JP2000103044A - Image output device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a print processing capability by rapidly drying an ink- discharged paper. SOLUTION: A drying part 11 is provided on an ink jet printer, and the drying part 11 has at least, a heating roller 12 and a support roller 13 arranged opposite to each other. An ink-discharged paper 10 is conveyed to a space between the heating roller 12 and the support roller 13, and sandwiched between both rollers 12, 13, so that heat generated by the heating roller 12 is directly conducted to ink on the paper 10, resulting in the rapid drying of the ink. Further, the ink on the paper 10 is pressed by the heating roller 12, so that the protuberance of the ink is crushed to flatten the surface of the ink and the ink becomes glossy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image output apparatus for outputting an image to a recording medium by discharging ink onto the recording medium in accordance with image data, as represented by an ink jet printer, for example. In particular, the present invention relates to an image output device provided with a drying mechanism for drying ink ejected on a recording medium.

[0002]

2. Description of the Related Art Hitherto, various image output apparatuses have been proposed which output images recorded by, for example, a digital camera or images created and processed by a personal computer on paper as a recording medium. The recording method in the image output device includes, for example, a thermal method, a thermal transfer method, an ink jet method, a laser printing method, etc. Among them, the ink jet method is a method in which ink is directly ejected onto a recording medium, and the running cost is particularly high. However, there is an advantage that it is inexpensive and has excellent quietness during printing. In addition, due to recent advances in technology, the quality of an image formed by an inkjet method has been sufficiently increased, and its use is gradually expanding.

Here, a conventional ink jet type image output apparatus (ink jet printer) will be described below. The above-described ink jet printers are roughly classified into an on-demand type and a continuous type, and each of these will be described below.

[0004] As shown in FIG. 4, an on-demand type ink jet printer is provided with an ink discharge section 51 for discharging ink for each dot of an image. The ink discharge section 51 includes a pressure chamber 52, a piezoelectric element (piezo element) 53, and a vibration partition 54.

In this configuration, when the piezoelectric element 53 vibrates according to an image signal, the vibration is transmitted to the vibration partition 54,
The ink 55 filled in the pressure chamber 52 is pressurized by the vibration of the vibration partition 54. Thus, the ink 55 is ejected from the ink ejection port 52a provided in the pressurized chamber 52 to the recording medium as an ink droplet 55a. That is, the on-demand type ink jet printer discharges the ink droplet 55a when a signal is input. The pressure chamber 52 contains the ink 55,
It communicates with a stored ink tank (not shown), and the ink 55 is supplied from the ink tank as needed.

The above-mentioned ink jet printer is of a so-called piezo type using a piezoelectric element 53. In addition to this, a type called a thermal type (bubble jet type, thermal ink jet type) has also been put to practical use. ing. The thermal method is a method in which a heating plate is disposed in a pressurized chamber and bubbles are generated by heating the heating plate, and ink is ejected from an ejection port by the expansion pressure of the bubbles.

On the other hand, as shown in FIG. 5, a continuous type ink jet printer includes an ink discharge section 61 for discharging ink in units of one dot of an image. The ink ejection unit 61 includes a PZT (piezo element) 62, a nozzle 63, a charge control electrode 64, a deflection electrode 65, an ink catcher 66, an ink reservoir 67, and a pump 68.
It has.

In this configuration, the ink stored in the ink reservoir 67 is pressurized by the ink pump 68 and reaches the nozzle 63. The ink that has reached the nozzle 63 is continuously discharged as an ink droplet 69 a from the tip of the nozzle 63 in response to the high frequency vibration of the PZT 62, and passes through the charge control electrode 64. An electric field is applied to the charge control electrode 64 in accordance with an image signal, whereby an electric charge is appropriately applied to the ink droplet 69a passing through the charge control electrode 64.

The ink droplet 69 that has passed through the charge control electrode 64
a passes through the deflection electrode 65. At this time, the ink drop 69
Of the a, the charged one is bent under the influence of the electric field applied to the deflecting electrode 65, and reaches the paper 70. On the other hand, the ink droplet 69a to which no charge is added proceeds straight as it is, and reaches the ink catcher 66. The ink in the ink catcher 66 moves to the ink reservoir 67 through the piping path, and is stored and accumulated.

