JPS61228985A - heat sensitive recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material capable of giving developed color images having absorption in near infrared region and excellent in color forming property and preservability, by incorporating a specified dye precursor and a specified color developer as color forming components. CONSTITUTION:A colorless or light-colored dye precursor and a color developer are incorporated as color forming components. A fluorene compound of general formula (I), wherein each of R1, R2, R3, R4, R5 and R6 is lower alkyl, is used as the dye precursor. At least one sulfone compound of general (II), wherein each of R1, R2, R3 and R4 is hydrogen, halogen, allyl or alkyl, with the proviso that they are not simultaneously hydrogen, is used as the color developer. The sulfone compound is excellent in color forming property and image preservability. Accordingly, developed color images can be read by semiconductor laser comprising near infrared rays, and a thermal recording material excellent in color forming property and preservability of images can be obtained.

Description

[Detailed Description of the Invention] (A) Field of Industrial Application ' The present invention relates to a two-component coloring type heat-sensitive recording material, and particularly to a heat-sensitive recording material capable of producing a colored image that absorbs in the near-infrared region. It is.

(B) Conventional heat-sensitive recording materials generally have a heat-sensitive recording layer on a support, the main components of which are an electron-donating, usually colorless or flame-colored dye precursor and an electron-accepting color developer. By heating with a thermal head, a thermal pen, a laser beam, etc., the dye precursor and color developer react instantaneously and a recorded image is obtained. has been disclosed. These heat-sensitive recording materials have the advantages of being able to record with relatively simple equipment, being easy to maintain, and producing no noise. It is used in a wide range of fields such as terminals, labels, automatic ticket vending machines, etc. ◇ In particular, thermal recording labels are used as barcode labels for PO8 (point of sale) systems, price display labels, shipping, etc.
POS systems are being used for applications that require temporary printing and pasting, such as shipping labels, and zero consumption.The popularity of POS systems is remarkable in large mass retailers such as supermarkets and department stores, chain specialty stores, restaurants, etc. The purpose is to aggregate and analyze product sales information in order to clearly understand customer needs and formulate rational management strategies. Currently, the method of optically reading OOR characters using a scanner is rapidly growing.

Therefore, various printing methods are currently being tried, and among them, the thermal recording method can be said to be the most excellent.

This is because the printing method uses chemical or physical changes in substances due to heating to record images, and does not require development and fixing, nor does it require replenishment of printing ink.

That is, it has many features such as being able to downsize and simplify the machine and speed up recording, and there is no need to worry about ink staining hands or products or ink fading.

Furthermore, to read colored images such as bar codes, He/Ne laser light with red light of a wavelength of 633 nm has traditionally been used, but semiconductor lasers have recently come into use. This has the advantages of being able to be directly modulated by current, allowing for miniaturization, being easy to use, low cost, and having an oscillation wavelength in the near-infrared range of 700 to 1500 nm, which reduces malfunctions due to dirt. Therefore, it is desired to obtain a colored image that can be read with a semiconductor laser even on a heat-sensitive recording label. However, in the conventionally used two-component heat-sensitive recording material consisting of a leuco dye and a color developer, even in a black color system, the absorption wavelength of the color image is 55% on the long wavelength side.
Because it has a wavelength of 0 to 620 nm, it can be read with a He5Ne laser beam, but it cannot be read with a semiconductor laser having a wavelength in the near-infrared range. The object of the invention is to provide a heat-sensitive recording material that can produce colored images, and another object is to provide a heat-sensitive recording material that has excellent color development and storage stability. In a heat-sensitive recording material containing a precursor and a color developer as coloring components, a fluorene compound represented by the following general formula (I) is used in front of the dye and in the electrolyte, and the general formula (I) (wherein R1, R8, R3, RRI and R6 each represent a lower alkyl group@) By using one or more sulfone compounds as the color developer represented by the following general formula (2), (in the formula,
R,, R,, R, and R4 are hydrogen atoms, halogen atoms,
Represents an allyl group or an alkyl group. However, R1, R,
, R, and R4 are not hydrogen atoms at the same time.The desired heat-sensitive recording material can be provided.

