JPS6232119B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel color former for pressure-sensitive or heat-sensitive recording paper. Conventionally, various compounds have been proposed as auxiliary coloring agents for pressure-sensitive copying paper and thermal copying paper. Among these, the most widely used compounds at present are those containing a lactone ring, for example, formulas () and (), crystal violet lactone
(CVL) It is a compound such as 3-diethylamino-6-methyl-7-anilinofluorane, and these compounds are said to form a complex () with a color developer as shown in formula (1) to develop color. . (In formula (1), KD means a color developer.) In other words, the color developer, which is a compound containing a lactone ring as described above, forms a complex with the color developer in a short period of time. Law is useful. However, it has been found that various problems occur when this type of coloring agent, particularly crystal violet lactone (hereinafter abbreviated as CVL), is used to produce a blue color. That is, CVL color images using acid clay-based color developers have disadvantages such as poor storage stability, discoloration or lightening in about a week, and extremely poor light resistance. Furthermore, CVL color images based on phenol resin systems and phenol derivative metal complex salt systems have drawbacks such as the color image disappearing when it comes into contact with a plasticizer and the light resistance of the color image being poor. Although these drawbacks have been improved with respect to specific performance through investigation of color developers, these improvements cannot necessarily be said to be fully satisfactory from the performance and practical aspects. The present inventors conducted various studies to solve these problems from the perspective of color formers, and found that the general formula () or () ₍ In _the formula _, R ₂ is combined

It has been discovered that a triphenylmethane compound represented by the formula I've reached it. The colored image produced by the auxiliary color former (hereinafter simply referred to as color former) of the present invention is superior in storage stability, light fastness and plasticizer resistance compared to the colored image produced by CVL. The color forming agent of the present invention develops color using a color development mechanism different from that of kraton type compounds, that is, color development occurs due to oxygen in the air, and therefore it takes time for color development. Therefore, in places where the same coloring speed as that of lactone-type compounds is desired, although it cannot completely replace them, it can be used in conjunction with lactone-type compounds as an auxiliary color-forming agent to compensate for their drawbacks. It is extremely useful. As such an auxiliary coloring agent, benzoyl lyucomethylene blue (hereinafter abbreviated as BLMB)
is used in combination with CVL, but this BLMB cannot produce practical color with a phenol developer, and is limited to color development with an acid clay developer. Besides, BLMB
The color image of the image has a markedly greenish hue and the visual density is light, so the hue of the image developed using CVL in combination with CVL will change over time as the color of CVL, which has poor light resistance, fades. It has the disadvantage of becoming pale and turning greenish. On the other hand, the color forming agent of the present invention not only allows selection of a compound whose hue of a developed image is similar to CVL from among the compounds represented by the general formula () or (), but also has excellent light resistance and storage stability. Therefore, it can be advantageously used in combination with CVX as an auxiliary color former. Although some compounds having a triphenylmethane skeleton have been proposed as color developers for acid clay, they are generally judged to have poor performance. For example, Hiroyuki Moriga, “Introductory Special Paper Chemistry” (first edition), Vol.
On page 46, it is stated that ``The speed of color development is generally slow, and the sublimation property or light fastness is poor.'' Also, Mitsuru Kondo et al. ``It has long been known that the leuco bodies of malachite green and crystal violet are generally colorless and easily develop color by oxidation or adsorption to acid clay. The disadvantage is that the body is easily oxidized in the air, causing unnecessary coloration of the paper. However, according to the study results of the present inventors, when the color former of the present invention is developed on acid clay, for example, the light fastness is better than that of CVL,
We discovered that the color hardly fades after 2 hours of irradiation using a fade-o-meter as described below, and that it has good sublimation resistance, and does not sublimate even under conditions of 100℃ and 2 hours, similar to CVL.
In addition, we discovered that pressure-sensitive copying paper prepared using microcapsules of this coloring agent exhibits little natural color development when left in the air, and can be stored without significant color development even for a fairly long period of time. Ta. In other words, the color developer of the present invention has practically improved the various drawbacks described in the above-mentioned literature. The color developer of the present invention is represented by the general formula () or (), and specific examples thereof include compounds shown in Table 1 below. Each of these compounds develops a unique hue, and a compound having a hue depending on the purpose of the recording paper is selected as the color former. Table 1 shows the compounds of the present invention and the color hues of commercially available acid clay-based paper sheets produced by the compounds.

【table】

【table】

[Table] Pressure-sensitive or heat-sensitive recording paper using the color former of the present invention is prepared by various known methods. for example,
It can be prepared by the method described below, which was carried out to evaluate the performance of the color former of the present invention. Table 2 shows the light fastness of the colored images produced by the color former of the present invention and CVL's acid clay color developer, and it is clear that the color developer of the present invention has excellent light fastness.

