JP3510486B2 - Ink jet recording apparatus, ink jet recording method, and ink jet recording head - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, an ink jet recording method, and an ink jet recording head which eject an ink droplet to record an image.

[0002]

2. Description of the Related Art Conventionally, as a method for producing fine particles having a size of several μm, in the field of image recording, colored ink is used as a liquid, and the ink is extruded from a small nozzle having a diameter of several tens of μm to form ink particles. There is a method of flying and obtaining characters and images on a recording medium.

This method is generally called an ink jet method, and A) a method for realizing ejection of ink by applying mechanical vibration or displacement to a colored ink using a piezoelectric element, B) using thermal energy, The method is classified as a method of ejecting ink, such as a method of ejecting ink by utilizing a pressure for heating and foaming ink as a liquid.

Various techniques have been disclosed and proposed for the system using the above-mentioned ink jet recording head.

1) Japanese Unexamined Patent Publication No. 6-31910 discloses a method for forming particles having different sizes in an ink jet head, in which a plurality of nozzles are formed in accordance with a required droplet diameter.

2) In Japanese Patent Laid-Open No. 6-191142,
A method of changing the droplet diameter by changing the head temperature is disclosed.

3) In Japanese Patent Laid-Open No. 6-286138,
A method is disclosed in which ink droplets ejected from a plurality of nozzles are individually combined or one of them is combined to change the droplet diameter.

4) In Japanese Patent Laid-Open No. 6-191026,
Although it is not possible to make the droplet diameter variable as in 1) to 3) above, it is possible to generate minute droplets by using a head of the same size as the conventional one by performing water repellent treatment in the vicinity of the ink ejection holes. The technology is disclosed.

[0009]

However, the above-mentioned ink jet recording apparatus, ink jet recording method, and ink jet recording head still have the following problems.

In the above 1), since a head having a nozzle diameter corresponding to the number of particle diameters is required, the apparatus becomes large and complicated. Further, in order to produce a liquid having a smaller diameter with an inkjet head, the head needs to be further finely processed, which is difficult in terms of manufacturing and processing technology.
Further, the processing accuracy at this time affects the size of the particles produced, and it is difficult to obtain a stable and uniform particle size.

In the above 2), it is difficult to control the temperature of the head, and there is a problem in that the droplet diameter changes due to changes in the environmental temperature.

In the above 3), it is necessary to form two or more ink ejection holes for one ink ejection portion, which requires fine processing, and there is a problem that high resolution cannot be dealt with. .

In the above 4), which is the closest technique to the present invention, liquid-repellent treatment is applied to the inner wall of the ink ejection hole to generate smaller droplets while using a head of the same size as the conventional one. Is possible. However, there is a problem that the size of the droplet cannot be arbitrarily changed after the head is manufactured.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is not to require a high-level fine processing technique, and to determine the ink ejection hole portion depending on the presence or absence of stimulation. An ink jet recording apparatus capable of arbitrarily changing the diameter of a droplet to be ejected by reversibly changing the contact angle on the inner wall surface, that is, reversibly controlling the ejection hole portion of the liquid enemy to be water repellent or hydrophilic. And an inkjet recording method and an inkjet recording head.

[0015]

According to another aspect of the present invention, there is provided an ink jet recording apparatus, an ink discharge hole, an ink flow path to the ink discharge hole, and an ink flow path in the ink flow path.
Has an ink ejection energy generating means for ejecting ink from the ink discharge hole, the inner wall surface from the ink discharge hole including at least the ink discharge hole to a predetermined position of the ink flow path is stimulated donor An ink jet recording apparatus provided with a recording head, which is formed of a member whose contact angle upon ink contact changes reversibly depending on the presence or absence of a stimulus, and a stimulus providing means for providing the stimulus,
A stimulus removing unit for removing the stimulus, and a control unit for controlling ink ejection after selecting one of the stimulus providing unit and the stimulus removing unit are provided.

An ink jet recording apparatus according to a second aspect of the present invention is the ink jet recording apparatus according to the first aspect, wherein the stimulus providing means applies a charge to a member whose contact angle to the inner wall surface of the ink reversibly changes. It is characterized in that it is given and charged.

An ink jet recording apparatus according to a third aspect of the present invention is the ink jet recording apparatus according to the first aspect, wherein the stimulus removing means charges a member whose contact angle to the inner wall surface of the ink reversibly changes. It is characterized by removing the electric charges that are present.

An ink jet recording apparatus according to a fourth aspect of the present invention is the ink jet recording apparatus according to the second or third aspect, wherein the member whose contact angle to the inner wall surface of the ink reversibly changes is an insulating member. It is characterized by being.

An ink jet recording apparatus according to a fifth aspect of the present invention is the ink jet recording apparatus according to the second or third aspect, in which the member whose ink contact angle with the inner wall surface reversibly changes is a photoconductive member. Is characterized in that.

An ink jet recording apparatus according to a sixth aspect of the present invention is the ink jet recording apparatus according to the fifth aspect, wherein the photoconductive member is formed by laminating a conductive layer, a charge transport layer and a charge generating layer in this order. It is characterized by having a multilayer structure.

An ink jet recording method according to a seventh aspect of the present invention is an ink jet recording method for recording an image by changing the amount of ink ejected onto a recording medium in accordance with an image recording signal, and a charge as a stimulus is applied. A stimulus applying step of performing a charging process, a stimulus removing step of performing a process of removing the charged electric charge, the presence / absence of an electric charge is controlled according to the image recording signal, and the inner wall surface of the ink ejection hole is controlled by the presence / absence of the electric charge. ink and stimulus control step of changing a discharge amount of ink reversibly changes, the contact angle of the ejection
An inkjet recording method, characterized in that it is included before delivery .

