Recording device and recording method

Abstract

To suppress shortage of color optical density of pixels to record a high-density image.SOLUTION: When a pixel immediately after a pixel of interest is a pixel that adds such energy that does not propagate heat to the pixel of interest, a recording device increases thermal energy to be added to the pixel of interest.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a recording apparatus and a recording method.

Background Art

[0002] Hitherto, in recording using a thermal print head, monochrome printing using thermal paper, color printing using an ink ribbon, and the like have been widely used. On the other hand, in recent years, color recording using paper having a plurality of color developing layers has been proposed and has spread as a simple printing means for photographs and the like. Each of the plurality of color developing layers has a different heating temperature and heating time required for color development, and a color image is recorded by causing a specific color developing layer to develop color by utilizing the difference (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in Patent Document 1, there is a risk that pixels with insufficient color density may appear. For example, in the rear end portion of a region where high-density color development is to be performed, if the energy applied to pixels after the rear end portion is small, heat does not propagate from the pixels after the rear end portion to the rear end portion. Therefore, the energy applied to the rear end portion is less than that applied to the central portion of the region where high-density color development is to be performed, and the color density may become insufficient.

[0005] The present invention has been made in view of the above problems, and an object thereof is to suppress a decrease in the color density of pixels for recording a high-density image.

Means for Solving the Problems

[0006] The present invention relates to a recording device that heats a sheet-shaped recording medium having multiple color-developing layers that correspond to multiple colors and develop color in response to heating, thereby developing a desired color-developing layer among the multiple color-developing layers to form an image on the recording medium, comprising: a recording head that heats the recording medium based on image data and includes multiple heating elements arranged in a predetermined direction; a first determination means that determines whether a first condition is met, which is whether the immediate subsequent pixel, located at the same position as the pixel of interest in the predetermined direction and recorded after the pixel of interest, is a pixel that develops a color that does not visually affect the development of the pixel of interest, or a pixel that does not develop any of the color-developing layers of the recording medium; and a pulse control means that controls the pulse applied to the recording head when forming the pixel of interest based on the determination result of the first determination means, wherein the pulse control means controls the pulse such that, when the value of the pixel of interest in the image data is a predetermined value and the first condition is met, the thermal energy applied by the recording head to the recording medium when forming the pixel of interest is greater than when the value of the pixel of interest in the image data is a predetermined value and the first condition is not met. [Effects of the Invention]

[0007] The present invention aims to suppress the decrease in color density of pixels that record high-density images. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram illustrating the overall configuration of the recording device. [Figure 2] This is a diagram illustrating the system configuration of the recording device. [Figure 3] This diagram illustrates the configuration of the recording head and recording medium during recording. [Figure 4] This is a diagram illustrating the layer structure of a recording medium. [Figure 5] This diagram illustrates the heating time and heating temperature required to produce color in each image-forming layer of a recording medium. [Figure 6]This flowchart shows the processing performed by the recording device and the host PC when a print service is executed. [Figure 7] This diagram explains the pulses that produce each color. [Figure 8] This figure illustrates the reference pixel and image pattern in the first embodiment. [Figure 9] Flowchart of the first embodiment. [Figure 10] This figure illustrates image formation in the first embodiment. [Figure 11] This figure illustrates pulse control in the first embodiment. [Figure 12] This figure illustrates high-concentration pulse control using thermal history in the first embodiment. [Figure 13] This figure illustrates the normality pulse control using thermal history in the first embodiment. [Figure 14] This figure illustrates pulse control in the second embodiment. [Figure 15] This diagram illustrates the thermal effects of each color pulse on the pixels before and after it. [Modes for carrying out the invention]

[0009] Preferred embodiments of the present invention will be described in more specific and detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0010] (First embodiment) <Overview of the recording device (Figures 1-3)> Figure 1 is a side cross-sectional view showing a schematic configuration of a recording device, which is a typical embodiment of the present invention.

[0011] As shown in FIG. 1, the recording apparatus 40 includes a recording head 30, a storage unit 41, a conveyance roller 42, a platen 43, and a discharge port 44. The storage unit 41 can store a plurality of sheet-like recording media 10, and the recording media 10 can be replenished by opening and closing a cover (not shown). During printing, the recording media 10 is conveyed by the conveyance roller 42 to the lower part of the recording head 30, an image is formed between the platen 43 and the recording head 30, and then discharged from the discharge port 44 to complete printing.

[0012] FIG. 2 is a block diagram showing the control configuration of a recording system composed of the recording apparatus shown in FIG. 1 and a host apparatus connected thereto. As shown in FIG. 2, this recording system is composed of the recording apparatus 40 shown in FIG. 1 and a personal computer (host PC) 50 as its host apparatus.

[0013] The host PC 50 includes a CPU 501, a RAM 502, an HDD 503, a data transfer interface (I / F) 504, a keyboard / mouse interface (I / F) 505, and a display interface (I / F) 506.

[0014] The CPU 501 executes processing according to programs held in the HDD 503 and the RAM 502. The RAM 502 is a volatile storage that temporarily holds programs and data. The HDD 503 is a non-volatile storage that also holds programs and data. The data transfer I / F 504 controls the transmission and reception of data between the recording apparatus 40. As this data transmission / reception transfer method, a wired connection such as USB, IEEE 1394, LAN, or a wireless connection such as Bluetooth (registered trademark), WiFi, etc. can be used. The keyboard / mouse (registered trademark) I / F 505 is an interface that controls a UI (user interface) such as a keyboard and a mouse, and the user can input information to the host PC through this. The display I / F 506 controls the display on a display (not shown).

[0015] On the other hand, the recording device 40 includes a CPU 401, RAM 402, ROM 403, data transfer interface (I / F) 404, head controller 405, and image processing accelerator 406.

[0016] The CPU 401 executes the processing of each embodiment described later, according to the programs stored in the ROM 403 and RAM 402. The RAM 402 is volatile storage and temporarily holds programs and data. The ROM 403 is non-volatile storage and holds table data and programs used in the processing of each embodiment described later. The data transfer I / F 404 controls the transmission and reception of data between the CPU 401 and the PC 50.

[0017] The head controller 405 controls the heating operation (described later) of the recording head 30 based on the recorded data. Specifically, the head controller 405 is configured to read control parameters and recorded data from a predetermined address in the RAM 402. In other words, when the CPU 401 writes the control parameters and recorded data to a predetermined address in the RAM 402, the head controller 405 starts processing and the heating operation of the recording head is performed.

[0018] The image processing accelerator 406 is hardware-based and performs image processing faster than the CPU 401. Specifically, the image processing accelerator 406 is configured to read the parameters and data necessary for image processing from a predetermined address in the RAM 402. When the CPU 401 writes the above parameters and data to the predetermined address in the RAM 402, the image processing accelerator 406 is activated and the predetermined image processing is performed.

[0019] Note that the image processing accelerator 406 is not necessarily a required component, and depending on the specifications of the recording device, the above table parameter creation process and image processing may be performed solely by the CPU 401.

[0020] <Overview of the recording head configuration (Figure 3)> Figure 3 is a side cross-sectional view showing the configuration of the recording head and the contact area between the recording head and the recording medium.

