JP2001162783A - Imaging apparatus and imaging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fix ink surely to a sheet P regardless of the type of the sheet P or the ink and to obtain an image having high gloss while avoiding offset phenomenon. SOLUTION: An ink jet printer is provided with a fixing section comprising a preheating section 25 and a hot press section. Ink is fixed to a sheet P by hot press at the hot press section and the surface of ink is flattened to set a gloss. The preheating section 25 comprises a light source 41, and a reflector 42. Abrupt temperature rise of the sheet P can be avoided by heating the ink and the sheet P prior to hot press. The reflector 42 is shaped such that the ink and the image receiving layer of the sheet P can be heated uniformly in a specified region with the light from the light source 41 impinging on the sheet P directly and the light impinging on the sheet P through the reflector 42.

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, since the surface of the ink is flattened by the heat roller, it is considered that desired glossiness can be obtained regardless of the type of sheet used.

However, in this method, since the heat roller is in direct contact with the ink surface, the temperature of the ink rises more intensely than the sheet. Then, even if the temperature of the ink is suitable for fixing to the sheet, the temperature of the sheet may not be suitable for fixing the ink. In this case, the ink does not settle well on the sheet, and as a result, so-called offset transfer occurs in which the ink peels off the sheet and is transferred to the heat roller.

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, and to improve glossiness. An object of the present invention is to provide an image forming apparatus and an image forming method capable of obtaining a high image.

[0010]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: an image forming unit configured to form an image on a recording medium by using ink. A fixing unit for fixing the image formed by the image forming unit on the recording medium, wherein the fixing unit heats the ink and the recording medium constituting the image and records the ink on the recording medium. A thermocompression unit for pressurizing the ink and the recording medium; and a preheating unit for preheating the ink and the recording medium before thermocompression by the thermocompression unit. The preheating unit uniformly heats the ink. And uniformly heating an image receiving layer for receiving an image formed by the ink on the recording medium.

According to the above arrangement, the image formed on the recording medium by the image forming means is fixed on the recording medium by the fixing means. The fixing unit includes a thermocompression unit (for example, a heating roller and a pressure roller). The image and the recording medium are thermocompressed by the thermocompression unit so that the image is applied to the recording medium. Be established. In addition, the above-mentioned thermocompression bonding can be realized, for example, by sandwiching the recording medium between a heating roller and a pressure roller and pressing one roller against the other roller.

Since the surface of the ink on the recording medium is flattened by the thermocompression bonding by the thermocompression bonding means, 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 preliminary heating means. Before the ink and the recording medium are thermocompressed by the thermocompression bonding means, the ink and the recording medium are preliminarily heated by the preheating means. Heated. As described above, by heating the ink and the recording medium stepwise, the amount of heat in one heating can be suppressed, and the ink and the recording medium can be gradually heated.

By such heating, the amount of heat is reliably transmitted to both the ink and the image receiving layer, so that the temperature of the ink alone does not rise rapidly. That is, the temperature difference between the ink and the image receiving layer can be reduced as compared with the case where heating is performed at once. Accordingly, since both the temperature of the ink and the temperature of the image receiving layer fall within the temperature range suitable for fixing, the ink can be reliably fixed to the image receiving layer, and the situation where the ink peels from the image receiving layer can be avoided. it can. As a result, the reverse transfer of the ink to the member that comes into contact with the ink at the time of thermocompression bonding, that is, the offset phenomenon can be reliably avoided.

Further, by gradually heating the ink and the recording medium, the amount of heat is transmitted not only to the image receiving layer but also to a deep layer of the recording medium, so that temperature unevenness in the thickness direction of the recording medium can be reduced. can do. Thus, the expansion coefficient does not significantly differ for each layer of the recording medium, and the recording medium is less likely to warp. In addition, when the temperature unevenness occurs, each layer is easily separated due to a difference in shrinkage ratio of each layer in the recording medium when the recording medium is subsequently cooled, but the above-described configuration can reduce the temperature unevenness. Therefore, such peeling hardly occurs.

Further, in the above configuration, since the preheating means heats the ink and the image receiving layer uniformly, the temperature rise of the ink and the image receiving layer does not vary depending on the position. That is, the temperature of the ink and the image receiving layer can be uniformly increased at any position. Thereby, good fixability of the ink to the recording medium can be reliably obtained on the entire image forming surface. As a result, the offset phenomenon can be avoided more reliably.

According to a second aspect of the present invention, there is provided an image forming apparatus according to the first aspect, wherein:
The preheating means includes a light source that emits light, and a reflecting member that reflects a part of the light from the light source toward a recording medium.

According to the above arrangement, by arranging the reflecting member on the side opposite to the recording medium with respect to the light source, for example, light can be applied to the recording medium from the light source directly or via the reflecting member. Therefore, the use efficiency of the light from the light source can be increased by providing the reflecting member.

According to a third aspect of the present invention, there is provided an image forming apparatus according to the second aspect, wherein:
The reflection member causes the ink and the image receiving layer to be irradiated by both the first light that directly reaches the recording medium from the light source and the second light that reaches the recording medium from the light source via the reflection member. It is characterized in that it is set so as to be able to generate at least the second light that is uniformly heated.

In the above structure, the reflection member is so formed as to generate at least the second light which can uniformly heat the ink and the image receiving layer by both the first light and the second light. For example, the shape and the reflectance are set.
For example, when a plurality of light sources are arranged side by side, the reflecting member can be configured to have a shape in which a plurality of curved surfaces almost covering each light source are arranged in parallel, or the light sources can be put together without bending the curved surface. The reflection member can be configured to have a shape so as to cover it. Further, the reflection member can be configured so that the reflectance varies depending on the distance from the recording medium.

As described above, according to the present invention, the setting of a single member, that is, the setting of the shape and the reflectance of the reflecting member, is performed.
Since the ink and the image receiving layer can be uniformly heated, the present invention can be easily realized with a simple configuration.

According to a fourth aspect of the present invention, there is provided an image forming apparatus according to the third aspect, wherein:
The preheating means includes a light-shielding member that cuts, among the light emitted from the light source, light used for unevenly heating the ink and the image receiving layer.

According to the above configuration, even if the preheating means emits not only light provided for uniform heating but also light provided for non-uniform heating by setting the reflecting member. In addition, since the light used for uneven heating is cut by the light shielding member, it is possible to uniformly heat the ink and the recording medium. Thereby, the accuracy in setting the reflection member can be reduced to some extent.

According to a fifth aspect of the present invention, there is provided an image forming apparatus according to the fourth aspect, wherein:
The light shielding member is arranged at a position corresponding to a light irradiation time on the recording medium.

The temperature rise characteristics of the recording medium vary according to the irradiation time of light on the recording medium. Therefore,
As in the above configuration, the light shielding member is arranged at a position corresponding to the irradiation time, that is, by changing the arrangement position of the light shielding member according to the irradiation time, the recording medium is always uniform regardless of the irradiation time. Can be heated.

According to a sixth aspect of the present invention, there is provided an image forming apparatus according to the first aspect, wherein:
The preheating means converts the light from the light source, which emits light, and the light from the light source into light capable of uniformly heating the ink and the image receiving layer on the recording medium, and emits the light toward the recording medium. Light conversion means.

The light beam converting means can be constituted by, for example, a convex lens or a gradient refractive index lens (for example, a GRIN lens). If this light flux conversion means is arranged, for example, between the light source and the recording medium, the light emitted from the light source to the side opposite to the recording medium cannot be used for heating the recording medium, but it is used for uneven heating. Since the light to be irradiated is not applied to the recording medium, for example, even in the case of a configuration in which the pre-heating unit emits not only light provided for uniform heating but also light provided for uneven heating, There is no need to arrange such a member that blocks light.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the second to sixth aspects, in order to solve the above-mentioned problem, the light source crosses the conveying direction of the recording medium. And is set so that light distribution in the extending direction can be made uniform.

