JP2010243161A - Manufacturing method of translucent member, translucent member and timepiece - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a translucent member, having an antireflection function and a sufficiently high hardness to secure scratch resistance, a translucent member, and to provide a timepiece which includes such a translucent member. <P>SOLUTION: The manufacturing method of the translucent member 10 includes a sputtering process for forming an antireflection layer 12, in at least a part of the surface of a translucent substrate, and the sputtering process is a step of alternately stacking a high refractive index layer 12C made from silicon nitride, and low refractive index layers 12B and 12D made from silicon oxide. In the sputtering process, a silicon target 1 for forming the high refractive index layer 12C made of silicon nitride, and a silicon target 2 for forming the low-refractive index layers 12B and 12D made of silicon oxide are used separately. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

    The present invention relates to a method for producing a translucent member used for a watch cover glass or the like.

Conventionally, in order to improve visibility such as time display, it is known to form an antireflection layer on a translucent member called a cover glass (windshield). This antireflection layer is generally composed of several to tens of layers of inorganic layers having different refractive indexes. When high hardness is required like a cover glass, the light transmittance is low. SiO ₂ having a high refractive index and a relatively high hardness is often formed on the outermost layer of the antireflection layer. For example, a technique for forming an antireflection layer in which SiO ₂ is the outermost layer and the lowermost layer and SiO ₂ layers and Si ₃ N ₄ layers are alternately laminated is disclosed on the surface of a watch cover glass (patent) Reference 1). Further, a windshield glass for a watch formed by forming a layer made of silicon oxide (SiO ₂ ) as the outermost layer and forming a layer made of silicon nitride on the surface of the watch cover glass is also disclosed (see Patent Document 2).

JP 2004-271480 A JP 2006-275526 A

By the way, the conventional wristwatch provided with the antireflection layer in which the SiO ₂ layer and the Si ₃ N ₄ layer are alternately laminated often has a deep scratch on the surface of the cover glass when used for daily life. However, the reason is not necessarily clear, and it has been difficult to form the antireflection layer on the outer surface of the cover glass. For this reason, the location where the antireflection layer having SiO ₂ as the outermost layer is formed is substantially limited to the inner surface of the cover glass.

  Accordingly, an object of the present invention is to provide a method for manufacturing a translucent member having an antireflection function and having a sufficiently high hardness and ensuring scratch resistance, a translucent member, and a timepiece including the translucent member. Is to provide

  The present inventor has found that the reason why the scratch resistance of the antireflection layer described above is not sufficient is the sputtering process when the antireflection layer is formed. In the conventional sputtering process, reactive sputtering using a silicon target is widely used. At that time, it is common to form both a high refractive index layer (silicon nitride layer) and a low refractive index layer (silicon oxide layer) by changing the atmospheric gas and voltage using the same silicon target. However, it has been found that the silicon target is altered by the oxygen-containing atmospheric gas when forming the silicon oxide film. That is, since the high refractive index layer (silicon nitride layer) was formed using the altered silicon target, the density and refractive index of the silicon nitride layer were not sufficiently increased. As a result, the hardness of the silicon nitride layer did not increase, and as a result, the scratch resistance of the antireflection layer was low. The present invention has been completed based on the above findings.

The present invention is a method for producing a translucent member comprising a substrate having translucency, comprising a sputtering step of forming an antireflection layer on at least a part of the surface of the substrate, the sputtering step comprising: A step of alternately stacking a high refractive index layer made of silicon nitride and a low refractive index layer made of silicon oxide, and in the sputtering step, a silicon target 1 for forming a high refractive index layer made of silicon nitride; The silicon target 2 for forming a low refractive index layer made of silicon oxide is used separately.
Here, examples of the translucent member include a hard and transparent member such as a watch cover member, an instrument cover member, or a spectacle lens. Examples of the base material of the translucent member include sapphire glass, quartz glass, and soda glass.

  According to the method for producing a translucent member of the present invention, a silicon target 1 for forming a high refractive index layer made of silicon nitride and a silicon target 2 for forming a low refractive index layer made of silicon oxide are obtained. Used separately. That is, the silicon target 2 for forming the low refractive index layer is not used for forming the high refractive index layer. Therefore, the silicon target 1 is not altered, and the density and hardness of the high refractive index layer made of silicon nitride can be sufficiently increased. As a result, the scratch resistance of the antireflection layer can be further enhanced. In addition, since the refractive index of the silicon nitride film does not decrease, an accurate optical design is possible.

