JP2003326692A - Inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively use ink collected from an inkjet head and to stably output high-quality images by a simple constitution by solving the problem that an amount of waste ink is large and the ink is wasted large in an inkjet recorder with many nozzles in the case where the ink collected from the inkjet head is disposed of without being recycled or that the apparatus becomes larger or a replacement frequency of an ink holding means becomes higher to turn the apparatus hard to use in the case where the waste ink is collected. <P>SOLUTION: A preliminary discharge means for maintaining or recovering a normal jet state of ink liquid drops, and a means for collecting and recycling preliminarily discharged ink are set. A liquid supplied into the inkjet head comprises at least a fresh ink and a recycled ink collected by the preliminary discharge. Moreover, the fresh ink is selected and supplied with priority at a preliminary discharge operation time, and the recycled ink is selected and supplied with priority at a printing operation time. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer, and more particularly to an ink jet printer which collects waste ink not used for printing and reuses it for printing again.

[0002]

2. Description of the Related Art In an ink jet printer which ejects ink for recording, if a normal ejection signal is sent at the start of printing if the ink is left for a long time without ejecting ink,
It is known that a defective phenomenon that ink is not ejected normally occurs. This is because the ink in the nozzle of the inkjet head comes into contact with the outside air, the solvent in the ink evaporates, and the viscosity of the ink changes, which changes the amount and speed of the ejected ink, causing ejection failure. Be done.

As a countermeasure against this, a predetermined pressure is applied to the ink flow path such as pressurizing the ink supply system or sucking the ink from the ink discharge port to forcibly discharge the ink whose viscosity is increased in the vicinity of the nozzle. There is a way. In a conventional inkjet printer, as disclosed in Japanese Patent Laid-Open No. 8-132640, the ink collected from the inkjet head is not used but discarded.

Further, there is a method of performing preliminary ejection in which ink whose viscosity has increased in the vicinity of a nozzle is automatically ejected onto a liquid absorber or the like for an appropriate number of times when ink is not ejected for a long time. -290720 publication. However, the ink ejected by the preliminary ejection was not used and was discarded.

[0005]

When the ink collected from the ink jet head is discarded without being reused, the amount of waste ink is small and the waste ink gradually evaporates if the ink jet head has a small number of nozzles. Therefore, the waste ink holding means is small and does not pose a big problem, but in an inkjet printer having a large number of nozzles, the amount of waste ink is large and the waste of ink is large. A large-sized ink holding unit is required, and a large-capacity waste ink holding unit capable of continuously collecting waste ink is also required, and the printer becomes large-sized or the ink holding unit is frequently replaced and becomes a printer that is difficult to use. .

Further, when the waste ink is directly collected in the ink holding means and reused, the following problems occur. Since the ink does not come into contact with the outside air from the ink holding means to the ink supply path and the inkjet head, the solvent of the ink hardly evaporates to increase the viscosity, but the nozzle of the inkjet head and the cap means for collecting the ink. Then, the outside air comes into contact with the ink, the solvent in the ink evaporates, and the viscosity of the ink changes.

As disclosed in JP-A-2000-272144 and JP-A-2000-309111, there has been proposed an ink jet printer equipped with means for adjusting the viscosity of ink collected from an ink jet head. However, in order to understand the increase rate of ink viscosity,
Since it was necessary to constantly measure the time count, the number of preliminary ejections, the number of printing ejections, etc., it was a very complicated system.

[0008]

In order to solve the above problems, in an on-demand type ink jet recording apparatus for ejecting ink droplets onto a recording medium to form recording dots, a normal ejection state of ink droplets is maintained or recovered. Preliminary ejection means for causing, a means for recovering and reusing the preliminarily ejected ink, the liquid supplied into the inkjet head, at least fresh ink and reused ink recovered by preliminary ejection, Further, it can be achieved by an inkjet head and an inkjet recording apparatus, which are characterized in that fresh ink is preferentially selected during the pre-ejection operation and recycled ink is preferentially supplied during the printing operation.

Further, there may be a case where the recovered ink amount becomes excessive depending on the frequency of the preliminary ejection operation during the printing operation interval. Therefore, it is preferable to have a sub-tank in the ink recovery path for adjusting the recovered ink amount. Further, the inkjet head is configured to have at least two liquid supply ports to prevent mixing of the fresh ink and the reused ink, so that stable operation performance for a long period can be secured.

An ink suitable for this purpose comprises water, a high-boiling point organic solvent, and a surface-oxidized self-dispersion type pigment, wherein the high-boiling point organic solvent has a boiling point of 120 ° C. or higher, and the total weight of the ink is 40%. It is preferable that it is blended in an amount of 70% by weight. Further, when the deaeration process is performed so that the dissolved oxygen amount in the ink is 40% or less, the ejection characteristics are stabilized. further,
Covering the ink in the ink tank and sub tank with a protective liquid that has a lower specific gravity than ink, is incompatible with the ink, is non-volatile, and is impermeable to gas, and suppresses the rise in the amount of dissolved oxygen. It is possible.

