JP2008094605A - Transfer belt for ink jet and ink jet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer belt for ink jet and ink jet recording apparatus, having excellent charging and static elimination performance, and favorable paper sucking performance. <P>SOLUTION: This transfer belt for an ink jet is a seamless belt, which is composed of two or more layers, wherein the resin components in the respective layers polyimide resin of the same kind, the volume resistivity value of the outermost layer is 10<SP>14</SP>-10<SP>16</SP>Ωcm, and the volume resistivity value of the innermost layer is 10<SP>8</SP>-10<SP>14</SP>Ωcm. This ink jet recording apparatus includes: a record medium transfer device including the transfer belt for an ink jet in accordance with the invention; and a recording head for discharging an ink drop to a record medium. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inkjet transport belt and an inkjet recording apparatus.

  Conventionally, in an ink jet recording apparatus, ink liquid is ejected while scanning an ink jet head in the main scanning direction, and when scanning of the ink jet head for one line is completed, the recording medium is conveyed by a predetermined amount in the sub scanning direction, and the ink jet is again performed. The head is scanned in the main scanning direction to form an image on the recording medium. Since the recording medium needs to be accurately conveyed by a predetermined amount, the conveying belt is charged and the recording medium is attracted to the surface of the conveying belt by static electricity and conveyed. Various types of such conveyor belts are known (see, for example, Patent Document 1).

The conveyance belt of Patent Document 1 has a structure having two layers made of ETFE, and the volume resistance value is desirably set to 10 ¹⁵ (Ωcm), and the charge due to AC charging is stabilized for recording. The medium is electrostatically adsorbed. However, the conveyance belt is likely to be attached with discharge products due to a discharge phenomenon or contaminated with paper dust, and the life may be shortened. Further, at the time of two-layer molding, it is difficult to control the film thickness when the resin is melted and to maintain smoothness due to the effect of residual strain. Furthermore, from a comprehensive point of view, it is inferior in charging and discharging performance, and it cannot be said that the sheet adsorbing property is good. Influence of molding unevenness and undulations during heat molding, uneven surface due to uneven distribution of conductive filler such as carbon black, cleanability due to deterioration of surface properties, image deterioration (decrease in color registration), surface dent due to thermoplastic polymer, pressure contact marks There were problems such as deformation and belt speed fluctuation.
JP 2003-103857 A

  The present invention aims to solve the above problems. That is, an object of the present invention is to provide an ink jet transport belt and an ink jet recording apparatus having good paper adsorbability and cleanability.

As a result of earnest studies to achieve the above object, the present inventor has conceived the following present invention and found that the problem can be solved. That is, the inkjet transport belt of the present invention is in the form of a seamless belt, is composed of two or more layers, the resin component contained in each layer is the same type of polyimide resin, and the volume resistance value of the outermost layer is the same. 10 ¹⁴ to 10 ¹⁶ Ω · cm, and the volume resistance value of the innermost layer is 10 ⁸ to 10 ¹⁴ Ω · cm.

  In the inkjet transport belt of the present invention, the outermost layer has a thickness of 30 to 500 μm, the innermost layer has a thickness of 30 to 1000 μm, and at least the surface smoothness on the outer surface is gloss (incident angle). 75 degrees) and preferably 75 or more. Moreover, it is preferable that 1-30 mass% of releasable fillers are included in the said outermost peripheral layer.

  In addition, an ink jet recording apparatus of the present invention includes a recording medium transport apparatus including the above-described ink jet transport belt of the present invention, and a recording head that discharges ink droplets onto the recording medium.

  According to the present invention, it is possible to provide an ink-jet transport belt and an ink-jet recording apparatus having good sheet adsorbability and cleanability.

[Conveyor belt for inkjet]
The ink jet transport belt of the present invention is a seamless belt, is composed of two or more layers, and the resin component contained in each layer is the same kind of polyimide resin. The volume resistance value of the outermost layer is 10 ¹⁴ to 10 ¹⁶ Ω · cm, and the volume resistance value of the innermost layer is 10 ⁸ to 10 ¹⁴ Ω · cm.

  Here, “the same kind of polyimide resin” refers to a resin appropriately selected from polyimide resins described later. The outermost layer is a seamless belt-like (endless) mode when applied to an ink jet recording apparatus, and refers to the outermost layer (also referred to as a surface layer), and the innermost layer. The term “innermost layer” (also referred to as a base material layer) is used.

  The inkjet transport belt is composed of two or more layers, and the resin component contained in each layer is the same kind of polyimide resin, so that the adhesion between the layers is improved, and the surface property and releasability of the belt are improved. It can be maintained in a good state. Further, by using two or more layers, it is possible to solve the problem that occurs when the polyimide is a single layer, that is, the problem that the belt surface is contaminated by ink mist or ink stains and the cleaning characteristics are deteriorated.

