1. Field of the Invention
The present invention relates to an ink jet recording apparatus which can control a dew point of air in the apparatus.
2. Description of the Related Art
An ink jet recording apparatus performs printing by ejecting ink of tens pico liter through many nozzle holes each having tens μm diameter onto a recording medium such as paper. An ink ejecting part comprises a nozzle plate in which many nozzle holes are provided, a pressure chamber communicating with each nozzle hole, a common liquid chamber for supplying the ink to the pressure chambers, and a unit that generates pressure in the pressure chamber.
There are two types of apparatuses that generate pressure in the pressure chamber. One of them is a type in which air bubbles are generated in the pressure chamber by Joule heat, and the other is a piezoelectric type in which the pressure chamber is deformed by a piezoelectric element. In the piezoelectric type, since the amount of ink to be ejected and ink ejection speed are more easily controlled than in the type that employs air bubbles, it is expected that exacter printing is possible.
In the piezoelectric type, in order to realize fine printing, it is necessary to increase the in-plane density of the nozzle holes, the pressure chamber, and the piezoelectric element set on the pressure chamber. Therefore, it is necessary to reduce the area of the piezoelectric element. In order to form the piezoelectric element having the predetermined area, a method is used, which comprises steps of: firstly, forming a piezoelectric film on the whole of a base material; and thereafter, forming a resist pattern by photolithography to remove the piezoelectric film of no-resist portion by etching. By this method, it is impossible to make the area of the piezoelectric element smaller than the thickness of the piezoelectric film. Therefore, in order to form a piezoelectric element having a smaller area, it is necessary to use a thinner piezoelectric film.
For the piezoelectric element used in the ink jet recording apparatus, it is necessary to have a high piezoelectric constant. As its material, lead titanate oxide (PT); lead titanate zirconium oxide (PZT); and magnesium additive, manganese additive, cobalt additive, iron additive, nickel additive, niobium additive, scandium additive, tantalum additive, and bismuth additive to PZT have been generally known. In order to generate the pressure in the pressure chamber, it is generally necessary to apply an electric field of several KV/cm or more to the piezoelectric element thereby to give strain to the element.
It has been known that many defects such as minute cracks and pores exist in the piezoelectric element. Under existence of moisture, generally, in a case where a high electric filed is applied to the piezoelectric element that includes lead, large electric current flows to the lead compound at the defect part and its surroundings, and their portions are broken by the Joule heat, so that a large hole can be formed.
In order to prevent formation of the hole due to the Joule heat, for example, two methods are known. A first method is to thicken the piezoelectric element. In a case where the piezoelectric element is thin, a large defect passing through the element is produced by a break, so that such disadvantage is produced that an upper electrode and a lower electrode can short electrically, or the displacement property changes. On the contrary, in a case where the element has the thickness of some degree, even if the defect breaks, such a hole passing through the element cannot be made, so that a large influence is given on the piezoelectric property. A second method is to seal the piezoelectric element and a desiccant in a container in order to remove the moisture. For example, this method is proposed in JP-A-4-349675.
However, according to the first method, in the case where the thickness of the piezoelectric element is made large, the break is not caused even under a high humidity. However, a high voltage must be applied in order to make the displacement large, which increases power consumption. Further, if the film thickness is large, it becomes difficult to increase the in-plane density of the element.
According to the second method, if the piezoelectric element is sealed, the sealing work must be performed in a low humidity environment where little moisture is present, which requires much labor in the case of mass production in a factory and increases the manufacturing cost. Further, since the piezoelectric element is covered with a box in order to seal the element, entry of moisture from a contact surface between the box and the element must be strictly prevented, which requires much labor and similarly increases the manufacturing cost.
Therefore, an object of the invention is to provide an ink jet recording apparatus which can achieve reduction of the film thickness of the piezoelectric element, and can readily prevent the element from breaking due to the voltage application to the piezoelectric element.
In order to solve these problems, an ink jet recording apparatus of the invention, which performs printing by ink ejection, comprises a pressure chamber in which ink liquid is filled; a nozzle hole which is formed, communicating with the pressure chamber; a piezoelectric element which is formed on the pressure chamber, and deforms the pressure chamber by mechanical expansion and contraction, whereby pressure is generated in the pressure chamber, and ink is ejected from the nozzle hole; and a dew point control unit which keeps a dew point in an atmosphere of the piezoelectric element and the vicinity of the piezoelectric element at a lower value than a dew point in an environment where the ink jet recording apparatus is set.
Accordingly, since the dew point in the vicinity of the piezoelectric element is lowered by the dry gas, the deterioration of the piezoelectric element caused by the voltage application can be prevented, so that reduction of the film thickness of the piezoelectric element can be achieved, and the element breaking due to the voltage application to the piezoelectric element can be readily prevented.
Embodiments of the invention will be described below with reference to
An ink jet recording apparatus 140 shown in
In
Next, the structure of the ink jet head 141 will be described with reference to
To the pressure chamber plate 112, a common liquid chamber plate 118 is bonded, in which a common liquid chamber 114 that supplies the ink liquid into the pressure chambers 111 is arranged in the ink liquid supply direction, an ink flow inlet 115 that communicates the common liquid chamber 114 and the pressure chamber 111, a communication hole 117 that communicates a nozzle hole 116 and the pressure chamber 111. To the common liquid chamber plate 118, a nozzle plate 119 is bonded, in which the nozzle hole 116 that communicates with the pressure chamber 111 and ejects an ink droplet is formed.