Assuming that the light source is composed of, for example, a halogen lamp, a method of making the light distribution uniform in the extending direction of the light source is to change the number of windings of the filament of the halogen lamp by the position in the extending direction. There is a method to change according to. By making the light distribution in the extending direction of the light source uniform in this way, it is possible to uniformly heat the ink and the recording medium in the extending direction.

Since the extending direction is a direction crossing the conveying direction of the recording medium (for example, a direction perpendicular to the conveying direction), if preheating is performed while conveying the recording medium at a constant speed, finally, It is possible to heat the entire ink and the entire image receiving layer uniformly.

According to an eighth 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; A second step of heat-pressing the recording medium, and a third step of preheating the ink and the recording medium before the second step, wherein the third step includes: The method is characterized in that the ink is uniformly heated and the image receiving layer of the recording medium, which receives an image formed by the ink, is uniformly heated.

According to the above arrangement, the ink forming 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, for example, by sandwiching the recording medium between a heating roller and a pressure 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.

Moreover, in the above configuration, before the ink and the recording medium are thermocompression-bonded, the ink and the recording medium are preheated. As described above, by heating the ink and the recording medium stepwise, the amount of heat in one heating can be suppressed, and the ink and the recording medium can be gradually heated.

By such heating, the amount of heat is reliably transmitted to both the ink and the image receiving layer, so that the temperature of the ink alone does not suddenly rise. That is, the temperature difference between the ink and the image receiving layer can be reduced as compared with the case where heating is performed at once. As a result, since both the temperature of the ink and the temperature of the image receiving layer can be kept within the temperature range suitable for fixing, the ink can be reliably fixed to the image receiving layer, and the situation where the ink peels from the image receiving layer is avoided. can do. As a result, the reverse transfer of the ink to the member that comes into contact with the ink at the time of thermocompression bonding, that is, the offset phenomenon can be reliably avoided.

Further, by gradually heating the ink and the recording medium, the amount of heat is transmitted not only to the image receiving layer but also to a deep layer of the recording medium, so that the temperature unevenness in the thickness direction of the recording medium can be reduced. can do. Thus, the expansion coefficient does not significantly differ for each layer of the recording medium, and the recording medium is less likely to warp. In addition, when the temperature unevenness occurs, each layer is easily separated due to a difference in shrinkage ratio of each layer in the recording medium when the recording medium is subsequently cooled, but the above-described configuration can reduce the temperature unevenness. Therefore, such peeling hardly occurs.

Further, in the above configuration, since the ink and the image receiving layer are uniformly heated, there is no unevenness in the temperature rise of the ink and the image receiving layer depending on the position. That is, the temperature of the ink and the image receiving layer can be uniformly increased at any position. Thereby, good fixability of the ink to the recording medium can be reliably obtained on the entire image forming surface. As a result, the offset phenomenon can be avoided more reliably.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
The following is a description based on FIGS. 1 to 18.

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 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 part 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 inks composed of MCs. As shown in FIG. 1, a sheet supply unit 11, an image forming unit 12 (image forming unit), and a fixing unit are provided. 13 (fixing means).

The sheet supply unit 11 supplies a sheet P for outputting an image to the image forming unit 12. As shown in FIG. 1, a sheet cassette 21 for storing the sheet P, and a sheet Transport rollers 22a and 22b for sending out the sheet P from the cassette 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 a plurality of ink discharge sections for discharging ink onto the sheet P in accordance with image data. Have.

FIG. 4 is an explanatory diagram showing the configuration of the ink discharge unit 23 in the image forming unit 12. The ink discharge unit 23 is an on-demand type recording head,
Is provided for each color. Then, each ink ejection unit 2
3 has a plurality of ink ejection ports 24 arranged in a line as shown in FIG. These ink discharge ports 24 have an image resolution of, for example, 400 dpi (dots pe
r inch) corresponding to each dot constituting the image.

The ink discharge section 23 has a configuration in which the image density can be controlled by changing the ink discharge amount for each dot. That is, in the ink discharge unit 23, while the amount of ink discharged from each ink discharge port 24 at a time is constant, the number of discharges of each ink discharge port 24 is changed for each dot, thereby discharging each dot. The total amount of ink to be applied is changed for each dot.

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

In the ink discharge unit 23, the amount of ink discharged 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.

Next, the fixing section 13 of the ink jet printer 1 will be described. The fixing unit 13 includes the image forming unit 12
The image formed by fixing the image on the sheet P is the most characteristic part of the inkjet printer 1 of the present invention. As shown in FIG. 3, the fixing unit 13 includes a pre-heating unit 25 (pre-heating unit),
(Thermocompression bonding means) and a paper discharge unit 27.

The pre-heating unit 25 pre-heats the sheet P and the ink from which the ink has been discharged in the image forming unit 12 before the thermo-compression unit 26 performs thermo-compression.
The present invention is characterized in that the inkjet printer 1 has a fixing unit 13 and the fixing unit 13 has a preheating unit 25. Therefore, a general description of the preheating unit 25 will be given first, but a specific configuration of the preheating unit 25 will be described later.

The heating of the sheet P by the preliminary heating section 25 is as follows.
This is performed so that the ink on the sheet P melts and the sheet P does not deteriorate. That is,
The preheating unit 25 adjusts the temperature of the sheet P so that the temperature of the sheet
Is set to heat. Hereinafter, this temperature range is referred to as a first temperature range.

Here, the softening point of the ink and the deterioration temperature of the sheet P will be described. As described above, the ink used in the inkjet printer 1 is a pigment-based ink. Such an ink contains a binder resin (resin) for binding pigments together. The softening point of the ink is a temperature at which the binder resin dissolves (the melting point of the resin).

That is, when the ink reaches the softening point, the binder resin is melted to form a jelly, and a part of the jelly penetrates into the sheet P, so that the bonding state between the ink and the sheet P is improved, and the fixability in 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.

The alteration temperature of the sheet P refers to the sheet P
Is the temperature at which the image receiving layer, which is the uppermost layer (the part where an image is formed), is peeled off from the sheet P, or the image receiving layer is cracked and the image is deteriorated. That is, the alteration temperature is the upper limit temperature at which the original properties of the sheet P can be exhibited.

Note that the softening point of the ink and the deterioration temperature of the sheet P differ depending on the properties of the ink and the sheet P. Therefore, in the inkjet printer 1,
The first temperature range is set for each image output based on the softened state of the ink used and the deteriorated state of the sheet P.

The thermocompression unit 26 heats the ink constituting the image (the ink on the sheet P sent from the image forming unit 12) and the sheet P, and applies the ink to the sheet P
To be crimped. By applying heat to the ink and pressurizing the ink and the sheet P, the ink can be softened and pressed against the sheet P. Also,
The thermocompression bonding section 26 also has a function of drying the ink because it applies heat to the ink on the sheet P.

Specifically, the thermocompression bonding section 26 has a heating roller 31 and a support roller 32 provided at positions facing each other as shown in FIG. The heating roller 31 and the supporting roller 32 are set so as to apply pressure to the sheet P and convey the sheet P in the direction of the paper discharge unit 27 by rotating in opposite directions with the sheet P interposed therebetween.

The heating roller 31 has a diameter of 50 mm, for example.
It is a hollow roller having a length in the rotation axis direction of 6 to 15 inches, and is a roller for pressing the image forming surface of the sheet P. The material forming the heating roller 31 includes J
Hardness measured by rubber hardness tester specified by IS standard is 70
To the extent silicon rubber can be used.

