JP2006334967A - Ink jet recorder and ink jet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recorder which can make the amount of ink delivery nearly constant and then suppress the color variation of recording image by controlling the temperature of an ink in a recording head within the set range. <P>SOLUTION: The ink jet recorder is equipped with a temperature control means for controlling a heating means of the recording head based on a temperature-difference information concerning the difference between the temperature of the ink in the recording head and the temperature of the ink supplied to the recording head and an ink-amount information concerning the ink amount required for recording that is computed from the image data of a predetermined area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus and an ink jet recording method.

  An ink jet recording apparatus records an image by supplying ink from an ink tank that contains ink to a recording head via a supply path, and discharging and landing the supplied ink on a recording medium based on image data. It is configured as follows.

  However, in the ink jet recording apparatus having the above configuration, when the temperature of the recording head is low, the ink discharge amount and the discharge speed are decreased, the dot diameter is reduced, and the ink discharge amount and the discharge speed with a high temperature of the recording head are increased. The dot diameter increases.

  For this reason, in order to obtain a stable dot diameter, it is necessary to maintain the recording head within a predetermined temperature range. Accordingly, it has been proposed to provide a recording head with a heater and a temperature sensor, and to control the heater based on the set temperature and the temperature detected by the temperature sensor.

Such temperature control of the recording head by the heater is generally performed by ON-OFF control of the heater without changing the power supplied to the heater (see Patent Document 1).
JP-A-62-77946

  By the way, when a high viscosity ink such as an ultraviolet curable ink is used as the ink, there is an advantage that a recorded image is hardly blurred and clear recording can be performed.

  However, when high-viscosity ink is used, the amount of ink discharged from the recording head and the discharge speed are reduced because of the high viscosity. Accordingly, the image quality of the recorded image is not stable and the quality is deteriorated. Therefore, it is necessary to stabilize the ink ejection amount and ejection speed of the recording head by providing a heater in the recording head and heating the recording head to reduce the viscosity of the high viscosity ink.

  That is, when high-viscosity ink is ejected by an ink jet recording apparatus, it is necessary to heat the recording head with a heater so that the ink viscosity is substantially constant and optimal for ejection.

  When ink is ejected from the recording head, ink corresponding to the ejected amount is supplied from the supply path to the recording head as needed.

  However, the temperature of the ink in the supply path supplied to the recording head is governed by the use environment temperature, and the temperature of the recording head varies depending on the temperature of the ink supplied from the supply path.

  Further, since the amount of ink necessary for recording is determined based on the image data, the amount of ink supplied to the recording head varies depending on the image data. Therefore, the larger the ink supply amount determined by the image data, and the lower the temperature of the ink in the supply path (the greater the temperature difference from the temperature of the heated printhead ink), the more the printhead becomes, It becomes easy to be cooled.

  Here, as in the prior art, the temperature control of the print head is performed by simply turning on the detected print head temperature and the set temperature, and controlling the heater on and off without changing the power supplied to the heater. If you have the following problems.

  The capacity of the heater needs to be set to the maximum value of power assumed from the heat capacity of the print head and ink, the maximum temperature of the print head temperature control, and the minimum temperature of the ink supplied to the print head. Since the worst value is assumed, the electric power supplied to the heater becomes considerably large. When ON-OFF control is performed with this electric power, the heater is heated rapidly when it is turned on, and the heater temperature significantly exceeds the set value. At OFF, if the difference between the temperature of the print head and the temperature of the ink supplied to the print head is large, the temperature is detected at a temperature lower than the set temperature. As a result, the temperature control of the print head is affected by a delay in control and repeats a vibration with a large amplitude temperature. The viscosity of the ink varies and the ink discharge amount varies, resulting in a color fluctuation of the print image and the image quality. Decreases.

  In particular, when the distance between the ink tank and the print head is long and the temperature difference between the set temperature and the ambient temperature is large, the ink tube that is the ink supply path is long even if the ink tank is kept warm and heated. A temperature drop occurs until the temperature reaches.

  In addition, even when the recording apparatus is stopped due to a jam or the like, the temperature of the ink in the ink tube is lowered, so that the recording head is easily cooled, and the temperature control of the recording head is greatly fluctuated.

  The present invention has been made in view of the above circumstances, and controls the temperature of the ink of the recording head within a set range even when the ink of the recording head is discharged onto the recording medium in a heated state. Accordingly, an object of the present invention is to provide an ink jet recording apparatus and an ink jet recording method capable of making the ink viscosity substantially constant, suppressing variations in ink discharge amount, and suppressing color fluctuations in a recorded image.

