JPH03259967A - Ink and method for ink jet recording using the same - Google Patents

Abstract

PURPOSE:To eliminate the spot in printing on plain paper and improve quickly drying properties and safety in the use in an office, etc., by compounding a water-sol. dye, a liq. medium contg. water, and a polypropylene glycol alkyl ether. CONSTITUTION:0.2-20wt.% water-sol. dye, 0.01-60wet.% polypropylene glycol alkyl ether shown by the formula (wherein R1 and R2 are each H or a 2C or higher alkyl group provided that they are not simultaneously H; and X is a propylene oxide homopolymer) and having a degree of polymn. of 3-20 and, pref., terminal 2-6C alkyl groups, a liq. medium, and required amts. of a dispersant, a surfactant, a viscosity modifier, a surface tension modifier, a fluorescent whitener, etc., are compounded to give an ink for ink jet recording. The liq. medium is prepd. by compounding 20-95wt.% (based on the ink) water and 2-50wt.% (based on the ink) org. solvent.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable not only to coated paper specially prepared for inkjet use, but also to other types of copy paper, report paper, pound paper, continuous slip paper, etc. The present invention relates to a high-speed fixing type ink capable of high-definition, high-quality recording even on uncoated paper, so-called plain paper, commonly used in offices and homes, and an inkjet recording method using the same.

[Conventional technology]

Conventionally, inkjet inks having a wide variety of compositions have been reported. In particular, in recent years, it has been found that it fixes at high speed even on plain paper commonly used in offices such as copy paper, report paper, notebooks, and stationery, has good quality, has high image robustness, and is safe. In order to develop ink with high properties, detailed research and development is being conducted from various aspects such as composition and physical properties.

For example, ink generally contains high-boiling organic solvents such as glycol for the purpose of preventing drying and clogging, but when recording with such ink on plain paper with a high degree of size, Since the ink does not easily penetrate into the paper and the drying properties of the recorded area are poor, there are problems such as the ink getting on your hands when you touch the recorded matter and the characters being rubbed and smudged.

Therefore, in order to improve the permeability of the ink into the inside of the paper, Japanese Patent Laid-Open No. 56-29546 proposes a method of adding a large amount of surfactant to the ink. In this case, depending on the paper, there may be a lot of bleeding, or when filling an inkjet head, depending on the structural conditions of the head, the ink may recede from the orifice surface and no ejection occurs, or conversely, the orifice may Problems such as the entire surface getting wet and ink not being ejected were observed.

Furthermore, JP-A-56-57862 proposes a method of making the pH of the ink strongly alkaline, but in this case it is dangerous if the ink is touched by hand, and it also For example, acid-free paper may bleed,
There are drawbacks such as poor drying properties.

Furthermore, JP-A No. 62-243666 describes that the toxicity of the ink and the water resistance of recorded images were improved by combining an oil-soluble dye and a butanol-propylene oxide addition polymer as an oil-based ink. .

Such ink has excellent fixability to paper and water resistance of recorded images, but when used in a type of recording method that ejects ink due to the ink bubbling phenomenon, the ink may not be ejected or may be unstable even if it is ejected. Moreover, there is a further drawback that a large amount of bleeding occurs when printing on plain paper.

Furthermore, such inks also have problems in storage stability because the solubility of oil-soluble dyes in solvents is generally low.

JP-A-1-110577 describes an ink containing methyl ether of polypropylene glycol, but even when such an ink is used, the fixing properties on plain paper, the occurrence of bleeding, and the water resistance of recorded images are improved. It is not possible.

In addition to the above, various improvements have been attempted up to now, but at present no ink has been known that simultaneously solves the problems of bleeding, fixing properties, and solidity of recorded images.

[Problems to be Solved by the Invention] Therefore, the purpose of the present invention is to solve the problem of ink when recording on uncoated paper, so-called plain paper, which is commonly used in offices such as copy paper, report paper, notebooks, and stationery. An object of the present invention is to provide an ink with improved bleeding and slow drying properties of recorded matter, and an inkjet recording method using the same.

