JP2002210973A - Inkjet print head - Google Patents

Abstract

(57) [Summary] [Object] To provide an ink jet print head in which the foaming behavior is the same from the initial stage to the late stage of ejection and stable ejection characteristics can be obtained. [Configuration] Multiple heaters (ejection energy generating elements)
31, an ink discharge port 41, a substrate 32 having an ink supply port 33, a common liquid chamber, a discharge port plate 34, and the substrate 31 and the discharge port plate 34 are joined to form a substrate 32 and a discharge port plate 34. Between the ink discharge ports 4
1 and an ink flow path 42 formed so as to communicate with the ink supply port 33, the center axis vector of the flow path start point of the ink flow path 42 and the center axis vector of the flow path end point The angle formed is set to 90 to 270 degrees.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet print head used in an ink jet recording system for recording on a recording medium by flying small ink droplets.

[0002]

2. Description of the Related Art Ink jet recording ink jetting methods widely used today include a method using an electrothermal transducer (heater) as an ejection energy generating element used for ejecting ink droplets and a piezoelectric device. There is a method using an element (piezo), and any of them can control the ejection of ink droplets by an electric signal.

For example, the principle of an ink droplet ejection method using an electrothermal transducer is that an electric signal is applied to the electrothermal transducer to instantaneously boil the ink near the electrothermal transducer, and the phase of the ink at that time is changed. Ink droplets are ejected at high speed by rapid growth of bubbles generated by the change.

On the other hand, the principle of the method of ejecting ink droplets using a piezoelectric element is that the piezoelectric element is displaced by applying an electric signal to the piezoelectric element, and the ink droplet is ejected by the pressure at the time of this displacement.

[0005] In particular, in some ink droplet ejection methods using an electrothermal transducer, it is relatively easy to increase the ejection density of ink droplets, and this method is most suitable for a printer for high-density printing of small droplets. .

FIGS. 8 and 9 (cross-sectional views taken along the line BB in FIG. 8) show the configuration of a conventional ink jet print head.

The drive board 32 shown in FIG.
2 rows at 8 dpi (84.7 μm pitch)
4.7 / 2 = 28 μm × 28 μm ejection energy generating element 3 arranged in a staggered manner offset by 42.35 μm
1 and 0.155 mm × l extending along the arrangement direction
An ink supply port 33 which is a 1 mm through-hole is formed, and a protective film layer 35 is formed on the surface.

The sub-ink tank 40 joined to the lower part of the drive substrate 32 in FIG. 9 supplies ink to a common liquid chamber 37 formed by the ink supply port 41. Drive board 32
In the discharge port plate 34 joined to the upper part of FIG. 9, a discharge port 41 having a diameter of 21 μm and an ink flow path 42 communicating the discharge port 41 and the common liquid chamber 37 are formed on each discharge energy generating element 31. ing.

Since the distance from the ink supply port 33 differs depending on the ejection energy generating element 31, the ink flow path 42
There are long and short ones. As shown in FIG. 6, the ink discharge ports 41 in each row are divided into m groups, and are arranged slightly shifted in the X direction between the groups. Generally, when ink is simultaneously ejected from all ejection ports, a large amount of electric power is required instantaneously. Therefore, ejection ports are divided into several groups, and each group is ejected with a slightly shifted timing. In order to correct the displacement of the ink droplet landing position due to the displacement of the ejection timing, the ejection ports are arranged shifted in the X direction. Assuming that the shift of the ejection timing of each nozzle group is t and the carriage speed is v, the shift is x = v · t. In the conventional example, t =
3.5 μsec, v = 338.8 mm / sec,
x = 1.2 μm.

Several proposals have been made as to the shape of the ink flow path 42, and an L-shaped flow path is described in JP-A-5-116317.
The balance between the front resistance and the rear resistance of the heater is very important in determining the discharge characteristics.

