JP2006146025A - Plastic optical component, optical unit using the same and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide plastic optical components having excellent characteristics such as lightweight, low cost and mass-productivity, as well as excellent moisture-resistant performance, and showing little changes in the optical performance such as a refractive index even when influences of a water content in an environment are added, and to provide an optical unit using the plastic optical components, and a method for manufacturing the components. <P>SOLUTION: The plastic optical parts have a moisture-resistant film applied on at least a surface in contact with external air. The moisture-resistant film is an inorganic compound layer comprising an inorganic compound having the average particle size of 3 nm to 20 nm dispersed to give 1 nm to 20 nm average intergranular interfaces. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention belongs to the technical field of plastic optical parts such as lenses and prisms, optical units using the same, and manufacturing methods thereof, and in particular, plastic optical parts that have very little change in optical performance due to moisture absorption. The present invention relates to an optical unit using the same, and a manufacturing method thereof.

  Conventionally, most of optical components such as various lenses and prisms, spectacle lenses, contact lenses, and magnifiers used for camera lenses, viewfinders, copy machines, printers, projectors, optical communications, etc., are manufactured from glass. ing.

However, with recent advances in plastic materials and plastic molding technology, optical components such as lenses and prisms have been manufactured with plastics that are cheap, lightweight, and suitable for mass production as inexpensive optical components. Yes.
However, because plastics change optical performance such as refractive index due to moisture absorption, glass lenses are still used for applications that require high precision such as high-resolution single-lens reflex cameras. Has been.
In order to solve such problems, the development of a plastic material itself having high moisture resistance, that is, low hygroscopicity, has been carried out by designing the polymer structure, etc., but its cost becomes high, There is a problem that the cost merit of plastic is lost.

In addition, in order to obtain a plastic optical component having moisture resistance, a hydrophobic substance is added in the molding step of the optical component, the optical component is covered with a moisture-impermeable barrier film, or an antireflection film of the optical component is formed. An antireflection layer coating layer subjected to water / oil repellent treatment is provided on the surface (see Patent Document 1). It is also known to form a moisture absorption adjusting film only on the gate cut portion in order to improve the humidity stability of the plastic optical component (see Patent Document 2). Furthermore, an optical block made of a low hygroscopic material is installed in the optical system to optically compensate for performance changes due to moisture absorption (see Patent Document 3).
However, the moisture-proof plastic optical component obtained by the above prior art method and the plastic optical component having the barrier film, the antireflection layer and the antireflection layer coating layer described in Patent Document 1 have sufficient moisture resistance. There is a problem that the optical performance such as the refractive index due to moisture absorption cannot be prevented. Further, in the technique described in Patent Document 2, even if a moisture absorption adjusting film is provided only on the gate portion, it is substantially difficult to make the moisture absorption rate from the surroundings constant, coupled with moisture absorption from the surface, There is a problem that it is inevitable that an optically unfavorable refractive index distribution or its deviation occurs inside the lens. Furthermore, the technique described in Patent Document 3 has a problem that the optical system becomes complicated and the cost increases.

JP 2002-148402 A JP-A-11-109107 JP 2000-137166 A

  The object of the present invention is to solve the above-mentioned problems of the prior art, and in addition to the characteristics excellent in light weight, low cost, mass production suitability, etc. of plastic optical parts, it has excellent moisture-proof performance, To provide a plastic optical component that hardly changes in optical performance such as refractive index even under the influence of moisture present in the environment, an optical unit using the plastic optical component, and a method of manufacturing the same. .

In order to achieve the above object, the present invention provides a plastic optical component having a moisture-proof coating formed on at least the outside air contact surface,
The moisture-proof coating is a plastic optical component characterized in that it is an inorganic compound layer in which inorganic compounds having an average particle size of 3 nm to 20 nm are distributed so as to form an average grain boundary of 1 nm to 20 nm.

  In the plastic optical component of the present invention, the inorganic compound is selected from the group consisting of silicon oxide, silicon nitride, silicon oxynitride, metal oxide, metal nitride, metal oxynitride, and diamond-like carbon. It is preferable that it is at least one kind. More preferably, the inorganic compound is silicon dioxide.

  In the plastic optical component of the present invention, the inorganic compound layer preferably has a thickness of 10 nm to 1 μm.

  In the plastic optical component of the present invention, the inorganic compound layer is formed on the plastic optical component at a film forming pressure of 0.005 Pa to 0.13 Pa using reactive sputtering based on impedance control. It is preferable.

  The plastic optical component of the present invention preferably has a Sherwood number of 10 or less for moisture movement.

  The present invention also provides an optical unit including at least two lenses having different Abbe numbers, wherein at least one of the lenses is the plastic optical component of the present invention.

  The optical unit of the present invention preferably has an autofocus mechanism.

Further, the present invention is a method for producing a plastic optical component having an inorganic compound layer as a moisture-proof coating on at least the outside air contact surface,
A method for producing a plastic optical component, comprising forming an inorganic compound layer on the plastic optical component at a film forming pressure of 0.005 Pa to 0.13 Pa using reactive sputtering by impedance control. I will provide a.

  In the method for producing a plastic optical component of the present invention, the reactive sputtering is preferably performed at a discharge pressure of 480V to 660V.

  In the method for manufacturing a plastic optical component according to the present invention, it is preferable that the reactive sputtering is performed in a transition region.

  In the method for producing a plastic optical component according to the present invention, the plastic optical component is disposed such that an axis perpendicular to the optical axis is parallel to the target, and the plastic optical component is disposed on the optical optical component. The reactive sputtering may be performed while rotating about an axis perpendicular to the axis.