On the pressure chamber 111, the piezoelectric element 113, and an upper individual electrode 120 corresponding to the pressure chamber 111 and a lower common electrode 121 which apply a voltage to the piezoelectric element 113 thereby to give mechanical displacement (contraction and expansion) to the piezoelectric element 113, are formed; and a vibration plate 122 is formed between the common electrode 121 and the pressure chamber plate 112.
The piezoelectric element 113 is subjected to displacement by the piezoelectric effect due to the voltage applied to the common electrode 121 and the individual electrode 120 corresponding to the pressure chamber 111, and the vibration plate 122 that vibrates following this displacement changes the volume of the pressure chamber 111, so that the ink liquid in the pressure chamber 111 is ejected from the nozzle hole 116.
In this embodiment, the common electrode 121 and the vibration plate 122 are formed separately. However, they may be formed integrally.
In the ink jet head, with the above structure as one unit, the units of the same structure are periodically arranged in the vertical direction to a paper surface of
As shown in
The dew point control unit 123, by introducing gas of a low humidity (for example, dew point −60° C.), for example, dry air, nitrogen gas, or argon gas to the piezoelectric element 113 and in the vicinity of the piezoelectric element 113, lowers the dew point. Namely, the dew point control unit 123 passes the gas from a compressor 123a to an air drier 123b thereby to remove moisture, and supplies this gas through an inlet 124a of a case 124 to the piezoelectric element 113 and the vicinity of the piezoelectric element 113. The dry gas introduced into the case 124 is discharged from an outlet 124b formed in the case 124 to the outside. However, without providing the case 124, the dry gas may be blown from the piezoelectric element 113.
Further, as the air drier 123b, a freeze type air drier which lowers the temperature thereby to remove the moisture in the gas; a filter type air drier which lets the gas pass through a filter thereby to remove the moisture in the gas; and an absorption type air drier which lets the gas pass through absorbent such as silica gel thereby to remove the moisture in the gas can be used.
Further, as the dew point control unit, as shown in
Further, as the dew point control unit for supplying the dry gas, the piping for dry gas installed in a building, such as a plant, can be used.
More, specifically, as shown in
Further, in a case where there are many ink jet heads, as shown in
The inventor, in order to seize characteristics of the piezoelectric element 113 in a dry atmosphere, has manufactured a sample element having the following structure and evaluated it.
Namely, on a silicon substrate having a diameter of 3 inch and a thickness of 0.5 mm, platinum of 100 nm has been evaporated as the lower electrode by sputtering, sequentially PbZr0.5Ti0.5O3 (hereinafter referred to as “PZT”) of 3 μm has been evaporated as the piezoelectric element, and sequentially platinum of 100 nm has been evaporated as the upper electrode. Thereafter, the silicon substrate has been cut into 20 mm by 20 mm, and platinum of the area of 5 mm by 7.5 mm has been evaporated on the PZT by use of a metal mask.
Further, as the air drier, a super drier unit SU3015B7 by CKD Company has been used. This air drier comprises an air filer for removing dust in air, an oil mist filter for removing an oil component in air, a drier body for removing moisture in air, and a regulator for regulating pressure. The drier body is composed of many hollow fibers made of special resin, and the compressed air passes through this hollow fiber. The resin constituting the hollow fiber has such a property that only moisture is caused to selectively pass through the outside of the hollow fiber, and air including the moisture passes through the hollow fiber, whereby the moisture in air is removed. In the embodiment, in order to generate dry air, compression air of about 0.5 Mpa is introduced from the air filter side by the compressor 23a. The introduced compression air passes through the air filter and the oil mist filter, whereby the dust and the oil component are removed. Further, the compression air passes through the drier body, whereby the moisture is removed, and the dry air comes out from the outlet.
As an evaluation system, the aforementioned sample has been set in an acryl-made case having a size of 40 mm by 40 mm by 50 mm so that a voltage can be applied between the upper electrode and the lower electrode. Further, this system is constituted so that the dry air generated by the air drier 123b can be introduced into the case. To the air drier 123b, the compression air of 0.5 Mpa has been introduced by use of the compressor 123a, and a flow regulating valve has been regulated so as to introduce the dry air into the case at a flow rate of 2 L/min. A dew point in the case when the dry air has been introduced has been −50° C. The case has been set in a constant humidity and temperature bath.