The object of the present invention is achieved by the following configurations.
(Claim 1)
A recording head for discharging ink onto a recording medium in a heated state;
First temperature detecting means for detecting the temperature of ink in the recording head;
Heating means for heating the ink of the recording head;
Second temperature detecting means for detecting the temperature of the ink supplied to the recording head;
Ink amount information calculating means for calculating ink amount information related to the ink amount necessary for recording the image data from image data in a predetermined image region;
Temperature difference information relating to a temperature difference between the temperature of the ink of the recording head detected by the first temperature detecting means and the temperature of the ink supplied to the recording head detected by the second temperature detecting means; and the ink An ink jet recording apparatus comprising: a temperature control unit that controls the heating unit based on the ink amount information calculated by the amount information calculating unit.
(Claim 2)
The temperature control unit controls the heating unit by controlling electric power supplied to the heating unit based on the temperature difference information and the ink amount information. Inkjet recording apparatus.
(Claim 3)
The temperature difference information is an absolute value of the temperature difference,
The temperature control means uses the power when the absolute value of the temperature difference is relatively large and the ink amount information is relatively large, the absolute value of the temperature difference is relatively small, and the The inkjet recording apparatus according to claim 2, wherein the ink amount information is controlled to be larger than the electric power when the ink amount information is relatively small.
(Claim 4)
The said temperature control means calculates the said electric power with reference to the table which prescribed | regulated the relationship between the said temperature difference information, the said ink amount information, and the said electric power, The said electric power is characterized by the above-mentioned. Inkjet recording apparatus.
(Claim 5)
Scanning means for scanning the recording head in the main scanning direction;
Transport means for transporting the recording medium in the sub-scanning direction,
5. The ink jet recording apparatus according to claim 1, wherein the ink amount information calculating unit calculates the ink amount information from image data in an image area for one main scan.
(Claim 6)
The recording head has an image recording width corresponding to the width of the recording medium;
Means for relatively moving the recording head and the recording medium in the sub-scanning direction;
5. The ink jet recording apparatus according to claim 1, wherein the ink amount information calculation unit calculates ink amount information from image data in an image area for one page.
(Claim 7)
The ink jet recording apparatus according to claim 1, wherein the ink is an ultraviolet curable ink that is cured by being irradiated with ultraviolet rays.
(Claim 8)
An ink jet recording method in an ink jet recording apparatus, comprising: a recording head that discharges ink onto a recording medium in a heated state; and a heating unit that heats ink of the recording head,
An ink amount information calculating step for calculating ink amount information relating to the ink amount necessary for recording the image data from image data in a predetermined image region;
A temperature detection step of ink of the recording head for detecting the temperature of ink of the recording head;
Detecting the temperature of ink supplied to the recording head for detecting the temperature of ink supplied to the recording head; and
The temperature difference between the ink temperature of the recording head obtained in the ink temperature detection step of the recording head and the temperature of the ink supplied to the recording head obtained in the temperature detection step of the ink supplied to the recording head. By controlling the heating unit based on the temperature difference information and the ink amount information obtained in the ink amount information calculating step, the ink is ejected onto the recording medium based on the image data. An ink jet recording method comprising: a recording step of recording.

  The inventor includes a recording head that discharges ink onto a recording medium in a heated state, a first temperature detection unit that detects a temperature of the ink of the recording head, and a heating unit that heats the ink of the recording head. A second temperature detecting means for detecting the temperature of the ink supplied to the recording head; and ink amount information for calculating ink amount information relating to the ink amount necessary for recording the image data from the image data in a predetermined image area. Temperature difference information relating to a temperature difference between the temperature of the ink of the recording head detected by the calculating means and the first temperature detecting means and the temperature of the ink supplied to the recording head detected by the second temperature detecting means. And temperature control means for controlling the heating means based on the ink quantity information calculated by the ink quantity information calculating means. Recording apparatus and an inkjet recording method using the inkjet recording apparatus, control delay can be suppressed, and the temperature of the recording head can be controlled within a set range. Therefore, the present invention has been achieved.

  According to the first aspect of the present invention, the ink temperature of the recording head can be controlled within the set range, and hence the ink viscosity can be made substantially constant, variation in the ink discharge amount can be suppressed, and color variation in the recorded image can be suppressed. be able to.

  According to invention of Claim 2, control of a heating means becomes easy by controlling the electric power supplied to a heating means.

  According to invention of Claim 3, it has the following effects.

  The larger the amount of ink necessary for recording, that is, the larger the amount of ink supplied to the recording head, and the larger the absolute value of the difference between the temperature of the recording head ink and the temperature of the ink supplied to the recording head, the larger the recording head. Becomes easier to cool. Accordingly, when the absolute value of the temperature difference is relatively large and the ink amount information is relatively large, the electric power supplied to the heating means of the recording head is relatively small and the absolute value of the temperature difference is relatively small. By controlling the amount information to be larger than the power when the amount information is relatively small, the temperature of the recording head can be controlled more effectively within the set range, and the ink viscosity can be made substantially constant, and the ink Variations in the ejection amount can be suppressed, and color variations in the recorded image can be suppressed.

  According to the fourth aspect of the present invention, the power can be calculated at high speed by referring to the table.

  According to the fifth aspect of the invention, in the shuttle type ink jet recording apparatus that scans the recording head in the main scanning direction, the ink temperature of the recording head can be controlled more effectively. In addition, power can be calculated by effectively using the time between recordings for each main scan.

  According to the sixth aspect of the present invention, in the line type ink jet recording apparatus, the ink temperature of the recording head can be controlled more effectively. In addition, power can be calculated by effectively using the time between recordings for each page.

