JPH03256787A - Heat-sensitive recording material - Google Patents

Abstract

PURPOSE:To prevent rubbing color development, to satisfy the matching with a thermal head and to enhance thermal sensitivity still more by adding a specific urethane compound to a heat-sensitive recording layer. CONSTITUTION:An urethane compound represented by formula I (wherein R<1> and R<3> are a 1-22C alkyl group, an alkenyl group, a 7-9C arylalkyl group or an arylalkenyl group, R<2> is a 1-10C alkylene group, a 7-14C arylene group or a group represented by either one of formula II-IV) is added to a heat-sensitive recording material. This compound is easily obtained by reacting 1-10C aliphatic diisocyanate, 7-14C aromatic diisocyanate, diisocyanate having a group represented by either one of the formulae II-IV with 1-22C aliphatic saturated or unsaturated alcohol or 7-9C aromatic substituted aliphatic saturated or unsaturated alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a heat-sensitive recording material comprising a heat-sensitive recording layer provided on a support.

[Conventional technology]

A heat-sensitive recording material has a heat-sensitive recording layer formed by dispersing and bonding a color-forming substance and a color-developing substance that develops color when heated in a binder as a heat-sensitive component on a support such as paper. In thermal recording, a color-forming substance and a color-developing substance are melted and bonded together by heating to cause a color-developing reaction.

In recent years, this type of material has been widely used in facsimile machines, various recorders, computer output printers, and POS (point-of-sale) systems. Since maintenance and repair costs for the equipment are low, demand for it is expanding in many areas.

In general, such recording materials are required to have the following characteristics: (high sensitivity to Al heat, (BL) not to easily develop color due to rubbing or pressure, (good matching with Cl thermal heads, In other words, there is less wear on the thermal head, the components of the coloring layer do not adhere to the thermal head as scum, and there is no sticking.Here, sticking refers to the thermal recording layer adhering to the thermal head, causing heat-sensitive recording. The problem is that the feeding of the recording material becomes difficult.

However, when the heat-sensitive recording layer is composed only of a color-forming substance, a color-developing substance, and a binder for dispersing and bonding these,
Since it is difficult to fully satisfy the above-mentioned required properties, various modifiers are usually added as a fourth component to improve the above-mentioned properties.

Examples of such modifiers include mineral waxes, animal and vegetable oils, higher fatty acids, higher alcohols, amide compounds, urea compounds, ester compounds, and inorganic substances.
No. 19231, Japanese Patent Publication No. 51-27599, Japanese Patent Publication No. 1983
-34939, JP-A-55-87597, JP-A-5
They are disclosed in various publications such as JP-A No. 6-72996, JP-A-58-98285, and JP-A-63-89379, among which stearamide, ethylene bisstearamide, etc. are relatively commonly used. ing.

[Problem to be solved by the invention]

However, recently, there has been a strong demand for increasing the recording speed of this type of material as quickly as possible, and the above-mentioned known modifiers cannot cope with such high-speed recording.
There is a growing need to further improve heat sensitivity.

In view of the above circumstances, the present invention has the above-mentioned required characteristics.
Satisfied with color development due to rubbing and matching with thermal head,
The object of the present invention is to provide a heat-sensitive recording material with further improved heat sensitivity.

[Means to solve the problem]

As a result of intensive studies to achieve the above object, the present inventors have found that by using a specific urethane compound that has never been used as a modifier to be added to a heat-sensitive recording layer, the above-mentioned requirements can be met. The present invention was completed based on the knowledge that it is possible to obtain a recording material that satisfies the properties to a high degree, and in particular has significantly improved heat sensitivity.

That is, the present invention provides a heat-sensitive recording material in which a heat-sensitive recording layer comprising a color-forming substance and a color-developing substance that develops color when heated is provided on a support, in which the heat-sensitive recording layer has the following general formula ( ■): (wherein RI and R3 are alkyl groups or alkenyl groups having 1 to 22 carbon atoms or 7 to 90 carbon atoms) 7U-/L/
Urethane represented by an alkyl group or an arylalkenyl group, R2 is an alkylene group having 1 to 1 carbon atoms, an arylene group having 7 to 14 carbon atoms, or a group represented by the following formula: The present invention relates to a heat-sensitive recording material characterized by containing a compound.