The reason why an introduction speed of the dry air is set to 2 L/min is as follows. Namely, in the embodiment, the generation of the dry air uses the dry air system, and the air including the moisture passes through the hollow fiber in the dry air system thereby to remove the moisture and generate the dry air. Since the amount of moisture that can be removed by the hollow fiber per time is limited, in case that the introduction flow rate is over the predetermined level, the dry degree of the dry air lowers and the dew point increases. In the dry air system of this embodiment, in case that the introduction flow rate is in a range of 2 to 10 L/min, the dew point becomes −50° C.; and in case that the flow rate is over this value, the dew point increases. Therefore, the dry air is caused to flow at the flow rate of 2 L/min. Since the maximum flow rate by which the dry air can flow is determined by specification of the system, the introduction speed is not limited to 2 L/min but the dry air may be introduced at the flow rate by which the dew point of the generated dry air becomes −50° C. Further, from the experiments by the inventor, it has been proved that when the flow rate of the dry air introduced into the case is 10 mL/min or more per volume of one cubic cm, the dew point in the case 124 is kept at −50° C. or less.
Further, the pressure inside the case 124 when the dry air has been introduced is generally higher than the outside air pressure, which is one air pressure or more. However, in accordance with the altitude of a place where the apparatus is used and the weather, the pressure inside the case can become lower than the outside air pressure.
Further, in a case where the inside of the case 124 is sealed, the internal pressure increases due to the introduced dry air, and the moisture attached onto the actuator cannot be exhausted to the outside of the case 124. Therefore, it is necessary to provide an outlet 124b for the case 124 like this embodiment.
Next, evaluation items of the sample will be described.
A first evaluation item is a characteristic evaluation of PZT under an atmosphere where the temperature is 60° C. and the humidity is 80%. The temperature and the humidity in the constant temperature and humidity bath have been set at 60° C. and 80%. In a state where the dry air is introduced into the case, direct current of 35V has been applied for sixteen hours between the upper electrode of the sample and the lower electrode so that polarity of the lower electrode becomes positive, and thereafter, a surface of the sample has been observed with a microscope. Next, using the same sample, in a state where the dry air is not introduced, the direct current of 35V has been applied for three hours, and thereafter, the surface of the sample has been observed with the microscope.
A second evaluation item is a characteristic evaluation of PZT under an atmosphere where the temperature is 25° C. and the humidity is 50%. The temperature and the humidity in the constant temperature and humidity bath have been set at 25° C. and 50%. In a state where the dry air is introduced into the case, the direct current of 35V has been applied for 150 hours between the upper electrode of the sample and the lower electrode so that polarity of the lower electrode becomes positive, and thereafter, the surface of the sample has been observed with a microscope. Next, using the same sample, in a state where the dry air is not introduced, the direct current of 35V has been applied for one hour, and thereafter, the surface of the sample has been observed with the microscope.
Results on the above evaluation items will be described.
Regarding the first evaluation item, a microscopic photograph after the test is shown in
Regarding the second evaluation item, as shown in
As described above, by introduction of the dry air, even in case that the voltage has been applied to the PZT, any break has not occurred. Further, it is surmised that: a reason why the number of the black spots in the first evaluation item is larger than that in the second evaluation item is that since the temperature of air in the constant temperature bath in the first evaluation item is higher, the absolute amount of the included moisture is larger than that in the second evaluation item, so that the break of the PZT has advanced more.
Next, similarly to the case of the second evaluation item, PZT incorporated into an ink jet head has been evaluated (refer to
The piezoelectric element 113 is basically the same as the PZT used in the first and second evaluations, and it is 3 μm in thickness and 100 μm by 1200 μm in area. The vibration plate 122 is 3 μm in thickness.
The ink jet head has been set in an acryl-made case so that the dry air generated by the air drier can be introduced into the case, and the case has been set in a constant temperature and humidity bath in which the temperature is 25° C. and the humidity is 50%. In the state where the dry air is introduced, the voltage has been applied so that the polarity of the common electrode becomes positive and that of the individual electrode becomes negative. Further, also in the state where the dry air is not introduced, the voltage has been similarly applied. An evaluation result is shown in
As described above, also in the PZT used for the actuator, by introducing the dry gas such as dry air, no break occurred in the PZT at all even in the case where the voltage is applied.
In the embodiment, since the piezoelectric element is manufactured by sputtering, a thin piezoelectric element that is good in crystal orientation can be obtained with good reproducibility. Therefore, also in case that the voltage applied to the piezoelectric element is small, the great displacement yields. Therefore, the ink can be ejected at a low voltage, so that consumed power of the printer can be reduced. Further, though the area of the used piezoelectric element is 100 μm by 1200 μm, the area can be reduced up to about 3 μm that is the film thickness of the piezoelectric element. As the area of the piezoelectric element is reduced, the in-plane density of the nozzle can be more improved, so that exacter printing can be performed.
As described above, according to this embodiment, since the dew point in the vicinity of the piezoelectric element is lowered by the dry gas, deterioration of the piezoelectric element due to the voltage application is prevented. Thus, while achieving reduction of the film thickness of the piezoelectric element, it is possible to readily prevent the element from breaking due to the application of voltage to the piezoelectric element.
In the above description, the direct voltage of 35V has been applied to the piezoelectric element to examine its characteristics. However, generally, it is not necessary to apply such a high voltage in order to eject the ink, and the voltage of a rectangular waveform is applied. Also in this voltage applied state, by introducing the dry gas, the deterioration of the piezoelectric element can be prevented, needless to say.
