JPH0749543B2 - Color image forming method and ink set used therefor - Google Patents

Description

The present invention relates to a method for forming a color image and an ink set used for the same, and more specifically, a color using a combination of yellow, magenta, cyan and black water-based inks. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method and an ink set used for the same, and more particularly, to a color image forming method by an ink jet method in which droplets are ejected from an orifice of a recording head to form a color image on a recording material such as paper and a resin film, and ink used therefor. Regarding the set.

(Prior Art) Ink jet methods include various ink ejection methods (for example, an electrostatic suction method, a method of mechanically vibrating or displacing ink by using a piezoelectric element, heating ink to foam it, and utilizing its pressure). Method, etc.) to form small droplets of ink, and a part or all of them are attached to a recording material such as paper for recording.

In this system, it is possible to form a color image by using a plurality of nozzles and using a plurality of inks having different hues in which various dyes are dissolved in water or an organic solvent. The ink used in such an inkjet system is required to have the following performance.

(1) Good recording can be performed on recording paper having high versatility and high size as a recording material.

(2) To give an image excellent in water resistance, light resistance, abrasion resistance and the like.

(3) Excellent resolution or color reproducibility in color image formation.

(4) It has high dissolution stability or storage stability with respect to liquid medium components, and is unlikely to cause clogging of the discharge orifice.

(5) To give an image with high optical density and clear color tone.

(6) In particular, in the inkjet method utilizing heat energy, it is desired that the inkjet method is thermally stable in addition to (1) to (5).

However, a method for forming a color image by using an ink satisfying all the characteristics (1) to (6) has not been heretofore known. In particular, in the ink jet method using heat energy, the heat energy is directly applied to the ink, and in particular, in the bubble generating part, since the temperature instantly exceeds 250 ° C, the ink characteristic is that the dye is thermally Characteristics such as high dissolution stability, no clogging of the orifice, no thermal color change of the ink, and no deposit on the bubble-generating portion are required. Therefore, the invention of the inkjet system satisfying the requirements (1) to (5) is disclosed in JP-A-59-9967, but the method (6) is not sufficiently satisfied.

Therefore, the object of the present invention is to satisfy the requirements (1) to (5) sufficiently, and also to have a sufficient inkjet system suitability by the system (6) to provide a sufficiently satisfactory color image. An object of the present invention is to provide an inkjet method and an ink set used therefor.

The inventors of the present invention have conducted extensive studies to achieve the above object, and the properties (1) to (6) required for the ink are greatly influenced by the properties of the water-soluble dye contained in the ink. I found a thing.

Then, the present inventors continued research on dyes, and found that a specific combination of dyes of the group (1) to
(6) The present invention was found to be a dye that is suitable for a color image forming method that satisfies all the characteristics, and has reached the present invention.

DISCLOSURE OF THE INVENTION That is, according to the present invention, in a method for forming a color image by an inkjet method using yellow, magenta, cyan and black aqueous inks, the magenta ink contains a dye represented by the following general formula (I). One or more types, the yellow ink contains one or more types of dyes represented by the following general formula (II), the cyan ink contains one or more types of dyes represented by the following general formula (III), and A black ink containing one or more kinds of dyes represented by the following general formula (IV) or (V), and a method for forming a color image, and yellow, magenta, and In the ink set having the cyan and black water-based inks, the magenta ink has the following general formula ( The dye represented by) contain one or more, dyes the yellow ink is represented by the following general formula (II) contain one or more, the cyan ink is represented by the following general formula (II
An ink set comprising one or more dyes represented by I), and the black ink containing one or more dyes represented by the following general formula (IV) or (V).

