JP7554035B2 - Printing stencil and its manufacturing method - Google Patents

Description

The present invention relates to a printing stencil and its manufacturing method.

Recently, there has been a strong demand for print position accuracy in multilayer electronic components in which internal electrodes are formed by printing. For example, there is now a demand for a control width of several microns for print position accuracy and bleeding of printed matter, which are related to the lamination accuracy of electronic components. Also, in multilayer electronic components with thin-film internal electrodes such as capacitors, the printing film thickness is falling below 100 nm. Thus, in the field of thin-film printing, such as printing of internal electrodes for electronic components, there is a steady demand for thinner, more precise printing with less print position misalignment.

The most popular emulsion screen printing stencils are made of a support made of stainless steel, tungsten, or a metal mesh formed by electroplating or etching, which is previously stretched on a frame, or a resin mesh such as polyester, and a photosensitive emulsion having fluidity is applied to the surface of the mesh by a bucket or a coating machine to form a photosensitive film, which is then exposed and developed by a known photolithography method to form a patterned screen printing plate.In addition, instead of applying the emulsion, a method is also known in which a photosensitive layer of a photosensitive film made by coating a film with a photosensitive layer is attached to the surface of the mesh, dried, and then the film is peeled off and exposed and developed in the same manner to form a printing patterning member (direct-indirect method).
Emulsion screen printing plates have problems in that the printing pattern itself is composed of a soft emulsion resin, and therefore the printing durability, the resistance to wiping and cleaning, and the resistance to the solvents used for cleaning are insufficient.

A mesh-integrated metal mask (suspended metal mask) in which a printed pattern is formed from metal foil or plated foil is known as a mask that has improved printing durability, wipe-cleanability, and resistance to solvents used during cleaning compared to emulsion screen plates. This is a mask in which a metal foil on which a printed pattern is formed by mechanical processing such as etching, drilling, or punching, or a method of irradiating holes with laser light, or a plated foil on which a printed pattern is formed by electroforming, is attached to the surface of a metal mesh that is previously stretched over a frame. However, masks other than those that use a material that can be bonded to the metal mesh by plating, such as Ni, Ni alloy, or stainless steel, for the metal foil or plated foil that forms the printed pattern, have not yet become widespread.

In the case of the above-mentioned emulsion screen plate, when forming the emulsion layer, it is common to manually apply liquid emulsion using a bucket to a screen mesh stretched over a frame, and it has been difficult to suppress the variation in the thickness of the emulsion layer, which determines the thickness of the printed matter, to the order of several hundred nm.
Furthermore, in the above-mentioned emulsion screen plate and mesh-integrated metal mask, an "intersection" where the fiber threads of the mesh fabric overlap is always located at the opening of the wiring pattern. The "intersection" is "bump-shaped" and is thicker toward the printed substrate than the thickness of a single fiber thread that constitutes the mesh, so that the part of the transferred printed wiring pattern that corresponds to the "intersection" is depressed (thinned) in a shape corresponding to the "bump", that is, a so-called "mesh mark" is generated. Since the printing film thickness of such a mesh mark is thinner than other wiring parts, the cross-sectional area of the printed wiring in the thin part determines the power transmission capacity of the entire wiring, and power transmission loss is also a problem.

On the other hand, metal masks are known as printing stencils that do not use mesh, in which a printing pattern (openings) is formed on a metal plate such as stainless steel by mechanical processing such as etching, drilling, punching, or by irradiating holes with laser light. A method for producing such a metal mask by electroforming is also known. In a method for producing a metal mask by electroforming, for example, a die on which a plating resist layer is formed using a photosensitive resin such as photoresist on the surface layer of a plate-like member such as a metal such as stainless steel or glass that has been polished smoothly in advance, called a plating mother die, is used, a plating metal layer is formed by depositing plating on the die, and the patterned plating metal layer is peeled off from the die to obtain a metal mask.

With printing stencils with openings, such as metal masks, there is no need to form an emulsion layer, so there is no variation in the thickness of the printed matter due to variations in the thickness of the emulsion layer, and because no screen mesh is installed at the openings, the aforementioned "mesh marks" do not occur. However, the absence of a screen mesh at the openings also means that there is nothing in the printing pattern that reduces the volume of ink that penetrates. In this case, the volume of ink that is the product of the area of the openings and the thickness of the mask is transferred from the openings during printing, so there is a problem with printing stencils with openings in that it is difficult to print thin films.

As a means for solving the above-mentioned problems, it has been proposed to make the mask have a dual structure consisting of a pattern portion having a pattern opening corresponding to the printing pattern, and a paste supply portion having a paste supply port for supplying conductive paste to the pattern opening and in contact with the squeegee (Patent Document 1).
In addition, as printing stencils of a multilayer (laminate) structure, there have been proposed a printing stencil (Patent Document 2) characterized in that an organic polymer layer having a thickness of 100 nm or more is provided via a coupling agent layer on a substrate made of an inorganic material, an organic material, or an inorganic and organic composite material, in which a printing pattern is opened; a mask for stencil printing having openings for a printing pattern provided on a substrate, the substrate having an aromatic polyimide resin layer and a diamond-like carbon film on its surface (Patent Document 3); and a mask (Patent Document 4) characterized in that a hard coating is formed on the outer peripheral surface of a mask substrate or at least a portion of the inner wall surface of a through hole formed in the mask substrate.

JP 2015-229287 A JP 2017-39320 A JP 2005-144973 A Japanese Patent Application Publication No. 11-245371

However, even the above-mentioned methods have not yet achieved the formation of a sufficiently thin printed layer.
Another method of forming a thin film using a printing stencil having openings is to process the openings into discrete holes and obtain a continuous desired printing pattern by the joining of ink or paste that passes through each of the openings during printing. However, in many cases, the ink or paste is divided by the walls of the openings, making it difficult to form a continuous planar pattern.
Another method is to reduce the thickness of the metal plate itself to reduce the amount of ink transferred during printing, but it is difficult to manufacture or obtain a uniform metal plate with a thickness of less than 10 μm, and when it comes to a thickness of submicron, handling is extremely difficult even if it is manufactured by electroforming or the like.

