JPH0729434B2 - Liquid jet print head and printing apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid jet print head and a printing apparatus, and more particularly to a liquid jet print head and a printing apparatus capable of printing with gradation. .

[Prior Art] Conventionally, the non-impact recording method has been attracting attention because noise generation during recording is extremely small to a negligible level. Among them, high-speed recording is possible,
Moreover, the liquid jet recording method (inkjet recording method), which can perform recording without requiring special processing such as fixing on plain paper, is an extremely effective recording method, and has proposed various methods and realized them. And a device for doing so have been devised, improved and put into practical use.

Among them, the methods described in, for example, Japanese Patent Laid-Open No. 54-51837 and German Publication (DOLS) 2843064 are said to obtain thermal power to act on liquid to form a driving force for forming flying droplets. In this respect, it has a feature different from other inkjet recording methods.

That is, in the recording method disclosed in the above publication, the liquid subjected to the action of thermal energy undergoes a state change accompanied by a sharp increase in volume including the generation of bubbles, and by the action force based on the state change, The droplets are ejected from the orifice at the tip of the recording head, fly, and adhere to the recording member to perform recording.

In particular, the inkjet recording method disclosed in DOLS 2843064 is not only very effectively applied to the so-called drop-on-demand recording method, but also the recording head part is a full line type and has a high density multi-orifice. Since it is easy to obtain, there is an advantage that an image of high resolution and high quality can be obtained at high speed.

As described above, the liquid jet recording method using heat energy has many advantages. However, in order to record an image with higher resolution and higher quality, it is necessary to provide the recording pixel with gradation. It is necessary to perform image recording including halftone information.

[Problems to be Solved by the Invention] In such a conventional image recording method for expressing gradation, first of all, a plurality of pixels in which one pixel can be occupied by only one of the image forming elements. According to the number of cells occupied by the image forming element and the array state of the image forming element occupying the cells. There is a recording method that digitally expresses a desired level of gradation. Also,
Second, one pixel is composed of only one of the image forming elements,
There is a recording method in which desired gradation expression is represented in an analog manner by changing the optical density of the image forming element.

However, in a liquid jet recording head that performs recording by ejecting a liquid by thermal energy, when controlling this in order to obtain gradation expression by the first method, the area of one pixel itself becomes large and There was a case where the degree of deterioration was reduced. Further, since the digital control is used, the gradation steps are coarse, and the image quality is sometimes poor.

On the other hand, the second method generally adopts a method of changing the size of one pixel, that is, the size of the image forming element by changing the electric energy applied to the size of the ejected droplet, but this method is used. In this case, the gradation control range is narrow and a sufficient gradation control range cannot be obtained. In addition, extremely strict quality control is required to keep the orifice diameter etc. uniform. Due to the above variation, ejection failure of the recording head, reliability and the like may be deteriorated.

[Means for Solving Problems] The present invention solves these problems and provides a liquid jet printhead and a printing apparatus capable of expressing fine gradation over a wide density range from high optical density to low optical density. The purpose is to provide.

Another object of the present invention is to provide a liquid ejecting print head and a printing apparatus which have improved reliability and droplet ejection stability.

Still another object of the present invention is to provide a liquid jet print head and a printing apparatus in which variations in ejection characteristics due to variations in manufacturing can be easily eliminated and yield can be improved.

A first aspect of the present invention that can achieve such an object is to hold a plurality of discharge ports for discharging a liquid, a plurality of liquid flow paths that respectively communicate with these discharge ports, and a liquid that is supplied to these liquid flow paths. And a discharge energy generating element that is formed between the liquid chamber and the liquid flow path and that applies an energy for discharging the liquid from the discharge port to the liquid. And a liquid amount control means which is provided in each of the liquid channels and changes the amount of the liquid in the liquid channels without directly ejecting the liquid from the ejection ports. And a liquid jet print head.

