JPH07132603A - Inkjet recording head and inkjet recording apparatus - Google Patents

Abstract

PURPOSE:To provide an ink jet recording head capable of discharge control and multicolor printing without providing multiple heads and sacrificing a resolution. CONSTITUTION:At least one light-to-heat converter 2 is provided in an electricity-to-heat converter 1 in a recording nozzle, the amount of light irradiated to the light-to-heat converter is controlled, the site of the light-to-heat converter 2 to which light is irradiated is controlled in response to discharge control information, and the part of ink whose temperature rises is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus capable of controlling a desired discharge amount.

[0002]

2. Description of the Related Art In recent years, office automation equipment such as personal computers and word processors have become widespread, and in these equipment, various recording methods such as a wire dot method, a thermal transfer method, and an ink jet method are used as methods for printing out input information. Is being developed. Each of these recording methods uses a recording head of a specific method to perform predetermined recording on a recording sheet conveyed.

The requirements for these recording devices are:
Examples include high-speed recording, high resolution, high image quality, and low noise. In particular, with the recent increase in the speed of MPUs and the higher integration of semiconductor memories, the handling of image images has increased, and therefore the demand for high image quality of halftones (halftones) has increased further.

As a method of expressing a halftone in an ink jet recording apparatus, a method of expressing the number of dots shot per unit area on a recording medium (pseudo halftone expression by binary value), a head or a density with different ejection amount is used. There is a method in which a plurality of heads for ejecting different inks are arranged, and the heads are selected and driven according to the halftone.

[0005]

However, the conventional means for expressing halftone has the following problems.

In the pseudo halftone expression means by binary, one pixel is expressed by a plurality of dots, so that the resolution is lowered.

Further, in the method of performing halftone expression in which heads having different ejection amounts or a plurality of heads for ejecting inks having different densities are arranged, there is not only a cost obstacle, but also downsizing and space saving. It will also hinder the computerized design. In particular, in the case of a multi-value full color recording apparatus, a plurality of heads must be arranged for each color, which is almost impossible.

The present invention solves the above conventional problems, but can control the ejection amount to a desired amount without sacrificing the resolution and mounting a plurality of inks or heads of the same color. In addition, it is an object of the present invention to provide an ink jet recording apparatus capable of stably performing high image quality by multi-value recording or the like.

[0009]

Means and Actions for Solving the Problems Means of an embodiment described below for solving the above problems have a plurality of recording nozzles, and the recording nozzles have an electrothermal converter for generating thermal energy. In a drop-on-demand type ink jet recording head, an ink jet recording head in which at least one light-heat converting body is further provided in addition to the electro-heat converting body in each recording nozzle is used, and ejection amount control information (multivalued Depending on the recording signal information, etc.)
This is achieved by an inkjet recording apparatus having a light irradiation unit that controls the light irradiation amount of the heat conversion body and changes the temperature of the ink in the nozzle. Furthermore, depending on the discharge amount control information,
This is achieved by an ink jet recording apparatus having a light irradiating means capable of changing the light irradiating portion of the light-heat converter in the nozzle and changing the ink portion of which temperature rises.

These problems can be achieved by an ink jet recording head equipped with these light irradiation means.

According to the above means, the present invention makes it possible to stably obtain a desired ejection amount in a wide range without sacrificing resolution and without mounting a plurality of inks or heads of the same color. This enabled high image quality such as multi-valued recording.

The present invention will be described in detail with reference to specific examples.

First, regarding an ink jet recording head having a light-heat converter in addition to the electric-heat converter of the present invention, a schematic view from above of the drop-on-demand type ink jet recording head having a multi-nozzle structure shown in FIG. Will be explained. Liquid chamber 3 in which _n nozzles N _{1 to} N _n are common
And has an electric-heat converting body 1 and a light-heat converting body 2 in each nozzle. The light-heat converter 2 may be on the same plane as the electricity-heat converter 1,
It may be on another surface, but from the viewpoint of light-heat conversion efficiency, it should be provided on the opposite surface of the electric-heat conversion body as shown in FIG. Is preferred.