Further, 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 used to raise the surface temperature of the heating roller 31 to a temperature equal to or higher than room temperature by being electrically heated by electric power supplied from the outside. For example, a halogen lamp or a flash lamp (xenon lamp) is used. It can be configured using. That is, in the inkjet printer 1, the heating roller 3
1, the heating roller 31 and the supporting roller 32
The ink on the sheet P sandwiched between the two is forcibly heated and dried.

In the ink jet printer 1, the surface temperature of the heating roller 31 is set to a temperature range in which the ink is easily dried by adjusting a driving force (amount of power) for driving the heater 31a. Has become.
Therefore, hereinafter, this temperature range is referred to as a second temperature range. The second temperature range varies depending on the properties of the sheet P and the ink.
It is about 0 to 150 ° C.

The surface of the heating roller 31 is coated with fluorine. This is the heating roller 31
This is for smoothing the surface and imparting water repellency and water resistance to the surface. Inkjet printer 1
Then, by this fluorine coating, the heating roller 31
Is less than Rmax (maximum height of the convex portion on the surface) ≦
It is set to be 1 μm.

The support roller 32 has a diameter of 30 to 50 mm,
The roller has a length of 6 to 15 inches in the rotation axis direction, and is arranged at a position facing the heating roller 31 so that the sheet P can be pressed together with the heating roller 31. As a material for forming the support roller 32, for example, a metal such as aluminum having a surface roughness of Rmax ≦ 1 μm can be used.

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

The pressure applied to the sheet P by the pressure roller 31 and the support roller 32 is preferably determined based on the material of the sheet P. For example, when using a soft sheet P, it is preferable to use a relatively weak pressure value. Therefore, hereinafter, a range of a preferable pressure value determined according to the material of the sheet P is referred to as a first pressure range. The first pressure range can be, for example, about several tens kg / cm ² .

The paper discharge section 27 includes transport rollers 33a and 33b.
And a paper discharge cassette 34. Transport roller 33a
33b sandwiches the sheet P pressed by the thermocompression bonding section 26 and rotates the sheet P
Are confronted with each other so that can be transported to the paper discharge cassette 34. The paper discharge cassette 34 receives the sheet P transported by the transport rollers 33a and 33b.

Further, the ink jet printer 1 includes transport rollers 22a and 22b and transport rollers 33a and 33b.
In addition, a number of transport rollers not shown in FIG. 3 are provided. These rollers assist the conveyance of the sheet P. The sheet P conveyed by each conveyance roller is conveyed while being supported by the conveyance guide 28 (see FIG. 1).

The transport rollers and the rollers of the thermocompression unit 26 in the ink jet printer 1 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 present image output system will be described.

FIG. 5 is a flowchart showing the flow of the operation in the present image output system. As mentioned above,
All operations of the present image output system are performed under the control of the image processing device 4. That is, as shown in FIG. 5, when the user inputs an image to be output to the image reading device 2 or the film scanner 3 (S1), the image processing device 4
Controls these to generate predetermined image data (S
2) Input the image data.

Next, the image processing device 4 performs image processing on the input image data, and converts the input image data into a form that can be output by the inkjet printer 1 (S3). Thereafter, an image based on the converted data is displayed on the monitor 5 (S4), and the user is requested to judge whether or not the image data after the image processing (after the conversion) is appropriate (S4).
5) Image processing is repeated until image data desired by the user is generated.

When the user inputs an instruction that desired image data has been generated, the image processing apparatus 4
The image data is transmitted to the inkjet printer 1. Then, the inkjet printer 1 is controlled to perform the following image output processing (S6), and the processing ends.

FIG. 6 is a flowchart showing the flow of the operation of the ink jet printer 1 at the time of the image output processing. Note that all operations in this processing are controlled by a control unit (not shown) provided in the inkjet printer 1.

That is, as shown in FIG. 6, when image data is input from the image processing device 4, the control unit controls the transport rollers 22a and 22b to take out the sheet P from the paper cassette 21 and The sheet is transported to the forming section 12 (S11).

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 (S12). 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.

The control unit determines the first pressure range and the first and second temperature ranges based on the characteristics of the ink and the sheet P before S12 is completed. Then, the control unit controls the heater 31 a to control the heating roller 31.
Is heated to a temperature within the second temperature range and the pressure control mechanism is controlled to set the pressure between the heating roller 31 and the support roller 32 to a value within the first pressure range. It is supposed to.

At this time, the control unit operates the driving force (preheating) of the preheating unit 25, which is necessary for setting the sheet P to the first temperature range, based on the conveying speed set in advance by the user. Power (current amount)).
That is, the control unit sets, for example, the driving force of the preheating unit 25 to be strong when the transport speed is high and to be weak when the transport speed is low. That is, the control unit adjusts the preheating power so that the preheating unit 2 adjusts the preheating power according to the transport speed.
From 5, the amount of heat supplied per unit time is controlled so that the temperature of the sheet P falls within the first temperature range.

After S12, the control unit controls a conveying roller (not shown) to convey the sheet P to the preheating unit 25 in order to give gloss to the image. Then, the pre-heating unit 25 is driven by the above-described pre-heating power, and pre-heats the sheet P so that the temperature is within the first temperature range (initial heating).
(S13). Thereby, the ink on the sheet P is heated and melted, the ink is softened, and the fixing property of the ink is improved.

Next, the control unit controls a transport roller (not shown) to transport the preheated sheet P to the thermocompression unit 26. Then, the heating roller 31 and the support roller 3
2, the sheet P is pressurized in the first pressure range while heating in the second temperature range (S14). Thereby, the ink on the sheet P is heated and pressed, giving gloss to the image and drying the image (ink).

Finally, the control section controls the transport rollers 33a and 3
By controlling 3b, the sheet P is stored in the paper discharge cassette 34 (S15), and the process is terminated.

As described above, the ink jet printer 1 in the present image output system first preheats the sheet P on which the image is formed by the image forming unit 12 and the ink constituting the image by the preheating unit 25, The pressure is applied while being heated by the thermocompression unit 26.

Since the surface of the ink on the sheet P is flattened by the heating / pressing in the thermocompression unit 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. In addition, compared to the case where natural drying is performed, the ink on the sheet P can be dried quickly and reliably, so that even if the discharged sheets P are stacked, the image adheres to another sheet P. There is nothing. This makes it possible to improve the processing speed by stacking the sheets P one after another after discharge.

In the present invention, preheating is performed before the sheet P and the ink are heated and pressed, so that the ink and the sheet P are heated.
Is heated to a certain degree, it is possible to avoid a rapid rise in the temperature of the ink and the sheet P during the subsequent thermocompression bonding. That is, since the ink and the sheet P are gradually heated in the two stages of the preliminary heating and the thermocompression bonding, the temperature of the ink and the sheet P can be gradually increased.

Here, when the temperature of the ink and the sheet P is rapidly increased, the following inconveniences occur.

The heat is not transmitted to the sheet P, so that the temperature difference between the ink and the sheet P increases. For this reason, even if the ink is melted, the ink does not fix well on the sheet P, and as a result, an offset phenomenon in which the ink on the sheet P is transferred to, for example, the heating roller 31 may occur. Further, if the temperature difference is large, when the sheet P is subsequently cooled, the ink on the sheet P tends to peel off from the sheet P due to the difference in shrinkage.

Since the temperature unevenness occurs in the thickness direction of the sheet P, the sheet P is warped due to the difference in the expansion coefficient of each layer of the sheet P. In addition, when the temperature unevenness occurs, when the sheet P is subsequently cooled, each layer is easily separated due to a difference in shrinkage rate of each layer in the sheet P.

