JPH0826260B2 - Ink and ink jet recording method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is applicable to office paper such as copy paper, report paper, bond paper, and continuous slip paper as well as designated paper specially adjusted for ink jet. An ink that can perform recording at high speed and with fast fixing property, excellent water resistance and printing quality, and excellent storage stability on paper and various cloths generally used at home, and the same. The present invention relates to an inkjet recording method.

[Conventional technology]

The ink jet recording method forms ink droplets by various ink ejection methods, and makes a part or all of them adhere to a recording material such as paper, processed paper, plastic film, and woven cloth for recording. As an ink used in such an ink jet recording method, various dyes or pigments dissolved or dispersed in water or a liquid medium composed of water and a water-soluble organic solvent are known and used. Has been done.

Such ink is generally required to have the following performance including the relationship with the recording material.

(1) A recorded image of good quality without bleeding can be obtained.

(2) The fixing speed of the ink is high.

(3) Even if printing is interrupted for a while, the nozzles of the printer should not be clogged.

(4) The frequency response is good so that ink can be ejected according to the printing speed of the printer.

(5) The storage stability of the ink is high.

(6) High safety.

(7) Excellent durability of the printed matter such as water resistance and light resistance.

In order to satisfy some or all of the above requirements, vigorous studies have been made from both sides of the ink and the apparatus, and considerable effects have been recognized depending on the required performance.

[Problems that the invention is trying to solve]

However, in spite of many researches up to now, among the above-mentioned required performances, the most strongly required performances at present are (1) no bleeding on a recording material having exposed fibers, and a good fixing property. Excellent, (2) compatible with high-speed recording and good frequency response, (3) excellent water resistance of a recorded image even when a water-soluble dye is used, (4) the above At present, it has not yet been sufficiently solved, including the fact that the performances (1) to (3) are satisfied and the storage stability is excellent.

First of all, regarding bleeding and fixability of the recording material with exposed fibers, especially when printing on ordinary plain paper such as copy paper, report paper, bond paper, continuous slip paper, etc. as the recording material. The problem is that the ink bleeds along the fibers of the paper and the fixability is insufficient due to the influence of the sizing agent contained in the plain paper.

Therefore, for the purpose of improving bleeding and fixing property, a method of recording using an ink in which PH is made strongly alkaline (JP-A-56-
57862 report), a method of recording using an ink to which a large amount of surfactant is added (JP-A-55-29546), and a method of recording a liquid as a liquid by heating solid ink at room temperature (JP-A-55-29546). 58-108271), etc. have already been tried. But,
The method of recording by making the pH of the ink strongly alkaline is dangerous when the ink is touched by hand, and the bleeding and fixing property may not be good for the paper using a certain size. There are drawbacks such as. In addition, in the method of adding a large amount of surfactant, bleeding may occur very much depending on the paper, or the ink may not be ejected because it may recede from the orifice surface depending on the conditions of the printer head.
On the contrary, the entire orifice surface gets wet, and there are problems such as ink not being ejected. Further, the method of heating a solid ink at room temperature to record it as a liquid has a certain effect on bleeding and print fixability. However, when designing a printer, a device or printer head for supplying ink while melting it is used. Since a heating device is required inside, there are problems that the printer becomes large and the cost is high.

Regarding the second problem, which is the improvement of the frequency response corresponding to high-speed recording, most of the studies are conducted from the viewpoint of the mechanical structure such as the head configuration, and the improvement of the ejection response frequency by ink is not so much studied. The reality is that it has not been done.

Generally, the frequency response is improved as the viscosity of the ink is decreased, however, the ejection stability is decreased accordingly. Therefore, it is difficult to develop an ink that improves the frequency response while maintaining the ejection stability. In particular, the on-demand type ink jet method has a problem that the frequency response and the ejection stability are poor under the driving condition of the frequency of 1 KHz or more, and this tendency becomes more remarkable when the driving frequency becomes 2 KHz and 4 KHz. This is a particularly serious problem in the ink jet method using a piezoelectric element or thermal energy.