Another object of the present invention is to provide an ink that is highly safe for use in offices and homes.

Another object of the present invention is to provide an ink that improves image fastness on plain paper, especially water resistance, despite the use of water-soluble dyes.

[Means for solving problems]

The above object is achieved by the present invention as follows.

That is, the present invention is characterized in that an ink mainly composed of a water-soluble dye and a liquid medium containing water contains an alkyl ether of polypropylene glycol represented by the following general formula [I]. It's ink.

R1(X) OR2・・・・・・・・・・・・・・・
... [I] (In the formula, R1 and R2 represent a hydrogen atom or an alkyl group having 2 or more carbon atoms, but they cannot be hydrogen atoms at the same time. Also, X represents a homopolymer of propylene oxide.

Further, the present invention is an inkjet recording method in which droplets are formed by applying thermal energy corresponding to a recording signal to the above ink, and recording is performed by applying the droplets to a recording material.

[Effect]

As a result of intensive studies on various ink compositions in order to improve the bleeding, drying properties, and permeability of ink on paper, the present inventors found that an ink containing water as well as a compound represented by the above general formula The inventors discovered that it is well-balanced in terms of permeability and also has high fastness of images on plain paper, leading to the present invention.

According to the findings of the present inventors, when using surfactants used in ordinary inks, there are cases where the bleeding and permeability of ink on paper are good and cases where it is not good depending on the type of paper. , it is difficult to obtain stable records.

On the other hand, when the liquid medium system used in the present invention is used, there is no difference depending on the paper, and extremely good results are obtained. The reason for this is that ink bleeding and permeability are mainly controlled by the phenomenon of wetting at the interface between ink droplets and paper; Whereas the surface and interior of a droplet have different wetting properties, the ink of the present invention is less likely to cause such a phenomenon, and the ink of the present invention has a different wetting property between the surface and internal additives added to the paper. This seems to be because the inkjet ink has an exquisite balance of affinity with the sizing agent for use with plain paper.

Note that ink containing methyl ether of polypropylene glycol has slower fixing properties and is more likely to cause irregular bleeding than the ink of the present invention. This is thought to be because the methyl ether of polypropylene glycol has insufficient affinity with the paper sizing agent compared to the compound used in the present invention.

Furthermore, the ink of the present invention has much better water resistance than conventional inkjet inks compatible with plain paper. This is considered to be because the ink of the present invention has strong penetrating power and easily blends into paper.

[Preferred embodiment]

Next, each component of the ink of the present invention will be explained.

The compound represented by the general formula [I] that mainly characterizes the present invention is an alkyl ether compound of polypropylene glycol, which can be obtained by a conventionally known method.

Specific examples of the above compounds are R 1 in the general formula [I]
+ R2+x is as shown in Table 1, but the present invention is not limited to these compound examples.

The compounds used in the present invention shown in Table 1 were derived from the inventor's extensive studies, depending on the addition polymerization number of propylene oxide and the selection of the terminal alkyl group. 6. Regarding the degree of polymerization, a range of 3 to 20 is particularly suitable.

Although the amount of the above-mentioned compounds added to the ink varies depending on the water-soluble dye used and other liquid medium components used together, the proportion of the above-mentioned compounds in the ink is about 0.
The proportion is approximately 60% by weight, preferably 0.1 to 40% by weight, and more preferably 1 to 30% by weight.

Water-soluble dyes constituting the ink of the present invention include direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, and soluble architectural dyes.

The content of these water-soluble dyes is determined depending on the type of liquid medium components, the properties required of the ink, etc.; The proportion is preferably 0.5 to 10%, more preferably 1 to 5%.

Furthermore, the proportion of water in the ink, which is an essential component of the present invention, is 20 to 95% by weight, preferably 50 to 9% by weight.
The proportion is 5% by weight, more preferably 60 to 95% by weight.