The present invention aims to solve the above problems and provide a printing stencil that has little variation in printing thickness and produces a thin printing layer.

The inventors conducted extensive research to find a solution to the above-mentioned problems, and discovered that the above-mentioned problems could be solved by forming a hard film with recesses or holes that define the printing pattern on the surface of the substrate side of the base material that forms the printing stencil so that the thickness variation is small, and by providing through holes that penetrate the printing pattern shape portion from within the recesses or holes to the squeegee side surface of the base material, and have an opening area smaller than the area of the printing pattern shape portion.

That is, in order to solve the above problems, the present invention employs the following means.
<1> A printing stencil comprising: a plate-shaped substrate having a surface facing a substrate to be printed and a surface facing a squeegee opposite thereto; a hard film formed on the substrate-to-substrate surface of the substrate, the hard film having recesses or holes defining a printing pattern; and through holes penetrating a portion shaped like a printing pattern from within the recesses or holes to the substrate surface facing the squeegee, the through holes having an opening area smaller than the area of the portion shaped like a printing pattern, the hard film having a thickness of 1 nm to 5 μm and a variation in thickness within 10%.
<2> The printing stencil according to <1>, wherein a plurality of the through holes are formed in the printing pattern shape portion.
<3> The printing stencil according to <1> or <2>, wherein the substrate has a surface having fine projections and recesses.
<4> The printing stencil according to any one of <1> to <3>, wherein the substrate has a corrosion-resistant layer on a surface thereof.
<5> The printing stencil according to any one of <1> to <4>, wherein the substrate is stretched over a printing frame.
<6> The printing stencil according to any one of <1> to <5>, wherein the hard film is one or more films selected from an amorphous carbon film, a metal (containing Si) oxide film, a metal (containing Si) nitride film, a metal (containing Si) carbide film, and a metal (containing Si) oxynitride film.
<7> The printing stencil according to <6>, wherein the amorphous carbon film contains one or more elements selected from the group consisting of N, O, Si, Ti, Al, Zr, B and As.
<8> The printing stencil according to any one of <1> to <7>, wherein the hard film has a Vickers hardness (Hv) of 100 or more.
<9> The printing stencil according to any one of <1> to <8>, wherein the hard film has a Vickers hardness (Hv) of 450 or more.
<10> The printing stencil according to any one of <1> to <9>, further comprising a water-repellent layer or a water- and oil-repellent layer formed on the printing substrate side of the hard film.
<11> The printing stencil according to any one of <1> to <10>, wherein the water-repellent layer or the water- and oil-repellent layer is mainly composed of a fluorine-containing coupling agent capable of forming a hydrogen bond and/or an -O-M bond (wherein M is any element selected from the group consisting of Si, Ti, Al, and Zr) with the hard film by a condensation reaction.
<12> A method for manufacturing a printing stencil having a hard film on a surface facing a printed substrate, comprising: preparing a plate-shaped substrate; forming a through hole having an opening area smaller than the area of the printed pattern shape portion in a printing pattern shape portion of the substrate; covering the printing pattern shape portion on the surface of the substrate facing the printed substrate with a masking material; forming a hard film by a dry process on the surface of the substrate facing the printed substrate that is covered with the masking material; and removing the masking material from the substrate on which the hard film has been formed.
<13> A method for manufacturing a printing stencil having a hard film on a surface facing a printed substrate, the method comprising: preparing a plate-shaped substrate; forming a hard film on the surface of the substrate facing the printed substrate by a dry process; removing a part or all of the hard film located in a printing pattern shape portion on the surface of the substrate facing the printed substrate; and forming a through hole in the printing pattern shape portion of the substrate, the opening area of which is smaller than the area of the printing pattern shape portion.
<14> The method for manufacturing a printing stencil according to <12> or <13>, further comprising forming a plurality of the through holes in the printing pattern portion.
<15> The method for producing a printing stencil according to any one of <12> to <14>, further comprising forming fine irregularities on a surface of the substrate before forming a hard film on the substrate.
<16> The method for producing a printing stencil according to any one of <12> to <15>, further comprising forming a corrosion-resistant layer on the surface of the substrate before forming the hard film on the substrate.
<17> The method for producing a printing stencil according to any one of <12> to <16>, further comprising stretching the substrate on which the hard film is formed on a printing frame.
<18> The method for manufacturing a printing stencil according to any one of <12> to <17>, wherein the hard film is one or more films selected from an amorphous carbon film, a metal (containing Si) oxide film, a metal (containing Si) nitride film, a metal (containing Si) carbide film, and a metal (containing Si) oxynitride film.
<19> The method for producing a printing stencil according to <18>, wherein the amorphous carbon film contains one or more elements selected from the group consisting of N, O, Si, Ti, Al, Zr, B and As.
<20> The method for producing a printing stencil according to any one of <12> to <19>, wherein the hard film has a Vickers hardness (Hv) of 100 or more.
<21> The method for producing a printing stencil according to any one of <12> to <20>, wherein the hard film has a Vickers hardness (Hv) of 450 or more.
<22> The method for producing a printing stencil according to any one of <12> to <21>, wherein a water-repellent layer or a water- and oil-repellent layer is further formed on the printing substrate side of the hard film.
<23> The method for producing a printing stencil according to any one of <12> to <22>, wherein the water-repellent layer or the water- and oil-repellent layer is mainly composed of a fluorine-containing coupling agent capable of forming a hydrogen bond and/or an -O-M bond (wherein M is any element selected from the group consisting of Si, Ti, Al, and Zr) with the hard film by a condensation reaction.

The present invention provides a printing stencil that has little variation in printing thickness and produces a thin printing layer.