Regarding the third water resistance, many methods such as a method using an ink using an oily dye or a pigment and a method using a special paper to which a waterproofing agent is added have been proposed.

However, in these methods, problems of storage stability of ink and high cost of recording paper newly occur.

The fourth storage stability is a problem that has been mostly solved in water-based inks composed of ordinary water-soluble dyes, water-soluble liquid media, etc., but it satisfies all of the above requirements (1) to (3). The current situation is that no ink that does this has been proposed yet.

Therefore, the main object of the present invention is not only the designated paper specially adjusted for ink jet, but also the copy paper, report paper, bond paper, continuous slip paper, etc. in which fibers are exposed on the recording surface and are further sized. Fixing speed is fast even on ordinary plain paper, and printing with less bleeding can be obtained.
An object of the present invention is to provide an ink which is safe and has excellent operability, and an ink jet recording method using the ink.

Another object of the present invention is to provide an ink having good frequency response even if the driving frequency is high, and to provide an ink jet recording method having a high printing speed.

Further, another object of the present invention is to provide an ink excellent in water resistance despite using a water-soluble dye.
An object of the present invention is to provide an ink jet recording method using such an ink, which can stably obtain good quality printing over time.

[Means and Actions for Solving Problems] The above object is achieved by the present invention described below.

That is, the first aspect of the present invention is an ink containing a dye that is an image-forming component and a liquid medium that dissolves or disperses the dye, and α-cyclodextrin, γ-cyclodextrin, or maltosyl cyclodextrin. An ink characterized by containing any one of the compounds, the second of the present invention is an ink containing a dye which is a component forming an image and a liquid medium which dissolves or disperses the dye, An ink containing any compound of α-cyclodextrin, γ-cyclodextrin, or maltosyl cyclodextrin, and having a viscosity at 25 ° C. of 5 cp or less, and the third invention. Is an ink jet recording method characterized in that a droplet of the ink is formed by using the above-mentioned first or second ink, and recording is performed by using this droplet.

The compound having a three-dimensional structure having pores inside (three-dimensional structure formed by bonding atoms or molecules), which characterizes the present invention, is a compound having an inclusion ability to take in another substance into the pores. More specifically, it is referred to as a host molecule having a hole and clathrating another substance.

The present invention is characterized by containing a host molecule having an inclusion ability, and the guest molecule corresponds to the dye matrix in the ink constituent or a part thereof.

By using an ink containing a compound having a three-dimensional structure having pores inside, which is formed by combining atoms or molecules as described above, water resistance and fixing property on a recording material and printing quality are excellent. The reason is still unclear.

Probably, the dye matrix or a part of the dye matrix is incorporated into the pores to form an inclusion compound, which has a higher affinity for the recording material, particularly for sized ordinary plain paper, than for the dye alone, and fixing It is considered that the properties and water resistance are improved.

Further, it is considered that the formation of the clathrate compound improves the wettability with the head constituent member and improves the frequency response.

In addition, the inclusion of these compounds does not cause a significant decrease in the surface tension of the ink, unlike the addition of various kinds of surfactants, and therefore does not adversely affect the ejection stability. Further, it is presumed that due to the formation of the clathrate compound, the dye molecules apparently become large and the fluidity is lowered, and there is no bleeding and recording with excellent print quality is obtained.

According to the study by the present inventors, in order to obtain good print quality without bleeding, the size of the host compound contained is important from the viewpoint of the fluidity of the clathrate compound containing a dye, and specifically, The molecular weight of the host compound is 400 or more, more preferably 8
It must be at least 00.

Therefore, the molecular weight is less than 400, urea said to have clathrate ability, thiourea, deoxycholic acid and 18-crown-described in JP-B-53-43843.
In the ink containing the host compound such as 6 or the like, the bleeding preventing effect is insufficient, and it is difficult to obtain a print with good printing quality.

