JP2007206717A - Inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet head recording method for forming a coloring layer having a uniform coating in a color filter of which the coloring layer is formed by discharging a coloring material by an inkjet head. <P>SOLUTION: The inkjet recording method is characterized in that a voltage to be applied to a signal electrode of the inkjet head is adjusted by selecting a correction voltage value from a predetermined correction voltage curve and a coating thickness correlation graph by taking a cell of the color filter as a unit only for a predetermined time period from recording start position of the inkjet head. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording method in which a colorant is discharged as fine droplets and a method for producing a color filter.

  Conventionally, in order to mitigate an increase in the viscosity of ink due to drying of the nozzle portion of the ink jet head, it has been proposed to give a slight vibration to the nozzle portion and the ink in the head within a range where the ink is not discharged. Japanese Patent Application Laid-Open No. 61-035963 proposes that ink is reliably ejected from the first recording signal by vibrating the ink in the ejection orifice by a vibrating means that applies minute vibrations to the vicinity of the nozzle. Further, in Japanese Patent Laid-Open No. 9-141882, in order to solve a discharge failure during printing in a non-recording state such as when waiting for printing, and printing under a low temperature and high temperature environment, the ink is not discharged by a discharge pressure generation signal regardless of the presence or absence of printing. It has been proposed to provide a signal to swing the meniscus. Japanese Patent Laid-Open No. 9-290505 proposes that a high frequency alternating electric field is applied to a piezoelectric vibrator of a non-ejection nozzle to vibrate in order to prevent clogging of a nozzle that does not eject ink during recording.

Further, in the production of a color filter using the ink jet method, the ink is periodically forcibly discharged outside the print area immediately before the start of ejection before the ink in the nozzle portion thickens due to drying, or in Public Notice 0596785, It has been devised to form a frame serving as a preliminary ejection region immediately before the color panel portion on the glass substrate to perform ink ejection necessary for stabilizing ink ejection.
Japanese Patent Laid-Open No. 61-035963 Japanese Patent Laid-Open No. 9-141882 JP-A-9-290505

  However, when microvibration is simply applied by the conventional method, clogging can be prevented, but the viscosity of the ink increases and the ejection amount changes. Further, applying a slight vibration during recording has a problem that residual vibration occurs in the head and the discharge amount of the discharge nozzle changes. These changes in the discharge amount have been a problem in printing that coats a color filter that requires a uniform discharge amount.

  Further, the forced ink discharge consumes ink more than necessary, and the ink is discharged away from the print area. Therefore, the viscosity is increased again at the start of printing, and the landing position shifts. In addition, setting the preliminary discharge area has a limitation on the number of panels on the glass substrate and pattern formation, and there is a problem that a sufficient area cannot be secured for stable discharge.

  The ink jet recording method of the present invention has been made to solve the above problems, and an object of the present invention is to provide an ink jet recording method for forming a uniform coating film with stable landing accuracy and coating amount.

  In order to solve the above-described conventional problems, in the ink jet recording method of the present invention, the voltage applied to the signal electrode of the ink jet head is a predetermined unit only for a predetermined time from the recording start position of the ink jet head. The voltage is adjusted.

  According to the recording method of the ink jet head of the present invention, it is possible to form pixels having a uniform discharge amount without discarding the ink in the nozzle portion that has been thickened due to the effect of drying at the start of printing.

  Embodiments of an ink jet head recording method according to the present invention will be described below in detail with reference to the drawings.

(Embodiment 1)
For the transparent substrate used in the present invention, for example, glass is often used. A pixel frame can be formed by forming a light shielding film on a glass substrate using a photosensitive resin, and then exposing and developing. This light shielding film is formed so that the pixel portion becomes a light transmission opening in the display area, and the peripheral area of the display area may be patterned in the same manner as the display area, and the light shielding film is formed on the entire surface. It may be provided. The top surface of the light shielding film is preferably subjected to a liquid repellent treatment so as to repel the discharged colorant. Thereby, the inflow of the colorant into the adjacent pixel is suppressed.

  In order to form a colored layer by the inkjet method, a transparent substrate 2 is placed on a stage 1 of a printing apparatus as shown in FIG. 1, and the transparent substrate 2 and the inkjet head 3 are moved relative to each other to obtain predetermined pixels. A predetermined number of ink droplets are ejected into 4 to form a color filter pattern. The ink ejected from the plurality of nozzles is controlled so as to have an appropriate ejection amount for each nozzle. There are three ink colors, R, G, and B, but printing may be performed for each single color or for three colors simultaneously. The glass substrate on which the ink has been applied is removed by a solvent using a hot drying device such as a hot plate or oven or a vacuum drying device, and is cured by a method suitable for the ink curing conditions to form a color filter coating film.

