JPH06262794A - Thermal printer - Google Patents

Abstract

PURPOSE:To measure an optimum environmental humidity and to eliminate disturbance of movement of a sheet retaining plate by mounting a humidity sensor above the plate for pressing a thermal recording material in a sheet feed cassette from above in a cassette charging chamber. CONSTITUTION:A cassette charging chamber 2 is partitioned to a placing plate 23 and a partition plate 24 of a box shape. In order to eliminate collapse of a color thermal recording sheet 4 in a sheet feed cassette 3 when a thermal printer is stood laterally, a substantially V-shaped sheet retaining plate 26 is rotatably mounted on the plate 24. The plate 26 is energized clockwise by a spring 27. Further, a humidity sensor 28 for measuring a humidity of the chamber 2 is provided above the plate 26. Thus, an environmental humidity of a place where a thermal recording material is most affected by its influence can be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer, and more particularly to a thermal printer which corrects a change in color density due to environmental humidity and thermally records an image on a thermal recording material.

[0002]

2. Description of the Related Art In a color thermal printer, a magenta thermosensitive heating layer, a cyan thermosensitive coloring layer, and a yellow thermosensitive coloring layer are sequentially formed on a support as described in JP-A-61-213169. A color thermosensitive recording material is used. In this color thermosensitive recording material, in order to selectively develop color in each thermosensitive coloring layer, the coloring heat energy is different, and the deeper thermosensitive coloring layer requires higher coloring heat energy. Also, when recording the next thermosensitive coloring layer, the electromagnetic wave, such as ultraviolet rays, which is peculiar to the thermorecorded coloring layer, is irradiated so that the thermorecording coloring layer on the thermosensitive recording layer is not recorded again. Optical fixing is performed.

[0003]

As shown in FIG. 5, the color-developing characteristics of the color thermosensitive recording material are such that the color-developing density varies depending on the environmental humidity even if the color-developing heat energy is the same. In order to remove the influence of this humidity, the printer described in JP-A-1-172982 is provided with a dehumidifier so that dehumidification is always performed during the operation of the printer. However, this printer has a problem that the size of the device is increased and the cost is increased.

In order to eliminate the influence of environmental humidity without increasing the size and cost of this apparatus, it is possible to solve it by correcting the heat generation amount of the thermal head according to the environmental humidity. This correction method requires a humidity sensor to measure the environmental humidity, but when determining the mounting position, it must be the place that most easily affects the color thermosensitive recording material and that it will not interfere with other members. Etc. are required to be considered.

An object of the present invention is to provide a thermal printer having a humidity sensor arranged at an optimum position.

[0006]

In order to achieve the above object, the present invention provides a humidity sensor mounting position in a cassette loading chamber for pressing a thermal recording material in a paper feeding cassette from above. It is located above a movable paper holding plate. Since the humidity sensor is arranged in the cassette loading chamber in which the thermosensitive recording material is stored, the humidity sensor can measure the optimum environmental humidity and does not disturb the movement of the paper pressing plate. In another invention, both absolute and relative humidity are measured, and a temperature sensor is arranged with the humidity sensor to measure the environmental humidity more accurately.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 2 showing an outline of a thermal printer, a paper feed cassette 3 is loaded in a cassette loading chamber 2 so as to be freely inserted and removed. A large number of color thermosensitive recording papers 4 are stored in the paper feed cassette 3, and the one at the top is
It is sent out by the paper feed roller 5.

The paper feed passage 6 is arranged between the cassette loading chamber 2 and the platen drum 7. A pair of conveyance rollers 8 are provided in the middle of the paper feed path 6, and the conveyance rollers 8 feed the color thermosensitive recording paper 4 toward the platen drum 7. The platen drum 7 is provided with a clamp member 10 that presses and fixes the front end of the color thermosensitive recording paper 4 to the outer peripheral surface, and a solenoid 11 that moves the clamp member 10. The platen drum 7 is driven by the stepping motor 12 in the arrow direction during thermal recording and optical fixing.

Around the platen drum 7, a thermal head 14 whose drive is controlled by a drive control unit 13, an ultraviolet lamp 15 for yellow fixing and an ultraviolet lamp 16 for magenta fixing are provided. The yellow fixing ultraviolet lamp 15 emits near ultraviolet rays having an emission peak of 420 nm to fix the yellow thermosensitive coloring layer. The magenta fixing ultraviolet lamp 16 emits near ultraviolet rays having an emission peak of 365 nm to fix the magenta thermosensitive coloring layer.

The color thermosensitive recording paper 4 on which the three color images of yellow, magenta and cyan are thermally recorded in a frame sequential manner passes through the paper discharge passage 18, is nipped by a pair of sending rollers 19 and is discharged to the tray 20. It Reference numeral 21 is a main body casing.