According to an eighth aspect of the present invention, there is provided an ink jet recording head, an ink discharge hole, an ink flow path to the ink discharge hole, an ink discharge energy generating means provided in the ink flow path, A recording head having at least an ink ejection hole of the recording head, and an inner wall surface from the ink ejection hole to a predetermined position in the ink flow path is in contact with the inner wall surface of the ink by an external stimulus. It is characterized by being formed of a photoconductive or insulating member whose corners reversibly change.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an ink jet recording apparatus, an ink jet recording method and an ink jet recording head according to the present invention will be described below with reference to the drawings.

First, the features of the ink jet recording apparatus, the ink jet recording method and the ink jet recording head according to the present invention will be described.

The feature is that the inner wall of the ink flow path is made lyophilic with respect to the ink, and a part of the inner wall of the outermost layer of the ink ejection hole is water-repellent in the non-charged state to prevent the leakage of the ink and form a meniscus. It is formed by forming inside the ink ejection hole, and in the charged state, the contact angle of the ink with respect to the inner wall of the ink ejection hole is reduced to leak the ink to the surface of the ink ejection hole and form a meniscus on the surface of the ink ejection hole. The point is that the amount of ink used is changed. By this variable control of the ink amount, the image resolution or the image gradation can be changed.

Next, the basic principle of water repellency / hydrophilicity used in the ink jet recording apparatus of the present invention will be described.

FIG. 1 is a diagram showing a state in which a droplet is applied on the film surface.

As shown in FIG. 1A, when the droplet D is placed on the surface of the liquid repellent insulating film 9, the contact angle θ on the film surface 9 becomes larger than 90 °. However, the droplet D does not wet the film surface 9. On the other hand, as shown in FIG. 1 (b), when the liquid repellent insulating film 9 is charged with an electric charge 10 to be charged, the contact angle θ between the film surface 9 and the droplet D decreases, and eventually becomes 90 ° or less. 9 can be made wet.

This property varies depending on the liquid repellency of the film surface 9, the type of the liquid D and the applied voltage. For example, when water droplets are placed on the trifluorochloroethylene resin film, θ = 110 before charging. The contact angle, which was deg., Decreases to .theta. '= 55.degree. By applying a voltage of minus 500 V so that the film surface 9 becomes wet.

Further, as shown in FIG. 1C, when the charge of the charged liquid-repellent insulating film 9 is removed, FIG.
As shown in (d), the contact angle θ of the droplet D on the film surface 9 becomes larger than 90 ° again.

By utilizing the above principle in the ink jet recording apparatus and the ink jet recording method, the size of the ink droplet to be ejected can be made variable.

The ink jet recording apparatus, the ink jet recording method, and the ink jet recording head which are the objects of the present invention will be described in detail below with reference to examples and application examples.

(First Embodiment) A first embodiment of the present invention will be described.

FIG. 2 shows a method for ejecting a variable amount of ink in the head of the ink jet recording apparatus in this embodiment.

The ink jet recording head 1 is composed of an upper head 2 and a lower head 3, and an energy generating means 31 is provided on the lower head 3 inside the ink ejection hole A. Further, in the ink flow path 5, the ink IN
K is filled and ink INK is supplied from an ink chamber (ink reservoir) not shown.
A functional layer 4 made of a liquid repellent insulating material is formed on the surface of the ink ejection hole A facing the recording medium P.

Here, in the functional layer 4, the portion B of the functional layer 4 eliminates the ink INK due to its liquid repellency when it is not charged, and FIG.
As shown in (a), the ink meniscus M1 is formed at a position retracted from the ink ejection hole A. When the energy generating means 31 is driven in this state, the ink droplet D1 flies toward the recording medium P.

On the other hand, when the functional layer 4 is charged, the portion B of the functional layer 4 becomes lyophilic, and the ink INK can leak to the ink ejection holes A. As a result, as shown in FIG. The meniscus M2 is formed near the surface of the ink ejection hole A. When the energy generating means 31 is driven in this state, the ink droplet D2 flies toward the recording medium P.

Here, the size of the ink droplets ejected differs depending on whether the functional layer 4 is uncharged or charged, and D1 (volume: V1 ') and D2, respectively.
(Volume: V2 '). Further, since V1 '<V2', the size of the ink dot formed on the recording medium P also becomes a size corresponding thereto. That is, it is possible to eject a large ink droplet when charged, as compared with the case where no charge is applied.

In this way, ink droplets formed on the recording medium P by stimulating the liquid-repellent insulating material formed on the surface of the ink ejection hole A, in this case, charging, as compared with the case of not charging. The diameter can be changed.

It is assumed that the ink flow path 5 formed by the upper head 2 and the lower head 3 is formed of a conductive substrate having a lyophilic property with respect to the ink. Further, the energy generating means 31 may be, for example, a heater which is an electro-thermal converter, or a piezoelectric element which is an electro-vibration converter.

Next, the content shown in FIG. 2 will be described as a more specific operation.

FIG. 3 shows an operation sequence of the ink liquid amount variable discharge method in the ink jet recording head.

FIG. 3A shows a state in which the ink jet recording head 1 is filled with the ink INK in a negative pressure state.