Further, according to the study by the present inventors, in consideration of the long-term storage stability of the ink, the solubility of the host molecule in water is 3%.
As described above, it is necessary to be 5% or more, more preferably.

For example, as described in Japanese Patent Application Laid-Open No. 56-14569, an ink containing β-cyclodextrin (solubility 1.58%) having a solubility in water of less than 3% tends to deposit a precipitate during long-term storage. There is a drawback that.

The compound used in the present invention has a molecular weight of 400 or more, has a three-dimensional structure having pores inside and is formed by bonding atoms or molecules, and has a solubility in water of 3% or more, that is, a host compound, For example, parinomycin-based natural anti-fungal substances, various polyether compounds, nidiuricin-based natural anti-fungal substances, or cyclic compounds having a plurality of pyranol rings, for example, monosaccharides such as glucose, fructose and galactose, and disaccharides such as sucrose, maltose and lactose. Examples include sugars and the like in which 1,4 and 1,6 bonds to form a cyclic compound, but are not limited to these substances. Among them, the particularly preferable substance is
Cyclodextrins in which 6 or more α-D-glucopyranose groups are α-1,4-bonded to form a cyclic compound are mentioned, and the effect is remarkable.

Among cyclodextrins, α-cyclodextrin in which 6 glucose molecules are bound to form a ring and γ-cyclodextrin in which 8 are bound, and further a derivative of the cyclodextrin, for example, maltose is bound for the purpose of improving solubility. Good examples include maltosyl cyclodextrin.

The content of the compound is 0.1 to 2 based on the total weight of the ink.
0% by weight, preferably 0.2-15% by weight, more preferably 0.
It is in the range of 5 to 10% by weight.

When the content of the compound is less than 0.1% by weight, the effect on the improvement of fixing property, print quality and ejection stability is not remarkable, and when the content of the compound exceeds 20% by weight, the viscosity of the ink is It is not preferable as an ink for ink jet from the viewpoint of rising and clogging.

As other components constituting the ink of the present invention, first, as the pigment, water-soluble dyes such as direct dyes, acid dyes, basic dyes, food dyes, reactive dyes, vat dyes, and soluble vat dyes can be mentioned.

In the case of the ink of the present invention, the standard of “water-soluble” is
If the solubility at least at 20 ° C. is 1% or more, there is no problem in the ink performance.

The content of these dyes is determined depending on the type of liquid medium component, properties required for the ink, etc., but generally 0.2 to 20% by weight, preferably 0.5 to 10% by weight, based on the total weight of the ink. It is more preferably in the range of 1 to 5% by weight.

As the aqueous liquid medium for dissolving the dye as described above in the present invention, any of the media used in the media of conventional general ink jet recording ink can be used, for example, water and / or an organic solvent is preferable, and Examples of the solvent include 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 and n-pentanol, Amides such as dimethylformamide and dimethylacetamide; Ketones and keto alcohols such as acetone and diacetone alcohol; Ethers such as tetrahydrofuran and dioxane; Polyalkylenes such as polyethylene glycol and polypropylene glycol Recalls; 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. Kinds; Glycerin; Ethylene glycol monomethyl (or ethyl) ether, Diethylene glycol monomethyl (or ethyl)
Lower monoalkyl ethers of polyhydric alcohols such as ether and triethylene glycol monomethyl (or ethyl) ether; lower dialkyl of polyhydric alcohols such as triethylene glycol dimethyl (or ethyl) ether and tetraethylene glycol dimethyl (or ethyl) ether Ethers: sulfolane, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like can be mentioned.

Although the essential components of the ink of the present invention are as described above, other conventionally known various dispersants, surfactants, viscosity modifiers, surface tension modifiers, optical brighteners, etc. may be added as necessary. You can

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

Further, in order to prepare the ink used in the ink jet recording method of charging the ink, 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 method in which ink is ejected by the action of thermal energy, thermal physical property values (for example, specific heat, coefficient of thermal expansion, thermal conductivity, etc.) may be adjusted.

