JP4345123B2 - Resin bonded optical element and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resin-bonded optical element in which a resin layer and an optical thin film layer are provided on a substrate, and a method for producing the same.
[0002]
[Prior art]
As a lens which is an optical element, there is an aspherical lens whose surface shape is an aspherical surface. Aspherical lenses are used heavily because they can eliminate spherical aberration caused by spherical lenses and distortion in wide-angle lenses.
Currently, there is a resin-bonded aspheric lens as an aspheric lens excellent in mass productivity. This lens is composed of a thin cured resin layer 12 (for example, having a thickness of 5 to 100 μm) as shown in FIG. 1 and a lens 11 as a substrate (base material).
[0003]
In the lens of FIG. 1, the lens substrate 11 has a spherical surface, and the cured resin layer 12 is bonded on the spherical surface with a thickness distribution that forms an aspherical surface. Further, optical thin film layers 13 are further formed on the optical surfaces of the cured resin layer 12 and the lens substrate 11, respectively.
The lens base material and the cured resin layer in such a resin-bonded aspheric lens are bonded by, for example, a process shown in FIG. In the following description of steps, the numbers in parentheses correspond to steps (1) to (4) in FIG.
[0004]
(1) A mold 23 having a predetermined surface shape (planar surface, spherical surface, aspherical surface, etc.) is placed horizontally, and a predetermined amount of photocurable resin liquid 22a is hung on the center of the surface.
(2) The lens base material (optical element base material) 21 is lowered toward the mold 23, and the base material 21 is brought close to the mold 23, so that the resin liquid 22 a is formed in the gap between the base material 21 and the mold 23. Push out.
[0005]
Here, as the material of the base material 21, glass or a crystalline optical material is used. Further, the surface of the base material 21 may be subjected to a silane coupling treatment for the purpose of improving the adhesive strength with the resin layer.
(3) The lens base material 21 and the mold 23 are brought close to each other so that the distance between the lens base material 21 and the mold 23 becomes a predetermined value, and this state is maintained, and light (ultraviolet rays) 24 is irradiated to the resin liquid 22a through the base material 21. The resin liquid 22a is cured by a polymerization reaction to form a cured resin layer (cured resin layer) 22.
[0006]
(4) The cured resin layer 22 integrated with the lens substrate 21 is peeled off from the interface with the mold 23.
Through the steps as described above, the lens substrate and the cured resin layer in the resin-bonded aspheric lens (resin-bonded optical element) can be bonded.
Thereafter, depending on the purpose of use of the optical element, for example, an optical thin film such as an antireflection film is applied to the surface of the cured resin layer on the substrate, or the surface of the cured resin layer and the substrate surface (the cured resin layer is formed). If it is provided on both of the uncoated base material surfaces, a resin-bonded optical element is completed.
[0007]
The optical thin film on the substrate surface side may be formed either before or after the resin layer joining step. Moreover, as a method for forming an optical thin film, for example, vacuum deposition, sputtering, plasma CVD, dip coating, or the like can be used.
[0008]
[Problems to be solved by the invention]
The resin-bonded optical element manufactured by such a conventional method often has an aspheric optical surface, and is incorporated into a camera lens or the like for the purpose of improving optical performance such as aberration. The
However, there is a problem that the surface of the resin layer of such a resin-bonded optical element has a larger surface roughness than the polished surface of a conventionally used glass optical element.
[0009]
In general, when an optical thin film is formed on a substrate, the surface roughness of the formed optical thin film is larger than the surface roughness of the substrate, and the degree depends on the surface roughness of the substrate.
That is, the surface roughness of an optical thin film formed on a conventional glass lens with a small surface roughness is not much different from that of a glass lens, but there is no problem, but the surface roughness of an optical thin film formed on the surface of a resin layer with a large surface roughness. Has a problem that it becomes larger than the surface of the resin layer.
[0010]
Therefore, when a resin-bonded optical element is used, some optical performance (such as aberrations) can be improved, but other optical performance such as large scattering on the optical surface of the resin layer, flare, etc. There was a problem of deteriorating.
