WO2024034219A1 - Manufacturing method for nozzle plate, nozzle plate, manufacturing method for inkjet head, inkjet head, and image forming device - Google Patents

Abstract

The present invention pertains to a manufacturing method for a nozzle plate, in which a substrate is press-punched to form a nozzle hole therein. The manufacturing method reduces sag width and better suppresses plastic deformation of the entire substrate, with a simpler configuration. This manufacturing method for a nozzle plate includes: a step for preparing a metal substrate having a thickness greater than 25 μm and a Vickers hardness of 250 HV or greater; and a step for press-punching the prepared substrate to form a nozzle hole for discharging droplets of a liquid.

Description

Nozzle plate manufacturing method, nozzle plate, inkjet head manufacturing method, inkjet head, and image forming device

The present invention relates to a nozzle plate manufacturing method, a nozzle plate, an inkjet head manufacturing method, an inkjet head, and an image forming apparatus.

An inkjet head used in an inkjet printer or the like has a nozzle plate equipped with a large number of minute nozzle holes for ejecting droplets (ink).

As a method for manufacturing a nozzle plate, for example, Patent Document 1 discloses that a photoresist pattern corresponding to the shape of the nozzle hole to be formed is formed on a substrate made of SUS or the like, and the substrate on which the photoresist pattern is formed is coated with a photoresist pattern. A method for manufacturing a nozzle plate is disclosed in which, after forming a Ni plating film, the substrate and the photoresist pattern are separated from the Ni plating layer to form nozzle holes. According to Patent Document 1, by forming a Ni-FEP plating layer on the nozzle plate and heat-treating the plating layer, it was possible to manufacture a nozzle plate in which decreases in rigidity and brittleness were suppressed. There is.

As one method for manufacturing a nozzle plate more simply, a punching method is known in which a punch is press-fitted into a substrate to form nozzle holes.

For example, Patent Document 2 discloses that after a punch is press-fitted into a substrate made of SUS or the like, a nozzle hole is formed by polishing and removing the protrusions produced by press-fitting the punch into the substrate. A method of manufacturing a nozzle plate is disclosed in which the surface of a formed metal plate is blasted. According to Patent Document 2, by blasting the surface of a polished nozzle plate, it is possible to appropriately adjust the surface roughness and increase the adhesive strength between the nozzle plate and a flow path forming member used for manufacturing an inkjet head. It is said that it was possible.

By the way, when the punching method is used, there is a problem in that as the punch is press-fitted, a sag is formed on the uppermost edge in the press-fitting direction of the punch. If the width of the sag is large, a problem arises in that a sufficient area of the flat portion of the surface of the substrate on the most upstream side in the droplet ejection direction cannot be secured. The flat portion becomes a bonding surface with another member (for example, a flow path member forming an ink flow path) during manufacture of the inkjet head, so it is necessary to ensure a sufficient area. Therefore, it is desired to develop a method for manufacturing a nozzle plate that can reduce the width of the sagging when nozzle holes are formed by punching.

For example, Patent Document 3 discloses that before forming a plurality of nozzle holes in a metal or resin plate by punching, sag is removed from the edge of the nozzle hole on the most upstream side in the droplet ejection direction. A method of manufacturing a nozzle plate is disclosed that forms a ring-shaped recess to reduce the width.

Japanese Patent Application Publication No. 2003-127345 Japanese Patent Application Publication No. 2004-255696 Japanese Patent Application Publication No. 2012-254531

However, the method described in Patent Document 3 requires two punching operations, one for forming the nozzle holes and the other for forming the recesses, which is time-consuming and difficult to manufacture the nozzle plate simply. there were.

Additionally, there is a desire to more fully suppress plastic deformation of the entire substrate during punching. This is because if the substrate is plastically deformed, when the nozzle plate is used in an inkjet head, the ink ejection direction will be bent with respect to the central axis of the nozzle, resulting in a decrease in ejection stability.

The present invention has been made in view of the above circumstances, and is a method for manufacturing a nozzle plate in which nozzle holes are formed by press-fitting a punch into a substrate, and it is possible to reduce the width of sag with a simpler configuration. It is an object of the present invention to provide a method for manufacturing a nozzle plate, a method for manufacturing a nozzle plate, an inkjet head, an inkjet head, and an image forming apparatus that can further suppress plastic deformation of the entire substrate.

One aspect of the present invention for solving the above problems relates to the method of manufacturing a nozzle plate described in [1] to [9] below.
[1] A step of preparing a metal substrate with a thickness of more than 25 μm and a Vickers hardness of 250 HV or more, and press-fitting a punch into the prepared substrate to form a nozzle hole for ejecting droplets. A method for manufacturing a nozzle plate, comprising: forming a nozzle plate.
[2] The method for manufacturing a nozzle plate according to [1], wherein in the step of forming the nozzle holes, a plurality of the nozzle holes are formed such that the distance between adjacent nozzle holes is 170 μm or less.
[3] The method for manufacturing a nozzle plate according to [1] or [2], wherein the substrate has a thickness of 30 μm or more and 45 μm or less.
[4] The method for manufacturing a nozzle plate according to any one of [1] to [3], wherein the thickness of the substrate is 35 μm or more and 45 μm or less.
[5] The step of forming the nozzle hole includes press-fitting the punch into the substrate, the punch having a first press-fitting part whose wall surface is inclined with respect to the press-fitting direction of the punch, according to any one of [1] to [4]. A method of manufacturing the nozzle plate described.
[6] The punch has a second press-fitting part that is continuous with the first press-fitting part on a lower side than the first press-fitting part with respect to the press-fitting direction of the punch, and the second press-fitting part has a second press-fitting part that is continuous with the first press-fitting part, and The method for manufacturing a nozzle plate according to [5], wherein the inclination with respect to the press-fitting direction is smaller than the inclination of the wall surface of the first press-fitting part with respect to the press-fitting direction.
[7] The method for manufacturing a nozzle plate according to [5] or [6], wherein the punch has a wall surface of the first press-fitting portion whose inclination relative to the press-fitting direction is 45° or more.
[8] The punch satisfies the relationship of formula (1), where θ _a is the inclination of the wall surface of the first press-fitting part of the punch with respect to the press-fitting direction, and H _A is the Vickers hardness of the metal. , the method for manufacturing a nozzle plate according to [5] to [7].
θ _a ≦0.0234×H _A +38.67 (1)
[9] In the step of forming the nozzle hole, the maximum width of the nozzle hole to be formed on the most downstream side in the droplet ejection direction is n, and the Vickers hardness of the metal is _H The method for manufacturing a nozzle plate according to any one of [1] to [8], wherein the nozzle hole is formed to satisfy the relationship (2).
n≦0.0672×H _A +2.01 (2)
[10] A step of preparing a substrate placed on a die having an opening, and a step of press-fitting a punch into the prepared substrate to form a nozzle hole for ejecting droplets, In the step of forming the nozzle hole, the maximum width of the nozzle hole to be formed on the lowermost side in the press-fitting direction of the punch is n, the maximum width of the opening of the die is d, and the thickness of the substrate is t. A method for manufacturing a nozzle plate, in which the nozzle hole is formed so as to satisfy the relationship of formula (A).
t+n<d≦2t+n (A)

One aspect of the present invention for solving the above problems relates to the nozzle plates of [11] to [22] below.
[11] A nozzle plate having a nozzle hole for ejecting droplets, the nozzle plate being made of metal with a thickness of more than 25 μm and a Vickers hardness of 250 HV or more.
[12] The nozzle plate according to [11], wherein the nozzle plate has a plurality of nozzle holes, and a distance between the plurality of adjacent nozzle holes is 170 μm or less.
[13] The nozzle plate according to [11] or [12], which has a thickness of 30 μm or more and 45 μm or less.
[14] The nozzle plate according to any one of [11] to [13], which has a thickness of 35 μm or more and 45 μm or less.
[15] The nozzle plate according to any one of [11] to [14], wherein the nozzle hole has a first flow path whose wall surface is inclined with respect to the ejection direction of the droplets.
[16] The nozzle hole has a second flow path arranged to communicate with the first flow path on the downstream side of the first flow path with respect to the ejection direction of the droplets. , the nozzle plate according to [15], wherein the inclination of the wall surface of the second channel with respect to the discharge direction is smaller than the inclination of the wall surface of the first channel with respect to the discharge direction.
[17] The nozzle plate according to [15] or [16], wherein the wall surface of the first channel has an inclination of 45° or more with respect to the discharge direction.
[18] When the Vickers hardness of the metal is _HB and the inclination of the wall surface of the first flow path of the nozzle hole with respect to the ejection direction of the droplet is θ ₁ , the relationship of formula (3) is satisfied; The nozzle plate according to any one of [15] to [17].
θ ₁ ≦0.0234×H _B +38.67 (3)
[19] When the Vickers hardness of the metal is _HB and the maximum width of the nozzle hole on the most downstream side in the droplet ejection direction is n, the relationship of formula (4) is satisfied, [11] The nozzle plate according to any one of ~[18].
n≦0.0672×H _B +2.01 (4)
[20] The nozzle plate has a bonding surface for bonding to an external member on the most upstream surface in the droplet ejection direction, and the bonding surface has a direction in which the plurality of nozzle holes are arranged. The nozzle plate according to any one of [11] to [19], wherein the width of the nozzle plate is 50 μm or more.
[21] The nozzle plate according to [20], wherein the joint surface has a groove.
[22] The nozzle plate according to any one of [11] to [21], wherein the width of the sag in the direction perpendicular to the droplet ejection direction of the nozzle plate is 14 μm or less.

