Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
  • B41M5/337—Additives; Binders
  • B41M5/3375—Non-macromolecular compounds

Definitions

• the present invention relates to a thermal recording material. More particularly, the present invention relates to a thermal recording material that is improved in color forming ability and other recording characteristics and which features a high degree of brightness and better image stability.
• thermal recording materials have been proposed that utilize the thermal color-forming reac­tion between at least one colorless or pale-colored basic dye and color developing agents such as phenols and organic acids (see Japanese Patent Publication No. 45-14039) and some of them are in extensive commercial use.
• Applications of these thermal recording materials cover a wide range including recorders for measurements, terminal printers of computers and information communications systems, facsimiles and automatic ticket vending machines.
• These recording apparatus have heating elements such as thermal heads and heat pens (styli), which are heated to produce imagewise color formation.
• both a color-forming material and a phenolic compound are dispersed as fine particles and it is generally held that upon heating, one or both of the components will fuse and come in intimate contact with each other to achieve color formation.
• Japanese Patent Public Disclosure No. 56-144193 proposes the use of benzyl p-­hydroxybenzoate or methylbenzyl p-hydroxybenzoate as a color developing agent for increasing the sensitivity of a thermal recording sheet.
• a problem with this idea is that the recording sheet is poor in image stability since white spots will appear in the image area during storage of the record.
• thermal recording materials have been capable of fully satisfying the requirements of the market for higher performance with regard to such aspects as color-forming characteristics, the degree of brightness and image stability.
• An object of the present invention is to provide a thermal recording material which not only has a practical level of sensitivity for color formation that guarantees its use in a wide range of applications but which also features a high degree of brightness.
• Another object of the present invention is to provide a thermal recording material which has the added advantage of better image stability.
• thermal recording material that contains in a thermal recording layer at least one colorless or pale-­colored basis dye and a dihydroxydiphenyl ether represented by the following general formula:
• the present inventors conducted intensive studies by screening a number of phenolic color-­developing materials.
• the dihydroxydiphenyl ether represented by the general formula set forth above is an effective color developing agent that ensures high sensitivity and high degree of brightness and which yet is free from the problem of white spots that has occurred in the use of benzyl p-hydroxybenzoate.
• the present invention has been accom­plished on the basis of this finding.
• the dihydroxydiphenyl ether having the general formula set forth above may be exemplified by 2,2′­dihydroxydiphenyl ether (m.p. l2l°C), 3,3′-dihydroxydiphenyl ether (m.p. 98°C) and 4,4′-dihydroxydiphenyl ether (m.p. l66°C)
• dihydroxydiphenyl ether used in the present invention attains a higher degree of brightness and a higher sensitivity for color formation than the conventionally used bisphenol A is not completely clear but this would probably be due to the miscibility of this compound with basic dyes or sensitizers that may be used in combination with these compounds.
• the dihydroxydiphenyl ether of formula (I) is normally used in an amount of 0.5 - 3 parts by weight, preferably 1 - 2 parts by weight, per part by weight of the color-forming basic dye.
• thermo recording material having a high degree of brightness and sensitivity for color formation is obtained and this recording material per se is normally suitable for practical use.
• the thermal paper after application of heat, is left to stand for 24 hours in a hot atmosphere (60°C x 20% R.H.) or in a humid atmosphere (40°C x 90% R.H.), the density of the image will decrease and the residual density may sometimes be reduced to 80% and below.
• the thermal recording material of the present invention is often required to have better image stability.
• a thermal recording material that had better image stability without compromising the degree of brightness and sensitivity could be attained by using a color developing agent made of the dihydroxydiphenyl ether of the general formula (I): in combination with at least one compound selected from the group consisting of 1,1,3-tris(2-methyl-4-hydroxy-5-­t-butylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-­cyclohexyl)butane, 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-­dimethylbenzyl isocyanuric acid, 1,1-bis(2-methyl-4-hydroxy-­5-t-butylphenyl) butane.
• 1,1,3-tris(2-methyl-4-­hydroxy-5-t-butylphenyl)butane is a substance represented by the formula (II):
• 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexyl)butane is a substance represented by the formula (III):
• 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid is a substance represented by the formula (IV):
• 1,1-bis(2-methyl-4-hydroxy-5-t-butylphenyl)butane is a substance represented by the formula (V):
• the dihydroxy­diphenyl ether is generally used in an amount of 0.5 - 3 parts by weight per part by weight of a color-forming basic dye, and one or more of the substances listed above are used in an amount of 0.1 - 20 parts by weight per part by weight of this color developing agent.
• dihydroxy­diphenyl ether is used in an amount of 1 - 2 parts by weight per part by weight of a color-forming basic dye and one or more of the substances of interest are used in an amount of 0.2 - 5 parts by weight per part by weight of dihydroxydi­phenyl ether.
• the image stability of a thermal recording material using these substances is 10 - 20% better than in the case where dihydroxydiphenyl ether is employed in the absence of these substances. This improvement will guarantee the storage of the thermal recording material of the present invention either in a hot or humid atmosphere after recording has been effected.