The present invention has been made in view of such problems, and has a resin-bonded optical element in which the surface roughness of an optical thin film is reduced as compared with the prior art to prevent optical performance deterioration phenomena such as scattering and flare, and a method for manufacturing the same. The purpose is to provide.
[0011]
[Means for Solving the Problems]
[0012]
The present invention includes the steps of forming a plating layer on the surface of a mold base material, and forming a mold surface by polishing the plating layer so that the average surface roughness Ra of the plating layer is 4 nm or less. A step of sandwiching a photocurable resin liquid between a lens base material having an average surface roughness Ra of 4 nm or less and the mold surface, and the lens base material and the mold surface while spreading the resin liquid. And a step of bringing both of them closer to a position where the distance between them is a predetermined value or a predetermined range, and irradiating the resin liquid with light while maintaining the positions of the lens base and the mold surface. Curing and forming a cured resin layer to be integrated with the lens base material, and transferring the shape of the mold surface to the surface of the cured resin layer so that the average surface roughness Ra of the cured resin layer is the metal mold. a step of substantially equal to the average surface roughness Ra of the mold surface, the hard A step of removing the lens substrate on which a resin layer is formed from the mold surface, the surface and the not hardened resin layer is formed surface of the lens base material of the cured resin layer, the average surface roughness Ra Forming an optical thin film layer of 5 nm or less, and a method for manufacturing a resin-bonded lens (claim 1).
[0013]
Further, the present invention is “a method for manufacturing a resin-bonded lens according to claim 1, wherein the mold is disposed substantially horizontally such that the mold surface faces upward, and the mold surface” Dropping the predetermined amount of the resin liquid on, placing the lens base material substantially horizontally on the resin liquid, and controlling the distance between the lens base material and the mold surface, A method for manufacturing a resin-bonded lens, comprising: a step of pushing the resin liquid to a predetermined range from a central part toward a peripheral part in a gap between the lens base material and the mold surface. To do.
[0014]
Further, the present invention is “a method for producing a resin-bonded lens according to claim 2, wherein a step of dropping a predetermined amount of the resin liquid near the center of the mold surface; the mold upward, the production method (claim of resin bonding type lens that includes a step of mounting substantially horizontally such that the optical center axis of said mold surface and said lens base material of the optical center axis coincides 4 ) ”.
[0015]
Further, the present invention is “a method for manufacturing a resin-bonded lens according to claim 3, wherein the mold has the optical center axis of the mold surface and the optical center axis of the lens substrate coincide with each other. By making the distance between the lens base and the lens base close, the resin liquid is brought into contact with the vicinity of the center of the mold surface, and the distance between the lens base and the mold surface is controlled. to provide a method of manufacturing a resin bonding type lens (claim 5) "that includes a step of pushing to a predetermined extent toward the peripheral portion from the central portion in the gap between the liquid and the lens substrate the mold surface.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
As a result of diligent research, the present inventors have determined that the surface roughness (Ra) of the optical thin film formed on the optical surface is 5 nm or less in order to prevent optical performance deterioration such as scattering and flare in the resin-bonded optical element. I found it necessary.
Therefore, in the resin-bonded optical element according to the present invention (claims 1 to 8) in which a resin layer and an optical thin film layer are provided on a base material, on the optical surface of the resin layer, or on the optical surface of the resin layer and The average surface roughness (Ra) of the optical thin film layer provided on the base material (base material surface provided with no resin layer) was 5 nm or less.
[0020]
According to the resin-bonded optical element according to the present invention (claims 1 to 8), the surface roughness of the optical thin film can be reduced as compared with the prior art, and optical performance deterioration phenomena such as scattering and flare can be prevented.
Furthermore, the present inventors have found the following as a result of earnest research.
1) The surface roughness (Ra) of the mold used during resin molding and the surface roughness (Ra) of the resin molding surface are substantially the same.
2) Factors that determine the surface roughness of the optical thin film include the apparatus conditions at the time of thin film formation and the surface roughness of the base material. The surface roughness of the base material has a greater effect.
3) In order for the average surface roughness (Ra) of the optical thin film to be 5 nm or less, the average surface roughness (Ra) of the optical surface of the substrate needs to be 4 nm or less.
