JPH11254822A - Reversible thermal recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the wear of the head of a recording printer without defects in a recorded part and ensure that there is no defective running of a recording medium inside the recording printer, in a reversible thermal recording medium which is capable of developing a color and decoloring by controlling heating conditions and maintaining the color development state and the decoloring state at ordinary temperature. SOLUTION: This reversible thermal recording medium is formed of a colorless or pale dye precursor and a heat-sensitive recording layer containing a developer which reversibly makes the dye precursor develop a color or decolorized, and performs the color development and the decoloring by difference in the heating temperature. In this case, under environments at a temperature of 20 deg.C and a relative humidity of 65%, the surface electric resistance value on the surface of the heat-sensitive recording layer side is 1×10<13> Ω/(square) or less and the coefficient of a surface static friction is 0.65 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording medium capable of performing color development and decoloring by controlling heating conditions and maintaining the color developing state and the color decoloring state at room temperature. To elaborate further,
The present invention relates to a reversible thermosensitive recording medium having extremely little head wear of a recording printer and having no defects in a recording portion.

[0002]

2. Description of the Related Art Conventionally, heat-sensitive recording media have a compact recording device, are inexpensive, and are easy to maintain. Therefore, computers, measuring instruments, registers, CD / ATMs, facsimile machines, automatic ticket vending machines, handy terminals, etc. However, recently, it has been used as a magnetic heat-sensitive card such as a prepaid card or a point card due to its combination with magnetic recording. In these magnetic cards, the magnetic information is rewritten each time it is used, but the thermal recording image is not rewritten. Therefore, new information such as the residual number is added to the portion where no image is recorded. However, since the area of the recordable portion is limited, the actual situation is that the amount of information to be thermally recorded is unavoidably reduced, or the card is recreated when the recording area is exhausted. As means for solving such a problem, development of a reversible thermosensitive recording medium which can be rewritten any number of times is strongly desired.

[0003] Against the background of garbage problems and deforestation problems that have been actively discussed in recent years, there is a demand for the recycling of thermal recording paper. There are various methods for regenerating thermosensitive recording paper. Among them, as a versatile method that does not require a large device such as a deinking device, the development of a reversible thermosensitive recording material that can be rewritten many times has been developed. Is desired. Further, the reversible thermosensitive recording medium has attracted attention as a recording material for a simple display as disclosed in JP-A-3-233490 and JP-A-5-42762, and is suitable for these apparatuses. The development of a reversible thermosensitive recording medium is also strongly desired.

[0004] Against this background, various reversible thermosensitive recording media have been proposed. For example, JP-A-63-107
584, JP-A-4-78573 and 4-
Japanese Patent No. 358878 and the like disclose a polymer type reversible thermosensitive recording medium utilizing a change in transparency due to heating conditions. In this type, the contrast between the color-developed portion and the decolored portion is low, visibility in a dark place is poor, and a white image is recorded on a color-developed area, so that a so-called paper-like recording material is obtained. Is also difficult.

As a method for improving these points, a dye-type reversible thermosensitive recording material which enables reversible recording while using a dye used in a conventional thermosensitive recording material has been proposed. The dye-type reversible thermosensitive recording medium can easily record a color image on a white background, and has a relatively high contrast because it is a recording method using a change in absorption wavelength due to heating conditions. As the dye type reversible thermosensitive recording medium, for example, the following are disclosed.

[0006] JP-A-5-124360 and JP-A-6-210954 disclose a method in which an organic phosphoric acid compound having a long-chain alkyl group or a phenolic compound is used as a developer. However, when erasing, there are drawbacks that the color may not be sufficiently erased, and the storability of the color image may be insufficient. In addition, the applicant of the present invention has proposed in JP-A-9-272261 a dye-type reversible thermosensitive recording material having excellent storage stability by using a developer having a long-chain alkyl group and a sulfonyl (thio) urea group. .

