JPH0454422B2 - - 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 color recorded images that are more faithful to the original, regardless of the physical properties of recording paper, recording liquid, etc. due to 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 the 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 spectral reflectance characteristics when magenta yellow ink is applied are shown below. In addition, the broken line d indicates a temperature T1℃ lower than the temperature T2℃ and a humidity H1%.
The dashed lines e and f show the spectral reflectance characteristics when magenta and yellow ink were applied under the same conditions as the broken line d, respectively. It shows. According to Figure 1, if the humidity is constant, the images obtained by applying magenta and yellow inks at a certain temperature will have shorter wavelengths than the images obtained at higher temperatures. It can be seen that the density of cyan ink increases as the temperature decreases. 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 line k shows the spectral reflectance characteristics under the same conditions as in the case of broken line j. This figure shows the spectral reflectance characteristics when magenta and yellow inks are applied. From Figure 2,
If 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 will have a lower spectral resolution than the image obtained under conditions of lower humidity. It can be seen that a spectral reflectance characteristic in which the slope of the characteristic slope rises and short wavelengths are emphasized can be obtained.

In this way, when forming color recorded images by ejecting cyan, magenta, and yellow inks onto recording paper under different conditions of temperature and humidity, even though the same color document is used, If the temperature rises above the predetermined temperature determined by the ink and recording paper used, an image with a reddish tinge may be obtained, and conversely, if the temperature falls, an image with a bluish tinge may be obtained. The inventor has found that it can be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a multicolor inkjet recording device that eliminates the above-mentioned drawbacks and can reproduce recorded images with more faithful tones to color originals without being affected by changes in the physical properties of ink due to temperature changes. Our goal is to provide the following.

Hereinafter, the present invention will be explained in detail 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. 5 is a reader that scans and reads the color original 2, and separates the light from the color original 2 into each color component of blue (B), red (R), and green (G), and calculates the amount of reflected light of each color component. The difference in the current value is interpreted as a change in the current value. That is, the reader 5 is red,
It has a photo sensor that detects blue and green light respectively, detects a spot usually about 60 μm in size that forms an image on a color document, and outputs document color component signals corresponding to red, blue, and green, respectively. 6 is an inkjet nozzle, and in this example, cyan, magenta,
Consisting of three nozzles corresponding to each color of yellow,
A recorded image is formed on the recording paper 3 by ejecting cyan (C), magenta (M), and yellow (Y) inks from each nozzle.

Reference numeral 7 denotes a support base to which the reader 5 and the inkjet nozzle 6 are fixed. Two sliders 8 are attached to this support stand 7, and the support stand 7 can move 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, the pulse motor 10 is installed at one end of the drum 1.
A pulley 11 is fixed to the output shaft of the pulse motor 10. Further, a pulley 12 is disposed on the other end side of the drum 1, and a pulley 12 is provided between the pulley 11 and the pulley 12 for moving the support base 7 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 can read the original color document 2 and the recording paper 3.
This means that the entire surface can be scanned both horizontally and vertically.

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. 17 is 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 temperature 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 humidity detection signal, and supplies the recording color component signal as a nozzle drive signal to the inkjet nozzle 6 via a drive circuit described later with reference to FIG. to control the ink jet nozzle 6. 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.
Details of the reader 5, temperature detector 15, and humidity detector 16 are shown, where 110 to 112 are photo sensors that constitute the reader 5 and detect red, green, and blue light, respectively. , changes in the amount of reflected light of the red, green, and blue color components in the color original 2 are taken as changes in photocurrent, and red, green, and blue color component signals are obtained. 113 to 115 are preamplifiers that convert the photocurrent signals obtained by the photo sensors 110 to 112 into voltage signals and amplify them, and 116 to 118 are preamplifiers 113 to 11
The analog voltage signals amplified in step 5 are converted into digital signals in accordance with each reference voltage whose magnitude is based on the temperature detection signal and humidity detection signal detected by the temperature detector 15 and humidity detector 16 (Fig. 3). This is an analog-to-digital converter (hereinafter referred to as an AD converter).

