JPH04347642A - thermal recording device - Google Patents

Abstract

PURPOSE:To make a temperature adjusting means compact and reduce the cost while the image quality is maintained by constituting thermal recording means of the same color series to be different in tone temperature adjusting ability. CONSTITUTION:In an inkjet recording apparatus wherein the graininess at a highlighting part is improved, the using amount of ink differs depending on the concentration thereof, and therefore the using frequency becomes greatly different, among dark and light recording heads 9. As compared with the recording head of low using frequency, the recording head of high using frequency is highly propably prone to change the image density due to the temperature rise. Therefore, recording heads of high using frequency, namely, four recording heads for cyan dark ink (9C dark), magenta dark ink (9M dark), yellow dark ink (9Y dark) and black dark ink (9B dark) are provided with radiation fins 11 to enhance the radiating efficiency. It, becomes possible to realize recording of images without, accompanying the image density change.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal recording device that forms an image on a recording material using thermal recording means, and more particularly to a thermal recording device that has a plurality of thermal recording means that record with recording materials of similar colors and different densities. Regarding.

0002

2. Description of the Related Art Recording devices that have functions such as printers, copiers, and facsimile machines, or that are used as output devices for multifunction electronic devices and workstations including computers, word processors, etc., print paper or paper based on image information. It is configured to record images on a recording material such as a thin plastic plate. The recording device includes:
Depending on the recording method of the recording means, it can be divided into inkjet type, wire dot type, thermal type, laser beam type, etc.

[0003] In a serial type recording device that employs a recording method that performs main scanning in a direction intersecting the conveying direction (sub-scanning direction) of a recording material, after setting the recording material at a predetermined recording position, An image is recorded (main scanning) by a recording means mounted on a carriage that moves along the line, and after one line of recording is completed, the paper is fed by a predetermined amount (pitch conveyance).
By repeating the operations of performing the following steps and then recording the next row of images (main scanning), the image is recorded on the entire recording material. On the other hand, in a line-type recording device that records only by sub-scanning in the conveyance direction of the recording material, the recording material is set at a predetermined recording position, one line is recorded at once, and then a predetermined amount of By repeating the operations of feeding the paper (pitch feeding) and then recording the next line all at once, the image is recorded on the entire recording material.

As the above-mentioned recording means (recording head), a type (thermal recording means) is used that records an image using thermal energy. This thermal recording means includes a thermal type, a thermal transfer type, a thermal inkjet type, and the like. These thermal recording means are configured to drive (energize) an electrothermal transducer such as a heating element based on image information.

In particular, inkjet recording apparatuses (inkjet recording apparatuses), including the thermal inkjet type described above, perform recording by ejecting ink from a recording means (recording head) onto a recording material, and the recording means is compact. It is easy to print, can record high-definition images at high speed, can record on plain paper without the need for special processing, has low running costs, and has low noise because it is a non-impact method. Moreover, it has the advantage that it is easy to record a color image using multicolor ink. Among these, line-type devices that use line-type recording means with a large number of ejection ports arranged in the width direction of the paper are
Further speeding up of recording is possible.

Among them, thermal inkjet recording means (recording heads) that eject ink using thermal energy are electrothermal conversion films formed on a substrate through semiconductor manufacturing processes such as etching, vapor deposition, and sputtering. body,
By forming the electrodes, liquid channel walls, top plate, etc., it is possible to easily manufacture a device having a high-density liquid channel arrangement (discharge port arrangement), and further compactness can be achieved.

In thermal recording apparatuses that form images using thermal energy, such as the thermal type, thermal transfer type, and thermal inkjet type described above, the characteristics of the recording material (ink, etc.) vary depending on the temperature of the recording head. For example, the viscosity of the ink changes and the diameter of the recorded dots changes, which may cause density fluctuations in the recorded image and deteriorate the recording quality. Therefore, in this type of thermal recording apparatus, it is common to perform recording by adjusting the temperature of the recording head to a certain constant temperature.

