KR101856623B1 - Sputtering method for a reflective particle - Google Patents

Abstract

One embodiment of the present invention relates to a method of manufacturing a semiconductor device comprising the steps of disposing a plurality of light transmitting particles on a conveyance belt moved by a roll and a step of applying impact to a target disposed at a position facing the conveyance belt under an inert gas atmosphere, A step of forming a reflective coating on a part of each outer surface, and a step of recovering a plurality of transparent particles on which a reflective coating is formed.

Description

[0001] Sputtering method for a reflective particle [

Embodiments of the present invention are directed to a method of sputtering reflective particles, reflective particles, and reflectors.

Reflex reflection means to reflect light along the same direction as incident light. For the safety of drivers and firefighters in dark surroundings, retroreflective is used in optical films attached to selected parts of uniforms such as road signs or fire brigades.

The present invention provides a method of sputtering reflective particles having a retroreflective function, reflective particles produced thereby, and reflectors comprising reflective particles.

The above-described problems are illustrative, and thus the scope of the present invention is not limited thereto.

One embodiment of the present invention relates to a process for producing a film, comprising the steps of: placing a plurality of transparent particles on a conveyance belt moved by a roll; Forming a reflective coating on a part of the outer surface of each of the plurality of light-transmitting particles by striking a target disposed at a position opposed to the conveyance belt in an inert gas atmosphere; And a step of recovering a plurality of translucent particles having the reflective coating formed thereon.

In the present embodiment, it may further include a step of rotating the conveyance belt.

In the present embodiment, the step of disposing the plurality of translucent particles may further include a step of unfolding the plurality of translucent particles so that each of the plurality of translucent particles contacts the conveyance belt.

In this embodiment, in the step of forming the reflective coating, a reflective coating of a metallic material may be formed only on a part of the outer surface of each of the plurality of light-transmitting particles using a target containing a metallic material.

In this embodiment, at least one of gravity and a separator may be used as the recovering step.

In the present embodiment, the step of forming the reflective coating may include the steps of forming a reflective coating on each of the plurality of light-transmitting particles using a first target containing a reflective material, The method may further include forming a protective coating to cover the reflective coating using a second target containing a material different from the first target.

In this embodiment, in the step of forming the protective coating, the protective coating may be formed only on a part of the surface of the light transmitting particle so as to cover the reflective coating.

In this embodiment, the step of forming the reflective coating and the step of forming the protective coating may be successively performed in the same chamber and under substantially the same pressure.

In the present embodiment, the conveyance belt may include a viscous resin.

In this embodiment, the step of disposing the plurality of translucent particles, the step of forming the reflective coating, and the recovering step may be performed in the same chamber.

Another embodiment of the present invention is a light-emitting device comprising: a light-transmitting core; And a shell covering a part of the surface of the light-transmitting core, the shell including a reflective material.

In this embodiment, the light transmitting core is a spherical core, and the shell may cover only a part of the surface of the light transmitting core.

In the present embodiment, the light transmitting core may include at least one of a glass material and a resin material.

In the present embodiment, the shell may be made of a metal such as copper, nickel, chromium, silver, gold, aluminum, palladium, titanium, Tin (Sn), molybdenum (Mo), and alloys thereof.

In this embodiment, it may further include a protective film which is located only on a part of the transparent core so as to cover at least the shell.

Yet another embodiment of the present invention is a lithographic projection apparatus comprising: a matrix material; And reflective particles.

In the present embodiment, the reflector may be a sheet type.

In the present embodiment, the reflector may be in a liquid state.

Other aspects, features, and advantages will become apparent from the following drawings, claims, and detailed description of the invention.

According to the embodiments of the present invention, it is possible to provide a large amount of the reflective particles excellent in durability and reflectivity. Of course, the scope of the present invention is not limited by these effects.

