JP4041942B2 - Thermal printer and thermal history control method thereof - Google Patents

Description

ここで、「・」は論理積を意味し、Ｄ（ｎ）は次に印刷を行う画素データ（バッファＢ1のビットデータ）、Ｄ（ｎ−１）は一列前の画素データ（バッファＢ2のビットデータ）、Ｄ（ｎ−２）は二列前の画素データ（バッファＢ3のビットデータ）、Ｄ（ｎ−３）は三列前の画素データ（バッファＢ4のビットデータ）を示す。従って例えば、Ｄ（ｎ）＝１、Ｄ（ｎ−１）＝１、Ｄ（ｎ−２）＝０、Ｄ（ｎ−３）＝１の場合（１は、印字を指す）、各論理回路の出力はＯI＝０、ＯII＝１、ＯIII＝０、ＯIV＝１の出力が得られる。これらの出力は、単色用セレクタ２５によって、先頭のＯＩから順に出力され、従って、印字ヘッド部１０には、１つのドットに対応するものとして、「０１０１」のビット列が与えられる。これらの各ビットは、上述のように、通電期間を４分割した期間のそれぞれに対応している。単色印字を行う場合、制御回路部２８は、図４に示すように、ストローブ信号として異なるパルス幅を有する４つのパルスＰI、ＰII、ＰIII及びＰIVを連続的に出力する。これらのパルスを合わせれば全通電期間となり、それぞれのパルスはその通電期間を分割したものとも考えられる。このパルス幅の割合はサーマルヘッドの熱容量や記録媒体の特性などに応じて最適値が異なるので、通常は実験によって決定することができる。本例では、ＰI：ＰII：：ＰIII：ＰIV＝１：２：３：４である。単色用セレクタ２５から出力される前記ビット列は、このストローブ信号の個々のパルスに対応しており、従って、ビットデータが「１」である箇所のパルスが対応する駆動回路１２に印加され、対応する発熱体にはそのパルス幅だけ通電される。前記「０１０１」が印字ヘッド部１０へ入力された場合、パルスII及びIVのみが印加され、その時間に応じて対応の発熱素子に与えられる熱エネルギーが決定される。
【００３６】
図５は、２色用論理回路２３の内部構成の一例を示すブロック図である。図のように、２色用論理回路２３は、３つの論理回路I、II及びIIIを備える。各論理回路には、バッファＢ1〜Ｂ4からの全データがそれぞれ入力され、それぞれ下記に示す演算を実行して１ビットを出力する。
【００３７】
【数２】

ここで、「・」は論理積、「＋」は論理和を意味し、Ｄｂ（ｎ）は次に印刷を行う黒色の画素データ（バッファＢ1のビットデータ）、Ｄｂ（ｎ−１）は一列前の黒色の画素データ（バッファＢ2のビットデータ）、Ｄｒ（ｎ）は次に印刷を行う赤色の画素データ（バッファＢ3のビットデータ）、Ｄｒ（ｎ−１）は一列前の赤色の画素データ（バッファＢ4のビットデータ）を示す。従って例えば、Ｄｂ（ｎ）＝１、Ｄｂ（ｎ−１）＝０、Ｄｒ（ｎ）＝０、Ｄｒ（ｎ−１）＝１の場合（１は、印字を指す）、ＯI＝０、ＯII＝１、ＯIII＝１の出力が得られる。これらの出力は、２色用セレクタ２６によって、先頭のＯＩから順に出力され、従って、印字ヘッド部１０には、１つのドット（発熱要素）に対応するものとして、「０１１」のビット列が与えられる。２色印字を行う場合、制御回路部２８は、図６に示すように、異なるパルス幅を有する３つのパルスＰI、ＰII及びＰIIIを連続的に出力する。このパルス幅の割合は、上記と同様、実験によって決定することができる本例では、ＰI：ＰII：ＰIII＝２：３：５である。２色用セレクタ２６から出力される前記ビット列は、このストローブ信号の個々のパルスに対応しており、従って、ビットデータが「１」である箇所のパルスが印加される。前記「０１１」が印字ヘッド部１０へ入力された場合、パルスＰII及びＰIIIのみが印加され、そのパルス幅に応じて対応する発熱素子に与えられる熱エネルギーが決定される。なお、図６には、過去及び現在の印刷画素データの組み合わせに応じて決定されるパルス幅が示されている（Ａ〜Ｆ）。
【００３８】
なお、前記２色印字を行う場合においては、ラインサーマルプリンタの印字速度を、単色印字を行う場合よりも遅くすることができる。これは、単色印字の場合には、印字に際し、３回前までの印字履歴が考慮され印字データが補正されるのに対し、２色印字を行う場合は、直前１回のみの印字履歴が考慮されるだけなので、２色印字における印字品質を向上させ、双方の印字品質をできるだけ近づけるようにするためである。
【００３９】
図７は、２色印字モードにおける制御信号のタイミングチャートを示している。図に示すように、２色印字モードにおいては、ホストから一行分の印字画素データとして、黒印字を行う画素データ及び赤印字を行う画素データが順次送られる。このデータは、不図示の受信回路で受信され、ＣＰＵ２１によって、それぞれ、バッファＢ1及びバッファＢ3にセットされる（ＣＰＵデータセット）。制御回路部２８からの制御開始トリガに基いて、２色用論理回路２３の演算結果が、印刷データとして印字ヘッド部１０のシフトレジスタ１３に与えられる（データイン）。データインの信号として最初に、論理回路Iの出力データ列が与えられ、所定のタイミングをおいて、論理回路II及び論理回路IIIの出力データ列が与えられる。
【００４０】
データインに論理回路Iの出力データ列が与えられると、ラッチ信号Ｌにより、該データ列がラッチレジスタ１４にセットされ、駆動回路１２に与えられる。次いで、ストローブ信号／Ｓt1〜／Ｓt4にパルスＰIが与えられ、前記ラッチレジスタ１４にセットされたデータ列に従って、駆動回路１２が駆動される。
【００４１】
