) -6-aminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-nitrophthalide,
3,3-bis (p-dimethylaminophenyl) -4,5,6,7-tetrachlorophthalide, 3-dimethylamino-7-methylfluorane, 3-diethylamino-
7-Chlorofluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3-N-ethyl-N-ventylamino-6-methyl-7-phenylaminofluorane, 3-N-methyl- N-cyclohexylamino-6-methyl-
7-Phenylaminofluorane, 3-dibutylamino-7-o-chlorophenylaminofluorane, 3-diethylamino-7-o-chlorophenylaminofluorane, 3-N-ethyl-Np-tolyl-6-methyl- 7-Phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-pn-butylphenylaminofluorane, 3
-N-Methyl-N-propylamino-6-Methyl-7-Phenylaminofluorane, 3-dibutylamino-7-o-fluorophenylaminofluorane, 3-diethylamino-7-trifluoromethylphenylaminofluorane, 3-N-Ethyl-p-Toluidino-7-Methylphenylaminofluorane, Rhodamine B lactam, 3-Methylspirodinaphthopyran, 3-Ethylspirininaftpyrrane,
Examples include 3-benzyl spironaftpyran.

Examples of the color developer include 4-phenylphenol, 4-hydroxyacetquinone, 2,2'-dihydroxydiphenyl, n-butylbis (4-hydroxyphenyl) acetate, and methylbis (4-hydroxyphenyl). ) Acetate, iso-butylbis (4-hydroxyphenyl) acetate, 2,2'-
Methylenebis (4-chlorophenol), 2,2'-methylenebis (4-methyl-6-t-butylphenol), 4,4'-isopropyridendiphenol (also known as bisphenol A), 4,4'-isopropyridenebis (also known as bisphenol A) 2-Chlorophenol), 4,4'-isopropyridenebis (2-methylphenol), 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,3-di {2- (4- (4-)
Hydroxyphenyl) -2-propyl} benzene, 4,4'-ethylenebis (2)
-Methylphenol), 4,4'-thiobis (6-t-butyl-3-methylphenol), resorseal monobenzoate, 1,1-bis (4-hydroxyphenyl) -cyclohexane, 2,2'-bis ( 4-Hydroxyphenyl) -N-heptane, 4,4'-cyclohexylidenebis (2-isopropylphenol),
4,4'-Dihydroxy-diphenylsulfone, 4-hydroxy-4'-iso
-Propyloxy-diphenyl sulfone, 4,4'-dihydroxy-3,3'-
Dialyldiphenylsulfone, salicylate nilide, novolak type phenolic acid, benzoic acid, pt-butylbenzoic acid, o-chlorobenzoic acid, p-chlorobenzoic acid, dichlorobenzoic acid, trichlorobenzoic acid, m-hydroxybenzoic acid, p -Hydroxybenzoic acid, p-hydroxybenzoic acid benzyl ester, o-toluic acid, m-toluic acid, p-toluic acid, phthalic acid, isophthalic acid, terephthalic acid,
Carbetic acid, trimellitic acid, salicylic acid, 3-ethylsalicylic acid, 4-ethylsalicylic acid, 3-phenylsalicylic acid, 5-phenylsalicylic acid, 3-hydroxysalicylic acid, 4-hydroxysalicylic acid, 5-hydroxysalicylic acid, 6-hydroxysalicylic acid, 4 Examples thereof include dimethyl-hydroxyphthalate, α-naphthoic acid and β-naphthoic acid.

In addition to the above-mentioned thermochromic components, natural composition-based binders such as starches, celluloses, and proteins, or synthetic binders such as polyvinyl alcohol, acrylic, and styrene-based binders are mixed and used as binders. Examples thereof include iso-water-soluble or organic solvent-soluble resins.

Inorganic pigments such as calcium carbonate, magnesium carbonate, silicic acid, aluminum silicate, barium sulfate, titanium oxide, zinc oxide or acrylics are used as pigments to increase whiteness and opacity and improve running performance with respect to thermal heads. Organic pigments such as styrene and styrene are used.

