JPS5922795A - Heat sensitive recording element - Google Patents

Abstract

PURPOSE:To provide a heat sensitive recording element excellent in sensitizing effect and image stabilizing effect, obtained by providing a recording layer prepared by dispersing the particle of a phenolic color forming agent based on alkyl gallate and the particle of a leuco color in a binder in a mutually independent form. CONSTITUTION:For example, a binder such as PVA is dissolved in hot water and, after cooling, a leuco color [e.g., 2-(2-chloroanilino)-6-diethylaminofluorane] and a phenolic color forming agent based on alkyl gallate shown by a formula (wherein R is 3-13C alkyl) (e.g., lauryl gallate) are respectively and separately dispersed in the prepared solution to prepare two liquids. These two liquids are mixed to be applied to a support such as paper to obtain an objective heat sensitive recording element. EFFECT:This heat sensitive recording element has the same capacity as a system containing a sensitizer from the viewpoint of sensitivity without using a sensitizer effecting adverse influence including background fog such as fatty amide.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive color-forming recording material having a remarkable sensitizing effect and an image stabilizing effect.

Conventionally, combinations of leuco dyes and color formers made of acidic substances have been widely used in various information recording applications, particularly in heat-sensitive recording, pressure-sensitive recording, electrostatic photographic recording, and the like. For example, as a recording element used for heat-sensitive recording, a leuco dye that is normally colorless or light-colored and a phenol that is solid at room temperature and heat-melting are mixed in a polymer binder, each of which has an independent zero phase. A recording layer having a dispersed shape on a suitable substrate is used.

In such a heat-sensitive recording medium, the coloring agent for leuco dye is melted in response to a thermal image and the leuco dye is colored by producing protons. The fer/fer color formers used in this product only melt at very high temperatures, so they have low sensitivity to heat.
Along with this, there is a drawback that the density of the recorded image is generally low. There is a problem that the shredded recording must be performed at a high temperature (therefore, a high temperature heat U is required), and the temperature of the conveyance system in the thermal recording device also rises, which causes fogging. In order to overcome this drawback, recently a method has been adopted in which a large amount of sensitizer such as fatty acid amide is contained to lower the coloring temperature, that is, to increase the sensitivity.
Satisfactory results have not yet been obtained regarding odor-C, such as high L concentration and reproducibility.

The inventors of the present invention have found that if a recording layer is prepared by dispersing alkyl tp acid as a phenolic coloring agent in a binder, the capri density can be achieved without the need to contain a special sensitizer. It would be interesting to noticeably improve thermal sensitivity without increasing the actual price, and it would be even more effective.”
It has been found that the flexibility and sticking properties can be improved.

That is, the present invention provides particles of a gallic acid alkyl ester represented by the general formula (where I< is a carbon & 3 to 13 alkyl group r as a main component) particles of a norlic coloring agent, particles of a leuco dye -r, T! 4. A heat-sensitive recording material is provided in which a recording layer comprising two layers independently dispersed in a binder is provided on a support J2.

Figure 1 is a diagram showing the relationship between applied temperature and coloring temperature, that is, the static coloring characteristics, using the 1ψ thermal recording medium and Jt Soft Tester 1 manufactured by Honshu. While
The characteristics of alkylnisder gallate when used as a phenolic coloring agent will be explained.

Bisphenol A (melting point 155-156°
C), but when it is used alone as a coloring i'flJ, it generally develops color at an applied temperature of about 130°C, as shown by the curve fli++ in FIG. 1)'1. -J- At about 140°C, color development is 7 @ degree 1.31'r! It shows a tendency to become a highly saturated coloring state. However, because its color development temperature, that is, its thermal sensitivity, is +30'C, when it is put into practical use, it tends to cause problems such as image (W concentration) [°C].
In addition, bisphenol A↑,) As my 11th birthday, @Kumahemeto's old history - Noru) Observation rluf degree change of bisphenol Δ molten solidification? 11, it becomes easy to cause the so-called sticking phenomenon in which the solidified molten material sticks to the heating head.

For the purpose of compensating for the above-mentioned drawbacks of using K, bisphenol A alone, we added a part, molding agent, and Q to Th1S.
In a system in which stearamide is added to bisphenol 8 as an agent, the temperature in the power generation chamber is approximately 75°C, the saturated coloring temperature is approximately +20°C (saturated coloring density 182), and the thermal sensitivity is slow. The defects caused by Kokichi are eliminated, but the background concentration (initial concentration in Figure 1) is 0.8 for bisphenol A, JP's yarn (open), but it is 0.8 for yarn with a sensitizer added. In the case of a), there is a tendency for the background density to increase up to 1.7 by 10%.Therefore, yarns that require as little sensitizer as possible are desirable as yarns.

