JP7631994B2 - Particulate filter and method for manufacturing particulate filter - Google Patents

Description

The present invention relates to a filter for capturing fine particles.

Particulate filters that can adequately capture foreign matter contained in solutions are in demand in many fields, including medical facilities, pharmaceutical manufacturing plants, and high-purity clean rooms.

International Publication No. WO2010/087483

One possible configuration for a filter for capturing fine particles is to provide minute through-holes in a part of the solution flow path of the filter, and capture the fine particles within the through-holes.

In addition, when mass-producing such particulate filters, it is possible to use laser processing technology, because this technology can quickly form a large number of through holes in the workpiece with high dimensional accuracy (for example, Patent Document 1).

However, in order to reliably capture particles, it is necessary to form extremely fine through-holes (fine through-holes) of, for example, about 0.6 μm or less in size in a particulate capture filter. However, generally, with laser processing technology, the diameter of holes formed in a workpiece having a thickness of 50 μm or more is limited to about 2 μm. For this reason, it is not easy to form the above-mentioned through-holes for capturing particles with high precision.

In particular, in particulate capture filters, it may be necessary to form a large number of through holes, for example 1,000 or more, in an inspection area of 1 mm x 1 mm. However, it is extremely difficult to form a large number of through holes with a diameter of less than 2 μm in such a small inspection area using laser processing technology.

Due to this background, there have been almost no examples to date of using laser processing technology to manufacture particulate filters. However, if it were possible to manufacture particulate filters using laser processing technology, it would be preferable in terms of quality and manufacturing costs.

The present invention has been made in consideration of the above background, and aims to provide a particulate filter having a configuration that can be manufactured using laser processing technology. It also aims to provide a method for manufacturing such a particulate filter.

The present invention provides a particulate filter, comprising:
a transparent body having a first surface and a second surface and a thickness of 50 μm or more;
a plurality of through holes extending from the first surface to the second surface of the body;
having
A position at a depth of 10 μm from the second surface is defined as a reference depth D _S ;
In each through hole, when the minimum cross-sectional dimension at the reference depth D _S is φ _P and the minimum cross-sectional dimension between the reference depth D _S and the second surface is φ _Q ,
A particulate filter is provided in which φ _Q ≦0.6 μm and φ _Q /φ _P ≦0.5.

The present invention also provides a method for producing a particulate filter, comprising the steps of:
(I) providing a transparent substrate having a first surface and a second surface opposed to each other;
(II) irradiating the first surface of the substrate with laser light to form a plurality of substrate through-holes penetrating the substrate from the first surface to the second surface;
(III) providing a coating layer on the second surface of the substrate to form a plurality of through holes through the substrate and the coating layer;
A method of manufacturing is provided, comprising:

The present invention provides a particulate filter having a configuration that can be manufactured using laser processing technology. It is also an object of the present invention to provide a method for manufacturing such a particulate filter.

1 is a top view showing a schematic diagram of a particulate filter according to an embodiment of the present invention; 2 is a schematic diagram showing an example of a cross section of an inspection region of the particulate filter according to the embodiment of the present invention shown in FIG. 1 ; FIG. 4 is a schematic diagram showing another cross section of a substrate through-hole in a substrate. FIG. 2 is a diagram showing an example of a flow of a method for manufacturing a particulate filter according to an embodiment of the present invention. 1A to 1C are diagrams illustrating a process for producing a particulate filter according to an embodiment of the present invention. 1A to 1C are diagrams illustrating a process for producing a particulate filter according to an embodiment of the present invention. 1A to 1C are diagrams illustrating a process for producing a particulate filter according to an embodiment of the present invention. 1A to 1C are diagrams illustrating a process for producing a particulate filter according to an embodiment of the present invention. 1 is a photograph showing an example of a cross section of a through hole formed in a sample according to an example. 13 is a photograph showing an example of a cross section of a through hole formed in a sample according to another embodiment. 13 is a photograph showing an example of a cross section of a through hole formed in a sample according to yet another embodiment.

One embodiment of the present invention is described below.

In one embodiment of the present invention, there is provided a particulate filter comprising:
a transparent body having a first surface and a second surface and a thickness of 50 μm or more;
a plurality of through holes extending from the first surface to the second surface of the body;
having
A position at a depth of 10 μm from the second surface is defined as a reference depth D _S ;
In each through hole, when the minimum cross-sectional dimension at the reference depth D _S is φ _P and the minimum cross-sectional dimension between the reference depth D _S and the second surface is φ _Q ,
A particulate filter is provided in which φ _Q ≦0.6 μm and φ _Q /φ _P ≦0.5.