Further, by containing a conductive filler and setting the volume resistance value of the innermost layer to 10 ¹⁰ to 10 ¹⁴ Ω · cm, accumulation of residual charges due to continuous use during charging is prevented, and stable paper It is possible to achieve both the adsorptivity and the releasability.
From the viewpoints of maintaining sheet adsorbability, releasability, suppression of belt speed fluctuation, uniformity of belt charge, and reduction of peel discharge property, the surface resistance value is preferably 10 ¹¹ to 10 ¹⁴ Ω / cm ² . More preferably, it is 10 ¹¹ to 10 ¹⁴ Ω / cm ² . By being 10 ¹¹ to 10 ¹⁴ Ω / cm ^2, it is possible to maintain stable surface charge, impart static eliminability, and stabilize the paper posture.

Electroconductive conductive materials that are conductive fillers include carbon black, graphite, Al, Ni, copper and other fillers, and composite oxides such as tin oxide, zinc oxide, potassium titanate, tin oxide-indium oxide, and antimony oxide. Things. Examples of the ion conductive material include ammonium salts, sulfonates, cations, nonions, and anionic surfactants. And these are used suitably and volume resistance value is controlled to 10 < ¹⁰ > -10 < ¹⁴ > (omega | ohm) cm. The content of the conductive filler depends on a desired volume resistance value and the like, but is preferably 1 to 50% by mass in the inkjet transport belt.

  The volume resistance value and the surface resistance value can be measured using a circular electrode (for example, “HRS probe” of Hirester IP manufactured by Mitsubishi Oil Chemical Co., Ltd.) in an environment of 23 ° C. and 55% RH. The measurement conditions are, for example, a load of 1.0 kg, a voltage of 100 V, and a charge time of 10 seconds.

The volume resistance value of the outermost layer is preferably 10 ¹⁴ to 10 ¹⁶ Ω · cm, and preferably 10 ¹⁴ to 10 ¹⁵ Ω · cm. In order to make the volume resistance value within the above range, the amount of the releasable filler such as carbon black to be added and the thickness of the layer may be adjusted. By setting it to 10 ¹⁴ to 10 ¹⁶ Ω · cm, it is possible to improve the sheet adsorbing property and the cleaning property.

  The releasable filler contained in the outermost layer is preferably 1 to 30% by mass, and more preferably 5 to 30% by mass. By including 1-30% by mass of such a releasable filler, the surface releasability by cleaning of the blade and the like can be maintained without deteriorating the gloss and surface properties (roughness) of the surface, and adhere to the surface. Residual ink residue, paper dust, and discharge products can be removed. The releasable filler is non-conductive carbon black, barium sulfate, silica (surface treated product), PTFE (polytetrafluoroethylene), resin powder (for example, styrene-acrylic), inorganic powder (molybdenum disulfide). , Zeolite, metal powder alumina), graphite and the like can be used, and these may be blended together during coating and processing.

  At least the surface smoothness on the outer surface is preferably 75 or more and more preferably 80 to 130 in terms of gloss (incidence angle of 75 degrees). The thickness of the outermost layer is preferably 30 to 500 μm, and more preferably 30 to 100 μm. The thickness of the innermost layer is preferably 30 to 1000 μm, and more preferably 50 to 200 μm. The surface smoothness is 75 or more and the thickness is in the above range, so that the surface texture is stable for improving the cleaning property of the blade and the like for reducing the undulation by the belt knit, reducing the habit, and reducing the ink adhesion on the surface. Can be held in.

  The surface smoothness can be measured by measuring Rz (10-point average roughness) with a surface roughness meter or surface reflectance with a digital precision gloss meter (incident angle 20 to 75 °).

  A conventionally well-known thing can be used for the polyimide-type resin (a polyimide resin, polyetherimide, a polyamideimide resin, etc.) as a resin component.

  Polyimides with high dimensional stability include varnish-like compounds with imide bonds, and powders that are melt-molded (injection / extrusion molding). Depending on the reaction process, condensation reactivity and addition reactivity are available. Or thermosetting and thermoplastic.

  Similarly, polyamide imides are polypyromellitic imides and imides having a polyamide bond, which retain mechanical properties, have excellent wear resistance, can be formed at low temperatures, and can be used at low cost as well. As the surface layer (the outermost layer), a polyimide precursor / polyamic acid in which a release filler is dispersed in a polar solvent such as NMP (N-methyl 2-pyrrolidone) or DMAc (dimethylacetamide) is added to these polyimides. A method of forming a film by applying to a predetermined film thickness, drying, and heat dehydrating imidized is common.

