JP2001328248A - Image forming device and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device and an image forming method, capable of obtaining an image with a high glossiness by certainly fixing an ink on a sheet without limitation of the sheet or the ink to be used. SOLUTION: An image forming device comprises a fixing part 13 for fixing an image formed on a sheet P onto the sheet P. The fixing part 13 comprises a heating roller 31 and a supporting roller 32 for heating an ink and the sheet P in a first region as well as for pressing the ink onto the recording medium in the first region, and a cooling roller 43 for discharging the heat of the ink and the sheet P in a second region after the heating and pressing operation. The second region is provided between the first region and a peeling point C in the sheet P conveyance direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus and an image forming method for forming an image on a recording medium such as recording paper (hereinafter, referred to as a sheet) based on image data input from the outside. In particular, the present invention relates to an image forming apparatus and an image forming method of an ink jet system.

[0002]

2. Description of the Related Art Hitherto, an image forming apparatus for outputting (printing) a digital image input from the outside to a sheet has been developed, and various configurations have been proposed. Here, the above digital image is, for example, an image taken by a digital camera or an image created and processed by a personal computer.

As an image output system in such an image forming apparatus, there are a thermal system, a thermal transfer system, a laser printing system, and the like. In addition, there is an ink jet system in which ink is directly ejected onto recording paper. In particular, the ink-jet method has the advantages that the running cost of the apparatus (ink-jet printer) is low and the quietness during image output is excellent. In addition, due to recent advances in technology, the quality of images output by inkjet printers has also become sufficiently high, and their applications are gradually expanding.

[0004]

By the way, in the conventional ink jet printer, most of the fixing of the discharged ink (image) to the sheet mainly depends on natural drying. In image fixing by natural drying, the glossiness of the output image depends on the characteristics of the sheet and ink used.

For example, when a sheet having a rough surface such as a silk-like photograph is used, the glossiness of an image is deteriorated. Also,
When a sheet having good ink absorbency is used, the surface of the ink constituting the image becomes flat (because the surface irregularities of the ink are reduced), so that irregular reflection on the image surface is reduced and the glossiness is improved. In addition, when ink having large particles (molecules) is used, the ink absorbency of the sheet deteriorates and the ink swells, so that irregular reflection on the ink surface increases and the glossiness deteriorates.

Therefore, in order to improve the glossiness of an image, it is necessary to use a sheet having a small surface roughness and good ink absorptivity, or use an ink having small particles. Is restricted.

As a method for avoiding the above-mentioned inconvenience, for example, a heat roller system in which an image is forcibly fixed to a sheet by heating and softening the ink by bringing a heat roller into contact with an ink surface on the sheet. Can be considered. In this method, the surface of the printed material is heated and pressurized at a predetermined fixing temperature by a heat roller to melt the coating layer and the ink on the surface of the sheet and press-heat the ink, thereby flattening the ink surface. As described above, according to the heat roller method, it is considered that a desired glossiness can be obtained regardless of the type of sheet used.

[0008] In addition to the above heat roller method, as a method for forcibly fixing an image on a sheet as described above, a printed material is heated by using a fixing belt stretched over a plurality of rollers instead of a heat roller. A belt fixing method in which pressure is applied is used.

However, in each of the above methods, if the sheet is instantaneously peeled off from the heat roller or the fixing belt after the image is fixed at the fixing temperature, a high-temperature offset occurs in which the ink adheres to the heat roller or the fixing belt. . This is because near the fixing temperature, the temperature of the ink becomes high and the viscosity of the ink decreases, and the ink not only adheres to the sheet but also easily adheres to the fixing belt. This is because the adhesion of the ink to the sheet and the adhesion (cohesion) between the inks are reduced.

Further, even when the ink temperature does not reach the vicinity of the fixing temperature, in a temperature region where the attraction force between the inks and the fixing force between the ink and the sheet are relatively low, the surface of the ink at the time of peeling of the sheet is reduced. A phenomenon of vandalism occurs.

On the other hand, when the fixing temperature is relatively low, the ink is insufficiently melted, and the ink fixing force to the sheet and the ink adsorbing force are insufficient, so that the ink adheres to the fixing belt (offset transfer). ) Occurs.

As described above, in the conventional image forming apparatus, the sheet is separated from the fixing belt in an inappropriate temperature range, so that the ink is not sufficiently fixed and the ink surface is roughened when the sheet is separated. As a result, there is a problem that the glossiness of the image is reduced and the image quality is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to reliably fix ink on a sheet without limiting the sheet or ink to be used. An object of the present invention is to provide an image forming apparatus and an image forming method capable of obtaining a high image.

[0014]

According to a first aspect of the present invention, there is provided an image forming apparatus for forming an image on a recording medium using ink to solve the above-mentioned problems. Fixing means for fixing the image formed on the recording medium to the recording medium, wherein the fixing means heats the ink constituting the image and the recording medium in a first area, and applies the ink to the first area. And a heat radiating means for radiating the ink and the recording medium to a predetermined temperature range in a second area, wherein the second area is provided with: In the transport direction of the recording medium, the first area is provided between the ink and the recording medium at a peeling position where the ink and the recording medium are peeled off from the thermocompression contact surface in contact with the first area. Is

According to the above arrangement, the image formed on the recording medium is fixed to the recording medium by the fixing means, for example, by means of forming an image by discharging ink. The fixing unit includes a thermocompression unit (for example, a heater, a heating roller, and a support roller). The image and the recording medium are thermocompressed in the first area to form the image on the recording medium. Is established.

Since the surface of the ink on the recording medium is flattened by the heating and pressing by the heating and pressing unit, irregular reflection of light on the ink surface is suppressed. This makes it possible to impart gloss to an image formed on the recording medium, regardless of the type of recording medium or ink used.

