Liquid jet recording apparatus

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a liquid injection recording device, more specifically, a liquid injection recording device using a recording liquid in which fine particles are dispersed.

【0002】

[Conventional technology]

The non-impact recording method has recently attracted attention in that the generation of noise during recording is extremely small to the extent that it can be ignored. Among them, the so-called inkjet recording method, which enables high-speed recording and can record on so-called plain paper without requiring a special fixing process, is an extremely powerful recording method, and various methods have been used so far. Some have been proposed and improved, and some have been commercialized, while others are still making efforts to put them into practical use.

【0003】

Such an inkjet recording method is to fly droplets of a recording liquid, so-called ink, and attach them to a recording member for recording. There are various methods as follows, depending on the method for controlling the flight direction of the generated recorded liquid droplets.

【0004】

For example, in the Tele type system disclosed in US Pat. No. 3,060,429, droplets of recording liquid are generated by electrostatic suction, and the generated droplets of recording liquid are generated according to a recording signal. There is an electrostatic suction type that controls the electric field and selectively adheres recording liquid droplets on the recording member to perform recording.

【0005】

In addition, it is a Sweet method disclosed in US Pat. No. 3,596,275, US Pat. No. 3,299,030, etc., and a small drop of a recording liquid whose charge amount is controlled by a continuous vibration generation method is generated, and this is generated. There are continuous flow type and charge control type that record on a recording member by flying small droplets with a controlled amount of charge between deflection electrodes to which a uniform electric field is applied.

【0006】

Another method is, for example, the Hertz method disclosed in US Pat. No. 3,416,153, in which an electric field is applied between the discharge port and the ring-shaped charging electrode, and the liquid is recorded by the continuous vibration generation method. There is a method of generating and atomizing small droplets of the above and recording them. That is, in this method, the atomization state of the droplets is controlled by modulating the electric field strength applied between the discharge port and the charging electrode according to the recording signal, and the recorded image is recorded with gradation.

【0007】

Further, as another method, for example, there is a Stemme method disclosed in US Pat. No. 3,747,120. This method is fundamentally different from the above three methods. That is, in each of the above three methods, the droplets of the recording liquid discharged from the discharge port are electrically controlled while flying, and the droplets carrying the recording signal are selectively adhered to the recording member. In contrast to this Stemme method, a small drop of the recording liquid is ejected and flew from the discharge port in response to the recording signal for recording. That is, in the Stemme method, an electric recording signal is applied to the piezo vibrating element attached to the recording head having a discharge port for discharging the recording liquid, and this electric recording signal is converted into the mechanical vibration of the piezo vibrating element. The recording is performed by ejecting a small drop of the recording liquid from the discharge port according to the mechanical vibration and adhering it to the recording member, which is a so-called drop-on-demand type.

【0008】

Further, as another method, there is a method previously proposed by the applicant in Japanese Patent Publication No. 56-9429. This method is also a so-called drop-on-demand type in which small droplets of the recording liquid are ejected from the discharge port according to the recording signal to record, but the ink in the liquid chamber is heated to generate bubbles in the ink. This is the so-called bubble jet type, in which ink droplets are ejected from the ejection port by the action force of the bubbles.

【0009】

As described above, there are various inkjet recording methods depending on the principle, but what can be said in common is that droplets of recording liquid, so-called ink, are made to fly and adhere to a recording member. This is the point of recording. Then, although it is a recording liquid called this ink, it is common to use a recording liquid in which a water-soluble dye is dissolved. However, in recent years, water resistance and light resistance have become more important, and it is expected that pigments having high fastness as colorants for recording liquids will be used for inkjet recording.

【0010】

For example, as water-based pigment inks for inkjet that satisfy basic problems such as print quality, ejection characteristics, storage stability, and fixability, JP-A-2-255875, JP-A-4-334870, and JP-A-4 The inks described in Japanese Patent Application Laid-Open No. -57859 and Japanese Patent Application Laid-Open No. 4-57860 are disclosed.

【0011】

However, unlike dyes, this pigment is dispersed rather than dissolved in the liquid medium, resulting in poor stability in the liquid medium, causing aggregation, sedimentation, and separation of the pigment in the ink, and nozzles. The problem of causing clogging of the part has not been solved yet.

【0012】

On the other hand, in recent years, the image quality and accuracy of inkjet recording have been improved, and the discharge port (nozzle) of the head used has conventionally been Φ33 μm to Φ34 μm (900 μm in terms of area).²From Φ50 μm to Φ51 μm (2000 μm in terms of area)²(Degree) was common, but finer discharge ports have been required. At that time, if a recording liquid in which a water-soluble dye is dissolved is used as the ink as in the conventional case, the problem of anti-clogging property can be dealt with because the dye is dissolved in the liquid medium. However, for pigment-based inks, clogging is a serious problem when the ejection port is finer (for example, Φ25 μm or less).

【0013】

In addition, the recording liquid in which the above pigments are dispersed scrapes the ink path of the inkjet recording head and damages it when used for a long time, as if river water containing gravel erodes the mountain. There is an action. If this is also a simple ink passage, there is no problem with some damage and wear, but damage and wear at the ejection port portion affect the ink droplet ejection performance, which is a problem.

【0014】

In particular, in recent years, the image quality and accuracy of inkjet recording have been improved, and the discharge port (nozzle) of the head used has conventionally been Φ33 μm to Φ34 μm (900 μm in terms of area).²From Φ50 μm to Φ51 μm (2000 μm in terms of area)²Generally, it is a finer discharge port (for example, Φ25 μm or less, 500 μm in area).²Less than) has been required. At that time, as in the past, those having a relatively large ejection port have almost no effect on the ink droplet ejection performance (injection stability, ink mass uniformity, etc.) even if there is some damage or wear. There is no problem, but if the ejection port is finer (for example, Φ25 μm or less), even if there is slight damage or wear, the ink droplet ejection performance (injection stability, ink mass uniformity) Etc.), which is a serious problem.

【0015】

[Problems to be Solved by the Invention]

The present invention has been made in view of the above circumstances, and the first object thereof is to disperse fine particles in a liquid to obtain a recording liquid, and the recording liquid is discharged from a fine opening and adhered to a recorded object. The purpose is to prevent clogging in the liquid injection recording device for recording. In particular, the discharge port diameter is Φ25 μm or less (500 μm in terms of area)²The purpose is to prevent clogging in a liquid injection recording device that requires unprecedented high definition, high water resistance, and high light resistance. The second purpose is to apply such a liquid injection recorder to color recording.

【0016】

The third purpose is to prevent clogging and to obtain stable dispersion of fine particles in such a liquid injection recording device. A fourth object is to apply a liquid injection recording device that uses a recording liquid in which such fine particles are stably dispersed for color recording.

【0017】

The fifth purpose is to prevent clogging in a liquid injection recording device in which fine particles are dispersed in a liquid to obtain a recording liquid, the recording liquid is discharged from a fine opening, and the recording liquid is adhered to a recording object to perform recording. To do. In particular, it is an object of the present invention to propose a condition for preventing clogging in a liquid injection recording device such as a discharge port having a depth portion in the discharge portion. The sixth purpose is to obtain high-quality recording by such a liquid injection recording device.

【0018】

The seventh purpose is to disperse fine particles in a liquid to make a recording liquid, discharge the recording liquid from a fine opening, and attach it to a recording object to perform recording. In a liquid injection recording device, the discharge port portion is made of resin. The purpose is to prevent damage and wear of the discharge port when it is formed in. The eighth purpose is to ensure the reliability of such a liquid injection recording device.

【0019】

The ninth purpose is to realize miniaturization when such a liquid injection recording device is applied to color recording. A tenth object is to provide a means for ensuring the reliability of such a color liquid injection recorder. The eleventh purpose is to reduce the running cost of such a color liquid injection recording device. The twelfth purpose is to further reduce the running cost of such a color liquid injection recording device.

【0020】

[Means for solving problems]

The invention of claim 1 is a liquid injection recording apparatus in which fine particles are dispersed in a liquid to form a recording liquid, the recording liquid is discharged from a fine opening, and the recording liquid is adhered to a recording object to perform recording. The opening is Ф25 μm or less. This is characterized in that 0.001 Dp / Do 0.01 when the size of the fine particles is Dp and the size of the fine openings is Do.

【0021】

The invention of claim 2 is the invention of claim 1, wherein the recording liquid is a recording liquid of a plurality of colors in which different fine particles are dispersed for each recording liquid, and the fine openings correspond to the recording liquid of the plurality of colors. It is characterized by having.

【0022】

The invention of claim 3 is a liquid injection recording apparatus in which fine particles are dispersed in a liquid to obtain a recording liquid, the recording liquid is discharged from a fine opening, and the recording liquid is adhered to a recording object to perform recording. The opening is Ф25 μm or less. The feature is that the content of the fine particles in the recording liquid is 2 to 10% by weight, and the amount of the solid content containing the fine particles in the recording liquid is 15% by weight or less. ..

【0023】

The invention of claim 4 is the invention of claim 3, wherein the recording liquid is a recording liquid of a plurality of colors in which different fine particles are dispersed for each recording liquid, and the fine openings correspond to the recording liquid of the plurality of colors. It is characterized by having.

