JP2002328201A - Optical member having antireflection film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical member in which an antireflection film is formed on a plastic substrate having good heat resistance. SOLUTION: The optical member has a plastic substrate and an antireflection film having the layer structure type of λ/4-λ/2-λ/4 or λ/4-λ/4-λ/2-λ/4 from the substrate side (wherein λ=500 nm). The λ/2 structure has a high refractive index layer and is an equivalent film to three or more layers having 1.80 to 2.40 refractive index. The layers with even numbers in the equivalent film are SiO2 layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical member having an anti-reflection film on a plastic substrate, and more particularly to an optical member having good heat resistance and having an anti-reflection film on a plastic substrate.

[0002]

2. Description of the Related Art Conventionally, optical members having an antireflection film formed on a plastic substrate are well known. For example, Japanese Patent Application Laid-Open No. 2-291501 discloses an optical member having an antireflection film having a high refractive index layer of λ / 2 containing titanium dioxide as a main component. However,
Generally, an optical member provided with an antireflection film on a plastic substrate cannot be heated at the time of vapor deposition.
Heat resistance is not good as compared with an optical member having an antireflection film provided on a glass substrate. Therefore, an optical member in which an antireflection film is formed on a plastic substrate having further improved heat resistance has been demanded.

[0003]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide an optical member having an antireflection film on a plastic substrate having good heat resistance.

[0004]

As a result of the inventor's intensive efforts to solve the above-mentioned problems, the present inventors have found that three or more layers are formed on the high refractive index layer by using a layer made of silicon dioxide which is a low refractive index substance. It has been found that the novel means of forming an equivalent film significantly improves the heat resistance of the optical member. Conventionally, λ / 2
In consideration of anti-reflection properties and production efficiency, the high refractive index layer is made of a single layer using a high refractive index deposition material such as titanium dioxide, zirconium oxide, and tantalum oxide. Since the provision of a layer made of silicon dioxide, which is a low-refractive-index substance, reduces the refractive index of the high-refractive-index layer and is likely to reduce the antireflection properties of the antireflection film, such a configuration is preferred. Had not been proposed.

That is, the present invention provides a plastic substrate and a λ / 4-λ / 2-
λ / 4 type or λ / 4-λ / 4-λ / 2-λ / 4 type (λ = 500n
m) and an antireflection film, wherein the λ / 2
Is an equivalent member having three or more layers having a refractive index of 1.80 to 2.40, and an even member of the equivalent film is a silicon dioxide layer.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, if the high refractive index layer of λ / 2 is made of three equivalent films, an optical member having good heat resistance and antireflection characteristics can be obtained. Furthermore, in order to obtain good heat resistance and antireflection characteristics, an equivalent film having more than three layers may be used.

The odd-numbered layers in the λ / 2 equivalent film are made of titanium oxide, zirconium oxide, tantalum oxide, and titanium oxide known as high-refractive-index deposition materials from the viewpoint of obtaining good heat resistance and reflectance characteristics. A layer containing a deposition material such as niobium is preferable, and in particular, TiO2, Ta2O5
And a layer composed of at least one kind of deposition material selected from Nb2O5, and most preferably N2O5.
b2 O5 is a layer made of a deposition material. From the viewpoint of production efficiency, it is preferable that all the odd layers have the same film composition. The combined refractive index of the high refractive index layer of λ / 2 is 1.80 to 2.
It is in the range of 40, and to obtain good physical properties, 1.85 to 2.25
Is particularly preferable, and the film configuration of the high refractive index layer of λ / 2 is made so as to satisfy this refractive index range.

In the present invention, a silicon dioxide layer is formed as the λ / 4 layer formed on the λ / 2 high refractive index layer. λ / 2
The λ / 4 layer formed below the high refractive index layer is preferably an equivalent film of two or more layers in order to obtain good antireflection characteristics and heat resistance. The film configuration is composed of a silicon dioxide layer, a two-layer equivalent film composed of a layer composed of a high-refractive-index deposition material such as titanium oxide, zirconium oxide, tantalum oxide, and niobium oxide, a silicon dioxide layer, and a layer composed of niobium oxide. A two-layer equivalent film is preferred. Further, from the viewpoint of production efficiency, the λ / 4
It is preferable to use the same vapor deposition material for producing the equivalent film as described above and the vapor deposition material for producing the λ / 2 equivalent film.

