JP2005178145A - Printing device, printing method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printing device designed for upgrading the image quality of a character image. <P>SOLUTION: The printing device has a drive signal generation part which generates a drive pulse; and a printing head which discharges small ink droplets each time the drive pulse is supplied to a pressure generating element, and can form dots of differing size in positions, on a printing medium, which correspond to pixels for constituting an image, in accordance with the number of the drive pulses to be supplied to the pressure generating element. In this printing device, a first dot is formed of a single undersized ink droplet in the positions, on the printing medium, which correspond to outline pixels laid out upto "N" dot inside the contour of the character image. Further, a second dot which is larger than the first dot is formed of a plurality of undersized ink droplets, in the positions, on the printing medium, which correspond to inside pixels surrounded by a plurality of the outline pixels. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a printing apparatus that performs printing on a printing medium such as paper. The present invention also relates to a printing method and a program.

2. Description of the Related Art A printing apparatus that prints an image by forming dots on a printing medium such as paper, cloth, or film is known. In this printing apparatus, it is required to prevent rattling (edge unevenness) in the contour portion of an image to be printed. As a conventional printing apparatus that can meet this requirement, for example, there is an apparatus that performs contour processing in which the amount of ink that lands on the contour portion of an image is smaller than the amount of ink that lands on the inner portion of the image. In this contour processing, dots are thinned out from the contour portion, or the dot size of the contour portion is made smaller than the dot size of the inner portion (see, for example, Patent Document 1).
JP 2002-292848 A

However, particularly for character images, it has been difficult to prevent rattling by simply reducing the amount of ink that lands on the contour portion. This is presumably because the ink bleeding that lands on the inner part of the image extends beyond the contour part to the edge of the character image.
An object of the present invention is to improve the quality of printed images, particularly character images.

A main invention for achieving the above object includes a drive signal generation unit that generates a drive pulse, and a head that ejects a small ink droplet every time the drive pulse is supplied to a pressure generating element. In a printing apparatus capable of forming dots of different sizes at positions on a print medium corresponding to pixels constituting an image according to the number of supplies to the pressure generating element, up to N dots from the edge to the inside of the character image A first dot formed by a single small ink droplet is formed at a position on the print medium corresponding to the outline pixel, and a plurality of positions are formed on the print medium corresponding to the inner pixel surrounded by the plurality of outline pixels. A second dot larger than the first dot is formed by the small ink droplet.
Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  According to the printing apparatus of the present invention, it is possible to prevent an excessive spread of bleeding with respect to ink landed on an inner portion of a printed image, particularly a character image, and to improve the image quality of the image.

=== Summary of disclosure ===
At least the following matters will become clear from the description of the present specification and the accompanying drawings.

A drive signal generator that generates a drive pulse; and a head that ejects a small ink droplet each time the drive pulse is supplied to the pressure generating element, according to the number of supply of the drive pulse to the pressure generating element. In a printing apparatus capable of forming dots of different sizes at positions on the print medium corresponding to the pixels constituting the image, at positions on the print medium corresponding to contour pixels from the edge to the N dots inside the character image Forming a first dot by a single small ink droplet, and at a position on a print medium corresponding to an inner pixel surrounded by the plurality of contour pixels, than the first dot by a plurality of the small ink droplets Is also characterized in that a large second dot is formed.
According to such a printing apparatus, it is possible to prevent excessive spreading of the ink landing on the inner portion of the character image and to improve the image quality of the character image.

In such a printing apparatus, it is preferable that the drive pulses generated by the drive signal generator have the same shape.
According to such a printing apparatus, the amount of the plurality of ink droplets to be the second dots is uniform. Thereby, bleeding of each ink droplet can be evenly dispersed. As a result, with respect to the ink that lands on the inner portion, excessive spread of bleeding can be effectively prevented, and the image quality of the character image can be improved.

In this printing apparatus, it is desirable that the contour pixel is one dot inside from the edge of the character image or two dots inside.
According to such a printing apparatus, it is possible to prevent excessive spread of bleeding with respect to the ink that lands on the inner portion of the character image. Further, uneven color and missing dots in the inner part can be prevented, and the quality of the character image can be improved.

In this printing apparatus, it is preferable that the plurality of small ink droplets forming the second dots are formed by shifting the positions in the scanning direction of the head.
According to such a printing apparatus, it is possible to effectively prevent excessive spreading of the ink landing on the inner portion of the character image and improve the image quality of the character image.

In this printing apparatus, it is preferable that the first dot is formed at a position on the inner pixel side in a region on the print medium where a contour pixel can be formed. According to such a printing apparatus, since the first dots are formed in the state of being close to the second dots, it is possible to reliably suppress the backlash of the outline portion and improve the image quality of the character image.
A driving signal generator for generating a driving pulse; and a head for ejecting small ink droplets each time the driving pulse is supplied to the pressure generating element. The number of the driving pulses supplied to the pressure generating element Accordingly, in a printing apparatus capable of forming dots of different sizes at positions on the print medium corresponding to the pixels constituting the image, on the print medium corresponding to contour pixels from the edge to the N dots inside the character image. A first dot formed by a single small ink droplet is formed at a position, and the first dot formed by a plurality of small ink droplets at a position on a print medium corresponding to an inner pixel surrounded by the plurality of contour pixels. The driving pulse that forms the second dot larger than the dot and is generated by the driving signal generator has the same shape, the contour pixel is one dot inward from the edge of the character image, The plurality of small ink droplets forming dots are formed by shifting positions in the scanning direction of the head, and the first dot is positioned on the inner pixel side in an area on the print medium where a contour pixel can be formed. It is good also as forming in.
A drive signal generator for generating a drive pulse; and a head for ejecting a small ink droplet each time the drive pulse is supplied to the pressure generating element. In a printing apparatus having a printer capable of forming dots of different sizes at positions on a print medium corresponding to pixels constituting an image in accordance with the number of pixels to be supplied, a contour of N characters inward from an edge in a character image Forming a first dot by a single small ink droplet at a position on the print medium corresponding to a pixel, and a plurality of the positions at a position on the print medium corresponding to an inner pixel surrounded by the plurality of contour pixels; A second dot larger than the first dot may be formed by a small ink droplet.

In the printing method for printing a character image on a print medium, a first dot is formed by a single small ink droplet at a position on the print medium corresponding to a contour pixel from the edge to the N dots inward from the edge of the character image. And forming a second dot larger than the first dot by a plurality of small ink droplets at a position on a print medium corresponding to an inner pixel surrounded by the plurality of contour pixels. It is characterized by that.
According to such a printing method, it is possible to prevent excessive spreading of the ink landing on the inner portion of the character image, and to improve the image quality of the character image.