【0024】

The invention of claim 5 is a liquid in which fine particles having a size of Dp are dispersed in a liquid to obtain a recording liquid, and the recording liquid is discharged from a fine discharge port and adhered to a recording object for recording. In the injection recording device, the discharge port is a discharge port in which the end of the flow path is used as it is or a discharge port is separately formed at the end of the flow path, and the discharge port is Φ25 μm or less. It is a feature that Dp / t 0.01 when the discharge port has a distance t of the depth portion.

【0025】

The invention of claim 6 is characterized in that, in the invention of claim 5, the distance from the discharge port to the surface to be recorded is 100 tons or less, and the recording liquid is discharged from the discharge port in the direction of gravity action. is there.

【0026】

The invention of claim 7 is a liquid injection recording apparatus in which fine particles are dispersed in a liquid to form a recording liquid, the recording liquid is discharged from a fine opening, and the recording liquid is adhered to a recording object to perform recording. The opening is a resin material. The resin material is characterized by having an opening diameter of Φ25 μm or less and a hardness of the resin material of 65 to 120 on the Rockwell M scale.

【0027】

The invention of claim 8 is characterized in that, in the invention of claim 7, the fine particles are pigments having a particle size of 0.02 μm to 0.2 μm.

【0028】

The invention of claim 9 is the invention of any one of claims 1 to 8, wherein the liquid injection recording device has a plurality of recording heads for discharging the recording liquids of the plurality of colors, and the plurality of recording heads. Is characterized by being an integrally formed head unit.

【0029】

The invention of claim 10 is characterized in that, in the invention of claim 9, the head unit is integrally formed with a head portion which is a recording liquid discharge portion and a recording liquid storage portion.

【0030】

The invention of claim 11 is characterized in that, in the invention of claim 9, the head unit is separable from a head portion which is a recording liquid discharge portion and a recording liquid storage portion.

【0031】

The invention of claim 12 is characterized in that, in the invention of claim 11, the recording liquid storage unit is separable according to the type of recording liquid.

【0032】

BEST MODE FOR CARRYING OUT THE INVENTION

First, the configuration and principle of the inkjet to which the present invention is applied will be described. As described above, there are various inkjet recording methods. Here, as a representative example, a bubble jet type example will be described, but it goes without saying that the present invention is not limited to this method, and is applied to all inkjet recording methods. However, among various inkjet recording methods, the so-called bubble jet recording method, in which the ink is heated to generate bubbles, is exposed to harsh conditions (there is a heat cycle), and therefore deteriorates and promotes chemical reactions. In terms of unstable dispersion of pigments, there are technical problems that are more unfavorable for inkjets such as clogging than other inkjet recording methods. The present invention is particularly preferably applied to a bubble jet recording method exposed to such harsh conditions.

【0033】

FIG. 1 is a diagram for explaining an example of a bubble jet type recording head, FIG. 1 (A) is a perspective view of the head, FIG. 1 (B) is a perspective view of a lid substrate constituting the head, and FIG. 1 (C). Is a perspective view of the lid substrate as viewed from the back side, and FIG. 1 (D) is a perspective view of the heating element substrate. In the drawing, 1 is a lid substrate, 2 is a heating element substrate, 3 is a recording liquid inlet, and 4 is. Discharge port, 5 is a flow path, 6 is a region for forming a liquid chamber, 7 is an individual (independent) control electrode, 8 is a common electrode, and 9 is a heating element.

【0034】

Here, the lid substrate 1 can be manufactured by forming a flow path 5 or a liquid chamber 6 on a glass substrate or a metal substrate by a method such as etching, but the most preferable manufacturing method is a method of forming by molding plastic. .. This is a little costly to make the first mold, but since it can be mass-produced after that, the manufacturing cost per piece can be very low. At that time, as will be described later, in the present invention, by appropriately selecting the hardness of the plastic to be used, damage and wear of the ejection port 4 portion are eliminated, and stable ink droplet ejection is obtained.

【0035】

FIG. 2 is a diagram for explaining the principle of ink droplet ejection of a bubble jet type inkjet. FIG. 2A shows a steady state, and the ink 10, surface tension, and external pressure are in equilibrium on the ejection port surface. FIG. 2B shows a state in which the heating element 9 is heated, the surface temperature of the heating element 9 rises sharply, and the adjacent ink layer is heated until a boiling phenomenon occurs, and microbubbles 11 are scattered.

【0036】

FIG. 2C shows a state in which the adjacent ink layer rapidly heated on the entire surface of the heating element 9 vaporizes instantly to form a boiling film, and the bubbles 11 grow. At this time, the pressure in the ejection port rises by the amount of growth of the bubbles, the balance with the external pressure on the ejection port surface is lost, and the ink column 10'begins to grow from the ejection port.

【0037】

FIG. 2D shows a state in which the bubble 11 has grown to the maximum, and ink corresponding to the volume of the bubble is extruded from the discharge port surface. At this time, no current is flowing through the heating element 9, and the surface temperature of the heating element 9 is decreasing. The maximum value of the volume of the bubble 11 is slightly delayed from the timing of applying the electric pulse.

【0038】

FIG. 2 (E) shows a state in which the bubbles 11 are cooled by ink or the like and begin to shrink. At the tip of the ink column 10', the ink moves forward while maintaining the extruded speed, and at the rear end, the ink flows back from the ejection port surface into the ejection port due to the decrease in the pressure inside the ejection port due to the contraction of the bubbles, and the ink column 10' Constriction 10 has occurred.

【0039】

In FIG. 2F, the bubbles 11 are further contracted, the ink 10 is in contact with the surface of the heating element 9, and the surface of the heating element is cooled more rapidly. On the discharge port surface, the external pressure is higher than the internal pressure of the discharge port, so that the meniscus greatly enters the discharge port. The tip of the ink column becomes droplet 12, which flies in the direction of the recording paper at a speed of 8 to 13 m / sec.

【0040】

In Fig. 2 (G), the bubbles are completely extinguished in the process of refilling the ejection port with ink due to the capillary phenomenon and returning to the state of Fig. 2 (A).

【0041】

Unlike the head shown in FIG. 1, FIG. 3 shows a nozzle plate 20 separately provided at the tip of the flow path. FIG. 3 (A) shows the state before the nozzle plate 20 is attached, and FIG. 3 (B). Indicates the state after installation. In this case as well, the nozzle plate is formed on a resin (plastic) film by, for example, punching the nozzle 21 with an excimer laser, or by etching, electroforming, punching, or the like of metal. It is necessary to properly select the hardness as described later.

【0042】

The above is the general configuration and principle of a bubble jet type recording head using heat, but as described above, the present invention is not limited to this method, and is applicable to all inkjet recording methods. Is.

【0043】

The present invention uses a recording liquid (ink) used in such an inkjet recording method as a colorant for the recording liquid using a pigment having excellent water resistance and light resistance. However, when this pigment is used as a colorant for a recording liquid, the pigment is dispersed rather than dissolved in the liquid medium like a dye, so that the stability in the liquid medium is poor and the pigment is contained in the ink. There is a problem that the pigment is aggregated, settled, separated, and the nozzle portion is clogged. In particular, clogging of the nozzle portion is a fatal problem for the inkjet because the ink does not eject.

【0044】

In order to solve this problem, the present invention has earnestly studied the material constituting the ink, the composition of the nozzle portion, the pigment particle size used, the pigment content in the ink, and the like. In the present invention, pigment ink is considered as a premise. That is, the colorant in the recording liquid is not a dye dissolved in a solvent such as water, but fine particles as pigments dispersed therein.

【0045】

Further, as described above, the present invention uses a recording liquid (ink) used in the inkjet recording method as a pigment having excellent water resistance and light resistance as a colorant for the recording liquid. However, this pigment When used as a colorant in a recording liquid, the pigment is like abrasive grains dispersed in the liquid medium and damages or wears the ink path of the inkjet head when a large amount of ink is used. There is a problem of letting them do it. In particular, scratches and wear on the ejection port portion affect the ink droplet ejection performance, which is a problem.

【0046】

In order to solve this problem, the present invention has earnestly studied the hardness of the material constituting the ejection port portion, the ink flow rate, the pigment particle size of the nozzle portion, and the like.

【0047】

Examples of the black pigment ink preferably applied to the present invention include a black pigment having a neutral or basic pH, a salt of a tertiary amine, an acrylic acid ester monomer having a quaternary ammonium group, or an acrylamide monomer. Is dispersed using a water-soluble polymer containing at least a constituent component of the above, and inks of other hues, for example, inks of yellow, magenta, cyan, etc., are also subjected to carboxyl groups of pigments of these hues. Alternatively, the dispersion treatment is carried out using an anionic polymer dispersant having a sulfone group as a water-soluble group.

【0048】

The pH of the black pigment referred to here generally refers to the pH value of the solution when the pigment is dispersed in pure water, as used in the method for measuring the physical characteristics of carbon black. Further, when the recording material used for recording is plain paper, the interfacial tension of the black pigment ink is higher than the interfacial tension of the color ink in the interfacial tension of the ink with respect to the plain paper, and further, the plain paper. It is preferable that the penetration rate of the black pigment ink is slower than the penetration rate of the color ink.