[0021] The recording head 30 is provided with a glaze 32 on the substrate 31. The glaze 32 may further include a "convex glaze" 33. The resistor 34 is placed on the surface of the convex glaze 33 if it is present, and on the flat surface of the glaze 32 if it is not present. It is preferable that a protective film layer is formed on the resistor 34, the glaze 32, and the convex glaze 33. Generally, the combination of the glaze 32 and the convex glaze 33, which are made of the same material, will be referred to below as the "glaze of the recording head". The thermistor 36 is placed near the resistor 34 on the glaze 32.

[0022] The substrate 31 is in contact with the heat sink 35 and is cooled using a fan or the like. The recording medium 10 is in contact with the glaze of the recording head, which is generally substantially longer than the length of the actual heating resistance. The resistor 34 is an electrothermal conversion element (heater or heating element) that generates heat when current is supplied to it. When the resistor 34 generates heat, the resistance value of the thermistor 36 placed nearby changes, and the temperature near the thermistor can be estimated. However, the thermistor 36 does not allow for the direct measurement of the temperature of the resistor 34, which corresponds to the surface of the recording head. Therefore, the temperature of the surface of the recording head can be estimated by experimentally associating the temperature near the thermistor 36 with the temperature of the surface of the recording head in advance. A typical resistor is about 120 μm long in the transport direction of the recording medium 10, but the thermal contact area of ​​the recording medium with the glaze of a typical recording head is 200 μm or more.

[0023] <Overview of the recording principle (Figures 4-5)> Figure 4 is a cross-sectional view showing the structure of a sheet-like recording medium used for image formation using infrared radiation as a heat source. As will be described in detail below, the recording medium 10 is heated by the heat rays (infrared radiation) emitted from the resistor 34 when current is supplied to the resistor, and multiple color-developing layers are superimposed, which develop color. When these color-developing layers develop color, a full-color image is formed, and therefore it is also called an infrared image component. Accordingly, in this sense, the recording medium 10 will be referred to as an infrared image component in the following description.

[0024] As shown in Figure 4, the infrared imaging member 10 has image forming layers 14, 16, 18, spacer layers 15, 17, and a protective film layer 13 formed on a light-reflecting substrate 12. The image forming layers 14, 16, and 18 are generally yellow (Y), magenta (M), and cyan (C) respectively when printing in full color, but other color combinations are also possible.

[0025] Each image-forming layer is initially colorless, but each layer changes to color when heated to a specific temperature called the activation temperature. The order of the colors of the image-forming layers can be arbitrarily selected. One preferred color order is as described above. Another preferred order is that the three image-forming layers 14, 16, and 18 are cyan (C), magenta (M), and yellow (Y), respectively. Here, we will describe an example where the layers are configured in the order of yellow (Y), magenta (M), and cyan (C) as described above.

[0026] The spacer layer 15 is preferably thinner than the spacer layer 17, unless the material comprising both layers has substantially the same thermal diffusivity. The function of the spacer layer is to control thermal diffusion within the infrared imaging member 10. Preferably, the spacer layer 17 is at least four times thicker if it is made of the same material as the spacer layer 15. All layers placed on the substrate 12 are substantially transparent before image formation. If the substrate 12 is a reflective color (e.g., white), the color image formed on the infrared imaging member 10 is visible through the protective film layer 13 against the reflective background provided by the substrate 12. Because the layers placed on the substrate 12 are transparent, the color combinations formed on each image-forming layer are visible.

[0027] Although the three image-forming layers 14, 16, and 18 of the infrared imaging member 10 are located on the same side of the substrate 12, some of the image-forming layers may be located on the opposite side of the substrate 12.

[0028] The image-forming layers 14, 16, and 18 are processed at least partially independently by two adjustable parameters, namely temperature and time. These parameters are adjustable, and by selecting the temperature and time period of the recording head while the infrared imaging member is heated, an image is formed on the desired image-forming layer.

[0029] Here, each of the image-forming layers 14, 16, and 18 is processed by heating while the recording head 30 is in contact with the uppermost layer of the material, i.e., the protective film layer 13 of the infrared image member 10. The activation temperature (Ta3) of the image-forming layer 14 (the third layer from the substrate 12 and the image-forming layer closest to the surface of the infrared image member 10) is greater than the activation temperature (Ta2) of the image-forming layer 16, and similarly, greater than the activation temperature (Ta1) of the image-forming layer 18.

[0030] Heating of image forming layers at a distance greater than the recording head 30 is delayed by the time required for heat to diffuse to those layers through the spacer layer. Due to this heating delay, even if the image forming layers closer to the recording head are substantially above the activation temperature of the image forming layers with lower activation temperatures (layers further from the recording head), they will not activate the image forming layers below them. This allows them to be heated above their activation temperature. Therefore, when processing the uppermost image forming layer 14, the recording head 30 is heated to a relatively high temperature for a short time, resulting in insufficient heating for both image forming layers 16 and 18, and these layers are not activated.

[0031] To activate only the image-forming layer closest to the substrate 12 (in this case, image-forming layer 16 or 18), heating is performed at a temperature below the activation temperature of the image-forming layer further from the substrate 12 for a sufficiently long period of time. In this way, if the lower-temperature image-forming layer is activated, the higher-temperature image-forming layer will not be activated.

[0032] Heating of the infrared imaging element 10 is preferably performed using the recording head 30, but any method for applying controlled heat to the infrared imaging element may be used. For example, any known means such as using a modulated light source (e.g., a laser light source) may be used.

[0033] Figure 5 illustrates the heating temperature and time required for the recording head to process the three image-forming layers shown in Figure 4.

[0034] In Figure 5, the vertical axis represents the heating temperature on the surface of the infrared imaging member 10 in contact with the recording head 30, and the horizontal axis represents the heating time. Region 21 (recording head at a relatively high temperature and relatively short heating time) provides imaging of the image forming layer 14, and region 22 (recording head at an intermediate temperature and intermediate heating time) provides imaging of the image forming layer 16. Region 23 (recording head at a relatively low temperature and relatively long heating time) provides imaging of the image forming layer 18. The time required to image the image forming layer 18 is substantially longer than the time required to image the image forming layer 14.

[0035] The activation temperature selected for the image forming layer is generally within the range of about 90°C to about 300°C. The activation temperature (Ta1) of the image forming layer 18 is preferably as low as possible and consistent with the thermal stability of the infrared image member during shipment and storage, and preferably about 100°C or higher. The activation temperature (Ta3) of the image forming layer 14 is preferably consistently low with respect to the activation of the image forming layers 16 and 18 by heating through this layer without being activated by the heating method of this embodiment, and preferably about 200°C or higher. The activation temperature (Ta2) of the image forming layer 16 is such that Ta1 < Ta2 < Ta3, and preferably between about 140°C and about 180°C.

[0036] The recording head 30 used herein includes a resistor array in which a plurality of resistors are linearly arranged so as to extend substantially over the entire width of the image (the direction perpendicular to the conveyance direction of the infrared image member).

[0037] Note that the recording width of the recording head may be shorter than the width of the image. In such a case, the recording head is configured to be moved with respect to the infrared image member 10 in order to process the entire width of the image, or used in combination with another recording head.

