JPS58138690A - Heat-sensitive recording material - Google Patents

Abstract

PURPOSE:To raise the stability of recorded pictures by a method in which a specific biphenyl compound is used as a developing agent for a heat-sensitive chromogenic layer containing a leuco dye and an organic filler is used as a filler. CONSTITUTION:1pt.wt. a well-known colorless or light-color leuco dye is mixed with 2-18pts.wt. a biphenyl compound of the formula (R1 and R2 are each H, halogen, alkyl, alkoxy, acyl, cyclohexyl or aromatic group), together with an organic filler (e.g., urea-formalin resin, styrene-methacrylic acid copolymer resin, etc.) having a grain size of 0.1-10mum and an usual auxiliary additive as needed. The dispersion thus obtained is coated on a supporter (e.g., paper, synthetic paper, etc.) and then dried. The preferred amounts of leuco dye, biphenyl compound, and organic filler in the chromogenic layer are 5-30wt%, 5-70wt% and 10-80wt%, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material on which a recorded image is formed by thermal printing using a thermal head, and particularly to a heat-sensitive recording material in which the stability of the recorded image is significantly improved.

In recent years, in line with social demands such as an increase in the amount of information, resource saving, labor saving, and pollution-free production, various recording methods have been put into practical use and improved in the information recording field. Thermal recording methods using materials are: 1) primary color development, no developing process required; 1) hardware is simple and compact, and maintenance costs are low; Due to its low cost, it has been put to practical use in computer output, medical measurement recorders, low-speed or medium-speed facsimiles, calculators and other printers, automatic ticket vending machines, thermal copying, etc. There is. A heat-sensitive recording material used in such a method is provided with a heat-sensitive coloring layer containing a colorless or light-colored leuco dye having a lactone, lactam, or spiropyran ring and an acidic substance, such as an organic acid or a phenolic compound, on a support. (tW!f Kosho 43-41
No. 60, No. 45-14039, etc.) are publicly known.

However, in the case of the above-mentioned leuco-based heat-sensitive recording material, the stability of the recorded image is poor and the color is difficult to erase. For example, there is the problem that the recorded image will fade when it comes into contact with sweat, oil, or the plasticizer (dioctyl phthalate, etc.) in the plastic film, and solving this problem is a major technical challenge for this type of recording material. It has become. Several methods have been proposed in the past to solve this problem, such as one in which the thermosensitive coloring layer contains a large amount of resin with good water and chemical resistance to increase the stability of the thermosensitive coloring layer. In addition, there are thermosensitive coloring layers that contain a resin that is cured by heat or light in the thermosensitive coloring layer to increase the stability of the thermosensitive coloring layer. There are products that protect the skin from the effects of chemicals and water. On the other hand, in the field of pressure-sensitive paper, products using color developers with good chemical resistance have been proposed (%
Publication No. 48-51716, Special Publication No. 51-25174
Although the use of a specific developer in this case is effective for pressure-sensitive paper, it is not effective for heat-sensitive recording paper, and when it comes into contact with plasticizers, the image is stable, but it is not. There is a problem that color development occurs in the image area (non-color development area).

□The present inventors have overcome the above-mentioned drawbacks found in conventional leuco-based heat-sensitive recording materials, and have achieved
As a result of intensive research to develop a highly stable product that does not cause color development in non-image areas and does not discolor image areas, we have developed a product that uses a specific bisphenyl compound in combination with a neutral organic filler. The inventors have discovered that the object can be achieved by doing so, and have completed the present invention.

That is, according to the present invention, in a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer for the leuco dye is provided on a support, the color developer is formed by the general formula (where R1 and R2 is a hydrogen atom, ), rogene, an alkyl group, an alkoxy group, an acyl group, a cyclohexyl group, or an aromatic group). A heat-sensitive recording material is provided which is characterized in that it contains an organic filler as a filler.