[0008] Furthermore, these recording apparatuses often perform binary recording, and there is a problem in that, for example, dots stand out in highlighted areas. To address this problem, it is known to improve the graininess in highlight areas by using multiple types of recording materials of similar colors but different densities (for example, light black ink and dark black ink).

[0009]

[Problem to be Solved by the Invention] However, when using a plurality of recording materials with different densities in a thermal recording device using thermal recording means, it is necessary to provide the number of recording means (recording heads) according to the type of density. Since a temperature control means (temperature control means) was provided for each recording means, there was a problem to be solved in that the device configuration around the recording section was large and expensive.

0010

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned technical problems, and the present invention provides a thermal recording device having a plurality of thermal recording means for recording with recording materials of similar colors and different densities. To provide a thermal recording device in which the thermal recording means of similar colors are configured to have different temperature adjustment capabilities, thereby achieving miniaturization and cost reduction of the temperature adjusting means while maintaining image quality. That's true.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic perspective view showing the configuration of main parts of an embodiment of a thermal recording device to which the present invention is applied. In FIG. 1, a recording material 5 wound into a roll is sandwiched between a pair of conveyance rollers 3 via guide rollers 1 and 2, and is driven by a conveyance (sub-scanning) motor 4 coupled to the pair of conveyance rollers 3. f in Figure 1
sent in the direction. Further, guide rails 6 and 7 are installed in parallel across this recording material 5, and a plurality of thermal recording means (recording heads) 9 are mounted on a carriage 8 guided and supported by these guide rails 6 and 7. It is installed. The carriage 8 can be moved back and forth (main scanning) in a direction across the recording material 5 (in the direction of arrow P) by a motor (carriage motor) not shown. The plurality of recording heads 9 are for cyan dark ink (9C dark), for cyan light ink (9C light), for magenta dark ink (9M dark), for magenta light ink (9M light), and for yellow dark ink (9Y). dark),
For black dark ink (9B dark), for black light ink (
It consists of a total of seven recording heads (9B light). In the following description, when all or any one of these thermal recording means (thermal recording heads) is referred to, it will be simply referred to as recording means 9 or recording head 9.

The embodiment shown in FIG. 1 shows a case where the thermal recording device is an inkjet recording device, and the thermal recording means (thermal recording head) 9 is an inkjet recording means that discharges ink using thermal energy. , equipped with an electrothermal converter for generating thermal energy. Also,
The recording means 9 records the growth of bubbles due to film boiling caused by the thermal energy applied by the electrothermal converter;
Recording is performed by ejecting ink from an ejection port using pressure changes caused by contraction.

FIG. 2 is a partial perspective view schematically showing the structure of the ink ejection section 20 of each recording means (recording head) 9 in FIG. In FIG. 2, a plurality of ejection ports 22 are formed at a predetermined pitch on an ejection port forming surface 21 that faces the recording material 5 with a predetermined gap (for example, about 0.5 to 2.0 mm).
is formed, and an electrothermal converter (such as a heating resistor) 25 for generating energy for ink ejection is arranged along the wall surface of each liquid path 24 that communicates the common liquid chamber 23 and each ejection port 22. has been done. In this example, the recording head 9 is mounted on the carriage 8 in such a positional relationship that the ejection ports 22 are aligned in a direction intersecting the scanning direction of the carriage 2. In this way, the corresponding electrothermal converter 25 is driven (energized) based on the image signal or the ejection signal, and the liquid path 24 is
The recording head 9 is configured to bring the ink inside to film boiling and eject the ink from the ejection ports 22 using the pressure generated at that time.

FIG. 3 is a front view showing the arrangement of a plurality of recording means (recording heads) 9 on the carriage 8 in FIG. Each of the plurality of recording heads 9 is provided with a temperature measuring element and an external heater for temperature control in order to maintain the recording head within a certain temperature range. In addition, as shown in FIG. 3, the dark ink heads 9C dark, 9M dark, 9
Only Y-dark and 9B-dense are provided with radiation fins 11 to improve heat radiation efficiency. The reason why the radiation fins 11 are provided only in the recording head for dark ink will be explained below.