(However, in the above formula, R represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a lower acylamino group, a nitro group or a halogen atom, and X represents an acetyl group, a benzoyl group, a paratoluenesulfonyl group, 4-chloro-6. −
It represents any of hydroxy-1,3,5-triazin-2-yl groups, M represents an alkali metal, ammonium or an organic amine, 1 represents 0 to 2, and m or n represents 0 or 1. ) (However, Q in the above formula is -NHCONH- or Represents a bond, X ₁ and X ₂ represent a hydrogen atom, —SO ₃ M, —COOM or a phenyl group and a naphthyl group substituted with a hydroxyl group, R represents a methyl group or a methoxy group, and n represents 0.
Or 1 and M represents an alkali metal, ammonium or an organic amine. ) (However, in the above formula, M represents an alkali metal, ammonium or an organic amine, m is 1 to 4, and n is 0.
~ 3. ) (However, in the above formula (IV) or (V) X represents a hydrogen atom, it may be substituted with a group or -NHCOCH ₃ of -SO ₃ M phenyl group or a naphthyl group, R ₁ represents a hydrogen atom, -
Phenyl group substituted with SO ₃ M or --COOM or --CH ₂ S
Represents O ₃ M, R ₂ is a hydrogen atom or M is an alkali metal, ammonium or an organic amine, and n is 0 or 1. Next, the present invention will be described in more detail. As a dye for an aqueous ink in an inkjet system, particularly an inkjet system utilizing heat energy, the characteristics of the aqueous ink required in a general inkjet system, that is, (1) ) To (5) are of course required, but in addition, the dye of the water-based ink is required to have high thermal stability, and in the ink jet system utilizing these thermal energy, Dyes of four colors (that is, yellow, magenta, cyan, and black) are required, and all the dyes of these four colors have the same level of the properties (1) to (5), particularly high thermal stability. Since it is required, it has been extremely difficult to find a combination of dyes of four colors having such characteristics. As a result of the research, the most excellent ink-jet type color image formation was realized by the combination of a specific group of dyes as described below.

The dyes represented by the general formulas (I) to (V) used in the present invention and mainly characterizing the present invention may be any dyes as long as they are included in the general formulas (I) to (V). It is good, but particularly preferable specific examples include the following. Further, the sulfonic acid group and the carboxyl group are shown as alkali metal salts, but it goes without saying that any other ammonium salt, amine salt or the like may be used.

Magenta dye Yellow dye Cyan dye Black dye The water-based ink used in the present invention is prepared by using the dyes represented by the general formulas (I) to (V) as described above to prepare four-color water-based inks of yellow, magenta, cyan and black. Any of these methods for adjusting the water-based ink of each color may be in accordance with the prior art. In addition, the water-based ink of each color used in the present invention needs to contain one or more dyes of the dyes of the general formulas (I) to (V), and the toning of the color tone of each water-based ink. Other dyes which are not included in the general formulas (I) to (V) due to the above are also included.

The content of each of the above-mentioned specific dyes in each ink is determined depending on the type of liquid medium component, the characteristics required for the ink, etc., but generally 0.1 to 0.1% by weight in the total weight of the ink. 20%, preferably 0.5-15
%, More preferably 1 to 10%. The dyes can be used alone or in combination of two or more kinds, or can be used in combination with other dyes such as other direct dyes and acid dyes with the dye as an essential component.

A suitable solvent for use in the ink used in 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, a water-soluble organic solvent, and a water-soluble solvent. As the organic solvent, a polyhydric alcohol having an effect of preventing ink drying is contained. Also, as water,
It is preferred to use deionized water rather than common water containing various ions.

Examples of the water-soluble organic solvent used by mixing with water include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol and the like. Alkyl alcohols having 1 to 4 carbon atoms; amides such as dimethylformamide and dimethylacetamide; ketones or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylenes such as polyethylene glycol and polypropylene glycol Glycols; ethylene glycol, propylene glycol, butylene glycol, triethylene glycol,
Alkylene glycols having an alkylene group of 2 to 6 carbon atoms such as 1,2,6-hexanetriol, thiodiglycol, hexylene glycol and diethylene glycol; glycerin; ethylene glycol methyl (or ethyl) ether, diethylene glycol methyl ( Or lower alkyl ethers of polyhydric alcohols such as ethyl) ether and 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 5 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.

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%, preferably 10% in the total weight of the ink. ˜70%, more preferably 20 to 70%.

The ink of the present invention prepared from such components has recording characteristics (signal responsiveness) by itself, stability of droplet formation, ejection stability, long-term continuous recording performance, and long-term recording suspension. Discharge stability), storage stability, fixability on a recording material, light resistance of a recorded image, weather resistance, water resistance, etc. are well balanced and excellent. In order to further improve such characteristics, various conventionally known additives may be further added and contained.

For example, viscosity adjusting agents such as polyvinyl alcohol, celluloses and water-soluble resins; various surface active agents such as cationic, anionic or nonionic surfactants, diethanolamine, triethanolamine, etc .; pH adjusting agents with buffer solutions, antifungal agents. Examples thereof include agents.