If the water content is less than 20% by weight, not only will the printing quality be poor, but also the orifice surface will become wet when ejecting with an inkjet head, making it difficult to eject.

Similarly, when the amount of water exceeds 95% by weight, the stability of ejection from the orifice of the nozzle and the resistance to clogging after stopping during printing are extremely poor.

The essential components of the ink of the present invention are as described above, but other general organic solvents used in conventionally known inks can also be used in combination.For example, organic solvents include methyl alcohol, ethyl alcohol, n-propyl alcohol, and isopropyl alcohol. Alkyl alcohols having 1 to 5 carbon atoms such as alcohol, n-butyl alcohol, 5ec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, and n-pentanol; amides such as dimethylformamide and dimethylacetamide; acetone and diacetone Ketones or keto alcohols such as alcohol; ethers such as tetrahydrofuran and dioxane; oxyethylene or oxypropylene addition polymers such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, and polypropylene glycol; ; Ethylene glycol, propylene glycol, trimethylene glycol, butylene glycol, l, 2
．． Alkylene glycols in which the alkylene group has 2 to 6 carbon atoms such as 6-hexandriol and hexylene glycol; thiodiglycol; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol 7-methyl (or ethyl) ether ,
Lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether; lower dialkyl ethers of polyhydric alcohols such as triethylene glycol dimethyl (or ethyl) ether and tetraethylene glycol dimethyl (or ethyl) ether; Examples thereof include sulfolane, N-methyl-2-pyrrolidone, (1), 3-dimethyl-2-imidazolidinone, and the like.

The content of the water-soluble organic solvent is generally 2 to 50% by weight, preferably 2 to 3% by weight based on the total weight of the ink.
The range is 0%.

When the above-mentioned media are used together, they can be used alone or as a mixture, but the most preferred liquid medium composition is one or more organic solvents, and the solvent is at least one water-soluble high-boiling organic solvent, such as diethylene glycol. , triethylene glycol, glycerin, and other polyhydric alcohols.

Various other dispersants, surfactants, viscosity modifiers, surface tension modifiers, fluorescent brighteners, etc. can also be added as necessary.

For example, viscosity modifiers such as polyvinyl alcohol, celluloses, and water-soluble resins; various cationic, anionic, or nonionic surfactants; surface tension modifiers such as jetanolamine and triethanolamine; pH modifiers using buffer solutions; Antifungal agents and the like can be mentioned.

Further, in order to prepare ink used in an inkjet recording method in which the ink is charged, a resistivity adjuster such as inorganic salts such as lithium chloride, ammonium chloride, and sodium chloride is added.

The ink of the present invention is particularly suitable when applied to an inkjet recording method in which the ink is ejected by a bubbling phenomenon of the ink caused by thermal energy, and is characterized in that the ejection is extremely stable and no satellite dots are generated. There is. In this case, physical property values (eg, specific heat, coefficient of thermal expansion, thermal conductivity, etc.) may be adjusted.

Furthermore, the ink of the present invention solves the problem of ink bleeding when recorded on plain paper, dryness, and permeability of the recorded material, and from the aspect of matching with inkjet heads, the ink physical property is that the surface tension at 25°C is 30. to 68 d
It is desirable that the y n e /cm and viscosity be adjusted to 15 cP or less, preferably 10 cP or less, more preferably 5 cP or less.

A suitable recording device for recording using the ink of the present invention includes a device that applies thermal energy corresponding to a recording signal to a recording liquid in a chamber of a recording head and generates droplets using the energy.

An example of the configuration of the head, which is the main part, is shown in FIG. 1(a).

(b), shown in FIG.

The head 13 includes a glass, ceramic, or plastic plate having grooves 14 through which ink passes, and a heat generating head 15 used for thermal recording (a thin film head is shown in the figure, but is not limited to this). Obtained by gluing. The heat generating head 15 includes a protective film 16 formed of silicon oxide or the like, aluminum electrodes 17-1. 17-2, a heating resistor N18 made of nichrome or the like, a heat storage layer 19, and a substrate 20 with good heat dissipation properties such as alumina.