The ink of the present invention as described above, in terms of physical properties, often requires performance for stable ejection from the printer head, particularly performance for stable ejection at a drive frequency of 1 KHz or more, and therefore, is preferable. The viscosity at 25 ° C. is 5 cP or less, the surface tension is 35 to 65 dyne / cm, and more preferably the viscosity is further adjusted to a low viscosity type of 3 cP or less.

When the viscosity of the ink exceeds 5 cP, even the ink containing the host compound having the inclusion ability according to the present invention has insufficient printing quality, fixing property and frequency response on plain paper.

The ink of the present invention and the ink used in the present invention obtained as described above have fibers exposed on the recording material, especially on the recording surface, and further, sized copy paper, report paper, bond paper, continuous slip paper, etc. It is excellent in water resistance, fixability and printing quality on office papers and plain papers generally used at home, and is effective as an ink for various types of ink jet, and excellent recording can be performed.

In addition, it can respond accurately to the driving frequency for high-speed recording, which has been required more and more at 1KHz, 2KHz, and 4KHz, and is especially an on-demand type system in general, especially a type that uses a piezoelectric element or thermal energy. Even in the ink jet method of (3), excellent recording can be performed for a long period of time.

〔Example〕

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the text, all parts and% are based on weight.

Example 1 Of the above components, first, α-cyclodextrin was dissolved in water, then the dye CI Food Black 2 was added and stirred for 1 hour, and then glycerin, ethylene glycol, and ethylene glycol monophenyl ether were added, and the mixture was mixed at 40 ° C. for 3 hours.
Stir for hours. Then, after adjusting the pH to 7.5 with a 0.1% aqueous solution of sodium hydroxide, pressure filtration was performed using a fluoropore filter (trade name; manufactured by Sumitomo Electric Industries, Ltd.) having a pore size of 1 μm, and the ink (A ) Got.

Next, using this ink, an ink jet printer (Olyphis size 40 x
50μm, heater size 30 × 150μm, 24 nozzles,
Using a driving voltage of 24.5 V and a frequency of 2 KHz), printing was performed on commercially available copy paper and bond paper, and the fixability, print quality, storability and water resistance of the obtained print were evaluated. Ink physical properties and evaluation results are shown in Table 1.

Example 2 Among the above ingredients, first, α-cyclodextrin was dissolved in water, and then the dye CI Acitide Red 35 was added and stirred, and glycerin and 1,3-dimethyl-2-imidazolidinone were further added and stirred at 40 ° C. for 3 hours. did. Thereafter, the pH of the solution was adjusted to 7.5 with a 0.1% aqueous solution of sodium hydroxide, and then pressure-filtered with a Fluoropore filter (trade name; manufactured by Sumitomo Electric Co., Ltd.) having a pore size of 1 μm to carry out the ink (B) of the present invention. ) Got.

Example 3 (adjustment of ink C) Among the above components, first γ-cyclodextrin was dissolved in water, then the dye CI Direct Blue 86 was added and stirred, and further diethylene glycol, ethylene glycol, ethylene glycol monophenyl ether was added.
The mixture was stirred at 40 ° C for 3 hours. Then the sodium hydroxide
After adjusting the pH to 7.5 with a 0.1% aqueous solution, pressure filtration was performed using a Fluoropore filter (trade name; manufactured by Sumitomo Electric Co., Ltd.) having a pore size of 1 μm to obtain the ink (C) of the present invention.

Example 4 Of the above components, first, maltosyl cyclodextrin is dissolved in water, then the dye CI Food Black 154 is added and stirred, and then diethylene glycol and N-methyl-
2-Pyrrolidone and a nonionic surfactant were added, and the mixture was stirred at 40 ° C. for 3 hours. Then 0.1% of sodium hydroxide
After adjusting the pH to 7.5 with an aqueous solution, pore size 1
μ Fluoropore Filter (trade name; Sumitomo Electric Industries, Ltd.)
Manufactured by pressure filtration to obtain the ink (D) of the present invention.

