JPS61228986A - Thermal recording material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a two-component color-developing type heat-sensitive recording material, and more particularly to a heat-sensitive recording material capable of producing a colored image having absorption in the near-infrared region.

@) Conventional technology 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 light-colored dye precursor and an electron-accepting color developer. , a dye precursor and a color developer instantaneously react by heating with a thermal pen, laser light, etc., and a recorded image is obtained, and is disclosed in Japanese Patent Publication No. 43-4160, Japanese Patent Publication No. 45-14039, etc. has been done. 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, and automatic ticket vending machines such as train tickets.

In particular, thermal recording labels include barcode labels for POS (point of sale) systems, price display labels, shipping and
It is used for applications that require pasting after printing, such as shipping labels. POS systems are becoming particularly popular in large-scale mass retailers such as supermarkets and department stores, as well as chain specialty stores and restaurants. The purpose of this service is to aggregate and analyze product sales information in order to clearly understand consumer needs and formulate rational management strategies.
b. As one of these methods, the method of optically reading barcodes and OCR characters displayed on products sold in stores using a scanner is currently 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, the machine has many features such as being compact, simple, and capable of speeding up recording, and there is no fear of ink staining hands or products or ink fading.

Traditionally, H@.Ne laser light with a red light wavelength of 633 nm has been used to read barcodes and the like, which are secondary colored images, but semiconductor lasers have recently come into use. It can be directly modulated by current and can be miniaturized, making it easy to use, low cost, and because the oscillation wavelength is in the near-infrared range of 700 to 1500 nm, there are fewer malfunctions caused by dirt, so it is widely used. It is becoming popular. Therefore, it is desired to obtain colored images that can be read with a semiconductor laser even on heat-sensitive recording labels. However, in the conventional two-component heat-sensitive recording material consisting of a leuco dye and a color developer, the absorption wavelength of a colored image is 550 on the long wavelength side even in a black coloring system.
Since the wavelength is ~620 nm, it can be read with Hξ·NeL/-f light, but it was not possible to read with a semiconductor laser having a near-infrared wavelength.

(C1 Purpose of the Invention The purpose of the present invention is to provide a heat-sensitive recording material from which a colored image having absorption in the near-infrared region can be obtained, and another purpose is to provide a heat-sensitive recording material with excellent color development and storage stability. It is to be.

(9) Structure of the invention In a heat-sensitive recording material containing a normally colorless or light-colored dye precursor and a color developer as color-forming components, a fluorene compound represented by the following general formula +1) is used as the dye precursor, and the general formula (In the formula, R1s R2% RB , R5 and R6 each represent a lower alkyl group.) By using a compound represented by the following general formula (m) as the color developer, , R1 represents a hydroxy group, and R2 and R3 represent a hydrogen atom, a halogen atom, or an alkyl group.) A thermosensitive recording material can be provided.

The fluorene compound represented by the general formula (1) itself is a colorless to light-colored crystal and has no absorption in the near-infrared region, but it develops a color from blue to green by reaction with a color developer, and its colored image is Absorbs in the near-infrared region.

Specific examples of the fluorene compound according to the present invention include 3,6-bis(dimethylamino)fluorene-9-
Spiro-3'-(6'-dimethylaminophthalide), 3
-diethylamino-6-dimethylaminofluorene-9
-spiro-3'-(6'-dimethylaminophthalide),
3.6-bis(diethylamino)fluorene-9-spiro-3'-(6',-dimethylaminophthalide), 3-
Dibutylamino-6-dimethylaminofluorene-9-
Spiro-3'-(6'-dimethylaminophthalide), 3
-dibutylamino-6-diethylaminofluorene-9
-spiro-3'-(6'-dimethylaminophthalide),
3.6-Bis(dimethylamino)fluorene-9-spiro-3'-(6'-diethylaminophthalide 1.3-diethylamino-6-dimethylaminofluorene-9-spiro-3'-(6'-diethylaminophthalide) ), 3-
Dibutylamino-6-dimethylaminofluorene-9-
spiro-3'-(6'-diethylaminophthalide), 3
．． 6-bis(diethylamino)fluorene-9-spiro-3'-(6'-diethylaminophthalide), 3.6-
Bis(diethylamino)fluorene-9-spiro-3'
-(6'-dibutylaminophthalide), 3-dibutylamino-6-diethylaminofluorene-9-spiro-3
'-(6'-diethylaminophthalide), 3-diethylamino-6-dimethylaminofluorene-9-spiro-
Examples include 3'-(6'-dibutylaminophthalide).

