Image forming apparatus and image recording method

Abstract

To suppress power consumption in recording of an image.SOLUTION: A temperature applied to an image member 10 in the case where a space frequency of an image recorded on the basis of image data is a low frequency is set to be lower than the case where a space frequency of the image recorded on the basis of the image data is a high frequency, by a preheating pulse.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus and an image recording method. [Background technology]

[0002] Up until now, in recording with a thermal printhead, monochrome printing using thermal paper and color printing using an ink ribbon have been widely used. Meanwhile, in recent years, color recording using paper equipped with multiple color developing layers has been proposed and has become widespread as a simple means of printing photographs, etc. The multiple color developing layers each require different heating temperatures and heating times to develop color, and a color image is recorded by utilizing these differences to develop a specific color developing layer (see Patent Documents 1 and 2).

[0003] In Patent Document 3, the color-forming layer is preheated before it is caused to develop color. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2013-506582 [Patent Document 2] Patent No. 4677431 [Patent Document 3] JP 2010-234811 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional method, the color-forming layer is preheated, but in some cases, the preheating is unnecessary. When the image formed on the recording medium is a low-frequency image, the pixels to be colored are often consecutive. Therefore, the heat applied to color the previous pixel is also transmitted to the next pixel, and the next pixel is preheated. Even if the pixel that has already been preheated is preheated in this way, the effect of the further preheating on the coloring of the color-forming layer is small, and unnecessary power is consumed.

[0006] The present invention has been made in view of the above problems, and has an object to reduce power consumption during image recording. [Means for solving the problem]

[0007] The present invention is an image forming device that heats an image member having multiple laminated color-forming layers that correspond to multiple colors and change color in response to heating, thereby causing a desired color-forming layer among the multiple color-forming layers to change color and form an image on the image member, and includes a print head having heating elements that apply thermal energy to the image member, an operating means that operates the multiple heating elements of the print head using a first pulse for preheating the color-forming layers and a second pulse for coloring the color-forming layers, and a generating means that generates pulses to be applied to the heating elements based on image data for forming an image on the image member, and is characterized in that when the spatial frequency of an image recorded based on image data is a low frequency lower than a predetermined frequency, the generating means generates the first pulse so that the temperature applied to the image member by the first pulse is lower than when the spatial frequency of the image data is a high frequency equal to or higher than the predetermined frequency. Effect of the Invention

[0008] According to the present invention, it is possible to reduce power consumption during image recording. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an imaging member according to a first embodiment. [Diagram 2] FIG. 3 is a diagram showing color development characteristics in an imaging member according to the first embodiment. [Diagram 3] FIG. 2 is a diagram illustrating the configuration of a print head according to the first embodiment. [Figure 4] 1 is a schematic diagram showing a cross-sectional configuration of an image forming apparatus according to a first embodiment. [Diagram 5] 1 is a diagram illustrating an example of a system configuration according to a first embodiment. [Figure 6] FIG. 4 is a sequence diagram of a print service according to the first embodiment. [Figure 7] FIG. 4 is a diagram showing a heating pulse in the first embodiment. [Figure 8] FIG. 4 is a diagram showing a preheat pulse in the first embodiment. [Figure 9] FIG. 2 is a diagram showing an example of an image in the first embodiment. [Figure 10] 4 is a flowchart of a process during image formation in the first embodiment. [Figure 11] FIG. 11 is a diagram for explaining region division of image data in the second embodiment. [Figure 12] 10 is a flowchart of a process during image formation in the second embodiment. [Figure 13] 10 is a table showing preheat pulses corresponding to the spatial frequencies of an image and main color layers in the second embodiment. [Figure 14] 13 is a flowchart of a process during image formation in the third embodiment. [Figure 15] FIG. 13 is a diagram showing a configuration example of a heating pulse in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <First embodiment> [Image material] 1 is a conceptual diagram for explaining the configuration of an imaging member according to the present embodiment. In addition, in the present embodiment, an infrared imaging method using infrared rays as a heat source for an image forming apparatus will be described, but other methods or heat sources may be used to apply thermal energy.

[0011] In Fig. 1, the image forming member 10 is composed of, from the bottom layer, a light-reflecting substrate 12, an image forming layer 18, a spacer layer 17, an image forming layer 16, a spacer layer 15, an image forming layer 14, and a protective film layer 13. The image forming layers 14, 16, and 18 are generally a yellow color forming layer, a magenta color forming layer, and a cyan color forming layer, respectively, during full-color printing, but may be other color combinations. In other words, in the example of Fig. 1, image forming layers (color forming layers) corresponding to three colors are provided, but more image forming layers may be provided, or the image member may be provided with image forming layers corresponding to two colors.

[0012] Each image forming layer is initially colorless (before image formation), but changes to a corresponding color when heated to a specific temperature called the activation temperature of each image forming layer. In this embodiment, the color development characteristics for color development in each image forming layer are different. The order of colors of the image forming layers in the image member 10 (order of stacking) can be selected arbitrarily. One suitable color order is as described above. Another suitable order is an order in which the three image forming layers 14, 16, and 18 are a cyan color developing layer, a magenta color developing layer, and a yellow color developing layer, respectively. In this embodiment, an example in which the layers are configured in the above-mentioned order of yellow, magenta, and cyan will be described. In FIG. 1, the image forming layers are stacked to the same thickness, but this is not limited to this, and the thickness may differ depending on the color (color material).

[0013] As shown in FIG. 1, a spacer layer is provided between each of the image forming layers. The thickness of the spacer layer may be determined according to the color development characteristics of each image forming layer, the thermal conduction characteristics and thermal diffusivity of each layer, etc. For example, each spacer layer may be made of the same material or different materials. The function of the spacer layer is to control the thermal diffusion within the image member 10. Preferably, the spacer layer 17 is at least four times thicker than the spacer layer 15 when the spacer layer 17 is made of the same material.

[0014] All layers disposed on substrate 12 are substantially transparent prior to imaging. If substrate 12 is a reflective color (e.g., white), the color image formed by imaging member 10 is viewed through overcoat layer 13 against the reflective background provided by substrate 12. The transparency of each layer deposited on substrate 12 allows the human eye to see the combination of colors printed on each of the imaging layers.

[0015] In this embodiment, the three image-forming layers 14, 16, and 18 in the imaging member 10 are disposed on the same side of the substrate 12, although some of the image-forming layers may be disposed on opposite sides of the substrate 12.

