JPH08259825A - Improved acid color developing-type achromatic dye - Google Patents

Abstract

PURPOSE: To obtain a new compound hardly developing a color or a stain on a coated surface which should be white color in the case of using it for a recording material such as a pressure sensitive recording material and a heat sensitive recording material. CONSTITUTION: This acid color developing-type achromatic dye comprises a compound of the formula [R<1> , R<2> , R<4> are each a lower alkyl or an aralkyl; R<3> is an aralkyl or phenyl (provided that the phenyl group may bind with the ring I to form a heterocyclic ring); R<5> is an aralkyl or phenyl; R<6> is an alkyl substituted by an ether]. For example, di(4-N-phenyl-N-methylaminophenyl)-3-N-n- butylcarbazolylmethyl 2-methoxyethyl ether. The compound of the formula is obtained e.g. as a precipitate by dissolving di(4-N-phenyl-N- methylaminophenyl)-3-N-n-butylcarbazolylmethane obtained by the condensation under an acidic condition of N-n-butycarbazole-3-aldehyde with N- methyldiphenylamine, in dioxane, adding 2, 3-dichloro-5, 6-dicyano-1, 4- benzoquinone, then adding sodium 2-methoxyethylate/2-methoxyethanol solution and then precipitating by adding methanol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording material applying a color-forming reaction between an electron-donating colorless dye and an electron-accepting developer.
For example, the present invention relates to a colorless dye suitable for use in a recording material such as a pressure-sensitive recording material and a heat-sensitive recording material, and more particularly to an acid-coloring type colorless dye capable of preventing undesired colored stains when used in a recording material.

[0002]

2. Description of the Related Art Conventionally, 3,3-bis (4-dimethylaminophenyl) -6 has been used as a colorless dye for image recording materials.
-Triphenylmethane lactone type dye represented by dimethylaminophthalide (so-called crystal violet lactone), 3-diethylamino-6-methyl-7-
Lactone dyes such as fluoran lactone type dyes typified by anilinofluorane were famous as primary dyes (dyes that develop color immediately upon contact with a color developer).

On the other hand, dye-reduced products such as benzoyl leuco methylene blue and carbazolylmethane compounds described in Japanese Patent Publication No. 60-16358 or acylated products thereof are also used as colorless dyes, but these have a developing color with oxidizing power. The density gradually increases after contact with an agent (eg, inorganic solid acid such as activated clay) and after a long time (called secondary dye), the density of the primary dye color image decreases over time. It is used to compensate for the above and does not develop color with a general-purpose organic acid type developer such as a phenol compound or a salicylic acid derivative polyvalent metal salt.

Conventionally, crystal violet lactone has been mainly used as a primary dye that gives a blue image, but the image, especially the image on an inorganic solid acid, is inferior in fastness, and its improvement has been desired.

Under the circumstances, the applicant of the present invention has already disclosed the Japanese Patent Application Laid-Open Nos. 62-124153 and 62-127353.
In JP-A No. 62-129357 and JP-B No. 6-67666, a novel colorless dye which gives a robust color image was proposed. Further studies have revealed that the dye proposed in JP-A-62-129357 gives a high-density image and has the best image fastness.

However, when the dye is used in, for example, a pressure-sensitive recording material or a heat-sensitive recording material, there is a problem in that some undesired colored stains may be observed on the coating surface which should be white, and its countermeasure is taken. As a result of the investigation, the present invention was born.

[0007]

An object of the present invention is to prepare an image recording material using an acid-coloring colorless dye,
An object of the present invention is to provide an improved colorless dye in which the coated surface, which should be white, is less likely to develop color or stain.

[0008]

The object of the present invention has been solved by using the dye represented by the general formula (1). In the chemical formula 1, R ¹ , R ² and R ⁴ are lower alkyl groups or aralkyl groups, R ³ is an aralkyl group or a phenyl group (however, the phenyl group may be bonded to ring I to form a heterocyclic group), R ⁵ represents an aralkyl group or a phenyl group, and R ⁶ represents an alkyl group substituted with an acyclic or cyclic ether group.

Specific examples of the colorless dye represented by Chemical Formula 1 are shown below.

[0010]

Embedded image

[0011]

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[0012]

[Chemical 4]

[0013]

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[0014]

[Chemical 6]

[0015]

[Chemical 7]

[0016]

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[0017]

[Chemical 9]

[0018]

[Chemical 10]

[0019]

[Chemical 11]

[0020]

[Chemical 12]

[0021]

[Chemical 13]

[0022]

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[0023]

[Chemical 15]

That is, in the present invention, the undesired color development / contamination is prevented by replacing the alkyloxy group bonded to the central carbon of the chemical formula 1 with an ether group-substituted alkyloxy group. When an acid-coloring colorless dye is mixed with other chemical materials to form a layer on a support such as paper, the already proposed dye (eg, Chemical formula 18) reacts with the surrounding trace acid substances and slightly develops color. However, it was considered that the ether group-substituted alkyloxy group bonded to the central carbon of the present invention is difficult to dissociate under slightly acidic conditions, or whether the leaving group decolorizes the color former even if dissociated.