119 is a temperature detector having the characteristics shown in FIG. 4, and corresponds to the detector 15 in FIG. 3. A preamplifier 120 amplifies changes in the voltage signal due to changes in the resistance value of the temperature detector 119. 121 is the fifth
This is a humidity detector having the characteristics shown in the figure, and corresponds to the detector 16 in FIG. This humidity detector 121
The preamplifier 122 amplifies the change in the voltage signal caused by the change in the resistance value. In addition, these temperature detectors 11
9. Apply a predetermined voltage Vc to the humidity detector 121. The temperature detection signal and humidity detection signal amplified by these preamplifiers 120 and 122 are supplied to an arithmetic circuit 123 to form control signals A1, A2, and A3 corresponding to the detected temperature and humidity,
These control signals A1, A2, and A3 are respectively supplied to the gates of field effect transistors, for example, MOS type field effect transistors (hereinafter referred to as MOSFETs) 124 to 126. These control signals A1,
The resistance values between the sources and drains of MOSFETs 124 to 126 are controlled by A2 and A3, and the resistances 127 to 129 to which voltage Vc is applied and MOSFET 12 are controlled.
4 to 126, and convert the output voltage to the aforementioned AD converters 116 to 126.
Used as reference voltages VR, VG, and VB of 118.
Therefore, the reference voltages VR, VG, and VB are controlled by control signals A1 to A3 corresponding to the temperature and humidity in the atmosphere. That is, AD converters 116 to 11
8 is provided with color component signals R, G, and B read by photo sensors 110 to 112 via preamplifiers 113 to 115, and the reference voltages VR,
Analog-to-digital conversion corresponding to VG and VB is executed, and 4-bit digital color component signals R,
Obtain G and B.

Here, the arithmetic circuit 12 is configured so that the control signals A1 to A3 change as follows with respect to temperature and humidity.
3 shall be set.

(1) When the humidity changes when the temperature is constant A1 (humidity: high) > A1 (humidity: low) A2 (humidity: high) A2 (humidity: low) A3 (humidity: high) < A3 (humidity) : Low) (2) When the temperature changes when the humidity is constant A1 (Temperature: High) > A1 (Temperature: Low) A2 (Temperature: High) A2 (Temperature: Low) A3 (Temperature: High) < A3 (temperature: low) 130 is a color signal calculator, and AD converter 11
Digital color component signals R, G, B from 6 to 118
is supplied, the following calculation is executed to convert the color component signals R, G, B into ink ejection signals C ₀ , M ₀ , Y ₀ .

C ₀ M ₀ Y ₀ = −a ₁₁ , −a ₁₂ , −a ₁₃ −a ₂₁ , a ₂₂ , −a ₂₃ −a ₃₁ , −a ₃₂ , a ₃₃ R G B (1) However, a ₁₁ ~ a ₃₃ >0 These signals C ₀ , M ₀ , Y ₀ are supplied to the ink jet nozzle 6 shown in FIG. 3 via ink jet nozzle drive circuits 134 to 136. At this time, the signal actually supplied is the inverted version of the above calculation result, and if the calculation result is negative, it is set to 0 and then inverted.

For example, in the above equation, R>0, G=B
= 0, the calculation result is C ₀ = a ₁₁ R>0, M ₀ =-
a ₂₁ R<0, Y ₀ = -a ₃₁ R<0, and if we perform processing to set the negative signal to 0, C ₀ = a ₁₁ R, M ₀
=0, Y ₀ =0. After that, we perform a reversal, but
This inversion means that the luminance signals R, G, B are maximum/minimum (=
0), the density signals C ₀ , M ₀ ,
Y ₀ is converted to have the minimum (=0)/maximum density. Of course, if the luminance is an intermediate value, the inverted density will also be an intermediate value. Therefore, in the above example, when R is the maximum brightness, the signal after inversion becomes C ₀ ′=0, M ₀ ′=Y ₀ ′=maximum density,
Cyan ink will not be ejected. In addition,
In the following explanation, it is assumed that the signals subjected to the above-mentioned inversion and other processing are treated as C ₀ , M ₀ , and Y ₀ .

Ink droplets corresponding to each signal obtained as described above are ejected from each inkjet nozzle 6. As a result, a recorded and reproduced image is formed on the recording paper 3.