When the insulating member 4 is not charged,
Since the portion B exhibits liquid repellency with respect to the ink INK, the ink meniscus M1 is formed at a position retracted from the ejection hole A as shown in the figure. In this case, the volume V1 ′ of the ejected ink droplet D1 is V1 ′ = k · V1 ... Using the ink volume V1 between the meniscus M1 and the ink ejecting means 31. Here, k is a constant, and in general, V1 ′ =
10 and several pl (picoliter).

By driving the energy generating means 31 in this state, the droplet D1 flies toward the recording medium P, and an image is formed on the recording medium P.

Next, as shown in FIG. 3B, when the stimulus SA is applied to the insulating member 4 by the external stimulus providing means 6, the portion B becomes lyophilic to the ink INK and the meniscus. M2 will be formed on the outermost layer of the ink ejection hole A (FIG. 3C). The volume V2 ′ of the ink droplet D2 ejected at this time is V2 ′ = k · V2> V1 ′ ... Using the ink volume V2 between the meniscus M2 and the ink ejection means 31. Here, k is a constant, and at this time, V2 ′ =
It becomes several 10 pl. Further, the coefficient k in the above equation and is simplified to be the same.

When the charging phenomenon is utilized as the stimulus SA, the stimulus providing means 6 may be, for example, a charger. This charger may be either a non-contact type or a contact type charging device generally used in electrophotographic recording devices and the like.

By driving the ink ejecting means 31 in this state, the droplet D2 flies toward the recording medium P,
An image is formed on the recording medium P. At this time, the volume V2 ′ of the ejected ink drop D2 is equal to the volume V2 of the ink drop D1.
Since it is larger than 1 ', the ink droplets formed on the recording medium P also become large.

As described above, since the ink volume V between the meniscus M and the energy generating means (ink ejecting means) 31 largely depends on the volume V'of the ejected ink, the insulating member 4 is not charged. The discharge ink volume can be made small, while the discharge ink volume can be increased by charging the insulating member 4.

In the above, from the state where the meniscus is M1 to M2
The case where the meniscus is changed from the state M2 to the state M1 is described below.

Since the insulating member 4 is already charged when the meniscus is M2, the stimulus removing means 7 applies the stimulus SB to remove the charged charge, as shown in FIG. 3 (d). As a result, as shown in FIG. 3 (e), the electric charges charged in the functional layer 4 are removed, and the state becomes the same as that in (a). That is, in this state, the insulating member 4 becomes lyophobic to the ink INK again, so that the meniscus is M
It becomes 1. The ejection volume of the ink droplet D1 becomes V1 ′, and a small ink droplet is ejected.

The stimulus removing means 7 uses a static eliminator. As the static eliminator, a charger such as a corotron, a scorotron, a dicorotron, a sawtooth charger, a static eliminator brush or a static eliminator blade can be used.
Alternatively, a method may be used in which the charging charge of the insulating member 4 is canceled by applying a voltage having a polarity opposite to that at the time of charging to the charging electrode of the charger used at the time of providing the stimulus.

Here, the stimulus providing means 6 and the stimulus removing means 7 may actually be arranged in the vicinity of the ink jet recording head 1 or as a part thereof.

Next, the detailed structure of the main part of the ink jet recording head 1 will be described.

FIG. 4 is a side sectional view showing the main structure of the ink jet recording head 1 shown in FIGS.

The ink jet recording head 1 has ink I
It is composed of a conductive upper head 2 and a lower head 3 which are lyophilic with respect to NK, and an energy generating element 31 provided inside the lower head 3.

<1> Upper Head 2 In the upper head 2, the substrate forming the head can be made of aluminum, iron, or alloys of various metals including them. Further, glass or polycarbonate subjected to conductive treatment, acrylic resin, polyvinyl alcohol, acrylic resin, styrene-acrylic copolymer, ethylene vinyl acetate polymer, starch, polyvinyl butyral, gelatin, casein, ionomer, gum arabic, carboxymethyl cellulose, Resins such as polyvinylpyrrolidone, polyacrylamide, phenol, melamine, epoxy, α-olefin, vinyl urethane, cellulose mixed ester, cellulose acetate, cellulose nitrate, and polyvinylidene fluoride, or ceramics can be used.

As a method for forming the hydrophilic layer on the head substrate 2, a roll coating method, a rod bar coating method, or a slurry mixture of the hydrophilic material and the binder is used.
A known method such as a spray coating method or an air knife coating method may be used in which the base material 2 is coated and dried. As the binder, organic substances such as starch and modified products thereof, polyvinyl alcohol and modified products thereof, SBR latex, NBR latex, hydroxycellulose, and polyvinylpyrrolidone can be generally used.

The substrate of the conductive head 2 is electrically grounded to the device casing.

<2> Lower Head 3 As the lower head 3, the substrate forming the head is the same as the substrate forming the upper head 2. However,
The lower head 3 has a structure in which an energy generating element 31 described in <3> below is embedded.

<3> Energy Generating Element 31 As the energy generating element 31, an electro-thermal converting element is used, and the heat generating element 31, which is the energy generating element 31, is made of silicon oxide, silicon nitride, silicon carbide or the like. The protective layer 32 is formed on a substrate 36 formed of a material having a good heat dissipation property such as aluminum, gold, and aluminum nitride. Reference numeral 34 is a heating resistor layer, and 35 is a heat storage layer.

When a pulsed electric signal is applied from the lower head 3 to the electrode 33 constituting the heat generating element 31, the area of the heat generating portion 37 of the heat generating element 31 rapidly generates heat and the heat generating portion 37 is heated. Bubbles are generated in the ink INK that is in contact with the surface, and the meniscus M projects due to the pressure, becomes ink droplets from the ink ejection holes A, and flies toward the recording medium P.

