JPH0677993B2 - Inkjet recording method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reciprocal recording type inkjet recording method capable of expressing density gradation.

2. Description of the Related Art Recently, a drop-on-demant type inkjet printer using electrostatic force or electrostatic force and air flow has been put into practical use. In this method, an ink droplet is pulled out by an electrostatic force generated by applying an ejection signal to the head, and the recording density, that is, the ink ejection amount is almost proportional to the pulse width of the ejection signal applied to the head.

FIG. 2 shows a time chart when two lines of the same recording image are recorded by using this ink jet head and a printer that performs one-way recording, such as a drum type printer or a flatbed scanning printer with one-sided recording tape. The operation will be described below with reference to FIG. In this time chart, A and A ′ are clock signals, which are generated at the beginning of each pixel and control the recording density.When the relative speed between the head and the recording paper is constant, this clock signal is since it generated every predetermined period T becomes _{T = T 1 = T 2 ......} T n = T n + 1 ....... B and B ′ are ink ejection signals and clock signals A and A ′
And pulse widths tn and tn + 1 which are equal to the time corresponding to the required ink ejection amount.
Further, the ink ejection signals B and B'are signals amplified to a high voltage in order to apply them to the head to generate an electrostatic force. C and C'are recording images, which are ejected from the head by the ink ejection signals B and B'and adhered to the recording paper. In the figure, τ ₀ is the time from the application of the signals B and B ′ to the head until the ink adheres to the recording paper.

The operation of the above configuration will be described below.

First, when recording the first line, a clock signal is output from pixel n
Ink ejection signal Bn with pulse width tn is generated in synchronization with An,
Accordingly, the recording image Cn is formed with a delay of τ ₀ . Next, in the pixel (n + 1), similarly, the recording image C _{n + 1} is formed with a delay of τ _{0 from} the ink ejection signal B _{n + 1} having the pulse width t _{n + 1} .

Similarly, recorded images C'n and C'n _{+ 1} are formed on the second line.

As described above, when the relative direction between the head and the recording paper is one direction, the recording images C and C ′ are generated after τ ₀ time from the rising of the clock signals A and A ′, and the marks of FIG. Since it is possible to obtain a recorded image having a density corresponding to the pulse width of the ink ejection signal as shown by the characteristic, a recorded matter with good reproducibility can be obtained.

Problems to be Solved by the Invention However, in the case where recording is performed at the time of reciprocation by a flatbed printer, that is, the relative movement direction of the head and the recording paper has both positive and negative directions, and both directions are In the case of recording with, the recording image is formed with a positional deviation. This deviation becomes larger as the density is lower, that is, as the pulse width of the ink ejection signal becomes shorter, and the printed matter has poor reproducibility. FIG. 4 shows a flatbed scanning printer that records at the time of reciprocation.
FIG. 7 is a time chart of signals and recorded images when the same recorded image is printed in the forward and backward passes. The outward route is the same as the case described above with reference to FIG. On the return path, the clock signal D is generated at the beginning of each pixel, and therefore becomes like D _{n + 1} , D _n , and D _{n-1 in} the figure. Next, since the ink ejection signal E is generated in synchronization with the rising edge of each clock signal, the signal E _{n + 1 having} the pulse width tn + 1 is obtained in the pixel (n + 1), and the pulse width tn is obtained in the pixel n.
Signal En. Next, assuming that the print image on the return path is F, in pixel (n + 1), in pixel n in which print image F _{n + 1} is formed with a delay of τ ₀ time from ink discharge signal E _{n + 1} , pixel A recording image Fn is formed with a delay of τ ₀ . As is clear from FIG. 4, the lower the density of the recording images Cn and Fn, the larger the deviation of the recording positions between the forward path and the backward path. Generally, it is said that the deterioration of the recording becomes conspicuous when the deviation of the recorded image becomes 1/3 pixel or more, and the recording deviation at a low density becomes a serious problem.

The present invention solves the above problems, and an object of the present invention is to reduce the recording deviation when the flatbed scanning printer reciprocates.

Means for Solving the Problems The present invention relates to a plane scanning type ink jet recording capable of reciprocating time recording, in which a cycle of a clock signal one pixel before is T,
When the pulse width of the ink discharge signal is τ ₀ from the time when the ink discharge signal is applied to the head to the time when the ink adheres to the recording paper, the ink is discharged according to the positive / negative of τ = T−2τ ₀ −t. The above object is achieved by controlling the generation timing of the ejection signal.