In the present invention, the antireflection layer preferably has a silicon nitride content of 30 to 50 vol% in a range from the outermost surface to a depth of 150 nm.
According to the invention of this configuration, the predetermined antireflection layer is formed on the base material, and the silicon nitride content in the range from the outermost surface of the antireflection layer to a depth of 150 nm is 30 vol% or more. High antireflection layer can be formed on the substrate. Further, since the silicon nitride content in the range from the outermost surface to a depth of 150 nm is 50 vol% or less, the antireflection effect is also excellent. When the content of silicon nitride in the range from the outermost surface of the antireflection layer to a depth of 150 nm is 40 to 50 vol%, it is possible to further improve the scratch resistance of the antireflection layer while maintaining the antireflection effect. Therefore, it is more preferable.
Moreover, the layer thickness of the outermost layer made of silicon oxide is preferably 70 to 110 nm, more preferably 75 to 105 nm. The layer thickness of the silicon nitride layer adjacent to the outermost layer is preferably 50 to 115 nm, more preferably 55 to 110 nm. When the thickness of each of these layers is out of the above range, the reflectance of the antireflection layer tends to increase.

In this invention, it is preferable that the surface hardness of this translucent member is 24000 N / mm < ² > or more. Here, the surface hardness is determined using a nanoindenter (based on ISO14577). The test load is 1.225 mN.
According to the invention of this configuration, since the surface hardness of the translucent member is 24000 N / mm ² or more, sufficient scratch resistance can be exhibited, and for example, it is excellent as a cover glass for a watch. Further, when the surface hardness of the translucent member is 30000 N / mm ² or more, further excellent scratch resistance can be exhibited.

The translucent member of the present invention is manufactured by the method for manufacturing a translucent member described in any of the above.
According to the translucent member of the present invention, since the translucent member is manufactured by the method for manufacturing a translucent member described above, a translucent member having both an excellent antireflection function and scratch resistance is provided. can do.

In the present invention, the translucent member is preferably a cover member, and the antireflection layer is preferably formed on at least the outer portion of the inner portion and the outer portion of the cover member.
According to the invention of this configuration, since reflection of light incident from the outside of the cover member can be prevented on the incident side, the reflection is better than when the antireflection layer is formed on the exit side portion inside the cover member. Preventive effect is obtained.

The timepiece of the present invention includes the above-described translucent member, and the translucent member is provided in a case that accommodates the timepiece.
According to the timepiece of the present invention, by providing the above-described translucent member, it is possible to enjoy the same operations and effects as described above. In addition, a translucent member is provided in a case as a cover glass (windshield), for example.

  According to the present invention, a translucent member having both an antireflection function and scratch resistance can be easily and easily manufactured. Moreover, the timepiece provided with this translucent member as a cover glass can be provided.

The schematic diagram which shows the cross section of the cover glass which concerns on one Embodiment of this invention. Sectional drawing of the timepiece provided with the cover glass which concerns on this embodiment.

  Hereinafter, an embodiment of the present invention will be described in detail. The translucent member of the present embodiment is a watch cover glass (hereinafter, also simply referred to as “cover glass”), and FIG. 1 shows a cross-sectional view of the translucent member 10. In FIG. 1, the translucent member 10 is provided with the transparent base material 11 and the antireflection layer 12 formed on it.

[Material of Substrate 11]
The material of the substrate 11 is an inorganic oxide, and examples thereof include sapphire glass, quartz glass, and soda glass. As a material of the watch cover glass, sapphire glass is particularly preferable from the viewpoints of hardness and transparency.

[Configuration of Antireflection Layer 12]
The antireflection layer 12 is a multilayer film formed on the substrate 11 and obtained by alternately laminating inorganic thin films having different refractive indexes. In the translucent member 10 shown in FIG. 1, the antireflection layer 12 includes four layers of 12A (high refractive index layer), 12B (low refractive index layer), 12C (high refractive index layer), and 12D (low refractive index layer). It is composed of layers.
Here, the high refractive index layers 12A and 12C are formed of silicon nitride (SiNx), and the low refractive index layers 12B and 12D are formed of silicon oxide (SiO ₂ ). The silicon nitride content in the range from the outermost surface of the antireflection layer 12 to a depth of 150 nm is 30 to 50 vol%. The surface hardness of the translucent member 10 is 24000 N / mm ² or more as measured according to ISO14577 using a nanoindenter.