FIG. 4 is a block diagram showing an example of the configuration of an image processing apparatus, taking as an example the configuration of an apparatus for improving graininess in a highlight area using dark black ink. In addition,
In many cases, the density of dark black ink is approximately twice the density of light black ink. In FIG. 4, an image signal is first sorted into a light black image signal and a dark black image signal by a light/dark distribution processing section 31 according to a light/dark distribution table, and then sent to the binarization processing section 32, respectively. It will be done. The binarization processing unit 32 binarizes the sent image signals and sends them to a head driver 33 for deep black and a head driver 33 for light black. Recording head 9B dark and 9B
Image recording is performed by driving the light.

FIG. 5 is a diagram illustrating the light/dark distribution table. In the figure, when the image signal value before the light/dark distribution is 0 to 127 (8 bits), only the light/dark recording head 9B is Driven. This is to express OD by recording many dots of light density ink and to maintain image quality by making each dot stand out. On the other hand, when the image signal value before the light/dark distribution is in the range of 128 to 255, the image signal value after the light/dark distribution for the recording head 9B light will increase as the image signal value before the light/dark distribution increases. It will continue to decrease. The reason is that the image signal value before light/dark distribution is 128~
In 255, the recording head 9 is used to express the OD.
The recording amount of dark black ink is increased by increasing the image signal value after the light and dark distribution for dark B, but at this time, unless the recording amount of light black ink is decreased, the ink recording amount will be decreased. This is because the ink capacity of the recording material 5 will be exceeded, resulting in ink overflow.

Furthermore, as shown in FIG. 5, the amount of light black ink used is approximately twice the amount of dark black ink used. The reason for this is that the area surrounded by the image signal value for the light recording head 9B shown by the horizontal axis (X-axis) and vertical axis (Y-axis) and the solid line in FIG. The ratio to the area surrounded by the dark image signal value of the recording head 9B is approximately 2:1.
This is because.

As explained above, in an inkjet recording device that uses light black ink and dark black ink to improve graininess in highlight areas, the amount used varies depending on the density of each ink. Unlike,
Therefore, the difference in usage frequency between the light and dark recording heads 9B dark and 9B light becomes large. Therefore, in a frequently used print head, there is a higher probability that image density fluctuations will occur due to temperature rise than in a less frequently used print head. Therefore, as shown in FIG. 3, by providing heat dissipation fins 11 on the frequently used dark side of the recording head 9B to increase the heat dissipation capability, it is possible to realize image recording without fluctuations in image density. Note that the setting of the temperature adjustment ability as described above is performed in the same manner for cyan and magenta dark and light inks as well as black light and dark ink.

FIGS. 6 and 7 are print head layout diagrams showing another embodiment in which the temperature of the print head 9 is adjusted by forced cooling using a cooling fan. In FIGS. 6 and 7, when forced cooling is performed using the cooling fan 51, cooling air is mainly blown to the recording heads 9C dark, 9M dark, 9Y dark, and 9B dark for dark ink. It is configured. For example, as shown in FIGS. 6 and 7, when a single cooling fan 51 performs forced air cooling for a plurality of recording heads 9 with dark and light inks in order to reduce costs, a dark ink recording head and a light ink recording head are By setting the air volume ratio of the cooling air to m:n (m>n), the number and capacity of cooling fans can be kept to the minimum required compared to the case where the air volume ratio is 1:1, simplifying the configuration. And we were able to effectively realize cost reductions. In addition,
The configuration of FIG. 7 shows a case where the air volume ratio is m>n=0.