Example 5 (Adjustment of Ink E) Among the above components, first α and γ-cyclodextrin are dissolved in water, then the dye CI Direct Yellow 86 is added and stirred, and further triethylene glycol, ethylene glycol, 1,3-dimethyl-2-imidazolidinone are added. And stirred at 40 ° C. for 3 hours. Then, after adjusting the pH to 7.5 with a 0.1% aqueous solution of sodium hydroxide, pressure filtration was performed using a fluoropore filter (trade name; manufactured by Sumitomo Electric Industries, Ltd.) having a pore size of 1 μm, and the ink of the present invention (E ) Got.

Example 6 (adjustment of ink C) Among the above components, monensin was first dissolved in water, then the dye CI Food Black 2 was added, and the mixture was stirred for 1 hour, glycerin, ethylene glycol and ethylene glycol monophenyl ether were further added, and the mixture was stirred at 40 ° C. for 3 hours.
After that, the pH was adjusted to 7.5 with a 0.1% aqueous solution of sodium hydroxide, and pressure filtration was performed using a fluoropore filter (trade name; manufactured by Sumitomo Electric Co., Ltd.) with a pore size of 1 μm to perform the ink (F) of the present invention. Got

Comparative Example 1 Of the components in Example 1, the components except α-cyclodextrin were stirred for 3 hours, adjusted to have a pH of 7.5 with a 0.1% aqueous solution of sodium hydroxide in the same manner as in Example 1, and then the pore size was 1 μm. Fluoropore filter (trade name;
A comparative ink (G) was obtained by pressure filtration with Sumitomo Electric Industries, Ltd.).

Comparative Example 2 Among the components in Example 2, the components except α-cyclodextrin were treated in the same manner as in Comparative Example 1 to obtain a comparative ink (H).

Comparative Example 3 A comparative ink (I) was obtained by treating the components in Example 3 except for γ-cyclodextrin in the same manner as in Comparative Example 1.

Comparative Example 4 (Preparation of Ink I) Comparative Ink (J) was obtained by the same procedure as in Example 1 except that sucrose was used instead of α-cyclodextrin in Example 1.

Comparative Example 5 In Comparative Example 1, the maltosyl cyclodextrin was removed, and 0.5 parts of a nonionic surfactant (Nitsusan Nonion P223 (trade name), manufactured by NOF CORPORATION) was added instead. The same process was performed to obtain a comparative ink (K).

Comparative Example 6 A comparative ink (L) was obtained in the same manner as in Example 1 except that β-cyclodextrin was used instead of α-cyclodextrin in the components of Example 1.

Comparative Example 7 A comparative ink (M) was prepared in the same manner as in Example 1 except that 18-crown-6 was used instead of α-cyclodextrin in the components of Example 1.

Comparative Example 8 An ink (N) for comparison was obtained by the same process as in Example 6 except that urea was used instead of monensin in Example 6.

The same recording as in Example 1 was performed for the inks (B-N) of Examples 2 to 6 and Comparative Examples 1 to 8. Ink physical properties and evaluation results are shown in Table 1.

* 1 Viscosity measurement Tokyo Keiki VISCONIC ELD * 2 Surface tension measurement Kyowa Kagaku Kiyowa CBVP SURFACE TENSIOMETER A-1 * 3 Fixability evaluation Printed on commercially available copy paper and bond paper 10 After 2 seconds and 30 seconds, the printing part is the filter paper (Product name: No.5C, Toyo Kagaku Sangyo Co., Ltd.)
Made).

(Evaluated under environmental conditions of 25 ° C and 60% RH) ◎ …………………… No blurring in 10 seconds ○ …………………… Scratch is small in 10 seconds △ …………………… … Small bleaching in 30 seconds × …………………… Scratchy in 30 seconds * 4 Print quality evaluation After printing on the above-mentioned copy paper and bond paper, leave it for 1 hour or more, and then seep and blur at the dot level. Was evaluated for sharpness.

