JPH05426B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD This invention relates to an improved inkjet storage ink. Prior Art In inkjet recording, in order to perform good recording over a long period of time, it is necessary that the ink used satisfies the following conditions. (1) Ink viscosity, surface tension, specific conductivity, and density should be within appropriate ranges depending on the droplet generation method and droplet flight direction control method, and should be suitable for long-term storage, long-term use, or No precipitation should occur due to chemical changes, or the physical properties of the ink should not change during the recording pause. The discharge nozzle of a recording device generally has a diameter of 10 to 60μ.
m, and if the nozzle is clogged due to precipitation,
Eventually, droplets cannot be ejected. Even if the nozzle is not completely clogged, there may be solid matter near the nozzle.
If sticky substances adhere to the ink or the physical properties of the ink that have been adjusted to desired values during ink preparation change, the recording performance, ejection stability, and ejection response will deteriorate. (2) The recorded image must have sufficiently high contrast and clarity. In conventional inks, the dye content in the ink was increased to increase the contrast of the image, but
Such a method tends to cause clogging of the discharge nozzle. Therefore, dyes with high solubility in the solvent used in ink and a high extinction coefficient have been sought, but a satisfactory dye has not yet been obtained. CIAcid Yellow 23 and 17 are particularly known as water-based inks, but they have the drawbacks of insufficient solubility (especially at low temperatures) and poor water resistance. (3) Printed images dry quickly. With conventional ink, in order to prevent nozzle clogging due to drying of the ink inside the nozzle during recording pauses,
The ink contains a large amount of wetting agent, so special paper with high ink absorption is used to speed up the drying time of the printing machine. However, the use of such special paper has the drawback that it not only causes significant image blurring, but also makes the use of many ordinary papers impossible. (4) In addition, the recorded image must of course be a clear image with no smearing and excellent water resistance, light resistance, and abrasion resistance. In order to satisfy the above requirements, we have
Although a number of proposals have been made for inkjet recording inks, at present no ink that fully satisfies all of the above conditions has yet been obtained. Purpose The present invention was made in view of the above-mentioned current situation, and its purpose is to satisfy all of the above conditions.
It is an object of the present invention to provide a recording ink for an inkjet having particularly excellent solubility, water resistance and light resistance. Composition The present invention is based on SO ₃ M or COOM present in the dye.
It is based on the knowledge that increasing the number of groups (M is, for example, an alkali metal) improves the water resistance on treated paper and also improves the solubility of the dye in water and wetting agents. That is, the present invention resides in the use of at least one dye represented by the following general formula or formula in an inkjet recording ink. general formula (In the formula, R ₁ represents a hydrogen atom, an alkyl group, a hydroxy group, a halogen, a carboxy group, or a -SO ₃ M group, R ₂ represents an alkyl group, a carboxyl group, or a -COOM group, and M represents an alkali metal, an amine cation or ammonium ion, and n represents 1 or 2.) General formula (In the formula, R ₃ represents a hydrogen atom, an alkyl group, a hydroxy group, a halogen, a carboxy group, or -SO ₃ M, R ₄ represents an alkyl group, a carboxyl group, or a -COOM group, and R ₅ represents a hydrogen atom, an alkyl group, hydroxy group, halogen, _-SO3M or -COOM group, _R6 - _SO3M or -COOM
