JP7129781B2 - spectacle lenses and spectacles - Google Patents

Description

TECHNICAL FIELD The present invention relates to spectacle lenses that optimally control transmitted light in the visible range and ultraviolet range from the front of spectacles and suppress reflected light from the back.

The applicant has already proposed a spectacle lens that suppresses glare by suppressing the transmittance on the short wavelength side of the visible range (Patent Document 1), and has been well received as a lens for sunglasses. there is In this invention, by depositing a mixture of chromium and chromium oxide (hereinafter referred to as a chromium layer) on the entire back surface of the lens, the transmittance of the short wavelength side of the visible range, which is said to have a large effect on the human body, is reduced. is declining. By combining it with a lens base material that has an ultraviolet absorption (UV cut) effect, we have realized sunglasses that minimize adverse effects on the human body.

Japanese Patent No. 4643233

However, in the above-described invention, since the chromium layer is provided on the entire rear surface of the lens, the reflectance of the rear surface increases, and there is a risk that the reflected light from the rear surface of the lens may affect the human body. For example, for ultraviolet rays from the front of the glasses, it is sufficient to use a lens substrate having a UV-cutting effect, but for ultraviolet rays incident from the rear side, the UV-cutting effect of the lens substrate does not function at all.

Here, of the ultraviolet A waves with a wavelength range of 315 to 380 nm and the ultraviolet B waves with a wavelength range of 280 to 315 nm, the ultraviolet A waves, which account for over 90% of the ultraviolet rays that reach the earth, are related to the progress of cellular substance replacement. For example, it is said to cause not only cosmetic problems such as age spots and wrinkles but also cataracts.

Therefore, not only the transmitted light from the front of the glasses but also the reflected light from the back should be appropriately suppressed from the near-ultraviolet rays in the wavelength range of 280 to 380 nm. It was confirmed that the back surface reflectance in this case reached 3.5 to 5.2 times the reflectance of the lens substrate without the chromium layer in the wavelength range of 280 to 380 nm.

In the case of an 8-curve or 9-curve lens with a small radius of curvature on the back side of the lens, there is almost no possibility that the reflected light will reach the eye. may reach the eye. Note that the following relational expression (1) holds for the radius of curvature R [mm] of the lens, the refractive index N, and the curve number C. R=(N−1)*1000/C (Formula 1)

Therefore, for example, in the case of a lens substrate with a refractive index of 1.523, the curvature radius R of the fourth curve is (1.523−1)*1000/4=130.75 mm, and the curvature radius R of the eighth curve is (1.523-1)*1000/8=65.375 mm.

FIG. 4(b) shows the relationship between the incident light and the rear surface of the lens. Depending on the curve of the lens, the incident light with an incident angle of about 5° to 45° is reflected by the rear surface of the lens and reaches the eye. It shows that it is possible.

SUMMARY OF THE INVENTION It is an object of the present invention to provide spectacle lenses and spectacles capable of appropriately suppressing reflected light from the rear surface of the lenses.

In order to achieve the above object, the spectacle lens according to the present invention provides a highly refractive spectacle lens having a refractive index of 1.6 to 2.5 at a wavelength of 550 nm as a vapor deposited film provided on the back side of the lens substrate facing the eyeball. A first layer made of a material, a second layer made of a low-refractive material having a refractive index of 1.3 to 1.5 at a wavelength of 550 nm, chromium Cr, an oxide of chromium Cr, or chromium A third layer made of one or more kinds of metal materials selected from Cr alloys, a fourth layer made of a low refractive material having a refractive index of 1.3 to 1.5 at a wavelength of 550 nm, By providing in this order, in the measuring method (a) of a reflecting object specified by JISZ8722, the reflectance for back incident light with an incident angle of 5° is suppressed to less than 10% at a wavelength of 280 nm to 380 nm. do.

As shown in FIG. 4A, the present invention is characterized in that a high refractive material, a low refractive material, a metal material, and a low refractive material are vacuum-deposited on the lens substrate in this order. The present invention is a lens for spectacles, and the back surface of the lens becomes mirror-finished by forming a deposited film on the back surface of the lens base material which has been mirror-finished. Therefore, in the reflectance measurement method (a) by the replacement method using a two-path spectrophotometer in "5.3 Reflective object measurement method" defined in "JIS Z8722", scattering on the back surface of the lens is not a problem. not.

In the present invention, the high refractive index and the low high refractive index are specified by their respective refractive indices, but since the refractive indices have wavelength dependence, they are specified by their refractive indices at a wavelength of 550 nm for convenience. .

Therefore, the metal materials of the examples are mixtures of chromium and chromium oxides, and CrO ₃ and Cr ₂ O ₃ are used as chromium oxides.

In the present invention, by providing the vapor deposition films of the first to fourth layers in this order, the reflectance for back incident light with an incident angle of 5° is suppressed to less than 10% at a wavelength of 280 nm to 380 nm. .

