JPH04276446A - Inspecting device for ink jet record head - Google Patents

Abstract

PURPOSE:To make it possible to inspect bubbling phenomenon and discharging phenomenon synchronously and in real time in a record head wherein ink is heated to bubble for discharging the ink. CONSTITUTION:There are provided two sets of measuring systems I and II respectively comprising objective lenses 9, 10 and TV cameras 11, 12 in positions facing each other in such a manner interposing a bubbling part and ink discharging part of a record head 100. An image signal processing circuit 30 is provided for reversing an image signal to be obtained from the camera 11 and for synthesizing the reversed image signal and an image signal to be obtained from the camera 12, so as to display the synthesized image on a monitor 21.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording head inspection device, and more particularly, to an inkjet recording head that ejects ink by applying heat to the ink and using the force of the ink to foam. The present invention relates to an inspection device.

0002

[Background Art] Among the recording methods of inkjet recording devices that record characters and images, compared to methods that use piezoelectric elements or methods that use electrostatic force, the force that heats the ink and causes it to foam at this time is A method that uses ink to eject ink is attracting attention. This is because it has the advantage of being easy to manufacture a large number of ink ejection ports and at a high density.

FIG. 4 shows an example of the configuration of the substrate and the top plate. On the silicon substrate 1, there is a heating element (discharge heater) 115 as an energy generating element, and an A for supplying electric power to the heating element (discharge heater) 115.
The wiring 116 such as 1 is formed by a film forming technique. A recording ink liquid path 12 is connected to this substrate 1.
The main part of the recording head is constructed by arranging a top plate 3 provided with a partition wall for forming a liquid chamber 5 and a groove for forming a common liquid chamber 123 for each liquid path.

FIG. 5 shows an example of a recording head constructed using such a structure, and the recording head designated by reference numeral 100 is supported by the above structure and a printed wiring board 136 on which ejection heater driving elements and the like are arranged. placed on the plate 132;
A board 1 having a discharge heater 115 and a printed wiring board 1
36 is electrically connected by a bonding wire 137. Further, an ink supply pipe 135 from an ink supply source (not shown) is connected to the ink supply port 124.
will be placed. Furthermore, in front of the liquid path 132, an ejection port forming member 134 is arranged in which an ink ejection port 138 is formed in advance or is formed later by laser processing or the like.

In the above configuration, ink is supplied to the common liquid chamber 123 from the supply port 124 provided in the top plate 3, and is guided into each liquid path 125 from here. Then, when the ejection heater 115 generates heat due to energization, the ink filled in the flow path 125 bubbles, and ink droplets are ejected from the ejection port 138.

However, at present, most inkjet recording heads are not sold immediately after production, but only those that have passed several inspection steps after production are put on the market. A recording head (hereinafter referred to as
A device using this method is simply referred to as a recording head) is no exception to this.

[0007] Therefore, it can be said that improving the inspection equipment on the production line is an essential condition for increasing the efficiency of the production line and for reducing the cost of recording heads.

[0008] Furthermore, in order to obtain a recording head with higher performance, it is necessary to advance the analysis of the bubbling phenomenon and ink ejection phenomenon of the recording head, and improving the inspection equipment is an essential condition for this as well. .

Conventionally, in the inspection process of an inkjet recording head, the recording quality was checked by actually performing a recording operation with the recording head on a recording medium such as paper. However, the cost of the recording medium in this checking step is not small, and this has been a factor in increasing the cost of the recording head.

[0010] Therefore, as a method that does not use a recording medium, it has been devised to inspect the bubbling phenomenon itself and the ink ejection phenomenon of the recording head itself.

FIG. 6 shows an apparatus for inspecting such an ink ejection phenomenon.

Here, the recording head 100 (shown in a simplified manner in the figure) is driven by a head driving section 2. As shown in FIG. When driven, ink droplets 4 are ejected from the ejection openings 138 of the recording head 100 in the right direction in the figure. The ejected ink droplets 2 are eventually collected by the ink collection section 5.

