JPH03258869A - Ink and ink-jet recording method using thereof - Google Patents

Abstract

PURPOSE:To obtain ink capable of recording having excellent responsibility of foaming to thermal energy, dignity without bleeding to normal paper and penetrability containing coloring matter, respectively specific amounts of water and cyclohexanol. CONSTITUTION:The aimed ink contains coloring matter, 50-95wt.% water, 0.01-3wt.% cyclohexanol and preferably a polyhydric alcohol. An ink-jet recording is performed using said ink.

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, bond paper, continuous slip paper, etc. The ink used in the inkjet recording method, which uses thermal energy, has extremely good fixing properties even on uncoated paper, so-called plain paper, which is commonly used in offices and homes, and enables high-definition, high-quality recording. The present invention relates to an inkjet recording method using this.

[Conventional technology]

Conventionally, inkjet inks having a wide variety of compositions have been reported. In particular, in recent years, detailed research and development has been carried out from various aspects such as composition and physical properties in order to perform good recording on plain paper commonly used in offices such as copy paper, report paper, notebooks, and stationery. has been done.

Various methods have also been proposed for inkjet recording, including a method in which electrically charged droplets are continuously generated and a portion of the droplets are used for recording, and a method in which a signal is applied to a recording head having a piezoelectric element. , a method in which recording is performed by generating droplets of recording liquid in response to the signal, or a method in which thermal energy corresponding to the recording signal is applied to the recording liquid in the chamber of the recording head, and droplets are generated by being absorbed by the energy to perform recording. There are ways to do this.

In particular, the type described in Japanese Patent Application Laid-open No. 54-59936, which ejects ink by the ink bubbling phenomenon caused by thermal energy, has been attracting particular attention recently because it is easy to increase the integration and density of the nozzles. This is a method that However, since it takes advantage of the phenomenon of foaming that is not found in other methods, more stringent conditions are required for the ink used.

Preferred conditions for the ink used in this method are listed below. does not occur.

(2) Even if the printer is left without a cap during a recording pause, stable ejection can be obtained immediately after recording is resumed. That is, the ink near the ejection ports is less likely to dry and clogging does not occur.

(3) High-quality images without irregular shapes or irregular bleeding can be obtained, especially on plain paper.

(4) Faster fixation (print drying) than on plain paper;
Even if you rub the printed matter, it will not get dirty.

(5) Good storage stability and ink performance maintained over a long period of time.

(6) Excellent safety in terms of toxicity and flammability.

etc.

In response to these demands, conventional ink formulations are not particularly limited to one type of ejection method using thermal energy, but for example, ink generally contains drying prevention,
Contains high-boiling point organic solvents such as glycol for the purpose of preventing clogging, etc. When recording with such ink on plain paper with a high degree of size, it is difficult for the ink to penetrate inside the paper and the recording area Due to the poor drying properties of ink, there were problems such as ink getting on your hands when you touched the recorded matter, and letters rubbing and staining.

Therefore, in order to improve the permeability of the ink into the inside of the paper, Japanese Patent Application Laid-Open No. 55-29546 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, Japanese Patent Application Laid-Open No. 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 with hands, and some types of
Papers using such sizing agents, such as neutral paper, have drawbacks such as bleeding and poor drying properties.

Further, JP-A-63-139963 proposes an ink containing 2 to 15% by weight of alkyl alcohol having 5 or less carbon atoms in order to improve frequency response and ejection stability.

According to studies conducted by the inventors, the use of alcohol as a penetrant itself is an extremely effective means for suppressing bleeding and promoting fixation.

However, in general, when the amount of these alcohols added is increased to improve fixing properties, irregular bleeding tends to occur, and the level of use for these alcohols is insufficient to meet the print quality goals aimed at in the present invention. I can no longer say yes. This tendency can be alleviated considerably if a lower alcohol with a carbon number of 3 or less is used, but since the vapor pressure of the alcohol is high, the alcohol evaporates from the head orifice, etc., making it easier to change the ink composition. . This phenomenon is particularly noticeable and problematic when the ink is used in an inkjet head of the type that has an atmosphere communication hole (the structure is a closed system to prevent negative pressure from building up inside).