In FIG. 1 showing the structure of the cassette loading chamber, a loading port 22 is formed in front of the cassette loading chamber 2, and the sheet feeding cassette 3 is inserted from the loading port 22.
The cassette loading chamber 2 is partitioned by a mounting plate 23 and a box-shaped partition plate 24. In addition, this partition plate 24
It does not have to be.

In order to prevent the color thermosensitive recording paper 4 in the paper feed cassette 3 from collapsing when the thermal printer is placed upright on the partition plate 24, a paper pressing plate 26 having a substantially V shape is rotated. The paper pressing plate 26 is freely attached, and is biased clockwise by a spring 27. In addition,
When the paper feed cassette 3 is put in or taken out, the tip end of the paper feed cassette 3 is brought into sliding contact with the taper surface and the paper pressing plate 26 rotates, so that there is no obstacle.

A humidity sensor 28 for measuring the humidity of the cassette loading chamber 2 is provided above the paper pressing plate 26. This humidity sensor 28 is fixed to the lower end of a support plate 29 screwed to the partition plate 24 so that it does not interfere with the rotation of the paper pressing plate 26 and is as close as possible to the color thermosensitive recording paper 4. I have to. Also,
An opening 26a is formed in the paper pressing plate 26 in order to measure the humidity in a place near the color thermosensitive recording paper 4.

FIG. 3 shows a paper feed cassette. The paper feed cassette 3 is composed of a rectangular cassette body 30 and a lid portion 31 for preventing outside light and moisture from entering the cassette loading chamber 2. Inside the cassette body 30, there are provided a metal basket 32 and a bottom plate 33 attached so as to be able to rise and fall freely. The color thermosensitive recording papers 4 are stacked on the bottom plate 33, and are indicated by a double-dotted line It is placed and stored in the basket 32 as shown in FIG.

Further, the cassette body 30 and the basket 3
Openings 35 and 36 are formed on the bottom surface of 2, respectively, and the up lever 37 shown in FIGS. 1 and 2 is inserted into these openings 35 and 36 during printing. When the up lever 37 is inserted, the bottom plate 33 is pushed up, and the uppermost color thermosensitive recording paper 4 comes into contact with the paper feed roller 5. When the paper feed roller 5 is rotated in this state, the color thermosensitive recording paper 4 is sent out of the paper feed cassette 3 from the front end side of the cassette body 30. Separation claws 38 are formed at both corners on the front end side of the basket 32, as shown in FIG. 3, and the separation claws 38 feed multiple sheets (multi-feed) when the color thermosensitive recording paper 4 is fed. To prevent.

A locking claw 40 is integrally formed at the tip of the cassette body 30. The locking claw 40 is latched by the latch mechanism 41 when the sheet feeding cassette 3 is inserted to the loading position as shown in FIG. It should be noted that the latch mechanism 41 is configured such that when the paper feed cassette 3 in the locked state at the loading position is further pushed inward, the locking claw 40 is provided.
Is released and the locking claw 40 is pushed back so that the paper feed cassette 3 can be easily pulled out, and a part of the lid portion 31 is projected to the outside of the main body casing 21.

In FIG. 4, the drive control unit 13 includes a data correction circuit 45 for correcting image data of a recorded image according to the humidity in the cassette loading chamber 2 and each heating element of the thermal head 14 according to the image data. It is composed of a head drive unit 46 that creates a drive pulse for driving the drive unit and a controller 47 that controls the drive of these units. A humidity sensor 28 is connected to the controller 47, and humidity data from the humidity sensor 28 is sent to the data correction circuit 45 via the controller 47.

In the drive controller 13, the controller 4
When humidity data is sent from the humidity sensor 28 to the controller 7, the controller 47 sends it to the data correction circuit 45. The data correction circuit 45 compares the humidity data with preset humidity data (hereinafter, referred to as set humidity data), and when the humidity data is high, the heat generation amount of the thermal head 14 is reduced according to the difference and is low. At times, the image data of each pixel is corrected so that the amount of heat generated by the thermal head 14 increases in accordance with the difference, and this is output to the head drive unit 46. The head drive unit 46 changes the width and voltage of the drive pulse of each pixel based on the corrected image data, and outputs this to the thermal head 14. As a result, each heating element of the thermal head 14
The color thermosensitive recording paper 4 is heated so as to have a desired color density.

The operation of the thermal printer of the present invention thus constructed will be described. When the power of the thermal printer is turned on, the humidity sensor 28 measures the humidity of the cassette loading chamber 2 from the change of its resistance value. The humidity data is sent to the data correction circuit 45 via the controller 47,
The set humidity data is compared. Thereafter, when a print start signal is sent to the control section of the thermal printer, the up lever 37 is rotated and the uppermost color thermal recording paper 7 comes into contact with the paper feed roller 5.