The ink 21 has reached the discharge orifice 22, and the pressure P
A meniscus 23 is formed by this.

Now, when an electric signal is applied to the electrodes 17-1 and 17-2, the area indicated by n of the heating head 15 suddenly generates heat, bubbles are generated in the ink 21 in contact with this area, and the pressure causes the meniscus 23 to protrudes, and the ink 21 becomes recording droplets 24 from the ejection orifice 22 and flies toward the recording medium 25. FIG. 2 shows an external view of a multi-head in which a large number of heads shown in FIG. 1(a) are arranged. The multi-head is made by adhering a glass plate 27 having multi-grooves 26 and a heating head 28 similar to that described in FIG. 1(a).

Note that FIG. 1(a) shows the head 13 along the ink flow path.
FIG. 1(b) is a sectional view taken along A-B in FIG. 1(a).
This is a cut plane along a line.

An example of an ink jet recording apparatus incorporating the head according to FIG. 3 is shown.

In FIG. 3, 61 is a blade as a wiping member, one end of which is held by a blade holding member and becomes a fixed end in the form of a cantilever. The blade 61 is disposed adjacent to the recording area of the recording head, and in this example, is held in a protruding form in the movement path of the recording head. A cap 62 is disposed at a home position adjacent to the blade 61, and is configured to move in a direction perpendicular to the direction of movement of the recording head and come into contact with the ejection port surface to perform capping. Furthermore, 63 is an ink absorber provided adjacent to the blade 61;
Like the blade 61, it is held in a protruding form in the movement path of the recording head. The blade 61 and cap 62
The absorber 63 constitutes an ejection recovery section 64, and the blade 61 and the absorber 63 remove moisture, dust, etc. from the ink ejection orifice surface.

Reference numeral 65 is a recording head that has an ejection energy generating means and performs recording by ejecting ink onto a recording material facing the ejection orifice surface on which ejection ports are arranged, and 66 is a recording head that mounts the print head 65 and moves the print head 65. It is a carriage for carrying out. The carriage 66 is slidably engaged with a guide shaft 67, and a portion of the carriage 66 is connected to a belt 69 (not shown) driven by a motor 68. This allows the carriage 66 to move along the guide shaft 67, allowing the recording head 65 to move the recording area and its adjacent area.

Reference numeral 51 denotes a paper feeding section for inserting a recording material, and 52 a paper feed roller driven by a motor (not shown). With these configurations, the recording material is fed to a position facing the ejection opening surface of the recording head, and as recording progresses, the recording material is discharged to a paper discharge section provided with a paper discharge roller 53.

In the above configuration, when the recording head 65 returns to the home position after recording ends, etc., the cap 6 of the head recovery section 64
2 is retracted from the moving path of the recording head 65, but the blade 61 protrudes into the moving path. As a result, the ejection port surface of the recording head 65 is wiped. Note that when the cap 62 contacts the ejection surface of the recording head 65 to perform capping, the cap 62 moves so as to protrude into the movement path of the recording head.

When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are in the same position as the wiping position described above. As a result, even during this movement, the ejection orifice surface of the recording head 65 is wiped.

The above-mentioned movement of the print head to the home position is not limited to the end of printing or recovery of ejection, but also the movement of the print head to the home position adjacent to the print area at predetermined intervals while moving the print area for printing. However, along with this movement, the above-mentioned wiping is performed.

FIG. 4 is a diagram showing an example of an ink cartridge containing ink supplied to the head via an ink supply tube. Here, 40 is an ink bag containing supply ink, and a rubber stopper 42 is provided at the tip of the ink bag. By inserting a needle (not shown) into this plug 42,
The ink in the ink bag 40 can be supplied to the head. 44 is an ink absorber that receives waste ink.

The inkjet recording device used in the present invention includes:
The head and ink cartridge are not limited to separate units as described above, but a unit in which they are integrated as shown in FIG. 5 may also be suitably used.