To form this niobium oxide layer, 100%
Of niobium oxide as a deposition material by an ion-assisted method or by sintering powder of niobium oxide, zirconium oxide and yttrium oxide, or further adding aluminum oxide, and mixing from the obtained sintered body It is preferable to use a method in which a vapor of an oxide is generated and the generated evaporant is deposited on a substrate. In the method of depositing the evaporant on the substrate, the mixing ratio of the sintered body is such that niobium oxide is 60 to 90% by weight and zirconium oxide is based on the total amount of the deposition composition in order to obtain good film properties. Is 5-20
% By weight and yttrium oxide is preferably from 5 to 35% by weight. Further, when adding aluminum oxide, it is preferable to add 0.3 to 7.5% by weight based on the total of niobium oxide, zirconium oxide and yttrium oxide.

In the optical member of the present invention, it is preferable that an underlayer is provided between the plastic substrate and the antireflection film. As the material of the underlayer, a silicon dioxide layer or niobium metal is preferable, and niobium metal is particularly preferable. preferable. Also,
In the case of a silicon dioxide layer, the thickness is preferably from 0.1 λ to 5 λ from the viewpoint of film strength and the like. When the material of the underlayer is made of niobium metal, it has advantages such as excellent adhesion between the plastic substrate and the antireflection film, excellent heat resistance, impact resistance, and abrasion resistance, and low absorptivity specific to metal.
The formation of the metal niobium (Nb layer) is preferably performed by an ion assist method. It is preferable to use argon (Ar) as an ionization gas for performing the ion assist method from the viewpoint of preventing oxidation during film formation. This makes it possible to stabilize the film quality and control with an optical film thickness meter.

Further, in order to ensure the adhesion between the plastic substrate and the underlayer and to make the state of forming the initial film of the deposition material uniform, an ion gun pretreatment may be performed before the underlayer is formed. Oxygen, argon, or the like can be used as the ionized gas in the ion gun pretreatment.
mA to 150 mA.

In the optical member of the present invention, as a method for forming the antireflection film, a usual vacuum deposition method, an ion assist method, or the like can be used. The plastic substrate used for the optical member of the present invention is not particularly limited. For example, methyl methacrylate homopolymer, methyl methacrylate and 1
Copolymers with at least one other monomer, diethylene glycol bisallyl carbonate homopolymer, copolymers of diethylene glycol bisallyl carbonate with one or more other monomers, sulfur-containing copolymers, halogen-containing copolymers, Examples thereof include polycarbonate, polystyrene, polyvinyl chloride, unsaturated polyester, polyethylene terephthalate, and polyurethane.

The optical member of the present invention may have a cured film between the plastic substrate and the underlayer. As the cured coating, a cured coating of a metal oxide colloid particle and an organosilicon compound is generally used. As the metal oxide colloid particles, for example, tungsten oxide (WO3), zinc oxide (ZnO), silicon oxide (SiO2), aluminum oxide (Al2O3), titanium oxide (TiO2), zirconium oxide (ZrO2), tin oxide ( SnO2), beryllium oxide (BeO) or antimony oxide (Sb2O)
5) and the like, and these can be used alone or in combination of two or more.

In the optical member of the present invention, preferred embodiments include, for example, the following structures (a) to (c).

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The physical properties of the optical members in Examples 1 to 6 were measured by the following test methods. (1) Luminous transmittance The luminous transmittance Y of the plastic lens was measured using a plastic lens having an antireflection film on both surfaces as a sample and using a Hitachi spectrophotometer U-3410. (2) Luminous Reflectance The luminous reflectance Z of the plastic lens was measured using a Hitachi spectrophotometer U-3410 using a plastic lens having an antireflection film on both surfaces as a sample. (3) Adhesion 100 squares of 1 mm x 1 mm were formed on the surface of the plastic lens with a razor, a cellophane tape was stuck on the squares, the tape was removed at a stretch, and the number of remaining squares was evaluated. In the table, it is described by the number of remaining cells / 100. (4) Abrasion resistance 1kg of steel wool on the surface of plastic lens
A load of f / cm ² was applied, rubbed for 20 strokes, and evaluated according to the following criteria according to the surface condition. UA: Almost no scratch A: Several fine scratches B: Many fine scratches, several thick scratches C: Many fine scratches, many thick scratches D: Almost peeling state

(5) Heat resistance The plastic lens is heated in a dry oven for one hour,
The crack generation temperature was measured. The heating temperature was started from 50 ° C. and increased by 5 ° C. at a time, and the temperature at which cracks were generated was examined. (6) Alkali Resistance A plastic lens was immersed in a 10% NaOH aqueous solution for 1 hour, and evaluated according to the following criteria according to the surface condition. UA: Almost no change A: There are several point-like film bale B: Point-like film bale is on the entire surface C: Point-like bale is all over, there are several planar bale D: Almost all the film bale (7 ) Impact resistance A lens having a center thickness of 2.0 mm and a lens power of 0.00 was manufactured and subjected to a drop ball test defined by the FDA.