[0016] In this embodiment, the imaging layers 14, 16, and 18 are processed at least in part independently by varying two adjustable parameters in the imaging device: temperature and time. These parameters are controlled by the print head temperature and time when heat is applied to the imaging member 10 to form an image in the desired imaging layer. That is, by controlling the temperature and time applied to the imaging member 10, a desired density of color can be developed in the desired imaging layer.

[0017] In this embodiment, each of the image forming layers 14, 16, and 18 is treated by applying heat while the print head is in contact with the top layer of the image member 10, i.e., the protective film layer 13 shown in FIG. 1. The color development characteristics of each image forming layer according to this embodiment will be described. The activation temperatures of the image forming layers 14, 16, and 18 are Ta3, Ta2, and Ta1, respectively. In this case, the activation temperature (Ta3) of the image forming layer 14 is higher than the activation temperature (Ta2) of the image forming layer 16, and is also higher than the activation temperature (Ta1) of the image forming layer 18. The relationship between the activation (color development characteristics) of each image forming layer will be described later with reference to FIG. 2.

[0018] Heating of the image forming layers located farther from the print head (i.e., the protective film layer 13) is delayed by the time required for heating because of conduction and diffusion to those layers through each spacer layer. Therefore, even if the temperature applied from the print head to the surface of the image member 10 (i.e., the protective film layer 13) is substantially higher than the activation temperature of the image forming layers located lower (layers farther from the print head), heating due to heat diffusion by each layer is delayed. This makes it possible to control the heating to the activation temperature for the image forming layers closer to the print head while not activating the image forming layers below it. Therefore, when processing (coloring) only the image forming layer 14 closest to the protective film layer 13, the print head heats up to a relatively high temperature (Ta3 or higher) in a short time. In this case, both the image forming layers 16 and 18 are insufficiently heated, and coloring (activation) of these layers is not performed.

[0019] Activation of only the imaging layer closer to substrate 12 (in this case, imaging layer 16 or 18) is accomplished by heating for a sufficiently long period of time at a temperature lower than the activation temperature of the imaging layer further from substrate 12 (e.g., imaging layer 14). In this way, when the lower imaging layer (imaging layer 16 or 18) is activated, the higher imaging layer (e.g., imaging layer 14) is not activated.

[0020] As noted above, heating of the image member 10 is preferably accomplished using a thermal print head, although other methods may be used, such as any known means, such as a modulated light source (such as a laser).

[0021] [Color development characteristics] 2 is a diagram for explaining the relationship between the heating temperature and heating time required to treat the image forming layers 14, 16, and 18 that compose the imaging member 10. In FIG. 2, the vertical axis indicates the heating temperature at the surface of the imaging member 10 that contacts the print head, and the horizontal axis indicates the heating time. The heating time here will be explained as being the same as the temperature supplied by the print head.

[0022] The region 21 indicates a relatively high heating temperature and a relatively short heating time. In this embodiment, the region 21 corresponds to the yellow of the image forming layer 14. That is, when the energy shown in the region 21 is supplied to the image forming layer 14, color development (image formation) is performed. The region 22 indicates an intermediate heating temperature and an intermediate heating time. The region 22 corresponds to the magenta of the image forming layer 16. That is, when the energy shown in the region 22 is supplied to the image forming layer 16, color development (image formation) is performed. The region 23 indicates a relatively low heating temperature and a relatively long heating time. The region 22 corresponds to the cyan of the image forming layer 18. That is, when the energy shown in the region 23 is supplied to the image forming layer 18, color development (image formation) is performed. The time required for imaging (color development) of the image forming layer 18 is substantially longer than the time required for imaging the image forming layer 14.

[0023] The activation temperature selected for the imaging layers is, for example, within the range of about 90° C. to about 300° C. The activation temperature (Ta1) of the imaging layer 18 is preferably as consistently low as possible for thermal stability of the imaging member 10 during shipping and storage, and is preferably about 100° C. or higher. The activation temperature (Ta3) of the imaging layer 14 is preferably consistently high, and is preferably about 200° C. or higher, for activation of the imaging layers 16, 18 by heating through this layer. The activation temperature (Ta2) of the imaging layer 16 is between Ta1 and Ta3, and is preferably between about 140° C. to about 180° C.

[0024] In addition, even when energy is applied to each image forming layer within the corresponding region, the density of the color formed varies depending on the position within the region. For example, when energy is applied to the image forming layer 16 within the region 22, an image with a higher density is formed when a temperature closer to Ta3 is applied than when a temperature closer to Ta2 is applied, even if the heating time is the same. The same is true when the heating time varies.

[0025] [Print head] The printhead of this embodiment includes a substantially linear array of resistors that extend across the width of the image, the printhead extending in a direction perpendicular to the transport direction of the image member 10 (the width of the image member 10) and the resistors disposed along the width of the image member 10.

[0026] By supplying a current to the resistors in the print head, the resistors act as heat sources and heating elements, and the image member 10 is conveyed while receiving heat from the resistors in the print head, so that each image forming layer forms an image. As described above, in this embodiment, the resistors are configured to be capable of irradiating infrared rays. The time during which heat is applied to the image member 10 by the print head typically ranges from about 0.001 to about 100 milliseconds per line of the image. The upper limit is set in consideration of the printing time, while the lower limit is defined by the constraints of the electronic circuit (not shown). The intervals between dots forming an image are generally in the range of 100 to 600 lines per inch in both the conveying direction and the width direction of the image member 10, and may be different in each direction.

[0027] FIG. 3 is a diagram showing an example of the configuration of the print head and the image member 10 during image formation according to this embodiment. In FIG. 3(a), the image member 10 is transported to the right during image formation. The width direction of the image member 10 corresponds to the depth direction in FIG. 3(a). The print head 30 includes a glaze 32 on a base 31. In this embodiment, the glaze 32 further includes a convex glaze 33. The resistor 34 is disposed on the surface of the convex glaze 33 and is disposed so as to contact the image member 10 transported in the transport direction. The convex glaze 33 may have another shape or may not be provided. In that case, the resistor 34 is configured to contact the image member 10. It is preferable that a protective film layer (not shown) is formed on the resistor 34, the glaze 32, and the convex glaze 33. The combination of the glaze 32 and the convex glaze 33, which are generally made of the same material, is hereinafter referred to as the "glaze of the print head".

