DE4009187C1 - Heat-transfer data recording material - comprises carrier paper coated with thermal data recording layer contg. colourless dye precursor and acidic component - Google Patents

Abstract

Heat-sensitive data recording material comprises a carrier paper coated on one side with a thermal data recording layer contg. a colourless or weakly coloured dye precursor and an acidic component, such that on heating, the acid reacts with the precursor to form a strongly coloured character image; and such that the difference in whiteness between the undeveloped heat-sensitive layer and the thermally developed film is at least 40 on the Berger scale. USE - The prods. are components for heat-sensitive data recorders and printers, producing stable records with good contrast.

Description

The invention relates to a heat-sensitive recording material, its front side provided with the thermosensitive recording layer of the carrier material deviates from the back of the carrier material Coloring.

Heat-sensitive recording materials with one on the surface of a support material applied heat-sensitive recording layer have been known for a long time. The recording layer usually contains a color precursor compound which upon exposure to heat with a suitable acidic compound as a reactant forms a color, one or more fusible compounds such as waxes, binders, pigments and usual adjuvants.

DE-A-38 37 889 is directed to a heat-sensitive recording material, a special sensitizer in the heat-sensitive recording layer contains, in order to increase the sensitivity, so that on the material transfer the imaging heat energy in a shorter period of time can be. The carrier material is paper, non-woven materials, Plastic films, metal foils and composite materials by combination of such materials are described.

To get a good contrast between the recording layer and the Ensuring recorded color development is the recording layer not only opaque, but is preferably neutral white educated. When using high quality support materials, eg. B. wood-free Coating base papers made of highly bleached pulp differ the recording side of the thermosensitive recording material in color hardly from the back, especially not then, albeit the recording layer opposite surface of the substrate, so the back also has a coating.

The object of the present invention is to provide a heat-sensitive recording material to create that a simple distinction of the recording side and the back of the thermosensitive recording material.

This object is achieved by a heat-sensitive recording material with a thermosensitive applied to the surface of the substrate Recording layer containing a colorless dye precursor and a to form a color suitable acidic compound as a reactant contains and is characterized in that  the coloration of the recording layer opposite Side of the carrier material of the still unused Recording layer is different, the difference in the whiteness after Berger is at least 40.

As support materials both films and papers be used. Preferred carrier material is paper.

A clearly visible white difference between the recording layer and the back of the heat-sensitive Recording material may according to a preferred embodiment of the invention are produced by that Place a wood-free base paper as carrier material a Holzschliffhaltiges or an unbleached or little bleached pulp-containing paper is used. Also suitable are so-called recycled papers made from waste paper are made.

Another possibility, the desired color difference according to the invention between front and back of the heat-sensitive To produce recording material is to that the back of the substrate is colored to the Difference of whites to Berger of at least 40 between form the recording layer and the back. The Coloring the back can also be done with setting treatments the flatness of the heat-sensitive recording material be combined. These include treating with colored Water or applying a thin coating, The color of the unused recording layer different. It is particularly preferred to color the support material on the recording layer form the opposite surface so that the whiteness to Berger within 70-10.

In the known thermosensitive recording materials the whiteness of the support material is on the recording layer opposite surface in one area from 72.5-95 (White from Berger).  

The whiteness after Berger becomes with a Elrefomaten type: DFC 5 determined by the company Zeiss.

The measurement is carried out at 10 ° normal viewers and 3 different wavelengths. From the reflections of the individual Wavelengths (Rx, Ry, Rz) may turn white after Berger be calculated by the following formula:

W _B = R _y + 3 (R _z -R _x )

Calculation of the standard color values XYZ according to the spectral method

S (λ) = relative spectral radiation distribution of the illumination source
, (λ) = standard spectral value functions
R () = spectral reflectance of the sample

Calculation of the standard color values XYZ according to the tristimulus method

X = a ^R X + b ^R Z
Y = R _y
Z = cR _z
R _x , R _y , R _z = measured color values for three-filter units
a, b, c = see table on page 5b

Calculation of the measured color values R _x , R _y , R _z from X, Y, Z from the standard color values X, Y, Z (necessary for whiteness determination according to the spectral method)

R _Y = Y

Table of a, b, c constants for 2 ° and 10 ° normal observers and the illuminants A, C, D 65 for calculating the standard color values from the measured color values and vice versa.