1A and 1B are schematic diagrams showing the structure of a printing stencil according to one embodiment of the present invention ((a): cross-sectional view, (b): view from the squeegee side). Schematic cross-sectional views showing the structure of a recess or hole in a hard film ((a): hole, (b): recess). FIG. 2 is a schematic cross-sectional view showing the structure of a printing stencil according to one embodiment of the present invention, on which a water-repellent layer or a water- and oil-repellent layer is formed. 1A to 1C are schematic diagrams showing a method for manufacturing a printing stencil according to an embodiment of the present invention.

The following describes the configuration and effects of the present invention, including technical concepts, with reference to the drawings.

[Printing stencil]
As shown in Fig. 1, the printing stencil according to one embodiment of the present invention (hereinafter, referred to as "the present embodiment") is based on a two-layer (or multi-layer) structure of a plate-shaped substrate 1 having a surface 11 on the printed substrate side and a surface 12 on the squeegee side, and a hard film 3 formed on the surface 11 on the printed substrate side of the substrate 1. The hard film 3 has a concave portion or a hole portion that defines a printing pattern to be described later in a printing pattern shape portion 2 of the substrate 1. The printing pattern shape portion 2 has a through hole 13 formed therein for passing ink or paste, which penetrates from the concave portion or the hole portion to the surface 12 on the squeegee side of the substrate 1. Details of each part will be described below.

<Substrate>
The substrate 1 in the printing stencil according to this embodiment is not particularly limited, and may be any of various metal elements such as Fe, Cu, Ni, Al, and W, various alloys such as stainless steel, chromium-molybdenum steel, Ni-Co, Ni-W, Ni-Cr, aluminum alloys, copper alloys, and iron alloys, various inorganic materials such as amorphous metals, carbon, carbon cloth, glass, glass cloth, and ceramics, and inorganic and organic composite materials such as FRP, CFRP, and various other engineering plastics. Also, composite materials may be used in which resins such as PET, PEN, PMMA, OPP, polyimide, polyimide amide, vinyl chloride, and polycarbonate, rubber, and cellulose (wood, paper, etc.) are provided on the substrate surface.

Since the thickness variation of the substrate 1 directly leads to the variation of the shape and thickness of the printed pattern, it is preferable to suppress the thickness variation and surface roughness to a low level. The surface roughness required for the substrate 1 cannot be generally stated because it varies depending on the printing object, but as an example, the arithmetic mean surface roughness (Ra) of the part requiring the print transfer thickness accuracy is 0.2 μm or less, preferably 0.1 μm or less. Furthermore, in the case of a stencil for capacitor printing, Ra is preferably 0.05 μm or less, more preferably 0.03 μm or less.
On the other hand, if the surface roughness of the substrate 1 is too low (if the surface is too smooth), the surface of the printing stencil on the substrate side may be difficult to introduce air into the contact surface when the stencil is released from the surface contact state with the substrate to be printed during printing, which may result in poor stencil release properties. In this case, the surface of the printing stencil on the squeegee side may be prone to problems such as the ink or paste moving on the plate surface with the squeegee slipping, making it difficult to fill the ink or paste, or the thixotropy caused by the rotation of the ink or paste. For this reason, the surface roughness of the entire substrate 1 or a necessary portion may be roughened, or a slit or uneven structure having a depth exceeding the surface roughness of the substrate may be intentionally formed on any portion of the substrate 1, within a range that does not affect the printing accuracy or printing workability. In this specification, the unevenness formed in this way is collectively referred to as "fine unevenness". A preferred height (depth) of the fine irregularities varies depending on the required printing precision and the properties of the ink or paste used, and therefore cannot be generally stated; however, an example is an arithmetic mean surface roughness (Ra) of about 0.01 μm to 0.1 μm.
As the specific position and shape of the fine unevenness, for example, in a printing stencil surface having a rectangular printing substrate surface of 300 mm, a cross-shaped portion of width 50 mm is set in the center, which does not form a printing pattern (group), and the surface roughness of only this portion is roughened, a slit is provided in this portion, or an unevenness is provided in this portion. Other examples include making the surface roughness of only a frame-shaped portion located within a distance of 100 mm from each side of the 300 mm rectangular printing substrate surface, or a specific portion where the stencil sheet and the printing sheet start to separate first, and providing a slit or unevenness only in each portion.

The thinner the thickness of the substrate 1, the thinner the printed pattern can be formed by suppressing the amount of ink or paste supplied during printing, but the strength is lower, so durability and handling tend to decrease. Conversely, the thicker the substrate 1, the better the durability and handling, but the amount of ink or paste supplied increases, which may make it difficult to form a thin printed pattern. For this reason, the thickness of the substrate 1 is determined in consideration of the area and thickness of the printed pattern to be formed, and the durability required for the printing stencil. An example of the thickness of the substrate 1 is 10 μm to 100 μm, but is not limited to this thickness.
The thickness of the substrate 1 can be changed within the same stencil sheet. For example, the thickness of the printing film can be reduced while maintaining the rigidity of the printing stencil sheet by making the portion where the printing pattern is present thinner and the peripheral portion where the printing pattern is not present thicker.

A corrosion-resistant layer that prevents corrosion of the substrate 1 may be formed on the surface of the substrate 1. The corrosion-resistant layer is not particularly limited as long as it can prevent corrosion of the substrate 1, and examples include plating.

