JPH0317673B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multicolor inkjet recording device,
In particular, it is possible to obtain a color memory image that is more faithful to the original, regardless of the physical properties of the recording paper, recording liquid, etc. due to humidity and temperature.

In a multicolor inkjet recording device that reads an original color document and forms a color recorded image on a recording paper, etc., multicolor ink, for example, yellow, magenta, and cyan ink, is ejected from different inkjet nozzles. A color recorded image that is faithful to a color original is reproduced depending on the degree of overlapping of inks or the degree of arrangement of ink dots corresponding to each color. However, the yellow, magenta, cyan, etc. inks and recording paper used in this type of multicolor inkjet recording device are easily affected by temperature and humidity.In particular, the physical properties of the ink change depending on the temperature, and the ink on the recording paper The degree of bleeding depends on the size and water absorption of the recording paper due to humidity, so even if recording is performed under the same recording conditions, the recorded images will differ depending on the temperature and humidity.

FIGS. 1 and 2 show the spectral reflectance of cyan, magenta, and yellow inks applied to high-quality paper under various temperature and humidity conditions and thoroughly dried. In Figure 1, solid line a shows the spectral reflectance characteristics when cyan ink is applied to high-quality paper under conditions of temperature T2℃ and humidity H1%, and solid lines b and c show the same conditions as solid line a. The graph below shows the spectral reflectance when magenta and yellow inks are applied. Also,
Broken line d indicates temperature T1℃ lower than temperature T2℃ and humidity H1
%, and the broken lines e and f show the spectral reflectance characteristics when magenta and yellow inks were applied under the same conditions as the broken line d. They are shown below. According to Figure 1, if the humidity is constant,
Images obtained by applying magenta and yellow inks at a certain temperature have spectral reflectance characteristics shifted toward shorter wavelengths than images obtained at higher temperatures, and cyan It can be seen that the lower the temperature of the ink, the higher the density.
Note that, from these facts, the overall image obtained by superimposing each ink becomes an image shifted to the shorter wavelength side as the temperature is lower.

In addition, in Fig. 2, the solid line g is the temperature T2℃,
It shows the spectral reflectance characteristics when cyan ink is applied under the condition of humidity H1%, and solid lines h and i show the spectral reflectance when magenta and yellow ink are applied under the same conditions as solid line g. Each shows its characteristics. Furthermore, dashed line j shows the spectral reflectance characteristics when cyan ink is applied under the conditions of temperature T2℃ and humidity H2% higher than humidity H1%, and dashed lines k and l show the spectral reflectance characteristics under the same conditions as in the case of dashed line j. The graph shows the spectral reflectance characteristics when magenta and yellow inks are applied. From Figure 2, it can be seen that when each ink is applied at a constant temperature in an atmosphere with different humidity, the image of each ink obtained under conditions of higher humidity is different from that obtained under conditions of lower humidity. It can be seen that a spectral reflectance characteristic in which the slope of the slope of the spectral characteristic is steeper and short wavelengths are emphasized is obtained as compared to the image obtained with the spectral characteristic.

In this way, when forming a color recorded image by ejecting cyan, magenta, and yellow inks onto recording paper under different conditions of temperature and humidity, even though the same color original is used, The inventors have discovered that when the temperature decreases or increases, an image with a reddish tinge is obtained, and conversely, when the humidity increases or the temperature decreases, an image with a bluish tinge is obtained.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to eliminate the above-mentioned drawbacks and reproduce recorded images with more faithful tones to the original without being affected by changes in the physical properties of memory paper and ink due to changes in temperature and humidity. The object of the present invention is to provide a multicolor inkjet recording device that can print images.

The present invention will be explained in detail below based on the drawings.