The flow path resistance is determined by the sum of the inertia term and the viscosity term.
The inertia term relates to the mass of the ink in the flow path, and the viscosity term relates to the flow resistance of the flow path. That is, inertia term ∝S × L (= volume) Viscosity term ∝L / (S × S) (= flow resistance) Here, S: sectional area, L: length, and V: volume.

In the early stage of foaming, the influence of the inertia term greatly contributes, and in the late stage of ejection, the influence of the viscous term is large. If the length of the ink flow path differs, the flow path resistance also changes, which affects the ejection characteristics. FIG. 10 shows the characteristics of the ink flow path length, the ejection amount Vd, and the refill time fr. In particular, when handling minute droplets, the effect cannot be ignored.

In order to make the rearward resistance uniform between nozzles having different flow path lengths because the distance between the heater and the ink supply port is different. Becomes Therefore, as shown in FIG. 11, there is a means for reducing the cross-sectional area in order to make the rearward resistance longer, and the viscosity term increases in inverse proportion to the square of the cross-sectional area. However, at this time, since the inertia term decreases in proportion to the cross-sectional area, it is necessary to further reduce the cross-sectional area.

Example 2) As shown in FIG. 12, by changing the width of the ink supply port 33 by the energy generation element 31, the energy generation element 31
It is also possible to make the flow path length the same and make the rearward resistance the same by making the distance to the constant.

[0015]

However, in the conventional example, as shown in FIG. 10, the ejection amount Vd and the refill time fr slightly differ depending on each ejection group (that is, each ink flow path length). When dealing with droplets, the effect cannot be ignored and adversely affects print quality.
In particular, since the ejection groups are arranged periodically, they tend to appear as streaks on printing.

In example 1), which is the above countermeasure, the discharge amount Vd
Can be made uniform to some extent, but the refill time fr becomes extremely bad because the viscosity term is extremely increased. In addition, since the balance between the viscous term and the inertia term is greatly disturbed, there may be an adverse effect due to a large change in the foaming behavior between the nozzles from the early stage to the late stage of ejection. In this method, it is difficult to make the inertia term and the viscosity term completely identical.

In Example 2), changing the supply port width depending on the nozzle position is a very difficult process as a practical matter.
Poor feasibility.

Accordingly, it is an object of the present invention to provide an ink jet print head in which the foaming behavior is the same from the early stage to the late stage of the discharge and stable discharge characteristics can be obtained.

Another object of the present invention is to increase the degree of freedom in flow path design by adopting a nozzle structure capable of arbitrarily setting flow path resistance regardless of the positions of the heater arrangement and the ink supply port. It is an object of the present invention to provide an ink-jet printhead capable of performing the above-mentioned.

[0020]

To achieve the above object, the present invention provides a plurality of ejection energy generating elements for generating energy used for ejecting ink droplets,
A substrate having an ink ejection port for ejecting the ink droplets, an ink supply port including a plurality of ejection energy generating elements arranged in rows, and a through-hole extending along an arrangement direction of the ejection energy generating elements; A common liquid chamber communicating with the ink supply port, a discharge port plate including the ink discharge port, the substrate and the discharge port plate are joined, and the ink discharge port and the substrate are disposed between the substrate and the discharge port plate. An ink jet print head having an ink flow path formed to communicate with the ink supply port,
An angle formed by a central axis vector of a flow path start point and a central axis vector of a flow path end point of the ink flow path is set to 90 degrees to 270 degrees.

The present invention also provides a plurality of ejection energy generating elements for generating energy used for ejecting ink droplets, an ink ejection port for ejecting the ink droplets,
An ink supply port comprising a plurality of discharge energy generating elements arranged in a row and having a through-hole extending along the direction in which the discharge energy generating elements are arranged, and the discharge energy generating element and the ink supply; A substrate having m (m> 1) distances from a port, a common liquid chamber communicating with the ink supply port, a discharge port plate including the ink discharge port, and the substrate and the discharge port plate being joined to each other. And an ink flow path formed between the substrate and the discharge port plate so as to communicate the ink discharge port and the ink supply port. The angle formed by the vector and the center axis vector of the flow path end point is set to 90 degrees to 270 degrees.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 5 is a partially cutaway perspective view of an ink jet printer having an ink jet print head according to the present invention.