Further, by keeping the relative humidity in the vicinity of the ink jet head at 40% RH or more, it is possible to suppress the drying of the ink in the vicinity of the nozzle of the ink jet head, and to secure a stable ejection operation for a long period of time. It has a step of applying a liquid to the recording paper, a step of heating the recording paper and the applied liquid, and further guides vapor of the liquid applied to the recording paper to the vicinity of the inkjet head to form a recording dot on the recording paper. Humidity can be controlled by installing the step above the step of applying the liquid to the recording paper. The liquid to be applied contains at least one of water and an organic solvent, and it is desirable to provide a heater for controlling the temperature of the liquid to be applied.

By using the recycled ink with the above-mentioned structure, the waste ink holding means is unnecessary, the ink is not wasted, and the economical ink jet printer can be realized.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 3 is an example of a schematic view of an ink jet recording apparatus provided with a liquid application section and a preheat plate 12 for heating a sheet in the present invention. The recording paper 10 is conveyed from the paper supply unit 15 by the guide roller 23 in the paper feeding direction. Liquid is applied to the surface of the conveyed recording paper 10 at the liquid applying section 11. Next, in the preheat plate 12, the applied liquid and the paper are heated, and the vapor of the applied liquid is guided to the vicinity of the inkjet head 4. Frame 13 for controlling liquid application amount and humidity of liquid application section 11
The humidity can be changed by the area of the opening / closing port provided on the upper part, and the humidity is measured by the hygrometer 14. Further, the recording paper 10 is stored in the paper stacker unit 16 after forming an image with the ink droplets ejected from the inkjet head 4.

Further, in the nozzle having a long ejection interval, the ink is dried or thickened not a little, so that the relative humidity in the vicinity of the ink jet head is preferably 40% RH or more. It is particularly preferably 45% RH or more, and further preferably 50% RH or more. As a result, the ink drying speed in the vicinity of the ink meniscus of the nozzle having a long ejection interval can be slowed down, and the thickening of the ink can be reduced. This can be achieved by including the step of applying the liquid to the recording paper and the step of heating the recording paper and the applied liquid.

Due to the construction of the apparatus, there is provided a means for guiding the vapor of the liquid applied to the recording paper to the vicinity of the ink jet head for forming the recording dots, and the step of forming the recording dots on the recording paper is performed on the recording paper. A predetermined humidity can be obtained by installing the liquid above the step of applying the liquid. When the inkjet head is installed above the liquid application section, it is possible to omit the means for guiding the vapor of the liquid to the vicinity of the inkjet head, but it is more efficient to install a humidity control frame in order to control the humidity efficiently. Is good. The liquid vapor introduction part and the humidity control frame may be made of metal or plastic as long as rust does not occur due to contact with water.

The step of applying the liquid to the recording paper may be a contact type method using a roller or the like, or a method of applying the liquid in a mist state by spraying or ultrasonic waves. It is desirable to coat the entire surface of the recording paper as evenly as possible. Furthermore, it is possible to apply the liquid using an inkjet head different from the recording head. By these methods, the generation of paper dust from the recording paper can be significantly reduced.

In the drying and heating step, even if the recording paper or the applied liquid is heated by contacting with the recording medium, it is heated without contacting the recording paper by irradiating infrared rays or blowing hot air. May be. The appropriate temperature for drying is the settability of the high-boiling organic solvent (the time required for the appearance to be dry, specifically, the time until the ink does not transfer even when lightly pressed with a finger or paper. 80 ° C. or higher is desirable for improvement in time). However, it does not need to be particularly limited because it depends on the printing speed. Although the upper limit temperature can be changed from the configuration of the apparatus, if the temperature is too high, smoke may be emitted from the recording paper or discoloration of the recording paper may occur.

The liquid to be applied may be any liquid containing at least one of water and an organic solvent. The organic solvent is not particularly limited, but high-speed printing can be achieved by mixing an organic solvent having a boiling point and a vapor pressure lower than that of water. This is because, even in the process of forming the recording dots, if a large amount of the applied liquid remains, it may cause deterioration of print quality such as ink bleeding or strike-through on the back surface of the recording paper.
This is because it is effective to mix an organic solvent having a low boiling point and a low vapor pressure that can efficiently generate liquid vapor. For example, acetone, methyl ethyl ketone, methyl isobutyl ketone, ketones such as methanol, ethanol, isopropanol and lower alcohols can be used alone or as a mixed solvent.

In order to further increase the speed, it is preferable to provide a heater (not shown) for controlling the temperature of the liquid to be applied, and to heat the temperature of the liquid to be applied to room temperature or higher.