Next, a method of controlling the ejection amount to a desired amount using the ink jet recording head having this structure will be described with reference to FIG. FIG. 3A is a schematic diagram of the inside of the ink nozzle when ejecting a large amount of liquid droplets. The ejection amount at this time is the nozzle cross-sectional area, the ejection port diameter, the size of the electro-thermal converter, and its position. It depends on these factors, but these factors cannot control the ejection amount to a desired value, and cannot be a variable factor for forming a halftone image. Although the discharge amount can be controlled by the drive voltage / drive pulse of the electro-thermal converter as a factor capable of controlling the discharge amount, the control range of the discharge amount is not sufficient.

Here, as a method for controlling the discharge amount in the smaller direction from the normal discharge state of FIG.
By irradiating the light-heat converter on the side opposite to the nozzle opening of the heat converter with light, heat is generated and the ink temperature in the vicinity thereof is raised. The ink in the portion opposite to the nozzle has a higher temperature than the ink in the vicinity of the electro-thermal converter portion and the nozzle, and as a result, the viscosity is lowered. In this state, if the electro-thermal converter is pulse-driven to cause foaming, the foaming will not only occur in the nozzle opening portion but also in the ink liquid chamber side as shown in FIG. Stretching, and the amount of discharged droplets is reduced. In this way, the ink temperature can be variably controlled according to the light irradiation amount at this time, and as a result, the ink droplet ejection amount can be controlled.

In order to exert such an effect, it is desirable to irradiate light to heat the vicinity before applying a pulse to the electrothermal converter as shown in FIG.

Further, as shown in FIG. 5, a light-heat converter is provided on the entire surface opposite to the surface provided with the electricity-heat converter, and the light irradiation position is set to 2 on the nozzle side and the liquid chamber side of the electricity-heat converter. As shown in FIG. 6, when the medium discharge amount region is used, the discharge by the thermal energy of the normal electric-heat converter is used, and when the small discharge amount region is used, the light-heat converter on the ink liquid chamber side is used. It is only necessary to irradiate 2 with light (hν ₁ ), and then to discharge with the heat energy of the electrothermal converter 1.

When discharging in a large discharge amount area, as shown in FIG. 6C, the light-heat converter on the nozzle side is irradiated with light (hν ₂ ) and then the heat of the electric-heat converter 1 is changed. It is sufficient to eject with energy. In order to control the discharge amount more finely in each discharge amount region, the energy input to the electro-thermal converter 1 may be controlled, and pulse width control and drive voltage control may be performed.

In addition to FIGS. 3 and 6, it is also possible to control the discharge amount by the combination of FIGS. 6 (b) and 6 (c).

As the above-mentioned light-heat converter, a carbon black vapor-deposited film or the like can be cited, and as the irradiation light, one having a wavelength range in which the above-mentioned light-heat converter absorbs / heats may be used. The method for controlling the light irradiation amount may be either analog or digital control, and there are a method of synchronizing a laser with a head nozzle by a polygon scanner, a method of irradiating light to each nozzle with an LED array, an LCD shutter, and the like.

[0021]

【Example】

Example 1 A head having a nozzle cross-sectional shape as shown in FIG. 5 was prepared, and a carbon vapor deposition film was provided as a light-heat converter. A transparent sealant was used as the head structure, and the inkjet recording head of FIG. 7 was produced.

Example 2 Inkjet recording having a structure in which an LED array having the same pitch as the pitch width of each nozzle was provided on the transparent sealant side with respect to the inkjet recording head of Example 1 A head was produced.

Example 3 The inkjet recording head of Example 2 was attached to a recording apparatus as shown in FIG. 8 to form an inkjet recording apparatus of the present invention.