The layer thickness of the outermost layer (low refractive index layer 12D) made of silicon oxide is preferably 70 to 110 nm, and more preferably 75 to 105 nm. The layer thickness of the silicon nitride layer (high refractive index layer 12C) adjacent to the outermost layer is preferably 50 to 115 nm, more preferably 55 to 110 nm. When the above-mentioned range of the layer thickness is deviated, the reflectance of the antireflection layer tends to increase.
The antireflection layer 12 need not be four layers, and may be five layers or more. From the viewpoint of enhancing the antireflection effect, a larger number of layers is preferable. However, if the number of laminated layers is too large, there is a possibility that a problem may occur from the viewpoint of translucency, so the range is preferably up to 9 layers.

[Formation process of antireflection layer 12]
When forming the above-mentioned antireflection layer 12 on the surface of the substrate 11, a sputtering method is used. As a sputtering method, a normal method used in forming an inorganic thin film can be applied. In this embodiment, a silicon target is used as a sputtering target. In the sputtering process, the silicon target 1 for forming the high refractive index layers 12A and 12C made of silicon nitride and the silicon target 2 for forming the low refractive index layers 12B and 12D made of silicon oxide are separately provided. Used for.
The translucent member 10 is manufactured by forming the antireflection layer 12 composed of the four layers described above on the base material 11.

Here, when performing the above-described sputtering, it is preferable from the viewpoint of improving the hardness and adhesion of the antireflection layer, to include a heating step of heating the substrate 11 to 100 ° C. or higher.
In addition, before the antireflection layer 12 is formed by sputtering, the surface of the base material 11 can be cleaned by providing a reverse sputtering process for removing deposits on the surface of the base material 11. From the viewpoint of improving the adhesion between the antireflection layer 11 and the antireflection layer 12.

[Clock structure]
FIG. 2 shows a cross-sectional view of a timepiece including the translucent member 10.
As shown in FIG. 2, in the timepiece 100 of the present embodiment, the translucent member 10 is provided as a cover glass 102 in a case 104 that houses a timepiece (movement) 103. The case 104 is provided with a back cover 105.
Here, the body surface portion of the cover glass 102 of the present embodiment includes a front surface portion 102A, a rear surface portion 102B, and a side surface portion 102C. The front surface portion 102 </ b> A corresponds to a portion outside the cover glass 102. The rear surface portion 102 </ b> B corresponds to an inner portion of the cover glass 102 and faces the dial 106 and the pointer 107.
In the present embodiment, the above-described antireflection layer 12 is located on the front surface 102 </ b> A of the cover glass 102.

According to the above-described embodiment, the following effects can be obtained.
(1) The translucent member 10 includes a base 11 having translucency and an antireflection layer 12. In the sputtering step for forming the antireflection layer 12, the silicon target 1 for forming the high refractive index layers 12A and 12C made of silicon nitride and the low refractive index layers 12B and 12D made of silicon oxide are formed. A silicon target 2 is used separately. Therefore, the silicon target 2 for forming the low refractive index layer is not used for forming the high refractive index. Therefore, the density and hardness of the high refractive index layers 12A and 12C made of silicon nitride can be sufficiently increased without altering the silicon target 1, and as a result, the scratch resistance of the antireflection layer can be further enhanced. . In addition, since the refractive indexes of the high refractive index layers 12A and 12C do not decrease, an accurate optical design is possible.

(2) The antireflection layer 12 is formed by alternately laminating high refractive index layers 12A and 12C and low refractive index layers 12B and 12D, and ranges from the outermost surface of the antireflection layer 12 to a depth of 150 nm. The silicon nitride content in is 30 vol% or more. Therefore, the surface of the antireflection layer 12 is a very hard layer. Moreover, since the silicon nitride content in the range from the outermost surface of the antireflection layer 12 to a depth of 150 nm is 50 vol% or less, the antireflection effect is also excellent. Further, when the content of silicon nitride in the range from the outermost surface of the antireflection layer 12 to a depth of 150 nm is 40 vol% or more, the scratch resistance of the antireflection layer can be further improved while maintaining the antireflection effect. It becomes possible.

(3) Since the surface hardness of the translucent member 10 is 24000 N / mm ² or more, it can exhibit sufficient scratch resistance and has sufficient scratch resistance when applied to a wristwatch or a portable information device. can get. Further, when the surface hardness is 30000 N / mm ² or more, further excellent scratch resistance can be exhibited.