Although the element which is the electro-thermal converter is used as the energy generating means 31 here, the element is not limited to this and an element having a piezoelectric function which is the electro-displacement converter may be used.

<4> Ink ejection hole A A liquid repellent insulating material is laminated as the functional layer 4 in the vicinity of the ink ejection hole A of the upper and lower heads 2 and 3, and the ink ejection hole A penetrating both is formed. The size of the ink ejection hole A is determined from the required image resolution and is about 10 to 100 μm.

Finally, the ink INK used in this embodiment
Is described.

The ink INK which is preferably used in the present embodiment has a contact angle of at least 90 ° or more with respect to the liquid repellent portion B of the inner wall of the ink ejection hole A, and the contact angle after giving a charge. Must be less than 90 °.

When the liquid repellent material is polyethylene, polystyrene, tetrafluoroethylene, trifluoroethylene, silicon varnish, or alkyd resin, water, glycerin, ethylene glycol or the like can be used as the liquid.

The colorant may be in the form of a solution or suspension, or a mixture of the two.

Therefore, when water is used as the liquid, direct dye, acid dye, metal-containing acid dye, basic dye, cationic dye, mordant dye, acid mordant dye, azoic dye, soluble sulfur dye, reactive dye, etc. In the case of containing the water-soluble dye of 1) and a small amount of alcohol as the contact angle adjusting agent, an alcohol-soluble dye such as Pigment Green or Carmine FB is used.

As the suspending colorant, carbon black, phthalocyanine, and other organic or inorganic pigments are dispersed in a liquid using a dispersant.

As described above, the size of the ink dot ejected from the ink jet recording head 1 is irreversibly controlled by controlling the stimulus applied to the functional layer 4 formed of the insulating material on the surface layer of the ink ejection hole A. Can be changed.

Although a single ink ejection hole has been described above, for example, as shown in FIG.
It is also applicable to a multi-head type having a plurality of inkjet recording heads 1 described in 4 to 4.
The arrangement of the ink ejection holes A is not limited to the line shape shown in the figure, and may be arranged in a matrix.

That is, this is a line-shaped ink jet recording head 1 in which a plurality of ink ejection holes A are formed in the main scanning direction of recording in character or image recording, or a plurality of ink ejection holes A in the sub scanning direction of recording. A serial type inkjet recording head in which the inkjet recording head 1 moves in the main scanning direction, or a plurality of ink ejection holes A in the main scanning direction and the sub scanning direction of recording.
Even if the inkjet recording head 1 is formed in a matrix, it may be similarly applied to the insulating member of each ejection hole A.

As described above, in this embodiment, by controlling the liquid repellency and the lyophilicity at a predetermined position on the inner wall surface of the ink ejection hole from the ejection hole by the presence or absence of the stimulus, the ink ejection amount is on-demand. It has the effect of being variable. Furthermore, since the ink jet recording head is an electro-thermal converter for generating heat by the ink ejecting means giving electric energy and causing the ink to change its state, it is possible to eject ink at high speed. You can Further, the stimulus providing means is performed by a charger for charging the insulating member, and the stimulus removing means is performed by a static eliminator for removing the electric charge charged in the insulating member. It also has an effect that charging and discharging can be performed using a corona charger. Further, since the insulating member is used as the functional layer, it can be easily realized structurally.

(Second Embodiment) A second embodiment of the present invention will be described.

FIG. 6 shows a method for ejecting a variable amount of ink in the head of the ink jet recording apparatus in this embodiment. It should be noted that here, only parts different from the above-described embodiment will be described.

The difference is that the functional layer 4 is made of a material having photoconductivity.

First, the functional layer 4 made of a photoconductive material will be described.

The photoconductive layer (photosensitive layer) 4, which is a functional layer made of a material having photoconductivity, is formed by applying a mixture of a powder photoconductor and a resin solution to a predetermined thickness by electrostatic coating or by spray coating. It is formed by applying an electric charge having a polarity opposite to that of the substrate to the fog droplets to be electrodeposited on the substrate. Alternatively,
When the layer 4 is a metal photoconductor such as amorphous selenium, it can be easily formed by applying a voltage and performing vacuum deposition.

Here, in order to impart liquid repellency to the photoconductive layer 4, the photoconductive layer 4 may be formed using a liquid repellent resin such as polyethylene trifluoride ethylene resin as a binder. A coating of the liquid repellent resin may be formed on the surface of No. 4.

The ink ejection holes A are formed after the photoconductive layer 4 is formed in this way.

On the other hand, contrary to the above method, the ink ejection hole A
It is also possible to form the photoconductive layer (photosensitive layer) 4 by a method such as dipping, printing, transfer, spray coating or the like after forming.

A liquid-repellent photoconductive layer (photosensitive layer)
The formation of 4 is not limited to the above method.

Next, a method for ejecting a variable amount of ink in the head of the ink jet recording apparatus in this embodiment will be described.

As shown in FIG. 6A, the ink INK
Since the photoconductive layer 4, which is a functional layer, is liquid repellent, it cannot reach the surface layer of the ink ejection hole A, and the ink meniscus M1 is formed at a position retracted from the ink ejection hole A. Therefore, when the energy generating means 31 is driven in this state, the ink (volume V1) existing between the energy generating means 31 and the ink meniscus M1 comes to be ejected.