FIG. 8 is a perspective view of a main part showing still another embodiment in which the present invention is applied to a full-line type thermal recording head 9. In FIG. 8, for the sake of clarity, only the dark black, light black, dark magenta, and light magenta recording heads are shown. In FIG. 8, each recording head has a heat pipe 61.
is provided. Therefore, the dark ink recording head 9B
A radiation fin 62 and a radiation fan 63 are provided at one end of the heat pipe 61 for the dark and 9M dark colors, and the radiation fins and fan 63 are also omitted for the light ink recording heads 9B light and 9M light. With the configuration of this embodiment, image quality can be maintained by differentiating the temperature adjustment capabilities of the recording heads for dark and light inks of similar colors, and cost can be significantly reduced by omitting heat dissipation fins and heat dissipation fans. An achievable thermal recording means configuration has been obtained.

Note that the present invention is applicable to a thermal recording device having a thermal recording means that performs recording using thermal energy.
Of course, it can be applied to thermal type, thermal transfer type, etc.
Among these, it brings about an excellent effect in an inkjet recording apparatus having a thermal recording means of a type that discharges ink using thermal energy. This is because, according to such a system, higher recording density and higher definition can be achieved.

For its typical configuration and principle, see, for example, US Pat. Nos. 4,723,129 and 4,740.
Preferably, this is done using the basic principles disclosed in the '796 specification. This method can be applied to both the so-called on-demand type and continuous type, but
In particular, in the case of the on-demand type, the electrothermal transducer placed corresponding to the sheet holding the liquid (ink) or the liquid path is required to respond to the recorded information and rapidly exceed nucleate boiling. By applying at least one drive signal that causes a temperature increase, the electrothermal transducer generates thermal energy that causes film boiling on the heat-active surface of the recording means (recording head), resulting in a pair of It is effective because it can form bubbles in the liquid (ink).

The growth and contraction of the bubble causes liquid (ink) to be ejected through the ejection opening to form at least one drop. It is more preferable to use this drive signal in a pulse form, since the growth and contraction of bubbles can be carried out immediately and appropriately, so that ejection of liquid (ink) with particularly excellent responsiveness can be achieved. This pulse-shaped drive signal is described in US Pat.
Those described in Japanese Patent No. 463359 and Japanese Patent No. 4345262 are suitable. Incidentally, US Pat.
If the conditions described in No. 24 are adopted, even more excellent recording can be achieved.

[0024] In addition to the configuration of the recording head that combines ejection ports, liquid paths, and electrothermal converters (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4 disclose a configuration in which a heat acting part is arranged in a bending region.
A configuration using the specification of No. 459600 is also included in the present invention. In addition, Japanese Patent Application Laid-open No. 123670 of 1982 discloses a configuration in which a common slit is used as a discharge part for a plurality of electrothermal converters, and a hole that absorbs pressure waves of thermal energy is disclosed. The present invention is also effective as a configuration based on Japanese Patent Application Laid-Open No. 138461 of 1981, which discloses a configuration in which a discharge portion corresponds to a discharge portion. That is, regardless of the form of the recording head, according to the present invention, recording can be performed reliably and efficiently.

Furthermore, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium that can be recorded by a recording apparatus. Such a recording head may have a configuration in which the length is satisfied by a combination of a plurality of recording heads, or a configuration as a single recording head formed integrally. In addition, even with the serial type shown in the example above, the recording head is fixed to the device body, or by being attached to the device body, electrical connection to the device body and ink supply from the device body is possible. The present invention is also effective when using a replaceable chip type recording head or a cartridge type recording head in which an ink tank is integrally provided in the recording head itself.

Further, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc., which are provided as a configuration of the recording apparatus, to the present invention because the effects of the present invention can be further stabilized. Specifically, these are:
Capping means, cleaning means, pressure or suction means, preheating means using an electrothermal transducer or another heating element, or a combination thereof, and ejection other than recording for the recording head. It is also effective to perform a preliminary ejection mode to perform stable printing.