A second aspect of the present invention is that a plurality of ejection openings for ejecting liquid, a plurality of liquid flow paths that respectively communicate with these ejection openings, and a liquid chamber portion that holds the liquid supplied to these liquid flow paths. And an ejection energy acting portion provided between the liquid chamber portion and the liquid flow path, and an ejection energy generating element provided with an ejection energy generating element for acting on the liquid energy for ejecting the liquid from the ejection port, A liquid ejecting print head that is provided in each of the flow paths, and that has a liquid amount control means for changing the amount of the liquid in these liquid flow paths without directly ejecting the liquid from the ejection port; Ejection control means for controlling the amount of liquid ejected from the ejection port by driving the ejection energy generating element according to the amount of liquid in the liquid flow path which is changed by the liquid amount control means. Special thing A liquid ejecting printing apparatus according to.

Here, it is possible to communicate a plurality of ejection energy acting portions with the liquid chamber portion and a plurality of liquid flow passages with each of these ejection energy acting portions. In this case, it is desirable that the ejection directions of the liquids from the ejection ports of the plurality of liquid flow paths communicating with any one ejection energy acting portion are set to overlap each other on the recording medium.

Further, as the ejection energy generation element and the liquid amount control means, an electrothermal conversion element for generating bubbles in the liquid by heat energy can be respectively adopted.

[Operation] According to the present invention, the amount of liquid in the liquid flow path is increased or decreased by the liquid amount control means.

Then, when the ejection energy generating element is driven by the ejection control means, a droplet having a volume corresponding to the amount of liquid in the liquid flow path at this time is ejected from the ejection port. That is, by controlling the drive timing of the ejection energy generating element by the ejection control unit according to the amount of liquid in the liquid flow path, a droplet having a size corresponding to the amount of liquid in the liquid flow path is formed. .

[Examples] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of the configuration of the liquid jet print head of the present invention. In the figure, 101 is a substrate, 110 to 113, 120 to 123 and 130 to 133 are electric / thermal conversion elements provided on the surface of the substrate 101, and 102 is a liquid chamber portion, a liquid flow path, a discharge port, etc. A pattern formed on the surface of the substrate 101 with a predetermined shape and depth, and 103 is a plate-shaped member further laminated thereon.

Reference numeral 104 is a liquid chamber portion that stores the recording liquid, and 105 is an ink supply port for introducing the recording liquid into the liquid chamber portion 104.

Although not shown in the figure, the electric / thermal conversion element group 110
Wiring for sending electric signals to ~ 113, 120 to 123, 130 to 133 is provided. Further, the pattern 102 can be formed by laminating a photosensitive resin film on the substrate 101 and then using a so-called photolithography process which is generally used. The plate member 103 can be arranged on the pattern 102 by adhesion or the like, and many materials such as metal, ceramics, plastic, and glass can be used as this material.

Electro-thermal conversion elements (hereinafter referred to as ejection energy generating elements) 110, 120 and 130 form flying droplets in association with one pixel and generate energy for ejecting the droplets. The discharge energy acting portions 119, 129, 139 are formed between the liquid flow path and the liquid chamber portion. Then, for each of these, three discharge ports, that is, orifices and three liquid flow paths leading to the orifices are arranged. That is, 211 to 213 and 311 to 313 are orifices and liquid flow paths corresponding to the discharge energy generating element 110, respectively, and 221-223 and 321 to 323 are orifices and liquid flows corresponding to the discharge energy generating element 120, respectively. The passages, and 231-233 and 331-333 are an orifice and a liquid flow path corresponding to the discharge energy generating element 130, respectively. The electric / thermal conversion elements 111 to 113, 121 to 123 and 131 to 133 as the liquid amount control means of the present invention correspond to the discharge energy generating elements 110, 120 and 130, respectively, and are provided for each liquid flow path. With respect to these element groups, bubbles are generated in the liquid flow path by the generated heat, but they are not directly used for forming flying droplets for recording, and the amount of the recording liquid in each liquid flow path is changed. Used to change.