  According to the seventh aspect of the present invention, when an ultraviolet curable ink is used as the ink, the ultraviolet curable ink is cured by irradiating ultraviolet rays after recording, so that the recorded image can be made difficult to disappear over a long period of time. The quality of the recorded image by the ink jet recording apparatus can be improved. Further, even if the recording medium is not a recording medium having good ink absorbability (for example, paper), recording can be performed even if the recording medium has no ink absorbability or a recording medium having low ink absorbability. Furthermore, since the ultraviolet curable ink is a high-viscosity ink, the effect of the invention according to any one of claims 1 to 6 appears more remarkably.

  According to the eighth aspect of the invention, similarly to the first aspect of the invention, the ink temperature of the recording head can be controlled within the set range, and the ink viscosity can be made substantially constant, and the ink discharge amount can be controlled. Variations can be suppressed, and color variations of recorded images can be suppressed.

Although the example of embodiment regarding this invention is shown below, the aspect of this invention is not limited to these.
[First Embodiment]
The shuttle type ink jet recording apparatus 1 exemplified in the first embodiment discharges and lands an ultraviolet curable ink (hereinafter sometimes abbreviated as “ink”) that cures when irradiated with ultraviolet rays. Recording.

  The ultraviolet curable ink used in the first embodiment includes, as main components, a polymerizable compound, a photopolymerization initiator, and a coloring material, and further has a viscosity of about 0.03 Pa · s at 25 ° C., and a temperature. The viscosity decreases with the rise. The ink is heated to 50 to 60 ° C., and the viscosity is lowered to about 0.01 to 0.015 Pa · s, and the ink is ejected from the recording head.

  As shown in FIG. 1, the main configuration of the ink jet recording apparatus 1 includes a recording medium conveying means 104 (FIG. 2) for conveying a sheet-like recording medium P forward (arrow B) in the sub-scanning direction during recording, A recording head 2 for discharging ink to the recording medium P, an ink supply unit 3 for supplying ink to the recording head 2, an ink supply path 12 for flowing ink from the ink supply unit 3 to the recording head 2, and a plurality of colors The carriage 4 having the recording head 2 mounted thereon, the maintenance unit 5 for performing maintenance of the recording head 2, and the carriage 4 reciprocating along the main scanning direction (arrow A) of the recording head 2 during recording or maintenance. Carriage scanning means 105 (FIG. 2) to be moved, a guide rail 6 for guiding the carriage 4 during the reciprocating movement, and a hoisting station for the carriage 4 A home position 7, and a control unit for controlling these units (temperature control means, the ink amount information calculating means) 30 (Fig. 2).

  The carriage scanning unit 105 is, for example, a scanning motor, and corresponds to a scanning unit that scans the recording head in the main scanning direction. In this example, recording is performed in both one scan in the forward direction of the main scan (movement from left to right in FIG. 1) and one scan in the reverse direction of the main scan (movement from right to left in FIG. 1). Configured to do.

  The recording medium transport unit 104 is, for example, a transport motor, and transports the recording medium P downstream for each scanning operation (forward or backward) of the carriage 4 during recording. At this time, the recording surface of the recording medium P passes through the recording area D by the recording head 2.

  In this example, in order to record each pixel on a two-dimensional surface, the faster recording speed between adjacent pixels is called the main scanning direction, and the slower recording speed is called the sub-scanning direction. That is, if the carriage 4 is moved, the recording speed of pixels recorded adjacent to the direction of movement of the carriage 4 is faster than the recording speed of pixels recorded adjacent to the direction of movement of the recording medium P. Therefore, the moving direction of the carriage 4 is the main scanning direction, and the moving direction of the recording medium P is the sub-scanning direction. Also, in the line type ink jet recording apparatus described later, since each ink droplet is ejected from the recording head almost simultaneously, the recording speed of the pixels that are recorded adjacent to the direction of the nozzle arrangement in the recording head is higher. It is faster than the recording speed of the pixels that are recorded adjacent to each other in the direction of transport of the medium P. Therefore, the nozzle alignment direction of the recording head is the main scanning direction, and the transport direction of the recording medium P is the sub-scanning direction.

  The recording head 2 is provided on the surface facing the recording medium P, and has a nozzle for ejecting ink, an ink ejecting means for ejecting ink, an ink flow path, and a manifold for guiding the ink to the ink flow path. Configured. This recording head 2 includes ink types (Y: yellow, LY: light yellow, M: magenta, LM: light magenta, C: cyan, LC: light cyan, K: black, LK: used in the inkjet recording apparatus 1. Depending on the light black), a plurality are provided. On the surface of each recording head, first temperature detecting means (for example, a temperature sensor) 102 (FIGS. 2 and 3) for detecting the ink temperature T1 of the recording head 2 and the ink of the recording head 2 are heated. The heating means 101 (FIG. 2) for reducing the viscosity is provided.

  Any heating means 101 may be used as long as the ink in the recording head is heated to lower the viscosity, and specifically, a halogen lamp, infrared rays, heating wire, or the like can be used.