An electron-accepting compound is used as the color developer 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 compound represented by the general formula (I) has been found to be excellent in color development and image preservability.

Specific examples of the compound represented by the general formula (seal) are:
For example, 4,4'-thiobis(2,5-dichlorophenol), 4,4'-thiodiphenol, 2,2'-thiobis(4-chlorophenol), 2゜2'-thiobis(
4,6-dichlorophenol), 4,4'-thiobis(
2,6-dimethylphenol), 4,4'-thiobis(
2,5-dimethylphenol), 4,4'-thiobis(
2-isopropyl-5-methylphenol), 4.4'
-thiobis(2-cyclohexylphenol), 4.4
'-Thiobis(2-isopropylphenol), 4.4
'-Thiobis (3-bimanual phenol), etc.
b.

The composition of each component constituting the heat-sensitive recording material of the present invention is as follows: 1 part by weight of the fluorene compound represented by the general formula (1) as the dye precursor, and 1 part by weight of the fluorene compound represented by the general formula (a) as the color developer.
It is preferable to use 0.1 to 6 parts by weight of the compound t represented by:

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.

As binders, water-soluble materials such as starches, hydroxyethyl cellulose, methyl cellulose, carboxylic dimethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, styrene-maleic anhydride copolymer, and styrene-maleic anhydride copolymer are used. latex-based water-soluble binders such as styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, and methyl acrylate-butadiene copolymers.

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 bencitriazole, 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 a 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 in order to protect the uncolored area and the colored image area from the external environment. In this case, the main components of the protective layer include various water-soluble resins, latex,
A photocurable resin is used. Further, pigments, water resistant agents, water repellents, antifoaming agents, ultraviolet absorbers, etc. can be added as necessary. Furthermore, for labels, an adhesive layer may be provided on the back surface so that it can be easily attached to the solid surface on the side after printing. In this case, a release paper is provided on the adhesive layer.

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

Example 1 3.6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylaminophthalide) 20! i
"t-1% polyvinyl alcohol aqueous solution sot was dispersed in a ball mill.Meanwhile, 4,4'-thiodiphenol 5011% polyvinyl alcohol aqueous solution sot was dispersed in a ball mill. After mixing these dispersions, 40% of calcium carbonate Dispersion 250Pt was added, and 25% zinc stearate dispersion 40?, stearamide 25Y; dispersion 200S', and 8% polyvinyl alcohol aqueous solution 6255Ft were added and sufficiently stirred to prepare a coating solution.

Tsubo this coating liquid! 6 as solids coating amount on 55 g-/- base paper. A heat-sensitive recording material was obtained by coating and drying so as to give /-.

Example 2 2 instead of 4,4'-thiobisphenol in Example 1
, 2'-thiobis(4-'70 lofer) was used in the same manner as in Example 1 to obtain a heat-sensitive recording material.

Comparative Example Instead of 4,4'-thiobisphenol in Example 1, 4
．． A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 4'-isopropylidene diphenol lfl was used.

Evaluation Examples 1 and 2. Table 1 shows the results of all the following evaluations of the heat-sensitive recording materials obtained in the comparative examples.

(1) Color density: Printing was performed under the conditions of 16.00 V and 3.0 milliseconds, and the optical density of the colored image was measured using Macbeth RD918.

(2) Image water resistance: The colored image was immersed in tap water 21 at 20° C. and stored for 20 hours. The optical density before and after storage was measured, and the image preservation rate was calculated from the formula below.

Optical density after storage Image storage rate = X100 Optical density before storage (3) Near-infrared pre-reading F); Possibility of reading after bar food printing was investigated using a GaAs semiconductor laser (780 nm).

(F) 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 all near-infrared light, and has improved image color development and storage stability. It turns out that it is excellent.

Claims (1)

[Scope of Claims] In a heat-sensitive recording material containing a normally colorless or light-colored dye precursor and a color developer as color forming components, 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.▼ (In the formula, R_1, R_2, R_3, R_4, R_5 and R_6 each represent a lower alkyl group.) The color developer is represented by the following general formula (II) A heat-sensitive recording material characterized by being a compound. General formula (II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R_1 represents a hydroxy group, R_2 and R_3 represent a hydrogen atom, a halogen atom, or an alkyl group.)