Furthermore, polyetherimide is an amorphous imide that has processability (fluidity when melted) and flexibility, and is excellent in flame retardancy and electrical characteristics. Is suitable.
These polyimides are filled with carbon black or a releasable filler, and by utilizing the rigidity and workability of the polymer, molding and film formation are performed, and a conductive base material layer is separated from this. It is possible to provide an ink-jet conveyance suction belt having a function-separated type two-layer structure having layers.

  For example, a polyimide resin film made of a polyimide resin is not particularly limited as long as it is a carboxylic acid and a diamine component, but is particularly obtained by reacting an aromatic tetracarboxylic acid component and an aromatic diamine component in an organic solvent. Preferably used.

  Examples of the aromatic tetracarboxylic acid component include pyromellitic acid, naphthalene-1,4,5,8 tetracarboxylic acid, 2,2 ′, 3,3′biphenyltetracarboxylic acid, naphthalene-2,3,6,7. -Tetracarboxylic acid, 2,3,5,6-biphenyltetracarboxylic acid, 3,3 ', 4,4'-diphenyl ether tetracarboxylic acid, 3,3', 4,4'-benzophenonenontetracarboxylic acid, 3 , 3 ′, 4,4′-diphenyltetracarboxylic acid, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic acid, 3,3 ′, 4,4′-azobenzenetetracarboxylic acid, bis (2,3 -Dicarboxyphenyl) methane, bis (3,4-dicarboxyphenylmethane), bis (3,4-dicarboxyphenylpropane), bis (3,4-dicarboxyphenyl) Hexafluoropropane and the like, may be mixtures of these tetracarboxylic acids.

  The aromatic diamine component is not particularly limited, and m-phenyldiamine, p-phenyldiamine, 2,4-aminotoluene, 2,6-aminotoluene, 2,4-diaminochlorobenzene, m-xylylenediamine, p- Xylylenediamine, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4′-diaminonaphthalene biphenyl, benzidine, 3,3-dimethylbenzidine, 3,3′-dimethoxy Benzidine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether (ODA), 4,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone, 4,4'-diaminophenyl sulfone, 4,4 '-Diaminoazobenzene, 4,4'-Diaminodipheny Methane, and a bis-aminophenyl propane.

  Examples of the organic solvent include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphonyltriamide, and the like. If necessary, phenols such as cresol, phenol and xylenol, and hydrocarbons such as hexanebenzene and toluene may be mixed. These may be used alone or as a mixture of two or more.

  In particular, as the material of the outermost layer, the tetracarboxylic acid of thermoplastic ODPA (3,3 ′, 4,4′-diphenyletheramines) and its derivatives are directly bonded as a substituted diamine component as a diamine component. Aromatic polyimide using carbonyl, isoporopyridene group, ether group, sulfide group, p-oxydianiline group can be mentioned. Specifically, ULTEM (GE), AVIMID (Dupont), etc. are soluble types.

  Further, two-color molding including a surface layer by melt molding is possible, and there is polypyromellitimide composed of an ether-based diamine compound having a biphenyl structure and PMDA. Specifically, AURUM (made by Mitsui Chemicals), LARK-TPI (NASA), Kaptone, Vespel (Dupont), etc. are mentioned.

Further, two-color molding including a surface layer by melt molding is possible, and there is polypyromellitimide composed of an ether-based diamine compound having a biphenyl structure and PMDA. Specifically, AURUM (made by Mitsui Chemicals), LARK-TPI (NASA), Kaptone, Vespel (Dupont), etc. are mentioned.
Depending on the heat resistance of the resin material used for the substrate, these surface coats (spray, dip, flow coat, electrostatic coat, coating coat by rotary molding, etc.) are fired to give the surface release properties. Can be mentioned. In addition, a two-layer structure having a two-layer film-like release property that is coated after the Na substrate is etched and the belt base material surface is activated.

  The inkjet transport belt of the present invention includes, for example, a coating process in which a polyimide resin composition or a polyamide-imide resin is spread and applied on a metal cylindrical core inner peripheral surface or outer peripheral surface, and heat curing (for example, 380). And a separation step of separating the formed cylindrical film.

  As a coating method in the coating process, from the viewpoint of maintaining surface leveling, suppressing dry skin, reducing film thickness, and reducing distortion during molding, one of flow coating, ring flow coating, and centrifugal molding Is preferably adopted. Hereinafter, these coating methods will be described by taking the case of polyimide resin as an example. In this specification, polyimide may be referred to as “PI”.

