JPH0729478B2 - INKJET RECORDING METHOD AND RECORDED MATERIAL USED IN THE METHOD - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ink jet recording method and a recording material used for the same, and particularly to an image having excellent sharpness, excellent ink fixability, and recording. The present invention relates to a highly reliable ink jet recording method and a recording material used therefor.

[Conventional technology]

The ink jet recording method includes various ink (recording liquid) ejection methods, for example, an electrostatic suction method, a method in which a piezoelectric element is used to mechanically vibrate or displace the ink, the ink is heated to foam, and the pressure is used. In this method, small droplets of ink are generated and ejected, and some or all of them are attached to a recording material such as paper for recording. It is attracting attention as a recording method that allows color printing.

As the ink for ink jet recording, one containing a water-soluble dye as a recording agent and a liquid medium as main components is used.

As the recording agent, a water-soluble dye, preferably an acid dye or a direct dye, is used in terms of safety, light resistance, recording characteristics, etc., while the liquid medium is mainly water in terms of safety and recording characteristics. The main component is used, and polyhydric alcohol or the like is often added to prevent nozzle clogging and improve discharge stability.

Further, as the recording material used in the ink jet recording method, conventionally, a recording material obtained by providing a porous ink receiving layer on a base material called ordinary paper or ink jet recording paper has been used. . However, with the improvement and spread of the performance of the ink jet recording apparatus such as high-speed recording or multi-color recording, the recording material is required to have higher and wider characteristics.

That is, it is necessary that the absorption of the ink is as fast as possible and that the bleeding of the ink is appropriate.

Further, in order to carry out color ink jet recording using color inks, a recording material which is particularly excellent in color development and vividness of a dye as a recording material and which gives high colorability is required.

Further, a recorded image recorded by ink jet recording is required to have excellent image storability, durability, water resistance and light resistance.

The ink jet recording method satisfying various required performances as described above is being improved to a considerable extent mainly by providing a special ink receiving layer on a recording material to be used.

In addition, when ink jet recording is performed on a conventionally known ink jet paper, paper dust is generated (= powder drop) from the recording material, and the paper dust contaminates the inside of the recording apparatus, and normal paper feeding cannot be performed. The paper dust adheres to the ink jet head, clogging the nozzles, and lowering the reliability during ink jet recording.

However, with the progress of ink jet recording methods,
Even for a recording material which is not provided with a special ink receiving layer, it is required to have excellent image sharpness and ink fixability and high reliability.

To meet these requirements, the shape of the ink dots applied to the recording surface must be close to a perfect circle, and the ink must penetrate quickly when it adheres to the recording material, and the reliability must be improved. Therefore, it is necessary to reduce the powder drop. For this reason, conventionally, efforts have been made to provide an ink receiving layer on a recording material and improve the ink receiving layer.

By improving the ink receiving layer of the recording material in this way,
The sharpness and resolution have been improved, and the fixing of the ink has become quicker, but especially for the recording material so-called plain paper that does not have an ink receiving layer, the current ink jet recording method can reduce the sharpness of the recorded image. There was nothing satisfactory in resolution and ink fixability.

[Problems to be solved by the invention]

Therefore, an object of the present invention is to provide a recorded image having excellent vividness and resolution to a recording material having no ink receiving layer, that is, so-called plain paper, and to have excellent ink fixability and reliability. An object of the present invention is to provide a high ink jet recording method and a recording material used for the same.

As a result of earnest research to solve the above-mentioned drawbacks of the prior art, the present inventor has found that, in the ink jet recording method, in order to achieve the above object, even if the recording material is not provided with an ink receiving layer. The present invention has been completed by finding that it is necessary to use a recording material containing a substance that reduces the function of a sizing agent and to control the physical properties of ink droplets within a specific range.

[Means for solving problems]

That is, the present invention is an ink jet recording method for performing recording by depositing ink droplets on a recording material, wherein the recording material has both a sizing agent and a component that reduces the function of the sizing agent. The ink jet recording method is characterized in that the Weber number (W) represented by the following formula of the ink droplet is in the range of 50 to 1000.

(Where ρ is the ink density (g / cm ³ ), d is the ink droplet diameter (μm), ν is the ink flight velocity (m / sec), and γ is the ink surface tension (dyne / cm). The present invention also provides a recording material used in an inkjet recording method for recording by applying ink droplets having the above-mentioned Weber number, which comprises a sizing agent and a component that reduces the function of the sizing agent. It is a recording material characterized by having both.

