JPH0720736B2 - Surface treatment method for thermal recording sheet - Google Patents

Description

The present invention relates to a surface treatment method for a heat-sensitive recording sheet, which is suitable for high-speed recording, which is excellent in smoothness, image quality, whiteness, color density, etc. without uneven coloring. And a method for producing a heat-sensitive recording sheet having

(Prior Art) A thermosensitive recording paper utilizing a heat-coloring reaction between a so-called basic colorless dye, which is usually colorless or light-colored, and a color developing agent such as phenols and organic acids, is disclosed in JP-B-43-4160 and JP-B-45- No. 14039,
It was announced in Japanese Patent Application Laid-Open No. 48-27736 and is widely put into practical use. In general, a thermal recording paper is prepared by separately grinding a basic colorless dye and a color developer into fine particles, and then mixing them together to form a binder, a filler, a sensitivity improver, a lubricant and other auxiliaries. A coating solution obtained by adding the composition is applied to a support such as paper and film, and color recording is obtained by an instantaneous chemical reaction by heating. In this case, color development of various hues can be obtained by selecting the type of colorless dye.

These thermal recording papers are being applied to a wide range of fields such as recording recorders for measurement in the medical field or industrial field, terminals for computers and information communication, facsimiles, printers of electronic desk calculators, ticket vending machines.

In recent years, thermal recording methods have become widespread and their applications have been diversified, and high-speed recording and high image density, that is, high density for increasing resolution have been emphasized. For this reason, the thermal energy of the thermal head of the recording device tends to become smaller and smaller, and for the thermal recording paper used for this,
It is required to have sufficient coloring sensitivity to obtain clear color recording even with a small amount of heat.

The smoothing treatment on the surface of the recording layer is also one of the measures, and the heat conduction efficiency can be improved by the good contact between the head and the surface of the recording layer.

(Problems to be Solved by the Invention) However, when a high-sensitivity recording sheet containing a composition for enhancing recording sensitivity is processed by a super calendar or a machine calendar, the recording layer surface is highly smoothed, but the color develops over the front surface of the recording layer. The unevenness easily occurs and the whiteness of the recording layer is reduced.

In view of the current situation, the present invention proposes a method for performing a smoothing process without causing color unevenness.

(Means for Solving the Problem) The applicant of the present invention has previously proposed a new calendar device as Japanese Patent Application No. 63-245524, but the present invention uses this calendar device to smooth the surface of the recording layer of a thermal recording sheet. It is proposed to be used for processing.

That is, the surface treatment method for a heat-sensitive recording sheet according to claim 1 of the present invention relates to a heat-sensitive recording sheet for a pressure nip composed of a metal roll and a long endless elastic belt that rotates and runs together with a backing roll. Is passed through so that the surface of the heat-sensitive recording layer or the protective layer is in contact with the surface of the metal roll, and the surface of the heat-sensitive recording layer or the protective layer is smoothed. A surface treatment method according to a second aspect is characterized in that the Beck smoothness is 200 to 2500 seconds in the first aspect.

FIG. 1 shows an example of a calendar device used in the smoothing process of the present invention, in which a metal roll 1 is rotatably attached to a calendar frame 10 via an attachment arm 11. On the other hand, the backing rolls 2 provided below the metal roll 1 so as to face each other are attached to a movable attachment arm 12 whose one end is pivotally attached to the calendar frame 10. A rotation drive device (not shown) is attached to the backing roll 2. Further, the operating portion of the booster 4 is attached to the free end side of the movable mounting arm 12, and the push-up pressure of the booster 4 pushes the movable mounting arm 12 upward with the pivot point as the fulcrum, and backing roll. 2 is in pressure contact with the metal roll 1. The endless elastic belt 3 is
Covering the nip part of the backing roll 2 and pressing it, it is stretched over the holding rolls 6a, 6b, 6c, 6d, the stretch roll 7, and the guide roll 8,
The correction of the traveling path of the endless elastic belt 3 when the movable mounting arm 12 is pushed upward by the pressure rising device 4 is performed by adjusting the position of the guide roll 8, and the tension is adjusted by the stretch roll 7.