In a printing apparatus having a drive signal generator for generating a drive pulse and a head for ejecting a small ink droplet each time the drive pulse is supplied to the pressure generating element, the number of the drive pulses supplied to the pressure generating element Accordingly, in a program for realizing a function of printing the image on the print medium by forming dots having different sizes at positions on the print medium corresponding to the pixels constituting the image, the inside of the character image from the edge The printing apparatus realizes a function of forming a first dot by a single small ink droplet at a position on a print medium corresponding to contour pixels up to N dots, and an inner pixel surrounded by a plurality of the contour pixels. And causing the printing apparatus to realize a function of forming a second dot larger than the first dot by a plurality of small ink droplets at a position on the print medium corresponding to And butterflies.
According to the printing apparatus controlled by such a program, it is possible to prevent excessive spreading of the ink landing on the inner portion of the character image and to improve the image quality of the character image.

=== Configuration of Printing System ===
Next, an embodiment of a printing apparatus will be described with reference to the drawings. Note that the description of the following embodiment includes an embodiment relating to a printing method, a computer program, a recording medium on which the computer program is recorded, and the like. The printing device means a system including a printer and a computer in a broad sense, and a printer in a narrow sense.

  FIG. 1 is an explanatory diagram showing an external configuration of the printing system 1000. The printing system 1000 includes an inkjet printer 1 (hereinafter simply referred to as the printer 1), a computer 1100, a display device 1200, an input device 1300, and a recording / reproducing device 1400. The printer 1 prints an image on a print medium such as paper, cloth, or film. For the sake of convenience, paper S (see FIG. 5) is taken as an example in the following description regarding this print medium. A computer 1100 is electrically connected to the printer 1. Then, the computer 1100 outputs print data corresponding to the image to be printed to the printer 1 in order to cause the printer 1 to print an image. The display device 1200 includes a display, and displays a user interface of the application program 1104, the printer driver 1110, and the like (see FIG. 2). The input device 1300 is a device for inputting information to the computer 1100, such as a keyboard 1300A or a mouse 1300B. The input device 1300 is used when, for example, operating the application program 1104 or setting the printer driver 1110 along the user interface displayed on the display device 1200. The recording / reproducing apparatus 1400 records information on an information recording medium (a computer-readable recording medium such as a flexible disk FD or a CD-ROM), or reads information stored on the information recording medium. Device. As this recording / reproducing apparatus 1400, for example, a flexible disk drive apparatus 1400A or a CD-ROM drive apparatus 1400B is used.

  A printer driver 1110 is installed in the computer 1100. The printer driver 1110 realizes a function of displaying a user interface on the display device 1200, and also outputs image data (data relating to an image, text data for a character image and image data for an image image) output from the application program 1104. Is a program for realizing a function of converting print data into print data. This program is composed of codes for realizing various functions. The printer driver 1110 is recorded on an information recording medium. The printer driver 1110 can be downloaded to the computer 1100 via the Internet and stored in an information recording medium.

=== Printer driver ===
<About the printer driver>
FIG. 2 is a schematic explanatory diagram of basic processing performed by the printer driver 1110. The components already described are denoted by the same reference numerals and description thereof is omitted. In the computer 1100, computer programs such as a video driver 1102, an application program 1104, and a printer driver 1110 are operating under an installed operating system. The video driver 1102 has a function of causing the display device 1200 to display a user interface, for example, in accordance with display commands from the application program 1104 and the printer driver 1110. The application program 1104 has a function of performing image editing, for example, and creates image data. The user can give an instruction to print an image edited by the application program 1104 via the user interface of the application program 1104. Upon receiving a print instruction, the application program 1104 outputs image data to the printer driver 1110.

  The printer driver 1110 receives image data from the application program 1104, converts the image data into print data, and outputs the print data to the printer 1. Here, the print data is data in a format that can be interpreted by the printer 1, and is data having various command data and pixel data. The command data is data for instructing the printer 1 to execute a specific operation. The pixel data is data relating to pixels constituting an image printed on the paper S (hereinafter referred to as a print image). For example, the color or size relating to dots formed at positions on the paper corresponding to certain pixels. It is data such as.

  The pixel data of the present embodiment is composed of 2-bit data indicating dot gradation. That is, no dot is formed at a position on the paper corresponding to the pixel of the pixel data [00]. In addition, small dots are formed at positions on the paper corresponding to pixels whose pixel data is [01]. Further, a medium dot is formed at a position on the paper corresponding to a pixel whose pixel data is [10]. A large dot is formed at a position on the paper corresponding to a pixel whose pixel data is [11]. In this way, if it is 2-bit pixel data, four gradations can be expressed for one pixel.

  The printer driver 1110 converts image data into print data by performing resolution conversion processing, color conversion processing, halftone processing, rasterization processing, and the like. Hereinafter, each process performed by the printer driver 1110 will be described.

  The resolution conversion process is a process for converting the image data output from the application program 1104 into a resolution for printing on the paper S. For example, when the resolution for printing an image on the paper S is specified as 720 × 720 dpi, the image data received from the application program 1104 is converted into image data having a resolution of 720 × 720 dpi. Note that the image data after the resolution conversion process is multi-gradation (for example, 256 gradations) RGB data represented by an RGB color space. In the following description, RGB data obtained by performing resolution conversion processing on image data is referred to as RGB image data.

  The color conversion process is a process for converting RGB data into CMYK data represented by a CMYK color space. This CMYK data is data corresponding to the ink color of the printer 1. That is, the data corresponds to each color of cyan (C), magenta (M), yellow (Y), and black (K). This color conversion processing is performed by the printer driver 1110 referring to a table (color conversion lookup table LUT) in which the gradation values of RGB image data and the gradation values of CMYK image data are associated with each other. With this color conversion process, RGB data for each pixel is converted into CMYK data. The data after the color conversion processing is CMYK data with 256 gradations represented by the CMYK color space. In the following description, CMYK data obtained by performing color conversion processing on RGB image data is referred to as CMYK image data.