Further, as additives, heat-soluble substances such as paraffin wax, stearic acid amide, ethylene bisstearoamide, zinc stearate, calcium stearate, and sulfonates such as dioctyl sulfosuccinate and sodium dodecylbenzene sulfonate. Alternatively, a surfactant such as a phosphate ester, an ultraviolet absorber such as a benzophenone type or a triazole type, a fluorescent dye or the like can be appropriately used in combination.

Further, a release agent such as silicone-based, fluorine-based, or funnel oil for improving peeling from the smooth body can also be preferably used.

The coating liquid for the heat-sensitive recording layer used in the present invention can appropriately combine these heat-coloring materials, binders, pigments, and other additives as necessary. For example, 5 heat-coloring materials are used. It is preferable that the content is ~ 50%, the binder is 3 to 40%, the pigment is 5 to 60%, and the other additives are 50% or less. Further, as the wetting liquid used for the above-mentioned wetting, a liquid that can dissolve or wet a binder such as water, toluene, mineral spirit, and hexane is appropriately selected.

Further, the coating liquid used for further coating on the dry heat-sensitive recording layer can be the same composition as the above-mentioned heat-sensitive recording layer coating liquid, but when the storage stability is particularly emphasized, the coating liquid can be used. Measures such as reducing the amount of heat-coloring material and increasing the amount of binder component, using a binder with strong storage resistance, or adding an ultraviolet absorber are used. On the contrary, when sensitivity is particularly important, adjustments such as using a highly sensitive thermochromic material and increasing the ratio are made as necessary.

The amount of the heat-sensitive recording layer applied is not particularly limited, but the total dry weight including the transfer layer or the rewetting layer is ² to 25 g / m 2, preferably 4-1.
It is 5 g / m ² . Further, the protective layer that does not contain the heat-sensitive coloring material or the layer that contains few heat-sensitive coloring materials is 1.
A range of 0 g / m ² or less, particularly 5 g / m ² or less is preferable.

As a method for producing the surface of the heat-sensitive recording sheet of the present invention, a general casting method (a method in which the coating liquid is brought into close contact with a smooth body in a plastic state and then peeled off after the plasticity is lost) is specifically described. The following two methods can be preferably applied. (Method A) This is a method of obtaining a thermal recording sheet by forming a transfer layer on the smooth body side and then transferring the transfer layer to the support side. More specifically, the transfer layer is applied onto the smooth body, and after being semi-dried or dried, it is bonded to the surface of the support or the surface of the thermal recording layer via an adhesive substance, and after bonding, it is peeled off from the surface of the smooth body. The method. At this time, the transfer layer does not necessarily have to contain a heat-developing component when the support already provided with the heat-sensitive layer is used. Finally, it suffices to contain a thermochromic component in one layer or in each layer. When it is necessary to dry the adhesive after joining the smooth surface and the support, the support is preferably breathable with an air permeability of 300 seconds or less, and in the case of an adhesive that does not require drying, It can also be used with a non-breathable film-like support.

(Method B) A heat-sensitive recording layer is applied to the support, and the support is bonded to the smooth body surface in a semi-dried state, a dry and re-wet state, or a dry and then heat-sensitive recording layer coating solution or a protective layer coating solution. This is a method of obtaining a thermal recording sheet having a smooth surface by drying the material while it is joined, and then peeling it off from the smooth material after drying. Among these methods, from the viewpoint of production stability, it is preferable to apply the thermal recording layer on the support, dry it once, and then apply the coating liquid again. At this time, the joint between the smooth body and the support At the inlet, adjustments are preferably made to allow continuous pooling of the coating. In this method, a breathable paper is suitable for the support, and an ^{undercoat layer containing a pigment and a binder as main components and having a coating amount of about 3 to 15 g / m 2 and} a backcoat layer if desired are also provided. good.

The smooth body used in the methods A and B has a sheet-like, roll-like, and endless belt-like shape, and the surface is parallel to the center line of the roughness curve based on the JIS-B-0601 method and has roughness. Those having a smooth surface having a contact rate of 20% or less, preferably 10% or less, with a straight line having a contact rate of 90% and a straight line drawn parallel to the center line at a position of 1.5 μm on the surface side. Used. If the straight line drawn in parallel with the center line at a position 1.5 μm on the surface side from the straight line having a contact rate of 90% and the contact rate with the roughness curve exceeds 20%, the smooth body surface Even if they are joined and dried, a high-quality heat-sensitive recording sheet cannot be obtained.