[0028] A base 31 and a heat sink 35 are provided on the glaze 32. The base 31 is in contact with the heat sink 35 and is cooled by a cooling section such as a fan (not shown). The image member 10 will be in contact with the printhead glaze which is typically longer than the length of the actual heating resistor in the transport direction. A typical resistor has a length in the transport direction of the image member 10 of about 120 microns, while the thermal contact area of ​​the image member 10 with the printhead glaze in a typical case is 200 microns or more.

[0029] 3(b) is a diagram showing an example of an arrangement of resistors 34 in the width direction. A plurality of resistors 34 are arranged in the width direction, so that the resistors 34 have a fixed length in the width direction of the image member 10, and an image of one line is formed along this arrangement. In the example shown below, an image is formed line by line while the image member 10 is transported in the transport direction.

[0030] [Image forming device] FIG. 4 is a cross-sectional view showing an example of the configuration of an image forming apparatus according to this embodiment. The image forming apparatus 40 includes the following components. The image forming apparatus 40 includes a print head 30 on the upstream side of the conveyance of the image member 10, a storage section 41, a conveying roller 42, a platen 43, an outlet 44, a temperature sensor 45, a camera 46, an image capture button 47, and a battery 48. The storage section 41 can store a plurality of image members 10, and the image members 10 can be replenished by opening and closing a cover (not shown). During printing, the image member 10 is sent to the print head 30 by the conveying roller 42, and after an image is formed between the platen 43 and the print head 30, it is discharged from the outlet 44 to complete the printing. In addition, a temperature sensor 45 is provided around the nip portion between the print head 30 and the platen 43 to detect the temperature supplied by the print head 30. The object to be detected by the temperature sensor 45 may be, for example, the temperature of a resistor 34 (heat source) of the print head 30, or the surface temperature of the image member 10. Furthermore, the temperature sensor 45 may be configured to detect the environmental temperature of the image forming apparatus 40 .

[0031] The transport speed of the image member 10 is controlled according to the speed of image formation, the resolution during image formation, etc. For example, when forming a high-resolution image, the transport speed may be slower than when forming a low-resolution image. Also, when priority is given to printing speed, the transport speed may be increased and the resolution may be decreased.

[0032] [System Configuration] Fig. 5 is a diagram showing an example of the overall configuration of a system according to this embodiment. As shown in Fig. 5, the system according to this embodiment includes the image forming apparatus 40 shown in Fig. 4 and a personal computer (PC) 50 as its host device.

[0033] The PC 50 includes the following components: a CPU (Central Processing Unit) 501, a RAM (Read Only Memory) 502, a HDD (Hard Disk Drive) 503, a communication I / F 504, an input device I / F 505, and a display device I / F. Furthermore, each component is connected to each other via an internal bus so that they can communicate with each other. The CPU 501 executes processing in accordance with programs and various data stored in the HDD 503 and RAM 502. The RAM 502 is a volatile storage device that temporarily stores programs and data. Furthermore, the HDD 503 is a non-volatile storage device that stores programs and data.

[0034] The communication I / F 504 is an interface that manages communication with an external device, and here controls transmission and reception of data with the image forming apparatus 40. The connection method for transmitting and receiving data here can be a wired connection such as USB, IEEE1394, or LAN (Local Area Network), or a wireless connection such as Bluetooth (registered trademark) or WiFi (registered trademark). The input device I / F 505 is an interface that controls a HID (Human Interface Device) such as a keyboard or mouse, and accepts input from a user's input device. The display device I / F 506 controls display on a display device such as a display (not shown).

[0035] The image forming apparatus 40 includes a CPU 401, a RAM 402, a ROM 403, a communication I / F 404, a head controller 405, a camera controller 406, and an image processing accelerator 407. Furthermore, each component is connected to each other via an internal bus so that they can communicate with each other. The CPU 401 executes the processes of each embodiment described below in accordance with programs and various data stored in the ROM 403 and RAM 402. The RAM 402 is a volatile storage and temporarily stores programs and data. Moreover, the ROM 403 is a non-volatile storage and stores table data and programs used in the processes described below.

[0036] The communication I / F 404 is an interface that manages communication with external devices, and in this case, controls the transmission and reception of data between the PC 50 and the head controller 405. The head controller 405 controls the heating operation of the print head 30 shown in FIG. 3 based on the recording data. Specifically, the head controller 405 can be configured to read control parameters and head recording data from a predetermined address in the RAM 402. Then, when the CPU 401 writes the control parameters and recording data to a predetermined address in the RAM 402, the head controller 405 starts processing and the print head 30 heats up. The camera controller 406 controls the camera 46 shown in FIG. 4. Specifically, when the user presses the image capture button 47, the camera controller 406 issues a shooting instruction to the camera 46, and the camera 46 takes a picture. The captured image is temporarily stored in the RAM 402. Then, when the captured image is to be printed, the head controller 405 starts processing and the print head 30 heats up. The image processing accelerator 407 is configured by hardware and executes image processing faster than the CPU 401. Specifically, the image processing accelerator 407 can be configured to read parameters and data required for image processing from a predetermined address of the RAM 402. When the CPU 401 writes the parameters and data to a predetermined address of the RAM 402, the image processing accelerator 407 is started and a predetermined image processing is performed. Note that the image processing accelerator 407 is not necessarily an essential element, and the above table parameter creation processing and image processing may be executed only by the processing by the CPU 401 according to the specifications of the printer. Also, the temperature sensor 45 detects the ambient temperature of the resistor 34 of the print head 30 as shown in FIG. 4, and provides the temperature information to the CPU 401 and the like. The CPU 401 generates a control parameter for controlling the heat generation of the resistor 34 of the head based on the acquired temperature information. Detailed control will be described later.

[0037] In this embodiment, the image forming device 40 and the PC 50 are described as different devices, but for example, they may be integrated into a system, or the image forming device 40 may be integrated into a system with an imaging device (not shown). Also, although a PC has been given as an example of the host device, this is not limiting, and for example, a mobile terminal such as a smartphone, a tablet terminal, or an imaging device may be used.

[0038] [Print service] Fig. 6 shows a sequence when a print service is performed in the system according to this embodiment. In Fig. 6, steps S601 to S605 show processing in the PC 50, and steps S611 to S616 show processing in the image forming device 40. Also, in Fig. 6, dashed arrows show data transmission and reception. Each step is realized by the CPU of each device reading and executing a program or the like stored in a storage unit. This sequence starts when a user attempts to perform printing.