By the way, the reversible thermosensitive recording medium differs from a normal thermosensitive recording medium in that recording and erasing are performed repeatedly.
Foreign matter adheres to the surface of the recording medium during recording and storage, which causes problems such as printing failure and head wear, especially when barcodes and small characters are recorded, leading to trouble such as reading errors. . In addition, when the reversible thermosensitive recording medium is used for a point card or the like, the recording medium is stored in various situations, and a foreign substance easily adheres to the surface due to triboelectric charging. In addition, there is a problem in practical use, such as poor color erasure of the foreign matter-attached portion on the recording medium, which deteriorates the visual impression. Furthermore, when these recording materials are frictionally charged,
There are also problems such as running defects such as jamming and double feeding in the printer.

[0008] In a normal thermosensitive recording medium, it has been proposed to regulate the electric resistance value of the surface layer of the recording medium to improve the running failure in a printer (Japanese Patent Laid-Open No. 60-4629).
4). That is, a method of providing a protective layer containing a water-soluble polymer, a filler and a conductive agent on the thermosensitive coloring layer and reducing the surface resistance to 10 ¹² Ω or less. Sufficient improvement is not seen for running failure, and it may worsen depending on the type of conductive agent. In particular, in the case of the reversible thermosensitive recording material as the object of the present invention, that is, the reversible thermosensitive recording material in which both coloring and decoloring are performed by heating, since the sheet is repeatedly heated, the surface resistance is simply controlled. The problem of poor running alone is not solved.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a reversible thermosensitive recording medium capable of performing color development and decoloring by controlling heating conditions and maintaining the color developing and decoloring states at room temperature. It is an object of the present invention to provide a reversible thermosensitive recording medium in which the wear of a head of a printer is extremely small, there is no defect in a recording portion, and there is no running defect in the recording printer.

[0010]

In order to solve the above problems, the present invention employs the following constitution. That is, the present invention
"On a sheet-like support, formed by providing a heat-sensitive recording layer containing a colorless or light-colored dye precursor and a developer for reversibly developing and decoloring the dye precursor, the difference in heating temperature In a reversible thermosensitive recording medium which develops and decolors by heat, the surface electric resistance value of the surface of the thermosensitive recording layer side is 20
1 × 10 ¹³ Ω /
□ or less, and the coefficient of static friction of the surface is 0.65 or less ”.

Usually, a reversible thermosensitive recording medium is composed of an organic substance, a polymer substance, and an inorganic substance having a high insulating property, and the surface electric resistance value is not considered at all. According to this, it has been found that a conventional reversible thermosensitive recording medium generally has a surface electric resistance value of 1 × 10 ¹⁴ Ω / □ or more and is located in a region where triboelectricity is liable to occur.

Under these circumstances, foreign matter easily adheres to the surface of the recording medium, resulting in recording defects such as missing dots and wear of the head. The foreign matter is mainly composed of paper dust, paint residue, and ordinary dust, and adheres to the recording medium due to frictional electrification generated during surface treatment, finish processing of the recording medium, running in the recording apparatus, storage of the recorded matter, and the like. When the size of the foreign matter is 10 to 1000 μm, it causes recording defects and head wear, and the size of 1000 μm or more does not adhere much on the recording layer. Does not affect head wear.

In order to solve these problems, the present inventors have first studied a method of suppressing the generation of foreign matter and a method of removing attached foreign matter immediately before recording. These methods have obtained some effects. There are drawbacks such as not being suitable for mass production and the equipment being expensive, and have not been adopted. On the other hand, the recording medium of the present invention has a low surface resistance value and prevents the adhesion of foreign substances less than 1000 μm, and has a remarkable effect in preventing recording defects and head wear caused by the foreign substances.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the surface of the heat-sensitive recording layer on which the surface electric resistance and the coefficient of friction are measured is the surface of the outermost layer on the side where the heat-sensitive recording layer exists, and the protective layer is formed of one or more layers. In some cases, the outermost protective layer is the outermost layer,
When there is no protective layer, the thermosensitive recording layer is the outermost layer. The easiest way to reduce the surface electric resistance to 1 × 10 ¹³ Ω / □ or less is to include one or more electric resistance adjusting agents in the outermost layer. The mixing amount of the electric resistance adjusting agent is such that the surface electric resistance value of the outermost layer becomes 1 × 10 ¹³ Ω / □ or less under an environment of 20 ° C. and a relative humidity of 65%.