Further, in this embodiment, the PZT is used as the piezoelectric element. However, the invention is not limited to this, but another piezoelectric element including lead may be used because the similar effect can be obtained. Further, though the piezoelectric element is formed by sputtering in this embodiment, the invention is not limited to this, but a piezoelectric element manufactured by sintering or sol-gel processing may be used because the similar effect can be obtained.
As described above, according to the invention, since the dew point in the vicinity of the piezoelectric element is lowered by the dry gas, deterioration of the piezoelectric element due to the voltage application is prevented. Accordingly, such an effective advantage can be obtained that it is possible to readily prevent the element from breaking due to the application of voltage to the piezoelectric element, thereby achieving reduction of the film thickness of the piezoelectric element.
Embodiments of the invention will be described below with reference to
An ink jet recording apparatus 240 shown in
In a case where the line head is constituted by combination of the plural nozzle heads, by characteristic unevenness between the nozzle heads and accuracy of alignment onto the nozzle head holding frame, a streak may appear in printing at a joint between the nozzle heads, so that printing quality lowers. Further, if the line head is constituted by combination of the plural nozzle heads, it is necessary to align the nozzle heads with a high degree of accuracy. However, depending on accuracy of components, it is difficult to yield alignment accuracy.
In the ink jet recording apparatus 240 of this embodiment, which can perform color printing, on the ink jet head 241, a line head 243 having an ink head from which yellow ink is ejected, an ink head from which magenta ink is ejected, an ink head from which cyan ink is ejected, and an ink head from which black ink is ejected is mounted; and plural nozzle holes are arranged in each ink head throughout the entire width of the recording medium 42.
The ink jet recording apparatus 240 has plural rollers (moving means) 245 which move the recording medium 242 in a transporting direction that is almost perpendicular to a width direction of the ink jet head 241.
Though the color ink jet recording apparatus 240 is shown in this embodiment, the invention can be also applied to a monochromatic ink jet recording apparatus in which printing of only one color can be performed.
As shown in
In the ink jet head 241, plural pressure chambers in which ink liquid is filled are formed. By deforming the pressure chamber by an energy generating source such as a piezoelectric element or air bubbles, the ink is ejected from the nozzle hole 247a communicating with the pressure chamber.
Here, in order to achieve simultaneously size-reduction of the nozzle head 247 and improvement of printing resolution, it is important to arrange the nozzle holes 247a on the nozzle surface efficiently. In this embodiment, the nozzle holes 247a of the nozzle head are arranged at a high density as follows.
Namely, as shown in
More specifically, in
According to such an arrangement, as shown in
The excessive ink removed by the cleaning blade 250 is collected to a blade holding portion 252 by gravity. The blade holding portion 252 is slidably held by the shafts 254 and 256, and is driven by a motor (not shown) in the sub-scanning direction.
According to the embodiment, because the nozzle head 247 is projected from a surface of the holding frame 246, even if the ink is collected at both ends of the cleaning blade 250, when the cleaning blade 250 squeegees the excessive ink attached with bottom face of the nozzle head 247, the excessive ink will not touch the surface of the holding frame 246. Thus, the printing degrade due to the ink adhered to the surface of the holding frame 246 is adhered to the printing media 242 can be prevented.
Here, in order to arrange the nozzle holes 247a with better space efficiency and prevent occurrence of the aforesaid warp of the nozzle plate, as shown in
Further, there is another arrangement as shown in
Thereby, the nozzle holes 247a are formed densely in the narrow region on the nozzle surface, so that the space efficiency can be more improved. Further, since the area of a region where the nozzle holes are not formed becomes large, rigidity of the nozzle plate improves and the occurrence of warp is prevented.
Supporting that the number of nozzle arrays is plural, for example, four, in the case where the nozzle arrays are arranged in order of A+B, and C+D in the sub-scanning direction, there can be a problem of a joint between the arrays A+B and the arrays C+D. Namely, due to working accuracy of the nozzle plate and attachment shift (rotation shift) of the head, a gap can be produced in the main scanning direction between a printing region by the nozzles in the arrays A+B and a printing region by the nozzles in the arrays C+D. Further, generally, in one nozzle array, abnormality (bad ejection of ink) is easy to be produced in the nozzle hole 247a located at the end because dust and an air bubble drift and attach to the nozzle hole 247a.
Therefore, as shown in
By such an arrangement, since the same line can be printed with ink ejected from the plural nozzle holes 247a, pseudo-scanning of plural times is performed, so that a portion where the joint readily appears can be made inconspicuous, and the nozzle hole 247a from which the ink has not been already ejected can be recovered.
Though the nozzle holes are arranged so that the nozzle hole 247a located at one end of the nozzle array overlaps with the nozzle hole 247a located at the other end of the other array in a sub-scanning direction, the nozzle holes 247a located at the both ends may be arranged thus. Further, the nozzle holes may be arranged so that not only the nozzle hole 247a located at the end but also a part or all of the nozzle holes 247a overlaps with the nozzle hole 247a in another array in the sub-scanning direction.
In the case where the nozzle holes 247a are thus arranged, the ink ejection in the sub-scanning direction may be performed alternately or irregularly from the nozzle holes 247a overlapping to each other in the sub-scanning direction. Thus, since the same line or lines in the vicinity of the line can be printed with the ink ejected from the plural nozzle holes, the portion where the joint readily appears can be made inconspicuous, and the nozzle hole 247a from which the ink has not been already ejected can be recovered.
