JP2002166581A - Image recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image recording method in which rewrite recording can be performed by a single pass on a recording medium rewritable of two color images while shortening a rewriting time significantly. SOLUTION: Using a recording medium 1 having a two-color rewritable recording layer where all developed colors are decolored by applying first thermal energy, a first color is developed by applying second thermal energy different from the first thermal energy, and a second color different from the first color is developed by applying third thermal energy different from the first and second thermal energy, a heat roller 2 applies the first thermal energy at least to the rewritable recording layer on the entire surface of the recording medium 1 to heat the rewritable recording layer thus erasing existing images. Subsequently, respective heaters in a thermal head 3 are driven selectively, in units of pixel, such that the second or third thermal energy is applied to the rewritable recording layer and the first and second colors are developed individually thus forming a new image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording method for rewriting an image using a recording medium having a two-color rewritable recording layer capable of repeatedly rewriting a two-color image.

[0002]

2. Description of the Related Art In conventional hard copy recording, an image is formed on a recording medium such as paper from the outside with a visual material such as ink or toner, or on a base material such as paper such as thermosensitive recording paper. In this method, a permanent image was recorded by providing a recording layer and forming a visible image on the recording layer.

[0003] However, with the construction of various network networks, the spread of facsimile machines, and copiers, the rapid increase in the consumption of these recording materials has caused natural destruction problems such as deforestation and social problems such as garbage disposal. In order to cope with these problems, there is a strong demand for reducing the consumption of recording material, such as reproduction of recording paper. In response to such a problem, attention has recently been paid to a recording material capable of repeatedly recording and erasing a visible image.

As a recording material having such characteristics, a recording material using a leuco dye whose color develops and decolors depending on the applied heating energy has been disclosed (Japa).
n Hardcopy '90, NIP2, p147 (1990)).

In connection with these, an image recording method for simultaneously recording and erasing a visible image using a single thermal head is disclosed in Japanese Patent Laid-Open No. 197647/1992. An image recording system for erasing a visible image using a plate-shaped erasing head provided with a heating resistor is disclosed in JP-A-5-4447.

On the other hand, a heat-sensitive recording material which cannot form rewrite recording but can form a single multicolor image has been developed (for example, see JP-A-8-150778).
For these reasons, there is a need for a recording material capable of multi-color rewritable recording.

Therefore, a recording material capable of rewriting two-color images has recently been developed. However, this recording material needs to form the first color image and the second color image separately, and has not yet been put to practical use due to problems such as the complexity of the rewriting process. .

[0008]

As described above, the conventional rewritable recording medium is limited to a single color, or
There are problems such as an increase in the number of rewriting steps when multicoloring is performed.

Accordingly, the present invention provides an image recording method that enables rewriting recording on a recording medium on which two-color image rewriting can be performed in one pass, thereby greatly reducing rewriting time. Aim.

[0010]

According to the image recording method of the present invention, all colors which have been colored by the application of the first thermal energy are erased, and the second thermal energy different from the first thermal energy is applied. A two-color rewritable color, in which a first color is formed by applying energy, and a second color different from the first color is formed by applying third heat energy different from the first and second heat energies. A recording medium having a recording layer is used, and the entire surface of the recording medium is heated by an image erasing heating means so as to apply at least the first thermal energy to the rewritable recording layer to erase an existing image. After
Each heating element of a single thermal head is selectively driven on a pixel-by-pixel basis so as to apply the second or third thermal energy to the rewritable recording layer, so that the first and second colors are individually obtained. To form a new image.

Further, the image recording method of the present invention uses a rewritable recording medium made of two kinds of heat-changeable rewritable recording materials having different coloring hues and partially identical erasable conditions, and covers the entire surface of the recording medium. On the other hand, after the already erased image is erased by the image erasing heating means under the common erasing conditions, each heating element of the single thermal head is driven by selectively changing the thermal energy in pixel units to drive two colors. A new image is formed by individually developing colors.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment will be described.

FIG. 1 is a diagram for explaining an image recording method according to the first embodiment, and schematically shows how an image on a recording medium 1 is rewritten. Here, although details will be described later, the recording medium 1 uses a recording material that can repeatedly rewrite two colors of blue and red due to a difference in heat energy. In the example of FIG. 1, the recording medium 1 in which the alphabetical letter “A” is drawn in blue and the number “1” is drawn in red as a pre-recorded image, Indicates that the character is rewritten so that the alphabetic character "B" is displayed. Note that, for the purpose of a schematic illustration, the blue portion is shown by solid black, and the red portion is shown by cross hatching.