Next, as shown in FIG. 6B, the surface of the liquid repellent photoconductive layer 4 is stimulated by a method according to the photoconductive layer 4 to form an electrostatic latent image IMG. The contact angle of the ink INK to the liquid repellent inner wall B is lowered to 90 ° or less by the electric field of the latent image charge to wet the inner wall, and an ink meniscus M2 is formed on the surface of the ink ejection hole A. The stimulus providing means for providing the stimulus may be the charging by the charger described in the above embodiment. When the energy generating means 31 is driven in this state, the ink (volume V2) existing between the energy generating means 31 and the surface of the ink ejection hole A is ejected.

As a result, the size of the ejected ink droplet is different between the state in which the photoconductive layer (photosensitive layer) 4 is not charged and the state in which it is charged, and D1 (volume: V
1 ') and D2 (volume: V2'). Here, V
Since 1 ′ <V2 ′, the size of the ink dot formed on the recording medium P also becomes a size corresponding thereto. That is, it is possible to eject a larger ink droplet when charged than when not charged.

In this way, by stimulating the liquid-repellent photoconductive material formed on the surface of the ink discharge hole A, in this case, charging, the recording medium P is compared with the case of not charging.
The diameter of the ink droplet formed on the top can be changed.

After that, when the residual charge of the electrostatic latent image IMG is removed by uniformly irradiating the entire surface of the photoconductive layer (photosensitive layer) 4 formed on the surface layer of the ink ejection hole A, the liquid repellency is restored. Then, the ink meniscus M1 retracts. That is, the state returns to the state of FIG. When the energy generating means 31 is driven in this state, the ink (volume V1) existing between the energy generating means 31 and the ink meniscus M1 is ejected. At this time, since V1 <V2,
It is possible to eject small ink droplets.

In this case, the stimulation removal method is as follows:
A so-called photo static elimination method, which is performed by irradiating light, is used.

As described above, a part of the inner wall of the ink ejection portion A is formed of a photoconductive member, and the charging and photo-erasing operations of the member are performed to control the position of the meniscus to be formed. This has the effect of making it possible to control the amount of ejected ink. Furthermore, the optical static elimination method can be used as the static elimination method, and as a result, it is not necessary to generate a high voltage and it is safe for the user. In addition, since no noise is generated, the electric circuit does not malfunction and has an effect of excellent reliability. This is EM
I (ElectroMagnetic Interface)
It is also excellent in terms of environment because it has a small amount of electromagnetic interference.

(Third Embodiment) A third embodiment of the present invention will be described.

FIG. 7 shows a method for ejecting a variable amount of ink in the head of the ink jet recording apparatus in this embodiment. It should be noted that here, only parts different from the above-described embodiment will be described.

The difference is that the functional layer 4 is formed by laminating the photoconductive resin in the ink ejection hole.
That is, the surface layer of the ink ejection hole 1 is formed of a photoconductive resin for the head bases 2 and 3, and the photoconductive resin has a further multilayer structure.

The functional layer 4 is formed by laminating a conductive layer 41, a charge transport layer (CTL) 42, a charge generation layer (CGL) 43, and a surface protective layer 44 in this order on each substrate of the upper and lower heads 2 and 3. The charge generation layer 43 uses a π-type metal-free phthalocyanine, which is a charge generation substance, dispersed in a melamine-modified thermosetting resin, and the charge transport layer 42 disperses a tetraphenylbutadiene derivative, which is a charge transport substance, in a polycarbonate resin. I am using what I did. Although the functional layer 4 has a function-separated structure having a multilayer structure, it is not limited to this.

Also in this example, as in the case of the above example, a charger was used as the stimulus providing means, and at this time, the surface potential of the photoconductive layer 4 was charged within the range of -500 to -900V. In addition, in this embodiment, the negative charging type photoconductive layer 4 is used.
However, the photoconductive layer 4 of positive charging type may be used.

When the above-mentioned head 1 was used, the ink meniscus was M1 in the non-charged state, and the ink discharge amount in this state was several hundred pl.

In practice, when the photoconductive layer (photosensitive layer) 4 portion was charged to 350 V by the charging means, the ink also wets the photoconductive layer (photosensitive layer) 4 portion, and the ink meniscus becomes M2. The ink ejection amount in this state was several tens of pl.

Further, when a light providing means such as a semiconductor laser light is used as the stimulus removing means and light is irradiated to the photoconductive layer (photosensitive layer) 4 portion, the charge is removed and the ink meniscus becomes M1 again. The ink ejection amount in this state was several hundred pl.

The light-providing means is not limited to the semiconductor laser, but is in agreement with the spectral sensitivity characteristics of the material used for the photoconductive layer (photosensitive layer) 4, more specifically, the charge generation layer (CGL) 43. A light source for Ie 6
In the case of a material having a spectral sensitivity in the wavelength range of 00 to 900 nm (nanometer), a commercially available semiconductor laser can be used as in the present embodiment, and if it is 633 nm, it is He-N.
If the e laser is 441 nm, the He-Cd laser is
Further, if it is 400 to 500 nm, it is possible to generate the second harmonic (SHG) of the semiconductor laser. In addition, since the characteristics of the laser are not required in this embodiment, an LED (Light Emitting Diode) is used.
e) Alternatively, incoherent light such as a visible light source such as an ultraviolet lamp, a halogen lamp, a fluorescent lamp, a cold cathode tube, a red or green neon lamp, or the like can be used.