FIG. 3 shows an example of the configuration of the multicolor inkjet recording apparatus of the present invention, where 1 is a drum around which a color original 2 and recording paper 3 are wound, and 4 is a drum 1.
This is a drive motor for rotating. Reference numeral 5 denotes a reader that scans and reads the color original 2, which separates the light from the color original 2 into each color component of blue B, red R, and green G, and calculates the difference between each color component and the amount of reflected light as a current value. I tried to think of it as a change. That is, the reader 5 has a photo sensor that detects each of red, blue, and green light, and detects a spot usually about 60 μm in size that forms an image of a color document, and detects the document color corresponding to each of red, blue, and green. Output component signals. 6 is an inkjet nozzle, and in this example, it consists of three nozzles corresponding to each color of cyan, magenta, and yellow, and from each nozzle,
A recorded image is formed on the recording paper 3 by ejecting cyan C, mazetan M, and yellow Y inks, respectively.

Reference numeral 7 denotes a support base to which the reader 5 and the ink jet 6 are fixed. Two sliders 8 are attached to this support stand 7, and the support stand 7 is movable left and right on the rail 9 via the slider 8, so that the reader 5 and the inkjet nozzle 6 are interlocked to move left and right. be able to move. That is, a pulse motor 10 is disposed at one end of the drum 1, and a pulley 1 is attached to the output shaft of the pulse motor 10.
Fix 1. Further, a pulley 12 is disposed on the other end side of the drum 1, and the support base 7 is moved between the pulley 11 and the pulley 12 so as to be parallel to the rotation axis 1A of the drum 1. The wire 13 is stretched. The wire 13 is fixed to the retaining plate 14, thereby connecting it to the support base 7. By driving the pulse motor 10, the wire 13 is driven, and the support base 7 is capable of linearly reciprocating in the direction of the rotation axis 1A of the drum 1. Therefore, due to the rotation of the drum 1 itself and the linear movement of the reader 5 and inkjet nozzle 6 in the direction of the rotation axis 1A, the reader 5 and inkjet nozzle 6 horizontally move the original color document 2 and the recording paper 3. This means that the entire surface can be scanned in the vertical direction.

15 is a temperature detector, for example a thermistor;
It has the temperature resistance value characteristics shown in FIG. That is, the resistance value decreases as the temperature increases. 1
Reference numeral 6 denotes a humidity detector, for example, Hume Serum (trade name: manufactured by Matsushita), which has the humidity resistance value characteristics shown in FIG. That is, the resistance value decreases as the relative humidity increases. Reference numeral 17 denotes a color signal correction control circuit, to which the color component signal of the color original 2 read by the above-mentioned reader 5, the temperature detection signal detected by the humidity detector 15, and the humidity detection signal detected by the humidity detector 16 are supplied. , corrects and converts the color component signal based on the temperature detection signal and the humidity detection signal, and controls the inkjet nozzle 6 by supplying a nozzle drive signal to the inkjet nozzle 6 via a drive circuit described later with reference to FIG. do. As a result, cyan, magenta, and yellow ink droplets are ejected from the inkjet nozzle 6, and a recorded color image is formed on the recording paper 3 by subtractive color mixing.

FIG. 6 shows the color signal correction control circuit 17 shown in FIG.
Reader 5, temperature detector 15 and humidity detector 16
Here, 110 to 112 are photo sensors for configuring the reader 5 and detecting red, green, and blue light respectively, and 110 to 112 are photo sensors for detecting red, green, and blue light, respectively.
The change in the amount of reflected light of each of the red, green, and blue color components is taken as a change in photocurrent, and the red, green, and blue color component signals are obtained. 113-115 are
This is a preamplifier that converts the photocurrent signals obtained by the photo sensors 110 to 112 into voltage signals and amplifies them, and outputs analog value original color component signals R, G, and B.
Output each.

Reference numeral 116 designates a temperature detector having the characteristics shown in FIG.
Obtain an analog value temperature detection signal T.

Reference numeral 118 denotes a humidity detector having the characteristics shown in FIG.
Obtain an analog value humidity detection signal H. It is assumed that a predetermined voltage V _C is applied to these temperature detector 116 and humidity detector 118.

120 is a temperature/humidity detection signal calculation circuit;
It is supplied with temperature detection signal T and humidity detection signal H output from preamplifiers 117 and 119, respectively, performs calculations based on these signals, and outputs temperature/humidity color correction signal A2. This signal A
2 increases as the temperature rises and decreases as the humidity rises.