[0038] By supplying current to these resistors, heating pulses are provided while the infrared image member is imaged while being conveyed in a direction perpendicular to the arrangement direction of the resistors of the recording head. The time for which the infrared image member 10 is heated by the recording head 30 is typically in the range of about 0.001 to about 100 milliseconds for each line of the image. The upper limit is reasonably set in consideration of the image printing time, while the lower limit is defined by the constraints of the electronic circuit. The dot interval for forming the image is generally in the range of 100 to 600 lines per inch in both the conveyance direction and the perpendicular direction of the infrared image member 10, and may be different intervals in each direction.

[0039] The recording device described above is a type of thermal printer, but the recording method it employs is also known as the ZINK (Zero Ink) method or Zero Ink technology (registered trademark).

[0040] <Flowchart of the recording system> Figure 6 is a flowchart showing the processing of the recording device 40 and the host PC 50 when a conventional print service is performed in the recording system described above. In Figure 6, steps S601, S602, S604-S606 show the processing of the host PC 50, and steps S611-S614, S616-S617 show the processing of the recording device 40. Also, as shown in Figure 6, when a user wants to print, the processing of the host PC 50 starts, and in response, the processing of the recording device 40 starts. Therefore, in step S611, the recording device 40 confirms that it is ready to print and starts the print service, and is in a print-ready state.

[0041] In this state, when the host PC 50 executes the print service Discovery in step S601, the recording device 40 responds to the Discovery in step S612, notifying that it is a device capable of providing print services. Subsequently, in step S602, the host PC 50 obtains print availability information. Basically, it requests print availability information from the recording device 40, and in response, in step S614, the recording device 40 notifies the host PC 50 of the information about the print services it can provide.

[0042] Furthermore, the host PC 50 constructs a user interface for creating a print job based on the printable information notified in step S604. Specifically, based on the printable information from the recording device 40, it displays the print size, printable paper size, and other appropriate options on the display and provides them to the user. Subsequently, in step S605, the host PC 50 issues a print job.

[0043] In response, the recording device 40 receives the print job in step S614 and executes the print job in step S616. Once printing based on the print job is completed on the recording device 40, the recording device 40 notifies the host PC 50 of the completion of printing in step S617. The host PC 50 receives the print completion notification in step S606 and notifies the user accordingly.

[0044] Once the print job is complete, the host PC 50 and the recording device 40 each complete a series of print service processes.

[0045] In the above explanation, various types of information transmission were described using an example where the host PC 50 makes a request to the recording device 40, and the recording device 40 responds to that request. However, communication between the host PC and the recording device is not limited to the so-called pull type; it may also be a so-called push type, where the recording device 40 proactively sends information to the host PC 50 (and other host PCs) on the network.

[0046] <Pulse applied to the recording head> Figure 7 shows an example of a heating pulse applied to the recording head of a recording device. In Figure 7, timing p0 is the earliest in terms of time, and the time decreases as you move from left to right along the time axis.

[0047] The left side of Figure 7 shows the colors to be produced, and the right side shows the corresponding heating pulses. For example, to produce yellow (Y), heating is performed once for a time Δt1 at timing p0 to achieve the heating temperature and heating time in region 21 of Figure 5. To produce magenta (M), heating is first performed once for a time shorter than Δt1 at timing p0 to achieve the heating temperature and heating time in region 22 of Figure 5. This heating is for preheating purposes and does not produce color. At timing p1, after Δt1+Δt2 from p0, heating is performed a total of five times for a time Δt3, with intervals of Δt4. To produce cyan (C), heating is first performed once for a time shorter than Δt1 at timing p0 to achieve the heating temperature and heating time in region 23 of Figure 5. The heating time may be longer than that for M. This heating is for preheating purposes and does not produce color. At the point p3, which is reached after Δt1 + Δt2 + ((Δt3 + Δ4) × 4 + Δt3) + Δt5 from p0, heating for a duration of Δt6 is performed a total of six times, each time with an interval of Δt7. Heating time for Y = Δt1 Heating time for M = Δt3 × 4 + Δt3 Heating time for C = Δt6 × 5 + Δt6 The relative relationship of heating time for each image-forming layer is as follows. Heating time for Y < Heating time for M < Heating time for C Here, Y, M, and C refer to image-forming layers 14, 16, and 18.

[0048] Furthermore, the amount of heat applied by the recording head 30 is conducted to the glaze 32, substrate 31, and heat sink 35 of the recording head 30 during the pulse intervals Δt2, Δt4, Δt5, and Δt7, which are not being heated, causing the temperature of the infrared image component 10 to decrease. Similarly, the amount of heat conducted to the infrared image component 10 is also transferred to the platen 43, etc., causing the temperature of the infrared image component 10 to decrease by that amount. When the amount of heat applied is the same at the same temperature, the larger the interval, the greater the temperature decrease. The relationship between the peak temperature when only each image forming layer is colored, based on the heating time and heating interval, is as follows. Peak temperature of Y > Ta3 Ta3 > M peak temperature > Ta2 Ta2 > C peak temperature > Ta1 By controlling it in the manner described above, it is possible to produce the colors Y, M, and C independently.

[0049] Next, we will explain the heating pulses that control the coloration of secondary colors R, G, and B, and tertiary color K.

[0050] In Figure 7, the heating pulse for red (R) is controlled to produce yellow (Y) followed by magenta (M). Similarly, the heating pulse for green (G) in Figure 7 is controlled to produce yellow (Y) followed by cyan (C). Likewise, the heating pulse for blue (B) in Figure 7 is controlled to produce magenta (M) followed by cyan (C). Finally, the heating pulse for black (K) in Figure 7 is controlled to produce yellow (Y) followed by magenta (M) followed by cyan (C).

[0051] When R is produced, the heating pulse for Y production has the same Δt1 as for monochromatic Y production, but the heating pulse for M production is one less than that for monochromatic M production. The reason for this is to prevent the C image forming layer from reaching the production temperature. When G is produced, the heating pulse is the OR of the monochromatic Y pulse and the monochromatic C pulse. The temperature inside the recording medium is lowered between the heating pulses for Y and C production to prevent M from producing color. When B is produced, a total of 10 heating pulses with Δt6 are executed at timing p0, with intervals of Δt7. By increasing the number of heating pulses compared to the monochromatic C pulse, the M image forming layer is also allowed to reach the production temperature. When K is produced, the heating pulse is the OR of the pulse for R production and the monochromatic C pulse.