Examples 1 to 6 Preparation of Substrate A and Hard Coat Layer A In a glass container, colloidal silica (Snotex®) was used.
40, Nissan Chemical) 90 parts by weight, 81.6 parts by weight of methyltrimethoxysilane as an organosilicon compound, 176 parts by weight of γ-glycidoxypropyltrimethoxysilane, 0.5N
A solution obtained by adding 2.0 parts by weight of hydrochloric acid, 20 parts by weight of acetic acid, and 90 parts by weight of water was stirred at room temperature for 8 hours, and then left at room temperature for 16 hours to obtain a hydrolysis solution. To this solution, 120 parts by weight of isopropyl alcohol, 120 parts by weight of n-butyl alcohol, 16 parts by weight of aluminum acetylacetone, 0.2 parts by weight of a silicone-based surfactant, and 0.1 part of an ultraviolet absorber
The mixture was stirred at room temperature for 8 hours and then aged at room temperature for 24 hours to obtain a coating liquid. Plastic lens substrate pretreated with an aqueous alkali solution (material: diethylene glycol bisallyl carbonate, refractive index 1.50, center thickness 2.0 mm, lens power 0.00,
It may be referred to as “substrate A”. ) Is immersed in the coating solution, and after the immersion, the lifting speed is 20 cm.
The heated plastic lens was heated at 120 ° C. for 2 hours to form a cured film. Thereafter, an ion gun treatment is performed using Ar gas under the conditions of the ion acceleration voltage and irradiation time described in Tables 1 to 6, and a hard coat layer (hereinafter, referred to as “A layer”) is formed as a cured film by an ion assist method. May be formed).

Preparation of Underlayer and Antireflection Film Next, the first to eighth layers shown in Tables 1 to 3 were formed on the hard coat A layer by the ion assist method under the conditions shown in Tables 1 to 3. A functional film composed of layers was formed to obtain a plastic lens. About the obtained plastic lens, the above (1)-
(7) was evaluated, and the results are shown in Tables 1 to 6.
In the table, λ is the wavelength of the irradiation light, and λ = 500 nm. Table 8 shows the combined refractive index of λ / 4 and λ / 2 in Examples 1 to 6.

[0021]

[Table 4]

[0022]

[Table 5]

[0023]

[Table 6]

Examples 7 to 24 and Comparative Examples 1 to 6 The physical properties of Examples 7 to 24 and Comparative Examples 1 to 6 were evaluated by the following evaluation methods. (1) Melting state of vapor deposition composition The melting state at the time of vapor deposition was determined according to the following criteria. UA: No splash generated A: Less splash generated B: Splash generated frequently C: Splash constantly generated (2) Attachment state of fine particles The attached state of fine particles on the lens surface due to splash etc. is as follows. Judgment was made based on the following criteria. UA: Not recognized at all A: Within 1 to 5 places B: 6 to 10 places C: 11 or more places (3) Alkali resistance test A lens was placed in a 10% by weight aqueous solution of NaOH, and after 30 minutes, 60
After one minute, the occurrence of film baldness on the surface and roughness of the lens surface was determined according to the following criteria. UA: almost no point bald A: small point bald of 0.1 mm or less overall or 0.3 mm in diameter
There is a little point baldness. B: The bald density is higher than that of A, and the ratio of large baldness is higher. C: The bald of about 0.3 mm occupies the entirety or the density of small balds is higher. D: The whole looks white at first glance. Bald is coming out densely. Below this is all D. (4) Scratch resistance test 1 surface reciprocation with # 0000 steel wool
Rubbing was performed 0 times and the scratch resistance was determined according to the following criteria. UA: Almost no damage A: Slightly scratched B: Many scratches C: Bloat of membrane occurs

