JPH0749544B2 - Recording liquid and recording method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording liquid (hereinafter referred to as ink) for recording on a recording material such as a paper or a resin film by an ink jet method or a writing instrument such as a fountain pen or a felt pen. And a recording method using the same).

[Conventional technology]

The ink jet recording method is one in which ink droplets are formed by various ink ejection methods, and some or all of them are adhered to a recording material such as paper for recording, and such an ink jet recording method is used. As the ink used in the recording method, various water-soluble dyes or pigments,
Those dissolved or dispersed in water or a solvate composed of water and a water-soluble organic solvent are known and used.

Further, the same ink as above is also used as ink for writing instruments such as fountain pens, felt pens, and ballpoint pens.

Paper, processed paper, surface-treated plastic film, and the like are used as recording materials for recording with these inks.

The ink as described above is required to have various properties such as water resistance and light resistance, and storage stability that does not cause precipitation during storage.

Many water-soluble dyes used in such inks are known, but if a single dye cannot achieve the desired performance, a mixture of two or more dyes is used. Is being used.

Although the ink itself can have the desired performance by mixing the dyes as described above, it was recorded on the paper commonly used in office such as notebook, report paper, copy paper, and stationery. At that time, as compared with the case where recording is performed using a single dye, the peripheral portion of the dot is blurred, so that an unclear image as a whole is often obtained.

As a result of repeated studies on this cause, the present inventor has a problem that a recorded image becomes unclear when a plurality of dyes have different color tones and the affinity between these dyes and cellulose fibers on plain paper is different between the dyes. Found.

That is, the dye having a high affinity and the dye having a low affinity are microscopically separated on the cellulose, and the different color tones of the individual dyes are separately displayed on the paper, so that the image becomes unclear.

[Problems to be solved by the invention]

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and, in particular, to papers having cellulose fibers exposed on the surface thereof, such as report papers and copy papers, which are excellent in coloration and sharpness. An object is to provide a recording liquid capable of obtaining an image and a recording method using the recording liquid.

[Means for solving problems]

The above object is achieved by the present invention described below. That is, the present invention provides a recording liquid containing a plurality of water-soluble dyes, wherein the color tone and chromatographic properties of the water-soluble dyes satisfy the following formulas (I) and (II), respectively. Yes, Further, a recording method is characterized in that the recording liquid is used to perform recording on a recording material having cellulose fibers exposed on the surface.

[Work]

The present invention will now be described in more detail. The ink of the present invention generally comprises two or more water-soluble dyes, a liquid medium for dissolving these dyes, and optional additives added as necessary. It is composed of an agent, but in these components, two or more kinds of water-soluble dyes have color tones close to each other and chromatographic properties close to each other.

In the present invention, the color tone is represented by the a ^* and b ^* values of the dye defined in the CIE1976 (L ^* , a ^* , b ^* ) space.

Conventionally, when a color image is formed by using an ink prepared by mixing a plurality of types of dyes, blurring around the ink dots due to color separation of these dyes causes blurring of the entire image. One of the causes of this is the difference in color tone between the mixed dyes. The smaller the difference (color tone), the less noticeable the blurring around the ink dots. In the present invention, when the value of the above formula (I) is set to 10 or less, since the color tones of the mixed dyes are similar to each other, even if there is color separation in the ink dots, the entire image becomes unclear. There is no.

The chromatographic property of the water-soluble dye can be obtained by using the mobility value by the paper chromatography method described below as one standard, and those having similar mobility values are used in combination. Thereby, the object of the present invention was achieved.

That is, the mobility of the water-soluble dye is determined as follows.

First, dye is water / diethylene glycol (volume ratio 55/4
5) Dissolve the mixed solvent in a concentration of 5% by weight to prepare a test solution. Toyo Filter Paper No. 5
After a charge of 2 μm was applied to the lower end of 0 (trade name; manufactured by Toyo Roshi Co., Ltd.), the mixed solvent was used as a developing solution and developed for a predetermined time according to a conventional method. At this time, the development distance (A) of the developing solvent from the charge point and the migration distance (B) of the dye from the charge point were measured, and the ratio B / A of the two was measured.
= Determine the value of Rf and use this Rf as the mobility of the test dye.

The present inventor determined the chromatographic properties of various water-soluble dyes based on this mobility. Two or more water-soluble dyes having a mobility difference of more than 0.20 were used in ink in combination with each other. As a result, it was found that even if recording is performed on a paper-based recording material, only an unclear image in which the dot peripheral portion is blurred can be obtained.

The above-mentioned difference in mobility is the difference in mobility between two types of water-soluble dyes, and the maximum mobility and the minimum in the case of three or more types. It is the difference in mobility.