On the other hand, when isoamyl gallic acid (melting point 142°C, carbon number 5) is used alone, as shown by curve (1), the humidity in the power generation room is approximately 80°C and the saturated light color temperature is At about 120℃, the thermal sensitivity is almost the same as that of yarn σ■ (+
k
97.5℃, carbon number 12) (!L- When used alone, the color development temperature is about 7 as shown in curve (11)
At 0°C, the saturated color development temperature is about 120°C, which is less than the thermal sensitivity Vi (+': 4-1 direct metal) than the system σ■.

In this way, when gallic acid alkyl ester is used as a phenolic coloring agent, it is possible to improve the sensitivity by using gold-containing sensitizers without using sensitizers such as fatty acid amide, which have negative effects such as coloring. It is understood that thermal paper with a sensitivity equal to that of a thread 'f' is ranked No. 1.

Another characteristic of the gallic acid alkyl ester used in Kidori J is that the number of gallic acid alkyl esters of the ester substituent R in 11 is
The melting point of the ester tends to be adjusted to IL (temperature). In other words, taking into account J compatibility with the equipment, etc. By substituting with a material having a certain number of carbon atoms, a thermal paper with a sensitivity of 100 to 100% is produced.

Used as a phenolic coloring agent in misfires
Q f' Among them, it is important to select an argyl group having 3 to 13 carbon atoms for ester substitution. That is, when the number of carbon atoms in the alkyl group is less than 3,
Due to the increase in water solubility, coloring is more likely to occur during coating, and when the number of carbon atoms is greater than 13, coloring may occur during coating or drying due to the low 1' contact point. , background fogging, etc. will occur.

From this point of view, typical examples of gallic acid alkyl esters that can be used for unexploded 1j14 include n-propyl gallate, butyl gallate, isoamyl gallate, octyl gallate, ucryl gallate, etc. I get kicked. Among these, gallic acid alkyl esters in which the number of carbon atoms in the argyl group is in the range of 3 to 7 are useful for image preservability of office supplies such as plastic erasers.

The gallic acid alkyl ester used in the present invention can not only be used alone, but also in combination with other phenolic coloring agents as long as the properties are not lost. It can be used as Other phenolic color formers that may be used include 44
'-isopropyritine diphenol (bisfuco, /-le A), 44'-methylene-his (phenol), 4.4
'-ia7'ropyritenebis(2-chlorophenol)
, 4.47-impropylidenobis (26-dichlorophenol), 44'-impropylidenobis (2-tertiary glutylphenol), 44'-th.

Imbutyritenebis (2-medilfe7-yl), 4.4
'-Cyclohexylitine diphenol, 22'-thiobis(4,6-dichlorophenol), P-tert-glylphenol, 3,4-dichlorophenol, 00'-diphenol, 4-hydroxydiphenoxide , 22'-dihydroxybisphenol, 2,2'-methylenebis(
4-chlorophenol), 2,6-dioxybenzoic acid,
Examples include 1-ogycy-2-su7tolic acid. When used in combination, the amount of other phenolic coloring agent is 100% by weight per 100% by weight of gallic acid alkyl ester.
There is no particular problem as long as it is within the following range.

Furthermore, all the leuco dyes used in this type of thermal recording paper can be used as leuco dyes, such as triphenylmethane thread leuco dyes, fluoran thread leuco dyes, and spiropyran thread leuco dyes. ,d
- Daminlactam thread leuco pigment, auramine thread leuco pigment, phenothiazine thread leuco pigment, etc. singly or in combination.”
used in combination of the two. A reasonable example is as follows.

triphenylmethane yarn leuco dye 33-bis(P-dimethylami/phenyl)phthalide,
3.3-bis(P-dimethylaminophenyl)-6-diethylaminophthalide, 33-bis(P-dimethylaminophenyl)-6-diethylaminophthalide, 33-bis(P-dimethylami/phenyl)-6-, /triphenyl, 4-hydroxy-41-dimethyl-ami7triphenylmethanelactone, 4,4'-bisdihydroxy-
331-bisdiaminotriphenylmethane lactone.

3-dimethylamino5.7-dimethylfluorane, 3-
Diethylamine 15.7-dimethylfluorane, 3-diethylamine/-6,7-dimethylfluorane, 3-cyclohexylamine/-6-chlorofluorane, 3-diethylamine-6β monomethoxyfluorane, 36-PisuW -methoxyethoxyfluorane, 3-diedylamino-7-'; benzylaminofluorane, 3-diJ.

thylamino-6-methyl-7-chlorofluorane, 3-
Diethylamide/-6-methyl-7-anilimethylolane, 37-bisdiethylamine/fluorane, 3-diethylamino-7-notoxyfluorane.