, M represents an alkali metal, an amine cation or an ammonium ion, and n and m represent an integer of 1 or 2. ) In addition, the -SO ₃ M group and -COOM group in the dye represented by the above general formula or are groups that increase the solubility in water, and in order to maintain the solubility as a recording ink for an inkjet, it is necessary to In the invention, the sum of the _-SO3M and -COOM groups must be at least 3. Furthermore, ^the -SO ₃ M and ^-COOM groups in the dye interact with Al ₃₊ on the paper surface when, for example, AlCl ₃ coated paper ^is used as a recording member, resulting in water resistance. , the sum must be at least 3 to achieve the desired effect. Those having the above general formula and structure, and the sum of the -SO ₃ M group and the -COOM group being at least 3, have good dye solubility, are less likely to cause clogging, and the resulting images are water resistant. becomes good. As is clear from the comparative example below, −SO ₃ M group and −
Dyes in which the sum of COOM groups is less than 3 Dyes represented by general formula B (Comparative Example 2) and dyes represented by general formula C (Comparative Example 3), or dyes in which the sum of -SO ₃ M groups and -COOM groups is less than 3. However, dyes such as Acid Yellow 23 (dye represented by general formula A (comparative example 1)), which do not have a specific structure such as the general formula and general formula, have low solubility and poor water resistance, so they cannot be used in the present invention. Examples of dyes that are particularly effective in the present invention are shown below. The inkjet recording ink of the present invention contains water, a water-soluble organic solvent, and a preservative and antifungal agent in addition to the dye represented by the above general formula or formula. A degree adjuster, a chelating reagent, a rust preventive agent, etc. can be added. A suitable water-soluble organic solvent is a mixed solvent of diethylene glycol and glycerin, but in addition, ethylene glycol, triethylene glycol,
Examples include propylene glycol, polyethylene glycol, polypropylene, glycol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, and the like. As the PH regulator that can be suitably used in the present invention, any substance can be used as long as it can control the PH of the ink within the range of 9.0 to 11.0 without adversely affecting the ink to be formulated. be able to. Examples include amines such as diethanolamine and triethanolamine, lithium hydroxide,
Examples include hydroxides of alkali metal elements such as sodium hydroxide and potassium hydroxide, and carbonates of alkali metals such as ammonium hydroxide, lithium carbonate, sodium carbonate, and potassium carbonate. Other substances that can be added to the ink include the following: Examples of specific electrical conductivity regulators for adjusting the specific electrical conductivity of the ink to 1 m〓/cm (25°C) or higher include inorganic salts such as potassium chloride, ammonium chloride, sodium sulfate, and sodium carbonate, and triethanolamine. There are water-soluble amines such as Examples of the chelating reagent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium laumyldiacetate. Examples of the rust preventive include acid sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite. As a water-soluble preservative, 2,2-dimethyl-
Examples include sodium 6-acetoxy-dioxane-1,3-dehydroacetate, butyl p-hydroxybenzoate, potassium sorbate, sodium 2-pyridinethiol-1-oxide, and anionic surfactants. In addition, depending on the purpose, a water-soluble ultraviolet absorber, a water-soluble infrared absorber, a magnetic fluid consisting of a dispersion of ultrafine magnetite particles, a latex emulsion, etc. can be added. Furthermore, as a recording member to which the inkjet recording ink of the present invention is applied, a member that can sufficiently absorb ink liquid or a member that has no ink liquid absorption ability can be used. Examples thereof include cellulose-based paper, synthetic Examples include paper, plastic film, metal plates, and glass. Furthermore, the effects of the present invention can be obtained by using, as a recording member, the above-mentioned member provided with a surface coating layer containing a pigment, a binder, and a water-soluble salt of a metal having an ionic valence of two or more as a water resistance improver. can be further increased. As the binder used in the surface coating layer, the following can be mentioned. A Resin system Oxidized starch, etherified starch, esterified starch dextrin, casein, gelatin, gum arabic, vegetable protein cellulose, carboxymethyl cellulose, hydroxyethyl cellulose,
