JPH0513064B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a liquid jet recording device that performs recording by discharging a liquid to form discharged droplets and attaching the droplets to a recording material such as paper, and in particular, The present invention relates to a liquid jet recording device that applies thermal energy to a liquid to form ejected droplets. [Prior Art] The liquid jet recording method is a recording method in which ejected droplets of recording liquid are formed using various methods and the droplets are attached to a recording material such as paper to perform recording. Among recording devices using droplets using such a recording method, a type of liquid jet recording that uses heat as energy to form ejected droplets is a device with a structure suitable for high-density multi-orifice recording heads. Equipment can be mentioned. Liquid jet recording devices that use heat as droplet ejection energy usually heat the recording liquid to give it a displacement that causes a rapid increase in volume, and then eject it from an orifice (droplet ejection hole). A recording head having a droplet forming means for forming droplets of recording liquid and an electrothermal energy conversion element (hereinafter referred to as a heater) capable of generating heat and heating the recording liquid by applying an electric signal. Equipped with On the other hand, as the recording liquid used when recording with a liquid jet recording apparatus, an aqueous recording liquid is mainly used from the viewpoint of recording characteristics, safety, and the like. This aqueous recording liquid is generally formed from a recording agent component such as a pigment or dye, and a solvent component mainly consisting of water or water and a water-soluble organic solvent for dissolving or dispersing the recording agent component. . In the above-mentioned recording device that uses heat as droplet ejection energy and other recording devices that apply a droplet formation method, the orifice (droplet ejection hole) provided at the tip of the nozzle from which the recording liquid is ejected is , are often constantly opened to the outside air outside the device regardless of whether or not the device is being driven. Therefore, if recording is not performed for a long period of time, water or volatile organic substances, such as water or volatile Solvent components such as solvent evaporate from the orifice into the outside air, and recording agent components and solvent components that are difficult to volatilize remain in the recording liquid, resulting in an increase in the viscosity of the recording liquid retained in this area, and as a result, the recording liquid Immediately after restarting recording, a droplet ejection failure is likely to occur in which droplets are not ejected even though an ejection signal is applied, and recording There was a problem that defects occurred in the initial printed portion of the image. On the other hand, in order to obtain a good droplet ejection condition even when the viscosity of the recording liquid increases at low temperatures, the temperature of the recording liquid can always be maintained within a predetermined range.
A recording method is known from JP-A-58-187364 in which an electric signal at a level at which recording droplets are not ejected is constantly applied to a heater to heat the recording liquid even when a droplet ejection signal is not applied. ing. However, even in a recording device employing this method, an electric signal is applied to the heater so that the recording liquid is always kept at a high temperature even during a relatively long recording pause or stop period. In some cases, the solvent component in the recording liquid evaporates more easily, and the above-mentioned droplet ejection failure upon resuming recording is more likely to occur. In addition, in this method, the area around the heater is constantly heated, which may impair the durability of the parts surrounding the heater, or the recording liquid may accumulate around the heater during the recording pause period. In some cases, the physical properties of the recording liquid change due to its own heat, causing problems such as discoloration of the recording liquid or the formation of precipitates in the recording liquid, which clog the orifice and cause droplet ejection failure. [Object of the Invention] The present invention was made in view of these problems, and mainly involves adjusting the viscosity of the recording liquid within a suitable range in order to always obtain a good droplet ejection condition during droplet ejection. This ensures that good droplet ejection conditions are always achieved.
