Patent Description:
As spectacle lenses with improved heat resistance, the products disclosed in <CIT> (<CIT>) and <CIT> (<CIT>) are known.

The spectacle lens disclosed in <CIT> includes antireflection films on an object-side surface and an eyeball-side surface of a lens base. The antireflection film contains at least one of silicon oxide, titanium oxide, lanthanum titanate, tantalum oxide, and niobium oxide, whereby the object-side antireflection film is caused to have a compressive stress, and the eyeball-side antireflection film is caused to have a compressive stress less than that of the object-side antireflection film or to have a tensile stress.

In the product disclosed in <CIT>, an antireflection film is formed of a combination of ternary materials, i.e., silicon oxide, a sintered mixture of titanium oxide, lanthanum oxide, and titanium, and a material having a refractive index higher than that of silicon oxide, thereby providing heat resistance performance.

<CIT> discloses a spectacle lens having a base material and the multilayered reflection preventing layer layered on the base material directly or via another layer. The multilayered reflection preventing layer has at least one organic layer and at least one inorganic layer and the uppermost layer thereof is an organic layer.

<CIT> discloses an optical component including a plastic substrate and an antireflection film disposed on the substrate, wherein the antireflection film is a multilayer film having alternately-laminated six or more layers including high refractive index layers and low refractive index layers.

<CIT> discloses an optical component including a plastic base which has a convex surface and a concave surface; and a multilayer film which is disposed on at least the convex surface of the plastic base. The multilayer film has an average reflectivity of <NUM>% to <NUM>% over a wavelength range of <NUM> to <NUM>.

<CIT> discloses a plastic lens in which a primer layer is formed on a plastic base, after that, a hard coat layer is formed on the primer layer and the antireflection coating is further formed on the hard coat layer.

In the product disclosed in <CIT>, the antireflection film should be formed so that silicon oxide or the like has a predetermined compressive stress or tensile stress. Therefore, the film structure for providing sufficient heat resistance while having antireflective performance is complicated, resulting in high costs.

Meanwhile, in the product disclosed in <CIT>, since the antireflection film is formed of the combination of the ternary materials as described above, difficulty in controlling film design and film formation is increased, resulting in high costs for film formation.

Therefore, the present invention has an object to provide an optical product, a spectacle lens, and spectacles, which have antireflective performance, require less number of types of materials for film formation, have a simple film structure which makes film formation easy and reduces costs, and have sufficient heat resistance.

The aforementioned object is attained by the optical product according to claim <NUM>.

The present invention exerts an effect of providing an optical product, a spectacle lens, and spectacles which require less number of types of materials for film formation, have a simple film structure which makes film formation easy and reduces costs, and have both antireflective properties and heat resistance.

An exemplary embodiment of the present invention will be described below with reference to the drawings as appropriate. The present invention is not limited to the exemplary embodiment described below.

A spectacle lens according to the present invention has an optical multilayer film on one surface or both surfaces of a base.

In the present invention, the base may be made of any material, and is preferably translucent. Examples of the material (base material) of the base include a polyurethane resin, a thiourethane resin, an episulfide resin, a polycarbonate resin, a polyester resin, an acrylic resin, a polyether sulfone resin, a poly(<NUM>-methylpentene-<NUM>) resin, and a diethylene glycol bis(allyl carbonate) resin. Further, examples of the material include, as a preferable material (for, in particular, a spectacle lens) having a high refractive index, an episulfide resin obtained by addition-polymerization of an episulfide group with polythiol and/or a sulfur-containing polyol.

Further, in the present invention, the optical multilayer film satisfies the following conditions. When the optical multilayer films are formed on both the surfaces, both of the films preferably satisfy the following conditions, and more preferably have the same layered structure.

Firstly, the optical multilayer film has a five-layer structure in which low refractive index layers and high refractive index layers are alternately layered. When a nearest layer to the base (the layer closest to the base) is a first layer, odd-numbered layers are the low refractive index layers and even-numbered layers are high refractive index layers.

Next, the low refractive index layers are formed by using silica (silicon dioxide, SiO<NUM>), and the high refractive index layers are formed by using zirconia (zirconium dioxide, ZrO<NUM>).

A quotient obtained by dividing the physical thickness of the fourth layer (high refractive index layer) by the physical thickness of the second layer (high refractive index layer) is defined in claim <NUM>.