As mentioned above, with laser processing technology, the diameter of holes formed in a workpiece having a thickness of 50 μm or more is limited to about 2 μm, and it is not easy to form finer holes with high precision. In particular, it is extremely difficult to mass-form through holes with a diameter of less than 2 μm in a tiny inspection area using laser processing technology.

In this regard, the particulate filter according to one embodiment of the present invention has the above-mentioned configuration. As will be described in detail later, a particulate filter having such a configuration has a thickness of 50 μm or more, but can be manufactured using laser processing technology.

Therefore, in one embodiment of the present invention, a particulate capture filter can be manufactured with high quality and low manufacturing costs.

(Particulate filter according to one embodiment of the present invention)
Hereinafter, an embodiment of the present invention will be described in more detail with reference to the drawings.

Figures 1 and 2 show a schematic diagram of an example of the configuration of a particulate filter according to one embodiment of the present invention. Figure 1 shows a top view of a particulate filter according to one embodiment of the present invention (hereinafter referred to as the "first filter").

As shown in FIG. 1, the first filter 100 has a transparent body 110. The body 110 has a first surface 112 and a second surface 114. An inspection area 120 is disposed in the body 110.

In the example shown in FIG. 1, the first filter 100 has a substantially circular shape when viewed from above. However, the shape of the first filter 100 is not particularly limited, and may be, for example, an ellipse, a triangle, a rectangle, or a polygon with pentagons or more sides.

In the example shown in FIG. 1, the inspection area 120 is arranged in a substantially square shape in a top view, substantially in the center of the main body 110. However, this is merely one example. The inspection area 120 may be arranged in a non-central portion of the main body 110. The inspection area 120 may also be arranged in a non-square shape, for example, a circle, an ellipse, a rectangle, or a polygon having pentagons or more sides.

In addition, the number of inspection areas 120 is not necessarily limited to one, and the inspection areas 120 may be provided in multiple locations on the main body 110.

Furthermore, in FIG. 1, the inspection area 120 is clearly represented by a rectangular frame. However, it should be noted that in the first filter 100, there are often cases where the boundary between the inspection area 120 and the non-inspection area cannot be clearly identified by visual inspection.

The circular frame on the left side of FIG. 1 shows an enlarged view of a portion of the inspection area 120. As shown in this frame, a number of through holes 122 are formed in the inspection area 120.

The density of the through holes 122 in the inspection area 120 is not particularly limited, but is, for example, 100 pcs/mm ² or more.

The form of the two-dimensional arrangement of the through holes 122 is not particularly limited. The through holes 122 may be arranged regularly or randomly.

When the through holes 122 are regularly arranged, the arrangement and pitch are not particularly limited. For example, as shown in FIG. 1, the through holes 122 may be regularly arranged vertically and horizontally. The pitch may be, for example, in the range of 10 μm to 100 μm.

Figure 2 shows a schematic example of a cross section of the inspection region 120 of the main body 110. Figure 2 shows a cross section along the longitudinal central axis of the multiple through holes 122.

As shown in FIG. 2, the main body 110 has a substrate 140 and a coating layer 150 formed on one surface of the substrate 140. The first surface 112 of the main body 110 corresponds to the surface of the substrate 140 on which the coating layer 150 is not provided, and the second surface 114 corresponds to the surface of the coating layer.

2, the dashed line D _i represents the boundary between the substrate 140 and the coating layer 150. However, in practice, this boundary D _i may often be unclear.

The body 110 includes a number of through holes 122. Each through hole 122 has a first opening 125 on the first surface 112 side of the body 110 and a second opening 127 on the second surface 114.

Each through hole 122 is formed by penetrating both the substrate 140 and the coating layer 150. Therefore, the first opening 125 of the through hole 122 is an opening on the substrate 140 side, and the second opening 127 is an opening on the coating layer 150 side.

In each through hole 122, the portion on the substrate 140 side is referred to as the "substrate through hole 132a," and the portion on the coating layer 150 side is referred to as the "coating layer through hole 132b."