Further, Japanese Patent Application Laid-Open No. 58-19373 discloses a non-aqueous piezo-driven inkjet ink containing cyclohexanol that has excellent drying properties for recording paper containing a sizing agent. However, in this case, although the fixing properties are extremely good, the level of bleeding that is targeted by the present invention cannot be achieved. Furthermore, since the system does not contain water, there is either no foaming response to thermal energy, or even if there is, it is extremely poor.

As mentioned above, various improvements have been attempted so far in addition to the above, but even if there is no limitation to use with thermal energy method, the above-mentioned bleeding and drying properties, furthermore, clogging properties, The current situation is that no ink has been known to date that satisfactorily solves all problems such as storage stability, and in addition, it has the ability to respond favorably to the phenomenon of foaming, which is unique to thermal energy systems. Designing such inks is an important but extremely difficult challenge.

[Problems to be Solved by the Invention] Therefore, the object of the present invention is to provide a non-coated material that has good foaming response to thermal energy and that 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 that solves the problems of ink bleeding and slow drying of recorded matter when recorded on paper, so-called plain paper.

Another object of the present invention is to provide an ink that is highly safe for use in offices and homes, and is resistant to changes in composition due to evaporation or the like even if left for a long period of time.

Furthermore, another object of the present invention is to provide an ink that is less likely to cause clogging due to noise in an inkjet head and has excellent storage reliability.

[Means for solving problems]

The above objects are achieved by the present invention as described below. That is, the present invention provides at least a pigment, 50 to 95% by weight of water,
This ink is characterized by containing 0.01 to 3% by weight of cyclohexanol, and thermal energy corresponding to a recording signal is applied to the ink to form ink droplets. This is an ink-jet recording method in which recording is performed by applying a substance to a recording material.

[For production]

The inventors of the present invention have conducted intensive studies on various ink compositions that are suitable for recording in which ink is ejected by the ink bubbling phenomenon caused by thermal energy, and that improve ink bleeding, drying properties, and permeability on paper. 5
The ink containing O, OI to 3% by weight of cyclohexanol along with 0 to 95% by weight of water is well-balanced in terms of bleeding and permeability, and has no adverse effects on clogging prevention and is highly reliable. It was discovered that it is a highly effective substance, and this led to the present invention.

According to the findings of the present inventor, when using a surfactant that is normally used in one ink, 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. However, it is difficult to obtain stable records. On the other hand, when cyclohexanol used in the present invention is used, there is little difference depending on the paper, and extremely good results are obtained.

The reason for this is that ink bleeding and permeability are mainly due to
It is largely controlled by the wetting phenomenon at the interface between the ink droplet and the paper, but when a surfactant is used, the wetting properties differ between the surface and the inside of the ink droplet attached to the paper. On the other hand, in the case of the ink of the present invention, such a thing is unlikely to occur. Furthermore, it is thought that the ink of the present invention has an exquisite balance of affinity with the surface and internal sizing agents added to paper as an inkjet ink for plain paper.

On the other hand, the reason why the response to foaming is good is that the ink of the present invention has a uniquely excellent mixing ratio of water and cyclohexanol, which are essential liquid media, and their content for controlling the boiling phenomenon that is optimal for recording. In addition, the wettability to each member inside the nozzle is optimal in terms of physical properties and affinity, so it operates extremely smoothly during the cycle of bubble disappearance and generation, and as a result, the response responsive to frequency is significantly improved. It is presumed that this has improved.

[Preferred embodiment]

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

The compound used in the present invention and which mainly characterizes the present invention is cyclohexanol, and the amount of cyclohexanol added to the ink varies depending on the pigment used and other liquid medium components used together, but The proportion is about .01 to 3% by weight, preferably 0.1 to 2.5% by weight, and more preferably 0.3 to 2% by weight.

When the amount of alcohol added is less than 0.01% by weight, no effect on foaming response and permeability is observed;
If it exceeds % by weight, the surface tension decreases, and depending on the paper, it may bleed easily, resulting in poor print quality.