【0049】

When color recording is performed on plain paper using the above inks, it is possible to obtain an image having good fixability, high density, and less border bleeding. Further, a clear projected image can be obtained even when recording is performed on a transparent material to be recorded. Needless to say, since it is a pigment ink, its resistance to light and water is extremely excellent as compared with the case where a conventional dye ink is used.

【0050】

The polymer dispersant used in the present invention is mainly obtained by polymerizing a vinyl monomer, and the cationic monomer constituting at least a part of the obtained polymer is a tertiary amine monomer as described below. Salts and quaternized compounds thereof.

【0051】

That is, N, N-dimethylaminoethyl methacrylate [CH2 = C (CH3) -COO-C2H4N (CH3) 2], N, N-dimethylaminoethyl acrylate [CH2 = CH-COO-C2H4N (CH3) 2], N , N-Dimethylaminopropyl methacrylate [CH2 = C (CH3) -COO-C3H6N (CH3) 2], N, N-dimethylaminopropyl acrylate [CH2 = CH-COO-C3H6N (CH3) 2], N, N- Dimethylacrylamide [CH2 = CH-CON (CH3) 2], N, N-dimethylmethacrylate [CH2 = C (CH3) -CON (CH3) 2], N, N-dimethylaminoethylacrylamide [CH2 = CH-CONHC2H4N] (CH3) 2], N, N-dimethylaminoethyl methacrylate [CH2 = C (CH3) -CONHC2H4N (CH3) 2], N, N-dimethylaminopropylacrylamide [CH2 = CH-CONH-C3H6N (CH3) 2] ], N, N-dimethylaminopropyl methacrylate [CH2 = C (CH3) -CONH-C3H6N (CH3) 2] and the like.

【0052】

In the case of a tertiary amine, examples of the compound forming a salt include hydrochloric acid, sulfuric acid, acetic acid and the like, and examples of the compound used for quaternization include methyl chloride, dimethyl sulfate, benzyl chloride, epichlorohydrin and the like. Can be mentioned. Among these, methyl chloride, dimethyl sulfate and the like are preferable for preparing a dispersant. The above-mentioned tertiary amine salt or quaternary ammonium compound behaves as a cation in water, and the acidity is a stable dissolution region under neutralized conditions. The content of these monomers in the copolymer is preferably in the range of 20 to 60% by weight.

【0053】

Other monomers used in the composition of the polymer dispersant include, for example, 2-hydroxyethyl methacrylate, an acrylate having a hydroxy group such as an acrylate having a long ethylene oxide chain in the side chain, and a styrene-based monomer. Examples of hydrophobic monomers such as acrylamide and water-soluble monomers that can be dissolved in water near pH 7 include acrylamides, vinyl ethers, vinyl pyrrolidones, vinyl pyridines, and vinyl oxazolines. As the hydrophobic monomer, hydrophobic monomers such as styrene, styrene derivative, vinylnaphthalene, vinylnaphthalene derivative, alkyl ester of (meth) acrylic acid, and acrylonitrile are used. In the polymer dispersant obtained by copolymerization, the water-soluble monomer is used in the range of 15 to 35% by weight in order to allow the copolymer to be stably present in the aqueous solution, and the hydrophobic monomer is the pigment of the copolymer. It is preferable to use it in the range of 20 to 40% by weight in order to enhance the dispersion effect on the material.

【0054】

The carbon black pigment (CI Pigment Black 7) used in the black ink of the present invention includes # 2600, # 2300, # 990, # 980, # 960, # 950, # 900, # 850, # 750, # 650. , MCF-88, MA-600, # 95, # 55, # 52, # 47, # 45, # 45L, # 44, # 40, # 33, # 32, # 30, # 25, # 20, # 10 , # 5 (above, manufactured by Mitsubishi Chemical), Printex95, Printex90, Printex85, Printex80, Printex75, Printex45, Printex40, PrintexP, Printex60, Printex300, Printex30, Printex35, Printex25, Printex200, PrintexA, PrintexG, PrintexL6, PrintexL (above, Degussa) , Raven850, Raven780ULTRA, Raven760ULTRA, Raven790ULTRA, Raven520, Raven500, Raven410, Raven420, Raven430, Raven450, Raven460, Raven890, Raven1020 (Made in Colombia), Regal 415R, Regal330R, Regal 250R, Regal 995R, Monarch800, Mon Examples include Monarch900, Monarch460, Monarch280, Monarch120 (above, made by Cabot).

【0055】

Pigments used in yellow ink include CI Pigment Yellow 1, CI Pigment Yellow 2, CI Pigment Yellow 3, CI Pigment Yellow 12, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 16, and CI Pigment Yellow 17 , CI Pigment Yellow 73, CI Pigment Yellow 74, CI Pigment Yellow 75, CI Pigment Yellow 83, CI Pigment Yellow 93, CI Pigment Yellow 95, CI Pigment Yellow 97, CI Pigment Yellow 98, CI Pigment Yellow 114, CI Pigment Yellow 128 , CI Pigment Yellow 129, CI Pigment Yellow 151, CI Pigment Yellow 154, etc.

【0056】

Pigments used in magenta ink include CI Pigment Red 5, CI Pigment Red 7, CI Pigment Red 12, CI Pigment Red 48 (Ca), CI Pigment Red 48 (Mn), CI Pigment Red 57 (Ca), CI. Pigment Red 57: 1, CI Pigment Red 112, CI Pigment Red 123, CI Pigment Red 168, CI Pigment Red 184, CI Pigment Red 202 and the like.

【0057】

Pigments used in cyan ink include CI Pigment Blue 1, CI Pigment Blue 2, CI Pigment Blue 3, CI Pigment Blue 15: 3, CI Pigment Blue 15:34, CI Pigment Blue 16, CI Pigment Blue 22, CI. Pigment Blue 60, CI Bat Blue 4, CI Bat Blue 60, etc.

【0058】

In addition to the above, when a neutral color other than the three primary colors such as red, green, and blue is required, it is preferable to use the following pigments alone or in combination. For example, CI Pigment Red 209, CI Pigment Red 122, CI Pigment Red 224, CI Pigment Red 177, CI Pigment Red 194, CI Pigment Orange 43, CI Bat Violet 3, CI Pigment Violet 19, CI Pigment Green 36, CI Pigment Green 7, CI Pigment Violet 23, CI Pigment Violet 37, CI Pigment Blue 15: 6, CI Pigment Blue 209, etc.

【0059】

Further, the dyes listed below may coexist in the color ink. Examples of dyes used for yellow ink include CI acid yellow 11, CI acid yellow 17, CI acid yellow 23, CI acid yellow 25, CI acid yellow 29, CI acid yellow 42, CI acid yellow 49, CI acid yellow 61. , CI Acid Yellow 71, CI Direct Yellow 12, CI Direct Yellow 24, CI Direct Yellow 26, CI Direct Yellow 44, CI Direct Yellow 86, CI Direct Yellow 87, CI Direct Yellow 98, CI Direct Yellow 100, CI Direct Yellow 130 , CI Direct Yellow 142 and the like.

【0060】

The dyes used in magenta ink are CI Acid Red 1, CI Acid Red 6, CI Acid Red 8, CI Acid Red 32, CI Acid Red 35, CI Acid Red 37, CI Acid Red 51, CI Acid Red 52, CI. Acid Red 80, CI Acid Red 85, CI Acid Red 87, CI Acid Red 92, CI Acid Red 94, CI Acid Red 115, CI Acid Red 180, CI Acid Red 254, CI Acid Red 256, CI Acid Red 289, CI Acid Red 315, CI Acid Red 317, CI Direct Red 1, CI Direct Red 4, CI Direct Red 13, CI Direct Red 17, CI Direct Red 23, CI Direct Red 28, CI Direct Red 31, CI Direct Red 62, CI Examples include Direct Red 79, CI Direct Red 81, CI Direct Red 83, CI Direct Red 89, CI Direct Red 227, CI Direct Red 240, CI Direct Red 242, and CI Direct Red 243.

【0061】

The dyes used for cyan ink are CI Acid Blue 9, CI Acid Blue 22, CI Acid Blue 40, CI Acid Blue 59, CI Acid Blue 93, CI Acid Blue 102, CI Acid Blue 104, CI Acid Blue 113, CI. Acid Blue 117, CI Acid Blue 120, CI Acid Blue 167, CI Acid Blue 229, CI Acid Blue 234, CI Acid Blue 254, CI Direct Blue 6, CI Direct Blue 22, CI Direct Blue 25, CI Direct Blue 71, CI Examples include Direct Blue 78, CI Direct Blue 86, CI Direct Blue 90, CI Direct Blue 106, and CI Direct Blue 199. However, even when these dyes coexist, the pigment particle size, the pigment content in the ink, and the like need to be within the range described later.

【0062】

In the present invention, when the pigment is dispersed by using the above-mentioned cationic water-soluble polymer as a dispersant, the pigment preferable from the viewpoint of physical properties is a pigment having an isoelectric point adjusted to 6 or more, or a pigment. A simple aqueous dispersion to be attached having a neutral or basic pH, for example, a pigment having a pH of 7 or more to 10 is preferable in terms of dispersibility. It is understood that this is because the ionic interaction force between the pigment and the cationic water-soluble polymer is strong.

