JP2015040945A - Lens unit for on-vehicle camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure oil resistant and chemical resistant properties sustainable for practical use.SOLUTION: A lens unit 1 for an on-vehicle camera is mounted on the on-vehicle camera. The lens unit 1 for the on-vehicle camera includes a resin object side lens 10 having a surface 12 exposed to outer air and an image side lens group 20 that is disposed at an image side to the object side lens 10 and composed of a plurality of resin lenses 22, 24, and 26. All the lenses of the object side lens 10 and the image side lens group 20 are made of resin. The object side lens 10 is configured by certain cycloolefin-based resin.

Description

  The present invention relates to an in-vehicle camera lens unit, and more particularly to an in-vehicle camera lens unit having oil resistance and chemical resistance.

  Conventionally, in order to eliminate blind spots from a driver who is driving a car, it has been proposed to mount an in-vehicle camera on the car. That is, a blind spot can be eliminated by installing a camera that captures the back and sides of the vehicle on the body of the vehicle and displaying an image captured by the camera at a position that can be viewed by the driver. Since such a vehicle-mounted camera is installed outside the vehicle, the lens mounted on the vehicle camera is required to have environmental resistance such as high temperature resistance, moisture resistance, weather resistance, water resistance, acid resistance, and alkali resistance.

In recent years, not only environmental resistance, but also resistance to oils and chemicals (for example, organic solvents) such as oil and washer fluid used in vehicles has been demanded. However, there is an increasing demand for resistance to more specific liquid types (products). For this reason, it is difficult to devise a technology that can satisfy all of these environmental resistances, oil resistance, and chemical resistances. However, it is necessary to consider a configuration that ensures a good balance of oil resistance and chemical resistance.
For example, taking alkali resistance as an example, outstanding alkali resistance that can withstand strong alkali is not always necessary, but in reality it is weak alkaline that seems to be related to vehicles such as washer fluid, car shampoo, glass cleaner, salt water, etc. Therefore, it is important to have appropriate resistance with respect to other liquid properties.

In this respect, in a lens unit for an in-vehicle camera composed of a plurality of lenses, in order to ensure chemical and physical durability, it is necessary to use a glass lens for at least the most exposed lens on the front side. It is effective as a configuration of a lens unit for use (see Patent Document 1).
On the other hand, with the expansion and popularization of in-vehicle camera lenses, the cost reduction required has become severe year by year. In particular, the cost of a glass lens in an in-vehicle camera lens unit is large, and the use of glass as a constituent material is an impediment to the cost reduction of the unit. For this reason, an all-plastic in-vehicle camera lens unit using a plastic lens has begun to be widely used for the lens exposed on the outermost surface (see Patent Documents 2 and 3).

JP 2008-233547 A JP 2010-181484 A JP 2010-156734 A

However, when using plastic lenses, it is difficult to adequately secure all the environmental resistance, oil resistance, and chemical resistance of the base material itself, and the functional film (layer) associated therewith, on the material, A lens unit for in-vehicle cameras that can withstand actual use has not yet been found in reality.
Accordingly, the main object of the present invention is to provide an in-vehicle camera lens unit that can ensure oil resistance and chemical resistance that can withstand actual use, even if it is an in-vehicle camera lens unit composed of a plurality of plastic lenses. Is to provide.

In order to solve the above problems, according to the present invention,
In the in-vehicle camera lens unit mounted on the in-vehicle camera,
A resin object side lens having a surface exposed to the outside air;
An image side lens group which is disposed on the image side from the object side lens and is composed of one or a plurality of resin lenses,
All the lenses of the object side lens and the image side lens group are made of resin,
An in-vehicle camera lens unit is provided in which the object side lens is made of a certain cycloolefin resin.

  According to the present invention, oil resistance and chemical resistance that can withstand actual use can be ensured.

It is sectional drawing which shows schematic structure of the lens unit for vehicle-mounted cameras. It is a figure for demonstrating schematically the formation method of an antireflection structure. It is an electron micrograph which shows an example of an antireflection structure. It is a figure which shows the external appearance after the chemical-resistance test of sample 1 (ZEONEX E48R). It is a figure which shows the external appearance after the chemical-resistance test of sample 2 (APL5514ML). It is a figure which shows the external appearance after the chemical-resistance test of sample 4 (WF100). It is a figure for demonstrating the structure and effect | action of a haze meter roughly.