As described above, the continuous type ink jet printer forms an image by circulating the ink while constantly discharging the ink droplet 69a from the nozzle 63 and controlling the flying direction of the ink in accordance with the image signal. Is what you do.

[0011]

However, in the conventional ink jet printer, the ink ejected on the paper is only dried naturally after that, and is not forcedly dried, so that the ink is fixed on the paper. Takes time to do. As a result, in the configuration of the conventional ink jet printer, it is impossible to discharge ink ejected sheets one after another one after another, which causes a problem that the processing speed of the ink jet printer is reduced.

Since the ink ejected onto the paper is absorbed to some extent by the paper, natural drying may be sufficient in some cases. However, the degree of natural drying depends on the ink absorbency and swelling of the paper. , Depending on the type of paper used, it takes a long drying time, and when an inkjet printer is used for industrial purposes, high-speed processing is required.
Considering such factors, the present situation is that natural drying cannot sufficiently cope.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to quickly dry ink ejected on paper regardless of the characteristics of the ink and the paper, thereby improving print processing performance. It is another object of the present invention to provide an image output device capable of improving the image quality.

[0014]

According to a first aspect of the present invention, there is provided an image output apparatus, comprising: an ink ejection unit for ejecting ink in units of dots constituting an image; An image output apparatus for outputting an image of at least one color on a recording medium by discharging the ink, further comprising a drying unit for drying the ink discharged on the recording medium.

According to the above arrangement, the ink ejected onto the recording medium is forcibly dried by the drying means, so that the drying time varies greatly depending on the paper and ink used, as in the case of natural drying. It is possible to dry the ink faster and more reliably than in the case of natural drying without occurrence. As a result, it is possible to discharge the sheets one after another, and as a result, the processing speed of the ink jet printer can be improved as compared with the related art.
Therefore, the image output device having the above configuration is very suitable for industrial applications that require a processing speed as high as possible.

As the above-mentioned drying means, for example, means for drying without contact with the recording medium (for example, means for blowing hot air to the recording medium, means for irradiating far-infrared rays), or a method for bringing a heat-generating material into direct contact with the recording medium Thus, it can be constituted by means for drying.

According to a second aspect of the present invention, there is provided an image output apparatus according to the first aspect, wherein:
The drying unit includes a heating member that generates heat, and the heating member is provided so as to be able to contact the recording medium.

According to the above arrangement, since the heating member that generates heat comes into direct contact with the recording medium, the efficiency of heat transfer from the heating member to the ink ejected onto the recording medium is reduced. It is significantly improved as compared with the case where the drying means is constituted by the means. This allows the ink to dry faster than the non-contact type.

When the heating member comes into contact with the recording medium, the ink on the recording medium is pressed by the heating member, and the swelling of the ink on the recording medium is flattened.
Thereby, irregular reflection on the ink surface can be reduced as much as possible, so that a further effect that the ink can have glossiness can be obtained.

According to a third aspect of the present invention, an image output apparatus includes:
At least the surface of the heating member has water repellency.

According to the above configuration, for example, the surface of the heating member is subjected to water repellency treatment, or the entire heating member is made of a material having water repellency, so that at least the surface of the heating member is provided with water repellency. It is possible. Since the surface has water repellency, the ink ejected on the recording medium is not transferred to the heating member by the contact between the heating member and the ink on the recording medium. This allows
It is possible to avoid a decrease in the image quality of the printed image and to prevent the surface of the heating member from being contaminated with ink.

According to a fourth aspect of the present invention, there is provided an image output apparatus according to any one of the first to third aspects, wherein the ink discharging unit is configured to detect an ink discharged onto a recording medium. The amount is controlled for each dot.

According to the above configuration, the gradation control can be performed for each dot by controlling the discharge of the ink discharge unit for each dot. As a result, a unit of gradation expression is compared with the conventional method in which the amount of ink ejection is not changed for each dot, and gradation is expressed in units of a plurality of dots depending on whether or not ink is ejected to each dot. Is smaller, so that the image quality can be improved as compared with the related art.