In the example shown in FIG. 2, in each through hole 122, the substrate through hole 132a has a tapered shape, with a "minimum cross-sectional dimension" decreasing monotonically from the first opening 125 to the boundary _Di.

Here, the "minimum cross-sectional dimension (of the through hole)" refers to the smallest distance between opposing side walls in a cross section passing through the central longitudinal axis of the through hole 122. Therefore, if the cross section of the through hole is circular, the "minimum cross-sectional dimension" represents the diameter, and if it is elliptical, the "minimum cross-sectional dimension" represents the dimension of the minor axis.

To be precise, the first opening 125 and the second opening 127 are not "cross-sections of the through holes." However, in this application, the term "minimum cross-sectional dimension" is used to describe the dimensions of these openings 125 and 127.

In the example shown in FIG. 2, the taper angle θ of the substrate through hole 132a is, for example, in the range of 65° to 89°. Here, the taper angle θ of the substrate through hole 132a is expressed as the angle between the normal to the first surface 112 and the side wall of the substrate through hole 132a.

Referring again to FIG. 2, the coating layer through-hole 132b of the through-hole 122 has a more complex cross-sectional shape than the substrate through-hole 132a.

2, the coating layer through hole 132b has a cross-sectional shape having a narrowed portion 154 with a minimum cross-sectional dimension between the boundary D _i and the second surface 114 (but not including the boundary D _i ). In other words, when the minimum cross-sectional dimension of the narrowed portion 154 is _φQ , _φQ represents the smallest minimum cross-sectional dimension among the through holes 122.

Here, in each through hole 122, a position 10 μm deep from the second surface 114 of the main body 110 is referred to as a “reference depth” and represented by D _S. As shown in Fig. 2, the reference depth D _S is located farther from the second surface 114 of the main body 110 than the boundary _Di. In addition, the minimum cross-sectional dimension of the through hole 122 at the reference depth D _S is represented by φ _P.

In the first filter 100, when the minimum cross-sectional dimensions φ _P and φ _Q defined as above are used, each through-hole 122 has a diameter of φ _Q ≦0.6 μm and φ _Q /φ _P ≦0.5.
It has the characteristic of satisfying the following.

In particular, φ _Q /φ _P ≦0.4 may be satisfied.

The first filter 100 has a narrowed portion 154 inside each through-hole 122 (or on the second surface 114) that satisfies the minimum cross-sectional dimension φ _Q ≦0.6 μm, which is difficult to form by a typical laser processing method.

Therefore, the first filter 100 can be used as a filter that captures fine particles, for example, with a particle size of more than 0.6 μm.

In addition, in the first filter 100, the substrate through-hole 132a can be formed using general laser processing technology. With laser processing technology, substrate through-holes 132a of the same shape can be formed with high precision. Therefore, the first filter 100 can be manufactured with high quality and low cost.

Furthermore, in the first filter 100, the depth position of the narrowed portion 154 can be aligned at any point from the second surface 114 to the boundary D _i (excluding the position of the boundary D _i ) in each through-hole 122. In this case, it becomes possible to capture particles at approximately the same depth position in each through-hole 122, making it easy to detect the particles.

Parts of a Particulate Filter According to an Embodiment of the Invention
Next, each part of the particulate filter according to one embodiment of the present invention will be described in more detail.

For clarity, each part of the particulate filter according to one embodiment of the present invention will be described using the first filter 100 described above as an example. Therefore, the reference symbols shown in Figures 1 and 2 will be used to represent each part.

(Main body 110)
1, the main body 110 has a substantially circular shape when viewed from above. However, the shape of the main body 110 is not particularly limited, and may be, for example, an ellipse, a triangle, a rectangle, or a polygon having pentagons or more sides.

The main body 110 is made of a transparent material. Here, "transparent" means that the average transmittance at wavelengths between 360 nm and 830 nm is 80% or more.

Therefore, when the first filter 100 is used, microparticles can be detected by common optical methods such as infrared spectroscopy, Raman spectroscopy, optical microscopy, and fluorescence microscopy.

The thickness of the main body 110 is 50 μm or more, and preferably 60 μm or more. There is no particular upper limit to the thickness of the main body 110, but the thickness of the main body 110 may be, for example, 1 mm or less.

When the minimum cross-sectional dimension of the first opening 125 of the main body 110 is φ ₁ , it is preferable that φ ₁ satisfies 5 μm≦φ ₁ ≦50 μm.