In the biphenyl compound represented by the general formula (1), examples of the 210 groups included in substituents R8 and R2 include chlorine and bromine, and examples of alkyl include carbon atoms such as methyl, ethyl, propyl, octyl, and dodecyl. Number 1-
Examples of the alkoxy group include those having 1 to 18 carbon atoms, such as methoxy, ethoxy, propoxy, ofthyrooxy, and dobyloxy, and examples of the acyl group include acetyl, propionyl, impropionyl, etc., and aromatic Examples of group groups include aryl groups such as phenyl, tolyl, xylyl, and pt-butylphenyl;
Examples include aralkyl groups such as al, phenethyl, and the like.

Specific examples of the compound include those having the structures shown below.

CH3 1 The amount of the biphenyl compound represented by the general formula 0 used in the present invention is usually 2 to 18 parts by weight per 1 part by weight of the leuco dye in the heat-sensitive coloring layer.

In the present invention, it is also possible to use other conventional color developing substances in combination, if necessary.

In the present invention, an organic filler is used together with the biphenyl compound represented by the general formula (summer), and examples of the organic filler in this case include urea-formalin resin, styrene-methacrylic acid copolymer resin, and polyethylene styrene. , nitrile-butadiene rubber, nylon,
The particle size of polyurethane etc. is usually in the range of 0.1 to 10 microns, preferably 0.2 to 5 microns.

In the present invention, in order to obtain good results, the general formula (+)
It is necessary to use the biphenyl compound in combination with an organic filler, and it is not preferable to use it in combination with an inorganic filler.

When an inorganic filler such as calcium carbonate, silica gel, aluminum hydroxide, zinc oxide, titanium oxide, clay, talc, etc. is used in combination, the image obtained by heating printing has a drawback of having a low initial density. The reason for this is not fully understood, but it is thought to be due to the biphenyl compound being sequestered with a metal or forming a salt with an alkali metal. Of course, this does not preclude the use of a small amount of inorganic filler as long as it does not impede the purpose of the present invention.

As the leuco dye used in the present invention, any dye can be used as long as it develops color when heated by the pimephenyl compound represented by the general formula (1) as a color developer, including triphenylmethane, Fluorane-based, phenothiazine-based, auramine-based, and spiropyran-based leuco dyes are preferably used. Specific examples of these leuco dyes are shown below.

As the leuco dye, usually colorless or light-colored leuco forms of the following dyes are used.

(a) Leuco compound of triphenylmethane dye represented by the following general formula: RX RY Rz (where flx > Ry and Rz are hydrogen, hydroxyl group,
These include halogen, alkyl group, nitro group, amino group, dialkylamino group, monoalkyl group, and allyl group. ) Specific examples of the above leuco compounds are as follows.

3) 3-bis(p-dimethylaminophenyl)-phthalide 3>3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone) 3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone) )-6-dimethylaminophenyl 393-bis(p-dimethylaminophenyl)-6-chlorophthalide 3?3-bis(p-dibutylaminophenyl)phthalide←) Leuco compound of fluoran dye represented by the following general formula: Rz In the formula, Rx9Ry and Rz are the same as in the above (a).

Specific examples of the above compounds are as follows.

3-Cyclohexylamino-6-chlorofluorane 3-(NtN-diethylamino)-5-methyl?
(NgN-dibenzylamino)fluoran 3-dimethylamino-597-dimethylfluoran 3-diethylamino-7-methylfluoran 3-diethylamine-718-benzfluoran (U) Leuco compound of fluoran dye: 3-diethylamino- 6-Methyl-7-chlorofluoran 3-pyrrolidino-6-methyl-7-anilinofluoran 2-IN-<3'-trifluoromethylphenyl)amino)-6-ethylaminofluoran 2- (3t 6
-bis(diethylamino)-9-(0-chloroanilino)xantylbenzoic acid lactam) Lacto/compound represented by the following general formula: (X4)
n In the formula, R1 and R2 are hydrogen, a lower alkyl group, a 7-substituted or unsubstituted alkyl group, a substituted or unsubstituted phenyl group, a cyanethyl group, or a β-halogenated ethyl group t
-a slightly or RI and R2 combine to +C! H.J.
s +OHr+also (-aHHO2(-OH2÷4
5 2
2, R3 and R4 represent hydrogen, a lower alkyl group, an alkyl group, an amine group, or a phenyl group, and either one of R8 and R4 is hydrogen, X1tX,
and X represents hydrogen, a lower alkyl group, a lower alkoxyl group, a halogen atom, a halogenated methyl group, a nitro group, an amino group, or a substituted amino group; It represents an alkoxyl group, and n represents O or an integer of 1 to 4.

