JPS63134249A - Liquid jet recording head - Google Patents

Abstract

PURPOSE:To enable fine gradation representation over a wide range of density, by providing a second electro-thermal converter for controlling the temperature of a recording liquid, in the vicinity of an electro-thermal converter. CONSTITUTION:A recording liquid 13 is heated by an electro-thermal converter 105 to cause expansion of the liquid or generation of a bubble, and a liquid droplet 18 is ejected according to the volume change of the recording liquid 13, thereby recording. A second electro-thermal converter 104 is provided in the vicinity of the electro-thermal converter 105 contributing to the ejection of the liquid droplet. Therefore, the diameter of the liquid droplet 18 ejected can be varied by heating the recording liquid 13 in the vicinity of the electro- thermal converter 105 by the electro-thermal converter 104 to such a degree as not to eject the liquid 13 and thereby regulating the viscosity of the liquid to a desired value. By this system, it is possible to smoothly represent intermediate gradations, and full-color pictorial images with high quality can be obtained at high speed by using inks of yellow, magenta, cyan and black colors or the like.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a liquid jet recording head, and more specifically,
The present invention relates to a liquid jet recording head that can perform recording with gradation.

[Prior Art] Conventionally, non-impact recording methods have attracted attention because the noise generated during recording is so small that it can be ignored. Among them, high-speed recording is possible,
Moreover, the liquid jet recording method (inkjet recording method), which allows recording on plain paper without the need for special processing such as fixing, is an extremely powerful recording method, and various methods have been proposed and implemented so far. A device has been devised, improved and put into practical use.

Among them, for example, the methods described in Japanese Patent Application Laid-open No. 54-51837 and German Opening Publication (DOLS) No. 284306 apply thermal energy to a liquid to obtain a driving force for forming flying droplets. In this respect, it has different characteristics from other inkjet recording methods.

In other words, in the method disclosed in the publication named ``-'', a liquid subjected to the action of thermal energy undergoes a state change accompanied by the generation of bubbles and a sharp increase in volume, and based on the state change, Due to the acting force, liquid droplets ascending the orifice at the tip of the recording head are ejected, fly γ11, and adhere to the recording member, thereby performing recording.

In particular, the inkjet recording method disclosed in DDLS No. 2843064 is not only very effectively applied to the so-called drop-on-demand recording method, but also allows the recording head to be a full-line type with high-density multi-orifices. Since it is easy to do this, it has the advantage that high-resolution, high-quality images can be obtained at high speed.

In this way, the liquid jet recording method that uses thermal energy has many advantages, but if you want to record images with even higher resolution and higher quality, it is necessary to give the recording pixels an R tonality. , it is necessary to perform pixel recording including halftone information.

[Problems to be Solved by the Invention] In conventional image recording methods that perform such gradation expression, first of all, one pixel is occupied by only one image forming element. First, the number of cells in one pixel that is not occupied by the image forming element and the image that occupies the cell are subdivided into a plurality of cells to obtain a matrix. There is a recording method that digitally expresses a desired level of gradation depending on the arrangement state of the formation elements.

Secondly, by constructing one pixel with only one image forming element and changing the optical density of the image forming element, the recording ability can be developed to express a desired gradation expression in an analog manner. There is.

However, in a liquid jet recording head that ejects liquid using thermal energy to perform recording, when controlling it to obtain gradation expression using the first method, the area of one pixel itself is small. In some cases, the image becomes too sharp, resulting in a decrease in clarity, etc. Furthermore, because it is digitally controlled, the gradation steps are coarse, resulting in a lack of fineness in image quality.

On the other hand, in the second method, the size of one pixel, that is, the image forming element body, is generally changed by changing the electric energy applied to the size of the droplets to be ejected. In this method, the gradation control range is narrow and it is not possible to obtain a gradation control range of 100%.Also, extremely strict quality control is required to keep the orifice diameter etc. uniform, and if this is not done, Due to manufacturing variations, ejection failure and reliability degradation of the recording head may be caused.

[Means for Solving the Problems] The present invention solves these problems and provides a liquid jet recording head capable of expressing fine gradation over a wide density range from high optical density to low optical density. With the goal.