Here, as described before, in the edge shoot type in which only one nozzle array is formed per a nozzle head, usually, the nozzle holes 247a cannot be arranged at a high density, so that the space efficiency is not good. Therefore, in a case in which the above-described plural nozzle heads are arranged and fixed on the holding frame so that the nozzle arrays tilt in the main scanning direction thereby to manufacture a line head, the resolution in the sub-scanning direction that is particularly important for the line head can be readily increased.
In a case where the line head comprises the plural nozzle heads, supporting that the number of nozzle arrays is, for example, four, in case that C+D nozzle arrays in one nozzle head and next A+B nozzle arrays in a nozzle head adjacent to its nozzle head are arranged, there can be a problem of a joint between the arrays C+D and the arrays A+B. Namely, due to working accuracy of the nozzle plate and attachment shift (rotation shift) of the head, a gap can be produced in the main scanning direction between a printing region by the nozzles in the arrays C+D and a printing region by the nozzles in the arrays A+B. Further, as described before, generally, in one nozzle array, the abnormality (bad ejection of ink) is easy to be produced in the nozzle hole 247a located at the end because dust and an air bubble drift and attach to the nozzle hole 247a.
Therefore, as shown in
By such an arrangement, since the same line can be printed with ink ejected from the plural nozzle holes 247a, pseudo-scanning of plural times is performed, so that the portion where the joint between the nozzle heads readily appears can be made inconspicuous, and the nozzle hole 247a from which the ink has not been already ejected can be recovered.
Herein, though the nozzle holes are arranged so that the nozzle hole 247a located at one end of the nozzle array of one nozzle head 247 overlaps with the nozzle hole 247a located at the end of the nozzle array of another nozzle head in the sub-scanning direction, the nozzle holes 247a located at the both ends may be arranged thus. Further, the nozzle holes may be arranged so that not only the nozzle hole 247a located at the end but also a part or all of the nozzle holes 247a other than its nozzle hole overlaps with the nozzle hole 247a of another array in the sub-scanning direction.
Here, if the accuracy of the nozzle head 247 is not good when the nozzle heads 247 adjacent to each other are attached closely, the position of the nozzle hole 247a is different, so that alignment accuracy does not appear. Therefore, as shown in
Due to scattering of ink in printing, or purge or blade operation, the ink enters in the gap between the nozzle heads 247, so that the gap between the heads can be covered with a film, that is, the gap can be bridged by the film. In the event that the amount of this ink increases, a large ink droplet drops on the recording medium and the recording medium can be stained with this ink droplet.
Therefore, as shown in
Embodiments of the invention will be described below with reference to
An ink jet recording apparatus 340 shown in
In the ink jet recording apparatus 340 of this embodiment, which can perform color printing, on the ink jet head 341, a line head 343 having an ink head from which yellow ink is ejected, an ink head from which magenta ink is ejected, an ink head from which cyan ink is ejected, and an ink head from which black ink is ejected is mounted; and plural nozzle holes are arranged in each ink head throughout the entire width of the recording medium 342.
The ink jet recording apparatus 340 has plural rollers (moving means) 345 which move the recording medium 342 in a transporting direction that is almost perpendicular to a width direction of the ink jet head 341.
Though the color ink jet recording apparatus 340 is shown in this embodiment, the invention can be also applied to a monochromatic ink jet recording apparatus in which printing of only one color can be performed.
As shown in
In this embodiment, the plural nozzle heads 347 are aligned with a high degree of accuracy by the following method and fixed onto the holding frame 346, whereby the ink ejecting direction is made uniform among the nozzle heads 347 and high quality printing is made possible.
Namely, in
The nozzle head 347 in which many nozzle holes 347a are provided is held by a head holding unit 349 which can move the nozzle head 347 in a horizontal direction and in a vertical direction. The plate 350 and the nozzle head 347 are opposed to each other to observe the nozzle head 347 through the transparent plate 350 by a camera means 351, and registration is performed between the alignment mark 350a of the plate 350 and the predetermined position (for example, nozzle hole 347a or nozzle mark 347b formed for alignment) of the nozzle head 347 on the basis of the alignment mark 350a, whereby alignment of the nozzle heads 347 is performed. After the alignment, the nozzle heads 347 are fixed onto the holding frame 346.
In
Here, as an example of the marks, shapes of a nozzle mark of the nozzle head 347 and shapes of the alignment mark 350a of the plate 350 are shown in
By performing such alignment in order, the plural nozzle heads 347 can be aligned easily and with a high degree of accuracy.
It is preferable that the plate 350 is made of glass and not of resin such as plastics. Namely, a material used as the plate 350 must be able to be used as gauge, that is, it must be small in expansion coefficient in relation to the temperature. The glass meets this condition. Further, since the glass itself having high smoothness is not a special material but cheap, the cost does not increase.