【0063】

In order to obtain a fine particle aqueous dispersion of a pigment using the above materials, it is preferable to adopt the following method. (1) In the case of carbon black: Carbon black is premixed in a cation dispersant solution, then milled with a disperser having a high shear rate, diluted, and then centrifuged to remove coarse particles. .. The material for the desired ink formulation is then added and, in some cases, aged. After that, a centrifugation treatment is performed to finally obtain a pigment dispersion having a desired average particle size. The pH of the ink thus produced is preferably in the range of 3-9.

【0064】

(2) For pigments of other hues: Basically the same as carbon black except that an anionic dispersant is used. However, in the case of organic pigments for which it is difficult to reduce the particle size, a surfactant treatment is performed at the same time as the pigment synthesis or in the middle of the synthesis to suppress the crystal growth of the pigment particles and improve the wettability. It is desirable to use pigments. The pH of the ink thus produced is preferably in the range of 5 to 10. In the case of both the carbon black ink and the color ink, it is essential for the stability of the dispersion that the average particle size is in the range of 0.02 to 1 μm, and preferably in the range of 0.03 to 0.4 μm. This is an essential condition from the viewpoint of the stability of the dispersion, but from the viewpoint that it is essential for so-called inkjet, which ejects ink from a fine opening, when considering this average particle size, the eyes at the fine opening, that is, the ejection port Clogs need to be taken into account, which will be discussed later. The surface tension of good ink is in the range of 10 to 60 dyn / cm.

【0065】

When recording on plain paper using these inks, it is preferable that the black pigment ink has a high interfacial tension with the paper from the viewpoint of the sharpness of the recorded characters. On the other hand, the color ink preferably has a high penetration rate in order to reduce bleeding (color bleeding) due to mutual diffusion between the color inks, and therefore has a low interfacial tension with the paper. In this way, when the black ink is acidic and has a high interfacial tension and the color ink is basic and has a low interfacial tension, the tendency of the black ink to flow into the color ink side is reduced, and the black ink and the color ink Color bleed is virtually gone. The interfacial tension between the ink and the paper is measured by, for example, a commercially available device (a device using the Wilhelmy method, manufactured by WET-3000 Reska Co., Ltd.) as a dynamic wettability tester. The amount. High interfacial tension means that the contact angle with plain paper is 90 ° or more even in a short time of 1 second to several seconds, and low interfacial tension means 90 ° or less.

【0066】

The dispersant used in the color ink used in the present invention is an alkali-soluble water-soluble fat tree, and has a weight average molecular weight of 1,000 to 30,000, preferably in the range of 3,000 to 15,000. Specifically, hydrophobic monomers such as styrene, styrene derivative, vinylnaphthalene, vinylnaphthalene derivative, alkyl ester of acrylic acid, alkyl ester of methacrylic acid, α, β-ethylene unsaturated carboxylic acid and its aliphatic alcohol Copolymers composed of hydrophilic monomers such as esters, acrylic acids, methacrylic acids, maleic acids, itaconic acids, fumaric acids and derivatives thereof, and salts thereof. The copolymer may have any structure such as random, block, and graft, and the acid value is in the range of 100 to 430, preferably 130 to 360.

【0067】

As the dispersant used in the present invention, water-soluble polymers such as polyvinyl alcohol and carboxymethyl cellulose, water-soluble resins such as naphthalene sulfonic acid formaldehyde condensate and polystyrene sulfonic acid can also be used. However, the alkali-soluble water-soluble fat tree has an advantage that the viscosity of the dispersion can be reduced and the dispersion is easy. The amount of these dispersants used is experimentally determined using the selected pigment and the dispersant, but the amount of resin dissolved without adsorbing on the pigment is 4% by weight or less in the ink. Is preferable.

【0068】

A base is required to use the above dispersant in an aqueous system. Suitable bases for this purpose include ethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, N-ethyldiethanolamine, 2-amino-2-methylpropanol, 2-ethyl-2-amino-1,3-propane. Organic bases such as diol, 2- (2-aminoethyl) ethanolamine, tris (hydroxymethyl) aminomethane, ammonia, piperidine, morpholine, β-dihydroxyethylurea, sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. Inorganic bases can be mentioned. The optimum base type varies depending on the type of pigment and dispersant selected, but is preferably non-volatile, stable, and has high water retention. The amount of base used is basically an amount calculated from the acid value of the dispersant, and is used as the amount of base required to neutralize it. In some cases, an amount of base that exceeds the equivalent of the acid may be used. It is performed for the purpose of improving dispersibility, adjusting the pH of ink, adjusting the recording performance, improving the moisturizing property, and the like.

【0069】

The solvent used for the ink in the present invention is an organic solvent miscible with water. Organic solvents can be divided into three groups as follows. That is, the first group of solvents, which have high moisturizing properties, are hard to evaporate, and have excellent hydrophilicity, and the second group of solvents, which are organic and have good wettability to hydrophobic surfaces and also have evaporative drying properties, are moderately wetted. It is a third group solvent (monohydric alcohols) with properties and low viscosity.

【0070】

Solvents belonging to Group 1 include ethylene glycol, diethylene glycol, triethylene glycol, tripropylene glycol, glycerin, 1,2,4-butanediol, 1,2,6-hexanetriol, and 1,2,5-pentanetriol. , 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, dimethylsulfoxide, diacetone alcohol, glycerin monoallyl ether, propylene glycol, butylene glycol, polyethylene glycol 300, thiodiglycol, N- Methyl-2-pyrrolidone, 2-pyrrolidone, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, sulforan, trimethylolpropane, trimethylolethane, neopentyl glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether , Ethylene glycol monoisopropyl ether, ethylene glycol monoallyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, β-dihydroxyethyl Examples thereof include urea, urea, acetonyl acetone, hentaerythritol, and 1,4-cyclohexanediol.

【0071】

The solvents belonging to the second group include hexylene glycol, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol monophenyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, and tri. Ethylene glycol monobutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, glycerol monoacetate, glycerol diacetate, glycerol triacetate, ethylene glycol monomethyl et chromatography ether acetate, diethylene glycol monomethyl ether acetate, cyclohexanol, 1,2-cyclohexanediol, 1-butanol, 3-Methyl-1,5-pentanediol, 3-hexene-2,5-diol, 2,3-butanediol, 1,5-pentanediol, 2,4-pentanediol, 2,5-hexanediol, etc. Can be mentioned.

【0072】

Examples of the solvent belonging to the third group include ethanol, n-propanol, 2-propanol, 1-methoxy-2-propanol, furfuryl alcohol, tetrahydrofurfuryl alcohol and the like. The total amount of the water-soluble solvent as described above is preferably used in the range of about 5 to 40% by weight with respect to the entire ink.

【0073】

Surfactants, pH adjusters, preservatives and the like can be added to each of the water-based pigment inks constituting the ink of the present invention. Surfactants are useful for preparing highly permeable color inks, heating heaters in the bubble jet method, and adjusting the wettability to the surface of the ejection nozzle. The material can be appropriately selected from existing commercially available products. Summarizing the physical characteristics of each ink composed of the above materials, black ink has a high surface tension (approximately 30 to 60 dyn / cm), while color ink has a low surface tension (approximately 10 to 40 dyn / cm). It is preferable to have cm).

【0074】

When color recording is performed on plain paper using the black water-based pigment ink and the color ink of the present invention as described above, black characters and the like are clear, and images and graphs and black characters are adjacent to each other. However, there is no mutual bleeding and each is clear.

【0075】

When the color ink of the present invention is used, any of general plain paper (for example, high-quality paper, medium-quality paper, bond paper, etc.), coated paper, plastic film for OHP, etc. should be used as the recording material. Can be done. As described above, the present invention can be applied to all inkjet recording methods, but is particularly suitable when used in an inkjet recording method of a type in which ink is ejected by a foaming phenomenon of ink due to thermal energy, and ink ejection is performed. Is extremely stable and does not generate satellite dots. However, in this case, it may be necessary to adjust thermal properties such as specific gravity, coefficient of thermal expansion, and thermal conductivity.

【0076】

Next, more characteristic points of the present invention will be described. As described above, the present invention relates to a so-called inkjet recording method in which ink is ejected from a fine opening, and clogging at the ejection port portion is fatal to the inkjet recording method. This is because, as in the present invention, in the case of using a pigment ink in which fine particles are dispersed in a solvent, the pigment is not dissolved like a dye but is only dispersed, as in the case of using a dye ink. Therefore, clogging is more likely to occur. Further, in the present invention, an unprecedented fine discharge diameter, for example, a discharge diameter of Φ25 μm or less (500 μm in terms of area)²This clogging is a very serious problem, as it assumes an inkjet recording head that is less than (less than).

【0077】

By the way, clogging is derived from the principle of the inkjet recording method itself, in which ink is ejected from a fine opening. That is, it occurs because the opening is fine. Therefore, there is a close relationship between the size of the opening and the size of the pigment, which can be said to be a foreign substance in the ink.