In addition, the metal roll 1 may include steam, warm water,
A temperature adjusting device 13 for heating means such as electric induction or cooling means such as cold water is built in, and the surface temperature of the metal roll is adjusted to a high temperature at which the heat-sensitive recording layer is not colored. On the other hand, a cooling device 5 such as an air shower or a water spray device is provided on the traveling path of the endless elastic belt 3, and the heated endless elastic belt 3 is cooled appropriately. Sheet roll
14a and 14b are for feeding the heat-sensitive recording sheet 9 between the metal roll 1 and the endless elastic belt 3, and when the heat-sensitive recording sheet 9 is processed by the above-mentioned pair of rolls. The surface of the heat-sensitive recording layer on the side in contact with the metal roll 1 is strongly smoothed.

In the present invention, the calendering device used for the smoothing treatment is not limited to the structure shown in FIG. 1, but the backing roll, the endless elastic belt, and the metal roll are essential elements, and the pressure nip between the endless elastic belt and the metal roll is used. Anything can be used as long as it is used.

The structure of the endless elastic belt is not particularly limited, but usually, a heat-resistant fiber base cloth is used, which is adhered or coated with a synthetic resin having a compressive elasticity with heat resistance and pressure resistance, In particular, it is preferable that the surface is polished to a roughness of 1 to 20 μm or less. In this case, by thinning the synthetic resin layer, the influence of heat generation can be suppressed and the life can be extended. On the contrary, if the synthetic resin layer is thickened, the surface of the thermal paper will be improved well, but if it is too thick, there will be a problem in durability. Therefore, a desirable synthetic resin layer thickness is 1-10.
It is about mm. Further, when the synthetic resin layers are provided on both sides of the base cloth, the surface-polished synthetic resin layer on the back surface side is placed on the polishing table, so that it is in a state suitable for polishing. The endless elastic belt does not necessarily need the base cloth as long as the strength is sufficiently maintained, and may be made of only synthetic resin, or a belt made of rubber, metal or the like may be used instead of the base cloth. You may use it.

The endless elastic belt used in the present invention is composed of an elastic body having a Shore D hardness of 40 to 75 degrees defined by ASTM standard, D-2240, and is used in a normal super calendar or the like. An elastic belt that is extremely soft as compared with an elastic roll having a Shore D hardness of 75 to 85 degrees is used.

An elastic belt softer than 40 degrees requires an excessive nip line pressure in order to obtain sufficient surface smoothness, which significantly shortens the life of the elastic belt itself during operation. On the contrary, since it is difficult to prevent the occurrence of uneven coloring in an elastic belt harder than 75 degrees, an elastic belt having a hardness of 40 to 75 degrees is used.

The elastic body constituting the endless elastic belt is not particularly limited as long as the hardness falls within the above specific range, and examples thereof include natural rubber, styrene rubber, nitrile rubber, chloroprene rubber, chlorosulfonated ethylene rubber, and butyl rubber. , Polysulfide rubber, silicon rubber, fluorine rubber, urethane rubber, various plastic resins, cotton,
Specific examples include paper, wool, tetron, nylon and the like. Among them, the endless elastic belt using the urethane resin is easy to handle, the elastic belt has a long life, and the desired effects of the present invention can be efficiently exhibited.

In the method of the present invention, the metal roll constituting the endless elastic belt and the pressure nip as described above is not particularly limited, and a normal super calender, a chilled roll used in a smoothing device such as a gross calender, An alloy chilled roll, a steel roll, and a metal roll having the surface of the roll hard-chrome plated are appropriately selected and used. The form of the pressurizing device, the number of pressurizing nips and the like are appropriately adjusted according to a normal smoothing device, but the Bekk smoothness of the recording layer surface is 200 to 2500 in order to obtain sufficient high-speed recording suitability. It is desirable to adjust the time to be seconds.