8'-methoxybenzoindolinospiropyran, 3-phenyl-8'-methoxybenzoindolinospiropyran, 6'-chloro-8'-methoxybenzoindolino/spiropyran, 56'-dichloro-8'-methoxybenzoindolinospiropyran, 4,7.8'-)rimethoxybenzoindolinospiropyran, benzo-β-naphthospiropyran, 3-methyl-diβ-naphthospiropyran,
1.3.3-Trimedel-6'-chloro-8'-methoxyindoly/-benzospiropyran.

Loaf three-lactam leuco dye 9-(p-nitroanilino)3.6-bis(diethylamino)-9-xanthyl-Noractam, fragrant nolactam,
Lactam of 2-(3,6-bis(diethylamino)-9-(o-chloroanilino)xanthyl]benzoic acid.

Auramine Thread Leuco Auramine 2,5-Si'/Roro N-7enyl Leuco Auramine, 4,4'-Bis-dimethylamino-34-chlorphenyl Leuco Auramine, 4,4'-His-dimethylamino/Piperazine Hyde Roll Fetch Asin Clues 4-Pigment Benzoyl Leucomethylene Glue p 90 Lopenzoyl Leucomethylene Flu, 3.4-'; Chlorobenzoyl Leucomethylene Glue, ■]-Methoxybenzoyl Leucomethylene Blue.

In the present invention, 1α of V”6 persimmons as banhgu
All of the water-soluble or moisture-friendly binders used in α fiery color recording materials are used, including polyvinyl alcohol, l'lR74), carboxymethyl sulfoxylfj cellulose, Examples include edylcellulose, arabic comb, seiratin, casein, polyvinylpyrrolidone, polyacrylamide, styrene-maleate copolymer, vinyl ether maleate copolymer, and styrene-butadiene copolymer latex. .

In non-explosion 1iJJ, the leuco dye is preferably used in an amount of IO to 400@Id% (hereinafter, percentages and parts are based on weight) based on the binder.It is particularly preferable to use it in a concentration of 50 to 200%, and it also plays a role as a phenolic coloring agent. Acetic acid alexyl ester is used in combination with other phenolic color formers, from 5 to 1000%, especially from 50 to 60096%, based on the total phenolic color removing component or binder. is preferable.

11 & ff ~ To improve various properties of the recording layer,
For the well-known arrangement of 'th' additives, which are themselves well-known. It can be blended with For example, white f! such as titanium dioxide is used to improve the whiteness of the recording layer or to increase its amount. di r'l,
Alternatively, fillers such as extensible clay and calcium carbonate can be blended, and in order to check the recording sensitivity, if it is not particularly necessary in case of short failures, paraffin wax, carnauba socks, etc. can be mixed with animal and plant-based waxes. Synthetic substances such as stearic acid, various soaps, higher fatty acids such as fatty acid amide or their derivatives, polyethylene socks, polypropylene wax, and polyethylene glycol can be blended. Aluminum such as triethanolamine can be used as an auxiliary agent to more effectively prevent background coloration (background coloration), although it is generally not necessary.
Contains lecameramine and other organic bases. May be combined.

Furthermore, in the case of the present invention, water control agents, antifoaming agents, etc. may be added as desired, although they are generally not necessary.

+f (S) In preparing the coating composition for the thermal recording layer, the above-mentioned combination calculus is dissolved in hot water, the resulting solution is completely cooled, and the leuco dye and phenolic coloring agent are added to this bath solution. Disperse each separately to form two liquids,
Finally, it is a good idea to mix these two liquids before application.

It is possible to use a laminated layer, etc. The recording layer has a dry weight of 2 to 10 g/nf, 4'! It is preferable that the coating amount be 3 to 89/r+.

The heat-sensitive recording element of the present invention can be used as a recording element for facsimiles, printers, telegraph communications, computer terminals, measuring instruments, ticket vending machines, copying machines, etc. that use thermal heads, thermal pens, infrared flash lamps, lasers, etc. as heat sources. Useful.

The invention is illustrated by the following example.

Example 1 A leuco dye fraction liquid containing 70 heavy acid parts and a phenolic color former dispersion liquid were separately pulverized and dispersed in a ball mill for 10 hours. After mixing both solutions, stir thoroughly and homogenize, then apply the coating solution to one side of a high-quality paper with a basis weight of about 50 Q/rd so that the coating weight after drying is about 6 Q/rd. The thermal recording paper of Example 1 was prepared by drying with a wire bar and drying with hot air at 40° C. for 5 minutes.

Static color development characteristics were determined from the color density at each temperature when the surface of the thermal paper thus obtained was heated for 10 seconds under a pressure of 5 kg/cJ using a Toyo Seiki thermal gradient tester. The results are shown as curve I in FIG.