【0078】

In view of this point, the present invention focuses on the size of the discharge port and the size of the pigment particles, and finds the relationship between the difficulty of clogging and the relationship between them. Specifically, inks having different pigment particle sizes are mixed, an inkjet recording head whose ejection port size is known is used, ink is ejected for a certain period of time, left for a certain period of time, and ink injection is restarted. The presence or absence of clogging of the discharge port was examined. In that case, not only complete clogging of the discharge port, but also partial clogging and the preceding signs (slight clogging) leading to it were considered as clogging and tested.

【0079】

The head used is an inkjet recording type head that uses thermal energy having the configuration shown in FIG. However, the head shown in FIG. 1 shows that the tip of the flow path is the discharge port as it is, but the one used in the experiment has the arrangement density of the flow path at this tip as shown in FIG. A nozzle plate 20 having nozzles 21 formed with the same array density as 4 is provided (FIG. 3 (A) is a perspective view before the nozzle plate 20 is attached, and FIG. 3 (B) is a perspective view after the nozzle plate 20 is attached. Is). Also, regarding the number of discharge ports (nozzles), those shown in FIGS. 1 and 3 have only four discharge ports for the sake of simplicity, or are partially shown, but they are actually shown. The number of discharge ports used was 128, and the arrangement density was 400 dpi. The size of the heating element was 22 μm × 90 μm, its resistance value was 110 Ω, the drive voltage for ink injection was 24 V, the drive pulse width was 6.5 μs, and the drive frequency was 12 kHz. Recording heads were prepared from H1 to H4 (each discharge port diameter was set to H1 = Φ25 μm, H2 = Φ20 μm, H3 = Φ15 μm, H4 = Φ10 μm). The thickness of the nozzle plate was 40 μm.

【0080】

The inks used were based on the following composition and manufacturing method, but those with pigment particle sizes changed to 0.005 to 1 μm were prepared and tested in combination with H1 to H4 having different ejection diameters. The conditions for leaving the ink after spraying ink for a certain period of time are 10 hours in an atmosphere with a temperature of 40 ° C and a humidity of 30%.

【0081】

The ink manufacturing method is shown below. Using an aqueous solution of a copolymer P consisting of styrene / methacrylic acid / butyl acrylate with an acid value of 325, a weight average molecular weight of 11,000, and a glass transition temperature of 84 ° C dissolved in potassium, the following carbon black dispersions D1 to D10 Was produced. 40 parts of copolymer P aqueous solution (solid content 20% by weight) Carbon black MCF-88 (manufactured by Mitsubishi Chemical Corporation) 24 copies 20 parts of diethylene glycol 10 parts of isopropyl alcohol 130 copies of water [0082]

These materials were charged into a batch type vertical sand mill (manufactured by IMEX), filled with glass beads having a diameter of 1 mm as a medium, and dispersed for 3 hours while being water-cooled. A crude dispersion having a viscosity of 17 cP and pH = 9.6 was obtained after the dispersion. The dispersion was centrifuged to remove coarse particles, and the average particle size of the pigment was changed to 0.005 to 1 μm by changing the centrifugation conditions to obtain dispersions D1 to D17. These dispersions were diluted with water to obtain black basic inkjet inks B1 to B17 having a viscosity of 2.5 cP, a surface tension of 45 dyn / cm, and a pH of 9.5. The solid content of the final preparation was about 7% by weight. The final pigment content in these inks is 5% by weight. The average particle size was measured with a particle size distribution measuring device ELS-800 (manufactured by Otsuka Electronics Co., Ltd.) by a dynamic light scattering method, and the average amount was shown as a value obtained from the initial gradient of the autocorrelation function.

【0083】

Tables 1 to 4 show the results of investigating the occurrence of clogging by combining these inks B1 to B17 and the heads H1 to H4 having different discharge diameters. However, Table 1 shows the case of head H1 (discharge diameter Do = Φ25 μm). Table 2 shows the case of head H2 (discharge diameter Do = Φ20 μm). Table 3 shows the case of head H3 (discharge diameter Do = Φ15 μm). Table 4 shows the case of head H4 (discharge diameter Do = Φ10 μm). Is shown.

【0084】

[table 1]

<img file="JP2000211124A_D0001.tif" />【0085】

[Table 2]

<img file="JP2000211124A_D0002.tif" />【0086】

[Table 3]

<img file="JP2000211124A_D0003.tif" />【0087】

[Table 4]

<img file="JP2000211124A_D0004.tif" />【0088】

From the above results, it can be seen that stable ink ejection without clogging can be obtained by satisfying the relationship of 0.001 Dp / Do 0.01 between the pigment particle size Dp and the discharge diameter Do. In the experiment, the discharge port is round, but in the case of other shapes (polygons), it may be within the range converted by the area ratio.

【0089】

Next, other features of the present invention will be described. As described above, the present invention is based on the premise of pigment ink. That is, the colorant in the recording liquid is not a dye dissolved in a solvent such as water, but fine particles as pigments dispersed therein. Therefore, the pigment content and the content of the pigment dispersant containing the solid content in the ink have a great influence on clogging. Therefore, here, the relationship between their content and clogging of the discharge port was investigated.

【0090】

The head used is the same as the head H2 (discharge port diameter Do = Φ20 μm), and in the ink (B4) having a pigment particle size Dp = 0.03 μm, its pigment content and styrene / methacrylic acid / as a pigment dispersant / By changing the amount of the copolymer P composed of butyl acrylate, the amount of solid content in the final ink and the susceptibility to clogging were examined. The clogging test method and the like are the same as the above-mentioned method. The results are shown in Table 5.

【0091】

[Table 5]

<img file="JP2000211124A_D0005.tif" />【0092】

From the above results, it can be seen that the pigment content in the ink may be set to 1 to 10% by weight, and if it is higher than that, clogging occurs. It is also found that not only the pigment content but also the final solid content including the pigment must be 15% by weight or less. When the pigment content is 1% by weight, there is no concern about clogging, but when this ink is used alone, the concentration is low and it is not practical. However, it can be suitably used as a light ink of a recording device that uses a plurality of types of so-called light and light inks. Moreover, even when this ink is used alone, it is possible to add a dye to make up for the insufficient concentration.

【0093】

Next, further other features of the present invention will be described. Since the inkjet recording head to which the present invention is applied is generally preferably applied to color recording, the configuration of the color inkjet recording head to which the present invention is preferably applied will be described here.

【0094】

FIG. 4 is a diagram showing an example of the inkjet head of the present invention. In the present invention, as shown in the drawing, a plurality of colors of ink ejection elements 31Y, 31M, 31C are placed on one common heating element substrate portion 30. Is formed. In this example, three colors of yellow (Y), magenta (M), and cyan (C) are shown as multi-color inks. In this example and subsequent examples, the ink ejection elements and ejection ports of each color will be described with 4 or 5 ink ejection ports for each color for the sake of simplicity, but in reality, 64 to 512 ink ejection ports for each color are used. It is preferably used.

【0095】

FIG. 5 shows a diagram in which the recording head portion of FIG. 4 is provided with an ink tank portion 40 for supplying inks of Y, M, and C, respectively. It should be noted that this figure is a diagram showing the concept of the inkjet recording head of the present invention composed of the recording head portion and the ink tank portion, and is different from the actual one (described later).

【0096】

FIG. 6 is a diagram showing a configuration of a so-called serial printer in which an inkjet head according to the present invention is mounted on a carriage for recording. In the figure, 50 is an inkjet head according to the present invention, 51 is a recording paper, and 52 is a carriage. 53 is the guide rod of the carriage, 54 is the screw rod for moving the carriage, 55 is the chart paper transport roller, 56 is the chart paper holding roller, and as is well known, Y in the vertical direction (movement direction of the chart paper 51). , M, C and the recording heads 50 arranged in a row (in the case of the illustrated example, the head shown in FIG. 5 is mounted) are recorded while reciprocating in the X direction in front of the recording paper 51. .. In the present invention, the recording paper is moved in the direction of the arrow Y in the figure each time the carriage is scanned once. Therefore, the area recorded in one scan is only the discharge element of the head, that is, the length of the row of discharge ports. In addition, since Y, M, and C are lined up in a row in the vertical direction, full-color recording can be performed for the first time when the printing areas of Y, M, and C ink overlap with each other by scanning two or more times. Can be done.

【0097】

Although the above description shows an example of three colors of Y, M, and C, the present invention also applies to an inkjet having a four-color ejection port row in which black (B) is added. An example thereof is shown in FIG. 7. In this case, as shown in the figure, an ink ejection element 31B for black is further added to the example shown in FIG.

【0098】

FIG. 8 is another example with a four-color outlet row. FIG. 4 shows an example in which the ink flow paths of each color are independently manufactured, and this figure is an example in which the flow paths for four colors are integrally manufactured by molding plastic 60. By doing so, the assembly cost can be significantly reduced.

