JP6695569B2 - Wiper blade, wiping unit, ink ejection unit and device for ejecting ink - Google Patents

Description

  The present invention relates to a wiper blade, a wiping unit, an ink ejection unit and an ink ejection device.

  In recent years, inkjet recording apparatuses have been developed for industrial use, and users are strongly demanding both high image quality and productivity. Therefore, in order to improve the permeability and quick-drying property of the ink after it has landed on the medium, the surface energy of the ink is reduced and an organic solvent is added within a range harmless to the human body.

In order to meet recent market demands, there is a growing demand for UV inks and solvent inks for ink prescription designs that improve outdoor weatherability and scratch resistance of printed matter by inkjet recording devices. However, the low molecular weight acrylate / methacrylate and the organic solvent contained in these inks impose a heavy load on the wiper blade which is the surface cleaning member of the ink repellent film of the inkjet head.
In order to eject such ink with high stability, an ink repellent film is provided on the ejection surface of the inkjet head, and a maintenance unit equipped with a wiper blade for removing the ink adhering to the surface is also used. ..

  Further, the method for cleaning the inkjet head and the wiper blade varies depending on the customer who uses the inkjet recording apparatus, and the adhered ink may be wiped off with an organic solvent that greatly swells rubber such as acetone. In the case of a rubber wiper such as EPDM that has been conventionally used, it easily swells due to the ink component or the cleaning solvent, so that it is largely worn by sliding friction with the ink repellent film or the SUS nozzle cover, or partially lacks an edge. This causes deterioration of ink wiping performance. In other words, ink is left unwiped and the ejection stability is reduced. However, if a resin film is used as a wiper because it does not swell, the resin film is too hard as compared with the ink repellent film, so that the ink repellent film is abraded early and the ejection stability is also deteriorated.

The maintenance unit that stabilizes the ejection state is equipped with a wiper blade that removes the deposits on the ink-repellent film provided on the ink ejection surface, and the rubber hardness is optimized to improve its removal function and extend its life. There is known a method of setting the range (Patent Document 1), and a method of treating the surface with an ink by using a condensate of the same fluorine-containing hydrolyzable compound as the ink repellent film (Patent Document 2).
Further, there is known a method corresponding to UV ink and solvent ink by using a fluorine-based elastomer as a wiper blade (Patent Document 3).

  As the ink repellent film provided on the ejection surface, for example, a fluorocarbon resin having an ether bond in a heterocyclic structure such as Teflon (registered trademark) AF is used. As a method for forming the ink repellent film, a dipping method, a transfer method, or a spray method is used. It is known that a coating method, a spin coating method, a wire bar coating method, a thermal evaporation method, a meniscus coating method, or the like, and heating at a temperature equal to or higher than the glass transition point after film formation (Patent Documents 4 to 8).

  The present invention has been made in view of the above circumstances, and an object thereof is to maintain ink ejection stability of an inkjet head for a long period of time.

In order to solve the above problems, a wiper blade for an inkjet head according to the present invention has the following configuration (1).
(1) A wiper blade for wiping the ink ejection surface of an inkjet head,
The wiper blade is made of elastic rubber, and the elastic rubber has a tan δ peak temperature of −10 ° C. or higher and 10 ° C. or lower, and an equilibrium swelling ratio with acetone of 10% or lower.

  By using the wiper blade for an inkjet head of the present invention, the ink ejection stability of the inkjet head can be maintained for a long period of time.

It is a figure which shows the arrangement | positioning relationship of an inkjet head and a wiping unit. It is a schematic diagram which shows the deformation state of the wiper blade in contact with the nozzle plate. It is a figure explaining the wear state of the wiper blade edge after long-term use. It is a schematic diagram explaining the mechanism in which edge chipping occurs. It is explanatory drawing of the chipped state of the wiper blade edge. It is a figure which shows an example of the viscoelasticity measurement result of a low crosslinking density material. It is a figure which shows an example of the viscoelasticity measurement result of a high crosslink density material. It is a plane explanatory view of the nozzle plate concerning the embodiment of the present invention. It is an expanded sectional explanatory view of one nozzle portion. FIG. 4 is a plan view of a nozzle hole portion for explaining the film thickness of an ink repellent film. It is an expanded sectional explanatory view of one nozzle portion of a nozzle plate concerning an embodiment of the present invention. It is an explanatory view with which an example of a manufacturing method of a nozzle plate is explained. It is a figure explaining the apparatus for obtaining an ink repellent film by vacuum evaporation. It is a description of the state of the ink repellent film before baking. (A) is a SEM photograph of the cross section of the ink repellent film, and (b) is a SEM photograph of the surface of the ink repellent film. It is a figure explaining the state of the ink repellent film after baking. (A) is a SEM photograph of the cross section of the ink repellent film, and (b) is a SEM photograph of the surface of the ink repellent film. It is an explanatory view with which a wiping resistance evaluation device is explained. It is a cross-sectional explanatory view of a direction (liquid chamber longitudinal direction) orthogonal to a nozzle array direction of an example of an inkjet head according to the present invention. FIG. 3 is a cross-sectional explanatory view of the same nozzle in the nozzle array direction (short direction of liquid chamber). FIG. 3 is a plan view illustrating a main part of an example of a device that ejects liquid according to the present invention. It is a principal part side explanatory view of the same apparatus. FIG. 8 is a plan view of a principal part of another example of the liquid ejection unit according to the present invention. It is a figure which shows the relationship between the ratio of TFE and PDD in tetrafluoroethylene perfluorodioxole (TFE / PDD), and glass transition temperature.