For example, when one image output system is configured by combining the image output device of the present invention with an image processing device or the like, the image processing device usually performs at least error diffusion processing in order to improve image quality. Done. However, according to the present invention, the image quality can be improved by adopting a configuration in which the ink ejection amount is controlled for each dot, so that it is no longer necessary to perform the error diffusion processing in the image processing apparatus. Therefore, the image processing time in the image processing apparatus can be significantly reduced, and as a result, the processing time of the entire system can be significantly reduced.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
This will be described below with reference to FIGS.

FIG. 2 shows a schematic configuration of an image output system to which an ink jet printer 1 as an image output device according to the present invention is applied. This image output system includes an image reading device 2, a film scanner 3, an image processing device 4, and a monitor 5, in addition to the inkjet printer 1.

The image reading device 2 reads image data recorded on a compact flash 6 which is a semiconductor memory card and other recording media. The above image data is obtained, for example, by imaging with a digital camera, or by creating an image with a personal computer or the like. Image data read by the image reading device 2 is supplied to the image processing device 4.

The film scanner 3 is a kind of image reading device for reading a negative (positive) image recorded on the film 7, and supplies image data corresponding to the read original image to the image processing device 4.

The image processing device 4 performs various conversion processes (image processing) on the image data supplied from the image reading device 2 or the film scanner 3 so that the image data becomes suitable for supply to the ink jet printer 1. Is what you do. As the above conversion processing, for example, RGB (Red, G
reen, Blue) format image data suitable for ink output
The processing includes conversion to C (Yellow, Magenta, Cyan) format, edge enhancement processing for enhancing the contour of the input image, red color correction processing, and the like.

The monitor 5 displays the image that has been converted by the image processing device 4. As a result, the state of the image can be confirmed, and whether or not image processing such as further color correction is necessary can be confirmed.

The ink-jet printer 1 forms an image on a recording medium such as paper by ejecting ink based on image data converted by the image processing apparatus 4. Of the recording head.

More specifically, as shown in FIG. 3, the ink jet printer 1 includes an ink ejection section 9 in which a plurality of ink ejection ports 8 are arranged in a line corresponding to each dot on a recording medium. Provided corresponding to the color of the ink used. Therefore, the inkjet printer 1 can output not only a monochrome image but also a color image.

The ink discharge section 9 is configured to be able to control the density of an output image by changing the discharge amount of ink for each dot. Specifically, the amount of ink ejected from each ink ejection port 8 at one time is fixed, and the number of ink ejections for each dot is changed.
That is, the amount of ink ejected to the recording medium is changed by over-strike of the ink on the recording medium. With such a configuration, the print dot size becomes a size corresponding to the number of times of ink ejection, as shown in FIG.

The ink discharge section 9 may of course have a structure capable of changing the amount of ink discharged from each ink discharge port 8 at one time.

Next, the drying mechanism of the ink jet printer 1 according to the present invention will be described.

As shown in FIG. 1, the ink jet printer 1 includes a drying unit 11 (drying means) for drying ink ejected on a sheet 10 as a recording medium.
The drying unit 11 is provided downstream of the ink ejection unit 9 (see FIG. 3) in the sheet transport direction, and is disposed opposite to the heating roller 12 (heating member), which is a hollow roller, and the heating roller 12. It is composed of a support roller 13 and transport rollers 14a and 14b opposed to each other. The transport rollers 14a and 14b are provided further downstream than the heating roller 12 and the support roller 13 in the sheet transport direction, and are configured to pinch the sheet 10 and transport it to the sheet discharge side by rotating in opposite directions.

The heating roller 12 is made of, for example, silicone rubber having a hardness of about 70 measured by a rubber hardness meter specified by the JIS standard, and has a diameter of 50 mm and a length of 6 to 15 inches in the rotation axis direction. The heating roller 12
Is disposed to face the support roller 13 so that the paper 10 can be appropriately pressed.

The material, hardness, diameter, and axial length of the heating roller 12 are not limited to these values. For example, the material of the heating roller 12 can be made of, for example, NBR (acrylonitrile-butadiene copolymer rubber) -based rubber, PTFE (polytetrafluoroethylene) -based rubber, metal, or the like. What is necessary is just to set suitably according to the material of the roller 13, a drying speed, etc. For example, if the heating roller 12 is made of a hard roller made of metal or the like, the surface of the ink on the paper 10 can be made flatter than in the case where it is made of a resin. It is assumed that it is possible to have.