  Next, preferred embodiments of the present invention will be described with reference to the drawings.

[Configuration of lens unit for in-vehicle camera]
The in-vehicle camera lens unit 1 in FIG. 1 is mounted on an in-vehicle camera. “In-vehicle camera” is a camera that is installed on the outside of the car body of an automobile, installed on the rear part of the car body and used for backward confirmation, or installed on the front part of the car body for forward confirmation. Alternatively, it is used for side confirmation and confirmation of the distance from the front car.

  The on-vehicle camera lens unit 1 includes a plurality of lenses, and more specifically includes an object side lens 10 disposed on the object side and an image side lens group 20 disposed on the image side. The image-side lens group 20 includes three lenses 22, 24, and 26, and diaphragms 30 and 32 are installed between the lenses 22 and 24 and between the lenses 24 and 26, respectively. The number of lenses and diaphragms of the image side lens group 20 may be changed as appropriate. Of the plurality of lenses, the left surface of the object side lens 10 in FIG. 1 is an exposed surface 12 exposed to the outside air.

All the lenses of the object side lens 10 and the image side lens group 20 are made of resin. In particular, the object side lens 10 is made of a certain cycloolefin resin.
In general, the cycloolefin-based resin refers to a polymer synthesized using cycloolefins as monomers and having a alicyclic structure in the molecular structure.
As described below, the cycloolefin resin (COP) mainly includes (a) a polymer synthesized by hydrogenating ring-opening metathesis polymerization of a norbornene cyclic olefin, and (b) a norbornene cyclic olefin and ethylene. There are two types: polymers synthesized by addition polymerization.

Specific examples of the former hydrogenated ring-opening metathesis polymerization type cycloolefin resin include ZEONEX (registered trademark) and ZEONOR (registered trademark) manufactured by Nippon Zeon, and ARTON (registered trademark) manufactured by JSR.
Specific examples of the latter addition polymerization type cycloolefin resin include APEL (registered trademark) manufactured by Mitsui Chemicals, and TOPAS (registered trademark) manufactured by Polyplastics.
In the present embodiment, the latter addition polymerization type cycloolefin resin is used. That is, the “certain cycloolefin-based resin” that can form the object-side lens 10 is a polymer synthesized by addition polymerization from norbornene-based cyclic olefin and ethylene as described below.

  In addition, in the addition polymerization type cycloolefin resin which is the certain cycloolefin resin, the kind of the substituent in the polymer, the degree of polymerization, and the like are selected and designed from known techniques.

  In the on-vehicle camera lens unit 1 described above, a light beam from the subject is incident from the object side lens 10 disposed on the object (subject) side, and the light beam is sequentially applied to each lens 22, 24, 26 of the image side lens group 20. It propagates and forms an image of the subject on the imaging surface.

[Structure of object-side lens surface]
As shown in the upper enlarged view of FIG. 1, a hard coat layer 40, an antireflection layer 50, and a water / oil repellent layer 60 may be formed on the exposed surface 12 of the object side lens 10. Of these three types of layers, only one arbitrarily selected layer may be formed, or two arbitrarily selected layers may be formed, or all three types of layers may be formed. Also good.
A hard coat layer 40 is preferably formed on the exposed surface 12 of the object side lens 10, more preferably a hard coat layer 40 and an antireflection layer 50 are formed, and further preferably, the hard coat layer 40 and the antireflection layer 50 are formed. And a water / oil repellent layer 60 are preferably formed.

Since the exposed surface 12 constitutes the outermost surface of the in-vehicle camera lens unit 1, the exposed surface 12 is required to have scratch resistance and wear resistance, and preferably a hard coat layer 40 is formed to transmit the lens. In consideration of securing the rate, more preferably, the hard coat layer 40 and the antireflection layer 50 are formed, and in consideration of suppressing the penetration of moisture and oil into the resin base material itself of the object side lens 10, More preferably, the hard coat layer 40, the antireflection layer 50, and the water / oil repellent layer 60 are formed.
In particular, when the antireflection layer 50 constitutes the outermost surface portion of the in-vehicle camera lens unit 1, the antireflection layer 50 is preferably made of an inorganic material in consideration of hardness that can withstand scratches and abrasion.
If an appropriate hard coat agent is selected and the hard coat layer 40 is formed, the penetration of moisture and oil into the resin base material itself of the object side lens 10 is suppressed, but the water / oil repellent layer 60 is a lens for an in-vehicle camera. When the outermost part of the unit 1 is configured, the effect of suppressing penetration is increased, and the friction coefficient of the outermost part is reduced, and the effect of further improving the wear resistance can be obtained.