The present invention relates to the wiper blade for an inkjet head described in (1) below, but since the following (2) to (10) are included as embodiments of the invention, these embodiments will also be described.
(1) A wiper blade for wiping the ink ejection surface of an inkjet head,
The wiper blade for an inkjet head, wherein the wiper blade is made of elastic rubber, and the elastic rubber has a tan δ peak temperature of −10 ° C. or higher and 10 ° C. or lower and an equilibrium swelling ratio with acetone of 10% or lower.
(2) The wiper blade for an inkjet head according to (1), wherein the equilibrium swelling ratio with acetone is 5% or less.
(3) The wiper blade for an inkjet head according to (1) or (2), wherein the wiper blade has a coefficient of static friction of 0.15 or less.
(4) A wiping unit including the wiper blade according to any one of (1) to (3) above and a wiper blade supporting member that supports the wiper blade.
(5) An ink ejection unit including an inkjet head and a wiper blade for wiping an ink ejection surface of the inkjet head, wherein the wiper blade is the inkjet head according to any one of (1) to (3) above. Ink discharge unit that is a wiper blade for use.
(6) The ink jet head has an ink repellent film formed on the ink ejection surface,
The static discharge coefficient of the wiper blade is smaller than the static friction coefficient of the ink repellent film.
(7) The ink discharge unit according to (6), wherein the ink repellent film is a film containing a fluororesin having a fluorine-containing heterocyclic structure having an ether bond in a PTFE skeleton.
(8) The inkjet head includes a nozzle base material in which nozzle holes are formed, and the ink repellent film is formed on the surface of the nozzle base material.
The ink discharge unit according to (7) above, wherein the ink repellent film is inclined in the outer peripheral portion of the nozzle hole in a direction in which the film thickness decreases toward the edge side of the nozzle hole.
(9) An apparatus for ejecting ink, comprising the ink ejection unit according to any one of (5) to (8) above.
(10) The device for ejecting the ink according to (9), wherein the ejected ink is an ink containing an acrylic / methacrylic monomer or a solvent ink.

  In the above-described embodiment, the point that the elastic rubber having a single-layer structure is used as the wiper blade is the same as the conventional technique, but the peak temperature of tan δ in the viscoelasticity measurement is in the range of −10 ° C. to 10 ° C. By selecting a rubber having an equilibrium swelling ratio of 10% or less, it becomes suitable as a wiper blade for removing ink containing a large amount of a component that greatly swells rubber, such as UV ink and solvent ink, from the surface of the ink repellent film. The equilibrium swelling ratio of acetone is preferably 5% or less.

At a temperature lower than the peak temperature of tan δ of the elastic rubber, the rubber becomes a glass state, and at a temperature higher than the peak temperature, it becomes a rubber state. As the crosslink density of the elastic rubber increases, the peak temperature shifts to the higher direction.
The operating environment temperature of the wiper blade (for example, the temperature inside the ink ejection device) is 10 to 35 ° C. If the peak temperature is 10 ° C. or less, the rubber can be used in a rubber state at the operating environment temperature. A conformability can be obtained with respect to surface irregularities.
An ordinary rubber has a tan δ peak temperature of −30 ° C., the lower limit is defined as −10 ° C. as a condition under which crosslinking does not occur and swelling occurs, and the upper limit is 10 ° C. in order to obtain rubber elasticity at a use environment temperature. And

  Another requirement of the market for inkjet printed materials is quick drying, and the surface tension of the ink is becoming smaller in order to improve the permeability of the media. When the dynamic surface tension is 25 mN / m or less, it cannot be easily repelled by a general silicone ink repellent film, and the ejection stability of the inkjet head cannot be obtained. To solve this problem, by using a film containing a fluororesin having a fluorine-containing heterocyclic structure having an ether bond such as Teflon (registered trademark) AF in a PTFE skeleton, dynamic surface tension is 20 mN / m or less. Ink repellency can be obtained even with the above ink.

  Therefore, the tan δ peak temperature is in the range of −10 ° C. or higher and 10 ° C. or lower, and the equilibrium swelling ratio of acetone is 10% or lower. The wiper blade is made of rubber and the ether such as Teflon (registered trademark) AF is used. By combining a fluorine-containing heterocyclic structure having a bond with an ink repellent film containing a fluororesin having a PTFE skeleton to form an ink ejection device, a general water-based dye ink, water-based pigment ink, solvent ink, or UV ink is obtained. , A system with a wide range of ink compatibility.

Next, the wiper blade will be described in detail with reference to FIGS.
FIG. 1 shows the inkjet head 404 and the wiping unit 50. The inkjet head 404 includes the nozzle plate 10 and the ink repellent film 40 formed on the surface of the nozzle plate 10. The wiping unit 50 includes a wiper blade 1 and a wiper blade support member 2 that supports the wiper blade 1.
FIG. 1 shows a state in which the wiper blade 1 is arranged so that the ink can be properly removed from the surface of the nozzle plate 10 having the ink repellent film.

Generally, elastic rubber is often used as the material of the wiper blade 1, and the elasticity moves the surface of the nozzle plate 10 while largely deforming as shown in FIG. 2 to remove the ink. Another reason why the elastic rubber is preferable is that fine unevenness is present on the surface of the nozzle plate 10, and it is necessary to deform following the unevenness when rubbing.
However, rubber that is easily deformed generally has low cross-linking density and thus has low abrasion resistance in the first place, and since it easily swells greatly in organic solvents, etc., it has even lower abrasion resistance when used as a wiper blade for solvent ink and UV ink. The state continues, and the wiper blade edge is greatly worn early as shown in FIGS. 5 is a view of the wiper blade in FIG. 3 as seen from the direction of the arrow shown in the figure. The contact pressure with which the wiper blade contacts the ink repellent film becomes uneven, and ink streaks occur on the surface of the ink repellent film where the wiper blade does not contact. cause.

  To solve this problem, it is sufficient to increase the crosslink density of rubber, but generally, when the crosslink density of rubber is increased, the tan δ peak temperature also rises. However, if the crosslinking density is increased to such an extent that rubber elasticity is lost in the operating temperature range of the wiper, that is, in the environment of 10 ° C. to 35 ° C., the fine irregularities on the nozzle plate surface cannot be tracked as described above, and the ink repellent film surface can not be followed. In addition to being unable to remove the ink, the locally high cross-linking density portion becomes harder than the ink repellent film, and the ink repellent film may be worn as if scratched by a sharp needle.

  Further, when the elastic rubber having a significantly increased crosslink density is exposed to the solvent ink or the UV ink for a long time, the low crosslink density portion (4 in FIG. 4) swells to lower the abrasion resistance, but the high crosslink density portion ( Since 5) in FIG. 4 is unlikely to swell, the intermolecular bond between the two is destroyed by wiping, so that a so-called “edge defect” occurs in which the high crosslink density portion is largely detached. Ink removal cannot be performed at the portion where the edge chipping occurs, and the ink adheres to the surface of the nozzle plate in a stripe shape, which causes ejection bending.