ストローブ信号／Ｓt1〜／Ｓt4へのパルスＰIの入力と並列して、シフトレジスタ１３には論理回路IIの出力データ列が与えられる。そして、次のラッチ信号Ｌにより、該データ列がラッチレジスタ１４の値を書き換える。これに対して、ストローブ信号／Ｓt1〜／Ｓt4にはパルスＰIIが与えられ、前記ラッチレジスタ１４にセットされたデータ列に従って、駆動回路１２が駆動される。同様に、論理回路IIIの出力データ列に従って、次のストローブ信号のパルス時間（パルスＰIII）だけ駆動回路１２が駆動される。以上により、一列分のドットが形成される。
【００４２】
上述したとおり、単色印字モードと２色印字モードとではストローブパルスの数即ち通電期間の分割数及びストローブパルスのパルス幅が異なる。本例では、ＣＰＵ２１が上記の印字モードの設定情報に基づき、制御回路部２８内の通電タイマ２８ｂの設定を変更することにより、ストローブパルスの仕様を変更している。しかし、本発明はこのような例に限定されるものではない。印字モードに応じて複数のストローブパルスを生成しておき、印字モードの設定情報に基づいてこれらを選択供給することによっても、同様の結果を得ることができる。
【００４３】
なお、セレクタ２７は単純なデータセレクタであり、単色用セレクタ２５からの出力と２色用セレクタ２６からの出力とを、上記の印字モード設定情報に基づく選択信号（本例ではＣＰＵ２１が生成して制御回路部２８を介して供給される）に応じて切替出力している。
【００４４】
図８は、２色用論理回路２３の他の実施形態を示すブロック図である。この実施形態においては、４つの論理回路I、II、III及びIVによって、印字ヘッド部へ出力するデータ列を生成する。この場合、ストローブ信号は、パルス幅の異なる４つの信号で構成され、２色用論理回路２３は、１つのドットに対し４ビットのデータを生成し出力する。論理回路I、II、III及びIVには、バッファＢ1〜Ｂ4からの全データがそれぞれ入力され、それぞれ下記に示す演算を実行して１ビットを出力する。
【００４５】
【数３】

図９は、本発明の更に他の実施形態に係る制御部のブロック図を示している。この例は、印字ヘッド部１０に与える印字データの列を２つに分割して並列に与えるものに対応している。すなわち、図示しないが、印字ヘッド部のシフトレジスタは、論理的に２つに区分され、並列して印字データの列を取り込む構成を有しており、各シフトレジスタの区分された領域に与えられるデータが、制御部３０によって生成される。
【００４６】
制御部３０は、基本的に、図２に示した制御部２０のデータ処理部分を並列に備えたものである。すなわち、データ処理部３１及びデータ処理部３２は、それぞれ一行分の印刷画素データ列の半分を取り込み、各論理回路によってこれを補正して、印字ヘッド部１０へ出力する。データ処理部３１及び３２の各構成部分の機能は、先の実施形態のものと同様であるので、ここではその説明を省略する。
【００４７】
以上、本発明の一実施形態を図面に沿って説明したが、本発明は前記実施形態において示された事項に限定されず、特許請求の範囲及び発明の詳細な説明の記載、並びに周知の技術に基づいて、当業者がその変更・応用を行うことができる範囲が含まれる。前記実施形態においては、４つの論理的バッファを用意したが、少なくとも２つのバッファによっても本発明を実現することができる。すなわち、単色印字の場合には、次に印字するデータと直前のデータをバッファに保持するようにし、また２色印字の場合には、一方のバッファを黒印字用に、他方のバッファを赤印字用に設定することができる。
【００４８】
【発明の効果】
以上の如く本発明によれば、履歴を考慮した高品質な単色による印刷と、複数色による印刷の双方を切り替えて実行できるラインサーマルプリンタを実現できる。この場合において、印刷画素データを保持するバッファを単色印刷の場合と複色印刷の場合で効率的に共用できる。
【００４９】
また、プリンタが、単色モードにセットされているか、複色モードにセットされているかに応じて、印刷の速度を切り替えるよう構成された本発明においては、両モードにおける印刷品質を一定にすることが可能となる。
【図面の簡単な説明】
【図１】本発明の一実施形態に係るラインサーマルプリンタの印字ヘッド部のブロック図である。
【図２】本発明の一実施形態に係るラインサーマルプリンタの制御ブロック図である。
【図３】単色用論理回路の内部構成の一例を示すブロック図である。
【図４】単色印字モード時におけるストローブ信号の例である。
【図５】２色用論理回路の内部構成の一例を示すブロック図である。
【図６】２色印字モード時におけるストローブ信号の例である。
【図７】２色印字モードにおける制御信号のタイミングチャートである。
【図８】２色用論理回路の他の実施形態を示すブロック図である。
【図９】本発明の更に他の実施形態に係る制御部のブロック図である。
【図１０】印刷履歴を考慮した従来のラインサーマルプリンタの制御ブロック図である。
【符号の説明】
１０ 印字ヘッド部
１１ 発熱体
１２ 駆動回路
１３ シフトレジスタ
１４ ラッチレジスタ
２０ 制御部
２２ 単色用論理回路
２３ ２色用論理回路
２４、２７ セレクタ
２５ 単色用セレクタ
２６ ２色用セレクタ
２８ 制御回路部
２８ａ 同期クロック出力回路
２８ｂ 通電タイマ
２８ｃ 通電信号出力回路
Ｂ1〜Ｂ4 バッファ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermal printer that develops different colors (including density) on a recording medium in accordance with the level of thermal energy applied to the recording medium.