[0052] Figure 8 illustrates the pixels referenced to control the heating pulse in this embodiment. The arrows indicate the transport direction of the recording medium 10. Figures 8(a) to (h) show the pixel of interest marked with a circle in the transport direction, the three pixels immediately preceding it, and the pixel immediately following the pixel of interest marked with a double circle. In the three preceding pixels, the shaded pixels indicate pixels that have been colored red, showing the red coloration pattern of the three pixels. Note that the end of the arrow (the top of the figure) is the pixel that is recorded first. In Figure 8(a), all three pixels are colored, so the temperature of the recording head 30 and the recording medium 10 immediately before the start of recording of the pixel of interest is the highest among Figures 8(a) to (h). In Figure 8(h), none of the three pixels are colored, so the temperature of the recording head 30 and the recording medium 10 immediately before the start of recording of the pixel of interest is the lowest among Figures 8(a) to (h). The closer the pixel to which red coloration is made is to the pixel of interest, the higher the temperature of the recording head 30 and the recording medium 10 immediately before the start of recording of the pixel of interest. Therefore, in the order shown in Figures 8(a) to (h), the temperatures of the recording head 30 and recording medium 10 immediately before the pixel of interest are high. The temperature of the recording head 30 or recording medium 10 due to the heating pulse applied to the pixels before the pixel of interest is called the thermal history. In this embodiment, the thermal history is defined as the surface temperature of the recording head 30. Here, we explain using an example where the three pixels immediately before the pixel of interest are referenced, but the number of pixels is not limited to this, and the surface temperature of the recording head 30 immediately before the pixel of interest can be estimated by referencing one or more pixels before the pixel of interest. However, since the temperature fluctuates depending on the history of multiple pixels before the pixel of interest, it is desirable to reference multiple pixels from the viewpoint of accuracy in temperature estimation. Also, since referencing too many pixels increases the processing load, it is advisable to set an appropriate number of reference pixels in advance through experimentation. The surface temperature of the recording head 30 for each pattern in Figures 8(a) to (h) is measured in advance through experimentation, and the correspondence between each pattern and the temperature of the recording head 30 is stored in the ROM 403 of the recording device 40. In this way, the surface temperature of the recording head 30 can be estimated from the patterns in Figures 8(a) to (h). Alternatively, the temperatures of the image forming layers 14, 16, and 18 of the recording medium 10 may be used as thermal histories. As with the case of the recording head 30, the temperatures of each image forming layer can be correlated with the patterns shown in Figures 8(a) to (h) through experiments beforehand.Since color development ultimately occurs when each image-forming layer is brought to a temperature that causes it to develop color, using the thermal history of each layer complicates control but improves control accuracy. Furthermore, even with the same pulse, the temperature of each image-forming layer changes depending on the surface temperature of the recording head 30, so using both the recording head 30 and the recording medium 10 provides the best accuracy. The temperatures of the recording head 30 and the recording medium 10 can be measured during image recording as described above, or they can be simulated values. When using simulated values, the specific heat, density, and thermal conductivity of the materials constituting the recording head 30 and the recording medium 10, as well as the heat generation of the heater equipped with the recording head 30, pulse data, and each size are prepared as parameters. By substituting the prepared parameters into the thermal conduction equation and solving the thermal conduction equation for elapsed time and transport direction, the simulated values ​​of each temperature mentioned above can be obtained. Alternatively, even without simulating the temperature, it is sufficient to simply determine the patterns in Figures 8(a) to (h) for the pixel values ​​to be judged. Therefore, the pixel value pattern can also be used as the thermal history.

[0053] Figure 9 is a flowchart of the print job execution process in step S616 of Figure 6. In this process, heating pulses are generated by referring to the pixels shown in Figure 8, and printing is performed using the generated pulses. The flow will be explained below in the order of the steps in Figure 9. The process in Figure 9 must be executed by the CPU according to the program stored in ROM 403.

[0054] In step S901, the printing process for the print job execution in step S616 of Figure 6 is started.

[0055] In step S902, the image data from the print job received in step S614 in Figure 6 is input.

[0056] In step S903, if the image data has been compressed or encoded, a decryption process is performed.

[0057] In step S904, it is determined whether the pixel of line n, which is the pixel of interest in the image data, is a red image. Whether or not it is a red image that emits red color can be determined from the R, G, and B values ​​of the input image data. This can be determined by defining a range of values, such as defining pixels with RGB values ​​of R=r0~r1, G=g0~g1, and B=b0~b1 as red. r0, g0, and b0 should be set according to the range of values ​​you want to define as red. If r0=255, g0=0, b0=0, r1=255, g=0, b=0, then pixel data with R=255, G=0, and B=0 will be determined to be red, and data with any other values ​​will be determined not to be red.

[0058] In step S905, assuming the pixel of interest is the n-line (marked with a circle in Figure 8), it is determined whether the pixels from the n-3 line to the n+1 line shown in Figure 8 exist as part of the data region. The n-line is the pixel of interest, n-3 to n-1 are the three preceding pixels, and the n+1 line is the one immediately following. If the result is Yes, proceed to step S906; if the result is No, proceed to step S909.

[0059] In step S906, the 8-bit (0-255) R, G, and B values ​​of the pixel data for lines n-3 to n+1 are passed to the processing steps from S907 onwards.

[0060] In step S907, thermal history determination 1 is executed. Thermal history determination 1 determines whether the pixels in lines n-3 to n-1, which are the three pixels immediately upstream in the transport direction from the pixel of interest marked with a circle in Figure 8, are red color patterns in Figures 8(a) to (h). Whether or not it is red can be determined from the R, G, and B values ​​of the input pixel data. The determination can be made based on the range of values ​​that are considered red for RGB values ​​R=r0 to r1, G=g0 to g1, and B=b0 to b1. r0, g0, b0, r1, g1, and b1 should be set according to the range of values ​​that you want to be considered red. If r0=255, g0=0, b0=0, r1=255, g=0, and b=0, then pixel data with R=255, G=0, and B=0 will be determined to be red (shaded in Figure 8), and data with any other values ​​will be determined not to be red (white pixels in Figure 8). Based on the above, the three preceding pixels are determined to be one of (a) to (h) in Figure 8.

[0061] In step S908, the next pixel determination 1 is performed. In the next pixel determination 1, a condition determination is made to determine whether the pixel marked with ◎, which is the first pixel upstream in the transport direction from the pixel of interest marked with ○ in Figure 8, satisfies the condition that all of the image forming layers 14, 16, and 18 of the recording medium 10 are pixels that do not require color development. At least white pixels that do not develop color (R=255, G=255, B=255) are determined to be pixels that do not require color development. Whether a pixel does not require color development can be determined by whether all of R=r2~255, G=g2~255, and B=b2~255 are satisfied. r2, g2, and b2 should be colors in which the heating pulse of the next pixel does not visually affect the color development of the preceding pixel of interest. For example, a threshold value of approximately three-quarters of 255 may be used, resulting in r2=191, g2=191, and b2=191. Furthermore, since the way heat propagates differs for each color-developing layer, the values ​​may be changed for each color. If r2=255, g2=255, and b2=255, then if the pixel immediately following the ◎ mark in Figure 8 has R=255, G=255, and B=255, then it is determined that color development is not necessary for the immediately following pixel. Here, we will explain why we focus on the pixel immediately following the pixel of interest. Figure 10 is a schematic diagram showing the color development process when red is recorded in the transport direction. It shows a total of 5 pixels from the (n-3)th line pixel to the (n+1)th line pixel in the transport direction. Figure 10(0) shows a state where all 5 pixels are not recorded, represented as white pixels. Figure 10(1) shows the result of applying the R pulse from Figure 7 to the (n-3)th line pixel with thin diagonal lines. Figure 10(2) shows the result of applying the R pulse from Figure 7 to the (n-3)th and (n-2)th line pixels. Furthermore, the heat from the pulse applied to the (n-2)th line pixel propagated enough to increase the coloration of the preceding pixel, the (n-3)th line pixel, resulting in the (n-3)th line pixel being more intensely colored than the (n-2)th line pixel. This intense coloration is indicated by thick diagonal lines. Similarly, in Figures 10(3) and 10(4), the results of applying the R pulse from Figure 7 to the (n-1)th line pixel in Figure 10(3) and to the (n-3)th line pixel in Figure 10(4) are indicated by diagonal lines. The increased coloration of the preceding pixels, the (n-2)th line pixel and the (n-1)th line pixel, is also indicated by thick diagonal lines.Thus, when R pulses are continuously applied to produce R color, the color of the immediately preceding pixel increases due to heating of the subsequent pixel (the pixel of interest), thereby increasing its density. As shown in Figure 7, since the R pulses are concentrated in the first half of the pixel, when a pulse is applied to the pixel of interest in the recording medium 10, the temperature of the image forming layer 14 and image forming layer 16 near the boundary with the immediately preceding pixel rises. Since heat propagates to the surrounding area where the temperature has risen, heat is also propagated to the immediately preceding pixel, which is close to the area where the temperature has risen. As a result, in the recording medium 10 of the immediately preceding pixel, the image forming layer 14 or image forming layer 16 reaches the color-producing temperature, and the color density of the immediately preceding pixel becomes denser. On the other hand, the distance from the area where the temperature of the pixel to which the R pulse is applied is closer for the immediately preceding pixel than for the immediately following pixel. Therefore, when an R pulse is applied to the pixel of interest, the heat propagated from the pixel of interest to the immediately following pixel is smaller than that of the immediately preceding pixel. As a result, when the R pulse shown in Figure 7 is applied to two consecutive pixels in the transport direction, the pixel recorded later will have a lower density than the pixel recorded earlier. In other words, immediately after applying the R pulse to a pixel of interest during printing of consecutive red pixels, the pixel of interest will have a lower density than the preceding pixel. Therefore, the trailing pixel of a solid red image will have a lower density than the internal pixels of the solid red image. For these reasons, in this embodiment, the focus is on the pixel immediately following the pixel of interest in the heating pulse control.