<Application process>
(Flow coat method)
The flow coat method is preferable in that a polyimide precursor solution (contains a conductive filler) can be applied to a substantially uniform thickness efficiently and reasonably. A method for applying such a preferred polyimide precursor solution will be described with reference to the drawings.

  FIG. 1A is a schematic view showing a method of applying the polyimide precursor solution in the present invention to the outer peripheral surface of a cylindrical core body whose surface water contact angle is controlled. On the other hand, FIG. 1 (B) is a cross-sectional view of the coated portion of the cylindrical core body shown in FIG. 1 (A). In FIG. 1, 51 is a cylindrical core body having a controlled surface water contact angle, 52 is a plate, 53 is a container, and 54 is a polyimide precursor solution.

  In this method, while rotating the cylindrical core body 51 at a constant speed in the direction of arrow A, a fixed amount of polyimide precursor solution is applied to the surface of the cylindrical core body 51 from the container 53 containing the polyimide precursor solution 54. It is a method of dripping and applying this while leveling the plate 52 in contact with the surface of the cylindrical core 51, and as a result, the uniform polyimide precursor solution 54 is applied to the surface of the cylindrical core 51. To be applied.

(Ring flow coat)
Ring flow coating is a method of forming a coating film while controlling the film thickness with an annular body, and it is easy to control the film thickness, can be adjusted by the discharge amount and the rotation speed, and can be applied from large to small diameter belts preferable. Hereinafter, a detailed description will be given with reference to FIGS. 2 and 3.

  FIG. 2 is a schematic cross-sectional view showing an example of an apparatus used for a dip coating method in which the film thickness is controlled by an annular body. However, the figure shows only the main part of coating, and other devices are omitted.

  In this dip coating method, as shown in FIG. 2, the PI precursor solution 2 placed in the dip coating tank 3 is provided with a circular hole 6 larger than the outer diameter of the cylindrical core body 1 on which the transferred portion is formed. In this coating method, the annular body 5 is floated, the cylindrical core body 1 is immersed in the PI precursor solution 2 through the circular hole 6, and then pulled up and applied.

  The material of the annular body 5 is selected from metals, plastics and the like that are not affected by the PI precursor solution 2. Moreover, a hollow structure may be used so as to easily float, and legs or arms that support the annular body 5 may be provided on the outer peripheral surface of the annular body 5 or the dip coating tank 3 in order to prevent sinking.

  The annular body 5 is suspended on the PI precursor solution 2 so that the annular body 5 can move with a slight force on the PI precursor solution 2, or the annular body 5 is supported by a roll or a bearing, the annular body It is installed so that it can move freely in the horizontal direction by a method such as supporting 5 with air pressure. Moreover, you may fix this temporarily so that the annular body 5 may be located in the center part of the immersion coating tank 3. FIG.

  Since the film thickness of the PI precursor coating film 4 is regulated by the gap between the outer diameter of the cylindrical core body 1 and the diameter of the circular hole 6, the inner diameter of the circular hole 6 is adjusted by a desired film thickness. Since the film thickness uniformity of the PI precursor coating film 4 is also determined by the gap, the roundness of the circular hole is important. When the roundness is low, the film thickness uniformity is deteriorated and the quality of the PI resin endless belt is deteriorated. Therefore, the roundness is preferably 20 μm or less, and more preferably 10 μm or less. Of course, it is optimal that the roundness is 0 μm, but it is difficult in processing.

  If the inner wall surface of the circular hole 6 has a wide lower part immersed in the PI precursor solution 2 and a narrow upper part, as shown in FIG. What consists of a surface is sufficient. Further, it may be stepped or curved.

  When applying, the cylindrical core body 1 is pulled up through the circular hole 6. The pulling speed is preferably about 0.1 to 1.5 m / min. The PI precursor solution 2 preferable for this coating method has a solid content concentration of 10 to 40% by mass and a viscosity of 1 to 100 Pa · s.

  When the cylindrical core body 1 is pulled up through the circular hole 6, the annular body 5 is free to move in the horizontal direction, so that the frictional resistance between the cylindrical core body 1 and the annular body 5 is constant in the circumferential direction. The body 5 moves, and a PI precursor coating film 4 having a uniform film thickness is formed on the surface of the cylindrical core body 1.

  Further, the coating apparatus used for the dip coating method includes a cylindrical core body holding means for holding the cylindrical core body 1, a first moving means for moving the holding means in the vertical direction, and / or a dip coating tank 3. You may have the 2nd moving means to move to a direction.