  The halftone process is a process of converting high gradation number data into gradation number data that can be formed by the printer 1. For example, data indicating 256 gradations is converted into 1-bit data indicating 2 gradations or 2-bit data indicating 4 gradations by halftone processing. In the halftone process, pixel data is created using the dither method, γ correction, error diffusion method, and the like so that the printer 1 can form dots dispersedly. When performing the halftone process, the printer driver 1110 refers to the dither table when performing the dither method. Further, the gamma table is referred to when γ correction is performed, and the error memory 63 for storing the diffused error is referred to when the error diffusion method is performed. The data subjected to the halftone process has a resolution (for example, 720 × 720 dpi) equivalent to the RGB data described above. The data subjected to halftone processing is composed of data of 1 bit (2 gradations) or 2 bits (4 gradations) for each pixel, for example. Hereinafter, of the halftone processed data, 1-bit data is referred to as binary data, and 2-bit data is referred to as multi-value data.

  The rasterizing process is a process of changing matrix image data in the order of data to be transferred to the printer 1. The rasterized data is output to the printer 1 as pixel data included in the print data.

<About printer driver settings>
FIG. 3 is an explanatory diagram of a user interface of the printer driver 1110. As described above, the user interface of the printer driver 1110 is displayed on the display device 1200 via the video driver 1102, and the user can make various settings of the printer driver 1110 using the input device 1300.

  The user can select a print mode from the screen of the user interface. For example, the user can select the high-speed print mode or the fine print mode as the print mode. Then, the printer driver 1110 converts the image data into print data so as to have a format corresponding to the selected print mode. Further, the user can designate the printing resolution (the interval between dots during printing) from this screen. For example, the user can select and specify 720 dpi or 360 dpi as the print resolution from this screen. Then, the printer driver 1110 performs resolution conversion processing according to the designated resolution, and converts the image data into print data. Furthermore, the user can also select a printing paper used for printing from this screen. For example, the user can select plain paper or glossy paper as the printing paper. If the type of printing paper (paper type) is different, the ink bleeding method and the drying method are also different, so that the ink amount suitable for printing is also different. Therefore, the printer driver 1110 converts the image data into print data in consideration of the selected paper type.

  As described above, the printer driver 1110 converts image data into print data in accordance with conditions set via the user interface. The user can make various settings of the printer driver 1110 from this screen, and can also know the remaining amount of ink stored in the ink cartridge 90 (see FIG. 5).

=== Configuration of Printer ===
<About printer configuration>
4 to 8 are explanatory diagrams of the printer 1. That is, FIG. 4 is a block diagram illustrating the configuration of the printer 1. FIG. 5 is a schematic configuration diagram of the mechanism portion. FIG. 6 is a cross-sectional view of the mechanism portion. FIG. 7 is an explanatory diagram showing the arrangement of the nozzles of the head 41. FIG. 8 is a block diagram illustrating a drive circuit for the head 41. Hereinafter, the basic configuration of the printer of this embodiment will be described.

  The printer 1 of this embodiment includes a transport unit 20, a carriage unit 30, a head unit 40, a sensor 50, and a controller 60.

  The transport unit 20 feeds the paper S to a printable position, and transports the fed paper S in a predetermined direction (hereinafter referred to as a transport direction) by a predetermined transport amount during printing. That is, the transport unit 20 functions as a transport mechanism that transports the paper S. The transport unit 20 includes a paper feed roller 21, a transport motor 22 (also referred to as a PF motor), a transport roller 23, a platen 24, and a paper discharge roller 25. In order for the transport unit 20 to function as a transport mechanism, all of these components are not necessarily required. That is, it suffices if it has the necessary components for transporting the paper S.

  The paper feed roller 21 is a roller for transporting the paper S inserted into the paper insertion slot to a paper feed position inside the printer. The paper feed roller 21 has a D-shaped cross-sectional shape, and the length of the circumferential portion is set longer than the transport distance to the transport roller 23 disposed at the paper feed position. For this reason, the paper S at the paper insertion port can be transported to the transport roller 23 by rotating the paper feed roller 21 with the circumferential portion in contact with the paper surface. The carry motor 22 is a motor serving as a drive source when carrying the paper S in the carrying direction, and is constituted by, for example, a DC motor. The transport roller 23 is a roller that transports the paper S fed by the paper feed roller 21 to a printable position, and is rotated by the transport motor 22. The platen 24 is a member that supports the paper S in a printable position from the back side. The paper discharge roller 25 is a roller for transporting the printed paper S in the transport direction. The paper discharge roller 25 rotates in synchronization with the transport roller 23.

  The carriage unit 30 is for moving (scanning) the head 41 in a predetermined direction (hereinafter referred to as a scanning direction). The carriage unit 30 includes a carriage 31 and a carriage motor 32 (also referred to as a CR motor). The carriage 31 can reciprocate in the scanning direction. The head 41 is attached to the carriage 31. For this reason, as the carriage 31 moves, the head 41 also moves along the scanning direction. Further, the carriage 31 detachably holds an ink cartridge 90 that stores ink. The carriage motor 32 is a motor for moving the carriage 31 in the scanning direction, and is constituted by, for example, a DC motor.

  The head unit 40 is for ejecting ink onto the paper S. The head unit 40 has a head 41. The head 41 has a plurality of nozzles that are ink ejection portions, and ejects ink intermittently from each nozzle. That is, each time the drive pulses W1 to W3 (see FIG. 13) are supplied to the piezo element 42 (see FIG. 8), ink droplets are ejected from the nozzles. The piezo element 42 is a pressure generating element (drive element) provided for each pressure chamber communicating with the nozzle, and is deformed each time the drive pulses W1 to W3 are supplied to cause pressure fluctuations in the ink in the pressure chamber. Let That is, when a voltage of a predetermined time width is applied between the electrodes provided at both ends of the piezoelectric element 42, the piezoelectric element 42 is deformed according to the voltage application time, and the elastic film (side wall) that partitions a part of the pressure chamber is deformed. Let The volume of the pressure chamber changes according to the deformation of the piezo element 42, and the pressure in the ink in the pressure chamber changes due to the change in volume of the pressure chamber. Ink droplets are ejected from the corresponding nozzles # 1 to # 180 due to pressure fluctuations generated in the ink. In addition to the piezo element 42, an electromechanical conversion element such as a magnetostrictive element or an electrostatic actuator can be used as the pressure generating element. A heat generating element can also be used as the pressure generating element.