In the ink jet printer shown in FIG. 5, a conveying device 30 is provided in a casing 8 along a longitudinal direction, and the conveying device 30 intermittently moves a sheet 28 as a recording medium in an arrow C direction in the drawing. Transport to or,
In the casing 8, a recording unit 10 reciprocated in a direction perpendicular to the transport direction C of the sheet 28 and a recording unit moving drive unit 6 as a driving unit for reciprocating the recording unit 10 are provided. I have.

The transfer device 30 includes a pair of roller units 22a and 22b, which are arranged in parallel and opposed to each other, a pair of roller units 24a and 24b, and a drive unit 20 for driving these. When the drive unit 20 is in the operating state, the paper 28 is conveyed by intermittent feeding while being nipped by the respective roller units 24a and 24b in the direction of arrow C in FIG.

The moving drive unit 6 is provided with pulleys 26a, 26
6b and the roller unit 2
A guide shaft 1 arranged in parallel with 2a and 22b to guide the movement of the carriage member 10a of the recording unit 10 in parallel
4 and a motor 18 for driving the belt 16 connected to the carriage member 10a in the recording section 10 in the forward and reverse directions.

When the motor 18 is activated and the belt 16 is driven to rotate in the direction of arrow S in FIG. 5, the carriage member 10a of the recording unit 10 is moved by a predetermined amount in the same direction. When the motor 18 is operated and the belt 16 is driven to rotate in the direction opposite to the arrow S in FIG. 5, the carriage member 10a of the recording unit 10 moves in a predetermined direction in the direction opposite to the arrow S in FIG. It can be moved by the movement amount.

Further, a recovery unit 26 for performing the ejection recovery process of the recording unit 10 is provided at one end of the movement driving unit 6 at the home position of the carriage member 10a so as to face the ink ejection port arrangement of the recording unit 10. It is provided.

The recording section 10 is provided with ink tanks for supplying inks of respective colors to the ink jet print heads 12Y, 12M, 12C, and 12B, which are detachably attached to a carriage member 10a of the recording section 10. still,
Inkjet print heads 12Y, 12M, 12
Since the structures of C and 12B are the same, only the ink jet print head 12Y will be described below, and the other ink jet print heads 12M, 12C and 12B will be described.
The description of is omitted.

The ink jet print head 12Y is
As shown in FIG. 4, a driving board 32 fixed to a sub ink tank 40 as an ink storage section, and the driving board 32
It comprises an ejection port plate 34 as an ink ejection port formation surface portion fixed above, and an electrode plate member 36 electrically connected to the drive substrate 32 by a group of wires 38. Then, the inkjet print head 1
In 2Y, the scanning speed is set to 338.8 mm / s in order to record at a pixel pitch of 42.35 μm and a maximum of 8000 pixels per second, for example.

The electrode plate member 36 has a plurality of electrode portions 36a electrically connected to the electrode portions of the recording portion 10 when the ink jet print head 12Y is mounted on the recording portion 10.

In addition, ink discharge ports 41 are provided on the discharge port plate 34 at predetermined intervals along a Y direction orthogonal to the arrow X direction (ie, the scanning direction X) in FIG.
The columns are provided in parallel. The shape of the ink ejection port 41 is
For example, it has a round shape with a diameter of 21 μm.

As shown in FIG. 6, the pitch P in the Y direction between the discharge ports 41 in each row is, for example, 84.7 μm, and the two rows have 84.7 / 2 = 42. 3
They are arranged offset by 5 μm. That is, the ink discharge ports 41 are arranged in a staggered manner. Further, the ink discharge ports 41 in each row are divided into m groups,
The groups are slightly shifted in the X direction between the groups.
Generally, when ink is simultaneously ejected from all ejection ports, a large amount of electric power is required instantaneously. Therefore, ejection ports are divided into several groups, and each group is ejected with a slightly shifted timing. In order to correct the shift of the ink droplet landing position due to the shift of the discharge timing, the ink discharge ports are arranged shifted in the X direction.