  The color layer ink used in the present invention uses a pigment as a coloring material, and is composed of a resin for forming a coating film, for example, a photosensitive resin such as an acrylic resin, and other additives, in order to disperse and dissolve them. Although it is a non-aqueous ink containing the organic solvent, there is no particular limitation.

  Next, the structure and operation of the head used in the present invention will be described with reference to FIGS. FIG. 2 shows a configuration diagram of the head. A plurality of channel grooves 6 that are parallel to each other and separated by a partition wall of the piezoelectric ceramic 5, a signal electrode 7 formed on both walls of the channel groove 6, and an ink supply port 8 are bonded to the upper wall of the channel groove 6. And a cover plate 9 serving as a separation groove and a nozzle 10 communicating with the channel groove 6.

  FIG. 3 shows a sectional view of the head. Electrodes are deposited up to the upper half of both side walls of the ink channel 11 and the adjacent channel 12 that are filled with ink and discharge ink, and a potential difference is generated between the signal electrode 13 in the discharge channel 11 and the common electrode 14 in the adjacent channel 12. Is applied to deform the partition wall, and ink is ejected according to the amount of displacement. In FIG. 3, when a positive voltage is applied to the common electrode 14, the volume of the ink channel 11 is deformed in a contracting direction, and when a positive voltage is applied to the signal electrode 13, the volume of the ink channel 11 is expanded. The structure is deformed.

  The ink ejection operation will be described with reference to FIG. FIG. 4A shows a driving waveform when ink is ejected. When the ejection signal is input, the voltage V is applied to the signal electrode 13 at time T1, the ink channel 11 expands, and ink is supplied from the ink tank. At the time T2 when the ink supply is completed, the voltage of the signal electrode 13 is returned to 0 V, and at the same time, the voltage V is applied to the common electrode 14, the ink channel 11 is contracted, and the ink in the ink channel 11 is converted into droplets from the nozzles. Discharge. After the ejection, the voltage of the common electrode 14 is set to 0 V again to restore the volume of the ink channel 11.

  Here, a voltage pulse that applies a voltage to the signal electrode 13 to restore expansion of the ink channel 11 is used as a preliminary pressure operation pulse, and a voltage pulse that applies a voltage to the common electrode 14 to restore contraction of the ink channel 11 is ejected operation pulse. And In this way, by applying the preliminary pressure operation pulse and the ejection operation pulse to the head in succession once, one ink ejection operation pulse is completed.

  In the present invention, only one of the preliminary pressure pulse or the ejection operation pulse is applied to the head as a swing signal that does not eject ink. FIG. 4B shows a waveform diagram of the preliminary pressure pulse applied as the swing signal. It was confirmed that ink was not ejected even when the frequency of the waveform was actually changed between 0.01 kHz and 8 kHz. Further, during the period when the head is not on the recording medium, the preliminary pressure operation pulse was printed at 8 kHz, which is the same frequency as the printing condition, for 300 seconds, and printing was possible with no landing position deviation even after printing the swing signal. The same result was obtained when only the preliminary ejection operation pulse was applied to the common electrode 14.

  When the swing signal was not applied, landing position deviation occurred in several pixels at the start of printing after leaving for 20 seconds. Thus, the swing operation could be realized without newly adding a swing pulse waveform to the circuit.

  The drawing conditions are shown below. As the initial conditions, the ink discharge conditions from the head were set to a discharge speed of 5 m / sec and a printing frequency of 8 kHz. The ink used was an ink having the following composition.

Pigment 7wt%
Resin (UV curable acrylic monomer) 27wt%
Polymerization initiator 3wt%
Surfactant 3wt%
Solvent (glycol acetate) 60wt%
For printing on the transparent substrate, 10 ink droplets were applied to each cell, and printing was continuously performed on 500 cells. The transparent substrate on which the ink was applied was desolvated in an oven at 60 ° C. for 20 minutes, and then UV irradiation was performed in a nitrogen atmosphere to form a coating film. After the coating film was cured, the height of the center of the coating film was measured from the glass surface with a film thickness meter to obtain the coating film thickness. As shown in FIG. 5A, the application time of the swing signal is a drawing standby time and a drawing operation time. The drawing standby time is 180 seconds in consideration of the time assumed in the actual printing apparatus, and the movement to the drawing position is performed. 20 sec. The frequency of the oscillation signal was set between 0.1 kHz and 8 kHz, and drawing and film thickness measurement were performed.