[0062] In step S909, the 8-bit (0-255) R, G, and B values ​​of the existing lines among the pixels from line n-3 to line n+1 shown in Figure 8 are passed to the processing from S910 onwards.

[0063] In step S910, thermal history determination 2 is performed. Thermal history determination 2 determines which of the red coloration patterns in Figures 8(a) to (h) the pixels in the n-3 line to n-1 line, which are the three pixels immediately preceding the pixel of interest marked with a circle in Figure 8 in the upstream direction of transport. Whether it is red can be determined from the R, G, B of the input pixel data as in step S907. If all of the n-3 line to n-1 line are input, the three preceding pixels are determined to be one of the patterns in Figures 8(a) to (h) in the same way as in step S907. If only the n-2 line to n-1 line are input, the n-2 line and n-1 line in Figures 8(b), (d), (f), and (h) are referred to determine which pattern it is. If only the n-1 line is input, the n-1 line in Figures 8(d) and (h) is referred to determine which pattern it is. If neither the n-1 line nor the n-1 line is input, it is determined to be the pattern in Figure 8(h).

[0064] In step S911, the next pixel determination 2 is performed. In the next pixel determination 2, if n+1 pixels are input, it is determined, in the same way as in step S908, whether the pixel immediately following the pixel of interest in the transport direction, which is marked with ◎, does not require color development in any of the image forming layers 14, 16, or 18 of the recording medium 10, which are color development layers. If n+1 pixels are not input, it is determined that the next pixel does not require color development.

[0065] In step S912, it is determined whether the pixel of interest marked with a circle in Figure 8 is possibly the trailing pixel of the solid red image. Here, if in step S907 it is determined to be one of (a) to (d) in Figure 8, and in step S908 it is determined that color development is not necessary for the immediately following pixel, then the process proceeds to step S913. Otherwise, the process proceeds to step S914.

[0066] In step S913, a high-density pulse is set for the pixel of interest marked with a circle in Figure 8. This can be set using a 3D lookup table (3D_LUT) as follows. High-concentration pulse = 3D_LUT[R][G][B][0] Here, the 3D_LUT described above consists of 256×256×256×3 data tables. Each data set is configured by a combination of R, G, and B values ​​for the timing, width, and number of heating pulses to be applied, as shown in Figure 7. High-density pulses are set to prioritize the color development of the trailing pixels of a solid color image. Figure 11 shows two types of high-density pulses, (0a) and (0b), for red, where R=255, G=0, and B=0, as well as a normal pulse (1) and a leading-edge pulse (2). The horizontal axis is the time axis. In this step S910, the high-density pulse shown in Figure 11(0a) or (0b) is set. The normal pulse will be described later in step S915, and the leading-edge pulse will be described later in step S916. In the high-density pulse in Figure 11(0a), the pulse width for Y color development applied at timing py0 is longer than the normal pulse width in Figure 11(1). Therefore, Figure 11(0a) can deliver more thermal energy to the pixel of interest. If the timing of py0 in Figure 11(0a) is the same as in Figure 11(1), the heat propagated to the preceding pixel will also increase due to the larger pulse width of py0. As a result, the density of the pixel of interest increases, but the density of the preceding pixel also increases further, creating a density difference between pixels. The purpose of delaying the timing of py0 in Figure 11(0a) is to suppress the heat propagated to the preceding pixel and reduce the density difference between the pixel of interest and the preceding pixel. Also, in Figure 11(0a), the number of M color-developing pulses applied at the pm0 timing is greater than that of the normal pulse in Figure 11(1). As a result, the thermal energy to the image forming layer 16 that develops M color can be increased. Let's explain Figure 11(0b), which is another high-density pulse. The Y color-developing pulse and M color-developing pulse applied at the pm0 and py0 timings in Figure 11(0b) are the same as the normal pulse in Figure 11(1). The difference is that Figure 11(0b) adds Y-coloring pulses and M-coloring pulses at the timings of py1 and pm1. The length from the first pulse applied (the pulse applied at the timing of py0) to the last pulse applied (the final pulse applied at the timing of pm1) in Figure 11(0b) is longer than the length from the first pulse applied to the last pulse applied in the normal Figure 11(1). Because the thermal energy increases, the concentration can be increased.Furthermore, since the timing of py1 is after time has elapsed since the boundary timing with the preceding pixel, the heat from the pulse added at this timing does not propagate enough to increase the color of the preceding pixel. Also, since it is far from the boundary with the following pixel, it does not color the following pixel either. By using a high-density pulse, the thermal energy to the trailing pixel of the solid red image is increased while the thermal energy propagated to the preceding pixel is kept the same as that of a normal pulse, thereby suppressing the density difference between the trailing pixel and the internal pixels of the solid red image. A high-density pulse is a pulse that increases thermal energy by doing at least one of the following compared to a normal pulse: increasing the pulse width or pulse interval (i.e., increasing the duty cycle), or increasing the number of pulses. The specific color for which a high-density pulse is set should be the color in which the density of the preceding pixel increases when a pulse is applied to two consecutive pixels in the transport direction, as explained in Figure 10. Then, the high-density pulse for that specific color should be set at the R, G, B value table position corresponding to that specific color. For colors that are not specific colors, the normal pulse for that color should be set at the R, G, B value table position.

[0067] In step S914, it is determined whether the pixel of interest is an internal pixel of the solid red image. Here, if in step S907 it is determined that the thermal history is greater than or equal to one of Figures 8(a) to (d), and in step S908 it is determined that the immediately following pixel is a target for color development, then the process proceeds to step S915. If it is determined that the thermal history is not greater than or equal to the predetermined value, the process proceeds to step S916.

