JPH0768474B2 - ink - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an ink used for various recording instruments such as writing utensils, printers, etc., and particularly inkjet recording for recording by ejecting a suitable liquid from an orifice of a recording head. The present invention relates to an ink suitable for the method.

(Prior Art) The inkjet recording system has advantages that noise during recording is small, color compatibility is easy, and a high-resolution recorded image can be obtained at high speed.

In the ink jet recording method, as the characteristics of the ink used, the physical properties such as viscosity and surface tension are in an appropriate range, the dissolution stability of the dissolved components is high, the fine orifice is not clogged, and the density is sufficiently high. It is required that the recorded image of No. 1 is given, and that changes in physical properties or precipitation of solid matter do not occur during storage.

Further, in addition to the above characteristics, recording can be performed without being restricted by the type of recording material, the fixing speed is high, and the recorded image is excellent in light resistance, water resistance, and solvent resistance (particularly alcohol resistance). In addition, properties such as providing a recorded image with excellent resolution are also required.

Conventionally, as the colorant of the ink in the inkjet recording system, a water-soluble dye is mainly used because the liquid medium is aqueous, and by using the water-soluble dye, many of the above basic requirements of the inkjet recording system are obtained. Is satisfied. However, when a water-soluble dye is used, these water-soluble dyes are originally inferior in light resistance, so that the light resistance of a recorded image often becomes a problem. That is, when a recorded image is exposed to sunlight, a fluorescent lamp, or light from a light source of a projector, the recorded image may disappear, become difficult to read, or discolor during storage for a long period of time.

There is also a problem in water resistance of the recorded image. That is, an image obtained by using a water-soluble dye is essentially inferior in water resistance, and therefore, when exposed to water, the image may become unclear or disappear.

Therefore, in order to solve these problems based on the use of water-soluble dyes, many inks using pigments instead of dyes have been proposed. For example, as typical examples of studies on dispersants for improving dispersion stability in practical use of pigment inks, for example, JP-A-60-118769, JP-A-60-155280 (above Pentel), and JP-A-60-155280. -235478 (Dainichi Seika) and the like are mentioned, and as a research example of the surface treatment of the pigment,
JP-A-59-120667 and JP-A-62-250084 (above Pentel) and the like can be mentioned. Further, as an application example to an inkjet recording system, JP-A-56-147859 to 147869, JP-A-56-147871 to 147872, JP-A-56-157467 to 157468, and JP-A-57-6791 (above) Canon), Nos. 62-27476, 62-74973 to 74974, (above Pentel), and the like.

Further, as to one of the most important problems in an ink using a pigment as a colorant, which is to improve the clogging at the tip of a pen or an orifice, JP-A-56-41261 (Sanyo dye) and 60- 51763, 60-72968, 62
It has been proposed to add urea and its derivatives, sorbitan, sorbitol, etc., as in Japanese Patent Publication No. 101672 (above Pentel).

However, in spite of the large amount of researches as described above, the fact is that an ink satisfying all the required performances has not been proposed yet, and in particular regarding clogging, it was used as an ink for inkjet recording system. In this case, an ink that does not cause clogging at the tip of a fine orifice for a long period of time has not yet been developed, which is a serious problem in terms of printer reliability.

Further, improvement in storage stability is also a major issue for pigment inks, and development of an ink that does not change in physical properties or precipitate solids even after long-term storage is desired.

Further, recently, there has been a strong demand for ink to have recording characteristics on plain paper, and not only paper specially adjusted for an ink jet recording system, but also copy paper, report paper, notebook, and notepaper commonly used in offices. There is a demand for an ink that has good fixability and can perform recording with good print quality.

However, conventional pigment inks often contain a large amount of a surfactant for stabilizing dispersion and / or defoaming, and therefore, when recording is performed on the plain paper, bleeding occurs in a printed portion. Then, there was a case where the quality deteriorated remarkably.

Therefore, an object of the present invention is to provide an ink that does not cause clogging of a pen tip or a fine orifice tip for a long period of time even in an ink using a pigment as a colorant.

Another object of the present invention is to provide an ink that does not generate a deposit even after long-term storage.

Further, another object of the present invention is to prevent bleeding not only on paper specially adjusted for an ink jet recording system but also on plain paper generally used in office such as copy paper, report paper, notebook, and notepaper. It is to provide an ink that gives good print quality.

(Means for Solving Problems) The above object is achieved by the present invention described below.

That is, the present invention is an ink in which a pigment is dispersed in a liquid medium containing water as a main component and which contains a compound represented by the following general formula (I).