Specific examples of the above compounds are as follows.

3-(2'-hydroxy-4'-dimethylaminophenyl) -3-(2'-methoxy-5'-crocin, -
enyl)phthalide 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-nitrophenyl)
Phthalide 3- (2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)phthalide 3- (2'-methoxy-4'-dimethylaminophenyl)'-3- (2'-hydroxy-4'-chloro-5'
-methylphenyl)phthalide.

Next, various color-developing substances can be used in combination with the above-mentioned pisophenyl compound of the present invention, and specific examples thereof are shown below.

2ν2-(p-hydroxyphenyl)furopane, 2t
2-(p-hy)”roxyphenyl)-butane, 2
-t2(ph)'roxyphenyl)hebutane, 1t
t-(p-hi)”roxyphenyl)cyclohexane, 2*2 (3-methyl-4-hydroxyphenyl)propane, 2t 2-(3-1crt-butyl-4-hydroxyphenyl)propa/, 2-phenyl cumylhydroquinone, hydroquinone monobenzyl, 494'-dihydroxyphenylsulfone 494'-dihydroxyphenylsulfide, isopropyl p-oxybenzoate, benzyl p-oxybenzoate, phenethyl p-oxybenzoate, octyl p-oxybenzoate, 4 -benzoylphenol, )\4-phenylacetylphenol, phenethyl procatechuate, 4-butyrocatechol 4ν4' -(2-ert-)゛thyl-5-methylphenol) sulfide, lauryl gallate, stearyl gallate, gallic acid Propyl, 4-phenylphenol.

As the binder for bonding and supporting the thermosensitive coloring layer on the support, various binders such as those shown below are commonly used.

Polyvinyl alcohol, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch, starch derivatives, gelatin, styrene.
Water-soluble ones such as maleic anhydride copolymer, imptyre/-maleic anhydride copolymer, or polystyrene/, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, 8BR latex, styrene-a
Aqueous emulsions such as monoacrylic acid esters can be used as binders.

In addition, if necessary, conventional auxiliary additives may be added to the heat-sensitive coloring layer, such as for improving head matching properties.
It is also possible to add waxes such as polyethylene wax, paraffin wax, carnauba wax, montan wax, higher fatty acid metal salts, and also surfactants.

Generally known methods can be used to obtain the heat-sensitive recording material of the present invention using the various heat-sensitive color forming layer forming components. That is, a color-forming substance, a color-developing substance, a binder,
Fillers and other additives are added alone or in a mixture except for color-forming substances to an aqueous medium together with a protective colloid substance such as polyvinyl alcohol, a surfactant, etc.
Grind and disperse using a dispersing machine such as a ball mill, attritor, or sand mill. Next, the respective dispersions are mixed to prepare a thermosensitive coloring layer coating solution 'tvI4, which is coated onto a support such as gold paper, synthetic paper, or plastic film, and dried. In this case, the leuco dye contained in the thermosensitive coloring layer is preferably 5 to 30% by weight, the compound is 5 to 70% by weight, and the organic filler is 10 to 80% by weight. It is better to express it as a percentage.

Examples and comparative examples are shown below. In addition, "S" and "z
” are based on weight.

Reference example A liquid mixture having the following composition was prepared.