  Each layer will be described in detail below.

(1) Hard coat layer (1.1) Prior surface treatment When the hard coat layer 40 is formed, the exposed surface 12 of the object side lens 10 is preferably subjected to a surface treatment in advance. As the surface treatment, for example, oxygen plasma treatment, corona treatment, UV ozone treatment, solvent treatment and the like are effective.
In the oxygen plasma treatment, an oxygen plasma is generated after the space in which the lens is installed is placed in a low vacuum environment, and the surface thereof is activated. In this embodiment, it is preferable to employ such a process. For example, after the processing conditions are set to a vacuum environment of 10 Pa, oxygen plasma is generated at an oxygen gas flow rate of 50 sccm and a power of 150 W, and the process is performed for 30 seconds.
Corona treatment, UV ozone treatment, and solvent treatment are useful as techniques for improving the adhesion between the object side lens 10 and the hard coat layer 40.

(1.2) Hard coating agent As the hard coating agent, an energy curable resin such as a UV curable resin or a thermosetting resin is preferably used. The material composition is preferably considered to be silicon based from the viewpoint of ensuring weather resistance. In recent years, acrylic resins that ensure UV resistance have been developed, and they may be used as hard coating agents. In addition, a hard coat agent in which organic and inorganic materials are hybridized has been developed as having excellent performance, and such a hard coat agent may be used.

(1.3) Forming Method When the hard coat layer 40 is formed, the hard coat agent is applied to the exposed surface 12 of the object side lens 10 (preferably the exposed surface 12 subjected to the surface treatment) and dried.
As a coating method, a dip method, a spray method, a spin method, a coating method using a bar coder, or the like is preferably used. In the present embodiment, from the viewpoint of forming the hard coat layer 40 only on the exposed surface 12 of the object-side lens 10 and ensuring a surface shape that satisfies the optical characteristics, among the application methods, preferably the spray method, The spin method should be used.
Further, a technique of thermoforming a resin having excellent hardness on the exposed surface 12 of the object side lens 10 may be employed.
The layer thickness of the hard coat layer 40 is preferably 1 to 20 μm (1 μm or more and 20 μm or less). If the layer thickness is 1 μm or more, sufficient hardness (abrasion resistance) and environmental resistance can be obtained, and if the layer thickness is 20 μm or less, induction of cracks at high temperature in the hard coat layer 40 is prevented. Can do.

(2) Antireflection layer The antireflection layer 50 can be formed using film-forming methods, such as a vacuum evaporation method, a sputtering method, and CVD method.
A dielectric material is preferably used as the material of the antireflection layer 50. For example, oxides such as Ti, Ta, Nb, Zr, Ce, La, Al, and Si, or an oxide compound that combines these are suitable. By stacking a plurality of different dielectric materials, it is possible to add a function of reducing the reflectance in the entire visible range. Depending on the required optical performance, it is possible to reduce the reflectivity of the entire visible range by laminating approximately 4 to 5 layers.
The layer thickness of the antireflection layer 50 (total thickness when a plurality of layers are laminated) is preferably 50 nm to 5 μm (50 nm or more and 5 μm or less). If the layer thickness is 50 nm or more, the optical properties of antireflection can be exhibited, and if the layer thickness is 5 μm or less, it is possible to prevent surface deformation due to the layer stress of the antireflection layer 50 itself. it can.

(3) Water / oil repellent layer The water / oil repellent layer 60 can be formed using a film forming method such as a vacuum deposition method or a coating method. The water / oil repellent layer 60 needs to be controlled to a thickness of 100 nm or less in order not to impair the antireflection performance of the antireflection layer 50 formed in the lower layer. preferable.
As a constituent material of the water / oil repellent layer 60, a fluorine-based compound is suitable.
The layer thickness of the water / oil repellent layer 60 is preferably 2 to 100 nm (2 nm to 100 nm). If the layer thickness is 2 nm or more, sufficient water / oil repellency can be ensured. If the layer thickness is 100 nm or less, the antireflection optical characteristics of the antireflection layer 50 are affected. Can be prevented.