It is an object of the present invention to provide a liquid jet recording device that can always obtain a good and stable droplet ejection state even when restarting recording after a particularly long recording stop or stop period. Another object of the present invention is to maintain good quality and stability at all times without reducing the durability of the parts surrounding the heater of the recording device, and without causing deterioration of the recording liquid stagnant near the heater when recording is stopped due to the influence of heat. It is an object of the present invention to provide a liquid jet recording device that can obtain a droplet ejection state that is as follows. Another object of the present invention is to use a droplet forming means that also serves as a recording liquid heating means for adjusting the viscosity of the recording liquid in order to obtain a good ejection condition, without providing a special recording liquid heating means. It is an object of the present invention to provide a liquid jet recording device that uses thermal energy to form droplets that can always achieve a good and stable droplet ejection condition. [Summary of the Invention] The above objects and other objects can be achieved by the present invention as described below. That is, the liquid jet recording apparatus of the present invention includes a recording head having an electrothermal energy conversion element capable of heating a liquid in accordance with a supplied electric signal to form flying droplets, and a recording head that generates droplets from the recording head. ejection signal generating means for outputting an ejection electric signal to the electrothermal energy conversion element for ejecting; and outputting a heating electric signal to the electrothermal energy conversion element under conditions in which droplets are not ejected from the recording head. control for heating the recording head by generating a plurality of the heating electric signals from the heating signal generating means according to the time during which the recording electric signal is not supplied to the recording head; The apparatus is characterized by comprising a control means for generating a plurality of electric ejection signals from an ejection signal generating means to preliminarily eject droplets from the recording head. The liquid jet recording apparatus of the present invention will be explained in detail below with reference to the drawings. The recording apparatus of the present invention will be described below, taking as an example a liquid jet recording head that uses heat as energy for forming droplets. FIG. 1 is a schematic diagram of a recording head section of an example of a liquid jet recording apparatus of the present invention, and FIG. 2 is a partially enlarged view of the vicinity of the nozzles of the recording head section of the apparatus shown in FIG. Reference numeral 1 denotes a main tank (not shown) for storing recording liquid and a sub tank 2 for temporarily storing recording liquid inside the recording head.
3 is a suction tube connected to a recovery pump (not shown), and 4 is a supply tube for supplying recording liquid from the sub-tank 2 to the liquid chamber 5. Supply pipe unit, 6 is a presser for the supply pipe unit 4, 7
Reference numeral 8 indicates a nozzle portion in which a predetermined number of orifices (droplet ejection holes) 12, which are parts for ejecting the recording liquid shown in FIG.
An electric wiring section consisting of an FPC (flexible printed circuit) for applying an electric signal to a heater 13 for imparting thermal energy to the recording liquid in 4; 9 is a supply pipe unit 4, a liquid chamber 5, and a nozzle section; 7 a supply pipe holder 6 and an FPC 8 are arranged, a base plate for supporting these; 10 a bushing for supporting the periphery of the nozzle portion; 11 a front plate. In this example, a droplet forming means for forming droplets to be ejected from the orifice 12 and a liquid flow path 14 that communicates with the orifice 12 and has a portion where heat from the heater is applied to the recording liquid is configured. , and heater 1
3 and an FPC 8 for applying an electric signal thereto as necessary, a liquid heating means is constituted.
Although not specifically shown in the drawings, this device also includes an ejection signal generating means for generating an electric signal to be applied to eject droplets, and an electric signal for heating the recording liquid, which will be described later. Heating signal generating means for generating the heating signal is provided. To perform recording using this apparatus, first, recording liquid is filled from the main tank into the sub tank 2, liquid chamber 5, and liquid flow path 14 via the supply tube 1 and supply pipe unit 4. Next, a recording signal, that is, an electric signal from the droplet ejection signal generating means is applied to the heater 13 by the FPC to energize the heater 13. As a result, the heater 13 generates heat, and thermal energy is applied to the recording liquid in the liquid flow path 14 near the heater 13, causing an instantaneous increase in the volume of the recording liquid in that area. Bubbles are generated, and the recording liquid located downstream of the heater 13 is discharged from the orifice 12, forming droplets of the recording liquid. The droplets of the recording liquid are attached to a recording material such as paper that is sent in front of the nozzle section 7, and recording is performed. In the liquid jet recording apparatus of the present invention, when performing recording by the above-described operation, that is, immediately before applying an electric signal to the heater 13 for ejecting droplets used for recording, the recording liquid heating A signal is applied. The signal for heating the recording liquid applied in the apparatus of the present invention heats the recording liquid to the heater 13 to a temperature at which a suitable viscosity of the recording liquid is obtained in order to obtain a good recording ejection state to the extent that no droplets are ejected. This is an electric signal for heating by heating, and is generated from a heating signal generating means. The heating time for the recording liquid by the heater 13, which generates heat due to the application of the heating electric signal, can be applied within the range that can heat the recording liquid to the predetermined temperature, and in the shortest possible time. preferable. By heating the recording liquid over a short heating time, the heater 13 and the components surrounding the heater are less likely to be affected by heat, which can cause deterioration, and the performance of these components is reduced. It also increases the lifespan of the heater, minimizes the diffusion of heat from the heater to the surrounding area, and reduces the amount of recording liquid that must be heated. It is possible to eliminate the influence of heat on the whole, and furthermore,