The ink droplets 2 are ejected by the ejection heater 115 in the liquid path which generates heat as described above, and by the bubbling energy generated when air bubbles are generated in the heated ink. This bubbling phenomenon is converted into an electrical signal by a television camera (TV camera) 20 through an optical system via an objective lens 6, and is displayed on a TV monitor 21. The tip of the recording head 1 and the ejected ink droplets 2 are visible on the TV monitor. When the ejection heater 115 is energized with an appropriate pulse width and voltage value to generate heat, normal ink ejection is normally performed. In abnormal cases, ejected ink droplets may fly in unexpected directions or fly at a slower speed than in normal cases. Also, ink may adhere to the tip of the recording head. Furthermore, there are cases where no ink is ejected at all. Furthermore, even if things appear to be normal at first glance, abnormalities may occur after a while. The applicant strictly controls the manufacturing process, and although these abnormalities appear as extremely rare phenomena, the applicant uses an ink ejection phenomenon inspection device to check for these abnormal phenomena that still occur. This is the purpose of the checking process.

However, in order to completely eliminate these few abnormalities, the process of inspecting the ink ejection phenomenon alone is not sufficient. Therefore, in order to check the inside of the nozzle of the recording head, the following bubbling phenomenon inspection is performed.

FIG. 7 shows an apparatus for testing the foaming phenomenon. The recording head 100 is driven by the head driving section 2 as described above, and the ejection ports 138 of the recording head 100 are driven accordingly.
Ink droplets 4 are ejected rightward in the figure. Then, the ejected ink droplets 4 are eventually collected by the ink collection section 5. This recording head has a top plate 3 made of an optically transparent material, and has a structure in which the bubbling phenomenon can be observed from above.

The bubbling phenomenon during ink ejection is caused by the objective lens 6.
It is converted into an electrical signal by the TV camera 20 via an optical system having a half mirror 13 and a half mirror 13, and is displayed on the TV monitor 21.
It is projected on the screen.

The discharge heater 115 can be seen in the liquid path 125 on the TV monitor screen. Immediately after ejecting ink droplets, the ink in the liquid path 125 has a concave meniscus formed by the outside air and the ink.

[0018] In this step, cases where abnormal bubbling occurs during ink ejection are eliminated. In normal cases, the generation of bubbles without distortion is observed. On the other hand, in abnormal cases, the generation of distorted bubbles is observed.

However, the above-mentioned bubbling phenomenon and ink ejection phenomenon were tested independently and could not be tested at the same time. The reason is as follows.

(a) When attempting to observe both the bubbling part and the ink ejecting part with one measurement system, the observation positions of the bubbling part and the ink ejecting part of the recording head may be slightly shifted (about several tens of microns). Therefore, it is not possible to increase the magnification, making detailed inspection of both difficult.

(b) When attempting to observe both the foaming part and the ink ejecting part using two measurement systems, there is a spatial conflict with the desire to place the two measurement systems at almost the same position. This makes setting up the device difficult.

[0022] Therefore, if you try to perform the above two tests, you will have to set up the test twice.
This takes a lot of time and results in an increase in the cost of the recording head.

SUMMARY OF THE INVENTION It is an object of the present invention to solve these problems and to make it possible to simultaneously inspect both the bubbling phenomenon and the ink ejection phenomenon of a recording head, and moreover, to be able to inspect them in real time.

[0024]

[Means for Solving the Problems] To this end, the present invention provides
In an inkjet recording head inspection device that has a heating element that generates thermal energy, uses the thermal energy to cause foaming in ink, and discharges ink based on the foaming, the thermal energy acts on the ink. a first optical system provided to observe the part, and a second optical system provided to observe the part from which the ink is ejected, the first optical system and the second optical system; The system is characterized in that the respective optical axes are substantially parallel and are disposed facing each other so as to sandwich the inkjet recording head.

[0025] Here, the first optical system has a first objective lens and a first television camera, and the second optical system has a second objective lens and a second television camera. It can be assumed that the

[0026] Also, the first optical system obtained from the first optical system
or a second image obtained from the second optical system, and means for mirror-inverting one of the images and combining the inverted image and the other image into a single image. and a means for providing the synthesized image for observation.

[0027]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an apparatus for simultaneously observing the bubbling portion and ink ejecting portion of a recording head, which is an embodiment of the recording head inspection apparatus of the present invention.

In the apparatus of this example, two measurement systems are disposed facing each other so as to sandwich a recording head 100 (for example, the one shown in FIGS. 4 and 5, which is shown in a simplified manner in this figure). Ru. The first measurement system I includes an objective lens (I) 9 and a T
It is composed of a V camera (I) 11. Further, the second measurement system II includes an objective lens (II) 10 and a TV camera (II).
It consists of 12. A light emitting source 8 is provided in the first measurement system via a half mirror 13. Further, although not necessarily required, the second measurement system is provided with a zoom system 14 that can change the optical amplification magnification, thereby making it possible to make minute magnification adjustments.