In the image recording method according to the first embodiment, the entire surface of the recording medium 1 moving in the direction of the arrow in FIG. Erasing is performed, and then red and blue recordings are simultaneously performed by a single line-type thermal head 3 serving as image recording means. That is, in the thermal head 3,
The level of the heat energy applied is changed on a pixel-by-pixel basis, and the pixels that emit red are driven to emit red heat, and the pixels that emit blue are driven to emit blue heat.

Here, when changing the thermal energy level of the thermal head 3 for each pixel, a plurality of pulses are applied within the recording cycle CL as shown by the driving waveform (negative logic) in FIG. This is done by changing the number of That is, a blue pixel that emits color with low heat energy has a small number of pulses as shown in FIG. 2A, and a red pixel that emits color with high heat energy has a large number of pulses as shown in FIG. 2B. The driving circuit of the thermal head 3 is controlled so as to be as follows.

In the case of a commercially available thermal head having a multi-value input function and capable of changing the pulse width in pixel units, the thermal energy can be controlled by changing the pulse width. It is. By performing rewriting in such a procedure, rewriting recording of a two-color image is realized in one pass.

Next, the configuration of an image recording apparatus necessary for realizing the image recording method of the present embodiment will be described with reference to FIG. In FIG. 3, the image recording apparatus includes a pair of conveying rollers 4 as conveying means for conveying the recording medium 1 in a direction indicated by an arrow, a timing sensor 5 for detecting a timing of erasing or recording an image on the recording medium 1, 1 includes the heat roller 2 and the thermal head 3 described above, and the platen roller 6 disposed to face the heat roller 2 and the thermal head 3.

In such a configuration, when the image on the recording medium 1 is rewritten, the recording medium 1 is conveyed by the conveying roller pair 4.
Based on the detection timing of the timing sensor 5, the heat roller 2 adjusted to a predetermined temperature is pressed against the recording medium 1 to make contact with the recording medium 1 to erase the existing image, and then the thermal head 3 is placed on the recording medium 1 By pressing, the recording operation as described above is performed. The recording medium 1 that has passed through the thermal head 3 is discharged to the outside by a pair of conveying rollers 4 provided on the downstream side, and a series of rewrite recording operations is completed.

Next, the heat roller 2 for erasing an image used in the image recording apparatus shown in FIG. 3 will be described in detail with reference to FIG. In FIG. 4, a heat roller 2 is provided with a conductive rotating shaft 12 that also serves as a power supply to the conductive ceramic 11 at both ends of a conductive ceramic 11 (cross hatched portion in the figure) that generates heat when energized. In addition, the outer peripheral surface is directly covered with heat-resistant rubber 13.

In the vicinity of the surface of the heat-resistant rubber 13, a thermopile 14 is provided as a temperature detecting means for detecting the surface temperature of the substance in a non-contact manner.
By controlling power supply to the conductive ceramics 11 based on the detected temperature of No. 4, temperature control is performed so as to maintain a constant temperature.

The conductive ceramics 11 can be manufactured by adding a metal powder to the ceramics and sintering the ceramics. Specifically, for example, the conductive ceramics 11 are sold by Tokai High Heat Industry Co., Ltd. It is possible to use the product name "Infralex Bark" (registered patent No. 2
627506). Since this material has a high degree of freedom in its heat generation characteristics and a high degree of freedom in its manufacturing shape, the heat roller 2 can be realized at low cost. In the present embodiment, the effective heating area is 52 mm, the outer diameter is 8 mm, and the metal powder to be contained is adjusted to 140 watts (24 VDC, 4.1 Ω).

The conductive rotating shaft 12 is made of, for example, brass whose surface is plated with nickel, and has an outer diameter of φ4 at its end.
A rotating shaft part of mm was formed and attached to both ends of the conductive ceramic 11. The heat-resistant rubber 13 is made of a silicone rubber containing a thermally conductive filler and having a thermal conductivity of 1.0 W / mK (rubber hardness of A75 / S) having a thickness of 1 mm so that heat can be efficiently transmitted to the recording medium 1. Was directly coated on the conductive ceramic 11.

The heat roller 2 configured as described above supplies power to the conductive ceramics 11 from the conductive rotating shaft 12 to generate Joule heat, thereby raising the temperature together with the heat-resistant rubber 13. Since the thermopile 14 has a fast thermal response time, overshoot and undershoot can be minimized even when controlling the temperature, and the heat roller 2
Even when controlling the temperature between 40 and 200 ° C., stable control can always be performed within ± 5 ° C. This makes it possible to heat the object to be heated to a predetermined temperature with a small size and reduced loss.