The fluorene compound represented by the general formula (I) itself is a colorless to light-colored crystal and does not have absorption in the near-infrared region, but when it reacts with a color developer, it develops a green color from the back, and the colored image is , O having absorption in the near-infrared region. Specific examples of the fluorene compound according to the present invention include 3,6-bis(dimethylamino)fluorene-9-
Spi, -s/-(61-dimethylaminophthalide),
3-diethylamino-6-dimethylaminofluorene-
9-spiro-a'-(6'-dimethylaminophthalide)
, 3.6-bis(diethylamino)fluorene-9-spiro-a/-(S/-dimethylaminophthalide), 3-
dibutylamino-6-di)f-ruaminofluorene-9-
spiro-a/-(6/-dimethylamino7thallide), 3
-dibutylamino-6-diethylaminofluorene-9
-spiro-37(6/-dimethylaminophthalide), 3
．． 6-bis(dimethylamino)fluorene-9-spiro-3/-(s/-diethylaminophthalide), 3-diethylamino-6-dimethylaminofluorene-9-spiro-3'-(6'-diethylaminophthalide) , 3-dibutylamino-6-dimethylaminofluorene-9-spiro-a/-(el-diethylaminophthalide), 3.
6-bis(diethylamino)fluorene-9-spiro-
a/-(S/-diethylaminophthalide), 3,6-bis(dimethylamino)fluorene-9-spiro-a/(
S/-dibutylaminophthalide), 3-dibutylamino-6-diethylaminofluorene-9-spiro-31-
(6/-diethylaminophthalide), 3-diethylamino-6-dimethylaminofluorene-9-spiro-37
-(6/-dibutylaminophthalide) and the like.

An electron-accepting compound is used as the monochromatic agent that causes the fluorene compound according to the present invention to develop color when heated.
There are few compounds that satisfy both aspects of image preservability, and among them, the sulfone compound represented by the above general formula (■) has been found to be excellent in color development and image preservability◎ Specific examples of the sulfone compound according to the present invention are as follows. , e.g. eva, bis(3-allyl-4-hydroxyphenyl)sulfone, bis(3-methyl-4-hydroxyphenyl)sulfone, bis(3-7'thyl-4-hydroxyphenyl)
Sulfone, bis(3,5-sialyl-4-hydroxyphenyl)sulfone, bis(3-chloro-4-hydroxyphenyl)sulfone, 3-allyl-4,4'-dihydroxydiphenylsulfone, bis(2-ethyl-4 -hydroxyphenyl) sulfone, 3-isofuropyru 4.4
'-dihydroxydiphenylsulfone, bis(2,5-
dimethyl-4-hydroxyphenyl) sulfone, bis(
Examples include 2,5-dichloro-4-hydroxyphenyl) sulfone.

The amount of each component constituting the heat-sensitive recording material of the present invention is preferably 0.1 to 6 parts by weight of the sulfone compound according to the present invention per 1 part by weight of the fluorene compound according to the present invention.

In the heat-sensitive recording material of the present invention, the main components that may be added as necessary in addition to the color-forming components will be specifically described.

Examples of the binder include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, water-soluble polymers such as sfL/:/-maleic anhydride m-cox combination, and ethylene-maleic anhydride copolymer. rubber binder, styrene-butadiene copolymer,
Examples include latex-based water-soluble binders such as acrylonitrile-butadiene copolymer and methyl acrylate-butadiene copolymer.

Examples of pigments include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin, and the like.

In addition, higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, oxidized paraffin, polyethylene, oxidized polyethylene, stearic acid amide, and castor wax are used to prevent head wear and stickiness. Examples include dispersants such as sodium dioctyl sulfosuccinate, ultraviolet absorbers such as benzophenone and benzotriazole, surfactants, and fluorescent dyes.

Paper is mainly used as the support for the heat-sensitive recording material of the present invention, but various nonwoven fabrics, plastic films, synthetic papers, metal foils, etc., or composite sheets made of a combination of these can also be used as desired.