  In the method for producing a plastic optical component of the present invention, the inorganic compound layer is preferably a layer in which an inorganic compound having an average particle diameter of 3 nm to 20 nm forms an average grain boundary of 1 nm to 20 nm.

  In the method for producing a plastic optical component of the present invention, it is preferable that the reactive sputtering is performed using silicon as a target and oxygen gas as a reactive gas.

  According to the present invention, while maintaining the performance of excellent plastic optical components such as light weight, low cost, and productivity, it has excellent moisture-proof performance, and even if it is affected by moisture present in the environment, It is possible to easily provide and provide a plastic optical component with very little change in optical performance.

Since the optical unit of the present invention uses the plastic optical component of the present invention, even if the environmental change, specifically, the humidity in the environment changes, the refractive index distribution in the lens is biased. The change in the refractive index of the lens itself is gradual and the change is uniform. When the refractive index of the lens itself changes uniformly, if it is a minute change due to moisture absorption, the substantial effect on the optical performance is limited to the change of the focal position, and this change should be done using the autofocus mechanism. It is solved with.
Therefore, according to the present invention, it is possible to realize an excellent optical unit whose optical characteristics are not affected by environmental changes.

  In addition, according to the method for producing a plastic optical component of the present invention, a plastic optical component having excellent moisture proof performance and having very little change in optical performance such as resolution even under the influence of moisture present in the environment. It can be manufactured stably and with high productivity.

The plastic optical component of the present invention will be described in detail below based on a preferred embodiment shown in the accompanying drawings.
FIG. 1 is a conceptual diagram showing an embodiment of a plastic optical component of the present invention having a lens shape, and FIG. 1 (a) is a front view of the optical component (viewed from the optical axis direction). FIG. 1B is a cross-sectional view taken along a plane including the optical axis.
As shown in FIGS. 1A and 1B, an optical component 1 of the present invention is formed on a plastic optical component main body (here, a lens) 10 and at least an outside air contact surface of the optical component main body 10. And a moisture-proof coating 2. In the optical component 1 shown in FIGS. 1A and 1B, the moisture-proof coating 2 is formed on the entire surface of the optical component body 10.
Hereinafter, in this specification, the optical component main body widely represents a known optical component such as a lens, and the optical component is a component in which a moisture-proof coating is formed on at least the outside air contact surface of the optical component main body. To express.

  An optical component body 10 shown in FIGS. 1A and 1B has a general plastic lens shape, and has a lens portion 10a having an optical surface, a flange portion 10b provided outside the lens portion 10a, Consists of. In the optical component 1 shown in FIGS. 1A and 1B, the moisture-proof coating 2 is formed on the entire surface of the optical component main body 10 including the lens 10a and the flange 10b.

  The optical component 1 of the present invention has an inorganic compound layer in which an inorganic compound having an average particle size of 3 nm to 20 nm is distributed as an moisture-proof coating on at least the outside air contact surface of the optical component body 10 so as to form an average grain boundary of 1 nm to 20 nm. It is formed.

When the moisture-proof coating is an inorganic compound layer formed by a vapor deposition method, the inorganic compound layer is configured as an aggregate of fine inorganic compound particles. As a result of intensive studies on the moisture-proof performance of the inorganic compound layer, the present inventor has found that the balance between the particle diameter of the inorganic compound constituting the layer and the size of the grain boundary in the layer is very important. I found it. As a result of intensive studies based on this knowledge, an excellent moisture-proof coating is obtained by setting the average particle size of the inorganic compound constituting the inorganic compound layer to 3 nm to 20 nm and the average grain boundary of the inorganic compound layer to 1 nm to 20 nm. I found out that
In addition, a particle size represents the magnitude | size of each inorganic compound particle which comprises the inorganic compound layer. The grain boundary represents the distance between the boundaries of the inorganic compound particles in the inorganic compound layer.

  When forming a film using a vapor phase film forming method, the particle diameter of the inorganic compound constituting the inorganic compound layer is usually 3 nm or more. On the other hand, if the average particle size is more than 20 nm, the particles are too large, so it is difficult to obtain an inorganic compound layer having a predetermined grain boundary, and the resulting inorganic compound layer is inferior in moisture-proof performance.

  Moreover, when forming into a film using a gaseous-phase film-forming method, the grain boundary of an inorganic compound layer is 1 nm or more normally. On the other hand, if the grain boundary of the inorganic compound layer is more than 20 nm, the grain boundary becomes too large and the desired moisture-proof performance cannot be obtained.

In the present invention, as long as the moisture-proof coating is an inorganic compound layer having a particle size and a grain boundary in the above-described range, the kind of inorganic compound constituting the layer is not particularly limited, and various inorganic compounds can be used.
Specific examples include silicon oxide, silicon nitride, silicon oxynitride, metal oxides such as aluminum oxide and titanium oxide, metal oxynitrides such as aluminum oxynitride, and diamond-like carbon. Among these, the inorganic oxide is silicon oxide represented by SiO _x (0 <x ≦ 2) because a film having a dense structure and less absorption of light of the target wavelength can be obtained. Is preferred.
In the present invention, the inorganic compound layer may be composed of only one of the inorganic compounds described above, or may be composed of two or more inorganic compounds described above.

  In the optical component of the present invention, the thickness of the inorganic compound layer is preferably 10 nm to 1 μm. If the thickness of the inorganic compound layer is less than 10 nm, pinholes are generated in the layer, and the desired moisture-proof performance may not be obtained. On the other hand, if the film thickness of the inorganic compound layer is more than 1 μm, the contribution is no longer small from the viewpoint of moisture-proof performance, and it is rather not preferable from the viewpoint of productivity. In addition, cracks may occur due to residual stress, and the desired moisture-proof performance may not be obtained. Furthermore, if the thickness of the inorganic compound layer exceeds 1 μm, the shape accuracy of the optical component may be adversely affected.