Next, the recording medium 1 used in the present embodiment will be described in detail with reference to FIG. In FIG. 5, the recording medium 1 has a base layer 2 for obtaining the strength of the entire recording medium 1.
1 underlayer 22, red coloring layer 23, intermediate adhesive layer 2
4, a blue coloring layer 25 and a protective layer 26 for preventing deterioration due to mechanical abrasion and heating. Here, the red coloring layer 23 and the blue coloring layer 25 as recording layers are
It is mainly composed of a dye material called a leuco dye and a color-reducing agent which reacts with the leuco dye by heating to develop or reduce the color.

This recording material does not originally rewrite an image by the above-mentioned method, but assumes that an image is rewritten in two steps (two passes). In the normal rewriting recording process on the recording material, first, as a first process, recording is performed by a thermal head while applying heat by a heat roller. At this time, due to the effect of the erasing heating, the blue coloring layer 25 in the upper layer of FIG. 5 does not develop color, and only the red coloring layer 23 in the lower layer develops color. In addition, at this time, if there is any image which has already been erased, it is erased by erasing heating.

Subsequently, as a second step, recording is performed by the thermal head alone without applying erasing heating. Then, the lower red coloring layer 23 does not develop color, and only the upper blue coloring layer 25 develops color. At this time, the red image recorded in the first step is not erased. Therefore, a two-color image of red and blue is formed by the two processes. When rewriting again, the same process is required every time.

The change shown here is based on the difference in the coloring / decoloring characteristics of the blue coloring layer 25 and the red coloring layer 23. The blue coloring layer 25 is relatively easy to erase and the red coloring layer 23
Are relatively difficult to erase.

The erasing characteristics of this recording material are caused by the cooling rate after heating, and the difference in ease of erasing is the difference in the lower limit of the erasable cooling rate. That is, since the blue coloring layer 25 is easy to erase, the color cannot be formed when there is erasing heating with a heat roller or the like, and only the lower red coloring layer 23 develops the color. The heat does not reach and only the blue coloring layer 25 develops a color.

On the other hand, a feature of the present invention is that it has been found that rewritable recording can be performed on this recording material without performing the above-described steps. Hereinafter, the results of evaluation of the characteristics of the recording medium 1 based on the image recording method of the present invention will be described. First, the transport speed is set to 40 mm / s
The recording medium 1 has a resolution of 12 do
The sensitivity characteristics when recording with the thermal head 3 of t / mm were evaluated. FIG. 6 shows the recording sensitivity characteristics when no erasing heating is applied.

In FIG. 6, the vertical axis represents the image density (monochrome), and the horizontal axis represents the recording energy of the thermal head 3.
As shown by the solid line a in FIG. 6, as the recording energy of the thermal head 3 is increased, the image density is increased, and the color is initially colored blue. Further, when the recording energy is increased, red begins to mix and blue and red are mixed. That is, a red color cannot be obtained even if the recording energy is increased by using the thermal head alone. In FIG. 6, the broken line b is the background average density.

Subsequently, using the recording medium 1 on which an image recording in which red and blue are mixed is performed, the conveying speed is set to 40 mm / s.
The erasing sensitivity characteristics when heating was performed using the heat roller 2 shown in FIG. 4 were evaluated. FIG. 7 shows the erasure sensitivity characteristics of the heat roller 2.

In FIG. 7, the vertical axis represents the image density (monochrome), and the horizontal axis represents the heating temperature of the heat roller 2. As indicated by the solid line c in FIG.
It turns out that it has disappeared well above. In this state, both blue and red have disappeared. At 160 ° C. or lower, although the blue color has disappeared, the red color has a shortage of heat and remains undissolved. Also, as shown by the broken line d, 180
Above ° C, unrecorded background will develop color. Therefore, the proper erasing temperature range is from 160 ° C. to 180 ° C. In FIG. 7, the broken line e is the initial background average density.

Subsequently, the sensitivity characteristics when recording was performed with the thermal head 3 while applying erasing heating were evaluated. The conveying speed of the recording medium 1 was 40 mm / s, and the temperature of the heat roller 2 was 180 ° C. The heat roller 2 and the thermal head 3 were arranged at a relative distance of 23 mm, and the time from erasing heating to recording was about 0.56 seconds. FIG. 8 shows recording sensitivity characteristics when recording is performed after erasing heating.