One or a combination thereof, such as cellulose derivatives, polyvinyl alcohol, polyvinylpyrrolidone, maleic anhydride resins, vinyl acetate polymers, polyvinyl butyral, polyacrylamide, copolymers and modified polymers of the above polymers. B Latex system Polyvinyl acetate polymer latex, styrene-isoprene copolymer latex, styrene-
Modified products such as butadiene copolymer latex, acrylic polymer latex, acrylic-vinyl acetate copolymer latex, methyl methacrylate-butadiene copolymer latex and other copolymers, and mixtures of two or more thereof. Specific examples of pigments in the surface recording layer include the following. Clay, talc, diatomaceous earth, calcium carbonate, calcium sulfate, magnesium carbonate, magnesium sulfate, barium sulfate, titanium oxide, zinc oxide, zinc sulfide, zinc carbonate, titanium white, aluminum silicate, silicon oxide, calcium silicate, aluminum oxide, Aluminum silicate hydroxide, aluminum hydroxide, zeolite. Among the above, whiteness,
Calcium carbonate, magnesium carbonate, barium sulfate and titanium white are preferred from the viewpoint of dispersibility and substance stability. Moreover, the following can be cited as specific examples of the water resistance improver used in the surface coating layer. Divalent _MgCl2 , _CaBr2 , _CaCl2 , Ca( _NO3 ) ₂ , _CaI2 ,
ZnCl ₂ , ZnBr ₂ , ZnI ₂ , Zn(ClO ₃ ) ₂ , ZnSO ₄ ,
Zn( _NO3 ) ₂ , _SrI2 , _SrBr2 , _BrCl2 , Br( _NO3 ) ₂ ,
_BaCl2 , Ba( _NO3 ) ₂ , Ba(OH) ₂ , _BaI2 ,
BaBr ₂ , Fe(NO ₃ ) ₂ , Ni(NO ₃ ) ₂ , Ni(SO ₄ ),
NiCl ₂ , CuCl ₂ , CuSO ₄ Trivalent AlCl ₃ , Al ₂ (SO ₄ ) ₃ , Al(NO ₃ ) ₃ , ScCl ₃ , Sc
( _NO3 ) ₃ , _Sc2 ( _SO4 ) ₃ , Ga( _NO3 ) ₃ , _GaCl3 ,
Ga ₂ (SO ₄ ) ₃ , InCl ₃ , Fe(NO ₃ ) ₃ , various alum tetravalent TiCl ₄ , GeCl ₄ , Zr(SO ₄ ) ₂ , SnCl ₄ , Sn
(SO ₄ ) ₂ Pb (CH ₃ COO) ₂ , Sn (NO ₃ ) ₄ , Ti
(NO ₃ ) ₄ . The above water resistance improvers may be used alone or in combination. Among these, when considering each item of whiteness, toxicity, water resistance effect, light resistance effect, and dye color tone change,
AlCl ₃ , Al ₂ (SO ₄ ) ₃ , Al (NO ₂ ) ₃ , ZnCl ₂ , ZnSO ₄ ,
Zn( _NO3 ) ₂ , _SnCl4 , Sn( _NO3 ) ₄ , _CaCl2 , Ca
( _NO3 ) ₂ , _MgCl2 , Mg( _NO3 ) ₂ , _InCl3 , In
(NO ₃ ) ₂ is preferably used. Particularly preferably,
AlCl ₃ , Al(NO ₂ ) ₃ , Zn(NO ₃ ) ₂ , ZnSO ₄ , Ca
(NO ₃ ) ₂ and Mg(NO ₃ ) ₂ are used. These water resistance improvers are used in the surface coating layer together with binders, pigments, etc., so that when the ink is attached to the layer, groups such as SO ^- ₃ and COO ^- in the ink molecules are removed. A salt that is insoluble or sparingly soluble in water is formed with a water-soluble dye containing . In other words, it is made into a lake pigment,
It is poorly soluble in water, making the image water resistant, and also has excellent light resistance, forming an overall robust image. For example, the recording medium is created as follows. A dispersion liquid mainly composed of pigment and binder is applied to the base.
Coat by blade coating method, air knife coating method, roll coating method, wire bar coating method, gravure coating method, reverse roller coating method, spray coating method, etc., and dry by hot air or heating. After drying, the coating amount is 0.1 to 50 g/ ^m2 preferably provide a surface coating layer of 3-20g/ ^m2 , then 0.1-30wt% of water resistance improver
An aqueous solution of is applied using one of the above surface coating layer forming coating methods and dried. In this case, the coating solid content is 0.01 to 40 g/ ^m2 , preferably 0.3 to 5 g/m2.