However, as will be described later, when the alkyloxy group bonded to the central carbon of the chemical formula 1 is replaced with an alkyloxy group substituted with an amino group having no ether group, which has stronger basicity (chemical formula 16), On the contrary, the pollution worsened. That is,
The fact of the present invention that the contamination was improved by using an ether group-substituted alkyloxy group was surprising.

The triphenylmethane-based leuco dyes having an ether group-substituted alkyloxy group bonded to the central carbon, which are newly provided by the present invention, are aromatic amines having an aldehyde group in the para position with respect to N (eg, N-ethyl). Carbazole-3
-Carboxaldehyde, N-n-butylcarbazole-3-carboxaldehyde, 4-N, N-dibenzylaminobenzaldehyde etc. 1 mol and an aromatic amine (eg, N, N-dibenzylaniline, N-methyl-diphenylamine) , N-ethylcarbazole, etc.) under an acidic condition to give tri (amino group-substituted aryl) methane as an oxidant (2,3-dichloro-).
Oxidation with 5,6-dicyano-1,4-benzoquinone is preferable to once form a dye cation (coloring in blue), and then an ether group-substituted alcoholate of an alkali metal (eg, Na) is allowed to act to give a colorless substance. Or, it can be obtained in a good yield as a light-colored solid, and can be produced by the same method as in the prior application (eg, JP-A-62-129357) which is the same applicant as the present invention.

The recording material, which is the main use of the colorless dye according to the present invention, will be briefly described. In a pressure-sensitive recording material, a microcapsule containing a solution of an electron-donating colorless dye is usually coated on the back surface and an electron receiving material. Basically it consists of a lower sheet that has a coating layer for developing color developer, and the colorless dye released from the microcapsules destroyed by the pressure of writing, impact printer, etc. reacts with the color developer to react and develop color. Produces an image. In a heat-sensitive recording material, a fine powdery colorless dye and a color developer are coated on a support,
When the image is heated by using a thermal head, a laser beam or the like, the colorless dye reacts with the developer at the heated portion to form a color image. In addition to these, there are colorless dye thermal transfer recording materials, electric heat-sensitive recording materials and the like, but they have the same coloring mechanism, and the colorless dye of the present invention is useful in any of them.

The known primary dye 3,3-bis (4-)
A lactone dye such as dimethylaminophenyl) -6-dimethylaminophthalide, a so-called crystal violet lactone, forms a cation by opening a lactone ring when it comes into contact with an acid substance and develops a color. The triphenylmethane type dye having an alkyloxy group bonded thereto has a substituted alkyloxy group which is desorbed to form a cation upon contact with an acid substance, which causes coloration, which is different from that of the lactone dye.

As the acid substance, a general-purpose developer, for example, clay such as activated clay, silica / magnesia semi-synthetic solid acid proposed by JP-A-57-15996, bisphenol A, para-hydroxybenzoic acid, etc. Phenolic compounds such as benzyl, novolac type phenolic resins, salicylic acid derivative polyvalent metal salts and the like can be used also for the colorless dye of the present invention, and when they are brought into contact with these, the color is instantly developed. Also,
Color is rapidly developed even in a system in which an acid is generated by a light beam, a laser, an electron beam or the like.

The colorless dye of the present invention may of course be used in combination with another type of colorless dye, and at that time, excellent effects are exhibited.

[0031]

EXAMPLES Next, the present invention will be specifically described by way of examples. The parts and% shown below are based on weight unless otherwise specified.

Example 1 (Synthesis Example) Di (4-N-phenyl-N-methylaminophenyl) obtained by condensing N-n-butylcarbazole-3-aldehyde and N-methyldiphenylamine under acidic conditions. -3
Dissolve 6.0 parts of -N-n-butylcarbazolylmethane (compound of Chemical formula 19) in 50 parts by volume of dioxane to give 2,3
4.5 parts of -dichloro-5,6-dicyano-1,4-benzoquinone was added little by little, and a dark blue liquid was obtained by stirring at room temperature for 2 hours. Next, 1 normal sodium-2-
A methoxyethylate / 2-methoxyethanol solution was added to erase the color, and methanol was added to cause precipitation. The precipitate was separated by suction filtration, washed with methanol, and dried to give 3.9 parts of a light brown powder. (Yield 58%) was obtained. According to FD mass spectrometry, M / Z = 673 was the main component, and the correspondence with the calculated molecular weight C ₄₆ H ₄₇ N ₃ O ₂ = 673 was good. Therefore, di (4-N-phenyl-N-methylaminophenyl) -3-Nn-butylcarbazolylmethyl-2-methoxyethyl ether (compound of Chemical formula 9)
It was found that

When a small amount of this powder and bisphenol A were mixed and heated, a deep blue color was immediately developed. Further, when an acetone solution (colorless) of the present compound was dropped onto silica gel, a deep blue color was developed instantaneously. However, in the case of an acetone solution (colorless) of di (4-N-phenyl-N-methylaminophenyl) -3-N-n-butylcarbazolylmethane (Chemical formula 19), a blue color was exhibited only after several days. .