[0039] In step S611, after power is turned on, the image forming apparatus 40 confirms that it is capable of printing, and goes into a standby state ready to provide a printing service.

[0040] On the other hand, in step S601, the PC 50 executes print service discovery. The print service discovery here may be configured to search for peripheral devices according to user operations, or to periodically search for an image forming device that is in a state where it can provide a print service. Alternatively, the PC 50 may be configured to make an inquiry when the PC 50 and the image forming device 40 are connected.

[0041] In step S612, upon receiving the print service Discovery from the PC 50, the image forming device 40 notifies the PC 50 in response that it is a device that can provide the print service.

[0042] In step S602, when the PC 50 receives a notification from the image forming apparatus 40 that the print service can be provided, the PC 50 requests printable information from the image forming apparatus.

[0043] In step S613, the image forming apparatus 40 notifies the PC 50 of information on the printing services that it can provide in response to the request for printable information from the PC 50.

[0044] Upon receiving the printable information from the image forming apparatus 40, the PC 50 constructs a user interface for creating a print job based on the printable information in step S603. Specifically, based on the printable information of the image forming apparatus 40, the PC 50 appropriately displays the designation of the print image, print size, printable paper size, etc., and provides appropriate options to the user via a display (not shown). Then, settings from the user are accepted via an input device (not shown) such as a keyboard.

[0045] In step S604, the PC 50 issues a print job based on the settings received from the user, and transmits it to the image forming apparatus 40.

[0046] In step S614, the image forming apparatus 40 receives the print job from the PC 50.

[0047] In step S615, the image forming apparatus 40 analyzes and executes the received print job. Details of image formation for a print job according to this embodiment will be described later.

[0048] When the printing is completed, in step S616, the image forming apparatus 40 notifies the PC 50 of the printing completion. Then, the processing on the image forming apparatus 40 side is completed, and the image forming apparatus 40 goes into a standby state.

[0049] In step S605, the PC 50 receives the print completion notification and notifies the user of that fact, thereby completing the processing on the PC 50 side.

[0050] In the above description, various types of information are transmitted by making a request from the PC 50 to the image forming apparatus 40, and the image forming apparatus 40 responds to the request. However, the communication is not limited to the above-described so-called pull-type communication, and may be a so-called push-type communication in which the image forming apparatus 40 spontaneously transmits information to one or more PCs 50 on the network.

[0051] [Head Control] The heating pulse signal used for heating control for the present invention will be described. FIG. 7 shows an example of a signal pattern (heating pulse) corresponding to each color applied to the print head. FIG. 7 shows an example of the configuration of the heating pulse for each color to be developed in the image member 10 in one pixel. From the top, yellow (Y), magenta (M), cyan (C), red (R), green (G), blue (B), black (K), and white (W) are shown. In FIG. 7, the heating pulse for one pixel is configured to include 14 sections (p0 to p13), and the length of one section is Δt0. In other words, the time of the heating pulse required to form one pixel is Δt0×14 sections (p0 to p13). In other words, the number of cycles of the pulse in the 14 sections is used to develop the color of one pixel, and the color development is controlled by the pulse signal train included in this. p0 to p8 are heating pulses required to cause each layer of the image member 10 to develop color, and p9 to p13 are heating pulses required to preheat the image member 10.

[0052] In FIG. 7, the signal shows two values, High and Low (ON and OFF). When it is High, heating is performed by the resistor 34, and when it is Low, heating is not performed. The color development is controlled by controlling the pulse width and number of pulses contained in the heating pulse for each color. In this embodiment, the pulse width of each pulse is adjusted by PWM (Pulse Width Modulation) control. As shown in FIG. 7, the starting point of each section will be described as the rising timing of the pulse (ON timing).

[0053] For example, when developing yellow (Y), in order to achieve the region 21 shown in FIG. 2 (relatively high heating temperature and relatively short heating time), heating is performed on p0 and p1 for a total of 2 times with an interval of Δt1 between each heating, and this is carried out with intervals. Also, when developing magenta (M), in order to achieve the region 22 shown in FIG. 2 (medium heating temperature and medium heating time), heating for a time of Δt2 is performed a total of 4 times with intervals. Here, the interval between the first pulse and the second pulse is (Δt0 - Δt2). Similarly, when developing cyan (C), in order to achieve the region 23 shown in FIG. 2 (relatively low heating temperature and relatively long heating time), heating for a time of Δt3 is performed a total of 8 times with intervals. Here, the interval between the first pulse and the second pulse is (Δt0 - Δt3). By providing this interval, it is possible to suppress the temperature of the image member 10 from rising above the target temperature (activation temperature). In other words, by controlling the ON time and the OFF time, the target temperature is maintained.

[0054] In FIG. 7, for ease of understanding, Δt1 = Δt2×2 = Δt3×4 is set such that, regardless of which color is developed, the total time of the heating pulses applied to the print head 30 is the same. t1 to t3 and Ta1 to Ta3 shown below correspond to the descriptions in FIG. 2.

[0055] The heating time required to exceed the activation temperature shown in FIG. 2 is t2 > heating time of Y, Δt1 + Δt0 > t1 t3 > heating time of M, Δt2 + Δt0×3 > t2 heating time of C, Δt3 + Δt0×7 > t3 and the relative relationship of the heating times is heating time of Y < heating time of M < heating time of C Here, Y, M, and C respectively refer to the image forming layers 14, 16, and 18.

[0056] Here, the energy (amount of heat) applied to the image member 10 by the print head 30 is thermally conducted to the glaze 32 (and convex glaze 33) of the print head 30, the base 31, the heat sink 35, and the like shown in FIG. 3 during the interval time of each signal. Therefore, the temperature of the image member 10 drops during the interval time. Similarly, the amount of heat conducted into the image member 10 is also propagated to the periphery, such as the platen 43 shown in FIG. 4, and the temperature of the image member 10 drops by that amount. As a result, when the input energy (amount of heat) is the same, the peak temperature due to heating is Y>M>C Here, Peak temperature of Y>Ta3 Ta3>M peak temperature>Ta2 Ta2>C peak temperature>Ta1 By controlling it in this way, it is possible to produce each of the colors Y, M, and C independently.