As long as a glass material or a plastic material is used as the lens base material, the refractive index of each material is approximately 1.5 and there is almost no difference. No difference in rate. Further, as long as the transmittance of the spectacle lens and the thickness of the lens substrate are about several millimeters, the thickness of the lens substrate is not related to the above reflectance.

However, in order to block the transmission of ultraviolet rays from the front of the spectacles, a lens base material with a UV cut function should be used. The material of the plastic lens is not limited at all, and thermoplastic resins such as acrylic resin, polystyrene resin, and polycarbonate resin, and thermosetting resins such as allyl diglycol carbonate resin, polyurethane resin, and polythiourethane resin are used. . Among these, allyl diglycol carbonate resin, which is also called CR-39, is particularly suitable.

Further, the spectacle lens of the present invention may or may not have a prescription. However, regardless of the lens, the present invention is preferably applied to a lens having a large radius of curvature on the back surface, and the relationship between the curve number, the radius of curvature R, and the refractive index N is determined by the above-described relational expression (1 ) is preferable.

Preferred high refractive materials having a refractive index of 1.6 to 2.5 at a wavelength of 550 nm include zirconia ZrO ₂ , tantalum pentoxide Ta ₂ O ₅ , titanium oxide TiO ₂ , hafnium oxide HfO ₂ and yttrium oxide Y ₂ . O ₃ , zinc oxide ZnO, niobium pentoxide Nb ₂ O ₅ , chromium oxide Cr ₂ O ₃ , aluminum oxide Al ₂ O ₃ or a combination thereof is used.

Among these, zirconia ZrO ₂ , titanium oxide TiO ₂ , and niobium pentoxide Nb ₂ O ₅ , which have a relatively high refractive index, are particularly suitable.

As the low-refractive material having a refractive index of 1.3 to 1.5 at a wavelength of 550 nm, preferably one selected from silicon dioxide SiO ₂ , magnesium fluoride MgF ₂ and barium fluoride BaF ₂ or a combination of a plurality of things are used. Of these, silicon dioxide SiO ₂ is particularly preferred.

Although not particularly limited, the thickness of the third layer, which is a metal layer, should preferably be 0.3 nm to 1.0 nm, more preferably 0.3 nm to 0.8 nm.

Corresponding to this film thickness, the film thickness of the first layer is preferably 10 times or more the film thickness of the third layer, more preferably 20 times or more, and even more preferably 10 to 30 nm. should be

The film thicknesses of the second and fourth layers are preferably two times or more the film thickness of the first layer, more preferably four times or more, and still more preferably 60 nm to 90 nm. be.

In any case, it is preferable that the total thickness of the first to fourth layers is 150 nm to 200 nm.

According to the present invention described above, it is possible to appropriately suppress the reflected light from the rear surface of the lens regardless of the radius of curvature of the spectacle lens, so that spectacles that are easy on the eyes can be realized.

FIG. 4 is a drawing showing the transmittance of a test sample and a comparison sample; FIG. It is a drawing which shows the back surface reflectance of a test sample and a comparison sample at an incident angle of 5 degrees. It is a drawing which shows the back surface reflectance of a test sample and a comparison sample at an incident angle of 45 degrees. 4 illustrates the structure of an antireflection film and the relationship between incident light and the rear surface of a lens.

Examples will be described in more detail below. However, the specific description does not particularly limit the present invention.

As a lens substrate, a CR-39 plastic lens having a plate thickness of 1.9 mm to which a UV cut function was added was used, and the following four layers were vacuum-deposited thereon. Both the front and back surfaces of the lens substrate are 0-curve flat surfaces.

First layer: ZrO ₂ 13 nm, second layer: SiO ₂ 77 nm, third layer: Cr 0.5 nm, fourth layer: SiO ₂ 77 nm were provided on the above lens substrate to form a UV antireflection film. It was used as a test sample.

Further, the same lens substrate was provided with Cr of 0.5 nm to prepare a comparison sample. In the test sample and the reference sample, Cr means a mixture of chromium and chromium oxide, and CrO ₃ and Cr ₂ O ₃ are used as the chromium oxide.

Spectral reflectance coefficients and spectral transmittance coefficients were measured based on JIS Z8722 for spectacle lens test samples having four layers. The measuring machine is an ultraviolet-visible-near-infrared spectrophotometer U-4100 (manufactured by Hitachi High-Tech Science).

Spectral transmittance and spectral reflectance at an incident angle of 5° and an incident angle of 45° were measured for each of the test sample and the comparison sample. In the case of an incident angle of 45°, a polarizer was used to separately measure the reflectances of the S-polarized light and the P-polarized light, and the average value thereof was taken as the reflectance.