【0099】

Usually, in a color inkjet recording device, one recording head as shown in FIG. 1 is filled with one color of ink, and the ink is arranged for a plurality of colors on a carriage 70 as shown in FIG. The 71B, 71C, 71M, and 71Y are recording heads for ejecting black, cyan, magenta, and yellow color inks, respectively. This is partly to ensure reliability such as measures against clogging. For example, when the heads 71B, 71C, 71M, 71Y filled with four colors of ink are arranged independently on the carriage 70 as shown in FIG. 5, if one of the heads of one color is clogged, that is the case. It can be restored to its original state by replacing the one-color head.

【0100】

On the other hand, in the present invention, the recording heads shown in FIGS. 4 to 8 for ejecting ink to a plurality of colors are integrally formed. As mentioned above, considering the recovery measures in case of clogging, as shown in FIG. 9, it is advantageous to configure the heads filled with inks of multiple colors independently on the carriage, but this book In the present invention, as described above, the pigment particle size, the content rate, or the amount of the solid content in the ink is carefully examined and optimized, so that the anxiety of clogging is eliminated. Therefore, it is not necessary to independently arrange heads filled with inks of multiple colors on the carriage as shown in FIG. 5, reducing assembly cost, realizing compactness, and improving the accuracy of dot positions of multiple colors. Therefore, as shown in FIGS. 4 to 8, a recording head for ejecting inks of a plurality of colors is integrally formed.

【0101】

The integral formation referred to here is not only an example in which the heating element substrate is a common single substrate as in the example of the bubble jet head shown in FIGS. 4 to 8, but also as shown in FIG. It also includes heads filled with inks of a plurality of colors, for example, those in which 71B, 71C, 71M, 71Y are laminated and integrated. In this example, an example in which one nozzle plate 73 common to the tips 72B, 72C, 72M, 72Y of the flow path is provided (FIG. 10 (A) shows FIG. 10 (B) before the nozzle plate 73 is attached. ) Is a perspective view after installation), in this case, since a common nozzle plate 73 that is perforated, assembled, and integrated with high precision is provided, not only the manufacturing cost is reduced, but also multiple colors are provided. High accuracy can be obtained for the dot position accuracy of.

【0102】

FIG. 11 shows an example in which a head unit capable of injecting ink of a plurality of colors (three colors of Y, M, and C in this example) is integrally formed with the ink container portion, and FIG. 11 (A) is an overall perspective view. , Fig. 11 (B) is an exploded perspective view. In the figure, 100 is the head unit, 101 is the head chip, 102 is the print circuit, 103 is the top lid, 104 is the ink container, and 105 (105Y, 105M, 105C) is Steres. Mesh filter, 106 (106Y, 106M, 106C) is a foam material containing ink, 107 is a bottom lid, in this example, the head part and the ink container part connecting to it are internally divided into three parts, Y, M, It is filled with C ink separately. In this way, the head unit that integrates multiple colors can be formed very compactly, so when it is mounted on the carriage, it is lightweight and compact, so a small carriage is sufficient, and the motor that drives the carriage is also small. Energy saving can be realized.

【0103】

FIG. 12 is a diagram for explaining an example in the case where only the ink container portion is separable in the head unit integrated with ink containers of a plurality of colors shown in FIG. 11, and FIG. 12 (A) is a diagram for explaining a case where only the ink container portion can be separated. The overall perspective view of 110, FIG. 12B, shows a perspective view of the head unit 110 in a state where the recording head portion 111 and the ink container portion 112 are separated. As a result, even if a large amount of ink is consumed in the color image printing, only the ink container portion 112 needs to be replaced, so that the cost can be reduced. Moreover, the advantages of the color integrated head described in FIG. 11 are maintained as they are.

【0104】

FIG. 13 is a diagram for explaining an example in which the ink container portion can be separated for each ink color in the integrated head unit as described above, and FIG. 13 (A) is an overall perspective view and FIG. 13 (A). B) shows a perspective view of the head unit 110 in a state where the recording head portion 111 and the ink container portion 112 (112Y, 112M, 112C) of each color are separated. The merit of doing this is that in color image printing, Y, M, and C inks are not always consumed at the same speed, so if any of the inks in the examples of FIGS. 11 and 12 is used. Even if other ink remains when the ink is exhausted, the head unit or the entire integrated ink container must be replaced, which is disadvantageous in terms of running cost, whereas the ink of each color as in the present invention. By keeping the containers separate, the running cost can be further reduced by replacing only the ink container that is gone.

【0105】

As described above, clogging is derived from the principle of the inkjet recording method itself, in which ink is ejected from a fine opening. That is, it occurs because the opening is fine. Therefore, there is a close relationship between each dimension, shape, and property of the opening, that is, the ejection port, and the size of the pigment, which can be said to be a foreign substance in the ink.

【0106】

In view of this point, the present invention focuses on each dimension, shape, property and size of pigment particles of the discharge port, and finds the difficulty of clogging and their relationship. Specifically, inks with different pigment particle sizes are mixed, and an inkjet recording head whose dimensions, shapes, and properties are known is used to eject ink for a certain period of time, and then leave it for a certain period of time to eject the ink. It was restarted and checked for clogging of the discharge port. In that case, not only complete clogging of the discharge port, but also partial clogging and the preceding signs (slight clogging) leading to it were considered as clogging and tested.

【0107】

The head used is an inkjet recording type head that uses thermal energy having the configuration shown in FIG. However, the head shown in Fig. 1 shows that the tip of the flow path is the discharge port as it is, but the one used in the experiment has the arrangement density of the flow path at this tip as shown in Fig. 3. A nozzle plate 20 having nozzles 21 formed with the same array density is provided. Also, regarding the number of discharge ports (nozzles), those shown in Fig. 1 and Fig. 3 have only four discharge ports for the sake of simplicity, but the one actually used was the discharge port. The number is 128, and the array density is 400 dpi. The size of the heating element was 22 μm × 90 μm, its resistance value was 110 Ω, the drive voltage for ink injection was 24 V, the drive pulse width was 6.5 μs, and the drive frequency was 12 kHz. The recording head has a discharge port diameter of Φ25 μm, and three types of heads (H1 to H3) with different thicknesses of the discharge port (distance of the depth of the discharge port) are prepared (each thickness of the discharge port). T = 40 μm (H1), 50 μm (H2), 60 μm (H3)).

【0108】

The inks used were based on the following composition and manufacturing method, but those with pigment particle sizes changed to 0.005 to 4 μm were prepared and tested in combination with heads H1 to H3 having different ejection diameters. The conditions for leaving the ink after spraying ink for a certain period of time are 10 hours in an atmosphere with a temperature of 40 ° C and a humidity of 30%.

【0109】

The ink manufacturing method is shown below. Anthraquinone pigment Pigment Red-177 using an aqueous solution of copolymer P consisting of styrene / acrylic acid / ethyl acrylate with an acid value of 290, a weight average molecular weight of 5,000, and a glass transition temperature of 77 ° C dissolved in monoethanolamine. Dispersions D1 to D20 were prepared. 40 parts of copolymer P aqueous solution (solid content 15% by weight) Pigment Red-177 (Kromoftal Red A2B, Made by Ciba Geigy) 24 copies 20 parts of diethylene glycol 10 parts of isopropyl alcohol 130 copies of water [0110]

These materials were charged into a batch type vertical sand mill (manufactured by IMEX), filled with glass beads having a diameter of 1 mm as a medium, and dispersed for 3 hours while being water-cooled. A crude dispersion having a viscosity of 30 cP and pH = 9.8 was obtained after the dispersion. The dispersion was centrifuged to remove coarse particles, and the average particle size of the pigment was changed to 0.005 to 4 μm by changing the centrifugation conditions to obtain dispersions D1 to D20. These dispersions are diluted with water, diethylene glycol, ethylene glycol monobutyl ether (60:25:15 weight ratio), and red basic inkjet inks R1 to R20 with a viscosity of 3 cP, a surface tension of 40 dyn / cm, and a pH of 9.5 are applied. Obtained. The solid content of the final preparation was about 7.5% by weight. The final pigment content in these inks is 5% by weight.

【0111】

The average particle size was measured with a particle size distribution measuring device ELS-800 (manufactured by Otsuka Electronics Co., Ltd.) by a dynamic light scattering method, and the average amount was shown as a value obtained from the initial gradient of the autocorrelation function. Tables 6 to 8 show the results of investigating the occurrence of clogging by combining these inks R1 to R20 and the heads with different thicknesses of the discharge port (distance of the depth of the discharge port). ..

【0112】

[Table 6]

<img file="JP2000211124A_D0006.tif" />【0113】

[Table 7]

<img file="JP2000211124A_D0007.tif" />【0114】

[Table 8]

<img file="JP2000211124A_D0008.tif" />【0115】

From the above results, if the relationship between the pigment particle size Dp and the distance (nozzle thickness) t of the depth portion of the ejection port satisfies the relationship of Dp / t 0.01, stable ink injection without clogging can be obtained. It turns out that it can be done. Depending on the configuration of the head, the flow path and the discharge port (nozzle) may be continuously connected, but the distance (nozzle thickness) t of the depth portion of the discharge port as referred to in the present invention. Means the distance and thickness of the parts that substantially constitute the nozzle.