  The optical component of the present invention is inorganic on at least the outside air contact surface of the optical component body by using a known vapor deposition method in which the film formation conditions are adjusted to satisfy the above conditions (average particle diameter and average grain boundary). It can be produced by forming a compound layer, but preferably, by using the method for producing an optical component of the present invention shown below, reactive sputtering is performed under specific conditions to form an inorganic compound layer. Form a film.

  The optical component manufacturing method of the present invention is characterized in that an inorganic compound layer is formed on the plastic optical component at a film forming pressure of 0.005 Pa to 0.13 Pa using reactive sputtering by impedance control. And

As is well known, reactive sputtering by impedance control is a technique in which the voltage applied to the cathode is kept constant, and the flow rate of the reaction gas such as oxygen gas is adjusted to keep sputtering voltage constant. It is.
Impedance control is originally known as a film formation voltage control method developed to increase the film formation rate. As a result of repeated studies to obtain an inorganic oxide layer excellent in moisture-proof performance, the present inventors obtain a dense inorganic oxide layer excellent in moisture-proof performance by setting the film forming pressure to 0.2 Pa or less. I found that it was possible.
However, when the film forming pressure is 0.2 Pa or less, the discharge is not stable and the film forming state becomes unstable. In order to solve this problem, the present inventor further examined and, if reactive sputtering is performed by impedance control, a stable discharge can be obtained even if the film forming pressure is lowered, and the film forming pressure is reduced to 0. It has been found that a dense inorganic compound layer satisfying the above conditions can be stably formed at a high film formation rate by setting the pressure to 0.005 Pa to 0.13 Pa.

  When the film forming pressure is less than 0.005 Pa, stable discharge cannot be maintained even by reactive sputtering by impedance control. On the other hand, when the film forming pressure is more than 0.13 Pa, it is not possible to form a dense inorganic compound layer that satisfies the above-described conditions.

If impedance control is not used, stable discharge cannot be obtained under this deposition pressure.
For adjusting the amount of reaction gas for impedance control, various known means can be used, but the response is high and the discharge voltage can be stably maintained even at a low film formation pressure. Therefore, it is preferable to use a piezo valve.

  In the production method of the present invention, when performing reactive sputtering discharge by impedance control under the above film forming pressure, the discharge voltage is not particularly limited, but stable discharge can be obtained and a realistic film forming rate can be obtained. Therefore, 480V to 660V is preferable, and 570V to 630V is particularly preferable.

  In the production method of the present invention, the reactive sputtering by impedance control under the film forming pressure is preferably performed in a transition region between the metal region and the reactive region (hereinafter simply referred to as “transition region”). When reactive sputtering is performed in the transition region, the film formation rate can be increased as compared with normal reactive sputtering performed in the reactive region, so that productivity can be improved. In addition, since the amount of the reaction gas is smaller than that of normal reactive sputtering, the film forming pressure can be lowered. This is preferable for maintaining the film forming pressure in the above-described range.

  By performing film formation with the discharge voltage in the above range, it becomes possible to stably perform reactive sputtering by impedance control at the film formation pressure described above in the transition region. When the discharge voltage is less than 480 V, it is difficult to control the impedance, and the film formation rate is lowered from the transition region to the reactive region. On the other hand, when the discharge voltage is higher than 660 V, the transition from the transition region to the metallic region causes the film quality to become metallic, and the inorganic compound layer is inferior in transparency and moisture resistance.

Note that the material and reaction gas used for the target material can be appropriately selected according to the type of the inorganic compound layer to be formed. As described above, since the inorganic compound layer has a dense structure and a film with little absorption of light having a target wavelength, a silicon oxide represented by SiO _x (0 <x ≦ 2) is obtained. Preferably it consists of. In order to form an inorganic compound layer made of silicon oxide, silicon may be used as a target material, and oxygen may be used as a reaction gas.
In the manufacturing method of the present invention, various sputtering methods such as RF sputtering and DC pulse sputtering can be used as long as the reactive sputtering is based on impedance control. Sputtering is preferably used.

The inorganic compound layer formed by the above-described procedure functions as a moisture-proof film excellent in moisture-proof performance, but tends to be slightly inferior in adhesion. Therefore, if the film formation is not uniform because the shape of the optical component body is complicated or the film thickness of the inorganic compound is relatively large, the adhesion of the inorganic compound layer is insufficient. Thus, the inorganic compound layer may be cracked or peeled off during use of the optical component.
The problem is that when performing reactive sputtering by impedance control, the optical component, more specifically, the optical component main body is set so that the axis perpendicular to the optical axis is parallel to the target. It can be solved by arranging and rotating the optical component body about an axis perpendicular to the optical axis. As shown in FIG. 1, when the optical component body 10 is a plastic lens, the axis perpendicular to the optical axis direction is an axis in the diameter direction of the plastic lens.

  FIG. 2 is a view showing a means for rotating the optical component main body 10 of FIG. 1 about a diametrical axis. In FIG. 2, the optical component main body 10 is held at both ends by dots by an elongated rod-shaped holder 30. The holder 30 is rotatable about its long axis. In FIG. 2, the optical component main body 10 whose side ends are held by the holder 30 is arranged with its optical surface facing the target 40, and the axis perpendicular to the optical axis direction is the target 40. Specifically, it is parallel to the surface of the target 40.