In FIG. 8, the vertical axis represents the image density (monochrome), and the horizontal axis represents the recording energy of the thermal head 3.
As shown by the solid line f in FIG. 8, as the recording energy of the thermal head 3 is increased, the image density is increased, and the color becomes blue. However, the density value is lower than the case where no erasing heating is applied as shown in FIG. Here, according to the above description, since blue is easily erased, it should not develop color immediately after erasing heating. However, as shown in the present result, by optimizing the time from erasing heating to recording, blue is reduced. But it can be colored. In FIG. 8, the broken line g is the background average density.

Subsequently, as the recording energy is increased, red begins to mix, but when the recording energy is further increased, blue is not developed, and only red is developed. Here, the density value of the portion where red color is developed is lower than the density value at the time of color mixture in FIG. 6, but this is because the value without the color mixture of blue is lower, and Is a color density at which sufficient visibility can be obtained.

Based on the result, the recording condition was set to 0 for blue.
When the recording energy of the thermal head 3 was controlled in pixel units so that 13 mJ / dot and red color became 0.23 mJ / dot, the two-color image was actually rewritten by the method shown in FIG. There was no remnant, and a rewritten image in which blue and red were clearly recorded was obtained.

Therefore, as shown by these evaluation data, according to the present image recording method, it is possible to rewrite and record an image in a single pass on the recording medium 1 capable of two-color rewriting recording. And the rewriting time can be greatly reduced.

Next, the relationship between the time (interval) from the erasing heating by the heat roller 2 to the recording by the thermal head 3 and the rewriting characteristics of the recording medium 1 will be described. As shown in the data of FIGS. 6 and 8, the recording state of the recording medium 1 changes depending on the erasing heating condition. That is, when recording, the recording medium 1
The red color develops when is warmed to a predetermined temperature or higher, but can only be developed into a blue or mixed color state when it is cooled.

Therefore, the rewriting characteristic was evaluated by changing the interval between the erasing heating and the recording heating by changing the conveying speed of the recording medium 1. Table 1 below shows the results of comparing the color development states of blue and red when the temperature of the heat roller 2 is 180 ° C. and the interval between the erasing heating and the recording heating is 0.25 seconds to 1.2 seconds. .

[0041]

[Table 1] As shown in Table 1, if the interval is long, red and blue are mixed. This is because the recording medium 1 cools down before performing the red recording, so that the blue color cannot be erased. In addition, when the interval is short, blue color does not develop. This is because the temperature of the recording medium 1 is too high, so that the blue color continues to be cooled even after the recording is heated, and is erased. That is, the interval between the erasing heating and the recording heating is desirably 0.3 to 1.0 seconds. Further, the erasing heating temperature was set to 160 ° C. and 17 ° C.
The same evaluation was performed when the temperature was set to 0 ° C., but the same result was obtained.

Next, a second embodiment will be described.

In the second embodiment, the entire surface of the recording medium 1 is heated by using a plate-shaped heater 31 having a strip-shaped heating resistor formed on a substrate as an image erasing heating means. The image is erased.

FIG. 9 shows a configuration diagram of the plate heater 31.
In FIG. 9, a plate-shaped heater 31 has a thickness of 31 mm on a ceramic substrate 32 and is formed of silver-palladium (Ag-P
The heating resistor 33 according to d) has a width of 3 mm and a thickness of 2 mm.
It is formed in a belt shape of 0 μm, and its surface has a thickness of 2 μm.
It is configured to be covered with a glass protective film 34 of 0 μm.
A power supply electrode 35 made of silver is provided at both ends of the heating resistor 33, and a power supply lead wire 36 is connected to the power supply electrode 35.

The ceramic substrate 32 is fixed to a heat-resistant heat-insulating holder 37 made of a polyamide-imide resin in order to prevent the heat generated by the heating resistor 33 from being released.
Further, a thermistor 38 is provided on the back surface of the ceramic substrate 32.
Is provided to control the temperature of the heating resistor 33 to a constant temperature based on the temperature detection of the thermistor 38.
Here, the resistance value of the heating resistor 33 was set to 4.1Ω, and was set to 140 watts (W) at DC 24V.

Since the plate-like heater 31 thus configured has a very good thermal response, it is only necessary to drive the heat generation for erasing heating. In addition, since the width of the heating resistor 33 is wide, a sufficient heating contact time with the recording medium 1 can be secured. Therefore, power consumption can be reduced as compared with the heat roller 2 used in the first embodiment.