[0057] Next, the heating pulses that control the coloring of the secondary colors red (R), green (G), and blue (B) will be described. Here, the N-th color means a color expressed by combining N color materials (image forming layers). The heating pulses are controlled so that red (R) develops in the order of yellow (Y) → magenta (M). That is, the image of red (R) is formed by coloring the image forming layer 14 corresponding to yellow (Y) and the image forming layer 16 corresponding to magenta (M). In addition, the heating pulses are controlled so that green (G) shown in FIG. 7 develops in the order of yellow (Y) → cyan (C). Similarly, the heating pulses are controlled so that blue (B) shown in FIG. 7 develops in the order of magenta (M) → cyan (C). The heating pulses are controlled so that black (K) shown in FIG. 7 develops in the order of yellow (Y) → magenta (M) → cyan (C). Since white (W) shown in FIG. 7 does not need to develop paper, no heating pulses are input.

[0058] Next, the signals used for preheat control will be described with reference to FIG. 8. Δt0 and Δt3 in FIG. 8 are the same as Δt0 and Δt3 in FIG. 7. Preheat pulse 1 performs a total of five pulses at p9, p10, p11, p12, and p13 for a time of Δt3, with intervals between pulses, to preheat the image member 10 so as not to exceed the activation temperature (Ta1). Similarly, preheat pulse 2 performs a total of four pulses at p10, p11, p12, and p13 for a time of Δt3, with intervals between pulses. Preheat pulse 3 performs a total of three pulses at p11, p12, and p13 for a time of Δt3, with intervals between pulses. Preheat pulse 4 performs a total of two pulses at p12 and p13 for a time of Δt3, with intervals between pulses. Preheat pulse 5 performs a total of one pulse at p13 for a time of Δt3, with intervals between pulses. The preheating temperatures applied to the image member 10 as preheating pulses are as follows: preheating pulse 1>preheating pulse 2>preheating pulse 3>preheating pulse 4>preheating pulse 5. The preheating pulses are applied between p9 and p13, and preheating is performed by applying them after the pulses for developing the colors shown in Fig. 7, which are applied between p0 and p8. Fig. 7 shows a preheating pulse in which the number of times heating is changed by Δt3, but the length of the pulse may be changed to such an extent that no color is developed, or both the number of times and the length may be changed.

[0059] FIG. 9(a) shows an example of a high-frequency image, and FIG. 9(b) shows an example of a low-frequency image. When the image to be recorded is low-frequency, the pixels that develop color are often continuous. Therefore, the heat of the pulse applied to the previous pixel is transmitted to the next pixel, and the pixel is already heated and is likely to develop color even without applying many preheating pulses. On the other hand, when the image to be recorded is high-frequency, the pixels that develop color are often discontinuous. Therefore, there are many pixels where the previous pixel is a pixel that does not develop color, and the next pixel is often not heated by the application of a pulse to the previous pixel. Therefore, even if the same pulse is applied to develop color, the way in which the pixels develop color varies depending on the frequency of the image.

[0060] Therefore, in this embodiment, the preheat pulse applied is switched according to the frequency of the image, specifically, the preheat temperature applied to the image member 10 for a high frequency image is made higher than that for a low frequency image.

[0061] [Processing flow] Fig. 10 is an image processing flowchart for implementing a heating pulse according to this embodiment. The flow shown in Fig. 10 is executed in the process of step S615 in Fig. 6. This flow is implemented, for example, by the CPU 401 of the image forming apparatus 40 reading and executing programs and data contained in the ROM 403, etc. Note that this process may be configured so that part of it is executed by the image processing accelerator 407.

[0062] In step S901, the CPU 401 acquires image data in the print job received in step S614 in Fig. 6. Here, the description will be given assuming that the image data is acquired page by page.

[0063] In step S902, the CPU 401 performs a decoding process on the image data. If the image data has not been compressed or encoded, this process may be omitted. The image data becomes RGB data through the decoding process. Examples of the type of RGB data include standard color information such as sRGB and adobe (registered trademark) RGB. In this embodiment, the image data has 8-bit information for each color, with a value range of 0 to 255, but may be composed of a different number of bits, such as 16 bits.

[0064] In step S903, the CPU 401 analyzes the spatial frequency of one page of image recorded on the entire image member. A known method such as FFT (fast Fourier transform) or DFT (discrete Fourier transform) is used to calculate the spatial frequency. When these calculation methods are used, the spatial frequency is calculated as one value. The calculated spatial frequency is judged by a threshold value and classified as high frequency or low frequency. The calculated classification result is stored in the RAM 402. In this embodiment, a value half the maximum value is set as the threshold value, and if it is smaller than the threshold value, it is classified as a low frequency image, and if it is equal to or greater than the threshold value, it is classified as a high frequency image. Some images have a mixture of high frequency and low frequency parts. For example, in the case of an image that has mostly high frequency components, a value indicating that it is a high frequency image is calculated as the calculation result.

[0065] In step S904, CPU 401 performs color correction processing on the image data. Note that color correction processing may be performed on the PC 50 side, or may be performed within image forming apparatus 40 when color correction is performed to match image forming apparatus 40. The image data after color correction processing is RGB data, but at this point it is in a format of RGB specialized for image forming apparatus 40, so-called device RGB.

[0066] In step S905, the CPU 401 performs luminance / density conversion on the image data using a three-dimensional lookup table. In a typical thermal printer, for example, the RGB signal of the image data is used to convert the luminance / density of the image data into the following: C=255-R M=255-G Y=255-B On the other hand, in the case of pulse control according to this embodiment, for example, the control parameters of magenta constituting a single color of magenta (M) and the control parameters of magenta constituting a suitable color of red (R) are different. Therefore, in order to set the two separately, it is desirable to perform luminance density conversion using a three-dimensional lookup table. Note that the conversion may be performed by any method, but here, an example using a three-dimensional lookup table, which is more preferable, will be described.

[0067] In this embodiment, luminance / density conversion is performed using a three-dimensional lookup table as follows. In the function 3D_LUT[R][G][B][N] of the three-dimensional lookup table used below, the variables R, G, and B are input with RGB data values, and the variable N is specified as one of C, M, and Y to be output. Here, 0, 1, and 2 are specified as C, M, and Y, respectively. C=3D_LUT[R][G][B][0] M=3D_LUT[R][G][B][1] Y=3D_LUT[R][G][B][2]

[0068] The above 3D_LUT is composed of 50,331,648 data tables of 256×256×256×3. Each data corresponds to the pulse width applied to p0 to p8 in FIG. 7. In order to reduce the amount of data in the lookup table, for example, the number of grids may be reduced from 256 to 17, and the result may be calculated by an interpolation operation using 14,739 data tables of 17×17×17×3. Of course, other than 17 grids, a suitable number of grids such as 16 grids, 9 grids, and 8 grids may be set as appropriate. Any method such as known tetrahedral interpolation may be used as the interpolation method. In this embodiment, the three-dimensional lookup table is defined in advance and is held in the ROM 403 of the image forming apparatus 40.