The constants are of the device specific weight coordinates dependent and therefore have slight deviations from the table values

Calculation of the whiteness according to Berger, WB WB = R _Y + 3 (R _Z -3 R _X )

The heat-sensitive recording layer contains on one side of the support material colorless or light-colored dyes that can be used in the preparation of a recording layer for the thermosensitive recording material, these are, for example, triarylmethane-based dyes, e.g. For example, 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-dimethyl-aminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide and 3-p-dimethylaminophenyl-3- (e.g. 1-methylpyrrole-3-yl) -6-dimethylaminophthalide;
Diphenylmethane, 4,4-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenylleucoauramine and N-2,4,5-trichlorophenylleucoauramine;
Thiazine dyes, e.g. B.
Benzoylleucomethylene blue and p-nitrobenzoylleucomethylene blue;
Spiro dyes, e.g. B.
3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methylnaphtho (6'-methoxybenzo) spiropyran and 3-propyl-spiro-dibenzopyran ;
Lactam dyes, e.g. B.
Rhodamine B-anilinolactam, rhodamine (p-nitroanilino) lactam and rhodamine (o-chloroanilino) lactam; and
Fluoran dyes, e.g. B.
3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3-diethylamino-7-methoxyfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-6, 7-dimethylfluoran, 3- (N-ethyl-p-toluidino) -7-methylfluoran, 3-diethylamino-7- (N-acetyl-N-methylamino) fluoran, 3-diethylamino-7-methylaminofluoran, 3-diethylamino-7 dibenzylaminofluoran, 3-diethylamino-7- (N-methyl-N-benzylamino) fluoran, 3-diethylamino-7- (N-chloroethyl-N-methylamino) fluoran, 3-diethylamino-7-diethylaminofluoran, 3- (N- Ethyl p-toluidino) -6-methyl-7-phenylaminofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluoran, 3-diethylamino-6-methyl-7- phenylaminofluoran, 3-diethylamino-7- (2-carbomethoxyphenylamino) fluoran, 3- (N -cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluoran, 3-pyrrolidino-6-methyl-7-phenylaminofluoran, 3-piperidino 6-methyl-7-phenylaminofluoran, 3-diethylamino-6-methyl-7-xylidinofluoran, 3-diethylamino-7- (o -chlorophenylamino) fluoran and 3-pyrrolidino 6-methyl-7-p-butylphenylaminofluoran, 3- (N-methyl-Nn-amylamino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-Nn-amylamino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluoran, 3- (N-methyl-Nn-hexylamino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-Nn-hexylamino ) -6-methyl-7-anilinofluoran and 3- (N-ethyl-N-ethylhexylamino) -6-methyl-7-anilinofluoran, 3-N-ethyl-N- (3'-methylbutyl) amino-6-methyl- 7-anilinofluoran, 3-N-ethyl-N-furfurylamino-6-methyl-7-anilinofluoran, 3-N, N-diethylamino-6-methyl-7-anilinofluoran, 3-N, N-di-n-butylamino 6-methyl-7-anilinofluoran, 3-N, N-di-n-butylamino-7-o-chloroanilino-fluoran, 3-N, N-diethylamino-7-o-chloroanilino-fluoran, 3-N-ethyl- Ni-pentylamino-6-methyl-7-anilinofluoran.

Numerous compounds are known as color developing materials which give a color on heating and in contact with the colorless or light colored basic dye, e.g. Inorganic acidic materials including active clay, acid clay, attapulgite, bentonite, colloidal silicic acid and aluminum silicate, and organic acidic materials including phenolic compounds such as 4-tert-butylphenol, 4-tert-octylphenol, 4-phenylphenol, 4-acetylphenol, α -Naphthol, β-naphthol, hydroquinone, 2,2'-dihydroxydiphenyl, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-chlorophenol) -4 , 4'-dihydroxy-diphenylmethane, 4,4'-isopropylidenediphenol (bisphenol A), 4,4'-isopropylidene-bis (2-tert-butylphenol, 4,4'-dihydroxydiphenylsulfide, 4,4'-thiobis (6 tert-butyl-3-methylphenol), 4,4'-dihydroxydiphenylsulfone, 4-hydroxybenzoic acid benzyl ester, hydroquinone monobenzyl ethers, novolac phenolic resins and phenolic polymers;
aromatic carboxylic acids such as
Benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3 - (α-methylbenzyl) salicylic acid, 3-chloro-5- (α-methylbenzyl) -salicylic acid, 3,5-di-tert-butylsalicylic acid, 3-phenyl-5- (α, α'-dimethylbenzyl) salicylic acid , 3,5-di (α-methylbenzyl) salicylic acid and terephthalic acid.

Also salts of such phenolic compounds or aromatic carboxylic acid with polyvalent metals such as zinc, magnesium, aluminum, calcium, Titanium, manganese, tin and nickel are considered acidic materials suitable.