[0068] In step S915, a normal pulse is set for the pixel of interest marked with a circle in Figure 8. This can be set using a 3D lookup table (3D_LUT) as follows. Normal pulse = 3D_LUT[R][G][B][1] The normal pulse is set to a pulse suitable for color development of the internal pixels of each solid color image. In this step S915, the normal pulse shown in Figure 11(1) is set for the red pixel. The normal pulse has a narrower pulse width or fewer pulses compared to the high-density pulse. The pulse interval may also be wider. In this way, the thermal energy applied to the recording medium 10 is reduced compared to the high-density pulse. When the red normal pulse is applied to the pixel of interest, it increases the red density of the preceding pixel as explained in Figure 10.

[0069] In step S916, a tip pulse is set for the pixel of interest marked with a circle in Figure 8. This can be set using a 3D lookup table (3D_LUT) as follows. Tip pulse = 3D_LUT[R][G][B][2] In step S916, a tip pulse as shown in Figure 11(2) is set for the red pixel. The tip pulse has a wider pulse width or a higher number of pulses compared to the high-density pulse. It is preferable to apply more thermal energy to the recording medium 10 in this way than to the high-density pulse. The pixel of interest in step S916 is likely to be the tip of the image, and heat propagation from the preceding pixel is smaller than that from the internal pixels of a solid image. Therefore, by applying more thermal energy to the recording medium 10 than to the high-density pulse, the color development at the tip of the image can be improved.

[0070] In step S917, head control is performed. A pulse set in step S913, step S915, or step S916 is applied to the head to cause the recording medium 10 to develop color.

[0071] In step S918, it is checked whether the recording of the page is complete. If the result is No, the process returns to step S903 and the next pixel is designated as the pixel of interest (the pixel of line n+1) to record the rest of the page. If step S918 is Yes, the printing process ends in step S919.

[0072] As shown in Figure 7 for each color pulse, the thermal energy differs depending on the color. Therefore, the thermal history differs depending on the color in the color pattern in Figure 8. As explained above, red represents a predetermined range of thermal history.

[0073] As described above, when the thermal history is within a predetermined range and the immediately following pixel does not require color development, a pulse with greater thermal energy is applied to the red pixel of interest compared to when the immediately following pixel is subject to color development, even if the thermal history is the same. As shown in Figure 11, increasing the pulse width or shortening the pulse interval, i.e., increasing the pulse duty cycle, can increase the thermal energy. Increasing the number of pulses can also increase the thermal energy. As a result of this increased thermal energy, high-density pulses can be applied to the trailing pixels of the solid red image, thereby suppressing the density difference between the trailing pixels and the pixels inside the solid red image during recording.

[0074] Next, we will explain a method for precisely controlling the heating pulse according to the thermal history. The more pixels to which the same heating pulse is applied consecutively in the transport direction, the higher the temperature of the recording head 30 will rise. As a result, the amount of thermal energy propagated from the recording head to the recording medium 10 increases, and the color development temperature corresponding to the applied heating pulse also increases. Furthermore, as the temperature rises further, the image forming layer, which is not intended to develop color, may exceed the color development temperature and develop color. Therefore, we will explain how to suppress density changes between pixels by controlling the heating pulse according to the thermal history. However, in a solid red image, while density changes between pixels can be suppressed in internal pixels by heating pulses according to the thermal history, the density of the trailing pixels will be lower than that of internal pixels because there is no heat propagation from the immediately following pixels. For this reason, it is desirable to combine thermal history control with high-density pulses to the trailing pixels, as explained below.

[0075] Figure 12 shows an example of finely controlling high-density pulses according to thermal history. The horizontal axis is the time axis. This control is performed in step S913. This explanation is given when, in step S907 or step S910, the pattern of the red-colored pixel is determined to be one of (a) to (d) in Figure 8, and when, in step S908 or step S911, it is determined that the immediately following pixel does not require color development. In S912, it is determined whether the above two conditions are met, and it is determined that the pixel of interest marked with a circle in Figure 8 is the trailing pixel of the solid red image. Then, in S913, heating pulses corresponding to (a) to (d) in Figure 8 are set as shown in (a) to (d) in Figure 12. This can be set using 3D_LUT. High-concentration pulse (a) = 3DLUT[R][G][B][0][0] High-concentration pulse (b) = 3DLUT[R][G][B][0][1] High-concentration pulse (c) = 3DLUT[R][G][B][0][2] High-concentration pulse (d) = 3DLUT[R][G][B][0][3] The 3D_LUT described above consists of 256×256×256×3×4 data tables. The heating pulse in Figure 12(d) is the same as the high-density pulse in Figure 11(0a). When the temperature estimated from the thermal history increases, heating pulses with less thermal energy than those in Figure 12(d) are set, as shown in Figures 12(a) and (b). Since the difference in the thermal history immediately before the pixel of interest between Figure 8(c) and Figure 8(d) is sufficiently small, the pulse in Figure 12(c) is the same as that in Figure 12(d). The high-density pulses in Figures 12(a) to (d) each have greater thermal energy than the normal pulses in Figures 13(a) to (d).

[0076] Figure 13 shows an example of finely controlling the pulse according to the thermal history. The horizontal axis is the time axis. This control is performed in step S915. The following explanation is given for the case where it is determined in step S907 or step S910 that one of Figures 8(a) to (d) is met, and in step S908 or step S911 that the immediately following pixel is determined to be the target for color development. In S913, it is determined whether the above two conditions are met, and it is determined that the pixel of interest marked with a circle in Figure 8 is an internal pixel of the solid red image. Then, in S915, the heating pulses of Figures 13(a) to (d), which correspond to Figures 8(a) to (d), are set. Normal pulse (a) = 3DLUT[R][G][B][1][0] Normal pulse (b) = 3DLUT[R][G][B][1][1] Normal pulse (c) = 3DLUT[R][G][B][1][2] Normal pulse (d) = 3DLUT[R][G][B][1][3] The heating pulse in Figure 13(d) is the same as the normal pulse in Figure 11(1). When the temperature estimated from the thermal history becomes high, a heating pulse with less thermal energy than that in Figure 13(d) is set, as shown in Figures 13(a) and (b). Since the thermal history immediately before the target pixel in Figures 8(c) and 8(d) is sufficiently small, the pulse in Figure 13(c) is the same as that in Figure 13(d). The normal pulses in Figures 13(a) to (d) have less thermal energy than the high-concentration pulses, as shown in Figures 12(a) to (d).

[0077] Even when precisely controlling pulses based on thermal history, the tip pulse can be set in step S916 by storing the pulse data shown in Figure 11(2) in the 3DLUT. The same tip pulse as in Figure 11(2) is applied in cases (e) to (h) of Figure 8. Tip pulse (e) = 3DLUT[R][G][B][2][0] Tip pulse (f) = 3DLUT[R][G][B][2][1] Tip pulse (g) = 3DLUT[R][G][B][2][2] Tip pulse (h) = 3DLUT[R][G][B][2][3] As explained using Figure 13, the control of normal pulses according to the thermal history can suppress the change in density of pixels inside the solid red image due to the temperature rise of the recording head 30. In addition, as explained using Figure 12, the control of high-density pulses according to the thermal history can suppress the density difference between the trailing pixels and the pixels inside the solid red image.

[0078] (Second embodiment) In the first embodiment, an example was described in which a high-density pulse was created by increasing at least one of the duty cycle or the number of times the heating pulse was applied. In this embodiment, an example is described in which a high-density pulse is created by making the blank time between the pulse of the trailing pixel and the pulse of the preceding pixel shorter than the normal pulse of the internal pixel.