One aspect of the present invention for solving the above problems relates to the method of manufacturing an inkjet head described in [23] and [24] below.
[23] A method for manufacturing an inkjet head, comprising a step of joining the nozzle plate according to any one of [11] to [22] and a flow path member for supplying ink to the nozzle holes of the nozzle plate. .
[24] The method for manufacturing an inkjet head according to [24], wherein the amount of adhesive used in the joining step is less than 0.1 g.

One aspect of the present invention for solving the above problems relates to the inkjet head described in [25] below.
[25] An inkjet head comprising the nozzle plate according to any one of [11] to [22].

One aspect of the present invention for solving the above problem relates to the image forming apparatus described in [26] below.
[26] An image forming apparatus having the inkjet head according to [25].

According to the present invention, there is provided a method for manufacturing a nozzle plate in which nozzle holes are formed by press-fitting a punch into a substrate, and the width of sag can be reduced with a simpler configuration, and plastic deformation of the entire substrate can be prevented. Provided are a method for manufacturing a nozzle plate, a nozzle plate, a method for manufacturing an inkjet head, an inkjet head, and an image forming apparatus that can more fully suppress the effects.

FIG. 1 is a flowchart showing a method for manufacturing a nozzle plate according to the first embodiment. 2A to 2C are schematic cross-sectional views showing how a punch is press-fitted into a substrate. FIG. 3 is a schematic cross-sectional view showing the shape of a punch used in the above-described nozzle plate manufacturing method. FIG. 4 is a schematic diagram of a nozzle plate showing the contents of each symbol in formulas (a) and (b). FIG. 5 is a schematic cross-sectional view showing an example of the nozzle plate according to the first embodiment. FIG. 6 is a perspective view showing an outline of the inkjet head according to the first embodiment. FIG. 7 is a perspective view showing a nozzle plate included in the inkjet head. FIG. 8 is a cross-sectional view taken along line AA in FIG. 6. FIG. 9 is a diagram schematically showing the configuration of an image forming apparatus according to the first embodiment. FIG. 10 is a schematic cross-sectional view showing a method for manufacturing a nozzle plate according to the second embodiment. FIG. 11 is a graph showing the relationship between the Vickers hardness of the substrate and the width of the sag. FIG. 12 is a graph showing the relationship between the Vickers hardness of the substrate and the maximum value of θ _a (θ ₁ ) for ensuring the width of the bonding surface. FIG. 13 is a graph showing the relationship between the Vickers hardness of the substrate and the maximum value of n for ensuring the width of the bonding surface.

Hereinafter, embodiments of the present invention will be described in detail. Note that the present invention is not limited to the following embodiments.

(Embodiment 1)
1. Method for Manufacturing a Nozzle Plate FIG. 1 is a flowchart showing a method for manufacturing a nozzle plate according to the present embodiment. As shown in FIG. 1, the method for manufacturing a nozzle plate according to the present embodiment includes a step of preparing a metal substrate having a Vickers hardness of 250 HV or more (step S10), and punching the prepared substrate. A step of press-fitting and forming a nozzle hole for ejecting droplets (step S20), and a step of polishing the surface of the substrate in which the nozzle hole is formed on the lowermost side in the press-fitting direction of the punch (step S30). ) and has.

As mentioned above, there is a growing demand for a nozzle plate manufacturing method that has a simple configuration and can reduce the width of sag. It is thought that the sag is formed by tensile stress generated when the punch is press-fitted into the substrate.

On the other hand, the inventor of the present invention, after extensive study, discovered that the width of the sag can be significantly reduced by using a metal substrate with a Vickers hardness of 250 HV or more as the substrate into which the punch is press-fitted. Ta. This is believed to be because the Vickers hardness of 250 HV or more can sufficiently suppress deformation of the uppermost edge portion of the nozzle hole in the punch press-fitting direction due to tensile stress generated during punch press-fitting.

By using a metal substrate with a Vickers hardness of 250 HV or more, the width of the sag can be easily reduced without increasing the number of steps as in Patent Document 3.

In addition, the present inventor has found that by making the thickness of a metal substrate with a Vickers hardness of 250 HV or more greater than 25 μm and press-fitting a punch, plastic deformation of the entire substrate can be more effectively suppressed. I found out. Because the thickness is greater than 25 μm, the stress caused by press-fitting the punch is less likely to reach the entire substrate, and because the Vickers hardness is 250 HV or more, the stress is even less likely to be applied to the substrate. It is thought that.

Note that in this specification, the "width of the sag" refers to the width of the sag formed on the nozzle plate in the direction perpendicular to the droplet ejection direction (see W in FIG. 4).

Furthermore, in this specification, the "upper side" of the punch in the press-fitting direction refers to the upstream side in the press-fitting direction, and the "lower side" refers to the downstream side in the press-fitting direction.

1-1. Step of preparing a substrate (step S10)
In this step, a metal substrate having a Vickers hardness of 250 HV or more is prepared.

The material of the substrate is not particularly limited as long as it is a metal with a Vickers hardness of 250 HV or more. Examples of metals having a Vickers hardness of 250HV or higher include stainless steel (SUS3042B, SUS304H, SUS304HTA), chrome steel (300HV), nickel-chrome steel (300HV), tungsten (340HV), and the like.

From the viewpoint of further reducing the width of the sag, the Vickers hardness is more preferably 300 HV or more, and even more preferably 400 HV or more. The Vickers hardness can be measured by a method according to JIS Z 2244:2009.

The thickness of the substrate is preferably 30 μm or more and 45 μm or less, more preferably 35 μm or more and 45 μm or less. When the thickness of the substrate is 30 μm or more, plastic deformation of the entire substrate can be suppressed when a punch is press-fitted into the substrate in the step of forming a nozzle hole (step S20), which will be described later. In this embodiment, since a metal substrate having a Vickers hardness of 250 HV or more is used, when the thickness of the substrate is 30 μm or more, the above-mentioned plastic deformation can be significantly suppressed.

In addition, when the thickness of the substrate is 45 μm or less, the width of the flat portion (hereinafter referred to as the bonding surface) on the most upstream surface of the nozzle plate in the droplet ejection direction tends to be larger. .

1-2. Step of forming a nozzle hole (step S20)
In this step, a punch is press-fitted into the substrate prepared in step S10 to form a nozzle hole for ejecting droplets.

FIG. 2 is a schematic cross-sectional view showing how a punch is press-fitted into a substrate (FIGS. 2A and 2B). In this embodiment, for example, by press-fitting the punch 120 into the substrate 100 placed on the die 110, a nozzle hole 210 (described later) having a shape corresponding to the shape of the punch 120 press-fitted into the substrate 100 is formed. (Figure 2C). Note that arrow A in FIG. 2 represents the press-fitting direction of the punch 120.

The punch 120 is preferably made of metal with a Vickers hardness of 780 HV or more. By using such a punch 120, damage to the punch 120 when press-fitting into the substrate 100 can be suppressed. Examples of metals having a Vickers hardness of 780 HV or higher include high speed steel, cemented carbide, and the like.

The press-fitting speed of the punch 120 is preferably 1 μm/s or more, more preferably 3 μm/s or more. When the press-fitting speed is 1 μm/s or more, the production efficiency of the nozzle hole can be further improved. Further, the upper limit of the press-fitting speed is not particularly limited, but is preferably 50 μm/s or less, for example. When the speed is 500 μm/s or less, it is easy to form a nozzle hole having a shape corresponding to the shape of the punch 120. Further, when the speed is 500 μm/s or less, the punch becomes less likely to be damaged.

In this step, it is preferable to form a plurality of nozzle holes in which the distance between adjacent nozzle holes is 170 μm or less. By forming the nozzle holes in this way, when the manufactured nozzle plate is used in an inkjet head, a higher definition image can be formed. In this specification, "the distance between adjacent nozzle holes" refers to the distance between the centers of adjacent nozzle holes.