Further, in order to prepare an ink used for an ink jet type of charging the ink, a specific resistance adjusting agent such as an inorganic salt such as lithium chloride, ammonium chloride or sodium chloride is added.

When the ink is ejected by the action of thermal energy, thermal physical property values (for example, specific heat, thermal expansion coefficient, thermal conductivity, etc.) may be adjusted.

The present invention forms a color image by an inkjet method using the above-described four color inks. As the inkjet method, any conventionally known method can be used, and particularly preferable method is thermal energy. Is a method of using.

The inkjet method may be any method as long as it can effectively separate the ink from the nozzle and apply the ink to the recording material that is a range. Typical of these methods are, for example, an eye IEEE Transactions on Industry Applications
s) Vol.JA-13, No.1 (February, March, 1977), Nikkei Electronics April 19, 1976, January 29, 1973 and May 6, 1974. ing.

The methods described in these are suitable for the recording method of the present invention, and some of them will be described. First, there is an electrostatic suction method. In this method, a nozzle and an acceleration electrode placed several mm ahead of the nozzle are used. A strong electric field is applied between the ink and the ink to atomize the ink from the nozzle, and the ink is drawn out one after another. While the drawn ink flies between the deflection electrodes, an information signal is applied to the deflection electrodes for recording, and the ink particles are deflected. There is a method of ejecting ink particles according to an information signal without doing so, and any of them is effective for the present invention.

The second method is to apply a high pressure to the ink with a small pump, and mechanically vibrate the nozzle with a crystal oscillator or the like to forcibly eject minute ink particles.
The ejected ink particles are charged at the same time as the ejection according to the information signal. When the charged ink particles pass between the deflection electrode plates, they are deflected according to the charge amount.

As another method using this method, there is a method called a micro dot inkjet method. In this method,
Keep the ink pressure and excitation conditions within a certain range,
Two types of ink droplets, large and small, are generated from the tip of the nozzle, and only these medium and small diameter droplets are used for recording.The characteristic of this method is that it is possible to obtain a group of minute droplets even with a nozzle diameter as thick as the conventional one. This is a point that can

A third method is a piezo element method, and in this method, a piezo element is used as a pressure means applied to ink, instead of a mechanical means such as a pump unlike other methods. In this method, an electric signal is applied to the piezo element to cause mechanical displacement, thereby applying pressure to the ink and ejecting it from the nozzle.

Further, the method of the present invention is a method described in Japanese Patent Application Laid-Open No. 54-51837, in which the ink subjected to the action of thermal energy undergoes a rapid volume change, and the action force due to this state change causes the ink to be nozzle The method of discharging from is especially preferable.

The recording material that can be used in the method of the present invention is various inkjet recording papers or OH which have been proposed in the past.
Of course, even if you use a plastic sheet for P, excellent recording is possible, and copy paper, report paper, bond paper, slip paper, continuous slip paper, computer embossed paper that are widely used for general office work. Etc. can be used, and these papers may be low size papers or high size papers.

According to the present invention as described above, 4 used in the present invention
Dyes used in color water-based inks are all at the same level and have excellent solubility and storage stability in a liquid medium, and therefore have suitability as a general ink-jet water-based ink. All of the dyes have excellent thermal stability against heat energy, so even in an inkjet method that uses heat energy, there is no generation of protrusions and no change in the color tone of the dye, and excellent discharge stability and discharge. It is possible to retain responsiveness and the like. Since the dyes of the water-based inks of any color have excellent light resistance, water resistance, sharpness, etc., a color image of excellent quality can be provided.

As the water-based ink used in the conventional inkjet system, one having excellent inkjet system suitability for any color is known, but the same level for all four colors of yellow, magenta, cyan and black. Since an aqueous ink having various aptitudes was not known, it was not possible to provide an excellent color image particularly in an ink jet system using heat energy. By selecting and combining dyes and using four color water-based inks, it has been possible to provide color images of superior quality to the extent not possible with the prior art.

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

Ink Production Example 1 The following components were mixed, and then pressure-filtered with a Teflon filter having an average particle size of 0.45 μm to obtain a recording example 1.
The yellow, magenta, cyan, and black water-based inks used in 1. were prepared.