【0116】

Next, other features of the present invention will be described. As described above, the colorant in the recording liquid of the present invention is not a dye dissolved in a desolving medium such as water, but fine particles which are pigments are dispersed. According to the above results, even with such so-called pigment ink, clogging does not occur if the relationship between the pigment particle size and the distance (nozzle thickness) of the depth portion of the ejection port is within a certain range. As I found, in order to eject ink droplets using such pigment ink, not only clogging but also stable ejection and thereby ink droplets on the recording object such as paper with high accuracy at the target position. Need to adhere to.

【0117】

Here, the relationship between the distance (nozzle thickness) t of the depth portion of the discharge port, which is often related to clogging, and the distance L from the discharge port surface to the recording object such as paper was investigated. The heads used were the above-mentioned H1 to H3 heads, the discharge port diameter was Φ25 μm, the number was 128, and the arrangement density was 400 dpi. The size of the heating element is 22 μm × 90 μm, its resistance value is 110 Ω, the drive voltage of ink injection is 24 V, the drive pulse width is 6.5 μs, and the drive frequency is 12 kHz.

【0118】

The ink used was the above-mentioned red basic inkjet head ink R5, and Mitsubishi Paper Mills Matte Coat NM was used as the recording object, and the printing experiment was performed by changing the distance from the head ejection port surface to the recording object. By evaluating the pixel position accuracy on the object to be recorded, it was evaluated whether high-quality recording (high dot position accuracy) could be obtained. It should be noted that, in the case of a head having a small ejection port and using pigment ink as in the present invention, which is harder to eject than before, it is considered that the action of gravity also has an effect in order to find even a little better condition, and it is vertical. Two types of injection directions were evaluated, one in which ink droplets were ejected in a direction substantially perpendicular to the direction and the other in which ink droplets were ejected in a substantially vertical direction. The results are shown in Table 9.

【0119】

[Table 9]

<img file="JP2000211124A_D0009.tif" />【0120】

In Table 9, indicates that the deviation from the target dot position is within 1/4 dot, and indicates that the deviation from the target dot position is 1/4 dot or more and within 1/2 dot. In the case, x is a case where the deviation from the target dot position is 1/2 dot or more. The size of one dot is about Φ60 μm.

【0121】

From the above results, the distance from the ejection port to the surface to be recorded is set to 100 tons or less even for a head having a small ejection port and using pigment ink as in the present invention, which is more difficult to eject than before. As a result, it can be seen that stable injection can be performed, highly accurate dot position accuracy can be obtained, and high-quality recording can be realized. In particular, it can be seen that the effect is increased by setting the injection direction to the vertical direction and using the gravitational action.

【0122】

It should be noted that the present invention is not necessarily limited to being completely vertical, and it is said that it is more effective if the action of gravity is used. Therefore, when the present invention is actually used, even if the injection direction cannot be completely vertical due to the configuration restrictions of the printer, the injection direction should be directed downward so that the gravitational action can be used as much as possible. It should be.

【0123】

Next, more characteristic points of the present invention will be described. As described above, the present invention relates to a so-called inkjet head recording method in which ink is ejected from a fine opening, and damage and abrasion of the ejection port portion caused by the pigment contained in the ink affect the ink droplet ejection performance. It was done to solve it in order to exert.

【0124】

In particular, in recent years, the image quality and definition of inkjet recording have been improved, and the discharge port (nozzle) of the head used has conventionally been Φ33 μm to Φ34 μm (900 μm in terms of area).²From Φ50 μm to Φ51 μm (2000 μm in terms of area)²Generally, it is a finer discharge port (for example, Φ25 μm or less, 500 μm in area).²Less than) has been required.

【0125】

At that time, if the discharge port diameter is relatively large as in the past, even if there is some damage or wear, the original discharge port is large, so the ratio of damage or wear to the size is almost negligible. This does not affect the ink droplet ejection performance (jet stability, ink mass uniformity, etc.) and does not pose a problem. However, a finer discharge port (for example, Φ25 μm or less, 500 μm in area)²If it is less than), even if there is slight damage or wear, the ratio of damage and wear to the size cannot be ignored because it is a fine ejection port, and ink droplet ejection performance (stable injection). It will affect the property, ink mass uniformity, etc.).

【0126】

By the way, it is considered that such damage and wear of the discharge port portion can be avoided by appropriately selecting the hardness of the material constituting the discharge port portion. Focusing on this point, the present invention has experimentally investigated the relationship between hardness, damage, and wear of various materials. Specifically, with the head as shown in FIG. 3, whether or not the nozzle plate is formed by changing the material and the ink is ejected for a certain period of time causes damage or wear to the ejection port, and whether ink is used. This is an investigation of whether or not the drop ejection performance deteriorates. The head used is an inkjet recording type head that uses the thermal energy of the configuration shown in Fig. 3, but the one shown in Fig. 3 shows only four outlets for the sake of simplicity. Absent. The number of discharge ports actually used was 128, and the arrangement density was 400 dpi.

【0127】

The size of the heating element was 22 μm × 90 μm, its resistance value was 110 Ω, the drive voltage for ink injection was 24 V, the drive pulse width was 6.5 μs, and the drive frequency was 12 kHz. For the discharge port portion (nozzle portion), a head with a different nozzle plate made of various resin materials or metal materials was prepared and tested. The discharge diameters of Φ25 μm (H1) and Φ20 μm (H2) were prepared.

【0128】

As a comparative reference example, a discharge diameter of Φ50 μm (reference head) was also prepared. In this case, the number of discharge ports is 48, and the arrangement density is 180 dpi. The size of this heating element was 40 μm × 180 μm, its resistance value was 120 Ω, the drive voltage for ink injection was 30 V, the drive pulse width was 7 μs, and the drive frequency was 1.8 kHz. The thickness of all nozzle plates was 40 μm. The hardness of various materials was evaluated by Rockwell hardness, but the actual hardness measurement was not performed with the nozzle plate, but the test piece was made with the same material as the material forming the nozzle plate. It was measured by

【0129】

The material on which the nozzle plate is formed is shown in Table 10 together with the hardness. The hardness was mainly shown on the Rockwell M scale, but some metallic materials were shown on the B scale (the B scale applies to those that are harder than those displayed on the M scale).

【0130】

[Table 10]

<img file="JP2000211124A_D0010.tif" />【0131】

The ink used is based on the following composition and manufacturing method, but prepare inks with pigment particle sizes changed to 0.02 to 1 μm, and combine them with heads with different discharge diameters and heads with different discharge port materials. Tested.

【0132】

The ink manufacturing method is described below. Pigment Red 122 dispersions D1 to D10 using an aqueous solution of copolymer P consisting of styrene / acrylate / butyl acrylate with an acid value of 265, a weight average molecular weight of 8,000, and a glass transition temperature of 67 ° C dissolved in ethanolamine. It was created. 40 parts of copolymer P aqueous solution (solid content 15% by weight) Pigment Red 122 (First Gen Suhar Magenta RT, Dainippon Ink) 24 copies 20 parts of diethylene glycol 10 parts of isopropyl alcohol 130 copies of water [0133]

These materials were charged into a batch type vertical sand mill (manufactured by IMEX), filled with glass beads having a diameter of 1 mm as a medium, and dispersed for 3 hours while being water-cooled. A crude dispersion having a viscosity of 18 cp and pH = 9.5 was obtained after the dispersion. The dispersion was centrifuged to remove coarse particles, and the average particle size of the pigment was changed to 0.02 to 1 μm by changing the centrifugation conditions to obtain dispersions D1 to D7. This microdisperse is diluted with water, diethylene glycol and ethylene glycol monobutyl ether (60:30:10 weight ratio), and has a viscosity of 3.3 cps, a surface tension of 35 dyne / cm, and a pH of 9.3 for magenta color basic inkjet ink M1. I got ~ M7. The solid content of the final preparation was about 7.5% by weight. The final pigment content in these inks is 5% by weight. The average particle size was measured with a particle size distribution measuring device ELS-800 (manufactured by Otsuka Electronics Co., Ltd.) by a dynamic light scattering method, and the average amount was shown as a value obtained from the initial gradient of the autocorrelation function.

【0134】

In combination with these inks M1 to M7 and the above-mentioned heads having different ejection diameters and heads having different materials for the ejection ports, 5 × 10 per ejection port.⁸Ink droplets were ejected from all 128 nozzles so that they became droplets. Tables 11, 12, and 13 show the results of investigating whether or not the ejection port is damaged or worn immediately after the start and after the ejection, and as a result, the ink droplet ejection performance is deteriorated. .. In the table, indicates that the ejection port was not damaged or worn, and the ink droplet ejection performance was not deteriorated. indicates that the ejection port was damaged or worn, but the ink droplet ejection performance was not deteriorated. No deterioration occurred, and x indicates that the ejection port was damaged or worn, and the ink droplet ejection performance was deteriorated.