[0021]
Based on this, the present inventor is a resin-bonded optical element in which a resin layer and an optical thin film layer are provided on a base material. In order to obtain a resin-bonded optical element having an average surface roughness (Ra) of 5 nm or less on the material (substrate surface on which no resin layer is provided), the average surface roughness (Ra The manufacturing method according to claims 2 to 8 is carried out using a mold having a mold surface of 4 nm or less.
[0022]
For example, the resin-bonded optical element according to the present invention uses a mold having a mold surface with an average surface roughness (Ra) of 4 nm or less to bond the optical element substrate and the resin layer, and then the resin It can be obtained by forming an optical thin film such as an antireflection film on the surface of the layer. Although this invention does not depend on the material and manufacturing method of the metal mold | die to be used, the metal mold | die manufactured by the following methods can be used, for example.
[0023]
1) A stainless steel block is machined with a lathe to form a mold and a mold base material.
2) A Ni-P plating layer is formed on the mold base material.
3) Cutting the mold surface (Ni-P layer) with an ultra-precision lathe to obtain the desired mold surface shape.
4) Polish the mold surface to the desired surface roughness.
[0024]
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
[0025]
【Example】
In the resin-bonded optical elements according to Examples 1 to 3 in which the resin layer and the optical thin film layer are provided on the base material, the optical thin film layer is on the optical surface of the resin layer and on the base material (no resin layer is provided). The average surface roughness (Ra) of the optical thin film layer is 5 nm or less.
[0026]
According to the resin-bonded optical elements according to Examples 1 to 3, the surface roughness of the optical thin film can be reduced as compared with the prior art, and optical performance deterioration phenomena such as scattering and flare can be prevented.
The resin-bonded optical elements according to Examples 1 to 3 were manufactured by the method according to claims 2 to 8.
[Example 1]
9. The manufacturing method according to claim 2, wherein a 100 μm-thick Ni—P plating layer formed on the surface of a stainless steel mold base material is polished, and the surface roughness (Ra) of the mold surface is 0.3 nm. A resin-bonded optical element of this example was manufactured using the mold described above.
[0027]
The average surface roughness (Ra) of the mold surface was measured using a scanning probe microscope M5 manufactured by Park Scientific Instruments, and 5 locations were selected from the entire mold surface within a 5 μm square measurement range. I went.
It was 0.4 nm when the average surface roughness (Ra) of the resin layer concerning a present Example was measured.
[0028]
Furthermore, an antireflection film (optical thin film layer) was formed on the surface of the resin layer by vacuum deposition, and the average surface roughness (Ra) was measured to be 0.7 nm.
When the resin-bonded optical element of this example was incorporated into a camera lens and confirmed, it was free from scattering and flare and had sufficient performance as an optical element.
[Example 2]
9. The manufacturing method according to claim 2, wherein a 100 μm-thick Ni—P plating layer formed on the surface of a stainless steel mold base material is polished, and an average surface roughness (Ra) of the mold surface is 1.2. A resin-bonded optical element of this example was manufactured using a mold having a thickness of nm.
[0029]
The average surface roughness (Ra) of the mold surface was measured in the same manner as in Example 1.
The average surface roughness (Ra) of the resin layer according to this example was measured and found to be 1.2 nm.
Further, an antireflection film (optical thin film layer) was formed on the surface of the resin layer by sputtering, and the average surface roughness (Ra) was measured to be 1.2 nm.
[0030]
When the resin-bonded optical element of this example was incorporated into a camera lens and confirmed, it was free from scattering and flare and had sufficient performance as an optical element.
[Example 3]
9. The manufacturing method according to claim 2, wherein a mold base material made of stainless steel (trade name: STAVAX) is polished and an average surface roughness (Ra) of the mold surface is 3.7 nm. Thus, a resin-bonded optical element of this example was manufactured.
[0031]
The average surface roughness (Ra) of the mold surface was measured in the same manner as in Example 1.
It was 3.6 nm when the average surface roughness (Ra) of the resin layer concerning a present Example was measured.