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 121 decreases from RH1 to RH2, and the preamplifier 1
The output voltage of 22 increases. As a result, the output signals A1 to A3 of the arithmetic circuit 123 are as described above: A1 (humidity H2%) > A1 (humidity H1%) A2 (humidity H2%) A2 (humidity H1%) A3 (humidity H2%) < A3 (Humidity H1%). When the signal A1 becomes large, the MOSFET
The resistance value between the source and drain of 124 becomes small, and the reference voltage VR becomes small. Also, signal A3
As VB becomes smaller, the resistance value between the source and drain of MOSFET 126 becomes larger, and the reference voltage VB becomes larger. Since the signal A2 hardly changes, the reference voltage VG also does not change. In other words, the relationship is VR (humidity H2%) < VR (humidity H1%) VG (humidity H2%) VG (humidity H1%) VB (humidity H2%) > VB (humidity H1%). Therefore, AD converters 116-1
18 respectively output color component signals R, G,
B is R (humidity H2%) < R (humidity H1%) G (humidity H2%) G (humidity H1%) B (humidity H2%) > B (humidity H1%), and each of these signals R, G _The ink ejection signals _{C 0 ,} M _{0 ,} Y ₀ calculated based on ₀ (Humidity H2%) > Y ₀ (Humidity H1%). Therefore, in the ink ejection signals C ₀ , M ₀ , and Y ₀ output from the color signal calculator 130, the higher the humidity is at a constant temperature, the more the long wavelength range is emphasized, and the short wavelength range is suppressed. Here, the ink ejection 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 131 to 133 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, as can be seen from FIG. 4, the resistance value of the temperature detector 119 decreases from RT1 to RT2, and the output voltage of the preamplifier 120 increases. As a result, the arithmetic circuit 123
As mentioned above, the output signals A1 to A3 are as follows: A1 (temperature T2℃) < A1 (temperature T1℃) A2 (temperature T2℃) A2 (temperature T1℃) A3 (temperature T2℃) > A3 (temperature T1℃) becomes. When the signal A1 becomes small, the MOSFET
The resistance value between the source and drain of 124 increases, and the reference voltage VR increases. Also, signal A3
When VB increases, the resistance value between the source and drain of MOSFET 126 decreases, and the reference voltage VB decreases. Since the signal A2 hardly changes, the reference voltage VG also does not change. In other words, the relationship is VR (temperature T2°C) > VR (temperature T1°C) VG (temperature T2°C) VG (temperature T1°C) VB (temperature T2°C) < VB (temperature T1°C). Therefore, AD converters 116-1
18 respectively output color component signals R, G,
B is R (temperature T2℃) > R (temperature T1℃) G (temperature T2℃) G (temperature T1℃) B (temperature T2℃) < B (temperature T1℃), and these signals R, G _{The ink} ejection signals _{C 0} , M _{0 ,} Y ₀ calculated based on ₀ (temperature T2℃) < Y ₀ (temperature T1℃). Therefore, in the ink ejection signals C ₀ , M ₀ , and Y ₀ outputted from the color signal calculator 130, the shorter wavelength range is emphasized and the longer wavelength range is suppressed as the temperature becomes higher under constant humidity. Here, the ink ejection 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 131 to 133 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, the color density of the recorded image can be controlled by using a plurality of nozzles that eject color ink of different densities for the same color, and by appropriately selecting these plurality of nozzles.
Any form of color density control may be used during recording.

As explained above, according to this embodiment, the temperature detection signal and the humidity detection signal corresponding to the temperature and humidity respectively detected by the temperature detector that detects the ambient temperature and the humidity detector that detects the ambient humidity are used. Since the color component signal is corrected to obtain a corrected color component signal, and the corrected color component signal is converted into an ink ejection signal to form a recorded image, changes in ink physical properties due to temperature changes, dyes, pigments, etc. It is possible to prevent variations in the recorded image due to changes in the mixing ratio of the ink composition, changes in the size and water absorption of the recording paper due to changes in humidity, etc., and it is possible to obtain a recorded color image that is more faithful to the original.

As explained above, according to the present invention, since a corrected color signal corrected according to the detected ambient temperature is converted into an ink ejection signal, variations in recorded images due to temperature changes can be prevented, and high-quality images can be obtained. can be obtained.

In particular, according to the present invention, when the temperature rises, the relatively short wavelength components of the color component signal are emphasized, and when the temperature decreases, the relatively long wavelength components are emphasized, so that redness appears due to the rise in temperature. To obtain an inkjet image faithful to the original and excellent in color reproducibility by preventing an inkjet image with a shading or a bluish inkjet image from being obtained due to a drop in temperature.

[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, 120,
122...Preamplifier, 116-118...AD
Converter, 119...Temperature detector, 121...Humidity detector, 123...Arithmetic circuit, 124-126...
...MOS type field effect transistor, 127-12
9...Resistance, 130...Color signal calculator, 131~
133...Drive circuit.

Claims (1)

[Scope of Claims] 1. A multicolor inkjet recording device that drives inkjet nozzles to form a recorded image on recording paper based on a given color component signal, comprising: a temperature detector that detects ambient temperature; Based on the temperature detection signal corresponding to the temperature detected by the temperature detector, it automatically emphasizes relatively short wavelength components when the temperature increases, and emphasizes relatively long wavelength components when the temperature decreases. ,
a circuit that corrects the color component signal to obtain a corrected color component signal; and a conversion circuit that converts the corrected color component signal into an ink ejection signal, and drives the inkjet nozzle based on the ink ejection signal. A multicolor inkjet recording apparatus characterized in that a recorded image is formed on the recording paper by