  Thus, by applying the dip coating method in which the film thickness is controlled by the annular body 5 using the high-viscosity PI precursor solution 2, the coating film droops at the upper end of the cylindrical core body 1 due to gravity. Thus, the film thickness can be made uniform both in the circumferential direction and in the axial direction.

  In the PI precursor coating film forming step, an annular coating method can also be applied. FIG. 3 is a schematic cross-sectional view showing an example of an apparatus used for the annular coating method.

  In FIG. 3, the difference from FIG. 2 is that an annular sealing material 8 having a hole slightly smaller than the outer diameter of the cylindrical core body 1 is provided at the bottom of the annular coating tank 7. The cylindrical core body 1 is inserted through the center of the annular sealing material 8 and the PI precursor solution 2 is accommodated in the annular coating tank 7. Thereby, the PI precursor solution 2 does not leak. The cylindrical core body 1 is sequentially lifted from the lower part to the upper part of the annular coating tank 7, and is inserted into the annular body 5, whereby the PI precursor coating film 4 is formed on the surface. Intermediate bodies 9 and 9 ′ that can be fitted to the cylindrical core body 1 may be attached above and below the cylindrical core body 1. The function of the annular body 5 is the same as described above.

  In such an annular coating method, the annular coating tank 7 can be made smaller than the dip coating tank 3 of FIG. 2, and thus there is an advantage that the required amount of the PI precursor solution can be reduced.

(Centrifugal molding)
Centrifugal molding is a coating method that is preferable in terms of providing film thickness uniformity by molding with a large-diameter belt, providing smoothness with a surface texture mold, and dealing with multilayering of two or more layers.

  FIG. 4 shows an example of a flow of a coating method using a centrifugal molding method. First, the PI precursor solution is charged into the cylindrical mold 13 (FIG. 4A). The cylindrical mold 13 can be rotated around the center of a circle by a drive motor or the like. The mold 13 is disposed in a heating furnace or the like and can be heated simultaneously with the rotation. By rotating the mold 13, the coating film 11 is formed on the inner wall surface (FIG. 4B).

  When the inner wall surface of the cylindrical mold 13 is subjected to a lining process using, for example, silicon resin or the like, the surface of the coating finally obtained can be mirror-finished. As a result, a conductive belt having a high surface smoothness with an Rz value of 1 μm or less can be produced without subsequent surface polishing treatment or the like. Furthermore, it is possible to suppress fluctuations in the film thickness at the time of molding, and to suppress shaft runout at the time of molding.

<Curing process>
In this step, for example, in the case of forming a polyimide resin film, the polyimide precursor film is preferably heated in the range of 300 to 450 ° C., more preferably around 350 ° C., for 20 to 60 minutes. Can be formed. During the heating reaction, if the aprotic polar solvent remains, the polyimide resin film may swell, so it is preferable to completely remove the residual solvent before reaching the final heating temperature. Specifically, before heating, the solvent is dried by heating at a temperature in the range of 150 to 200 ° C. for 30 to 60 minutes, and then the temperature is increased stepwise or at a constant rate. It is preferable to form a polyimide resin film.

  At this time, in the present invention, the surface water contact angle is lower at the end than at the center of the cylindrical core, and the adhesion and adhesion of the coating film and the resin film are high in the entire circumference of the end. Therefore, the film does not shrink due to the heating reaction, and no non-uniform shrinkage is observed.

  Regarding the shrinkage of the coating that occurs before and after the heating reaction, the axial shrinkage of the cylindrical core with respect to the coating of the resin coating is preferably 6% or less, and more preferably 3% or less. If the shrinkage rate exceeds 6%, the axial film thickness displacement of the cylindrical core may be 10 μm or more, and the axial volume resistance displacement may be 0.5 digits or more. The axial contraction rate of the cylindrical core body with respect to the coating film of the resin coating is the axial length of the cylindrical core body of the resin coating C, and the axial length of the cylindrical core body of the coating film. When D, the shrinkage ratio [(D−C) / D] × 100 is obtained.

<Separation process>
After the curing step, the seamless tubular product of the present invention can be obtained through this step of cooling the cylindrical core body to room temperature and peeling off the formed resin film. In this step, after cooling, the cylindrical core contracts more than the resin coating, so that the resin coating can be extracted from the cylindrical core. At that time, in the present invention, the surface water contact angle at the end of the cylindrical core body is set to a certain value or more, so it is not difficult to separate the resin coating, and at least one of the ends attached to the both ends of the cylindrical core body. There is no need to insert a sheet or the like into the part.

  The extracted resin film may be inferior in film thickness uniformity at both ends or may have fragments of the film attached thereto, and the portion is cut as an unnecessary portion. In the present invention, the unnecessary portion is preferably in the range of 30 to 40 mm from the end.