  In this example, the ink inside the recording head is heated by heating the recording head, and the temperature of the ink inside the recording head is indirectly detected by detecting the temperature of the surface of the recording head. The temperature detecting unit 102 and the heating unit 101 may be provided in the recording head so as to come into contact with the ink of the recording head 2 so that the ink is directly heated and the temperature of the ink is directly detected. .

  The heating means 101 is supplied with electric power from an electric power supply means 103 (FIG. 2) that can vary the electric power supplied to the heating means 101.

  In this example, the recording head 2 uses a shear mode type piezoelectric element that is deformed in a shear mode by applying an electric field as an ink ejection means for ejecting ink. However, the present invention is not limited to these, and other types of piezoelectric elements such as a single plate type piezoelectric element and a longitudinal vibration type stacked piezoelectric element may be used as the piezoelectric element. Also, other ink discharge means such as an electromechanical conversion element using an electrostatic force or a magnetic force or an electrothermal conversion element for applying pressure using a boiling phenomenon may be used.

  The ink supply unit 3 includes an ink tank 8 that stores ink, and a supply valve 9 that regulates the amount of ink flowing out from the ink tank 8 to the ink supply path 12. Are communicated by the ink supply path 13. Note that a plurality of these units are provided for each recording head according to the type of ink. As shown in FIG. 2, the supply valve 9 is electrically connected to the control unit 30, and flows a predetermined ink amount into the ink supply path 12 based on the control of the control unit 30.

  The ink tank 8 is, for example, a replaceable ink cartridge or the like, and is formed of a flexible container and changes its shape according to the amount of ink stored.

  The ink supply path 12 allows each ink supply path 13 and the corresponding recording head 2 to communicate with each other so that ink can be supplied from the ink tank 8 to the recording head 2 for each color. The ink supply path 12 is formed of a flexible member (for example, an ink tube) so as to correspond to the movement of the recording head 2.

  The carriage 4 repeats reciprocating movement along the main scanning direction (arrow A) of the recording head 2 while being guided by the guide rail 6, and moves the recording head 2 along the recording surface of the recording medium P in the recording area D. Let Further, a UV light source (not shown) for irradiating ultraviolet rays is provided on the side of the carriage 4 in order to cure the ink ejected from the recording head 2.

  The maintenance unit 5 is provided outside the recording area D on one end side of the path along which the carriage 4 reciprocates. As shown in FIG. 1, the maintenance unit 5 covers a nozzle face having the nozzles of the recording head 2 and seals the suction cap 5a for sucking ink from the nozzles, and sucking ink by the suction cap 5a. After being performed, the blade portion 5b for wiping off the ink remaining on the nozzle surface, the blade cleaner portion (not shown) for cleaning the blade portion, and the nozzle where ink has been sucked are discharged in order to fill with ink. And an empty discharge tray (not shown) for collecting the ink. The empty discharge tray is provided with a liquid amount sensor (not shown) for detecting the amount of ink discharged empty.

  The home position 7 is provided on the other end side of the path along which the carriage 4 reciprocates. The home position 7 is provided with the same number of moisturizing caps 7a as the recording head 2 for moisturizing the nozzle surface of the recording head 2, and covers the nozzle surface of the recording head 2 when the carriage 4 is on standby. ing.

  FIG. 3 shows a block diagram of temperature detection. In this figure, the supply valve is omitted. Here, the K (black) print head is representatively shown, but the same applies to print heads of other colors, and the temperature is independently detected and input to the control unit 30. On the surface of the ink supply path 12 in the vicinity of the connection portion with the recording head 2 in the ink supply path 12, a second temperature detecting means 100 for detecting the temperature T2 of the ink supplied to the recording head 2 is provided.

  The second temperature detection unit 100 may be provided at any position of the ink supply unit 3 and the ink supply path 12 as long as the temperature of the ink supplied to the recording head 2 can be detected. In order to further increase the control accuracy, it is possible to provide the ink supply path 12 in the vicinity of the recording head 2 so that the temperature of the ink immediately before being supplied to the recording head 2 can be detected as in this example. preferable.

  In this example, the temperature of the ink supplied to the recording head 2 is indirectly detected by detecting the temperature of the surface of the ink supply path 12, but the second temperature detecting means 100 is used to supply the ink. The temperature of the ink may be directly detected by providing it in the ink supply path 12 in a form of contacting the ink in the path 12.

  As shown in FIG. 2, the control unit 30 includes an interface (I / F) 31, a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Central Processing Unit) 34, and the like. Various devices connected to the interface 31 are controlled in accordance with the control program and control data written in the. Further, the control unit 30 constitutes ink amount information calculating means for calculating ink amount information relating to the ink amount necessary for recording the image data from the image data in a predetermined image area stored in the RAM 33. Further, the control unit 30 detects a temperature difference related to a temperature difference between the temperature of the ink of the recording head detected by the first temperature detection unit and the temperature of the ink supplied to the recording head detected by the second temperature detection unit. Based on the information and the ink amount information calculated by the ink amount information calculating unit, a temperature control unit is configured to control the heating unit of the recording head. Here, the recording head 2 and the ink supply path 12 are represented by K (black). The same applies to other colors, and each color is controlled independently.