Regarding the type and number of recording heads to be mounted, for example, in addition to one that corresponds to single-color ink, there are also configurations that correspond to multiple inks with different recording colors and densities. A plurality of them may be provided. That is, for example, the recording mode of the recording device is not only a recording mode for mainstream colors such as black, but also a recording mode for only mainstream colors such as black.
The recording head may be configured integrally or in combination, but the present invention is also extremely effective for devices equipped with at least one of multiple colors of different colors or full color by mixing colors.

In addition, in the embodiments of the present invention described above, the ink is described as a liquid, but ink that solidifies at room temperature or below, softens or liquefies at room temperature, or ink jet In this method, the temperature of the ink itself is generally adjusted within the range of 30°C to 70°C to keep the viscosity of the ink within the stable ejection range. Any liquid may be used. In addition, the temperature rise caused by thermal energy can be actively prevented by using it as energy to change the state of the ink from a solid state to a liquid state, or ink that solidifies when left unused is used to prevent ink evaporation. In any case, the ink is liquefied by applying thermal energy according to the recording signal, and the liquid ink is ejected, or the ink already begins to solidify by the time it reaches the recording medium. The present invention is also applicable when using ink that is liquefied only by thermal energy.

[0029] The ink used in such a case is disclosed in Japanese Patent Application Laid-Open No. 1986-
56847 or Japanese Unexamined Patent Publication No. 60-71260, a form in which the porous sheet is held as a liquid or solid in the recesses or through holes and faces the electrothermal converter. You can also use it as In the present invention, the most effective method for each of the above-mentioned inks is to implement the above-mentioned film boiling method.

In addition, the inkjet recording device according to the present invention can be used as an image output terminal for information processing equipment such as a computer, a copying device combined with a reader, etc., and a facsimile device having a transmitting/receiving function. It may also take the form of

[0031]

As is clear from the above description, according to the present invention, in a thermal recording device having a plurality of thermal recording means for recording with recording materials of similar colors and different densities, the thermal recording means of said similar colors are Since the temperature adjustment capability is made different between the two, a thermal recording device is provided that can reduce the size and cost of the temperature adjustment means while maintaining image quality.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing the configuration of main parts of an embodiment of a thermal recording device to which the present invention is applied.

FIG. 2 is a partial perspective view schematically showing the structure of an ink ejection section of the recording means in FIG. 1;

FIG. 3 is a partial front view showing the arrangement of each recording means in FIG. 1;

FIG. 4 is a block diagram illustrating the configuration of an image processing device of the thermal recording device in FIG. 1;

FIG. 5 is a table for allocating shades of image signals in the image processing device of FIG. 4;

FIG. 6 is a partial front view showing the arrangement of recording means of a second embodiment of a thermal recording device to which the present invention is applied.

7 is a partial front view showing a configuration example in which the second embodiment of FIG. 6 is partially modified; FIG.

FIG. 8 is a partial perspective view showing the configuration of main parts of an embodiment of a line-type thermal recording device to which the present invention is applied.

[Explanation of symbols]

3 Conveyance roller pair 4 Conveyance motor (paper feed motor) 5
Recording material 8 Carriage 9 Thermal recording means (thermal recording head) 11
Heat dissipation fin 20 Ink discharge section 21 Discharge port forming surface 22 Discharge port 25 Electrothermal converter 31 Light/dark distribution processing section 32 Binarization processing section 51 Heat dissipation fan 61 Heat pipe 62 Heat dissipation fin 63 Heat dissipation fan

Claims (3)

[Claims] Claim 1. A thermal recording device having a plurality of thermal recording means for recording with recording materials of similar colors and different densities,
A thermal recording device characterized in that the thermal recording means of similar colors have different temperature control abilities. 2. The thermal recording apparatus according to claim 1, wherein the thermal recording means is an inkjet recording means equipped with an electrothermal converter for generating thermal energy for ink ejection. 3. The thermal recording device according to claim 2, wherein the thermal recording means ejects the ink from the ejection port by utilizing film boiling that occurs in the ink due to thermal energy applied by the electrothermal converter. Recording device.