[0069] By using the above three-dimensional lookup table, it is possible to set the control parameters for yellow (Y), magenta (M), and cyan (C) that make up each color individually. In other words, it is possible to set the control parameters for the yellow and magenta that make up red (R), the cyan and yellow that make up green (G), the magenta and cyan that make up blue (B), and the yellow, magenta, and cyan that make up black (K) independently. This allows for more precise control of color development, which contributes to improved color reproducibility.

[0070] In step S906, the CPU 401 performs output correction on the converted image data. First, the CPU 401 calculates a pulse width for achieving the density of each C, M, and Y using a conversion table corresponding to each color. c, m, and y indicate pulse widths corresponding to the values ​​of C, M, and Y, respectively. The conversion table (conversion formula) here is defined in advance and is held in the ROM 403 of the image forming apparatus 40, etc. c=1D_LUT[C] m=1D_LUT[M] y=1D_LUT[Y]

[0071] Here, the maximum value of the pulse width indicated by c is Δt3 in FIG. 7. The maximum value of the pulse width indicated by m is Δt2 in FIG. 7. The maximum value of the pulse width indicated by y is Δt1 in FIG. 7. Since the image forming apparatus 40 can modulate the color intensity in the image member 10 by modulating the pulse width, when the above-mentioned c, m, and y are smaller than the maximum values, the pulse width can be shortened appropriately to achieve the desired gradation. This process may be performed by using a known means.

[0072] Furthermore, the CPU 401 modulates the heating pulse according to the temperature of the imaging member 10 (or the print head 30) acquired by the temperature sensor 45. Specifically, the CPU 401 controls so that the pulse width of the heating pulse used to reach the activation temperature is shortened as the temperature detected by the temperature sensor 45 increases. This process may be performed using known means. In addition to acquiring the temperature of the imaging member 10 using the temperature sensor 45, the PC or the image forming apparatus 40 may estimate the temperature of the imaging member 10 or the print head 30, and control may be performed based on the estimated temperature. The method of temperature estimation is not particularly limited, and any known method may be used.

[0073] In step S907, the preheat pulses shown in FIG. 8 are added in accordance with the spatial frequency of the image to be recorded based on the image data of the entire page in the cmy data generated in step S906. If the result of the spatial frequency analysis stored in RAM 402 determined in step S903 indicates that the frequency of the entire image data is high, preheat pulse 1 is added to increase the preheat temperature of image member 10. On the other hand, if the image data indicates that the entire image data is low frequency, preheat pulse 3 is added to make the preheat temperature of image member 10 relatively lower than in the case of high frequency. In this embodiment, the method of classifying spatial frequencies into two types has been described, but the number of classifications of spatial frequencies may be increased. In that case, it is sufficient to increase the number of types of corresponding preheat pulses.

[0074] In step S908, the CPU 401 controls the print head 30 via the head controller 405 in accordance with the pulses generated in step S907. The Y heating pulse, M heating pulse, and C heating pulse shown in Fig. 7 are controlled to heat the image member 10 by the print head 30, thereby forming a desired color on the image member.

[0075] In step S909, CPU 401 determines whether recording of the page is complete. If it is complete (YES in step S909), this processing flow ends, and the process proceeds to the next page or to step S616 in Fig. 6. If it is not complete (NO in step S909), the process proceeds to step S904, and image formation processing for the page continues.

[0076] As explained above, in the examples of Figures 7 and 8, the preheat pulse can be controlled according to the spatial frequency of the image recorded based on the image data. As a result, unnecessary preheat pulses can be reduced, and the battery life can be extended.

[0077] <Second embodiment> In the above first embodiment, an example was described in which the spatial frequency of the entire image data was analyzed to determine the preheat pulse. In this embodiment, an example in which the image data is divided into regions and a preheat pulse is determined for each region, and further an example in which a preheat pulse is determined for a main coloring layer, will be described with reference to Fig. 12. Differences from the first embodiment will be mainly described.

[0078] The flow of FIG. 12 is realized by the CPU 401 of the image forming apparatus 40 reading and executing programs and data stored in the ROM 403 and the like.

[0079] Steps S1201 to S1202, steps S1205 to S1207, and steps S1209 to S1210 in Fig. 12 are similar to steps S901 to S902, steps S904 to S906, and steps S908 to S910 in Fig. 6 of the first embodiment, respectively, and therefore will not be described in this embodiment.

[0080] The difference from the first embodiment is that in step S1203, the image data is divided into regions and the spatial frequency is calculated for each divided region. In step S1203, the image data is divided into a predetermined size.

[0081] In step S1204, the spatial frequency is calculated for each divided region. In Fig. 11, 1001 is image data, and 1002 to 1005 are regions in which the image data is divided vertically and horizontally into 2 x 2 regions, each of which has m pixels in the x direction and n pixels in the y direction. Reference numeral 1002 is an upper left region of the divided region, in which lines of cyan (C) ((R,G,B)=(0,255,255) and white (W) ((R,G,B)=(255,255,255) are repeated. Reference numeral 1003 is an upper right region of the divided region, which is uniformly cyan (C). Reference numeral 1004 is a lower left region of the divided region, in which lines of yellow (Y) ((R,G,B)=(255,255,0) and white (W) are repeated. Reference numeral 1005 is a lower right region of the divided region, which is uniformly yellow (Y). The spatial frequency is analyzed by a method similar to that described in the first embodiment, and regions 1002 and 1004 are classified as high frequency regions, and regions 1003 and 1005 are classified as low frequency regions, and the calculated classification results are stored in the RAM 402.