Make it m ² . Next, this recording medium is heated and pressurized using a calendering method at a heating temperature of 50 to 200°C, preferably 60 to 120°C, and a pressure of 40 to 150 kg/cm, preferably
Calendaring at 50-80Kg/cm will result in a better recording medium. If the calender pressure exceeds 150 kg/cm, the drying properties of the recording paper will decrease, and if it is less than 50 kg/cm, the surface will be uneven and the color limit will be poor. Furthermore, when forming the surface coating layer, the recording medium may be prepared by dispersing pigments, binders, water resistance improvers, and other additives in the same manner, coating, drying, and calendering. EXAMPLES The present invention will be explained in more detail below by way of examples together with comparative examples, but the present invention is not limited thereto. In the examples, all percentages are by weight. Example 1 Dye (1) listed in the preamble (M=Na) 3% Diethylene glycol 22.5% Glycerin 7.5% Deltop (manufactured by Takeda Pharmaceutical Co., Ltd.) 0.2% Ion exchange water 66.8% The above mixture was heated to 70°C. After stirring and dissolving, the pH was adjusted to 10.0 with an aqueous NaOH solution, and the mixture was passed through a 0.2 μm filter twice to prepare an ink. Next, using commercially available coated paper for inkjet as a recording material and treated paper prepared as described below, the ink was tested for the following items, and the following results were obtained. The above-mentioned treated paper is made by applying a coating liquid having the following composition: 17% calcium carbonate powder, 8% Al(OH) ₃ powder, 12% methyl methacrylate-butadiene copolymer latex, 63% water at 15g/cm ² onto high-quality paper. Further, a 3% aqueous solution of AlCl ₃ was coated thereon at 35 g/m ² by an air knife coating method, and then finished using a heating and pressure calender. (1) Image clarity and image dryness: Particle frequency 100KHz from a nozzle with an inner diameter of 30μm
When the ink was jet-recorded on a commercially available inkjet coated paper and the above-mentioned treated paper under the following conditions, clear images were obtained. The drying time of the recorded material was within 10 seconds at room temperature and humidity. (2) Storage: The ink is sealed in a glass container and stored at -20°C for 1 month, at 4°C for 1 month, at 20°C for 1 year, and at 90°C.
Although each sample was stored at ℃ for one week, no precipitation was observed. Further, no change was observed in the physical properties or color tone of the ink. (3) Jetting stability: The jet recording described in (1) above was performed continuously for 1000 hours, and stable recording was possible without any clogging of the nozzle or change in the jetting direction. (4) Injection response: After recording the jet according to (1) above,
1 month at room temperature and humidity and 1 month at 40℃ and 30%RH
After leaving it for a week, I performed the jet recording in (1) again, and as in (3) above, stable recording was possible. (5) Lightfastness of image: When exposed to light for 4 hours using a carbon arc lamp, the fading rate was less than 5%. (6) Image water resistance test: The image was immersed in water at 30°C for 1 minute, and the image density and amount of change before and after immersion were evaluated as the density fading rate. Commercially available coated paper had poor water resistance compared to treated paper. Furthermore, when the color tone and dyeing density of the recorded images were evaluated, satisfactory results were obtained for both commercially available coated paper and treated paper. Examples 2-8 and Comparative Examples 1-3 Water-based inks were prepared as described in Example 1, except that in place of the dyes used in Example 1, the dyes shown in the table below were used and When each item was tested, the results shown in the table below were obtained.

【table】

[Table] In the above table, the marks ○, △, etc. shown in each column represent the following meanings. Injection stability/responsiveness/solubility: ○ Under the conditions described in Example 1, changes in injection direction among the 10 nozzles were all within 50 μm. All were within 100 μm. Preservability: ○ Satisfies the conditions of Example 1 (preservability section). Light resistance: ○ Fading rate of 3% or less in 4 hours using a fade meter △ 〃 5% to 3% Water resistance: ◎ Fading rate of 3% in 1 minute of water at 30℃ ○ 〃 10% or less △ 〃 10 to 20% × 〃 20% The inkjet recording ink of the present invention has improved solubility even when recording on plain paper, and therefore has better jetting stability than conventional dyes. Furthermore, when the recording ink of the present invention is recorded on treated paper treated in the present invention, the water resistance of the recorded image is significantly improved.

Claims (1)

[Scope of Claims] 1. A recording ink for an inkjet, characterized in that it contains at least one dye represented by the following general formula or general formula. general formula (In the formula, R ₁ represents a hydrogen atom, an alkyl group, a hydroxy group, a halogen, a carboxy group, or a -SO ₃ M group, R ₂ represents an alkyl group, a carboxyl group, or a -COOM group, and M represents an alkali metal,
It represents an amine cation or an ammonium ion, and n represents 1 or 2. ) General formula (In the formula, R ₃ represents a hydrogen atom, an alkyl group, a hydroxy group, a halogen, a carboxy group, or -SO ₃ M, R ₄ represents an alkyl group, a carboxyl group, or a -COOM group, and R ₅ represents a hydrogen atom, an alkyl group, hydroxy group, halogen, _-SO3M or -COOM group, _R6 - _SO3M or -COOM
, M represents an alkali metal, an amine cation or an ammonium ion, and n and m represent an integer of 1 or 2. )