  The unnecessary portion of the end portion is cut to obtain the inkjet transport belt of the present invention, but punching, ribbing, or the like may be performed as necessary.

  The inner diameter of the inkjet transport belt of the present invention produced as described above is determined in accordance with the outer diameter of the cylindrical core, but is preferably in the range of 10 mm to 1000 mm, preferably 15 mm to 600 mm. A range is more preferable. When the inner diameter of the seamless tubular material is in the range of 10 mm to 1000 mm, it is preferable for forming a uniform film thickness.

  Furthermore, the thickness of the inkjet transport belt is preferably in the range of 10 to 100 μm, and more preferably in the range of 20 to 80 μm. When the thickness of the seamless tubular product is in the range of 10 to 100 μm, it is preferable for forming a uniform film thickness.

  The surface layer may be surface-coated and formed in advance before curing, or after forming the surface layer by centrifugal molding in advance, the base material layer is formed, or two layers are formed by simultaneous extrusion and the method is performed until film formation. Can be used.

[Inkjet recording apparatus]
As shown in FIG. 5, the inkjet recording apparatus 10 of the present invention includes an inkjet head unit 12 that ejects ink droplets onto a recording paper P that is a recording medium. The inkjet head unit 12 includes cyan (C) and magenta. (M), yellow (Y), and black (K) ink jet heads (not shown) for ejecting ink droplets from the nozzles onto the recording paper P are provided. The ink jet head is a long head having an effective print area that is equal to or larger than the width of the recording paper P, and ejects ink droplets all at once in the print area in the width direction of the recording paper P. In addition, as a method of ejecting ink droplets from the nozzles of the inkjet head, a known method such as a method of pressurizing the ink chamber with a piezoelectric element or a thermal method can be applied.

  Ink is supplied from an ink tank (not shown) disposed above the ink jet head unit 12 to the ink jet head through a pipe. The ink type is a known ink such as water-based ink, oil-based ink, or solvent-based ink. Applicable.

  A paper feed tray 16 is detachably provided at the bottom of the ink jet recording apparatus 10. A recording paper P is loaded on the paper feed tray 16, and a pick-up roll 18 is placed on the uppermost recording paper P. Are in contact. The recording paper P is fed one by one from the paper feed tray 16 to the downstream side in the transport direction by the pick-up roll 18 and is fed below the inkjet head unit 12 by the transport rolls 20 and 22 arranged in order along the transport path. Paper.

  In addition, an endless conveyance belt 24 that is an inkjet conveyance belt of the present invention is disposed below the inkjet head unit 12, and the conveyance belt 24 is stretched around the drive roll 26 and the driven rolls 28 and 30. Thus, a recording medium conveying apparatus is configured. Further, the driven roll 30 is grounded.

  Further, on the upstream side of the position where the recording paper P contacts the transport belt 24, a charging roll 32 to which a power supply device 34 is connected is disposed. The charging roll 32 is driven while sandwiching the conveyance belt 24 with the driven roll 30, and is movable between a pressing position for pressing the conveyance belt 24 and a separation position separated from the conveyance belt 24. At the pressing position, a predetermined potential difference is generated between the driven roll 30 and the ground, and therefore, the discharge can be applied to the transport belt 24 to give an electric charge. Further, the case where the charging roll 32 is disposed is on the upstream side of the position where the recording paper P is in contact with the transport belt 24. However, the present invention is not limited to this, and paper dust, ink mist, etc. It can be installed at a position where the influence of dirt in the apparatus becomes less. The power supply unit 34 includes an arbitrary waveform generator and an amplifier that generate an arbitrary voltage waveform that is known.

  Further, a plurality of discharge roll pairs 40 constituting a discharge path for the recording paper P are provided on the downstream side of the inkjet head unit 12, and a discharge tray 42 is provided at the end of the discharge path formed by the discharge roll pairs 40. Is provided.

  As shown in FIG. 6, each unit of the inkjet recording apparatus 10 is controlled by a control unit 56 including a CPU, a ROM, and a RAM, and a plurality of motors 46 that drive the inkjet head unit 12, the charging roll 32, and various rolls. The entire inkjet recording apparatus 10 including the above is controlled.

  Next, the printing operation of the inkjet recording apparatus 10 will be described. First, when receiving a print job command, the control unit 56 drives the pickup roll 18, all the transport rolls, and the transport belt 24 to send out the recording paper P from the paper feed tray 16. Furthermore, a head control unit (not shown) that performs dummy jets, initializes the performance of the nozzles of the inkjet head unit 12, and controls the ejection of ink droplets by the inkjet head unit 12 is applied to the piezoelectric elements of the nozzles corresponding to image signals. A drive voltage is applied at a timing according to the image signal.

