JP2002166555A - Electrostatic ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic ink jet recorder in which a desired image is formed by preventing crosstalk. SOLUTION: The recorder 1 comprises an ink jet head 2 comprising an ink chamber 6 for containing ink, a plurality of ink ejection openings 8 communicating with the ink chamber 6, control electrodes 20 disposed in the vicinity of respective ink ejection openings 8, and a back face electrode 16 disposed oppositely to the ink ejection openings 8 of the ink jet head 2. Furthermore, a conductive member 26 set at a constant potential is provided as a field shielding member between the ink ejection openings 8. A voltage is applied to the back face electrode 16 and a specific control electrode 20b so that ink 4 flies toward the back face electrode 16 through an ink ejection opening 8b corresponding to the control electrode 20b, and adheres to a recording medium 30 facing the ink ejection openings 8 of the ink jet head 2. In this regard, no ink is ejected from ink ejection openings 8a and 8c adjacent to the ink ejection opening 8b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electrostatic ink jet recording apparatus which performs recording by flying ink using electrostatic force.

[0002]

2. Description of the Related Art Conventionally, electric charges are injected into conductive ink,
There is known an electrostatic ink jet recording apparatus that causes an electric field to act on the ink to fly the ink toward a recording medium, thereby forming an image on the recording medium.

As such a conventional ink jet recording apparatus, an ink chamber containing ink, a plurality of ink ejection ports communicating with the ink chamber and connected to the atmosphere, and a control electrode arranged near each ink ejection port are provided. Some have an ink jet head provided and a back electrode arranged opposite to an ink ejection port of the ink jet head.
The ink chamber is always filled with ink.By applying a predetermined voltage to the back electrode, the ink in the ink chamber is urged toward the back electrode by electrostatic force, and an ink meniscus is formed at each ink ejection port. It is formed. In this state, by applying a predetermined voltage to a predetermined control electrode,
An electrostatic force is applied to the ink meniscus formed at the ink ejection port corresponding to the predetermined control electrode to cause the ink droplet to fly from the ink ejection port and adhere to the recording medium conveyed to the area facing the inkjet head. .

[0004]

However, as described above, an electric field generated by applying a voltage to a predetermined control electrode is formed in an ink discharge port adjacent to the ink discharge port corresponding to the predetermined control electrode. In addition, there is a problem of so-called crosstalk in which the ink also acts on the ink meniscus and the ink is ejected from an adjacent ink ejection port. In order to solve this problem, for example, it is conceivable to increase the interval between the ink ejection ports, but a reduction in resolution cannot be avoided.

Accordingly, an object of the present invention is to provide an electrostatic ink jet recording apparatus that forms a desired image while preventing crosstalk.

[0006]

In order to achieve the above object, an electrostatic ink jet recording apparatus according to claim 1 is provided.
An ink chamber that contains ink, a plurality of ink ejection ports that communicate with the ink chambers, and an inkjet head that includes a control electrode disposed near each of the ink ejection ports. In an electrostatic ink jet recording apparatus in which ink in the ink chamber flies toward the opposite side of the ink chamber with respect to the ink discharge port and thereby adheres to a recording medium opposed to the ink discharge port of the ink jet head, the ink jet recording apparatus is used. And an electric field shielding member is provided on the second member.

According to a second aspect of the present invention, in the recording apparatus of the first aspect, the electric field shielding member is a conductive member set at a constant potential.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic partial sectional view of an ink jet recording apparatus according to the present invention. The recording apparatus 1 has an ink jet head 2 (hereinafter, referred to as a “head”). The head 2 has an ink chamber 6 for storing ink 4 and a predetermined shape ( A plurality of ink ejection ports 8 having, for example, a cylindrical shape)
(Three ink ejection ports 8a, 8b, 8
c) are formed. The ink chamber 6 is fluidly connected to an ink cartridge 12 via a pipe 10 so that the ink chamber 6 is always filled with the ink 4. Above the drawing of the head 2, a back electrode 16 is provided at a predetermined distance from the ink ejection surface of the head 2 (the outlet of the ink ejection port 8). A first bias power supply 18 is connected to the back electrode 16 and has a predetermined voltage (in the example shown, a positive bias voltage V _B1 of, for example, +2000 V).
Can be applied.