  On the lower surface of the head 41, a plurality of nozzle groups are formed for each discharged color. Specifically, a black ink nozzle group NK, a cyan ink nozzle group NY, a magenta ink nozzle group NM, and a yellow ink nozzle group NY are formed. Each nozzle group includes a plurality of nozzles (180 in this embodiment) that are ejection openings for ejecting ink of each color. The plurality of nozzles of each nozzle group are formed at regular intervals (nozzle pitch: k · D) along the transport direction. Here, D is the minimum dot pitch in the carrying direction (that is, the interval at the highest resolution of dots formed on the paper S). K is an integer of 1 or more. For example, when the nozzle pitch is 180 dpi (1/180 inch) and the dot pitch in the transport direction is 720 dpi, k = 4. In addition, the nozzles belonging to each nozzle group are assigned a lower number in the downstream nozzle (# 1 to # 180). That is, the nozzle # 1 is located downstream of the nozzle # 180 in the transport direction.

  As described above, when the carriage 31 moves in the scanning direction, the head 41 also moves in the scanning direction. For this reason, when ink droplets are ejected while the head 41 is moving in the scanning direction, dot lines (raster lines) along the scanning direction are printed on the paper S.

  The sensor 50 includes a linear encoder 51, a rotary encoder 52, a paper detection sensor 53, a paper width sensor 54, and the like. The linear encoder 51 is for detecting the position of the carriage 31 in the scanning direction. The linear encoder 51 is provided with a belt-like slit plate installed along the scanning direction and a slit formed on the slit plate. It has a photo interrupter to detect. The rotary encoder 52 is for detecting the amount of rotation of the transport roller 23, and is a disc-shaped slit plate that rotates as the transport roller 23 rotates, and a photo interrupter that detects a slit formed in the slit plate. Have

  The paper detection sensor 53 is for detecting the position of the leading edge of the paper S to be printed. The paper detection sensor 53 is provided at a position where the leading edge of the paper S can be detected while the paper supply roller 21 feeds the paper S toward the transport roller 23. The paper detection sensor 53 is a mechanical sensor that detects the leading edge of the paper S by a mechanical mechanism. More specifically, the paper detection sensor 53 has a lever that can rotate in the paper transport direction, and this lever is disposed so as to protrude into the paper S transport path. Therefore, the leading edge of the paper S comes into contact with the lever, and the lever is rotated. Therefore, the paper detection sensor 53 detects the position of the leading edge of the paper S by detecting the movement of the lever with a photo interrupter or the like.

  The paper width sensor 54 is attached to the carriage 31. In the present embodiment, with respect to the position in the paper conveyance direction, the nozzle is attached at substantially the same position as the nozzle # 180 on the most upstream side. The paper width sensor 54 is an optical sensor, and receives the reflected light of the light irradiated on the paper S from the light emitting unit by the light receiving unit, and detects the presence or absence of the paper S based on the received light intensity at the light receiving unit. The paper width sensor 54 detects the position of the end of the paper S while being moved by the carriage 31, and detects the width of the paper S. The paper width sensor 54 can also detect the leading edge of the paper S depending on the situation. Since the paper width sensor 54 is an optical sensor, the position detection accuracy is higher than that of the paper detection sensor 53.

  The controller 60 is a control unit (control means) for controlling the printer 1. The controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a unit control circuit 64. The interface unit 61 transmits and receives data between the computer 1100 that is an external device and the printer 1. The CPU 62 is an arithmetic processing unit for controlling the entire printer 1. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and includes storage elements such as a RAM and an EEPROM. The CPU 62 controls each unit via the unit control circuit 64 in accordance with a program stored in the memory 63.

  The printer 1 that has received print data from the computer 1100 (printer driver 1110), which is an external device, controls each unit (conveyance unit 20, carriage unit 30, and head unit 40) by the controller 60. The controller 60 controls each unit based on the print data received from the computer 1100 and forms an image on the paper S. The situation in the printer 1 is monitored by a sensor 50, and the sensor 50 outputs a detection result to the controller 60. The controller 60 receiving the detection result from the sensor 50 controls each unit based on the detection result.

  A drive circuit for the head 41 is provided in the unit control circuit 64. This drive circuit includes an original drive signal generation unit 644A and a drive signal shaping unit 644B. These original drive signal generation unit 644A and drive signal shaping unit 644B constitute a drive signal generation unit that generates drive pulses W1 to W3. In this embodiment, such a drive circuit is provided for each nozzle group, that is, for each nozzle group of black (NK), cyan (NC), magenta (NM), and yellow (NY). Therefore, the driving of the piezo element 42 is performed individually for each nozzle group. In the figure, the number in parentheses at the end of each signal name indicates the number of the nozzle to which the signal is supplied.

  The original drive signal generator 644A generates an original drive signal ODRV that is used in common by the nozzles # 1 to # 180. The original drive signal ODRV is a signal including a plurality of drive pulses W1 to W3 within a main scanning period for one pixel (within a time during which the nozzle crosses a region corresponding to one pixel). The drive signal shaping unit 644B receives the original drive signal ODRV from the original drive signal generation unit 644A and the print signal PRT (i). The drive signal shaping unit 644B shapes the original drive signal ODRV according to the level of the print signal PRT (i) and outputs it as the drive signal DRV (i) to the piezo elements 42 of the nozzles # 1 to # 180. . The piezo elements 42 of the nozzles # 1 to # 180 are driven based on the drive signal DRV from the drive signal shaping unit 644B. The original drive signal ODRV generated by the original drive signal generation unit 644A, the print signal PRT, and the drive signal DRV shaped by the drive signal shaping unit 644B will be described later.

<About printing operation>
FIG. 9 is a flowchart of processing during printing by the printer 1. Each process described below is executed by the controller 60 controlling each unit 20, 30, 40 according to a program stored in the memory 63. This program has a code for executing each process.

  Print command reception (S001): The controller 60 receives a print command from the computer 1100 via the interface unit 61. This print command is included in the header of print data transmitted from the computer 1100. Then, the controller 60 analyzes the contents of various commands included in the received print data, controls each unit, and performs the following paper feed processing, transport processing, ink ejection processing, and the like.

  Paper feed process (S002): First, the controller 60 performs a paper feed process. The paper feed process is a process of supplying the paper S to be printed into the printer 1 and positioning the paper S at a print start position (also referred to as a cue position). In this process, the controller 60 rotates the paper feed roller 21 and sends the paper S to be printed to the transport roller 23. The controller 60 rotates the transport roller 23 to position the paper S sent from the paper feed roller 21 at the print start position. When the paper S is positioned at the print start position, at least some of the nozzles of the head 41 are opposed to the paper S.

  Dot Formation Processing (S003): Next, the controller 60 performs dot formation processing. The dot forming process is a process of forming dots on paper by intermittently ejecting ink from the head 41 moving along the scanning direction. In this process, the controller 60 drives the carriage motor 32 to move the carriage 31 in the scanning direction. Then, the controller 60 discharges ink from the head 41 based on the print data while the carriage 31 is moving.