The electric resistance adjusting agent used in the present invention is not limited thereto, but includes the following. (1) Metal oxides such as zinc oxide, tin oxide, antimony oxide and surface-treated titanium oxide (2) Metal halides such as magnesium chloride, potassium oxide, potassium bromide, zinc chloride and sodium chloride (3) Polyvinyl benzyl trimethyl ammonium chloride, polydimethyl diallyl ammonium chloride, triethylammonium styrene acrylate chloride quaternary ammonium salt polyelectrolyte, such as chloride (4) glycerin, magnesium chloride (Mg ₂ Cl ₂ · 6
H ₂ O), hygroscopic substances such as calcium chloride (CaCl ₂ .6H ₂ O), etc. Note that metal halides may cause a corrosive effect on some of the recording heads at high temperatures and are not sufficient for use. You need to pay attention.

It is also possible to add the above-mentioned electric resistance adjusting agent not only to the outermost layer but also to the coloring layer and the intermediate layer. The amount of addition to the recording layer and the intermediate layer is the same as that to the surface layer, and the surface electric resistance of the outermost layer is 1 ×.
It is necessary to adjust it appropriately so as to be 10 ¹³ Ω / □ or less.

The added amount of the electric resistance adjusting agent is 1 × 1
0 ¹³ Ω / □ at the same time that falls below, the static friction coefficient of the surface layer must be adjusted to 0.65 or less.
This is because the surface becomes sticky when an electric resistance adjuster, particularly an ion conductive type conductive agent such as a quaternary ammonium salt polymer electrolyte, is used, leading to poor running such as jamming in the printer. The present inventors have studied the prevention of recording defects and the improvement of running defects, and as a result, have completed the present invention. The addition amount of the electric resistance adjusting agent for achieving both the surface electric resistance value and the static friction coefficient varies depending on the electric resistance adjusting agent used, and also greatly changes depending on other materials of the surface layer. . As a method of controlling the static friction coefficient, for example, when an ion conductive type conductive agent is added to the outermost layer as an electric resistance adjusting agent, various pigments are added to the outermost layer to control the static friction coefficient. The content of the pigment in the outermost layer is preferably 1 to 80% by weight, and particularly preferably 20 to 60% by weight. The coefficient of static friction is appropriately adjusted so as to be 0.65 or less, preferably 0.5 or less.

As a method of reducing the electric resistance value to 1 × 10 ¹³ Ω / □ or less except for adding the electric resistance adjusting agent, a method of increasing the water content of the recording medium can be mentioned. In the production of ordinary thermosensitive recording materials and reversible thermosensitive recording materials, moisture is also controlled, but this is for the purpose of preventing quality deterioration such as blocking and background fogging. Did not. The present inventors have conducted intensive studies on the moisture and the surface electric resistance of the recording medium. As a result, the surface electric resistance was controlled to 1 × 1 by controlling the moisture of the recording medium.
A recording medium of 0 ¹³ Ω / □ or less was obtained. That is, when paper is used as the support, 5.0% to 10.0%, preferably 6.0%.
It is desirable to set the range to 8.5%. When synthetic paper is used as the support, the range is preferably 0.01 to 1.0%, and more preferably 0.1 to 0.7%. If the water content falls below this range, the electrical resistance of the surface increases, making it easier to adsorb dust and dirt in the air.If the water content exceeds the range, blocking during the manufacturing process and background fogging during long-term storage It is not preferable because it causes a practical problem such as generation of the slag.

The reversible thermochromic recording and decoloring method of the reversible thermosensitive recording medium according to the present invention is characterized in that the thermosensitive coloring layer of the recording medium is heated to color-record an image, and after the recording has been used,
The heat-sensitive coloring layer is heated at a temperature lower than the coloring heating temperature to erase the color-developed image.