Further, the fixing means further includes a heat radiating means (for example, a cooling roller in which a refrigerant is circulated along a rotation axis), and the ink and the recording medium are heated and pressed by the heating and pressing means. In the second area, heat is radiated by the heat radiating means until the temperature reaches a predetermined temperature area. Further, the second area includes, in the transport direction of the recording medium, the first area, the ink and the recording medium being the first area.
In the region, a portion is provided between the heat-pressing surface and the peeling position where the contact is made. Therefore, since the ink and the recording medium reach the predetermined temperature range and are separated from the abutting surface at the time of the heat and pressure bonding, the temperature range falls within a temperature range suitable for fixing, for example. By appropriately setting the ink, the ink can be reliably fixed to the recording medium, and a situation in which the ink peels from the recording medium can be avoided. As a result, it is possible to reliably avoid reverse transfer of the ink to a member (for example, a heating roller) that comes into contact with the ink during thermocompression bonding, that is, the offset phenomenon.

According to a second aspect of the present invention, in order to solve the above-mentioned problems, the heat-pressing means are provided to face each other, and rotate in opposite directions to pinch and convey the recording medium. And a pair of rotating rollers that form the first region according to their contact positions, and a driven roller rotatably provided with one of the pair of rotating rollers, A fixing belt that conveys the recording medium in the conveying direction, and the second area is provided on the fixing belt downstream of the first area in the conveying direction.

According to the above configuration, the pressure bonding in the first region can be realized by the set of rotating rollers, the fixing belt is provided, and the fixing belt is provided. By providing the second area on the downstream side in the transport direction of the first area, the second area is provided.
Can be realized in the region of (1).

According to a third aspect of the present invention, in order to solve the above-mentioned problem, the heat radiating means includes the fixing belt forming the second area.

According to the above arrangement, the heat radiating means includes the fixing belt, so that the ink and the recording medium abut on the fixing belt moved from the first area to the second area. The heat radiation is completed while the recording medium is transported. Therefore, without separately providing heat dissipation means,
Since the heat can be dissipated, the configuration of the device itself constituting the fixing unit can be simplified.

According to a fourth aspect of the present invention, in order to solve the above-mentioned problem, the fixing unit separates the recording medium at the separation position by using a curvature of the driven roller. .

According to the above arrangement, since the recording medium is separated at the separation position by using the curvature of the driven roller, there is no need to separately provide a separation claw or the like. The configuration of itself can be simplified.

According to a fifth aspect of the present invention, in order to solve the above-mentioned problems, the heat radiating means includes a cooling roller which is in contact with the fixing belt and radiates the ink and the recording medium with a refrigerant. And

According to the above arrangement, not only the fixing belt forming the second region but also a cooling roller as a heat radiating means is provided, so that the ink and the recording medium can be more reliably moved to the peeling position. It is possible to lower the temperature to a predetermined temperature range.

According to a sixth aspect of the present invention, in the image forming apparatus, the predetermined temperature range is determined by comparing the ink and the recording medium with each other by comparing the adhesive force between the ink and the thermocompression unit. It is characterized by a release temperature range in which the adhesion force between the ink and the medium and the attraction force between the inks are increased.

According to the above arrangement, the adhesion between the ink and the recording medium and the adsorption between the inks are larger than the adhesion between the ink and the thermocompression unit. In such a temperature range, the ink and the recording medium are separated from the thermocompression-bonded surface. For this reason, it is possible to prevent high-temperature offset due to the attraction force between the inks and the adhesion force between the ink and the recording medium being smaller than the adhesion force between the ink and the thermocompression unit. In addition, it is possible to avoid a phenomenon in which the ink surface is damaged by peeling and the gloss of the ink surface is reduced. Further, the attraction force between the inks and the fixing force between the ink and the recording medium become insufficient, so that the ink is not sufficiently fixed to the recording medium, and the ink is relatively fixed between the ink and the thermocompression unit. Can be prevented from being offset at a low temperature due to an increase in the adhesive force.

According to a seventh aspect of the present invention, there is provided an image forming method comprising: a first step of forming an image on a recording medium using ink; and an ink forming the image and the recording medium. And a third step of radiating the ink and the recording medium to a predetermined temperature range after the second step,
After the third step, the ink and the recording medium are separated from the thermocompression bonding surface.

According to the above configuration, the ink constituting the image formed on the recording medium is heated and pressed against the recording medium, so that the image is fixed on the recording medium. The thermocompression bonding can be realized by, for example, providing a heater inside the heating roller, sandwiching the recording medium between the heating roller and the support roller, and pressing one roller against the other roller.

Since the surface of the ink on the recording medium is flattened by the heat and pressure bonding, irregular reflection of light on the surface of the ink is suppressed. This makes it possible to impart gloss to an image formed on the recording medium, regardless of the type of recording medium or ink used.

Further, in the above configuration, after the ink and the recording medium are thermocompression-bonded and before the ink and the recording medium are separated from the thermocompression bonding surface, the ink and the recording medium reach a predetermined temperature range. Heat is dissipated. Therefore, by appropriately setting the predetermined temperature range to fall within a temperature range suitable for fixing, for example, a transfer offset at the time of peeling can be reliably avoided, and damage to the ink surface due to peeling can be prevented. As a result, reverse transfer of the ink to a member (for example, a heating roller) that comes into contact with the ink at the time of thermocompression bonding,
That is, it is possible to reliably avoid the offset phenomenon.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
The following is a description based on the drawings.

FIG. 2 is an explanatory diagram showing the configuration of an image output system according to the present embodiment (hereinafter referred to as the present image output system). This image output system outputs an image to a predetermined recording medium based on an image or image data input from the outside. As shown in FIG. 1, the inkjet printer 1 (image forming apparatus), The apparatus includes a device 2, a film scanner 3, an image processing device 4, and a monitor 5.

In this embodiment, as a recording medium,
A case in which sheet-shaped paper cut into a predetermined size (hereinafter simply referred to as a sheet) will be described.
The present invention can be applied to a case where roll-shaped paper is used.

First, each configuration of the image output system will be described.

The ink jet printer 1 forms an image on a sheet based on input image data, and is a characteristic configuration of the present image output system. The detailed configuration of the inkjet printer 1 will be described later.

The image reading device 2 has a compact flash (registered trademark) 6 which is a semiconductor memory card. The image reading device 2 reads image data recorded on the compact flash 6 and outputs the image data to the image processing device 4. .