(4) In the timepiece 100, since the translucent member 10 is provided in the case 104 as the cover glass 102, the information visibility is improved by the antireflection function of the translucent member 10. Furthermore, since the cover glass 102 is also excellent in scratch resistance, the transparency and antireflection property of the cover glass 102 itself can be maintained over a long period of time.

The present invention is not limited to the above-described embodiments, and various improvements and modifications can be made within a range in which the object of the present invention can be achieved.
In the said embodiment, the example in which the manufacturing method of the translucent member 10 was applied to manufacture of the cover glass 102 as a windshield of a timepiece was shown. However, the translucent member to which the manufacturing method of the present invention is applied is not limited to a cover glass as a windshield. In a mechanical timepiece or the like, a translucent member as a cover member is provided at a position where a back cover is provided, and a see-through back specification is provided in which a mechanism inside the watch body can be visually recognized through the translucent member. Sometimes. In such a case, the present invention can be applied as a method of manufacturing the light transmissive member.
In addition, as a base material of a translucent member, high-hardness sapphire glass is suitable, but use of quartz glass, soda glass, or the like may also be considered.

The translucent member obtained by the manufacturing method of the present invention is not limited to a cover member used for a watch, but is a mobile phone, a portable information device, a measuring device, a digital camera, a printer, a diving computer, a pulse meter, and other devices Can be suitably used as a cover member for an information display section.
The translucent member of the present invention is not limited to the cover member. The antireflection layer according to the present invention is formed at any location where hardness, antireflection function and scratch resistance are required in the base material of the translucent member.

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples. Specifically, general sapphire glass was used as a base material for a watch cover glass, a predetermined antireflection layer was formed on the surface, and various evaluations were performed.

[Example 1, Comparative Example 1]
(Pretreatment of substrate)
After sapphire glass was immersed in hot concentrated sulfuric acid at 120 ° C. for 10 minutes, it was thoroughly washed with pure water and dried in the atmosphere for 30 minutes in an oven set at 120 ° C. Next, after this sapphire glass was placed inside the sputtering apparatus, the inside of the apparatus was brought to a pressure of 10 ⁻⁶ Torr while heating to 120 ° C. Subsequently, Ar gas was introduced into the apparatus, and the surface of the sapphire glass was cleaned by reverse sputtering at 0.8 mTorr.

(Antireflection layer forming process)
Using silicon as a target, reactive sputtering was performed under the following conditions to form an antireflection layer (four layers) composed of a high refractive index layer and a low refractive index layer on the surface of the sapphire glass substrate. Here, in Example 1, the silicon target 1 for forming the high refractive index layer and the silicon target 2 for forming the low refractive index were used separately, and in Comparative Example 1, the same silicon target was used. Other sputtering conditions are the same in both Example 1 and Comparative Example 1.
High refractive index layer: silicon nitride (SiNx)
Ar gas: 270sccm
Nitrogen gas: 100 sccm
Gas pressure: 0.60 Pa
Sputtering power: 2.5 kW
Low refractive index layer: silicon oxide (SiO ₂ )
Ar gas: 85sccm
0 ₂ Gas: 50sccm
Gas pressure: 0.20 Pa
Sputtering power: 2.5KW
The specific configuration of the antireflection layer is as follows in both Example 1 and Comparative Example 1.
SiO ₂ (88 nm) / SiNx (91 nm) / SiO ₂ (12 nm) / SiNx (27 nm) // Base material

[Evaluation items and methods]
The following evaluation was performed on each of the substrates obtained above, and the results are shown in Table 1. A single sapphire glass is also shown as a reference example.
(1) Reflectance (%)
The reflectance of standard light incident on the substrate surface at an incident angle of 90 ° is obtained, and this reflectance is multiplied by the luminous sensitivity at an incident angle of 90 ° at each wavelength in the visible light region. It calculated based on the integrated value.

(2) Light transmittance difference before and after the sandfall test (△ T%)
First, the following sandfall test is performed. The cover glass is arranged at an inclination angle of 45 ° with respect to the horizontal plane. At this time, the cover glass is arranged so that the side on which the antireflection layer is formed becomes the upper surface side. Then, the sand is dropped toward the antifouling layer from a height of 1 m from the horizontal plane. Thereafter, the cover glass was washed, and the difficulty of scratching was evaluated based on the difference ΔT% between the light transmittance of the cover glass before the test and the light transmittance of the cover glass after the test.
Here, the sand used is a carborundum produced by pulverizing and classifying black silicon carbide ingot and green silicon carbide ingot. In this test, 800 cm ³ of Carborundum # 24 having a center particle size of 600 to 850 μm was used.