[Action]

The present invention will be described in detail. A feature of the present invention is that, when carrying out ink jet recording, a recording material having both a sizing agent and a component that reduces the performance of the sizing agent is used as the recording material. In addition, the Weber number (W) of the ink droplets used is controlled within the range of 50 to 1000, and the object of the present invention is achieved for the first time by such a configuration.

The recording material used in the present invention reduces the function of the sizing agent, that is, the water repellent effect on the liquid when the recording liquid adheres, and the liquid permeates and diffuses quickly into the recording material. Therefore, apparent drying, absorption and fixing are dramatically improved.

As described above, when an image is formed on a commercially available medium-quality paper by using various conventionally known ink jet recording methods, there is the above-mentioned problem, that is, the ink absorbency is not prompt. In other words, these papers contain a sizing agent in order to prevent liquid bleeding, and have good compressibility in the thickness direction of the paper in order to have writing properties, in other words, the porosity of the paper is small and so on. , Ink absorption is poor.

On the other hand, when ink jet recording is performed on the recording material according to the present invention, the ink contains a component that deteriorates the function of the sizing agent, so that the diffusion and penetration of the ink are rapid and the ink absorbability is improved. It is preferable to use a recording material having a sizing degree of 10 seconds or less, since the ink absorbency becomes particularly good.

Further, when ink jet recording is performed on the recording material according to the present invention, feathering does not occur and a dot close to a perfect circle can be obtained.

When ink jet recording is performed on a medium-quality paper on the market in the related art, feathering occurs because the sizing agent that hinders the diffusion and penetration of the liquid is unevenly distributed.

The recording material according to the present invention contains a sizing agent that inhibits the penetration of a liquid, and further contains a component that reduces the effect of the sizing material, even though the sizing agent may be present unevenly. Therefore, the penetration of the ink becomes uniform, and the penetration of the ink becomes more uniform by using a material having a sizing degree of 10 seconds or less. Therefore, when ink jet recording is performed on the recording material according to the present invention, dots with almost no feathering can be obtained.

On the other hand, when the ink jet recording is performed on a recording material having a sizing agent of 10 seconds or less without containing a component that reduces the effect of the sizing agent, the ink receptivity is satisfactory, but the feathering is likely to occur. The dot shape may be bad.

The ink used in the present invention is an aqueous ink containing 50 to 90% by weight of water and has a surface tension of 25 dyne / cm to 70 dyne / cm.
cm, more preferably 40 dyne / cm to 70 dyne / cm.

In order for this ink to quickly and uniformly permeate the recording material, there is a method in which a component such as a surfactant that deteriorates the function of the sizing agent is mixed into the recording material in advance.

Further, a component that deteriorates the function of the sizing agent may be applied immediately before ink jet recording, or may be applied during the manufacturing process of the recording material.

The recording material used in the present invention is mainly composed of fibers,
It contains a sizing agent, a component that reduces the function of the sizing agent, and the like. As other components, a defoaming agent, a whitening agent, a dye or the like may be added.

It has been known that ink jet paper contains a surfactant.

For example, when a surfactant is used for a dispersant in the manufacturing process or for improving drainage, it is used as a fixing agent for a dye.

However, in the present invention, different from the functions of these conventionally known surfactants, the purpose is to reduce the function of the sizing agent, and the interface contained in the recording material used in the present invention The activator is different from that which reacts with the dye to insolubilize the dye or stabilizes the dispersion of the raw materials in the manufacturing process.

As the surfactant as a component that reduces the function of the sizing agent used in the present invention, nonionic and anionic surfactants that are easy to control the dot diameter and improve the ink absorbability are preferable, and more preferably nonionic. The thing of the system is used.

Further, a silicon-based or fluorine-based surfactant may be used, but it must reduce the function of the sizing agent as described above.

The amount of the surfactant used in the present invention is required to be able to reduce the function of the sizing agent, that is, the amount of the side of the recording material to be 10 seconds or less. The amount is 0.1 mg to 1 g, and more preferably 0.3 mg to 0.5 g per 1 m ^{2 of} the recording surface, depending on the surface activity of the surfactant used.

In the present invention, as the method for applying the surfactant to the substrate, any conventionally known method such as a size press method, a spray coating method, a roll coating method, a rod bar coating method, an air knife coating method or the like can be used. .