(Evaluated under environmental conditions of 25 ° C and 60% RH) ◎ ... No bleeding and edge is extremely sharp.

○: Some bleeding is seen, but the edge of the dot is sharp.

△: Almost all dots are blurred and the edges of the dots are slightly blurred.

×: All dots are blurred and the edges of the dots are not clear.

* 5 Storability Put the ink in the storage pin (SCHOTT bottle, made by DURAN) and -3
It was stored at 0 ° C. and 60 ° C. for 1 month and evaluated for the presence of precipitates.

○: No precipitate.

△: There are some precipitates.

×: There are a large amount of precipitates.

* 6 Water resistance After printing on the above-mentioned copy paper, the printed sample was left for 1 day and then immersed in water for 1 minute to evaluate image bleeding.

B: Almost no bleeding is seen.

B: Some bleeding is seen.

×: A large amount of bleeding occurs, making it difficult to read the image.

Examples 7 to 21 and Comparative Examples 9 to 23 Using the inks A to E and G to K obtained in Examples 1 to 5 and Comparative Examples 1 to 5, the following printers i and b were used and the frequency was set to 1 Set within the range of up to 6 KHz and perform solid printing of 15 x 4 cm ² area and character printing of 130 characters of Alphabet on commercially available copy paper to obtain ink followability and landing point accuracy of the obtained print. The frequency response of the ink was investigated and evaluated, and the evaluation results are shown in Table 2.

(Printer) Uses a heating element as a source of ink discharge energy (heater size 30 x 150 μm ² ) ORIFICE size 40 x 5
Inkjet printer with 24 0 μm ² nozzles (driving voltage 24.5V).

(Printer) Using a piezo element as a pressure means to apply to ink,
Ink is ejected by causing a mechanical displacement in the piezo element by an electric signal. An ink jet printer (driving voltage 60V) with 8 nozzles with an orifice size of 50 μm and a channel length of 40 mm.

* 7 Evaluation of frequency responsiveness The printed state of the obtained printed matter, that is, the state of blurring or white spots and the state of defective landing point such as splashing and twisting was visually observed and evaluated.

⊚: The ink follows the frequency well, and neither solid prints nor charactor prints are free of scratches, white spots, and defective landing points.

◯: The ink followability with respect to frequency is almost good, and there is no blur, white spots, or defective landing point in charactor printing, but slight blur in solid printing.

△: No blemishes or white spots are seen in the charactor print,
Some defective landing points are seen. Also, in solid printing, blurring,
White spots are seen in about 1/3 of the whole solid.

X: There are many scratches and white spots in solid printing, and many scratches and defective landing points are also seen in charactor printing.

[Effect]

As described above, according to the present invention, not only the designated paper specially adjusted for the ink jet but also the ordinary plain paper, for example, copy paper, in which the fibers are exposed on the recording surface and further sized, Report paper, bond paper,
It is possible to perform ink jet recording with good water resistance, fast fixing speed, and printing with little bleeding even on continuous slip sheets and the like.

Furthermore, since the ink of the present invention has excellent storage stability,
Ink jet recording that is safe and has excellent ejection stability and ink operability can be performed for a long period of time.

Furthermore, since the frequency response of the ink is good, high-speed and stable recording with a high driving frequency is possible.

Claims (3)

[Claims] 1. An ink comprising a dye which is an image forming component and a liquid medium which dissolves or disperses the dye, and is selected from α-cyclodextrin, γ-cyclodextrin and maltosyl cyclodextrin. An ink containing a compound. 2. An ink containing a dye which is a component for forming an image and a liquid medium which dissolves or disperses the dye, wherein either α-cyclodextrin, γ-cyclodextrin or maltosyl cyclodextrin is used. Contains Compound, 25
An ink having a viscosity of 5 cp or less at ° C. 3. An ink jet recording method, which comprises using the ink according to claim 1 or 2 to form droplets of the ink, and recording with the droplets.