  Therefore, it is not necessary to simply increase the crosslink density, and it is also necessary that the peak temperature of tan δ in viscoelasticity measurement is 10 ° C. or lower. However, even if the crosslink density is increased to a tan δ peak temperature of 10 ° C. using general EPDM or the like, sufficient swelling resistance cannot be obtained with respect to the organic solvent in the solvent ink.

  Therefore, as the rubber, a fluororubber having high chemical resistance is used as a main material, and the crosslink density is adjusted so that the tan δ peak temperature is in the range of -10 ° C to 10 ° C. It becomes a wiper blade that deforms following minute irregularities on the surface of the nozzle plate 10 while maintaining rubber elasticity at ambient temperature.

  Viton and Kalrez manufactured by DuPont and Daiel manufactured by Daikin Co., Ltd. are mainly used as the fluororubber, and crosslinking by peroxide vulcanization is preferable in order to further improve chemical resistance. The glass transition temperature can be set in the range of -10 ° C to 10 ° C by adjusting the addition amount of peroxide.

Here, regarding the measurement of the glass transition temperature, according to JIS K6394, a dynamic viscoelasticity measurement is performed in a tensile mode using a DMS7100 manufactured by SII Nano Technologies, Inc., which is a ratio of a storage elastic modulus to a loss elastic modulus, tan δ. Can be obtained as the peak temperature of. 6 and 7 are diagrams showing an example of the viscoelasticity measurement result. The measurement sample is obtained by cutting an elastic member of a wiper blade into a strip shape of 40 × 10 × 2 mm or cutting a sheet after press molding. The measurement frequency was 1 Hz, the temperature rising rate was 3 ° C./min, and the measurement was performed from −30 ° C. to 50 ° C. tan δ is a tangent loss which is a ratio of a storage elastic modulus and a loss elastic modulus as shown by the following formula.
tan δ = loss elastic modulus E ″ / storage elastic modulus E ′

Next, the equilibrium swelling rate with acetone was calculated according to JIS K6258 by immersing the rubber pieces cut out into 10 × 5 × 2 mm in acetone for 72 hours, and changing the mass before and after.
Equilibrium swelling rate = (w2-w1) / w1 × 100 [%]
w1: initial rubber piece mass [g]
w2: Mass of rubber piece after immersion for 72 hours [g]

  The reason why acetone was selected from the organic solvents is that it is suitable for relative comparison of differences in crosslink density because it swells rubber easily, and that it uses an inkjet recording device that ejects solvent ink or UV ink. This is because it is a normal user's work to wipe the surface of the nozzle plate of the inkjet head and the edge of the wiper blade with a non-woven fabric impregnated with acetone. Therefore, it is preferable to evaluate using acetone as the condition with the largest load.

The static friction coefficient of the wiper blade is preferably smaller than the static friction coefficient of the ink repellent film formed on the ink ejection surface of the inkjet head. As a result, the sliding stress between the ink repellent film and the wiper blade is reduced, wear of both is suppressed, and the meniscus position of the nozzle hole does not change for a long period of time, thereby maintaining ejection stability. The coefficient of static friction of the wiper blade is preferably 0.15 or less.
Generally, the higher the crosslink density of an elastic rubber is, the smaller the stick-slip motion is, and the tackiness is lost, so that the friction coefficient of the surface becomes smaller.
Therefore, by using the elastic rubber having a high crosslink density as the wiper blade, the frictional force when sliding on the surface of the nozzle plate is reduced, and the effect of suppressing the progress of wear of both the wiper blade and the nozzle plate can be obtained.

Next, the ink repellent film of the nozzle plate 10 will be described with reference to FIGS. 8 and 9.
The nozzle plate 10 includes a nozzle base material 20 in which holes 21 (hereinafter, referred to as “nozzle holes”) to be nozzles 11 for ejecting a liquid are formed, an intermediate layer 30 formed on the surface of the nozzle base material 20, The ink-repellent film 40 is formed on the liquid ejection surface side surface.

  The nozzle base material 20 is, for example, a metal flat plate member. Although a flat plate member made of stainless steel is used as the nozzle base material 20, the present invention is not limited to this. In this embodiment, the nozzle hole 21 of the nozzle substrate 20 is composed of a cylindrical portion 21a on the liquid ejection surface side and a truncated cone-shaped portion 21b on the opposite side to the liquid ejection surface side.

The intermediate layer 30 is composed of one or a plurality of layers such as a layer serving as a base of the ink repellent film 40, for example, a SiO ₂ layer, a layer of a silane coupling agent, or the like.

  The ink repellent film 40 is a film containing a fluororesin having a fluorine-containing heterocyclic structure having an ether bond in the PTFE skeleton (hereinafter, also referred to as “fluororesin layer”). The ink-repellent film 40 has a sloped area 41 in the outer peripheral portion of the nozzle 11 in which a sloped surface 41 a is formed in a direction in which the film thickness decreases toward the edge 11 a side of the nozzle 11. The sloped surface 41a of the sloped area 41 may be linearly slanted in a cross-sectional shape, or may be curvilinearly slanted.

  The region 42 of the ink repellent film 40 other than the slope region 41 except the slope region 41 has a substantially constant film thickness and is flat. As described above, since the ink-repellent film 40 is provided with the inclined surface region 41 in the outer peripheral portion of the nozzle 11, the ink-repellent film 40 due to the wiper blade being caught by the edge of the ink-repellent film 40 when wiping with the wiper blade. Can be reduced and prevented. Thereby, the durability of the ink repellent film 40 can be improved.

  In addition, it is preferable that the intermediate layer 30 be a silane coupling agent layer having an amino group as a base layer of the ink repellent film 40. As a result, the amino group and the material of the ink repellent film interact with each other to obtain high adhesion.

Next, the ink repellent film in each of the above embodiments will be described.
The ink repellent film 40 is a film containing a fluororesin having a fluorine-containing heterocyclic structure having an ether bond in the PTFE skeleton (hereinafter, also simply referred to as “fluororesin”). The fluororesin preferably has a glass transition point Tg at room temperature or higher.

The PTFE (polytetrafluoroethylene) skeleton is a main chain in which structural units of TFE (tetrafluoroethylene) represented by the following structural formula (1) are repeated.

  The fluorine-containing heterocyclic structure having an ether bond is a structure of a 5- to 8-membered ring organic compound containing 1-2 oxygen as a hetero atom in the chemical structural formula.