  In the state shown in FIG. 2, when the holder 30 is rotated around its long axis, the optical component main body 10 held by the holder 30 rotates. Here, since the major axis of the holder 30 coincides with the diametrical axis of the optical component main body 10, the optical component main body 10 rotates around the diametrical axis. By performing reactive sputtering by impedance control in this state, the inorganic compound layer can be uniformly formed on the entire surface of the optical component body 10, and the resulting inorganic compound layer has excellent adhesion.

  In the state shown in FIG. 2, the inorganic compound layer is not formed at the two points on the side end portion of the optical component main body 10 held by the holder 30, but the joint portion between the optical component main body 10 and the holder 30. Is formed on the side end portion of the optical component body 10 while forming the film again by holding the vertical end portion (end portion in the direction perpendicular to the drawing) of the optical component body 10 with the holder 30. The inorganic compound layer can be uniformly formed on the entire surface of the optical component main body 10 by performing the film formation locally or by performing the film formation while being removed from the holder 30.

  In FIG. 2, the inorganic compound layers are formed on the surfaces of the three optical component bodies 10, but the number of optical component bodies on which the inorganic compound is formed using the manufacturing method of the present invention is not particularly limited. . Therefore, an inorganic compound layer may be formed on one optical component body, or an inorganic compound layer may be formed on a plurality of optical component bodies. From the viewpoint of productivity, it is preferable to form an inorganic compound layer on a plurality of optical component bodies at once.

  Further, in the production method of the present invention, other conditions, specifically, the film formation rate of the inorganic compound layer, the film formation power, the amount of reaction gas introduced, etc., depend on the required productivity, film formation material, etc. Accordingly, it may be determined appropriately.

In the optical component of the present invention, the Sherwood number relating to the movement of moisture represented by the following formula is preferably 10 or less.
kc · d / D
Here, kc is a water transfer coefficient in the moisture-proof coating, and D is a water diffusion coefficient [mm ² / s] in the constituent material of the optical component body. d is the length [mm] of the optical component body in the optical direction, and in the case of a plastic lens (optical component body) 10 as shown in FIG. 1, it is the thickness of the central portion of the lens portion 10a.

Here, kc is a flat plate sample made of the same material as the constituent material of the optical component body, and the moisture absorption rate is measured by JIS K7209 (equivalent to ISO 62) for the moisture-proof coating-added sample to which the moisture-proof coating is applied. Then, the moisture absorption rate is measured for a sample that has not been provided with a moisture-proof coating, which is a flat plate sample to which a moisture-proof coating is not applied, and is determined from the difference between the two moisture absorption rates.
Further, the water diffusion coefficient D [mm ² / s] in the constituent material of the optical component main body is described in JIS K7209 (corresponding to ISO 62) with respect to the flat plate sample, which is made of the same material as the constituent material of the optical component main body. Find by the method.
Further, the length d (mm) in the optical direction of the optical component main body may be accurately obtained from the shape and dimensions of the optical component main body. However, when the optical component main body is a plastic lens 10 as shown in FIG. May be the thickness of the central portion of the lens portion 10a.

The optical component of the present invention has a Sherwood number of 10 or less for moisture movement, so that even if there is moisture absorption or dehumidification to the optical component due to environmental changes, the water absorption distribution is biased inside the optical component. No deviation of the refractive index distribution caused by the deviation of the water absorption distribution occurs.
In the optical component of the present invention, the Sherwood number related to moisture movement is more preferably 5 or less, and further preferably 2 or less.

In the optical component of the present invention, it is sufficient that the moisture-proof coating is formed at least on the outside air contact surface, and the moisture-proof coating 2 is formed on the entire surface of the optical component main body 10 as in the optical component 1 shown in FIG. Not required.
FIG. 3 is a conceptual diagram for explaining another embodiment of the optical component of the present invention. The optical component 1 ′ of the present invention in the form of a lens is incorporated in the optical unit 20. In FIG. 3, the optical unit 20 is shown as a cross-sectional view cut along a plane including the optical axis. The optical unit 20 shown in FIG. 3 has a general optical unit configuration used for a lens mechanism of a silver salt camera, an imaging module of a digital camera, a video camera, and a small camera for incorporation into a mobile phone. That is, the optical unit 20 of FIG. 3 incorporates two lenses 1 ′ and 21 having different Abbe numbers into a substantially cylindrical lens barrel 22, and the lenses 1 ′ and 21 are fixed by a lens holder 24. It will be.
Further, in the optical unit 20 of FIG. 3, a spacer 23 is disposed between the lens 1 ′ and the lens 21.

Here, the lens 21 is a lens having a high Abbe number, specifically, an Abbe number of about 45 to 60.
Specific examples of the lens having such an Abbe number include a glass lens and an alicyclic polyolefin lens represented by ZEONEX ^™ manufactured by Nippon Zeon. These lens materials are generally known to have a very low saturated moisture absorption of 0.02% by mass or less. It is not necessary to form a moisture-proof coating on the lens 21 made of such a lens material having a low moisture absorption rate.
On the other hand, the lens 1 ′ is the optical component 1 ′ of the present invention, and an Abbe number suitable for correcting chromatic aberration in combination with the lens 21, specifically, a plastic lens having an Abbe number of about 23 to 35 is used as the optical component. Let it be a main body 10 '.