There is a case in which the many alignment marks 350a are required on the transparent plate 350. Though the alignment mark 350a may be formed by any work on the plate 350, this formation is difficult in regard to accuracy and man-hours in order to form the many marks freely. In such a case, the alignment mark 50a is formed by sputtering of chromium (Cr), whereby the many alignment marks 350a can be readily formed because they can be formed by a usual method using a photo mask. Further, since accuracy of the photo mask is so accurate that position accuracy of the mark on the glass having the large area of 500 mm by 500 mm is ±2 μm, the alignment mark 50a can be formed at a low cost and with a good accuracy.
Further, as shown in
Here, it is good that at least two, that is, plural alignment marks 350a are formed on one nozzle head 347. The reason is that: in a case where the registration is performed by only one alignment mark 350a, there is a fear of generation of rotational deviation, but in a case where the alignment is performed by the plural alignment marks 350a, as shown in
Further, it is good that the registration is performed by the nozzle hole 347a of the nozzle head 347 and the alignment mark 350a. As a mark to be formed on the nozzle head 347 itself, a mark obtained by any previous work on the nozzle head 347 may be used. However, accuracy in the positional relation between its worked part and the nozzle hole 347a is not always insured. Further, though it is thought that the registration is performed at an edge portion of the nozzle head 347, accuracy in the positional relation between the edge part and the nozzle hole 347a is not also always insured. On the other hand, in the case where the alignment is performed by the nozzle hole 347a and the alignment mark 350a, even if the nozzle hole 347a formed in the nozzle head 347 shifts from its natural position as shown in
Here, it is good that the registration between the plate 350 and the nozzle head 347 is performed in the center of the plural alignment marks 350a. Since the nozzle hole 347a requires a complicated tapered shape, the positional accuracy when the nozzle hole 347a is worked is inevitably inferior to that of the alignment mark 350a having a high degree of accuracy. Thus, the work of performing registration between members that do not completely coincide with each other in their position is required. Further, in case that the position of only one alignment mark 350a coincides with that of the nozzle hole 347a, the registration error between the other alignment mark 350a and the nozzle hole 347a of the next nozzle head 347 is readily produced. On the other hand, if the registration between the plate 350 and the nozzle head 347 is performed in the center of the plural alignment marks 350a, as shown in
It is desirable that the registration is performed between the nozzle holes 347a located at both ends of the nozzle head 347 and the alignment marks 350a. In the case where the alignment is performed at the adjacent plural nozzle holes 347a, even if the deviation amount in relation the alignment mark 350a is the same, the whole deviation amount becomes large. However, in case that the registration is performed at the nozzle holes 347a located at the both ends as shown in
Further, the registration may be performed by an alignment mark 350a and a nozzle mark 347b formed on the nozzle head 347 in the same process as the nozzle hole 347a. Namely, before the alignment process, in a case where a filling examination and an ejection examination of ink liquid are performed in a single nozzle head 347, a leading end of the nozzle hole 347a may get wet with the ink in the alignment, and a nozzle edge may become dim. In this case, using not the nozzle hole 347a used for ink ejection but a dummy nozzle hole worked in the same process as the nozzle hole 347a, that is, the nozzle mark 347b, as shown in
Further, the registration may be performed by an alignment mark 350a and a nozzle mark 347b formed on a line connecting two nozzle holes 347a located at both ends of the nozzle head 347. Hereby, the alignment can be performed with the same degree of accuracy as the accuracy in a case where the registration is performed at the nozzle holes 347a located at the endmost, or with higher accuracy in case that the distance between the nozzle marks 347b is farther than the distance between the nozzle holes 347a located at the endmost. Such registration is particularly effective when the nozzle head 347 is arranged on the holding frame 46 slantingly. Here, the two nozzle holes 347a located at the both ends of the nozzle head 347 may be, as shown in
Even if the alignment is thus performed, if the work accuracy of the nozzle head 347 is bad or the thickness of an adhesive when the nozzle plate is bonded is not uniform, the nozzle surfaces of the plural nozzle heads 347 are different in plane from each other. Namely, in a case where deviation is produced in a Z-direction, the distance between the nozzle surface and the recording medium 342 is different in each nozzle head 347, or its distance has an inclination in the Z-direction, so that an impact position of the ink droplet is different in each nozzle head 347, and high quality printing is impossible. In such a case, as shown in
In order to adjust the nozzle heads 347 so that the nozzle surfaces of the plural nozzle heads 347 are located on the same plane, as shown in
An ink jet head unit used in a conventional ink jet recording apparatus will be described.
As shown in
In the ink jet head unit, conventionally, mounted parts 25a, 25b are formed between the nozzle arrays 20a, 20b and side portions of the head, and the flat cables 22a, 22b are fixed at the mounted parts 25a, 25b onto the head 20.
The head 20 is composed of a laminate of thin films constituting the nozzle hole, a pressure chamber, an ink flow path, and an actuator. These thin films are weak in close attachment power in the vicinity of the side portions. Therefore, the mounted parts 25a, 25b must be formed, not in the vicinity of the side portions of the head, but at portions which are distant from the side portions, that is, on the insides of the side portions.
According to the conventional construction, the mounted part must be formed on the inside of the head. Therefore, a dead space is formed between the mounted part and the side portion of the head, so that the size of the head becomes large.