The heat-sensitive recording material of the present invention is generally used in ordinary facsimiles,
In addition to being used in printers, it is also used for special purposes that detect near-infrared light. When a high preservability of the colored image is desired depending on the application, for example when used for a label, a protective layer may be laminated on the heat-sensitive recording layer to protect the uncolored area and the colored image area from the external environment. 0 In this case, the main components of the protective layer include various water-soluble resins, latex,
When a photocurable resin is used, pigments, water resistant agents, water repellents, antifoaming agents, ultraviolet absorbers, etc. can be added as necessary. Furthermore, for label binding, an adhesive layer may be provided on the back side so that it can be easily attached to the solid surface after printing. In this case, a release paper is provided on the adhesive layer.

(Gai Example Next, the present invention will be explained in more detail with reference to Examples.

Example 1 3.6-bis(dimethylamino)fluorene-9-spiro-a/-(t,l-dimethylaminophthalide 20I
was dispersed in a ball mill with 1% polyvinyl alcohol aqueous solution 80II, 90. On the other hand, bis(3-allyl-4-hydroxyphenyl) sulfone 50I was dispersed in a ball mill with 1% polyvinyl alcohol aqueous solution 2001.0 After mixing these dispersions. Add 250JF of a 40% dispersion of calcium carbonate, and further add 250JF of a 25% dispersion of zinc stearate, 4011 a 25% dispersion of stearamide,
．． A 9.8% polyvinyl alcohol aqueous solution 625I was added and thoroughly stirred to prepare a coating liquid. This coating liquid was coated and dried on a base paper with a basis weight of 55 mm to a solid coating amount of 617 m'' to obtain a heat-sensitive recording material. Example 2 Bis(3-allyl- 4-hydroxyphenyl) sulfone, bis(3-allyl-4-
hydroxyphenyl) sulfone and 3-71j Ru4*4
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that a mixture of '-dihydroxydiphenylsulfone was used.

Comparative Example A heat-sensitive recording material was obtained in the same manner as in Example 1, except that K, 4,4'-isopropylidene diphenol was used instead of bis(3-allyl-4-hydroxyphenyl)sulfone used in Example 1. Ta.

The following evaluations were performed on the heat-sensitive recording materials obtained in Evaluation Examples 1 and 2 and Comparative Examples, and the results are shown in Table 1.

(1) Color density; Printed under the conditions of 16.00 V and 3.0 milliseconds, and measured the optical density of the colored image using Macbeth RD 9.
(2) Image storage stability: The colored image was stored in an environment of 60°C for 24 hours, and the optical density was measured before and after storage at 90°C, and the image storage rate was calculated from the formula below. (3 ) Image water resistance: The colored image was immersed in 20° C. tap water and stored for 20 hours.The optical density before and after storage was measured, and the image preservation rate was determined in the same manner.

(4) Near-infrared light reading; GmAs semiconductor laser (
780 mm) to check whether the bar code could be read after printing.

Table 1 [ (Takumi Effects of the Invention) As shown in Table 1, the heat-sensitive recording material of the present invention has a color image that can be read by a semiconductor laser that emits near-infrared light, as well as improved color development and storage stability of the image. It turns out that it is excellent.

Claims (1)

[Scope of Claims] A heat-sensitive recording material containing a normally colorless or light-colored dye precursor and a color developer as coloring components, wherein the dye precursor is a fluorene compound represented by the following general formula (I), and the dye precursor is a fluorene compound represented by the following general formula (I), (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, in the formula, R_1, R_2, R_3, R_4, R_5
and R_6 each represent a lower alkyl group. ) A heat-sensitive recording material, wherein the color developer is one or more sulfone compounds represented by the following general formula (II). General formula (II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R_1, R_2, R_3 and R_4 represent a hydrogen atom, a halogen atom, an allyl group or an alkyl group. However, R_1, R_2, R_3, R_4 are not hydrogen atoms at the same time.)