  Transport Process (S004): Next, the controller 60 performs a transport process. The transport process is a process of moving the paper S relative to the head 41 along the transport direction. The controller 60 drives the carry motor 22 and rotates the carry roller 23 to carry the paper S in the carrying direction. By this carrying process, the head 41 can form dots at positions different from the positions of the dots formed by the previous dot formation process (S003).

  Paper discharge determination (S005): Next, the controller 60 determines whether or not to discharge the paper S to be printed. At the time of this determination, if there is still data for printing related to the paper S, the paper is not discharged. Then, the controller 60 alternately repeats the dot formation process (S003) and the conveyance process (S004) until there is no more data to be printed, and gradually prints an image composed of dots on the paper S. When there is no more data for printing on the paper S, the controller 60 discharges the paper S. In other words, the controller 60 discharges the printed paper S to the outside by rotating the paper discharge roller 25. Note that whether or not to discharge paper may be determined based on a paper discharge command included in the print data.

  Print end determination (S006): Next, the controller 60 determines whether or not to continue printing. If printing is to be performed on the next paper S, the process returns to the paper feed process (S002) to continue printing, and the paper feed process for the next paper S is started. If printing is not performed on the next paper S, the printing operation is terminated.

=== Printing Method of the Present Embodiment ===
<Conventional printing method>
2. Description of the Related Art An apparatus that performs contour processing is known in order to prevent rattling caused by blurring of a contour portion (edge portion) in an image. In this contour processing, dots in the contour portion are thinned out, or the dot size is made smaller than the dot size in the inner portion. However, when this contour processing is simply applied to a character image, blurring of the contour portion may not be effectively suppressed. This is because the blur from the pixels constituting the inner portion extends beyond the contour portion. Generally, since character images are required to be printed at high speed, they are recorded at a lower resolution than image images (painting images). In this case, the amount of ink in the inner pixels constituting the inner portion is increased, and bleeding is noticeable.

<The main points of the printing method of this embodiment>
In consideration of such circumstances, the printing method according to the present embodiment, when printing a character image, has a single small ink droplet at a position on the paper corresponding to the contour pixels from the edge of the character image to N dots inside. And forming a second dot larger than the first dot by a plurality of small ink droplets at a position on the paper corresponding to the inner pixel surrounded by the plurality of contour pixels. . The N dot is the number of dots defined by the width of the contour portion, and is set to 1 dot or 2 dots, for example.

<About contour pixels and inner pixels>
FIG. 10A and FIG. 10B are diagrams schematically illustrating the outline pixel and the inner pixel of the character image, and show an example in which the outline pixel is one dot (N = 1). In these drawings, a range indicated by each rectangle is an area on paper corresponding to one pixel (hereinafter referred to as a pixel area). That is, a small dot, medium dot, or large dot is formed in this pixel region. For convenience, in the following description, each region will be described using two-dimensional coordinates (X, Y). In this two-dimensional coordinate, the X axis is the scanning direction of the head 41 and the Y axis is the transport direction of the paper S. For example, in FIG. 10A, an area indicated by reference numeral R1 (hereinafter referred to as area R1) has coordinates (4, 2) and an area R4 has coordinates (9, 11).

  FIG. 10A illustrates an example of a filled image. In such a filled image, the outer peripheral portion of the image is a contour pixel, and the pixels surrounded by these contour pixels are inner pixels. That is, as shown by thin shading, each pixel on a straight line from the region R1 (4, 2) to the region R2 (9, 2), from the region R3 (4, 11) to the region R4 (9, 11). Each pixel on the straight line, each pixel on the straight line from the region R1 to the region R3, and each pixel on the straight line from the region R2 to the region R4 are contour pixels. Then, as shown by dark shading, pixels in a rectangular region having the regions R5 (5, 3) and the region R6 (8, 10) as diagonal ends are inner pixels.

  FIG. 10B illustrates an example of a hollow image. In such a hollow image, the inner peripheral portion (boundary with the hollow portion) is also a contour pixel. That is, as shown by thin shading, each pixel on a straight line from the region R7 (2, 2) to the region R8 (11, 2), from the region R9 (2, 11) to the region R10 (11, 11) Each pixel on the straight line, each pixel on the straight line from the region R7 to the region R9, and each pixel on the straight line from the region R8 to the region R10 are outer contour pixels. Similarly, each pixel on the straight line from region R11 (5, 5) to region R12 (8, 5), each pixel on the straight line from region R13 (5, 8) to region R14 (8, 8), region Each pixel on a straight line from R11 to region R12 and each pixel on a straight line from region R13 to region R14 are inner contour pixels. Then, as shown by dark shading, an area between the outer contour pixel group and the inner contour pixel group becomes the inner pixel.

<Setting of pixel data to contour pixel and inner pixel>
11A and 11B are diagrams schematically illustrating the relationship between the outline pixels and the inner pixels of the character image and the dots formed. That is, FIG. 11A explains dots when the filled image in FIG. 10A is printed. FIG. 11B illustrates dots used when printing the hollow image in FIG. 10B. In these drawings, [small] indicates that a small dot is formed in the pixel area, and [large] indicates that a large dot is formed in the pixel area. That is, in the dot formation process (S003) described above, small dots are formed on the contour pixels and large dots are formed on the inner pixels.

  The printer driver 1110 performs designation of small dots for contour pixels and designation of large dots for inner pixels. For example, the printer driver 1110 performs contour processing, and based on the multivalued data created by halftone processing, small dot data is set for the contour pixels in the character image, and large dot data is set for the inner pixels. . Specifically, the printer driver 1110 performs the operation shown in the flowchart of FIG.

  First, the printer driver 1110 receives a print command from the application program 1104 (S101). This print command is issued when the user commands printing on the application. This print command includes, for example, image data of an original image edited on an application. The printer driver 1110 converts the image data included in the print command into print data as follows, and outputs the print data to the printer 1.

  Next, the printer driver 1110 converts the image data into RGB image data having a designated resolution (S102: resolution conversion processing). In this case, the printer driver 1110 converts the resolution of the image data received from the application program 1104 into RGB image data having a resolution equal to the resolution when printing on the paper S. Note that the RGB image data after resolution conversion processing in this embodiment is 256-gradation RGB data.

  Next, the printer driver 1110 converts RGB image data into CMYK image data (S103: color conversion process). The resolution of CMYK image data obtained by color conversion processing is the same as the resolution of RGB image data. For example, when the resolution of the RGB image data is 720 × 720 dpi, the resolution of the CMYK image data is also 720 × 720 dpi. Note that the CMYK image data after color conversion processing in this embodiment is CMYK data of 256 gradations.