However, according to the present invention, it is possible to avoid a rapid rise in the temperature of the ink and the sheet P, so that it is possible to reliably apply heat to both the ink and the sheet P, Temperature unevenness in the thickness direction can be minimized. As a result, according to the present invention, the above inconvenience can be reliably avoided.

Further, since the ink is fixed to the sheet P, the offset phenomenon in which the ink adheres to the heating roller 31 can be suppressed, so that the image quality of the output image can be prevented from deteriorating.
Can be protected from contamination by ink.

Further, since the preheating unit 25 heats the ink and the sheet P in a non-contact manner, the ink softened and melted by the heating is not reversely transferred to a member other than the sheet P. At 25, no offset phenomenon occurs.

Further, in the ink jet printer 1, the heating roller 31 is controlled so that the surface roughness is Rmax ≦ 1 μm.
Is coated with fluorine to increase its smoothness. Thus, the sheet P can be pressed on a very smooth surface, so that the glossiness of the image can be further increased. Further, due to the water repellency of the fluorine coating, the transfer of the ink on the sheet P to, for example, the heating roller 31, that is, the offset phenomenon can be suppressed.

Further, in the ink jet printer 1,
By pressing and heating the ink on the sheet P, the color fastness of the image can be improved. Criteria for evaluating the degree of color fastness of an image include, for example, a rate of decrease in density of each monochromatic light, a rate of change in density between colors, deterioration of resolution, and water resistance (such as dropping of ink when wet with water, Decreases (concentration decreases)
That).

In the ink jet printer 1, before the sheet P is conveyed to the thermocompression bonding section 26, the temperature of the sheet P is raised to a first temperature range by the preheating section 25. I have. For this reason, it is possible to soften the ink and fix the ink to the sheet P before pressurization by the thermocompression unit 26. Accordingly, the softening of the ink facilitates the press-fitting of the ink by the heat-pressing unit 26, and can promote an improvement in glossiness.

As described above, in the ink jet printer 1, the preheater 25
After the heating in the first temperature range, the image is pressed by the thermocompression bonding section 26 having high smoothness, thereby making it possible to extremely increase the glossiness of the image. In addition,
As a result of measurement with various types of the ink and the sheet P, it has been found that the glossiness of the image output by the inkjet printer 1 reaches a gloss value of 70 or more.

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 representing 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.

Further, the sheet P
If the pressure applied to the sheet P is increased, the glossiness of the image can be increased even when the temperature of the sheet P does not reach the first temperature range and the ink is not sufficiently softened.

For example, if the pressure is sufficiently increased at a very high pressure, sufficient gloss can be provided even for an image that has not undergone preheating and has not been softened at all.
In such a case, both the preheating unit 25 and the heater 31a become unnecessary.

The pre-heating unit 25 also has a function of softening the ink and enhancing the pressurizing effect of the heating / compression unit 26 described later.

In the present embodiment, the preheating unit 25
After the temperature of the sheet P is raised to the first temperature range, the sheet P is pressed by the thermocompression unit 26 in the first pressure range based on the material of the sheet P.

However, the preliminary heating unit 25 and the heater 3
If the sheet P does not reach the first temperature range and the ink is not sufficiently softened due to a driving force shortage 1a or the like, the heating and pressing unit 26 applies a pressure higher than the first pressure range. It is preferable to press the sheet P by the value. That is, it is preferable that the pressure value of the thermocompression bonding section 26 be determined based on the material of the sheet P and the softened state of the ink in the sheet P.

In the above description, the heating roller 31 is provided with the heater 31a, and the heater 31a
To dry. However, when it is not necessary to dry the ink, such as when using ink having a very fast drying property, the heater 31a is not necessary.

Further, in the above description, the heating roller 31 and the supporting roller 32 rotate in opposite directions with the sheet P interposed therebetween, but one of the heating roller 31 and the supporting roller 32 is a driven roller. There may be.

Further, 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 rollers (including tubes, sheets, rubber, etc.) having physically different surface roughness as the above-mentioned 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.

As the material of the heating roller 31, besides silicone rubber, NBR (acrylonitrile-butadiene copolymer rubber) rubber, PTFE (polytetrafluoroethylene) rubber, metal and the like can be used. . Further, when the heating roller 31 is formed of a hard roller made of metal or the like, the surface of the ink on the sheet P can be flattened more than the case where the heating roller 31 is formed of a resin. Can be improved.

Further, the coating on the surface of the heating roller 31 is not limited to the above-mentioned fluorine coating.
It may be a TFE coating. If the entire heating roller 31 is made of PTFE-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 ink jet 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 the present embodiment, all operations of the image output system are performed under the control of the image processing device 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 this embodiment, the image output processing in the ink jet printer 1 shown in FIG. 6 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, in the present embodiment, in the image output process shown in FIG. 6, the control unit determines the first pressure range and the first pressure range based on the characteristics of the ink and the sheet P before S12 is completed. A second temperature range is determined; However, these pressure and temperature ranges
It may be determined before the image output processing. Furthermore, these ranges will be changed before the image output process is performed.
It may be set to be transmitted from the outside to the control unit.

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.

In the present embodiment, the ink ejection unit 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.

The softening point and melting point of the ink can be expressed as follows. That is, the softening point of the ink is a temperature at which the ink is softened (softening point → high viscosity), and is a temperature at which the ink can be deformed by a pressing force. The melting point of the ink is a phase transition temperature at which the ink melts (melting point → low viscosity), and is a temperature at which the ink melts and spreads.

Further, even if the ink does not reach the melting point, it becomes softer when the temperature is raised. Further, even when the temperature of the sheet is equal to or lower than the melting point of the ink, the glossiness of the image can be increased by increasing the pressure applied to the sheet.

Next, the details of the preheating unit 25, which is a feature of the present invention, will be described.

As shown in FIG. 1, the preheating unit 25 includes a light source 41, a reflector 42 (reflection member), and a light shielding plate 43.
(Light-shielding member), so that the ink on the sheet P and the image receiving layer (the layer for receiving the image formed by the ink) on the sheet P are heated in a non-contact manner by irradiation of light from the light source 41. It has become. In the following, unless otherwise specified, the ink on the sheet P is simply described as ink, and the image receiving layer on the sheet P is simply described as the image receiving layer.

The light source 41 may be anything that generates heat by light irradiation. For example, it can be constituted by a halogen lamp or a flash lamp (xenon lamp) often used as a general light source. In the present embodiment, the light source 41 is constituted by a halogen lamp extending in a bar shape in the width direction of the sheet P (the direction perpendicular to the conveying direction of the sheet P). That is, the ink and the sheet P are heated by irradiating the ink and the sheet P with light from a halogen lamp.

The extending direction of the light source 41 is not limited to the width direction of the sheet P, but may be any direction as long as it crosses the conveyed sheet P. FIG. 1 shows an example in which two rod-shaped light sources 41 are arranged side by side. However, the number of light sources 41 is not limited to this, and may be one or three or more. The light sources 41 may be provided side by side.

Here, the light emitted from the light source 41 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 reflector 42 reflects a part of the light emitted from the light source 41 toward the sheet P.
For example, it is configured by depositing a reflective film on the surface of a metal such as aluminum. The heat resistance temperature of the reflective film is, for example, about 350 ° C., and the light reflectance of the reflective film is set to a high reflectivity, for example, about 80%. Here, the reflectance is represented by (energy of reflected light / energy of incident light) × 100.

By providing such a reflector 42, it is possible to irradiate the sheet P with light directly from the light source 41 or through the reflector 42. Therefore,
The utilization efficiency of the light from the light source 41 can be increased, and thereby the ink and the sheet P can be efficiently heated.