The weight ratio of the color developing material to the basic dyestuff is generally from 50 to 700% by weight. Parts and preferably at 100 to 300 parts by weight per 100 Parts by weight of the basic dye. In addition, if desired both the basic dye and the Color developing material as a mixture of two or more components be used.

In addition to the color-forming reactants contains the heat-sensitive Recording layer usually still amide waxes, Fatty acid amide compounds such as acetamide, stearic acid amide, Linolenic acid amide, lauric acid amide, myristic acid amide, the amide of hardened beef fatty acid, palmitate Fatty acid, coconut fatty acid amide, methylol compounds the above-mentioned fatty acid amides, methylenebisstearic acid amide and ethylenebisstearic acid amide, zinc stearate or other metal stearates.

The amounts of waxes or amides or stearates are in general 10 to 1000 parts by weight of the color developing material.

The coating generally contains a binder. Examples for binders include starch, oxidized starch, esterified Starch, other modified starches, hydroxyethylcellulose,  Methylcellulose, carboxymethylcellulose, gelatin, casein, Gum arabic, polyvinyl alcohol, styrene-maleic anhydride copolymer salts, Styrene-acrylic acid copolymer salts and styrene Butadiene copolymer emulsions. The amount of used Binders is generally 2-40% by weight, and preferably 5 to 25 wt .-% based on the weight of the total solids.

The coating can also contain a number of adjuvants contain. Examples of such auxiliaries are dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, Sodium lauryl sulfate and defoamer.

Furthermore, the coating composition for the heat-sensitive layer inorganic pigments such as koal, Clay, aluminum silicate, talc, calcium carbonate, calcined Clay, activated clay and oil-absorbing pigments (eg Diatomaceous earth and fine-grained anhydrous silica).

The amount of inorganic pigments in the recording layer can be based on dry coating 10-60 wt .-% be.

In general, water is used as the dispersion medium for Preparation of the heat-sensitive coating composition as used to form the recording layer in the present invention is used.

The basic dye and the color developing material become generally separated by means of a stirrer or a Pulverizing device such as a ball mill or a Sand mill dispersed, and the two dispersions become too a coating composition which is then applied to a Carrier is applied.  

Preferably, the stabilizing agent is combined with the Color developer brought in a dispersed state.

In the formation of the recording layer can be usual Apply a method of forming the recording layer. So you can, for example, suitable coating devices like an air knife, a squeegee and the like for the Coating of the heat-sensitive coating composition apply to a carrier.

Likewise, there is no special limitation regarding the coating amount of the coating composition, generally 2 to 12 g / m² and preferably 3 to 10 g / m² on a dry weight basis. In addition, one more can Underline between the recording layer and the substrate be applied.

For the formation of the color different according to the invention Rear side of the heat-sensitive recording material the following carrier materials are particularly preferred.

The properties of usable carrier materials are as follows Table specified:

example 1 Whiteness after Berger on the recording layer 112.32 Whiteness after Berger on the recording layer opposite surfaces  52.51 difference 59.81

Example 2 recording layer 107.21 back  40.01 difference 67.20

Example 3 recording layer 112.32 back  59.03 difference 53.29

Example 4 recording layer 107.21 back  55.32 difference 51.89

The following table contains whiteness measurements according to Berger at usual thermoreactive materials

The above comparison shows that the inventive design of a opposite the recording page different hue or White confusion of front and back of the Recording material are excluded. In addition, there is the advantage in lower quality requirement for the carrier material.

Claims (7)

A heat-sensitive recording material having a heat-sensitive recording layer coated on a surface of the support material and containing a colorless dye precursor and an acidic compound suitable for forming a color with the dye precursor, characterized in that the coloration is opposite to that of the recording layer Surface of the substrate differs from the still unused recording layer, the difference in whiteness after Berger is at least 40. 2. A heat-sensitive recording material according to claim 1, characterized in that the carrier material is paper. 3. A heat-sensitive recording material according to claim 2, characterized in that the carrier material is a wood pulp-containing Paper is. 4. A heat-sensitive recording material according to claim 2, characterized in that the carrier material is unbleached or contains little bleached pulps. 5. A heat-sensitive recording material according to claim 2, characterized in that the carrier material from a waste paper produced paper is. 6. A heat-sensitive recording material according to any one of claims 1-5, characterized in that the coloring of the Carrier material on the opposite of the recording layer Surface has a whiteness to Berger of 70-10.   7. A heat-sensitive recording material according to any one of the claims 1-5, characterized in that the coloring of the Carrier material on the opposite of the recording layer Surface has a whiteness after Berger of 60-20.