A heater 12a is provided inside the heating roller 12, and the surface of the heating roller 12 is heated to a normal temperature or higher by heating the heater 12a. Therefore, the surface temperature of the heating roller 12 is adjusted to, for example, 80 to 1 by adjusting the amount of electricity to the heater 12a.
It is possible to vary up to 50 ° C. Note that the surface temperature is not limited to this range.

The heating roller 12 has a surface coated with fluorine and has water repellency and water resistance. Thus, when the ink ejected onto the paper 10 comes into contact with the heating roller 12, the so-called offset phenomenon in which the ink is transferred to the heating roller 12 on the contrary can be avoided. As a result, it is possible to avoid a decrease in the image quality of the print image, and to
2 It can be avoided that the surface is contaminated with ink.

The water-repellent treatment on the surface of the heating roller 12 is as follows.
Not limited to the above fluorine coating, for example, PTF
It may be an E coating. The heating roller 12
Is made of, for example, the above-mentioned PTFE-based rubber, the heating roller 12 itself has water repellency. In this case, the above-mentioned water repelling treatment on the surface of the heating roller 12 can be unnecessary.

The supporting roller 13 is made of, for example, a metal such as aluminum, and has a diameter of 30 to 50 mm and a length of 6 in the rotation axis direction.
~ 15 inches. The material, diameter, and axial length of the support roller 13 are not limited to these values, and may be appropriately set in consideration of the material of the heating roller 12 and the like.

The above-mentioned heating roller 12 and supporting roller 13
That is, the paper 10 can be rotated in opposite directions so that the paper 10 on which ink has been ejected can be sandwiched between the papers and transported to the transport rollers 14a and 14b.

Next, the operation of the ink jet printer 1 and the image output system according to the present invention will be described with reference to FIGS.

In the above configuration, the image data recorded on the compact flash 6 by, for example, imaging with a digital camera is read by the image reading device 2 and transmitted to the image processing device 4. On the other hand, an original image recorded on film 7 by shooting with an analog camera is scanned by film scanner 3 and converted into image data corresponding to the original image, and the image data is transmitted to image processing device 4. Is done.

The image processing device 4 performs various image processings on the image data so that an appropriate image is output from the ink jet printer 1. At this time,
The operator checks the processed image displayed on the monitor 5 and causes the image processing device 4 to perform image processing until a desired image is obtained. After that, the processed image data is transmitted to the inkjet printer 1.

In the ink jet printer 1, the ink discharger 9 discharges ink while controlling the amount of ink discharged on the paper 10 for each dot constituting an image according to the image data from the image processing device 4. Thus, a dot having a size corresponding to the ink ejection amount is formed for each dot (see FIG. 3). Paper 10 on which ink ejection has been completed
Is transported to the drying section 11 at the subsequent stage.

In the drying section 11, a heater 12a
As a result, the surface of the heating roller 12 is heated to a predetermined temperature. The paper 10 on which ink has been ejected is
And is conveyed and held between the support rollers 13 and
Thereby, the ink on the paper 10 is heated and pressed and dried. Thereafter, the dried paper 10 is discharged to the paper discharge side by the rotation of the pair of transport rollers 14a and 14b.

As described above, in the present embodiment, the drying section 11 is provided at the subsequent stage of the ink discharge section 9 to forcibly dry the paper 10 on which the ink has been discharged. This allows
The ink can be dried quickly and reliably regardless of the ink absorption and swelling properties of the paper and the characteristics of the ink itself. Therefore, even when the ink-discharged papers 10 are stacked, the ink does not adhere to the back surface of the paper 10 on which the ink is discharged, and therefore, the ink-discharged papers 10 can be discharged one after another. Thus, the processing speed of the inkjet printer 1 can be improved. As a result, the inkjet printer 1 can be suitably used for industrial applications that require a processing speed as high as possible.

In the present embodiment, a case where the drying unit 11 has the heating roller 12 and the ink on the paper 10 is dried by directly contacting the paper 10 has been described as an example. It is not limited. For example, the drying unit 11 may be configured to dry the ink on the paper 10 by a non-contact method, such as blowing hot air on the paper 10 or irradiating far infrared rays.