(5) Adhesion test According to JIS-Z-1522, 10 × 10 gobangs are made and a peeling test is performed three times with a cellophane adhesive tape.
The remaining Goban eyes were counted. (6) Luminous Reflectance The luminous reflectance Y was determined using a U-3410 type self-recording spectrophotometer manufactured by Hitachi, Ltd. (7) Luminous transmittance The luminous transmittance Z was determined using a U-3410 type self-recording spectrophotometer manufactured by Hitachi, Ltd. (8) Absorbance The value obtained by subtracting the luminous transmittance and the luminous reflectance from 100% was determined as the absorptivity. (9) Heat resistance test The optical member having the antireflection film immediately after the formation of the vapor-deposited film was heated in an oven for 1 hour, and the presence or absence of cracks was examined. The heating temperature was started from 50 ° C. and increased in steps of 5 ° C., and the temperature at which cracks occurred was examined. In addition, a heat resistance test with time was performed on the optical member having the antireflection film immediately after the formation of the deposited film.
It was exposed outdoors for a period of five months, and then evaluated by the same method as the heat resistance test described above.

Preparation of Substrate A and Hardcoat A Layer A substrate A and a hardcoat layer A were prepared in the same manner as in Examples 1 to 6. Preparation of Substrate B and Hard Coat B Layer To a glass container, 142 parts by weight of an organosilicon compound, γ-glycidoxypropylmethoxysilane, are added, with stirring, 1.4 parts by weight of 0.01 N hydrochloric acid, water 32 parts by weight were added dropwise. After completion of the dropwise addition, the mixture was stirred for 24 hours to obtain a hydrolysis solution of γ-glycidoxypropyltrimethoxysilane. In this solution, 460 parts by weight of a stannic oxide-zirconium oxide composite sol (methanol dispersion, 31.5% by weight of all metal oxides, average particle diameter of 10 to 15 millimicrons), 300 parts by weight of ethyl cellosolve, and as a lubricant 0.7 parts by weight of a silicone-based surfactant and 8 parts by weight of aluminum acetylacetonate as a curing agent were added, sufficiently stirred, and then filtered to obtain a coating liquid. Furthermore, a plastic lens substrate pretreated with an alkaline aqueous solution [HOYA CORPORATION, plastic lens for eyeglasses (trade name: EYAS), refractive index 1.60 or less, this substrate may be referred to as “substrate B”. Is immersed in the coating solution, and after the immersion, a lifting speed of 20 c
Plastic lens raised at m / min.
Heating was performed for a time to form a hard coat layer (hereinafter, this layer may be referred to as "B layer").

Preparation of Substrate C and Hard Coat C Layer 100 parts by weight of the organosilicon compound γ-glycidoxypropyltrimethoxysilane was added to a glass container, and 1.4 parts by weight of 0.01 N hydrochloric acid was added with stirring. And 23 parts by weight of water. Thereafter, stirring was carried out for 24 hours to obtain a hydrolyzate of γ-glycidoxypropyltrimethoxysilane. Next, as a particulate inorganic substance, a composite particulate sol mainly composed of titanium oxide, zirconium oxide and silicon oxide (methanol dispersion, total solid content 20% by weight, average particle diameter 5 to 15 millimicron, atomic ratio Ti / Si = 10, and the weight ratio of the coated portion to the core portion was 0.25).
After mixing 00 parts by weight with 100 parts by weight of ethyl cellosolve, 0.5 part by weight of a silicone surfactant as a lubricant, and 3.0 parts by weight of aluminum acetylacetonate as a curing agent, the above-mentioned γ-glycidoxypropyl was mixed. After adding to the hydrolyzate of trimethoxysilane and stirring thoroughly,
Filtration was performed to prepare a coating liquid. Furthermore, a plastic lens substrate [HO, pretreated with an aqueous alkali solution]
A plastic lens for eyeglasses (trade name: Teslalid), manufactured by YA Corporation, having a refractive index of 1.71, hereinafter this substrate is sometimes referred to as “substrate C”] was used in the coating liquid prepared by the method described above. After immersion, the plastic lens pulled up at a pulling speed of 20 cm / min.
C. for 2 hours to form a hard coat layer (hereinafter, this hard coat layer may be referred to as "C layer").

Preparation of Underlayer and Antireflection Film Next, on the hard coat A layer, B layer or C layer,
Under the conditions shown in Table 7, functional films consisting of the multilayer films shown in Tables 4 to 7 were formed, and plastic lenses were obtained. The above plastic lenses were evaluated for the above (1) to (7), and the results are shown in the same table. In the table, λ is the wavelength of the irradiation light, and λ = 500 nm. Examples 7-1
Regarding the composition No. 2, a film was formed on the composition A in the table without using the ion assist method. Moreover, the film formed from the vapor deposition composition A in Examples 13 to 18 and Examples 19 to
Regarding the niobium oxide layer in No. 24, when forming the film, the ratio of oxygen: argon was 9: 1, 320 A and 140 m.
Under the condition A, ion assist was used. Example 2
Regarding 5 to 27, films were formed without using the ion assist method, using titanium oxide as a high refractive index.