Further, the proportion of water in the ink, which is an essential component of the present invention, is 50 to 95% by weight, preferably 55 to 95% by weight.
, more preferably 60 to 95% by weight. When the amount of water is less than 50% by weight, the amount of organic solvent is large;
The paper will curl and the quality of printing on plain paper will deteriorate significantly. When the amount of water exceeds 95% by weight, the stability of discharge from the nozzle orifice and the clogging resistance during stoppage are significantly deteriorated.

The pigments constituting the ink of the present invention include direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse dyes,
architectural dyes, soluble architectural dyes, reactive disperse dyes, oil dyes,
Various pigments may be used, but water-soluble dyes are particularly preferred from the viewpoint of ink performance.

The content of these pigments is determined depending on the type of liquid medium components, the properties required of the ink, etc., but the content of these pigments in the shell is about 0.2 to 20% by weight of the total amount of ink, preferably 0. ．．
The proportion is 5 to 10%, more preferably 1 to 5%.

The above are the essential components constituting the ink of the present invention, but other general organic solvents used in conventionally known inks can also be used in combination. Some, such as amides such as formamide, dimethylformamide, and dimethylacetamide, are incompatible with the alcohols used in the present invention and cannot be used in combination; for example, ketones or keto alcohols such as acetone and diacetone 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, 1,2.6
- Alkylene glycols in which the alkylene group has 2 to 6 carbon atoms such as hexanetriol and hexylene glycol; thiodiglycol; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene Lower alkyl ethers of polyhydric alcohols such as 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; sulfolane; Examples include N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and the like.

The content of the water-soluble organic solvent is generally 1 to 49% by weight, preferably 2 to 3% by weight based on the total weight of the ink.
The range is 0%.

When the above-mentioned medium is also used, it can be used alone or as a mixture, but the most preferable liquid medium composition is that the solvent is at least one water-soluble high-boiling organic solvent, such as a polyhydric compound such as diethylene glycol, triethylene glycol, or glycerin. It contains alcohol.

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.

Furthermore, the ink of the present invention better resolves ink bleeding when recorded on plain paper, dryness, and permeability of recorded materials, and from the aspect of matching with inkjet heads, the ink physical properties at 25 ° C. Tension is 30 to 68 dyne/cm.

It is desirable that the viscosity is 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 layer 18 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. Said blade 61. 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 has been evacuated from the movement path of the recording head 65,
The blade 61 projects into the path of movement. As a result,
The ejection port surface of the recording head 65 is wiped. In addition,
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, 70 is an inkjet cartridge, which houses an ink absorber impregnated with ink. It is configured to be discharged after closing. .

Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the cartridge with the atmosphere.

This inkjet cartridge 70 is used in place of the recording head 65 shown in FIG. It 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 ingredients shown in Table 1 and stirring for 5 hours, the pH was adjusted to 7.5 with a 0.1% aqueous solution of sodium hydroxide, and the pore size was 0.22 microns. The inks A to E of the present invention were obtained by pressure filtration using a membrane filter (trade name: Fluorobor Filter manufactured by Sumitomo 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: Canon ■) modified machine (the ink sub-tank near the head has a capacity of 2 crrrJ, is completely sealed except for the ink flow pipe with the head, and has a diameter of 0.5 m at the top)
The fixing properties of the resulting recorded matter and the incidence of bleeding were evaluated by recording on commercially available copy paper.

At the same time, the clogging resistance during reprinting after a printing stop, clogging recovery during reprinting after a long printing stop, frequency response, and ink storage stability were also evaluated.

Regarding the items of fixability and bleeding, a recovery operation was performed after a long period of suspension, and the evaluation was performed again. The results are shown in Table 3. (Evaluation was normally carried out under conditions of 25°C and 60%.) Comparative Examples 1 to 6 were obtained by treating all the components shown in Table 2 in the same manner as Examples 1 to 5. Obtain inks F to K of
Various evaluations were performed in the same manner as in the examples. The results are shown in Table 3.