A ring-shaped control electrode 20 (20a, 20b, 20c) is provided on the surface or inside of the head 2 on the side of the back electrode 16 so as to surround each ink ejection port 8 (8a, 8b, 8c).
c) is provided. These control electrodes 20 are supplied with a predetermined pulse voltage Vp (for example, +
(300 to 500 V positive polarity) can be applied. A ring-shaped electrode 24 is provided near the entrance of each ink ejection port 8 so as to surround the entrance of each ejection port 8. Each electrode 24 is in contact with the ink 4 in the ink chamber 6,
It is set to a constant potential (grounded in the example in the figure).

The magnitude of the bias voltage V _B1 is determined by the fact that the ink 4 contained in the ink chamber 6 is attracted toward the back electrode 16 by an electric field formed between the ink 4 and the back electrode 16 due to the potential difference between the ink 4 and the back electrode 16. Then, a meniscus is formed in the ink discharge port 8, but the suction force alone is adjusted so that the ink is not separated from the ink 4 in the ink chamber 6 as droplets and does not fly. The magnitude of the pulse voltage Vp is such that, when a predetermined voltage is applied to the back electrode 16 to form a meniscus, the magnitude of the electric field formed between the back electrode 16 and the control electrode 20 and the ink meniscus is Is set to a value sufficient to separate and fly from the ink 4 in the ink chamber 6 as a droplet.

A conductive member 26 set at a constant potential (grounded in the illustrated example) is provided between the ink discharge ports 8 as an electric field shielding member.
Does not substantially affect the ink meniscus of the ink ejection port adjacent to the ink ejection port 8 corresponding to the control electrode 20, and therefore,
The ink 4 is prevented from separating and flying from the ink meniscus.

As shown in FIG. 2A which is a top view of the head 2, the conductive member 26 is formed so as to cross between the ink discharge ports 8. However, the present invention
The shape of the conductive member 26 is not limited.

According to these configurations, a desired control electrode 20 (in the illustrated example, 20) is formed with the ink meniscus formed.
By applying the pulse voltage Vp to b), a part of the ink is separated from the ink 4 in the ink chamber 6, and the ink discharge port 8 corresponding to the desired control electrode 20 (8b in the example in the figure)
Flies as an ink droplet 28 At this time, the ink 4 does not fly from the ink discharge ports 8 (8a and 8c in the example in the drawing) adjacent to the ink discharge ports 8 from which the ink droplets 28 have been discharged. The ink droplet 28 further flies straight toward the recording medium 30 conveyed between the head 2 and the back electrode 16 by an electric field formed between the control electrode 20 and the back electrode 16 by a potential difference between the control electrode 20 and the back electrode 16. Recording medium 3
0 to form an image.

Although the conductive member 26 shown in FIG. 1 is provided inside the substrate on the side of the back electrode 16 of the head 2, the conductive member 26 may be located at any position between the ink discharge ports 8. Even so, the effects of the present invention can be obtained. For example,
As shown in FIG. 3A, the conductive member 26 'is
May be provided so as to be exposed on the surface on the side of the back electrode 16, or may be a groove-shaped conductive member 26 ″ as shown in FIG. 3B. Alternatively, FIGS. ), (B)
Unlike FIG. 3, as shown in FIG.
Between them, the effect of the present invention can be obtained without providing the conductive member 26 '''between the adjacent control electrodes 20.

Further, the control electrode 20 does not need to be formed in a ring shape so as to surround the ink discharge port 8 as shown in FIG. For example, as shown in FIG. 2B, a pair of rectangular electrodes 20 ′ that are arranged substantially symmetrically with respect to the center axis of the ink discharge port 8 may be used. The former shape has an advantage that the ink can easily fly stably when a voltage is applied to the control electrode 20, while the latter shape has an advantage that the ink is easily processed.