Therefore, in the present invention, the recording liquid in the liquid flow path communicating with the orifice is heated using an electrothermal converter to cause a state change in the recording liquid, and the pressure increases due to the generation of bubbles. In the liquid jet recording head that ejects the recording liquid from the orifice toward the recording medium, a second electrothermal entity (described in 11η≦1) for controlling the liquid temperature of the liquid is provided near the electrothermal converter. Established.

[Function] That is, in the present invention, the recording liquid is heated by an electrothermal converter, a state change is caused in the recording liquid, that is, liquid expansion or bubbles are generated, and droplets are ejected according to the change in the volume of the recording liquid. When performing recording, since the second electrothermal transducer is provided near the electrothermal transducer involved in ejecting the liquid layer, the recording liquid near the electrothermal transducer is not ejected by the second electrothermal transducer. By heating the liquid to a certain degree and changing its viscosity to a desired value, the diameter of the ejected droplets can be varied.

Therefore, the smooth halftone expression (gradation expression), which was difficult to achieve in the conventional Infusiera 1-recording method in which recording is performed by ejecting liquid using thermal energy, has been achieved by the second method according to the present invention. This is made possible by making the droplet diameter variable using a recording head with a heating element, and furthermore, it is possible to create full-color, Victorian, high-quality images using yellow, magenta, cyan, and black inks. can also be obtained at high speed.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

First, the recording principle of the liquid jet recording head according to the present invention will be described using FIG.

The recording liquid (ink H3) is supplied into the liquid chamber 11 constituting the recording head whose tip is formed into a nozzle shape by applying a supply pressure P to an extent that the liquid does not leak from the orifice 12. When the ink 13a in the liquid chamber 11 at a distance ll!tλ from 12 receives the action of thermal energy from a microelectrothermal converter (not shown) in a portion with a width Δ1, a state change occurs in the ink in that portion, and as a result, Depending on the amount of energy applied as the pressure within the liquid chamber 11 increases, part or all of the ink 13b existing within the width 1 of the liquid chamber 11 is ejected from the orifice 12.The ejected droplets 18 are recorded. Recording is performed by flying toward a recording medium 14 such as paper and adhering to a predetermined position thereof.

When the supply of thermal energy from the electrothermal converter is stopped, ink is replenished into the liquid chamber 11 due to the supply pressure P, and the liquid chamber 11 is filled.

In an inkjet recording method that uses thermal energy to eject ink, by applying thermal energy to the ink 13 in a temporally discontinuous manner, the applied thermal energy can carry recorded information. That is, if the electrothermal transducer is made to generate heat according to the panel-shaped recording information signal, the ink 13a
Will it be ejected from the orifice 12 due to a change in the state inside? & ? The recording information can be carried on the R18, so that desired recording can be performed by adhering it to the recording paper 14.

FIG. 1 shows an embodiment of the liquid jet recording head of the present invention.
Multiple orifices! In Figure 0, which shows a cross-sectional view in the alignment direction of the recording heads arranged in stacked stacks, 101 is the entire recording head, 102 is the orifice arranged to face the recording medium, and 1028 is the orifice arranged to face the recording medium. Saliva flow passages communicate with each orifice 102, and 103 is a partition wall that separates each liquid flow passage 102A. Reference numeral 105 denotes an electrothermal converter (hereinafter referred to as a main heater) provided in each liquid flow path 1028 in order to eject droplets, and its heat accumulation layer generates heat in response to the supply of a recording signal, and the generated heat causes the ink to flow. Evaporate and eject droplets. Reference numeral 104 denotes an electrothermal converter (hereinafter referred to as an electrothermal converter) which is provided in front of the main heater 105 (on the orifice 102 side) in each liquid flow path 102 to change the temperature of the ink, and has a heat accumulation layer thinner than the heat accumulation layer of the main heater. It is called a brejita).

Now, when the main heater 105 is driven with an electric signal of a constant frequency and a constant voltage to generate heat, the orifice 10
2, a droplet of a constant volume is ejected.