Also in the case of the present embodiment, the image rewriting procedure and the device configuration can be used as they are, just by using the plate heater 31 instead of the heat roller 2 used in the first embodiment. is there.

As in the first embodiment, the plate-like heater 3
When rewriting recording of a two-color image was performed on the recording medium 1 using No. 1, the rewriting image in which the blue image and the red image were clearly recorded was obtained in exactly the same manner, with the old image remaining unchanged. The effect that image rewrite recording is realized in one pass is also the same as that of the first embodiment.

Next, a third embodiment will be described.

The third embodiment uses a two-color rewritable recording medium 41 having different coloring characteristics and erasing characteristics from the recording medium 1 used in the first and second embodiments. is there.

FIG. 10 schematically shows the structure of the recording medium 41. The recording medium 41 has the same configuration as the recording medium 1 except that the base layer 21, the underlayer 22, and the protective layer 26 have the same configuration.
Two-color coloring layer 4 capable of forming two colors in one layer as a recording layer
2 is used. The two-color coloring layer 42 is a mixture of two types of rewritable recording materials having the same erasing characteristics but different coloring characteristics. Here, a material that emits red at a low recording energy and a material that emits black at a high recording energy are mixed.

The result of evaluating the characteristics of the recording medium 41 will be described. First, as in the case of the recording medium 1,
The sensitivity characteristics were evaluated when recording was performed with the thermal head 3 having a resolution of 12 dots / mm without applying erasing heating at a transport speed of 40 mm / s. FIG. 11 shows recording sensitivity characteristics when the erasing heating of the recording medium 41 is not performed.

In FIG. 11, the vertical axis represents the image density (monochrome), and the horizontal axis represents the recording energy of the thermal head. As shown by a solid line h in FIG. 11, as the recording energy of the thermal head 3 is increased, the image density is increased, and the color is initially colored red. Further, when the recording energy is increased, the black color starts to mix, and eventually the color becomes almost black in appearance. This is because the red color has not been erased when heated with high recording energy, but the black color has become dominant, making the red color visually difficult to understand. In FIG. 11, the broken line i is the background average density.

Subsequently, the erasing sensitivity characteristics when the heating was performed at a transport speed of 40 mm / s using the recording medium 41 in which the image was recorded in black was evaluated. FIG.
2 shows the erase sensitivity characteristics of the recording medium 41.

In FIG. 12, the vertical axis represents the image density (monochrome), and the horizontal axis represents the heating temperature of the heat roller 2. FIG.
As shown by a solid line j in FIG.
It turns out that it disappeared well above ℃. In other words, both red and black have disappeared. Further, as shown by a broken line k, at 200 ° C. or higher, the unrecorded background develops color. Therefore, 180 ° C. to 200 ° C. is the proper erasing temperature range. In FIG. 12, the broken line 1 is the initial background average density.

Subsequently, sensitivity characteristics when recording was performed with the thermal head 3 while erasing and heating were applied were evaluated. The temperature of the heat roller 2 was 190 ° C. Also, the transport speed,
The interval from erasing heating to recording heating is the recording medium 1
It is the same as when FIG. 13 shows recording sensitivity characteristics when recording is performed on the recording medium 41 after erasure heating.

In FIG. 13, the vertical axis represents the image density (monochrome), and the horizontal axis represents the recording energy of the thermal head 3.
As shown by the solid line m in FIG. 13, although the recording medium 41 tends to have a slightly lower image density as a whole, the recording medium 41 shows almost the same characteristics as when no erasing heating is applied (FIG. 11). This is because the erasing characteristics of red and black are the same, and erasing heating is applied under exactly the same conditions as when erasing heating is applied in a single color.

Based on this result, the recording condition was set to 0 for red.
16mJ / dot, 0.25mJ / d for black and red
When the recording energy of the thermal head 3 was controlled in pixel units so as to be ot, and the two-color image was actually rewritten and recorded by the method shown in FIG. A clearly recorded rewrite image was obtained.

That is, in the present image recording method, it is possible to rewrite and record a two-color image in a single pass even on the recording medium 41 as described above, thereby greatly shortening the rewriting time. Can be.

In the above embodiment, the case where the heat roller and the plate heater are used as the image erasing means has been described. However, the image recording method of the present invention is not limited to this. A stamp or the like may be used. Also, the recording medium may be freely selected for the color to be developed.