[Configuration of image side lens group]
(1) Anti-reflective structure In recent years, high heat resistance is being demanded inside the in-vehicle camera lens unit 1. When the present inventor examined the endurance temperature, initially, the endurance temperature required for the imaging system was 85 ° C as a standard. In view of ensuring the above, a durability temperature of 105 ° C. is required, and for the resin, a durability performance that is considerably high is required.
In this regard, an inorganic antireflection film usually formed on a resin base material may cause cracks or cracks due to a difference in linear expansion coefficient between the resin base material and the antireflection film material. As a countermeasure, there is a measure to use an organic material having a small difference in linear expansion coefficient as compared with the resin for the antireflection film material. However, it is technically difficult to stably secure sufficient antireflection performance. As another measure, there is a vapor deposition method using ion assist as a technique that enables high-density lamination of inorganic materials in recent years. However, although high temperature resistance can be ensured, there is a possibility that moisture resistance may be deteriorated.

  In view of this, there is a method of obtaining an antireflection performance by forming a fine structure on the surface of the resin base material itself, instead of forming an antireflection film inside the lens unit 1 for an in-vehicle camera. That is, in this embodiment, the lenses 22, 24, and 26 of the image side lens group 20 may be formed with irregularities on the surfaces thereof to realize a structural antireflection function. For example, as shown in the lower enlarged view of FIG. 1, an antireflection structure 52 may be formed on the object-side surface of the lens 24 to realize the antireflection function in the image side lens group 20. According to this configuration, since the resin base material itself has antireflection performance, there is no induction of cracks or cracks due to the difference in linear expansion coefficient, and the high temperature performance is high due to the heat resistance of the resin itself.

The antireflection structure 52 is composed of a concavo-convex structure layer having fine concavo-convex shapes arranged randomly. The antireflection structure 52 is an antireflection layer having a tapered structure in which the concave and convex volume density increases toward the lens center side. That is, the antireflection structure 52 is a collection of substantially conical microscopic projections and forms a surface layer. The roughness (Rz: 10-point average roughness) of the antireflection structure 52 is 10 nm or more and 1000 nm or less. The roughness Rz of the antireflection structure 52 is preferably 50 nm or more and 800 nm or less, and more preferably 250 nm or more and 800 nm or less.
The antireflection structure 52 is formed by using, for example, an ion beam. That is, the antireflection structure 52 is formed by etching the surface of the lens 24 with an ion beam.

The antireflection structure 52 may be formed on the lenses 22 and 26 other than the lens 24. The antireflection structure 52 may be formed on any one of the lenses 22, 24, and 26, may be formed on any two lenses, or may be formed on all three lenses. May be.
Ion etching is possible regardless of the resin type of the lenses 22, 24, and 26. Optimum resins are olefin, PC (polycarbonate), and acrylic resins.

Here, in general, the reflectance at a certain interface is determined by the difference in refractive index between the two spaces sandwiching the interface, and the surface reflectance increases as the difference increases. Since the antireflection structure 52 has a concavo-convex shape that is formed on the optical surface of the lens 24 and is at or below the operating wavelength level, there is a sudden change in refractive index between the antireflection structure 52 and the optical surface of the lens 24. There are no interfaces. Thereby, the refractive index change in the antireflection structure 52 becomes gradual, and the surface reflectance decreases. This effect does not depend on the wavelength or the incident angle. Therefore, the antireflection structure 52 can suppress wavelength dependency and angle dependency as compared with a conventional antireflection film having a low refractive index layer and a high refractive index layer.
The principle of antireflection by a conventional antireflection film having a high and low refractive index layer is due to light interference. When light is perpendicularly incident on an antireflection film having a low refractive index layer or the like, the reflectance is reduced most at a wavelength four times the film thickness, and the apparent film thickness is substantially reduced for light having an incident angle θ. It appears as the product of the film thickness and cos θ. As a result, in the case of an antireflection film having a low refractive index layer or the like, unlike the case of the present embodiment, wavelength dependency and incident angle dependency appear.