The configuration of the optical unit 20 shown in FIG. 3 will be described more specifically. The lens barrel 22 has a configuration in which three cylindrical regions having the same center and different diameters are arranged in the optical axis direction of the optical unit 20 in order from the larger diameter side. An annular rib portion 22a is formed on the end surface of the cylindrical region of the smallest diameter of the lens barrel 22 so as to protrude inward. The inside of the rib portion 22a is an opening through which light (photographing light or the like) enters.
In the lens barrel 22, the lens 21 can be incorporated in the smallest diameter region. That is, the inner diameter is substantially the same as the outer diameter of the lens 21 and is slightly larger than the outer diameter of the lens 21. In the largest diameter region, the optical component 1 ′ of the present invention can be incorporated. That is, the inner diameter is substantially the same as the outer diameter of the optical component 1 ′ of the present invention, and is slightly larger than the outer diameter of the optical component 1 ′.
The lens 21 is incorporated in the region of the smallest diameter on the rib portion 22a side (opening = light incident side) of the lens barrel 22, and the position in the optical axis direction is determined by contacting the flange portion with the rib portion 22a. . On the other hand, the optical component 1 ′ of the present invention is incorporated in the region of the maximum diameter of the lens barrel 22.

The spacer 23 is a substantially cylindrical member having a portion that contacts the lens 21 and the optical component 1 ′ of the present invention at both ends, and as described above, the lens 21 and the optical component 1 ′ of the present invention within the lens barrel 22. Inserted between. By selecting the length of the spacer 23 in the optical axis direction, the relative position of the lens 21 and the optical component 1 ′ of the present invention in the optical axis direction can be positioned at an appropriate position.
Further, the lens 21, the optical component 1 'of the present invention, the lens barrel 22, and the spacer 23 are all in a state in which the lens 21 and the optical component 1' of the present invention are properly assembled in the lens barrel 22. The optical component 1 'is formed so that the optical axes thereof coincide with each other.

  In the optical unit 20 shown in FIG. 3, a lens 21, a spacer 23, and an optical component 1 ′ of the present invention are sequentially incorporated in a lens barrel 22, and the optical component 1 ′ of the present invention is directed toward a rib 22 a by a lens holder 24. Press. In this state, the optical unit 20 is assembled by fixing the lens holder 24 to the lens barrel 22 with an adhesive or the like.

4 (a) and 4 (b) are front views (viewed from the optical axis direction) of the optical component 1 'of the present invention, and FIG. 4 (b) is a sectional view in the same direction as FIG. 1 (b). It is. As shown in FIGS. 4A and 4B, in the optical component 1 ′ of the present invention, the optical component main body 10 ′ is a lens similar to the optical component main body 10 shown in FIGS. 1A and 1B. It consists of a portion 10'a and a flange portion 10'b.
In the optical unit 20 shown in FIG. 3, the optical component 1 ′ of the present invention has a flange portion sandwiched between the rib portion 22 a and the spacer 23, and this portion does not come into contact with outside air. Therefore, it is thought that there is almost no moisture absorption and dehumidification from this part.
For this reason, as shown in FIG. 4B, in the optical component 10 ′ of the present invention, the moisture-proof coating 2 is formed only on the surface of the lens portion 10′a of the optical component main body 1 ′, and the flange portion 10′b. The moisture-proof coating 2 is not formed on. Such a configuration may be used as long as the Sherwood number of the optical component 1 ′ relating to moisture movement is 10 or less. Due to the difficulty in forming the moisture-proof coating, the moisture-proof coating formed on the flange portion 10'b may have poor adhesion. As a result, when the optical unit 20 is in use, the moisture-proof coating may be easily peeled off from the flange portion 10'b and become a contamination source. In the optical component 1 ′ shown in FIGS. 4A and 4B, such a problem does not occur because the moisture-proof coating is not formed on the flange portion 10′b.

Further, in the optical unit 20 having the configuration shown in FIG. 3, the inside of the lens barrel 22 is hermetically held, or the opening existing in the lens barrel 22 is very small, and air flows from the outside to the lens barrel 22. If it is configured so as to reduce, the influence of moisture absorption and dehumidification on the surface located inside the lens barrel 22, that is, the convex surface portion, of the surface of the lens portion 10'a of the optical component body 10 'of the present invention. Is considered very small. In such a case, it is not necessary to form the moisture-proof coating 2 on the convex surface portion.
On the other hand, depending on the material constituting the lens, the lens 21 forming the high Abbe number lens may be affected by moisture absorption and dehumidification. In such a case, you may comprise the lens 21 with the optical component of this invention.

  In order to form a moisture-proof coating only on the outside air contact surface of the optical component body 10 ', that is, the lens portion 10'a, as in the optical component 1' shown in FIGS. 4 (a) and 4 (b), a moisture-proof coating is used. When forming, the moisture-proof coating may be formed in a state where the flange portion 10'b is masked or held by a holder or the like.

  The optical component of the present invention is used by being incorporated in the optical unit 20 as shown in FIG. 3 because the refractive index distribution is not biased inside the optical component body even if moisture absorption or dehumidification occurs due to environmental changes. It is suitable as a plastic lens.

  The present invention also provides an optical unit incorporating the above-described optical component of the present invention as a plastic lens. That is, the present invention provides an optical unit that includes at least two lenses having different Abbe numbers, and at least one of the lenses is the plastic optical component of the present invention. Therefore, FIG. 3 is also a diagram showing an embodiment of the optical unit of the present invention.

However, the optical unit of the present invention includes at least two lenses having different Abbe numbers from each other, and one of the lenses is not particularly limited as long as it is the optical component of the present invention, and has a configuration different from the optical unit 20 shown in FIG. It may be. For example, in an optical unit for high-resolution applications, a desired resolution and accuracy are achieved by using a plurality of, for example, three or more imaging lenses in combination. The optical unit of the present invention may include three or more such lenses as long as at least one lens is the optical component of the present invention.
When the optical unit of the present invention includes three or more lenses, it is not necessary that all the lenses have different Abbe numbers. If at least two lenses included in the optical unit have different Abbe numbers and are optically designed so that chromatic aberration is corrected as a whole, two or more lenses having the same Abbe number May be included.