<Through holes in substrate>
The substrate 1 of the printing stencil according to this embodiment has through holes 13 for supplying ink or paste to the printing pattern shape portion 2. The through holes 13 partially replace the functions of conventional stencil components, but their structures are significantly different. Conventional printing stencils have a "printing pattern through hole portion" that is approximately the same shape as the actual printing pattern to define the printing pattern, but the through holes 13 in this embodiment have an opening area smaller than the actual printing pattern, and their shape does not need to be similar to the actual printing transfer pattern.
In this embodiment, the shape, size, number and position of the through holes 13 are not particularly limited as long as a printing pattern corresponding to the printing pattern shape portion 2 can be formed on the printed substrate (sheet). For example, the shape of the cross section or opening of the through holes 13 can be set to a circle, an ellipse, a polygon, a star, a slit, an indefinite shape, or the like. If the cross section or opening shape of the through holes 13 has corners, stress is concentrated at the corners when tension is applied to the substrate 1, and the substrate 1 may be damaged from the corners. Therefore, in the case of a shape having corners, it is preferable that the corners have a curved shape (R).

<Hard film>
In this embodiment, the hard film 3 is a film having a Vickers hardness Hv larger than that of the substrate 1. The hard film 3 is formed on the surface 11 of the substrate 1 facing the substrate to be printed, and has a function of defining a print pattern in the print pattern shape portion 2. Specifically, the hard film 3 is provided with a concave portion or hole portion 31 corresponding to the print pattern shape portion 2, and is configured so that the ink or paste filled in the concave portion or hole portion 31 is transferred to the substrate to be printed. Here, the concave portion or hole portion 31 means a portion (corresponding to a hole portion) where the hard film 3 is not formed on the substrate 1 as shown in FIG. 2(a), or a portion (corresponding to a concave portion) where the hard film 3 is formed thinner than other portions as shown in FIG. 2(b).
The thickness of the hard film 3 is 1 nm to 5 μm. If the hard film 3 is too thick, there is a risk that the hard film 3 may peel off due to deformation of the substrate during printing or handling. Furthermore, the variation in thickness is within 10%. By reducing the variation in the thickness of the hard film 3, the variation in the thickness of the obtained print pattern can be reduced.
In this embodiment, the hard film 3 only needs to be formed on one surface of the substrate 1 (surface 11 facing the printed substrate). However, in cases where a thin substrate 1 is used, for example, forming the hard film 3 only on the surface 11 facing the printed substrate of the substrate 1 would cause the substrate 1 to warp due to residual stress in the hard film 3. In such cases, the hard film 3 can be formed also on the opposite surface of the substrate 1 (surface 12 facing the squeegee) to eliminate or mitigate the warping.

As the hard film 3, an amorphous carbon film, a metal (including Si) oxide film, a metal (including Si) nitride film, a metal (including Si) carbide film, and a metal (including Si) oxynitride film can be suitably used. More preferably, the amorphous carbon film contains one or more elements selected from N, O, Si, Ti, Al, Zr, B, and As. Specific examples of suitable hard films include those made of one or more selected from diamond-like carbon (DLC), TiAlN, TiCrN, TiC, TiN, CrC, SiC, SiO _x , ZrO _x , c-BN, and the like.

The amorphous carbon film contains nitrogen (N), oxygen (O) and metal elements such as silicon (Si), titanium (Ti), aluminum (Al) and zirconium (Zr), which makes it easier for polar functional groups such as hydroxyl groups to adhere or bond to the surface layer of the film. Therefore, when a water-repellent layer or a water-repellent/oil-repellent layer is formed on a hard film as described below, a chemical bond such as a dehydration condensation reaction or a hydrogen bond is formed with the polar functional group contained in the fluorine-containing silane coupling agent, which is a component of the hard film, and the adhesion to the water-repellent layer or the water-repellent/oil-repellent layer can be improved. Examples of such DLC films include a film containing titanium (Ti) in addition to carbon (C) and hydrogen (H) (a-C:H:Ti film), and a film containing silicon (Si) in addition to carbon (C) and hydrogen (H) (a-C:H:Si film). When the DLC film contains Si, the content is, for example, 0.1 to 50 atomic %, and preferably 10 to 40 atomic %.

In addition, when oxygen or nitrogen is contained in the amorphous carbon film, the wettability of the amorphous carbon film to water (for example, wettability to water-based ink) can be improved. Therefore, as described above, when a hard film is also formed on the squeegee side of the substrate to prevent warping of the substrate due to residual stress, by making the hard film an amorphous carbon film containing oxygen or nitrogen, it is possible to promote the wetting and spreading of the ink or paste during squeegeeing, and to suppress the occurrence of voids (air bubbles) in the printed matter due to insufficient wettability, and the occurrence of smearing or pinfall in the printed matter due to the inclusion of voids.

Furthermore, when the amorphous carbon film contains either Si, Si and oxygen, or Si and nitrogen, it has a high affinity with an adhesive made of a resin material, so that when the substrate 12 is made into a printing stencil, it can be reliably fixed to a frame using an adhesive.

The hard film 3 as described above is formed by various methods such as CVD (chemical vapor deposition) methods such as plasma CVD, physical vapor deposition (PVD) methods such as plasma sputtering, ECR plasma, etc. The plasma CVD methods used in this embodiment include high-voltage DC micropulse plasma CVD, high-voltage pulse plasma CVD, high-frequency plasma CVD using high-frequency discharge, direct-current plasma CVD using direct-current discharge, and microwave plasma CVD using microwave discharge.
The hard film 3 can also be formed by a wet plating method. Any wet plating method can be selected as appropriate as long as it can form a hard film on the base material with sufficient bonding strength.

The Vickers hardness Hv of the hard film 3 is preferably 100 or more, and more preferably 450 or more. By providing a hard film 3 with a high Hv, it is possible to form a print pattern opening that is resistant to wear or abrasion. By making the Vickers hardness Hv 100 or more, the film becomes harder than the hardness of stainless steel (Hv = 100 to 200), which is a general-purpose base material. In addition, ceramic coatings such as the above-mentioned DLC, TiAlN, TiCrN, and TiN can achieve an Hv of 450 or more, and those with high hardness can achieve an Hv of nearly 4000.