  As a result, the recording paper P conveyed by the conveying belt 24 is printed. This printing process will be described in detail later. Then, the printed recording paper P is transported to the paper discharge tray 42 by the transport belt 24 and the discharge roll pair 40.

  Here, the printing process will be described. First, when receiving a print job, the control unit 56 turns on the charging roll 32, and causes the charging roll 32 to apply a voltage that changes in the above-described superimposed waveform from the power supply device 34. When the charging roll 32 discharges to the conveyor belt 24, the residual charge is averaged in the charging region on the surface of the conveyor belt 24 by the voltage that changes in the superimposed high-frequency voltage waveform, and the frequency of the low-frequency voltage waveform is supported. Only the charging pattern to be generated appears on the belt surface, and the surface of the conveyor belt 24 is alternately charged with positive charges and negative charges as shown in FIG. The recording paper P is stably electrostatically adsorbed on the surface of the conveying belt 24 by the stress (Maxwell stress) caused by the non-uniform electric field due to the positive charge and the negative charge. Since the positive charge and the negative charge are alternately charged, the influence of the electric field on the ejection of the ink droplets of the inkjet head unit 12 from the surface of the transport belt 24 is small, and the recording paper P is not directly charged. The effect of the attractive force due to the characteristics (electric resistance value, thickness, etc.) of the recording paper P is small.

  As a result, the recording paper P fed to the transport belt 24 is electrostatically attracted to the transport belt 24 and passes through the print area of the inkjet head unit 12. At that time, the control unit 56 operates the inkjet head unit 12 to print on the recording paper P. Then, the recording paper P is discharged to the paper discharge tray 42 by the discharge roll pair 40. Further, the portion of the conveyance belt 24 where the recording paper P is adsorbed is rotated and moved again to the pressing portion of the charging roll 32 by the driving roll 26 and the driven rolls 28 and 30, and is a superimposed waveform applied to the charging roll 32. Charges remaining on the conveyor belt 24 are averaged by the changing voltage, and again positive and negative charges are alternately charged on the conveyor belt 24 corresponding to the frequency of the low-frequency voltage waveform. Maintain the attractive force.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the following examples, “part” means part by mass.

(Example 1)
100 parts of thermosetting polyimide (manufactured by Dupont) KAPTON and 30 parts of conductive special black 4 (manufactured by Cabot) were dispersed and mixed in a DMAc solvent to prepare a coating solution having a resin content of 30% by mass. A coating liquid is applied by ring flow coating to an aluminum cylindrical core body having an outer diameter of 250 mm and a length of 500 mm, which is preliminarily coated with a silicone release material (TS700 made by Shin-Etsu Silicone) on the outer peripheral surface, and fired at 230 ° C. for 4 hours. And a polyimide substrate was formed.

  Then, ULTEM (GE polyimide resin) as a thermoplastic polyimide material was spray-applied to the surface of the polyimide base layer so as to have a thickness of 30 μm, and baked at 380 ° C. for 1 hour. The endless belt having a two-layer structure was removed from the drum core, cut to a width of 365 mm, and an inkjet transport belt having a film thickness of 122 μm was produced.

(Example 2)
A polyimide solution containing 15% by mass of PTFE particles (Lublon manufactured by Toray Industries, Inc.) was spray-coated on the surface of the polyimide substrate layer of Example 1, and baked at 380 ° C. for 1 hour to form a surface layer having a thickness of 42 μm. . Thereafter, in the same manner as in Example 1, an inkjet transport belt was produced.

(Example 3)
A polyimide solution containing 5% of a surface silicate-treated silica powder (Degussa R972 particles) in ULTEM (GE polyimide resin) as a thermoplastic polyimide material is the same as in Example 1 on the polyimide substrate layer surface of Example 1. And applied. At this time, the coating was applied so that the film thickness of the surface layer was 55 μm. After coating, firing was carried out at 380 ° C. for 1 hour, and an inkjet transport belt was produced in the same manner as in Example 1.

Example 4
An inkjet transport belt was produced in the same manner as in Example 1 except that 15 parts of carbon black was used for the thermosetting polyimide resin.

(Comparative Example 1)
An inkjet transport belt was produced in the same manner as in Example 1 except that the thickness of the base material layer in Example 4 was changed to 550 μm and the surface layer was changed to 110 μm.

(Comparative Example 2)
An inkjet transport belt was produced in the same manner as in Example 1 except that the base material layer of Example 4 was 50 μm and the surface layer was 22 μm.