Furthermore, when the minimum cross-sectional dimension of second opening 127 of main body 110 is _φ2 , _φ1 preferably satisfies 0.2 μm≦ _φ2 ≦5 μm.

Furthermore, the minimum cross-sectional dimension φ _Q of the narrowed portion 154 is preferably 0.2 μm or more.

As mentioned above, it is difficult to form through holes with a minimum cross-sectional dimension of 0.6 μm or less using laser processing technology alone.

However, the main body 110 has a substrate 140 and a coating layer 150. Therefore, in the first filter 100, the through-hole 122 having the narrowed portion 154 with a minimum cross-sectional dimension φ _Q of 0.6 μm or less can be formed in the main body 110.

When the depth of the narrowed portion 154 from the second surface 114 is d, the narrowed portion 154 may be present in the range of 0≦d<5 μm. The narrowed portion 154 may be present on the second surface 114, but at a position different from the boundary _Di.

The through holes 122 are preferably formed at a density of 100 pcs/mm ² or more in the inspection region 120 of the main body 110. The density of the through holes 122 is more preferably in the range of 500 pcs/mm ² to 15,000 pcs/mm ² .

(Substrate 140)
There is no particular limitation on the type of the base material 140 that constitutes a part of the main body 110. The base material 140 may be made of a transparent material such as glass or resin.

The thickness of the substrate 140 is preferably 50 μm or more. The thickness of the substrate 140 may be, for example, 1 mm or less.

Note that the cross-sectional shape of the substrate through hole 132a shown in FIG. 2 is merely an example, and the substrate through hole 132a may have a different cross-section. For example, the substrate through hole 132a may have a cross-sectional shape as shown in FIG. 3.

Figure 3 shows another cross section of the substrate through hole 132a. Note that in Figure 3, only the substrate 140 portion of the main body 110 is shown, and the coating layer 150 is not shown.

As shown in FIG. 3, the substrate through hole 132a has a substrate narrowing portion 148 inside the substrate 140. The substrate through hole 132a has a shape such that the "minimum cross-sectional dimension" increases from the substrate narrowing portion 148 toward each surface of the substrate 140.

Substrate through-holes 132a having such a cross-sectional shape are likely to occur when a substrate 140 having fine through-holes is subjected to a wet etching process, as described below.

As such, it should be noted that in one embodiment of the present invention, the cross-sectional shape of the substrate through hole 132a is not particularly limited.

(Coating layer 150)
The type of coating layer 150 is not particularly limited as long as it is transparent.

The material of the coating layer 150 is not particularly limited as long as it is transparent, but materials mainly made of silica, alumina, magnesium oxide, and magnesium fluoride are preferred because they have a low refractive index and can maintain high transmittance. Materials mainly made of silica, hafnium oxide, tantalum oxide, and magnesium fluoride are also preferred because they have a small extinction coefficient in the ultraviolet range.

It is particularly preferable that the coating layer 150 be made of silica or magnesium fluoride, which has a low refractive index and a low extinction coefficient over a wide wavelength range.

The thickness of the coating layer 150 is not particularly limited, but is preferably in the range of 0.1 μm to 5 μm, for example.

The thickness of the coating layer is 10 μm or less at most. Therefore, the depth from the second surface 114 of the body 110 to the boundary D _i is equal to or smaller than the distance from the second surface 114 to the reference depth D _S.

The above describes one embodiment of the present invention using the first filter 100 as an example.

However, the above description is merely an example, and the particulate capture filter according to one embodiment of the present invention may have other configurations.

2, the coating layer through hole 132b of the first filter 100 has a minimum cross-sectional dimension that gradually increases from the narrowed portion 154 toward the second surface 114. However, differently from this, the coating layer through hole 132b may have a form in which the minimum cross-sectional dimension gradually decreases from the boundary _Di toward the second surface 114. In that case, the minimum cross-sectional dimension of the second opening 127 is _φQ .

For example, the coating layer through hole 132b may have a straight portion that extends parallel to the thickness direction of the coating layer.

That is, in a particulate filter according to one embodiment of the present invention, the substrate through-hole 132a and the coating layer through-hole 132b may have any shape as long as they have the above-mentioned characteristics.

Furthermore, in the above description, a particulate filter according to one embodiment of the present invention has been described using an example in which through-holes are formed in a transparent body. However, a particulate filter according to one embodiment of the present invention may have slits instead of through-holes.

(Method of manufacturing a particulate filter according to one embodiment of the present invention)
Next, an example of a method for manufacturing the particulate filter according to one embodiment of the present invention will be described with reference to FIGS.

Figure 4 shows a schematic flow diagram of a method for manufacturing a particulate filter according to one embodiment of the present invention (hereinafter referred to as the "first method").

As shown in FIG. 4, the first method is as follows:
(1) preparing a transparent substrate having a first surface and a second surface opposed to each other (step S110);
(2) Irradiating the first surface of the substrate with laser light to form a plurality of substrate through holes penetrating the substrate from the first surface to the second surface (step S120);
(3) providing a coating layer on the second surface of the substrate to form a plurality of through holes penetrating the substrate and the coating layer (step S130);
has.

Each step will be described below with reference to Figures 5 to 8. Note that the manufacturing method will be described using the first filter shown in Figures 1 and 2 as an example of a particulate capture filter. Therefore, when referring to each part of the particulate capture filter, the reference symbols shown in Figures 1 and 2 will be used.

(Step S110)
First, a transparent substrate 140 is prepared.

Figure 5 shows a perspective view of substrate 140. Substrate 140 has a first surface 142 and a second surface 144.

In the example shown in FIG. 5, the first surface 142 and the second surface 144 have a substantially circular shape. However, the shapes of the first surface 142 and the second surface 144 are not particularly limited. The first surface 142 and the second surface 144 may have shapes such as an ellipse, a triangle, a rectangle, or a polygon with pentagons or more sides.

The substrate 140 may be made of any material as long as it is transparent. The substrate 140 may be made of, for example, glass or resin.

The thickness of the substrate 140 is preferably 50 μm or more.

In addition, an absorbent material may be placed on the first surface 142 of the substrate 140 before the next step S120. When an absorbent material is placed, the energy of the laser light irradiated to the substrate 140 can be absorbed more efficiently. Therefore, in the next step S120, it becomes possible to perform high-quality laser processing with lower energy.

However, the installation of the absorbent material 220 is optional.

Figure 6 shows a schematic diagram of an absorbent material 220 placed on the first surface 142 of the substrate 140.

The material of the absorption layer 220 is not particularly limited as long as it has the function of absorbing at least a portion of the energy of the pulsed laser used. The absorption layer 110 may be, for example, a synthetic resin ink or a pigment containing carbon black, etc.

(Step S120)
Next, a laser beam is irradiated from the side of the first surface 142 of the substrate 140 to form the substrate through-hole 132a.

The type of laser light is not particularly limited, but a UV laser is preferred.

The laser light may be, for example, a short pulse laser.

Figure 7 shows a schematic cross section of a substrate 140 in which a substrate through hole 132a is formed. Note that the absorbent material 220 is omitted in Figure 7.

By irradiating the laser light, a plurality of substrate through-holes 132a are formed in the substrate 140, extending from the first surface 142 to the second surface 144.

As shown in FIG. 7, the substrate through-hole 132a formed by laser light irradiation tends to have a cross-sectional shape that tapers from the first surface 142 to the second surface 144.

The taper angle θ ₁ is, for example, in the range of 65° to 89°.

Each substrate through hole 132a has a first opening 226a on the first surface 142 of the substrate 140 and a second opening 226b on the second surface 144.

The minimum cross-sectional dimension of the first opening 226a is, for example, in the range of 4 μm to 30 μm, and preferably in the range of 4 μm to 15 μm.

The minimum cross-sectional dimension of the second opening 226b is, for example, in the range of 2 μm to 10 μm, and preferably in the range of 2 μm to 5 μm.

The number of the base material through holes 132a to be formed is not particularly limited. When used in a particulate filter, the density of the base material through holes 132a is, for example, 100 pieces/ ^mm2 or more, and preferably in the range of 500 pieces/ ^mm2 to 15,000 pieces/ ^mm2 .

After the substrate through-hole 132a is formed, the substrate 140 may be subjected to a wet etching process.

By performing wet etching, the absorbent material 220 and debris generated during laser processing can be removed.

For example, if the substrate 140 is glass, the wet etching process may be performed in a hydrofluoric acid solution.

When a wet etching process is performed, the shape of the substrate through hole 132a may often change. For example, the first opening 226a of the substrate through hole 132a may vary in the range of 4.1 μm to 30.1 μm. The minimum cross-sectional dimension of the second opening 226b may vary in the range of 2.1 μm to 10.1 μm.