1 is a front view schematically illustrating a reflective particle according to an embodiment of the present invention.
2 is a cross-sectional view of a reflective particle according to an embodiment of the present invention.
Figures 3 and 4 are cross-sectional views of reflective particles in accordance with further embodiments of the present invention.
5 is a cross-sectional view schematically showing a sputtering apparatus for a reflective particle (hereinafter referred to as a sputtering apparatus) according to an embodiment of the present invention.
6 is an enlarged view showing an excerpt of the portion VI in Fig.
7 is a cross-sectional view schematically showing a sputtering apparatus for a reflective particle (hereinafter referred to as a sputtering apparatus) according to still another embodiment of the present invention.
8 is a flowchart schematically showing a process for producing the reflective particles according to an embodiment of the present invention.
9 is a cross-sectional view schematically illustrating a reflector according to another embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. The effects and features of the present invention and methods of achieving them will be apparent with reference to the embodiments described in detail below with reference to the drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals refer to like or corresponding components throughout the drawings, and a duplicate description thereof will be omitted .

In the following embodiments, the terms first, second, and the like are used for the purpose of distinguishing one element from another element, not the limitative meaning.

In the following examples, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

In the following embodiments, terms such as inclusive or possessive are intended to mean that a feature, or element, described in the specification is present, and does not preclude the possibility that one or more other features or elements may be added.

In the drawings, components may be exaggerated or reduced in size for convenience of explanation. For example, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, and thus the present invention is not necessarily limited to those shown in the drawings.

If certain embodiments are otherwise feasible, the particular process sequence may be performed differently from the sequence described. For example, two processes that are described in succession may be performed substantially concurrently, and may be performed in the reverse order of the order described.

Reflective particles

FIG. 1 is a front view schematically showing a reflective particle according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a reflective particle according to an embodiment of the present invention, FIGS. 3 and 4 show another embodiment Sectional views of the reflective particles according to the present invention.

1 and 2, the reflective particle 10 includes a transparent core 11 and a shell 13 covering a part of the surface of the transparent core 11 and containing a reflective material.

The light transmitting core 11 includes a light transmitting material. The translucent material may include at least one of a transparent glass material and a transparent resin. The transparent resin may include an acrylic resin such as polymethyl methacrylate (PMMA) and polymethyl acrylate. Alternatively, the transparent resin may include a styrene acrylonitrile copolymers (SAN) resin, or may include a general purpose polystyrene (GPPS) resin. Alternatively, the transparent resin may include resins such as polycarbonate (PC), polyimide (PI), and polyethylene terephthalate (PET), but the present invention is not limited thereto.

The light transmitting core 11 may be a spherical core having a smooth surface. The diameter of the transparent core 11 may be selected in the range of 1 占 퐉 to 200 占 퐉. The transparent core 11 according to the embodiments of the present invention is a spherical core whose inside is filled with a light-transmitting material, and is clearly distinguished from a core in which an empty cavity is formed.

The shell 13 comprises a reflective material. The reflective material may comprise a metallic material. The metallic material may be selected from the group consisting of copper (Cu), nickel (Ni), chromium (Cr), silver (Ag), gold (Au), aluminum (Al), palladium (Pd), titanium (Ti), tin Mo), and an alloy thereof. The shell 13 may be formed as a single layer or multiple layers formed of the above-described reflective material. In one embodiment, the shell 13 may comprise aluminum to reflect white light. In another embodiment of the present invention, the shell 13 may comprise copper to reflect yellow light, but embodiments of the invention are not so limited.

The shell 13 may further include a protective shell 15 as shown in Figs. For example, when the shell 13 is formed of a metal that is easily oxidizable, such as copper, the protective shell 15 may be positioned on the shell 13 to cover the shell 13 with an alloy of nickel and chromium . The protective shell 15 may be placed on the shell 13 so as to cover the entire shell 13 but only a part of the transparent core 11. [ For example, the area of the protective shell 15 is substantially equal to the area of the shell 13 as shown in Fig. 3, or larger than the area of the shell 13 as shown in Fig. 4, And it is possible to make contact with the transparent core 11 partially.

The shell 13 is located in the transparent core 11 so as to cover only a part of the surface of the transparent core 11 and the reflective particles 10 having such a structure can have the feature of retro-reflection. As shown in FIG. 2, the light incident on the transparent core 11 may be reflected on the inner surface of the shell 13 and then travel in the same direction as the incident direction.

The shell 13 may be selected to cover the range of about 35% to 75% of the surface of the transparent core 11. [ When the area of the shell 13 falls within the above-mentioned range, the reflective particles 10 having excellent retroreflective efficiency can be obtained.