In the printing stencil according to this embodiment, the opening area of the through hole 13 for supplying the ink or paste is configured to be smaller than the area of the printing pattern shape portion 2, so that the amount of ink or paste supplied to the concave portion or hole portion 31 defining the printing pattern formed in the printing pattern shape portion 2 can be reduced. The concave portion or hole portion 31 defining the printing pattern is formed of a hard film having a very thin and uniform thickness, so that the small amount of ink or paste supplied from the through hole 13 can be formed into a printing pattern having a very thin and uniform thickness. When a plurality of through holes are opened in one concave portion or hole portion, the ink or paste supplied to each through hole merges in the concave portion or hole portion to form one printing pattern.
In addition, in the printing stencil according to this embodiment, the through holes 13 and the base material 1 in which they are formed do not come into direct contact with the substrate to be printed during printing. Therefore, unlike a conventional screen stencil with a mesh, mesh marks are not formed in the printing pattern due to the intersections of the mesh, and the printing pattern is not divided by the walls of the openings, as in a stencil stencil in which the openings through which the ink or paste passes are processed and formed as discrete holes.

The printing stencil according to this embodiment may be accompanied by a support frame (plate frame) made of cast iron, aluminum alloy, wood, or any other material. The plate frame is not limited to a frame-shaped one, but may be cylindrical, such as a rotary printing plate. Furthermore, it may be a flat plate without a frame, and may be chucked to a printing machine or plate frame during printing.

<Water-repellent layer/water- and oil-repellent layer>
The printing stencil according to this embodiment may have a water-repellent layer or a water-repellent/oil-repellent layer 4 formed on the substrate 1 or the hard film 3. FIG. 3 shows a schematic cross-sectional view of a printing stencil having a water-repellent layer or a water-repellent/oil-repellent layer 4 formed on the hard film 3. The formation of the water-repellent layer or the water-repellent/oil-repellent layer 4 provides the following: UV scattering prevention effect of the hard film 3; gas barrier effect for preventing contact of the hard film 3 with atmospheric gas; anticorrosion effect of the hard film 3; improvement of the abrasion resistance and slidability of the hard film 3; prevention of adhesion of soft metal, which is a component of the ink or paste used during printing, to the hard film; and prevention of bleeding of the ink or paste or of its wrapping around the substrate 1 during printing.

The water-repellent layer or the water- and oil-repellent layer 4 is preferably a thin film made of a fluorine-containing coupling agent, although the composition is not particularly limited. Furthermore, if the fluorine-containing coupling agent is any one of a silane coupling agent, a titanate coupling agent, a zirconate coupling agent, and an aluminate coupling agent, it is more preferable because it is possible to provide a stable water- and oil-repellent surface to the openings of the printing stencil.
The fluorine-containing coupling agent can be formed into a thin film of about 10 to 20 nm, and is also preferable in that it can suppress deterioration of the shape precision of the aperture pattern of the stencil.

The water-repellent layer or the water- and oil-repellent layer 4 can be appropriately formed on the required parts according to the printing application, such as the surface of the printing stencil facing the substrate to be printed, the wall surface of the printing pattern shape portion 2, the surface facing the squeegee, etc.
The printing stencil according to this embodiment is often used in such a way that the ink or paste supplied to the surface on the squeegee side is slid by the squeegee to pass through the through holes 13 after being placed in contact with the substrate without offset (without leaving a gap). In this printing method, the ink or paste tends to bleed more easily than in normal screen printing, and the releasability (plate release) of the stencil from the printing substrate tends to be poor. In addition, some inks used in thin film printing have low viscosity and high fluidity like water, and it may be difficult to print according to the printing pattern shape of the stencil. For this reason, in the printing stencil according to this embodiment, it may be extremely effective to perform water repellent treatment or water-repellent and oil-repellent treatment on the necessary parts where the ink is likely to bleed, and conversely, not to perform the treatment on the unnecessary parts that will hinder the filling of the ink. Specifically, when the printing stencil according to this embodiment is used for thin-film printing, it is preferable to form the water-repellent layer or water- and oil-repellent layer 4 only on the "surface facing (contacting) the substrate to be printed" of the hard film 3 having the "surface facing (contacting) the substrate to be printed" and the "inner wall of the concave portion or hole that defines the printing pattern". Since the viscosity of the ink or paste used in thin-film printing is low, if the water-repellent treatment or water- and oil-repellent treatment is performed on the "inner wall of the concave portion or hole that defines the printing pattern", there is a risk that the filling of the ink or paste into the concave portion or hole 31 that defines the printing pattern may be hindered. In addition, when the water-repellent layer or water- and oil-repellent layer 4 is formed on the surface on the squeegee side, the wetting spread and the uniformity of the thickness may be hindered when the ink or paste is precoated on the surface on the squeegee side with a scraper or the like. On the other hand, applying water-repellent or water- and oil-repellent treatment to the "surface facing (contacting) the printed substrate" is extremely effective in preventing the highly fluid, low-viscosity ink or paste from seeping out of the opening of the printed pattern or from wrapping around the printed substrate side of the screen. If the viscosity of the ink or paste is relatively high, it is possible to apply water-repellent or water- and oil-repellent treatment to both the "surface facing (contacting) the printed substrate" and the "inner wall of the recessed portion or hole that defines the printed pattern." In addition to these, it is also possible to apply water-repellent or water- and oil-repellent treatment to the bottom surface of the recessed portion or hole that defines the printed pattern (which may also be the surface of the screen substrate), and further it is also possible to apply water-repellent or water- and oil-repellent treatment to the inner wall of the through hole 13 opened in the substrate 1.

[Method of manufacturing printing stencils]
The printing stencil according to this embodiment is preferably manufactured by a method including the steps of preparing a plate-shaped substrate 1, forming through holes 13 having an opening area smaller than the area of the printing pattern in the printing pattern shape portion 2 of the substrate 1, covering the printing pattern shape portion 2 on the surface 11 of the substrate 1 facing the substrate to be printed with a masking material 5, forming a hard film 3 by a dry process on the surface 11 of the substrate 1 facing the substrate to be printed that is covered with the masking material 5, and removing the masking material 5 from the substrate 1 on which the hard film 3 has been formed. Details of each operation are described below.

<Preparation of substrate>
The substrate 1 used may be a commonly available plate material as it is, or may be formed by electroforming. When the substrate is formed by electroforming, it may be a flat plate without through holes, or a flat plate with through holes formed in advance.

In order to adjust the surface condition of the substrate 1, when forming the substrate part by electroforming, the type and amount of additives such as leveling agents in the electroforming bath may be adjusted to give a mirror finish or a matte finish. After forming the substrate part, a mirror finish may be performed by electrolytic polishing or other processes such as blasting, honing, matte finish, hairline processing, laser processing, scoring, drilling, pressing, and etching, or a corrosion-resistant layer may be formed by a wet or dry plating coating. When the above-mentioned "fine irregularities" are formed on the squeegee-side surface of the substrate, these surface condition adjustment methods can be used to form one or more grooves, openings, other irregularities, or wavy structures in any part in an arrangement perpendicular or oblique to the direction of travel of the moving squeegee during printing.

When forming a portion of the substrate 1 that is thinner than other portions, the corresponding portion is partially etched (half-etched), or a protrusion called a C.O.B. mask is formed by welding or other methods to increase the thickness of the portion other than the corresponding portion.

<Formation of through holes in substrate>
The through holes 13 can be formed in the substrate 1 by various methods, including, but not limited to, mechanical processing such as drilling, punching, pressing, etc., irradiation with high-energy ions or electron beams such as laser light or focused ion beams, irradiation with high-pressure liquid (water), etching, or a combination of the above methods.

In the embodiment of the present invention, when through holes 13 are formed in a substrate 1 which is an aggregate of fine fibers such as carbon fiber cloth or glass cloth, there is a risk that the fibers may escape from the vicinity of the opening or the inner wall of the through holes 13. In order to prevent this, it may be effective to perform a surface treatment on the surface layer of the cloth by a known wet plating method or formation of a dry thin film to fix the fibers before performing the hole drilling process, or to drill holes in the cloth and then perform a surface treatment by a known wet plating method or formation of a dry thin film to fix the fibers.
Among fiber aggregates, carbon fiber cloth is suitable for use as the substrate 1 because it is robust, highly corrosion resistant, and conductive, making it easy to perform wet plating, and also easy to drill holes in by laser processing.

The through holes 13 may be formed at any appropriate time during the process of creating the screen. For example, the through holes 13 may be formed in advance in the print pattern shape portion 2 of the substrate 1, the through holes 13 may be formed after forming a hard film 3 on the surface layer of the substrate 1, or the through holes 13 may be formed after forming a water-repellent layer or a water-repellent/oil-repellent layer 4 on the surface layer of the hard film 3. When the through holes 13 are formed with laser light after forming the water-repellent layer or the water-repellent/oil-repellent layer 4, it is also possible to destroy the hard film 3 and the water-repellent layer or the water-repellent/oil-repellent layer 4 that have been formed in advance in the laser irradiated portion.

<Masking>
Masking of the substrate 1 is performed by disposing a masking material 5 on the substrate 1 in the shape of the print pattern shape portion 2 prior to the formation of the hard film 3. The type of masking material 5 is not particularly limited, and may be an ink, a film, or a three-dimensional object as long as it can prevent the hard film 3 from being formed at the location where the masking material is disposed when the hard film 3 is formed. When forming a fine masking portion on the substrate 1 with good positional accuracy, a resist liquid or resist film used in known photolithography is suitable. When masking the substrate 1 with a resist liquid or resist film, the resist liquid or resist film is applied or disposed on the entire surface of the substrate 1 to be the surface 11 on the printed substrate side, and then the resist liquid or resist film is irradiated (scanned) with a light beam capable of altering the resist, such as a laser beam, in accordance with the position and shape of the print pattern shape portion 2, and exposed to light by a "direct imaging method" (direct imaging method) in which only the resist located in the print pattern shape portion 2 is exposed to light, and then development is performed. It is of course possible to place another patterned exposure mask on the resist formed on the substrate 1 and modify the necessary portions (exposed portions) of the resist, and the method is not particularly limited.

<Formation of hard film>
The method for forming the hard film 3 on the surface of the substrate 1 is not limited as long as it can provide a hard film having a desired thickness and surface roughness, but a dry process is preferred, and a vacuum plasma process is more preferred, in that it can form a thin film with small thickness variations. A specific method will be described below using an example in which an amorphous carbon film is formed as the hard film 3.

When forming an amorphous carbon film by plasma CVD, a hydrocarbon gas such as methane, acetylene, or benzene is used as the raw reactive gas. The conditions for film formation, such as the substrate temperature, gas concentration, pressure, and time, are appropriately set by known methods according to the composition and film thickness of the amorphous carbon film (a-C:H film) to be produced.

In this case, when forming an amorphous carbon film (a-C:H:Si film) that contains silicon (Si) in addition to carbon (C) and hydrogen (H), for example, tetramethylsilane, methylsilane, dimethylsilane, trimethylsilane, dimethoxydimethylsilane, and tetramethylcyclotetrasiloxane are used as the raw reactant gas.

In this case, when forming an amorphous carbon film (a-C:H:Ti film) containing titanium (Ti) in addition to carbon (C) and hydrogen (H), a gas containing Ti such as titanium chloride (TiCl ₄ ), titanium iodide (TiI ₄ ), titanium isopropoxide (Ti(OC ₃ H ₇ ) ₄ ), or the like, mixed with a hydrocarbon gas such as acetylene, ethylene, or methane is used as a raw reactive gas in the above-mentioned plasma CVD method.