  The interface 31 includes a display unit 17 that displays an error, a state of each unit, a power supply unit 103 that supplies power to a heating unit 101 that heats ink of the recording head 2, and a first unit that detects an ink temperature T1 of the recording head 2. The first temperature detecting means 102, the second temperature detecting means 100 for detecting the ink temperature T2 of the ink supply path 12, the carriage 4 and the like are electrically connected.

In the ROM 32, the ink temperature T1 of the recording head and the ink temperature T2 of the ink supply path 12 are stored.
Table defining the relationship between the temperature difference information regarding the temperature difference of the ink, the ink amount information regarding the ink amount necessary for recording the image data from the image data in a predetermined image area, and the power supplied to the heating means 101 (FIG. 5), various control programs and control data concerning the set temperature of the recording head, the operation of each part of the ink jet recording apparatus, and the like are written. In this example, the table is commonly used for a plurality of recording heads having different colors.

  The RAM 33 can store a plurality of input data only while power is supplied to the recording apparatus, and a storage area for storing various data such as image data for recording an image on the recording medium P. A work area by the CPU 34 is provided. The area for storing image data consists of a memory map composed of row and column cells corresponding to one page of image data. Each cell constituting this area has a one-to-one correspondence with a dot formation position, which will be described later, and data that is information on dots formed at each dot formation position by each cell is stored. This data has a value of 1 or 0 depending on whether or not to form dots. The control unit 30 counts cells having black data (data = 1) in a predetermined image area, and calculates a dot density to be described later.

  The CPU 34 develops a program designated from various programs stored in the ROM 32 in a work area in the RAM 33, and executes various processes according to the program in accordance with an input signal from each temperature detection means. .

  In this example, dot density is used as the ink amount information described above.

  First, the dot density recorded on the recording medium by the recording head will be described.

  Here, a dot refers to the minimum unit of an image formed on a recording medium by ejecting ink from a nozzle. That is, a region where ink is applied on the recording medium by ejecting one drop of ink from one nozzle corresponds to one dot. A value indicating the diameter (dot diameter) of the dot is defined as a dot size.

  The dot formation position is defined as follows. That is, the dot formation position refers to a position where a dot can be formed.

  In the following, a case will be described in which the dot formation positions are arranged in a matrix and all the distances between the dot formation positions and the adjacent dot formation positions in the row direction and the column direction are equal. The row direction and the column direction correspond to the main scanning direction and the sub scanning direction, respectively.

  In this example, it is assumed that the dot size of each dot is the same (dot size, that is, the amount of ink of one drop is fixed). Therefore, in this case, the dot density of a predetermined image area constituted by the dot formation positions of m rows × n columns is defined by Equation 1.

Dot density S = p0 / (m × n) Equation 1
Note that p0 indicates the number of dots formed in the predetermined image area, that is, the number of dots actually formed with respect to the dot formation position in the predetermined image area. This p0 is determined by the image data in the predetermined image area. Further, m indicates the number of rows of dot formation positions constituting the predetermined image area, n indicates the number of columns of dot formation positions constituting the predetermined image area, and therefore m × n is the dot formation position within the predetermined image area. It becomes the number of. Hereinafter, the dot density S is appropriately expressed as a percentage.

  A specific example of the dot density S is shown in FIG. FIG. 4 is a plan view showing the arrangement of dots on the recording medium P, and shows dot density S of 25%, 50%, 75%, and 100%, respectively. That is, FIG. 4 shows a case where dots are formed at 1/4, 1/2, 3/4, and all of the dot formation positions.

  In the figure, dots are represented by circles and dot formation positions are represented by grid points, and the number of dot formation positions is 5 rows × 8 columns = 40. The dot size of each dot is set to the ideal dot size.

  As described above, in a region where the dot density S is high, a larger amount of ink is required when recording an image in the predetermined image region than in a region where the dot density S is low.

  In this example, for a predetermined image area, an image area for one main scan (one scan in either the forward direction or the backward direction) is used, and m and n are one main scan. The value corresponds to the image area of minutes.

  In this example, the absolute value of the temperature difference between T1 and T2 is used as the temperature difference information. Since T1 and T2 have a relationship of T1> T2, the absolute value of T1-T2 or T2-T1 may be set as the absolute value of the temperature difference.

  FIG. 5 shows an example of the table. The horizontal axis is the temperature difference | T1-T2 |, and the vertical axis is the dot density S. The temperature difference | T1-T2 | and the dot density S are each divided into four regions, and the power increases as the temperature difference | T1-T2 | increases and the dot density S increases corresponding to each region. Changed to

  For example, the calculation is performed as follows.

  1. When the temperature difference is as small as 0 ° C. <| T1-T2 | <10 ° C., the dot density is 0% ≦ S <25%, and the ink amount is small, the power is 8 W, which is the minimum.

  2. When the temperature difference is as large as 30 ° C. ≦ | T1−T2 | ≦ 40 ° C., the dot density is 0% ≦ S <25% and the amount of ink is small, the power is medium 14 W.