In a case where the flat cable pulled out from the head is bent with a small curvature, since there is a fear of breaking the wire, it must be bent with a curvature of some degree. In this case, in the conventional ink jet head unit in which the mounted part is formed between the nozzle array and the side portion of the head, the flat cable sticks out of a width W of the head orthogonal to a surface of the flat cable.
In the conventional construction, not only the head itself is made large but also the pull-around space of the flat cable connected to the head is required in the width direction. Therefore, the ink jet head unit itself becomes large, which is contrary to the market demand of miniaturization.
Therefore, an object of the invention is to provide an ink jet head unit in which a head having a mounted part connected to a flat cable can be miniaturized. Further, another object of the invention is to provide an ink jet head unit in which the flat cable connected to the head can be compactly pulled around.
An embodiment of the invention will be described below with reference to
An ink jet head unit 1 shown in
The ink jet head unit 1 comprises the head 2 from which the ink is ejected, a head base 3 on which the head 2 is mounted, and two flexible flat cables 4a, 4b that are attached to the head 2. The flat cables 4a and 4b are formed by covering many transmission wires with an insulation film, and drivers 5a and 5b that generate an ink ejection signal for driving the head 2 are provided respectively in midway positions of the plural flat cables. Heat radiation plates 6a and 6b for radiating heat generated during operation efficiently are attached to the drivers 5a and 5b.
As shown in
One end side where the transmission wire of the flat cable 4a is exposed is fixed, in the mounted part 7a, onto the head 2, and one end side where the transmission wire of the flat cable 4b is exposed is fixed, in the mounted part 7b, onto the head 2. Further, as shown in
The ink ejecting signals generated by the drivers 5a and 5b are transmitted to the flat cables 4a and 4b, and supplied to the head 2 from the flat cables 4a and 4b. Thereby, the dielectric thin film element is subjected to displacement, and the ink droplet is ejected.
In the embodiment, though the four nozzle arrays are formed, two or more, that is, plural nozzle arrays are sufficient, and the invention is not limited to the four arrays. Further, though the two flat cables are used, one, or three or more flat cables may be used.
Since the mounted parts 7a and 7b are thus formed in the position between the nozzle arrays 2a, 2b and the nozzle arrays 2c, 2d, the nozzle holes, which are comparatively difficult to receive an influence caused by weak close attachment power of thin films constituting the head 2, can be formed at side portions of the head. Accordingly, since the mounted parts 7a, 7b and the nozzle arrays 2a, 2b, 2c, 2d can be arranged on the head 2 efficiently, a dead space is eliminated, and the head 2 can be miniaturized.
Further, since the mounted parts 7a and 7b are formed in the position between the nozzle arrays 2a, 2b and the nozzle arrays 2c, 2d, even in a case where the flat cables 4a and 4b are arranged within a width W of the head 2 in a direction orthogonal to a surface of the flat cable, along the head base 3 (
A notch part is formed on a side surface of the head base 3. The notch part 3a recieves the flat cables 4a and 4b therein. Thereby, the flat cables 4a and 4b can be compactly housed within the width of the head 2 in the direction orthogonal to the surface of the flat cable.
A metallic interference preventing member 8 or a nonmetallic interference preventing member 8, in which a metal layer is formed, is positioned between the flat cables 4a and 4b. Thereby, electromagnetic mutual interference between the flat cables 4a and 4b is relaxed. The interference preventing member may not be arranged. Further, though the interference preventing member 8 is arranged partly between the flat cables 4a and 4b in the figure, it may be arranged throughout the whole between the flat cables 4a and 4b.
Further, as another means for relaxing the electromagnetic mutual interference, the flat cables 4a and 4b may be arranged so that the transmission wires formed in these flat cables 4a and 4b are nonparallel to each other.
As shown in
The flat cables 4a and 4b have respectively at least two bending parts 9 that bend in the length direction of each of the flat cables 4a, 4b, at their parts extending from the head base 3. Thus, an extra length can be provided for the flat cables 4a, 4b, so that work performance in assembly of the apparatus can be improved by adjusting the forming position of the bent part 9.
As described above, according to the ink jet head unit of the embodiment, since the mounted parts 7a, 7b are formed in the position between the nozzle arrays 2a, 2b and the nozzle arrays 2c, 2d, the nozzle holes which are comparatively difficult to receive the influence caused by weak close attachment power of the thin films constituting the head 2 can be formed at the side portions of the head, so that the mounted parts 7a, 7b and the nozzle arrays 2a, 2b, 2c, 2d can be arranged on the head 2 efficiently. Therefore, the dead space is eliminated, and the head 2 can be miniaturized.
Further, since the mounted parts 7a, 7b are formed in the position between the nozzle arrays 2a, 2b and the nozzle arrays 2c, 2d, even in case that the flat cables 4a, 4b are arranged within the width W of the head 2 in the direction orthogonal to the surface of the flat cable, along the head base 3, the flat cables can be bent with such a comparatively large curvature that breaking of wire can be prevented, so that the flat cables 4a, 4b can be pulled around compactly.
As is understandable from the preceding description, the above described various embodiments may be combined with each other to attain its function.