Further, when manufacturing a heat-sensitive recording sheet using these smooth bodies, if a material having a glossy surface is desired, a smooth body having a glossy appearance is used, and a matte-like heat-sensitive recording sheet is desired. In this case, the surface is matted by a chemical treatment or a treatment such as a sandblasting method, but in any case, the surface must have the above-mentioned surface smoothness. Such a material is a plastic film such as PET, PP, PE, or a metal, and a material having a metal-plated surface or a resin-processed material such as Teflon is preferable. Further, in order to improve the releasability, it is preferably treated with silicone, fluorine, a surfactant, wax or the like. In the present invention, a roll-shaped smooth body having a chrome-plated surface is preferable from the viewpoints of operability, durability, peelability, etc., and a Teflon-processed surface on the chrome-plated surface is also superior in terms of peelability.

0025

[Action and effect]

The surface of the heat-sensitive recording sheet obtained by drying while being bonded to the smooth body in a wet state as described above has a surface smoothness of the heat-sensitive recording layer at the center line of the roughness curve based on the JIS-B-0601 method. The contact rate between the straight line drawn 1.5 μm inward from the straight line intersecting with the roughness curve at 10% and parallel to the center line is 8
A smooth surface of 0% or more can be obtained, and the thermal recording sheet having such a smooth surface has good smoothness with respect to the thermal head and is excellent in image quality and sensitivity. By using a smooth body having a glossy or matte finish, it is possible to obtain a thermal recording sheet having a uniform glossy or matte surface appearance without deteriorating the image quality and sensitivity of the thermal recording sheet. ..

0026

【Example】

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the description of these Examples. The measurement method in the examples of the present invention is as follows. 1. 1. Gloss: Murakami Color Research Institute Co., Ltd. Gloss meter GM-3 Angle 75 ° 2. Image quality / sensitivity: Applied voltage 16.0V using a test machine manufactured by Matsushita Electronic Components Co., Ltd.
After drawing with a pulse width of 1.0 to 3.4 ms, the image density was measured with a Macbeth reflection densitometer (RD-914). In addition, the dot reproducibility of the image portion was evaluated by visual inspection and enlarged photographs. 3. 3. Smoothness: A Wangken type smoothness measuring machine was used. 4. Appearance: Gloss unevenness and background stains were visually observed and evaluated. 5. Optical surface roughness Rp: A microtopograph manufactured by Toyo Seiki Seisakusho Co., Ltd. was used. Measurement conditions: Applied pressure 10 kgf / cm ² Sampling time 100 ms 6. As the values of the average wavelength Rλa, the center line average roughness Ra, and the 10-point average roughness RRZ, the values output by the measuring device Surfcom 1500A were used.

Example 1 Solution A: 10 parts of leuco dye (3-N-ethyl-N-ventylamino-6-methyl-7-phenylaminofluorane: S-205 manufactured by Yamada Chemical Co., Ltd.), P-
20 parts of hydroxybenzoic acid benzyl ester, 5 parts of dibenzyl terephthalic acid, 10 parts of zinc stearate, and 30 parts of calcium carbonate dispersed with a sand grinder so that the average particle size is 2 μm or less, and 20 parts of binder (staroxide oxide). 15 parts, 5 parts of PVA) were mixed with water to prepare a heat-sensitive layer coating liquid having a solid content concentration of 23%. Using a cast coater as shown in FIG. 1, the solution A is applied to the glossy surface of a single glossy paper 1 having a paper density of ^{47 g / m 2} as a support with an air knife 3 so ^{that the dry weight is 3 g / m 2.} did. After that, it was dried by passing it through a hot air dryer 4, and then bonded to the smooth surface of the cylinder roll 8 using a press roll 5 having a hardness of 90 °. At this time, the liquid A was supplied from the liquid supply nozzle 6 at the joint inlet portion of the press roll 5 and the cylinder roll 8 so that the liquid pool 7 was continuously formed. The press pressure was adjusted so that the amount of the rewetting liquid applied was 1 g / m ² (4 g / m ^{2 including the lower layer) in terms of dry weight.} The heat-sensitive recording sheet weighed and applied in this way is dried by a hot air dryer 9 while being bonded to the smooth surface of the cylinder roll 8, and after drying, the heat-sensitive recording sheet 10 is peeled off from the surface of the cylinder roll 8. Obtained. The surface (smooth body surface) of the cylinder roll 8 in this embodiment has a mirror surface that has been chrome-plated and buffed. The obtained heat-sensitive recording sheet had a contact rate of 90% from a straight line having a contact rate of 10% on the roughness curve to a straight line 1.5 μm inside with the roughness curve, and was excellent in image quality and sensitivity. The glossiness was 45%, and the surface had a uniform glossy surface with no uneven gloss. The evaluation results are shown in Table 1.