Furthermore, all the characteristics of six persimmons were measured as described later.

Example 2 A thermal paper was produced in exactly the same manner as in Example 1, except that isoamyl gallate was used instead of the acrylic acid used in Example 1, and static coloring was carried out in the same manner as in Example 1. Characteristic,
Various other characteristics were also measured. In addition, 4 of the static coloring characteristics
I! The constant results are shown by the curve ■ in Figure 1.

Comparative Example 1.2 As Comparative Example 1, instead of Ryoko Acidacrylate of Example 1,
A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that Bispher/-A was used, and a 30% aqueous dispersion of stearamide was added to the coating solution of Comparative Example 1 as a sensitizer. Add and mix parts by weight to make it homogeneous, other than that,
A wI thermal recording paper was prepared in the same manner as in Example 1, and this was designated as Comparative Example 2. The static color development characteristics V of these thermosensitive recording papers were measured, and the results are shown as curve III for Comparative Example 1 and curve ■ for Comparative Example 2. Furthermore, other characteristics were measured.

Comparison Example 3 False Heat-sensitive recording paper was prepared in exactly the same manner as in Example 1 except that ethyl gallate (alkyl group has 2 carbon atoms) was used in place of the gallic acid salt used in Example 1. This was prepared as Comparative Example 3.

As is clear from the measurement results of static coloring characteristics shown in Figure 1,
The heat-sensitive recording material of the present invention not only has a greatly improved thermal sensitivity compared to Comparative Example 1 using Bispher/-Ak phenolic coloring agent, but also completely improves the sensitivity with Comparative Example 1'z stearamide. The recording surface was highly sensitive and had a very white background, without causing any scratches as seen in Comparative Example 2.

Therefore, Examples 1 and 2. In order to measure the degree of background fogging regarding Comparative Example 2.3, reflection density was measured using a densitometer PDA-65 manufactured by Roku Konishi Photo Industry using light transmitted through an ASIPER filter. The results are shown in Table 1.

Table 1 From the results, it is clear that the thermal paper of the present invention has less background fog than Comparative Example 2 in which a sensitizer was added, and that the number of carbon atoms in the alkyl group of the gallic acid alkyl ester is 2
Comparative Example 3 using ethyl gallate as the phenolic coloring agent
It is clear that the background fog increases significantly.

Next, the thermal recording papers of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were calendered, and the respective ktq
After the surface smoothness was made hot for about 700 seconds, commercially available CC
I TT-Gl11 standard thermal facsimile p-3
1OS (+J'F: manufactured by iJ Theta Instruments) was used to thermally record the image of ``Seiko Gakkai Facsimile Test Chart No. 1''. Table 2 shows the evaluation of the dot reproducibility of recorded images and the occurrence of sticking during recording. still,
The recording density of the heat-sensitive facsimile E IJ is 8 dots/lT1m in the scanning direction, and 385 dots/llllll1 in the sub-scanning direction.
The applied voltage per dot is approximately 6W.

As is clear from the above results, thermal paper with a misfire of 1.
Images with good dot reproducibility are obtained, and there is no occurrence of sticking to the heating head.

On the other hand, in Comparative Example 1, in which the phenolic coloring agent was bisphenol A alone, the dots were blurred, and severe sticking occurred to the heating head, and in Comparative Example 2, in which a sensitizer was added to Comparative Example 1, , there was no sticking, but the smearing of doy) was so bad that it was hard to see.
+Iti image was obtained.

Next, Example 2, Comparative Example 1, Comparative Example 2
Fully color the thermal paper at 150°C, and use a commercially available unused plastic eraser (5eed Rubber Co,
4'X on the full color development of the rubber surface of L'rl) S-100)
After leaving it in a dark room for 72 hours, the residual density was measured and compared between the eraser contact area on the colored paper surface of the thermal recording paper and the 111X contact area of the thermal recording paper.
The results are shown in Table 3.

In Example 2 of Table 3, Non-exposure 1, no change in concentration was observed.
] However, Comparative Examples 1 and 2. ,! : There was a noticeable change in density.

[Brief explanation of the drawing]

Figure 1 shows the unexploded 8IJ and h! obtained in a comparative example. Z
The static color development characteristics of J thermal paper are shown. Procedural amendment (formality) 1. Indication of the case 1982 Patent Application No. 133266 2, Name of the invention Thermal recording medium 3 - Person making the amendment IO month 26, 1988 (Shipping date)

Claims (1)

[Scope of Claims] Particles of a phenolic coloring agent whose main component is an alkyl ester of botanical acid represented by the general formula (wherein R is an alkyl group having 3 to 13 carbon atoms), and particles of a leuco dye. A heat-sensitive recording material having a recording layer on a support, in which a recording layer is formed by independently dispersing the following: