JP4041989B2 - Liquid discharge head, liquid discharge apparatus, and method of manufacturing liquid discharge head - Google Patents

Description

  The present invention relates to a liquid discharge head used in a thermal inkjet printer head that discharges liquid using thermal energy, a liquid discharge apparatus including the liquid discharge head, and a method of manufacturing the liquid discharge head. More specifically, the present invention relates to a technique for minimizing distortion of each member due to temperature change and reducing characteristic deterioration that occurs.

  Among the liquid discharge heads, for example, in an inkjet printer head used in an inkjet printer, a thermal chip using thermal energy uses a head chip in which several hundred heating elements are formed on a semiconductor substrate. In the case of a single color, one head chip is used. However, in a color head (for example, four colors), three colors of Y (yellow), M (magenta), and C (blue green) are used for color. In many cases, only K (black) is independently used as a two-block structure for black and white at an equal interval in an integrated structure.

  Further, one method for increasing the printing speed is to provide as many liquid ejection units (including nozzles, heating elements, and liquid chambers) as possible in one head. Here, in order to form the liquid discharge portion, it is necessary to provide a nozzle, a heating element, and a liquid chamber, and it is necessary to provide a flow path that communicates with all the liquid chambers, and a minimum area for that purpose. Is required. Therefore, at present, the limit is, for example, about 600 DPI (42.3 [μm] pitch). For example, when a head having 256 liquid ejection units at 600 DPI is used, the length is 10.8 [mm]. The larger the head chip is, the more difficult it is to handle, and the yield decreases, which in turn increases the cost.

Therefore, as a thermal type line head, a technique is known in which a plurality of head chips are arranged to form one large line head (see, for example, Patent Document 1).
JP 2002-127427 A

  By adopting the above structure, for example, a head chip (length: 15.4 mm) provided with 320 heat generating elements at 600 DPI is formed, and by arranging 64 of these head chips, the paper width of A4 size is reduced to 1 It became possible to form a line head capable of recording each time.

  FIG. 6 is a diagram schematically showing this type of line head 1. In FIG. 6, illustration of a portion of electrical connection to each head chip 4 (4A to 4D) is omitted. In addition, the ratios of the thicknesses, lengths, and the like of each member are illustrated so as to be different from actual ones for easy understanding. In the case of an A4 size line head, as described above, 64 head chips are connected and formed, but in FIG. 6, for the sake of simplification, four head chips 4 (4A to 4D) are described. To do.

In FIG. 6, the line head 1 includes a nozzle plate 3, four head chips 4 (4A to 4D) bonded on one surface of the nozzle plate 3, and six dummy chips 5 (5A to 5F). Prepare. Further, a flow path plate 2 is provided at the upper part.
FIG. 7 is a cross-sectional view showing the flow path plate 2, the head chip 4, and the nozzle plate 3 in detail. As shown in FIG. 7, the head chip 4 has a heating element 4b provided on a semiconductor substrate 4a. In the case of 600 DPI, 320 heating elements 4 b are arranged in one head chip 4. A barrier layer 4c that forms a liquid chamber is provided on the surface on which the heat generating element 4b is provided.

In the nozzle plate 3, a row of nozzle holes 3 a is formed at positions corresponding to the respective heat generating elements 4 b of the head chip 4.
The head chips 4 are arranged in a staggered manner in the example of FIG. Further, the dummy chips 5 (5A to 5F) are arranged between the head chips 4 with almost no gap (for example, the dummy chip 5C is arranged between the head chips 4A and 4C). The dummy chip 5 is at least the same height as the head chip 4 and may have the same shape as the head chip 4, but may not be provided with the heating element 4 b, for example. The dummy chip 5 is a chip that does not discharge ink.

Further, of the dummy chips 5A to 5F, the dummy chips 5A and 5F are arranged at both ends in the longitudinal direction of the head chips 4A to 4D, and the liquid supply path 2a is formed by the head chips 4A to 4D and the dummy chips 5A to 5F. Be surrounded. In addition, the head chip 4A to 4D and the dummy chips 5A to 5F form a flat adhesive surface with the flow path plate 2.
The flow path plate 2 is bonded onto the surface formed by the head chips 4A to 4D and the dummy chips 5A to 5F. The flow path plate 2 includes a liquid supply port 2 b formed in the upper center portion, a liquid supply path 2 a formed inside the flow path plate 2 and communicating with the liquid supply port 2 b and the flow paths of the head chips 4. Is provided.

  In FIG. 7, when the heating element 4b provided on the head chip 4 is heated, bubbles are generated on the heating element 4b, and the generated bubbles disappear in a short time. The flying force is applied to the liquid on the heating element 4b by the pressure change due to the above. And a droplet is discharged from the nozzle hole 3a with the flying force.

  Further, most of the heat generated by the head chip 4 is generated by the heating element 4b. Furthermore, since the heat generating element 4b is in contact with the semiconductor substrate 4a even on the side not in contact with the liquid, the heat generated by the heat generating element 4b is also transmitted to the semiconductor substrate 4a side.

  The heat generated in the head chip 4 is dissipated to the liquid that moves every time the droplet is ejected. However, in other places, for example, on the back surface side of the head chip 4, between the head chip 4 and the flow path plate 2. It is transmitted to the flow path plate 2 side through the adhesive layer 6. Further, on the surface side of the head chip 4, it is transmitted to the nozzle plate 3 through the barrier layer 4 c of the head chip 4.