[0002]
[Prior art]
Thermal printers such as line thermal printers are provided with a large number of heating elements that are independently driven and heated in rows, and selectively drive and heat them so that the corresponding portions of the opposed thermal paper are colored by the heat. By doing so, printing is realized. In this type of printer, the color of the thermal paper varies depending on the amount of thermal energy applied to the heating element, so the printing result such as the print density depends on whether the target heating element was driven immediately before. It will be different.
[0003]
In order to avoid such problems and improve the quality of printing, the past print pixel data is conventionally retained as its history, and in consideration of this, the energization pulse width to be applied next to the heating element is changed. The energization drive time is adjusted.
[0004]
FIG. 10 is a control block diagram of a conventional line thermal printer considering past printing history. One dot line of the print pixel data from the host is temporarily stored in the print buffer 1 and sent to the print head unit 10 via the selector 4. When printing pixel data for the next dot line is stored in the print buffer 1, the data in the print buffer 1 is moved to the history buffer 2 prior to this. The data stored in the history buffer 2 and the data stored in the print buffer 1 are calculated by the logic circuit 3 for each bit, that is, for each heating element, and output to the selector 4. The selector 4 is a kind of sequencer, and sequentially outputs data from the print buffer 1 and data from the logic circuit 3 according to a data selector signal transmitted from the control circuit unit 5. That is, the energization period is divided into a part (period 1) corresponding to the data from the print buffer 1 and a part (period 2) corresponding to the data from the logic circuit 3. In the period 1, the data selector signal described above is divided. Thus, the data from the print buffer 1 and the data from the logic circuit 3 in the period 2 are output to the print head unit 10, respectively.
[0005]
On the other hand, there is a printing technique in which any color is developed by superimposing layers of different colors on a thermal paper and changing the heat energy applied thereto by a heating element (for example, Japanese Patent No. 2836584). . In such a printer, when printing one color, the pulse width of the drive circuit of the heating element is increased so as to apply high level thermal energy, and when printing the other color, The pulse width is shortened so that low level energy is applied. Further, when gradation printing is performed even with a single color, it is necessary to energize with a pulse width corresponding to the density to be developed.
[0006]
[Problems to be solved by the invention]
In such a background, in a printing method that generates a plurality of coloring states such as multi-color printing and gradation printing, the energization history becomes complicated, so the conventional heat history control as described above should be used as it is. Is difficult. In addition, there is a demand for a thermal printer capable of switching and executing both high-quality single-color printing considering the history and printing using the plurality of coloring states. In order to realize such a thermal printer, a technique for flexibly controlling a buffer that holds history data corresponding to print pixels is required, and it can be efficiently shared particularly in the case of monochromatic printing and multicolor printing. The technology to do is necessary.
[0007]
Accordingly, an object of the present invention is to provide a technique for easily realizing thermal history control even in a printing method for generating a plurality of color development states.
[0008]
It is another object of the present invention to provide a thermal printer capable of switching and executing both high-quality single color printing and history printing in consideration of history.
[0009]
Another object of the present invention is to enable efficient sharing of a buffer for holding print pixel data for single color printing and multicolor printing when realizing such a thermal printer.
[0010]
[Means for Solving the Problems]
  In order to achieve such an object, the thermal printer of the present invention is a thermal printer that can generate two different color states according to the level of thermal energy applied to a recording medium.