When used in an imaging module such as a lens mechanism of a silver halide camera, a digital camera, a video camera, or a small camera for incorporation into a mobile phone, the optical unit of the present invention preferably has an autofocus mechanism.
Even if the plastic optical component of the present invention absorbs moisture or dehumidifies due to environmental changes, the refractive index distribution does not deviate inside, but the refractive index of the entire optical component gradually increases due to environmental changes. Change. Therefore, the optical characteristics of the optical unit using the optical component change due to environmental changes. However, this change in refractive index is gradual and uniform. If the refractive index of the optical component itself, which is a plastic lens, changes evenly, if the change is minute enough to be due to moisture absorption, the optical performance will only have a substantial effect on the optical performance, and this change will be It is solved by using the focus mechanism. Accordingly, the optical unit of the present invention having an autofocus mechanism can always exhibit excellent optical characteristics without being affected by environmental changes.

  As an autofocus mechanism used in an imaging module such as a lens mechanism of a silver salt camera, a digital camera, a video camera, or a small camera for incorporation into a mobile phone, those using various principles and control methods are known. Among such known autofocus mechanisms, the autofocus mechanism used in the optical unit of the present invention directly detects the focus state of the subject based on the image obtained through the optical unit, and the focus state is appropriately set. It is preferable that the mechanism uses a method for controlling the position of the lens constituting the optical unit in the optical axis direction.

  FIG. 5 is a conceptual diagram showing a configuration example of an imaging module using the optical unit of the present invention and an autofocus mechanism, and a configuration of a general digital camera is simply shown. In the imaging module 50 of FIG. 5, the optical unit 20 ′ includes at least two lenses having different Abbe numbers, and one of the lenses is the optical unit of the present invention configured by the optical component of the present invention. The image that has passed through the optical unit 20 ′ is taken into the CCD image sensor 51. The optical image information captured by the image sensor 51 is output as an electrical signal and sent to the AF processing unit 52. The AF processing unit 52 detects the focus state of the subject based on the image information sent from the image sensor 51 and sends a drive signal to the actuator 53. Based on the drive signal from the AF processing unit 52, the actuator 53 moves all or a part of the lenses constituting the optical unit 20 ′ back and forth in the optical axis direction so as to achieve an appropriate focus state. Various means can be used as the actuator 53. Specifically, for example, a stepping motor, a linear motor, a piezoelectric element, a voltage bending polymer, or the like can be used.

  The optical component of the present invention has been described by taking the plastic lens used in the optical unit as an example, but the optical component of the present invention is not limited to this. The optical component of the present invention widely includes structures known as plastic optical components. Therefore, in addition to optical elements such as lenses having various shapes and functions other than the illustrated lenses, in addition to lenses, for example, prisms, optical filters, optical screens, deflecting elements, polarizing elements, light reflecting members, viewfinders, Widely includes known optical elements or optical components such as glasses, contact lenses, reflecting mirrors, curved mirrors and the like. In addition, it is incorporated in various optical devices such as photographing optical systems of imaging devices such as cameras (silver salt cameras, digital cameras, video cameras, etc.), image forming devices such as copying machines and printers, projectors, telescopes, binoculars, and magnifiers. Widely known optical elements or optical components used in

  Further, the material for forming the optical component body is not limited, and various plastic materials (resin materials) used in known optical elements and ordinary optical components can be used. Examples include methacrylic resins (for example, PMMA), acrylic resins including alicyclic acrylic resins, polycarbonate resins, polyester resins including aromatic polyester resins, polystyrene resins, acrylonitrile / styrene (AS) resins, alicyclic polyolefins, Examples thereof include resins containing a tricyclodecane ring, cycloolefin polymers, polymethylpentene, styrene / butadiene copolymers, and polyesters having a fluorene group.

Among these plastic materials, the water absorption rate is relatively high, specifically, the saturated water absorption rate is more than 0.02% by mass because of the feature of the optical component of the present invention that does not cause unevenness in the water absorption distribution inside the optical component. The plastic material is preferably methacrylic resin, acrylic resin containing alicyclic acrylic resin, polycarbonate resin, polyester resin containing aromatic polyester resin, polystyrene resin, polyester resin, alicyclic polyolefin, etc. . As described above, some alicyclic polyolefins have a saturated moisture absorption of 0.02% by mass or less, such as ZEONEX ^™ . On the other hand, the saturated moisture absorption is 0.02%. Some of them exceed mass%.

  3 is used as the optical component 1 ′ of the optical unit 20 shown in FIG. 3, the optical component main body 10 ′ is combined with the lens 20 having a high Abbe number, specifically, an Abbe number of 45 to 60, to correct chromatic aberration. It is preferable to have an Abbe number suitable for performing, and specifically the Abbe number is preferably about 23 to 35. As a material having such an Abbe number, a polycarbonate resin or an aromatic polyester resin is suitable.

Furthermore, the method for forming the optical component body is not particularly limited, and all known plastic molding methods such as injection molding, injection compression molding, and compression molding can be used depending on the plastic material used.
In addition, the shape and size (length, diameter, and thickness) of the optical component main body are not particularly limited, and may be appropriately selected according to the use of the optical component.