[0082] In step S1208, the difference from the first embodiment is that a preheat pulse is set according to the spatial frequency of each divided region, and the main color-forming layer is specified for each divided region by the pulse used for the cmy data generated in step S1207. Specifically, the cmy data of each pixel is referenced, and the number of pixels (Sum14) that cause the image-forming layer 14 (Y) to develop color, the number of pixels (Sum16) that cause the image-forming layer 16 (M) to develop color, and the number of pixels (Sum18) that cause the image-forming layer 18 (C) to develop color are calculated. The maximum value of Sum14, Sum16, and Sum18 is set as the main color-forming layer. For example, since the image recorded in 1003 is a uniform cyan (C) image, Sum14=0, Sum16=0, and Sum18=m×n, and since the maximum value is Sum18, the main color-forming layer is the image-forming layer 18. As a result of the calculation, 1002 to 1005 are classified as follows. 1002 is a high frequency region, and the main color-developing layer is an image-forming layer 18 1003 is a low frequency region, and the main color-developing layer is an image-forming layer 18 1004 is a high frequency region, and the main color-developing layer is an image-forming layer 14 1005 is a low frequency region, and the main color-developing layer is an image-forming layer 14

[0083] 13 shows an example table of spatial frequencies and preheat pulses to be added to the main color-forming layer. 1002 is a high frequency region, and the main color-forming layer is image-forming layer 18, so preheat pulse 1 is added to the cmy data generated in step S1207. Similarly, 1003 is a low frequency region, and the main color-forming layer is image-forming layer 18, so preheat pulse 3 is added to the cmy data generated in step S1207. 1004 is a high frequency region, and the main color-forming layer is image-forming layer 14, so preheat pulse 2 is added to the cmy data generated in step S1207. 1005 is a low frequency region, and the main color-forming layer is image-forming layer 14, so preheat pulse 4 is added to the cmy data generated in step S1207. Furthermore, 1006 is included in region 1003 and is adjacent to 1002, which was determined to be a high frequency region. Similarly, 1007 is included in the 1005 region and is adjacent to 1004, which is determined to be a high frequency region. The high frequency region has a higher preheat temperature than the low frequency region. Therefore, the preheat applied in the 1002 region may propagate to 1006, causing 1006 to erroneously develop color. Similarly, the preheat applied in the 1004 region may propagate to 1007, causing 1007 to erroneously develop color. Therefore, the preheat temperature is further lowered in the low frequency region near the high frequency region, including the portion adjacent to the high frequency region. Therefore, since 1006 is a low frequency region, and the main coloring layer is the image forming layer 18, which is adjacent to the high frequency region, preheat pulse 4 is added to the cmy data generated in step S1207. Since 1007 is a low frequency region, and the main coloring layer is the image forming layer 14, which is adjacent to the high frequency region, preheat pulse 5 is added to the cmy data generated in step S1207. In this embodiment, an example has been described in which the preheat pulse in a low frequency region adjacent to a high frequency region is changed, but a method of changing the preheat pulse in an adjacent low frequency region when there is a difference in spatial frequency between the regions of a predetermined value or more may also be used.

[0084] As described above, the preheat pulse can be controlled in accordance with the spatial frequency and the main coloring layer of the image data for each divided region. As a result, unnecessary preheat pulses can be reduced, and the battery life can be extended.

[0085] <Third embodiment> In the above embodiment, an optimal pulse was generated by adding the preheat pulse shown in Fig. 8 to the heating pulse shown in Fig. 7. Therefore, in this modified example, an example in which the pixel value is changed for preheating without adding a preheat pulse will be described with reference to Figs. 14 and 15. The following mainly describes the parts that differ from the above embodiment.

[0086] Steps S1301 to S1305, steps S1307 to S1307, and steps S1309 to S1310 in Fig. 14 are similar to steps S1201 to S1205, steps S1206 to S1207, and steps S1209 to S1210 in Fig. 12 of the second embodiment, respectively, and therefore will not be described in this embodiment.

[0087] The difference from the second embodiment in step S1306 is that instead of adding a preheat pulse, the pixel value is changed for preheating. FIG. 15 is a diagram for explaining an example of a heating pulse in this embodiment. In FIG. 15, Y shows a heating pulse of yellow (Y) ((R,G,B)=(255,255,0), and Y' shows a heating pulse of yellow (Y) ((R,G,B)=(255,255,10). Similarly, C shows a heating pulse of cyan (C) ((R,G,B)=(0,255,255), and C' shows a heating pulse of cyan (C) ((R,G,B)=(10,255,255). Y' is a pulse that causes the image forming layer 14 to develop a slight color, and similarly, C' is a pulse that causes the image forming layer 18 to develop a slight color.

[0088] In FIG. 11, 1002 denotes a high frequency region, and since the main color-forming layer is the image-forming layer 18, the cmy data of white (W) ((R,G,B)=(255,255,255) is replaced with a heating pulse C'. By doing so, the preheating temperature of the region 1002 becomes higher at a position corresponding to a white pixel in the original image data than when recording is performed based on the cmy data of white (W) ((R,G,B)=(255,255,255). Similarly, 1004 denotes a high frequency region, and since the main color-forming layer is the image-forming layer 14, the cmy data of white (W) ((R,G,B)=(255,255,255) is replaced with a heating pulse C'. The preheat temperature of the 1004 region is increased by replacing the cmy data of (255, 255, 255) with the heating pulse Y'. Even in cases other than white pixels, the pixel values ​​may be replaced so that the heating temperature is increased to heat the image member 10. Since changing the pixel values ​​to increase the preheat temperature is less effective for low frequency images such as 1003 and 1005, the cmy data of each pixel is not replaced. The pixel signal values ​​to be replaced are just an example, and the pixel values ​​to be replaced can be determined based on a trade-off between the preheat temperature and erroneous color development.

[0089] As described above, the preheat temperature for each area can be controlled by replacing the image value. [Explanation of symbols]

[0090] 10 Image material 14, 16, 18 Image forming layer 30 Print Head 34 Resistance 40 Image forming device

Claims

1. An image forming apparatus for forming an image on an image member having a plurality of color-forming layers that correspond to a plurality of colors and that develop color in response to heating, by heating a desired color-forming layer among the plurality of color-forming layers to develop color, the apparatus comprising: a printhead having heating elements for applying thermal energy to the imaging member; an operating means for operating the plurality of heating elements of the print head with a first pulse for preheating the color-forming layer and a second pulse for coloring the color-forming layer; generating means for generating pulses to be applied to the heating elements based on image data for forming an image on the imaging member; An image forming apparatus characterized in that the generating means generates the first pulse so that the temperature applied to the image member by the first pulse is lower when the spatial frequency of an image recorded based on image data is a low frequency lower than a predetermined frequency than when the spatial frequency of the image data is a high frequency equal to or higher than the predetermined frequency.