  3. When the temperature difference is as small as 0 ° C. <| T1−T2 | <10 ° C., the dot density is 75% ≦ S ≦ 100%, and the amount of ink is large, the power is 14 W in the middle.

  4). When the temperature difference is as large as 30 ° C. ≦ | T1−T2 | ≦ 40 ° C., the dot density is 75% ≦ S ≦ 100% and the amount of ink is large, the power is 20 W at the maximum.

  The control unit 30 controls the entire operation of the ink jet recording apparatus 1. Here, a control procedure performed when recording is performed by ejecting ink from a recording head onto a recording medium based on image data. explain. Here, the recording head 2 and the ink supply path 12 are represented by K (black). The same applies to the other colors, and each color is controlled independently.

  First, the recording apparatus is in a standby state. At this time, the recording head is heated by the heating means 101, and T1 is maintained within the set temperature range. The supply valve 9 is in an open state.

  At the start of recording, the dot density is calculated from the image data for the first scan (outward path) stored in the RAM 33. The detected temperature T1 of the first temperature detecting means and the detected temperature T2 of the second temperature detecting means are read, and the temperature difference | T1-T2 | is calculated.

  From the calculated dot density and temperature difference | T1-T2 |, the power supplied to the heating means 101 of the recording head is calculated with reference to the table (FIG. 5).

  When recording is started, the recording head ejects ink as fine droplets from each nozzle toward the recording surface of the recording medium while moving along the forward path of the carriage 4. At this time, the control unit 30 supplies the electric power obtained from the table to the heating unit 101, and controls the heating unit on and off based on the detection temperature T1 of the first temperature detection unit. The ink is heated to a predetermined temperature (in this example, 50 to 60 ° C.) and discharged as fine droplets from each nozzle of the recording head. In this manner, ink is ejected and landed on the recording medium P, and an image for the first scan is recorded.

  Further, during recording, the dot density is similarly obtained from the image data for the next one scan (return pass).

  When the recording for the first one scan (outward path) is completed, the recording medium is conveyed in the sub-scanning direction to make a line feed, and similarly, the detection temperature T1 of the first temperature detection means and the second temperature detection means The temperature difference | T1-T2 | is calculated, and the power supplied to the heating means 101 is calculated from the dot density and temperature difference | T1-T2 | with reference to the table (FIG. 5). To do. At this time, it is preferable to detect T1 and calculate electric power in a state where T1 is kept within the set temperature range.

  Thereafter, the forward path and the backward path are alternately repeated one scan at a time until recording for one page is completed.

  As described above, according to the ink jet recording apparatus 1 of this embodiment, the ink temperature T1 of the recording head detected by the first temperature detecting unit and the recording head detected by the second temperature detecting unit are supplied. Based on the absolute value of the temperature difference between the ink temperatures T2 and the ink amount calculated by the ink amount information calculating unit, the power supply unit adjusts the ink temperature of the recording head to be within the set temperature range. Since the power supplied to the heating means for heating the print head ink is controlled, the temperature of the print head ink can be controlled within the set range, and the ink viscosity can be made substantially constant, and the ink discharge amount. Variation in the color of the recorded image can be suppressed.

  In the above embodiment, since the ink amount per main scan is calculated from the image data corresponding to one main scan, in the shuttle type ink jet recording apparatus, the recording head of the recording head is more effectively used. Temperature control is possible. Further, it is possible to perform power calculation processing by using the time between recordings for each main scanning. However, the range of image data for calculating the ink amount is not limited to this. For example, the ink amount may be calculated from image data for one page.

  The ink amount information is not limited to the dot density, and any information corresponding to the ink amount necessary for recording may be used. For example, the ink amount may be directly calculated. This is particularly effective when the dot size of each dot is not the same (dot size, that is, when the amount of ink per drop is modulated), and the ink drop weight per drop and the number of dots per ink drop weight can be determined. For example, the ink amount can be calculated by multiplying the ink droplet weight by the number of dots for each ink droplet having a different weight and calculating the sum.

  In the case of a plurality of recording heads, the table shown in FIG. 5 may be changed for each recording head (for example, for each ink color). The storage means storing the table may be configured to be rewritable. The table may be prepared in advance in consideration of the heat capacity of the ink and / or the recording head, the amount of ink dropped from the nozzle, and the like.

  Specifically, for a recording head having a relatively large heat capacity of the ink and / or the recording head, the temperature rise during heating of the recording head is delayed, so the power value D1 is increased so that there is no delay. On the other hand, it is effective to create a table so that the power value D2 is smaller than D1 for a recording head in which the heat capacity of the ink and / or the recording head is relatively small. Here, the power values D1 and D2 mean power values when the dot density and the temperature difference are the same.

  In addition, for a recording head in which the amount of ink discharged from a nozzle is relatively large, the recording head is easily cooled by the ink supplied to the recording head, and the temperature rise during heating is delayed. It is effective to create a table so that the power value D4 is smaller than D3 for a recording head in which D3 is increased so that there is no delay, and conversely for a recording head in which the amount of ink of one drop is relatively small. It is. Here, the power values D3 and D4 mean power values when the dot density and the temperature difference are the same.