Magenta ink (1) Exemplified dye M-1 3 parts Water 60 parts Diethylene glycol 30 parts Glycerin 7 parts Yellow ink (1) Exemplified dye Y-1 2.5 parts Water 70 parts Diethylene glycol 20 parts N-methylpyrrolidone 7.5 parts Cyan ink (1) Exemplified dye Cy-1 4 parts Water 60 parts Ethylene glycol 10 parts Polyethylene glycol # 300 20 parts N-methylpyrrolidone 10 parts Black ink (1) Exemplified dye Bk-2 3 parts Exemplified dye Bk-3 2 parts Water 60 parts Diethylene glycol 30 Part N-methylpyrrolidone 10 parts Magenta ink (2) Exemplified dye M-2 3 parts Water 60 parts Diethylene glycol 30 parts Glycerin 7 parts Yellow ink (2) Exemplified dye Y-2 2.5 parts Water 70 parts Diethylene glycol 20 parts N-methylpyrrolidone 7.5 parts Cyan ink (2) Exemplified dye Cy-2 4 parts Water 60 parts Ethylene glycol 10 parts Polyethylene glycol # 300 20 parts N-methylpyrrolidone 10 parts Black ink (2) Exemplified dye Bk-1 3 parts Exemplified dye Bk-4 2 parts Water 60 parts Diethylene glycol 30 parts N-methylpyrrolidone 10 parts Comparative Example 1 Ink production In the same manner as in Example 1, yellow, magenta, cyan and black aqueous inks having the following compositions and used in Comparative Recording Examples were prepared.

Magenta ink Food Red No. 104 (Fluoroxin, Acid Red 92, Daiwa Kasei) 3 parts Water 60 parts Diethylene glycol 30 parts Glycerin 7 parts Yellow ink Food Yellow No. 4 (Tartrazine, Acid Yellow 23, Daiwa Kasei) 3 parts Water 70 parts Diethylene glycol 20 parts N-Methylpyrrolidone 7.5 parts Cyan ink Food Blue No. 1 (Brilliant Blue, Acid Bull 9, Daiwa Kasei) 3 parts Water 60 parts Ethylene glycol 10 parts Polyethylene glycol # 300 20 parts N-methylpyrrolidone 10 parts Black ink Acid Blue Black 10B (Sumitomo Chemical Co., Acid Black-1) 5 parts Water 60 parts Diethylene glycol 30 parts N-Methylpyrrolidone 10 parts Recording Example 1 Recording was carried out using each ink obtained in Ink Production Example 1 above. Thermal energy to the ink in the head Given to generate droplets, on- mind the type of multi-head for recording (ejection orifice diameter 35 [mu] m, the resistance value of the heating resistor
An image of each color is formed by a recording device having 50 ohms, a driving voltage of 30 V, and a frequency of 2 KHz, and the following (T1)
As a result of the examination of (T5) to (T5), good results were obtained as shown in Table 1 below.

(T1) Long-term storability of ink: Ink was sealed in a plastic film bag and stored at -30 ° C and 60 ° C for 6 months. Evaluated.

(T2) Discharge stability: Continuous discharge was performed for 24 hours in each of the atmospheres at room temperature, 5 ° C., and 40 ° C., and the quality of the formed image was evaluated.

(T3) Discharge response: Intermittent discharge every 2 seconds and discharge after being left for 2 months were examined and evaluated by the presence or absence of clogging at the tip of the orifice.

(T4) Lightfastness of recorded image: The density of the image recorded on the recording material in the table below was measured, and the rate of decrease (%) in density after exposure to room light for 6 months was evaluated.

(T5) Fixability to various recording materials: After printing on the recording material of the recording shown in the table below, the printed area is rubbed with a finger after 15 seconds, and the image is misaligned.
Evaluation was made based on the presence or absence of bleeding.

Recorded material name Classification Manufacturer Silver ring Fine paper Sanyo Kokusaku Pulp Co., Ltd. Seven Star fine paper Yamakoshi Paper Co., Ltd. Shirabotan Medium paper Honshu Paper Co., Ltd. Toyo Roshi Paper No.4 Non-size paper Toyo Roshi Co. The material name is a product name.

Recording Comparative Example 1 An image was formed in the same manner as in Recording Example 1 except that each ink of Comparative Example 1 was used, and the same evaluation was performed. The results are shown in Table 2 below.