Conventionally, when the distance between adjacent nozzle holes is reduced, the width of the joint surface between the nozzle holes tends to become smaller. Therefore, when the width of the sag is large, it tends to become more difficult to secure the above-mentioned bonding surface. On the other hand, in the method for manufacturing a nozzle plate according to the present embodiment, the width of the sag can be reduced by using a metal substrate having a Vickers hardness of 250 HV or more. Even if the distance between them is made small, the above-mentioned bonding surface can be easily secured.

The lower limit of the distance between the adjacent nozzle holes is not particularly limited, but is, for example, 85 μm or more.

FIG. 3 is a schematic cross-sectional view showing the shape of the punch 120. In this step, it is preferable that a punch 120 having a first press-fitting part 121 whose wall surface is inclined with respect to the press-fitting direction of the punch 120 (arrow A in FIG. 3) is press-fitted into the substrate 100 in the same direction as the droplet ejection direction. In particular, this embodiment includes a first press-fitting part 121 and a second press-fitting part 122 that is continuous with the first press-fitting part 121 on the downstream side of the first press-fitting part 121 with respect to the press-fitting direction of the punch 120. However, the slope of the wall surface 122a of the second press-fitting part 122 with respect to the press-fitting direction (θ _b in FIG. 3) is smaller than the slope of the wall surface 121a of the first press-fitting part 121 with respect to the press-fitting direction (θ _a in FIG. 3). It is preferable that the punch 120 having the above-mentioned shape be press-fitted into the substrate 100 in the same direction as the droplet ejection direction. By forming nozzle holes corresponding to such a shape, when an inkjet head using a nozzle plate is used, the ejection stability of ink droplets can be further improved. The reason for this is thought to be as follows.

When ink is continuously ejected, the ink remaining in the nozzle hole is drawn into the inkjet head immediately before the ink is ejected. As a result, air is drawn into the inkjet head (upstream of the nozzle plate with respect to the droplet ejection direction) along with the ink, so the next time the ink is ejected, air bubbles may be included in the ink. As a result, the ejection stability tends to deteriorate. On the other hand, since the nozzle hole has a shape corresponding to the first press-fitting part 121, the area of the cross section of the nozzle hole perpendicular to the droplet ejection direction increases as it goes upstream in the ejection direction. Therefore, due to pressure loss, it becomes difficult for the drawn air to reach the inside of the inkjet head. Moreover, since the nozzle hole has a shape corresponding to the shape of the second press-fitting part 122, bending of ink ejection can be further suppressed. For these reasons, by using a punch having the above-mentioned shape, it is possible to further improve ink ejection stability when the manufactured nozzle plate is used in an inkjet head.

In addition, in this specification, among the angles formed by the straight line P1 parallel to the press-fitting direction of the punch and the wall surface 121a of the first press-fitting part 121, an acute angle is referred to as "the wall surface 121a of the first press-fitting part 121". The slope of θ _a is ``. Furthermore, an acute angle between the straight line P2 parallel to the press-fitting direction of the punch and the wall surface 122a of the second press-fitting section 122 is defined as "the inclination θ _b of the wall surface 122a of the second press-fitting section 122."

The above-mentioned inclination θ _a of the first press-fitting portion 121 is preferably 15° or more, more preferably 30° or more, and even more preferably 45° or more. When the above-mentioned inclination θ _a is 15° or more, the inclination of the wall surface of the formed nozzle hole with respect to the droplet ejection direction becomes larger. Thereby, when the manufactured nozzle plate is used in an inkjet head, it is possible to make it more difficult for the drawn-in air to reach the inside of the inkjet head, thereby further improving ejection stability. When the inclination θ _a is 45° or more, the ejection stability can be improved more fully, and the fluid resistance during ink ejection can be lowered to further improve the ejection stability. Furthermore, it is possible to further suppress a decrease in the robustness of the nozzle plate due to variations in shape and dimensions during manufacturing and processing.

From the viewpoint of further reducing the width of the sag, the above-mentioned inclination θ _a is preferably 50° or less.

The maximum width (W _a in FIG. 3 ) of the first press-fitting part 121 on the uppermost side in the press-fitting direction of the punch 120 is preferably 100 μm or more and 200 μm or less. By setting the maximum width W _a within the above range, the punch 120 can be manufactured more easily.

The length of the first press-fitting portion 121 in the press-fitting direction of the punch 120 (L _a in FIG. 3) is preferably 40 μm or more and 55 μm or less. When the above-mentioned L _a is 40 μm or more, the length of the nozzle hole to be formed can be more sufficiently ensured, and the drawing of air into the inside of the inkjet head can be further suppressed. Thereby, the ejection stability can be further improved. Moreover, when the above-mentioned L _a is 55 μm or less, space saving of the nozzle plate in the inkjet head can be more easily achieved.

The above-mentioned inclination θ _b of the second press-fitting part 122 is preferably 0° or more and 9° or less, more preferably 0° or more and 5° or less, and even more preferably 0° or more and 3° or less, It is particularly preferable that the angle is 0° or more and 1° or less. When the above-mentioned inclination θ _b is 9° or less, when the manufactured nozzle plate is used in an inkjet head, ink ejection bending can be further suppressed and ink ejection stability can be further improved.

The maximum width (W _b in FIG. 3 ) of the second press-fitting portion 122 on the lowermost side in the press-fitting direction of the punch 120 is preferably 18 μm or more and 50 μm or less. By setting the maximum width W _b to 18 μm or more, the punch 120 is less likely to be damaged during press-fitting into the substrate 100 . When the maximum width W _b is 50 μm or less, the width of the droplet ejection opening of the formed nozzle hole can be made smaller, and a higher definition image can be formed.

The length of the second press-fitting portion 122 in the press-fitting direction of the punch 120 (L _b in FIG. 3) is preferably 10 μm or more and 25 μm or less. When the above-mentioned L _b is 10 μm or more, when the manufactured nozzle plate is used in an inkjet head, ink ejection bending can be further suppressed and ink ejection stability can be further improved. Moreover, when the above-mentioned L _b is 25 μm or less, space saving of the nozzle plate in the inkjet head can be more easily achieved.

In the punch 120, it is preferable that the above-mentioned inclination _θa of the first press-fitting portion 121 satisfies the relationship of equation (1), where _HA is the Vickers hardness of the metal that is the material of the substrate 100.
θ _a ≦0.0234×H _A +38.67 (1)

FIG. 4 is a schematic diagram of a nozzle plate showing the contents of each symbol in the following formula (a). Equation (1) can be derived as follows.

(1) Create a correlation formula for the relationship between the Vickers hardness of the substrate (250 HV or more) and the width of the sag formed (W in Fig. 4, hereinafter referred to as sag width), and calculate the sag at a given Vickers hardness. Find the width W. (2) Substitute the calculated sag width W into equation (a) to find θ _a for the minimum value (x _min ) of the width of the joint surface (x in FIG. 4) to be 50 μm. (3) The above operations (1) and (2) are performed while changing the Vickers hardness, and the relationship between the Vickers hardness and θ _a can be derived by creating a correlation equation. Note that in deriving equation (1), the fixed values shown below are used for values other than θ _a and W in equation (a).
x _min =P-(n+2L _a・tanθ _a +2L _b・tanθ _b +2W) (a)
(P=170 μm, n=20 μm, L _a =40 μm, L _b =5 μm, θ _b =0°)

In formula (a), P indicates the distance between adjacent nozzle holes (the distance between the centers of the nozzle holes), and n indicates the most downstream distance in the droplet ejection direction (arrow B in FIG. 4) of the nozzle holes to be formed. Indicates the maximum width of the side.

Equation (1) derived in this way is based on θ a and _H in order to secure the junction width x of 50 μm or more when P, n, L _a , L _b , and θ _b are the above values. represents the relationship between Therefore, as long as L _a , L _b , and θ _b have the above values, when θ _a and H are adjusted to satisfy formula (1), the junction width x is at least 50 μm, From (a), P and n can be adjusted as appropriate. Thereby, a sufficient bonding width can be ensured while adjusting the distance between adjacent nozzle holes and the maximum width of the nozzle to desired values.

Furthermore, when the relationship of equation (1) is satisfied, the larger the Vickers hardness value of the material of the substrate 100, the larger the value of θ _a can be. Therefore, in an inkjet head using a nozzle plate, it is possible to further suppress the drawing of air from the nozzle holes, further improve ejection stability, and make it easier to secure a bonding surface.

In this step, the maximum width n of the nozzle hole to be formed on the most downstream side in the droplet ejection direction and the Vickers hardness _HA of the metal that is the material of the substrate 100 satisfy the relationship of formula (2). Preferably, the nozzle hole is formed by press-fitting the punch 120 in the same direction as the droplet ejection direction.
n≦0.0672×H _A +2.01 (2)

Equation (2) can be derived as follows.