【0135】

[Table 11]

<img file="JP2000211124A_D0011.tif" />【0136】

[Table 12]

<img file="JP2000211124A_D0012.tif" />【0137】

[Table 13]

<img file="JP2000211124A_D0013.tif" />【0138】

From the above results, it can be seen that, in the case of a head having a large discharge port as in the comparative reference example, even if the discharge port portion is slightly damaged or worn, the discharge performance is not deteriorated. On the other hand, when the ejection port diameter targeted by the present invention is very fine such as Φ25 μm or less, if the ejection port portion is damaged or worn, the ink droplet ejection performance deteriorates, so that stable ink droplet ejection can be performed. It can be seen that in order to do so, conditions must be selected so that the discharge port portion is not damaged or worn. The present invention is preferably applied even when the shape of the discharge port is not a circle but a rectangle, a trapezoid, or the like. In that case, Φ25 μm or less is equivalent to the area and is about 500 μm.²Less than, and the present invention has an area of about 500 μm even if it has a shape other than a circle.²Applies to those with outlets that are less than.

【0139】

Specifically, as can be seen from Tables 11 and 12, the resin material forming the discharge port portion may be a material (S3 to S11) of 65 to 120 on the Rockwell M scale. Further, an ink having a pigment particle size in the range of 0.02 μm to 0.2 μm may be used. Even if the Rockwell M scale is less than 65 as in Samples S1 and S2, if ink with a pigment particle size of 0.02 μm is used, the ink droplet ejection performance will not deteriorate, but the inks that can be used are very limited. Therefore, it is not very practical.

【0140】

Although all of the above description has been described with the example of bubble jet, the present invention is not limited to this, and is applied to all inkjets having a fine ejection port and using pigment ink. .. Further, although the recording head example is also described by giving an example of a single color ink, it goes without saying that it can also be applied to a color inkjet.

【0141】

[Effect of the invention]

Effect corresponding to claim 1: In a liquid injection recording device in which a pigment which is fine particles is dispersed as a coloring material to make a recording liquid, the fine particle diameter is optimized for the discharge port diameter, so that there is no conventional case where the diameter is Φ25 μm or less. By using a very fine discharge port, high-precision printing is realized, high water resistance and high light resistance are realized, and the discharge port is not clogged and reliability is improved.

【0142】

Effect corresponding to claim 2: Since the relationship between the ejection port diameter and the fine particle diameter shown in claim 1 is applied to the liquid injection recording device using color ink, the ejection port is clogged even if various color pigments are used. It was possible to realize high-definition color printing, which was not possible in the past, and to achieve high water resistance and high light resistance.

【0143】

Effect corresponding to claim 3: In a liquid injection recording apparatus in which a pigment which is fine particles is dispersed as a coloring material to obtain a recording liquid, the content of fine particles and the amount of solids in the recording liquid have been optimized, and thus it is practically used. Sufficient concentration was obtained, the pigment was stably dispersed, high water resistance and high light resistance were realized, and clogging of the discharge port was eliminated, improving reliability.

【0144】

Effect corresponding to claim 4: Since the content of fine particles in the recording liquid and the amount of solids are optimized, the color pigments in the recording liquid are stably dispersed even when various color pigments are used, and the discharge port It was possible to realize high-definition color imprinting without clogging, which was not possible in the past, and to achieve high water resistance and high light resistance.

【0145】

Effect corresponding to claim 5: In a liquid injection recording device that disperses a pigment that is fine particles as a coloring material to make a recording liquid, the distance of the depth portion of the discharge port and the diameter of the fine particles are optimized, so that the size is Φ25 μm or less. By using a very fine discharge port, which has never been seen before, high-definition printing is realized, high water resistance and high light resistance are realized, and the discharge port is not clogged and reliability is improved.

【0146】

Effect corresponding to claim 6: In a liquid injection recording device that disperses a pigment that is fine particles as a coloring material to make a recording liquid, the structure is such that ink droplets can be easily ejected, so that the ejection port is not clogged. Stable injection and high-quality recording were achieved.

【0147】

Effect corresponding to claim 7: In a liquid injection recording device in which a pigment which is fine particles is dispersed as a coloring material to obtain a recording liquid, when the discharge port portion is formed of resin, the hardness of the resin is optimized. , Damage and wear of the ejection port are eliminated, ink droplet ejection performance is not deteriorated, and stable high-quality recording can be obtained.

【0148】

According to the invention of claim 7, by optimizing the hardness of the resin, damage and wear of the ejection port portion are eliminated, ink droplet injection performance is not deteriorated, and stable high-quality recording can be obtained. However, as in the conventional case, when the discharge port diameter is relatively large, the hardness of the resin is not optimized as in the present invention, and even if the discharge port portion is slightly damaged or worn, the discharge port diameter is not optimized. Since the ratio of damage and wear to is small, it is unlikely that the ink droplet ejection performance will deteriorate.

【0149】

However, when a very fine discharge port having a discharge port diameter of Φ25 μm or less, which is the object of the present invention, is used, the hardness of the resin is not optimized and the discharge port portion is not optimized. If the damage and wear are left unattended, the ratio of the damage and wear to the fine ejection diameter is large, so that the ink droplet ejection performance is significantly deteriorated, which causes a problem. As is clear from the above description, the present invention is particularly effective when a very fine discharge port having a discharge port diameter of Ф25 μm or less, which has never existed in the past, is used.

【0150】

Effect corresponding to claim 8: In a liquid injection recording device in which a pigment which is fine particles is dispersed as a coloring material to obtain a recording liquid, the fine particle diameter is optimized, so that even when the discharge port portion is formed of resin, In addition to obtaining stable ink droplet injection, there was no damage or wear on the ejection port, no deterioration in ink droplet injection performance was achieved, and stable high-quality recording could be obtained over a long period of time.

【0151】

Effect corresponding to claim 9. By forming a head unit in which a plurality of recording heads for discharging a plurality of color recording liquids are integrally formed, the entire color liquid injection recording device can be miniaturized and a plurality of colors can be used. Since the integrated head unit can be formed very compactly, it is lightweight and compact when mounted on the carriage, so that a small carriage is required, and the motor that drives the carriage is also compact and energy saving can be realized.

【0152】

Further, in a head unit in which a plurality of recording heads are integrally formed in this way, the number of ejection ports is also a plurality of times that in the case of a single color, and various color pigments are used, which is common. However, in the present invention, the particle size of the pigment, the content of the pigment in the recording liquid, and the amount of solid content are optimized, so that there is no clogging of the discharge port. High-definition color printing was realized, and high water resistance and high light resistance were realized.

【0153】

Effect corresponding to claim 10: In addition to the effect of claim 9, the effect of claim 9 is further reduced because the ink injection heads of a plurality of colors are integrally formed and the ink container portion for supplying ink to the head is also integrally formed. It was realized, and a very easy-to-use product was realized.

【0154】

Effect corresponding to claim 11: Since the head portion, which is the recording liquid discharge portion, and the recording liquid storage portion can be separated, the running cost can be reduced in addition to the effect of claim 9.

【0155】

Effect corresponding to claim 12: Since the recording liquid reservoir can be separated according to the color of the ink, when any of the inks runs out, only the ink container needs to be replaced according to the color of the ink. In addition to the effect of claim 11, the running cost can be further reduced.

[Simple explanation of drawings]

[Figure 1]

It is a figure for demonstrating an example of a bubble jet type recording head.

[Figure 2]

It is a figure for demonstrating the principle of ink droplet ejection of a bubble jet type inkjet.

[Fig. 3]

It is a figure which shows the example of the inkjet head which has a nozzle plate.

[Fig. 4]

It is a figure which shows an example of the inkjet head of this invention.

[Fig. 5]

It is a figure which shows the example which provided the ink tank in the recording head part of FIG.

[Fig. 6]

It is a figure which shows an example of an inkjet head as a serial printer configuration.

[Fig. 7]

It is a figure which shows the example which has the discharge port row of 4 colors.

[Fig. 8]

It is a figure which shows the example which integrated the head of four colors.

[Fig. 9]

It is a figure which shows the example which arranged the head of 4 color independently on a carriage.

[Fig. 10]

It is a figure which shows the example which laminated and integrated the head of a plurality of colors.

[Fig. 11]

It is a figure which shows the example which formed the head unit and the ink container part integrally.

[Fig. 12]

It is a figure which shows the example of the case where only the ink container part is made separable.

[Fig. 13]

It is a figure which shows the example which made it possible to separate an ink container for each ink color.

[Explanation of symbols]

1 ... lid substrate, 2 ... heating element substrate, 3 ... recording liquid inlet, 4 ... discharge port, 5 ... flow path groove, 6 ... common liquid chamber, 7. .Individual lead electrode, 8 ... common lead electrode, 9 ... heating element, 10 ... ink, 10'... ink column, 11 ... bubble, 12 ... droplet, 30 .. Heating element board, 31Y, 31M, 31C, 31B ... ink ejection element, 40 ... ink tank, 50 ... recording head, 51 ... recording paper, 52 ... carriage, 53 ... Guide rod, 54 ... screw rod, 55 ... chart paper feed roller, 56 ... chart paper holder roller, 70 ... carriage, 71B, 71C, 71M, 71Y ... head, 72B, 72C, 72M, 72Y ... Discharge port, 73 ... Nozzle plate, 100 ... Head unit, 101 ... Head tip, 102 ... FPC, 103 ... Top lid, 104 ... Ink container part, 105 ... filter, 106 ... foam material for ink impregnation, 107 ... bottom lid, 110 ... head unit, 111 ... head part, 112 ... ink container part.