The shell 13 covers only a part of the transparent core 11 and is a film continuously formed in a region covering the transparent core 11. [ The shell 13 according to the embodiments of the present invention is clearly distinguished from the shells separated from each other on the surface of the light-transmitting core, for example, a discontinuous shell, i.e., an island type, which covers a part of the light-

The thickness of the shell 13 can be made substantially constant. For example, the thickness of the shell 13 may be selected from the range of about 0.001 탆 to 10 탆.

The shortest distance d1 from the arbitrary point on the outer surface of the shell 13 to the center of the translucent core 11 and the shortest distance d1 from the arbitrary point on the outer surface of the shell 13 to the center of the translucent core 11 The distance d2 may be substantially the same. The minimum distance d1 from the arbitrary point on the outer surface of the shell 13 to the center of the transparent core 11 and the center of the transparent core 11 from any other point on the outer surface of the shell 13 For example, 0 占 퐉 to 0.1 占 퐉, as another example, in the range of 0 占 퐉 to 0.01 占 퐉, and in another embodiment, in the range of 0 占 퐉 to 0.001 占 퐉 Lt; / RTI > In other words, the deviation between the thicknesses of the shell 13 measured at arbitrary points of the shell 13 is about 0 탆 to 1 탆, for example, 0 탆 to 0.1 탆, as another example, Lt; RTI ID = 0.0 > pm, < / RTI >

The reflective particles 10 according to the embodiments of the present invention have a structure in which the transparent core 11 and the shell 13 are in direct contact with each other and a part of the surface of the transparent core 11 is tightly sandwiched by the shell 13 Can be covered. That is, the shell 13 may have a dense membrane structure. The reflective particles 10 according to the embodiments of the present invention can improve the reflection efficiency of light as compared with the reflective particles having the structure of the shell 13 which is relatively deformed. The shell 13 of the reflective particles 10 according to embodiments of the present invention may be formed to have a dense structure by a sputtering method.

Hereinafter, the sputtering apparatus for the reflective particles 10 and the sputtering method of the reflective particles 10 will be described.

Of the reflective particles Sputtering  Device

FIG. 5 is a cross-sectional view schematically showing an apparatus for sputtering reflective particles (hereinafter referred to as a sputtering apparatus) according to an embodiment of the present invention, and FIG. 6 is an enlarged view excerpted from FIG.

5, a sputtering apparatus 100 according to an embodiment of the present invention includes a chamber 110, a supply unit 120 disposed in the chamber 110 and storing transparent particles 11 to be sputtered, transparent particles 11, A target 140, and a collecting unit 170 for collecting the conductive particles 10. The collecting unit 170 collects the conductive particles 10, Here, the translucent particles 11 correspond to the translucent core 11 described with reference to Figs. 1 to 4, and are referred to as translucent particles 11 hereinafter.

The chamber 110 includes a gas outlet (not shown) for forming a vacuum state (a degree of vacuum of about 0.1 mTorr to 10 mTorr), and is used for introducing a gas used for the sputtering process, for example, an inert gas such as argon And an introduction port (not shown).

The supply unit 120 has a space for storing a plurality of transparent particles 11. The supply unit 120 can discharge a plurality of the transparent particles 11 stored in the supply unit 120 onto the transfer belt 135 through the discharge port provided at one side.

The transport belt 135 transports the translucent particles 11 along a predetermined direction, for example, toward the recovery section 170 by the rotation of the rolls 131 and 132. In one embodiment, the conveyor belt 135 may comprise a resin. In one embodiment, the conveyance belt 135 may include a layer that is tacky on the surface to prevent movement of the translucent particles 11 disposed on the conveyance belt 135 during the sputtering process, It may be formed of a material having a predetermined adhesive property. PDMS (polydimethylsiloxane) can be used as a sticky material, but the present invention is not limited thereto.

The target 140 is disposed to face the conveyance belt 135. The target 140 includes a reflective material for forming a reflective coating on a part of the surface of the transparent particles 11. Here, the reflective coating corresponds to the shell 13 described above with reference to Figs. 1 to 4, and is referred to as a reflective coating 13 hereinafter.