When the quotient is less than <NUM> and the physical thickness of the second layer is greater than the physical thickness of the fourth layer, the reflectance in a visible region (in which the wavelength is greater than or equal to <NUM> nanometers (nm) and not greater than <NUM>, or is greater than or equal to <NUM> and not greater than <NUM>) is likely to increase, which makes it difficult to design an optical multilayer film for preventing reflection of light in the visible region. In contrast, in the present invention, since the quotient is greater than or equal to <NUM> and the physical thickness of the second layer is less than the physical thickness of the fourth layer, it is easy to increase the transmittance in the visible region, whereby sufficient antireflective performance can be provided.

On the other hand, when the quotient is greater than <NUM>, the physical thickness of the fourth layer exceeds four times the physical thickness of the second layer. In this case, a stress in the second layer and a stress in the fourth layer, which occur during heating, are not well balanced, and one of the stresses becomes excessively greater than the other stress, whereby an excess force is applied to the optical multilayer film and the base during heating. Such excess force causes distortion or crack, and heat resistance becomes relatively insufficient. In contrast, in the present invention, since the quotient is not greater than <NUM>, the stress in the second layer and the stress in the fourth layer, which occur during heating, are well balanced, whereby an excess force is prevented from being applied to the optical multilayer film and the base during heating. Thus, distortion and crack are prevented, and sufficient heat resistance performance can be provided. Further, as the quotient approaches closer to <NUM>, the stresses are better balanced, and the heat resistance is more improved.

The optical multilayer film is preferably formed by a vacuum deposition method or a sputtering method.

In the present invention, another kind of film such as a hard coating film or an antifouling film (water repellent film) may be additionally provided between the optical multilayer film and the base and/or on the surface of the optical multilayer film. When the optical multilayer films are formed on both the surfaces, the kind of the film to be additionally provided may be different between both the surfaces, or whether or not the film is provided may be determined for each surface.

When a hard coating film is used as the film to be provided between the optical multilayer film and the base, the hard coating film is advantageously formed by hard coating solution being uniformly applied to the surface of the base.

Further, for the hard coating film, an organosiloxane resin containing inorganic oxide particles can be preferably used. An organosiloxane resin obtained by hydrolyzing and condensing an alkoxysilane is preferred as the organosiloxane resin. Further, specific examples of the organosiloxane resin include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, methyl trimethoxysilane, ethyl silicate, and a combination thereof. The hydrolysis condensates of the alkoxysilanes are manufactured by hydrolyzing the alkoxysilane compounds or a combination thereof by an acidic aqueous solution such as hydrochloric acid.

Meanwhile, as an exemplary material of the inorganic oxide particles, specifically, a sol of zinc oxide, silicon dioxide (silica particulates), aluminum oxide, titanium oxide (titania particulates), zirconium oxide (zirconia particulates), tin oxide, beryllium oxide, antimony oxide, tungsten oxide, or cerium oxide, or mixed crystals of two or more of the sols, can be used. The diameter of the inorganic oxide particle is preferably greater than or equal to <NUM> and not greater than <NUM>, and more preferably greater than or equal to <NUM> and not greater than <NUM> in order to ensure transparency of the hard coating film. Further, an amount (concentration) of the inorganic oxide particles to be blended is preferably greater than or equal to <NUM>% by weight of all the components of the hard coating film and not greater than <NUM>% by weight thereof in order to ensure appropriate levels of hardness and toughness of the hard coating film. In addition, the hard coating solution may contain an acetylacetone metal salt, an ethylenediaminetetraacetic acid metal salt, and/or the like, as a curing catalyst. Further, the hard coating solution may contain a surfactant, a colorant, a solvent, or the like, as necessary for, for example, ensuring adhesion to the base, facilitating formation, and coloring with a desired (semi)transparent color.

The physical film thickness of the hard coating film is preferably greater than or equal to <NUM> (micrometer) and not greater than <NUM>. When the film thickness is in the range, a sufficient hardness is obtained and a possibility of occurrence of physical problems is not high. In other words, when the film thickness is less than the lower limit, a sufficient hardness is not obtained, and when the thickness is more than the upper limit, the possibility of occurrence of the physical problems such as generation of cracks or fragility is significantly increased.

Further, a primer layer may be additionally provided between the hard coating film and the base surface. Examples of a material of the primer layer include a polyurethanebased resin, an acrylic resin, a methacrylic resin, an organosilicon resin, and a combination thereof.

The optical multilayer film of the optical product has the five-layer structure in which the low refractive index layers and the high refractive index layers are alternately layered. The low refractive index layers are formed by using SiO<NUM>, and the high refractive index layers are formed by using ZrO<NUM>. Therefore, the optical multilayer film has a simple film structure, and is easily formed at low costs.