The cross-sectional shape of the substrate through hole 132a can also be broadly divided into two types.

In the first mode, the cross-sectional dimension of the substrate through-hole 132a is expanded while the taper angle θ ₁ is maintained.

In the second embodiment, a cross-sectional shape as shown in FIG. 3 is obtained. That is, the substrate through-hole 132a is shaped to have a substrate narrowing portion 148 between the first surface 142 and the second surface 144.

The cross-sectional shape shown in FIG. 3 is likely to occur when the thickness of the substrate 140 is large and/or when the dimensions of the first opening 226a and the second opening 226b are small.

That is, if the dimensions of the first opening 226a and the second opening 226b are small, it becomes difficult for the etching solution to sufficiently penetrate into the interior of the substrate through hole 132a. In that case, the portions close to both surfaces 142, 144 of the substrate through hole 132a are selectively etched, and a substrate through hole 132a having a substrate narrowing portion 148 as shown in FIG. 3 is formed.

The same applies when the thickness of the substrate 140 is large.

In this way, the shape of the substrate through hole 132a may change before and after the wet etching process. However, in this application, the substrate through hole 132a after the wet etching process will be referred to as "substrate through hole 132a" as it is.

In addition, when the first surface 142 and the second surface 144 of the substrate 140 are etched by wet etching, a different surface (a new surface) is exposed.

However, the amount of etching of the first surface 142 and the second surface 144 of the substrate 140 is small. Therefore, in this specification, even after the wet etching process, the exposed surfaces of the substrate 140 will be referred to as the "first surface 142" and the "second surface 144".

(Step S130)
A coating layer is then applied to the second surface 144 of the substrate 140 .

This process is performed to adjust the dimensions and shape of the tip of the substrate through hole 132a.

The method for applying the coating layer is not particularly limited.

The coating layer may be applied to the second surface 144 of the substrate 140, for example, by sputtering or vapor deposition.

The sputtering or vapor deposition method can significantly reduce the possibility of the substrate through-holes 132a becoming blocked, and can properly form a coating layer having coating layer through-holes 132b that are connected to the substrate through-holes 132a.

As described above, the type of the coating layer is not particularly limited. The coating layer may be made of, for example, silica, alumina, MgO, MgF, or _{Ta2O5 .}

The thickness of the coating layer is at most 10 μm, for example, in the range of 0.1 μm to 5 μm.

Fig. 8 is a schematic diagram showing a state after the coating layer 150 is provided on the second surface 144 of the substrate 140. In Fig. 8, a dashed line L1 represents a boundary, i.e., D _i , between the substrate 140 and the coating layer 150. However, the boundary D _i is often difficult to recognize using an optical microscope and an electron microscope.

As shown in FIG. 8, the coating layer 150 is formed to have a coating layer through hole 132b corresponding to each substrate through hole 132a. In other words, the coating layer through hole 132b of the coating layer 150 is formed to extend the substrate through hole 132a formed in the substrate 140 to the surface 152 of the coating layer 150.

This allows the formation of a through hole 122 that penetrates from the first surface 142 of the substrate 140 to the surface 152 of the coating layer 150.

The through hole 122 has a third opening 240c on the side of the surface 152 of the coating layer 150.

The third opening 240c has a minimum cross-sectional dimension _φ2 in the range of 0.2 μm to 5 μm.

In this manner, the first method can form a plurality of through holes 122 extending from the first surface 142 of the substrate 140 to the surface 152 of the coating layer 150.

When the minimum cross-sectional dimensions φ _P and φ _Q defined as above are used, these through holes 122 have the following dimensions:
φ _Q ≦0.6 μm, and φ _Q /φ _P ≦0.5
Meet the following.

Here, φ _P is the minimum cross-sectional dimension of the through hole 122 at the position of the reference depth Ds (not shown in FIG. 8).

In addition, in the through hole 122, the position where the minimum cross-sectional dimension φ _Q is obtained may be the third opening 240c. In this case, φ ₂ =φ _Q.

In the first method, it is possible to form a narrowed portion 154 satisfying a minimum cross-sectional dimension φ _Q ≦0.6 μm inside each through hole 122 (or on the surface 152 of the coating layer 150), which is difficult to form by a general laser processing method.

Therefore, the filter manufactured by the first method can be used as a filter that captures fine particles, for example, with a particle size of more than 0.6 μm.

In addition, in the first method, the substrate through-hole 132a can be formed using general laser processing technology. Therefore, the first method can manufacture a high-quality, low-cost filter for capturing fine particles.

Furthermore, in the first method, the depth position of the narrowed portion 154 can be aligned at any point from the surface 152 of the coating layer 150 to the boundary D _i (excluding the position of the boundary D _i ) in each through-hole 122. In this case, it becomes possible to capture particles at approximately the same depth position in each through-hole 122, making it easy to detect the particles.

Next, examples of the present invention will be described. In the following description, Examples 1 to 3 are examples, and Example 11 is a comparative example.

(Example 1)
The evaluation samples were prepared by the following method.

First, a substrate having a first surface and a second surface facing each other was prepared. The substrate was a glass substrate having a thickness of 200 μm.

Next, a laser beam was irradiated onto the first surface side of the substrate to form multiple through holes (substrate through holes). A pulsed laser was used for the laser beam.

Next, a coating layer was formed on the second surface of the substrate by sputtering. The coating layer was a silica layer with a thickness of 3.1 μm. After the coating, through holes were obtained that penetrated from the substrate to the coating layer.

This resulted in the preparation of an evaluation sample (hereafter referred to as "Sample 1").

The minimum cross-sectional dimension φ ₁ of the first opening on the substrate side and the minimum cross-sectional dimension φ ₂ of the second opening on the coating side were measured for the through hole of Sample 1. The results were φ ₁ =8.0 μm and φ ₂ =3.4 μm.

(Example 2)
An evaluation sample was prepared in the same manner as in Example 1. However, in this Example 2, the thickness of the coating layer was set to 4.3 μm.

The evaluation sample prepared is referred to as "Sample 2."

The minimum cross-sectional dimension φ ₁ of the first opening on the substrate side and the minimum cross-sectional dimension φ ₂ of the second opening on the coating side were measured for the through hole of Sample 2. The results were φ ₁ =8.0 μm and φ ₂ =2.7 μm.

(Example 3)
An evaluation sample was prepared in the same manner as in Example 1. However, in this Example 3, the thickness of the coating layer was set to 4.9 μm.

The evaluation sample prepared is referred to as "Sample 3."

The minimum cross-sectional dimension φ ₁ of the first opening on the substrate side and the minimum cross-sectional dimension φ ₂ of the second opening on the coating side were measured for the through hole of Sample 3. The results were φ ₁ =8.0 μm and φ ₂ =2.8 μm.

(Example 11)
A through hole was formed in a glass substrate in the same manner as in Example 1, and the resulting substrate was used as an evaluation sample. That is, in Example 11, no silica layer coating was performed.

The resulting evaluation sample is referred to as "Sample 11."

The minimum cross-sectional dimension φ ₁ of the first opening on the substrate side and the minimum cross-sectional dimension φ ₂ of the second opening on the coating side were measured for the through-hole of Sample 11. The results were φ ₁ =8.0 μm and φ ₂ =2.0 μm.

The preparation conditions for each sample are summarized in Table 1 below.

（断面評価）
作製された各サンプルを、いくつかの貫通孔の長手中心軸を通る断面で切断し、評価用試料を作製した。また、評価用試料を用いて、以下の寸法を測定した：
基準深さＤ_Ｓ（コーティング層の表面から１０μｍの位置）における貫通孔の最小断面寸法φ_Ｐ、および
貫通孔の狭窄部における最小断面寸法φ_Ｑ。

(Cross-section evaluation)
Each of the prepared samples was cut at a cross section passing through the longitudinal central axis of some of the through holes to prepare evaluation samples. The following dimensions were measured using the evaluation samples:
The minimum cross-sectional dimension φ _P of the through hole at a reference depth D _S (a position 10 μm from the surface of the coating layer), and the minimum cross-sectional dimension φ _Q of the through hole at a constriction.

Here, the narrowed portion is defined as the depth position where the minimum cross-sectional dimension of the through hole is smallest.

Except for sample 11, the narrowed portion was located inside the coating layer. On the other hand, in sample 11, the narrowed portion was located on the second surface of the substrate.

Figures 9 to 11 show examples of cross sections of through holes on the coating layer side in Samples 1 to 3, respectively.