In the reversible thermosensitive recording medium of the present invention, the thermosensitive recording layer containing the dye precursor and the color developer rapidly develops a color by heating, and the developed state is maintained at room temperature by rapidly cooling. On the other hand, the color image portion held at room temperature can be erased by heating to a color development temperature or lower, and the decolored state is maintained even when cooled to room temperature. The mechanism of this decolorization is unclear, but when the color former is heated below the color development temperature, the long-chain alkyl groups in the color developer are oriented to induce crystallization of the color developer, causing the dye to develop color. It is considered that the agent separates and discolors. Generally, the heating temperature for color development is 80 to 180 ° C., the temperature range in which decoloration occurs is 50 to 120 ° C., and lower than the color heating temperature. Generally, color development is performed by a thermal head or the like, which is easy to cool quickly after heating.
This is performed by maintaining the temperature in a temperature range equal to or lower than the color heating temperature, and there is no need to control the heating / cooling rate. The temperature holding time at the time of decoloring is preferably 0.1 second or more.

As the developer used in the reversible thermosensitive recording medium of the present invention, a compound represented by the following formula (I), (II) or (III) is preferable.

[0022]

Embedded image (However, R ₁ represents a member selected from a naphthyl group or a phenyl group substituted by a hydrogen atom, a halogen atom, a lower alkyl group and a lower alkoxy group;
₁ is the following chemical formula:

Embedded image Represents one member selected from the divalent group represented by
Represents an integer of 10 to 29. )

[0023]

Embedded image (However, Y ₂ is the same as Y _1, m represents an integer of 11-30.)

[0024]

Embedded image (However, p represents an integer of 14 to 30.)

In the above formula, the length of the long-chain alkyl group needs to be 11 or more, and preferably 30 or less. Even in that region, it is more preferable that the number is 14 to 21. If the number of carbon atoms is less than 11, the decoloring ability does not reach a practical level, and if it exceeds 30, the color developing ability may be reduced.

Specific examples of the aromatic compound of the formula (I) used as a color developer in the reversible thermosensitive recording medium of the present invention are represented by the following chemical formula:

Embedded image Is a compound represented by

In the reversible thermosensitive recording medium of the present invention, specific examples of the aromatic compound of the formula (II) used as a color developing agent are represented by the following chemical formula:

Embedded image Is a compound represented by

Further, specific examples of the compound of the formula (III) used as a developer in the reversible thermosensitive recording medium of the present invention are represented by the following chemical formula:

Embedded image Is a compound represented by These compounds may be used alone or in combination of two or more.

The dye precursor used in the present invention includes:
Leuco compounds such as triaryl, diphenylmethane, thiazine, spiro, lactam, and fluoran compounds can be preferably used. Specific examples are shown below. As the dye precursor giving black color, 2,2-bis @ 4-
[6 ′-(N-cyclohexyl-N-methylamino)-
3'-methylspiro [phthalide-3,9'-xanthen] -2'-ylamino] phenyl} propane, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-
Diethylamino-7- (m-trifluoromethylanilino) fluoran, 3- (N-isoamyl-N-ethylamino) -7- (o-chloroanilino) fluoran, 3-
(N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-2-tetrahydrofurfurylamino) -6-methyl-7-anilinofluoran, 3 -Diethylamino-6-chloro-7-anilinofluoran, 3-di (n-butyl) amino-6-
Methyl-7-anilinofluoran, 3-di (n-amyl) amino-6-methyl-7-anilinofluoran, 3
-(N-isoamyl-N-ethylamino) -6-methyl-7-anilinofluoran, 3- (Nn-hexyl-
N-ethylamino) -6-methyl-7-anilinofluoran.

Further, 3- [N- (3-ethoxypropyl) -N-ethylamino] -6-methyl-7-anilinofluoran, 3- [N- (3-ethoxypropyl) -N
-Methylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-7- (2-chloroanilino)
Fluoran, 3-di (n-butyl) amino-7- (2-
Chloroanilino) fluoran, 3-diethylamino-6
-Methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (2,6-dimethylanilino) fluoran, 3-diethylamino-6-methyl-7-
(2,4-dimethylanilino) fluorane, 2,4-dimethyl-6- (4-dimethylaminoanilino) fluoran and 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilino At least one kind such as fluoran can be used.

Among the above fluoran compounds, 2,2-
Bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-
Xanthene] -2′-ylamino] phenyl} propane is particularly preferred.