(1) Create a correlation formula for the relationship between the Vickers hardness of the substrate (250 HV or more) and the width of the sag formed (W in Fig. 4, hereinafter referred to as sag width), and calculate the sag at a given Vickers hardness. Find the width W. (2) Substitute the obtained sag width W into equation (a) to find n for the minimum width (x _min ) of the joint surface to be 50 μm. (3) The above operations (1) and (2) are performed while changing the Vickers hardness, and the relationship between the Vickers hardness and n can be derived by creating a correlation equation. Note that in deriving equation (1), for values other than n and W in equation (a), θ _a =45° and the above-mentioned values of P, L _a , L _{b, and} θ _b are used.

Equation (2) derived in this way is based on n and H in order to ensure the junction width x of 50 μm or more when P, L _a , L _b , θ _a , and θ _b are the above values. represents the relationship between Therefore, as long as L _a , L _b , and θ _b have the above values, P , n can be adjusted as appropriate. Thereby, a sufficient bonding width can be ensured while adjusting the distance between adjacent nozzle holes and the above-mentioned inclination of the punch to desired values.

Further, when the relationship of formula (2) is satisfied, the value of n can be increased as the value of the Vickers hardness of the substrate 100 is larger. Therefore, in an inkjet head using a nozzle plate, it is possible to further reduce fluid resistance during ink ejection, further improve ejection stability, and make it easier to secure a bonding surface.

In this embodiment, for example, the punch 120 is attached to the substrate 100 such that the maximum width W _b of the second press-fitting part 122 on the lowest side in the press-fitting direction of the punch 120 satisfies W _b ≦0.0672×H+2.01. By press-fitting, a nozzle hole that satisfies formula (2) can be formed.

The shapes of the cross sections of the first press-fitting part 121 and the second press-fitting part 122 in the direction orthogonal to the press-fitting direction are, for example, circular or oval, but from the viewpoint of further increasing ink ejection stability, they should be circular. is preferred.

When this step is performed using the die 110, the maximum width of the nozzle hole to be formed on the lowest side in the press-fitting direction of the punch is n, the maximum width of the opening of the die 110 is d, and the maximum width of the opening of the die 110 is d. When the thickness is t, the above-mentioned nozzle hole is formed that satisfies the relationship of formula (A) (see FIG. 2).
t+n<d≦2t+n (A)

The maximum width d of the opening of the die 110 is larger than the sum (t+n) of the maximum width n of the nozzle hole and the thickness t of the substrate, thereby making it easier for the punch 120 to penetrate the substrate 100. Can be done. This makes it easier to form the nozzle hole in accordance with the shape of the punch 120. Further, the load on the punch 120 can be reduced, and deterioration of the punch 120 can be further suppressed.

Further, since the maximum width d of the opening of the die 110 is 2t+n or less, the press-fitting pressure of the punch 120 applied to the substrate 100 is difficult to be dispersed, and the punch 120 can be press-fitted into the substrate 100 more easily. can.

In the present embodiment, the punch 120 may have a third press-fitting part that is continuous with the second press-fitting part 122 on the downstream side of the second press-fitting part 122 with respect to the press-fitting direction of the punch 120. It is preferable that the third press-fitting part has a shape in which the inclination of the wall surface with respect to the press-fitting direction is different from the above-mentioned inclination of the wall surface of the second press-fitting part, and the maximum width becomes smaller toward the downstream side in the press-fitting direction.

1-3. Process of polishing the substrate surface (process S30)
The method for manufacturing a nozzle plate according to the present embodiment may include a step of polishing the surface of the substrate in which the nozzle holes are formed in step S20 on the lowermost side in the press-fitting direction of the punch.

In this step, in order to remove the protrusion 130 caused by press-fitting the punch 120 into the substrate 100 in step S20, the surface of the substrate 100 on the lowermost side in the press-fitting direction of the punch is polished (FIG. 2B, C).

The method of polishing is not particularly limited, but can be performed using, for example, a parallel plane honing grinder (FS-35AN, manufactured by Fuji Sanki Co., Ltd.).

Note that the method for manufacturing a nozzle plate according to the present embodiment may include a step of forming a groove on the uppermost surface of the substrate in the press-fitting direction of the punch 120 after the above step S20. By forming the above-mentioned grooves, when the manufactured nozzle plate and the channel member for manufacturing the inkjet head are joined using adhesive, it is sufficiently suppressed that the adhesive protrudes from the joint part. can do.

The method for forming the groove is not particularly limited, but, for example, the groove may be formed by press-fitting a punch corresponding to the shape of the groove into the substrate.

Note that in this embodiment, the punch may be press-fitted into the substrate in the opposite direction to the direction in which droplets are ejected from the nozzle hole to be formed.

2. Nozzle Plate The nozzle plate according to this embodiment has a nozzle hole for ejecting droplets, and is made of metal with a Vickers hardness of 250 HV or more. The above-mentioned nozzle plate can be obtained by the above-mentioned nozzle plate manufacturing method.

The material of the nozzle plate is not particularly limited as long as it is a metal with a Vickers hardness of 250 HV or more. The type of metal having a Vickers hardness of 250 HV or more can be the same as that described in the nozzle plate manufacturing method. When used in an inkjet head, the Vickers hardness is more preferably 300 HV or more, and even more preferably 400 HV or more, from the viewpoint of suppressing deformation of the nozzle plate during use.

The thickness of the nozzle plate is preferably 30 μm or more and 45 μm or less, more preferably 35 μm or more and 45 μm or less. When the thickness is 30 μm or more, a sufficient length of the nozzle hole can be ensured, and the drawing of air into the inside of the inkjet head can be further suppressed. Thereby, the ejection stability can be further improved. Further, since the thickness is 45 μm or less, space saving can be more easily achieved when the nozzle plate is used in an inkjet head.

It is preferable that the nozzle plate has a plurality of nozzle holes in which the distance between adjacent nozzle holes is 170 μm or less. By having such a plurality of nozzle holes, when the manufactured nozzle plate is used in an inkjet head, a higher definition image can be formed. The lower limit of the distance between the adjacent nozzle holes is not particularly limited, but is, for example, 85 μm or more.

FIG. 5 is a schematic cross-sectional view showing an example of the nozzle plate 200. It is preferable that the nozzle hole 210 has a first channel 211 whose wall surface is inclined with respect to the droplet ejection direction (arrow B in FIG. 5). In particular, in this embodiment, the nozzle hole 210 is connected to the first flow path 211 and the second flow path that is continuous with the first flow path 211 on the downstream side of the first flow path 211 with respect to the droplet ejection direction. 212, and the slope of the wall surface of the second flow path 212 with respect to the discharge direction (θ ₂ in FIG. 5) is smaller than the slope of the wall surface of the first flow path 211 with respect to the press-fitting direction (θ ₁ in FIG. 5). It is also preferable to have a small shape. Since the nozzle plate 200 has such nozzle holes 210, the ejection stability of ink droplets can be further improved when an inkjet head using the nozzle plate is used.

Note that, in this specification, among the angles formed by the straight line P3 parallel to the droplet ejection direction and the wall surface 211a of the first flow path 211, an acute angle is referred to as "the wall surface of the first flow path 211". 211a is assumed to be θ ₁ . Furthermore, an acute angle between the straight line P4 parallel to the droplet ejection direction and the wall surface 212a of the second flow path 212 is defined as "the inclination θ ₂ of the wall surface 212a of the second flow path 212."

The above-mentioned inclination θ ₁ of the first flow path 211 is preferably 15° or more, more preferably 30° or more, and even more preferably 45° or more. When the above-mentioned inclination θ ₁ is 15° or more, when the nozzle plate is used in an inkjet head, the drawing of air from the nozzle holes can be further suppressed, and the ejection stability can be further improved. When the above-mentioned inclination θ ₁ is 45° or more, the ejection stability can be more fully improved, and the fluid resistance during ink ejection can be lowered to further improve the ejection stability. When the nozzle plate is used in an inkjet head, the above-mentioned slope θ ₁ is preferably 50° or less, from the viewpoint of making it easier to adjust the amount of ink droplets to be ejected.

The length of the first channel 211 in the droplet ejection direction (L ₁ in FIG. 5) is preferably 40 μm or more and 55 μm or less. When L ₁ is 40 μm or more, a sufficient length of the nozzle hole can be ensured, and the drawing of air into the inside of the inkjet head can be further suppressed. Thereby, when the nozzle plate is used in an inkjet head, ejection stability can be further improved. Further, when _L1 is 55 μm or less, space saving of the nozzle plate in the inkjet head can be more easily achieved.