[0079] Figure 14 shows pulses with varying blank times in the pulse value range, as described later. The horizontal axis is the time axis. Figures 14(0a) and 14(0b) show the normal pulse and high-density pulse of the pixel immediately preceding the trailing pixel of the solid red image. Figure 14(1) shows the normal pulse of the two pixels before and after in the internal region of the solid red image. The normal pulses in Figures 14(0a), 14(0b), and 14(1) will be described as the same pulse. In the normal pulse, pulse blank times are provided before and after each pixel, and a heating pulse is provided closer to the center. This ensures pulse blank time between the preceding and succeeding pixels. The high-density pulses in Figures 14(0a) and 14(0b) are characterized by shorter pulse blank times between the preceding and succeeding pixels compared to the normal pulse in Figure 14(1). During the blank time, the temperature of the recording head 30 and the recording medium 10 decreases. Therefore, the pulses in Figures 14(0a) and 14(0b), which have shorter blank times than when a normal pulse is applied to the rearmost pixel, result in a smaller temperature drop per pixel. As a result, the rearmost pixel can maintain a temperature or time above the color development temperature of the image forming layer, equivalent to the internal pixels of the image, even without heat transfer from the immediately following pixel. Furthermore, the reason why the Y color development pulse, which is the leading pulse for the rearmost pixel in Figure 14(0a), is shorter than that for the pixel immediately preceding the rearmost pixel is as follows: Because the blank times before and after are short, the thermal energy of the rearmost pixel is more easily transferred to the immediately preceding pixel. Therefore, the width of the Y color development pulse is shortened so that the heat transfer to the immediately preceding pixel is equivalent to that of the normal pulse in Figure 14(1). This makes the immediately preceding rearmost pixel the same density as the internal pixels in Figure 14(1). In Figure 14(0b), the M color development pulse is applied first in the pulse for the rearmost pixel. Although the blank time with the preceding pixel is short, the M color pulse does not reach a higher temperature than the Y color pulse, thus suppressing excessive heat transfer to the preceding pixel.

[0080] The flow for controlling thermal pulses for printing can be the same as the flow described using Figure 9 of the first embodiment. The differences are as follows: In step S913, High-concentration pulse = 3DLUT[R][G][B][0] Instead of setting the pulse data in Figure 11(0a) or Figure 11(0b) in the 3DLUT, set the pulse data in Figure 14(0a) or Figure 14(0b). Then, in step S912, a high-density pulse in Figure 14(0a) or Figure 14(0b) can be set for the red of the pixel of interest that has been determined to be the trailing pixel of the solid red image.

[0081] Furthermore, in step S915, Normal pulse = 3DLUT[R][G][B][1] In the 3DLUT, set the pulse data shown in Figure 14(1) instead of Figure 11(1). Then, in step S914, set the normal pulse shown in Figure 14(1) for the red of the pixel of interest that has been determined to be an internal pixel of the solid red image.

[0082] As described above, when the thermal history is within a predetermined range and the immediately following pixel does not require color development, a pulse with a shorter blank time from the immediately following pixel is applied to the red pixel of interest compared to when the thermal history is the same but the immediately following pixel is subject to color development. As a result, by applying a high-density pulse to the rearmost pixel of the solid red image, it is possible to suppress the decrease in density of the rearmost image and achieve recording with reduced density difference between the rearmost image and the internal pixels of the solid red image.

[0083] (Other embodiments) In the first embodiment, we described using red with R=255, G=0, and B=0, but other values ​​may be set for r0, g0, b0, r1, g1, and b1. In other words, this embodiment can be applied to any color where there is a high possibility that the color development of the trailing pixels will be insufficient due to insufficient heat propagation. For example, blue with R=0, G=0, and B=255 may also be used. However, it is preferable to set the values ​​for a color where the temperature immediately before the pixel of interest is estimated to be within a predetermined range based on the thermal history, where it can be determined that the immediately following pixel does not require color development, and where the density difference between the trailing pixels and internal pixels of the solid image can be suppressed by applying a high-density pulse to the trailing pixels of the solid image.

[0084] In the first and second embodiments, examples of controlling high-density pulses and normal pulses for red were described. The reason for focusing on red is explained using Figure 15. Figure 15 shows the heating pulses of preceding and succeeding pixels in the transport direction within a solid image of each of the six hues: Y, M, C, R, G, and B. The arrows in Figure 15 indicate the direction of greater heat propagation between preceding and succeeding pixels; if there is no arrow, heat propagation to the preceding and succeeding pixels is small. In Figure 15, heat propagation is considered large when the thermal energy from one pulse affects the color development caused by the other pulse. In Figure 15, the R pulse shows that the subsequent pulse affects the color development of the preceding pulse, which is why red was the focus in the first and second embodiments. In Figure 15, the B pulse shows that the preceding and succeeding pulses affect each other's color development. If the effect of the subsequent pulse is greater than the effect of the preceding pulse, then in the first and second embodiments, it is preferable to apply a high-density pulse to the trailing pixels of the blue solid image and a normal pulse to the internal pixels. To determine if something is blue, if r0=0, g0=0, b0=255, r1=0, g1=0, b1=0, then R=0, G=0, B=255 can be determined as blue. The processing flow is the same as the flow in Figure 9. Also, for normal pulses, the B pulse shown in Figure 7 can be used. High-density pulses can be added to the blank region in the latter half of the B pulse using the pulse width and pulse interval of the B pulse in Figure 7. The number of added pulses should be adjusted to reduce the density difference with the internal pixels. [Explanation of Symbols]

[0085] 10 Recording medium (infrared imaging component) 14, 16, 18 Image forming layers 30 Recording heads 34 resistors, 35 Heatsink 36 Thermistor 40 Recording device 41 Storage Unit 42 Conveyor rollers, 43 Platen 44 Outlet 50 Host PCs

Claims

1. A recording device that heats a sheet-shaped recording medium having multiple color-developing layers that correspond to multiple colors and develop color in response to heating, thereby developing a desired color-developing layer among the multiple color-developing layers to form an image on the recording medium, A recording head comprising multiple heating elements arranged in a predetermined direction, which heats the recording medium based on image data, A first condition determination means for determining whether the immediately following pixel, which is at the same position as the pixel of interest in the predetermined direction and is recorded immediately after the pixel of interest, satisfies the first condition that the pixel is either a pixel that produces a color that cannot be visually perceived as affecting the color of the pixel of interest, or a pixel that does not produce color in any of the color-producing layers of the recording medium. The system includes a pulse control means that controls the pulse applied to the recording head when forming the pixel of interest, based on the determination result of the first condition determination means, The recording apparatus is characterized in that, when the value of the pixel of interest in the image data is a predetermined value and the first condition is met, the pulse is controlled such that the thermal energy applied by the recording head to the recording medium when forming the pixel of interest is greater than when the value of the pixel of interest in the image data is a predetermined value and the first condition is not met.

2. The recording apparatus according to claim 1, characterized in that the pulse control means controls the pulse such that when the recording head increases the thermal energy applied to the recording medium, at least one of the heating temperature or heating time of the recording head becomes larger than when the recording head does not increase the thermal energy applied to the recording medium.