121 is a color signal calculator, and a preamplifier 11
It is supplied with the output signals R, G, and B of 3 to 115 and the output signal A2 of the arithmetic circuit 120, and executes arithmetic processing, which will be described later, based on these respective signals. The cyan, magenta, and yellow recording color component signals C ₀ , M ₀ , and Y ₀ as the results of this calculation are supplied as nozzle drive signals to the inkjet nozzle 6 shown in the third figure via the drive circuits 122 to 124. , ink droplets responsive to these recording color component signals C ₀ , M ₀ , and Y ₀ are ejected from the respective ink jets 6 . As a result, a recorded and reproduced image is formed on the recording paper 3.

Here, the recording color component signals C ₀ , M ₀ , and Y ₀ outputted from the color signal calculator 121 are signals obtained by correcting and converting the original color component signals R, G, and B, respectively. In order to perform this, the color signal calculator 121 performs the following calculation to obtain recording color component signals C ₀ , M ₀ , and Y ₀ . That is, in the color signal calculator 121, C ₀ =a ₁₁ −a ₁₂ G−a ₁₃ B−b1(A1−A2) (1) M ₀ =−a ₂₁ R+a ₂₂ G−a ₂₃ B (2) Y ₀ = −a ₃₁ −a ₃₂ G+a ₃₃ B+b1(A1−A2) (3) (However, a ₁₁ to a ₃₁ > 0, b1 > 0, A1 is a reference value.) Execute each calculation to determine the original color. The component signals R, G, and B are corrected and converted into recording color component signals C ₀ , M ₀ , and Y ₀ for driving the ink jet nozzle 6 .

In the multicolor inkjet recording apparatus constructed as described above, suppose that in an atmosphere of temperature T2°C shown in FIG. 4 and humidity H1% shown in FIG. 5, only the humidity becomes high and rises to humidity H2%. At this time,
As can be seen from FIG. 5, the resistance value of the humidity detector 118 decreases from RH1 to RH2, and the preamplifier 1
The output voltage of 19 increases. As a result, the temperature/humidity color correction signal A2 outputted from the arithmetic circuit 120
decreases. Therefore, the recording color component signals C ₀ , M ₀ , Y ₀ respectively output from the color signal calculator 121
From equations (1) to (3), C ₀ (humidity H2%) < C ₀ (humidity H1%) M ₀ (humidity H2%) M ₀ (humidity H1%) Y ₀ (humidity H2%) >Y ₀ (humidity H1%). Therefore, the recording color component signals C ₀ , M ₀ , Y ₀
Under a certain temperature, the higher the humidity, the more the long wavelength range is emphasized and the short wavelength range is suppressed. Here, the correction conversion signals C ₀ , M ₀ , and Y ₀ are supplied to the ink jet nozzle 6 (see FIG. 3) via the ink jet nozzle drive circuits 122 to 124 to increase the humidity. Accordingly, the number of recorded dots per unit area is controlled to form a recorded image that emphasizes the long wavelength region.

Next, it is assumed that in the atmosphere with the temperature T1°C shown in FIG. 4 and the humidity H1% shown in FIG. 5, only the temperature becomes higher and rises to the temperature T2°C. At this time, the fourth
As can be seen from the figure, the resistance value of the temperature sensor 116 decreases from RT1 to RT2, and the resistance value of the temperature detector 116 decreases from RT1 to RT2.
7's output voltage increases. As a result, the arithmetic circuit 1
The temperature/humidity color correction signal A2 output from 20 decreases. Therefore, the recording color component signals C ₀ , M ₀ , and Y ₀ outputted from the color signal calculator 121 are calculated as follows from equations (1) to (3): C ₀ (temperature T2°C) > C ₀ ( Temperature T1℃) M ₀ (Temperature T2℃) M ₀ (Temperature T1℃) Y ₀ (Temperature T2℃) < Y ₀ (Temperature T1℃). Therefore, the recording color component signals C ₀ , M ₀ , Y ₀
Under constant humidity, the higher the temperature, the more the short wavelength range is emphasized, and the longer wavelength range is suppressed. Here, the correction conversion signals C ₀ , M ₀ , Y ₀ are supplied to the ink jet nozzle 6 (see FIG. 3) via the ink jet nozzle drive circuits 122 to 124 to increase the temperature. Accordingly, the number of recorded dots per unit area is controlled to form a recorded image that emphasizes the short wavelength region.