Example 2 In Example 1, a thermal recording sheet was obtained in exactly the same manner as in Example 1 except that a cylinder roll having a matte surface was used as a smooth body. The surface of this cylinder roll is chrome-plated, buffed, and sandblasted to give a matte surface. The obtained heat-sensitive recording sheet had a contact rate of 93% from a straight line having a contact rate of 10% on the roughness curve to a straight line 1.5 μm inside with the roughness curve, and was excellent in image quality and sensitivity. The glossiness was 17%, and the surface had a uniform matte surface with no uneven gloss. The evaluation results are shown in Table 1.

Comparative Example 1 In the same manner as in Example 1, solution A was applied onto the support so as to have a dry weight of 6 g / m ² , dried with a hot air dryer, and wound as it was. Liquid A was further applied onto this heat-sensitive recording sheet so as to have a dry weight of 2 g / m ² (8 g / m ^{2 including the} bottom), and dried with a hot air dryer. Since the obtained heat-sensitive recording sheet had low smoothness, supercalender processing was performed to improve the smoothness, but both the image quality and the sensitivity were insufficient. The glossiness was 28%, and there were background stains and uneven gloss that seemed to be caused by the calendar processing. The thermal recording sheet had a contact rate of 53% from a straight line having a contact rate of 10% on the roughness curve to a straight line 1.5 μm inside with the roughness curve. The evaluation results are shown in Table 1.

Example 3 Liquid B (transfer layer coating liquid) ... 5 parts of leuco dye (S-205), bisphenol A2
PV of 10% aqueous solution as a binder by mixing 0 parts and 25 parts of ethylene bisstearoamide dispersed with an attritor so that the average particle size is 2 μm or less.
30 parts of A, 70 parts of oxidized starch in a 10% aqueous solution, and 40 parts of a styrene-maleic acid copolymer emulsion (35% concentration) were added. Further, 60 parts of a silica dispersion having a 20% concentration as a pigment was added to this mixed solution to prepare a coating liquid having a solid content concentration of 22%. A smooth body having a glossy surface obtained by cutting liquid B into B-4 size (PET 75 μm thickness:
Using a wire bar on Toray Industries, Inc.'s Lumirror), it was coated with WET so that it would be ^{10 g / m 2.} Semi-dried with hot air after coating (judged visually and by touch)
Then, liquid A was coated on a piece of glossy paper (47 g / m ^{2 of} paper density) with a dry weight of 6 g / m ² and joined using a rubber roller and dried as it was joined. A thermal recording paper was obtained by peeling the transfer layer from the film after drying. The obtained thermal recording paper had excellent surface properties and good image quality and sensitivity. The glossiness was 85%, which was homogeneous.

Example 4 The smooth body used in Example 3 was sandblasted to use a smooth body having a matte surface. This smooth body is drawn parallel to the center line of the roughness curve based on the JIS-B-0601 method and at a position 1.5 μm on the surface side from a straight line where the contact rate with the roughness curve is 90%. The contact rate with the straight line was 15%. Other conditions are Example 3
A thermal recording sheet was prepared in exactly the same manner as above. The obtained thermal recording sheet had a homogeneous matte surface with a glossiness of 15%, and both image quality and sensitivity were good.