In the following, light that directly reaches the sheet P from the light source 41 is referred to as first light, and light that reaches the sheet P from the light source 41 via the reflector 42 is referred to as second light. To

The light-shielding plate 43 is used to control the light emitted from the light source 41 to the ink and the sheet P.
This is to cut off the light provided for the non-uniform heating.
One light shielding plate 43 includes, for example, one plate member or a plurality of plate members arranged side by side. By changing the number of plate members constituting one light shielding plate 43, the light shielding plate 43 is provided. The width of the sheet P in the conveyance direction at 43 can be freely adjusted. Each light shielding plate 43 is slidably inserted between the light source 41 and the sheet P.

In the present invention, as will be described later, the shape of the reflector 42 is set so that the ink and the sheet P can be uniformly heated. When the distance is within a predetermined range, the distance can be reliably realized. However, in other ranges, at least the amount of the first light is drastically reduced. Therefore, no matter how much the shape of the reflector 42 is set with high accuracy, it is practically impossible to compensate for the reduced amount with the second light. May be. As a result, it is conceivable that the heating of the ink and the sheet P becomes uneven in the conveying direction of the sheet P, and the fixing property of the ink is lowered in the same direction.

Therefore, in the present invention, the width of the light-shielding plate 43 is set and arranged so that the light used for uneven heating of the ink and the sheet P can be shielded. The ink and the sheet P can be heated uniformly using only the light. Thereby, it is possible to reliably obtain good fixing properties of the ink in the transport direction of the sheet P.

Next, a feature of the present invention, that the preheating unit 25 is configured to heat the ink uniformly and to heat the image receiving layer uniformly, will be described.
This configuration can be realized, for example, by appropriately setting the shape of the reflector 42, the reflectance of the reflection film, the light distribution characteristics of the light source 41, and the like. Therefore, hereinafter, the preheating unit 2 of the present invention
Each setting in 5 will be described in order.

[Setting of Shape of Reflector and Reflectivity of Reflective Film] The shape of the reflector 42 is such that the ink and the image receiving layer are uniformly heated by both the first light and the second light. The setting is such that at least the second light can be generated.

For example, FIG. 7 shows that when the preheating unit 25 is composed of one light source 41 and a reflector 42, the shape of the reflector 42 is adjusted so that light can be uniformly irradiated on a sheet P having a large area. , The light source 41 is set so as to substantially wrap the light source 41 from the side opposite to the sheet P in a non-contact manner. In the figure, each of the lines reaching the sheet P indicates the optical path of the light from the light source 41.

By setting the shape of the reflector 42 so as to irradiate the reflected light with an amount of light that varies according to the optical path length of the light that directly reaches the sheet P from the light source 41,
The unevenness in light amount due to the difference in the optical path length can be eliminated by using the reflected light. Thus, the ink and the image receiving layer can be uniformly heated by both the first light and the second light.

In FIG. 7, the light source 4 on the sheet P
The portion immediately below the portion 1 is not irradiated with the reflected light from the reflector 42 so that the ink and the image receiving layer are uniformly heated. May be uniformly heated.

Even when a plurality of light sources 41 are arranged in parallel, including the configuration shown in FIG. 1, the shape of the reflector 42 can be set using the same principle as described above. That is, the light source 41
When a plurality of reflectors 42 are arranged side by side so that a plurality of curved surfaces almost wrapping the individual light sources 41 from the opposite side of the sheet P are formed in a non-contact manner with each light source 41.
Is set, the first light from each light source 41 and the second light
The ink and the image receiving layer can be uniformly heated by both of the light.

By the way, the shape of the reflector 42 is not limited to that shown in FIG. 7 as long as at least the second light capable of uniformly heating the ink and the image receiving layer can be generated. For example, as shown in FIG. 8, a reflector 42 ′ having a shape such that a plurality of light sources 41 are collectively covered in a non-contact manner from the opposite side of the sheet P without bending a curved surface.
Can also be used. In this case, for example, the reflector 4
By appropriately adjusting the reflectance of the reflective film on the 2 ′ surface depending on the position, the ink and the image receiving layer can be uniformly heated. For example, the reflectance of the reflection film at a position close to the sheet P is set low, and the reflectance of the reflection film at a position far from the sheet P is set high. If the reflectance of the reflective film is set according to the distance, the ink and the image receiving layer can be uniformly heated even in the configuration of FIG.

In addition, depending on the setting of the reflectance of the reflection film, the reflector is formed, for example, in a wavy shape (not shown), and at least one light source 41 is installed so as to substantially cover the sheet P from the opposite side in a non-contact manner. It is also possible. In this case, by reflecting the light from the light source 41 in all directions, the heat supply efficiency may be somewhat inferior to the configuration in FIG. 7 or FIG. 8, but it is possible to uniformly heat the ink and the image receiving layer. There is no substitute for what you can do.

As described above, according to the present invention, by appropriately setting the shape and the reflectance of a single member called the reflector 42,
Since the ink and the image receiving layer can be uniformly heated, the present invention can be easily realized with a simple configuration.

Next, in this embodiment, when the reflectors 42 and 42 'shown in FIGS. 7 and 8, respectively, are used, the rise in the surface temperature of the sheet P with respect to the change in the distance between the light source 41 and the sheet P is described. Investigate the differences. The results will be described below as Examples 1 to 4.

In each of the embodiments, the ink and the image receiving layer cannot be uniformly heated if the distance from the light source 41 is out of the predetermined range, that is, in order to show the necessity of the light shielding plate 43. Then, the temperature rise characteristics of the sheet P were examined without arranging the light shielding plate 43.

The light source 41 used in each embodiment is a halogen lamp with a power consumption of 500 W. The range for supplying heat to the sheet P is, for example, 120 mm in the conveying direction of the sheet P and the width of the sheet P is The preheating unit 25 was set so as to cover the entire area in the direction (perpendicular to the transport direction).

Embodiment 1 In this embodiment, as shown in FIG. 9, a reflector 42 having the shape shown in FIG.
The distance between the sheet 1 and the sheet P was set to 33 mm. And
At this time, the surface temperature of the sheet P is changed from nine positions that differ by about 13 mm in the sheet P conveyance direction.
Was measured over time. Table 1 shows the measurement results, and FIG. 10 shows the results of Table 1 as a graph.

[0148]

[Table 1]

In this embodiment, when the irradiation time of the ink and the sheet P is in the range of 0 to 4 seconds, the position and
It can be seen that almost the same temperature rise curve was obtained.
Therefore, when heating is performed in the irradiation time range of 0 to 4 seconds, if the light shielding plate 43 is arranged at a position corresponding to the remaining positions, the ink and the sheet P can be uniformly heated. Become.

Further, when the irradiation time of the ink and the sheet P is further in the range of 4 to 10 seconds,
It can be seen that almost the same temperature rise curve is obtained at the position. Therefore, when heating is performed even in the irradiation time range of 4 to 10 seconds,
If the light shielding plate 43 is arranged at a position corresponding to the above, the ink and the sheet P can be continuously heated uniformly.

If the processing speed in the fixing unit 13 is emphasized, it is naturally preferable that the irradiation time be 0 to 4 seconds. Here, the range for supplying heat to the sheet P is set to 120 mm with respect to the transport direction of the sheet P, so that the irradiation time of the ink and the sheet P is 0 to 4 seconds. Transport speed is 30mm / se
It suffices if it is at least c.