The compositions A described in Examples 7 to 18 in Tables 4 and 5 are Nb2O5 powder, ZrO2
Powder, Y2O3 powder, and mix at 300 kg / cm ²
Pressurized and sintered at a sintering temperature of 1300 ° C. to obtain a three-component vapor-deposition composition A (% by weight, Nb 2 O 5: Zr
O2: Y2O3 = 76% to 90%: 16.6% to 5
%: 7.4% to 5%). The combined refractive indices of λ / 4 and λ / 2 of the equivalent films in Examples 1 to 27 are as described in Table 8.

In Comparative Examples 1 and 2, tantalum oxide was used as a high-refractive-index deposition material, and an underlayer made of silicon dioxide was used.
A λ / 4 two-layer equivalent film composed of a tantalum oxide layer and a silicon dioxide layer, a λ / 2 tantalum oxide layer, and a λ / 4 silicon dioxide layer were formed. Comparative Example 3 shows that the substrate C and the hard coat layer C
Further, using tantalum oxide as a high refractive index deposition material, a third layer of silicon dioxide, a two-layer equivalent film of λ / 4 composed of a tantalum oxide layer and a silicon dioxide layer, a tantalum oxide layer of λ / 2, / 4 silicon dioxide layer was formed.

In Comparative Examples 4 and 5, titanium oxide was used as a high-refractive-index deposition material. A titanium oxide layer and a λ / 4 silicon dioxide layer were formed. In Comparative Example 6, a substrate C and a hard coat layer C were further used, and titanium oxide was used as a high-refractive-index deposition material, and a third layer composed of silicon dioxide, a two-layer of λ / 4 composed of a titanium oxide layer and a silicon dioxide layer. Equivalent film, λ / 2 titanium oxide layer, λ
/ 4 silicon dioxide layer was formed. Regarding Comparative Examples 1 to 6, films were formed without using the ion assist method.
As a result, Comparative Example 1 was inferior to Example 22, Comparative Example 2 was inferior to Example 23, and Comparative Example 3 was inferior to Example 24 in heat resistance.

[0032]

[Table 7]

[0033]

[Table 8]

[0034]

[Table 9]

[0035]

[Table 10]

[0036]

[Table 11]

[0037]

[Table 12]

[0038]

As described above in detail, the optical member having the antireflection film of the present invention has good luminous reflectance, luminous transmittance, adhesion, abrasion resistance, alkali resistance and impact resistance. And the heat resistance is further improved.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hitoshi Kamura 2-7-5 Nakaochiai, Shinjuku-ku, Tokyo F-term in Hoya Corporation (reference) 2K009 AA02 AA06 AA09 AA15 BB11 CC03 CC09 CC42 DD03 DD07 4F100 AA17C AA17D AA17E AA20B AA20C AA20E AA21D AA21E AH02B AH06B AK01A AK45A AR00B AS00C AT00A BA05 BA07 BA10A BA10E EJ53B GB90 JJ03 JK12B JN18C JN18D JN18E JN30 JN30Y JNY00N

Claims (11)