In the method of the present invention, any of the components of the water-based ink applied to the recording material as described above by the ink jet recording method may be known.

For example, as the dye, a direct dye, an acid dye, a basic dye, a reactive dye, a water-soluble dye represented by an edible pigment, etc., particularly suitable as an ink of the ink jet recording system, and the above-mentioned recording material In the combination of, for example, CI direct black 17,19,32,51,71,108,146,154; CI direct blue 6, to give an image that satisfies the required performance such as color development, sharpness, stability, light resistance and the like. 22,25,71,86,90,106,199; CI Direct Red 1,4,17,28,83; CI Direct Yellow 12,24,26,86,98,142; CI Direct Orange 34,39,44,46,60; CI Direct Violet 47,48; CI Direct Brown 109; CI Direct Green 59 and other direct dyes, CI Acid Black 2,7,24,26,31,52,63,112,118; CI Acid Blue 9,22,40,59,93,102,104,113,117, 12
0,167,229,234; CI Assisted Thread 1,6,32,37,51,52,80,85,87,92,94,1
15,180,256,317,315; CI Acid Yellow 11,17,23,25,29,42,61,71; CI Acid Orange 7,19; CI Acid Acid Ole dye 49 and other acidic dyes,
Others, CI Basic Black 2; CI Basic Blue 1,3,5,7,9,24,25,26,28,29; CI Basic Credit 1,2,9,12,13,14,37; CI Basic Stick violet 7,14,27; CI food black 1,2 etc. can also be used.

The above dye examples are particularly preferable for the ink applicable to the recording method of the present invention, and the dye for the ink used in the present invention is not limited to these dyes.

Such water-soluble dyes are generally used in conventional inks in a proportion of about 0.1 to 20% by weight,
Also in the present invention, this range is sufficient.

The solvent used in the ink used in the present invention is water or a mixed solvent of water and a water-soluble organic solvent, and particularly preferable one is
As a water-soluble organic solvent, a polyhydric alcohol-based organic solvent having an ink drying preventing effect is contained.

Further, as the water, it is preferable to use deionized water instead of general water containing various ions.

Examples of the water-soluble organic solvent used by mixing with water include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, se.c-butyl alcohol, tert-butyl alcohol, isobutyl alcohol. C1-8 alkyl alcohols such as; amides of dimethylformamide and dimethylacetamide; ketones or ketone alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyethylene glycol, polypropylene glycol, etc. Polyalkylene glycols; ethylene glycol, propylene glycol, acetylene glycol, triethylene glycol, 1,
2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol and other alkylene groups having an alkylene group containing 2 to 6 carbon atoms; glycerin; ethylene glycol methyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ) Lower alkyl ethers of polyhydric alcohols such as ether and triethylene glycol monomethyl (or ethyl) ether; N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like.

Among these many water-soluble organic solvents, polyhydric alcohol organic solvents such as diethylene glycol and lower alkyl ethers of polyhydric alcohol organic solvents such as triethylene glycol monomethyl (or ethyl) ether are preferable.

In addition to the above components, the ink used in the present invention may contain various additives such as a surfactant, a viscosity modifier and a surface tension modifier, if necessary.

The ink used in the present invention is as described above, but the density (ρ) of the ink is generally 0.9 to 1.2 g by changing the composition of the ink as described above or by incorporating the additive as described above. / cm ³ , surface tension (γ) is 15-65 dyne /
The value is about cm.

In the method of the present invention, an ink jet recording method for recording by applying the above ink to the recording material,
Any method can be used as long as it can effectively separate ink from the nozzle and apply the ink to the recording material that is a range. Typical of these methods are, for example, IEE Trans Accion On. Industry Applications (IEEE Trans actions
on Industry Applications) Vol.JA-13, No.1 (1977
February, March issue), Nikkei Electronics. The methods described in these are suitable for the method of the present invention, and some of them will be described. First, there is an electrostatic attraction method. In this method, a nozzle and an accelerating electrode placed several mm ahead of the nozzle are used. A strong electric field is applied between the nozzles to atomize the ink from the nozzle, and the ink is drawn out one after another. While the drawn ink flies between the deflection electrodes, an information signal is applied to the deflection electrodes for recording, and the ink particles are deflected. However, there is a method of ejecting ink particles in response to an information signal, both of which are effective for the method of the present invention.