(In the formula, R ₁ , R ₂ and R ₃ represent a hydrogen atom, a hydroxyl group or an alkyl group, R ₄ and R ₅ represent a hydrogen atom or a methyl group, and m
And n represent a numerical value of 1 to 30, and m + n is a numerical value in the range of 2 to 50. (Operation) As a result of earnest studies on various ink compositions for improving the clogging property of the pigment ink at the pen tip and the tip of the orifice, the present inventor has found that the addition of the compound represented by the general formula (I) is the It was found that it is effective in preventing clogging.

Further, the addition of such a compound is effective not only for improving clogging, but also for improving storage stability, and further suppresses ink bleeding on plain paper commonly used in offices, The present invention has been found to be effective also for improving print quality, and has led to the present invention.

According to the research conducted by the present inventor, the compound represented by the general formula (I) is a substance having a low vapor pressure and also has a surface active ability. Therefore, when it is added to the ink, evaporation of the liquid medium in the ink is prevented. It is possible to prevent the clogging and prevent the pigments from aggregating with each other to prevent clogging and improve the storage stability.

Further, when printed on plain paper such as copy paper, report paper, notebook, and notepaper, the fixing ability can be improved without degrading the printing quality due to the surface activity of the compound represented by the general formula (I).

(Preferred Embodiment) Next, the present invention will be described in more detail with reference to preferred embodiments.

Preferred specific examples of the compound represented by the general formula (I) which is used in the present invention and which mainly characterizes the present invention include the following compounds, but the present invention is not limited thereto.
In the formula, m and n exceed 30, or m + n is 50
If it exceeds the range, the viscosity of the obtained ink becomes too high, which is not preferable. The compound of general formula (I) may be a mixture in which m and n are different, in which case m and n are represented by average values.

The amount of the compound represented by the general formula (I) added to the ink varies depending on the colorant used and other liquid medium components used in combination, but is preferably about 0.5 to 30% by weight in the ink, preferably The proportion is 1 to 20% by weight, more preferably 2 to 15% by weight. When the addition amount is less than 0.5% by weight, not only the effect of suppressing the evaporation of the ink liquid medium is insufficient, but also the storage stability is improved and the fixing property on a recording material such as plain paper is improved by mitigating the aggregation of the pigment. It becomes insufficient and the object of the present invention is not sufficiently achieved. On the contrary, the addition amount is 30
When the content is more than wt%, the viscosity of the ink becomes large, and in particular, there is a problem in terms of matching with the head for inkjet recording system. In addition, the dryness of plain paper is also adversely affected.

As the pigment used in the ink of the present invention, almost all of the organic pigments described in the dye manual and the color index can be used in addition to carbon black. For example, many azo pigments such as azo lake pigments, insoluble azo pigments, condensed azo pigments, chelate azo pigments and phthalocyanine pigments, perylene and perinone pigments, atraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc. Cyclic pigments, basic dye type lakes, acid dye type lakes and other dye lakes, nitro pigments, nitroso pigments, aniline black, daylight fluorescent pigments and other organic pigments, titanium oxide, iron oxide and other inorganic pigments You can In addition, any pigment that is not listed in the color index but is dispersible in the aqueous phase can be used in the present invention.

Further, of course, those obtained by surface-treating the above-mentioned pigment with a surfactant or a polymer dispersant, such as graft carbon, can also be used.

These pigments are generally used in the ink of the present invention in a proportion of about 0.5 to 20% by weight. It is preferably used in the range of 3 to 15% by weight.

Prior to preparing the ink of the present invention, the pigment is preferably subjected to dispersion treatment by a conventionally known method together with a suitable dispersant, solvent, pure water and, if necessary, other additives.

As the dispersant, conventionally known polymer dispersants and surfactants used for pigment dispersion can be used, and as the polymer dispersant, proteins such as gelatin, albumin and casein, natural gums such as gum arabic and tragacanth, etc. , Glucosides such as saponin, cellulose derivatives such as methyl cellulose, carboxy cellulose, hydroxymethyl cellulose, lignin sulfonate, natural polymers such as shellac,
Polyacrylic acid salt, styrene-acrylic acid copolymer salt, vinylnaphthalene-acrylic acid copolymer salt, styrene-maleic acid copolymer salt, vinylnaphthalene-maleic acid copolymer salt, β-naphthalene sulfone Acid formalin condensate sodium salt, anionic polymer such as phosphate, polyvinyl alcohol, polyvinylpyrrolidone,
Polymer dispersants such as non-ionic polymers such as polyethylene glycol, as surfactants fatty acid salts, higher alcohol sulfate ester salts, liquid fatty oil sulfate ester salts,
There are anionic surfactants such as alkylallyl sulfonates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, nonionic surfactants such as polyoxyethylene sorbitan alkyl esters, These 1 type, or 2 or more types can be appropriately selected and used. The amount used depends on the dispersant, but is generally 1 for the total amount of ink.
It is preferably from 20 to 20% by weight.