  For example, in the illustrated optical component, a moisture-proof coating is formed directly on the surface of the optical component main body. However, the present invention is not limited to this, and the refractive component is refracted between the optical component main body and the moisture-proof coating. A film for adjusting the rate, an antireflection film, a film for improving adhesion, and the like may be included. Further, it may have an anti-reflection film, a film for adjusting the refractive index, a film for improving adhesion, a barrier film for preventing damage, etc. covering the moisture-proof film. In other words, in the plastic optical component of the present invention, a layer configuration in which various coatings are formed can be used as long as at least the outside air contact surface of the optical component body is covered with a moisture-proof coating.

Hereinafter, the present invention will be described in more detail with reference to specific examples of the plastic optical component according to the present invention.
In the example, in order to evaluate the optical performance of the plastic optical component of the present invention, the optical unit 20 shown in FIG. 3 was used. In the optical unit 20 shown in FIG. 3, the lens 21 is a glass lens having an Abbe number of 56 (lens radius of the incident side is 6.4 mm, lens radius of the exit side is 4.9 mm, and average thickness is 2.9 mm). The optical component body 10 ′ is a lens made of polycarbonate resin having an Abbe number of 30 (radius side lens portion 10 ′ radius 9.0 mm, emission side lens portion 10 ′ radius 7.5 mm, average thickness 2.5 mm). is there.
When the resolution of the optical (lens) unit 20 is measured after being left for one week in an environment of a temperature of 25 ° C. and a humidity of 30%, an MTF (modulation transfer function) with a contrast of 50% is 30 lines / mm at the center of the optical axis, The average of the peripheral part was 25 / mm.

[Example]
In this example, SiO _x (0 <x ≦ 2) is formed on the entire surface of the lens (optical component main body) 10 made of polycarbonate resin, similarly to the optical component 1 shown in FIG. ) To form a moisture-proof coating 2.
In the vacuum chamber, the lens 10 made of polycarbonate resin was disposed so as to face the silicon target. After evacuating until the pressure in the vacuum chamber reached 4 × 10 ⁻⁴ Pa, argon gas as a discharge gas was introduced into the vacuum chamber.
After introducing the discharge gas, the pressure in the vacuum chamber was set to 0.27 Pa, and a film formation power of 7 kW was supplied from the discharge power source to perform pre-sputtering.

Oxygen gas was introduced as a reaction gas when 5 minutes had elapsed since the start of pre-sputtering. After introducing the oxygen gas, the supply voltage of argon gas and oxygen gas is reduced while controlling the discharge voltage to 610 V by impedance control, the final film forming pressure is lowered to 0.03 Pa, and the film is formed on the entire surface of the lens 10. A 50 nm thick SiO _x (0 <x ≦ 2) layer was formed.

The surface of the SiO _x layer formed on the outer surface of the lens 10 by the above procedure was observed with an AFM (Atomic Force Microscope). As a result, the average particle diameter of the particles constituting the SiO _x layer was 10 nm, and the average grain boundary of the SiO _x layer was 15 nm.

The Sherwood number of the optical component of this example was determined by the following procedure.
A sample in which a flat plate sample is made of the same polycarbonate resin as the constituent material of the optical component main body, and a SiO _x layer is formed on the flat plate sample in the same manner as described above (a moisture-proof film forming sample), is JIS K7209 (ISO62). The moisture absorption rate was measured according to Similarly, the moisture absorption rate was measured without forming the SiO _x layer on the flat plate sample. Kc (water transfer coefficient in the moisture-proof coating) was determined from the difference between the moisture absorption rates of the two. The results are shown below.
Moisture absorption rate (moisture-proof film formation sample): 3.0 × 10 ⁻⁶ [wt% / s]
(Moisture-proof film non-forming sample): 4 × 10 ⁻⁵ [wt% / s]
kc: 5 × 10 ⁻⁶ mm / s
In addition, the water diffusion coefficient D [mm ² / s] in the constituent material of the optical component body is a flat plate sample made of the same polycarbonate resin as the constituent material of the optical component body, and this flat plate sample is equivalent to JIS K7209 (ISO 62). ). As a result, D was 5.0 × 10 ⁻⁶ mm ² / s. Since the thickness of the central portion of the lens portion of the optical component body 10 (10 ′) is 2.5 mm as described above, the Sherwood number can be obtained as follows.
Sherwood number (kc · d / D) = (5 × 10 ⁻⁶ ) × (2.5) ÷ (5 × 10 ⁻⁶ )
= 2.5
Therefore, it was confirmed that the optical component 1 of Example 1 has a Sherwood coefficient of 5 or less for the moisture-proof coating relating to moisture movement.

The optical component 1 of the present invention in which the SiO _x layer is formed on the surface of the lens (optical component main body of the present invention) 10 obtained by the above procedure is placed in a dryer at 50 ° C. for 7 days and sufficiently dried. The optical unit 20 shown in FIG. Similarly, a glass lens (Abbe number 56) was incorporated in the optical unit 20 as the lens 21. Thereafter, the lens orientation and the distance between the lenses were finely adjusted to obtain predetermined resolutions. Next, the optical unit 20 was left in an environment of 25 ° C. and 30% humidity for one week, and then placed under conditions of a relative humidity of 90% and a temperature of 25 ° C., and the temporal change in resolution was measured. An MTF measuring instrument manufactured by Trioptics was used for the resolution measurement. The resolution was measured as an MTF with a contrast of 50%. The resolution of the peripheral portion was expressed as an average value of MTFs in the tangential direction and the sagittal direction. The results are shown in Table 1.