By the way, in JP-A No. 63-218394, in order to improve the reproducibility of printed dots of heat-sensitive recording materials, a melting point of 7.
In addition to amide derivatives and urea derivatives having a temperature of 5°C or higher, it is disclosed that a wide range of urethane derivatives can be used, including compounds similar to those of the present invention and compounds such as 3°3'-bis(octadecyloxycarbonylamino)dipropyl ether. has been done.

However, in the above-mentioned publication, the above-mentioned various derivatives are included in the undercoat layer that serves as the base of the heat-sensitive recording layer, and the statement that they are added to the heat-sensitive recording layer as in the present invention is different from the above-mentioned publication. I can't see it anywhere. On the other hand, in the present invention, which is completely different from the technology disclosed in the above publication, by selectively using a specific urethane compound represented by the above general formula (1) and including it in the heat-sensitive recording layer. Specifically, it is possible to obtain a recording material that does not easily develop color when rubbed or under pressure, but is extremely sensitive to heat.Moreover, this recording material has good head matching, so it does not generate dust on thermal heads, etc. It has been discovered that the paper does not stick to the paper and does not cause sticking, which is inconvenient when feeding paper, and this is a major feature of the present invention.

[Structure and operation of the invention]

The urethane compound represented by the general formula (1) used in the present invention is, for example, an aliphatic diisocyanate having 1 to 0 carbon atoms, an aromatic diisocyanate having 7 to 14 carbon atoms, or the above formulas (a) to (C). By reacting a diisocyanate having a group represented by any of the above with an aliphatic saturated or unsaturated alcohol having 1 to 22 carbon atoms or an aromatic substituted aliphatic saturated or unsaturated alcohol having 7 to 9 carbon atoms,
can be obtained easily.

Specific examples of the above diisocyanates include methylene diisocyanate, ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate,
Octamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, 2,4 tolylene diisocyanate, 2.6-)lylene diisocyanate, 4,4'-diphenylmethane diisocyanate,
Examples include naphthylene diisocyanate, toridine diisocyanate, isophorone diisocyanate, xylylene diisocyanate, dicyclohexylmethane diisocyanate, and the like.

Further, specific examples of each of the above alcohols include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, 5ec-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, isoagol alcohol, hexyl alcohol, heptyl alcohol,
Examples include octyl alcohol, decyl alcohol, dodecyl alcohol, tetradecyl alcohol, hexadecyl alcohol, octadecyl alcohol, eicosyl alcohol, tocosyl alcohol, allyl alcohol, crotyl alcohol, propargyl alcohol, benzyl alcohol, and cinnabar alcohol.

The reason why the type and number of carbon atoms of the diisocyanate and the type and number of carbon atoms of the alcohol are limited as described above is that the effects of the present invention cannot be sufficiently obtained with other substances, or This is because it is difficult to obtain and impractical.

Specific examples of the urethane compound represented by the general formula (I) used in the present invention include methyl hexamethylenebiscarbamate, ethyl hexamethylenebiscarbamate, furovir hexamethylenebiscarbamate, and hexamethylenebiscarbamate. Isopropyl short acid, octyl hexamethylene biscarbamate, hensyl hexamethylene biscarbamate, methyl ethylene biscarbamate,
Dodecyl ethylenebiscarbamate, octadecyl ethylenebiscarbamate, benzyl ethylenebiscarbamate, methyl octamethylenebiscarbamate, propyl octamethylenebiscarbamate, isoarol octamethylenebiscarbamate, octamethylenebiscarbamate Allyl, cinnamyl octamethylenebiscarbamate, methyl nonamethylenebiscarbamate, isobutyl nonamethylenebiscarbamate, decyl nonamethylenebiscarbamate, eicosyl nonamethylenebiscarbamate, allyl nonamethylenebiscarbamate, benzyl nonamethylenebiscarbamate , ethyl decamethylene biscarbamate, isopropyl decamethylene biscarbamate, dodecyl decamethylene biscarbamate, octadecyl decamethylene biscarbamate, propargyl decamethylene biscarbamate, cinnamyl decamethylene biscarbamate, ethyl isophorone biscarbamate, isophorone Dodecyl biscarbamate, hexadecyl isophorone biscarbamate, allyl isophorone biscarbamate, benzyl isophorone biscarbamate, ethyl 4.4'-diphenylmethane biscarbamate, 4.4'-octyl diphenylmethane biscarbamate, 4.4'- Examples include benzyl diphenylmethane biscarbamate, tocosyl dicyclohexylmethane biscarbamate, and cinnamyl dicyclohexylmethane biscarbamate.