Here, assuming that the deviation of the ejection timing of each nozzle group is t and the carriage speed is v, x = v · t
It is only shifted. In the present embodiment, t = 3.5 μs
Since c and v = 338.8 mm / sec, x = 1.
2 μm.

The drive substrate 32 is made of, for example, silicon, and has an opening that opens in a tapered shape inside the sub-ink tank 40 as shown in FIGS. 2 and 3 (a cross-sectional view taken along the line AA in FIG. 2). Ink supply port 33 is a discharge port plate 34
Are provided to extend along the arrangement of the ink ejection ports 41. Here, the ink supply port 33 is formed by, for example, anisotropic etching.

On the entire surface of the drive substrate 32 to which the discharge port plate 34 is fixed, for example, silicon nitride (Si)
A protective film 35 made of N) is formed. This protective film 35 is formed, for example, to a thickness of 0.6 μm. As shown in FIGS. 2 and 3, a heater 31 serving as an ejection energy generating element is arranged on a surface of the drive substrate 32 covered by the protective film 35, facing the ink ejection port 41.

The ink ejection port 4 of the ejection port plate 34
1 and the protective film 35, the ink flow paths 42 for guiding the ink supplied through the ink supply ports 33 to the respective heaters 31 are symmetrically opposed to each other with the ink supply ports 33 interposed therebetween, and the discharge port plate 34. It is formed integrally.

As shown in FIG. 1, the ink flow path 42 is formed between a pair of partition walls 44 separating the ink flow paths 42, and has an open end opening toward the ink supply port 33. It is constituted by a U-Uji having a starting point and the other end connected to the accommodation room 50 accommodating the heater 31.
The central axis vector at the starting point of the ink flow path 42 is outwardly perpendicular to the longitudinal central axis of the ink supply port 33 on the paper surface of FIG. 1, and after passing through the straight portion T1,
The direction is changed by 180 degrees at U Ube, and further connected to the accommodation room 50 at straight part T2. During this time, the flow path width Wa is 3
It is constant at 2 μm. 1. The total length T1 + T2 of the straight portion of the ink flow path 42 in the upper part of FIG.
2, the total length T1 '+ T2' of the straight portion is equal to T1 '
+ T2 = T1 ′ + T2 ′ = k, and this relationship is established between all the ink flow paths 42.

The accommodating portion 50 is formed by a wall portion surrounding three sides of the heater 31 at predetermined intervals. The heater 31 is a square having a side of 28 μm, and the distance between each side and the wall surface formed by the partition 44 is 2 μm.

Further, as shown in FIG. 3, the distance Ha between the surface of the heater 31 and the ink discharge port 41 on the inner surface of the discharge port plate 34 is 13 μm.
The thickness Hb of the ink discharge port 41 of No. 4 is 12 μm.

When the bubble Ba is expanded due to the film boiling phenomenon in the ink near the heater 31, the thickness of the discharge port plate 34 is relatively small, so that the bubble Ba is easily affected by the pressure of the bubble Ba. 50 is formed by a wall portion surrounding three sides of the heater 31 at predetermined intervals, so that the ejection port plate 34 is
Is avoided.

Since the distance Ha is relatively small, the amount of ink flowing backward toward the ink supply port 33 is small.

Although not shown, the ink jet printer according to the present embodiment is provided with a recording operation control unit for controlling the recording operation of the ink jet print head. The recording operation control unit performs a predetermined image process on recording data representing an image to be recorded on the paper 28 to form a drive control pulse signal based on the binarized data. Supply to the inkjet print head at the timing

With this configuration, when the recording unit 10 is moved in the scanning direction, when a drive control pulse signal from the recording operation control unit is supplied to each heater 31, the ink in the vicinity of the heater 31 The bubble Ba is expanded by the film boiling phenomenon, the ink is pushed up to the ink discharge port 41 side, and the ink is discharged to the surface of the paper 28 by forming the ink droplet Do.