This is because it is possible to prevent accelerated evaporation of part of the solvent component of the recording liquid from the orifice due to a long heating time. The heating time of the recording liquid is appropriately selected depending on various conditions such as temperature characteristics such as heat capacity of the recording liquid, structure of the apparatus, and temperature suitable for the recording liquid to be ejected. Taking these requirements into consideration, when applying a heating electric signal in the liquid jet recording device of the present invention, the application conditions of the droplet ejection signal in the device,
For example, the voltage, frequency, pulse width, etc. may be adjusted individually depending on various conditions such as the temperature characteristics of the recording liquid used, especially the temperature characteristics of the viscosity of the recording liquid, and changes in the viscosity of the recording liquid during recording pauses or stops. It is sufficient to control the voltage to a predetermined value and apply it to the heater. Various methods can be applied to control the electrical signal and convert it into an electrical signal for heating, but among these methods, there are some methods that can be easily carried out using an electrical signal circuit built into the recording device, such as: It is possible to make the ejection signal generation means also serve as the heating electric signal generation means, and to control the electric signal from the ejection signal generation means as follows to generate the heating electric signal. In other words, the relationship between the frequency voltage, pulse width, and heating temperature in the applied electrical signal is, for example, when applying electrical signals of various frequencies (10kHz, 5kHz, 2kHz) to the heater with an applied voltage of 23.5V and a pulse width of 5μs. The temperature change over time when the voltage is applied is as shown in Figure 3. a. Shorten the pulse width of the droplet ejection signal used in the device to the necessary extent and increase the frequency; b. Methods such as lowering the voltage and increasing the frequency of the droplet ejection signal used in the device, c. lowering both the pulse width and voltage of the droplet ejection signal used in the device and increasing the frequency, etc. can be applied to achieve the above purpose. The specific values when applying such a method vary depending on the physical properties of the recording liquid used, the characteristics of the device, etc., and cannot be defined unconditionally, but usually in the case of method a. The pulse width of the heating electric signal is preferably about 1/1.25 to 1/100, more preferably 1/2 of the pulse width of the droplet ejection signal.
It is desirable to set it to about 1/20. In the case of method b, the voltage of the heating electric signal is preferably about 1/1.25 to 1/10, more preferably about 1/1.4 to 1/2.4 of the voltage of the droplet ejection signal, and the heating electric signal is It is desirable that the frequency of the signal is preferably about 2 to 100 times, more preferably about 5 to 50 times, the frequency of the droplet ejection signal. In the case of method c, the voltage of the electric signal for heating is preferably about 1/1.25 to 1/10, more preferably about 1/1.4 to 1/2.4, of the voltage of the signal for ejecting droplets, and The pulse width of the electrical signal is preferably about 1/1.25 to 1/100, more preferably about 1/2 to 1/20 of the pulse width of the droplet ejection signal, and the frequency of the heating electrical signal is set to Preferably the frequency of the droplet ejection signal is 2 to 2.
It is desirable to make it about 100 times, more preferably about 5 to 50 times. Note that the ejection signal generating means and the heating electric signal generating means may be provided independently. The heating electric signal applied in the device of the present invention may be always applied immediately before the droplet ejection signal is applied to the heater, and the recording device may be powered on for a certain period of time. Recording pause in the state,
Alternatively, it may be applied immediately before the droplet ejection signal is applied after recording is stopped while the power of the recording apparatus is turned off. In other words, under the environmental conditions such as the temperature when the recording device is used, the viscosity of the recording liquid in the liquid flow path changes.
If there is a possibility that the viscosity of the recording liquid is not necessarily within a suitable range, always apply this signal immediately before the droplet ejection signal is applied to the heater to always adjust the viscosity of the recording liquid to a suitable value during droplet ejection. be able to. Alternatively, the viscosity of the recording liquid may be maintained within a suitable range under the environmental conditions such as the temperature during use of the recording device, but after a certain period of recording suspension or stoppage, as mentioned above, If the viscosity of the recording liquid increases due to the evaporation of solvent components into the outside air, count the time during which recording is paused or stopped, and when resuming recording after a certain period of time has elapsed. It is only necessary to apply a heating electric signal to the heater. Furthermore, how long should the electrical heating signal be applied to the heater when resuming recording after a recording pause period?