  A heating element for generating the colored state;
  A heating element driving circuit provided corresponding to the heating element and driving the heating element;
  A receiving circuit for receiving color information for designating one of the two color development states and no color development;
  First to fourth storage units for storing the coloring information received by the receiving circuit;
  A setting circuit for setting the number of recording colors;
  An allocation circuit that determines color information to be stored in the storage unit according to the number of the recording colors set in the setting circuit;
  When the number of recording colors is set to two colors, based on the coloring information received by the receiving circuit,By applying high energyIn the first and second storage units, the presence / absence of designation of the color development state of the first color in the current and past,By applying low energyStoring the presence / absence designation of the color development state of the second color in the third and fourth storage units, respectively,
  When the number of the recording colors is set to one color, based on the color development information received by the reception circuit, whether the first color development state is designated in the present and the past is determined in the first and In addition to storing in the second storage unit, in place of the current and past designations of the color development state of the second color, the third and third designations indicate whether or not the color development state of the first color is designated in the past. 4 storage unit,
  A first energization period dividing circuit that divides the energization period of the heat generating element drive circuit into a first plurality of periods that are shortened in order corresponding to the first color, the second color, and the past designation; and
An energizing period dividing circuit having a second energizing period dividing circuit that divides the energizing period of the heating element driving circuit into a plurality of periods that become shorter in the order corresponding to the current and past designations of the first color;
Whether or not the current color state of the first color is specified;
The presence or absence of designation in the past of the coloring state of the first color;
Whether or not the current color state of the second color is specified;
A first logic circuit for determining the presence / absence of energization in the first plurality of periods based on the presence / absence of designation of the color development state of the second color in the past;
Whether or not the current color state of the first color is specified;
A logic circuit having a second logic circuit for determining the presence / absence of energization in the second predetermined plurality of periods based on the presence / absence of designation of the color development state of the first color in the past,
The drive control circuit includes:
When the number of recording colors is set to two colors, the first energization period dividing circuit and the first logic circuit are selected, and the first and second colors of the current and past are selected. Based on the color designation information, a drive signal for driving the heating element is supplied,
When the number of recording colors is set to one color, the second energization period dividing circuit and the second logic circuit are selected, and the current and past designation information of the first color is selected. Based on the above, a drive signal for driving the heating element is supplied.It is characterized by that.
[0017]
  In this case, the energization period division circuit includes a first energization period division circuit that divides the energization period of the drive circuit into a first predetermined plurality of different width periods, and an energization period of the drive circuit. And a second energization period dividing circuit that divides the first predetermined plurality of different width periods from a second predetermined plurality of different width periods, wherein the logic circuit includes the first color. Whether the color development state of the second color is currently designated, whether the color development state of the first color is designated in the past, whether the color development state of the second color is currently designated, and the past color development state of the second color A first logic circuit for determining whether or not energization is performed in a plurality of different periods of the first predetermined number based on the presence / absence of designation in the first, and the presence / absence of current designation of the coloring state of the first color In the past of the color development state of the first color And a second logic circuit for determining the presence / absence of energization during a period of the second predetermined plurality of different widths based on the presence / absence of designation of the recording color, and the drive control circuit When the number is set to two colors, the first energization period dividing circuit and the first logic circuit are selected, and when the number of recording colors is set to one color It is desirable to select the second energization period dividing circuit and the second logic circuit.
[0018]
  The drive control circuit may be configured to set a cycle from one energization to the next energization according to the number of the recording colors set by the setting circuit.
[0019]
The present invention is also extremely effective as a thermal history control method having a control process corresponding to the above configuration.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a print head unit of a line thermal printer according to an embodiment of the present invention. In the figure, the print head unit 10 of the printer has a heating element 11 composed of a number of heating elements (resistors) for simultaneously printing print pixel data for one line. The heating element 11 is arranged at the front end of a print head extending along the width direction of thermal paper as a recording medium, and pixels for one row are simultaneously formed on the paper by selective heating driving of the heating elements. A plurality of drive circuits 12 are connected to the heating element 11 for heating the heating elements independently. The drive circuit 12 can be composed of a PNP transistor. By selectively driving the drive circuit 12, the corresponding heating element is heated, and the corresponding position on the thermal paper is colored. The reason why the drive circuit 12 is expressed by a NAND circuit is to show the logical operation of the circuit. In other words, when the strobe signal is inactive (High level), the operation of the drive circuit 12 is prohibited. Such a circuit can be easily realized by connecting data and a strobe signal (positive logic) to the base of the PNP transistor in a wired OR circuit configuration.
[0021]
The drive circuit 12 inputs four strobe signals / St1 to / St4 inverted signals (positive logic) generated by a delay circuit (not shown) and data (positive logic) output from the latch register, and sets the levels of both signals. Driven accordingly. That is, when “1” data indicating “print” is given as the print pixel data, if the strobe signal is changed from “High” to “Low”, that is, effectively transitioned, the NAND circuit is configured. The drive circuit 12 outputs “Low”. As a result, a potential difference from the head power supply voltage is generated in the corresponding heat generating element and heated, and the corresponding area of the thermal paper is colored by receiving this heat pulse. The strobe signal is supplied as three or four divided signals having different pulse widths. Details of this will be described later. Note that the four strobe signals / St1 to / St4 can be given by shifting their output timings by the delay circuit, thereby avoiding the problem of power supply voltage drop caused by energizing a large number of drive circuits simultaneously. it can.