In the present invention, a conventionally known color developer comprising a phenol or an organic acid and a sulfonyl (thio) urea aromatic compound having no long-chain alkyl group as long as the desired effect is not impaired. Can be used in combination with the sulfonylurea developer having a long-chain alkyl group according to the present invention.

These conventional developers are, for example, 2,2-
Bis (4-hydroxyphenyl) propane (bisphenol A), 1,1-bis (4-hydroxyphenyl)-
1-phenylethane, 1,4-bis (1-methyl-1-
(4′-hydroxyphenyl) ethyl) benzene, 1,
3-bis (1-methyl-1- (4'-hydroxyphenyl) ethyl) benzene, dihydroxydiphenyl ether (JP-A-1-180382), benzyl p-hydroxybenzoate (JP-A-52-140483), bisphenol S, 4-hydroxy-4'-isopropyloxydiphenyl sulfone (JP-A-60-13)
852), 1,1-di (4-hydroxyphenyl) cyclohexane, 1,7-di (4-hydroxyphenylthio) -3,5-dioxaheptane (Japanese Unexamined Patent Publication No.
52694), 3,3'-diallyl-4,4'-
Dihydroxydiphenyl sulfone (JP-A-60-208)
286).

Further, N- (p-toluenesulfonyl) -N'-phenylurea, N- (p-toluenesulfonyl) -N '-(p-methoxyphenyl) urea,
-(P-toluenesulfonyl) -N '-(o-tolyl)
Urea, N- (p-toluenesulfonyl) -N '-(m
-Tolyl) urea, N- (p-toluenesulfonyl)-
N '-(p-tolyl) urea, N- (p-toluenesulfonyl) -N'-benzylurea
No. 2061), 4,4′-bis (p-toluenesulfonylaminocarbonylamino) -diphenylmethane,
4,4'-bis (o-toluenesulfonylaminocarbonylamino) -diphenylmethane, 4,4'-bis (benzenesulfonylaminocarbonylamino) -diphenylmethane, 1,2-bis [4 '-(p-toluenesulfonylaminocarbonyl) Amino) phenyloxy] ethane, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenyl ether and 3,3′-
Bis (p-toluenesulfonylaminocarbonylamino) diphenylsulfone (as described in JP-A-5-14735)
No. 7).

The reversible thermosensitive recording medium of the present invention may contain a thermofusible substance generally known as a sensitizer in the thermosensitive recording layer. These include, for example, oxalic acid diesters (JP-A 64-1583), di (4-methylbenzyl) oxalate (JP-B 5-62597), 1,
2-bis (m-tolyloxy) ethane (JP-A-60-5)
6588), diphenyl sulfone (JP-A-60-1985)
15667), p-benzylbiphenyl (Japanese Patent Application Laid-Open No. 60-82382), 1,4-bis [2- (4-
Methylbenzyloxy) ethoxy] benzene, these compounds, in addition to the ability to enable high density color development of a reversible thermosensitive recording medium with relatively low applied energy, promote the decoloration reaction and increase the reversibility. It also has the ability to improve.

The heat-sensitive recording layer of the present invention may further contain waxes and pigments within a range not to impair the effects of the present invention, and usually contains a binder. Known waxes such as paraffin, amide wax, bisimide wax, and metal salts of higher fatty acids can be used.

Examples of the pigment include inorganic fine particles such as silica, clay, calcined clay, talc, calcium carbonate, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, and surface-treated calcium carbonate and silica. In addition to powder, organic fine powder such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin can be used. As the binder, polyvinyl alcohol of various molecular weights,
Starch and derivatives thereof, methoxycellulose, carboxymethylcellulose, methylcellulose, cellulose derivatives such as ethylcellulose, sodium polyacrylate,
Polyvinylpyrrolidone, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and Water-soluble polymer materials such as casein, and polyvinyl acetate, polyurethane,
Latexes such as styrene / butadiene copolymer, polyacrylic acid, polyacrylate, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, and styrene / butadiene / acrylic copolymer Can be used.