The image data read by the image reading device 2 is obtained, for example, by photographing with a digital camera or image processing with a personal computer. The image reading device 2 has a function of reading image data recorded on a recording medium other than the compact flash 6.

The film scanner 3 is for generating image data corresponding to a negative or positive original image recorded on the film 7, and is a kind of image reading device. That is, the film scanner 3 is set to read the original image by scanning the film 7, generate image data corresponding to the original image, and output the image data to the image processing device 4.

The image processing device 4 performs predetermined processing on input image data and outputs the processed image data to the ink jet printer 1. That is, the image processing device 4 performs image processing on image data input from the image reading device 2 or the film scanner 3 and converts the image data into a form that can be processed by the inkjet printer 1. Then, it is set so that the image data after the image processing is output to the inkjet printer 1 or the monitor 5.

The image processing performed by the image processing device 4 includes, for example, converting image data in RGB (Red, Green, Blue) format into YMC (Yellow, Magenta, Cyan) suitable for ink output.
There are a process of converting to a format, an edge emphasizing process for emphasizing the outline of an image, a red correcting process, and the like.

Further, the image processing device 4 also has a function as a central unit for controlling all operations in the present image output system.

The monitor 5 inputs image data processed by the image processing apparatus 4 and displays an image corresponding to the data. Thus, the user can confirm the form of the image data after the processing and determine the necessity of further image processing.

Next, the configuration of the ink jet printer 1 will be described.

FIG. 3 is an explanatory diagram showing the structure of the ink jet printer 1. The ink-jet printer 1 performs Y-based printing based on the image data input from the image processing device 4.
A color image is output on a sheet by ejecting three color pigment-based inks composed of MCs. As shown in the drawing, a sheet supply unit 11, an image forming unit 12, and a fixing unit 13 are provided.
(Fixing means) and a paper discharge unit 27.

The sheet supply section 11 supplies a sheet P for outputting an image to the image forming section 12, and as shown in the drawing, a sheet cassette 21 for storing the sheet P, and a sheet cassette The transport rollers 22a and 22b for sending out the sheet P from the printer 21 are provided.

The image forming section 12 forms an image on the sheet P supplied from the sheet supply section 11 using ink, and includes an ink discharge section 23 for discharging ink onto the sheet P in accordance with image data. Have multiple.

The ink discharge section 23 is an on-demand type recording head, and is provided for each color of YMC. Each of the ink discharge sections 23 has a plurality of ink discharge ports (not shown) arranged in a line. These ink discharge ports have an image resolution of, for example, 400 dpi.
(dots per inch) so as to correspond to each dot constituting the image.

The ink discharge section 23 is configured to be able to control the image density by changing the ink discharge amount for each dot. That is, in the ink ejection unit 23, while the amount of ink ejected from each ink ejection port at one time is fixed, the number of ejections of each ink ejection port is changed for each dot, thereby ejecting each dot. The total amount of ink is changed for each dot.

Therefore, ink is overprinted on the dots corresponding to the high-density portions, and as shown in FIG.
Has a size corresponding to the number of times of ink ejection.

In the ink discharge section 23, the discharge amount of ink for each dot is controlled in, for example, 16 steps. Therefore, the image formed by the image forming unit 12 is expressed in 16 gradations. Note that the method of controlling the ink ejection amount and the number of gradations are not limited to the above.

The fixing section 13 fixes the image formed by the image forming section 12 on the sheet P, and is the most characteristic part of the ink jet printer 1 of the present invention. Specifically, the fixing unit 13 includes a heating unit 26 as shown in FIG.

The heating unit 26 (heating and pressing means) heats and presses the ink constituting the image and the sheet P and presses the ink onto the sheet P. The heating roller 31 and the support roller 32 are set so as to convey the sheet P in the sheet conveying direction shown in FIG. Hereinafter, each component of the heating unit 26 will be described in detail.

FIG. 1 is an explanatory diagram showing a schematic configuration of the heating unit 26. As shown in FIG. 1, the heating unit 26 has a configuration in which a heating roller 31 and a driven roller 41 (for example, made of rubber or the like) stretch a belt 42 (fixing belt) having a surface formed seamlessly. ing. A cooling roller 43 is provided inside the belt 42, that is, on the surface (back side surface) opposite to the contact surface with the sheet P, which is located between the heating roller 31 and the driven roller 41 on the transport direction side. It is provided in contact. Further, as shown in FIG.
A cleaning roller 44 for removing dust from the surface of the belt 42 is provided at an appropriate position on the front side surface (front surface) of the belt 42, that is, on the contact surface side with the sheet P. The cleaning roller 44 cleans the surface of the belt 42 and
In order to facilitate the peeling of the sheet P, a release agent such as silicone or a cleaning agent can be applied to the surface of the belt 42 as needed.

As shown in FIG. 1, the heating roller 31 is a hollow roller having a diameter of, for example, 50 mm and a length of 6 to 14 inches in the direction of the rotation axis, and is a roller for pressing the ink on the sheet P onto the sheet P. It is. Inside the heating roller 31, a rod-shaped heater 31a extending in the rotation axis direction of the heating roller 31 is provided. The heater 31a is energized and heated by electric power supplied from the outside, so that
It emits heat (radiant heat) together with light. For example, halogen lamps and flash lamps (xenon lamps)
Can be configured.

Here, the light emitted from the heater 31a refers to an electromagnetic wave having a wavelength range of about 1 nm to 1 mm. Therefore, the light may be visible light, infrared light, or the like.

The material for forming the heating roller 31 is as follows.
For example, glass or a transparent heat-resistant resin can be used. Examples of the transparent heat-resistant resin include PFA (ethylene tetrafluoride-perfluoroalkyl vinyl ether copolymer resin), FEP (polytetrafluoride-hexafluoroethylene), and E
There are fluorine resins such as TFE (ethylene-tetrafluoroethylene resin) and heat-transmissive materials (light-transmissive materials) such as PC (polycarbonate).