  From the viewpoint of liquid repellency (contact angle), it is preferable to use a fluorine resin having a fluorine content of 50% by mass or more. The ratio of the ring structure in the main chain is preferably 20% by mass or more, and more preferably 30% by mass from the viewpoint of the strength of the target coating film, the solubility in a solvent, the adhesion to the nozzle base material, and the like. % Or more is preferable.

  Among the fluororesins, it is particularly preferable to use an amorphous fluororesin. Since the amorphous fluororesin is excellent in film strength, adhesion to a substrate, film uniformity, etc., the effects of the present invention can be further exerted.

  Examples of the structural unit having a fluorine-containing heterocyclic structure having an ether bond include those represented by the following structural formulas (2) to (6).

  The fluororesin having a fluorine-containing heterocyclic structure having an ether bond of the structural unit represented by the above structural formula (5) in the PTFE skeleton is issued by DuPont under the trade name of Teflon (registered trademark) AF. Teflon (registered trademark) AF is a copolymer [TFE / PDD: tetrafluoroethylene-perfluorodioxole copolymer] having a tetrafluoroethylene structure and a dioxole structure having a perfluoroalkyl group, and is an ink repellent for various inks. It is excellent and preferable in terms of properties.

  The tetrafluoroethylene-perfluorodioxole copolymer is an amorphous fluororesin, which is a transparent resin. As the tetrafluoroethylene-perfluorodioxole copolymer, those synthesized appropriately may be used, or commercially available products may be used.

  The tetrafluoroethylene-perfluorodioxole copolymer has a glass transition point as shown in FIG. 22 as the ratio of the perfluoroidioxole copolymer (PDD) component to the tetrafluoroethylene (TFE) component increases. To rise. Commercially available products are Teflon (registered trademark) AF1600 having a glass transition point of 160 ° C. and Teflon (registered trademark) AF2400 having a glass transition point of 240 ° C.

  Further, a fluororesin having a fluorine-containing heterocyclic structure having an ether bond of the structural unit represented by the above structural formula (2) in the PTFE skeleton is issued by Solvay under the trade name of Hyflon.

  Further, a fluororesin having a fluorine-containing heterocyclic structure having an ether bond of the structural unit represented by the structural formula (6) in the PTFE skeleton is a trade name of CYTOP CTX-105 or CYTOP CTX-805, and Asahi Glass Co., Ltd. It is issued by the company.

  The average thickness of the ink repellent film 40 (fluorine resin layer) is preferably 1 μm to 3 μm.

  In order to obtain a smooth surface without the irregularities present on the surface of the nozzle substrate 20 affecting the surface of the fluororesin layer forming the ink repellent film 40, the ink repellent film 40 may have a thickness of 1 μm or more. preferable. Further, the ink repellent film 40 is preferably thin from the viewpoint of maintaining the shape of the nozzle 11 and the nozzle diameter. When the average thickness of the ink repellent film 40 is in the range of 1 μm to 3 μm, it is preferable from the viewpoint of wiping durability and the shape of the nozzle 11. The average thickness can be measured by, for example, a cross-section SEM.

  The arithmetic average roughness Ra of the ink repellent film 40 (fluorine resin layer) is preferably 1.0 nm or less. When the average roughness Ra is 1.0 nm or less, the nozzle surface becomes extremely smooth, less unwiping is left by wiping, and wear resistance is excellent.

  The arithmetic mean roughness Ra is defined as follows. In the section of length l, only the reference length is extracted from the roughness curve in the direction of the average line, the X axis is taken in the direction of the average line of the extracted portion, and the Y axis is taken in the direction of longitudinal magnification. When the roughness curve is represented by y = f (x), the value obtained by the following formula (1) is represented by micrometers (μm).

Next, an example of a method for manufacturing the wiper blade according to the present invention will be described.
It is preferable to use fluororubber as the material of the elastic rubber.
By adding peroxide to fluororubber and press-molding at a temperature of 150 to 300 ° C., the rubber is cross-linked and a rubber sheet having a predetermined thickness is molded.
The wiper blade is obtained by cutting or punching this into the shape of the wiper blade.

Next, an example of a method for manufacturing a nozzle plate according to the present invention will be described with reference to FIG.
In the base material preparing step of FIG. 12A, the metal plate-like member serving as the nozzle base material 20 is subjected to mirror polishing step and cleaning step.
The nozzle base material 20 is, for example, a metal flat plate member having a length of 30 mm, a width of 15 mm, and a thickness of 0.05 mm, in which the nozzle holes 21 are formed by press working.

  Stainless steel, which is a typical example of an iron-based alloy, can be used as the metal flat plate member. The "stainless steel" is a steel having a Cr content of 10.5% or more as described in JIS G0203: 2000, No. 4201, and various steel types can be used.

  Cr: 10.5 to 35 mass%, preferably 11 to 30 mass%, Ni: 5 to 30 mass% if austenitic, Cr: 10.5 to 35 mass% if ferritic. , Preferably about 15 to 30% by mass of steel can be used. For example, the steel types specified in JIS G4305: 2005 and JIS G4312-1991 can be exemplified. Alternatively, stainless steel having various characteristics improved by adding other alloying elements based on these standard steel types can also be used.

As the nickel-based alloy, a highly corrosion resistant Ni-Cr-Fe alloy containing Cr: 12 to 27 mass% and Fe: 5 to 18 mass% can be used. This type of alloy is known as an "Inconel alloy".

  Then, punching is performed on the metal flat plate member from the side opposite to the ejection surface, and burrs generated by the punching are removed by polishing or chemical etching.

Next, in the intermediate layer forming step of FIG. 12B, a SIO ₂ film 31 is formed as the intermediate layer 30 on the surface of the nozzle substrate 20 by a sputtering method or the like, and the tape is formed on the surface opposite to the liquid ejection surface side. After attaching 60, the silane coupling agent layer 32 is formed on the surface of the SIO ₂ film 31.

  As the silane coupling agent, an aminosilane coupling agent is preferable, and 3-aminopropyltriethoxysilane is particularly preferable. Specific examples include KBE-903 (Shin-Etsu Chemical) and A1100 (Momentive Performance Material). The silane coupling agent layer 32 may be formed by any method such as a dipping method, a spin coating method, or a spray method.

  Aminosilane-based coupling agents have a good affinity between the ether portion of the heterocycle and the amino group in the fluororesin molecule. Therefore, by providing a single silane coupling agent having an amino group on the silica layer, the fluororesin The fixing property of is greatly improved.