In the thermosensitive recording layer of the reversible thermosensitive recording material of the present invention, the content of the dye precursor is generally preferably from 5 to 40% by weight of the dry weight of the thermosensitive recording layer, and the content of the developer Is preferably 5 to 50% by weight of the dry weight of the heat-sensitive recording layer. 5% by weight of developer
If the amount is less than 50%, the color developing ability becomes insufficient. Even if it is used in a large amount exceeding 50% by weight, the color developing ability is saturated, and there is no particular improvement in the contrast between the coloring density and the decoloring density. May be economically disadvantageous. The content of the sensitizer of the present invention is generally 5 to 5 times the dry weight of the heat-sensitive recording layer.
It is preferably 0% by weight. When the content of the sensitizer is less than 5% by weight, the effect of accelerating the decoloring is insufficient.
When used in a large amount exceeding the weight%, the color density may be insufficient.

Further, the heat-sensitive recording layer is formed of a phenol, an organic acid, or a sulfonyl (thio) having no long-chain alkyl group.
When a conventionally known color developer comprising a urea-based aromatic compound is contained, its content is preferably 10% by weight or less of the weight of the heat-sensitive recording layer. Phenols, organic acids,
Alternatively, if the content of a conventionally known color developer comprising a sulfonyl (thio) urea-based aromatic compound having no long-chain alkyl group is more than 10% by weight, the decoloring reaction is inhibited, and the color-developing portion and the decoloring portion May decrease in contrast.

When waxes and pigments are contained in the heat-sensitive recording layer, their contents are 5 to 20% by weight, respectively.
It is preferably from 0 to 50% by weight, and the content of the binder is generally from 5 to 20% by weight.

The support used in the reversible thermosensitive recording medium of the present invention has paper (including acidic paper and neutral paper) used for the conventional thermosensitive recording medium, and a surface coated with a pigment, latex or the like. It can be selected from glass paper, conductive rubber sheet and the like, in addition to plastic paper such as coated paper, laminated paper, synthetic paper made of polyolefin resin, polyolefin, polyester, polyimide and the like. On at least one surface of such a support, a coating solution containing a mixture of the above-mentioned required components is applied and dried to produce a reversible thermosensitive recording medium. The coating amount is preferably from 1 to 15 g / m ² in a state where the coating liquid layer has dried, 2 to 10 g / m ² is particularly preferred.

In the present invention, an undercoat layer may be provided below the reversible thermosensitive coloring layer. Further, a back layer can be provided on the back surface of the reversible thermosensitive recording medium to prevent blocking at the time of contact between the surfaces, suppress permeation of water or oil from the back surface, and control curl. Further, a coating layer such as a protective layer or a printing layer can be formed on the reversible thermosensitive coloring layer in order to improve heat resistance, printing suitability, and repeated durability of coloring and decoloring.

In the present invention, the reversible thermosensitive recording medium can be further processed in order to increase the added value of the reversible thermosensitive recording medium to give a higher function. For example, adhesive paper, re-wet adhesive paper, delayed-tack paper by applying processing with adhesive, re-wet adhesive, delayed-tack adhesive on the back surface, or reversible heat-sensitive that can be magnetically recorded by magnetic processing It can be a recording medium. In addition, a recording paper capable of recording on both sides can be provided by using the back surface to have a function as thermal transfer paper, inkjet paper, carbonless paper, electrostatic recording paper, and xerographic paper. Of course, a double-sided reversible thermosensitive recording medium can also be used. The device for recording (coloring) and erasing (erasing) images can be selected from thermal heads, thermostats, heating rollers, hot pens, sheet heating elements, laser light, infrared light, etc., depending on the purpose of use. It is not particularly limited to these.

[0044]

The present invention will be specifically described below with reference to examples. Unless otherwise specified, “parts” and “%” represent “parts by weight” and “% by weight”, respectively. <Example 1> A reversible thermosensitive recording medium was prepared by the following operation. Preparation of Dispersion A: 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthen] -2'-ylamino] f Enyl @ propane 20 parts 10% -polyvinyl alcohol aqueous solution 10 parts water 70 parts The above composition was subjected to sand-grinding with an average particle size of 1 μm.
m or less.