In this embodiment, the surface of the heating roller 31 is coated with fluorine (for example, PFA, FEP, E
TFE coating). This is to make the surface of the heating roller 31 smooth and to impart water repellency and oil repellency to the surface. In the ink jet printer 1, the surface roughness of the heating roller 31 is set such that Rmax (maximum height of the convex portion on the surface) ≦ 1 μm by the fluorine coating.

The support roller 32 has a diameter of 30 to 50 mm,
A roller having a length in the rotation axis direction of 6 to 15 inches, and faces the heating roller 31 so that the sheet P can be sandwiched between the heating roller 31 and the support roller 32 to press the ink onto the sheet P. Is located in the position. As a material for forming the support roller 32, for example, a metal such as aluminum or a resin such as rubber having a surface roughness Rmax ≦ 1 μm can be used.

When the heating roller 31 is made of glass, the supporting roller 32 is preferably made of resin.
When the heating roller 31 is made of the above-described heat permeable resin, the support roller 32 is preferably made of a hard roller such as a metal. When the heating roller 31 and the supporting roller 32 are both hard rollers made of glass or metal, the heating roller 31 and the supporting roller 32 come into contact with each other in a state of almost linear contact in the rotation axis direction, and the ink is pressed onto the sheet P. Is performed in a line shape, so that the efficiency of pressure bonding of the ink to the sheet P decreases.

In this embodiment, at least one of the heating roller 31 and the supporting roller 32 is made of resin, and as shown in FIG. 1, the contact portion between the heating roller 31 and the supporting roller 32 is a line. Instead, a so-called nip forming portion is formed. Therefore, since the ink can be two-dimensionally pressed on the sheet P at the nip forming portion, the pressure can be reliably performed.
As described above, the ink and the sheet P are heated by the radiant heat from the heater 31a, and at the same time, the heating roller 31 and the support roller 32 allow the ink on the sheet P to be heated and pressed on the sheet P in an area such as a nip forming portion. To
It is referred to as a thermocompression bonding area B (first area).

The support roller 32 can be moved up and down by a pressure control mechanism (not shown).
The pressure control mechanism controls the pressure applied to the sheet P passing between the heating roller 31 and the support roller 32 by adjusting the position of the support roller 32.

The pressure value applied to the sheet P by the heating roller 31 and the supporting roller 32 is ensured until the sheet P is separated (peeled) from the belt 42 in the heat radiation area A described in detail below. The temperature of the sheet P falls within a predetermined range where the temperature falls to a release temperature range (described later).
Is preferably determined based on factors such as the conveyance speed of the sheet P, the hardness of the material used for the heating roller 31 and the support roller 32, and the material of the sheet P. In relation to the material of the sheet P, for example, when a soft sheet P is used, it is preferable to use a relatively weak pressure value. Therefore, hereinafter, a range of a preferable pressure value determined according to each of the above factors is referred to as a first pressure range. Note that the first pressure range can be, for example, about 2-3 kg / cm ² .

Next, the heat radiation area A (second area), which is a feature of the ink jet printer 1 of the present embodiment, will be described in detail below.

In this embodiment, the heat radiation area A is
The point shown in FIG. 1, that is, the point downstream of the heat-compression bonding area B formed of the nip forming part in the conveying direction and where the leading end of the sheet P in the sheet conveying direction starts to separate from the belt 42 (separating point C, Position) to the area of the surface of the belt 42 up to the position. That is, while the sheet P heated and pressed in the heat-compression region B is being conveyed to the heat radiation region A, the surface of the sheet P and the ink
The two surfaces are in contact with each other.

As described above, in the heat radiating area A, in order to maintain the surface of the sheet P and the ink in contact with the surface of the belt 42, the heating unit 26 of the present embodiment employs the pressing force in the thermocompression bonding area B. Is set as a first pressure range, and the hardness of the surface material of the heating roller 31 and the support roller 32 such as rubber hardness is adjusted to be within a predetermined range. Thereby, the sheet P subjected to the heat-compression bonding in the heat-compression bonding area B is
The sheet P and the ink are conveyed so as not to be separated from the surface of the belt 42 in the heat radiation area A, and the sheet P and the ink are radiated while always in contact with the belt 42. I do.

In the above configuration, the belt 42 in the heat radiation area A
When the contact surface contacts the ink and the sheet P, the heat applied to the ink and the sheet P is radiated by a predetermined amount in the thermocompression bonding area B, and the temperature of the sheet P and the ink is reduced to the release temperature area. After that, the sheet P can be peeled from the belt 42. The release temperature range is a temperature range in which a high-temperature offset or a low-temperature offset does not occur.
This is a temperature region where the cohesion between inks and the adhesion between the ink and the sheet P are greater. The release temperature range will be further described later.

The distance of the heat radiation area A along the sheet conveying direction depends on the type of the material used for the belt 42, the sheet P, and the ink, the pressure value at the time of heat compression, the sheet conveying speed, and the like. The temperature can be appropriately set within a range where a temperature range can be obtained.

Further, as shown in FIG. 1, in the present embodiment, a cooling roller 43 (heat radiating means) is provided at an appropriate position in the heat radiating area A so as to contact the back side surface of the belt 42. By providing the cooling roller 43, the cooling roller 4
3 cools the surface of the belt 42 (contact surface) and the contact surface between the ink and the sheet P in the heat radiation area A. Cooling roller 43
Is supplied with a coolant such as cooling oil or water from a cooling device (not shown), and the supply amount is appropriately adjusted according to the sheet conveyance speed. Thus, even when the sheet conveyance speed is high, the ink and the sheet P
Can be reliably lowered to the mold release temperature range.

The position of the cooling roller 43 in the sheet conveying direction is not particularly limited.
In the case where the fixing unit 13 is installed in the heat radiation area A in the vicinity of 1, there is an advantage that the fixing unit 13 itself can be reduced in size, but a cooling device having a high cooling effect is required.