Other colorless dyes according to the present invention could be synthesized in basically the same manner.

Example 2 Each of the colorless dyes synthesized by the same method as in Example 3.9.
Part was dissolved in 100 parts of 1,1-phenylxylylethane and added to 100 parts of a 5% styrene-maleic anhydride copolymer aqueous solution adjusted to pH = 4.5, and the emulsion (A) was added using a homogenizer. ). Separately, melamine 10
Part, 37% formaldehyde aqueous solution 25 parts and water 65
The parts were mixed, sodium hydroxide was added to adjust the pH to 9.0, and the mixture was heated at 60 ° C. until a transparent solution was obtained to obtain an aqueous melamine / formaldehyde initial condensate solution (B).
Solution (B) was added to solution (A), and the mixture was heated and stirred at 60 ° C. for 3 hours to obtain a melamine-formaldehyde resin film microcapsule aqueous emulsion containing a colorless dye solution.

Next, 100 parts of solid content corresponding to each of these microcapsule emulsions was sampled, and 35 parts of wheat starch particles, 30 parts of oxidized starch and water were added to obtain a total solid content of 2 parts.
A 0% coating liquid was used, and a high-quality paper having a basis weight of 40 g / m ² was coated with a wire bar at a dry coating amount of 5 g / m ² and dried to obtain pressure-sensitive recording paper.

As the lower paper, a silica / magnesia type semi-synthetic solid acid manufactured by Mizusawa Chemical Co., Ltd. (trade name SS-
1) Using 10g / m ² of SBR latex coated on high-quality paper as a binder, the upper paper and the coated surface are overlapped so that the coated surface faces each other, and calender pressure is applied at a constant nip pressure to develop color on the lower paper. Let Then, after 1 minute and 24 hours of pressurization, the reflection density when the red filter was used was measured by a Macbeth densitometer, and the white background density of the coated surface of the lower paper was subtracted to obtain the color density.

On the other hand, with respect to the upper paper, in order to evaluate the degree of coloring stain on the microcapsule coated surface, 10 sheets of the same kind of upper paper were piled up in order to emphasize the coloring condition, and the whiteness was visually judged to determine the whiteness. ○, △, ×,
It is represented by the symbol XX.

For comparison, JP-A-62-129357 is used.
In the same manner using the same amount of di (4-N-phenyl-N-methylaminophenyl) -3-Nn-butylcarbazolylmethyl-methyl ether (Chemical Formula 18) proposed in Japanese Patent Publication No. It was prepared and color-developed under pressure on the same type of lower paper. The whiteness of the upper paper was also evaluated by the same method.

The results of the tests are shown in Table 1 together with those for comparison and colorless dyes not included in the present invention.

[0041]

[Table 1]

The chemical structural formulas of the colorless dyes used in this example for comparison and outside the present invention are as follows.

[0043]

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[0044]

[Chemical 17]

[0045]

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[0046]

[Chemical 19]

It can be seen from Table 1 that even if the tri-arylmethyl structure, which is the basic skeleton of the colorless dye according to the present invention, is exactly the same, if the alkyloxy group bonded to the central carbon is different, it is applied to the pressure-sensitive recording paper. The difference appears in the whiteness of the surface,
When the alkyl group is an alkyloxy group substituted with an ether group, the whiteness of the coated surface is improved, while when the alkyl group is substituted with an amino group (Chemical Formula 16), the whiteness is rather deteriorated. A clear bluish coated paper was obtained.
Further, no improvement is observed even if halogen substitution is performed (Chemical formula 17). However, in terms of image coloring performance, even if the alkyloxy group bonded to the central carbon was different, no significant difference was observed, and all of them rapidly developed a high density on the lower paper.

[0048]

As described above, the alkyloxy group, which is a leaving group at the time of acid contact, of a tri-arylmethyl-alkyl ether compound having three aromatic organic amine groups bonded, is replaced with an alkyl group substituted with an ether group. By replacing the alkyloxy group consisting of ## STR6 ## with the above-mentioned alkyloxy group, undesired coloring stains when applied to an image recording material were prevented, and the desired image coloring ability was maintained, resulting in a practical improvement.

Claims (1)

[Claims] 1. An improved acid-coloring colorless dye comprising a compound represented by formula 1. Embedded image (In Chemical Formula 1, R ¹ , R ² , and R ⁴ are lower alkyl groups or aralkyl groups, and R ³ is an aralkyl group or a phenyl group (however, the phenyl group may be bonded to ring I to form a heterocyclic group). , R ⁵ represents an aralkyl group or a phenyl group, and R ⁶ represents an alkyl group substituted with an acyclic or cyclic ether group.)