On the other hand, the disperser used for dispersing the pigment may be any general disperser, and examples thereof include a ball mill, a roll mill and a sand mill. Among them, a high speed type sand mill is preferable, and examples thereof include a super mill, a sand grinder, a bead mill, an agitator mill, a grain mill, a dyno mill, a pearl mill, and a coball mill (both are trade names).

The ink of the present invention is obtained by dissolving and dispersing the above components as main components in a liquid medium containing water as a main component. Water as a liquid medium can be used alone, but it is generally preferable to use it in combination with an organic solvent. As the organic solvent used in combination, for example, as the organic solvent,
Alkyl alcohols having 1 to 5 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, n-pentanol; dimethylformamide , Dimethylacetamide and other amides; acetone,
Ketones or keto alcohols such as 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 groups containing 2 to 6 carbon atoms; glycerin; ethylene glycol Lower alkyl ethers of polyhydric alcohols such as monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether; triethylene glycol dimethyl (or ethyl) ether, tetraethylene glycol dimethyl ( Or lower dialkyl ethers of polyhydric alcohols such as ethyl) ether; sulfolane, N-methyl-2-pyrroind, 1,3-dimethyl-2
-Imidazolidinone and the like. Among these many 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 is generally 2 to 40% by weight, preferably 5 to 20% by weight based on the total weight of the ink.
Is the range.

Although the essential components of the ink of the present invention are as described above, various other surfactants, viscosity modifiers, surface tension modifiers, binder resins for improving the fixability of the ink on the recording material, etc. It can be added if necessary.

For example, polyvinyl alcohol, celluloses, viscosity modifiers or binders such as water-soluble resins; various cationic, anionic or nonionic surfactants, secondary alcohols and / or surfactants such as ethylene oxide adducts thereof, diethanolamine, A surface tension adjusting agent such as triethanolamine; a pH adjusting agent using a buffer solution, an antifungal agent and the like can be mentioned.

Further, in order to prepare the ink used in the ink jet recording method of charging the ink, lithium chloride,
A resistivity adjusting agent such as an inorganic salt such as ammonium chloride or sodium chloride is added.

When applied to an ink jet recording method 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.

Furthermore, the ink of the present invention has a surface tension at 25 ° C. of 25 to 65 dyne / cm, preferably 30 to 55 dyne / cm, and a viscosity of 15 cps or less as a physical property of the ink from the viewpoint of matching with a writing instrument or an inkjet recording system head. Is
It is desirable to adjust to 10 cps or less, more preferably 5 cps or less.

The ink of the present invention obtained as described above has solved the problems of the prior art, and in spite of using a pigment as a colorant, it is possible to use a pen tip or a fine orifice tip for a long period of time. No clogging occurs over a long period of time, almost no solids are deposited even after long-term storage, and in addition to paper specially adjusted for inkjet recording, copy paper, report paper, notebooks, and paper notes It is possible to perform recording with excellent fixability and excellent printing quality even on plain paper that is commonly used in offices.

(Examples) Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. In the text, parts and% are based on weight unless otherwise specified.

Examples 1 to 5 The following components were dispersed in a pearl mill (Ashizawa Co., Ltd.), and the resulting dispersion was subjected to a centrifuge (manufactured by Hitachi Ltd.) to remove coarse particles, thereby obtaining Inks A to E of the invention. It was

Next, using the obtained inks A to E, an ink jet printer BJ-80 (trade name: manufactured by Canon Inc.) that uses a heating element as an ink discharge energy source is used as an ink jet recording device, and clogging property is obtained. Evaluation, storage stability evaluation and fixability evaluation were performed. The following evaluations are shown in Table 1 below.