Although uniform heating can be realized even if the light-shielding plates 43 are disposed one after another as in this embodiment, if the light-shielding plates 43 are arranged at positions corresponding to the positions between the light sources 41, 41. Not only is the overall temperature-raising effect itself reduced, but also the temperature of the heated sheet P is temporarily reduced by the light shielding before reaching the position, which causes a temperature fluctuation. Absent. In consideration of such a point, the light-shielding plate 43 is arranged so as to absorb only the variation in the temperature rise at the ends of the pre-heating unit 25 (the input side and the output side of the pre-heating unit 25). It is desirable to have a configuration. For example, in the case of this embodiment,
The light shielding plate 43 may be arranged only at a position corresponding to the above.

(Embodiment 2) In this embodiment, except that the distance between the light source 41 and the sheet P is set to 20 mm.
The surface temperature of the sheet P was measured under the same conditions as described above. The results are shown in Table 2, and the results of Table 2 are shown in a graph in FIG.

[0154]

[Table 2]

In the present embodiment, almost the same temperature rise curve is obtained regardless of the time at the position 〜, and the temperature rise is not too rapid and not too gentle. Therefore, it can be said that the ink and the sheet P can be uniformly heated by disposing the light shielding plate 43 at the positions corresponding to the remaining positions.

Example 3 In this example, as shown in FIG. 12, the surface temperature of the sheet P was measured under the same conditions as in Example 1 except that a reflector 42 'having the shape shown in FIG. 8 was used. . Table 3 shows the results, and FIG. 13 shows the results of Table 3 as a graph.

[0157]

[Table 3]

In this embodiment, substantially the same temperature rise curve is obtained at the position and regardless of the time. Therefore, the ink and the sheet P can be uniformly heated by arranging the light shielding plate 43 at the positions corresponding to the remaining positions.

In addition, there is no rapid temperature rise at the position, as can be seen from the temperature rise curve. Therefore, problems such as warpage of the sheet P can be surely solved.

(Embodiment 4) In this embodiment, except that the distance between the light source 41 and the sheet P is set to 20 mm.
The surface temperature of the sheet P was measured under the same conditions as described above. Table 4 shows the results, and FIG. 14 shows the results of Table 4 as a graph.

[0161]

[Table 4]

In this embodiment, almost the same temperature rise curve is obtained at the positions 1 to 5. Therefore, by arranging the light shielding plate 43 at a position corresponding to the remaining positions..., The ink and the sheet P can be uniformly heated.

From the above examples, it can be seen that the temperature rise characteristics of the sheet P fluctuate according to the irradiation time of the sheet P with light. Therefore, by arranging the light shielding plate 43 at a position corresponding to the irradiation time of the sheet P, the sheet P can be uniformly heated regardless of the irradiation time.

If the shape of the reflector 42 is set appropriately, it is possible to achieve a certain degree of uniform heating without providing the light-shielding plate 43 described above.

By the way, the shorter the distance between the light source 41 and the sheet P, the higher the efficiency of heat supply to the ink and the sheet P. However, on the other hand, the temperature of the ink rapidly rises and the sheet P is easily warped. . Conversely, the longer the distance is, the more rapid the temperature rise of the ink and the warp of the sheet P can be avoided, but the efficiency of supplying heat to the ink and the sheet P deteriorates.

Therefore, the distance between the light source 41 and the sheet P,
Heat supply efficiency to ink and sheet P, temperature rise of ink,
Examples 1 and 2 and Examples 3 and 4 were compared in order to investigate the relationship with the warpage of the sheet P. As a result, when the distance was 20 mm, a result was obtained in which it was possible to avoid a rapid rise in the temperature of the ink and warpage of the sheet P while avoiding a decrease in the heat supply efficiency to some extent.

[Setting of Light Distribution Characteristics of Light Source] As described above, the light source 41 has a rod shape extending in a direction crossing the sheet P (for example, a direction perpendicular to the conveying direction of the sheet P).
Therefore, the light distribution characteristics referred to here indicate light emission characteristics in the extending direction of the light source 41.

When the light source 41 is a halogen lamp, a filament (for example, tungsten) is wound in the extending direction of the halogen lamp. Here, when the filament is uniformly wound in the extending direction, the halogen lamp has a temperature characteristic in which the temperature is highest near the center and lowest at both ends.
This is because the central portion of the halogen lamp is affected by light emitted from both sides. Therefore, in this case, the light distribution characteristics of the light source 41 in the extending direction are non-uniform, and the ink and the image receiving layer cannot be uniformly heated in the extending direction in this setting.

Therefore, in the present invention, the number of windings of the filament is changed according to the position. Specifically, the number of times the filament is wound is reduced as it approaches the center of the halogen lamp, and is increased as it approaches both ends. By setting the light source 41 extended in the direction crossing the conveying direction of the sheet P such that the light distribution in the extending direction can be made uniform, the ink and the image receiving layer are moved in the extending direction. It becomes possible to heat uniformly.

However, with the above-described setting of the light source 41 alone without the reflector 42, even if uniform heating in the extending direction of the light source 41 can be realized, uniform heating in the sheet P conveying direction cannot be realized. . In addition, unevenness in temperature increase in the transport direction of the sheet P in the case where the reflector 42 is not provided tends to be more remarkable than unevenness in temperature increase due to uneven light distribution in the extending direction of the light source 41.

Accordingly, the conveying speed of the sheet P is made constant,
If the setting of the light source 41 and the setting of the shape and the reflectance of the reflector 42 described above are performed together, a uniform heating area of the ink and the image receiving layer can be created. The entire surface can be heated uniformly.

As described above, by performing the above-described settings in the pre-heating unit 25, it is possible to reliably avoid unevenness in the temperature rise of the ink and the image receiving layer depending on the position. In other words, the temperature difference between the ink and the image receiving layer does not differ depending on the position in the conveying direction and the width direction of the sheet P. This makes it possible to obtain good fixability of the ink to the sheet P in the subsequent thermocompression bonding section 26. As a result, it is possible to reliably prevent the offset phenomenon from occurring depending on the position.

For example, when the ink is heated to 100 ° C. in 2 seconds, the image receiving layer and its lower layer (consisting of a plurality of layers) are heated to 80 ° C., 60 ° C., 30 ° C.. I knew it. On the other hand, the ink was heated to 80 ° C in 4 seconds.
When heated to 70 ° C., the image receiving layer and the lower layer
It was experimentally found that the temperature was increased to 65 ° C, 45 ° C, 45 ° C ... That is, when the ink is heated gently, the image receiving layer can be heated so that the temperature difference with the ink becomes small, and the sheet P can be reliably heated to a deep layer.

Therefore, as shown in FIGS. 7 and 8, a plurality of light sources 41 are arranged in parallel to increase the irradiation area, while each light source 4
If the preliminary heating unit 25 is configured so that the temperature of the ink and the image receiving layer can be gradually increased by suppressing the heat supply from the first and the like, both the ink and the sheet P fall within a temperature range suitable for fixing the ink. Become like This makes it possible to easily and reliably fix the ink on the sheet P. Further, when the temperature of the image receiving layer is raised, the temperature of the ink is not rapidly increased, so that the ink itself does not burn. Further, since the temperature difference in the thickness direction of the sheet P is reduced, the warpage of the sheet P, peeling of the image receiving layer, and the like can be reliably avoided. Further, the juxtaposition of the light sources 41 is also effective when one light source 41 has a shortage of heat.

In general, the amount of heat to be supplied to the sheet P (energy required to fix the ink) in consideration of the fixing property of the ink is determined by the component of the ink, the sheet P
Type, sheet P width, ink fixing width on sheet P, input energy to light source 41, ink fixing efficiency,
Since it varies depending on various factors such as the environmental temperature, it is difficult to directly measure the heat supply amount by experiment. However, the heat supply amount can be obtained indirectly from the power amount of the entire apparatus if the heat supply amount is a standard.