  Further, the temperature difference information is not limited to the absolute value of the temperature difference, and any information that corresponds to the temperature difference between T1 and T2 may be used. For example, T1 is set when reading the detection temperature T1 of the first temperature detection means and the detection temperature T2 of the second temperature detection means in order to obtain power in the time between recordings for each main scan. If control is possible within the temperature range, the value of T2 may be used as temperature difference information regarding the temperature difference.

  Further, T2 may be used instead of the environmental temperature at the time of recording.

  In addition, the ink amount obtained by the calculation process from the image data for one scan does not necessarily need to be the ink amount for one scan, as long as it can relatively compare the ink amount for one scan, For example, the ink amount obtained by dividing the ink amount for one scan by the number of dot formation positions for one scan may be used.

  Further, when the number of nozzles of the recording head is large, a method of performing temperature control by dividing the nozzles into a plurality of regions is also possible. For example, as shown in FIG. 6, the nozzle is divided into two regions, and a first temperature detection unit and a heating unit are provided for each nozzle region, and the power supplied to the heating unit is calculated independently to control the temperature. do it. As a result, power calculation errors can be reduced, and more stable ejection can be achieved. In the case of a line type ink jet recording apparatus to be described later, the number of nozzles of the recording head is large, which is particularly effective.

Further, in this example, since the ultraviolet curable ink is used as the ink, the ultraviolet curable ink is cured by irradiating the ultraviolet ray after recording, and the recorded image can be made difficult to disappear over a long period of time. Excellent weather resistance can be exhibited even when they are arranged in the above. That is, the recorded image by the inkjet recording apparatus 1 is hard to bleed, clear recording can be performed, and the quality of the recorded image can be improved. Further, when the ultraviolet curable ink is used, the recording medium P is not a recording medium having good ink absorbability (for example, paper), but is a recording medium having no ink absorbability or a recording medium having low ink absorbability. Can also be recorded. Here, a recording medium having no ink absorbability or a recording medium having a low ink absorbability is a recording medium formed from a material having no ink absorbability, a material having a low ink absorbability, a material having no ink absorbability, A recording medium having a surface layer (recording layer) made of a material having low ink absorbability. Examples of the material having no ink absorbability or the material having a low ink absorbability include various plastics and metals.
[Second Embodiment]
A second embodiment will be described with reference to FIG. The second embodiment is the same as the first embodiment except for the parts unique to the second embodiment. Therefore, the same parts as those in the first embodiment are denoted by the same reference numerals. The description is omitted.

  The line type inkjet recording apparatus 600 exemplified in the second embodiment has a longitudinal direction (main scanning direction, arrow A) so as to have an image recording width corresponding to the width of the recording medium (width in the main scanning direction). ) Is provided with a recording head 602 in which a large number of nozzles are provided at predetermined intervals.

  A plurality of recording heads 602 are provided according to the type of ink (Y: yellow, M: magenta, C: cyan, K: black) used in the ink jet recording apparatus 600, and these recording heads 602 are mutually connected. Are aligned in the transport direction of the recording medium P (sub-scanning direction, arrow B) so that the longitudinal directions of the recording medium P are parallel. An ink tank 608 is attached to the top of the recording head 602 via a short ink supply path 612. With the recording head 602 fixed, the recording medium P is moved relatively in the sub-scanning direction (arrow B) by the recording medium conveying means (means for moving the recording head and the recording medium relatively in the sub-scanning direction). To record. The recording medium P may be fixed and the recording head 602 may be moved in the sub-scanning direction (arrow B).

  According to the line type ink jet recording apparatus 600 of this embodiment, the temperature of the ink of the recording head can be controlled within the set range, and the ink viscosity can be made substantially constant, as in the first embodiment. Variations in the ink ejection amount can be suppressed, and color variations in the recorded image can be suppressed.

  In this embodiment of the line type ink jet recording apparatus, since it has an image recording width corresponding to the width of the recording medium (width in the main scanning direction), the image data for one page of one (one color) recording head is used. It is preferable to calculate the ink discharge amount per page of one (one color) recording head. This makes it possible to control the temperature of the recording head more effectively. In addition, power calculation processing can be performed by using the time between recording for each page.

  Further, as shown in FIG. 7A, the recording head used in the line type ink jet recording apparatus may be a single long recording head 602. However, as shown in FIG. The recording head 603 having a length shorter than the width may be combined and lengthened. In such a case, it is possible to perform a temperature control by dividing the recording head into short recording heads. Specifically, a first temperature detection unit, a heating unit, an ink supply path, and a second temperature detection unit are provided for each short-length recording head, and the power supplied to the heating unit is calculated independently. The temperature may be controlled. As a result, power calculation errors can be reduced, and more stable ejection can be achieved.

  In the first and second embodiments described above, the recording head is provided with heating means to perform heating. However, the present invention is not limited to this. For example, not only the recording head but also the ink tank is used. A heating means may be provided for heating. Specifically, a halogen lamp, infrared ray, heating wire, or the like can be used. In addition, although an ultraviolet curable ink is exemplified as the ink, the ink used is not limited to this, and may be an ultraviolet curable ink or other ink. The present invention is particularly effective for high viscosity inks.