[0022]
The print head unit 10 mounted on the printer according to the present embodiment includes a shift register 13 and a latch register 14 for temporarily storing print pixel data for one line. Print pixel data for one row corresponding to the period is input and held in the shift register 13 in synchronization with the clock signal. Note that the print pixel data is data corresponding to each print pixel for one line, but strictly speaking, it is data indicating whether or not energization is performed for the print pixel for one line during the period. It consists of a bit string of “1” meaning “energized” and “0” meaning “not energized”. As will be described later, in the present invention, the shift register 13 is inputted with a predetermined calculation of the current print pixel data and the past print pixel data for each predetermined energization period. The latch register 14 is connected to the shift register 13 in parallel, and each bit data on the shift register is transferred and held in the corresponding storage area simultaneously and in parallel. Accordingly, print pixel data corresponding to the next energization period can be input to the shift register 13 even during the energization period. The data transfer timing from the shift register 13 to the latch register 14 is controlled by the input timing to the latch register 14 of the latch signal L output from the control circuit described later. This timing is after the previous energization period and before the next energization period, and after print pixel data corresponding to the next energization period is set in the shift register 13. As described above, each storage area of the latch register 14 is connected to one input terminal of the drive circuit 12, and when new data is taken into the latch register 14 by the input of the latch signal L, according to the contents thereof. The input data to the drive circuit 12 changes immediately. Each of the drive circuits 12 energizes and drives the corresponding heating element of the heating element 11 according to the data of the latch register 14 during a period when the delay strobe signal applied thereto is “Low” (active).
[0023]
FIG. 2 is a control block diagram of the line thermal printer according to the embodiment of the present invention. The control unit 20 basically corrects the print pixel data given from the host in consideration of the past printing history and gives it to the print head unit 10. The line thermal printer according to the present invention can realize both monochromatic printing with black and two-color printing with two different colors such as black and red or black and blue by switching the setting. Details of the control will be described below with reference to the drawings.
[0024]
In the figure, the control unit 20 has four buffers B1 to B4 which are logically partitioned storage areas. These buffers can be secured by one or a plurality of RAMs (Random Access Memory). A column of print pixel data received from the host by a receiving circuit (not shown) is temporarily stored in any of these buffers B1 to B4 via the CPU. The line thermal printer according to the present invention has two types of printing modes, that is, single color printing with black (hereinafter referred to as single color mode) and two color printing with black and red (hereinafter referred to as two color mode) (hereinafter referred to as 2 color mode). As an example of the color mode, black and red will be described as an example.) The print mode can be set by setting means such as a DIP switch provided in the printer. Further, the print mode may be set according to the control command received from the host device. In the latter case, it is desirable that the print mode setting is stored in a predetermined location in a storage device such as a RAM or a non-volatile memory and referred to during print processing.
[0025]
When the print mode of the line thermal printer is set to the single color mode, the first buffer B1 stores a column of print pixel data to be printed next (for example, print pixel data for one line), and the remaining three In the buffers B2 to B4, three columns of print pixel data (also referred to as history data) printed three times immediately before, that is, in the past, are stored. Accordingly, when the next print pixel data is D (n) (n is a serial number of the print pixel data), the data D (n) is stored in the buffer B1, and the data D (n-1) is stored in the buffer B2. Data D (n-2) is stored in B3, and data D (n-3) is stored in buffer B4. The past print pixel data is set by sequentially shifting from buffer B1 to B2, from B2 to B3, and from B3 to B4. The data to be printed next time is sent from the receiving circuit to the buffer B1 and stored.
[0026]
On the other hand, when the print mode of the line thermal printer is set to the two-color mode, a black print pixel data row and a red print pixel data row are sequentially sent from the host. That is, the presence / absence of designation for each of the black and red coloring states is stored in each buffer. In this case, the buffers B1 and B2 are used for the black print pixel data, and the next print pixel data and the print pixel data immediately before are respectively stored in the buffers B1 and B2. Used for pixel data, each stores the next print pixel data and the print pixel data immediately before it. That is, when the black next print pixel data is Db (n) and the red next print pixel data is Dr (n), the data Db (n) is stored in the buffer B1, and the data Db ( n-1), data Dr (n) is stored in the buffer B3, and data Dr (n-1) is stored in the buffer B4.
[0027]
The storage process of the print pixel data in the buffers B1 to B4 is performed by the CPU 21. That is, the CPU 21 functions as a memory allocation circuit in accordance with a control program stored in a program ROM (not shown), and stores print pixel data in the above buffer and stores past history data according to the set print mode. Controls movement within the buffer.
[0028]
The control unit 20 further includes two logic circuits, that is, a single color logic circuit 22 and a two color logic circuit 23. These logic circuits are selectively used by the selectors 24 and 27 in accordance with the print mode of the printer. That is, when the printer is in the single color print mode, the data in each of the buffers B1 to B4 is input to the single color logic circuit 22 by the selector 24, and the output is output to the print head unit 10 as print pixel data by the selector 27. Is done. On the other hand, when the printer is in the two-color printing mode, similarly, the data in each of the buffers B1 to B4 is input to the two-color logic circuit 23 by the selector 24, and the output is sent to the print head unit 10 by the selector 27. It is output as print pixel data.
[0029]
In the monochrome printing mode, the monochrome logic circuit 22 calculates the print pixel data and history data input to the buffers B1 to B4 in bit units, and outputs the result as data of several bits (4 bits in this example). As will be described later, in this example, the energization period is divided into four periods having different widths, and each bit of the result corresponds to each of the four divided periods. For example, when the value of a certain bit is “1”, energization driving is performed on the heating element corresponding to the period corresponding to that bit, and when the value of the bit is “0”, energization driving is performed. It is not done.