However, there are the following problems in putting the above-described conventional technology into practical use.
Since the size of the single head chip 4 is about 20 mm as described above, the nozzle plate 3 in which the nozzle holes 3a are formed or the flow path plate 2 and the head chip 4 are attached. However, in the serial system, thermal stress is generated between the members due to thermal expansion, and even if distortion occurs, it is not at a level that causes failure.

  On the other hand, when a large number of head chips 4 are connected as in the line head 1, the length in the longitudinal direction of the line head 1 becomes longer, so the front side (nozzle plate 3 side) and the back side of the head chip 4. Depending on the material (on the flow path plate 2 side), expansion / contraction difference due to thermal expansion, that is, a difference in linear expansion coefficient becomes a problem.

  Here, when the flow path plate 2, the head chip 4, and the nozzle plate 3 are all made of the same (including substantially the same range) material, there is no problem of thermal expansion. However, in selecting materials for the flow path plate 2, the head chip 4, and the nozzle plate 3, since each member has different required characteristics or functions, each member has the required characteristics or functions. Must meet.

  For example, as the flow path plate 2, firstly, one obtained by casting aluminum is cited. This is because it has excellent workability and good thermal conductivity. Second, an acrylic resin injection-molded can be mentioned. This is because the wettability and workability are good and the Young's modulus is lower than that of aluminum.

Further, examples of the barrier layer 4c include polymer materials typified by a photosensitive cyclized rubber resist and an exposure curable dry film resist. This is because the adhesive strength is strong, the hardness is higher than that of acrylic after thermosetting, and it is inexpensive.
Moreover, as the nozzle plate 3, what formed nickel by electroforming etc. is mentioned. This is because the formation of the nozzle hole 3a is relatively simple, the thermal expansion is relatively small, and the wettability and cost are within the practical range.

  As described above, it is necessary to select a material, a material, and a processing method for each member so as to satisfy required characteristics and functions. And if the material of the flow path plate 2, the head chip 4, and the nozzle plate 3 is selected from such a viewpoint, the respective linear expansion coefficients will be different.

  FIG. 8 is a cross-sectional view for explaining generation of thermal stress and distortion in the line head 1. In FIG. 8, (A) shows qualitatively how much displacement occurs when a temperature change occurs. In this figure, the center of the line head 1 in the longitudinal direction is the origin. When the center is taken as the origin, the length of the nozzle plate 3 and the flow path plate 2 increases as the temperature rises. Therefore, as shown in FIG. On the other hand, the displacement increases. The size of the arrow indicates the magnitude of the displacement.

  FIG. 8B is a cross-sectional view showing an example of deformation due to temperature change. When the linear expansion coefficient of the flow path plate 2 and the nozzle plate 3 is different from that of the head chip 4 (in this example, the linear expansion coefficient of the flow path plate 2 and the nozzle plate 3 is larger than that of the head chip 4). Since the flow path plate 2 and the nozzle plate 3 tend to be longer than the row of the head chips 4, the flow path plate 2, the head chip 4, and the nozzle plate 3 are fixed by adhesion, and the rest are pressed down. Otherwise, it should be bowed as shown in the figure due to the bimetal phenomenon.

  If the line head 1 becomes bowed in this way, the distance between the recording medium and each head chip 4 changes. For example, in the head chips 4 located at both ends, the distance between the nozzle hole 3 and the recording medium does not change so much, but the head chip 4 is inclined with respect to the recording medium (not parallel). On the other hand, in the head chip 4 located at the center, the parallelism does not change when the line head 1 becomes a bow, but the position moves upward, so that the distance from the recording medium becomes long.

Therefore, in order to prevent such bow-like deformation, a force is applied to the line head 1 to maintain the positional relationship between the line head 1 and the recording medium.
FIG. 8C supports the lower side of both ends of the line head 1 and prevents a bow from being formed by the forces F1 to F3 as shown in the figure if the center part is pressed from the upper side ( Level).
However, in this case, as indicated by the arrows in the figure, shear stress is generated between the flow path plate 2 and the head chip 4 and between the head chip 4 and the nozzle plate 3, and the magnitude thereof is , Both ends become larger.

  In particular, the barrier layer 4c is provided on the head chip 4 as described above, and a liquid chamber and individual flow paths are formed by the barrier layer 4c. These portions are formed on the semiconductor substrate 4a of the head chip 4. Since the strength is weak with respect to the nozzle plate 3, the shear stress causes elastic deformation or plastic deformation, and the liquid chamber and the individual flow path may not be able to satisfy the required characteristics.

  FIG. 9 shows the result of taking a picture of the liquid ejection part of the line head 1 when subjected to the thermal stress as described above. In the figure, (A) shows the center of the line head 1. As shown in (A) in the figure, almost no deformation (distortion) is seen in the central portion. On the other hand, as shown in FIG. 5B, the barrier layer 4c is deformed at both ends of the line head 1, which may affect the ejection characteristics.

  In order to avoid such influence, for example, it is conceivable to reduce the distortion by applying a compressive load from both ends of the flow path plate 2, but the general operation guarantee temperature range of the printer, for example, 15 to In the range of 35 ° C., it is required to further reduce the change in the ejection characteristics with respect to the temperature change.

  Therefore, the problem to be solved by the present invention is to minimize a change in ejection characteristics due to a temperature change when a line head is formed by arranging a plurality of head chips.

The present invention solves the above-described problems by the following means.
According to a first aspect of the present invention, there is provided a nozzle plate having nozzle holes for discharging droplets, a first support formed in a frame shape, and a plurality of heating elements on a semiconductor substrate. Each of the heat generating elements and the nozzle holes, respectively, and a head support arranged at least in part in a frame-shaped inner peripheral region of the first support. A liquid discharge head in which a plurality of head chips are joined in a line on the nozzle plate so as to face each other, and the linear expansion coefficient of the head chips is substantially the same as the linear expansion coefficient of the first support. Yes, the linear expansion coefficient of the nozzle plate is larger than the linear expansion coefficient of the first support, the linear expansion coefficient of the second support is larger than the linear expansion coefficient of the first support, and the nozzle plate is And joined to the first support, and the first support and the front In a temperature environment in which no thermal stress is generated on the joint surface with the second support, the nozzle plate is caused to have a tensile stress by the first support, and the second support is At least a part of the outer side surface at both ends is joined to the first support body so as to be sandwiched by at least a part of the inner peripheral side surface of the first support body, and the second support body is the first support body. When the thermal expansion occurs, compressive stress is generated in the second support and distortion of the second support is regulated by the first support.

(Function)
In the said invention, while the nozzle plate is joined to the 1st support body, the linear expansion coefficient of a nozzle plate is larger than the linear expansion coefficient of a 1st support body. Thereby, if a nozzle plate is joined to a 1st support body at high temperature, a nozzle plate will follow the expansion-contraction of a 1st support body at normal temperature. Further, since the linear expansion coefficient of the head chip and the first support is substantially the same and the head chip is joined to the nozzle plate, the head chip expands and contracts according to the first support.

  Moreover, the 2nd support body is joined to the 1st support body so that it may be pinched | interposed by the 1st support body, and the linear expansion coefficient of a 2nd support body is larger than the linear expansion coefficient of a 1st support body. And when a 2nd support body thermally expands with respect to a 1st support body, the distortion of a 2nd support body is controlled by the 1st support body.

  The liquid discharge head corresponds to the line head 10 in the following embodiments. The first support corresponds to the frame 11 in the embodiment, and the second support corresponds to the head support member 14 that also serves as the flow path plate in the embodiment.

  According to the first aspect of the present invention, when a line type liquid discharge head is formed by connecting head chips, distortion due to a difference in thermal expansion coefficient between members is minimized. be able to. Thereby, it is possible to prevent the print quality from being affected by the temperature change.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following embodiments, an ink jet printer is taken as an example of one form of the liquid ejecting apparatus, and a thermal type line head is taken as an example as one form of the liquid ejecting head used in the liquid ejecting apparatus.

Further, the following terms in the present specification and claims are used in the following meanings.
“Bonding” means permanent bonding not premised on separation (or peeling), (1) bonding members through an adhesive, and (2) applying thermocompression bonding and ultrasonic vibration. This includes both joining (bonding) without using an adhesive (without an adhesive between the two members) by ultrasonic bonding or welding.
Furthermore, “adhesion” is a kind of the above-mentioned joining, and means that members are bonded (bonded) to each other via an adhesive (with an adhesive interposed between the members), and separated (or It is intended for permanent bonding that does not assume peeling.

1A and 1B are diagrams showing a line head 10 according to the present embodiment, in which FIG. 1A is an exploded plan view before assembly, and FIG. 1B is a side view before assembly. (C) is a cross-sectional view of the side surface after assembly.
The line head 10 includes an outer frame 11 (corresponding to the first support in the present invention), a nozzle plate 12, a head chip 13, and a head support member 14 (corresponding to the second support in the present invention). With.

  The outer frame 11 is formed in a substantially rectangular frame shape, and the material thereof is, for example, in the range of 0.5 to 1.5 times the linear expansion coefficient of silicon single crystal or polycrystal. Ceramics having a linear expansion coefficient (in the present embodiment, powder sintered ceramics produced by molding and sintering raw material powder). In this case, the linear expansion coefficient of the outer frame 11 (ceramics) is about 3 to 3.5 [ppm], and the linear expansion coefficient of the head chip 13 (semiconductor substrate), that is, silicon is about 2.5 to 3. It becomes a value close to 0 [ppm] (substantially the same). Thus, if the outer frame 11 is ceramics, the Young's modulus of the outer frame 11 can be made comparable to a metal material. Further, the linear expansion coefficient can be adjusted depending on the ceramic composition and processing method.

  The nozzle plate 12 is a very thin film having a thickness of about 10 to 20 [μm], and is formed with a plurality of nozzle holes. In consideration of workability, cost, wettability, Young's modulus, etc., for example, nickel is used for the nozzle plate 12 if it is a metal material, and is formed by an electroforming technique. Moreover, if it is a polymeric material, it will be formed from polyimide.

  The head chip 13 is obtained by forming a heat generating element on a semiconductor substrate made of silicon or the like and further forming a barrier layer on the upper surface thereof (this point is similar to the head chip 4 shown in the prior art). Is the structure). The barrier layer is made of, for example, a photosensitive sensitized rubber resist or an exposure curable dry film resist, and is laminated on the entire surface of the semiconductor substrate where the heating elements are formed, and then unnecessary portions are removed by a photolithography process. It is formed by. The barrier layer forms a part of the liquid chamber (ink liquid chamber) and a flow path for supplying ink to the liquid chamber (individual flow path for each liquid chamber).

In this embodiment, the head support member 14 functions as a flow path plate, and as shown in FIG. 1, a liquid supply port 14a penetrating in a cylindrical shape in the vertical direction is formed.
Unlike the nozzle plate 12 having a thin film shape, the head support member 14 is required to withstand not only tension but also compression, bending, and twisting (not plastically deformed). For this reason, it basically has a plate-like or bar-like shape.

  Here, for example, the head support member 14 may be formed of the same ceramic as the outer frame 11. Thereby, the linear expansion coefficient of the head support member 14 can be made the same as the linear expansion coefficient of the outer frame 11. However, the workability of ceramics is not as good as that of metal materials and polymer materials. Therefore, the head support member 14 is formed by, for example, the following material and manufacturing method.

  First, the linear expansion coefficient of the head support member 14 is formed from a material having a linear expansion coefficient of 1.0 to 1.5 times that of the outer frame 11. For example, if the head support member 14 is made of a material having substantially the same linear expansion coefficient as that of the outer frame 11, the rigidity (eg, Young's modulus (longitudinal elastic modulus) E and the secondary cross-section when the head support member 14 has bending rigidity). There is no limit to the product of moment I (expressed by E × I). On the other hand, when the linear expansion coefficient of the head support member 14 is larger than the linear expansion coefficient of the outer frame 11 within the above range, it is a condition that the rigidity of the head support member 14 is smaller than the rigidity of the outer frame 11.

Second, the material of the head support member 14 may be a polymer material having substantially the same linear expansion coefficient as that of the ceramics, for example, liquid crystal plastic (also referred to as LCP or liquid crystal polymer. Specifically, For example, Polyplastics Co., Ltd., Vectra B230) is preferable. The linear expansion coefficient of the liquid crystal plastic is about 3.0 [ppm]. Since the polymer material has a small coefficient of linear expansion, it can be set to a value close to the coefficient of linear expansion of the outer frame 11, is excellent in mechanical strength, and has good wettability.
Third, the material of the head support member 14 is Invar (iron-36% nickel alloy), titanium or an alloy thereof, nickel steel, nickel-plated steel (which improves the liquid contact property by nickel plating), stainless steel, or The use of aluminum nitride can be mentioned.

  Furthermore, since the liquid supply port 14a is provided in the head support member 14 as shown in FIG. 1, it is necessary that the material and the processing method can form the liquid supply port 14a. In this case, for example, it can be formed by any one of the following.

  First, the above-described invar, nickel steel, nickel-plated steel, or stainless steel flat plate is plastically processed to form a liquid supply port 14a and to form a flow path communicating with the liquid supply port 14a. Is mentioned. For example, a space is formed inside the head support member 14 to form an equivalent to the liquid supply path 2a shown in FIG. 6 of the prior art (refer to the liquid supply path 14b in FIG. 2 described later). Is mentioned. If the flat plate is plastically processed, the strength can be increased with respect to bending, twisting, compression, and the like, rather than the flat plate itself.

  Second, the liquid supply port 14a may be formed by injection molding a polymer material (for example, the above-mentioned liquid crystal plastic (LCP)) having substantially the same linear expansion coefficient as the ceramic. Further, similarly to the above, a liquid supply path (liquid supply path 14b in FIG. 2) communicating with the liquid supply port 14a may be formed.

  Thirdly, in the second method, a strain absorbing plate may be provided on the lower surface side of the head support member 14. FIG. 2 is a diagram showing a head support member 14A provided with a strain absorbing plate 14c. In addition to the liquid supply path 14a, the head support member 14A forms a space inside and forms a liquid supply path 14b that communicates with the liquid supply path 14A.

Further, the strain absorbing plate 14c is a flat plate, and when placed on the head chip 13, the upper surface of the head chip 13 and the strain absorbing plate 14c are bonded. Further, the upper surface of the strain absorbing plate 14c and the lower surface side of the head support member 14A are bonded.
A plurality of oblong holes 14d are formed in the strain absorbing plate 14c. The liquid supply path 14b and the head chip 13 side communicate with each other through the hole 14d.

  In this case, the strain absorbing plate 14c is formed of a flat plate of invar, nickel plated steel, stainless steel, or ceramics, and the portion other than the strain absorbing plate 14c of the head support member 14A is similar to the second, It can be formed from a polymer material. By forming the head support member 14A from such a composite material of a metal material and a polymer material, the performance of the linear expansion coefficient and compression is ensured by the strain absorbing plate 14c of the metal material, and the workability and cost are reduced. On the other hand, it becomes possible to cope with this by injection molding a polymer material.

Next, a method for manufacturing the line head 10 will be described.
First, in FIG. 1B, the nozzle plate 12 is bonded to the outer frame 11 (first step). The frame-like lower surface side of the outer frame 11 is bonded to the nozzle plate 12. And adhesion | attachment is performed in the environment of temperature T1 (in the embodiment, 150 degreeC or more) which is the highest temperature during the manufacturing process of the line head 10. FIG. The temperature T1 is higher than the maximum temperature when the line head 10 is driven. Examples of the adhesive include a thermosetting sheet adhesive, and more specifically, an epoxy resin-based sheet adhesive.

  Here, in this embodiment, the linear expansion coefficient of the nozzle plate 12 is larger than the linear expansion coefficient of the outer frame 11. In particular, in the present embodiment, when the nozzle plate 12 is made of nickel, the linear expansion coefficient is about 12 to 13 [ppm]. On the other hand, in the case of ceramics, the outer frame 11 has a linear expansion coefficient of about 3 to 3.5 [ppm].

  When the nozzle plate 12 and the outer frame 11 are bonded under a temperature environment of 150 ° C., a force in the contracting direction acts on the nozzle plate 12 at a temperature lower than that. That is, at a temperature of 150 ° C. or less, a tensile stress is always generated in the nozzle plate 12. Thereby, under the temperature environment of 150 ° C. or less, the nozzle plate 12 maintains a tensioned state.

  Next, the head chip 13 is bonded to the nozzle plate 12 (second step). Adhesion between the head chip 13 and the nozzle plate 12 is performed in an environment having a temperature T2 lower than the temperature T1. Here, the temperature T2 in the present embodiment is 120 ° C. In order to bond the head chip 13 to the nozzle plate 12, it is necessary to bond the barrier layer of the head chip 13 to the nozzle plate 12. However, the bonding temperature is caused by the characteristics of the barrier layer. The barrier layer is cured under a temperature environment of 120 ° C.

  Here, nozzle holes are formed in the nozzle plate 12 so that the nozzle holes correspond to the heating elements of the head chip 13 (in the vertical direction, the central axis of each nozzle hole and the head chip 13 Adhering so that the center axis of each heating element coincides. Thus, nozzle holes are arranged on the heating elements, and a liquid chamber is formed around the heating elements by the side barrier layer and the top nozzle plate 12.

  Here, under the temperature environment of 120 ° C., tensile stress is generated in the nozzle plate 12. That is, since the nozzle plate 12 and the outer frame 11 are bonded (without distortion) in a temperature environment of 150 ° C., at 120 ° C., the difference between the linear expansion coefficient between the nozzle plate 12 and the outer frame 11 causes the nozzle. This is because the plate 12 contracts more. However, the rigidity of the outer frame 11 is stronger than the force with which the nozzle plate 12 contracts. For this reason, even if the temperature decreases from 150 ° C., the outer frame 11 is hardly distorted, and the contraction of the nozzle plate 12 coincides with the contraction of the outer frame 11.

  Although not shown in FIG. 1, dummy chips that enter with almost no gap are arranged between the head chips 13 in the longitudinal direction, and the structure is the same as that shown in FIG. . The dummy chip may be the same as the head chip 13 in which a heating element, a barrier layer, and an individual flow path are formed, or the heating element and the individual flow path are not provided, and the dummy chip is provided on the semiconductor substrate. Only the barrier layer may be provided in substantially the entire region. In any case, the dummy chip does not discharge droplets.

Next, the head support member 14 is bonded to the outer frame 11 and the head chip 13 in an environment at a temperature T3 lower than the temperature T2 (third step).
Here, the relationship between the assembly environment temperature and the strain will be described. FIG. 3 is a graph showing the relationship when the temperature change is plotted on the horizontal axis and the (arbitrary) strain is plotted on the vertical axis. For simplicity of explanation, it is assumed that temperature and strain are in a proportional relationship within the range of the graph of FIG.

In FIG. 3, a straight line L <b> 1 indicates a distortion characteristic of assembly at normal temperature (in this embodiment, 25 ° C.). When the guaranteed operation temperature of the printer is 15 to 35 ° C., the characteristic of the straight line L1 is obtained when the printer is assembled at a median value of 25 ° C. That is, at a temperature of 25 ° C., the strain amount is zero. The amount of strain when the temperature changes, for example, reaches 35 ° C. is Dmin.
Here, when considering the assembly temperature considering only the range of the guaranteed operating temperature, the median value of 25 ° C. (normal temperature) can minimize the distortion.
However, when the printer is actually used, the temperature of the line head 10 is estimated to be higher than room temperature, for example, about 45 ° C. at a room temperature of 25 ° C.

  Therefore, when the assembly is performed at 25 ° C. on the straight line L1, when the line head 10 is operated and the temperature of the line head 10 reaches 45 ° C., the distortion amount becomes Dave. On the other hand, when the assembly temperature is 45 ° C., which is the average operating temperature (estimated value) of the line head 10, the straight line L 2 is obtained, and the strain becomes 0 at 45 ° C.

  Therefore, in the present embodiment, the temperature at which the head support member 14 is bonded is 45 ° C. (design values are within a range of 45 ± 10 ° C. with a margin of 10 ° C.), and the average operating temperature (45 ° C.) The head support member 14 is prevented from being distorted. That is, the temperature T3 is 45 ° C. ± 10 ° C.

  When the printer is started after it has not been used for a long time, the temperature of the line head 10 has dropped to room temperature (25 ° C.) or lower, and at this time, the head support member 14 is distorted. However, in such a case, preliminary heating may be performed as necessary.

  Further, under a temperature environment of 45 ° C., as shown in FIG. 1, the length between the side surfaces outside the both ends in the longitudinal direction of the head support member 14 and the length between the side surfaces inside both ends in the longitudinal direction of the outer frame 11 are The head support member 14 is formed to be substantially the same (slightly shorter in length). Thereby, at the temperature T3, the head support member 14 enters the outer frame 11 with almost no gap. Therefore, no thermal stress is generated in the head support member 14 and the outer frame 11 under a temperature environment of 45 ° C.

  1, the outer side surface in the longitudinal direction of the head support member 14 and the inner side surface in the longitudinal direction of the outer frame 11 are bonded by an adhesive (the adhesive layer 15 is formed between them). ). Further, the lower surface side of the head support member 14 and the upper surface side of the head chip 13 (and a dummy chip, not shown in FIG. 1) are adhered by an adhesive, and an adhesive layer 15 is formed between the two in the same manner as described above. It is formed.

  FIG. 4 is a plan view showing the positional relationship between the head support member 14, the outer frame 11, and the adhesive layer 15. Although there is no gap as shown in FIG. 4 between the head support member 14 and the outer frame 11, it is exaggerated. As shown in FIG. 4, the adhesive layer 15 is provided not only at both longitudinal ends of the head support member 14 and the outer frame 11 but also at a substantially central portion.

  In the line head 10 having the above-described configuration, the temperature is 150 ° C. or lower during operation standby and during operation, so that the nozzle plate 12 is always in a tensile stress state. Further, the expansion and contraction of the nozzle plate 12 follows the expansion and contraction of the outer frame 11 at 150 ° C. or less. Furthermore, although the head chip 13 is bonded to the nozzle plate 12, the linear expansion coefficient of the head chip 13 and the outer frame 11 is substantially the same, and the nozzle plate 12 follows the expansion and contraction of the outer frame 11. Even if it occurs, the positional relationship between the heating element of the head chip 13 and the nozzle hole of the nozzle plate 12 does not shift.

  Furthermore, at the average operating temperature (45 ° C.) of the line head 10, no thermal stress is generated in the head support member 14 and the outer frame 11, and there is no distortion. Further, when the linear expansion coefficient of the head support member 14 is larger than the linear expansion coefficient of the outer frame 11, a compressive stress (arrow P1 in FIG. 4) is generated in the adhesive layer 15 when the temperature becomes higher than 45 ° C.

  In this case, the extension amount of the head support member 14 exceeds the extension amount of the outer frame 11, but both end portions in the longitudinal direction of the head support member 14 are sandwiched by the outer frame 11. The rigidity of the outer frame 11 is set to be larger than the rigidity of the head support member 14. That is, when the temperature becomes higher than 45 ° C., compressive stress is generated in the head support member 14, and distortion of the head support member 14 is restricted by the outer frame 11.

  Further, as shown in FIG. 4, the head support member 14 is provided with the adhesive layer 15 not only at both ends in the longitudinal direction but also at a substantially central portion in the longitudinal direction. The phenomenon that the head support member 14 becomes bowed does not occur. Further, since both ends in the longitudinal direction of the head support member 14 are suppressed by the outer frame 11, when the temperature rises, distortion also occurs in a direction perpendicular to the longitudinal direction (arrow P2 in FIG. 4). Therefore, the gap between the head support member 14 and the outer frame 11 needs to allow for a clearance especially in the vertical direction, and the adhesive layer 15 preferably has flexibility (rubber elasticity).

  For example, the polyurethane resin adhesive may have flexibility (rubber elasticity) depending on the combination of materials. Further, since the elastomer-based adhesive is based on the one that retains rubber elasticity after curing, the cured product has rubber elasticity although there is a difference in degree. For example, in a silicone resin system, the cured product has rubber elasticity regardless of whether it is a room temperature curing system or a heat curing system, due to polysiloxane as a main raw material.

As described above, when the line head 10 is formed using a plurality of types of materials having different linear expansion coefficients, distortion due to temperature change can be minimized.
The line head 10 is mounted on the ink jet printer main body, and the line head 10 and the recording medium are relatively moved. For example, the recording medium is moved in a direction perpendicular to the longitudinal direction of the line head 10 with the line head 10 side fixed to the printer body.

  Further, during this relative movement, droplets are ejected from each head chip 13 of the line head 10. That is, the heating element provided on the head chip 13 is heated, and a flying force is applied to the liquid on the heating element by a pressure change due to the generation and disappearance of bubbles on the heating element. With this flying force, droplets are ejected from the nozzle holes, and the droplets land on the recording medium, thereby forming an image.

  Although the temperature of the line head 10 is increased by driving the line head 10 as described above, the head chip 13 and the recording medium can be used even if the temperature of the line head 10 changes (even if thermal stress is generated inside the line head 10). Since the distance between and is almost unchanged, high-quality printing can be performed.

(Example)
Next, examples of the present invention will be described. The line head 10 of this example is a color line head of four colors (Y: yellow, M: magenta, C: cyan, K: black).
First, the outer frame 11 was made of ceramics (powder sintered ceramics). Since this is an outer frame 11 for a four-color color line head, it is assumed that four grooves (oval) are formed in parallel, and the major axis, minor axis, and thickness of each groove are 227 [mm] and 6.0, respectively. [Mm] and 5.0 [mm].

Further, a nickel electroformed thin film (thickness 13 [μm]) was pasted on both surfaces of the outer frame 11 under a temperature environment of 160 ° C. The lower surface side is the nozzle plate 12, and the upper surface side is a reinforcing plate for improving the balance of tension. By applying tension to both sides of the outer frame 11, the difference in stress acting on both sides of the outer frame 11 is reduced.
FIG. 5 is a diagram showing the positional relationship between the head chip 13 and the nozzle plate 12 when the ellipse for one color of the outer frame 11 is viewed from the lower surface.

  In the embodiment, since the bonding number of each head chip 13 is large and the long bonding work hole 12b is provided at a time, the distortion of the nozzle plate 12 attached at 160 ° C. increases, so that the bonding terminal has a large number of pads. However, for the head chip 13, the electrodes were divided into two groups, each corresponding to a half ellipse, so that the amount of distortion on the nozzle plate 12 was reduced.