FIG. 2 shows the correlation between the ink temperature T and the ejected droplet volume V at this time. This correlation is mainly due to the exponential temperature characteristic of the ink viscosity η, that is, ηQCIIXI) [7]. Further, the temperature of the ink can be varied by driving the preheater 104 placed in front of the main heater 105 as necessary. That is, by controlling the liquid temperature T of the ink using the brake heater 104, it is possible to change the ejection volume.

Also, one pixel is composed of one dot or multiple dots,
By making the dot size (dot diameter) variable, the obtained optical reflection density value (hereinafter referred to as OD value) can also be changed.

FIG. 3 shows the relationship between the OD value and the dot diameter at this time. If the recording paper used is the same, the size of the dot is determined by the volume of the ejected droplet. That is, the third
As shown in the figure, it is possible to change the recorded OD value by changing the volume of the ejected droplet.

FIGS. 4(A) to 4(D) show the preheater 10 shown in FIG.
FIG. 4 is an explanatory diagram when recording is performed using a head 101 having a head 101 having a head 101 having a head 101 having a head 101 having a head 101 having a head 101 having a head 101 having a head 101 having a head 101 having a head 101 having a head 101 having a head 101 having a head 101 having a head 101 having a head 101 having a head 101; (^) in the figure is the recording signal, that is, the input signal to the main heater 105, (B) in the figure is the liquid temperature control signal, that is, the λ force signal to the brake heater 104, and (C) in the figure is the ejected droplet. In the figure, (D) shows the recording dot and diameter i1, respectively. As is clear from the figure, even if the applied voltage for ejecting droplets is constant, the dot diameter changes depending on fs and τ when the signal force to the heater 104 is appropriately determined.

Figure 5 shows the relationship between the OD value and the number of pulses applied to the brake heater when gradation is expressed using the head 101 with black ink having the composition shown below. It can be seen that smooth gradation expression is obtained.

Composition C, 1, Food B1ack2 3
nt% water 70 mouth t%
Diethylene glycol 30 nt% In addition, in the same way, one image is recorded using the four-color ink of yellow, magenta, cyan, and black using a head that uses a breech heater.
Over the 0 degree range, it was possible to fold a 1'111-multicolor image into a gradation representation.

In addition, in this example, the breviator may be driven by changing the number of pulses to 11, or by changing the voltage value. The voltage value may be changed by m:.

[9', Effect of Brightness] As explained above, according to the present invention, a liquid recording head capable of expressing fine gradation over a wide density range can be realized.

[Brief explanation of the drawing]

Figure 1 is an example of an uninvented liquid jet Q1 recording head; a cross-sectional view (not showing an example); Figure 2 is a diagram showing the relationship between ink temperature and ejected droplet volume; Figure 3 is optical reflection. A diagram showing the relationship between the concentration value and the appropriate volume of ejected liquid; Figures 4 (8) to (D) are explanatory diagrams for explaining the state when recording is performed using the recording head shown in Figure 1; , Fig. 5 is a diagram showing the relationship between the optical reflection density value and the number of pulses supplied to the brake heater in Fig. 1 when gradation recording is performed using the recording head shown in Fig. Utilize energy 1. Liquid injection record 1-
FIG. 11... night chamber, 12.102... orifice, 13... ink, 14... recording paper, 18... T & drop, lot... recording head, 1Q2A-... liquid flow path , 103... Partition wall, 104... Electrothermal converter (break heater), 105...
- Electrothermal converter (main heater). T('l;L5L) (''C) Do, Soto

Claims (1)

[Claims] 1) Heating the recording liquid in the liquid flow path communicating with the orifice using an electrothermal converter to cause a state change in the recording liquid, and increasing the pressure due to the generation of bubbles. In the liquid jet recording head that discharges the recording liquid from the orifice toward the recording medium according to the temperature, a second electrothermal converter is provided near the electrothermal converter for controlling the temperature of the recording liquid. A liquid jet recording head characterized by: 2) The liquid jet recording head according to claim 1, wherein the heat storage layer of the second electrothermal converter is formed thinner than the heat storage layer of the electrothermal converter.