In this example, one discharge energy generating element is made to correspond to three electrothermal conversion elements, liquid flow paths and orifices as one set (hereinafter, this one set is referred to as a "cell").
Called. ) By forming the pattern 102 by appropriately setting the direction of the liquid flow path (droplet discharge direction) for one cell, flying droplets discharged from three orifices included in the cell during recording. On the way to the recording medium or on the recording medium so that one pixel is formed to form one pixel.

Next, in the print head having such a configuration, a driving mode at the time of recording will be described by taking a cell including the protrusion pressure generating element 110 as a typical example.

2A to 2D show the ejection energy generating element 11
0 shows the drive waveforms of the electrothermal conversion elements 111 to 113, where the vertical axis is the voltage and the horizontal axis is the time axis.

FIG. 2A shows a drive waveform for obtaining a recording dot (pixel) having a large diameter, and the voltage E ₀ is applied to the ejection energy generating element 110 from time t ₁ to time t ₂ . As a result, the discharge energy generating element 110, which is an electricity / heat conversion element, is generated.
Generates heat and produces bubbles. By the pressure of this foam,
Droplets are ejected from the orifices 211, 212, and 213, respectively, and these are later combined into one droplet. In this example, driving was performed at t ₂ −t ₁ = 10 μsec and E ₀ = 20 V, and an average value of 10 samples was obtained. As a result, a dot diameter of about 283 μm was obtained.

Next, FIG. 2 (B) shows a drive waveform for obtaining a recording dot having a slightly larger diameter. Here, the ejection energy generating element 11
Before time t ₁ when the voltage is applied to ₀ , that is, time t ₀
Applies a voltage E ₂ to the electricity / heat conversion element 112. As a result, the electricity / heat conversion element 112 generates heat and generates bubbles,
The recording liquid is pushed out of the orifice 212. However, the magnitude of the voltage E ₂ is appropriately determined so that the bubbling energy of the electrothermal conversion element 112 is not ejected as a droplet of the recording liquid but is pushed out of the orifice 212. . As a result, the amount of recording liquid occupied in the channel 312 is reduced due to the bubbles generated. Then, the voltage E is applied to the ejection energy generating element 110 from time t ₁ to t _{2.
Apply 0} . The voltage E ₂ is applied until time t ₂ , that is, the time when the application of the voltage E ₀ to the ejection energy generating element 110 is ended.

As a result, droplets are discharged from the orifices 211, 212, and 213, respectively, and these droplets are combined after being discharged. However, the droplet discharged from the orifice 212 has a smaller diameter than the droplet discharged from the other two orifices 211 and 213 because the recording liquid amount in the flow path 312 is small.

In this embodiment, t ₂ −t ₁ = 10 μsec, E ₀ = 20 V, t ₁ −t ₀ = 30
Driving was performed with E ₂ = 10 V for μsec, and an average value was obtained in the same manner as above, and a dot diameter of about 250 μm was obtained.

Next, FIG. 2 (C) shows a drive waveform when a recording dot having a slightly smaller diameter is obtained.
Before time t ₁ when voltage is applied to 110, that is, time t _{1.
From 0} to the electric / thermal conversion elements 111 and 113, voltage E ₁
And E ₃ are applied. As a result, the electricity / heat conversion element 11
1 and 113 generate heat and generate bubbles, and the bubble causes the recording liquid to be pushed out of the orifices 211 and 213.
However, it is not possible to discharge the recording liquid as a droplet by appropriately setting the magnitudes of the voltages E ₁ and E ₃ , etc., and to obtain a foaming energy that pushes the recording liquid out of the orifices 211 and 213. To do. As a result, channels 311 and 313
The volume occupied by the recording diameter is reduced due to the bubbles formed. After that, the discharge energy generating element 110 is changed from t ₁ to t ₂
The voltage E ₀ is applied for up to. Also, the voltages E ₁ and E ₃
With respect to, the application is continued until time t ₂ .