Comparative Example 2 The smooth body used in Example 3 was sandblasted to use a smooth body having a matte surface. This smooth body is drawn parallel to the center line of the roughness curve based on the JIS-B-0601 method and at a position 1.5 μm on the surface side from a straight line where the contact rate with the roughness curve is 90%. The contact rate with the straight line was 43%. A thermal recording sheet was prepared in exactly the same manner as in Example 3. As can be seen from the performance evaluation results of the obtained heat-sensitive recording sheet, it had a homogeneous matte surface with a glossiness of 13%.
There were some omissions in the transfer layer, which seemed to be due to poor peeling, and the results were slightly inferior in both image quality and sensitivity.

Example 5 Liquid C ... 10 parts of leuco dye (S-205), 25 parts of P-hydroxybenzoic acid benzyl ester, 5 parts of dibenzyl terephthalate, 15 parts of zinc stearate, and 30 parts of aluminum silicate are averaged. Dispersed with a sand grinder so that the particle size is 2 μm or less and 20 parts of binder (10 parts of PVA, 10 parts of oxidized ester)
Part) was mixed with water to prepare a thermal layer coating liquid having a solid content concentration of 22%. This coating liquid C is applied to the glossy surface of a single-sided glossy paper (paper density 47 g / m ^{2 ) so that the dry weight becomes 7 g / m 2} at the coater head 3 of the coater as shown in FIG. It is dried by passing it through a hot air dryer 4 so as to be about 50%, and the coated surface of the obtained heat-sensitive recording sheet is joined to the cylinder roll 8 and dried, and after drying, it is peeled off from the roll and heat-sensitive recording is performed. A sheet was obtained. Here, the cylinder roll 7 is treated with a fluororesin to improve the peelability on the surface. The surface temperature of the roll is adjusted to 50 to 60 ° C., and a hot air blower 9 is installed on the outside of the roll to promote drying. Various evaluations were performed on the heat-sensitive recording sheet thus obtained, and the results are shown in Table 1. As can be seen from the results, the smoothness was 3000 seconds, there was no background fog, and the image quality and sensitivity were excellent.

Example 6 Liquid D: (Adjustment of heat-sensitive recording layer coating liquid) Leuco dye PSD-150 (Nippon Soda Processing Co., Ltd.) 10 parts, bisphenol A3
0 parts, 10 parts of ethylene bisstearyl amide, and 40 parts of calcium stearate dispersed in a sand mill so that the average particle size is 2 μm or less, and 25 parts of a binder (polyvinyl alcohol) are mixed with water to coat a thermal recording layer. I got D. (Formation of Thermal Recording Layer) The obtained coating liquid D was ^{applied and dried on a base paper of 60 g / m 2 so} as to have a dry coating amount of 6 g / m ² to obtain a thermal recording sheet. Liquid E: (Adjustment of protective layer coating liquid) 60 parts of acrylic coating agent (F-846 15% aqueous solution; manufactured by Showa Denko), 20 parts of oxidized starch (MS-3600 15% aqueous solution, manufactured by Nippon Foods) and 50% clay 10 parts of an aqueous dispersion, 10 parts of a 30% zinc stearate aqueous dispersion, and 1 part of dimethylol urea were mixed with water to prepare a protective layer coating solution E. The protective layer coating liquid E having the above composition was applied onto the recording layer of the heat-sensitive recording sheet obtained as described above so that the coating amount after drying was 3 g / m ^2, and then the coated surface was chrome-plated. The bonded state was dried, and after drying, the sheet was peeled off from a roll to obtain a protective layer-coated heat-sensitive recording sheet. The performance evaluation results of the obtained sheet are shown in Attachment Table 1. The obtained heat-sensitive recording sheet had little change in optical density in the imaged portion and the non-imaged portion with respect to water, alcohol, a plasticizer, etc., and was excellent in storage stability. In addition, both image quality and sensitivity
It was good.