  Here, the high-viscosity ink is preferably a liquid having a viscosity at 25 ° C. of 0.01 to 0.04 Pa · s. If it is less than 0.01 Pa · s, bleeding is easy and clear recording cannot be performed. On the other hand, if it exceeds 0.04 Pa · s, the smoothness of the image quality is lost. Furthermore, it is preferable that the ink has a viscosity of 0.005 to 0.015 Pa · s at a heating temperature (for example, 50 ° C.) during ink ejection. If it is less than 0.005 Pa · s, there is a risk of causing problems in high-speed discharge, and if it exceeds 0.015 Pa · s, the discharge property may be deteriorated. In particular, when the pressure generating means is ejected from a recording head composed of a shear mode type piezoelectric element, the viscosity of the ink upon ejection is preferably 0.01 to 0.015 Pa · s.

  Further, as an example of controlling the power of the heating unit, an example of controlling the power supplied to a single heating unit has been described. For example, a plurality of heating units are provided in one recording head. The electric power supplied to the entire heating means may be changed by changing the number of heating means that operate.

  Further, although the ink tank is divided for each color, the present invention is not limited to this. For example, the ink tanks may be integrated.

It is a perspective view showing the principal part of the inkjet recording device of 1st Embodiment to which this invention is applied. It is a main control block diagram of the control part with which the inkjet recording device of FIG. 1 is equipped. FIG. 2 is a block diagram of temperature detection in the ink jet recording apparatus of FIG. 1. FIG. 6 is a plan view illustrating a specific example of dot density and dot arrangement on a recording medium. It is an example of the table which concerns on the temperature control of the inkjet recording device of FIG. It is an example which shows the other structure which concerns on the temperature control of the inkjet recording device of FIG. It is a perspective view showing the principal part of the inkjet recording device of 2nd Embodiment to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Recording head 8 Ink tank 30 Control part (Temperature control means, ink amount information calculation means)
DESCRIPTION OF SYMBOLS 100 2nd temperature detection means 101 Heating means 102 1st temperature detection means 103 Electric power supply means P Recording medium

Claims (8)

A recording head for discharging ink onto a recording medium in a heated state;
First temperature detecting means for detecting the temperature of ink in the recording head;
Heating means for heating the ink of the recording head;
Second temperature detecting means for detecting the temperature of the ink supplied to the recording head;
Ink amount information calculating means for calculating ink amount information related to the ink amount necessary for recording the image data from image data in a predetermined image region;
Temperature difference information relating to a temperature difference between the temperature of the ink of the recording head detected by the first temperature detecting means and the temperature of the ink supplied to the recording head detected by the second temperature detecting means; and the ink An ink jet recording apparatus comprising: a temperature control unit that controls the heating unit based on the ink amount information calculated by the amount information calculating unit. The temperature control unit controls the heating unit by controlling electric power supplied to the heating unit based on the temperature difference information and the ink amount information. Inkjet recording apparatus. The temperature difference information is an absolute value of the temperature difference,
The temperature control means uses the power when the absolute value of the temperature difference is relatively large and the ink amount information is relatively large, the absolute value of the temperature difference is relatively small, and the The inkjet recording apparatus according to claim 2, wherein the ink amount information is controlled to be larger than the electric power when the ink amount information is relatively small. The said temperature control means calculates the said electric power with reference to the table which prescribed | regulated the relationship between the said temperature difference information, the said ink amount information, and the said electric power, The said electric power is characterized by the above-mentioned. Inkjet recording apparatus. Scanning means for scanning the recording head in the main scanning direction;
Transport means for transporting the recording medium in the sub-scanning direction,
5. The ink jet recording apparatus according to claim 1, wherein the ink amount information calculating unit calculates the ink amount information from image data in an image region for one main scan. The recording head has an image recording width corresponding to the width of the recording medium;
Means for relatively moving the recording head and the recording medium in the sub-scanning direction;
5. The ink jet recording apparatus according to claim 1, wherein the ink amount information calculation unit calculates ink amount information from image data in an image area for one page. The ink jet recording apparatus according to claim 1, wherein the ink is an ultraviolet curable ink that is cured by being irradiated with ultraviolet rays. An ink jet recording method in an ink jet recording apparatus, comprising: a recording head that discharges ink onto a recording medium in a heated state; and a heating unit that heats ink of the recording head,
An ink amount information calculating step for calculating ink amount information relating to the ink amount necessary for recording the image data from image data in a predetermined image region;
A temperature detection step of ink of the recording head for detecting the temperature of ink of the recording head;
Detecting the temperature of ink supplied to the recording head for detecting the temperature of ink supplied to the recording head; and
The temperature difference between the ink temperature of the recording head obtained in the ink temperature detection step of the recording head and the temperature of the ink supplied to the recording head obtained in the temperature detection step of the ink supplied to the recording head. By controlling the heating means based on the temperature difference information and the ink amount information obtained in the ink amount information calculating step, the ink is ejected onto the recording medium based on the image data. An ink jet recording method comprising: a recording step of recording.

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