In the above-described optical product, the quotient obtained by dividing the physical thickness of the fourth layer by the physical thickness of the second layer is defined in claim <NUM>. Therefore, it is possible to provide sufficient heat resistance while ensuring antireflective properties in a visible region (in which light has, for example, a wavelength greater than or equal to <NUM> and not greater than <NUM>, a wavelength greater than or equal to <NUM> and not greater than <NUM>, a wavelength greater than or equal to <NUM> and not greater than <NUM>, or the like).

In the above-described optical product, preferably, the base is a spectacle lens base, and the optical product is a spectacle lens. Further, spectacles that are excellent in heat resistance while preventing reflection of light in the visible region can be produced at relatively low costs by using the spectacle lens.

Next, Examples <NUM> to <NUM> of the present invention according to the above-described embodiment, together with examples <NUM> and <NUM> and Comparative Examples <NUM> to <NUM> that do not belong to the present invention, will be described. The embodiment of the present invention is not limited to the examples described below.

A plurality of spectacle lens bases of the same type were prepared, and intermediate films and optical multilayer films were formed on both surfaces of each spectacle lens base such that the kinds of these films are different among the spectacle lens bases, to produce the spectacle lenses according to Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM>.

The spectacle lens base was a spherical lens base made of a thiourethane-based resin and having the power of S-<NUM>, and the refractive index was <NUM>, and the Abbe number was <NUM>, and a circular lens having a standard size as a spectacle lens was obtained.

Further, the intermediate film was implemented as a hard coating film formed by application of hard coating solution.

The hard coating solution was produced as follows.

Firstly, <NUM> (grams) of methanol, <NUM> of a methanol-dispersed titania sol (made by JGC Catalysts and Chemicals Ltd. , solid content: <NUM>%), <NUM> of γ-glycidoxypropyltrimethoxysilane, <NUM> of γ-glycidoxypropylmethyldiethoxysilane, and <NUM> of tetraethoxysilane were dropped into a container, and <NUM> N (normality) of a hydrochloric acid aqueous solution was dropped into the mixed solution. The resultant mixed solution was stirred and hydrolyzed.

Then, <NUM> of a flow regulating agent and <NUM> of a catalyst were added, and the resultant mixed solution was stirred at room temperature for <NUM> hours.

This hard coat solution was applied to each surface of the spectacle lens base as follows.

That is, the hard coating solution was uniformly applied by a spin coating method, and was left as it was in an environment of <NUM> for <NUM> hours, whereby the hard coating solution was heat-cured.

In any of the hard coating films having been thus formed, the physical film thickness was <NUM>.

Further, for the optical multilayer films, in the same spectacle lens base, the film structure was the same on both the surfaces, and each of the optical multilayer films had a five-layer structure in which the low refractive index layers and the high refractive index layers were alternately deposited. The film thicknesses of at least one of the low refractive index layers and the high refractive index layers are different for each of Examples <NUM> to <NUM> and Comparative Examples. Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM> have the same refractive index of SiO<NUM>, and the same refractive index of ZrO<NUM>.

Each of the optical multilayer films according to Examples <NUM> to <NUM> and Comparative Examples was formed by a vacuum deposition method.

The odd-numbered layers (the first, the third, the fifth layers) were the low refractive index layers, and were formed of silicon dioxide. The even-numbered layers (the second, the fourth layers) were the high refractive index layers, and were formed of zircon dioxide.

In the following [Table <NUM>], the refractive index, the film thickness, and the like of each layer in the optical multilayer film of each of Examples <NUM> to <NUM> and Comparative Example <NUM> are shown. In [Table <NUM>], the refractive index, the film thickness, and the like of each layer in the optical multilayer film in each of Comparative Examples <NUM> to <NUM> are shown.

In Example <NUM>, a quotient obtained by dividing the physical thickness of the fourth layer by the physical thickness of the second layer is about <NUM> which is almost <NUM>. The quotient being almost <NUM> can be translated into the ratio of the physical thickness of the fourth layer to the physical thickness of the second layer being about <NUM>:<NUM>, as shown in "ZrO<NUM> physical thickness ratio between 2nd layer and 4th layer" column in [Table <NUM>].

Likewise, in Example <NUM>, the quotient is about <NUM>, and the ratio is about <NUM>:<NUM>. In Example <NUM>, the quotient is <NUM>, and the ratio is <NUM>:<NUM>. Examples <NUM> and <NUM> do not fall under the scope of protection as defined in claim <NUM>.