The present inventor, as a result of examining various dyes in combination,
It has been found that a clear image having a desired color tone can be obtained only by using a combination of dyes which are close to each other in both color tone and chromatographic characteristics, that is, which satisfy the above formulas (I) and (II).

A sufficiently satisfactory image cannot be obtained with the combination of dyes in which only one of the color tone and the chromatographic property is similar.

The plurality of water-soluble dyes used in the present invention are used in conventional inks, and any of the water-soluble dyes can be used. Direct dyes such as.

From the above dyes, the color tone and chromatographic properties are (I),
Select a combination that satisfies the formula (II) and mix and use it.

The water-soluble dye used in the present invention is not limited to the above-mentioned ones, and any dye may be used as long as the color tone and the chromatographic characteristics are similar.

These water-soluble dyes are used as a plurality of dyes, generally in an amount of 0.5 to 3% by weight, more preferably 1 to 10% by weight in the ink.

The solvent used in the ink of the present invention is water or a mixed solvent of water and a water-soluble organic solvent, and particularly preferable is a mixed solvent of water and a water-soluble organic solvent, which is a water-soluble organic solvent for drying the ink. It contains a polyhydric alcohol having a preventive effect.

Further, as the water, it is preferable to use deionized water instead of general water containing various ions.

Examples of the aqueous solution organic solvent used by mixing with water include carbon such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol and isobutyl alcohol. Number 1 to 4 alkyl alcohols; amides such as dimethylformamide and dimethylacetamide; ketones or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol Ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,
2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol and other alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms; glycerin; ethylene glycol methyl (or ethyl) ether, diethylene glycol methyl (or ethyl ) Ethers, lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether; N-methyl-2-pyrrolidone, 1,3-
Dimethyl-2-imidazolidinone and the like can be mentioned. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferable.

The content of the water-soluble organic solvent in the ink is generally in the range of 0 to 95% by weight, preferably 10 to 80% by weight, more preferably 20 to 50% by weight based on the total weight of the ink. is there.

The content of water at this time is determined in a wide range depending on the kind of the solvent component, its composition or desired properties of the ink, but is generally 10 to 90% by weight with respect to the total weight of the ink, It is preferably in the range of 10 to 70% by weight, more preferably 20 to 70% by weight.

The basic composition of the ink of the present invention is as described above, but other conventionally known various dispersants, surfactants, viscosity modifiers,
A surface tension adjusting agent or the like can be added if necessary.

For example, viscosity adjusting agents such as polyvinyl alcohol, celluloses and water-soluble resins; surface tension adjusting agents such as cationic, anionic or nonionic surfactants, diethanolamine and triethanolamines; pH by buffer solution
Examples thereof include regulators and fungicides.

Further, in order to prepare an ink used in an ink jet recording method of a type in which a recording liquid is charged, a specific resistance adjusting agent such as lithium chloride, ammonium chloride or an inorganic salt of sodium chloride is added. When applied to an ink jet system of a type that ejects ink by the action of thermal energy, thermal physical property values (for example, specific heat, thermal expansion coefficient, thermal conductivity, etc.) may be adjusted.

The ink of the present invention as described above has sufficiently solved the problems of the prior art, and various recording materials, for example, a recording material formed by exposing paper-based cellulose to the surface of the ink jet system or a general When recording with a writing instrument, the desired color tone toned by multiple water-soluble dyes in the ink is reproduced on the recording material to the extent that there is no practical problem, so not only general black ink Even in full-color recording using a plurality of color inks, a clear and high-contrast, high-quality image excellent in light resistance and water resistance can be obtained.

On the other hand, in the case of the conventional compounded ink, since the attention was paid only to the color mixing of the water-soluble dyes used for them, it is possible to easily obtain a desired color tone as the ink. It was difficult to reproduce the color tone of the recording material on the recording material, especially the recording material formed by exposing the cellulose fiber on the surface thereof. By adopting the standard of chromatographic characteristics, the above-mentioned problems of the prior art have been sufficiently solved.

Next, the present invention will be described more specifically with reference to Examples, Comparative Examples and Examples of Use. In the text, “part” or “%” is based on weight unless otherwise specified.

〔Example〕

Examples 1 to 5 and Comparative Examples 1 and 2 After dissolving the water-soluble dyes by stirring the components having the following compositions, the insoluble matter was removed by using a filter, and 5 kinds of the inks of the present invention and 2 kinds of the comparative inks. Got

The numerical value in parentheses attached to the dye name represents the color tone and mobility of the dye.