[Claims] 1. A plastic substrate and a λ / 4-λ / 2-λ / 4 type or λ / 4-λ on the plastic substrate from the substrate side.
An optical member having a / 4-λ / 2-λ / 4 type (λ = 500 nm) antireflection film, wherein the λ / 2 layer has a refractive index of 1.80.
An optical member having an anti-reflection film in which three or more equivalent films of up to 2.40, and an even number of the equivalent films are silicon dioxide layers. 2. The antireflection method according to claim 1, wherein the odd layer of the λ / 2 equivalent film is a layer made of at least one metal oxide selected from titanium oxide, niobium oxide and tantalum oxide. An optical member having a film. 3. The optical member having an antireflection film according to claim 1, wherein the odd layer of the equivalent film of λ / 2 is a layer made of niobium oxide. 4. The antireflection film according to claim 1, wherein the λ / 4 layer formed below the λ / 2 layer is an equivalent film of two or more layers. Optical members. 5. The optical member having an anti-reflection film according to claim 4, wherein the λ / 4 layer is formed of a metal oxide layer used as an odd layer and an even layer of the λ / 2 layer. 6. The optical member having an antireflection film according to claim 4, wherein the equivalent film of λ / 4 is composed of a layer made of niobium oxide and a silicon dioxide layer. 7. An optical member having an antireflection film according to claim 1, wherein a base layer is provided between the plastic substrate and the antireflection film. 8. An optical member having an antireflection film according to claim 7, wherein said underlayer is made of metal niobium. 9. An underlayer and a λ / 4 on a plastic substrate.
A λ / 2-λ / 4 type antireflection film is provided, and a base layer (first layer) and λ / 4 (second to third layers); λ / 2 (fourth to sixth layers);
λ / 4 (seventh layer) composed of first to seventh layers, wherein the first layer is a silicon dioxide layer having a refractive index of 1.43 to 1.47, the second layer is a high refractive index layer having a refractive index of 2.04 to 2.37, The third layer is a silicon dioxide layer having a refractive index of 1.43 to 1.47, the fourth layer is a high refractive index layer having a refractive index of 2.04 to 2.37, the fifth layer is a silicon dioxide layer having a refractive index of 1.43 to 1.47, and the sixth layer is A high refractive index layer having a refractive index of 2.04 to 2.37, the seventh layer is a silicon dioxide layer having a refractive index of 1.43 to 1.47,
The combined refractive index of λ / 4 (second and third layers) is 1.65 to 1.80, λ / 2
(The fourth to sixth layers) have a combined refractive index of 1.85 to 2.25, and the high refractive index layer is made of at least one metal oxide selected from titanium oxide, niobium oxide and tantalum oxide. An optical member having an antireflection film. 10. A plastic substrate, comprising: a base layer;
/ 4-λ / 2-λ / 4 type antireflection film is provided, and an underlayer (first layer) and λ / 4 (second to third layers) −λ / 2 (fourth to eighth layers) are provided.
Layer) -λ / 4 (ninth layer), wherein the first layer is a silicon dioxide layer having a refractive index of 1.43 to 1.47, and the second layer is a high refractive index having a refractive index of 2.04 to 2.37. The third layer is a silicon dioxide layer having a refractive index of 1.43 to 1.47, the fourth layer is a high refractive index layer having a refractive index of 2.04 to 2.37, the fifth layer is a silicon dioxide layer having a refractive index of 1.43 to 1.47, Six layers are high refractive index layers having a refractive index of 2.04 to 2.37, a seventh layer is a silicon dioxide layer having a refractive index of 1.43 to 1.47, an eighth layer is a high refractive index layer having a refractive index of 2.04 to 2.37, and a ninth layer is A silicon dioxide layer having a refractive index of 1.43 to 1.47,
The combined refractive index of λ / 4 (second and third layers) is 1.65 to 1.80, λ / 2
(The fourth to eighth layers) have a combined refractive index of 1.85 to 2.25, and the high refractive index layer is made of at least one metal oxide selected from titanium oxide, niobium oxide and tantalum oxide. An optical member having an antireflection film. 11. An underlayer and a λ on a plastic substrate.
/ 4-λ / 2-λ / 4 type antireflection film is provided, and an underlayer (first layer) and λ / 4 (second to fourth layers) −λ / 2 (5 to 7
Layer) -λ / 4 (eighth layer), wherein the first layer is a metal niobium layer having a thickness of 0.005λ to 0.015λ and a refractive index of 1.40 to 1.47, and the second layer is A silicon dioxide layer having a refractive index of 1.43 to 1.47, a third layer being a high refractive index layer having a refractive index of 2.04 to 2.37, a fourth layer being a silicon dioxide layer having a refractive index of 1.43 to 1.47, and a fifth layer being a refractive index of 2.04 to A high refractive index layer with a refractive index of 2.37, a sixth layer is a silicon dioxide layer with a refractive index of 1.43 to 1.47, a seventh layer is a high refractive index layer with a refractive index of 2.04 to 2.37, and an eighth layer is a dioxide layer with a refractive index of 1.43 to 1.47. A silicon layer,
The combined refractive index of λ / 4 (second to fourth layers) is 1.65 to 1.80, λ / 2
(The fifth to seventh layers) have a combined refractive index of 1.85 to 2.25, and the high refractive index layer is made of at least one metal oxide selected from titanium oxide, niobium oxide and tantalum oxide. An optical member having an antireflection film.