  Next, the printer driver 1110 converts the CMYK image data having 256 gradations into binary data having a designated resolution (S104: halftone process). In the present embodiment, the halftoned data is multi-value data in which 2-bit data is assigned to each pixel. Normally, [11] is set as pixel data for the pixels constituting the character image. That is, large dots are formed at positions on the paper corresponding to the pixels constituting the image. This is to prevent missing dots in the character image by filling the solid.

  After the halftone processing, the printer driver 1110 performs contour processing (S105). In this contour processing, outline pixel extraction processing and replacement processing are performed, and small dots are designated for contour pixels and large dots are designated for inner pixels.

  In the outline pixel extraction process, a pixel (hereinafter referred to as an outline pixel) located at a boundary with a background image (image image) in a character image is extracted. The extraction of the outline pixels is performed based on, for example, image density or color difference. That is, since the character image is recorded in the same color, the density and color of the outer pixel are different from those of the adjacent background pixel. Therefore, the density and color of the target pixel are compared with the density and color of surrounding pixels existing around the target pixel, and an outer pixel is extracted depending on whether there is a significant difference between the two.

  In the replacement process, first, outline pixels are set based on the outline pixels extracted in the outline pixel extraction process. The contour pixels of this embodiment are set to pixels of N dots (N = 1, 2) inward from the edge in the character image. For this reason, in the case of 1 dot (N = 1) from the edge, the outline pixel is directly used as the outline pixel. In the case of 2 dots (N = 2) from the edge, the outline pixel and the pixel adjacent to the inside of each outline pixel are set as the outline pixel. If the contour pixel is set, the content of the pixel data is changed to small dot data ([01]) for the set contour pixel. For the inner pixels surrounded by the contour pixels, the already set large dot data ([11]) is used as it is.

  A character image is generated from a character font. For this reason, in the contour processing, the contour pixel and the inner pixel may be determined based on the character font, a small dot may be designated for the contour pixel, and a large dot may be designated for the inner pixel.

  Next, the printer driver 1110 performs rasterization processing (S106), and outputs print data to the printer 1 (S107). The printer 1 forms an image on the paper S based on the received print data.

<About the head drive signal>
As described above, in the printing method of the present embodiment, small dots formed by a single small ink droplet are formed at positions on the paper corresponding to the contour pixels. On the other hand, a large dot is formed by three small ink droplets at a position on the paper corresponding to the inner pixel. For this reason, in this embodiment, the signal shown in FIG. 13 is used. In the figure, the original drive signal ODRV, the print signal PRT (i), and the drive signal DRV (i) are shown.

  The original drive signal ODRV of the present embodiment is the first pulse W1, the second pulse W2, and the third pulse W3 within the main scanning period for one pixel (within the time during which the nozzle crosses the interval of one pixel). Includes one drive pulse. These drive pulses have the same shape and are generated at regular intervals within the main scanning period. When one drive pulse is supplied to the piezo element 42, a small ink droplet corresponding to a small dot is ejected from the nozzle. For example, 4.5 ng ink droplets are ejected.

  The print signal PRT is a signal corresponding to the dot size assigned to one pixel. That is, the print signal PRT is a signal corresponding to the pixel data included in the print data. The print signal PRT of the present embodiment is a signal having 3-bit information for one pixel. That is, when the 2-bit multi-value data subjected to halftone processing is data indicating a large dot of [11], the print signal PRT (i) is [111]. When the multi-value data is data indicating medium dots of [10], the print signal PRT is [011], and when the multi-value data is data indicating small dots of [01], printing is performed. The signal PRT becomes [010]. When the multi-value data is data indicating [00] no dot (non-printing), the print signal PRT (i) is [000]. Note that the unit control circuit 64 performs conversion from the multi-value data to the print signal PRT.

  Then, the drive signal shaping unit 644B shapes the original drive signal ODRV according to the signal level of the print signal PRT and outputs the drive signal DRV. That is, the drive signal DRV (i) in one pixel section is shaped to have three different waveforms according to three different values of the print signal PRT (i).

  The drive signal DRV is a signal obtained by controlling the supply of the original drive signal ODRV according to the level of the print signal PRT. That is, when the print signal PRT is at the [1] level, the drive signal shaping unit 644B passes the drive pulse corresponding to the original drive signal ODRV as it is to obtain the drive signal DRV. On the other hand, when the print signal PRT is [0] level, the drive signal shaping unit 644B blocks the drive pulse of the original drive signal ODRV. Then, the drive signal shaping unit 644B outputs the shaped drive signal DRV to the piezo element 42, and the piezo element 42 is driven according to the drive signal DRV.

  In the printer 1, dots having different sizes can be formed at positions on the paper corresponding to the pixels in accordance with the number of drive pulses supplied to the piezo elements 42. When the print signal PRT (i) corresponds to the 3-bit data [010], only the second pulse W2 is output to the piezo element 42. The output timing of the second pulse is set to the timing at which the ink droplet lands at the substantially center position (center position in the scanning direction) of the pixel area described above. Accordingly, in this case, a small ink droplet is ejected once from the nozzle, and a small dot (first dot) is formed on the paper S.

  When the print signal PRT (i) corresponds to the 3-bit data [011], the first pulse W1 and the second pulse W2 are output continuously. Here, the output timing of the first pulse W1 is set to the timing at which the ink droplet lands at the first half position of the pixel area (position on the near side with respect to the head movement direction), and the output timing of the second pulse W2 is The timing is set so that the ink droplet lands in the approximate center. Therefore, in this case, small ink droplets are continuously ejected from the nozzle twice, and medium dots (second dots) are formed on the paper S.

  When the print signal PRT (i) corresponds to the 3-bit data [111], the first pulse W1, the second pulse W2, and the third pulse W3 are output continuously. Here, the output timing of the third pulse W3 is set to the timing at which the ink droplet lands at the latter half position of the pixel area (the position on the back side with respect to the head movement direction). The output timing of the first pulse W1 and the second pulse W2 is as described above. Accordingly, in this case, small ink droplets are continuously ejected from the nozzle three times, and a large dot (second dot) is formed on the paper S.

<About dot formation processing>
FIG. 14A is a diagram illustrating dots formed by the dot formation process. In the figure, a rectangular area is a pixel area. The left column in the pixel area is a pixel area corresponding to the contour pixel. Further, the center column and the right column in the pixel region are pixel regions corresponding to the inner pixels.