As described above, also in the present embodiment, as in the second embodiment, the photoconductive layer (photosensitive layer) 4 portion formed inside the surface layer of the ink ejection hole A is charged and light-erased. The position of the ink meniscus can be varied, and as a result, the amount of ejected ink can be varied. Furthermore, the optical static elimination method can be used as the static elimination method, and as a result, it is not necessary to generate a high voltage and it is safe for the user. In addition, since no noise is generated, the electric circuit does not malfunction and has an effect of excellent reliability. This means that EMI (Elec
troMagnetic Interference:
It is also environmentally friendly as it has little electromagnetic interference.

An embodiment of an application example in which the ink jet recording apparatus, the ink jet recording method and the ink jet recording head according to the present invention are actually applied to an image recording apparatus will be described below.

Application Example 1 Application example 1 will be described.

Particularly, in this application example, a high resolution recording method for controlling the size of a droplet based on image information will be described with reference to the drawings. In the description, the description of the same parts as those of the above-described embodiments will be omitted (for the sake of simplicity, the numbers used in any of the above drawings will be used).

FIG. 8 shows an example of an ink jet recording apparatus using the ink jet recording head 1 of the present invention. Further, FIG. 9 is a functional block diagram of its main constituent elements, and FIG. 10 shows its flowchart.

Here, the stimulation control means 102, the stimulation providing means 103A, and the stimulation removal means 103B shown in FIG.
In practice, they may be arranged in the vicinity of the inkjet recording head 1 or as a part thereof.

As shown in FIG. 9, when the input signal 101 is input as the print operation signal S1 to the control means 102 through the operator, another control device or the network, the control means 102 is based on the print additional information. Determine the recording resolution. Here, the print additional information is, for example, a print resolution of 150 DPI (dot per inch), 3
Information on whether it is 00 DPI, 600 DPI, or the number of print gradations is 2 ⁴ = 16 colors, 2 ⁸ = 256 colors, 2 ¹⁶ = 6
Information such as 5000 colors, ...

In this application example, in order to simplify the explanation, for example, when the input additional information has two of 1) resolution 150 DPI 2) resolution 300 DPI, the operation corresponding to each will be described.

When the above 1) is input as the input signal S1, the control means 102 uses the stimulus providing means 1 as the control signal.
The drive signal S2A is output to 03A. As a result, the stimulus providing means 103A, for example, a corona charger, charges the functional layer 4 formed on the outermost surface portion of the ejection hole A of the inkjet recording head 1 to form the ink meniscus M2 on the surface layer of the ink ejection hole A. (See FIG. 3).

Next, the control means 102 outputs a drive signal S3 to the energy generating means 104, whereby the energy generating means 104 is driven in accordance with the image data and ink is ejected (path of FIG. 10). AA sequence).

The size of the ink dot ejected at this time is such that a resolution of 150 DPI can be obtained when reaching the recording medium P, and the ink jet recording head 1 is designed so as to be 240 μm, for example.

In FIG. 8, when the ink jet recording head 1 has a plurality of ink ejection holes A as shown in FIG. 5, for example, individual energy generating means provided for each ink ejection hole A. 31 is driven according to the image data, and the ink jet recording head 1 is moved to the arrow A1.
Printing is performed in the main scanning direction by moving in the main scanning direction. Further, by printing the recording medium P in the direction of arrow A2, printing is performed in the sub-scanning direction, and a two-dimensional image is finally obtained.

As a result, an image having an image resolution of 150 DPI can be formed.

Next, when the above 2) is input as the input signal S1, the control means 102 outputs the drive signal S2B to the stimulus removal means 103B as a control signal. As a result, the stimulus removing means 103B, for example, the optical static eliminator, removes the charged charges of the functional layer 4 formed on the outermost surface of the ink ejection hole A, so that the ink meniscus M1 is formed inside the ink ejection hole (FIG. See 3).

After that, the control means 102 outputs a drive signal S3 to the energy generation means 104 to drive the energy generation means 104 in accordance with the image data and eject ink (path BB in FIG. 10). Sequence).

In this case, the size of the ink dot to be ejected is smaller than that in the case of 1), and for example, it is 1 on the recording medium P.
The thickness of the functional layer 4 and the like are designed so as to be 20 μm.

As a result, an image having an image resolution of 300 DPI can be formed.

FIG. 11 shows a conceptual diagram of ink dots on the recording medium P in the above 1) and 2). FIG. 11 (a)
Shows the print result at a resolution of 300 DPI, and FIG. 11B shows the print result at a resolution of 150 DPI.

In the above 1) and 2), the speed at which the inkjet recording head 1 is moved in the main scanning direction indicated by the arrow A1 or the print timing for recording one pixel and the speed at which the recording medium P is conveyed in the sub scanning direction indicated by the arrow A2. Are adjusted so that the desired resolution is obtained.

As described above, for the purpose of performing high-definition printing, a printing method of performing printing with high resolution and printing with low resolution is possible for the purpose of shortening the printing time.

The case of an ink jet recording apparatus having a single ink jet recording head 1 has been described above, but the present invention is not limited to this, and color inks of yellow (Y), magenta (M), cyan (C), etc., are used. In the case of an inkjet recording apparatus having a plurality of inkjet recording heads 1 provided, full-color printing is possible by superimposing each color.

Further, although the application example has been described based on the liquid ink, an ink which is solid at room temperature may be used. In this case, the solid ink is heated during use so as to be discharged in a molten state.

From the above, control is performed so as to drive either the stimulus applying step or the stimulus removing step based on the image resolution, so that it is small for high-precision printing of characters and the like. By producing ink, printing is performed at high resolution, and for the purpose of shortening the printing time, it is possible to select a printing method of printing at low resolution.

