JPS6341153A - Liquid jet recording method - Google Patents

Abstract

PURPOSE:To achieve smooth gradation expression over a wide density range, by providing a heat generator for controlling the temp. of a recording liquid and a cooling means for cooling a liquid chamber on the side of the orifice of the heat generator and controlling the diameter of a liquid droplet being emitted. CONSTITUTION:A recording head 101 is constituted so that a predetermined number of grooves having a predetermined width and depth are provided to the surface of a substrate 103, which has a heat generator 110 for emission and a liquid temp. control heat generator 111 provided to the surface thereof, at predetermined line density. A plate 104 and a substrate 102 having piercing holes are bonded so as to cover the grooves to form orifices 105, a liquid chamber 109 and liquid flow passages 108 and, further, a cooling tank 106 is bonded to the under side of the substrate 103. Therefore, when a dot larger than a liquid droplet or dot at ambient temp. is desired, the temp. of a liquid may be raised by a heat generator 111 and, when a dot smaller than the dot at ambient temp. is desired, the temp. of the liquid may be lowered by the recirculation of cooling water.

Description

DETAILED DESCRIPTION OF THE INVENTION [Prior Art] Non-impact recording methods have attracted much attention because the generation of noise during recording is so small that it can be ignored. Among them, the liquid jet recording method is an extremely powerful recording method because it enables high-speed recording, does not require special processing such as fixing on so-called plain paper, and can easily perform color printing (full color printing).

Among the liquid jet recording methods, the liquid jet recording method using thermal energy, which is disclosed in German Publication No. 2843064, is the so-called drop-on-demand (dropon dem) method.
and) method, the recording head can be miniaturized, orifices for ejecting liquid can be arranged in high density, and the so-called full line method in which orifices are arranged throughout the entire recording process can be used. It has the advantage of being easily achievable.

By the way, when recording an image having gradation even during image recording, it is useful to change the amount of ink adhesion per unit area and/or the density of the ink. Conventional image recording methods with such gradation control properties include:
Subdividing a pixel into a matrix of cells that can be occupied by only one of the image-forming elements (e.g., an area formed by the deposition of a single ink drop) and configuring the matrix of pixels. Depending on how many image-forming elements occupy a cell, and the arrangement of the occupied cells, a desired level of gradation can be digitally expressed, and one pixel can be represented by one image-forming element. A method in which a desired gradation is expressed in an analog manner by changing the optical density of the image forming element, or a method in which one pixel is formed by only one image forming element, but the image forming A method of expressing a desired gradation in an analog manner by changing the size and area of the element is generally known.

[Problem that the invention seeks to solve]

However, in the case of digital expression, it is necessary to make the size of one image forming body minute, but currently it is not possible to make the size smaller than a certain level. Therefore, not only does the area of each pixel itself become large, leading to a decrease in sharpness and resolution, but also because the gradation is controlled digitally, the gradation steps become rough (so that the quality of the image cannot be said to be good). was occurring.

In addition, when changing the optical density of the image forming element,
Inks with different densities must be prepared in accordance with the number of gradation steps, which may result in a large-scale apparatus and complicated maintenance and inspection.

Furthermore, if a method of changing the size and area of the image forming element is used, the gradation control range may not be as wide as that, and a sufficient gradation control range may not be obtained, or there may be problems such as poor liquid ejection, etc. This may lead to a decrease in reliability.

That is, with the conventionally known gradation recording methods, it is difficult to express smooth gradation over a wide range from high optical density to low optical density.

The heating element heats the recording liquid in the liquid chamber communicating with the orifice, causes a state change in the recording liquid, and in response to the increase in the pressure in the liquid chamber, small droplets of the recording liquid are released from the orifice. In a recording method for recording on a recording member by ejecting the recording liquid, a heating element for controlling the temperature of the recording liquid and a cooling means for cooling the liquid chamber are provided on the orifice side of the heating element, It is characterized by recording by controlling the diameter of the ejected droplets.

〔Example〕

Hereinafter, the present invention will be explained using the drawings.

FIG. 1 shows a recording head 1 for explaining an embodiment of the present invention.
01 is a schematic perspective view. However, the discharge heater and the liquid temperature control heater are omitted in the figure. The recording head 101 shown in the figure has a predetermined width and depth at a predetermined linear density on the surface of a substrate 103 on which a heating element for ejection and a heating element for liquid temperature control (both not shown) are provided. An orifice 105, a liquid chamber 109, and a liquid flow path 108 are formed by joining a plate 104 and a substrate 102 having a through hole so as to cover the groove in which a predetermined number of grooves are provided, and further downstream of the substrate 103. It has a structure in which a cooling water tank 106 is joined.