[Liquid A]

10% polyvinyl alcohol aqueous solution 11
3 parts water
487 parts were dispersed in a ball mill for 24 hours.

[Liquid B]

10% polyvinyl alcohol aqueous solution l1
3 parts water
487 parts were dispersed in a ball mill for 16 hours.

[Liquid C]

10% polyvinyl alcohol aqueous solution 11
3 parts water
487 parts were dispersed in a ball mill for 16 hours.

[Liquid D]

Calcium carbonate (average particle size 1.5μ) 1
50 parts lO% polyvinyl alcohol soluble in water t) I [75 parts water
525 parts The mixture was stirred for 2 hours using a homomixer.

[Liquid E]

Aluminum hydroxide 150 parts 10%
Polyvinyl alcohol aqueous solution 75 parts water
525 parts The mixture was stirred for 2 hours using a homomixer.

[F liquid]

Urea-formalin condensation resin 15
0 parts lO% polyvinyl alcohol aqueous solution
75 parts water
525 parts The mixture was stirred for 2 hours using a homomixer.

[G liquid]

Styrene-methacrylic acid copolymer resin 15
0 parts 10% polyvinyl alcohol water soluble i
75 parts water
525 parts The mixture was stirred for 2 hours using a homomixer.

Example 1 [Liquid A], [Liquid 0], and [Liquid F] were mixed in a ratio of 1:3:3, stirred uniformly, and deposited on a high-quality paper with a basis weight of 7 m'' to a dry solid content of 3. It was coated using Labo Coat In Blonde to a length of 517 m' and dried.

This is calendered and smoothness 'I! f-300~4
00 seconds, a heat-sensitive recording material was obtained.

Example 2 A product was obtained in the same manner as in Example 1, except that [Liquid A], [Liquid C], and [Liquid G] were mixed at a ratio of 1:3:3.

Example 3 [Liquid A], [Liquid B], [Liquid C], [Liquid F] at 2:3:3
A product was obtained in the same manner as in Example 1, except that the mixture was mixed at a ratio of: :6.

Comparative Example 1 A product was obtained in the same manner as in Example 1, except that [Liquid A], [Liquid B] and [Liquid D] were mixed at a ratio of 1:3:3.

Comparative Example 2 A product was obtained in the same manner as in Example 1, except that [Liquid A], [Liquid B], and [Liquid F] were mixed in a ratio of 1:3:3.

Comparative Example 3 A product was obtained in the same manner as in Example 1, except that [Liquid A], [Liquid C], and [Liquid D] were mixed at a ratio of 1:3:3.

Comparative Example 4 (AF, ), [Liquid C], [Liquid E] at 1:3:3 Harm 11
A product gold was obtained in the same manner as in Example 1 except that the mixture was mixed in the same manner as in Example 1.

For each product obtained above, the following 11 loss determination meetings were conducted.

(1) Image density: 1 with thermal gradient tester (manufactured by Toyo Seiki)
Measure the image after contacting for 1 second at 50℃ with a Macbeth densitometer. Measure the image density 1 hour after applying it to the area (6) Heat resistance: 24°C under dry conditions at 60°C.
Measured with a Macbeth densitometer after being left for a period of time (7) Humidity resistance: Measured with a Macbeth densitometer after being left for 24 hours under conditions of 40°C and 90% humidity (RH).

As can be seen from the results shown below in the margins, it can be seen that the recording material of the present invention has a major feature not found in conventional thermal paper: it does not disappear at all even with plasticizers.

Patent applicant Ricoh Co., Ltd. Agent Patent Attorney Toshiaki Ikeura

Claims (1)

[Scope of Claims] (11 A heat-sensitive recording material in which a heat-sensitive coloring layer containing a leuco dye and a color developer for the leuco dye is provided on a support,
As the color developer, a biphenyl compound represented by the general formula or an aromatic group is used as a main component, and the heat-sensitive coloring layer contains an organic filler as a filler. A heat-sensitive recording material.