The above-mentioned inclination θ ₂ of the second flow path 212 is preferably 0° or more and 9° or less, more preferably 0° or more and 5° or less, and even more preferably 0° or more and 3° or less, It is particularly preferable that the angle is 0° or more and 1° or less. When the above-mentioned inclination θ ₂ is 9° or less, when the manufactured nozzle plate is used in an inkjet head, ink ejection bending can be further suppressed and ink ejection stability can be further improved.

The length of the second flow path 212 in the droplet ejection direction (L ₂ in FIG. 5) is preferably 10 μm or more and 25 μm or less. When the above-mentioned _L2 is 10 μm or more, when the manufactured nozzle plate is used in an inkjet head, ink ejection bending can be further suppressed and ink ejection stability can be further improved. Moreover, when the above-mentioned _L2 is 25 μm or less, space saving of the nozzle plate in the inkjet head can be more easily achieved.

The maximum width (n in FIG. 5) of the second flow path 212 on the most downstream side in the droplet ejection direction is preferably 18 μm or more and 50 μm or less. When the maximum width n is 18 μm or more, when the nozzle plate is used in an inkjet head, thickening of the ink due to aggregation of pigments in the ink near the ejection ports can be further suppressed. As a result, variations in ink ejection speed are less likely to occur, and ejection stability can be further improved. When the maximum width n is 50 μm or less, the width of the droplet ejection opening can be made smaller and a higher definition image can be formed.

The cross-sectional shapes of the first flow path 211 and the second flow path 212 in the direction perpendicular to the ejection direction are, for example, circular or oval, but from the viewpoint of further increasing ink ejection stability, the shape is circular. is preferred.

It is preferable that the nozzle plate 200 has a bonding surface 220 for bonding to an external member on the most upstream surface in the droplet ejection direction. The width of the joint surface 220 in the direction in which the plurality of nozzle holes 210 are arranged (x in FIG. 5) is preferably 25 μm or more, more preferably 50 μm or more.

The bonding surface 220 may have a groove. Since the bonding surface 220 has the groove, when the nozzle plate and the channel member are bonded using adhesive to manufacture an inkjet head, the adhesive is sufficiently prevented from protruding from the bonding surface 220. can do.

In the nozzle hole 210, it is preferable that the above-mentioned inclination θ ₁ of the first flow path 211 satisfies the relationship of equation (3), where _HB is the Vickers hardness of the metal that is the material of the nozzle plate.
θ ₁ ≦0.0234×H _B +38.67 (3)

Equation (3) can be derived as follows.

(1) Create a correlation formula for the relationship between the Vickers hardness of the metal that is the material of the nozzle plate (250 HV or more) and the width of the sag (W in Figure 4) of the nozzle plate, and calculate the sag at a given Vickers hardness. Find the width W. (2) Substitute the determined sagging width W into equation (b) to determine θ ₁ for the minimum width (x _min ) of the joint surface to be 50 μm. (3) The above operations (1) and (2) are performed while changing the Vickers hardness, and the relationship between the Vickers hardness and the maximum value of θ ₁ can be derived by creating a correlation equation. In deriving equation (3), fixed values shown below are used for values other than θ ₁ and W in equation (b).
x _min =P-(n+2L ₁・tanθ ₁ +2L ₂・tanθ ₂ +2W) (b)
(P=170 μm, n=20 μm, L ₁ =40 μm, L ₁ =5 μm, θ ₂ =0°)

When the nozzle plate has nozzle holes that satisfy the relationship of formula (3), a sufficient width of the joint surface of the nozzle plate in the direction in which the nozzle holes are arranged can be ensured. Further, when the relationship of equation (3) is satisfied, the value of θ ₁ can be increased as the Vickers hardness value of the metal that is the material of the nozzle plate increases. Therefore, in an inkjet head using a nozzle plate, it is possible to further suppress the drawing of air from the nozzle holes, further improve ejection stability, and make it easier to secure a bonding surface.

It is preferable that the maximum width n of the nozzle hole on the most downstream side in the droplet ejection direction and the Vickers hardness _HB of the metal that is the material of the nozzle plate satisfy the relationship of equation (4).
n≦0.0672×H _B +2.01 (4)

Equation (4) can be derived as follows.

(1) Create a correlation formula for the relationship between the Vickers hardness (250 HV or more) of the metal that is the material of the nozzle plate and the width of the sag (W in Figure 4) that is formed, and calculate the sag at a given Vickers hardness. Find the width W. (2) Substitute the calculated sagging width W into equation (b) to find the maximum value of n so that the minimum value (x _min ) of the width of the joint surface is 50 μm. (3) The above operations (1) and (2) are performed while changing the Vickers hardness, and the relationship between the Vickers hardness and the maximum value of n can be derived by creating a correlation equation. Note that in deriving equation (4), for values other than n and W in equation (b), θ _a =45° and the above-mentioned values of P, L _a , L _{b, and} θ _b are used.

When the nozzle holes satisfy the relationship of formula (4), a sufficient width of the joint surface of the manufactured nozzle plate in the direction in which the nozzle holes are arranged can be secured. Furthermore, when the relationship of formula (5) is satisfied, the value of n can be increased as the Vickers hardness value of the metal that is the material of the nozzle plate increases. Therefore, in an inkjet head using a nozzle plate, it is possible to further reduce fluid resistance during ink ejection, further improve ejection stability, and make it easier to secure a bonding surface.

The sagging width W of the nozzle plate 200 in the direction perpendicular to the droplet ejection direction is preferably 14 μm or less.

3. Method for Manufacturing an Inkjet Head The method for manufacturing a nozzle plate according to the present embodiment includes the step of joining the above-described nozzle plate and a channel member for supplying ink to the nozzle holes of the nozzle plate.

The method of joining the nozzle plate and the flow path member is not particularly limited, and examples thereof include a method of joining using an adhesive, a method of joining using a diffusion bonding method, and the like. In the step of bonding, the amount of adhesive used is preferably less than 0.1 g from the viewpoint of suppressing deterioration of the adhesive due to the use of ink and further suppressing a decrease in bonding strength. Furthermore, when the amount of adhesive used is less than 0.1 g, it is possible to suppress the adhesive from flowing out into areas not involved in bonding, such as the flow path of the nozzle plate.

The channel member used in the above bonding step will be described in detail in the explanation of the inkjet head described later.

The method for manufacturing an inkjet head according to the present embodiment includes bonding a channel member for supplying ink to nozzle holes of a nozzle plate and a pressure chamber forming substrate having pressure chambers for applying pressure to the ink. It may have a step.

The method for joining the flow path member and the pressure chamber forming substrate is not particularly limited, and may be the same as the method for joining the nozzle plate and the flow path member.

The pressure chamber forming substrate to be joined to the flow path member will be described in detail in the explanation of the inkjet head described later.

4. Inkjet Head The inkjet head according to this embodiment has the above-described nozzle plate. Hereinafter, an inkjet head having the nozzle plate 200 shown in FIG. 5 will be described, but the inkjet head according to this embodiment is not limited to this.

FIG. 6 is an exploded perspective view showing an overview of the inkjet head 1 according to the present embodiment. As shown in FIG. 6, the inkjet head 1 includes a housing 2, a circuit board 3, a head base 4, and a head chip 5 shown in FIG.

The housing 2 is a rectangular box with an open bottom surface. A notch 2a connected to the inside is provided on the top surface of the casing 2, and the circuit board 3 is housed in the casing 2 through this notch 2a. A drive circuit for driving an actuator in a head chip 5 (described later) is mounted on the circuit board 2. Circular holes 2b are provided on the X-axis positive side and the X-axis negative side of the notch 2a, respectively. The hole 2b is for guiding an ink supply tube (not shown) into the housing 2. Further, a common ink chamber (not shown) is provided within the housing 2.

The head base 4 is a frame body that has a rectangular opening 4a in the center that passes through it vertically. A head chip 5 shown in FIG. 7 is provided at the lower end of the opening 4a. A circuit board 3 and an FPC (flexible printed circuit board) are electrically connected to the head chip 5 within the opening 4a.

FIG. 8 is a cross-sectional view taken along line AA in FIG. 7, showing an outline of the head chip 4 included in the above-described inkjet head 1.

The head chip 5 includes a nozzle plate 200, a flow path member 10, a pressure chamber forming substrate 20, a drive plate 30, and a wiring board 40. Further, in the head chip 4, a nozzle plate 200, a channel member 10, a pressure chamber forming substrate 20, a drive plate 30, and a wiring board 40 are stacked in this order from the ink ejection surface side.