Operation According to the present invention, the positive or negative of τ = T−2τ ₀ −t is determined for each pixel on either the forward path or the backward path according to the above configuration, and when (T−2τ ₀ )> t, ink ejection is performed. The signal is generated with a delay of (T−2τ ₀ −t) from the rising edge of the clock pulse, and when (T−2τ ₀ ) ≦ t, the ink ejection signal is generated without a delay from the rising edge of the clock pulse. It was done like this.

Embodiment One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a time chart of a signal and a recording image of a printer capable of performing reciprocal recording and expressing density gradation in one embodiment of the present invention. The pixel n in the figure is the nth pixel in the relative movement direction of the head and the recording paper. Now, a case where recording is performed at the nth pixel and the (n + 1) th pixel will be described. In the relative movement direction of the head and the recording paper, as shown in FIG. 1, the left-to-right direction is the forward path and the right-to-left direction is the return path. Further, the relative moving speeds of the head and the recording paper are substantially uniform, and especially the speeds when passing over the same pixel by reciprocating motion are equal.

Further, the time required to pass the nth pixel is defined as Tn. Next, it is assumed that the clock signal generated for each pixel is generated at the first point where the head passes over each pixel.

In FIG. 1, A and X are clock signals. B and Y are ink ejection signals, which have a pulse width equal to the time corresponding to the required ink ejection amount, which is generated in synchronization with the rising edge of the clock signal. Further, the ink ejection signals B and Y are signals amplified to a high voltage in order to apply them to the head to generate an electrostatic force. C and Z are recording images, which are ejected from the head by the ink ejection signals B and Y and adhered to the recording paper. Further, τ ₀ is the time from the application of the head to the ink ejection signals B and Y until the ink adheres to the recording paper. Also tn, tn + 1
Is the pulse width of the ink ejection signals B and Y at pixel n and pixel (n + 1). Also signal and recorded images A, B, C, X, Y, Z
Suffix n for those generated at pixel n
And suffixes n + 1 are added to those generated at pixel (n + 1). In addition, A, B, C are the outbound, X,
Y and Z are signals and recorded images on the return path.

The operation of the above arrangement will be described below.

First, on the outward path, at the first point of pixel n, the clock signal
An occurs, and this signal An synchronizes with the rising edge and pulse width tn
Ink ejection signal Bn is generated. After a delay of τ ₀ from this signal Bn, a print image Cn having an ink ejection amount corresponding to tn is formed. Next, similarly for the pixel (n + 1), the clock signal A
_{n + 1} of the ink ejection signal B _{n + 1} pulse width tn + 1 in synchronism with the rising occurs, recording image C _{n + 1} delayed by tau ₀ hours is formed.

Next, the operation on the return path will be described. First, the storage means in the recording circuit of the printer stores the pixel transit time of the head, that is, the cycle T of the clock signal X, every time a new pixel is passed. Even if the relative speed between the head and the recording paper changes as a whole, it is considered to be uniform among several pixels, so the clock cycle of the pixel of the clock signal ahead of 1 to 2 is the clock cycle stored at that time. Can be regarded as the same as. Now, consider formation of the recorded image Z _{n + 1} of the pixel (n + 1). To record the recording image Z _{n + 1} of the return path on the vertical line of the recording image C _{n + 1} recorded in the forward path, as is clear from FIG. 1 in consideration of the delay of tau ₀ hours, pixel n The ink ejection signal Y _{n + 1} may end at the beginning of the point, that is, 2τ ₀ before the rising timing of the clock signal Xn. However, since the ink ejection signal Y _{n + 1} is generated after the rising of the clock signal X _{n + 1} , T _{n + 3} ≧ t _n + 1 ≧
T _{n + 3} when -2Tau ₀ becomes the pulse width tn + 1, the clock signal
The signal Y _{n + 1} is generated in synchronization with the rising edge of X _{n + 1} . Since the recorded image Z _{n + 1 in} this case has a large dot diameter, there are many portions that overlap with the recorded image C _{n + 1} in the outward path, and the positional deviation is less noticeable.