Next, referring to FIG. 4, the head 2 shown in FIG.
An example of a method for manufacturing the device will be described. First, a through hole 42 corresponding to an ink discharge port and a groove 44 corresponding to an ink chamber are formed on a first substrate 40 made of photosensitive glass by etching [FIG. Next, a second borosilicate glass
The substrate 46 is thermally bonded to the first substrate 40 from the groove 44 side to form the ink chamber 6 [FIG. Subsequently, a groove 48 for a conductive member is formed in the first substrate 40 using a diamond cutter [FIG. Then, a thermosetting conductive paste material is poured into the groove 48 and is heated and cured to form the conductive member 26 [FIG. As the conductive paste material, for example, a conductive epoxy adhesive containing a silver filler can be used. On the other hand, in the third substrate 50 made of polyimide, a through-hole 51 corresponding to the through-hole 42 of the first substrate 40 is formed, and the control electrode 20 is patterned by lithography [FIG. Then, the third substrate 50 is placed on the first substrate 40.
Is bonded [FIG. (F)]. Finally, the control electrode 20 is coated with the insulator 52 to form the head 2 [FIG. The insulator 52 is desirably made of a resin having a surface tension of 1 × 10 ⁻³ N / m or less in order to prevent contamination by a water-repellent effect. Specific examples include polypropylene, ethylene tetrafluoride-ethylene copolymer, paraffin, polytetrafluoroethylene, hexatriacontane, and propylene hexafluoride.

As a method of manufacturing the head 2 'shown in FIG. 3A, for example, in the step (e) of the above-described manufacturing method, a first substrate 50 made of polyimide is applied to the first substrate 50.
In addition to the through hole 51 corresponding to the through hole 42 of the substrate 40,
A through hole corresponding to the groove 48 may be formed. On the other hand, FIG.
As a method of manufacturing the head 2 ″ shown in FIG. 2B, for example, the third substrate 50 is
In addition to the through-hole 51 corresponding to the through-hole 42 of the first substrate 40, a through-hole corresponding to the groove 48 is formed. On the other hand, instead of the step (d), a mask is applied to portions other than the groove 48 on the first substrate 40, and Au, Pt, or the like is sputtered on the groove 48 to form the groove-shaped conductive member 26 ″. The steps may be performed.

The present invention is not limited to the type of ink, but is preferably a pigment-dispersed aqueous ink. This is because the pigment dispersion has excellent coloring properties, weather resistance, and water resistance, and the aqueous ink is environmentally friendly. Further, not limited to carbon black, cyan, magenta, yellow and the like may be used. A preferable range of the viscosity of the ink is 100 cps or less,
More preferably, it is 50 cps or less. Viscosity 100c
If it is larger than ps, the response of the ink ejection to the application of the voltage to the control electrode 20 deteriorates, which is not preferable.

FIG. 5 is a perspective view of an embodiment of the ink jet recording apparatus 100. The recording apparatus 100 includes a pair of vertically extending support walls 102a and 102b facing each other at a predetermined interval, and the support walls 102a and 102b.
Vertically extending intermediate wall 1 provided in the space sandwiched by 2b
03. Support wall 102b and intermediate wall 1 on the right side of the drawing
03, a sheet feeding tray 104 for storing sheets (paper) S to be printed by the recording apparatus 100 is provided.
The sheet S stored in the paper feed tray 104 is supplied to the space.