(3) Surface hardness (N / mm ² )
Using a nanoindenter, the surface hardness of the antireflection layer side of the substrate at a test load of 1.225 mN was measured (based on ISO14577).

〔Evaluation results〕
The light transmittance difference (ΔT%) before and after the sandfall test is desirably 2% or less from the viewpoint of practical scratch resistance. From the results shown in Table 1, the ratio (occupancy) of silicon nitride (SiNx) in the depth range of 150 nm from the outermost surface of the antireflection layer is set to 30% by mass or more. It can be seen that the light transmittance difference (ΔT%) before and after the sand test can be reduced to 2% or less. However, in Example 1, it is 1.50%, but in Comparative Example 1, a considerable difference is 1.70%. There is also a difference in surface hardness, confirming the result of light transmittance difference (ΔT%).
On the other hand, the reflectance is 0.40% in Example 1, while it is 0.51% in Comparative Example 1, which is a considerably large value.

[Confirmation experiment]
When the silicon nitride layer or silicon oxide layer is formed by sputtering, the physical properties of the silicon nitride layer or silicon oxide layer obtained are different depending on whether the same silicon target is used or a different silicon target is used. Further confirmation was made as to whether they differ to some extent.
Specifically, using the silicon target 1 and the silicon target 2 after use according to Example 1, four types of single-layer films as shown in Table 2 were formed on each sapphire substrate. Thereafter, the refractive index and surface hardness of the obtained monolayer film were measured. The refractive index is a value measured with an ellipsometer at a wavelength of 550 nm. The sputtering conditions other than the formation of the single layer film are the same as those in Example 1.

From the results shown in Table 2, even when the same silicon nitride single layer film (877 nm thickness) is used, the refractive index and surface hardness of the silicon target 2 using the silicon target 2 are considerably lower than those using the silicon target 1. You can see that However, there is almost no difference between the refractive index and the surface hardness of the silicon oxide single layer film depending on the target used.
Therefore, the difference in reflectance, light transmittance difference (ΔT%) and surface hardness in Example 1 and Comparative Example 1 is presumed to be due to the change in the target material when the silicon oxide layer is formed.
From the influence on the refractive index, it can be seen that it is better to use the sputtering target separately for forming the silicon nitride layer and for forming the silicon oxide layer in the optical design related to the antireflection performance.

DESCRIPTION OF SYMBOLS 10 ... Translucent member, 11 ... Base material, 12 ... Antireflection layer, 12A, 12C ... High refractive index layer, 12B, 12D ... Low refractive index layer, 100 ... Clock, 102 ... Cover glass, 102A ... Front part, 102B: Rear surface portion, 102C ... Side surface portion, 104 ... Case, 105 ... Back cover, 106 ... Dial, 107 ... Pointer

Claims (7)

A method for producing a translucent member comprising a substrate having translucency,
A sputtering process for forming an antireflection layer on at least a part of the surface of the substrate, wherein the sputtering process alternately stacks a high refractive index layer made of silicon nitride and a low refractive index layer made of silicon oxide. Process,
In the sputtering step,
A silicon target 1 for forming a high refractive index layer made of silicon nitride;
A method for producing a translucent member, wherein a silicon target 2 for forming a low refractive index layer made of silicon oxide is used separately. In the manufacturing method of the translucent member of Claim 1,
The method for producing a translucent member, wherein the antireflection layer has a silicon nitride content of 30 to 50 vol% in a range from the outermost surface to a depth of 150 nm. In the manufacturing method of the translucent member of Claim 1 or Claim 2,
The surface hardness of this translucent member is 24000 N / mm < ² > or more. The manufacturing method of the translucent member characterized by the above-mentioned. In the manufacturing method of the translucent member of Claim 3,
The surface hardness of this translucent member is 30000 N / mm < ² > or more. The manufacturing method of the translucent member characterized by the above-mentioned.   A translucent member produced by the method for producing a translucent member according to claim 1. In the translucent member of Claim 5,
The translucent member is a cover member;
The translucent member, wherein the antireflection layer is formed on at least an outer portion of an inner portion and an outer portion of the cover member. The translucent member according to claim 6,
A timepiece characterized in that the translucent member is provided in a case for accommodating a timepiece.

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