For example, when the light source 41 is constituted by a halogen lamp, the electric energy of the entire apparatus when the ink on the sheet P reaches the softening point by supplying heat is about 1.5 kJ. Therefore, if this electric energy is divided by the irradiation area of the sheet P, the required heat supply amount per unit area of the sheet P can be obtained as a guide. The heat supply amount obtained in this way depends on the size of the sheet P, but is about 1 to 4 J.
/ Cm ² . On the other hand, when the light source 41 is constituted by a flash lamp, when the heat supply amount is calculated based on the power amount of the entire apparatus when satisfactory fixing properties of the ink are obtained, it is approximately 0.8 to 1.0 J / cm. ^{Was 2} .

Incidentally, the reflector 42 described above is used.
Alternatively, the ink and the image receiving layer can be uniformly heated by using a lens, for example.

For example, FIG. 15 shows a schematic configuration of a preheating unit 35 in which a semi-cylindrical convex lens 44 corresponding to each light source 41 is provided between the light source 41 and the transport guide 28. The convex lens 44 constitutes a light beam conversion unit that converts the incident diffused light into light (for example, parallel light) that can uniformly heat the ink and the image receiving layer and emits the light toward the sheet P. That is, by providing the convex lens 44, the incident light can be condensed on the sheet P without unevenness. If such a condensing convex lens 44 is provided, light emitted from the light source 41 to the opposite side to the sheet P cannot be effectively used for heating the sheet P, but is provided for uneven heating. Since there is no light, there is no need to dispose the above-mentioned light shielding plate. Therefore, in this case, it is possible to uniformly heat the ink and the image receiving layer while simplifying the configuration of the preliminary heating unit 35.

The above-mentioned condensing does not mean that the light is collected at one point, but that it is not diffused to a portion other than the sheet P.

Also, instead of the above-mentioned convex lens 44,
As shown in FIG. 16, GRIN (Gradient Index Lens)
The preheating unit 36 may be configured by providing the lens 45 between the light source 41 and the transport guide 28. The GRIN lens 45 is a lens whose refractive index changes continuously as a function of spatial coordinates in a medium, and is also called a gradient refractive index lens or a distributed refractive index lens. That is, the GRIN lens 45 has a refractive index that is not uniform but has a refractive index gradient inside the lens.

By setting the refractive index in one GRIN lens 45 freely and having a plurality of refractive index gradients, the diffused light incident on the GRIN lens 45 can be
The lens 45 can convert the light into light that can uniformly heat the ink and the image receiving layer and emit the light toward the sheet P. Therefore, the above GRIN lens 4
5 also constitutes the same light beam conversion means as the convex lens 44,
The same effect as when the convex lens 44 is used can be obtained.

As shown in FIG. 17 and FIG.
The preheating units 37 and 38 can be respectively configured by using the configuration of FIG. 5 or 16 in combination with the configuration of providing the reflector 42. However, in this case, the shape and refractive index of the convex lens 44 and the refractive index distribution of the GRIN lens 45 are as shown in FIG.
16 is set slightly different from the case of the configuration of FIG.

In the configuration shown in FIGS. 17 and 18, the reflector 4
2, the light emitted from the light source 41 to the opposite side to the sheet P can be effectively used for heating the sheet P. In addition, if the shape and the refractive index of the convex lens 44 and the GRIN lens 45 are devised, it is possible to give the ink and the sheet P a uniform light amount to some extent. You can do it. That is, according to the configuration of FIGS. 17 and 18,
The design accuracy of the reflector 42 can be reduced to some extent.

Note that the above-described convex lens 44 is
, It is desirable to be made of a heat-resistant material such as quartz, for example. Further, it is desirable that the GRIN lens 45 is similarly made of a heat-resistant material.

In the configuration shown in FIGS. 17 and 18, the reflector 42 may of course be a reflector 42 '.

[0186]

According to the first aspect of the present invention, there is provided an image forming apparatus comprising:
As described above, the image forming apparatus includes the fixing unit that fixes the image formed by the image forming unit on the recording medium. The fixing unit heats the ink and the recording medium that constitute the image, and records the ink on the recording medium. The heat and pressure means for pressing the medium, the ink and the recording medium,
A preheating means for preheating before the thermocompression bonding by the thermocompression bonding means. The preheating means uniformly heats the ink and receives an image formed by the ink on the recording medium. In this configuration, the image receiving layer is uniformly heated.

[0187] Therefore, the surface of the ink on the recording medium is flattened by the thermocompression bonding by the thermocompression bonding means, so that 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.

In addition, before the ink and the recording medium are thermocompressed by the thermocompression unit, the ink and the recording medium are preheated by the preheating unit in advance. As described above, by heating the ink and the recording medium stepwise, the amount of heat in one heating can be suppressed, and the ink and the recording medium can be gradually heated. As a result, since both the temperature of the ink and the temperature of the image receiving layer can be kept within the temperature range suitable for fixing, the ink can be reliably fixed to the image receiving layer, and the situation where the ink peels from the image receiving layer is avoided. can do. As a result, reverse transfer of the ink to a member that comes into contact with the ink at the time of thermocompression bonding, that is, the offset phenomenon can be reliably avoided.

Further, by gradually heating the ink and the recording medium, the amount of heat is transmitted not only to the image receiving layer but also to a deep layer of the recording medium, so that the temperature unevenness in the thickness direction of the recording medium can be reduced. can do. Thus, the expansion coefficient does not significantly differ for each layer of the recording medium, and the recording medium is less likely to warp. In addition, when the temperature unevenness occurs, each layer is easily separated due to a difference in shrinkage ratio of each layer in the recording medium when the recording medium is subsequently cooled, but the above-described configuration can reduce the temperature unevenness. Therefore, such peeling hardly occurs.

Further, in the above configuration, since the preheating means uniformly heats the ink and the image receiving layer, the temperature of the ink and the image receiving layer does not vary depending on the position. Thereby, good fixability of the ink to the recording medium can be reliably obtained on the entire image forming surface. As a result, the effect that the offset phenomenon can be suppressed more reliably is also achieved.

In the image forming apparatus according to the second aspect of the present invention, as described above, in the configuration of the first aspect, the preheating means records a light source for emitting light and a part of the light from the light source. And a reflecting member for reflecting the light toward the medium.

Therefore, in addition to the effect of the configuration of claim 1, there is an effect that the utilization efficiency of light from the light source can be improved.

As described above, in the image forming apparatus according to the third aspect of the present invention, in the configuration of the second aspect, the reflecting member includes: a first light that directly reaches a recording medium from the light source;
Both the light and the second light that reaches the recording medium via the reflective member can generate at least the second light that uniformly heats the ink and the image receiving layer. This is the configuration set to.

Therefore, the ink and the image receiving layer can be uniformly heated by setting a single member such as setting the shape and reflectance of the reflecting member. The present invention has an effect that the present invention can be easily realized with a simple configuration.

According to a fourth aspect of the present invention, as described above, in the configuration of the third aspect, the pre-heating means includes, among the light emitted from the light source, the ink and the image receiving layer. This is a configuration including a light-blocking member that cuts light provided for uneven heating.

Therefore, even if the preheating means emits not only light used for uniform heating but also light used for non-uniform heating by setting the reflecting member, the light shielding member may be used. Since the light used for the non-uniform heating is cut, the ink and the recording medium can be heated uniformly. Thereby, in addition to the effect of the configuration of claim 3, there is an effect that accuracy in setting the reflecting member can be reduced to some extent.

According to a fifth aspect of the present invention, as described above, in the configuration of the fourth aspect, the light shielding member is disposed at a position corresponding to a light irradiation time on the recording medium. is there.