Ink A Compound of general formula (I) (No.1) 7 parts Carbon black (MA-100, manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) 1
0 parts Styrene-maleic anhydride copolymer (molecular weight 10,000, acid value 175) 7 parts Ethylene glycol 15 parts Ethanolamine 1 part Nikkor TS-30 (Nikko Chemicals) 2 parts Water 55 parts Ink B General formula (I) Compound (No.5) 4 parts Quinacridone red (manufactured by Fuji Dye) 9 parts Styrene-acrylic acid copolymer (molecular weight 11,000, acid value 15
0) 6 parts Aminomethyl propanol 1 part Glycerin 10 parts Nikkor BL-9EX (manufactured by Nikko Chemicals) 0.5 parts Water 63.5 parts Ink C Compound of general formula (I) (No. 16) 4 parts Phthalocyanine blue (manufactured by Toyo Ink) ) 8 parts α-methylstyrene-styrene-acrylic acid copolymer (molecular weight 12,500, acid value 197) 5 parts ethylene glycol 5 parts glycerin 10 parts diethanolamine 1 part Nikkor MYL-10 (manufactured by Nikko Chemicals) 0.5 parts water 62.5 parts Ink D Compound of general formula (I) (No. 24) 5 parts Carbon black (MCF-88, manufactured by Mitsubishi Kasei Co., Ltd.)
9 parts styrene-acrylic acid copolymer (molecular weight 10,000, acid value 19
5) 7 parts N-methyl-diethanolamine 1 part Glycerin 13 parts Ethanol 5 parts Water 57 parts Ink E Compound of general formula (I) (No. 43) 6 parts Hansaello 3G 6 parts Polyoxyethylene alkyl ether phosphate 2 parts Solbit 5 parts Ethylene glycol 7 parts Diethylene glycol 10 parts Nikkor NP-7.5 (manufactured by Nikko Chemicals) 1 part Water 62 parts Comparative Examples 1 to 5 Compounds of general formula (1) in Inks A to E of Examples 1 to 5 were added. Example 1 except for the components whose contents were replaced by water
Comparative inks F to J were obtained in the same manner as above.

Comparative column 6 Ink D for comparison was obtained by treating in the same manner as in Example 4 except that the compound of general formula (I) was replaced with urea in the components of ink D of Example 4.

Comparative Example 7 Ink D for comparison was obtained by treating in the same manner as in Example 4 except that the compound of the general formula (I) was replaced with sorbitol in the components of the ink D of Example 4.

Next, using the obtained ink, the clogging property and the print quality were evaluated in the same manner as in the example, and the results are shown in Table 1 below.

Comparative Example 8 Ink D for comparison was obtained by treating in the same manner as in Example 4 except that the compound of the general formula (I) was replaced with polyethylene glycol (molecular weight 500) in the components of the ink D of Example 4.

Next, using the obtained ink, the clogging property and the print quality were evaluated in the same manner as in the example, and the results are shown in Table 1 below.

* 1 Clogging property evaluation After filling the printer with the specified ink and printing alphanumeric characters continuously for 10 minutes, stop printing, put the cap on and leave for 30 days (Left condition: 40 ° C, 10 ± 5 % RH)
The nozzle clogging recovery operation was performed, the alphanumeric characters were printed again, and the judgment was made based on the number of recovery operations and the presence or absence of defective parts such as scratches or missing characters.

◯: Printing similar to the initial printing is possible with 0 to 5 recovery operations.

Δ: Printing similar to the initial printing is possible after 6 to 10 recovery operations.

×: Printing similar to the initial printing is possible with 10 recovery operations.

* 2 Storage stability evaluation Put 80 cc of ink in a shot bottle (made by Duran) and store at 50 ° C.
Stored in the oven for 1 month. Then, after returning the sample to room temperature, the bottle was turned upside down and the deposit adhering to the bottle wall was evaluated.

◯: Almost no precipitate.

Δ: A small amount of precipitate was generated.

X: A large amount of precipitate is generated.

* 3 Fixability evaluation 10 seconds after printing on commercially available copy paper and bond paper, 30 seconds later, the printing part was filtered paper (trade name: No. 5C, Toyo Kagaku Sangyo Co., Ltd.)
Made).

(Evaluated under environmental conditions of 25 ° C. and 60% RH) ○: Scratch is hardly seen in 10 seconds △: Scratch is small in 30 seconds × Scratch is large in 30 seconds (effect) According to the present invention as described above, Even in an ink using a pigment as a colorant, it is possible to perform highly reliable recording without causing clogging with a pen tip or a fine orifice tip for a long period of time.

In addition, the ink of the present invention is excellent in stability because no change in physical properties or precipitation of solid matter is observed even after long-term storage.

Further, according to the ink of the present invention, not only the paper specially adjusted for ink jet, but also the plain paper generally used in the office such as copy paper, report paper, notebook, and notepaper, the fixability is good and printing is possible. It is possible to obtain a record of excellent quality.

Claims (1)

[Claims] 1. An ink obtained by dispersing a pigment in a liquid medium containing water as a main component, which contains a compound represented by the following general formula (I). (In the formula, R ₁ , R ₂ and R ₃ represent a hydrogen atom, a hydroxyl group or an alkyl group, R ₄ and R ₅ represent a hydrogen atom or a methyl group, and m
And n represent a numerical value of 1 to 30, and m + n is a numerical value in the range of 2 to 50. )