2. 2. The image forming apparatus according to claim 1, wherein the generating means generates the first pulse so as to apply the first pulse less times when the spatial frequency of the image recorded based on the image data is low than when the spatial frequency of the image recorded based on the image data is high.

3. an analyzing means for analyzing a spatial frequency of an image to be recorded based on image data of an image formed on the imaging member; 3. The image forming apparatus according to claim 1, wherein the generating means generates the first pulse based on a spatial frequency of an image to be recorded on the basis of image data analyzed by the analyzing means.

4. 4. An image forming apparatus according to claim 3, wherein said analyzing means analyzes a spatial frequency of the image to be recorded on the basis of image data of the image to be recorded on the entire image member.

5. 5. The image forming apparatus according to claim 4, wherein the generating means generates the first pulse so as to apply the same first pulse to all pixels of the image member based on the spatial frequency of the image to be recorded based on the image data analyzed by the analyzing means.

6. 4. The image forming apparatus according to claim 3, wherein said analyzing means divides the image to be recorded on said image member, and analyzes the spatial frequency of the image to be recorded based on image data for each divided area.

7. 7. The image forming apparatus according to claim 6, wherein the generating means generates the first pulse so as to apply the same first pulse to pixels within the divided areas based on the spatial frequency of the image to be recorded based on the image data analyzed by the analyzing means.

8. An image forming apparatus as described in claim 6 or 7, characterized in that, in the generating means, when the spatial frequency of an image recorded based on image data of the divided area is low and the spatial frequency of an image recorded based on image data of a divided area adjacent to the divided area is high, the first pulse is generated so that the temperature applied to the image member by the first pulse is lower in an area adjacent to the divided area having a high spatial frequency among the divided areas having a low spatial frequency than in an area not adjacent to the divided area having a high spatial frequency.

9. A means for identifying a color-developing layer having a largest color-developing area in the divided areas; 9. The image forming apparatus according to claim 6, wherein the generating unit generates the first pulse based on the color-developing layer identified by the identifying unit.

10. the imaging member has a first color-forming layer and a second color-forming layer that develops color at a temperature lower than that of the first color-forming layer; 10. An image forming apparatus as described in claim 9, characterized in that the first pulse is generated so that the temperature applied to the image member by the first pulse is higher when the color-forming layer having the largest color-forming area identified by the identification means is the second color-forming layer than when the first color-forming layer is the first color-forming layer.

11. A recording apparatus for forming an image on an image member, the image member having a plurality of color-forming layers that correspond to a plurality of colors and that develop color in response to heating, by heating a desired color-forming layer among the plurality of color-forming layers to develop color, the apparatus comprising: a print head having heating elements; operating means for operating the plurality of heating elements of the print head with pulses to preheat a color-forming layer; generating means for generating pulses to be applied to the heating elements based on image data for forming an image on the imaging member; The image forming apparatus is characterized in that the generating means generates a pulse so that, when the pixel value at a specified position of the image data is the same, the temperature applied to the specified position is higher when the spatial frequency of the image recorded based on the image data is high than when the spatial frequency of the image recorded based on the image data is low.

12. The image forming apparatus according to claim 11, characterized in that the generating means generates a pulse so that when the spatial frequency of the image recorded based on the image data is high, the temperature applied to the position corresponding to the white pixel of the image member is higher than when the spatial frequency of the image recorded based on the image data is low.

13. 13. The image forming apparatus according to claim 12, wherein the generating means generates pulses so as not to apply pulses to positions corresponding to white pixels of the image member when the spatial frequency of the image recorded based on the image data is a low frequency.

14. the imaging member includes color-forming layers corresponding to yellow, cyan, and magenta, The image forming apparatus according to claim 12 or 13, characterized in that, when the spatial frequency of the image recorded based on the image data is high, the generating means generates pulses so as to apply pulses that cause a slight yellow color or a slight cyan color to positions corresponding to white pixels of the image member.

15. an analyzing means for analyzing a spatial frequency of an image to be recorded based on image data of an image formed on the imaging member; 15. The image forming apparatus according to claim 11, wherein the generating means generates a pulse based on a spatial frequency of an image to be recorded on the basis of the image data analyzed by the analyzing means.

16. 16. The image forming apparatus according to claim 15, wherein said analyzing means analyzes a spatial frequency of the image to be recorded on the imaging member based on image data for each predetermined area of ​​the image to be recorded.

17. 17. An image forming apparatus according to claim 1, wherein the image member includes color-forming layers corresponding to yellow, cyan and magenta, respectively.

18. 18. The image forming apparatus according to claim 17, wherein the color forming layers are layered in the order of a yellow color forming layer, a magenta color forming layer and a cyan color forming layer from the side to which thermal energy is applied by the print head.

19. 19. An image forming apparatus according to claim 1, wherein the generating means outputs a signal pattern for controlling the thermal energy applied to the image member by the print head, and the signal pattern specifies a heating temperature and heating time for the image member by a pulse width and a pulse number.

20. A method for recording an image, comprising the steps of: heating an image member having a plurality of color-forming layers, the plurality of color-forming layers corresponding to a plurality of colors and each of which develops color in response to heating, by a print head having a heating element, to cause a desired color-forming layer among the plurality of color-forming layers to develop color, thereby forming an image on the image member, the method comprising the steps of: a generating step of generating a first pulse for preheating the color-forming layer using the heating element based on image data for forming an image on the image member, and a second pulse for coloring the color-forming layer; operating the plurality of heating elements of the print head using the generated first pulse and the generated second pulse; having An image recording method characterized in that, in the generating step, when the spatial frequency of the image recorded based on image data is low, the first pulse is generated so that the temperature applied to the image member by the first pulse is lower than when the spatial frequency of the image recorded based on image data is high.

21. A method for recording an image, comprising the steps of: heating an image member having a plurality of color-forming layers, the plurality of color-forming layers corresponding to a plurality of colors and each of which develops color in response to heating, by a print head having a heating element, to cause a desired color-forming layer among the plurality of color-forming layers to develop color, thereby forming an image on the image member, the method comprising the steps of: generating pulses for application to the heating elements based on image data for forming an image on the imaging member; operating the plurality of heating elements of the print head with the generated pulses; having An image recording method characterized in that, in the generating step, when the pixel value at a specified position of the image data is the same, a pulse is generated so that the temperature applied to the specified position is higher when the spatial frequency of the image recorded based on the image data is high than when the spatial frequency of the image recorded based on the image data is low.

Images