[0030] Then, the first
A second measurement system I is used for observing the ink ejection portion. The top plate 3 placed on the right side of the recording head 100 in FIG. 1, that is, on the side of the first measurement system, is optically transparent near the foamed portion, so that the inside of the recording head can be seen. ing. By observing this part, the foaming phenomenon is examined. On the other hand, the left side of the recording head 100, that is, the center of the optical axis on the second measurement system side, is set several tens of microns lower in the figure than the central axis of the optical axis on the first measurement system side. Observe the ink ejection phenomenon. The optical axes of the two measurement systems are set substantially parallel.

The ejection of ink from the recording head 100 is controlled by the head driving section 2. In synchronization with the timing of this ink ejection, the light emitting source control circuit 7 causes the strobe type light emitting source 8 to emit light. The emitted light illuminates the vicinity of the tip of the recording head via the half mirror 13 and the objective lens 9.

By the way, TV obtained from observation of the foamed part
The image is a video signal I, and is similar to the TV monitor screen in FIG. Furthermore, the TV image obtained from observation of the ink ejection unit is a video signal II, and is similar to the screen of the TV monitor in FIG.

The video signal processing circuit 30 synchronizes the two TV cameras using the synchronization signal I and the synchronization signal II, and also synchronizes the two TV cameras I and II with the signal from the head drive unit 2. Video signal I and video signal II, respectively.
It has a function to output. Furthermore, the video signal processing circuit 30 also has a function of combining the video signal I and the video signal II and outputting the composite to the TV monitor 21.

FIG. 2 is a block diagram showing an example of a schematic configuration of a video signal synthesis circuit, and the portion within the dotted line indicates the video signal synthesis circuit. Further, arrows in the figure indicate the flow of signals.

[0035] Normally, the head drive unit 2 has a power of 100 to 30 KH.
Drive the recording head with z. On the other hand, the video signal of the TV camera is NTS, which is commonly used here.
Since a C-type camera was used, the vertical synchronization signal was approximately 30 Hz in units of frames. Therefore, the synchronization signal generating section 31 generates a synchronization signal for the TV camera at a timing closest to 30 Hz synchronized with the ink ejection signal from the head driving section 2 and later than 30 Hz. In this example, the two TV cameras 11 and 12 have external synchronization input.

The video signal I obtained from the TV camera (I) 11 is input to a horizontal/vertical synchronizing signal separating section 33 and a horizontal image inverting section 35. Horizontal/vertical synchronization signal separation section 33
detects a horizontal synchronization signal and a vertical synchronization signal from the video signal I. Among these, the horizontal synchronization signal is sent to the counter 37,
The horizontal image inversion section 35 receives the image data.

The horizontal image inversion section 35 has two line memories inside, and these two line memories are
FILO (first in last)
This is a (out) type register. Then, the video signal I
The horizontal video signals are alternately input to two line memories and output. That is, when one of them performs an input operation, the other performs an output operation. Since the FILO register is used, the video signal I is left and right inverted, that is, mirror inverted, and output as the video signal I'. As a result, the left and right relationships between both video signals are aligned, and they are correctly superimposed. Note that although a time delay of one horizontal scanning line occurs here, this does not pose a problem because of the relationship between the operating speed of the recording head and the horizontal scanning time.

Video signal I output from the horizontal image inversion section 35
', the count signal output from the counter 37, and the video signal II from the TV camera II are input to the video signal switching section 39, and the video signal switching section 39 switches between the video signal I' and the video signal II. timely switching the video signal I.
It is output to the TV monitor 21 as II. In other words, images are synthesized using this part. Video signal III is
The signal from the counter 37 until the number of horizontal synchronizing signals becomes approximately half the number of horizontal scanning lines in the field signal unit of the video signal I is defined as a video signal I', and thereafter is defined as a video signal II.

By the above-described operations, an image obtained by photographing the bubbling portion and mirror-reversed is displayed on the upper part of the TV monitor 21, and an image obtained by photographing the ink ejection portion is displayed on the lower part of the TV monitor 21.

[0040] In the above embodiment, a method was shown in which the upper and lower parts of the TV monitor are combined, but this may also be done by combining the left and right parts of the TV monitor. To achieve this, the horizontal image inversion section is replaced with a vertical inversion section that has a field memory or frame memory, and the counter section and video signal switching section are slightly modified so that the horizontal scanning signal is switched at the center of scanning. This is achieved by doing.

[0041] Furthermore, although the above has shown a method of inverting and compositing TV signals captured by a TV camera, the present invention is not limited to this, and it is also possible to perform inversion and compositing optically. A similar effect can be obtained.