  In addition, the above-described dummy chip D was disposed between the head chips 13 and bonded in the same manner as the head chip 13. However, the dummy chip D has no electrical connection. Further, the gap between the head chip 13 and the dummy chip D is sealed after being bonded to the nozzle plate 12 so that the liquid does not come out of the area surrounded by the head chip 13 and the dummy chip D.

  Moreover, three types of head support members 14 were manufactured. The first one is made of aluminum as a base and the surface is covered with a polyimide resin. The second is an injection molded liquid crystal plastic. The third one uses a stainless steel flat plate (thickness 0.3 mm). Further, grooves for making a gap (10 mm × 0.9 mm) into which a bonding terminal can be inserted were provided at both ends of the head support member 14.

The assembly process is as follows.
(1) The nozzle plate 12 (and the above-described reinforcing plate) is bonded to the outer frame 11 under a temperature environment of 160 ° C.
(2) The head chip 13 is pasted in accordance with the nozzle holes 12a formed on the nozzle plate 12 with high precision by photolithography in advance.
(3) The dummy chip D is pasted while referring to the position of the head chip 13.
(4) The gap between the dummy chip D and the head chip 13 is sealed.

(5) An adhesive is applied to the upper surfaces of the head chip 13 and the dummy chip D, and the head support member 14 is dropped from above the groove formed in the outer frame 11 to bond the head support member 14 and the head chip 13 together.
(6) Fill a predetermined position around the head support member 14 with an adhesive, press the head support member 14 with a fixing jig, and leave it for a specified time (for fixing the adhesive). This process was attempted at room temperature (25 ° C.) as well as in an environment of 45 ° C., which is the average operating temperature of the line head 10.

(7) After confirming the adhesion and fixing of the head support member 14, the fixing jig is removed, and the required number of bonding terminals (16 in one embodiment, 64 in one color in the embodiment) are precisely placed on the printed circuit board in advance. The terminal board arranged in (1) is inserted from above the head support member 14 and fixed to the outer frame 11 with an adhesive.
(8) Perform wire bonding.
(9) The bonding work hole 12b is sealed.

  Printing was performed using the line head 10 manufactured in the above process. The head support member 14 is made of aluminum and polyimide resin. Both the head support member 14 bonded at normal temperature (25 ° C.) and the one bonded at average operating temperature (45 ° C.). Then, printing was performed at room temperature of 35 ° C. As a result, it was confirmed that the print quality was better than before and the influence of thermal stress could be reduced.

It is a figure which shows the line head of this embodiment, (A) is an exploded plan view before an assembly, (B) is a side view before an assembly, (C) is sectional drawing of the side surface after an assembly. It is a figure which shows the head support member which provided the distortion absorption board. It is a figure which shows a relationship when a temperature change is taken on a horizontal axis | shaft and a distortion amount is taken on the vertical axis | shaft on a graph. It is a top view which shows the positional relationship with a head support member, an outer frame, and an adhesive layer. It is a figure which shows the positional relationship of a head chip and a nozzle plate when the ellipse for one color of an outer frame is seen from the lower surface. It is a figure which shows this kind of line head typically. It is sectional drawing which shows a flow-path board, a head chip, and a nozzle plate in detail. It is sectional drawing explaining generation | occurrence | production of the thermal stress and distortion in a line head. 3 shows the result of taking a picture of the liquid ejection part of the line head when subjected to thermal stress.

Explanation of symbols

10 Line head (liquid discharge head)
11 Outer frame (first support)
12 Nozzle plate 12a Nozzle hole 13 Head chip 14 Head support member (second support)
14a Liquid supply port 14b Liquid supply path 14c Strain absorbing plate 15 Adhesive layer

Claims (15)