In the heating section 26 shown in FIG. 1, only the cooling roller 43 is provided as a heat radiating means. However, the heat radiating means may be provided on the driven roller 41, or may be provided on both the driven roller 41 and the cooling roller 43 in order to further improve the cooling efficiency. Also, the heat radiation means
In addition to the configuration provided on the cooling roller 43 and the driven roller 41, a configuration in which only the portion of the fixing belt 42 where the second region is formed may be used.

FIG. 4 is an explanatory diagram showing a schematic configuration of the heating section 26 in which both the driven roller 41 and the cooling roller 43 have a configuration as a heat radiating means. The heating unit 26 includes the driven roller 41 and the cooling roller 43.
In addition to the above, an air cooling device 45 is further provided as a heat radiation means.

As shown in the figure, the air cooling device 45 includes two bent plates having curved surfaces substantially parallel to each other for forming an air path along the outer periphery of the support roller 32 and the surface of the belt 42. It mainly comprises a cross roll fan 45a inserted between the two bent plates and for blowing air along the wind direction and air path indicated by the arrow. If the air cooling device 45 is used, it is possible to prevent heat from staying in the vicinity of the heat radiation area A due to the air blown by the rotation of the cross roll fan 45a, so that the heat radiation efficiency in the heat radiation area A can be further improved. .

Of the two bent plates, a brush 45b is provided at an end of the bent plate on the belt 42 side in the air blowing direction along a direction perpendicular to the sheet conveying direction on the surface of the belt 42. The tip of the brush 45b is the belt 42.
It is arranged to contact the surface. By arranging the brush 45b in this manner, it is possible to prevent the wind from leaking from the air path, to remove dust and clean the surface of the belt 42, and to remove static electricity generated near the surface of the belt 42. . At this time, a heat radiation effect due to the brush contacting the recording medium can also be obtained.

On the other hand, the cooling roller 43 and the driven roller 4
In 1, a pipe for supplying a coolant is penetrated along each rotation axis direction. As shown in the figure, the pipe is supplied to the pipe that has passed through the cooling roller 43. For example, a coolant such as cooling oil or water has passed through the driven roller 41 near both ends of the driven roller 41. And circulates in one direction through a circulation pump 46. Then, the circulating pump 4 is connected to a pipe passing through the cooling roller 43 and the driven roller 41.
The refrigerant sent to 6 radiates heat while passing near the circulation pump 46 and is reused again for heat radiation.

In the heating section 26 shown in FIG. 4, as described above, in addition to providing the cooling roller 43 and the driven roller 41 with the heat radiating means, an air cooling device 45 is further provided as the heat radiating means. As described above, a plurality of heat dissipating means may be installed in combination as needed, or a configuration in which any one or two of the above members may be installed.

Here, the release temperature range set in the heating section 26 of the present embodiment will be described below.

FIG. 5 shows the adhesive force (f1) between the ink and the belt 42 in the heating unit 26,
(F2) and the attraction (f
3) is an explanatory diagram for explaining (3). FIG. As mentioned above,
If f1 is larger than f2 or f3, a high or low temperature offset may occur. Accordingly, the release temperature range specifically means a temperature range in which f2 and f3 are larger than f1.

As described above, the ink used in the ink jet printer 1 is a pigment-based ink. Such an ink contains a binder resin (resin) for binding pigments together. The temperature at which the binder resin dissolves (the melting point of the resin) is called the softening point of the ink.

That is, when the ink reaches the softening point, the binder resin melts and becomes jelly-like, and a part of the jelly penetrates into the sheet P, so that the bonding state between the ink and the sheet P improves, that is, f2 increases. As a result, the fixability of the image is increased. Further, in this state, deformation due to pressure is likely to occur. The softening point of the ink changes depending on the ratio and material of the binder resin.

However, even when the ink is at or above the softening point as described above, the temperature of the ink and sheet P (fixing temperature) at the time of heating and pressing is high, so that the ink and sheet P When the temperature of the ink and the sheet P at the time of peeling from the ink is too high, the viscosity of the ink is reduced, so that the attraction force f3 between the inks is relatively smaller than the adhesion force f1 between the ink and the belt 42. Weakened. For this reason, at the time of peeling, a high-temperature offset in which the ink adheres to the surface of the belt 42 occurs.

Even if the temperature at the time of peeling is not high enough to cause high-temperature offset, f
In a temperature range where f2 and f3 are smaller than 1, the ink surface is damaged by peeling, and the gloss of the ink surface is reduced.

On the other hand, since the temperature at the time of peeling is low, the ink cannot sufficiently reach the softening point. In such a state, since f2 is insufficient, the ink is not sufficiently fixed on the sheet P, and f1 becomes relatively large, so that a low-temperature offset can occur. That is,
If the temperature range at the time of peeling is not the release temperature range where f2 and f3 are larger than f1, transfer offset and damage to the ink surface will occur.

FIG. 6 shows the conveyance time of the sheet P in the ink jet printer 1 of this embodiment and the temperature of the contact portion between the surface of the belt 42 and the ink or the sheet (hereinafter, referred to as “belt-ink contact portion temperature”). 6 is a graph showing a relationship with the graph. In the figure, the horizontal axis represents a conveyance time (zero time in the figure, where the time when the leading end of the sheet P in the conveyance direction is conveyed to the thermocompression bonding area B is zero when the sheet conveyance speed is constant). Shown).

First, in the range indicated by B in the figure, the sheet P is conveyed to the thermocompression bonding area B, and the ink and the sheet P are thermocompression bonded, so that the temperature of the belt-ink contact portion gradually increases. In the thermocompression bonding area B,
The belt-ink contact portion is heated by the heater 31a, and its temperature becomes equal to or higher than the ink softening point.
After the temperature rises to 30 ° C., it is transported to the heat radiation area A (indicated by “A” in the figure). At the time of being transferred to the heat radiation area A,
The sheet P does not peel off from the surface of the belt 42 and maintains a state of contact. Then, in the heat radiation area A, the temperature of the ink and the sheet P gradually decreases due to the action of the heat radiation means, and the temperature of the belt-ink contact portion falls to 60 ° C. which is within the mold release temperature area.