The target 140 may be formed of a material selected from the group consisting of Cu, Ni, Cr, Ag, Au, Al, Pd, Ti, Sn), molybdenum (Mo), and alloys thereof. In one embodiment, when forming the reflective particles 10 having a single reflective coating 13 as described above with reference to FIG. 2, only one target 140 may be provided. In another embodiment, when a protective shell 15 (hereinafter referred to as a protective film) is formed on the reflective coating 13 as described with reference to FIGS. 3 and 4, the target 140 may be disposed apart from one another And may include a first target 141 and a second target 142. The first target 141 may include a reflective material for forming the reflective coating 13 and the second target 142 may include a material for forming a protective coating. In another embodiment, when the reflective coating 13 is multi-layered, the target 140 may include first and second targets 141 and 142 that are spaced from one another and that contain the same material or that include different materials .

A spreader 150 is disposed between the feeder 120 and the first target 141. The translucent particles 11 are spherical particles having a diameter in the range of about 1 탆 to 200 탆, and the plurality of transparent particles 11 discharged from the supply part 120 are in a powder state. It is necessary for the transparent particles 11 to be disposed on the conveyor belt 135 so as to form a single layer in order for the transparent particles 11 to be exposed to the target 140 during the sputtering process. The dispersing device 150 can spread the light transmitting particles 11 evenly on the conveying belt 135. [ For example, the dispersing device 150 may be a stamp type having a predetermined surface, in which the transparent particles 11 between the dispersing device 150 and the conveying belt 135 form a single layer as shown in FIG. 6, (Rubbing operation) along one direction on the support member 135, but the present invention is not limited thereto.

The shielding plates 161, 162 and 163 are disposed between the supply unit 120 and the first target 141, between the first target 141 and the second target 142, and between the second target 142 and the recovery unit 170).

The collecting unit 170 stores the reflective particles 10 having the reflective coating 13 formed thereon through the region where the target 140 is disposed. The reflective particles 10 may be placed at one side of the conveyor belt 135 and placed under the gravity to enter the collection unit 170. [ Alternatively, the reflective particles 10 may be physically separated from the conveyor belt 135 by the separator 180 and stored in the collection unit 170.

7 is a cross-sectional view schematically showing a sputtering apparatus for a reflective particle (hereinafter referred to as a sputtering apparatus) according to still another embodiment of the present invention.

Referring to FIG. 7, a sputtering apparatus 100 'includes a chamber 110, a supply unit 120, a conveyance belt 135, a target 140, a dispersing unit 150, shutters 161, 162, and 163, And a separator 180. The specific structure of the sputtering apparatus 100 is substantially the same as that of the sputtering apparatus 100 described with reference to FIG. 5, and therefore, differences will be mainly described below.

The conveying belt 135 can be moved by one roll 133. [ For example, the conveyor belt 135 may rotate in place about the axis of the roll 133. [ The conveyance belt 135 of the sputtering apparatus 100 'according to the present embodiment may include a viscous material in order to prevent the light-transmitting particles 11 on the conveyance belt 135 from being separated or moved during the sputtering process.

Of the reflective particles Sputtering  fair

FIG. 8 is a flowchart schematically illustrating a process for producing the reflective particles according to an embodiment of the present invention.

Referring to FIGS. 5 and 8, the transparent particles 11 are disposed on the conveyance belt 135 (S10). The transparent particles 11 may be made of a light transmitting material such as a glass material and a resin. The transparent resin may include an acrylic resin such as polymethyl methacrylate (PMMA) and polymethyl acrylate. Alternatively, the transparent resin may include a styrene acrylonitrile copolymers (SAN) resin, or may include a general purpose polystyrene (GPPS) resin. Alternatively, the transparent resin may include resins such as polycarbonate (PC), polyimide (PI), and polyethylene terephthalate (PET), but the present invention is not limited thereto.

The inside of the chamber 110 is evacuated to a predetermined pressure and then the conductive film 13 is formed on the surface of the light transmitting particles 11 on the conveyance belt 135 while moving the conveyance belt 135 S20).

