JPS58136489A - Heat-sensitive recording sheet - Google Patents

Abstract

PURPOSE:To lower the start temperature of a color producing reaction and obtain an excellent sensitizing effect with a smaller amounts of materials, by incorporating a specified carbonic acid diester as a sensitizer in a color producing layer of a heat-sensitive recording sheet. CONSTITUTION:A carbonic acid diester of the formula (wherein each of R1 and R2 is a methyl group, a ethyl group or a propyl group; n is 0-2) is incorporated into the heat-sensitive color producing layer comprising a well-known colorless or light-colored basis dye and an organic color developer such as a phenol. 3-10 parts of the organic developer and 0.5-1 part of the diester are used per 1 part of the dye. After pulverizing these materials by a mill or the like, 1-20 parts of a filler and 10-25 parts (based on the total amount of solids) of a binder are added thereto together with other additives, and the resultant coating liquid is applied to a paper, a film or the like to obtain the heat-sensitive recording sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a heat-sensitive sickle sheet Kml, 41 to 1 high! Z placed on the chest of a high-sensitivity heat-sensitive sickle sheet suitable for F station and high-speed recording
It is something.

Normally colorless or light-colored, Daiboku Netsu Le-sheet is produced by utilizing a heating reaction between a basic colorless dye and an organic primary coloring agent such as phenol or organic acid.
11th meeting 1E145-140841, special-1B4g-1
It has been widely put into practical use, such as T-Ding $6.

In general, heat-sensitive sickle sheets are made by grinding and dispersing basic colorless dyes and organic primary colorants into fine particles, then mixing the two, and adding binders, fillers, device improvers, lubricants, and other auxiliaries. The obtained am is applied to a support KI such as a film in paper
It has been processed to produce color through an instant chemical reaction when heated! It is for getting a plow. In this case, various hues can be obtained by selecting the type of colorless dye.・These thermographic sheets are used for industrial measurement recording needles, combiators, information overconfidence terminals, facsimile machines, printers for electronic desk calculators, and automatic ticket vending machines for transportation, etc. Applications are underway. These recording devices are equipped with a heating element such as a thermal head medium heat vent, and the heat-sensitive brass sheet is heated by touching these heating elements KII, or by being heated by the energy of a specific light. , color develops to obtain f#. A thermal head is a device in which a minute resistor is placed on a substrate, and the color forming layer of the thermosensitive recording sheet is The amount of heat generated in the thermal head causes a color reaction to occur and records have been obtained.Thermal heads have been developed in a wide variety of toilet materials and shapes, and each has its own performance and
The requirements for thermosensitive recording vary greatly depending on the control method, recording conditions (applied voltage, pulse width, temperature, pressure, recording interruption [shi and recording information], etc.), so the matching between them is superimposed, but 41 Recently, with the diversification of uses and the improvement of performance, the thermal recording sheets used have become more diverse.
For example, in printer #C, a 5x7 dot matrix was sufficient to express alphabets and numbers in the past, but it is now possible to express kanji in precision KII. Tame K 16
A large number of dots of X 1g & 82x82 are a must! As a result, the factor of using a thermal head which has become much better is to improve the image quality, i.e. to solve the problem.
Conventional 4 books/Kaku l to increase! The density has increased to more than 8 songs per song. Furthermore, the recording speed [K Tsukisha, conventionally 80 to 60 characters/second was the standard, but recently it has been increased to K14 speed of 120 characters/second or more, and the factor tV
However, what used to take several minutes to write on A4 size paper is now 1
It is required to be able to record within minutes. In order to increase the speed, it is necessary to shorten the current heating time, that is, the pulse width, but as a way to compensate for the decreased amount of heat, increasing the applied voltage and raising the temperature of the head is a thermal Considering the durability of the head, you can expect less than 7%/h.

High like this! Since the thermal energy of the t-maru head of the high-speed brass marking device is increasing and becoming smaller, this Kf! The heat-sensitive recording sheet used is required to have sufficient **color sensitization to obtain clear color recording even with a minute amount of tS. For this purpose, the colorless dye or organic color developer that meets the coloring layer is smelted with a small amount of heat.
It is superposition to cause a color reaction, and if possible, it is possible to produce a color at a temperature of 70 to 120 C. The melting point of the color-forming colorless dye is usually 160 to 240 C, and bispheno-kAly, which is the most widely used organic color developer, has a melting point of 160 to 240 C.
) 1111 points are 166-168C terrorism! .

The color development temperature of a heat-sensitive recording sheet depends on the melting of both or one of the color-forming materials consisting of a color-forming dye and an organic color developer. If the three substances are made to co-exist and the color-forming material is dissolved by the melting of the three substances, it becomes possible to cause a color-forming reaction even at low temperatures. For this reason, special II@5B-89189
No., JP-A-58-26189, JP-A-68-6418
No. 6, 4111 No. 68-110j 1, etc., each coated with waxes, 1 fat, 5 alkylated biphenyls.
It has been proposed to add low melting point heat-melting substances such as substituted biphenyl alkanes, coumarin compounds, and diphenylamines as sensitizers or melting point depressants.