Next, when the leading end of the sheet P in the conveying direction has passed the separation point C, the sheet P starts to be separated from the surface of the belt 42. That is, in FIG. 6, the heating unit 26 is set so that the belt-ink contact portion temperature at the time when the leading end of the sheet P in the conveyance direction passes the peeling point C, that is, at the time of peeling, is within the release temperature range. I have. In the range referred to as the “peeling portion” in the drawing, the leading end of the sheet P in the conveyance direction is peeled from the surface of the belt 42, and the fixing of the ink is completed. In this way, by peeling the sheet P in the release temperature range where f2 and f3 are larger than f1, high-temperature or low-temperature offset and damage to the ink surface at the time of peeling can be prevented, and the image quality is improved. be able to.

In the example of FIG. 6, the release temperature range is around 60 ° C. The release temperature range depends on the type of sheet P used,
Although it varies depending on the transport speed, the material of the surface of the belt 42, and the like, it is generally in the range of 50 to 20 ° C.

In the present embodiment, the transport rollers of the inkjet printer 1 and the rollers of the fixing unit 13 are set to rotate at a speed desired by the user. Therefore, the transport speed of the sheet P in the inkjet printer 1 can be freely set by the user.

Next, the operation of the image output system will be described.

The operation at the time of image output processing in the ink jet printer 1 is controlled by a control unit (not shown) provided in the ink jet printer 1.

That is, when image data is input from the image processing device 4, the control unit controls the transport rollers 22a and 22b.
Is controlled to take out the sheet P from the paper cassette 21 and transport the sheet P to the image forming unit 12.

Next, the control unit controls the image forming unit 12 based on the input image data, and forms an image corresponding to the data on the sheet P. At this time, the control unit controls the ink ejection units 23 in the image forming unit 12 to adjust the amount of ink ejected from each ink ejection port 24. Thus, the ink ejection amount is adjusted for each dot forming the image, and an image of 16 gradation display is formed. In addition, the control unit controls the fixing unit 1 by the time the image formation is completed.
The pressure control mechanism is controlled such that the pressure between the heating roller 31 and the support roller 32 in Step 3 falls within the first pressure range.

At this time, the control unit also controls the amount of power to the heater 31a based on the transport speed set in advance by the user. In other words, the control unit sets, for example, the energization amount of the heater 31a to be large when the conveyance speed of the sheet P is high and to be small when the conveyance speed of the sheet P is low. In this way, by adjusting the amount of electricity to be supplied to the heater 31a in accordance with the conveying speed of the sheet P, the amount of heat supplied per unit time in the heat-compression bonding area B is adjusted, and heat radiation corresponding to the conveying speed of the sheet P is performed. The temperature can be lowered to the release temperature range in the region A.

Next, the control unit controls a transport roller (not shown) to transport the sheet P to the heat-compression bonding area B.
Then, the sheet P is pressurized in the first pressure range while heating the ink and the sheet P by the heater 31a.
As a result, the ink on the sheet P is heated and pressed, giving gloss to the image and drying the image (ink). As described above, the heating roller 31 and the support roller 3
2 is adjusted by the control unit so as to be within the first pressure range, so that the sheet P is always in contact with the surface of the belt 42 while being conveyed through the heat radiation area A. Can be maintained.

At this time, when the sheet conveying speed is equal to or higher than a predetermined value, the control unit sends a forced cooling refrigerant (cooling) from a not-shown refrigerant supply unit into a pipe constituting a rotating shaft portion of the cooling roller 43. Oil). Further, the flow rate of the refrigerant from the refrigerant supply unit is adjusted to a predetermined amount per unit time by the control unit. Accordingly, even when the sheet conveying speed is high, the temperature of the ink and the sheet P can be reliably lowered to the release temperature range.

The control unit monitors the temperature of the peeling point C with a thermistor (not shown) disposed near the intermediate portion in the transport direction between the cooling roller 43 and the driven roller 41, and according to the temperature, Control the supply. The thermistor is set at a temperature corresponding to a release temperature range determined by the type of ink or sheet P used by the user. Thus, in the heating unit 26 of the present embodiment, the temperature control according to the type of the ink or the sheet P to be used can be performed by the operation of the control unit and the thermistor.

Finally, the control unit controls a transport roller (not shown) to store the sheet P in the paper discharge unit 27, and ends the processing.

As described above, the ink jet printer 1 in the present image output system is configured such that the sheet P on which the image is formed by the image forming unit 12 and the ink constituting the image are fixed by the fixing unit 13.

In the fixing section 13, since the ink surface on the sheet P is flattened by the heating roller 31 of the heating section 26, irregular reflection of light on the ink surface is suppressed. Thereby, gloss can be given to the image formed on the sheet P without using a specific sheet and ink.
Further, since the ink and the sheet P are forcibly heated by the fixing unit 13, the ink on the sheet P can be dried quickly and surely as compared with the case where natural drying is performed. Even if the sheets P are stacked, the image does not adhere to another sheet P. This makes it possible to improve the processing speed by stacking the sheets P one after another after discharge.

After the thermocompression bonding in the thermocompression bonding area B,
Since the sheet P is not immediately separated from the surface of the belt 42 and the temperature of the sheet P is lowered to the release temperature range in the heat radiation area A, the fixing force between the ink and the sheet P (f2)
The sheet P in a state where the suction force (f3) between the inks and the ink is larger than the adhesion force (f1) between the ink and the belt 42.
From the surface of the belt 42. This can prevent high-temperature or low-temperature offset and damage due to peeling of the ink surface, so that the glossiness can be easily improved. As a result, in the present embodiment, as a result of measurement with various types of ink and sheet P, it was found that the glossiness of the image output by inkjet printer 1 reached a gloss value of 70 or more. Have been.

Here, the gloss value is a value based on the ratio of the amount of light between the totally reflected light and the specularly reflected light on the image surface, and is a kind of index for expressing photographic image quality. Normally, the gloss value of an image output by a conventional inkjet printer is limited to about 40 to 60, which is inferior in glossiness to a photograph (a gloss value of about 80 to 100). However, since the inkjet printer 1 can output an image having a gloss value of 70 or more, it is possible to obtain an image having a gloss similar to a photograph.