For example, in a non-limiting embodiment of the present invention, after evacuating the interior of the chamber 110 to a vacuum degree of about 0.1 mTorr to 10 mTorr, an inert gas such as argon gas is supplied into the chamber 110, And power is applied to the cathode electrode of the target 140 to generate plasma. The inert gas may be supplied at a flow rate of 10 sccm to 500 sccm, but the present invention is not limited thereto. As the power source applied to the cathode electrode, RF or DC power source can be used. The ions or neutral particles of the generated plasma strike the surface of the target 140 and the atoms separated from the target 140 are attached to each of the transparent particles 11 to form the reflective coating 13.

In an embodiment of the present invention, when forming the reflective coating 13 of a single layer as shown in FIG. 2, only the first target 141 may be provided in the chamber 110. The first target 141 may be at least one selected from the group consisting of Cu, Ni, Cr, Ag, Au, Al, Pd, Ti, ), Molybdenum (Mo), and alloys thereof. In another embodiment, when the reflective coating 13 is multi-layered, a first target 141 and a second target 142 may be formed in the chamber 110. The second target 142 may include the same material as the first target 141, or may include another material.

In another embodiment of the present invention, when the protective coating 15 is formed on the reflective coating 13 as shown in FIGS. 3 and 4, the first target 141 forms the reflective coating 13 And the second target 143 may comprise a material for forming the protective coating 15. The second target 143 may comprise a material for forming the protective coating 15. In a non-limiting embodiment of the present invention, the first target 141 may comprise copper and the second target may comprise an alloy of nickel and chromium. The sputtering process (the step of forming the reflective coating 13) using the first target 141 and the sputtering process (the step of forming the protective coating 15) using the second target 14 are performed in the same chamber 110, Can be carried out continuously under substantially the same pressure.

The translucent particles 11 are spherical particles having a diameter in the range of 1 탆 to 200 탆 as described above, and the translucent particles 11 stored in the supply part 120 are in a powder state. The transparent particles 11 initially discharged from the supply part 120 onto the conveyance belt 135 may be piled up with a predetermined volume. For example, some of the light-transmitting particles 11 are placed in direct contact with the conveying belt 135, while the remaining remaining light-transmissive particles 11 are formed on some of the light-transmitting particles 11 so as to overlap with the above- The light transmitting particles 11 are arranged on the conveying belt 135 as a plurality of layers. In this case, the reflective coating 13 may be formed on the portion of the surface of the transparent matrix 11 positioned on the uppermost layer facing the target 140, but the transparent matrix particle 11 positioned on the lowermost layer may be exposed to the target 140 There is a problem that the reflective coating 13 is not formed.

In order to prevent this, the embodiments of the present invention may be applied to the step of forming the reflective coating 13 (step S20) or the step of forming the reflective coating 13 (step S20) And dispersing the transparent particles 11 such that the particles 11 are arranged in a single layer.

In one embodiment, the dispersing process may comprise a rubbing process. The dispersing device 150 is a stamp type having a predetermined surface and can move along one direction with the light-transmitting particles 11 interposed therebetween (rubbing) with the conveying belt 135. The translucent particles 11 disposed under the dispersing device 150 by the rubbing process of the dispersing device 150 can be dispersed to form a single layer as shown in FIG. 6 while being in direct contact with the conveying belt 135.

In yet another embodiment, the dispersing process may comprise a step of applying vibration. The dispersing device 150 is a kind of vibrating device and can apply a predetermined vibration to the light transmitting particles 11 on the conveying belt 135. By the step of applying a vacuum, the transparent particles 11 can be dispersed to form a single layer on the conveying belt 135.

In the present embodiment, the case of using rubbing or vibration as the process of dispersing the transparent particles 11 has been described, but the present invention is not limited thereto. Various methods such as using a brush may be used.

Transparent particles 11 arranged to form a single layer on the conveying belt 135 are exposed to the target 140. At this time, the reflective coating 13 is formed on a part of the surface of the transparent matrix 11, for example, on the surface of the transparent matrix 11 exposed toward the target 140. On the other hand, the reflective coating 13 is not formed on the lower portion of the surface of the transparent conductive particle 11 that directly contacts another portion of the surface of the transparent conductive particle 11, for example,

In the case where the positions of the respective transparent particles 11 change as the upper and lower portions of the light transmitting particles 11 on the conveying belt 135 are changed during the process S20 in which the reflective coating 13 is formed, 13 may be formed so as to cover the entire surface of the transparent particles 11. In order to prevent the formation of such defective reflective particles 10, according to some embodiments, the conveyance belt 135 may comprise a viscous material.

