JPH01271250A - Ink jet recording head - Google Patents

Abstract

PURPOSE:To suppress the ink sump on the end surface of an ink emitting orifice to the minimum and to obtain a high grade image even at high temp., by chamfering the peripheral edge part of the end surface around the ink emitting orifice and setting the maximum value of the thickness of the part flush with said end surface to 125mum or less. CONSTITUTION:The peripheral edge part of the end surface around an ink emitting orifice 1 is chamfered as shown by a numeral 10. The maximum value of the thickness (t) of the part flush with the chamfered end surface is set to 125mum or less, pref., to 75mum or less. By this method, even in such a case that meniscus vibration is increased at the time of recording at high temp. and ink is suspended from the end surface of the ink emitting orifice 1, the ink pump 9 on the end surface of the ink emitting orifice 1 is suppressed to the minimum and the emission of the ink is stabilized without generating oblique emission to obtain a high grade image.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording head that forms four images on a recording sheet such as paper by ejecting ink droplets in an inkjet recording apparatus.

[Conventional technology]

Inkjet is a recording method used in recording devices such as printers and facsimiles that ejects ink droplets from the ink ejection openings of the head onto a sheet (recording medium such as paper or thin plastic plate), forming a dot pattern of adhered ink. There is a method.

Such inkjet recording apparatuses can be roughly classified into three types: continuous jet type, impulse type (on-demand type), and electrostatic attraction type.

Continuous-jet type printers use the principle of recording by charging and deflecting continuously ejected ink, which makes the device configuration complex and requires devices for ink recovery and cleaning. Therefore, there is a problem that the cost of the equipment increases.

In addition, although the electrostatic attraction type has a relatively simple structure, it requires high voltage, which poses problems in terms of energy saving and safety.Furthermore, there are limitations on the physical properties of the ink, such as electrical conductivity. Moreover, there was a problem that the frequency response of the recording operation was inferior.

On the other hand, the on-demand type ejects ink droplets only when necessary using ejection energy provided by an energy generating means such as an electromechanical transducer or an electrothermal transducer, and has a very simple structure. It is highly expected to be used as a recording device because it is economical and has excellent reliability and σ properties.

[Problem that the invention seeks to solve]

By the way, when recording 62 is performed at a high temperature using an inkjet recording device, the viscosity of the ink decreases due to high temperature discharge M, and the meniscus vibration at the ink ejection port increases by 1 (increasingly, the ink adheres around the ink ejection port 7). , an ink pool occurs.If the ink ejection port is constituted by a nozzle tip, an ink pool occurs on the nozzle tip surface.

Then, the shadow W of the ink pool around this ink ejection port
(From , 7) Ink ejection was skewed, the ink landing point on the sheet was misaligned, and uneven streaks and density reduction occurred in the printed image.

An object of the present invention is to solve the above-mentioned problems of the prior art, eliminate ink accumulation around one ink ejector with a simple configuration, and produce high-quality images even at high temperatures. The goal is to provide the following.

[Means for solving problems]

In an inkjet recording head that records by ejecting ink droplets from an ink ejection port, the peripheral edge of the end face around the ink ejection port is chamfered, and the maximum thickness of the portion flush with the end face is chamfered. The above object can be achieved by setting the chamfer to 125 μm or less, preferably 7511 m or less, and it is preferable that the angle of the chamfer to the end face is set to 10 degrees or more.

[Effect]

The peripheral edge of the end face around the ink ejection port is chamfered to minimize the area of the part that is flush with the end face, and a receding slope is formed around it, so that ink is removed from the ink ejection port due to increased meniscus vibration. Even if the ink drips, ink accumulation due to adhering ink on the end surface around the ink ejection opening is minimized, thereby eliminating skewed movement of the ejected ink.

〔Example〕

The present invention will be specifically described below with reference to the drawings.

FIG. 1 is a schematic diagram of an inkjet recording head suitable for carrying out the present invention.

In Fig. 1, 1 is the ink ejection opening formed on the tip surface of the nozzle, 2 is the flying ink droplet ejected from the ink ejection opening, 3 is the nozzle, and 4 is the ink droplet provided around the nozzle 3. 5 is a filter provided at f&+41 of the nozzle 3; 6 is an ink chamber formed in the nozzle 3 at a position corresponding to the piezoelectric element 4; 7 is the pressure ffl A head drive unit that generates a drive pulse to be applied to the element 4 is shown.

In the above configuration, when ink is supplied into the nozzle 3 through the filter 5 and a pulse as shown in FIG. The pressure of the ink chamber 6 inside the piezoelectric element (piezo) 4 changes, and ink droplets 2 are ejected from the ink ejection opening 1 formed at the tip of the nozzle 3.

In this case, if recording is performed at a high temperature as described above, the meniscus vibration at the ink ejection port 1 increases because the viscosity of the ink has decreased due to being left at a high temperature.

When the meniscus vibration increases in this way, a part of the ink drips out and hits the tip surface of the nozzle 3, that is, the ink ejection port 1.
There is a tendency for the ink to adhere to the edges around the edges and form ink puddles there.

FIG. 3 shows the condition of ink accumulation on the nozzle tip surface of a conventional inkjet recording head, and FIG. 4 shows the condition of ink accumulation on the nozzle tip surface of an inkjet recording head according to the present invention. .

In the conventional inkjet recording head, as shown in FIG. 3, the portion r! Because I-T is large,
When some of the ink 8 drips due to the increase in meniscus vibration, a considerable amount of ink adheres to the nozzle tip surface.
An ink reservoir 9 is formed.