Further, in Example <NUM>, the quotient is about <NUM>, and the ratio is about <NUM>:<NUM>. Furthermore, in Example <NUM>, the quotient is about <NUM>, and the ratio is about <NUM>:<NUM>.

On the other hand, as shown in [Table <NUM>], in Comparative Example <NUM>, the quotient is about <NUM>, and the ratio is about <NUM>:<NUM>. In Comparative Example <NUM>, the quotient is <NUM>, and the ratio is <NUM>:<NUM>. Further, in Comparative Example <NUM>, the quotient is <NUM>, and the ratio is about <NUM>:<NUM>. Furthermore, in Comparative Example <NUM>, the quotient is about <NUM>, and the ratio is about <NUM>:<NUM>. Moreover, in Comparative Example <NUM>, the quotient is <NUM>, and the ratio is <NUM>:<NUM>.

As shown in [Table <NUM>], in Comparative Example <NUM>, the quotient is about <NUM>, and the ratio is about <NUM>:<NUM>.

In Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM>, spectral reflectance distributions in the visible region were measured by using a measuring machine. <FIG> shows the spectral reflectance distributions in the visible region according to Examples <NUM> to <NUM> and Comparative Example <NUM>, and <FIG> shows the spectral reflectance distributions in the visible region according to Comparative Examples <NUM> to <NUM>.

According to the reflectance distributions shown in <FIG>, in each of Examples <NUM> to <NUM> and Comparative Example <NUM>, the maximum reflectance in the visible region (in which the wavelength is greater than or equal to <NUM> and not greater than <NUM>) is not greater than <NUM>%. More specifically, the transmittance of <NUM>% at the wavelength of <NUM> in Example <NUM> is the maximum reflectance. Therefore, it is found that each of Examples <NUM> to <NUM> and Comparative Example <NUM> has antireflective performance in the visible region.

In contrast, according to the reflectance distributions shown in <FIG>, in Comparative Examples <NUM> to <NUM>, the maximum reflectance in the visible region is about <NUM> to <NUM>%, and therefore it is hard to say that Comparative Examples <NUM> to <NUM> have sufficient antireflective performance in the visible region.

That is, when the quotient obtained by dividing the physical thickness of the fourth layer by the physical thickness of the second layer is greater than or equal to <NUM> as in Examples <NUM> to <NUM> and Comparative Example <NUM>, a sufficient antireflective function in the visible region can be achieved. On the other hand, when the quotient obtained by dividing the physical thickness of the fourth layer by the physical thickness of the second layer is less than <NUM> as in Comparative Examples <NUM> to <NUM>, it is difficult to provide a sufficient antireflective function in the visible region.

Examples <NUM> to <NUM> and Comparative Example <NUM> were examined for heat resistance by a heat resistance test and an accelerated heat resistance test. Comparative Examples <NUM> to <NUM> were not examined for heat resistance because the antireflective properties thereof were insufficient.

Firstly, the heat resistance test will be described. Samples of Examples <NUM> to <NUM> and Comparative Example <NUM> were loaded in ovens which were set at temperatures indicated next to "Result of heat resistance test" in the following [Table <NUM>]. Measurement of a loading time during which each sample was placed in the oven was started simultaneously with loading of the sample in the oven. The measurement of the loading time was suspended each time the loading time reached <NUM> minutes, and the sample was taken out of the oven to visually recognize whether or not crack occurred. At a point in time when crack occurred, the heat resistance test for each of Examples <NUM> to <NUM> and Comparative Example <NUM> was ended. On the other hand, when crack did not occur, each sample was returned to the oven and measurement of the loading time was resumed. When the loading time for each temperature reached <NUM> minutes in total, loading at that temperature was ended, and the sample was loaded in the oven set at a one-stage (<NUM>) higher temperature, and then measurement of the loading time was started from the beginning.

The result of the heat resistance test is shown in [Table <NUM>].

According to [Table <NUM>], in Comparative Example <NUM> (having the quotient of about <NUM>, and the ratio of about <NUM>:<NUM>), the sample was loaded in the oven at <NUM>, and withstood until <NUM> minutes elapsed at <NUM>, but crack occurred after <NUM> minutes elapsed at <NUM>.