The color-forming substance used in the present invention is generally known as a leuco dye, which develops color by reacting with a color-developing substance such as an organic acid, and specifically includes triphenylmethane, fluoran, phenothiazine, and auramine. and spiropyran series. Color-developing substances used as reaction components together with the above-mentioned color-forming substances include organic acids such as salicylic acid, phthalic anhydride, and stearic acid, and bisphenol A.
, 4-tert-butylphenol, 4-phenylphenol, catechol, octylphenol, and the like are typically used.

In the present invention, the binder for dispersing and binding the above-mentioned heat-sensitive component is polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, modified starch, styrene, etc., since water is usually used as a medium when coating on the support. Water-soluble salts of maleic anhydride copolymers or diisobutylene-maleic anhydride copolymers are used.

The heat-sensitive recording layer of the present invention may contain a white pigment or a dispersion, if necessary, for the purpose of improving writability, whiteness, matching with a thermal head, solid particle dispersibility, coating suitability, and film water resistance. There is no problem in adding various known additives such as a wetting agent, a wetting agent, and a film waterproofing agent.

The heat-sensitive recording material of the present invention is generally prepared by preparing a paint in which the above-mentioned components, that is, a binder, a reactive component (a color-forming substance and a color-developing substance), and solid fine particles of a urethane compound are dispersed in water. It can be obtained by applying it on top and drying it.

In preparing the above-mentioned paint, the color-forming substance, the color-developing substance, and the urethane compound are each ground separately in an aqueous medium containing a binder to particle sizes of several micrometers or less using a dispersing machine such as a ball mill, attritor, or sand grinder. It is convenient to prepare a dispersion liquid and mix them in a predetermined ratio.

Further, the urethane compound may be mixed with one of the reaction components to form a dispersion, and then mixed with a dispersion of the other reaction component.

The amount of color-forming substance and color-developing substance to be used in this paint is appropriately determined depending on its type and performance. On the other hand, the amount of the urethane compound to be used varies depending on the type of the above-mentioned reaction components, but it is usually from I to 50% by weight, preferably from 3 to 30% by weight based on the total solid content. 1
If it is less than 50% by weight, it will be difficult to obtain the effects of the present invention, and if it exceeds 50% by weight, there will be problems such as deposits on the thermal head or sticking, which is not preferable.

The support on which the heat-sensitive recording layer is to be provided is usually paper, but when used as a photographic film, a transparent plastic film is used. However, there is no particular limitation as long as it does not interfere with forming a heat-sensitive recording layer and performing color recording using thermal means.

〔Effect of the invention〕

As described above, in the present invention, by including a specific urethane compound in the heat-sensitive recording layer, a recording material that does not easily develop color due to rubbing or pressure, but is extremely sensitive to heat. can be obtained. Further, since this recording material has good head matching, there is no adhesion of debris to the thermal head or the like, and there is no problem of sticking that is inconvenient when feeding the paper.

Due to the above-mentioned excellent properties, the heat-sensitive recording material of the present invention can be effectively used for various purposes such as recording in facsimiles and recorders, computer output printers, and POS labels.

〔Example〕

Next, the present invention will be explained in more detail based on examples. In addition, parts and % below refer to parts by weight and % by weight, respectively.

Example 1 20 parts of crystal violet lactone, 50 parts of a 10% polyvinyl alcohol aqueous solution, and 30 parts of water were pulverized and mixed in a ball mill for 24 hours to obtain a color-forming substance dispersion (hereinafter referred to as liquid A).