Table 1 - Table 3 Ink (1) Fixability (Initial) (After being left unused) (2) Smearing rate (Initial) (After being left unused) (3) Printing - Clogging after stopping ( 4) Clogging resistance when reprinting after a long printing stop (5°) Frequency response (6) Ink storage stability O◎
◎ ◎ ◎ O O Comparative example Kei ink F (l゛) Fixability (initial) × (after standing) × (2°) Occurrence of bleeding (initial) ○ (after standing) ○ (3°) Printing - Clogging after stopping △ (4°) After a long printing stop ○ Recovery from clogging when reprinting (5) Frequency response × (6) Ink storage stability ○△ △ △ X ○ △ × O (1") Evaluation of fixing properties Ten and 30 seconds after printing on commercially available copy paper, the printed area was rubbed with a filter paper (trade name: No. 5C1 manufactured by Toyo Roshi ■).

◎...Cast in 10 seconds None○...Cast in 10 seconds Small△...Cast in 30 seconds Small After printing 300 dots in a non-consecutive manner on copy paper using a printer, the dots were left to stand for more than 1 hour, and then the number of dots that had smeared was counted using a microscope and expressed as a percentage.

○: 10% or less △: 11 to 30% After filling with ink and printing alphanumeric characters continuously for 10 minutes, stop printing and leave it for 10 minutes without cap etc., then print alphanumeric characters again and see if there are any casts or missing characters. Judgment was made based on the presence or absence of defective parts.

○No defects starting from the knee letter.

△A part of the knee letters is cast or missing.

×The knee character cannot be printed at all.

(4”) Recovery from clogging when reprinting after a long printing stop After filling the printer with the specified ink and printing alphanumeric characters continuously for 10 minutes, stop printing and leave the printer without a cap, etc. After leaving it for a day, we performed an operation to recover from the nozzle clogging, and determined how many times it took to print normally without character casts or missing parts (60℃, 10±5%R).
Leave it at H).

○: Normal printing is possible after 1 to 5 recovery operations.

△: Normal printing is possible after 6 to 10 recovery operations.

×: Normal printing is possible after 11 or more recovery operations.

(51) Evaluation of Frequency Responsiveness The printing condition of the obtained printed matter, that is, the condition of cast and white spots, and the condition of landing point defects such as splash and wobbling were observed and evaluated with the naked eye.

◎・・・The tracking ability of the ink to the frequency is good,
There are no casts, 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 no cast, white spots, or poor landing points are observed in character printing, but a slight cast is observed in solid printing.

△...No cast or white spots are observed in character printing, but some impact point defects are observed.

Also, in solid printing, cast and white spots are Approximately 1/3 of the total amount is observed.

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

(61) Storage stability Pour 100 cc of each ink into heat-resistant raspin.
After the sample was sealed and stored in a constant temperature bath at 60° C. for 3 months, it was mounted on the recording device and printed on 100 sheets of continuous slip paper, and evaluated according to the following criteria.

○...No abnormality ×...Failure to eject, irregular print or discoloration [Effects] As explained above, the ink of the present invention has good foaming response to thermal energy, and can be used on copy paper. ,
Even on ordinary plain paper commonly used in offices such as report paper, notebooks, and stationery, it is possible to record with no bleeding, excellent quality, and good permeability.

Further, according to the present invention, it is possible to obtain an ink that is highly safe for use in offices and homes, and is resistant to structural changes due to evaporation even if left for a long period of time.

Further, according to the ink of the present invention, it is possible to perform highly reliable recording in terms of << no clogging in the nozzles of the inkjet head, preservation vermilion, etc.

[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 apparatus. FIG. 4 is a longitudinal sectional view of the ink cartridge. FIG. 5 is a perspective view of the inkjet cartridge.

Claims (4)

[Claims] (1) at least a pigment, 50 to 95% by weight water and 0.5% by weight;
An ink characterized by containing 01 to 3% by weight of cyclohexanol. (2) The ink according to claim (1), further containing a polyhydric alcohol. (3) In an inkjet recording method in which thermal energy corresponding to a recording signal is applied to ink to form ink droplets, and the droplets are applied to a recording material to perform recording, the ink contains at least a pigment, 50-95% by weight water and 0.0
An inkjet recording method characterized by containing 1 to 3% by weight of cyclohexanol. (4) The inkjet recording method according to claim (3), wherein the recording material is uncoated paper.