For example, the conveyance belt 135 may include a layer having adhesiveness to the surface, or the conveyance belt 135 itself may be formed of a material having a predetermined adhesive property. PDMS (polydimethylsiloxane) may be used as a sticky material, but the present invention is not limited thereto.

Next, a step (S30) of recovering the reflective particles (10) having the reflective coating (13) formed on only a part of the surface of the transparent particles (11) is performed. The reflective particles 10 can be charged by the gravity from the one side of the conveying belt 135 to the collection part 170 arranged below. Alternatively, the reflective particles 10 may be physically separated from the conveyor belt 135 by the separator 180 and stored in the collection unit 170.

The reflective particles 10 according to the embodiments of the present invention can form the reflective coating 13 only on a part of the surface of the transparent particles 11 by using a sputtering process. The reflective particles 10 according to the present embodiments are clearly distinguished from the reflective particles having a reflective coating formed by a plating method, a coating method or the like. It is difficult to form the reflective coating 13 only on a part of the surface of the transparent particles 11 or to form the reflective coating 13 having a uniform thickness because the reflective coating formed by the plating method, . Further, the reflective particles formed by the plating method, the coating method, or the like have a problem that the structure of the reflective coating is insufficient and cracks are generated. It is difficult to expect a reflection performance as described with reference to Fig. 2 when a crack occurs.

reflector

9 is a cross-sectional view schematically illustrating a reflector according to another embodiment of the present invention.

Referring to FIG. 9, the reflector 200 may include a matrix material 210 and reflective particles 10 in sheet form. In a non-limiting embodiment of the present invention, the matrix material 210 may comprise an adhesive material. Alternatively, the matrix material 210 may further include at least one of a cross-linking agent and a dispersing agent in the adhesive material.

The reflective particles 10 may be disposed in a mixed state with the matrix material 210 and may have a function of retroreflective reflection to emit incident light in the same direction as described above with reference to FIG. The reflector 200 according to the embodiment of the present invention can be used for a road sign, a safety bar, and the like because it can reflect light of a specific wavelength band (for example, yellow light) upon retroreflection.

In FIG. 9, the reflector 200 is in the form of a sheet, but the present invention is not limited thereto. The reflector may be of the liquid type including reflective particles that are blended into the matrix material and matrix material described above. The liquid reflector may be provided by spraying or spraying. For example, the reflector may be used when printing lanes or the like on the road.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the exemplary embodiments, and that various changes and modifications may be made therein without departing from the scope of the present invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

10: reflective particles
11: Transparent core (translucent particle)
13: Shell (reflective coating)
15: Protective shell (protective coating)
100: Sputtering apparatus.
110: chamber
120:
135: conveying belt
140: target
150: Dispersing machine
161, 162, 163:
170:
180: separator
200: reflector

Claims (18)

A method of sputtering reflective particles having a recursive reflection function,
Disposing a plurality of light transmitting particles on a conveying belt which is moved by a roll and contains a tacky resin on a surface; Forming a reflective coating on a part of the outer surface of each of the plurality of light-transmitting particles by striking a target disposed at a position opposed to the conveyance belt in an inert gas atmosphere; And a step of recovering a plurality of translucent particles having the reflective coating formed thereon,
Wherein the step of disposing the plurality of translucent particles comprises the step of disposing the plurality of translucent particles so that each of the plurality of translucent particles is in contact with a conveyance belt comprising a tacky resin on the surface and arranged in a single layer on the conveyance belt, Further comprising an expanding process,
Wherein the step of forming the reflective coating is a step of forming a reflective coating of a metallic material on only a part of the outer surface of each of the plurality of light transmitting particles using a target containing a metallic material . delete delete delete delete The method according to claim 1,
Further comprising the step of forming a protective coating on the reflective coating using an additional target comprising a different material from the target. The method according to claim 6,
The step of forming the protective coating may comprise:
Wherein the protective coating is formed only on a part of the surface of the light transmitting particle so as to cover the reflective coating. The method according to claim 6,
Wherein the step of forming the reflective coating and the step of forming the protective coating comprise:
In the same chamber, continuously under the same pressure. delete delete delete delete delete delete delete delete delete delete

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