A first guide rail 106 extending in the horizontal direction is supported by the pair of support walls 102a and 102b. A second guide rail 107 extending in the horizontal direction is provided on the opposite side of the paper feed tray 104 with the first guide rail 106 interposed therebetween. These guide rails 10
A carriage 110 on which an inkjet head 108 is mounted is movably supported by 6 and 107. The head 108 is connected via a film-shaped wiring board 109 to a drive circuit (not shown) for applying a predetermined voltage to a control electrode (not shown, which corresponds to the control electrode 20 in FIG. 1). On the carriage 110, ink cartridges 111 of black, yellow, magenta, and cyan are also provided.
B, 111Y, 111M, and 111C are detachably mounted. These ink cartridges supply ink to the head 108 via a manifold (not shown). A scanning mechanism 112 for reciprocating the carriage 110 along the guide rails 106 and 107 includes a pair of pulleys 114a and 114b supported near the support walls 102a and 102b, and the pulleys 114a and 114b.
A belt 116 wound around 14b and a motor 118 for rotating one of the pulleys 114b in the forward and reverse directions are provided. A carriage 110 is connected to a part of the belt 116.

Between the intermediate wall 103 and the support wall 102b, the sheet S conveyed from the paper feed tray 104
A paper feed roller 122 that folds back by 0 ° and conveys in the direction of arrow 121 (transport direction), and a pressing roller 124 that contacts the paper feed roller 122 and presses the sheet S against the paper feed roller 122, is orthogonal to the transport direction 121 And is rotatably supported by the intermediate wall 103 and the support wall 102b.

The paper feed roller 122 is, for example, a metal roller, and can apply a predetermined voltage, and as a result, functions as a back electrode. The paper feed roller 122 is also drivingly connected to a motor (not shown).
2 rotates to convey the sheet S in the direction of arrow 121. The paper feed roller 122 can be manually rotated by a user.

The paper feed roller 122 further includes a head 1
08 while the head 108 moves with the carriage 110, the ink ejection surface of the head 108 (the outlet of the ink ejection port of the head) is substantially spaced from the outer peripheral surface of the paper feed roller 122. I try to keep it.
Although not shown in the figure, the ink ejection orifice array including a plurality of ink ejection orifices is arranged in the vertical direction for the black, yellow, magenta, and cyan inks (scanning mechanism 112).
(In the direction perpendicular to the direction in which the head 108 moves). The number of the ink ejection port array may be one or plural for each color.

Between the first guide rail 106 and the second guide rail 107, these guide rails 106,
A belt-like timing slit 1 in the form of a film in parallel with 107
26 are provided. One end of the timing slit 126 is fixed to the support wall 102b on the right side in the drawing, and the other end is connected to a hook 128 provided on the wall of the support wall 102a on the left side in the drawing.
The timing slit 126 is locked under an appropriate tensile force.

As shown in detail in FIG. 6, the timing slit 126 is formed by forming a large number of transparent portions 130 and non-transparent portions 132 having a predetermined width alternately in the longitudinal direction. The carriage 110 has a timing slit 12
A light-emitting element and a light-receiving element (both not shown) are arranged with 6 interposed therebetween. Transparent part 1 between light emitting element and light receiving element
When 30 is present, the light receiving element receives light from the light emitting element. Non-transparent portion 13 between light emitting element and light receiving element
When 2 exists, the light receiving element does not receive light from the light emitting element. Therefore, the position of the carriage 110 can be obtained based on the signal output from the light receiving element while the carriage 110 moves in the horizontal direction.
Specifically, for example, when the light receiving element outputs a “HIGH” signal when receiving light from the light emitting element and outputs a “LOW” signal when not receiving light from the light emitting element,
By counting the “HIGH” signal output intermittently, the position of the carriage 110 from a predetermined position (for example, a standby position during non-printing) can be calculated.

A cap 134 that protects the head 108 when the ink jet recording apparatus 100 is not used for a long time is disposed between the intermediate wall 103 and the support wall 102a. The cap 134 can be moved between a position where the head 108 is sealed and a position where the head 108 is separated from the head 108 in a state where the carriage 110 is arranged at a standby position facing the cap 134. The cap 134 is disposed on a surface facing the ink ejection surface of the head 108 at the standby position at a position that communicates with a negative pressure applying unit (not shown) and that corresponds to the plurality of ink ejection ports of the head 108. A plurality of suction ports (not shown) are provided to suck air bubbles and defective ink from the ink discharge ports of the head 108 via the suction ports.