A liquid-repellent film may be formed on the ink ejection side surface of the nozzle plate 200. The material contained in the liquid-repellent film is not particularly limited, but may be, for example, a fluororesin. Further, the thickness of the liquid-repellent film is not particularly limited, but is, for example, 1 nm or more and less than 100 nm.

The flow path member 10 is a member for supplying ink to the nozzle holes 210 of the nozzle plate. The flow path member 10 includes an inlet forming substrate 11, a supply flow path forming substrate 12, and an air chamber forming substrate 13.

The inlet forming substrate 11 has an inlet 11a. The inlet 11a is a through hole formed between a pressure chamber 21, which will be described later, and a supply channel 12a, and supplies ink from the pressure chamber 21 to the supply channel 12a. The inlet 11a may have a throttle function for adjusting the amount of ink to be supplied.

The thickness of the inlet forming substrate 11 can be, for example, 30 μm or more and 100 μm or less. The maximum opening width of the inlet 11a can be, for example, 10 μm or more and 80 μm or less.

The inlet forming substrate 11 has a second communication hole 11b. The second communication hole 11b communicates with a third communication hole 24 and a first communication hole 12b, which will be described later.

The supply channel forming substrate 12 has a supply channel 12a. The supply channel 12a is a channel for supplying ink supplied from the outside to the pressure chamber 21.

The supply channel forming substrate 12 has a first communication hole 12b. The first communication hole 12b communicates with the second communication hole 11b, and communicates with the supply channel 12a.

The air chamber forming substrate 13 has a damper 13a and an air chamber 13b. The damper 13a is a flexible membrane that can be plastically deformed in response to pressure fluctuations in the pressure chamber 21. When the pressure in the supply channel 12a increases due to pressure fluctuations in the pressure chamber 21, the damper 13a is plastically deformed toward the air chamber 13b, and when the pressure in the supply channel 12a decreases, the damper 13a deforms the supply flow. It is plastically deformed toward the path 12a. Thereby, it is possible to further suppress sudden fluctuations in the pressure within the supply channel 12a.

The flow path member 10 has a silo 14. The silo 14 is a through hole for supplying ink in the pressure chamber 21 to the nozzle hole 210.

The pressure chamber forming substrate 20 has a plurality of pressure chambers 21 and a diaphragm 22. Moreover, the pressure chamber 21 penetrates from one surface of the pressure chamber forming substrate 20 to the other surface. The pressure chamber 21 applies ejection pressure to the ink to be ejected from the nozzle hole 210 by changing its volume. Furthermore, partition walls 23 are formed between the plurality of pressure chambers 21 . In this embodiment, the partition wall 23 is entirely formed of a metal that can be electroplated, such as nickel (Ni). Thereby, the rigidity of the partition wall 23 can be increased, and the inkjet head 1 can have a stable structure that is less likely to be destroyed by vibration. The thickness of the pressure chamber forming substrate 20 can be, for example, 50 μm or more and 300 μm.

The diaphragm 22 is arranged to cover the opening of the pressure chamber 21 on the side opposite to the nozzle plate 200. The diaphragm 22 is provided with a third communication hole 24 . A drive plate 30 is arranged on one surface of the diaphragm 22 on the pressure chamber 21 side and one surface on the opposite side. The thickness of the diaphragm 22 is, for example, 1 μm or more and 10 μm or less. Note that an insulating layer may be disposed between the pressure chamber forming substrate 20 and the drive plate 30.

The drive plate 30 has a space 31 and a fourth communication hole 32 that communicates with the third communication hole 24 . The space portion 31 is arranged at a position facing the pressure chamber 21 with the diaphragm 22 in between. The actuator 50 is housed in the space 31 .

The actuator 50 has a piezoelectric element 51, a first electrode 52, and a second electrode 53. The first electrode 52 is laminated on one surface of the diaphragm 22 . Note that an insulating layer may be disposed between the first electrode 52 and the diaphragm 22. The piezoelectric element 51 is stacked on the first electrode 52 and is arranged for each pressure chamber 21 (for each channel) at a position facing the pressure chamber 21 with the diaphragm 22 and the first electrode 52 in between. The first electrode 52 and the second electrode 53 may be formed by a method such as sputtering or vapor deposition, and patterned by a method such as photolithography.

The piezoelectric element 51 is made of a material that deforms when a voltage is applied, and is made of a ferroelectric material such as lead zirconate titanate (PZT), for example. Further, a second electrode 53 is laminated on the surface of the piezoelectric element 51 opposite to the first electrode 52 . The second electrode 53 is connected to a wiring layer 41 provided on a wiring board 40, which will be described later, via a bump 54. The thickness of the piezoelectric element 51 is, for example, 10 μm or less.

The wiring board 40 has a wiring layer 41 and a silicon layer 42 on which the wiring layer 41 is formed over one surface. The wiring layer 41 is connected to the bump 54 provided on the second electrode 53 via solder 41a. Further, the outer edge of the wiring layer 41 is connected to a flexible wiring board. Furthermore, a silicon layer 42 is arranged on one surface of the wiring layer 41 on the side opposite to the drive plate 30. The silicon layer 42 is bonded to the holding part 3.

Further, the wiring board 40 is provided with a fifth communication hole 43 that penetrates the wiring layer 41 and the silicon layer 42. The fifth communication hole 43 communicates with the fourth communication hole 32 of the drive plate 30 and the common ink chamber within the housing.

In the present embodiment, the fifth communication hole 43 of the wiring board 40, the fourth communication hole 32 of the drive plate 30, the third communication hole 24 of the diaphragm 22, and the second communication hole 11b of the inlet forming board 11 communicate with each other. , the first communication hole 12b of the supply flow path forming substrate 12, and the supply flow path 12a constitute a flow path for supplying ink in the common ink chamber 2 to the pressure chamber 21. Further, the nozzle holes 210 of the nozzle plate 200 constitute an outlet for ejecting ink within the pressure chamber 21 toward the recording medium.

In the inkjet head 1 with such a configuration, the ink stored in the common ink chamber in the housing 2 is distributed through the fifth communication hole 43, the fourth communication hole 32, the third communication hole 24, the second communication hole 11b, and the second communication hole 11b. It passes through the first communication hole 12b, flows into the supply channel 12a, and then flows into the pressure chamber 21 via the inlet 11a. Then, by applying a voltage between the first electrode 52 and the second electrode 53, the piezoelectric element 51 is deformed (vibrated), and along with the deformation of the piezoelectric element 51, the diaphragm 22 is deformed (vibrated). . The deformation (vibration) of the diaphragm 22 generates pressure within the pressure chamber 21 to eject ink. Due to the generation of this pressure, the ink in the pressure chamber 21 is pushed out through the silo 14 to the nozzle hole 210, and is ejected from the tip (nozzle opening) of the nozzle hole 210 toward the recording medium.

In this embodiment, the inkjet head 1 only needs to include the nozzle plate 200, and may be a piezoelectric inkjet head in which the piezoelectric element 51 constitutes the wall of the pressure chamber 21, or a thermal inkjet head. good.

5. Image Forming Apparatus FIG. 9 is a diagram schematically showing the configuration of an image forming apparatus 300 according to the present embodiment.

As shown in FIG. 9, the image forming apparatus 300 includes the above-described inkjet head 1, an ink supply device 310, a transport device 320, and a main tank 330.

The inkjet head 1 is arranged so as to be able to scan freely in a direction transverse to the transport direction D of the recording medium M on which an image is to be formed, for example, by a scanning method.

In this embodiment, the type of ink ejected by the inkjet head 1 is not particularly limited, and includes, for example, actinic radiation-curable ink, solvent-based ink, water-based ink, and hot-melt ink.

The transport device 320 is a device for transporting the recording medium M to the inkjet head 1. The conveyance device 320 includes, for example, a belt conveyor 321 and a rotatable feed roller 322. The belt conveyor 321 includes a plurality of rotatable pulleys 321a and an endless belt 321b stretched around the pulleys 321a. The feed roller 322 is disposed at a position facing the pulley 321a on the upstream side in the transport direction D of the recording medium M so as to sandwich the recording medium M between the belt 321b and feed the recording medium M onto the belt 321b.

The ink supply device 310 is arranged integrally with the inkjet head 1. The ink supply devices 310 are arranged for each type of ink. For example, when using four color inks of Y (yellow), M (magenta), C (cyan), and K (black), four ink supply devices 310 are arranged in the inkjet head 1.

Each ink supply device 310 is supplied with ink in the main tank 330 via a pipe 341 and a valve 342 connected to the main tank 330. Further, each ink supply device 310 communicates with the common ink chamber of the inkjet head 1 via a pipe 344, and is connected to be able to supply ink of each color to the ink supply port 2a of a desired common ink chamber.