[Comparative example]
A plastic optical component was produced by forming a 50 nm thick SiO _x layer on the surface of the lens 10 in the same procedure as in the example except that the final film forming pressure was 0.27 Pa.
The surface of the SiO _x layer formed on the outer surface of the lens 10 was observed with an AFM (Atomic Force Microscope). The average particle diameter of the particles forming the SiO _x layer is 25 nm, the average grain boundaries SiO _x layer was 30 nm.
Moreover, the moisture-proof-film formation sample and the moisture-proof-film non-formation sample were created in the procedure similar to an Example, the moisture absorption rate was calculated | required, and kc was computed. The results are shown below.
Moisture absorption rate (moisture-proof film forming sample): 4 × 10 ⁻⁵ [wt% / s]
(Moisture-proof film non-forming sample): 4 × 10 ⁻⁵ [wt% / s]
kc: 2.6 × 10 ⁻⁵ mm / s
Since the water diffusion coefficient D [mm ² / s] in the constituent material of the optical component main body and the thickness of the central portion of the lens portion of the optical component main body 10 (10 ′) are the same as in the embodiment, the Sherwood number is as follows: Can be requested.
Sherwood number (kc · d / D) = (2.6 × 10 ⁻⁵ ) × (2.5) ÷ (5 × 10 ⁻⁶ )
= 13
Further, the obtained optical component was incorporated in the lens unit 20 as the optical component 1 ′, and optical performance evaluation was performed in the same manner as in Example 1. The results are shown in the table.

As is clear from Table 1, in the optical unit of the example, even when time elapses from the start of the measurement of the resolution, the resolution change, that is, the decrease is extremely small in both the central portion and the peripheral portion of the optical unit. Was confirmed.
On the other hand, in the optical unit of the comparative example, the resolution returns to the resolution at the measurement start time after 5 days from the start of measurement, but in both the central part and the peripheral part of the optical unit after 1 day and 2 days after the measurement start. , It was confirmed that the resolution was clearly reduced.

FIG. 1 is a conceptual diagram showing an embodiment of a plastic optical component of the present invention having a lens shape, and FIG. 1 (a) is a front view of the optical component (viewed from the optical axis direction). FIG. 1B is a cross-sectional view taken along a plane including the optical axis. FIG. 2 is a view showing a means for rotating the optical component main body 10 of FIG. 1 about a diametrical axis. FIG. 3 is a schematic cross-sectional view (cut along a plane including the optical axis) of one embodiment of an optical unit using the optical component of the present invention. FIG. 4 is a view for explaining the shape of the optical component 1 ′ of the present invention shown in FIG. 3, and FIG. 4 (a) is a front view of the optical component 1 ′ (viewed from the optical axis direction). 4B is a cross-sectional view in the same direction as FIG. FIG. 5 is a conceptual diagram showing one configuration example of an imaging module using the optical unit of the present invention and an autofocus mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1 ': Optical component 10, 10': Optical component main body 10a, 10'a: Lens part 10b, 10'b: Flange part 2: Moisture-proof coating 20, 20 ': Optical unit 21: Lens 22: Lens barrel 22a : Rib part 23: Spacer 24: Lens holder 30: Holder 40: Target 50: Imaging module 51: Image sensor 52: AF processing part 53: Actuator

Claims (14)

A plastic optical component having a moisture-proof coating formed on at least the outside air contact surface,
2. The plastic optical component according to claim 1, wherein the moisture-proof coating is an inorganic compound layer in which inorganic compounds having an average particle size of 3 nm to 20 nm are distributed so as to form an average grain boundary of 1 nm to 20 nm.   2. The inorganic compound is at least one selected from the group consisting of silicon oxide, silicon nitride, silicon oxynitride, metal oxide, metal nitride, metal oxynitride, and diamond-like carbon. Plastic optical components as described in 1.   The plastic optical component according to claim 2, wherein the inorganic compound is silicon dioxide.   The plastic optical component according to any one of claims 1 to 3, wherein the inorganic compound layer has a thickness of 10 nm to 1 µm.   The inorganic compound layer is formed on the plastic optical component at a film forming pressure of 0.005 Pa to 0.13 Pa by using reactive sputtering based on impedance control. The plastic optical component described.   The plastic optical component according to any one of claims 1 to 5, wherein the Sherwood number relating to moisture movement is 10 or less.   7. An optical unit comprising at least two lenses having different Abbe numbers, wherein at least one of the lenses is a plastic optical component according to claim 1.   The optical unit according to claim 7, comprising an autofocus mechanism. A method for producing a plastic optical component having an inorganic compound layer as a moisture-proof coating on at least an outside air contact surface,
A method for producing a plastic optical component, comprising forming an inorganic compound layer on the plastic optical component at a film forming pressure of 0.005 Pa to 0.13 Pa using reactive sputtering by impedance control. .   The method of manufacturing a plastic optical component according to claim 9, wherein the reactive sputtering is performed at a discharge pressure of 480V to 660V.   The method of manufacturing a plastic optical component according to claim 9 or 10, wherein the reactive sputtering is performed in a transition region between a metal region and a reactive region.   The plastic optical component is arranged so that the axis perpendicular to the optical axis is parallel to the target, and the plastic optical component is rotated around the axis perpendicular to the optical axis. The method for manufacturing a plastic optical component according to claim 9, wherein the reactive sputtering is performed.   The method for producing a plastic optical component according to claim 9, wherein the inorganic compound layer is a layer in which an inorganic compound having an average particle diameter of 3 nm to 20 nm forms an average grain boundary of 1 nm to 20 nm.   The method for producing a plastic optical component according to claim 9, wherein the reactive sputtering is performed using silicon as a target and oxygen gas as a reactive gas.

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