Thereafter, a step of forming a vapor deposition film 44 to be the ink repellent film 40 shown in FIG. 12C is performed, and the vapor deposition film 44 in which an ink repellent material (denoted as AF) is vapor deposited on the nozzle base material 20 by the vapor deposition method. To form a film. At this time, the vapor deposition film 44 to be the ink repellent film 40 is formed on the surface of the silane coupling agent layer 32 (the surface of the intermediate layer 30) on the nozzle substrate 20, as described above. The fluororesin layer includes a fluororesin having ink repellency. As the fluororesin, a fluororesin having a PTFE skeleton having a fluorine-containing heterocyclic structure having an ether bond is used.

  As such a fluororesin, as described above, tetrafluoroethylene perfluorodioxole copolymer (Teflon (registered trademark) AF: manufactured by DuPont), CYTOP CTX-105 (trade name, manufactured by Asahi Glass Co., Ltd.), Alternatively, CYTOP CTX-805 (trade name, manufactured by Asahi Glass Co., Ltd.) is particularly preferable.

The fluororesin is heated to 350 to 420 ° C. under a high vacuum of 1.5 to 8.0 × 10 ⁻³ Pa so that the thickness of the vapor deposition film is on the nozzle base material 20 facing the vapor deposition source. Vacuum deposition is performed until the thickness is about 1 to 3 μm. For example, as shown in FIG. 13, the vacuum vapor deposition is performed by disposing the vapor deposition source 501 and the nozzle base material 20 in a vacuum chamber 500 so as to face each other.

Then, as shown in FIG. 12D, a flattening process by annealing is performed.
The nozzle base material 20 is not particularly heated, and a film obtained by vapor deposition at a certain temperature is baked (annealed) at a temperature not lower than the glass transition temperature of the fluororesin.

  Baking may be carried out by any method such as a convection drying oven, a circulating air drying oven, a flash annealing device, a halogen lamp heater and a vacuum dryer, but it is preferable to carry out the baking in a nitrogen atmosphere.

  By baking (annealing) at a temperature not lower than the glass transition temperature of the fluororesin, the ink repellent film (fluororesin layer) 40 that is dense, has a smooth surface, and has a sloped region 41 that becomes thinner toward the nozzle 11 is obtained. Becomes

FIG. 14A shows a SEM photograph of the cross section and FIG. 14B shows a SEM photograph of the surface of the ink repellent film before baking.
A cross-sectional SEM photograph of the ink-repellent film after baking is shown in FIG. 15A, and a surface SEM photograph thereof is shown in FIG. 15B.

  As shown in FIG. 14 (a), the surface of the fluororesin film had pores 600 inside the film, and the film surface had a contact angle to pure water of 129 ° and Ra = 8 nm. On the other hand, after baking, as shown in FIG. 15 (a), the nozzle 11 has a taper shape (slope shape) within a range of 40 nm from the edge 11 a and a flat surface outside the periphery of 40 nm. ..

  It should be noted that, when performing the vapor deposition process of vapor-depositing the fluorocarbon resin on the nozzle base material 20, by performing vapor deposition while heating the nozzle base material 20 at a temperature lower than the glass transition temperature, the same as when baking is performed after the vapor deposition. The effect of can be obtained.

  Further, the obtained film does not flow even at a temperature of 150 ° C. or higher, which is generally required to cure the adhesive, and therefore, even when exposed to a high temperature environment after vapor deposition, a region other than the film-forming region is liquid repellent. As a result, a nozzle plate having high ejection reliability can be obtained without being contaminated with the material.

  Here, the film thickness of the ink repellent film 40 will be described with reference to FIG. FIG. 10 is a plan view of a nozzle hole portion used for the same description.

  As shown in FIG. 10, the film thickness was measured at 20 points on a circle CC 5 μm away from the edge 11a of the nozzle 11 in the direction normal to the nozzle center 11o on the normal line from the edge 11a, and the following formula (2) was used. Let the arithmetic mean of the population of film thicknesses obtained in step 3 be the average film thickness m.

  Then, the amount obtained by the following equation (3) is defined as the variance, and the positive square root σ of this variance is defined as the standard deviation of the population (film thickness).

Here, the smaller the variation coefficient “film thickness standard deviation σ / average film thickness m”, the smaller the film thickness variation with respect to the film thickness and the more flat it is.
The average film thickness a on the circumference CC was measured by an ellipsometer with a spot diameter of φ10 μm at equal intervals on the circumference CC.

When the presence or absence of unwiped liquid on the surface after wiping when changing σ / m was evaluated, σ / m = 0.03: none, σ / m = 0.06: none, σ / m = 0. 09: None, but σ / m = 0.12: Yes, σ / m = 0.15: Yes. When there is no unwiped portion of the liquid, the ejection bending of the ejected liquid does not occur.
Therefore, by setting σ / m <0.1, the injection bending can be reduced.

Next, another embodiment of the nozzle plate will be described based on the enlarged sectional view of the nozzle portion shown in FIG.
In the nozzle plate 10, the intermediate layer 30 is formed also on the inner wall surface of the nozzle hole 21 of the nozzle base material 20, and the ink repellent film 40 is also formed on the inner wall surface of the nozzle 11.

  Here, the film thickness t2 of the ink repellent film 40b on the inner wall surface of the nozzle 11 (corresponding to the wall surface of the nozzle hole 21 of the nozzle base material 20) is the film thickness t1 of the region 42 other than the inclined surface region of the ink repellent film 40a. 1/10 or less (t2 / t1 <0.1) is preferable.

The film thickness t2 of the ink repellent film 40a on the inner wall surface of the nozzle 11 is preferably thin in order to realize stable ejection, as the nozzle diameter varies more as the film thickness increases. On the other hand, generally, the thicker the thickness t1 of the ink repellent film 40a on the liquid ejection surface side is, the more the durability is improved.
The ink-repellent film 40 having these contradictory film thicknesses can be obtained, for example, by using a vapor phase method.
The film thickness can be measured by exposing the nozzle cross section by ion polishing and observing with a SEM.

  The relationship between the film thickness t2 of the ink repellent film 40b on the inner wall surface of the nozzle 11 and the film thickness t1 of the region 42 other than the inclined surface region of the ink repellent film 40a was evaluated. When the ratio of t2 / t1 exceeds 0.1, the ink-repellent film is formed by the dip method, and then the dip liquid that has flowed into the nozzle is blown out and opened. A sample was obtained by drying.