These thermal f1MlIl substances have static coloring 11f obtained by pressing a hot plate at a certain temperature for a certain period of time.
For KII, sensitization is uniformly observed. However, the quality of a heat-sensitive recording sheet that is colored using minute thermal energy, such as in high-speed facsimile, cannot be accurately evaluated depending on the static coloring conditions. In other words, since the general static color development conditions are to heat 70 to 160 CK and press a friendly metal plate against it for a few seconds to develop color, it can be used for popular fax machines etc. that instantly increase the K of a minute thermal head by 200 to 400 CK. This is clearly different from the dynamic color development conditions in the conventional method, in which the heating time is considerably longer and the total amount of thermal energy given to the heat-sensitive recording sheet is also more intense. 18I
1μV Therefore, even if static coloring is used on a thermal recording sheet where coloring occurs at 80 to 9QC, when yy is actually used for thermal, the coloring layer l may become insufficient even if a high voltage is applied. many.

As a result of examining various melting point depressing properties based on dynamic color development conditions, the present inventors found that, as a sensitizer, it melts at a relatively low temperature, and the melt contains a color-forming colorless dye and an organic color developer. It has been found that, in addition to the fact that both are easy to dissolve, high dissolution 1 and high dissolution rate are very superimposed quality determining factors.

By using a sensitizer that has high solubility and a fast dissolution rate, not only the color development starts quickly and disappears quickly, but also the maximum density that can be reached is improved.

Sensitizers that dissolve only -1 of the colorless dye and organic color developer, or have poor solubility and slow dissolution rate, may require a small amount to be added, even if static coloring starts at a low temperature. If the amount is not increased, a sufficient sensitizing effect cannot be obtained, and when printing at high speed with short pulses on 41, the desired color density is often not obtained. Regarding wax-based sensitizers such as condensates of fatty acid amines, fatty acid adducts, and methylolated esters of fatty acid acetates, their melts have almost no ability to dissolve color-forming dyes, and bisphenol A Therefore, even if it is possible to lower the point at which color development starts, the desired effect cannot be obtained if the amount of Lt added is large.For this reason, the thermal response to the minute amount of short pulses is sufficient. Not only is this not possible, but it also tends to cause problems such as lees adhesion to the thermal head, stains, Ashikaga stains, and ghosting.
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The object of the present invention is to include a carbonic acid diester represented by the following general formula as a sensitizer in a heat-sensitive coloring layer containing a basic colorless dye and an organic color developer.

(In the formula, R1 and R2 represent a methyl group, an ethyl group, or a propyl group, and n is an integer of O-2.) Examples of carbonic acid diesters represented by the above general formula include diphenyl carbonate, dicarbonate, and 4-methyl carbonate. Examples include phenyl, di-4-ethylphenyl, carbonyl-4-bilphenyl, and di(2,4-dimethyl)phenyl carbonate. These carbonate diesters are generally synthesized in the presence of phenol and phosgene in a more alkaline solution.

Next, let's compare the solubility characteristics of diphenyl carbonate, an example of carbonic diester, and stearamide, which is widely used as a wax-based sensitizer, to dyes and color developers. ! There are 10 ways.

1!1 (Foundation) (1) Dissolution rate [: Sensitizer IJ16C dissolution-11 [50j
Kll in which the dye or primary colorant 10j' is completely dissolved
Calculate using the following formula, keeping the time constant.

(RIlIj!1[:Sensitizer IF)186C111111
1110 (weight of dye or developer dissolved in IKIO minutes).

The proboscis above! It is clear from the properties of 141 that when carbonic acid diester is melted by heating, colorless dyes and organic primary colorants are easily incorporated, so that sufficient sensitizing effect can be obtained even in small amounts. Therefore, it is possible not only to simply lower the temperature at which color development starts, but also to obtain a heat-sensitive recording sheet with an extremely high maximum density.

The features of the heat-sensitive ink sheet containing diester carbonate in the heat-sensitive sickle layer are as follows.

(1) Excellent thermal response to minute amounts of heat from short pulses.

(2) Compared to conventional wax-based sensitizers, a sufficient sensitizing effect can be obtained with a smaller amount of compounding.

(8) As a result of being able to reduce the amount of sensitizer compounded, it is possible to reduce the amount of application and the manufacturing work can be carried out using mobile vehicles.

(4) The ground color is stable.