As driving conditions, drive voltage V _OP = 20.0 V drive pulse width T _PW = 5.0 μsec drive frequency 4 kHz As head configuration, nozzle pitch 63.5 μm nozzle opening diameter 21 × 21 μm 128 nozzles, 16 blocks 25% Duty printing The weight of the liquid droplet per dot was measured from the weight reduction amount of the recording head when the pattern was printed on the coated paper without light irradiation by the above head and the total discharge amount of the print, and it was 28.1 ng / dot. It was

Next, the emission intensity is 10 mW and the emission wavelength is 720.
In the LED array of nm, 400 dpi, and 128 cells, the light irradiation and the heater are driven by changing t ₁ (light irradiation time) in synchronization with the driving of the electro-thermal converter at the above light irradiation timing for each nozzle. The relationship between t ₁ and dot weight was determined. As a result, as shown in FIG. 10, it was found that the dot weight decreased as the t ₁ irradiation time increased, and the printed dot diameter decreased accordingly. This enabled multi-value recording.

[0026]

According to the present invention, the ejection amount can be controlled without mounting a plurality of heads and without sacrificing the resolution, and images such as multi-value recording can be stably performed. This also made it possible to downsize the device.

[Brief description of drawings]

FIG. 1 is a see-through schematic diagram from above of a drop-on-demand type inkjet recording head having a multi-nozzle structure.

FIG. 2 is a schematic diagram of the arrangement of a liquid chamber in the vicinity of a nozzle.

FIG. 3A is a schematic view of the inside of an ink nozzle when ejecting a large amount of droplets. FIG. 6B is a schematic view of the inside of the ink nozzle when ejecting a small amount of droplets.

FIG. 4 is a schematic diagram showing timings of light irradiation and driving of an electrothermal converter.

FIG. 5 is a schematic diagram in which a light-heat converter is installed at two places.

FIG. 6A is a schematic diagram showing ejection in the case of performing normal light irradiation. FIG. 6B is a schematic diagram showing ejection when light is irradiated to a distance farther than the nozzle. FIG. 6C is a schematic diagram showing ejection when light is irradiated to a distance shorter than the nozzle.

FIG. 7 is a diagram showing an inkjet head (N is a nozzle portion).

FIG. 8 is a schematic view of the inside of a recording apparatus equipped with an inkjet head.

FIG. 9 is a schematic diagram showing a relationship between driving by an electric-heat conversion body and a light-heat conversion body and its duration.

FIG. 10 is a graph showing the relationship between dot weight and light irradiation time.

[Explanation of symbols]

 1 Electric-Heat Converter 2 Light-Heat Converter 3 Liquid Chamber 5 Blade 14 Inkjet Head Cartridge 16 Flexible Cable 17 Carridge Drive Motor 18 Recording Paper 19 Paper Feed Roller 20 Cleaning Motor 21 Guide Shaft 22 Cartridge Drive Belt 25 Cap Part 101 Head part 104 Inkjet head 110 Cartridge top lid 112 Same as above 114 Side of cartridge

Claims (6)

[Claims] 1. A drop-on-demand ink jet recording head having a plurality of recording nozzles, the recording nozzles having an electro-thermal converter for generating thermal energy. And an ink-jet recording head, further comprising at least one light-heat converter. 2. The ink jet recording head according to claim 1, wherein the light-heat converter in each recording head has a light irradiation unit that can be independently controlled. 3. An ink jet recording apparatus for ejecting ink droplets from an ink jet recording head onto a recording medium to perform recording in an ink jet recording head according to claim 1, wherein a light-heat conversion element in a nozzle is provided with a light-heat conversion element in accordance with ejection amount control information. Control the light dose,
An ink jet recording apparatus comprising a light irradiation means for changing the temperature of ink in a nozzle. 4. An ink jet recording apparatus according to claim 3, wherein a light irradiating means capable of changing a light irradiating portion of a light-heat converting member in a nozzle and changing an ink portion of which temperature rises according to ejection amount control information. An inkjet recording apparatus comprising: 5. An ink jet recording apparatus, comprising an input energy control means capable of controlling the input energy to the electro-thermal converter according to the light irradiation amount. 6. An ink jet recording apparatus comprising an input energy control means capable of controlling the input energy to the electro-thermal converter according to the light irradiation site.