[0030]
The single color selector 25 sequentially outputs these bits serially to the selector 27 in accordance with the timing signal from the control circuit unit 28 that controls the energization timing. The timing signal is synchronized with a synchronization signal, a latch signal, and a strobe signal supplied from the control circuit unit to the print head unit 10 and is generated for each divided period. The specific configuration and operation of the monochrome logic circuit 22 will be described later.
[0031]
Similarly, in the two-color printing mode, the two-color logic circuit 23 calculates black and red print pixel data and black and red history data input to the buffers B1 to B4 in bit units, and outputs the result to several bits. It is output as data (3 bits in this example). Similarly to the above, the energization period is divided into three periods having different widths, and each bit as an output result corresponds to each period.
[0032]
The two-color selector 26 sequentially outputs these bits serially to the selector 27 in accordance with a timing signal from the control circuit unit 28 that controls the energization timing. The specific configuration and operation of the two-color logic circuit 23 will be described later.
[0033]
The control circuit unit 28 includes a synchronous clock output circuit 28a, an energization timer 28b, an energization signal output circuit 28c, and the like, and performs various controls on the printer. That is, the input / output timing of data to the buffers B1 to B4 and the switching of the selectors 24 to 27 are performed by the control signal of the control circuit unit 28, and the synchronization clock, latch signal, and A strobe signal is generated.
[0034]
FIG. 3 is a block diagram illustrating an example of the internal configuration of the monochrome logic circuit 22. As shown in the figure, the monochrome logic circuit 22 includes four logic circuits I, II, III, and IV. Necessary data is input from the buffers B1 to B4 to each logic circuit, and the following operation is executed to output 1 bit.
[0035]
[Expression 1]

Here, “·” means a logical product, D (n) is pixel data to be printed next (bit data of the buffer B1), and D (n−1) is pixel data of the previous column (bits of the buffer B2). Data), D (n-2) indicates the pixel data of the previous two columns (bit data of the buffer B3), and D (n-3) indicates the pixel data of the previous three columns (bit data of the buffer B4). Therefore, for example, when D (n) = 1, D (n-1) = 1, D (n-2) = 0, D (n-3) = 1 (1 indicates printing), each logic circuit Output of OI = 0, OII = 1, OIII = 0, OIV = 1. These outputs are sequentially output from the head OI by the single color selector 25, and accordingly, the print head unit 10 is given a bit string of "0101" as corresponding to one dot. Each of these bits corresponds to each of the periods obtained by dividing the energization period into four as described above. When performing monochromatic printing, the control circuit 28 continuously outputs four pulses PI, PII, PIII and PIV having different pulse widths as strobe signals, as shown in FIG. When these pulses are combined, the entire energization period is obtained, and each pulse is considered to be a division of the energization period. Since the ratio of the pulse width varies depending on the thermal capacity of the thermal head, the characteristics of the recording medium, and the like, it can usually be determined by experiment. In this example, PI: PII :: PIII: PIV = 1: 2: 3: 4. The bit string output from the single color selector 25 corresponds to each pulse of the strobe signal, and accordingly, a pulse at a location where the bit data is “1” is applied to the corresponding drive circuit 12 and corresponds. The heating element is energized by the pulse width. When “0101” is input to the print head unit 10, only the pulses II and IV are applied, and the thermal energy applied to the corresponding heating element is determined according to the time.
[0036]
FIG. 5 is a block diagram showing an example of the internal configuration of the two-color logic circuit 23. As shown, the two-color logic circuit 23 includes three logic circuits I, II, and III. Each logic circuit receives all the data from the buffers B1 to B4, and executes the following operations to output one bit.
[0037]
[Expression 2]

Here, “·” means logical product, “+” means logical sum, Db (n) is black pixel data (bit data of the buffer B1) to be printed next, and Db (n−1) is one line. Previous black pixel data (bit data of buffer B2), Dr (n) is red pixel data to be printed next (bit data of buffer B3), Dr (n-1) is red pixel data of the previous column (Bit data of buffer B4). Therefore, for example, when Db (n) = 1, Db (n-1) = 0, Dr (n) = 0, Dr (n-1) = 1 (1 indicates printing), OI = 0, OII = 1 and OIII = 1 are obtained. These outputs are sequentially output from the leading OI by the two-color selector 26. Therefore, the print head unit 10 is given a bit string of “011” as corresponding to one dot (heat generating element). . When performing two-color printing, the control circuit 28 continuously outputs three pulses PI, PII and PIII having different pulse widths as shown in FIG. The ratio of the pulse width is PI: PII: PIII = 2: 3: 5 in this example, which can be determined by experiment, as described above. The bit string output from the two-color selector 26 corresponds to each pulse of the strobe signal. Therefore, a pulse at a location where the bit data is “1” is applied. When “011” is input to the print head unit 10, only the pulses PII and PIII are applied, and the thermal energy applied to the corresponding heating element is determined according to the pulse width. FIG. 6 shows pulse widths determined according to a combination of past and present print pixel data (A to F).