Next, an example of a schematic configuration diagram of an ink path in the ink jet recording apparatus of the present invention is shown. In the present invention, the fresh ink stored in the ink tank 1 is supplied by the first pump 2 (which is not always necessary).
It is supplied to the inkjet head 4 via the switching valve 3. The ink jet head 4 in the print halt state is in close contact with the cap 5 to prevent the ink in the ink jet head 4 from drying. At the time of preliminary ejection for maintaining or recovering the normal ejection state of the ink droplets, the preliminarily ejected ink is collected in the sub tank 7 by the second pump 6. The recycled ink collected in the sub-tank 7 is transferred by the third pump 8 (not necessarily required) during the printing operation.
It is supplied to the inkjet head 4 via the switching valve 3. The switching valve 3 is controlled to preferentially select and supply fresh ink during the preliminary ejection operation and reuse ink during the printing operation. As a result, it is possible to prevent the recovered reused ink from being supplied to the recovery path by the preliminary ejection, and it is possible to prevent the increase in the viscosity of the ink that affects the printing characteristics.

FIG. 2 is another example of a schematic configuration diagram of ink paths in the ink jet head and ink jet recording apparatus according to the present invention. The fresh ink stored in the ink tank 1 is supplied to the inkjet head 4 by the first pump 2 (not necessarily required). The ink jet head 4 in the print halt state is in close contact with the cap 5 to prevent the ink in the ink jet head 4 from drying. At the time of preliminary ejection for maintaining or recovering the normal ejection state of the ink droplets, the preliminarily ejected ink is collected in the sub tank 7 by the second pump 6. The reused ink collected in the sub-tank 7 is supplied to the inkjet head 4 by the third pump 8 (not necessarily required) during the printing operation. It should be noted that control is performed so that fresh ink is preferentially selected during the preliminary ejection operation and reusable ink is preferentially selected and supplied during the printing operation. Since the print head 4 has two ink supply ports and the mixing of the fresh ink and the recycled ink is reduced, it is possible to prevent the recycled ink from being supplied to the recovery path by the preliminary ejection. Therefore, in comparison with the configuration of FIG. 1, there is an advantage that it is possible to prevent thickening of the ink that further affects the printing characteristics.

FIG. 4 shows an example of a sectional view of a sub tank in the ink jet recording apparatus of the present invention. An ink phase 19 and an air phase 21 are formed inside the sub-tank 7 of the ink jet recording apparatus, and protection between the ink 9 and the air phase 10 is incompatible with the non-volatile ink having a lighter specific gravity than the ink. A liquid 20 is provided and is configured to cover the ink. Atmosphere opening means is provided on the upper part of the sub tank, and an ink supply port 18 for supplying ink to the inkjet head 4 and an ink receiving port 17 for collecting ink from the nozzle surface of the inkjet head 4 are provided on the bottom surface. is set up.

As described above, since the protective liquid 20 is configured to separate the ink and the air phase in the ink tank and the sub tank, the ink does not come into direct contact with the air, and the dissolved oxygen amount of the ink is low. It is possible to hold the ink at a high temperature, and it is possible to prevent ink evaporation.
Further, since the protective liquid 20 is separated by the difference in specific gravity from the ink, the adhesion between the ink and the protective liquid does not deteriorate due to vibration or the like, and the ink and the air phase can be reliably separated with a simple configuration. it can.

The protective liquid is incompatible with the ink in the ink tank and the sub tank. Even if the protective liquid is in contact with the ink in the ink tank and the sub tank for a long period of time, it does not mix with the ink, and the defective ejection of the ink or the print quality on the print head caused by the mixing of the protective liquid with the ink Is less likely to decrease. The solubility of the protective liquid in the ink is preferably 0.1% by weight or less at room temperature (25 ° C.).

Further, the protective liquid is preferably non-volatile. If it is non-volatile, it does not evaporate during storage and the state of protection against ink by the incompatible protective liquid does not change. As a result, the ink and the air phase in the ink tank and the sub tank can be separated over a long period of time. Vapor pressure is about 1.33 kPa (1 at room temperature (25 ° C)
It is preferably 0.0 mmHg) or less, more preferably about 133 Pa (1.0 mmHg) or less. Further, it is particularly effective when it is about 13.3 Pa (0.1 mmHg) or less.

Furthermore, it is preferable that the protective liquid is impermeable to gas. Even when the ink in the ink tank and the sub tank is separated from the air phase for a long period of time, the dissolved air amount of the ink can be kept low. The thickness of the protective liquid is preferably 0.1 mm or more.

The protective liquid may be used in one layer alone or in two or more layers. Further, when the ink tank and the sub tank are divided into two or more, only the portion connected to the atmosphere communication port may be covered with the protective liquid.

Further, it is preferable that the protective liquid in the ink tank and the sub tank is in a state where the ink and the air phase are separated without any gap in the ink tank. From this point of view, the protective liquid preferably has a small contact angle with the members in the ink tank and the sub tank, and specifically, the contact angle is preferably 120 ° or less.