FIG. 3 shows an example of an inkjet printer constructed using the recording head manufactured and inspected as described above. Here, 214 is a head cartridge,
The recording head described above and an ink tank serving as an ink supply source are integrated. This head cartridge 21
4 is fixed on the carriage 215 by a holding member 241, and these can be reciprocated in the longitudinal direction along the shaft 221. The ink ejected from the print head reaches a print medium 218 whose print surface is regulated by a platen 219 at a slight distance from the print head, and forms an image on the print medium 218.

An ejection signal corresponding to image data is supplied to the printed wiring board 6 or the recording head from an appropriate data supply source via a cable 216 and a terminal connected thereto. One or more head cartridges 214 (two in the figure) can be provided depending on the color of ink used and the like.

In FIG. 3, 217 is a carriage motor for causing the carriage 215 to scan along the shaft 221, and 222 is a wire for transmitting the driving force of the motor 217 to the carriage 215. Further, 220 is a feed motor coupled to the platen roller 219 for conveying the recording medium 218.

(Others) The present invention is particularly applicable to inkjet recording systems, which include a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as the energy used to eject ink. This provides excellent effects in recording heads and recording apparatuses that use the thermal energy to cause a change in the state of ink. This is because such a system can achieve higher recording density and higher definition.

For its typical configuration and principle, see, for example, US Pat. Nos. 4,723,129 and 4,740.
Preferably, it is carried out using the basic principles disclosed in the '796 specification. This method is the so-called on-demand type.
It is applicable to both continuous types, but in particular, in the case of on-demand type, it is applicable to the electrothermal converter placed corresponding to the sheet holding the liquid (ink) or the liquid path. , by applying at least one drive signal that corresponds to recorded information and provides a rapid temperature rise exceeding nucleate boiling, the electrothermal transducer generates thermal energy to produce film boiling on the thermally active surface of the recording head. liquid (ink) that corresponds one-to-one to this drive signal.
This is effective because it can form air bubbles inside. The growth and contraction of the bubble causes liquid (ink) to be ejected through the ejection opening to form at least one droplet. It is more preferable to use this drive signal in a pulse form, since the growth and contraction of bubbles can be carried out immediately and appropriately, making it possible to eject liquid (ink) with particularly excellent responsiveness. This pulse-shaped drive signal is described in US Pat. No. 4,463,359 and US Pat.
345262 are suitable. Furthermore, if the conditions described in US Pat. No. 4,313,124 concerning the invention regarding the temperature increase rate of the heat acting surface are adopted, even more excellent recording can be performed.

In addition to the configuration of the recording head, which is a combination of ejection ports, liquid paths, and electrothermal converters (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, U.S. Pat. No. 4,558,333 and U.S. Pat. No. 44 disclose a configuration in which a heat acting part is arranged in a bending region.
A configuration using the specification of No. 59600 is also included in the present invention. In addition, JP-A-59-123670 discloses a configuration in which a common slit is used as a discharge part for a plurality of electrothermal converters, and a hole that absorbs pressure waves of thermal energy is disclosed. The effects of the present invention are also effective even with a configuration based on Japanese Patent Application Laid-open No. 138461/1985 which discloses a configuration corresponding to the discharge section. That is, regardless of the form of the recording head, according to the present invention, recording can be performed reliably and efficiently.

Furthermore, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium that can be recorded by a recording apparatus. Such a recording head may have either a configuration in which the length is satisfied by a combination of a plurality of recording heads, or a configuration as a single recording head formed integrally.

In addition, even in the case of a serial type as in the above example, the recording head is fixed to the main body of the apparatus, or by being attached to the main body of the apparatus, electrical connection with the main body of the apparatus and ink flow from the main body of the apparatus are possible. The present invention is also effective when using a replaceable chip-type recording head that can be supplied with ink or a cartridge-type recording head in which an ink tank is integrally provided in the recording head itself.

Furthermore, it is preferable to add a recovery means for the recording head, a preliminary auxiliary means, etc., which are provided as a configuration of the recording apparatus, to the present invention because the effects of the present invention can be further stabilized. . Specifically, these include capping means for the recording head, cleaning means, pressure or suction means, preheating means using an electrothermal transducer or another heating element, or a combination thereof; It is also effective to perform a preliminary ejection mode in which ejection is performed separately from printing in order to perform stable printing.