3. The recording apparatus according to claim 1 or 2, characterized in that when the recording head increases the thermal energy applied to the recording medium, the pulse control means increases the interval between the pulse applied to the immediate preceding pixel, which is recorded at the same position as the pixel of interest in a predetermined direction and immediately before the pixel of interest, and the pulse applied to the pixel of interest, compared to when the recording head does not increase the thermal energy applied to the recording medium.

4. The recording apparatus according to claim 1 or 2, characterized in that when the recording head increases the thermal energy applied to the recording medium, the pulse control means increases the length from the first pulse applied to the pixel of interest to the last pulse applied, compared to when the recording head does not increase the thermal energy applied to the recording medium.

5. The system includes a second condition determination means for determining whether a second condition is met, which indicates that the thermal history, which is the temperature of each image forming layer of the recording head or the recording medium, is greater than or equal to a predetermined value in the formation of a preceding pixel that is recorded in the same position as the pixel of interest in the predetermined direction and before the pixel of interest. The recording apparatus according to any one of claims 1 to 4, characterized in that the pulse control means controls the pulse such that, when the value of the pixel of interest in the image data is a predetermined value and the first condition and the second condition are met, the amount of thermal energy that the recording head applies to the recording medium when forming the pixel of interest is less than when the value of the pixel of interest in the image data is a predetermined value and the first condition and the second condition are not met.

6. The recording apparatus according to claim 5, characterized in that the pulse control means controls the pulse such that when the second condition is met and the temperature indicated by the thermal history is a first temperature, the thermal energy that the recording head applies to the recording medium is greater than when the second condition is met and the temperature indicated by the thermal history is greater than the first temperature (second temperature).

7. The recording apparatus according to claim 5 or 6, characterized in that the second condition determination means determines whether the second condition is met based on the thermal history in the formation of a plurality of preceding pixels that are recorded in the same position as the pixel of interest in the predetermined direction and before the pixel of interest.

8. The recording apparatus according to any one of claims 1 to 7, characterized in that, if the first condition is not met, the value of the pixel of interest in the image data is the predetermined value, and the preceding pixel recorded immediately before the pixel of interest at the same position as the pixel of interest in the predetermined direction in the image data is a value indicating that no color layer is colored, the pulse is controlled such that the thermal energy applied by the recording head to the recording medium when forming the pixel of interest is greater than in the case where the first condition is not met and the value of the pixel of interest and the value of the preceding pixel in the image data are the predetermined values.

9. The recording device according to any one of claims 1 to 8, characterized in that the aforementioned pixel of interest is a pixel that emits red color.

10. The recording device according to any one of claims 1 to 8, characterized in that the aforementioned pixel of interest is a pixel that emits blue color.

11. A recording device that heats a sheet-shaped recording medium having multiple color-developing layers that correspond to multiple colors and develop color in response to heating, thereby developing a desired color-developing layer among the multiple color-developing layers to form an image on the recording medium, A recording head is provided which has multiple heating elements arranged in a predetermined direction and which heats the recording medium based on image data, A recording device characterized in that, when the image data is data that causes red to be generated in the pixel of interest, and does not cause any of the color-generating layers of the recording medium to be generated in the immediate next pixel, which is at the same position as the pixel of interest in the predetermined direction and is recorded immediately after the pixel of interest, the recording head applies more thermal energy when forming the pixel of interest than when the image data is data that causes red to be generated in the pixel of interest and red to be generated in the immediate next pixel.

12. The recording apparatus according to claim 11, characterized in that, if the image data is data that causes the pixel of interest to produce red color, the pixel immediately following it to produce red color, and the preceding pixel recorded at the same position as the pixel of interest in the predetermined direction and immediately before the pixel of interest does not cause any of the color-producing layers of the recording medium to produce color, the recording apparatus according to claim 11 is characterized in that the thermal energy applied by the recording head when forming the pixel of interest is greater than if the image data is data that causes the pixel of interest to produce red color, the pixel immediately following it to produce red color, and the preceding pixel to produce red color.

13. The recording apparatus according to claim 12, characterized in that, when the thermal energy applied by the recording head is increased, the pulse applied when the image data is data that causes red to be emitted in the pixel of interest and does not cause any color layer to be emitted in the immediately following pixel is compared with the pulse applied when the image data is data that causes red to be emitted in the pixel of interest and the immediately following pixel and does not cause any color layer to be emitted in the immediately preceding pixel, by making the interval between the pulse applied to the immediately preceding pixel and the pulse applied to the pixel of interest longer.

14. The recording apparatus according to claim 12, characterized in that, when the thermal energy applied by the recording head is increased, the pulse applied when the image data is data that causes red to be emitted in the pixel of interest and no color layer to be emitted in the immediately following pixel is compared with the pulse applied when the image data is data that causes red to be emitted in the pixel of interest and red to be emitted in the immediately following pixel and no color layer to be emitted in the immediately preceding pixel, by shortening the interval between the pulse applied to the pixel of interest and the pulse applied to the immediately following pixel.

15. The recording apparatus according to claim 12, characterized in that, when the thermal energy applied by the recording head is increased, the pulse when the image data is data that causes red to be emitted in the pixel of interest and does not cause any color layer to be emitted in the immediately following pixel is compared with the pulse when the image data is data that causes red to be emitted in the pixel of interest, causes red to be emitted in the immediately following pixel, and does not cause any color layer to be emitted in the immediately preceding pixel, by making the length of the pulse from the first pulse applied to the pixel of interest to the last pulse applied to the pixel of interest longer.

16. A recording method for forming an image on a recording medium by heating a sheet-shaped recording medium having multiple color-developing layers that correspond to multiple colors and develop color in response to heating, thereby causing a desired color-developing layer among the multiple color-developing layers to develop color, A heating step in which a recording head having multiple heating elements arranged in a predetermined direction is heated based on image data, A condition determination step to determine whether the immediate next pixel, which is at the same position as the pixel of interest in the predetermined direction and is recorded immediately after the pixel of interest, satisfies the condition that it is a pixel that produces a color that cannot be visually perceived as affecting the color of the pixel of interest, or a pixel that does not produce color in any of the color-producing layers of the recording medium. The system includes a generation step that generates pulses to be applied to the recording head when forming the pixel of interest, based on the determination result of the condition determination step, The generation step, if the value of the pixel of interest in the image data is a predetermined value and the conditions are met, generates the pulse such that the thermal energy applied by the recording head to the recording medium when forming the pixel of interest is greater than when the value of the pixel of interest in the image data is a predetermined value and the conditions are not met. A recording method characterized in that the heating step heats the recording head according to the pulses generated in the generation step.

17. A recording method for forming an image on a recording medium by heating a sheet-shaped recording medium having multiple color-developing layers that correspond to multiple colors and develop color in response to heating, thereby causing a desired color-developing layer among the multiple color-developing layers to develop color, The heating step includes heating a recording head, which has multiple heating elements arranged in a predetermined direction, based on image data. In the heating step, if the image data is data that causes black to develop in the pixel of interest and does not cause any of the color-developing layers of the recording medium to develop color in the immediate next pixel, which is at the same position as the pixel of interest in the predetermined direction and recorded after the pixel of interest, the recording head applies more thermal energy to form the pixel of interest than if the image data is data that causes red to develop in the pixel of interest and red to develop in the immediate next pixel.

Images