In this embodiment, since the flow resistance of all the nozzles is exactly the same for both the inertia term and the viscous term, the discharge amount Vd between the nozzles and the refill time fr are exactly the same. Thus, extremely uniform and stable ink ejection is performed.

[0046]

As is apparent from the above description, according to the present invention, the foaming behavior is the same from the initial stage to the late stage of the discharge, and stable discharge characteristics can be obtained.

Further, according to the present invention, the degree of freedom in designing a flow path can be increased by adopting a nozzle structure capable of arbitrarily setting the flow path resistance regardless of the positions of the heater arrangement and the ink supply port.

[Brief description of the drawings]

FIG. 1 is a sectional view of a nozzle portion of an ink jet print head according to the present invention.

FIG. 2 is a partial plan view of the inkjet print head according to the present invention.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a perspective view of an inkjet print head according to the present invention.

FIG. 5 is a partially cutaway perspective view of an inkjet printer having an inkjet print head according to the present invention.

FIG. 6 is an arrangement diagram of discharge ports.

FIG. 7 is a discharge characteristic diagram.

FIG. 8 is a partial plan view of a conventional inkjet print head.

FIG. 9 is a sectional view taken along line BB of FIG. 8;

FIG. 10 is a discharge characteristic diagram.

FIG. 11 is a partial plan view of a conventional inkjet print head.

FIG. 12 is a partial plan view of a conventional ink jet print head.

[Explanation of symbols]

12Y, 12M, 12C, 12B Ink-jet printhead 31 Heater 32 Drive board 33 Ink supply port 34 Discharge plate 35 Protective film 40 Sub-ink tank 41 Discharge port 42 Ink channel 44 Partition wall 50 Storage chamber

Claims (4)

[Claims] A plurality of ejection energy generating elements for generating energy used for ejecting ink droplets;
A substrate having an ink ejection port for ejecting the ink droplets, an ink supply port including a plurality of ejection energy generating elements arranged in rows, and a through-hole extending along an arrangement direction of the ejection energy generating elements; A common liquid chamber communicating with the ink supply port, a discharge port plate including the ink discharge port, the substrate and the discharge port plate are joined, and the ink discharge port and the substrate are disposed between the substrate and the discharge port plate. An ink jet print head having an ink flow path formed to communicate with an ink supply port, wherein an angle formed by a central axis vector of a flow path start point and a central axis vector of a flow path end point of the ink flow path is 90 degrees or more. An ink jet print head, which is set at 270 degrees. 2. A plurality of ejection energy generating elements for generating energy used for ejecting ink droplets,
An ink discharge port for discharging the ink droplets, and an ink supply port including a through-hole arranged along the direction in which the plurality of discharge energy generating elements are arranged in a row and the discharge energy generating elements are arranged; The distance between the ejection energy generating element and the ink supply port is m (m> 1).
Types of substrates, a common liquid chamber communicating with the ink supply port, and a discharge port plate including the ink discharge port,
An ink jet print head comprising an ink flow passage formed between the substrate and the discharge port plate, wherein the substrate and the discharge port plate are joined to communicate the ink discharge port and the ink supply port between the substrate and the discharge port plate. An ink jet print head, wherein an angle formed by a central axis vector of a flow path start point of the ink flow path and a central axis vector of a flow path end point is set to 90 degrees to 270 degrees. 3. The ink flow path according to claim 1, wherein even if the distance between the ejection energy generating element and the ink supply port is different, there is a combination having the same flow path length. Or the inkjet print head according to 2. 4. A combination of the ink flow paths having the same flow path cross-sectional area and the same flow path length even when the distance between the discharge energy generating element and the ink supply port is different. The ink jet print head according to claim 1 or 2, wherein