Whether or not the viscosity of the recording liquid in the liquid flow path, especially near the orifice, deviates from the preferred range due to a recording pause or stop time of this length depends on the characteristics of the device used, the physical properties of the recording liquid, and the performance of the device. Since it varies depending on the environmental conditions such as temperature and humidity of the place where it is installed and used, it may be selected appropriately depending on the individual device and its usage condition. In the recording apparatus of the present invention, after the electric signal for heating is applied to the heater, the electric signal for ejecting droplets not used for recording is applied to the heater, and then the electric signal for ejecting droplets not used for recording is applied to the heater. A signal may also be applied to the heater. In the apparatus of the present invention, the electric signal for ejecting droplets not used for recording refers to the electric signal for ejecting droplets that is applied to the heater to eject droplets, and the droplets are collected in the apparatus. This is a signal that is applied to prevent the recording material from being used for recording on the recording material. In this way, if an electric signal for ejecting droplets that is not used for recording is applied to the heater after the electric signal for heating is applied to the heater, the recording pause or stop period will be extremely long, and the recording liquid will be damaged due to evaporation of the solvent component. Even if there is a significant increase in the viscosity of the recording liquid, the electric signal for heating causes the heater to generate heat, which heats the high viscosity part of the recording liquid, raising its temperature and making it impossible to form good droplets. , the viscosity of the recording liquid is lowered to the extent that droplets can be ejected, and in that state, an electric signal for droplet ejection is applied to the heater, so that the recording liquid in this area flows through the liquid flow path. Therefore, a recording liquid whose viscosity is within a suitable range for ejection is supplied to the vicinity of the heater, and a good recording liquid ejection condition can be obtained from then on. Therefore, if the electric signal for ejecting droplets not used for recording is simply applied to the heater, the recording liquid whose viscosity is not within the range suitable for ejecting droplets during recording will be ejected. The liquid is applied under such conditions that it can be removed from the liquid flow path. An example of a flowchart of a mechanism for controlling recording in the apparatus of the present invention is shown in FIGS. 4 and 5. In the figure, t is the upper limit of the recording pause time, which does not require preheating, that is, the heating electric signal is applied and the recording liquid is heated within the range where the recording liquid is not ejected; It indicates the upper limit of the pause time that requires preheating, and further indicates the time that requires preheating and predischarge when T is exceeded. Further, preliminary ejection refers to ejecting droplets that are not used for the above-mentioned recording. In the control mechanism shown in Fig. 4, when a print signal, that is, an electric signal for ejecting droplets used for recording, is applied after the power is turned on, before the recording liquid for recording is ejected. First, preliminary heating and preliminary ejection are performed in this order, and then an electric signal for ejection is generated from the ejection signal generating means and applied to the heater, and the recording liquid is ejected to perform printing. Further, when the recording pause time exceeds t, preheating is performed, and when the recording pause time further exceeds T, preheating and preliminary ejection are performed. In the control mechanism shown in Figure 5, the power supply
When turned on, preheating and preliminary discharge are performed,
If no printing is performed after the power is turned on, the recording pause time is counted, and if the recording pause time exceeds t, preheating is performed, and if the recording pause time further exceeds T. Preheating and predischarging are now performed. The control after the recording is stopped after printing is performed is the same as that in FIG. 4. The apparatus of the present invention described so far is of a type that uses thermal energy to form droplets, and includes an energy generating element for ejection (heretofore referred to as a heater) and an area in which recording liquid is not ejected. However, these may be provided individually, and in devices that do not use heat to form droplets, separate heaters, etc. The liquid jet recording apparatus of the present invention can be provided with recording liquid heating means to perform the control as described above. In the liquid jet recording apparatus of the present invention described above, when performing recording, that is, immediately before applying the electric signal for droplet ejection to the heater 13, the signal for heating the recording liquid and the electric signal used for recording as necessary are used. The viscosity of the recording liquid to be ejected is mainly adjusted within a suitable range in order to always obtain a good droplet ejection condition during droplet ejection. In particular, even when restarting recording after a long recording stop or stop period, a good and stable droplet ejection condition can always be obtained. Furthermore, since heating of the recording liquid using the recording liquid heating signal is not