The backing roll 2 is preferably a metal roll, and a chilled roll may be used as it is, or a crown-controlled roll may be used to adjust the paper thickness.

In the present invention, the pressurizing conditions during the smoothing treatment include the hardness of the elastic belt used, the type of recording sheet, the processing speed,
It is adjusted appropriately according to various processing conditions such as the number of nips, temperature and humidity conditions, but generally the nip linear pressure is 30 to 35
It is desirable to adjust within the range of 0 kg / cm. Nip line pressure 30kg
If it is less than / cm, even when a relatively hard elastic belt is used, the occurrence of color unevenness can be prevented, but satisfactory performance for high-speed recording aptitude cannot be obtained. Also, 35
With a nip linear pressure of more than 0 kg / cm, it is difficult to prevent color development even with a soft elastic belt.

The heat-sensitive recording sheet to be smoothed by the method of the present invention is not particularly limited.

Generally, as the basic colorless dye, triphenylmethane type, fluorane type, azaphthalide type, fluorene type and the like are used.

In addition, as the organic color developer, generally, bisphenol A,
4-hydroxybenzoic acid esters, 4-hydroxyphthalic acid diesters, phthalic acid monoesters, bis-
(Hydroxyphenyl) sulfides, 4-hydroxyphenyl aryl sulfones, 4-hydroxyphenyl aryl sulfonates, 1,3-di [2- (hydroxyphenyl) -2-propyl] -benzenes, 4-hydroxybenzoyloxy Benzoic acid ester, bisphenol sulfone and the like are used.

The binder used in the heat-sensitive recording layer has a degree of polymerization of 200 to 1900, completely saponified polyvinyl alcohol,
Partially saponified polyvinyl alcohol, carboxy modified polyvinyl alcohol, amide modified polyvinyl alcohol, sulfonic acid modified polyvinyl alcohol, butyral modified polyvinyl alcohol, other modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, Styrene-butadiene copolymer and cellulose derivatives such as ethyl cellulose and acetyl cellulose, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic acid ester, polyvinyl butyral polystyrol and their copolymers, polyamide resin, silicone resin, Examples include petroleum resin, terpene resin, ketone resin, and coumarone resin. These polymeric substances are used by dissolving them in solvents such as water, alcohols, ketones, esters, hydrocarbons, etc., or in the state of being emulsified or pasty dispersed in water or other medium, depending on the required quality. It can also be used together.

Further, as sensitizers, fatty acid amides such as stearic acid amide and palmitic acid amide, ethylene bisamide,
Montan wax, polyethylene wax, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, di-p-tolyl carbonate, p-benzyl biphenyl, phenyl α-naphthyl carbonate, 1,4-diethoxynaphthalene, 1-hydroxy-2 -Naphthoic acid phenyl ester, 1,2-di (3-methylphenoxy) ethane, bis [2- (4-methoxyphenoxy) ethyl]
Ether, dibenzyl-4,4-ethylenedioxydibenzoate, m-terphenyl and the like can also be added.

As the filler used in the present invention, it is possible to use all inorganic organic fillers used in the field of ordinary paper processing, for example, clay, talc, silica, magnesium carbonate,
Alumina, aluminum hydroxide, magnesium hydroxide,
Examples of the fine particles include barium sulfate, kaolin, titanium oxide, zinc oxide, calcium carbonate, aluminum oxide, urea, formalin resin, polystyrene and phenol resin.

The type and amount of the organic developer, basic colorless dye, sensitizer, and other various components used in the present invention are determined according to the required performance and recording suitability, and are not particularly limited, but usually, To 1 part of the basic colorless dye, 3 to 12 parts of organic developer, 3 to 12 parts of sensitizer, and 1 to 20 parts of filler are used, and the binder is 10 to 25% in the total solid content. Appropriate.