  As a result, the presence / absence of injection bending was t2 / t1 <0.05: none, t2 / t1 <0.10: none, and t2 / t1 ≧ 0.3: yes. Therefore, if t2 / t1 <0.10, the injection bending can be reduced or prevented.

  Next, an example of the inkjet head according to the present invention will be described with reference to FIGS. 17 and 18. 17 is a cross-sectional explanatory view of the same head in a direction orthogonal to the nozzle arrangement direction (liquid chamber longitudinal direction), and FIG. 18 is a cross-sectional explanatory view of the same head in the nozzle arrangement direction (liquid chamber short-side direction).

  In this inkjet head, a nozzle plate 101 according to the present invention, a flow path plate 102, and a diaphragm member 103 made of a thin film member as a wall member are laminated and bonded. A piezoelectric actuator 111 for displacing the diaphragm member 103 and a frame member 120 as a common liquid chamber member are provided.

  By the nozzle plate 101, the flow path plate 102, and the vibrating plate member 103, the individual liquid chamber 106 that communicates with the plurality of nozzles 104 that eject the liquid, the fluid resistance portion 107 that supplies the liquid to the individual liquid chamber 106, and the fluid resistance portion 107. And a liquid introducing section 108 leading to the.

  Then, the liquid is supplied from the common liquid chamber 110 serving as the common flow path of the frame member 120 to the individual liquid chamber 106 through the liquid inlet portion 108 and the fluid resistance portion 107 through the supply port 109 formed in the diaphragm member 103. A filter may be provided at the supply port 109.

The diaphragm member 103 is a wall member that forms a wall surface of the individual liquid chamber 106 of the flow path plate 102. The vibrating plate member 103 has a three-layer structure, and one layer on the flow path plate 102 side forms a deformable vibrating region (vibrating plate) 130 in a portion corresponding to the individual liquid chamber 106.
Then, on the opposite side of the vibration plate member 103 from the individual liquid chamber 106, an actuator means for deforming the vibration region 130 of the vibration plate member 103 and a piezoelectric actuator 111 including an electromechanical conversion element as a pressure generating means are arranged. There is.

  This piezoelectric actuator 111 has a plurality of laminated piezoelectric members 112 bonded to a base member 113 with an adhesive, and the piezoelectric member 112 is grooved by half-cut dicing so that a required number of piezoelectric members 112 are formed. The columnar piezoelectric elements (piezoelectric columns) 112A and 112B are formed in a comb shape at predetermined intervals.

Although the piezoelectric elements 112A and 112B of the piezoelectric member 112 are the same, they are a piezoelectric element 112A that is driven by giving a driving waveform and a piezoelectric element 112B that is used as a mere column without giving a driving waveform.
Then, the piezoelectric element 112A is joined to the convex portion 130a which is an island-shaped thick portion formed in the vibration region 130 of the diaphragm member 103. Further, the piezoelectric element 112B is joined to the convex portion 130b which is the thick portion of the diaphragm member 103.
The piezoelectric member 112 is formed by alternately stacking piezoelectric layers and internal electrodes. The internal electrodes are drawn to the end faces to provide external electrodes, and the piezoelectric members 112 are flexible for applying a drive signal to the external electrodes of the piezoelectric element 112A. The FPC 115 as a wiring member is connected.

  The frame member 120 is formed by injection molding of polyphenylene sulphite, which is an epoxy resin or a thermoplastic resin, for example, and a common liquid chamber 110 to which liquid is supplied from a head tank or a liquid cartridge is formed.

  In this ink jet head, for example, by lowering the voltage applied to the piezoelectric element 112A from the reference potential, the piezoelectric element 112A contracts, the vibration region 130 of the diaphragm member 103 is pulled, and the volume of the individual liquid chamber 106 expands. Then, the liquid flows into the individual liquid chamber 106.

  After that, the voltage applied to the piezoelectric element 112A is increased to expand the piezoelectric element 112A in the stacking direction, deform the vibrating region 130 of the vibrating plate member 103 in the nozzle 104 direction, and contract the volume of the individual liquid chamber 106. As a result, the liquid in the individual liquid chamber 106 is pressurized, and the liquid is ejected (jetted) from the nozzle 104.

Then, by returning the voltage applied to the piezoelectric element 112A to the reference potential, the vibrating region 130 of the vibrating plate member 103 is restored to the initial position, and the individual liquid chamber 106 expands to generate negative pressure. The liquid is filled from the liquid chamber 110 into the individual liquid chamber 106. Therefore, after the vibration of the meniscus surface of the nozzle 104 is attenuated and stabilized, the operation for the next droplet ejection is started.
The method of driving the head is not limited to the above example (pull-push ejection), and pull ejection or push ejection may be performed depending on the method of giving the drive waveform.

  Next, an example of an apparatus for ejecting ink according to the present invention will be described with reference to FIGS. 19 and 20. FIG. 19 is a plan view of the main part of the apparatus, and FIG. 20 is a side view of the main part of the apparatus.

  This apparatus is a serial type apparatus, and the carriage 403 reciprocates in the main scanning direction by the main scanning moving mechanism 493. The main scanning movement mechanism 493 includes a guide member 401, a main scanning motor 405, a timing belt 408, and the like. The guide member 401 is bridged between the left and right side plates 491A and 491B and movably holds the carriage 403. Then, the carriage 403 is reciprocally moved in the main scanning direction by the main scanning motor 405 via the timing belt 408 that spans between the driving pulley 406 and the driven pulley 407.

  An inkjet head 404 is mounted on the carriage 403. The inkjet head 404 ejects ink of each color of yellow (Y), cyan (C), magenta (M), and black (K), for example. Further, the inkjet head 404 is arranged such that a nozzle row composed of a plurality of nozzles is arranged in the sub-scanning direction orthogonal to the main scanning direction, and the ejection direction is directed downward.

  The ink stored in the liquid cartridge 450 is supplied to the head tank 441 by the supply mechanism 494 for supplying the liquid stored outside the inkjet head 404 to the inkjet head 404.

  The supply mechanism 494 includes a cartridge holder 451, which is a filling unit for mounting the liquid cartridge 450, a tube 456, a liquid sending unit 452 including a liquid sending pump, and the like. The liquid cartridge 450 is detachably attached to the cartridge holder 451. Ink is supplied from the liquid cartridge 450 to the head tank 441 by the liquid supply unit 452 via the tube 456.