  In this embodiment, small dots are formed by a single small ink droplet at a position on the paper corresponding to the contour pixel, and large dots are formed by three small ink droplets at a position on the paper corresponding to the inner pixel. As described above, a single ink droplet that becomes a small dot lands on the approximate center of the pixel region corresponding to the contour pixel. Then, the three ink droplets that become large dots land at different positions on the near side, substantially the center, and the far side of the pixel area corresponding to the inner pixel. By performing such a dot formation process, the amount of ink for the contour pixel is smaller than that for the inner pixel, and therefore, compared to the case where the contour process is not performed, it is possible to suppress the backlash of the edge portion in the character image, Can print smoothly. This is because the contour pixel is printed with a single small ink droplet, so that the amount of ink in the contour portion is reduced, and the overflow of ink in this contour portion is suppressed.

  In addition, by printing the inner pixels with large dots of three small ink droplets, it is possible to prevent the ink bleeding that reaches the inner part of the character image from spreading to the edge of the character image. This is because the amount of ink required for a large dot is ejected in three ink droplets. That is, since the amount of each ink droplet is reduced, the ink bleeding when each ink droplet is landed is reduced. Since each ink droplet lands with a time difference, at the time of landing of the subsequent ink droplet, at least a part of the previously landed ink droplet is absorbed inside the paper. Thereby, compared with the case where the ink amount required for a large dot is ejected at once, the ink bleeding can be suppressed.

  Further, in this printing method, each ink droplet is landed with its position shifted in the scanning direction, so that also in this respect, absorption of the previously landed ink droplet into the paper is promoted and ink bleeding can be suppressed. Further, in the present embodiment, the drive pulses (first pulse W1 to third pulse W3) for ejecting each ink droplet have the same shape. For this reason, the amount of each ink droplet that becomes a large dot is equal. Thereby, bleeding of each ink droplet can be evenly dispersed. As a result, it is possible to effectively prevent the ink bleeding of the inner pixels from spreading to the edge of the character image, thereby improving the image quality of the character image.

  FIG. 14B is a diagram illustrating another example of dots formed by the dot formation process. This example is characterized in that small ink droplets serving as contour pixels are formed at positions on the inner pixel side in the pixel region. As shown in the figure, in this example, three positions where ink droplets can land are arranged in the scanning direction in the pixel region corresponding to the contour pixel. Then, a small ink droplet to be a contour pixel is landed on the innermost pixel side position in this pixel region. Such control can be realized by setting the print data of the contour pixel to [001] or [100]. The selection of [001] and [100] of the print data is performed according to the scanning direction of the head 41 and the positional relationship between the contour pixel and the inner pixel. According to this control, since the small ink droplets serving as the contour pixels are formed in the state of being close to the inner pixels, it is possible to reliably suppress the blurring of the contour portion and improve the image quality of the character image.

<When the outline pixel is 2 dots from the edge of the character image>
FIG. 15A is a diagram schematically illustrating the contour pixel and the inner pixel when the contour pixel is 2 dots, and FIG. 15B is a diagram schematically illustrating the relationship between the contour pixel and the inner pixel and the formed dots. It is. FIG. 16A is a diagram illustrating dots formed by the dot formation process. As shown in these figures, when the contour pixel is 2 dots from the edge of the character image, the same control is performed as when the contour pixel is 1 dot from the edge of the character image. That is, small dot pixel data [010] is set for the contour pixel, and large dot pixel data [111] is set for the inner pixel. Then, a small dot by a single small ink droplet is formed at a position on the paper corresponding to the contour pixel, and a large dot by three small ink droplets is formed at a position on the paper corresponding to the inner pixel.

  In this example, the same effect as in the case of 1 dot can be obtained. That is, since the ink amount of the contour pixel is smaller than the ink amount of the inner pixel, the edge portion of the character image can be printed more smoothly than when the contour processing is not performed. In addition, by printing the inner pixels with large dots of three small ink droplets, it is possible to prevent the spread of ink landing on the inner portion of the character image from spreading beyond the edge of the character image. Furthermore, since each ink droplet has the same ink amount and is landed with its position shifted in the scanning direction, it is possible to suppress ink bleeding from these points. As a result, it is possible to effectively prevent the ink bleeding of the inner pixels from spreading to the edge of the character image, thereby improving the image quality of the character image.

  FIG. 16B is a diagram illustrating another example of dots formed by the dot formation process. This example is characterized in that since the outline pixel is for two dots, a small ink droplet to be the outline pixel is formed at a position on the inner pixel side in the pixel region. As shown in the figure, in this example, a small ink droplet that is an outer pixel is landed on the innermost pixel side position in this pixel region. This control can also be realized by setting the print data of the contour pixel to [001] or [100] as described above. In addition, for the second outline pixel sandwiched between the outer pixel and the inner pixel, a small ink droplet is landed at a substantially central position of this pixel region. In other words, in this example, a small ink droplet that becomes the outer pixel is formed at a position on the inner pixel side in the pixel region, and a small ink droplet that becomes the second pixel contour pixel is approximately halfway between the outer pixel and the inner pixel. Formed in position.

  With this configuration, the amount of ink at the edge of the character image is smaller than the amount of ink at the inner pixel, so that bleeding can be suppressed and the edge can be printed smoothly. In addition, since the second-dot outline pixel is formed at a substantially intermediate position between the outer pixel and the inner pixel, the edge can be printed more smoothly. As a result, the image quality of the character image can be improved.

=== Other Embodiments ===
The above-described embodiment is mainly described for the printer 1, and includes a printing apparatus, a printing method, a printing system, a computer program, a storage medium storing the program, a display screen, a screen display method, and a printed material. Disclosures of methods, etc. are also included.

  Further, the printer 1 and the like as one embodiment have been described, but the above-described embodiment is for facilitating understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<Original drive signal>
In the above-described embodiment, the configuration in which the three driving pulses are generated during the period in which the head 41 passes through one pixel region has been described. However, the number of driving pulses is not limited thereto. For example, five drive pulses may be generated during a period of passing through one pixel region.

<About the printer driver>
According to the above-described embodiment, the printer driver on the computer side performs the contour processing. However, the contour processing is not limited to the printer driver. For example, if a program for realizing the functions necessary for performing the contour processing of this embodiment is stored in the memory 63 of the printer 1, the contour processing may be performed by the controller 60 on the printer 1 side. . Even if it does in this way, there can exist an effect similar to the above-mentioned embodiment.