A desired heat-sensitive recording sheet can be obtained by applying a coating liquid having the above composition to an arbitrary support such as paper, synthetic paper, film and plastic.

The heat-sensitive recording sheet may be provided with a protective layer on the surface of the recording layer for the purpose of imparting water resistance, printing characteristics, imprintability, etc., or an underlayer may be provided between the recording layer and the support. The surface treatment method is also effective for such a thermal recording sheet. The protective layer is composed of various binders and various fillers used in the heat-sensitive recording layer.

The above-mentioned organic developer, basic colorless dye, sensitizer and, if necessary, materials to be added are finely divided into particles with a particle size of several microns or less by a grinder such as a ball mill, flitter, sand grinder or an appropriate emulsifying device. Then, the binder and various additives according to the purpose are added to obtain a coating liquid.

This coating liquid contains a release agent to prevent sticking of fatty acid metal salts, a lubricant such as fatty acid amide, ethylene bisamide, montan wax, and polyethylene wax to prevent color development under pressure, sodium dioctylsulfosuccinate, and dodecylbenzenesulfone. Sodium acid,
A dispersant such as sodium laurate, sodium lauryl alcohol sulfate, and alginate, a benzophenone-based or triazole-based ultraviolet absorber, other defoaming agent, a fluorescent brightening agent, and a water-proofing agent can be added.

(Operation) In the present invention, a calendar device having a novel structure, in particular, an endless elastic belt made of a soft material is used. Therefore, when the heat-sensitive recording sheet passes through the nip portion, the surface of the recording layer or the protective layer is pressed by the metal roll and the back surface is pressed by the endless elastic belt. When the metal roll presses, the unevenness on the surface of the recording layer is leveled and the unevenness on the back surface side is amplified, but all the unevenness is absorbed by the elasticity of the endless elastic belt. Therefore, the metal roll can be processed to have an appropriate smoothness without causing uneven coloring on the surface of the recording layer.

(Examples) Examples of the present invention will be shown below. In the description, parts indicate parts by weight.

[Example 1] Liquid A (dye dispersion) 3-diethylamino-6-methyl-7-anilinofluorane 2.0 parts 10% polyvinyl alcohol aqueous solution 4.6 parts water 2.5 parts liquid B (developing agent dispersion) bisphenol A 6.0 Part Zinc stearate 0.5 part 10% polyvinyl alcohol aqueous solution 30.0 parts C liquid (sensitizer dispersion) 4-biphenyl p-tolyl ether 4.0 parts 10% polyvinyl alcohol aqueous solution 5.0 parts water 3.0 parts Sandwiching each liquid of the above composition Grind to an average particle size of 1 micron with a grinder.

Next, the dispersion liquids are mixed at the following ratios to prepare a coating liquid.

Liquid A (dye dispersion) 9.1 parts Liquid B (developer dispersion) 36.5 parts Liquid C (sensitizer dispersion) 12.0 parts Kaolin clay (50% dispersion) 20.0 parts This coating liquid is applied with a bar blade coater. A 50 g / m ² base paper having a Bekk smoothness of 50 seconds which was not subjected to calendaring was applied and dried so that the application amount was 6.0 g / m ² . The thermal paper obtained was used with a calendering device composed of a metal roll having a diameter of 300 mm, a backing roll having a diameter of 300 mm, and an endless elastic belt made of urethane resin having a Shore D hardness of 53 degrees according to FIG. 1, with a nip linear pressure of 100 kg / cm and a nip width. Under the condition of 10mm,
A thermal recording paper was obtained by smoothing at a speed of 500 m / min. However, the following endless elastic belt was used. Nylon filament thread is used for the base cloth, and the belt running direction is 0.43 in diameter.
mm, width is 0.52 mm, and triple weave is used for thickness
It was 1.8 mm. Urethane resin was impregnated and applied from one side of this base fabric with an extruder to make the thickness of the surface urethane resin layer 1.67 mm.