The second method is a method of forcibly ejecting minute ink particles by applying a high pressure to the ink with a small pump and mechanically vibrating the nozzle with a crystal oscillator or the like.
The ejected ink particles are charged at the same time as the ejection according to the information signal. When the charged ink particles pass between the deflection electrode plates, they are deflected according to the charge amount. Another method using this method is called the microdot ink jet method.In this method, ink pressure and excitation conditions are maintained within a certain range of appropriate values, and two types of ink droplets, large and small, are ejected from the nozzle tip. Is generated, and only the small and medium-sized small droplets are used for recording. The feature of this method is that a small droplet group can be obtained even with a nozzle diameter as thick as the conventional one.

As a third method, there is a piezo element method. In this method, a piezo element is used as a pressure means to be applied to ink, instead of a mechanical means such as a pump as in other methods.
In this method, an electric signal is applied to the piezo element to cause mechanical displacement, thereby applying pressure to the ink and ejecting it from the nozzle.

Further, in the method described in Japanese Patent Laid-Open No. 54-59936, the ink subjected to the action of thermal energy causes a rapid volume change, and the ink force is ejected from the nozzle by the action force due to this state change. Can also be used effectively.

As described above, in the conventionally known ink jet recording method and apparatus, the diameter (d) of the ink droplet that can be formed is slightly different depending on the nozzle diameter, the applied voltage, the physical properties of the ink, and the like.
The flying speed (ν) of the ejected ink droplets is 10 to 150 μm and 1 to 30 m / sec.

In the ink jet recording method as described above, when the values of density (ρ), surface tension (γ), ink droplet diameter (d), and flight velocity (ν) are individually changed within the above range, The Weber number (W) shown in the equation (1) changes from 0.138 to 10800.

However, in the present invention, in order to perform ink jet recording excellent in image clarity and ink fixability and excellent in reliability, the Weber number (W) of the recording material is set to 50.
It became possible by controlling to ~ 1000.

When the weber number (W) is less than 50, the ink fixability is poor, especially on a recording material having no ink receiving layer,
Not suitable for ink jet recording.

The number of webers (W) for any recording material
When the number exceeds 1000, splatter (splash of ink) occurs, but up to 1000, it is almost indistinguishable from the naked eye, so ink jet recording is possible. However, if it exceeds 1000, the splatter is clearly detected by visual observation, and the image quality is extremely deteriorated, which is not suitable for ink jet recording. Therefore, the number of Webers (W) is 1000
It is necessary to be 50 or less, more preferably 700 or less and 50 or more.

As described above, the recording material having both the sizing agent and the component that reduces the function of the sizing agent has a Weber number of 50 to 1000.
The object of the present invention can be achieved for the first time by performing ink jet recording with.

〔Example〕

Next, the present invention will be described more specifically with reference to examples.
In the text, “part” or “%” is based on weight unless otherwise specified.

Recording condition 1 An on-demand ink jet recording head in which ink is ejected by a piezo-vibrator using ink of the following composition, a piezo-vibrator drive voltage 100V, frequency 2KHz) , Weber number about 620 (ρ = 1.0g / cm ² , d = 65μm, ν = 18.5m / sec, γ = 36d
yne / cm), recording was performed under the ink jet recording condition 1 of the present invention.

Ink composition CI direct black 154 5 parts Glycerin 20 parts Water 75 parts Polyoxyethylene lauryl ether (added so that the surface tension is 36 dyne / cm) Recording condition 2 The ink composition and additives used in recording condition 1 produce surface tension With ink of 47 dyne / cm, the piezo vibrator drive voltage is 8
Assuming 0 V, the number of Webers is about 110 (ρ = 1.0 g / cm ³ , d = 80 μ
Recording was performed under m, ν = 8 m / sec, γ = 47 dyne / cm).

Recording condition 3 With the ink composition and additives used in recording condition 1 and surface tension of 30 dyne / cm, the piezoelectric transducer drive voltage was set to 1
As 20V, the number of Webers is about 1200 (ρ = 1.0g / cm ³ , d = 90
Recording was performed under the ink jet recording condition 3 under the conditions of μm, ν = 20 m / sec, γ = 30 dyne / cm).