[0038]
In the case of performing the two-color printing, the printing speed of the line thermal printer can be made slower than that in the case of performing the single-color printing. This is because, in the case of single color printing, the print history up to three times before is considered and the print data is corrected, whereas in the case of two color printing, the print history only once before is considered. This is to improve the printing quality in the two-color printing and make the printing quality as close as possible to each other.
[0039]
FIG. 7 shows a timing chart of control signals in the two-color printing mode. As shown in the figure, in the two-color printing mode, pixel data for black printing and pixel data for red printing are sequentially sent from the host as printing pixel data for one line. This data is received by a receiving circuit (not shown), and is set in the buffer B1 and the buffer B3 by the CPU 21, respectively (CPU data set). Based on the control start trigger from the control circuit unit 28, the calculation result of the two-color logic circuit 23 is given as print data to the shift register 13 of the print head unit 10 (data-in). First, an output data string of the logic circuit I is given as a data-in signal, and output data strings of the logic circuit II and the logic circuit III are given at a predetermined timing.
[0040]
When the output data string of the logic circuit I is given to the data-in, the data string is set in the latch register 14 by the latch signal L and given to the drive circuit 12. Next, a pulse PI is applied to the strobe signals / St1 to / St4, and the drive circuit 12 is driven in accordance with the data string set in the latch register 14.
[0041]
In parallel with the input of the pulse PI to the strobe signals / St1 to / St4, the output data string of the logic circuit II is given to the shift register 13. Then, the data string rewrites the value of the latch register 14 by the next latch signal L. On the other hand, the pulse PII is given to the strobe signals / St1 to / St4, and the drive circuit 12 is driven according to the data string set in the latch register 14. Similarly, the drive circuit 12 is driven for the pulse time (pulse PIII) of the next strobe signal in accordance with the output data string of the logic circuit III. As a result, one row of dots is formed.
[0042]
As described above, the number of strobe pulses, that is, the number of divided energization periods and the pulse width of the strobe pulse differ between the single-color printing mode and the two-color printing mode. In this example, the CPU 21 changes the specification of the strobe pulse by changing the setting of the energization timer 28b in the control circuit unit 28 based on the print mode setting information. However, the present invention is not limited to such an example. A similar result can be obtained by generating a plurality of strobe pulses in accordance with the print mode and selectively supplying them based on the print mode setting information.
[0043]
The selector 27 is a simple data selector. The output from the single-color selector 25 and the output from the two-color selector 26 are selected based on the print mode setting information (in this example, generated by the CPU 21). Is supplied via the control circuit unit 28).
[0044]
FIG. 8 is a block diagram showing another embodiment of the two-color logic circuit 23. In this embodiment, a data string to be output to the print head unit is generated by four logic circuits I, II, III and IV. In this case, the strobe signal is composed of four signals having different pulse widths, and the two-color logic circuit 23 generates and outputs 4-bit data for one dot. All the data from the buffers B1 to B4 are input to the logic circuits I, II, III, and IV, respectively, and the following operations are performed to output one bit.
[0045]
[Equation 3]

FIG. 9 shows a block diagram of a control unit according to still another embodiment of the present invention. This example corresponds to one in which the print data sequence given to the print head unit 10 is divided into two and given in parallel. In other words, although not shown, the shift register of the print head unit is logically divided into two, and has a configuration in which a column of print data is taken in parallel, and is given to a divided area of each shift register. Data is generated by the control unit 30.
[0046]
The control unit 30 basically includes a data processing part of the control unit 20 shown in FIG. 2 in parallel. That is, each of the data processing unit 31 and the data processing unit 32 takes in half of the print pixel data string for one row, corrects it by each logic circuit, and outputs it to the print head unit 10. Since the function of each component of the data processing units 31 and 32 is the same as that of the previous embodiment, the description thereof is omitted here.
[0047]
As mentioned above, although one embodiment of the present invention has been described with reference to the drawings, the present invention is not limited to the matters shown in the above embodiment, and the description of the claims and the detailed description of the invention, as well as the well-known technology. Based on the above, a range in which those skilled in the art can make changes and applications thereof is included. In the above embodiment, four logical buffers are prepared. However, the present invention can be realized by at least two buffers. That is, in the case of single color printing, the data to be printed next and the previous data are held in the buffer, and in the case of two color printing, one buffer is printed for black printing and the other buffer is printed in red. Can be set for.
[0048]
【The invention's effect】
As described above, according to the present invention, it is possible to realize a line thermal printer capable of switching and executing both high-quality single-color printing and history printing in consideration of history. In this case, the buffer for holding the print pixel data can be efficiently shared for single color printing and multicolor printing.
[0049]
Further, in the present invention configured to switch the printing speed depending on whether the printer is set to the single color mode or the multi-color mode, the print quality in both modes can be made constant. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a block diagram of a print head unit of a line thermal printer according to an embodiment of the present invention.
FIG. 2 is a control block diagram of a line thermal printer according to an embodiment of the present invention.
FIG. 3 is a block diagram illustrating an example of an internal configuration of a monochrome logic circuit.
FIG. 4 is an example of a strobe signal in a single color printing mode.
FIG. 5 is a block diagram illustrating an example of an internal configuration of a two-color logic circuit.
FIG. 6 is an example of a strobe signal in the two-color printing mode.