[Examples 2 to 7] Thermal recording papers were obtained in exactly the same manner as in Example 1 except that an urethane resin endless belt having a Shore D hardness of 40, 45, 50, 60, 65, 70 degrees was used.

[Examples 8 to 10] In Example 1, an endless elastic belt made of urethane resin having a Shore D hardness of 53 degrees is used, and a nip line pressure is 80,200,250 kg / c.
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that m and nip widths were set to 7, 15 and 20 mm.

Example 11 A surface coating liquid was prepared by mixing 4 parts of aluminum hydroxide with 3.2 parts (solid content) of 10% polyvinyl alcohol,
The surface of the recording layer of the thermosensitive recording paper obtained in Example 1 was coated at a coating amount of 3.0 kg / m ² .

The thermal recording paper with the protective layer was smoothed under the same conditions as in Example 1.

[Comparative Example 1] Example 1 except that a soft nip calender using a normal control having a Shore D hardness of 82 degrees and a chilled roll was used, and smoothing treatment was performed under the conditions of a nip linear pressure of 70 kg / cm and a nip width of 5 mm. A thermosensitive recording paper was obtained in the same manner as in (1).

[Comparative Example 2] Example 1 except that a soft nip calender using Woolun paper having a Shore D hardness of 63 degrees and a chilled roll was used and smoothing treatment was performed under the conditions of a nip linear pressure of 100 kg / cm and a nip width of 5 mm. A thermosensitive recording paper was obtained in the same manner as in (1).

The 13 types of thermal recording papers thus obtained were subjected to a comparative test of Bekk smoothness and whiteness of the recording layer surface, print density, image quality and uneven coloring, and Table 1 shows the quality performance test results. The printing density is Matsushita Densen-Thermal facsimile UF.
-1000 is used, applied energy 0.58 mj / Dot, pulse width
The image density recorded at 0.97 milliseconds was measured by the Macbeth densitometer (RD-
914 amber filter was used). The whiteness was measured by Hunter whiteness. Regarding the image quality, the degree of print unevenness in the halftone portion of the above print was visually determined, and for the color unevenness, the degree of partial whiteness reduction of the paper surface was visually determined. The evaluation criteria for image quality, uneven coloring, and comprehensive judgment are as follows.

1: Excellent 2: Excellent 3: Normal 4: Slightly inferior 5: Extremely inferior (Effects of the Invention) By carrying out the smoothing treatment of the present invention, a thermal recording sheet having high speed recording suitability excellent in smoothness, image quality, whiteness, color density and the like can be obtained without causing uneven coloring.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a calendar device used in an embodiment. 1 ... Metal roll, 2 ... Backing roll, 3 ... Endless elastic belt, 9 ... Thermal recording sheet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Maruyama 5-21-1 Oji, Kita-ku, Tokyo Inside the Central Research Laboratory of Tojo Paper Co., Ltd. (56) Reference JP-A-49-60744 (JP, A) JP JP-A-58-65694 (JP, A) JP-A-59-155094 (JP, A) JP-A-55-21219 (JP, A)

Claims (2)

[Claims] 1. A heat-sensitive recording sheet comprising a sheet-like support, a heat-sensitive recording layer containing a basic colorless dye and an organic color developer as main components, and a protective layer provided on the upper surface of the support if necessary. In the method of smoothing the surface, the surface of the heat-sensitive recording layer or the protective layer is formed of the metal with respect to a pressure nip formed of a metal roll and a long endless elastic belt that rotates while traveling with a backing roll. A surface treatment method for a heat-sensitive recording sheet, characterized in that the surface of the heat-sensitive recording layer or the protective layer is smoothed by passing the paper so as to be in contact with the surface of the roll. 2. The surface treatment method for a heat-sensitive recording sheet according to claim 1, wherein the surface of the heat-sensitive recording layer or the protective layer is smoothed to a Beck smoothness of 200 to 2500 seconds.