In FIG. 5, reference numeral 50 denotes an inkjet cartridge, which houses an ink absorber impregnated with ink. It is configured to be discharged as

Reference numeral 52 denotes an atmospheric air passage port for communicating the inside of the cartridge with the atmosphere.

This inkjet cartridge 50 is used in place of the recording head 65 shown in FIG. 3, and is detachable from the carriage 66.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. In the text, parts and percentages are based on weight unless otherwise specified.

After mixing the following ingredients and stirring for 5 hours, the pH was adjusted to 7.5 with a 0.1% aqueous solution of sodium hydroxide, and a membrane filter with a pore size of 0.22 microns was added. The inks A to E of the present invention were obtained by pressure filtration using Fluorobor Filter (trade name: Fluorobor Filter, manufactured by Sumira Electric Industries, Ltd.).

Next, using the obtained inks A to E, an inkjet printer BJ130 that uses a heating element as an ink ejection energy source is used as an inkjet recording device.
(Product name: manufactured by Canon ■) was used to record on commercially available copy paper and bond paper. The clogging resistance, frequency response, and water resistance were evaluated. The results are shown in Table 2. Evaluation is usually at 25℃, 60%RH
It was evaluated.

Ink A C King Direct Yellow 86 Diethylene glycol compound example 1 Water 2 parts 5 parts 15 parts 78 parts Ink B C,1, Acid Red 35 Glycerin compound example 11 Ethylene glycol Water 2 parts IO parts 10 parts 5 parts 73 parts Ink C C, 1. Food black 2 Triethylene glycol compound example 3 Water 3 parts 10 parts 15 parts 72 parts Ink D C. 1. Direct blue 199 Polyethylene glycol (molecular weight 300) Diethylene glycol Triethylene glycol monomethyl ether Triethanolamine Compound example 7 Water ink E C, 1, Direct Black 154 Thiodiglycol diethylene glycol compound example 12 2 parts water 3 parts 5 parts 10 parts Amount up to 80 parts JLij Process all the ingredients below in the same manner as in Examples 1 to 5. Inks F to J of Comparative Examples 1 to 5 were obtained, and various evaluations were performed in the same manner as in the Examples. The results are shown in Table 2.

Ink FC, 1, Direct Yellow 86
2-part diethylene glycol
15 parts water
83 parts Ink G
3 (manufactured by NOF ■) Water 3 parts 10 parts 10 parts 0.5 parts 76.5 parts Ink HC, 1, Acid red ethylene glycol water ink IC, 1, Food black 2 Triethylene glycol N-methyl-2- Pyrrolidone ethanol water ink JC, 1, Solvent Yellow 149 5.5 parts 72.5 parts 3 parts 10 parts 2 parts 1 part 84 parts Benzyl alcohol 77 parts Measures - Table 51 Examples Ink (1'') Fixability (Copy Paper) (Bond paper) (2) Bleeding incidence (Copy paper) (Bond paper) (3) Clogging resistance after stopping during printing (4) Frequency response (51) Water resistance 2 × 4 Mutual CDE ○ ◎ ○ ○ ◎ ◎ ◎ ◎ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ O (Copy paper) (Bond paper) (3°) Printing - Clogging after stop (44) Frequency response (51) Water resistance Kei 2 Dan 4 GHIJ × ◎ × △ ◎ △ ◎ △ ○ ◎ ○ × △ ○ × ○ × ○ ○ × △ × △ × × × △ △ △ × △ × △ × ○ (Do) Fixability evaluation 10 seconds after printing on commercially available copy paper and bond paper, 30
After a few seconds, remove the printed part from the filter paper (product name: No.

50, manufactured by Toyo Roshi @).

◎...Cast in 10 seconds None ○...Cast in 10 seconds Small △...Cast in 30 seconds Small ×...Cast in 30 seconds Large (29) Rate of bleeding Commercially available copy paper and bond paper After printing 300 dots in a non-consecutive manner using a printer, the dots were left to stand for more than 1 hour, and then the number of dots in which whisker-like bleeding had occurred was counted using a microscope and expressed as a percentage.