Example 7 Liquid F (black color development first layer heat-sensitive recording layer component) 10 parts of leuco dye (3-N-methyl-N-cyclohexylamino-6-methyl-7-phenylaminofluorane: Shin Nisso Kako PSD-150) manufactured by Co., Ltd., 30 parts of bisphenol A, and 20 parts of zinc stearate dispersed with a sand grinder so that the average particle size is 2 μm or less, and then a 30% concentration aluminum silicate dispersion. 100 parts is added, and P of a 10% aqueous solution is further used as a binder.
Liquid F was prepared by adding 80 parts of VA and 70 parts of oxidized starch in a 10% aqueous solution. The coating solution concentration was set to 20% and used. Liquid G (blue color development second layer heat sensitive layer component) Leuco dye 10 parts (crystal violet lactone (CVL)) bisphenol A 20 parts, 1-hydroxy-2-naphthoic acid phenyl ester (HS-1094 manufactured by Dainippon Ink Co., Ltd.) 10 parts and 20 parts of zinc stearate each have an average particle size of 2
Mix those dispersed with a sand grinder to less than μm, then 40%
100 parts of calcium carbonate dispersion with a high concentration was added, and PVA1 was added as a binder.
The G solution was prepared by adding 200 parts of a 0% aqueous solution. The coating solution concentration was 22%. Liquid F was applied to woodfree paper (rice tsubo 53 g / m ² ) with an air knife coater so as to have a dry weight of 6 g / m ² to obtain a black coloring layer. Next, as the second layer, G solution is applied onto the first layer ^{with an air knife coater so that the dry weight is 4 g / m 2} , and then joined to the chrome-plated metal roll in the dry state in the latter half of the coating using a press roll. did. This heat-sensitive layer was dried in a state of being bonded to the metal roll, and after drying, the heat-sensitive layer was peeled off from the metal roll to obtain a multicolored heat-sensitive recording paper. The obtained thermal recording paper had a smoothness of 350 seconds, and no background fog was observed. Next, as a result of drawing with an applied voltage of 12.0 V and a pulse width of 3.0 ms as a blue color image and an applied voltage of 16.0 V and a pulse width of 2.5 ms as a black color image, the blue image density was 0.55 and the black image density was 0.55. The density was as high as 1.37, the dot reproducibility was good, and no color mixing was observed.

Comparative Example 3 H liquid ... Silicon oxide as a pigment (Mizukasil P-832: Mizusawa Chemical Industry Co., Ltd.)
50 parts of average particle size 2.7 μm, 50 parts of organic hollow pigment (Lopec OP-84J: average particle size 0.55 μm manufactured by Nippon Acrylic Chemical Co., Ltd.), and styrene-butadiene copolymer latex (solid content) as a binder. 48%) 30 parts were mixed to adjust a coating liquid having a solid content concentration of 30% to obtain an undercoat layer coating liquid H. H liquid in paper density 4
It was prepared under the same conditions as in Comparative Example 1 except that a 5 g / m ² high-quality paper coated with a dry weight of 7 g / m ^{2 was used as a support.} Table 1 shows the performance evaluation results of the obtained sheet. As can be seen from the results in Table 1, those having an average wavelength of 60 μm or less were excellent in image quality, sensitivity and appearance.

[Simple explanation of drawings]

FIG. 1 It is a conceptual diagram of the manufacturing apparatus of the thermal recording sheet used in the Example of this invention.

FIG. 2 It is explanatory drawing of the roughness curve and the contact rate calculation method.

[Table 1]

Claims (3)

[Claims] 1. When forming the outermost surface layer of a heat-sensitive recording sheet provided with a heat-sensitive recording layer that develops color by heating on a support, the outermost surface layer is parallel to the center line of the roughness curve based on the JIS-B-0601 method. And 1.5μ from the straight line where the roughness curve and the contact rate are 90% to the surface side
The outermost surface layer in a wet state (plastic state) was joined to a smooth body surface having a smooth surface having a contact rate of 20% or less with a straight line drawn parallel to the center line at the position of m. In the method for producing a high-quality thermal recording sheet in which the outermost surface layer is separated from the smooth body surface after being dried in a dry state to make the outermost surface layer dry (non-plastic state), the outermost surface layer is in a wet state. , A semi-dry state, a state in which a solvent is applied to a dry surface and re-wetted, or a state in which a heat-sensitive recording layer coating solution or a protective layer coating solution is further applied to a dry surface and re-wetted. A method for manufacturing a high-quality heat-sensitive recording sheet, which is characterized in that. 2. The method for manufacturing a high-quality thermal recording sheet according to claim 1, wherein the support is an undercoat paper having an air permeability of 300 seconds or less. 3. The method for manufacturing a high-quality thermal recording sheet according to claim 1, wherein the thermal recording layer comprises a plurality of thermal recording layers that develop colors in different hues.