• the colorless or pale-colored basic dye for use in the formation of a thermal recording layer in the present invention may be selected from among those which are commonly employed for this purpose, and representative examples are listed below:
• Triarylmethane dyes such as 3,3-bis(p-­dimethylaminophenyl)-6-dimethylaminophthalide, 3,3-bis(p-­dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-­3-(1,2-dimethylindol-3-yl)phthalide, 3-(p-­dimethylaminophenyl)-3-(2-methylindol-3-yl )phthalide, 3,3-bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarbazol-3-yl)-6-dimethylaminophthalide, 3,3-bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, and 3-p-d
• An exemplary additive is a sensitizer which may be illustrated by 1,1­bis-(4-hydroxy-phenyl)-cyclohexane, parabenzyl biphenyl, dibenzyl terephthalate, phenyl-1-hydroxy-2-naphthoate, dibenzyl oxalate, di-o-chlorobenzyl adipate, 1,2-di(3-­methylphenoxy)ethane and di-p-chlorobenzyl oxalate.
• the support on which the thermal recording layer of the thermal recording material of the present invention is formed may be made of any suitable material that is selected from among paper, pigment-coated paper, paper made of synthetic fibers, synthetic paper, synthetic resin films, etc. Paper is normally preferred.
• the basic dye, dihydroxydiphenyl ether of formula (I) and a substance capable of improving image stability are dispersed in water by means of a grinder such as a ball mill, attritor or a sand grinder.
• the resulting coating solution contains 2 - 40 wt%, preferably 5 - 25 wt%, of the total solids content of a binder selected from among starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene, salts of maleic acid copolymers, styrene-butadiene copolymer emulsions, etc.
• a binder selected from among starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene, salts of maleic acid copolymers, styrene-butadiene copolymer emulsions, etc.
• auxiliary agents may be incor­porated as required in the coating solution.
• Illustrative additives include: dispersants such as sodium dioctylsulfo­succinate, sodium dodecylbenzenesulfonate, sodium salt of laurylalcohol sulfate esters, and metal salts of aliphatic acids; antifoaming agents; fluorescent dyes; and pigment dyestuffs.
• dispersants such as sodium dioctylsulfo­succinate, sodium dodecylbenzenesulfonate, sodium salt of laurylalcohol sulfate esters, and metal salts of aliphatic acids
• antifoaming agents such as sodium dioctylsulfo­succinate, sodium dodecylbenzenesulfonate, sodium salt of laurylalcohol sulfate esters, and metal salts of aliphatic acids
• antifoaming agents such as sodium dioctylsulfo­succinate, sodium dodec
• waxes such as dispersions or emulsions of stearic acid, polyethylene, carnauba wax, paraffin wax, calcium stearate, zinc stearate, ester waxes, etc. may also be incorporated in appropriate amounts in the coating solution.
• the method of forming the recording layer of the thermal recording material of the present invention is not limited in any particular way.
• a thermal coating solution may be applied to the support with any suitable coating apparatus such as an air-knife coater or a blade coater.
• the coating weight of the thermal color-forming layer is not limited to any particular value but it is generally formed in a dry weight of 1 - 15 g/m2, the range of 3 - 8 g/m2 being preferred.
• an improved thermal recording material which not only has a practical level of sensitivity for color formation that guarantees its use in a wide range of applications but which also features a high degree of brightness.
• This composition was ground into particles of an average size of 1 ⁇ m with a sand grinder.
• This composition was ground into particles of an average size of 1.5 ⁇ m with a sand grinder.
• Parabenzyl biphenyl 40 10% Aqueous polyvinyl alcohol solution 20 parts Water 20 parts
• This composition was ground into particles of an average size of 1.5 ⁇ m with a sand grinder.
• This composition was ground into particles of an average size of 1.5 ⁇ m with a sand grinder.
• a thermal recording sheet was prepared as in Example 1 except that Solution B had 2,2′-dihydroxydiphenyl ether replaced by the same amount of 4,4′-dihydroxydiphenyl ether.
• a thermal recording sheet was prepared as in Example 1 except that Solution B had 2,2′-dihydroxydiphenyl ether replaced by the same amount of 3,3′-dihydroxydiphenyl ether.
• a thermal recording sheet was prepared as in Example 4 except that Solution D had 1,1,3-tris(2-methyl-4-hydroxy-­5-t-butylphenyl)-butane replaced by the same amount of 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexyl)butane.
• a thermal recording sheet was prepared as in Example 4 except that Solution D had 1,1,3-tris(2-methyl-4-hydroxy-­5-t-butylphenyl)-butane replaced by the same amount of 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethyl) isocyanuric acid.
• a thermal recording sheet was prepared as in Example 4 except that Solution D had 1,1,3-tris(2-methyl-4-hydroxy-­5-t-butylphenyl)-butane replaced by the same amount of 1,1-­bis(2-methyl-4-hydroxy-5-t-butylphenyl)butane.
• a thermal recording sheet was prepared as in Example 1 except that Solution B had 2,2′-dihydroxydiphenyl ether replaced by the same amount of 2,2-bis(4′-­hydroxyphenyl)propane (bisphenol A).
• thermal recording sheet thus prepared were supercalendered and the degree of their brigh­tness was measured with a Hunter brightness meter. After performing thermal recording on these sheets with Model UF-60 of Matsushita Graphic Communication Systems, Inc., the density of the image was measured with a densitometer, Model RD-100R of Macbeth Instrument Corporation.
• the samples of the thermal recording material of the present invention are superior to the sample of Comparative Example 1 in terms of recording density.
• the samples prepared in Examples 4 - 7 are better in image stability than those of Examples 1 - 3.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Heat Sensitive Colour Forming Recording (AREA)

Applications Claiming Priority (4)

Publications (2)

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ID=26338284

Family Applications (1)

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• 1988
  • 1988-12-30 CA CA000587318A patent/CA1312730C/fr not_active Expired - Fee Related
• 1989
  • 1989-01-10 EP EP89300177A patent/EP0324576A3/fr not_active Withdrawn

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