A nozzle plate having nozzle holes for discharging droplets;
A first support formed in a frame shape;
A head chip in which a plurality of heating elements are arranged on a semiconductor substrate;
And at least a part of the second support disposed in a frame-like inner peripheral region of the first support,
A liquid discharge head in which a plurality of the head chips are joined in a line on the nozzle plate such that each of the heating elements and each of the nozzle holes are opposed to each other,
The linear expansion coefficient of the head chip is substantially the same as the linear expansion coefficient of the first support.
The linear expansion coefficient of the nozzle plate is larger than the linear expansion coefficient of the first support,
The linear expansion coefficient of the second support is greater than the linear expansion coefficient of the first support,
The nozzle plate is bonded to the first support, and in a temperature environment in which no thermal stress is generated on the bonding surface between the first support and the second support, A tensile stress is generated by the first support;
The second support is joined to the first support so that at least a part of the outer side surface at both ends in the longitudinal direction is sandwiched by at least a part of the inner peripheral side of the first support,
When the second support is thermally expanded with respect to the first support, a compressive stress is generated in the second support, and distortion of the second support is regulated by the first support. A liquid discharge head characterized by that. The liquid discharge head according to claim 1,
At the average operating temperature of the liquid discharge head, compressive stress is not generated on the joint surface between the second support and the first support, and the nozzle plate is supported by the first support. A liquid discharge head characterized in that tensile stress is generated. The liquid discharge head according to claim 1,
Within the range of 45 ± 10 ° C., which is the average operating temperature of the liquid discharge head, it is possible to prevent compressive stress from being generated on the joint surface of the second support with the first support, and to the nozzle plate. Is a liquid discharge head characterized in that a tensile stress is generated by the first support. The liquid discharge head according to claim 1,
The liquid ejection head according to claim 1, wherein a linear expansion coefficient of the second support is larger than a linear expansion coefficient of the first support and is 1.5 times or less of a linear expansion coefficient of the first support. The liquid discharge head according to claim 1,
The first support is formed of a ceramic having a linear expansion coefficient within a range of 0.5 to 1.5 times the linear expansion coefficient of a silicon single crystal or a silicon polycrystal. Liquid discharge head. The liquid discharge head according to claim 1,
The liquid ejection head, wherein the nozzle plate is made of nickel or polyimide. The liquid discharge head according to claim 1,
The second support is ceramic, silicon single crystal, or silicon polycrystal having a linear expansion coefficient within a range of 0.5 to 1.5 times the linear expansion coefficient of the silicon single crystal or silicon polycrystal. A polymer material having a linear expansion coefficient in the range of 0.5 to 1.5 times the linear expansion coefficient of the body, Invar, titanium or an alloy thereof, nickel steel, nickel-plated steel, stainless steel, or aluminum nitride Of these, a liquid ejection head is formed of a combination of one or two or more materials. The liquid discharge head according to claim 1,
The second support is
A liquid supply port formed by partly opening;
A liquid discharge head comprising: the liquid supply port; and a supply path communicating with the heating element of the head chip. The liquid discharge head according to claim 1,
The second support is
A liquid supply port formed by partly opening;
A liquid supply port and a supply path communicating with the heat generating element of the head chip;
With respect to the linear expansion coefficient of ceramics, silicon single crystal body or silicon polycrystal body having a linear expansion coefficient within the range of 0.5 to 1.5 times the linear expansion coefficient of silicon single crystal body or silicon polycrystal body One or more of polymer materials having a linear expansion coefficient in the range of 0.5 to 1.5 times, invar, titanium or an alloy thereof, nickel steel, nickel-plated steel, stainless steel, or aluminum nitride A liquid discharge head characterized by being formed of a combination of materials. The liquid discharge head according to claim 1,
The second support is
A liquid supply port formed by partly opening;
A supply path communicating with the liquid supply port and the heating element of the head chip;
With ceramics, invar, nickel steel, nickel-plated steel, or stainless steel having a linear expansion coefficient within a range of 0.5 to 1.5 times the linear expansion coefficient of silicon single crystal or silicon polycrystal, A portion including a liquid supply port is formed;
The supply path is formed of a polymer material having a linear expansion coefficient in a range of 0.5 to 1.5 times the linear expansion coefficient of a silicon single crystal or a silicon polycrystal. Liquid discharge head. A nozzle plate having nozzle holes for discharging droplets;
A first support formed in a frame shape;
A head chip in which a plurality of heating elements are arranged on a semiconductor substrate;
And at least a part of the second support disposed in a frame-like inner peripheral region of the first support,
A liquid ejection head in which a plurality of the head chips are joined in a line on the nozzle plate so that each of the heating elements and each of the nozzle holes face each other;
The linear expansion coefficient of the head chip is substantially the same as the linear expansion coefficient of the first support.
The linear expansion coefficient of the nozzle plate is larger than the linear expansion coefficient of the first support,
The linear expansion coefficient of the second support is greater than the linear expansion coefficient of the first support,
The nozzle plate is bonded to the first support, and in a temperature environment in which no thermal stress is generated on the bonding surface between the first support and the second support, A tensile stress is generated by the first support;
The second support is joined to the first support so that at least a part of the outer side surface at both ends in the longitudinal direction is sandwiched by at least a part of the inner peripheral side of the first support,
When the second support is thermally expanded with respect to the first support, a compressive stress is generated in the second support, and distortion of the second support is regulated by the first support. A liquid ejection device characterized by that. A nozzle plate having nozzle holes for discharging droplets;
A first support formed in a frame shape;
A head chip in which a plurality of heating elements are arranged on a semiconductor substrate;
And at least a part of the second support disposed in a frame-like inner peripheral region of the first support,
The linear expansion coefficient of the head chip is substantially the same as the linear expansion coefficient of the first support.
The linear expansion coefficient of the nozzle plate is larger than the linear expansion coefficient of the first support,
The linear expansion coefficient of the second support is larger than the linear expansion coefficient of the first support.
A first step of joining the nozzle plate to the first support under an environment of temperature T1;
A second step of joining a plurality of the head chips to the nozzle plate such that each of the heating elements and each of the nozzle holes face each other under an environment of a temperature T2 lower than the temperature T1;
In an environment of temperature T3 lower than the temperature T2, the second support is sandwiched between at least a part of the outer side surfaces at both ends in the longitudinal direction by at least a part of the inner peripheral side surface of the first support. And a third step of bonding to the first support. In the manufacturing method of the liquid discharge head according to claim 12 ,
In the third step, the second support is bonded to the first support using an adhesive in the environment of the temperature T3, and solidification of the adhesive is completed. Manufacturing method of the head. In the manufacturing method of the liquid discharge head according to claim 12 ,
The temperature T3 in the third step is an average operating temperature of the liquid discharge head. A method of manufacturing a liquid discharge head, wherein: In the manufacturing method of the liquid discharge head according to claim 12 ,
The method for manufacturing a liquid discharge head, wherein the temperature T3 in the third step is within a range of 45 ± 10 ° C. which is an average operating temperature of the liquid discharge head.