In contrast, in Example <NUM> (having the quotient of about <NUM>, and the ratio of about <NUM>:<NUM>), the sample was placed in the oven at <NUM>, and crack did not occur until <NUM> minutes elapsed at <NUM>. Also in Example <NUM> (having the quotient of about <NUM>, and the ratio of about <NUM>:<NUM>), crack did not occur until <NUM> minutes elapsed at <NUM>. Further, in Example <NUM> (having the quotient of <NUM>, and the ratio of <NUM>:<NUM>), crack did not occur until <NUM> minutes elapsed at <NUM>. Furthermore, in Example <NUM> (having the quotient of about <NUM>, and the ratio of about <NUM>:<NUM>), crack did not occur until <NUM> minutes elapsed at <NUM>. Moreover, in Example <NUM> (having the quotient of about <NUM>, and the ratio of about <NUM>:<NUM>), crack did not occur until <NUM> minutes elapsed at <NUM>.

Accordingly, it is found that, as compared to the Comparative Example, Example <NUM> has the higher heat resistance, and Examples <NUM>, <NUM>, <NUM> and <NUM> have still higher resistances in this order.

Next, the accelerated heat resistance test will be described. Samples of Examples <NUM> to <NUM> and Comparative Examples were loaded in a constant temperature constant humidity tester (LHU-<NUM> manufactured by ESPEC Corp. ) kept at a temperature of <NUM> and a humidity of <NUM>%, and were left continuously for <NUM> days (<NUM> hours). Thereafter, the samples were taken out of the constant temperature constant humidity tester, and were subjected to the same procedure as the heat resistance test by using ovens set at temperatures indicated next to "Result of accelerated heat resistance test" in the following [Table <NUM>]. Loading of the samples in the constant temperature constant humidity tester provides, in a short time, the same states of the samples as those obtained after a long period of time.

[Table <NUM>] shows the result of the accelerated heat resistance test.

According to [Table <NUM>], in Comparative Example <NUM> (having the quotient of about <NUM>), the sample was loaded in the oven at <NUM>, and withstood until <NUM> minutes elapsed at <NUM>, but crack occurred after <NUM> minutes elapsed at <NUM>.

In contrast, in Example <NUM> (having the quotient of about <NUM>), the sample was loaded in the oven at <NUM>, and crack did not occur until <NUM> minutes elapsed at <NUM>. Also in Example <NUM> (having the quotient of about <NUM>), crack did not occur until <NUM> minutes elapsed at <NUM>. Further, in Example <NUM> (having the quotient of <NUM>), crack did not occur until <NUM> minutes elapsed at <NUM>. Furthermore, in Example <NUM> (having the quotient of about <NUM>), crack did not occur until <NUM> minutes elapsed at <NUM>. Moreover, in Example <NUM> (having the quotient of about <NUM>), crack did not occur until <NUM> minutes elapsed at <NUM>.

Accordingly, it is found that, as compared to Comparative Example, Example <NUM> has the equivalent heat resistance (durability of heat resistance performance) after elapse of a long period of time, Example <NUM> has a little higher heat resistance after elapse of a long period of time, and Examples <NUM>, <NUM> and <NUM>, in this order, have still higher heat resistances after elapse of a long period of time.

As in Examples <NUM> to <NUM>, when the quotient obtained by dividing the physical thickness of the fourth layer in the optical multilayer film by the physical thickness of the second layer is not greater than <NUM>, it is possible to achieve sufficient heat resistance while providing an antireflective function in the visible region, in the simple and easy-to-form optical multilayer film having the five-layer structure using SiO<NUM> and ZrO<NUM>. When the quotient is less than <NUM> as in Comparative Examples <NUM> to <NUM>, it is difficult to design the optical multilayer film for providing a sufficient antireflective function in the visible region.

As is understood from Example <NUM> to Example <NUM> seen in order, as the quotient approaches closer to <NUM> (the ratio of the physical thickness of the fourth layer to that of the second layer approaches closer to <NUM>:<NUM>), the heat resistance is more improved while the antireflective function is maintained.

Claim 1:
An optical product having, on one or both of surfaces of a base, an optical multilayer film that satisfies each of the following conditions:
(<NUM>) a five-layer structure in which SiO<NUM> and ZrO<NUM> are alternately layered, is formed; and
(<NUM>) with a layer closest to the base being a first layer, a quotient obtained by dividing a physical thickness of a fourth layer that is ZrO<NUM> by a physical thickness of a second layer that is ZrO<NUM> is greater than or equal to <NUM>, characterized in that
the quotient is <NUM> or <NUM> so that a crack did not occur when the optical product was placed in an oven at least until <NUM> minutes elapsed at <NUM>, or
the quotient is <NUM> so that a crack did not occur when the optical product was placed in an oven at least until <NUM> minutes elapsed at <NUM>.