(2) Method of forming antireflection structure In order to form antireflection structure 52 on surface 24A of lenses 22, 24, and 26 (here, lens 24 is taken as an example), an ion beam is irradiated. As a pretreatment, a mask pattern MA is formed on the surface 24A (left side in FIG. 2).
The mask pattern MA is a fine island pattern. The mask pattern MA has a plurality of islands IM arranged at random. Such a patterning step is performed using a technique such as film deposition, photoresist application, or etching. For example, when a film deposition method is used, an initial process of thin film growth is used. In the initial growth process of the thin film, a state where the growth nucleus of the film grows as an island IM, that is, island growth occurs. In the state of island growth before the film is layered, there are a portion where the island IM exists and a portion where the surface 24A is exposed, so that it functions as a mask pattern.

Thereafter, the ion beam is emitted in a vacuum state, and the surface 24A of the lens 24 is irradiated with ions. At this time, the acceleration energy of ions is 1 W to 100 kW. By irradiation with the ion beam, as shown in the central part of FIG. 2, the part of the lens 24 where the resin is exposed is etched together with the island IM of the mask pattern MA. Thereby, the antireflection structure 52 having a structure in which the volume density of the concavo-convex shape increases from the incident light side toward the lens center side is formed (right side of FIG. 2, FIG. 3).
If the island IM of the mask pattern MA is not completely removed after the etching process is completed, the mask pattern MA may be removed by adjusting the ion beam.

As described above, the exposed surface 12 of the object-side lens 10 of the in-vehicle camera lens unit 1 is required to have scratch resistance and wear resistance, and the hard coat layer 40 is preferably formed. From this point of view, the hard coat layer 40 functions as an intermediate layer between the resin base material of the object side lens 10 and the antireflection layer 50, and absorbs a large expansion / contraction difference between the resin base material and the antireflection material. Play a role in mitigating.
In this respect, since the exposed surface 12 of the object side lens 10 needs to have hardness, the performance cannot be maintained with the structural antireflection structure 52 whose shape is destroyed by contact or wear. Conversely, after the unit is assembled, the lens surface inside the unit where no objects come into contact (specifically, all the lens surfaces of the lenses 22, 24, and 26) is hardened with a hard coat layer 40 from the necessity and cost reduction. It is rather preferable not to have.
Therefore, in the present embodiment, it is preferable to form the inorganic antireflection layer 50 on the hard coat layer 40 on the exposed surface 12 of the object side lens 10, and conversely, the lenses 22, 24, 26 inside the unit. It is preferable to form an antireflection structure 52 having high temperature resistance on the lens surface.

According to the above embodiment, since the object side lens 10 is made of a certain cycloolefin resin, it is possible to ensure not only environmental resistance but also oil resistance and chemical resistance that can withstand actual use. .
Further, if the object side lens 10 is made of a certain cycloolefin-based resin, the hard coat layer 40 can be formed (attached) to the exposed surface 12, and the hard coat layer 40 can be used for various oils and chemicals. Even if the penetration of the object side lens 10 into the resin base material cannot be completely prevented, it is possible to suppress the deterioration of the object side lens 10.

Further, in the in-vehicle camera lens unit 1, an antireflection layer 50 is formed on the exposed surface 12 of the object side lens 10, and an antireflection structure 52 is formed on the lenses 22, 24, and 26 of the image side lens group 20, respectively. Are interrelated and can function.
That is, in the lens unit 1 for in-vehicle cameras, some of the lens surfaces of the lenses 22, 24, and 26 have a large curvature due to optical design. When an inorganic antireflection layer such as the antireflection layer 50 is to be formed on the surface having a large curvature, an antireflection layer capable of reducing both the reflectance at the center and the outer periphery of the lens is manufactured. It is very difficult. This is due to the fact that the inorganic antireflection layer has an incident angle dependency and that the film thickness (layer thickness) becomes thinner toward the outer periphery when the film is formed into a curved shape by a normal method. . As a result, multiple reflections other than the normal optical path may occur at the interfaces of the lenses 22, 24, and 26 inside the in-vehicle camera lens unit 1, and an optical abnormality called a ghost may be induced.
Also from these viewpoints, it is preferable to form an antireflection structure 52 having a small incident angle dependency on the lens surfaces of the lenses 22, 24, and 26 in the in-vehicle camera lens unit 1. That is, if the antireflection structure 52 is formed on the lens surface inside the in-vehicle camera lens unit 1, the ghost can be prevented from being induced.