Therefore, when ink droplets 2 are ejected, the ink pool 9 causes the ink droplet 2 to be ejected in an oblique direction as shown in FIG. There were streaks and decreased density in the printed image.

In contrast, in the inkjet recording head of the present invention, as shown in FIG. The structure is such that the value is 125 μm or less, preferably 75 μm or less.

The angle of the chamfer 10 with respect to the end surface of the ink discharge port 1 (the end surface of the nozzle 3) is set to have a sufficient setback of 10 degrees or more.

Therefore, even if some of the ink 8 drips due to increased meniscus vibration during recording under high temperatures, the nozzle tip surface (the part flush with the end surface around the ink ejection port 1)
(Thickness t) is minimized and a chamfer (retreating angle) 10 is formed around the end face, so that the dripped ink is removed by the chamfer 10 as shown by the ink pool 9 in FIG. The ink ejection port 1
The amount of adhesion on the surrounding end faces can be minimized.

Therefore, when the ink droplet 2 is ejected, the ejection direction has stable straightness as shown in Fig. 4, and it is possible to eliminate deviations in the landing point of the ink droplet on the recording sheet, thereby improving the quality of the printed image. It is now possible to maintain integrity.

Test example 1: A glass nozzle was used as nozzle 3, and ink discharge port 1
The diameter of the nozzle is always constant at 50 μm, and by changing only the outer diameter of the nozzle tip by changing the size of the chamfer 10 provided on the peripheral edge of the nozzle tip, it can be made flush with the end surface around the ink ejection port 1. By changing the thickness t of the part, the ink droplet 2
The direction of discharge was observed.

In this case, if the discharge direction is perpendicular to the nozzle tip surface (the fourth
Figure) is considered to be a good product, and one with even a slight skew (Figure 3)
was considered a defective product.

Figure 5 shows the outer diameter D of the vertical surface of the nozzle tip (ink ejection opening l).
12 is a graph showing the results of an investigation of the incidence of defective products (defective rate) with respect to the thickness t of a portion flush with the surrounding end surface.

From the test results shown in Figure 5, almost all of the products are defective when the outer diameter of the vertical part of the nozzle tip surface is 300 μm or more (vertical surface thickness t is 125 μm); All samples with a diameter of 75 μm or less were good.

From the above test results, in order to obtain an inkjet recording head that does not cause oblique discharge, the maximum value of the thickness t of the vertical part of the tip surface around the ink discharge port 1 should be 125 μm or less, preferably 75 μm or less. It has been found that it is sufficient to form the chamfer 10 until the chamfer 10 is formed.

Test Example 2: The same inkjet recording apparatus as in Test Example 1 was used, and a stainless steel nozzle was used as the material for the nozzle 3 of the recording head.

The diameter of the ink discharge port of the stainless steel nozzle is 50 μm, and the end face f! The outer diameter of the straight part is 200. When ink was ejected using a recording head with a chamfer of 10 up to +1 m, stable ink ejection without oblique ejection was obtained, and a high-quality printed image without uneven streaks etc. was obtained.

Test Example 3: The same inkjet recording device as in Test Example 1 was used, the nozzle material of the recording head was made of stainless steel, and the periphery was chamfered so that the vertical profile of the nozzle tip was a square of 156 μm x 156 μm. Furthermore, the shape of the ink ejection opening 1 was made into a square of 50 μm×50 μm.

When ink was ejected using such an inkjet recording head, a stable ejection operation without oblique ejection was obtained.

In this case, the maximum value of the thickness t of the vertical portion on the end face around the ink ejection port 1 is 75 μm.

In the above embodiments, the present invention is applied to a recording head having a nozzle-type ink discharge means, but the present invention is also applicable to a configuration in which boat-shaped ink discharge ports are arranged on the front surface of a common liquid chamber. It is also applicable to other inkjet recording heads.

(Effects of the Invention) As is clear from the above description, according to the inkjet recording head of the present invention, the peripheral edge of the end face around the ink ejection port is chamfered, and the maximum thickness of the portion flush with the end face is Since the value is set to 125.+1 m or less, preferably 75 μm or less, even if meniscus vibration increases and ink drips onto the ink ejection port end surface, such as when recording at high temperatures, ink accumulation on the ink ejection port end surface can be prevented. It is possible to obtain an inkjet recording device that can reduce the amount of ink to a minimum, enable stable ink ejection without skew ejection, and improve image quality7.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view of an inkjet recording head suitable for implementing the present invention, FIG. 2 is a graph showing the waveform of the drive pulse applied to the piezoelectric element in FIG. 1, and FIG. FIG. 4 is a cross-sectional view of an ink ejection port portion of a conventional inkjet recording head, and FIG. This is a 1" graph showing the defective rate of ink ejection against the thickness (outer diameter) q of the vertical part of the surrounding end face. 1... - ink ejection opening, 2 - - ink droplet , 3・・・・・−１１−Nozzle, 4・・・・・−
・-piezoelectric element, 8-・-・−・−・−ink, 9・−・
... Ink pool, 10------- Chamfering, Ray --- 1111, j7 of the vertical part of the end surface, D.
・−・−・Outer diameter of the vertical part of the end face.

Claims (3)

[Claims] (1) In an inkjet recording head that records by ejecting ink droplets from an ink ejection port, the peripheral edge of the end face around the ink ejection port is chamfered, and the maximum thickness of the portion flush with the end face is 125 μm. An inkjet recording head characterized by the following. (2) The inkjet recording head according to claim 1, wherein the maximum value of the wall thickness is 75 μm or less. (3) The inkjet recording head according to claim 1 or 2, wherein the angle of the chamfer is 10 degrees or more with respect to the end surface.