The inkjet head 1 is also connected to the main tank 330 by a bypass pipe 343 branching from the pipe 341 described above. At the branching point between the pipe 341 and the bypass pipe 343, a valve 342 is arranged that can switch and set the ink flow path in one or both of the pipes 341 and the bypass pipe 343. The pipe 341, the pipe 344, and the bypass pipe 343 are all flexible tubes, for example. Valve 342 is, for example, a three-way valve.

The main tank 330 is a tank for storing ink to be supplied to the inkjet head 1. The main tank 330 is arranged separately from the inkjet head 1. The main tank 330 includes, for example, a stirring device (not shown). The main tank 330 can be appropriately determined depending on the image forming performance, size, etc. of the image forming apparatus 300. For example, when the image forming speed of the image forming apparatus is 1 to 3 m ² /min, the capacity of the main tank 330 is, for example, 1 L.

(Embodiment 2)
2. Method for manufacturing a nozzle plate The method for manufacturing a nozzle plate according to Embodiment 2 of the present invention includes the steps of preparing a substrate placed on a die having an opening, and press-fitting a punch into the prepared substrate to form a liquid. forming a nozzle hole for discharging the droplet, and the step of forming the nozzle hole is such that the maximum width of the formed nozzle hole on the most downstream side in the press-fitting direction of the punch is n, When the maximum width of the opening of the die is d, and the thickness of the substrate is t, the nozzle hole is formed to satisfy the relationship of formula (A).
t+n<d≦2t+n (A)

2-1. Step of preparing a substrate placed on a die In this step, a substrate placed on a die having an opening is prepared.

The type of die is not particularly limited as long as it has an opening that satisfies formula (A). The type of substrate is not particularly limited, but it is preferably a metal substrate with a Vickers hardness of 250 HV or more. The type of metal having a Vickers hardness of 250 HV or more can be the same as described above.

The thickness of the substrate is not particularly limited as long as it satisfies formula (A), but it is preferably 30 μm or more and 45 μm or less, more preferably 35 μm or more and 45 μm or less.

2-2. Step of Forming Nozzle Holes In this step, a punch is press-fitted into the substrate prepared above to form nozzle holes for ejecting droplets.

FIG. 10 is a schematic cross-sectional view showing a method of manufacturing a nozzle plate according to this embodiment. In this step, when the maximum width of the nozzle hole to be formed on the most downstream side in the press-fitting direction of the punch is n, the maximum width of the opening of the die is d, and the thickness of the substrate is t, the following formula is used: The nozzle hole is formed to satisfy the relationship (A).
t+n<d≦2t+n (A)

By making the maximum width d of the opening of the die larger than the sum (t+n) of the maximum width n of the nozzle hole and the thickness t of the substrate, it is possible to make it easier for the punch 120 to penetrate the substrate 100. can. This makes it easier to form the nozzle hole in accordance with the shape of the punch 120. Further, the load on the punch 120 can be reduced, and deterioration of the punch 120 can be further suppressed.

Further, since the maximum width d of the opening of the die is 2t+n or less, the press-fitting pressure of the punch 210 applied to the substrate 100 is difficult to be dispersed, and the punch 120 can be press-fitted into the substrate 100 more easily. . Further, it is possible to more easily form a nozzle hole having the shape of the punch 210.

This step may be performed using a holding member 140 to make it easier to fix the substrate. The holding member has an opening 140a for press-fitting the punch 120 into the substrate 100. The minimum width of the opening 140a may be at least the maximum width of the punch 120 press-fitted into the substrate 100, and is preferably larger than the maximum width of the punch 120 by 50 μm or more. This makes it easier to press-fit the punch 120 into the substrate 100, making it easier to form a nozzle hole corresponding to the shape of the punch 120.

Hereinafter, the present invention will be specifically explained with reference to Examples, but the scope of the present invention is not limited to the description of Examples.

(Preparation of nozzle plates 1 to 10)
A metal plate 1 made of stainless steel (SUS304BA) with a thickness of 45 μm and a Vickers hardness of 180 HV was prepared. The prepared metal plate 1 was placed on a die (the maximum width of the opening was 85 μm), and the metal plate 1 was fixed from above with a pressing member. Then, a punch having a shape similar to that shown in FIG. 3 was press-fitted into the metal plate 1 at a press-fitting speed of 3 μm/s, and then the punch was taken out from the metal plate 1. Next, the protrusion formed by press-fitting the punch was removed by polishing using a parallel plane honing grinder (FS-35AN, manufactured by Fuji Sanki Co., Ltd.) to form a nozzle hole. A plurality of nozzles were formed on the metal plate 1 using a similar method so that the distance P between adjacent nozzle holes was 170 μm. In this way, nozzle plate 1 was produced.

The punch used had an inclination θ _a of the wall surface of the first press-fitting part with respect to the press-fitting direction of the punch of 0°, an inclination θ _b of the wall surface of the second flow path with respect to the above-mentioned discharge direction of 45°, and The length L _a in the press-fitting direction was 5 μm, and the length L _b of the second press-fitting portion in the press-fitting direction was 45 μm.

The formed nozzle hole has a first flow path and a second flow path, the inclination θ ₁ of the wall surface of the first flow path with respect to the droplet ejection direction is 0°, and the wall surface of the second flow path is The inclination θ ₂ with respect to the discharge direction was 45°, the length L ₁ of the first channel in the discharge direction was 5 μm, and the length L ₂ of the second flow channel in the discharge direction was 45 μm. Further, the maximum width n of the nozzle hole on the most downstream side in the above-mentioned ejection direction was 20 μm. Note that the cross-sectional shape of the nozzle hole in the direction orthogonal to the above-mentioned discharge direction was circular.

Nozzle plates 2 to 4 were produced in the same manner as nozzle plate 1, except that the metal plates used were changed to metal plates 2 to 4 shown in Table 1. In each nozzle plate, the shapes of the nozzle holes formed were the same.

For nozzle plates 1 to 4, by observing the cross section of the nozzle plate with an SEM, the width of the slope formed at the most upstream edge of the nozzle hole in the droplet ejection direction is defined as the sagging width W [μm]. It was measured. The sag width in each nozzle plate is shown in Table 1, and the relationship between the Vickers hardness of the metal plate and the sag width is shown in the graph of FIG. Note that the equation in FIG. 11 is an equation representing an approximate straight line of the graph.

As shown in Table 1 and FIG. 11, it was found that when the Vickers hardness was 250 HV or more, the sagging width was significantly reduced.

(Preparation of nozzle plates 5 to 10)
In producing the nozzle plate 1, the type of metal plate and the thickness t [μm] were changed as shown in Table 2, and the shape of the punch and the shape of the nozzle hole to be formed were changed to the following conditions. Nozzle plates 5 to 10 were produced in the same manner except that .
θ _a , θ ₁ :45°
θ _b , θ ₂ :0°
L _a , L ₁ :t-L _2
Lb , _L2 : 5μm
n: 20μm

(Adhesion level evaluation)
For the nozzle plates 5 to 10, the width (adhesion white) x [μm] of the joint surface included in the most upstream surface in the droplet ejection direction in the direction in which a plurality of nozzle holes are arranged is calculated using the above formula (b ) was calculated. The measurement results of the adhesion margin were evaluated according to the following evaluation criteria. Note that the sag width W in equation (b) was calculated from the equation of the approximate straight line in the graph of FIG. 11 using the Vickers hardness of the metal plate.
x=P-(n+2L ₁・tanθ ₁ +2L ₂・tanθ ₂ +2W) (b)
◎ Adhesive margin is 50 μm or more ○ Adhesive margin is 40 μm or more and less than 50 μm △ Adhesive margin is 25 μm or more and less than 40 μm × Adhesive margin is less than 25 μm

(Deformation evaluation)
Regarding the nozzle plates 5 to 10 after fabrication, it was observed whether the entire substrate was plastically deformed (curved) before and after fabrication. Further, ink was ejected using an inkjet head using nozzle plates 5 to 10, and it was observed whether the ejection direction was bent with respect to the central axis of the nozzle hole. Evaluation was made according to the following criteria.
○ No deformation was confirmed.
△ Although slight deformation was observed, no bending in the droplet ejection direction was observed.
× Deformation was clearly visible, and bending in the droplet ejection direction was confirmed.

The evaluation results are summarized in Table 2.