Furthermore, when an antireflection film (optical thin film layer) was formed on the surface of the resin layer by sputtering, and the average surface roughness (Ra) was measured, it was 4.9 nm.
[0032]
When the resin-bonded optical element of this example was incorporated into a camera lens and confirmed, it was free from scattering and flare and had sufficient performance as an optical element.
In addition, the predetermined amount was dripped at the resin liquid concerning each said Example with a dispenser using brand name Aronix UV3700 or Aronix 3033HV (made by Toa Gosei Chemical Co., Ltd.).
[0033]
Moreover, in order to improve the adhesive force with the cured resin layer, the surface of the optical element substrate was subjected to silane coupling treatment. As the silane coupling agent, a product name KBM503 (manufactured by Shin-Etsu Chemical Co., Ltd.) diluted in ethanol to give a 2 wt% ethanol solution was used.
In addition, a cured resin layer was formed by polymerizing the resin liquid by irradiating for 60 seconds using a xenon lamp with an output of 150 W as a light source.
[0034]
【The invention's effect】
As described above, according to the resin-bonded optical element according to the present invention (Claims 1 to 8), the surface roughness of the optical thin film is reduced as compared with the prior art, and optical performance deterioration phenomena such as scattering and flare are reduced. Can be prevented.
ADVANTAGE OF THE INVENTION According to this invention, the surface roughness of an optical thin film is small, and it can provide the resin bonded optical element with few scattering and flare.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a resin-bonded optical element.
FIG. 2 is a process diagram showing an example of a method for joining a resin layer and an optical element substrate in a resin-bonded optical element.
[Explanation of symbols]
11, 21 ... optical element base material 12, 22 ... cured resin layer 22 a ... resin liquid 13 ... optical thin film layer, 23 ... mold

Claims (4)

Forming a plating layer on the surface of the mold base material;
Polishing the plated layer to form a mold surface such that the average surface roughness Ra of the plated layer is 4 nm or less;
Sandwiching a photocurable resin liquid between a lens substrate having an average surface roughness Ra of 4 nm or less and the mold surface;
While spreading the resin liquid, the step of bringing both closer to a position where the distance between the lens substrate and the mold surface is a predetermined value or a predetermined range;
The resin liquid is cured by irradiating the resin liquid with light while maintaining the position of the lens base and the mold surface, and a cured resin layer is formed and integrated with the lens base. Transferring the shape of the mold surface to the surface of the cured resin layer to make the average surface roughness Ra of the cured resin layer substantially the same as the average surface roughness Ra of the mold surface;
Peeling the lens substrate on which the cured resin layer is formed from the mold surface;
Forming an optical thin film layer having an average surface roughness Ra of 5 nm or less on the surface of the cured resin layer and the surface of the lens base material on which the cured resin layer is not formed. Production method. A method for producing a resin-bonded lens according to claim 1,
A step of installing a substantially horizontal countercurrent memorial said mold on said mold surface,
Dropping a predetermined amount of the resin liquid onto the mold surface;
Placed substantially horizontally on top of the resin solution the lens substrate, and by controlling the distance between the lens substrate and the mold surface, the mold surface and the lens substrate the resin solution method for manufacturing a resin bonding type lens that includes a step of pushing to a predetermined extent toward the peripheral portion from the central portion in the gap between the. A method for producing a resin-bonded lens according to claim 2,
A step of dropping the liquid resin of a predetermined amount near the center of the mold surface,
Wherein the lens substrate in the mold upper, resin bonding type lens that includes a step in which the optical center axis of said mold surface and said optical center of the lens substrate axis is placed substantially horizontally to match Manufacturing method. It is a manufacturing method of the resin junction type lens according to claim 3,
While is matched with the optical center axis of the optical center axis of the mold surface lens substrate, by approximating the distance between the lens substrate and the mold, near the center and the resin liquid of the mold surface And controlling the distance between the lens base material and the mold surface to allow the resin liquid to flow in a predetermined range from the central part to the peripheral part in the gap between the lens base material and the mold surface. method for manufacturing a resin bonding type lens that includes a step of pushing up.

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