FIG. 2 is a partial view taken along a plane parallel to the orifice surface of a liquid jet recording head to which the present invention is applied (a view taken along the line AA' shown in FIG. 1). In the figure, 110 is a heating element (main heater) that vaporizes the recording liquid (liquid) to eject droplets, and 111 is a heating element (preheater) that changes the temperature of the recording liquid.

In the liquid jet recording device having the above structure, when a pulse-like signal is applied to the heating element 110, the recording medium liquid on the heating element surface is vaporized to form bubbles, and the recording medium liquid on the heating element 111 is 105 to eject it as a droplet.

At this time, there is a relationship as shown in FIG. 3 between the temperature T of the recording liquid and the volume V of the ejected droplets. This is mainly due to the exponential temperature characteristic of the viscosity of the recording liquid, ηcl: expT 77: viscosity, T: liquid temperature. Therefore, if you want droplets or dots larger than those at room temperature, you can increase the liquid temperature, and if you want smaller dots than dots at room temperature, you can lower the liquid temperature. When increasing the liquid temperature, use the heating element 11
It is sufficient to apply a pulsed electric signal to 1 to drive the liquid, and to lower the liquid temperature, cooling water may be circulated in the cooling water tank 106.

Figure 4 shows how the temperature of the recording medium liquid is raised to 15% by circulating cooling water.
2 is an explanatory diagram when recording is performed while controlling the temperature at .degree. C. and applying a heating signal to the preheater 111 using a head having the structure shown in FIG. 1. In the figure, (a) is the recording signal (input signal to the main heater 110), (b) is the liquid temperature control signal (input signal to the brake heater 111), (C) is the ejected droplet volume, and (d) is the recorded dot. Represents the diameter. Furthermore, FIG. 5 shows how the recording dots change when recording is performed in the same manner as in FIG. 4, except that the recording medium liquid is not cooled. As is clear from FIGS. 4(d) and 5, a wider change in dot diameter can be obtained by controlling the liquid temperature while cooling the liquid temperature.

Figure 6 shows the relationship between the OD value (optical density) and the number of pulses applied to the brake heater when gradation recording is performed using the above head using black ink with the following composition, and is smooth and wide due to the preheater control signal. It can be seen that the recording OD range can be obtained.

Composition C, 1, Food Black2 3
wt% water 70・
・Diethylene glycol 3011 also,
When an image was recorded using the head having the above structure using inks of four colors: yellow, cyan, magenta, and black, a full-color image with smooth intermediate tones was obtained.

As described above, the temperature of the recording medium liquid is controlled to be 5 to 20 degrees Celsius, preferably 10 to 15 degrees Celsius, lower than the ambient temperature, and the temperature of the liquid is pre-discharged to the ejection heater (main heater) according to the input signal. By recording while changing the number of pulses applied to the control heater (breaheater), it has become possible to express a wide range of smooth gradations.

〔effect〕

According to the present invention, it is possible to provide a liquid jet recording method that can express smooth gradation over a wide density range from high optical density to low optical density.

Further, according to the recording method of the present invention, smooth halftone expression (gradation expression) that could not be achieved with the conventional inkjet recording method in which recording is performed by ejecting liquid using thermal energy becomes possible.

Furthermore, if yellow, magenta, cyan, and black inks are used, high-quality full-color pictorial images can be obtained at high speed.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of a recording head according to an embodiment of the present invention;
FIG. 2 is a cutaway partial view of a recording head according to an embodiment of the present invention, FIG. 3 is a diagram showing the relationship between recording liquid temperature and ejected droplet volume, and FIGS. 4 to 4 are examples of the present invention. FIG. 101... Recording head, 102... Plate member,
103... Board, 104... Grooved plate,
105... Orifice, 106... Cooling water tank, 107... Through hole, 108... Liquid flow path, 109... Liquid chamber.

Claims (1)

[Claims] A heating element heats the recording liquid in a liquid chamber communicating with the orifice to cause a state change in the recording liquid, and in response to an increase in pressure in the liquid chamber based on this, droplets of the recording liquid are ejected from the orifice. In a recording method for recording on a recording member, a heating element for controlling the temperature of the recording liquid and a cooling means for cooling the liquid chamber are provided on the orifice side of the heating element, and the recording liquid is discharged. A liquid jet recording method using thermal energy, which is characterized in that recording is performed by controlling the diameter of droplets.