(Evaluation)
(1) Volume resistance value, surface resistance value and surface gloss:
The volume resistance value and the surface resistance value of the base material layer and the surface layer were measured.
The volume resistance value is 23 kg and 55% RH, using a cylinder electrode HR probe of Hiyrester IP made by Mitsubishi Oil Chemical Co., Ltd. with a load of 1 kg and a voltage of 100 V (10-second charge). The average value obtained by point measurement was used. Similarly to the volume resistance value, the surface resistance value was an average value obtained by measuring the counter electrode with the HR probe between the outer electrode and the inner electrode under the same conditions.
Further, gloss (surface gloss, incident angle of 75 degrees) was measured with a digital precision gloss meter manufactured by Murakami Color Research Center.

In addition, the difference in the measured value between LL (10 ° C., 15% RH) and A (28 ° C., 86% RH) at the time of measuring the volume resistance value was also examined. The results are shown in Table 1 below.
When the difference (LL-A) is 1.5 digits or less, there is little change in the paper adsorbability due to the environment, and the effect of residual surface charge due to the paper peeling discharge at the time of peeling and its charge removal performance are good. It means that there is.

(2) Paper adsorption:
Images were formed by attaching the inkjet transport belts of Examples and Comparative Examples to an inkjet image forming apparatus, and the image quality was evaluated. Further, the adsorptivity of the paper with respect to the DC voltage (3 kV) supplied to the surface of the inkjet transport belt was observed, and the peelability after printing (paper adsorbability) was evaluated. The results are shown in Table 1 below.
“○” in the table means that there is no problem with the paper adsorbing property / peeling property at the time of conveyance when the paper, adsorbing property / peeling property is conveyed at 500 mm / sec, and “△” is performed in the same manner. In this case, partial peeling and conveyance stability are insufficient, and “X” means that there is almost no paper adsorption / peeling property when the same is performed.

(3) Ink stains: stains on the belt surface when running at 200 kpv (paper dust, ink residue, mist,
The backside stain was transferred to a belt tape, and the ink stain was evaluated. The results are shown in Table 1 below.
In the table, “◯” means that there is almost no stain visually, “△” means that partial stain is seen, and “×” means that the ink stain is sufficiently on the entire surface of the tape. It means being seen.

  In the evaluation of the inkjet transport belt of Example 4, there was no problem with the sheet adsorbability, but there was some manufacturing resistance variation, and the sheet float and ink stains were likely to adhere, and some blade cleaning was required. However, the level was practically acceptable. Further, in the evaluation of the inkjet transport belts of Comparative Examples 1 and 2, the practically problematic level was obtained. In contrast, all of the inkjet transport belts of the examples had good sheet adsorbing properties and cleaning properties.

It is a figure explaining the flow coat method, (A) is the schematic which showed the method of apply | coating a polyimide precursor solution to the outer peripheral surface of a cylindrical core, (B) is FIG. 1 (A). It is sectional drawing in the application part of the cylindrical core of description. It is a schematic sectional drawing which shows an example of the apparatus used for the dip coating method which controls a film thickness with an annular body. It is a schematic sectional drawing which shows the other example of the apparatus used for the dip coating method which controls a film thickness with an annular body. It is explanatory drawing explaining an example of the flow of the coating method using a centrifugal molding method. 1 is a schematic diagram illustrating a configuration of an ink jet recording apparatus according to an embodiment of the present invention. 2 is a block diagram showing a control system of the ink jet recording apparatus according to the embodiment of the present invention. FIG. It is an image figure which shows the electric charge charged on the conveyance belt which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device 12 ... Inkjet head unit 24 ... Conveyor belt 32 ... Charging roll 34 ... Power supply device 56 ... Control part P ... Recording paper

Claims (4)

In a seamless belt shape, comprising two or more layers, the resin component contained in each layer is the same type of polyimide resin, and the outermost layer has a volume resistance of 10 ¹⁴ to 10 ¹⁶ Ω · cm, An inkjet transport belt, wherein the innermost layer has a volume resistance of 10 ⁸ to 10 ¹⁴ Ω · cm.   The outermost layer has a thickness of 30 to 500 μm, the innermost layer has a thickness of 30 to 1000 μm, and at least the surface smoothness on the outer surface is 75 (incidence angle 75 degrees) or more. The inkjet transport belt according to claim 1.   3. The inkjet transport belt according to claim 1, wherein the outermost layer contains 1-30% by mass of a releasable filler. 4. An ink jet recording apparatus comprising: a recording medium transport apparatus comprising the ink jet transport belt according to claim 1; and a recording head that ejects ink droplets onto the recording medium.

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