(Relationship between Vickers hardness and slope θ ₁ )
The sag width W [μm] when the Vickers hardness of the metal plate was 250 HV was determined from the equation of the approximate straight line in the graph of FIG. Next, under the following conditions, the maximum values of θ _a and θ ₁ such that the adhesion margin of the nozzle plate was 50 μm or more were determined from the above equations (a) and (b). Similarly, the maximum values of θ _a and θ ₁ were calculated when the Vickers hardness of the metal plate was 200 HV, 300 HV, 350 HV, and 400 HV. The calculation results are shown in Table 3, and a graph showing the relationship between the Vickers hardness and the above maximum values of θ _a and θ ₁ is shown in FIG.
P: 170.0μm
θ _b , θ ₂ :0°
L _a , L ₁ :40.0 μm
_Lb , _L2 : 5.0 μm
n: 20.0μm
W: 5.2μm

As shown in FIG. 12, Equation (1) (Equation (3)) was derived under the condition that a metal plate with a Vickers hardness of 250 HV or more was used.

As shown in Table 3 and Figure 12, it has been found that when the Vickers hardness is 250 HV or more, the maximum value of θ _a (θ ₁ ) can be significantly increased in order to make the adhesive margin 50 μm or more. . It was found that by doing this, it was possible to sufficiently secure the adhesive margin while increasing θ _a (θ ₁ ). It is thought that because the Vickers hardness was 250 HV or more, sagging was less likely to occur even if the taper angle was made larger.

(Relationship between Vickers hardness and maximum width n of the most downstream side of the nozzle hole)
The sag width W [μm] when the Vickers hardness of the metal plate was 250 HV was determined from the equation of the approximate straight line in the graph of FIG. Next, under the following conditions, the maximum value of n such that the adhesion margin of the nozzle plate was 50 μm or more was determined from equation (a). Similarly, the maximum value of n was calculated when the Vickers hardness of the metal plate was 200HV, 300HV, 350HV, and 400HV. The calculation results are shown in Table 4, and a graph showing the relationship between the Vickers hardness and the above maximum value of n is shown in FIG.
P: 170.0μm
θ _a , θ ₁ :45°
θ _b , θ ₂ :0°
L _a , L ₁ :40.0 μm
_Lb , _L2 : 5.0 μm
W: 5.2μm

As shown in FIG. 13, Equation (2) (Equation (4)) was derived under the condition that a metal plate with a Vickers hardness of 250 HV or more was used.

As shown in Table 4 and FIG. 13, it was found that when the Vickers hardness was 250 HV or more, the maximum value of n to make the adhesive margin 50 μm or more could be significantly increased. It has been found that this allows a sufficient adhesion margin to be secured while increasing n. It is thought that because the Vickers hardness was 250 HV or more, sagging was less likely to occur even if the nozzle diameter was made larger.

This application claims priority based on Japanese Patent Application No. 2022-128845 filed on August 12, 2022. All contents described in the application specification and drawings are incorporated herein by reference.

By using the nozzle plate manufacturing method of the present invention, the width of the sag can be reduced with a simpler configuration, and plastic deformation of the entire substrate can be further suppressed. Therefore, the present invention is useful, for example, in a method for manufacturing a nozzle plate using a punching method.

1 Inkjet head 2 Housing 3 Circuit board 4 Head base 5 Head chip 10 Channel forming board 20 Pressure chamber forming board 30 Drive plate 40 Wiring board 50 Actuator 100 Board 110 Die 120 Punch 130 Projection 140 Holding member 200 Nozzle plate 210 Channel 220 Joint surface 300 Image forming device

Claims (26)

1. preparing a metal substrate having a thickness of more than 25 μm and a Vickers hardness of 250 HV or more;
   press-fitting a punch into the prepared substrate to form a nozzle hole for ejecting droplets;
   A method for manufacturing a nozzle plate, comprising:
2. The step of forming the nozzle holes includes forming a plurality of nozzle holes in which the distance between adjacent nozzle holes is 170 μm or less.
   A method for manufacturing a nozzle plate according to claim 1.
3. The method for manufacturing a nozzle plate according to claim 1 or 2, wherein the thickness of the substrate is 30 μm or more and 45 μm or less.
4. The method for manufacturing a nozzle plate according to claim 1 or 2, wherein the thickness of the substrate is 35 μm or more and 45 μm or less.
5. The step of forming the nozzle hole includes press-fitting the punch into the substrate, the punch having a first press-fitting part whose wall surface is inclined with respect to the press-fitting direction of the punch.
   The method for manufacturing a nozzle plate according to claim 1 or 2.
6. The punch has a second press-fitting part that is continuous with the first press-fitting part on a downstream side of the first press-fitting part with respect to the press-fitting direction of the punch, and the second press-fitting part is continuous with the first press-fitting part, and the wall surface of the second press-fitting part is arranged in the press-fitting direction. the inclination with respect to the press-fitting direction is smaller than the inclination of the wall surface of the first press-fitting part with respect to the press-fitting direction;
   The method for manufacturing a nozzle plate according to claim 5.
7. In the punch, the wall surface of the first press-fitting part has an inclination of 45° or more with respect to the press-fitting direction.
   The method for manufacturing a nozzle plate according to claim 5.
8. The punch is
   When the inclination of the wall surface of the first press-fitting part of the punch with respect to the press-fitting direction is θ _a , and the Vickers hardness of the metal is H _A ,
   satisfies the relationship of formula (1),
   The method for manufacturing a nozzle plate according to claim 5.
   θ _a ≦0.0234×H _A +38.67 (1)
9. The step of forming the nozzle hole includes:
   When the maximum width of the formed nozzle hole on the most downstream side in the droplet ejection direction is n, and the Vickers hardness of the metal is H _A ,
   forming the nozzle hole that satisfies the relationship of formula (2);
   The method for manufacturing a nozzle plate according to claim 1 or 2.
   n≦0.0672×H _A +2.01 (2)
10. providing a substrate mounted on a die having an opening;
    press-fitting a punch into the prepared substrate to form a nozzle hole for ejecting droplets,
    In the step of forming the nozzle hole, the maximum width of the nozzle hole to be formed on the lowermost side in the press-fitting direction of the punch is n, the maximum width of the opening of the die is d, and the thickness of the substrate is t. When, the nozzle hole is formed so as to satisfy the relationship of formula (A),
    Method of manufacturing a nozzle plate.
    t+n<d≦2t+n (A)
11. A nozzle plate having a nozzle hole for discharging droplets,
    The thickness is greater than 25 μm,
    Made of metal with a Vickers hardness of 250HV or more,
    nozzle plate.
12. The nozzle plate has a plurality of nozzle holes,
    The distance between the plurality of adjacent nozzle holes is 170 μm or less,
    The nozzle plate according to claim 11.
13. The nozzle plate according to claim 11 or 12, having a thickness of 30 μm or more and 45 μm or less.
14. The nozzle plate according to claim 11 or 12, having a thickness of 35 μm or more and 45 μm or less.
15. The nozzle hole has a first flow path whose wall surface is inclined with respect to the ejection direction of the droplet.
    The nozzle plate according to claim 11 or 12.
16. The nozzle hole is
    a second flow path arranged to communicate with the first flow path on the downstream side of the first flow path with respect to the ejection direction of the droplets;
    The inclination of the wall surface of the second flow path with respect to the discharge direction is smaller than the slope of the wall surface of the first flow path with respect to the discharge direction.
    The nozzle plate according to claim 15.
17. The nozzle plate according to claim 15, wherein the wall surface of the first flow path has an inclination of 45° or more with respect to the discharge direction.
18. When the Vickers hardness of the metal is _HB , and the inclination of the wall surface of the first flow path of the nozzle hole with respect to the ejection direction of the droplet is _θ1 ,
    The nozzle plate according to claim 15, which satisfies the relationship of formula (3).
    θ ₁ ≦0.0234×H _B +38.67 (3)
19. Claim 11 or 12, wherein the metal satisfies the relationship of formula (4), where the Vickers hardness of the metal is _HB and the maximum width of the nozzle hole on the most downstream side in the droplet ejection direction is n. Nozzle plate as described.
    n≦0.0672×H _B +2.01 (4)
20. The nozzle plate has a bonding surface for bonding to an external member on the most upstream surface in the droplet ejection direction,
    The width of the joint surface in the direction in which the plurality of nozzle holes are arranged is 50 μm or more,
    The nozzle plate according to claim 12.
21. The nozzle plate according to claim 20, wherein the joint surface has a groove.
22. The nozzle plate according to claim 11 or 12, wherein the width of the sagging of the nozzle plate in a direction perpendicular to the ejection direction of the droplets is 14 μm or less.
23. A method for manufacturing an inkjet head, comprising the step of joining the nozzle plate according to claim 11 or 12 and a flow path member for supplying ink to the nozzle holes of the nozzle plate.
24. The method for manufacturing an inkjet head according to claim 23, wherein the amount of adhesive used in the bonding step is less than 0.1 g.
25. An inkjet head comprising the nozzle plate according to claim 11 or 12.
26. An image forming apparatus comprising the inkjet head according to claim 25.