In this example, as the temperature rises and humidity falls, the ejection of each ink is controlled so as to emphasize short wavelengths, and as the temperature falls and humidity rises, the ejection of each ink is controlled so as to emphasize long wavelengths. Since the ejection is controlled, a recorded image that is more faithful to the color original can be obtained.

Note that in this example, the correction of the recorded image density was controlled by the number of recorded dots per unit area of each color, but in the present invention, a plurality of nozzles with different orifice diameters are used for the same color, When ejecting ink, the color density of a recorded image can also be controlled by ejecting ink from appropriately selected nozzles. In addition, by using multiple nozzles that eject color ink of different densities for the same color,
By appropriately selecting these plurality of nozzles, the color density of the recorded image can be controlled, and any form of color density control during printing may be used.

As explained above, according to the present invention, the temperature detection signal and the humidity detection signal correspond to the temperature and humidity detected by the temperature detector that detects the ambient temperature and the humidity detector that detects the ambient humidity, respectively. Since a recorded image is formed by correcting the signal and converting it into an ink ejection signal, it is possible to prevent changes in ink physical properties due to temperature changes, changes in the mixing ratio of ink compositions such as dyes and pigments, and changes in humidity. It is possible to prevent variations in recorded images due to changes in recording paper size, water absorption, etc., and to obtain recorded color images that are more faithful to the original.

In particular, according to the present invention, the relatively short wavelength components of the color component signal are emphasized when the humidity decreases or the temperature increases, and the relatively long wavelength components are emphasized when the humidity increases or the temperature decreases. This prevents an inkjet image from becoming reddish due to a drop in humidity or a rise in temperature, or a bluish inkjet image from being obtained due to a rise in humidity or a fall in temperature. It is possible to obtain an inkjet image with excellent color reproducibility that is faithful to the image.

[Brief explanation of the drawing]

FIGS. 1 and 2 are spectral reflectance characteristic curve diagrams of recorded images formed on recording paper using each ink,
FIG. 3 is a block diagram showing an example of the structure of the multicolor inkjet recording apparatus of the present invention, FIG. 4 is a characteristic curve diagram of the temperature detector shown in FIG. 3, and FIG. 5 is a characteristic curve of the humidity detector shown in FIG. 3. 6 are block diagrams showing detailed examples of the color signal correction control circuit, reader, temperature detector, and humidity detector shown in FIG. 3, respectively. 1...Drum, 2...Color original, 3...Recording paper, 4...Drive motor, 5...Reader, 6...Inkjet nozzle, 7...Support stand, 8...Slider, 9... Rail, 10...Pulse motor, 1
1, 12...Pulley, 13...Wire, 14...
Retaining plate, 15...Temperature detector, 16...Humidity detector, 17...Color signal correction control circuit, 110-11
2...Photo sensor, 113 to 115, 117,
119...Preamplifier, 116...Temperature detector,
118...Humidity detector, 120... Arithmetic circuit, 1
21... Color signal calculation circuit, 122-124... Drive circuit.

Claims (1)

[Claims] 1. A multicolor inkjet recording device that drives inkjet nozzles to form a recorded image on recording paper based on color component signals, comprising: a temperature detector that detects ambient temperature; and a temperature detector that detects ambient humidity. a humidity detector that detects the temperature and humidity detected by the temperature detector and the humidity detector, respectively; and a conversion circuit that corrects the color component signal and converts it into an ink ejection signal so as to relatively emphasize the short wavelength range according to a decrease in temperature or an increase in humidity, based on the ink ejection signal. A multicolor inkjet recording apparatus characterized in that the inkjet nozzle is driven to form a recorded image on the recording paper.