FIG. 7 is a timing chart of control signals in the two-color printing mode.
FIG. 8 is a block diagram showing another embodiment of a two-color logic circuit.
FIG. 9 is a block diagram of a control unit according to still another embodiment of the present invention.
FIG. 10 is a control block diagram of a conventional line thermal printer considering printing history.
[Explanation of symbols]
10 Print head
11 Heating element
12 Drive circuit
13 Shift register
14 Latch register
20 Control unit
22 Logic circuit for single color
23 Two-color logic circuit
24, 27 selector
25 Single color selector
26 2-color selector
28 Control circuit section
28a Synchronous clock output circuit
28b Energizing timer
28c energization signal output circuit
B1-B4 buffer

Claims (2)

In a thermal printer capable of generating two different color states according to the level of thermal energy applied to the recording medium,
A heating element for generating the colored state;
A heating element driving circuit provided corresponding to the heating element and driving the heating element;
A receiving circuit for receiving color information for designating one of the two color development states and no color development;
First to fourth storage units for storing the coloring information received by the receiving circuit;
A setting circuit for setting the number of recording colors;
An allocation circuit that determines color information to be stored in the storage unit according to the number of the recording colors set in the setting circuit;
When the number of recording colors is set to two colors, based on the color development information received by the receiving circuit, the presence / absence of designation of the color development state of the first color by high energy application in the past and the past respectively In the first and second storage units, the current and past designations of the color development state of the second color by applying low energy are stored in the third and fourth storage units, respectively.
When the number of the recording colors is set to one color, based on the color development information received by the reception circuit, whether the first color development state is designated in the present and the past is determined in the first and In addition to storing in the second storage unit, in place of the current and past designations of the color development state of the second color, the third and third designations indicate whether or not the color development state of the first color is designated in the past. 4 storage unit,
A first energization period dividing circuit that divides the energization period of the heat generating element drive circuit into a first plurality of periods that are shortened in order corresponding to the first color, the second color, and the past designation; and
An energizing period dividing circuit having a second energizing period dividing circuit that divides the energizing period of the heating element driving circuit into a plurality of periods that become shorter in the order corresponding to the current and past designations of the first color;
Whether or not the current color state of the first color is specified;
The presence or absence of designation in the past of the coloring state of the first color;
Whether or not the current color state of the second color is specified;
A first logic circuit for determining the presence / absence of energization in the first plurality of periods based on the presence / absence of designation of the color development state of the second color in the past;
Whether or not the current color state of the first color is specified;
A logic circuit having a second logic circuit for determining the presence / absence of energization in the second predetermined plurality of periods based on the presence / absence of designation of the color development state of the first color in the past,
The drive control circuit includes:
When the number of recording colors is set to two colors, the first energization period dividing circuit and the first logic circuit are selected, and the first and second colors of the current and past are selected. Based on the color designation information, a drive signal for driving the heating element is supplied,
When the number of recording colors is set to one color, the second energization period dividing circuit and the second logic circuit are selected, and the current and past designation information of the first color is selected. And supplying a drive signal for driving the heating element . In a thermal history control method of a thermal printer capable of generating two different color states according to the level of thermal energy given to a recording medium by a plurality of heating elements for forming a print pixel,
Receiving color development information specifying one of the two color development states and no color development;
A storage step of storing the color development information received in the reception step;
A step of setting the number of recording colors;
Determining color development information to be stored in the storing step according to the number of the recording colors set in the setting step;
In the storing step,
When the number of recording colors is set to two, the current and past designations of the color development state of the first color by applying high energy are respectively determined based on the color development information received in the reception step. The first and second storage units store the current and past designations of the color development state of the second color by applying low energy in the third and fourth storage units, respectively.
When the number of the recording colors is set to one color, based on the color development information received in the reception step, the first and second designations of the color development state of the first color in the past and the past In addition to storing in the second storage unit, in place of the current and past designations of the color development state of the second color, the third and third designations indicate whether or not the color development state of the first color is designated in the past. 4 storage unit,
A first energization period dividing step of dividing the energization period for color development into a first plurality of periods whose periods become shorter in the order corresponding to the first color, the second color, and the past designation;
A dividing step having a second energizing period dividing step of dividing the energizing period for the color development into a plurality of second periods that become shorter in order corresponding to the current and past designations of the first color;
Whether or not the current color state of the first color is specified;
The presence or absence of designation in the past of the coloring state of the first color;
Whether or not the current color state of the second color is specified;
A first logical operation step for determining the presence / absence of energization in the first plurality of periods based on the presence / absence of designation of the color development state of the second color in the past;
Whether or not the current color state of the first color is specified;
A logic operation step having a second logic operation step for determining the presence or absence of energization in the second plurality of periods based on the presence or absence of designation of the color development state of the first color in the past,
In the colored state generation step,
When the number of recording colors is set to two colors, the first energization period dividing step and the first logical operation step are selected, and the current and past first colors and first colors are selected. Based on the designation information of two colors, a drive signal for driving the heating element is supplied,
When the number of recording colors is set to one color, the second energization period dividing step and the second logic operation step are selected, and the second logic circuit is selected. And supplying a driving signal for driving the heating element based on the current and past designation information of the first color .

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