  This apparatus includes a transport mechanism 495 for transporting the sheet 410. The transport mechanism 495 includes a transport belt 412, which is a transport unit, and a sub-scanning motor 416 for driving the transport belt 412.

The conveyance belt 412 adsorbs the sheet 410 and conveys it at a position facing the inkjet head 404. The conveyor belt 412 is an endless belt, and is stretched between a conveyor roller 413 and a tension roller 414. The adsorption can be performed by electrostatic adsorption or air suction.
Then, the transport belt 412 is rotated in the sub-scanning direction by the sub-scanning motor 416 rotatably driving the transport roller 413 via the timing belt 417 and the timing pulley 418.
Further, on one side of the carriage 403 in the main scanning direction, a maintenance / recovery unit 420 for maintenance / recovery of the inkjet head 404 is arranged beside the transport belt 412.

  The maintenance / recovery unit 420 includes a wiping unit (see FIG. 1) having a wiper blade 422 according to the present invention, and a cap member 421 for capping a nozzle surface (a surface on which nozzles are formed) of the inkjet head 404, for example. There is.

  The main-scanning moving mechanism 493, the supply mechanism 494, the maintenance / recovery mechanism 420, and the transport mechanism 495 are attached to a housing including side plates 491A and 491B and a back plate 491C.

In this apparatus configured as described above, the sheet 410 is fed onto the transport belt 412 and adsorbed, and the sheet 410 is transported in the sub-scanning direction by the orbital movement of the transport belt 412.
Therefore, by moving the carriage 403 in the main scanning direction and driving the inkjet head 404 in accordance with the image signal, the liquid is ejected onto the stopped paper 410 to form an image.
As described above, since this apparatus includes the wiper blade according to the present invention, it is possible to stably form a high quality image.

Next, an example of the ink ejection unit according to the present invention will be described with reference to FIG. FIG. 21 is a plan view of an essential part of the ink ejection unit.
The ink discharge unit is configured to include at least an inkjet head and a wiper blade (wiping unit) according to the present invention. In the liquid discharge unit shown in FIG. 21, among the members constituting the device for discharging the ink, the side plate It is composed of a housing portion composed of 491A, 491B and a back plate 491C, a main scanning movement mechanism 493, a carriage 403, a maintenance / recovery unit 420, and an inkjet head 404. The supply mechanism 494 can be further attached to the ink discharge unit shown in FIG.

  In the present application, the “device that ejects ink” is a device that includes an inkjet head or an ink ejection unit and that drives the inkjet head to eject ink. For example, an inkjet recording device that forms an image on a recording material such as paper with ink is included.

The "ink ejecting device" may include a means for feeding, conveying, and discharging a material to which ink can be attached, a pretreatment device, a posttreatment device, and the like.
Further, the “device for ejecting ink” is not limited to a device in which a significant image such as characters and figures is visualized by the ejected ink. For example, it also includes one that forms a pattern or the like that has no meaning per se, and one that forms a three-dimensional image.

  The above-mentioned "ink can be adhered" means that the ink can be at least temporarily adhered, and that the ink is adhered and fixed, the ink is adhered and penetrated, and the like. Specific examples include recording media such as paper, recording paper, recording paper, film and cloth, electronic substrates, electronic components such as piezoelectric elements, powder layers (powder layers), organ models, inspection cells and other media. Yes, and unless otherwise specified, includes everything to which the ink adheres.

  Further, “device for ejecting ink” includes both a serial type device that moves the inkjet head and a line type device that does not move the inkjet head, unless otherwise specified.

  Further, the "ink jet head" is not limited to the pressure generating means used. For example, in addition to the piezoelectric actuator (which may use a laminated piezoelectric element) as described in the above embodiment, a thermal actuator using an electrothermal conversion element such as a heating resistor, a vibration plate and a counter electrode. An electrostatic actuator or the like may be used.

  Further, in the terms of the present application, image formation, recording, printing, printing, printing, modeling, etc. are synonymous.

  The present invention will be described in more detail based on the following examples, but the technical scope of the present invention is not limited to the following examples.

[Wiper blade]
Viton GBL-200 was used as fluororubber, 5 parts of peroxide was added to 100 parts of rubber, and secondary vulcanization was performed by press molding at 180 ° C. for 1 hour and at 250 ° C. for 5 hours. A 1 mm rubber sheet was obtained. This was cut to obtain a wiper blade.

[Nozzle base material]
A metal flat plate member made of SUS316L having a length of 30 mm, a width of 15 mm and a thickness of 0.05 mm was punched from the side opposite to the liquid ejection surface by punching. The punch used for the punching process has a cylindrical tip portion having a length of 10 μm and a diameter of 20 μm. Burrs generated on the liquid ejection surface side were removed by polishing.

  Accordingly, the diameter of the cylindrical portion 21a on the ink ejection surface side is 20 μm, the diameter of the opening of the truncated cone-shaped portion 21b on the surface opposite to the ink ejection surface is 40 μm, and the height of the cylindrical portion 21a is 10 μm. The nozzle base material 20 in which 384 of 21 were formed was obtained.

[Ink repellent film]
A tetrafluoroethylene perfluorodioxole copolymer (Teflon (registered trademark) AF2400: manufactured by DuPont) on the ink ejection surface side of the nozzle substrate 20 in a high vacuum of 1.5 to 8.0 × 10 ⁻³ Pa. Below, it was heated to 350 to 420 ° C., and vacuum vapor deposition was performed until the thickness of the vapor deposition film became about 1 to 3 μm at the portion facing the vapor deposition source.
The obtained vapor-deposited film was baked at a temperature not lower than the glass transition temperature of the fluororesin to form a fluororesin film which is a dense and smooth ink repellent film.

[Evaluation of wiping durability]
Wiping durability was evaluated using the evaluation device shown in FIG. Specifically, the nozzle plate 1 is fixed in the container 601 containing the ink 610 by the fixing jig 602, the wiper 611 is fixed in the fixing jig 612, and the nozzle plate 1 is wiped with respect to the surface of the ink repellent film 40. (Wiping) operation was performed.

  As the ink 610, SPC-0371 (UV ink) and SS-21 (solvent ink), which are ink jet inks manufactured by Mimaki Engineering Co., Ltd., were used.