<About the printer>
In the above-described embodiment, the printer 1 has been described as an example, but the present invention is not limited to this. For example, the same technique as that of the present embodiment may be applied to various printing apparatuses using an inkjet technique such as a plotter, a facsimile apparatus, and a dyeing apparatus. These methods and manufacturing methods are also within the scope of application.

It is explanatory drawing which showed the external appearance structure of the printing system. FIG. 3 is a schematic explanatory diagram of basic processing performed by a printer driver. 3 is an explanatory diagram of a user interface of a printer driver. FIG. FIG. 2 is a block diagram illustrating a configuration of a printer. It is a schematic block diagram of the mechanism part of a printer. It is a cross-sectional view of the mechanical part of the printer. It is explanatory drawing which shows the arrangement | sequence of the nozzle of a head. 3 is a block diagram illustrating a head drive circuit. FIG. It is a flowchart of the process at the time of printing of a printer. FIG. 10A is a diagram schematically illustrating outline pixels and inner pixels of a character image, and is an example of a filled image. FIG. 10B is a diagram schematically illustrating the outline pixel and the inner pixel of the character image, and is an example of a hollow image. FIG. 11A is a diagram for explaining the relationship between the outline pixels and inner pixels of the character image and the dots formed when the filled image in FIG. 10A is printed. FIG. 11B is a diagram for explaining the relationship between the outline pixels and the inner pixels of the character image and the dots formed when the outlined image in FIG. 10B is printed. FIG. 5 is a schematic flowchart of an operation in a printer driver. It is a timing chart explaining an original drive signal, a print signal, and a drive signal. FIG. 14A is a diagram illustrating dots formed by the dot formation process. FIG. 14B is a diagram illustrating another example of dots formed by the dot formation process. FIG. 15A is a diagram for describing a contour pixel and an inner pixel when the contour pixel is 2 dots. FIG. 15B is a diagram for explaining the relationship between outline pixels and inner pixels and dots formed. FIG. 16A is a diagram illustrating dots formed by the dot formation process. FIG. 16B is a diagram illustrating another example of dots formed by the dot formation process.

Explanation of symbols

1 inkjet printer, 20 transport unit, 21 paper feed roller,
22 transport motor, 23 transport roller, 24 platen, 30 carriage unit,
31 carriage, 40 head unit, 41 head, 42 piezo element,
50 sensors, 51 linear encoder, 52 rotary encoder,
53 Paper detection sensor, 54 Paper width sensor, 60 Controller,
61 interface unit, 62 CPU, 63 memory, 64 unit control circuit,
90 ink cartridge, 1000 printing system, 1100 computer,
1102 video driver, 1104 application program,
1110 printer driver, 1200 display device, 1300 input device,
1300A keyboard, 1300B mouse, 1400 recording and playback device,
1400A flexible disk drive device,
1400B CD-ROM drive device

Claims (10)

A drive signal generator for generating a drive pulse, and a head for ejecting small ink droplets each time the drive pulse is supplied to a pressure generating element;
In a printing apparatus capable of forming dots of different sizes at positions on a print medium corresponding to pixels constituting an image according to the number of supply of the drive pulse to the pressure generating element,
Forming a first dot by a single small ink droplet at a position on the print medium corresponding to a contour pixel of N dots inward from the edge in the character image;
A second dot larger than the first dot is formed by a plurality of small ink droplets at a position on a print medium corresponding to an inner pixel surrounded by the plurality of contour pixels. The printing apparatus according to claim 1,
The drive pulses generated by the drive signal generator have the same shape. The printing apparatus according to claim 1 or 2, wherein
The contour pixel is one dot inside from the edge of the character image. The printing apparatus according to claim 1 or 2, wherein
The contour pixels are two dots inside from the edge of the character image. The printing apparatus according to claim 1, wherein:
The plurality of small ink droplets forming the second dots are formed by shifting the positions in the scanning direction of the head. The printing apparatus according to claim 5,
The first dot is formed at a position on the inner pixel side in a region on a print medium where a contour pixel can be formed. A drive signal generator for generating a drive pulse, and a head for ejecting small ink droplets each time the drive pulse is supplied to a pressure generating element;
In a printing apparatus capable of forming dots of different sizes at positions on a print medium corresponding to pixels constituting an image according to the number of supply of the drive pulse to the pressure generating element,
Forming a first dot by a single small ink droplet at a position on the print medium corresponding to a contour pixel of N dots inward from the edge in the character image;
Forming a second dot larger than the first dot by a plurality of small ink droplets at a position on a print medium corresponding to an inner pixel surrounded by the plurality of contour pixels;
The drive pulses generated by the drive signal generator have the same shape,
The contour pixel is one dot inward from the edge in the character image,
Forming a plurality of the small ink droplets forming the second dots by shifting the positions in the scanning direction of the head;
The first dot is formed at a position on the inner pixel side in a region on a print medium where a contour pixel can be formed. Computer,
as well as,
A drive signal generator for generating a drive pulse, and a head for ejecting small ink droplets each time the drive pulse is supplied to a pressure generating element;
A printer capable of forming dots having different sizes at positions on a print medium corresponding to pixels constituting an image, in accordance with the number of the drive pulses supplied to the pressure generating element;
In a printing apparatus having
Forming a first dot by a single small ink droplet at a position on the print medium corresponding to a contour pixel of N dots inward from the edge in the character image;
A second dot larger than the first dot is formed by a plurality of small ink droplets at a position on a print medium corresponding to an inner pixel surrounded by the plurality of contour pixels. In a printing method for printing a character image on a printing medium,
Forming a first dot by a single small ink droplet at a position on a print medium corresponding to a contour pixel from an edge to N dots inward from an edge in the character image;
Forming a second dot larger than the first dot by a plurality of small ink droplets at a position on a print medium corresponding to an inner pixel surrounded by the plurality of contour pixels. And In a printing apparatus having a drive signal generating section for generating a drive pulse and a head for discharging a small ink droplet every time the drive pulse is supplied to a pressure generating element,
The image is printed on the print medium by forming dots having different sizes at positions on the print medium corresponding to the pixels constituting the image according to the number of the drive pulses supplied to the pressure generating element. In the program that realizes the function,
A function of forming a first dot by a single small ink droplet at a position on a print medium corresponding to a contour pixel from an edge to an N dot inward from an edge in a character image;
Causing the printing apparatus to realize a function of forming a second dot larger than the first dot by a plurality of small ink droplets at a position on a print medium corresponding to an inner pixel surrounded by the plurality of contour pixels. It is characterized by.

Images