When a water-based ink is used, an organic solvent or oil which is liquid at room temperature can be used as the protective liquid. More specifically, octane, nonane, decane, tetradecane, dodecane, oleic acid, linoleic acid, n-decanol, dimethylbutanol, dibutyl phthalate, dioctyl phthalate, bis-2-ethylhexyl phthalate, dibutyl maleate, malein. Organic solvents such as dioctyl acid and isomers and derivatives thereof, and oils such as vegetable oils, mineral oils, silicone oils and fluorine oils are preferable. The protective liquid is preferably a liquid having a specific gravity lower than that of the ink. The specific gravity of the water-based ink is about 1.0-1.
Was 1 g / cm ^3, the specific gravity of these organic solvents and oils are especially effective for at room temperature (25 ° C.) of about 0.6~1.0g / cm ^3.

These may be used alone or in combination of two or more, and may not be uniformly mixed. Further, a plurality of materials may be mixed to adjust the viscosity and surface tension to a preferable range before use.

Further, in order to prevent bubbles from being inadvertently generated in the ink in the ink jet recording apparatus, the dissolved oxygen content of the ink is preferably 40% or less, particularly preferably the dissolved oxygen content of 30. It is better to be less than or equal to%. More preferably, it is particularly effective when 20% or less of ink is used. Here, dissolved oxygen amount (DO value: DO
= Dissolve Oxygen) is represented by mg amount (mg / L) of oxygen contained in 1 liter of the solution. Since the amount of dissolved oxygen varies depending on the temperature, it is expressed as the saturation (%).

In the ink jet recording apparatus,
The inkjet head 4 is particularly suitable for inkjet recording in which a piezoelectric element is formed in a part of a pressure generating chamber communicating with a nozzle opening for ejecting an ink droplet via a vibration plate and the ink droplet is ejected by displacement of the piezoelectric element. It is valid.

The ink composition used is
Various materials are used without limitation. Generally used as a main material for colorants and solvents, as a binder, viscosity, surface tension, and pH.
It is constituted by adding a physical property adjusting agent such as, a fungicide, and the like. In addition to the function as a solvent, these solvents may have an action such as an anti-drying agent (wetting agent), a penetrating agent (surface tension reducing agent), a viscosity, an evaporation rate controlling agent, etc.
Materials exhibiting surface tension, solubility, boiling point, evaporation rate, flash point, etc. are used. Examples thereof include alcohols such as diethylene glycol, polyethylene glycol, glycerin, NMP, sodium lactate, DMSO, polyoxyethylene alkylphenol, polyoxyethylene fatty acid ester, ethylene glycol alkyl ether, diethylene glycol alkyl ether, ethanol and propanol. Examples of the physical property modifier include metal hydroxides such as KOH, various surfactants, alcohol amines such as diethanolamine and triethanolamine, phosphoric acid, alcohol amine salts of strong acids, ammonium salts, lower carboxylic acids,
Hydroxycarboxylic acids such as glycolic acid and lactic acid, fungicides such as sodium benzoate, potassium sorbate, thiabendazole and benzimidazole, chelating agents,
Various additives such as an oxygen scavenger, a defoaming agent, and a conductivity-imparting agent can be used according to the application.

The preferred ink composition in the present invention is
Water, a high-boiling organic solvent, and a surface-oxidized self-dispersion pigment are essential components, and the high-boiling organic solvent has a boiling point of 120 ° C. or higher and 40% to 70% by weight based on the total weight of the ink.
It is contained. If the high boiling point organic solvent is less than 40% by weight, the effect as a wetting agent is not sufficient, and drying of the vicinity of the meniscus due to evaporation of water and ink non-ejection due to an increase in viscosity are likely to occur. On the other hand, if it exceeds 70% by weight, it takes a long time to dry the ink, and the printing tends to bleed.

Examples of the high boiling point organic solvent include ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol, triethylene glycol, tetraethylene glycol, tripropylene glycol, glycerin, polyethylene glycol having a molecular weight of 400 or less, pentamethylene glycol, polyethylene glycol. (Made by Wako Pure Chemical Industries, Ltd.), acetylene glycol, acetylene alcohol, etc., methyl glycol,
Ethylene glycol-based ethers such as methyldiglycol, methyltriglycol, methylpolyglycol, butylglycol, butyldiglycol, butyltriglycol, isobutylglycol (all manufactured by Nippon Emulsifier) and methylpropylene glycol, methylpropylenediglycol, methylpropylene Propylene glycol ethers such as triglycol, propyl propylene glycol, propyl propylene diglycol, butyl propylene glycol, butyl propylene diglycol, phenyl propylene glycol (above, manufactured by Nippon Emulsifier), etc., as well as carboxylic acid salts and sulfuric acid ester salts. , Sulfonates, phosphoric acid ester salts, and other anionic surfactants, alkylamine salts, dialkylamine salts, tetraalkylammonium salts Cationic surfactants such as benzalkonium salt, alkylpyridinium salt and imidazolinium salt, amphoteric surfactants such as carboxybetaine, sulfobetaine aminocarboxylic acid and phosphate ester salt, ether type, ester type, ether ester type, There is a nitrogen type, and specifically, polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, sucrose ester, polyoxyethylene ether of glycerin ester, sorbitan ester. Polyoxyethylene ether, sorbitol ester polyoxyethylene ether, fatty acid alkanolamide, polyoxyethylene fatty acid amide,
Nonionic surfactants such as amine oxide, acetylene alcohol, acetylene glycol and formamide can be widely used.

