TIMEPIECE COVER GLASS AND TIMEPIECE

• US 20110176396A1
• Filed: 01/18/2011
• Published: 07/21/2011
• Est. Priority Date: 01/19/2010
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: SUZUKI, Katsumi
• Granted Patent: US 8,867,320 B2
• Time in Patent Office: Days
• US Class Current: 368/296
• CPC Class Codes: C03C 17/3435 comprising a nitride, oxynitride, boronitride or carbonitride
• CPC Class Codes: C03C 2217/734 comprising an alternation of high and low refractive indexes
• CPC Class Codes: C03C 2218/365 Coating different sides of a glass substrate
• CPC Class Codes: G04C 10/02 the power supply being a radioactive or photovoltaic source
• CPC Class Codes: G04G 17/02 Component assemblies

Abstract

A timepiece cover glass used in a timepiece with a solar battery is provided. The timepiece cover glass covers the solar battery. The timepiece cover glass includes an antireflective layer is formed on at least both sides of the timepiece cover glass. A formula (1) is satisfied. f(x, y, z)≦40 (1), where (f(x, y, z) expresses the absolute value of the difference between the maximum value and minimum value among x, y, and z, where z=550.), xnm represents a wavelength exhibiting a minimum reflectance in a reflectance curve based on the antireflective layer, ynm represents a maximum sensitivity wavelength of the solar battery, and znm represents a maximum visible sensitivity wavelength, and the luminous reflectance is 0.6% or less.

Claims

1. A timepiece cover glass used in a timepiece in which a solar battery is provided, the timepiece cover glass covering the solar battery, the timepiece cover glass comprising:

an antireflective layer is formed on at least both sides of the timepiece cover glass, and formula (1) below is satisfied,

f(x,y,z)≦

40 

 

(1)

where (f(x, y, z) expresses the absolute value of the difference between the maximum value and minimum value among x, y, and z, where z=550.),

xnm represents a wavelength exhibiting a minimum reflectance in a reflectance curve based on the antireflective layer,

ynm represents a maximum sensitivity wavelength of the solar battery, and

znm represents a maximum visible sensitivity wavelength, and the luminous reflectance is 0.6% or less.

2. The timepiece cover glass according to claim 1, wherein

the wavelength considered to be the wavelength exhibiting the minimum reflectance is a center wavelength between two points on the reflectance curve that can be intersected by a straight line running parallel to the wavelength axis at a reflectance of 2%.

3. The timepiece cover glass according to claim 1, wherein

the antireflective layer is an inorganic multilayer film obtained by a high-refraction layer and a low-refraction layer being stacked in an alternating fashion.

4. The timepiece cover glass according to claim 3, wherein

the high-refraction layer comprises silicon nitride and the low-refraction layer includes silicon oxide.

5. A timepiece characterized in comprising the timepiece cover glass according to claim 1.