When the paper feed roller 5 is rotated, the color thermosensitive recording paper 4 is fed toward the platen drum 7. When the tip of the color thermosensitive recording paper 4 is fixed by the clamp member 10, the platen drum 7 is rotated and the color thermosensitive recording paper 4 is conveyed toward the thermal head 14. During this period, one line of yellow image data is sent to the data correction circuit 45, and the image data is corrected according to the humidity in the cassette loading chamber 2.

When the color thermosensitive recording paper 4 reaches the printing start position by the rotation of the platen drum 7, the head driving section 46 converts the corrected yellow image data into drive pulses and sends them to the thermal head 14. The thermal head 14 energizes each heating element by a drive pulse to thermally record a one-line yellow image on the color thermosensitive recording paper 4. Thereafter, in the same manner, thermal recording is sequentially performed on the second and subsequent lines. When the portion on which the yellow image is thermally recorded reaches the yellow fixing ultraviolet lamp 15, near-ultraviolet rays of about 420 nm are irradiated on the color thermosensitive recording paper 4 and the yellow thermosensitive coloring layer is fixed.

After that, when the platen drum 7 is further rotated and the conveyance of the color thermosensitive recording paper 4 enters the second lap, the data correction circuit 45 outputs magenta image data to the head drive section 46 line by line. Here, it is converted into a drive pulse. By this drive pulse, a magenta image is thermally recorded line by line on the color thermosensitive recording paper 4. In the thermal recording of the magenta image, the yellow fixing ultraviolet lamp 15 is turned off, and instead, the magenta fixing ultraviolet lamp 16 is turned on, and about 365 n emitted from this is emitted.
The magenta thermosensitive coloring layer is fixed by the ultraviolet ray of m.

When the color thermosensitive recording paper 4 is conveyed in the third round, the cyan image is thermally recorded line by line based on the humidity-corrected cyan image data. The cyan thermosensitive coloring layer is not fixed.

After that, when the conveyance of the color thermosensitive recording paper 4 enters the fourth round and the clamp member 10 faces the paper discharge passage 18, the platen drum 7 stops its rotation. After the stop, the solenoid 11 is driven and the fixing of the color thermosensitive recording paper 4 by the clamp member 10 is released. When the platen drum 7 rotates in this state, the thermal head 14
The color thermosensitive recording paper 4 sandwiched by is sent out to the paper discharge passage 18 from between the platen drum 7 and the clamp member 10. The color thermosensitive recording paper 4 is fed by the pair of feeding rollers 19 and fed to the tray 20. When the rear end of the color thermosensitive recording paper 4 enters the paper discharge passage 18, the platen drum 7 is rotated to the position shown in the drawing to prepare for the next print.

In the above embodiment, the thermal printer for color has been described, but the present invention can be applied to a monocolor thermal printer to obtain the same effect. Further, it can be applied to a serial printer as well as a line printer. Also, with the humidity sensor 28, FIG.
By arranging the temperature sensor 50 as shown in FIG. 3, both the absolute humidity and the relative humidity may be measured and used to correct the heat generation amount of the thermal head 14.

[0026]

As described in detail above, according to the present invention, since the humidity sensor is installed in the cassette loading chamber, it is possible to measure the environmental humidity at the place where the thermal recording material is most affected. Further, since the humidity sensor is arranged above the rotatable paper pressing plate, the rotation of the paper pressing plate is not obstructed. Also, by arranging the temperature sensor together, both absolute humidity and relative humidity can be measured, and more accurate environmental humidity can be measured.

[Brief description of drawings]

FIG. 1 is a view showing a cassette loading chamber.

FIG. 2 is a diagram showing a schematic configuration of a thermal printer.

FIG. 3 is a perspective view of a paper feed cassette.

FIG. 4 is a block diagram of a drive control unit.

FIG. 5 is a diagram showing the correlation between the concentration of the color thermosensitive recording material and the environmental humidity when the coloring heat energy is constant.

[Explanation of symbols]

 2 cassette loading chamber 3 paper feed cassette 4 color thermal recording paper 13 drive control unit 14 thermal head 26 paper pressing plate 28 humidity sensor 40 locking claw 41 latch mechanism 45 data correction circuit 46 head drive unit 47 controller 50 temperature sensor

Claims (2)

[Claims] 1. A thermal printer which corrects an amount of heat generated by a thermal head according to environmental humidity to thermally record an image on a thermal recording material, wherein a cassette loading chamber in which a paper feed cassette is loaded,
A thermal printer characterized in that a humidity sensor is arranged above a rotatable paper pressing plate for pressing a thermal recording material in a paper feed cassette from above. 2. The thermal printer according to claim 1, wherein a temperature sensor is arranged together with the humidity sensor.