However, according to the contact type as in this embodiment, the following effects can be obtained. That is, in the contact type, the heat from the heating roller 12 is directly transmitted to the paper 10, so that the thermal efficiency is good and the ink can be dried faster than in the non-contact type. In the case of the contact type, the heating roller 12
The ink on the paper 10 is pressed by the pressing of
The rise of the ink is flattened. Thereby, irregular reflection on the ink surface can be reduced as much as possible, and a further effect that the ink can have glossiness can be obtained.

In the field of copying machines, for example, a heating roller which is considered to be equivalent to the present invention is used as a fixing means for fixing the toner image on the paper after transferring the toner image onto the paper. However, the heating roller 12 in the ink jet printer 1 of the present invention is different from the above-described copying machine in that it has a function of imparting gloss to the ink as well as a function of drying the ink as described above.

In this embodiment, an example in which the heating member is constituted by the heating roller 12 alone has been described. However, for example, an endless belt may be stretched by a plurality of rollers. In this case, at least one of the stretching rollers may be replaced with the heating roller 12 described above.

The configuration of the present invention in which the amount of ink ejected on the paper 10 is controlled for each dot can be applied to a continuous system. However, in this case, since a member corresponding to each nozzle cannot be provided in common among a plurality of nozzles, there is a disadvantage that the price of the apparatus is inevitably extremely high.

Next, the ink jet printer 1 of the present invention
According to the present invention, since the ink ejection unit 9 that controls the amount of ink ejected to the recording medium for each dot is provided, the image quality of a printed image can be improved, and the processing speed of the system as a whole can be increased. it can. The reason why such an effect is obtained will be described below.

Conventionally, as a method of expressing the density of a print image, an area consisting of several vertical dots × several horizontal dots is defined as a unit area, and the number of ink-discharged dots in this unit area is used as the unit area. The density (gradation) is determined, and the density of the entire image is expressed by a combination of these unit areas. For example, when the unit area is formed of a square area of 16 dots consisting of 4 dots in the vertical direction and 4 dots in the horizontal direction, one unit area can be expressed by 16 gradations depending on whether or not ink is ejected to each dot. .

On the other hand, in the configuration of the present invention, since the ink discharge amount is controlled for each dot, the density can be expressed for each dot, that is, the minimum unit of the density expression can be one dot. . As a result, the density expression can be performed more finely than in the above-described conventional method in which the density is changed for each unit region including a plurality of pixels, and as a result, the image quality can be significantly improved.

In the prior art in which the density is changed for each unit area, it is necessary to perform an error diffusion process at a stage preceding the ink jet printer (image processing apparatus). This error diffusion processing is performed to prevent a boundary between adjacent unit areas from being unnaturally expressed or to prevent a periodic stripe pattern called moiré or texture from being generated in the entire image. When expressing the gradation, the gradation information (dot formation position information) of the unit area adjacent thereto is reflected, and the density gradient between these adjacent unit areas and the line drawing formed between the adjacent unit areas are continuously displayed. This is the process to be performed. Therefore, in the error diffusion processing, complicated calculation processing is usually performed for each unit area, and a huge amount of calculations are performed in total to form one image. For this reason, conventionally, much time has been spent on image processing in the former stage of the ink jet printer, and this has also caused an increase in the processing time of the entire system.

However, in the configuration of the present invention, the image quality can be improved as described above by controlling the ink ejection amount for each dot. Therefore, the image quality can be improved by the error diffusion processing in the image processing apparatus. There is no longer any need to improve. Therefore, according to the above configuration, it is possible to greatly reduce the image processing time in the image processing apparatus by eliminating the need for error diffusion processing in the previous stage of the ink jet printer, thereby greatly reducing the processing time of the entire system. be able to.

In general, as the number of ink ejection units of an on-demand type ink jet printer is increased, the image processing time per line is increased. It takes time. However, according to the present invention, the image processing time can be shortened by eliminating the need for the error diffusion processing in the image processing device 4 as described above. Can be increased. In this case, the speed of the printing process by the inkjet printer 1 can be further increased.