Therefore, the temperature rise characteristics of the recording medium fluctuate according to the irradiation time of light to the recording medium. In the above configuration, the light shielding member is disposed at a position corresponding to the irradiation time. In addition to the effect of the configuration of 4, the recording medium can be heated uniformly regardless of the irradiation time.

In the image forming apparatus according to a sixth aspect of the present invention, as described above, in the configuration of the first aspect, the preheating means comprises: a light source for emitting light; And a light beam converting means for converting the light into a light capable of uniformly heating the ink and the image receiving layer and emitting the light toward the recording medium.

Therefore, the recording medium is not irradiated with light which is subjected to uneven heating by the light beam converting means. In addition to the effect of the first aspect, for example, the preliminary heating means provides uniform heating. In the case of a configuration in which not only light to be emitted but also light to be subjected to non-uniform heating is emitted, there is an effect that it is not necessary to dispose a member for shielding such light.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the second to sixth aspects, the light source extends in a direction transverse to a conveying direction of the recording medium. In this configuration, the light distribution in the extending direction is set to be uniform.

Therefore, since the light distribution in the extending direction of the light source becomes uniform, it is possible to uniformly heat the ink and the recording medium in the extending direction. At this time, since the extending direction is a direction transverse to the conveying direction of the recording medium, if the preheating is performed while conveying the recording medium at a constant speed, the effect of the configuration according to any one of claims 2 to 6 can be obtained. In addition, there is an effect that it is possible to finally heat the entire ink and the entire image receiving layer uniformly.

According to the image forming method of the present invention, as described above, the first step of forming an image on a recording medium by using ink, and the step of forming the image forming ink and the recording medium are performed. The method includes a second step of thermocompression bonding, and a third step of preheating the ink and the recording medium before the second step. In the third step, the ink is uniformly dispersed. And an image receiving layer for receiving an image formed by the ink on the recording medium is uniformly heated.

[0204] Therefore, the surface of the ink on the recording medium is flattened by the heat and pressure bonding of the ink and the recording medium, and 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, before the ink and the recording medium are thermocompression-bonded, the ink and the recording medium are preliminarily heated. As described above, by heating the ink and the recording medium stepwise, the amount of heat in one heating can be suppressed, and the ink and the recording medium can be gradually heated. As a result, since both the temperature of the ink and the temperature of the image receiving layer can be kept within the temperature range suitable for fixing, the ink can be reliably fixed to the image receiving layer, and the situation where the ink peels from the image receiving layer is avoided. can do. As a result, reverse transfer of the ink to a member that comes into contact with the ink at the time of thermocompression bonding, that is, the offset phenomenon can be reliably avoided.

Also, by gradually heating the ink and the recording medium, the amount of heat is transmitted not only to the image receiving layer but also to a deep layer of the recording medium, so that the temperature unevenness in the thickness direction of the recording medium can be reduced. can do. Thus, the expansion coefficient does not significantly differ for each layer of the recording medium, and the recording medium is less likely to warp. In addition, when the temperature unevenness occurs, each layer is easily separated due to a difference in shrinkage ratio of each layer in the recording medium when the recording medium is subsequently cooled, but the above-described configuration can reduce the temperature unevenness. Therefore, such peeling hardly occurs.

Further, in the above configuration, since the ink and the image receiving layer are uniformly heated, the temperature rise of the ink and the image receiving layer does not vary depending on the position. Thereby, good fixability of the ink to the recording medium can be reliably obtained on the entire image forming surface. As a result, the effect that the offset phenomenon can be suppressed more reliably is also achieved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a schematic configuration of a preheating 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 an image forming unit of the inkjet printer.

FIG. 5 is a flowchart showing a flow of an operation in the image output system.

FIG. 6 is a flowchart illustrating a flow of an operation in an image output process of the inkjet printer.

FIG. 7 shows that the sheet can be uniformly irradiated with light.
FIG. 4 is an explanatory diagram illustrating a schematic configuration of a preheating unit when a shape of a reflector is set.

FIG. 8 is an explanatory diagram showing another configuration example of the reflector.

FIG. 9 is an explanatory diagram illustrating a schematic configuration of a fixing unit using the reflector illustrated in FIG. 1 as a preheating unit.

FIG. 10 is a graph showing a temperature rise characteristic of a sheet according to one embodiment of the present invention.

FIG. 11 is a graph showing a temperature rise characteristic of a sheet according to another embodiment of the present invention.

FIG. 12 is an explanatory diagram illustrating a schematic configuration of a fixing unit using the reflector illustrated in FIG. 8 as a preheating unit.

FIG. 13 is a graph showing a temperature rise characteristic of a sheet according to still another example of the present invention.

FIG. 14 is a graph showing a temperature rise characteristic of a sheet according to still another example of the present invention.

FIG. 15 is an explanatory diagram illustrating another configuration example of the preheating unit.

FIG. 16 is an explanatory diagram showing still another configuration example of the preliminary heating unit.

FIG. 17 is an explanatory diagram showing still another configuration example of the pre-heating unit.

FIG. 18 is an explanatory diagram showing still another configuration example of the preliminary heating unit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Inkjet printer (image forming apparatus) 12 Image forming unit (image forming unit) 13 Fixing unit (fixing unit) 25 Preheating unit (preheating unit) 26 Heat bonding unit (heating bonding unit) 35 Preheating unit (preheating unit) ) 36 Pre-heating unit (pre-heating unit) 37 Pre-heating unit (pre-heating unit) 38 Pre-heating unit (pre-heating unit) 41 Halogen lamp (light source) 42 Reflector (reflective member) 43 Light shielding plate (light shielding member) 44 Convex lens ( Light flux conversion means) 45 GRIN lens (light flux conversion means)

Claims (8)

[Claims] 1. An image forming apparatus comprising: an image forming unit that forms an image on a recording medium using ink; and a fixing unit that fixes an image formed by the image forming unit on the recording medium. The fixing unit heats the ink and the recording medium constituting the image and presses the ink against the recording medium; And a pre-heating means for pre-heating the ink, and the pre-heating means uniformly heats the ink and uniformly heats an image receiving layer for receiving an image formed by the ink on the recording medium. An image forming apparatus comprising: 2. The apparatus according to claim 1, wherein said preheating means includes a light source for emitting light, and a reflecting member for reflecting a part of the light from said light source toward a recording medium. The image forming apparatus as described in the above. 3. The reflection member according to claim 1, wherein the first light reaches the recording medium directly from the light source, and the second light reaches the recording medium from the light source via the reflection member.
The image forming apparatus according to claim 2, wherein the image forming apparatus is configured to generate at least the second light that uniformly heats the ink and the image receiving layer. 4. An image forming apparatus according to claim 3, wherein said preheating means includes a light shielding member for cutting light used for unevenly heating said ink and said image receiving layer. . 5. The image forming apparatus according to claim 4, wherein the light shielding member is arranged at a position corresponding to a time of irradiating the recording medium with light. 6. The pre-heating means converts the light from the light source to a light capable of uniformly heating the ink and the image receiving layer on the recording medium by converting the light from the light source to the recording medium. The image forming apparatus according to claim 1, further comprising a light beam converting unit that emits light toward the light source. 7. The light source is provided so as to extend in a direction transverse to a direction in which the recording medium is conveyed, and is set so that light distribution in the extending direction can be made uniform. The image forming apparatus according to claim 2. 8. 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 preheating the ink and the recording medium before the third step. In the third step, the ink is uniformly heated and formed by the ink on the recording medium. An image forming method, wherein an image receiving layer for receiving an image is uniformly heated.