Application Example 2 Application example 2 will be described.

Particularly, in this application example, a high gradation recording method for controlling the size of a droplet based on image information will be described with reference to the drawings. It should be noted that, in the description, the description overlapping with the above-described embodiments and application examples will be omitted (for the sake of simplicity, the numbers used in any of the above drawings will be used).

In the first application example, the stimulus providing means 103A or the stimulus removing means 103B is selected depending on the image resolution. On the other hand, in this application example, the stimulus providing unit 103A is driven or the stimulus removing unit 103 is driven according to the number of image gradations.
A method of controlling the number of image gradations by selecting whether to drive B will be described.

For simplicity in this application example, for example,
When the input additional information is two of 3) the number of gradations 4 4) the number of gradations 16, the operation according to each will be described with reference to FIGS. At this time, both resolutions are the same.

In order to express gradation in an ink jet type printer, the area gradation method is generally used. This corresponds to an m × n matrix for one pixel,
It is expressed by a plurality of area patterns.

When the above 3) is input as the input signal S1, the control means 102 uses the stimulus providing means 1 as the control signal.
The drive signal S2A is output to 03A. As a result, the stimulus providing means 103A, for example, a charger, charges the functional layer 4 formed on the outermost surface of the ejection hole A of the inkjet recording head 1 to form an ink meniscus on the surface layer of the ink ejection hole A (FIG. See 3).

Next, the control means 102 outputs a drive signal S3 to the energy generation means 104, whereby the energy generation means 104 is driven according to the image data and ink is ejected (path of FIG. 10). AA sequence).

The head 1 is designed so that the size of the ink dot ejected at this time is, for example, 120 μm when it reaches the recording medium P.

As a result, ink dots having an image resolution of 300 DPI can be formed. This is as described in the application example 1 above.

The difference is that gradation expression (here, m = n =
2 and 4 ink dots are used for one pixel to be printed in order to perform m × n = 4 matrix). FIG. 12 shows this state. Therefore, the substantial resolution in this case is 300/4 = 75 DPI.

As a result, four gradations can be expressed for one recorded pixel.

Next, when the above 4) is input as the input signal S1, the control means 102 outputs the drive signal S2B as the control signal to the stimulus removing means 103B. As a result, the stimulus removing means 103B, for example, an optical static eliminator, removes the charged charges of the functional layer 4 formed on the outermost surface of the ejection hole A of the inkjet recording head 1 to form an ink meniscus inside the ink ejection hole A. (See FIG. 3).

After that, the control means 102 outputs a drive signal S3 to the energy generation means 104 to drive the energy generation means 104 in accordance with the image data and eject ink (path BB in FIG. 10). Sequence).

In this case, the size of the ejected ink dot is smaller than that in the case of 3), and for example, 3 on the recording medium P.
The thickness of the functional layer 4 and the like are designed so as to be 0 μm.

As a result, ink dots having an image resolution of 1200 DPI can be formed.

In this case, 16 ink dots (m = n
= 4 and one pixel is represented by a matrix of m × n = 16), the actual resolution is 1200/16 = 75 DPI. That is, it is possible to express gradation four times (= 16/4) while maintaining the same resolution as 3). FIG. 13 shows the gradation expression at this time.

As a result, it is possible to change only the number of gradations without changing the image resolution.

Also in this application example, the above method is applied to each color in the ink jet recording apparatus having the ink jet recording head 1 provided with color inks such as yellow (Y), magenta (M) and cyan (C). By doing so, printing is performed in the high gradation mode when high-quality recording that is photo-like is required, and when high image quality is not required or when the time required for printing is shortened, the low gradation mode is used. It can be used by printing with.

In this application example, the description has been given based on the liquid ink, but an ink which is solid at room temperature may be used. In this case, the solid ink is heated during use so as to be discharged in a molten state.

Furthermore, in actual operation, the application example 1 is applied.
It is also possible to use in combination with this application example.

From the above, control is performed so as to drive either the stimulus providing step or the stimulus removing step based on the number of image gradations, so that the number of gradations can be changed as necessary. have.

The contents including the examples and application examples in the above-mentioned embodiments are not limited to the above contents unless the gist of the present invention is changed.

[0146]

The ink jet recording apparatus, the ink jet recording method and the ink jet recording head according to the present invention have the following effects in each claim.

According to the first aspect of the present invention, by controlling the contact angle of the inner wall surface of the ink ejection hole from the ejection hole to a predetermined position, the contact angle of the ink with the inner wall surface is controlled by the presence or absence of stimulation to the portion. This has the effect that the ink ejection amount can be varied on demand.

According to the second and third aspects of the present invention, there is an advantage that a general charger for supplying / removing electric charge can be used as a means for supplying / removing stimulation. As a result, the device configuration can be easily realized.

In the fourth aspect of the present invention, since the member is an insulating member, the structure of the device can be easily realized. Furthermore, in the means of providing / removing the stimulus, the charge is provided /
There is an advantage that a general charger for removing can be used.

According to the fifth and sixth aspects of the present invention, since the member is a photoconductive member, a photo-static elimination method can be used as a stimulus removing method, and as a result, it is not necessary to generate a high voltage and use. It is safe for the person. In addition, since no noise is generated, the electric circuit does not malfunction and has an effect of excellent reliability. In addition, EMI (Select
It is also environmentally friendly as it has low roMagnetic Interference.