O: 10% or less △: ll to 30% ×: 31% or more (38) Print - Clogging when reprinting after stopping Print - For clogging when reprinting after stopping, check the printer according to the specified After filling the ink and printing alphanumeric characters continuously for 10 minutes, stop printing, leave it for 10 minutes without caps, etc., then print alphanumeric characters again and remove any gaps, missing characters, etc. Judgment was made based on the presence or absence of defective parts.

○No defects starting from the knee letter.

△A part of the knee letter is missing or missing.

×Knee characters are all (unable to print.

(49 Evaluation of Frequency Responsiveness) The printing condition of the obtained printed matter, that is, the condition of smudges and white spots, and the condition of poor impact points such as splash and wobbling were visually observed and evaluated.

◎・・・The tracking ability of the ink to the frequency is good,
There are no spots, white spots, or poor impact points in both solid printing and character printing.

Good: The followability of the ink to the frequency is almost good, and there are no casts, dropouts, or poor landing points in character printing, but there is a slight cast in solid printing.

△: There are no clumsiness or white spots in character printing, but there are some poor impact points.

Also, in solid printing, there may be shadows or white spots. Approximately 1/3 of the total solid color can be seen.

×: There are many spots and white spots in solid printing, and there are many spots and poor landing points in character printing.

(58) Water resistance For water resistance, after printing a black patch on commercially available copy paper using a printer, leave it for more than 24 hours, and immerse it in still water for 5 minutes.
8) was measured.

○...80% or more △...60-80% intimidator ×...60% or less [Effect] As explained above, according to the ink of the present invention, copy paper, report paper, notebooks, stationery, etc. Even on ordinary plain paper commonly used in offices, it is possible to record with no bleeding, excellent quality, and good permeability.

Further, according to the present invention, it is possible to obtain ink that is highly safe even when used in offices and homes.

Further, according to the ink of the present invention, it is possible to provide an ink with improved image fastness on plain paper, particularly water resistance. In particular, in a type of recording in which ink is ejected by a bubbling phenomenon of ink caused by thermal energy, the response to frequency is significantly improved.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are a longitudinal cross-sectional view and a cross-sectional view of a head section of an inkjet recording apparatus. FIG. 2 is an external perspective view of a multi-head head shown in FIG. 1. FIG. 3 is a perspective view showing an example of an inkjet recording device. FIG. 4 is a longitudinal sectional view of the ink cartridge. FIG. 5 is a perspective view of the inkjet cartridge.

Claims (5)

[Claims] (1) An ink composed mainly of a water-soluble dye and a liquid medium containing water, which is characterized by containing an alkyl ether of polypropylene glycol represented by the following general formula [I]. R_1-(X)-O-R_2...[I] (In the formula, R_1 and R_2 represent a hydrogen atom or an alkyl group having 2 or more carbon atoms, but they cannot be hydrogen atoms at the same time. , X represents a homopolymer of propylene oxide.) (2) Moisture content is 20 to 95% by weight of the total weight of the ink
The ink according to claim (1), which falls within the range of. (3) The content of the alkyl ether represented by the general formula [I] is 0.01 to 60% by weight based on the total weight of the ink.
The ink according to claim (1), which falls within the range of. (4) In an inkjet recording method in which thermal energy corresponding to a recording signal is applied to ink to form droplets, and the droplets are applied to a recording material to perform recording, the ink contains at least a water-soluble dye. , water, and an alkyl ether of polypropylene glycol represented by the following general formula [I]. R_1-(X)-O-R_2...[I] (In the formula, R_1 and R_2 represent a hydrogen atom or an alkyl group having 2 or more carbon atoms, but they cannot be hydrogen atoms at the same time. , X represents a homopolymer of propylene oxide.) (5) The inkjet recording method according to (4), wherein the recording material is uncoated paper.