Note that in Figures 9 to 11, some areas appear whitish due to light reflection, and that such areas do not necessarily correspond to the outline of the through-hole. In particular, there is a sharp, whitish area near the narrowed portion in the coating layer, but this is not the tip of the through-hole. In all of the figures, the through-hole has an opening on the surface of the coating layer.

Table 2 below summarizes the dimensions obtained for each evaluation sample.

測定の結果から、サンプル１～サンプル３では、コーティング層内に、最小断面寸法φ_Ｑが０．６μｍ以下の狭窄部が形成されていることがわかった。

The measurement results showed that in Samples 1 to 3, a narrowed portion having a minimum cross-sectional dimension φ _Q of 0.6 μm or less was formed in the coating layer.

Moreover, it was found that in Samples 1 to 3, the ratio φ _Q /φ _P was 0.5 or less.

100 First filter 110 Body 112 First surface of body 114 Second surface of body 120 Inspection area 122 Through hole 125 First opening 127 Second opening 132a Substrate through hole 132b Coating layer through hole 140 Substrate 142 First surface of substrate 144 Second surface of substrate 148 Substrate narrowing portion 150 Coating layer 152 Surface of coating layer 154 Narrowing portion 220 Absorbing material 226a First opening 226b Second opening 240c Third opening

Claims (16)

A particulate filter comprising:
a transparent body having a first surface and a second surface and a thickness of 50 μm or more;
a plurality of through holes extending from the first surface to the second surface of the body;
having
A position at a depth of 10 μm from the second surface is defined as a reference depth D _S ;
In each through hole, when the minimum cross-sectional dimension at the reference depth D _S is φ _P and the minimum cross-sectional dimension between the reference depth D _S and the second surface is φ _Q ,
A particulate filter, wherein φ _Q ≦0.6 μm and φ _Q /φ _P ≦0.5. 2. The particulate filter according to claim 1, wherein said φ _Q is 0.2 μm or more. 3. The particulate filter according to claim 1, wherein when the minimum cross-sectional dimension of each through-hole in said first surface is _φ1 , 5 μm≦ _φ1 ≦50 μm. In each through hole, when the minimum cross-sectional dimension at the second surface is _φ2 ,
4. The particulate filter according to claim 1, wherein 0.2 μm≦φ ₂ ≦5 μm. 5. The particulate filter according to claim 1, wherein the through holes have a minimum cross-sectional dimension that decreases monotonically from the first surface to the reference depth _Ds . 6. The particulate filter according to claim 1, wherein the position at which the minimum cross-sectional dimension φ _Q is obtained is in a range of a depth from the second surface of 0 to less than 5 μm. The body has a substrate and a coating layer;
7. The particulate filter according to claim 1 , wherein the second surface is a surface of the coating layer. 8. The particulate filter according to claim 7 , wherein the substrate is made of glass or resin. 9. The particulate filter according to claim 7 , wherein the coating layer has a thickness in the range of 1 μm to 5 μm. A method for manufacturing a particulate filter, comprising the steps of:
(I) providing a transparent substrate having a first surface and a second surface opposed to each other;
(II) irradiating the first surface of the substrate with laser light to form a plurality of substrate through-holes penetrating the substrate from the first surface to the second surface;
(III) providing a coating layer on the second surface of the substrate to form a plurality of through holes through the substrate and the coating layer;
having
A position at a depth of 10 μm from the surface of the coating layer is defined as a reference depth D _S ,
In each through hole, when the minimum cross-sectional dimension at the reference depth D _S is φ _P , the minimum cross-sectional dimension at the surface of the coating layer is φ ₂ , and the minimum cross-sectional dimension between the reference depth D _S and the surface of the coating layer is φ _Q ,
A manufacturing method wherein φ _Q ≦0.6 μm and φ _Q /φ _P ≦0.5 . Before the step (II),
The method of claim 10 , further comprising providing an absorbent layer on the first surface of the substrate. After the step (II),
The method according to claim 10 or 11 , further comprising a step of subjecting the substrate to a wet etching treatment. The method according to claim 10 , wherein the substrate through-holes are arranged at a density of 100 pcs/mm ² or more. The method according to claim 10 , wherein the substrate has a thickness of 50 μm or more. The method according to claim 10 , wherein the substrate is made of glass or resin. The method according to any one of claims 10 to 15 , wherein the coating layer has a thickness in the range of 1 μm to 5 μm.

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