Preparation of Dispersion B: N- (2-naphthylsulfonyl) -N ′-[4- (n-octadecanoylamino) phenyl] urea 20 parts 10% -Polyvinyl alcohol aqueous solution 10 parts Water 70 Part The above composition was subjected to a sand grinder to give an average particle size of 1 μm.
m or less. Preparation of Dispersion C: 1,4-bis [2- (4-methylbenzyloxy) ethoxy] benzene 20 parts 10% -polyvinyl alcohol aqueous solution 10 parts Water 70 parts The above composition was averaged with a sand grinder. 1μ diameter
m or less.

Formation of reversible thermosensitive recording layer: Coating solution for reversible thermosensitive recording layer A solution 75 parts B solution 150 parts C solution 75 parts Calcined clay 30 parts 25% paraffin wax emulsion 2 parts 10% polyvinyl alcohol aqueous solution 100 parts The above composition was mixed and stirred to obtain a coating solution. This coating solution was coated on one side of a paper support with a coating amount of 5.0 g / m ² after drying.
And dried to form a reversible thermosensitive recording layer.

Formation of protective layer: Coating solution for protective layer Kaolinite clay dispersion (solid content: 60%) 5 parts Carboxylic acid-modified polyvinyl alcohol aqueous solution (solid content: 10%) 200 parts Conductive titanium oxide (manufactured by Ishihara Techno Co., Ltd.) ET-500W) 5 parts The above composition was mixed and stirred to prepare a coating liquid for an intermediate layer. This coating solution was applied on the heat-sensitive recording layer so that the coating amount after drying was 1.5 g / m ^2, and dried to form an overcoat layer, and the water content of the recording medium was 6.5%. To obtain a reversible thermosensitive recording medium 1.

<Example 2> A reversible thermosensitive recording medium 2 was prepared and tested in the same manner as in Example 1. However, when preparing the dispersion B, N- (2-naphthylsulfonyl) -N'-
Instead of [4- (n-octadecanoylamino) phenyl] urea, N- (4-hydroxyphenyl) -N′-n
-Octadecyl urea was used.

<Example 3> A reversible thermosensitive recording medium 3 was prepared and tested in the same manner as in Example 1. However, when preparing the dispersion B, N- (2-naphthylsulfonyl) -N'-
Octadecylphosphonic acid was used instead of [4- (n-octadecanoylamino) phenyl] urea.

<Example 4> A reversible thermosensitive recording medium 4 was prepared and tested in the same manner as in Example 1. However, using the following reversible thermosensitive recording layer coating solution as the reversible thermosensitive recording layer,
The following protective layer coating solution was used as the protective layer. Coating liquid for reversible thermosensitive recording layer A liquid 75 parts B liquid 150 parts C liquid 75 parts Fired clay 20 parts Conductive titanium oxide (EW-500 manufactured by Ishihara Techno) 10 parts 25% paraffin wax emulsion 2 parts 10% polyvinyl alcohol Aqueous solution 100 parts Coating solution for protective layer Kaolinite clay dispersion (solids concentration 60%) 10 parts Carboxylic acid-modified polyvinyl alcohol aqueous solution (solids 10%) 200 parts

<Example 5> A reversible thermosensitive recording medium 5 was prepared and tested in the same manner as in Example 1. However, the following coating liquid for a protective layer was used as the protective layer, and the obtained reversible thermosensitive recording medium was humidified to make the water content 6.0%. Coating solution for protective layer Kaolinite clay dispersion (solid content: 60%) 10 parts Carboxylic acid-modified polyvinyl alcohol aqueous solution (solid content: 10%) 180 parts Quaternary ammonium salt type conductive aqueous solution (Chemistat 6300 manufactured by Sanyo Chemical Industry Co., Ltd.) 20 copies

Comparative Example 1 A reversible thermosensitive recording medium 6 was prepared in the same manner as in Example 1. However, the protective layer was formed using the protective layer coating solution.