FIG. 1 shows the front-to-back transmittance of the lens substrate at an incident angle of 5°. As shown in the figure, the test sample has a slightly lower transmittance in the visible range due to the provision of the UV antireflection film, but in the visible range of 400 to 800 nm, the transmittance is about 64% to 77%. Satisfies the specifications as a lens base material for

Moreover, the test sample, like the reference sample, has a lower transmittance in the short wavelength region of the visible region in correspondence with the wavelength, effectively relieving the stress on the eyes. That is, since the light energy E is inversely proportional to the wavelength λ (E=h·c/λ), the transmittance decreases corresponding to the wavelength, thereby eliminating adverse effects on the eyes. The transmittance of the test sample and the comparison sample in the near-ultraviolet region is 10% or less due to the UV cut function of the lens substrate.

FIG. 2 shows the reflectance from the back surface of the lens substrate at an incident angle of 5°. As shown, the back reflectance of the test sample is significantly lower than that of the control sample at wavelengths of 520 nm and below due to the provision of the UV antireflection coating.

The test sample maintains a reflectance of 6% or less particularly in the near-ultraviolet region with a wavelength of 380 nm or less, which is significantly different from the reference sample whose reflectance is 15% or more. In another experiment, the reflectance of the lens substrate itself was measured, and the back reflectance of the test sample was lower than that of the lens substrate in the near-ultraviolet region (wavelength: 280 to 380 nm).

FIG. 3 shows the reflectance from the back surface of the lens substrate at an incident angle of 45°. As shown, the test sample maintains a reflectance of 7% or less at a wavelength of 280 nm to 380 nm for light with an incident angle of 45°, which is significantly different from the control sample which is 11% or more.

Experimental results for a plastic lens with a UV cut function have been shown above. In the case where the UV cut function is not added, the reflectance increases very slightly at wavelengths of 280 nm to 380 nm. This is probably because the UV light entering the lens substrate from the rear surface of the lens is reflected by about 4% on the lens surface. %, and does not affect the effect of the antireflection films shown in FIGS.

In addition, even if the material of the plastic lens is changed or a glass lens is used, the refractive index of each lens substrate is around 1.5 and there is no significant difference, so UV rays entering the lens substrate from the rear surface of the lens are Light reflecting off the lens surface has virtually no effect. This point is the same when the plate thickness of the material of the spectacle lens is changed.

Claims (12)

As a vapor deposition film provided on the back side of the lens substrate facing the eyeball,
a first layer made of a highly refractive material having a refractive index of 1.6 to 2.5 at a wavelength of 550 nm;
a second layer made of a low-refractive material having a refractive index of 1.3 to 1.5 at a wavelength of 550 nm;
a third layer made of one or more metal materials selected from chromium Cr, chromium Cr oxides, and chromium Cr alloys;
By providing a fourth layer formed of a low refractive material having a refractive index of 1.3 to 1.5 at a wavelength of 550 nm in this order,
1. A spectacle lens, characterized in that, in the measuring method (a) of a reflecting object defined by JIS Z8722, the reflectance for back incident light with an incident angle of 5° is suppressed to less than 10% at a wavelength of 280 nm to 380 nm. The spectacle lens according to claim 1, which has a reflectance of less than 12% at a wavelength of 380 nm to 800 nm for back incident light with an incident angle of 5°. 3. The spectacle lens according to claim 1 , wherein the third layer has a film thickness of 0.3 nm to 1.0 nm. The spectacle lens according to any one of claims 1 to 3 , wherein the film thickness of the first layer is 10 times or more the film thickness of the third layer. 5. The spectacle lens according to claim 4 , wherein the film thickness of the first layer is 10 nm to 30 nm. The spectacle lens according to any one of claims 1 to 5 , wherein the film thicknesses of the second layer and the fourth layer are two times or more the film thickness of the first layer . 7. The spectacle lens according to claim 6 , wherein the film thicknesses of the second layer and the fourth layer are 60 nm to 90 nm. The first layer comprises one or more selected from zirconia ZrO2, tantalum pentoxide Ta2O5, titanium oxide TiO2, hafnium oxide HfO2, yttrium oxide Y2O3, zinc oxide ZnO, niobium pentoxide Nb2O5, chromium oxide Cr2O3, and aluminum oxide Al2O3. The spectacle lens according to any one of claims 1 to 7 , which is configured in combination. The spectacles according to any one of claims 1 to 8 , wherein the second layer and the fourth layer are composed of one or more combinations selected from silicon dioxide SiO2, magnesium fluoride MgF2, and barium fluoride BaF2. lens. The spectacle lens according to any one of claims 1 to 9 , wherein the lens substrate has a UV cut function. The spectacle lens according to any one of Claims 1 to 10 , wherein the back surface of the lens substrate is formed with a curve number of less than 8. Spectacles using the lens according to any one of claims 1 to 11.

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