As a result, droplets are ejected from the orifices 211 to 213, respectively, and these droplets are combined after being ejected. However, the droplets discharged from the orifices 211 and 213 are
Since the amount of recording liquid in 1 and 313 is small, it has a smaller diameter than the liquid droplets ejected from the other orifices 212.

In this embodiment, t ₂ −t ₁ = 10 μsec, E ₀ = 20 V, t ₁ −t ₀ = 30 Vs
Driving was performed with ec and E ₁ = E ₃ = 10 V, and an average value was obtained in the same manner as above, and a dot diameter of about 212 μm was obtained.

Next, FIG. 2 (D) shows a drive waveform for obtaining a recording dot having a small diameter. Here, the ejection energy generating element 11 is used.
Before time t ₁ when the voltage is applied to ₀ , that is, time t ₀
From the electric / thermal conversion elements 111, 112 and 113 respectively.
Apply E ₁ , E ₂ and E ₃ . As a result, the electrothermal conversion elements 111, 112 and 113 generate heat to generate bubbles, and the bubbles cause the recording liquid to be pushed out of the orifices 211, 212 and 213. However, the size of the voltages E _{1 to} E ₃ should be appropriately determined so that the recording liquid cannot be ejected as droplets, and the foaming energy should be sufficient to push the recording liquid out of the orifices 211, 212 and 213. To do. As a result, the amount of recording liquid occupied in the channels 311, 312 and 313 decreases due to the bubbles formed. Then, the voltage E ₀ is applied to the ejection energy generating element 110 from t ₁ to t ₂ , and the voltages E ₁ , E ₂ and E ₃ are also applied until time t ₂ .

As a result, droplets are respectively ejected from the orifices 211, 212 and 213, and these droplets are combined into one droplet after ejection, but the droplets ejected from the respective orifices 211, 212, 213 are the liquid flow paths 311, 312. Since the amount of recording liquid in and 313 is small, it has a smaller diameter accordingly.

In this embodiment, t ₂ −t ₁ = 10 μsec, E ₀ = 20 V, t ₁ −t ₀ = 30.
Driving was performed for μsec, E ₁ = E ₂ = E ₃ = 10V, and an average value was obtained in the same manner as above. A dot diameter of about 175 μm was obtained.

According to the above-described embodiment, the head having three orifices in one cell is subjected to drive control by appropriately selecting any one of the four types of drive waveforms by the discharge control means and performing drive control. In, it became possible to form droplets having four kinds of diameters.

That is, a bubble generating means as a liquid amount control means is provided between the discharge energy generating element and the orifice, one discharge energy generating element is associated with a plurality of orifices, and the plurality of orifices are extended in the discharge direction. By arranging them in a fan shape so as to concentrate on one point, and by varying the voltage applied to the bubble generating means and the ejection energy generating element to eject droplets of different diameters, different dimensions are achieved on the recording medium. Since the dots can be recorded, it is possible to easily and surely express a natural density change over a wide range from a dark portion to a light portion.

In this embodiment, the liquid jet print head including three orifices in one cell has been described.
It is also easy to make a printhead including a larger number of orifices in the cell, and in that case, it is possible to change the droplet diameter to a larger number.

Further, although the liquid jet print head in which the orifices are aligned over the entire width of the recording medium is described in FIG. 1, various forms can be adopted according to the liquid jet printing apparatus to which the present invention is applied. The orientation of each liquid flow path in each cell is such that flying droplets coalesce on the way to the recording medium or on the recording medium,
Of course, it can be appropriately determined in consideration of the arrangement direction of the print head.

Furthermore, in the above example, the case where the electrothermal conversion element is used as the ejection energy generating means for ejection or the like is described.
The present invention can be very easily and effectively applied to other things, for example, a liquid jet print head having an electromechanical conversion element as a discharge energy generating means.