Further, 10 parts of bisphenol A, 20 parts of calcium carbonate, 50 parts of a 10% polyvinyl alcohol aqueous solution, and 20 parts of water were ground and mixed in the same manner as above to obtain a dispersion of a color developer (hereinafter referred to as liquid B).

Furthermore, 20 parts of methyl hexamethylenebiscarbamate, 20 parts of 1O% casein aqueous solution, and 60 parts of water were ground and mixed in the same manner as above to obtain a dispersion of the modifier component (hereinafter referred to as liquid C).

Next, a paint was prepared by mixing 6 parts of liquid A, 45 parts of liquid B, C1) S part, and 34 parts of a 20% polyvinyl alcohol aqueous solution, and this was coated on high-quality paper with a basis weight of 50 g1rd in terms of solid content of IOg. /m, 30℃, 10
A thermosensitive recording paper was obtained by drying for 30 minutes under reduced pressure of 0 mHg.

Examples 2 to 6 Instead of methyl hexamethylene biscarbamate in Solution C of Example 1, benzyl hexamethylene biscarbamate (Example 2), dodecyl isophorone biscarbamate (Example 3), allyl isophorone biscarbamate (Example 4), tocosyl dicyclohexylmethane biscarbamate (Example 5), and cinnamyl dicyclohexylmethane biscarbamate (Example 6) were used in the same amount.
A dispersion of each modifier component was obtained. Five types of thermal recording paper were obtained in the same manner as in Example 1, except that each of these dispersions was used.

Comparative Examples 1 to 3 Instead of methyl hexamethylenebiscarbamate in Solution C of Example I, ethylenebisstearamide (Comparative Example 1), stearamide (Comparative Example 2), 3.
Dispersions of each modifier component were obtained using the same amount of 3'-bis(octadecyloxycarbonylamino)dipropyl ether (Comparative Example 3). Except for using each of these dispersions,
Three types of thermal recording paper were obtained in the same manner as in Example 1.

For each of the thermal recording papers of Examples 1 to 6 and Comparative Examples 1 to 3 above, the color density when printing was performed by changing the energization time using a thermal facsimile device with a built-in thermal head (applied voltage 10 V), At this time, the skin density, adhesion of residue to the thermal head, and sticking were investigated. Furthermore, apart from the printing test using the thermal printer mentioned above,
As a pressure color development test, each recording paper was pulled onto a wire with a diameter of 0.8 vm under a load of 500 g, and the color density was examined.

The results of these tests are shown in Table 1 below. Note that the color density developed by the thermal printer, the background density, and the pressure color density were all measured using a Macbeth reflection densitometer. Needless to say, the higher the numerical value of the coloring density produced by a thermal printer, the better, and conversely, the smaller the numerical value of the background density and the pressure coloring density. Also, regarding the adhesion and sticking of debris to the thermal head, ○ is normal, △ is normal when it can be used, and × is bad enough to be impractical.
It was evaluated as follows.

As is clear from Table 1 above, the thermal recording paper of the present invention not only has good heat sensitivity, but also has low pressure color development and background density.
Moreover, it matches well with the thermal head,
It can be seen that the heat-sensitive recording papers according to Comparative Examples 1 to 3 using conventional ordinary modifiers have low heat sensitivity and poor matching with the thermal head.

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive recording layer containing a color-forming substance and a color-developing substance that develops color when heated is provided on a support, the heat-sensitive recording layer has the following general formula (I).
▲There are mathematical formulas, chemical formulas, tables, etc.▼...(I) (In the formula, R^1 and R^3 are an alkyl group or alkenyl group having 1 to 22 carbon atoms, or an arylalkyl group having 7 to 9 carbon atoms. or an arylalkenyl group, R^2 is an alkylene group having 1 to 10 carbon atoms, an arylene group having 7 to 14 carbon atoms, or the following formulas (a) to (c); ▲There are numerical formulas, chemical formulas, tables, etc.▼...・(a) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(b) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(c) It is a group shown by any of the following) A heat-sensitive recording material characterized by containing a urethane compound.