Example 1 CI assisted black 107 2.5 parts (a ^* = 0.6, b ^* = 3.4, Rf = 0.85) CI assisted black 24 2.5 parts (a ^* = 2.0, b ^* = 2.0, Rf = 0.93) Diethylene glycol 30 parts Ion-exchanged water 65 Part Example 2 CI Assisted Yellow 29 2.5 parts (a ^* = 2.0, b ^* = 42.4, Rf = 0.82) CI Assisted Yellow 38 2.5 parts (a ^* = 3.7, b ^* = 43.4, Rf = 0.85) Diethylene glycol 30 Part Ion-exchanged water 65 parts Example 3 CI Acid Red 106 2.5 parts (a ^* = 43.9, b ^* = 5.2, Rf = 0.99) CI Acid Red 161 2.5 parts (a ^* = 42.7, b ^* = 3.7, Rf = 0.86) Diethylene glycol 30 parts Ion-exchanged water 65 parts Example 4 CI Acid Red 145 2.5 parts (a ^* = 39.2, b ^* = 21.0, Rf = 0.92) CI Acid Red 131 2.5 parts (a ^* = 37.8, b ^* = 19.8, Rf = 0.96) Diethylene glycol 30 parts Ion-exchanged water 65 parts Example 5 CI acid black 26 2.0 parts ^{a * = 2.3, b * =} 4.8, Rf = 0.90) CI Ashitsudoburatsuku 52: 1 1.5 parts ^{(a * = 4.2, b *} = 4.7, Rf = 0.97) CI Ashitsudoburatsuku 139 1.5 parts ^{(a * = 4.1, b *} = 5.3, Rf = 0.90) Diethylene glycol 30 parts Ion-exchanged water 65 parts Comparative Example 1 CI assisted black 24 2.5 parts (a ^* = 2.0, b ^* = 2.0, Rf = 0.93) CI assisted black 110 2.5 parts (a ^* = 4.4, b ^*) = 11.9, Rf = 0.86) Diethylene glycol 30 parts Ion-exchanged water 65 parts Comparative Example 2 C.I. Acid Black 24 2.5 parts (a ^* = 2.0, b ^* = 2.0, Rf = 0.93) CI Direct Black 154 2.5 parts (a ^* = 0.7, b ^* = 1.1, Rf = 0.72) Diethylene glycol 30 parts Ion-exchanged water 65 parts Here, (I) and (I
The values of formula I) are summarized in the table below.

Using the inks of the above-mentioned examples and comparative examples, an on-demand type recording head for ejecting ink by a piezo oscillator (ejection orifice diameter 50 μm, piezo oscillator driving voltage 60 V,
The recording apparatus having a frequency 4KH _Z), recording was performed on various recording materials described below, when using the ink of the present invention, no separation of the more water-soluble dyes, the desired color tone reproduction As a result, a clear image having excellent color development was obtained. On the other hand, when the ink of the comparative example was used, the color tone of the ink could not be reproduced, and an image with an unclear color tone was obtained.

Recording material (1) Silver ring (trade name, high-quality paper, Sanyo Kokusaku Pulp) (2) Seven Star (trade name, high-quality paper, Hokuetsu Paper Manufacturing) (3) White Peony (trade name, medium-quality paper, Honshu) Paper manufacturing) (4) Toyo Roshi No. 4 (trade name, non-size paper, Toyo Roshi) Each ink of the above-mentioned Examples and Comparative Examples was filled in different felt pens and written on the paper. However, the one using the ink of the present invention does not cause color separation on paper,
A clear image with the same color tone as the ink was reproduced. On the other hand, when the ink of the comparative example was used, the separation of the dye occurred on the paper, the clear color tone of the ink was not reproduced, and an image with an unclear color tone was obtained.

Claims (6)

[Claims] 1. A recording liquid containing a plurality of water-soluble dyes,
A recording liquid, wherein the color tone and chromatographic properties of the water-soluble dye satisfy the following formulas (I) and (II), respectively. 2. The recording liquid according to claim 1, wherein the content of the dye is in the range of 0.5 to 30% by weight based on the total weight of the recording liquid. 3. The recording liquid according to claim 1, which contains water and a water-soluble organic solvent as a liquid medium for dissolving or dispersing the dye. 4. A method for performing recording by depositing droplets of a recording liquid on a recording material, wherein the recording liquid contains a plurality of water-soluble dyes, and the color tone and chromatographic characteristics of the water-soluble dyes are as follows. A recording method which satisfies the formulas (I) and (II) and is characterized in that the recording material has cellulose fibers exposed on the surface thereof. 5. The recording method according to claim 4, wherein the content of the dye in the recording liquid is in the range of 0.5 to 30% by weight based on the total weight of the recording liquid. 6. The recording method according to claim 4, wherein the liquid medium for dissolving or dispersing the dye in the recording liquid contains water and a water-soluble organic solvent.