When forming an amorphous carbon film by plasma CVD, if oxygen (O) is to be contained in the film, a method of introducing oxygen together with the main raw material gas during film formation can be used. The oxygen content in the resulting hard film is determined by adjusting the flow rate of oxygen in the total flow rate of the main raw material gas and oxygen. The flow rate is, for example, 0.01 to 12%, preferably 0.5 to 10%. Another method of incorporating oxygen (O) into the amorphous carbon film may be to irradiate a previously formed film with oxygen plasma.

The amorphous carbon film can also contain nitrogen (N). In this case, a method can be used in which the formed amorphous carbon film is irradiated with nitrogen plasma.

When oxygen (O) or nitrogen (N) is introduced into an amorphous carbon film by plasma irradiation, after the amorphous carbon film is formed in an amorphous carbon film forming apparatus, plasma irradiation can be performed in the same apparatus without breaking the vacuum, and the formation of the amorphous carbon film and the introduction of oxygen (O) or nitrogen (N) into the film can be performed continuously.

The amorphous carbon film can also be formed by a physical vapor deposition method (PVD method). In this case, the substrate 1 is placed in a film forming apparatus, the inside of the apparatus is made into a vacuum atmosphere, and then a sputtering gas (e.g., an inert gas such as argon gas) is introduced at a predetermined pressure and flow rate to sputter a carbon target, thereby forming an amorphous carbon film on the substrate 1. In this case, an Si target or a Ti target is sputtered simultaneously with the carbon target, thereby forming an amorphous carbon film containing Si and/or Ti.
In addition, by mixing a hydrocarbon gas such as acetylene, oxygen (O), nitrogen (N) or a mixed gas of these with the gas used for sputtering a Si target or Ti target, an amorphous carbon film containing silicon, titanium, carbon and hydrogen, oxygen or nitrogen can be formed by a reactive sputtering method.

After forming the hard film 3 on the surface of the substrate 1 as described above, the masking material 5 is removed to obtain a printing stencil according to this embodiment, in which the hard film 3 is formed with recesses or holes 31 that define the printing pattern in the printing pattern forming portion 2 on the surface 11 of the substrate 1 facing the printed substrate.

When manufacturing the printing stencil according to this embodiment, the entire surface of the substrate 1 is covered with a hard film 3, and then part or all of the hard film 3 is removed by irradiation with laser light or an ion beam, etc., to form recesses or holes 31 that define the printing pattern.
In particular, according to the method of forming the recesses 31 that define the printing pattern by removing only a part of the hard film 3, the substrate 1 is covered with the hard film except for the through holes 13, so that a material with low chemical durability such as corrosion resistance can be used for the substrate. Therefore, it is possible to use a material that has good mechanical properties such as strength but is poor in chemical durability and therefore cannot be used for a printing stencil as the substrate 1. For example, medium carbon steel for machine construction (S45C) (Young's modulus 205 GPa, shear elasticity 82 GPa, yield strength 727 MPa, tensile strength 828 MPa, elongation 22%), high tensile steel (HT80) (Young's modulus 203 GPa, shear elasticity 73 GPa, yield strength 834 MPa, tensile strength 865 MPa, elongation 26%), chromium molybdenum steel (SCM440) (yield strength 833 MPa, tensile strength 980 MPa, elongation 12%), etc. ), nickel chrome molybdenum steel (SNCM439) (yield strength 1471 MPa, tensile strength 1765 MPa, elongation 8%), precipitation hardening stainless steel (SUS631) (Young's modulus 204 GPa, yield strength 1029 MPa, tensile strength 1225 MPa, elongation 4%), martensitic stainless steel (SUS410) (Young's modulus 200 GPa, yield strength 345 MPa, tensile strength 540 MPa, elongation 25%) , Hastelloy (registered trademark) X (Young's modulus 197 GPa, shear modulus 75 GPa, yield strength 384 MPa, tensile strength 775 MPa, elongation 43%), hot die tool steel (SKD6), spring steel (SUP7), 9% Ni steel for low-temperature pressure vessels (SL9N590), maraging steel (350 grade), Monel metal, Nichrome (GNC108), titanium 6Al-4V alloy (60 types), and titanium 5-2.5 alloy, etc. Considering the mechanical properties of stainless steel (SUS304) (Young's modulus 197 GPa, shear modulus 74 GPa, yield strength 205 MPa, tensile strength 520 MPa, elongation 40%) and nickel (99.99Ni) (Young's modulus 204 GPa, shear modulus 81 GPa, yield strength 58 MPa, tensile strength 335 MPa, elongation 28%), which are widely used as substrates for printing stencils, there is a high possibility that they can be used as the substrate 1.

<Formation of Water-Repellent Layer/Water- and Oil-Repellent Layer>
When the above-mentioned water-repellent layer or water- and oil-repellent layer 4 is formed on the substrate 1 or hard film 3, the method of formation is not particularly limited and can be appropriately selected. For example, a liquid starting material (coupling agent liquid) may be applied to the portion where the water-repellent layer or water- and oil-repellent layer 4 is to be formed by penetrating a nonwoven fabric or the like, by hand coating, brush coating, squeegee coating, roller coating, or the like, or may be sprayed with a spray or the like. In addition, a screen may be dipped in the coupling _agent liquid, or it may be coated with a bar coater or spin coater, or it may be applied by screen printing. Furthermore, it may be formed by a resistance heating method or other known vacuum process. Examples of the vacuum process include plasmatizing a raw material gas containing at least fluorine, such as _CF4 or _C6F6 , in a vacuum or at atmospheric pressure (atmospheric pressure plasma) to give fluorine to the substrate 1 or hard film 3, or forming a layer containing fluorine on the substrate 1 or hard film 3.