<Evaluation of ink adhesion / jet bending>
An inkjet head including the nozzle plates of Examples 1 to 10 and Comparative Examples 1 to 4 was constructed and mounted on IPSiO G515 manufactured by Ricoh Co., Ltd., and residual ink adhesion after wiping and jetting bending were evaluated. The evaluation is jetting by observing the presence or absence of ink on the nozzle plate surface after performing the wiping durability test 10,000 times (after the durability test), printing the nozzle check pattern, and visually observing the printed nozzle check pattern. Evaluation was made based on the presence or absence of bending.

  The evaluation results are shown in Tables 1 and 2. In Tables 1 and 2, “Δ” means that the ink is within a level that does not cause any problem in actual use, and “x” means that the ink adheres and bends to the extent that it cannot be used in actual use. “O” means less ink adhesion and ejection deflection than “Δ”, and “⊚” means less ink attachment and ejection deflection than “O”.

In any of Examples 1 to 10, after the wiping durability test, ink adhesion on the nozzle plate and bending of the nozzle check pattern are not a problem in practical use.
On the other hand, in each of Comparative Examples 1 to 4, the ink repellent film is greatly worn after the wiping durability, and the ink wiping function of the wiper blade is deteriorated. It is bent at a level that cannot withstand actual use.
In Comparative Example 1, since the wiper blade was the EPDM rubber used conventionally, the ink swelled and greatly worn, and the ink wiping function deteriorated at an early stage.
In Comparative Example 2, a urethane rubber blade that was conventionally used as a cleaning blade in the electrophotographic field was used as a wiper blade. However, as in Example 1, it swollen due to the ink component and thus was greatly worn and the ink wiping function deteriorated early.
In Comparative Example 3, since the ink repellent film in the vicinity of the nozzle hole has a right angle shape, the nozzle check pattern is bent after the wiping endurance test, and the nozzle check pattern is bent at a level that cannot be actually used.
In Comparative Example 4, a wiper blade was prepared by increasing the crosslinking degree of the EPDM used in the past and increasing the tan δ peak temperature to a temperature higher than 10 ° C. However, a large number of blade ridge lines were missing and a spot where ink wiping could not be performed occurred at an early stage. ..

DESCRIPTION OF SYMBOLS 1 Wiper blade 2 Wiper blade support member 3 Wear part of wiper blade edge 4 Low cross-linking density part of elastic rubber 5 High cross-linking density part of elastic rubber 6 Wiper blade edge lacking part 7 tan δ peak temperature 10 Nozzle plate 11 Nozzle 11a Edge 11o Nozzle Center 20 Nozzle base material 21 Nozzle hole 21a Cylindrical portion on the liquid ejection surface side of the nozzle hole 21b Frustroconical portion on the opposite side of the liquid ejection surface side of the nozzle hole 30 Intermediate layer 31 SIO ₂ film 32 Silane coupling agent layer 40 Ink-repellent film 40a Ink-repellent film on liquid ejection surface side 40b Ink-repellent film on inner wall of nozzle 41 Slope area of ink-repellent film 41a Slope of ink-repellent film 42 Area other than sloped area of ink-repellent film 44 Evaporated film 50 Wiping unit 60 tape 101 nozzle plate 102 flow path plate 103 vibrating plate member 104 nozzle 106 individual liquid chamber 107 fluid resistance part 108 liquid introduction part 109 supply port 110 common liquid chamber 111 piezoelectric actuator 112 piezoelectric member 112A, 112B piezoelectric element 113 base member 115 FPC
120 frame member 130 vibration area 130a, 130b convex portion 401 guide member 403 carriage 404 inkjet head 405 main scanning motor 406 drive pulley 407 driven pulley 408 timing belt 410 paper 412 transport belt 413 transport roller 414 tension roller 416 sub-scan motor 417 timing belt 418 Timing pulley 420 Maintenance recovery unit 421 Cap member 422 Wiper blade 440 Liquid ejection unit 441 Head tank 450 Liquid cartridge 451 Cartridge holder 452 Liquid delivery unit 456 Tube 491A, 491B Side plate 491C Back plate 493 Main scanning moving mechanism 494 Supply mechanism 495 500 vacuum tank 501 vapor deposition source 600 pores 601 container 602 fixing jig 610 ink 611 wiper blade 612 fixing jig

Japanese Patent Laid-Open No. 09-076517 JP, 2006-159730, A Japanese Patent No. 5138475 JP-A-4-21119 JP, 2008-188911, A JP, 2010-5994, A JP, 2010-260281, A JP, 7-68765, A

Claims (10)

A wiper blade for wiping the ink ejection surface of an inkjet head,
The wiper blade is made of elastic rubber, and the elastic rubber has a tan δ peak temperature of −10 ° C. or higher and 10 ° C. or lower, and an equilibrium swelling ratio with acetone of 10% or lower.   The wiper blade for an inkjet head according to claim 1, wherein the equilibrium swelling ratio with acetone is 5% or less.   The wiper blade for an inkjet head according to claim 1 or 2, wherein a static friction coefficient of the wiper blade is 0.15 or less.   A wiping unit including the wiper blade according to claim 1, and a wiper blade support member supporting the wiper blade.   An ink ejection unit comprising an inkjet head and a wiper blade for wiping an ink ejection surface of the inkjet head, wherein the wiper blade is the inkjet head wiper blade according to any one of claims 1 to 3. Discharge unit. The inkjet head has an ink-repellent film formed on the ink ejection surface,
The ink ejection unit according to claim 5, wherein a static friction coefficient of the wiper blade is smaller than a static friction coefficient of the ink repellent film.   The ink ejection unit according to claim 6, wherein the ink repellent film is a film containing a fluororesin having a PTFE-containing heterocyclic structure having an ether bond in a PTFE skeleton. The inkjet head includes a nozzle base material having nozzle holes formed therein, and the ink repellent film is formed on a surface of the nozzle base material.
The ink ejection unit according to claim 7, wherein the ink-repellent film is inclined in the outer peripheral portion of the nozzle hole in a direction in which the film thickness decreases toward the edge side of the nozzle hole.   An apparatus for ejecting ink, comprising the ink ejection unit according to any one of claims 5 to 8.   The device for ejecting the ink according to claim 9, wherein the ejected ink is an ink containing an acrylic / methacrylic monomer or a solvent ink.