Comparative Example 2 A reversible thermosensitive recording medium 7 was prepared and tested in the same manner as in Example 1. However, the following coating liquid for a protective layer was used as the protective layer. Coating solution for protective layer Kaolinite clay dispersion (solid content: 60%) 10 parts Carboxylic acid-modified polyvinyl alcohol aqueous solution (solid content: 10%) 190 parts Quaternary ammonium salt type conductive aqueous solution (Chemistat 6300 manufactured by Sanyo Chemical Industry Co., Ltd.) 10 copies

Comparative Example 3 A reversible thermosensitive recording medium 8 was prepared and tested in the same manner as in Example 1. However, the following coating liquid for a protective layer was used as the protective layer. Coating solution for protective layer Kaolinite clay dispersion (solid content: 60%) 10 parts Carboxylic acid-modified polyvinyl alcohol aqueous solution (solid content: 10%) 100 parts Quaternary ammonium salt type conductive aqueous solution (Chemistat 6300 manufactured by Sanyo Chemical Industry Co., Ltd.) ) 100 copies

<Coloring and Decoloring Tests> The reversible thermosensitive recording media thus obtained were subjected to a printing voltage of 21.7 V and a printing pulse of 1.0 ms by using a thermal coloring tester THPMD manufactured by Okura Electric. Printed under the following conditions. The print color density was measured with a Macbeth reflection densitometer RD-914. Further, the color-developed sample was heated at a heating temperature of 100 ° C., a pressure of 1 kg / cm ² , and a heating time of 1 second using a thermal gradient tester manufactured by Toyo Seiki, and the decoloring density was measured using a Macbeth reflection densitometer RD-9.
Measured at 14. If the recording density is 1.30 or more and the decoloring density is 0.15 or less, preferably the recording density is 1.40 or more and the decoloring density is 0.10 or less, there is no practical problem. Tables 1 and 2 show the test results.

<Heat resistance test> After measuring the print color density in the same manner as in the above color test, the obtained color sample was subjected to 50 tests.
The color density after standing for one day at a temperature of ° C. was measured in the same manner. At this time, the storage stability of the image area was evaluated by the image storage ratio: (color density after standing at 50 ° C. for one day) / (color density immediately after printing). Preservation rate is 70% or more, preferably 8
If it is 0% or more, there is no practical problem. Tables 1 and 2 show the test results.

<Measurement of Surface Electric Resistance Value> The surface electric resistance value of the obtained recording medium in an environment of 20 ° C. and 65% relative humidity was measured by using a surface electric resistance meter (manufactured by Dia Instruments, Hirester UL). It was measured at 100V. Tables 1 and 2 show the test results.

<Evaluation of Recording Defects> Defective portions per one sample A4 printed and colored in the same manner as in the above color development test were visually evaluated for each 100 samples. Recording defects were evaluated as ○ for less than 1.0 / A4, and as x for 1.0 or more. Tables 1 and 2 show the test results.

<Static Friction Coefficient Test> The static friction coefficient of each recording medium obtained by the static friction coefficient measuring method described in JIS P8147 was measured. Tables 1 and 2 show the test results. <Running test> Each recording medium was cut to A4 size, and a thermal recording paper printer (PC-PR101 / TN103A:
(Manufactured by NEC), 100 sheets were continuously recorded. At this time, running defects such as double feeding and jamming were evaluated. The results are shown in Tables 1 and 2.

In Tables 1 and 2 below, the developer A was N-
(2-naphthylbenzenesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea, and the developer B is N- (4-hydroxyphenyl) -N'-n-
Octadecyl urea, and the developer C is octadecyl phosphonic acid.

[0061]

[Table 1]

[0062]

[Table 2]

[0063]

According to the present invention, it is possible to provide a reversible thermosensitive recording medium having very little head wear of the recording printer, no defect in the recording portion, and no running failure in the recording printer.

Claims (1)

[Claims] 1. A heat-sensitive recording layer comprising a colorless or light-colored dye precursor and a developer for reversibly developing and decoloring the dye precursor is formed on a sheet-like support, In a reversible thermosensitive recording medium that develops and decolors according to the difference in heating temperature, 1 × in an environment where the surface electric resistance of the surface of the thermosensitive recording layer is 20 ° C. and the relative humidity is 65%.
10 ¹³ Ω / □ or less, and the static friction coefficient of the surface is 0.6
A reversible thermosensitive recording material, wherein the number is 5 or less.