Therefore, actually, a recording image on the return path is formed by the following method. First, when the head is passing through the pixel (n + 2), τn + 1 = T _{n + 3} −2τ _{0 by} the arithmetic means in the recording circuit.
-Tn + 1 calculation is performed. Then the comparison means, when τn + 1> 0 using the delay means, the ink ejection signal Y _{n + 1} is delayed from the rising of the clock signal X _{n + 1} by the time .tau.n + 1
Generate. The recorded image Z is delayed by τ ₀ hours from the signal Y _{n + 1.
If n + 1} is moved vertically, they will overlap and no deviation will occur. A recorded image Z _{n + 1} in the figure is formed. The recorded image Z _{n + 1} is overlapped by vertically moving the recorded image C _{n + 1} on the outward path, and no shift occurs. The recorded image Z _{n + 1} in the figure shows this state. If τn
In the case of + 1 ≦ 0, when the ink ejection signal Y _{n + 1} is generated in synchronization with the rising of the clock signal X _{n + 1} , the recording image Z _{n + 1} corresponding to the ink image is formed after the time τ ₀ .

The same applies to the recording of the pixel n, and when the head passes the pixel (n + 1), τn = T _{n + 2} −2τ ₀ −tn is calculated, and if the same processing is performed depending on whether the τn is positive or negative, A backward recorded image Zn is formed on the vertical line of the forward recorded image Cn.

As is clear from the above description, according to the present embodiment, τn = T _{n + 2} −2τ ₀ −tn one pixel before in the backward recording.
When τn> 0, the ink ejection signal is generated by delaying by τn from the rising edge of the clock pulse,
When .tau.n.ltoreq.0, an ink ejection signal is generated in synchronization with the rising edge of the clock pulse to form a recorded image, so that the deviation between the recorded image on the forward path and the recorded image on the return path can be minimized.

In the above description, the case where the rising edge of the clock signal is used as a reference has been described, but the same applies when the rising edge is used as a reference. Also, although the case where the clock signal is generated at the beginning of each pixel has been described, it may be generated at the middle or at the end of each pixel. In the above description, the case where the relative speeds of the ink jet head and the recording paper are different has been described, but the same applies to the case where the speeds are constant. In this case, the cycle T of the clock signal is T = T _{1
= T 2 = ...... = T n} -1 = Tn = T n + 1 = T n + 2 = ...... = a constant and becomes the storage means have to store the Tn each passing through each pixel is not necessary. Further, in the above description, the case of delaying the ink ejection signal during the backward pass in the reciprocal recording has been described, but the delay may be performed during the forward pass.

As described above, according to the present invention, the printer capable of reciprocating recording can print more than 2 pixels from the pixel to be recorded during the forward or backward pass.
When the period of the clock before the pixel is T, the time from application of the ejection signal to the inkjet head until the ink adheres to the recording paper is τ _0, and the pulse width of the ink ejection signal is t, then τ = T−2τ ₀ −t is calculated, and when τ> 0, an ink ejection signal is generated with a delay of τ from the rising edge of the clock signal, and when τ ≦ 0, there is no delay and at the same time when the clock signal rises. By generating the ink ejection signal, it is possible to minimize the deviation of the recording image in the direction perpendicular to the recording direction and improve the recording quality.

[Brief description of drawings]

FIG. 1 is a time chart of a signal and a recording image of a printer capable of reciprocal recording and density gradation expression in the embodiment of the present invention, and FIG. 2 is a signal and a recording image time of a unidirectional recording printer in a conventional example. A chart, FIG. 3 is a characteristic diagram of the pulse width and density of the head applied signal, and FIG. 4 is a time chart of signals and a recording image of the printer for reciprocal recording in the conventional example. A, X ... Clock signal, B, Y ... Ink ejection signal, C, Z ...
… Recorded image.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location B41J 2/205 9012-2C B41J 3/04 104 D (56) Reference JP-A-55-27287 ( JP, A) JP 59-76267 (JP, A) JP 60-206665 (JP, A) JP 60-208255 (JP, A) JP 61-84256 (JP, A) JP Sho 62-109657 (JP, A)

Claims (1)

[Claims] 1. A cycle of a clock signal generated for each pixel on the forward path or the backward path at the time of reciprocal recording is T, from when an ink ejection signal is applied to an inkjet head until ink adheres to a recording sheet. the time and tau _0, the pulse width of the ink ejection signal is t, when the τ = T-2τ ₀ -t, in the case of tau> 0 delaying the clock signal from the tau time, the ink ejection signal And τ ≦ 0, the ink ejection signal is generated at the same time as the generation of the clock signal without delay.