Regarding the type and number of recording heads to be mounted, for example, in addition to one type that corresponds to a single color ink, there are also types and number of recording heads installed to correspond to a plurality of inks of different recording colors and densities. A plurality of them may be provided. That is, for example, the recording mode of the recording apparatus is not limited to a recording mode for only a mainstream color such as black, but may also be a recording mode in which the recording head is configured integrally or in a combination of multiple colors, The present invention is also extremely effective for devices equipped with at least one full color by color mixture.

In addition, in the embodiments of the present invention described above, the ink is described as a liquid, but ink that solidifies at room temperature or lower, softens or liquefies at room temperature, or inkjet method. In general, the temperature of the ink itself is adjusted within the range of 30°C to 70°C to keep the viscosity of the ink within the stable ejection range. Any eggplant is fine. In addition, the temperature increase caused by thermal energy can be actively prevented by using the energy to change the state of the ink from a solid state to a liquid state, or ink that solidifies when left standing is used to prevent ink evaporation. In any case, the ink is liquefied by applying thermal energy in accordance with the recording signal, and the liquid ink is ejected, or the ink has already begun to solidify by the time it reaches the recording medium. The present invention is also applicable when using ink that is liquefied only by energy. The ink used in such cases is disclosed in Japanese Patent Application Laid-Open No. 54-56847 or Japanese Patent Application Laid-Open No. 60-1989.
As described in Japanese Patent No. 71260, the material may be held in a liquid or solid state in a porous sheet recess or through-hole and face an electrothermal converter. In the present invention, the most effective method for each of the above-mentioned inks is to implement the above-mentioned film boiling method.

In addition, the inkjet recording apparatus of the present invention can be used as an image output terminal for information processing equipment such as a computer, a copying machine combined with a reader, or a facsimile machine having a transmitting and receiving function. It may also take a form.

[0054]

[Effects of the Invention] As explained above, according to the present invention,
Both the bubbling phenomenon and the ink ejection phenomenon of the recording head can be observed simultaneously and in real time. As a result, both the foaming inspection process and the ink ejection inspection process can be performed at the same time during mass production of recording heads, making it possible to shorten the inspection process and lower production costs. Moreover, since it is possible to inspect the recording head without using a recording medium, the cost of recording media can be reduced, making it possible to further reduce production costs and increasing the amount of recording media used for inspection. This also eliminates the environmental inconvenience caused by waste being disposed of.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an apparatus for simultaneously observing a foaming part and an ink discharge part of an inkjet recording head according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic configuration example of the video signal synthesis circuit.

FIG. 3 is a perspective view illustrating a schematic configuration example of an inkjet recording apparatus that can be configured using the recording head tested in the example.

FIG. 4 is a perspective view showing the structure of a substrate and a top plate in a recording head that can be inspected by the present invention.

FIG. 5 is a schematic side view showing an example of the recording head.

FIG. 6 is a schematic diagram showing an ink ejection phenomenon inspection device that is the background of the present invention.

FIG. 7 is a schematic diagram showing an inspection device for a foaming phenomenon.

[Explanation of symbols]

1 Head board 2 Head drive section 3 Top plate 4 Ink droplets 5 Ink collection section 6 Objective lens 7 Light emitting source control circuit 8 Light source 9 Objective lens I 10 Objective lens II 11 TV camera I 12 TV camera II 13 Half mirror 14 Zoom system 20 TV camera 30 Video signal processing circuit

Claims (4)

[Claims] Claim 1: A heating element that generates thermal energy; the thermal energy is used to cause foaming in the ink;
In an inspection device for an inkjet recording head that ejects ink based on the foaming, a first optical system is provided to observe a portion where the thermal energy acts on the ink, and a portion where the ink is ejected is observed. a second optical system provided for the purpose of the present invention, and the optical axes of the first optical system and the second optical system are substantially parallel to each other;
An inkjet recording head inspection apparatus, characterized in that the inkjet recording head is disposed facing each other so as to sandwich the inkjet recording head therebetween. 2. The first optical system includes a first objective lens and a first television camera, and the second optical system includes a second objective lens and a second television camera. 2. The inkjet recording head inspection device according to claim 1, further comprising: 3. Mirror-inverting either the first image obtained from the first optical system or the second image obtained from the second optical system, and inverting the inverted image. 3. Inspection of an inkjet recording head according to claim 1 or 2, further comprising means for synthesizing the image and the other image into one image, and means for providing the synthesized image for observation. Device. 4. Inspection of an inkjet recording head according to claim 1, wherein the heating element is an electrothermal conversion element that generates thermal energy that causes film boiling in the ink. Device.