Recording Example 2 Using the yellow ink (1), the magenta ink (1), the cyan ink (1) and the black ink (1) of Ink Production Example 1, respectively, a full-color photograph was reproduced by the apparatus of Recording Example 1. . Each color of the obtained image was extremely clear and the color reproduction was good.

Recording Example 3 A yellow ink (2), a magenta ink (2), a cyan ink (2) and a black ink (2) of Ink Production Example 1 were used, respectively, and a full-color photograph was reproduced by the apparatus of Recording Example 1. . Each color of the obtained image was extremely clear and the color reproduction was good.

Recording Comparative Example 2 A full-color photograph was reproduced in the same manner as in Recording Example 1 using the yellow, magenta, cyan, and black inks of Comparative Example 1 respectively. The obtained image had insufficient color reproducibility and was significantly inferior in sharpness and light resistance as compared with the case of the recording example.

Claims (3)

[Claims] 1. A method for forming a color image by an ink jet method using yellow, magenta, cyan and black aqueous inks, wherein the magenta ink contains at least one dye represented by the following general formula (I): The yellow ink contains one or more dyes represented by the following general formula (II), the cyan ink contains one or more dyes represented by the following general formula (III), and the black ink contains the following general formula: (IV) or (V)
A method for forming a color image, which comprises one or more kinds of dyes represented by (However, in the above formula, R represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a lower acylamino group, a nitro group or a halogen atom, and X represents an acetyl group, a benzoyl group, a paratoluenesulfonyl group, 4-chloro-6. −
It represents any of hydroxy-1,3,5-triazin-2-yl groups, M represents an alkali metal, ammonium or an organic amine, 1 represents 0 to 2, and m or n represents 0 or 1. ) (However, Q in the above formula is -NHCONH- or Represents a bond, X ₁ and X ₂ represent a hydrogen atom, —SO ₃ M, —COOM or a phenyl group and a naphthyl group substituted with a hydroxyl group, R represents a methyl group or a methoxy group, and n represents 0.
Or 1 and M represents an alkali metal, ammonium or an organic amine. ) (However, in the above formula, M represents an alkali metal, ammonium or an organic amine, m is 1 to 4, and n is 0.
~ 3. ) (However, in the above formula (IV) or (V) X represents a hydrogen atom, it may be substituted with a group or -NHCOCH ₃ of -SO ₃ M phenyl group or a naphthyl group, R ₁ represents a hydrogen atom, -
Phenyl group substituted with SO ₃ M or --COOM or --CH ₂ S
Represents O ₃ M, R ₂ is a hydrogen atom or M is an alkali metal, ammonium or an organic amine, and n is 0 or 1. ) 2. The method according to claim 1, wherein the ink jet system is a system utilizing heat energy. 3. An ink set having water-based inks of yellow, magenta, cyan and black, which is applied to the formation of a color image by an ink jet method, wherein the magenta ink contains one dye represented by the following general formula (I). The above, the yellow ink contains one or more kinds of dyes represented by the following general formula (II), the cyan ink contains one or more kinds of dyes represented by the following general formula (III), and the above black ink Is an ink set containing at least one dye represented by the following general formula (IV) or (V). (However, in the above formula, R represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a lower acylamino group, a nitro group or a halogen atom, and X represents an acetyl group, a benzoyl group, a paratoluenesulfonyl group, 4-chloro-6. −
It represents any of hydroxy-1,3,5-triazin-2-yl groups, M represents an alkali metal, ammonium or an organic amine, 1 represents 0 to 2, and m or n represents 0 or 1. ) (However, Q in the above formula is -NHCONH- or Represents a bond, X ₁ and X ₂ represent a hydrogen atom, —SO ₃ M, —COOM or a phenyl group substituted with a hydroxyl group and a naphthyl group, R represents a methyl group or a methoxy group, and n represents 0.
Or 1 and M represents an alkali metal, ammonium or an organic amine. ) (However, in the above formula, M represents an alkali metal, ammonium or an organic amine, m is 1 to 4, and n is 0.
~ 3. ) (However, in the above formula (IV) or (V) X represents a hydrogen atom, it may be substituted with a group or -NHCOCH ₃ of -SO ₃ M phenyl group or a naphthyl group, R ₁ represents a hydrogen atom, -
Phenyl group substituted with SO ₃ M or --COOM or --CH ₂ S
Represents O ₃ M, R ₂ is a hydrogen atom or M is an alkali metal, ammonium or an organic amine, and n is 0 or 1. )