[Effects of the Invention] As described above, according to the present invention, it is possible to realize a liquid jet print head and a printing apparatus capable of expressing fine gradations over a wide density range from high optical density to low optical density. Further, since the gradation expression is performed not by dividing one pixel but by making only one orifice correspond to one pixel and performing the gradation expression, the influence of manufacturing variations is eliminated. In addition, the reliability of the print head or the printing apparatus and the stability of droplet discharge are improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing one structural example of the liquid jet print head of the present invention, and FIGS. 2A to 2D are waveform diagrams showing various examples of drive waveforms for driving the recording head shown in FIG. Is. 110,120,130 …… Discharge energy generating element, 111,112,113,121,122,123,131,132,133 …… Electric / heat conversion element, 311,312,313,321,322,323,331,332,333 …… Liquid flow path, 211,212,213,221,222,223,231,232,233 …… Orifice (ejection port), 101 …… Substrate, 102 …… Photosensitive resin film pattern, 103… ... plate, 104 ... liquid flow chamber, 105 ... recording liquid supply port, 119, 129, 139 ... discharge energy acting part.

Claims (10)

[Claims] 1. A plurality of discharge ports for discharging a liquid, a plurality of liquid flow paths respectively communicating with these discharge ports, a liquid chamber section for holding a liquid supplied to these liquid flow paths, and this liquid chamber section. And a liquid flow path, and a discharge energy acting portion provided with a discharge energy generating element that acts on the liquid with energy for discharging the liquid from the discharge port, and is provided in the liquid flow path, respectively. And a liquid amount control means for changing the amount of the liquid in these liquid flow paths without directly ejecting the liquid from the ejection port. 2. A plurality of discharge energy acting portions communicate with the liquid chamber portion, and a plurality of liquid flow paths communicate with each of these discharge energy acting portions. The liquid jet print head according to item 1. 3. The discharge directions of liquids from respective discharge ports of a plurality of liquid flow paths communicating with one arbitrary discharge energy acting portion are set so as to overlap each other on a recording medium. The liquid jet print head according to claim 2. 4. The liquid jet print head according to claim 1, wherein the discharge energy generating element is an electrothermal converting element that generates bubbles in the liquid by heat energy. 5. A liquid jet print head according to claim 1 or 4, wherein the liquid amount control means is an electrothermal conversion element for generating bubbles in the liquid by thermal energy. . 6. A plurality of ejection ports for ejecting a liquid, a plurality of liquid flow paths respectively communicating with these ejection ports, a liquid chamber section for holding the liquid supplied to these liquid flow paths, and this liquid chamber section. And a liquid flow path, and a discharge energy acting portion provided with a discharge energy generating element that acts on the liquid to generate energy for discharging the liquid from the discharge port; And a liquid ejecting print head having a liquid amount control means for changing the amount of liquid in these liquid flow paths without directly ejecting the liquid from the ejection port, and the liquid amount control means Discharge control means for controlling the amount of the liquid discharged from the discharge port by driving the discharge energy generating element according to the changing amount of the liquid in the liquid flow path. Liquid jet pre Winding device. 7. A liquid chamber part is communicated with a plurality of discharge energy acting parts, and a plurality of liquid flow paths are communicated with each of these discharge energy acting parts. The liquid jet printing apparatus according to item 6. 8. A discharge direction of liquid from each discharge port of a plurality of liquid flow paths communicating with any one discharge energy acting portion is set so as to overlap each other on a recording medium. The liquid jet printing apparatus according to claim 7. 9. The liquid jet printing apparatus according to claim 6, wherein the discharge energy generating element is an electrothermal converting element that generates bubbles in the liquid by thermal energy. 10. A liquid jet printing apparatus according to claim 6 or 9, wherein the liquid amount control means is an electrothermal conversion element for generating bubbles in the liquid by thermal energy. .