As described above, according to the invention, since the dew point in the vicinity of the ink ejecting unit is lowered by the dry gas, it is prevented that the ink ejecting unit deteriorates due to the voltage application. Accordingly, such an effective advantage can be obtained that it is possible to readily prevent break and deterioration due to the voltage application to the ink ejecting unit, thereby achieving reduction of the film thickness of the ink ejecting unit.
According to the first aspect of the invention, an ink jet recording apparatus, which performs printing by ink ejection, comprises a pressure chamber in which ink liquid is filled; a nozzle hole which is formed, communicating with the pressure chamber; a piezoelectric element which is formed on the pressure chamber, and deforms the pressure chamber by mechanical expansion and contraction, whereby pressure is generated in the pressure chamber, and ink is ejected from the nozzle hole; and a dew point control unit which keeps a dew point in an atmosphere of the piezoelectric element and the vicinity of the piezoelectric element at a lower value than a dew point in an environment where the ink jet recording apparatus is set. Accordingly, reduction of the film thickness of the piezoelectric element can be achieved, and breakage of the element due to the application of voltage to the piezoelectric element can be readily prevented.
According to the second aspect of the invention, in the ink jet recording apparatus according to the first aspect of the invention, the dew point control unit introduces dry gas to the piezoelectric element and in the vicinity of the piezoelectric element. Thus, reduction of the film thickness of the piezoelectric element can be achieved, and the element breakage due to the voltage application to this piezoelectric element can be readily prevented.
According to the third aspect of the invention, in the ink jet recording apparatus according to the second aspect of the invention, the dew point control unit supplies dry gas by use of an air drier. Accordingly, reduction of the film thickness of the piezoelectric element can be achieved, and breakage of the element due to the application of voltage to the piezoelectric element can be readily prevented.
According to the fourth aspect of the invention, in the ink jet recording apparatus according to the second aspect of the invention, the dew point control unit supplies the dry gas from a cylinder. Accordingly, reduction of the film thickness of the piezoelectric element can be achieved, and breakage of the element due to the application of voltage to the piezoelectric element can be readily prevented.
According to the fifth aspect of the invention, in the ink jet recording apparatus according to any one of the second to fourth aspects of the invention, a dew point of the dry gas is −50° C. or less. Accordingly, reduction of the film thickness of the piezoelectric element can be achieved, and breakage of the element due to the application of voltage to the piezoelectric element can be readily prevented.
According to the sixth aspect of the invention, in the ink jet recording apparatus according to any one of the first to sixth aspects of the invention, there is provided a case which includes an inlet from which the dry gas is introduced, and an outlet from which the dry gas is exhausted, and surrounds the piezoelectric element; and the dry gas is introduced from the inlet into the case at 10 mL/sec or more per volume of one cubic cm, and the internal pressure of the case is maintained higher than its external pressure. Accordingly, reduction of the film thickness of the piezoelectric element can be achieved, and breakage of the element due to the application of voltage to the piezoelectric element can be readily prevented.
According to the seventh aspect of the invention, in the ink jet recording apparatus according to any one of the first to sixth aspects of the invention, the piezoelectric element includes a lead compound. Accordingly, reduction of the film thickness of the piezoelectric element can be achieved, and breakage of the element due to the application of voltage to the piezoelectric element can be readily prevented.
According to the eighth aspect of the invention, in the ink jet recording apparatus according to any one of the first to seventh aspects of the invention, the film thickness of the piezoelectric element is 100 μm or less. Accordingly, reduction of the film thickness of the piezoelectric element can be achieved, and the breakage of the element due to the application of voltage to the piezoelectric element can be readily prevented.
According to the ninth aspect of the invention, an ink jet recording apparatus which performs printing by ink ejection, comprises a pressure chamber in which ink liquid is filled; a nozzle hole which is formed communicating with the pressure chamber; an ink ejecting unit which ejects the ink liquid filled in the pressure chamber from the nozzle hole; and a dew point control unit which keeps a dew point in peripheral atmosphere of the ink ejecting unit is kept at a lower value than a dew point in an environment where the ink jet recording apparatus is set. Accordingly, breakage of the and deterioration of the ink ejecting unit can be suppressed.
The present disclosure relates to subject matter contained in priority Japanese Patent Application Nos. 2003-124099, 2003-124100, 2003-124101 and 2003-124102 all filed on Apr. 28, 2003, the content of which is herein expressly incorporated by reference in its entirety.
Number | Date | Country | Kind |
---|---|---|---|
P.2003-124099 | Apr 2003 | JP | national |
P.2003-124100 | Apr 2003 | JP | national |
P.2003-124101 | Apr 2003 | JP | national |
P.2003-124102 | Apr 2003 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
3894419 | Mator et al. | Jul 1975 | A |
5344474 | Null | Sep 1994 | A |
5912684 | Fujii et al. | Jun 1999 | A |
20020012029 | Miyata | Jan 2002 | A1 |
Number | Date | Country |
---|---|---|
0 863 007 | Sep 1998 | EP |
4-349675 | Dec 1992 | JP |
2001-300421 | Oct 2001 | JP |
3302785 | Apr 2002 | JP |
2002-240283 | Aug 2002 | JP |
Number | Date | Country | |
---|---|---|---|
20050001868 A1 | Jan 2005 | US |