In the above description, the surface roughness of the heating roller 31 and the support roller 32 is set to Rmax ≦ 1 μm, but the surface roughness of each roller is limited to a value within this range. Not something. However, it is preferable that the surface roughness of each roller is set to a sufficiently small value so that the glossiness of an image output by the inkjet printer 1 is 70 or more.

That is, since the surface roughness of each roller is directly reflected on the glossiness of the image, the glossiness of the image is 70%.
As described above, it is preferable to appropriately set the material constituting the rollers, the processing accuracy, and the like.

The glossiness of an image can also be controlled by selecting and using a roller (including a tube, a sheet, rubber, or the like) having a physically different surface roughness as each of the above rollers.

Further, in the above, various characteristics such as the material, hardness, diameter, and axial length of the heating roller 31 and the support roller 32 have been described. However, the characteristics of each roller are not limited to these values. For example, the length of each roller in the rotation axis direction may be set to be longer than the width of the sheet to be used.

In the present embodiment, the heating roller 31
Although the surface is coated with fluorine, for example, if the entire heating roller 31 is made of fluorine-based rubber, the heating roller 31 itself has water repellency. In this case, the coating of the heating roller 31 is unnecessary. .

In the present embodiment, the inkjet printer 1 forms a color image using three color pigment inks of YMC. However,
The color of the ink ejected by the inkjet printer 1 is Y
The color is not limited to the MC, and any color may be used as long as a color image can be output. Further, the setting may be made so as to output a monochrome image. Further, the ink used by the inkjet printer 1 is not limited to the pigment-based ink, but may be a dye-based ink.

In this embodiment, all operations of the image output system are performed under the control of the image processing apparatus 4. However, the present invention is not limited to this, and the image output system may be provided with a control device for controlling operations, and the control device may be set so that all operations are controlled.

In the present embodiment, the image output processing in the ink jet printer 1 is controlled by a control unit (not shown) of the ink jet printer 1. However, the image output processing may be set to be controlled by the image processing device 4 of the present image output system.

Further, a program for performing all or a part of the processing in the control unit of the image processing apparatus 4 and the ink jet printer 1 is stored in a CD-ROM (Re-
An information processing device that can be recorded on a recording medium such as an ad only memory (FD) or a floppy disk (FD) and that can read this program may be used in place of the image processing device 4 and the control unit.

Further, in the present embodiment, the ink ejection section 2
No. 3 controls the amount of ink ejected to each dot by making the amount of ink ejected at one time constant and changing the number of ejections of each ink ejection port 24 for each dot. However, the present invention is not limited to this, and the ink ejection unit 23 may be set so as to change the amount of ink ejected at one time, thereby changing the ejection amount of ink for each dot.

[0112]

According to the first aspect of the present invention, there is provided an image forming apparatus for forming an image on a recording medium using ink as described above, wherein the image formed on the recording medium is recorded on the recording medium. A fixing unit that fixes the ink on the medium, the fixing unit heats the ink constituting the image and the recording medium in a first area, and presses the ink on the recording medium in the first area. A thermocompression bonding means; and a heat radiating means for radiating the ink and the recording medium to a predetermined temperature range in a second area.
Area is the first direction in the transport direction of the recording medium.
And a peeling position where the ink and the recording medium are peeled off from the thermocompression contact surface in contact with the first region.

Therefore, the image formed on the recording medium by means for forming an image by, for example, discharging ink is fixed on the recording medium by the fixing means.
Since the surface of the ink on the recording medium is flattened by the thermocompression bonding by such a thermocompression unit, irregular reflection of light on the ink surface is suppressed. This makes it possible to impart gloss to an image formed on the recording medium, regardless of the type of recording medium or ink used.

Further, the above-mentioned fixing means further includes a heat radiating means. After the ink and the recording medium are heated and pressed by the heat and pressure bonding means, the ink and the recording medium are brought into a predetermined temperature range by the heat radiating means in the second area. Heat is dissipated until it becomes. Further, the second area is located between the first area and a peeling position where the ink and the recording medium are peeled off from the thermocompression contact surface in contact with the first area in the transport direction of the recording medium. It is provided in. Accordingly, the ink and the recording medium are separated from the contact surface that has been in contact at the position where the ink and the recording medium have reached the predetermined temperature range and are heated and pressed, so that the temperature range falls within a temperature range suitable for fixing. The ink can be reliably fixed to the recording medium by setting the value appropriately, and the situation in which the ink peels off from the recording medium can be avoided. As a result, there is an effect that the offset phenomenon can be reliably avoided.

According to a second aspect of the present invention, as described above, the heating and pressing means are provided to face each other, and rotate and rotate in opposite directions to sandwich and convey the recording medium. The recording medium is conveyed by being stretched between a pair of rotating rollers that form the first area according to the contact position and a driven roller rotatably provided with one of the rotating rollers. A fixing belt that conveys the fixing belt in the conveying direction, and the second region is provided downstream of the first region in the fixing belt in the conveying direction.

Therefore, there is an effect that the heat compression bonding in the first region and the heat radiation in the second region can be realized.

As described above, the image forming apparatus according to the third aspect is configured such that the heat radiating means includes the fixing belt forming the second area.

Therefore, since the heat radiating means includes the fixing belt, the recording medium is conveyed in a state where the ink and the recording medium are in contact with the fixing belt moved from the first area to the second area. During this time, the above heat dissipation is completed. Therefore, the heat can be dissipated without separately providing a heat dissipating means, so that the effect of simplifying the configuration of the device itself constituting the fixing means is achieved.

According to a fourth aspect of the present invention, as described above, the fixing unit separates the recording medium at the separation position by using the curvature of the driven roller.

Therefore, the recording medium is separated at the separation position by utilizing the curvature of the driven roller.
Since there is no need to separately provide a separation claw or the like, an advantage is obtained in that the configuration of the apparatus itself constituting the fixing unit can be simplified.