Although the colorant is not particularly limited,
In the present invention, a pigment which is easily surface-oxidized and is well dispersed in the above vehicle and has excellent weather resistance is desirable. Furthermore, pigments having a high safety such as a negative mutagenicity test and no chromosomal abnormality are particularly preferable. For example, the following organic or inorganic pigments listed in the color index can be used.

As the red or magenta pigment, Pigmen
t Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48:
3, 48: 4, 48: 5, 49: 1, 53: 1, 57: 1, 57: 2, 58:
4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 10
4, 108, 112, 122, 123, 144, 146, 149, 166, 168, 16
9, 170, 177, 178, 179, 184, 185, 208, 216, 226, 25
7, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, P
Pigment Blue 1, 15, 15: 1, 15: 2, 15: 3, 1 as a blue or cyan pigment.
5: 4, 15: 6, 16, 17-1, 22, 27, 28, 29, 36, 60, as a green pigment, Pigment Green 7, 26, 36, 50, as a yellow pigment, Pigment Yellow 1, 3, 12, 13, 14, 17, 3
4, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 10
9, 110, 137, 138, 139, 153, 154, 155, 157, 166, 16
7, 168, 180, 185, 193, Pigment Bla as black pigment
ck 7, 28, 26 etc. can be used according to the purpose. Pigment
Yellow 74, Pigment Red 122 and Pigment Blue 15: 4 are preferable because they are easy to process. The oxidation treatment of the self-dispersion pigment is carried out by heating the pigment in an aqueous medium together with an oxidizing agent such as nitric acid, sulfuric acid, potassium persulfate, potassium permanganate,
It can be performed by a method of washing with water.

Specific product names are, for example, Chromo Fine Yellow 2080, 5900, 5930, AF-1300, 2700.
L, Chromo Fine Orange 3700L, 6730, Chromo Fine Scarlet 6750, Chromo Fine Magenta 6880, 68
86, 6891N, 6790, 6887, Chromo Fine Violet
RE, Chromo Fine Red 6820, 6830, Chromo Fine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 50
26, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 494
0, 4973, 5205, 5208, 5214, 5221, 5000P, Chromo Fine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830,
Chromo Fine Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400
(B), 2500, 2600, ZAY-260, 2700 (B), 2770, Seika Fast Red 8040, C405 (F), CA120, LR-116, 1
531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016,
3820, 3891, ZA-215, Seika Fast Carmine 6B1476T
-7, 1483LT, 3840, 3870, Seika Fast Bordeaux 10B
-430, Seika Light Rose R40, Seika Light Violet B800, 7805, Seika Fast Maroon 460N, Seica Fast Orange 900, 2900, Seica Light Blue C71
8, A612, Cyanine Blue 4933M, 4933GN-EP, 4940, 49
73 (above made by Dainichi Seika Kogyo), KET Yellow 401, 402, 40
3, 404, 405, 406, 416, 424, KET Orange 501, KET Re
d 301, 302, 303, 304, 305, 306, 307, 308, 309, 31
0, 336, 337, 338, 346, KET Blue 101, 102, 103, 10
4, 105, 106, 111, 118, 124, KET Green 201 (above made by Dainippon Ink and Chemicals), Colortex Yellow 301, 314, 31
5, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U2
63, Finecol Yellow T-13, T-05, Pigment Yellow170
5, Colortex Orange 202, Colortex Red101, 103, 11
5, 116, D3B, P-625, 102, H-1024, 105C, UFN, UC
N, UBN, U3BN, URN, UGN, UG276, U456, U457, 105C, U
SN, Colortex Maroon601, Colortex BrownB610N, Color
tex Violet600, PigmentRed 122, Colortex Blue516, 5
17, 518, 519, A818, P-908, 510, Colortex Green40
2,403, Colortex Black 702, U905 (above Sanyo dye), Lionol Yellow1405G, Lionol Blue FG7330, FG73
50, FG7400G, FG7405G, ES, ESP-S (all manufactured by Toyo Ink Mfg. Co., Ltd.), Toner Magenta E02, Permanent RubinF6B, To
ner Yellow HG, Permanent Yellow GG-02, Hostapeam
BlueB2G (made by Hoechst Industry), carbon black # 2600, # 2400, # 2350, # 2200, # 1000, # 99
0, # 980, # 970, # 960, # 950, # 850, MCF88, # 75
0, # 650, MA600, MA7, MA8, MA11, MA100, MA100R, MA
77, # 52, # 50, # 47, # 45, # 45L, # 40, # 33, # 3
2, # 30, # 25, # 20, # 10, # 5, # 44, CF9 (manufactured by Mitsubishi Chemical) and the like. It is also possible to use a dispersion liquid in which the pigment is dispersed in water or a solvent in a high concentration in advance.
For example, MICROPIGMO WMBK-5, WMBE-5, WMRD-5, WMYW-
5, AMBK-2, AMYW-2, AMBE-4, Micro Jet CW-1 (above Orient Chemical), JA Black 25W, GA Black 2821, GA
Yellow 1, GA Magenta1, GA Cyan 2 (Mikuni dye)
CAB-O-JET200, CAB-O-JET300, IJX273, IJX444, IJX26
6, IJX253 (above made by Cabot Specialty Chemicals) and the like.