【table】

[Table] The color developer of the present invention is not limited to acid clay color developer.
It shows excellent performance when applied to color developers for various pressure-sensitive dyes such as phenol-based, carboxylic acid-based, and metal complex-based dyes. It can also be applied to various color developers that can be blended with pressure-sensitive dyes for heat-sensitive recording paper. Hereinafter, the method for synthesizing and applying the color former of the present invention will be described in more detail with reference to Reference Examples and Examples. The text middle part means the weight part. The pressure-sensitive copying paper used in the Examples was prepared and various performance evaluations were carried out in the following manner. (1) Encapsulation method of color former A method of encapsulating a color former utilizes coacervation of a hydrophilic colloid sol, according to US Pat. No. 2,860,457 and US Pat. No. 2,800,458. That is, 0.48 g of color former was dissolved in 12 g of diisopropylnaphthalene oil as a solvent, and then 25 g of 6% gelatin solution was added.
Mix and emulsify at a constant speed at 55℃, then mix with 50g of a 1% carboxymethyl cellulose aqueous solution while continuing to stir, dilute by adding 30g of warm water, adjust the pH to 4.3 with 10% acetic acid, and make a core. Form cellvation. After that, the liquid temperature was cooled to 8~9℃, 1.75 g of 37% formalin was added, and then 3% caustic soda solution was gradually added dropwise to adjust the pH to 10.5 to harden the coacervation membrane, and then the liquid Raise the temperature to 40-45 °C to complete microencapsulation. (2) Method for producing top paper for pressure-sensitive copying paper A suspension of 100 parts of microcapsules (in terms of dry weight) and 5 parts of oxidized starch (in terms of dry weight) was applied onto high-quality paper at a dry coating amount of 3 g/m ² It was coated using a bar coater and dried to obtain a top sheet for pressure-sensitive copying paper. (3) Measuring method of color density The coated paper and the commercially available acid clay color developer paper were placed on top of each other and printed using an electric typewriter by key press to develop color. The X value and Z value of the colored paper were read using a direct reading color difference computer (here, Suga Test Instruments KK was used), and the color density was determined by converting to the reflectance A value of a Hunter colorimeter using the following formula. A = (X - 0.18 / 1.18Z) / 0.8 = (X - 0.1525Z) / 0.8 Comparison of color density was performed 24 hours after printing, and the A value of the sample before printing was taken as A ₀ , and the color density was compared. The color development rate D was calculated by setting the A value after 24 hours as _A1 . D (%) = 100 × A ₀ - A ₁ /A ₀ (%) (4) Measurement of light resistance The colored paper was irradiated for 2 hours and 6 hours with a carbon arc fade-o-meter, and the color development rate D ₀ before and after irradiation was , D _2hr , and D _6hr are determined, and the residual rate of color development P: P _2hr = 100×(D _2hr /D ₀ ) (%) and P _6hr
Light resistance was expressed as =100×(D _6hr /D ₀ )(%). The higher the residual rate of color development, the better the light resistance. Reference Example 1 Synthesis of 4-morpholinolyucomalachite green (Compound No. 1 in Table 1) Mixture of 2.7 parts of Michler's Hydrol, 1.7 parts of N-phenylmorpholine (slight excess), 6 parts of concentrated hydrochloric acid, and 6 parts of water The mixture was stirred and heated under reflux for 6 hours. Then, the mixture was made alkaline with caustic soda, a small amount of hydrosulfite was added, and steam distillation was performed to remove unreacted impurities. After cooling, the remaining solid was recrystallized from hot xylene to obtain white crystals with a melting point of 203-205°C. Reference example 2 4-dimethylamino-4′,4″-dibenzylaminotriphenylmethane (Table 1 Compound No. 3)
Synthesis of 1.5 parts of paradimethylaminobenzaldehyde,
4 parts of N-methyl-N-benzylaniline was mixed with 6 parts of concentrated hydrochloric acid and 6 parts of water, and the mixture was stirred and heated under reflux for 8 hours. Then, the mixture was made alkaline with caustic soda, a small amount of hydrosulfite was added, and steam distillation was performed to remove unreacted impurities. After almost no organic matter has been distilled out and the content has become a pale yellow oil, steam distillation is stopped, the oil is cooled, the solidified oil is separated, and extracted with ligroin containing a small amount of benzene.
When the extract was stored in a cold place for a long time, it crystallized. These crystals were similarly recrystallized from ligroin containing a small amount of benzene to give white crystals with a melting point of 94.5-96.1°C. Example 1 4-N-Methyl-N-p-chlorobenzylamino leucomalachite green (Compound No. 6 in Table 1) was microencapsulated and applied to paper to form a top paper. This upper paper was layered with a commercially available acid clay-based color developing paper with the coated side aligned, and the paper was printed using an electric typewriter to develop color. Color development rate is after 48 hours
30.1%, and stopped at this value at 33.9% after 120 hours.
The light resistance of this sample after 2 hours of exposure was 98%. Examples 2 to 4 The same tests as in Example 1 were conducted by changing the coloring agent. The results were as shown in Table 3.

[Table] Example 5 In the same manner as in Example 1, a top paper containing the five types of dye microcapsules shown in Table 4 was prepared. The coated surfaces of each of these five types of paper were overlapped with a commercially available acid clay color developing paper, and the key prints were colored using an electric typewriter. Table 4 shows the visual hue, color development rate (after 24 hours), and light fastness (carbon arc fade-o-meter) of the colored paper. From the results in Table 4, it is clear that the compounds of the present invention compensate for the lack of light fastness, which is a drawback of CVL (particularly fading due to short-term light exposure), and that compared to the auxiliary color former BLMB, the compounds of the present invention have a lower hue. It is clear that since there was no significant change, the blending amount could be increased, and that a relative improvement in durability was obtained compared to the case of BLMB blending. Example 6 The upper paper produced in Example 1 was mixed with a lower paper coated with a dioxydiphenylsulfonate metal complex salt color developer (hereinafter referred to as lower paper S) in the same manner as in Example 1. We developed a color and obtained a colored product with similar effects.

【table】

[Table] Also, upper paper D produced in Example 5
(CVL 70%, No. 4 30%) and upper paper A (100%
CVL) and the lower sheet S was colored in the same manner as in Example 1 to obtain a colored product having similar luminous density and hue. Table 5 shows the color development rate and the light resistance of this colored product at 2 hours and 6 hours of carbon arc fade meter irradiation. The colored product produced by upper paper D was better than that produced by upper paper A.

【table】

Claims (1)

[Claims] 1 General formula () or () ₍ In _the formula _, A new triphenylmethane-based auxiliary coloring agent for pressure- and heat-sensitive recording paper, which is represented by the formula [formula] in which R ₂ is combined.