In the seventh aspect of the present invention, the stimulus control step controls either the stimulus applying step or the stimulus removing step, whereby the ejected ink amount can be variably controlled. This has an effect that it is possible to select the image resolution or the number of image gradations according to the preference of the user, since the operations of providing the stimulus and removing the stimulus are controlled according to the image signal.

That is, since control is performed such that either the stimulus applying step or the stimulus removing step is selected and processed based on the image resolution, it is small for high-precision printing of characters and the like. It is possible to select a printing method in which printing is performed at a high resolution by generating ink and printing is performed at a low resolution for the purpose of shortening the printing time. Further, since control is performed such that either the stimulus providing step or the stimulus removing step is selected and processed based on the number of image gradations, the number of gradations can be changed as necessary.

According to the eighth aspect of the present invention, by controlling the contact angle of the inner wall surface of the ink ejection hole from the ejection hole to a predetermined position, the contact angle of the ink with the inner wall surface is controlled by the presence or absence of stimulation to the portion. This has the effect that the ink ejection amount can be varied on demand.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of a liquid amount varying method according to the present invention.

FIG. 2 is a diagram for explaining an outline of a liquid amount varying method in an inkjet recording head according to the present invention.

FIG. 3 is a diagram for explaining details of a liquid amount varying method in an inkjet recording head according to the present invention.

FIG. 4 is a diagram showing an example of a structure of an inkjet recording head according to the present invention.

FIG. 5 is a diagram showing an example of an external appearance of an inkjet recording head according to the present invention.

FIG. 6 is a diagram for explaining an outline of a liquid amount varying method in another ink jet recording head according to the present invention.

FIG. 7 is a diagram for explaining an outline of a liquid amount varying method in another ink jet recording head according to the present invention.

FIG. 8 is a schematic perspective view showing a main part of an inkjet recording apparatus according to the present invention.

FIG. 9 is a diagram showing a function control block of the inkjet recording apparatus according to the present invention.

FIG. 10 is a diagram showing a control sequence in a function control block of the inkjet recording apparatus according to the present invention.

FIG. 11 is a conceptual diagram of a print sample according to a difference in recording resolution in the inkjet recording apparatus according to the present invention.

FIG. 12 is a diagram showing a state during low gradation expression in the inkjet recording apparatus according to the present invention.

FIG. 13 is a diagram showing a state of high-gradation expression in the inkjet recording apparatus according to the present invention.

[Explanation of symbols]

1 Inkjet recording head 2 upper head 3 lower head 4 functional layers 5 ink channels 6 stimulus providing means 7 Stimulus removal means A ink ejection hole M Meniscus

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Claims (10)

(57) [Claims] 1. An ink discharge hole, an ink flow path to the ink discharge hole, and an ink discharge energy generating unit for discharging ink in the ink flow path from the ink discharge hole, The inner wall surface from at least the ink ejection hole including at least the ink ejection hole to a predetermined position in the ink flow path is formed of a member whose contact angle at ink contact reversibly changes depending on the presence or absence of stimulation. An inkjet recording apparatus comprising a head, wherein any one of a stimulus applying means for applying the stimulus, a stimulus removing means for removing the stimulus, and a stimulus applying means and the stimulus removing means. An ink jet recording apparatus, comprising: a control unit for controlling ink ejection after selecting. 2. The ink jet recording apparatus according to claim 1, wherein the stimulus providing means charges a member whose contact angle to the inner wall surface of the ink reversibly changes by charging the member. 3. The ink jet recording apparatus according to claim 1, wherein the stimulus removing means removes the electric charge charged on the member whose contact angle with the inner wall surface of the ink reversibly changes. 4. The ink jet recording apparatus according to claim 2, wherein the member whose contact angle of ink with the inner wall surface reversibly changes is an insulating member. 5. The ink jet recording apparatus according to claim 2, wherein the member whose contact angle of ink with the inner wall surface reversibly changes is a photoconductive member. 6. The photoconductive member comprises a conductive layer, a charge transport layer,
The ink jet recording apparatus according to claim 5, wherein the ink jet recording apparatus has a multilayer structure in which charge generation layers are laminated in this order. 7. An inkjet recording method for recording an image by changing the amount of ink ejected onto a recording medium according to an image recording signal, comprising a stimulus applying step of performing a process of charging an electric charge as a stimulus, and the charging. A step of removing a stimulus for removing the electric charge, and controlling the presence or absence of the electric charge according to the image recording signal, and reversibly changing the contact angle of the ink to the inner wall surface of the ink ejection hole depending on the presence or absence of the electric charge. And a stimulus control step of changing the ejection amount of the ink before the ink ejection. 8. A recording head having an ink ejection hole, an ink flow path to the ink ejection hole, and an ink ejection energy generating means provided in the ink flow path, the recording head comprising: Including at least ink ejection holes,
The inner wall surface from the ink ejection hole to a predetermined position in the ink flow path is formed of a photoconductive or insulating member in which the contact angle of the ink with the inner wall surface is reversibly changed by an external stimulus. An inkjet recording head characterized by the following. 9. An ink jet recording method for recording an image by changing the amount of ink ejected onto a recording medium according to an image recording signal, wherein a stimulus applying step for performing a process of charging a charge as a stimulus and a charged charge. The stimulus removing step for removing the ink is selected according to the image recording signal to reversibly change the contact angle of the ink with the inner wall surface of the ejection hole to eject the ink. And a stimulus control step for changing the stimulus, wherein the stimulus control step performs the selection before ink ejection. 10. The ink jet recording method according to claim 9, wherein in the stimulus control step, the selection is performed based on the resolution or the number of gradations.