An appropriate amount is 1 to 10% by weight. 1
If it is less than 10% by weight, the image quality is deteriorated, and if it exceeds 10% by weight, the ink viscosity characteristics are adversely affected. In addition, two or more kinds of colorants can be appropriately mixed and used for color adjustment or the like. To further exhibit functionality, light stabilizers, surface treatment agents, surfactants, viscosity reducers, antioxidants, antioxidants, crosslinking accelerators, oxygen absorbers, plasticizers, preservatives, rust inhibitors , An evaporation accelerator, a pH adjuster, an antifoaming agent, a moisturizing agent, a dispersant, a dye and the like can be mixed.

The viscosity of the ink composition used in the present invention is not particularly limited, but the viscosity at 25 ° C. is 5 to 20 mP.
The range of a · s is preferable for maintaining stable ejection characteristics. If the viscosity is less than 5 mPa · s, the shape of the ink droplet and the high-speed ink ejection frequency characteristics tend to be poor, and
If the viscosity exceeds aS, it is difficult to eject ink and it is difficult to stabilize. In addition, it is desirable that the ink composition exhibits Newtonian fluid behavior under the temperature conditions used, but if the shear speed (usually about 100 rpm) normally used for measurement meets the above conditions, the apparent viscosity will depend on the shear speed to some extent. It does not matter if sex exists.

A stirrer, a bead mill and a homogenizer are most suitable for mixing and dispersing the above-mentioned pigment and other components, but various known stirring, pulverizing or dispersing devices can be used without particular limitation.

The present invention can be effectively applied to an ink jet head having a large number of nozzles having a length corresponding to the maximum width of a recording medium. Such an inkjet head may have either a configuration that satisfies the length by a combination of a plurality of inkjet heads or a configuration that is one integrally formed inkjet head. In addition, among the serial type inkjet heads, an inkjet head fixed to the device body, or a replacement that enables electrical connection with the device body and supply of ink from the device body when mounted on the device body The present invention is also effective when a flexible chip-type inkjet head or a cartridge-type inkjet head in which an ink tank is integrally provided in the inkjet head itself is used.

Further, as the constitution of the recording apparatus to which the present invention can be applied, the ejection recovery means (including the preliminary auxiliary means) of the ink jet head may have various forms. Specifically, a capping unit for the inkjet head, a cleaning unit such as a blade, a unit for removing the ink from the ink discharge port by pressurizing or sucking the ink supply system, and a preliminary discharge for discharging other than the recording. It may include means.

Further, as a form of the ink jet recording apparatus which can be applied to the present invention, other than the one used as an image output terminal of information processing equipment such as a computer, a copying apparatus combined with a reader or the like, and further a facsimile apparatus having a transmission / reception function. It may be a form or the like. [Examples 1 to 3] 35 parts by weight of purified water, 60 parts by weight of glycerin (manufactured by Wako Pure Chemical Industries, Ltd.), and 5 parts by weight of ethylene glycol monoisobutyl ether (manufactured by Wako Pure Chemical Industries, Ltd.) were mixed, and pigment water dispersion was performed. Liquid 1; CAB-O-JET200 manufactured by Cabot Specialty Chemicals, pigment content 1
9.5% by weight, and a total of 300 g of the composition was rotated with a homogenizer (HG30 manufactured by Hitachi Koki Co., Ltd.) at a rotation speed of 2,000.
The mixture was dispersed at 0 rpm until a homogeneous mixture was obtained, and further filtered to remove impurities and the like to obtain a homogeneous ink composition.

The ink viscosity of the obtained ink was measured at 25 ° C. using a rotational viscometer (ELD model manufactured by Tokimec), and the result was 8.9 mPa · s. Add a 500mL beaker containing this ink to the vacuum desiccator.
It was left for 0 minutes or more and deaerated. Using a dissolved oxygen meter (TOX-90i manufactured by Toko Kagaku Kenkyusho), the amount of dissolved oxygen was measured while gently stirring with a magnetic stirrer. The amount of dissolved oxygen was 20.5%. The dissolved oxygen amount (DO value: DO = Dissolve Oxygen) is represented by mg amount (mg / L) of oxygen contained in 1 liter of the solution. Since the amount of dissolved oxygen varies depending on the temperature, it is expressed as the saturation (%).