  A graph of the coating thickness with respect to the print cell is shown in FIG. Line A is a graph in which an oscillation signal of 1 kHz is applied, and line B is an application of an oscillation signal of 8 kHz. In both cases, the film thickness at the start of printing is low. The initial printing of 1 kHz is extremely low, and the return to the normal state is fast. On the other hand, printing at 8 kHz takes a little time to return although the initial decrease is small. This is because at 1 kHz, the number of oscillations is small and the ink circulation between the ink channel and the nozzle is insufficient, so that the ink viscosity around the nozzle is high. At 8 kHz, the ink circulation force is sufficient, but it can be presumed that the amount of drying is increased by the heat generated by the piezo and the ink viscosity inside the ink channel is increased on average.

  Therefore, in the present invention, as shown in FIG. 5B, the frequency f1 of the oscillation signal applied during drawing standby is 1 kHz with a low calorific value, and the frequency of the oscillation signal applied during the movement time to the drawing position. f2 was printed at the same drawing frequency of 8 kHz. As a result, as shown in line C of the graph of FIG. 6, the film thickness reduction of the initial cell could be reduced to a level that can be ignored in terms of performance.

(Embodiment 2)
Next, an embodiment in the case where the swing signal is not used will be described.
When the swing signal is not applied, the viscosity of the ink in the nozzle increases during the time required for the head to move from the cleaning position to the drawing position of the recording medium, and the discharge amount at the start of recording decreases.

  When the color filter is manufactured by the ink jet method, the discharge drop at the start of recording appears as a change in the film thickness of the cells arranged in the panel. FIG. 7A is a relationship diagram between a cell and a film thickness. The vertical axis represents the film thickness, and the horizontal axis represents the cell number of one panel. The first side of the cell is the head writing start position. As shown by the solid line in the figure, it can be seen that the film thickness without correction does not recover until about 10 cells.

  In order to eliminate this change in film thickness and maintain a constant film thickness, the present invention changes the voltage applied to the signal electrode in units of pixels (cells) according to the time that the head reaches the recording medium from the cleaning position.

  FIG. 7B shows the drive timing applied to the signal electrode. Since each cell is filled with about 10 drops of ink, 10 drops of ejection pulses are applied to the first cell as shown in the figure, and then the number of cells constituting the second cell, the third cell, and one panel is as follows. The procedure is such that 10 drops of ejection pulses are applied. In the present invention, as shown in the shaded area pulse in the figure, the voltage is adjusted in units of cells in which these 10 drops are made into one lump.

  As the correction voltage for each cell, a correction voltage value is selected from a voltage prepared in advance as shown by a correction voltage curve (broken line) in FIG. Then, a cell and voltage data table is created as shown in FIG. This table may be either a head unit or a nozzle unit, but a normal nozzle unit is selected. The numerical value described in the data table represents the voltage correction amount, and the change of numerical value 1 means the change of voltage 0.1V.

  As a result of performing film thickness correction using the data table according to the present invention at an ejection frequency of 8 kHz, an inter-cell frequency of 100 Hz, and a corrected film thickness of 1.8 μm, it was possible to adjust the fluctuation to 0.05 μm or less. Although a comparison experiment of such cell-by-cell correction and drop-by-drop correction was also performed, it was found that there was almost no difference in film thickness change between the two methods, and that cell-by-cell correction was sufficient.

  The ink jet recording method according to the present invention can form a uniform coating film with stable landing accuracy and coating amount, so that a color filter capable of displaying a uniform color with little color unevenness can be produced at a high yield. It can be manufactured with good performance.

Schematic diagram of color filter manufacturing method by inkjet method Structure diagram of inkjet head used in the present invention Sectional view of the inkjet head used in the present invention (A) The figure which shows the drive waveform at the time of the ink discharge of an inkjet head (b) The figure which shows the rocking | fluctuation waveform applied at the time of the discharge stop used for this invention (A) The figure which shows the application pattern of the conventional fluctuation waveform (b) The figure which shows the application pattern of the fluctuation waveform of this invention Graph of coating thickness with respect to print cell when swing signal of the present invention is applied (A) Graph of correction voltage when controlling discharge amount and film thickness before and after correction (b) Diagram showing driving waveform of voltage control in cell unit in discharge amount control (c) Diagram showing data table after discharge amount correction

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stage 2 Transparent substrate 3 Inkjet head 4 Pixel 5 Piezoelectric ceramics 6 Channel groove 7 Signal electrode 8 Ink supply port 9 Cover plate 10 Nozzle 11 Ink channel 12 Adjacent channel 13 Signal electrode 14 Common electrode

Claims (3)

In the ink jet recording method, the voltage applied to the signal electrode of the ink jet head is adjusted in a predetermined unit only for a predetermined time from the recording start position of the ink jet head. 2. The ink jet recording method according to claim 1, wherein the predetermined unit is a cell unit of a color filter. 2. The ink jet recording method according to claim 1, wherein the voltage adjustment is selected from a predetermined correction voltage curve and a coating film thickness correlation graph.

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