Incidentally, the performance of the image processing apparatus is improving day by day, and the time required for the error diffusion processing is being greatly reduced. That is, the reduction of the image processing time in the former stage of the inkjet printer has already been advanced. Further, since the present invention is configured to control the ink discharge amount for each dot, the image output time is slightly longer than in the related art in which an image is output by simply discharging ink to each dot. . However, even considering the current performance of the image processing apparatus and the length of the image output time in the present invention, the fact that the processing speed of the system as a whole at this time does not become slower than before is as follows.
It is known from experiments under predetermined conditions.

[0062]

According to the first aspect of the present invention, there is provided an image output apparatus comprising:
As described above, the configuration further includes the drying unit that dries the ink ejected onto the recording medium.

Therefore, the ink ejected onto the recording medium is forcibly dried by the drying means, so that the ink can be dried faster and more reliably than in the case of natural drying, regardless of the characteristics of the paper and ink used. Can be done.
This makes it possible to discharge ink-ejected sheets one after another in a stacked manner, thereby achieving an effect that the processing speed of the ink jet printer can be improved as compared with the related art.

According to a second aspect of the present invention, as described above, in the configuration of the first aspect, the drying unit includes a heating member that generates heat, and the heating member can contact the recording medium. It is a structure provided in.

Therefore, since the heating member that generates heat is in direct contact with the recording medium, the efficiency of heat transfer from the heating member to the ink ejected on the recording medium is reduced by a non-contact type drying means. It is much improved compared to the case where it is done. Thereby, in addition to the effect of the configuration of the first aspect, there is an effect that the ink can be dried faster than the non-contact type.

When the heating member comes into contact with the recording medium, the ink on the recording medium is pressed by the heating member. As a result, the swelling of the ink on the recording medium is flattened, so that the ink also has an effect of being able to have glossiness.

As described above, the image output device according to the third aspect of the present invention is the image output device according to the second aspect, wherein at least the surface of the heating member has water repellency.

Therefore, the ink ejected on the recording medium is not transferred to the heating member by the contact between the heating member and the ink on the recording medium. Accordingly, in addition to the effect of the configuration of the second aspect, it is possible to avoid a decrease in the image quality of the printed image and to prevent the surface of the heating member from being contaminated with ink.

According to a fourth aspect of the present invention, in the image output apparatus according to any one of the first to third aspects, the ink discharge unit is configured to determine the amount of ink discharged to the recording medium for each dot. This is a configuration for controlling

Therefore, the gradation expression can be performed for each dot, and the unit of the gradation expression can be made smaller than in the related art in which the gradation is expressed in units of a plurality of dots. As a result, in addition to the effect of any one of the first to third aspects, an effect that the image quality can be improved as compared with the related art is obtained.

Since the image quality can be improved,
For example, when an image output system is configured in combination with an image processing apparatus, error diffusion processing for improving image quality no longer needs to be performed by the image processing apparatus. As a result, the image processing time in the image processing apparatus can be significantly reduced, and the processing time of the entire system can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a drying unit included in an inkjet printer according to the present invention.

FIG. 2 is a block diagram showing a schematic configuration of an image output system to which the inkjet printer is applied.

FIG. 3 is an ink ejection section of the inkjet printer,
FIG. 4 is an explanatory diagram illustrating a relationship between ink droplets ejected on a sheet and a dot size formed.

FIG. 4 is a cross-sectional view showing a schematic configuration of a conventional on-demand type inkjet printer.

FIG. 5 is a cross-sectional view illustrating a schematic configuration of a conventional continuous type inkjet printer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink jet printer (image output device) 9 Ink discharge part 10 Paper (recording medium) 11 Drying part (drying means) 12 Heating roller (heating member)

Claims (4)

[Claims] 1. An image output apparatus comprising: an ink ejection section for ejecting ink in units of dots constituting an image for each color of ink; and outputting at least one color image on a recording medium by ejecting the ink. An image output apparatus further comprising a drying unit for drying ink ejected on a recording medium. 2. The image output apparatus according to claim 1, wherein the drying unit includes a heating member that generates heat, and the heating member is provided so as to be able to contact the recording medium. 3. The image output apparatus according to claim 2, wherein at least a surface of said heating member has water repellency. 4. An image output apparatus according to claim 1, wherein said ink discharge section controls the amount of ink discharged on a recording medium for each dot.