The ink path in the recording apparatus is constructed by using the switching valve shown in FIG. 1, and is controlled so that fresh ink is preferentially selected during the preliminary ejection operation and recycled ink is preferentially supplied during the printing operation. Silicone oil (silicone manufactured by Shin-Etsu Chemical Co., Ltd.) was added in a thickness of about 5 mm as a protective liquid for separating the ink and the air phase in the ink tank and the sub tank.

The entire structure of the recording apparatus is based on FIG. Water was used as the liquid to be applied, and Quick Spray EH-53 (manufactured by AS ONE Co., Ltd.) was used to apply it on the paper. The water used may be ordinary tap water, but distilled water was used in this example. As the paper heating means, a preheater portion of a laser beam printer (LB16 manufactured by Hitachi Koki) was extracted and used. The surface temperature of the preheater was set to 95 ± 5 ° C., and heating was performed so that the paper temperature was 80 ° C. or higher. In addition, direct plate making machine (SJ02A made by Hitachi Koki)
The inkjet head portion was extracted, fixed and used for printing, and printing was performed with a maximum ink ejection frequency of 6 kHz and a paper feed speed of 10 ips and a resolution of 600 (× 600) dpi. As recording paper, recycled paper NIP150
0RGT (made by Kobayashi recording paper) was used.

In this experiment, since the ink jet head was installed above the liquid coating section, the means for guiding the vapor of the liquid to the vicinity of the ink jet head was omitted. However, in order to control humidity efficiently, a humidity control frame made of acrylic resin was installed. In addition, the humidity near the inkjet head is measured by the Tanddy temperature and humidity meter TR.
The sensor portion of -72S was set at a position about 2 mm below the head portion for measurement. By changing the amount of liquid to be applied and changing the area of the opening / closing port installed on the upper surface of the humidity control frame, the humidity (1 ... 50% RH, 2 ... 45) shown in Table 1 can be obtained.
% RH, 3 ... 40% RH) and the experiment was performed.

Preliminary discharge was performed once every 10 minutes for printing time, and printing was carried out for a total of 1 hour (6 times printing for 10 minutes). Occurrence of print image distortion at the beginning and end of each printing time,
Presence / absence of non-ejection nozzles and presence / absence of occurrence of the ejection nozzles were magnified 20 times and observed. The results are shown in Table 1.

[0051]

[Table 1]

[Example 4] 15 parts by weight of purified water and 80 parts by weight of polyethylene glycol 200 (manufactured by Wako Pure Chemical Industries, Ltd.),
And 5 parts by weight of ethylene glycol monoisobutyl ether (manufactured by Wako Pure Chemical Industries, Ltd.), and pigment water dispersion 1; CAB-O manufactured by Cabot Specialty Chemicals
-Add JET200, pigment content 19.5% by weight,
An ink composition was obtained in the same procedure as in Example 1. The results of evaluation using this ink in the same manner as in Example 1 are shown in Table 1. [Example 5] 50 parts by weight of purified water, 45 parts by weight of polyethylene glycol 400 (manufactured by Wako Pure Chemical Industries), and ethylene glycol monoisobutyl ether (manufactured by Wako Pure Chemical Industries)
5 parts by weight were mixed, and an aqueous pigment dispersion 2; IJX253 manufactured by Cabot Specialty Chemicals, and a pigment content of 15.2% by weight were added thereto, and an ink composition was obtained in the same manner as in Example 1. The results of evaluation using this ink in the same manner as in Example 1 are shown in Table 1. Comparative Example 1 Using the same ink composition as in Example 1,
The experiment was conducted at a humidity of 35% RH without applying the liquid. The evaluated results are shown in Table 1. [Comparative Example 2] A printing experiment was conducted using the same ink composition as in Example 1 without degassing. The amount of dissolved oxygen in the ink was 55.3%. The evaluated results are shown in Table 1.

[0053]

As described above, in the ink jet printer of the present invention, since the ink discharged from the ink jet head is also collected and reused, all the ink can be used for printing, the ink replenishment interval is long, and the economy is high. Since a waste ink holding unit is unnecessary, a small inkjet recording apparatus can be realized. In particular, it is particularly effective in an ink jet recording apparatus using a line head having a large number of nozzles.

The step of applying the liquid to the recording paper may be a contact type method using a roller or the like, or a method of applying the liquid in a mist state by spraying or ultrasonic waves. It is desirable to coat the entire surface of the recording paper as evenly as possible. Furthermore, it is possible to apply the liquid using an inkjet head different from the recording head. By these methods, it is possible to significantly reduce the generation of paper dust from the recording paper, and it is possible to perform stable printing for a long time.