As the normally colorless or light-colored basic colorless dye used in the present invention, various known colorless dyes can be used.
For example, crystal violet lactone (back color), 8-
Diethyl annor 6-methyl-7-anilinofluorane (black), 8-(N-ethyl-P-)luideino)-6
-Methyl-7-anilinofluorane (black), 8-diethylamino-6-methyl-7-(ortho, para-dimethylanilino)fluoran (black), 8-pyrrolidino-6-methyl-7-anilinofluorane (black), 8-bipetudino-6-methyl-7-anilinofluorane (black), 8-(N-cyclohexyl-h-methylamino)
-6-methyl-7-anilinofluorane (black), 8-
Diethylamino-7-(ortho-p-roroaelino)fluoran (black), 8-diethylamino-7-(meta-trifluoromethylanilino)fluoran (J1 color), 8
-diethylamino-6-methyl-7-trifluorane (red), 8-diethylamino-6-methyl-fluorane (red), and 8-cyclohexylamino-6-chlorofluorane (11 colors). Can be done.

On the other hand, as an organic primary color agent, its use and necessity I@
The conventionally used bisphenol A (4-
4'-isopropylidenediphenol), P, P'
(1-methyl-n-hexylidene fudiphenol,
P-tert-butylphenol, P-phenylphenol, 2,4-dihydroxybenzophenone, 4,
Phenols or organic acids such as 4'-thiobis (4-tert-butyl-3-methylphenol), 4,4'-cyclohexylidene diphenol, novolac type phenol resin, and P-human tetraoxybenzoic acid ester are used alone. , or used in combination.

The particles are atomized to a particle diameter of several microns or less using the organic primary colorant, basic colorless dye, and carbonic acid, and various additive materials are added depending on the purpose to form a coating liquid. This coating liquid usually contains polyvinyl alcohol, modified polyvinyl alcohol, droxyethyl cellulose, methyl cellulose, starches, styrene-maleic anhydride copolymer, vinyl acetate maleic anhydride copolymer, styrene-butadiene copolymer. Inorganic or organic fillers such as kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, calcium carbonate, magnesinium carbonate, and aluminum hydroxide are added, but in addition to these, fatty acid metals are added. It is possible to use mold release agents such as salts, lubricants such as waxes, ultraviolet collecting agents such as benzophenone or triazole, water resistance agents such as glyoxypur, dispersants, antifoaming agents, etc. By applying this Ik liquid and applying it to various films, the desired heat-sensitive binding sheet can be obtained.

The amount of carbonic acid diester used in this W14, and the types and amounts of various components in the same, are the required characteristics II! and recording suitability, and is usually determined according to the recording suitability, but is not limited to 41. Normally, the basic colorless dye is 111, and the organic color developer is 88.
~10s% carbonic acid diester Q6~tos, filling bag is 1~
2011vr1! The binder is 10-16 in total solids.
11 would be appropriate.

■Specifically describe the present invention! For clarity, a typical example will be described.

〔Example〕

A11 (dye dispersion) Solution B (developer dispersion) Solution C (sensitizer dispersion) Solution D (sensitizer dispersion) The canned liquid of the above composition was mixed with an attritor with a particle size of 8 p7.
Grind until fine.

Next, each dispersion liquid and the kaolin clay dispersion liquid were mixed in the proportions shown below to make 1 m5i.

Invention example Comparative example 1 Comparative example 2h liquid fhsll
all alliBi[84L5#8
a6#JIa6' 011 0, O-10,
0#D1[1a0. 0. 0 #Kaolin clay 2αo, 2αO#
2αol (50% dispersion) Each of the above coating liquids was applied in an amount #t on one side of 60117- base paper.
Coat on BaON/lt/Ktk 5 and dry, then supercalender these sheets to a smoothness of 2o.

~1 every 800 seconds! Niruyo K16H1L, ta. Table 2 shows the results of a quality performance test performed on the obtained black heat-sensitive adhesive sheet.

Table 2 (1) Dynamic coloring depth f: Matsushita Electric Transmission Heat Sensitive 7 Axis z% +
7 ([1-Hli), a pulse width of 5 ms, and an applied voltage of 176 @V. Image 1) f was measured with a Macbeth density needle RD-104.

(2) Static color development sensitization rate: (r
The color was measured by pressing on a hot plate for 6 seconds at a pressure of 25 GN/- with a Macbeth density needle and calculated using the following formula.

+81 reached jljlil & dark [: 150 t, 0 hot plate K
Press the surface with 26011/Cd pressure for 6 seconds to develop color and measure with Macbeth density needle.

(4) Ground color: Measure the uncolored area with a Macbeth machine scale needle.

As is clear from Table 2, the example of the present invention shows a remarkable improvement in dynamic coloring acidity compared to Comparative Example 1 in which no sensitizer was used and Comparative Example 2 in which a conventional wax-based sensitizer was blended. The maximum concentration achieved is high and the ground color is stable.

Claims (1)

[Claims] (1) A thermosensitive recording sheet having a coloring layer containing a basic colorless dye and an organic primary coloring agent, characterized in that the wrinkled coloring layer contains a carbonic acid diester represented by the following general formula. sheet. (In the formula, I'l and R1 represent a methyl group, an ether group, or a propyl group, and %n is a II number from 0 to 2.)