As described above, in the image forming apparatus according to the fifth aspect, the heat radiating means includes the cooling roller which is in contact with the fixing belt and radiates the ink and the recording medium by the refrigerant.

Therefore, by providing not only the fixing belt forming the second area but also a cooling roller as a heat radiating means, the ink and the recording medium can be more reliably brought to the predetermined temperature range until the peeling position. This has the effect that the temperature can be lowered to the maximum.

In the image forming apparatus according to the sixth aspect, as described above, the predetermined temperature range may be set between the ink and the recording medium by comparing the adhesive force between the ink and the thermocompression unit. And a releasing temperature range in which the adhering force of the ink and the attraction force of the inks are increased.

Therefore, as compared with the adhesive force between the ink and the thermocompression bonding means, the temperature range in which the adhesive force between the ink and the recording medium and the attraction force between the inks are increased. In this case, the ink and the recording medium are peeled off from the thermocompression bonding surface. For this reason, it is possible to prevent high-temperature offset due to the attraction force between the inks and the adhesion force between the ink and the recording medium being smaller than the adhesion force between the ink and the thermocompression unit. In addition, it is possible to avoid a phenomenon in which the ink surface is damaged by peeling and the gloss of the ink surface is reduced. Further, the attraction force between the inks and the fixing force between the ink and the recording medium become insufficient, so that the ink is not sufficiently fixed to the recording medium, and the ink is relatively fixed between the ink and the thermocompression unit. This has the effect of preventing low-temperature offset due to an increase in the adhesive force of the substrate.

According to the image forming method of the present invention, as described above, the first step of forming an image on a recording medium using ink, and the ink forming the image and the recording medium are heated and pressed. A second step, and after the second step, a third step of radiating the ink and the recording medium to a predetermined temperature range, and after the third step, In this configuration, the ink and the recording medium are separated from the thermocompression bonding surface.

Therefore, the ink constituting the image formed on the recording medium is heated and pressed against the recording medium, so that the image is fixed on the recording medium. The thermocompression bonding can be realized by, for example, providing a heater inside the heating roller, sandwiching the recording medium between the heating roller and the support roller, and pressing one roller against the other roller. In addition, since the surface of the ink on the recording medium is flattened by such heat compression, irregular reflection of light on the ink surface is suppressed. This makes it possible to impart gloss to an image formed on the recording medium, regardless of the type of recording medium or ink used.

Further, in the above configuration, after the ink and the recording medium are thermocompression-bonded and before the ink and the recording medium are separated from the thermocompression bonding surface, the ink and the recording medium reach a predetermined temperature range. Heat is dissipated. Therefore, by appropriately setting the predetermined temperature range so as to fall within a temperature range suitable for fixing, transfer offset at the time of peeling can be reliably avoided, and damage to the ink surface due to peeling can be prevented. As a result, there is an effect that the offset phenomenon can be reliably avoided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a heating unit provided in an ink jet printer as an image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram illustrating a schematic configuration of an image output system including the inkjet printer.

FIG. 3 is an explanatory diagram illustrating a schematic configuration of the entire inkjet printer.

FIG. 4 is an explanatory diagram illustrating a schematic configuration of a heat radiating unit provided in a heating unit of the inkjet printer.

FIG. 5 is an explanatory diagram for explaining an adhesive force between the ink and the belt, a fixing force between the ink and the sheet, and a suction force between the inks in the heating unit.

FIG. 6 is a graph showing a relationship between a sheet conveyance time and a temperature of a contact portion between the belt surface and the ink or the sheet in the inkjet printer according to the embodiment.

DESCRIPTION OF THE SYMBOLS 1 Inkjet printer (image forming apparatus) 13 Fixing unit (fixing unit) 26 Heating unit (heating and pressing unit) 31 Heating roller (heating and pressing unit, pressing member) 31a Heater (heating and pressing unit) 32 Supporting roller ( Heating / compression means) 41 Followed roller (heat radiating means) 42 Belt (heating / compression means, heat radiating means, fixing belt) 43 Cooling roller (heat radiating means) A Heat radiating area (second area) B Heat / compression bonding area (first area) C Peeling point (peeling position) P sheet (recording medium)

Claims (7)

[Claims] 1. An image forming apparatus for forming an image on a recording medium using ink, comprising: fixing means for fixing the image formed on the recording medium to the recording medium; Heating and pressing means for heating the ink and the recording medium constituting the image in a first area and pressing the ink on the recording medium in the first area; A heat radiating means for radiating heat until the temperature reaches a predetermined temperature range in the area 2;
An image forming apparatus is provided between the first area and a peeling position where the ink and the recording medium are peeled off from the heat-pressed surface in contact with the first area. 2. The thermocompression bonding means are provided to face each other, and rotate in mutually opposite directions to pinch and convey the recording medium and form the first region by their contact positions. A set of rotating rollers, and a fixing belt that is stretched over any one of the set of rotating rollers and a driven roller that is rotatably provided, and that conveys the recording medium in a conveying direction. 2. The image forming apparatus according to claim 1, wherein the second area is provided on the fixing belt at a downstream side of the first area in a conveying direction. 3. 3. The image forming apparatus according to claim 2, wherein said heat radiating means includes said fixing belt forming said second area. 4. The image forming apparatus according to claim 2, wherein said fixing means peels off said recording medium at said peeling position by using a curvature of said driven roller. 5. The image according to claim 2, wherein said heat radiating means includes a cooling roller which abuts on said fixing belt and radiates ink and said recording medium by a refrigerant. Forming equipment. 6. The predetermined temperature range is characterized in that the adhesive force between the ink and the recording medium and the attraction force between the inks are compared with the adhesive force between the ink and the thermocompression bonding means. The image forming apparatus according to any one of claims 1 to 5, wherein the release temperature range is such that the release temperature increases. 7. A first step of forming an image on a recording medium using ink, a second step of heat-pressing the ink constituting the image and the recording medium, and a second step of: And a third step of radiating the ink and the recording medium until the temperature reaches a predetermined temperature range. After the third step, the ink and the recording medium are separated from the heat-pressed surface. An image forming method.