Since the inside of the ink tank and the sub-tank is covered with a protective liquid having a lower specific gravity than the non-volatile ink, and is arranged so as to separate the ink and the air, the ink supply path is used during the operation and storage of the apparatus. Among these, it is possible to prevent a decrease in the degree of deaeration of ink, prevent non-ejection due to bubble feeding to the inkjet head, and create a stable recording state. Further, since the ink and the air are arranged so as to be separated from each other, the evaporation of the ink can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an ink path in an inkjet recording apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing another example of an ink path in the inkjet recording apparatus of the present invention.

FIG. 3 is a schematic diagram showing an example of an inkjet recording apparatus according to the present invention.

FIG. 4 is a sectional view showing an example of a sub tank used in the present invention.

[Explanation of symbols]

1 is an ink tank, 2 is a first pump, 3 is a switching valve, 4 is an inkjet head, 5 is a cap, 6 is a second pump, 7 is a sub-tank, 8 is a third pump, 9 is an inkjet device, and 10 is recording paper. , 11 is a liquid application part, 12 is a preheat plate, 13 is a humidity control frame, 14 is a hygrometer, 1
5 is a paper supply unit, 16 is a paper stacker unit, 17 is an ink receiving port for a sub tank, 18 is an ink supply port for a sub tank, 19 is ink, 20 is a protective liquid, 21 is an air phase, 2
2 is an atmosphere communication port.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B41M 5/00 B41J 3/04 102Z (72) Inventor Hidetoshi Fujii 1060 Takeda, Hitachinaka City, Ibaraki Hitachi Koki Co., Ltd. Company (72) Inventor Kunihiro Tamahashi 1060 Takeda, Hitachinaka City, Ibaraki Hitachi Koki Co., Ltd. (72) Inventor Kunio Sato 1060 Takeda Hitachinaka, Ibaraki Hitachi Koki Co., Ltd. (72) Inventor Hitoshi Kida 1060 Takeda, Hitachinaka City, Ibaraki Prefecture F-Term inside Hitachi Koki Co., Ltd. (reference) 2C056 EA19 EC15 EC21 EC29 FC02 JC23 KB37 KC09 2H086 BA02 BA52 BA53 BA55 BA60 BA62

Claims (15)

[Claims] 1. An on-demand type ink jet recording apparatus for ejecting ink droplets onto a recording medium to form recording dots, a preliminary ejection means for maintaining or recovering a normal ejection state of ink droplets, and preliminary ejection. It has a means to collect and reuse ink, and the liquid supplied into the inkjet head consists of at least fresh ink and recycled ink recovered by preliminary ejection, and prints fresh ink during preliminary ejection operation. An ink jet recording apparatus characterized in that reusable ink is preferentially selected and supplied during operation. 2. The ink jet recording apparatus according to claim 1, further comprising a sub tank for adjusting the amount of recovered ink in the ink recovery path. 3. The ink jet recording apparatus according to claim 1, wherein the ink jet head has at least two liquid supply ports. 4. A high-boiling organic solvent containing water, a high-boiling organic solvent and a surface-oxidized self-dispersing pigment, wherein the high-boiling organic solvent has a boiling point of 1.
40% by weight to 7% of the total weight of the ink at 20 ° C or higher
The ink jet recording apparatus according to claim 1, wherein an ink composition containing 0% by weight is used. 5. The relative humidity in the vicinity of the inkjet head is 4
The ink jet recording apparatus according to claim 3 or 4, wherein the ink content is 0% RH or more. 6. An ink jet head for forming a recording dot by vapor of the liquid applied to the recording sheet, which has a step of applying the liquid to the recording sheet and a step of heating the recording sheet and the applied liquid. The ink jet recording apparatus according to claim 5, further comprising means for guiding it to the vicinity. 7. A step of forming recording dots on a recording sheet,
The inkjet recording apparatus according to claim 6, wherein the inkjet recording apparatus is located above the step of applying the liquid to the recording sheet. 8. The liquid to be applied contains at least one of water and an organic solvent.
The inkjet recording device described. 9. The ink jet recording apparatus according to claim 6, further comprising a heater for controlling the temperature of the liquid to be applied. 10. The ink jet recording apparatus according to claim 4, wherein the ink in the ink tank and the ink in the sub tank are covered with a protective liquid. 11. The ink jet recording apparatus according to claim 10, wherein the protective liquid is a liquid having a lower specific gravity than ink. 12. The ink jet recording apparatus according to claim 10 or 11, wherein the protective liquid is incompatible with ink. 13. The ink jet recording apparatus according to claim 10, wherein the protective liquid is a non-volatile liquid. 14. The ink jet recording apparatus according to claim 10, wherein the protective liquid is impermeable to gas. 15. The ink according to claim 5, wherein the ink is an ink having a dissolved oxygen content of 40% or less.
15. The inkjet recording device according to any one of 14 to 14.