[0061]

As described above in detail, according to the present invention, 2
Rewriting and recording can be performed in a single pass on a recording medium on which color image rewriting can be performed, and an image recording method that can significantly reduce rewriting time can be provided.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a state in which an image on a recording medium is rewritten by an image recording method according to a first embodiment.

FIG. 2 is a waveform diagram showing an example of a driving waveform of a thermal head.

FIG. 3 is a configuration diagram schematically showing a configuration of an image recording apparatus for realizing the image recording method according to the first embodiment.

FIG. 4 is a perspective view showing a configuration of a heat roller used in the first embodiment.

FIG. 5 is a vertical sectional side view schematically showing the configuration of a recording medium used in the first embodiment.

FIG. 6 is a characteristic diagram showing recording sensitivity characteristics when no erasing heating is applied to the recording medium in the first embodiment.

FIG. 7 is a characteristic diagram showing erasing sensitivity characteristics of the recording medium by the heat roller according to the first embodiment.

FIG. 8 is a characteristic diagram showing recording sensitivity characteristics when recording is performed after erasing heating of the recording medium in the first embodiment.

FIGS. 9A and 9B schematically show a configuration of a plate heater used in the second embodiment, wherein FIG. 9A is a front view and FIG. 9B is a vertical side view.

FIG. 10 is a vertical sectional side view schematically showing a configuration of a recording medium used in a third embodiment.

FIG. 11 is a characteristic diagram showing recording sensitivity characteristics when no erasing heating is applied to a recording medium according to a third embodiment.

FIG. 12 is a characteristic diagram showing erasing sensitivity characteristics of a recording medium by a heat roller according to the third embodiment.

FIG. 13 is a characteristic diagram showing recording sensitivity characteristics when recording is performed after erasing and heating of the recording medium in the third embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Recording medium, 2 ... Heat roller (heating means for image erasure), 3 ... Thermal head (image recording means), 4 ... Conveying roller pair (conveying means), 6 ... Platen roller, 11 ... Conductive ceramics, 21 ... Base layer, 22 ... Underlayer, 23 ...
Red coloring layer, 24 ... intermediate adhesive layer, 25 ... blue coloring layer, 26 ...
Protective layer, 31: plate-shaped heater (heating means for erasing images), 4
1 ... recording medium, 42 ... two-color coloring layer.

Claims (6)

[Claims] 1. The method according to claim 1, wherein all of the colors that have developed are decolored by the application of the first thermal energy, and the first color is developed by the application of the second thermal energy that is different from the first thermal energy. A recording medium having a two-color rewritable recording layer that emits a second color different from the first color by applying a third heat energy different from the first and second heat energies, After heating the entire surface of the recording medium by the image erasing heating means so as to apply at least the first thermal energy to the rewritable recording layer to erase the existing image, each heating element of the single thermal head is heated. Is selectively driven on a pixel-by-pixel basis so as to apply the second or third thermal energy to the rewritable recording layer, thereby forming the first and second colors individually to form a new image. Characterized by Image recording method. 2. The method according to claim 1, wherein all of the colors that have developed are erased by applying the first thermal energy, and the first color is developed by applying the second thermal energy that is different from the first thermal energy. A recording medium having a two-color rewritable recording layer that emits a second color different from the first color by applying a third heat energy different from the first and second heat energies, After heating the entire surface of the rewritable recording layer so as to apply the first thermal energy to at least the rewritable recording layer and erasing the existing image, the rewritable recording layer is heated to a predetermined temperature or higher. Meanwhile, each of the heating elements of the single thermal head is selectively driven on a pixel-by-pixel basis so as to apply the second or third thermal energy to the rewritable recording layer.
And forming a new image by individually developing the second color. 3. A rewritable recording medium composed of two kinds of heat-changeable rewritable recording materials having different coloring hues and partially identical erasable conditions, and the entire surface of the recording medium is heated by image erasing heating means. After erasing an existing image under common erasure conditions,
An image recording method, wherein a new image is formed by driving each heating element of a single thermal head by selectively changing thermal energy in pixel units to individually develop two colors. 4. The image recording method according to claim 1, wherein said image erasing heating means is a heat roller. 5. The image recording method according to claim 1, wherein the heating means for erasing the image is a plate heater. 6. The image forming apparatus according to claim 1, wherein the formation of the new image by the single thermal head is performed 0.3 seconds to 1.0 second after the erasing heating by the image erasing heating unit. 3. The image recording method according to any one of 3.