performed frequently and the heating time is extremely short, the durability of the parts surrounding the heater of the recording apparatus may be reduced due to the influence of heat. Moreover, a good and stable droplet ejection condition can always be obtained without causing any deterioration of the recording liquid stagnant near the heater when recording is stopped due to the influence of heat. In addition, in the apparatus of the present invention to which a method of using thermal energy is applied for droplet formation, a recording liquid heating means is provided mainly to adjust the viscosity of the recording liquid in order to obtain a good droplet ejection state. The droplet forming means can also be used, and there is no need to provide a means for heating the recording liquid, resulting in a liquid jet recording apparatus that can always provide a good and stable droplet ejection condition. Example 1 24 orifices (orifice diameter 50 x 40 μm)
However, using a liquid jet recording apparatus of the present invention having a recording head section as shown in FIG. Filled inside and heated to 25℃30%
When resuming recording after a 1-hour recording pause in an RH environment, a heating electric signal with a voltage of 23.5V, a pulse width of 5μs, and a frequency of 10KHz is ejected as a droplet with a voltage of 23.5V, a pulse width of 10μs, and a frequency of 2KHz. Immediately before applying an electric signal to the heater, perform recording, and measure the number of non-ejected droplets with respect to the recording signal until the droplets of the recording liquid used for recording are ejected from all 24 orifices. The recording apparatus was evaluated regarding ejection failure after recording was stopped. The results are shown in Table 1. The composition of the recording liquid used for recording was as follows. [Recording liquid composition] CI Direct Black 19 2 parts by weight Diethylene glycol 30 parts by weight Water 70 parts by weight Comparative Example 1 The composition was similar to that of Example 1, and during recording, electricity was used to eject recording droplets used for recording. Using a recording device in which only the signal is applied to the heater, it is filled with the recording liquid used in Example 1,
When resuming recording after a 1-hour recording pause in an environment of 25°C and 30% RH, the voltage was 23.5V and the pulse width was 23.5V.
Recording was performed by applying only a droplet ejection electric signal of 10 μs and a frequency of 2 KHz to the heater, and in the same manner as in Example 1, the ejection failure of this device after recording was stopped was evaluated. The results are shown in Table 1. Example 2 Using the apparatus used in Example 1, the recording pause time was 12 hours, and after applying the heating electric signal,
Recording was performed in the same manner as in Example 1, except that a 100-pulse droplet ejection electrical signal was applied to the heater to eject droplets not used for recording, and then an electrical signal for recording droplet ejection was applied to the heater. Using the apparatus of the present invention for performing this, the apparatus was filled with the recording liquid used in Example 1, recording was performed, and the ejection failure of this apparatus after recording was stopped was evaluated in the same manner as in Example 1. Ta. The results are shown in Table 1. Comparative example 2 Comparative example 1 except that the recording pause time was 12 hours
Recording was carried out in the same manner as in Example 1, and ejection failure of this apparatus after recording was stopped was evaluated in the same manner as in Example 1. The results are shown in Table 1. 【table】

[Brief explanation of the drawing]

1 is a schematic perspective view of the recording head section of the liquid jet recording apparatus of the present invention, FIG. 2 is a partially enlarged view of the nozzle periphery of the recording head section shown in FIG. 1, and FIG. 3 is an electrothermal Diagrams showing changes in heat generation temperature over time when three types of electrical signals are applied to the energy conversion element, and FIGS. 4 and 5 are flowcharts of the mechanism for controlling recording of the apparatus of the present invention. . 1... Supply tube, 2... Sub tank, 3...
...Suction tube, 4... Supply pipe unit, 5...
Liquid chamber, 6... Supply pipe unit holder, 7... Nozzle section, 8... FPC, 9... Base plate, 10
...butsuthing, 11...front plate, 12...
...orifice, 13...heater, 14...liquid flow path, t...upper limit of recording pause time that does not require preheating, T...upper limit of recording pause time that requires preheating.

Claims (1)

[Scope of Claims] 1. A recording head having an electrothermal energy conversion element capable of forming flying droplets by heating a liquid in accordance with a supplied electric signal, and for ejecting droplets from this recording head. ejection signal generating means for outputting an ejection electric signal to the electrothermal energy conversion element; and a heating signal for outputting a heating electric signal to the electrothermal energy conversion element under conditions in which droplets are not ejected from the recording head. generating means; control for heating the recording head by generating a plurality of the heating electric signals from the heating signal generating means according to the time during which the recording electric signal is not supplied to the recording head; and generating the ejection signal. A liquid jet recording apparatus comprising: control means for generating a plurality of electric signals for ejection from the means to preliminarily eject droplets from the recording head;