When printing is performed by the recording apparatus 100 having the above-described configuration, the user holds the leading end of the sheet S from the paper feed tray 104 against the paper
By rotating the sheet S manually, the sheet S is moved to the intermediate wall 1.
It is guided between the support wall 03 and the support wall 102b. Subsequently, the user turns back the sheet S by about 180 ° and presses the pressing roller 12.
4 and a paper feed tray 122, thereby pressing the sheet S against the outer peripheral surface of the paper feed roller 122, and causing the sheet S and the ink ejection surface of the head 108 to move in the horizontal direction by the scanning mechanism 112 during printing. Make the intervals constant.

In this state, the sheet S is conveyed in the direction of arrow 121 by the rotation of the sheet feeding roller 122 based on the driving of a motor (not shown).

In synchronization with the movement of the sheet S, the carriage 1
The guide rail 10 is rotated by the rotation of the belt 116.
The ink is ejected from the head 108 to the portion of the sheet S that reciprocates along the sheets 6 and 107 and moves on the sheet feeding roller 122 to perform printing. The control of the ejection of the ink is performed by a drive circuit connected to the control electrode applying a voltage to a predetermined control electrode according to the position of the carriage 110. The printed sheet S is discharged onto the paper feed tray 104 again.

When printing is not performed, especially when printing is not performed for a long time, the carriage 110 moves to the standby position, where the head 108 is sealed by the cap 134 and the head 10 is closed.
8 is prevented from drying. If necessary, the negative pressure applying means sucks bubbles or defective ink from the ink ejection ports of the head 108, so that the head 108 can normally eject ink at the next printing.

The recording apparatus 100 shown in FIG. 5 uses a serial type ink jet head. However, the plurality of ink ejection ports for each color are printed at the same density as the image resolution to be printed in the sheet conveyance direction (arrow 1 in FIG. 5).
It is more preferable to form an image without moving the head by using a line-type inkjet head arranged so as to cover at least the printing width of the printing area of the sheet in a direction orthogonal to (21). . The reason is that in the line type ink jet head, the distance between the sheet and the ink ejection surface of the head is easily made constant, and thus the electric field for ejecting ink can be formed stably.

[0032]

According to the present invention, when ink is ejected from an ink ejection port corresponding to a desired control electrode, ink does not fly from an ink ejection port adjacent to the ink ejection port. A desired image can be formed on a recording medium.

[Brief description of the drawings]

FIG. 1 is a schematic partial sectional view showing an electrostatic ink jet recording apparatus according to the present invention.

FIG. 2A is a top view of the inkjet head of FIG. 1; (B) A top view of an ink jet head showing another embodiment of the control electrode.

FIG. 3 is a schematic partial cross-sectional view of an inkjet head showing another embodiment of a conductive member.

FIG. 4 is a process chart showing an example of a method for manufacturing the ink jet head of FIG.

FIG. 5 is a perspective view showing an embodiment of an electrostatic ink jet recording apparatus according to the present invention.

FIG. 6 is an enlarged front view of a timing slit provided in the recording apparatus of FIG.

[Explanation of symbols]

1: inkjet recording apparatus, 4: ink, 6: ink chamber, 8: ink ejection port, 16: back electrode, 20: control electrode, 24: electrode, 26: conductive member, 30: recording medium,
100: inkjet recording device; 108: inkjet head.

Claims (2)

[Claims] 1. An ink jet head comprising: an ink chamber for accommodating ink; a plurality of ink ejection ports communicating with the ink chambers; and control electrodes arranged near each of the ink ejection ports. To apply ink to the ink chamber so that the ink in the ink chamber flies to the opposite side of the ink chamber across the ink ejection port,
An electrostatic type ink jet recording apparatus which adheres to a recording medium facing an ink ejection port of an ink jet head by this means, wherein an electric field shielding member is provided between the ink ejection ports. 2. The recording apparatus according to claim 1, wherein the electric field shielding member is a conductive member set at a constant potential.