Recording condition 4 With the ink composition and additives used in recording condition 1, the surface tension is 48 dyne / cm, and the piezoelectric vibrator drive voltage is 45V.
Is about 9.8 (ρ = 1.0 g / cm ³ , d = 60 μm,
Recording was performed under the ink jet recording condition 4 under the condition of ν = 2.8 m / sec, γ = 48 dyne / cm.

Recorded material 1 Hardwood bleached kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP) were mixed in H: 1 and freeness (C.
SF) was beaten to 420 ml and used as raw material pulp.

To the raw pulp, the following composition was blended, Use a bar coater to add lignosulfonic acid before the drying process.
0.3 g / m ² was applied to prepare a handmade sheet.

Recording Material 2 With respect to the raw material pulp used in Recording Material 1, And anionic surfactant Perex OT / P (manufactured by Kao Co., Ltd.) were mixed by air spray before the drying process.
0 mg / m ^{2 was} applied to make a handmade sheet.

Recording material 3 Fine paper (silver ring (trade name), Sanyo Kokusaku Pulp Co., Ltd.)
The fluorochemical surfactant Florard FC-430 (manufactured by Sumitomo 3M Limited) was applied to 100 mg / m ² by air spray to prepare a handmade sheet.

Recording Material 4 A hand-made sheet was prepared in the same manner as in Recording Material 1 except that Lignosulfonic acid was not applied to Recording Material 1.

Recording Material 5 Recording Material 5 was obtained in the same manner as Recording Material 2 except that Perex OT / P was not applied to Recording Material 2.

The combinations of recording conditions and recording materials in Examples 1 to 4 and Comparative Examples 1 to 4 are as shown in Table 1 below.

The recording evaluation results of Examples 1 to 4 and Comparative Examples 1 to 4 are shown in the second item below.
Shown in the table.

Each physical property value in the present invention, that is, ink density (g / cm ³ ), ink droplet diameter (μm), ink flight speed (μ / sec), and ink surface tension (dyne / cm) are determined by the following methods. It was measured at.

The density of the ink was measured under the condition of 20 ° C. using a hydrometer.

The surface tension of the ink is measured by a surface tensiometer (Kyowa Scientific Co., Ltd.).
Was measured under the condition of 2.20 ° C.

The diameter and flight speed of the ink droplet were measured by the following methods.

The time required for the tip of the ink droplet to reach the distance of 1.0 mm from the orifice surface of the recording head was measured by delaying the time t seconds after the signal was applied to the recording head and applying the measurement strobe signal.

The diameter of the ink droplet was the maximum width in the direction perpendicular to the flight direction of the ink under the above measurement conditions.

The measurement of each evaluation item in Table 2 below was performed according to the following methods.

The dot shape is measured by visually observing the printed matter with an optical microscope.
Good shape ○ Good slightly distorted △, markedly bad shape ×.

The ink fixability was evaluated as follows: ○ 20 seconds after printing, a filter paper was pressed against the recording material, and if the ink was not transferred to the filter paper, ○ was a little transferred and Δ was completely transferred.

[Effects] As described above, according to the present invention, it is possible to perform recording with quick ink absorption and good dot shape.

Further, the recording material used in the present invention is excellent in ink absorbency and color developability to the same extent as conventional ink jet paper even if a coating layer is not intentionally provided. It is also excellent.

Claims (4)

[Claims] 1. An inkjet recording method for recording by recording ink droplets on a recording material, wherein the recording material has both a sizing agent and a component that reduces the function of the sizing agent.
In addition, the number of webbers (W) represented by the following formula of ink drops is 50
Inkjet recording method characterized by being in the range of up to 1000. (In the formula, ρ is the ink density (g / cm ³ ), d is the ink droplet diameter (μm), ν is the ink flight velocity (m / sec), and γ is the surface tension (dyne / cm)) 2. The ink jet recording method according to claim 1, wherein the size of the recording material is 10 seconds or less. 3. The ink jet recording method according to claim 1, wherein the amount of the component that reduces the function of the sizing agent in the recording material is in the range of 0.1 mg to 1 g per 1 m ^{2 of the} recording surface. 4. The number of Webers (W) represented by the following formula is
A recording material used in an inkjet recording method for recording by applying ink droplets in the range of 50 to 1000, characterized in that it has both a sizing agent and a component that reduces the function of the sizing agent. Material. (In the formula, ρ is the ink density (g / cm ³ ), d is the ink droplet diameter (μm), ν is the ink flight velocity (m / sec), and γ is the surface tension (dyne / cm))