A SUS304 stainless steel plate with a rectangular shape of 400 mm on each side and a thickness of 30 μm was prepared, and in a 50 mm×50 mm area in the center of the SUS plate, rectangles with a width of 150 μm and a length of 400 μm, which correspond to the printing pattern of the internal electrodes of one capacitor, were virtually arranged at intervals of 100 μm. Next, holes of φ20 μm were formed at equal intervals of 30 μm inside the virtually arranged rectangles by a known YAG laser beam to form a mesh shape. After that, the SUS plate was immersed in an etching solution mainly composed of hydrofluoric acid to remove dross, and then a known electrolytic polishing method was used to remove smut, and a plate with a surface smoothed to about Ra 0.03 μm was produced.
Next, a known photoresist film (Hitachi Chemical RY series RY3325, thickness 25 μm) having a thickness of 25 μm was applied to the entire surface of a 50 mm square printing pattern area in the center of one side of the SUS plate (the side that faces the printed substrate in the printing stencil), and a pattern was directly drawn using a UV laser light direct imaging device (Dainippon Screen LI9500 (Mercurex)) so that the photoresist film remained in the virtually arranged rectangular area.
Next, the SUS plate masked with the photoresist film was placed in a vacuum chamber of a high-pressure DC micro-pulse plasma CVD apparatus, and the vacuum chamber was evacuated to 1×10 ⁻³ Pa. Then, argon gas at a pressure of 1 Pa was introduced into the vacuum chamber at a flow rate of 30 SCCM, and the substrate surface was plasma-cleaned for 10 minutes by applying a voltage of −3 kVp. After argon gas was evacuated from the vacuum chamber, trimethylsilane gas at a pressure of 1 Pa was introduced into the vacuum chamber at a flow rate of 30 SCCM, and a voltage of −5 kVp was applied to form a 300 nm thick Si-containing amorphous carbon film (hard film) on the surface of the SUS plate masked with the photoresist film (the surface that is the surface of the printing stencil that faces the substrate to be printed), and then the vacuum was broken to remove the SUS substrate, and the photoresist film (pattern portion) was developed and removed by a known method.
The obtained SUS plate was stretched over a casting frame measuring 650 mm in length and 550 mm in width by a known method and made into a printing stencil.

The resulting printing stencil had a rectangular printing pattern area on the surface of a 400 mm x 400 mm rectangular SUS plate facing the printed substrate, with a 150 μm wide, 400 μm long rectangular printing pattern portion with a mesh of φ20 μm holes formed therein, surrounded by a 300 nm thick Si-containing amorphous carbon film. When viewed from the printed substrate side, the rectangular printing pattern portion was recessed by 300 nm (corresponding to the film thickness of the Si-containing amorphous carbon film) from the surface on which the Si-containing amorphous carbon film was formed. In other words, when the Si-containing amorphous carbon film was brought into contact with the printed substrate, the SUS plate located in the printing pattern portion had a space of 300 nm between the printed substrate and the Si-containing amorphous carbon film.

Next, the thickness and the variation in thickness of the Si-containing amorphous carbon film (hard film) formed on the substrate were confirmed.
The printing stencil was disassembled, and test pieces measuring approximately 5 mm x 5 mm were cut out from a total of five locations, including the four corners and the center of the printing pattern area. The cross sections were observed under an electron microscope to measure and compare the film thickness of the Si-containing amorphous carbon film in each test piece.
As a result, it was confirmed that the difference in film thickness between the thickest and thinnest of the five test pieces was within 10% (within a range of 30 nm). It is difficult to achieve such a narrow film thickness variation industrially with good reproducibility by manually applying the emulsion resin liquid while contacting a bucket onto a screen mesh, and the effectiveness of the present invention was confirmed.

The printing stencil of the present invention allows thin-film printing patterns to be formed with high precision. Therefore, the printing stencil of the present invention can be suitably used for stencil stencils, offset printing plates, etc.

REFERENCE SIGNS LIST 1 Substrate 11 Surface on the printed substrate side 12 Surface on the squeegee side 13 Through hole 2 Print pattern shape portion 3 Hard film 31 Concave portion or hole portion 4 Water-repellent layer or water- and oil-repellent layer 5 Masking material

Claims (10)

a plate-shaped substrate having a single layer and a surface facing a substrate to be printed and a surface facing a squeegee;
a hard film formed on the surface of the base material facing the printed substrate and having a concave portion or a hole portion that defines the printing pattern in the printing pattern shape portion;
a plurality of through holes penetrating the printing pattern shape portion from within the recessed portion or hole portion to the squeegee side surface of the base material, the opening area of which is smaller than the area of the printing pattern defined by the recessed portion or hole portion of the printing pattern shape portion;
Equipped with
The hard film has a thickness of 300 nm to 5 μm, and the variation in thickness is within 10%. The printing stencil according to claim 1, wherein the substrate has a surface with fine irregularities. The printing stencil according to claim 1 or 2, wherein the substrate has a corrosion-resistant layer on its surface. The printing stencil according to any one of claims 1 to 3, in which the substrate is stretched over a printing frame. The printing stencil according to any one of claims 1 to 4, wherein the hard film is one or more films selected from an amorphous carbon film, a metal (including Si) oxide film, a metal (including Si) nitride film, a metal (including Si) carbide film, and a metal (including Si) oxynitride film. The printing stencil according to claim 5, wherein the amorphous carbon film contains one or more elements selected from N, O, Si, Ti, Al, Zr, B and As. The printing stencil according to any one of claims 1 to 6, wherein the Vickers hardness (Hv) of the hard film is 100 or more. The printing stencil according to any one of claims 1 to 7, wherein the Vickers hardness (Hv) of the hard film is 450 or more. The printing stencil according to any one of claims 1 to 8, further comprising a water-repellent layer or a water- and oil-repellent layer formed on the printing substrate side of the hard film. The printing stencil according to claim 9, wherein the water-repellent layer or the water- and oil-repellent layer is mainly composed of a fluorine-containing coupling agent capable of forming hydrogen bonds and/or -O-M bonds (wherein M is any element selected from the group consisting of Si, Ti, Al, and Zr) with the hard film by condensation reaction.