On the other hand, in the in-vehicle camera lens unit 1, the object side lens 10 is larger than the size of the lenses 22, 24, and 26 in the unit or has a strong tendency in terms of optical design. In particular, the exposed surface 12 of the object side lens 10 has a size close to the diameter of the unit. Therefore, the object side lens 10 is also a convex lens with a certain degree of curvature of the exposed surface 12, but the amount of reflected light from the inside of the unit that reaches the outer peripheral portion of the exposed surface 12 of the object side lens 10 is small in size. It is easy to design the lens so that it does not reach it.
Therefore, regarding the antireflection of the object side lens 10, there is little cause of ghosting, and the antireflection layer 50 is formed on the exposed surface 12 of the object side lens 10 from the viewpoint of emphasizing scratch resistance and wear resistance. Is preferred. That is, if the antireflection layer 50 is formed on the exposed surface 12 of the object side lens 10, the scratch resistance and the wear resistance can be improved while suppressing the occurrence of ghost.

(1) Sample preparation The following six types of resins A to F, which can be candidates for optical performance, are prepared as object-side lenses for in-vehicle camera lens units. Each resin is molded into a predetermined lens shape. Samples 1 to 6 ”(see Table 2).
"A": Cycloolefin resin (ZEONEX E48R, manufactured by Nippon Zeon)
"B": cycloolefin resin (APL5514ML, manufactured by Mitsui Chemicals)
"C": Polycarbonate (AD5503, manufactured by Teijin Chemicals Ltd.)
"D": General acrylic (WF100, manufactured by Mitsubishi Rayon Co., Ltd.)
"E": Chemical resistant acrylic (VH4, manufactured by Mitsubishi Rayon Co., Ltd.)
"F": heat-resistant acrylic (VH5, manufactured by Mitsubishi Rayon Co., Ltd.)

(2) Oil resistance / chemical resistance test The following 13 kinds of test chemicals listed in Table 1 and strong acid (pH 1) test chemicals were prepared, and oil resistance / chemical resistance tests of each sample were performed using these test chemicals.
In the oil resistance / chemical resistance test, the following treatments (i) to (iv) were performed for each sample for a total of 3 cycles. The total immersion time of each sample in the test chemical in the oil resistance / chemical resistance test is 90 minutes.
(I) Heat for 30 minutes at a temperature of 80 ° C. and 0% humidity (ii) Soak in test chemical for 30 minutes (iii) Leave at room temperature for 6-15 hours (iv) Soak in water for 1 minute, then Wipe the surface

(3) Evaluation of sample The sample after the oil resistance / chemical resistance test was evaluated as follows from the following viewpoints.
In the relationship between the optical properties of optical components and chemicals (including oil), if any appearance defects (clouding, white turbidity, scratches, cracks, melting, erosion, etc.) occur on the optical surface, the optical properties may be affected. It becomes a problem. Specifically, when the light that has entered the normal optical path is bent or scattered due to an appearance defect of the optical component, the amount of light in the normal optical path is attenuated, and this phenomenon becomes a problem. A haze meter (scattered light measuring device) is often used as a means for measuring the light loss of such an optical component.
In this example, the loss of light amount was measured by a method based on “How to determine haze of plastic-transparent material (JIS K 7136)” to evaluate oil resistance and chemical resistance. As a haze meter, “NDH 5000” manufactured by Nippon Denshoku Industries Co., Ltd. was used.
Briefly, as shown in FIG. 7, a haze meter 70 is used to transmit light from a light source 72 through a lens 74, a diaphragm 76, a lens 78, and a sample 80 in this order, and the transmitted light is transmitted in an integrating sphere 82. The light is received by the light receiver 84 (the sample after the oil resistance / chemical test is set as the sample 80). Based on the received light amount, the total light transmission amount is “TT”, and the transmission amount other than the parallel light is “ As DIF, scattered light (HAZE) was calculated from the conditional expression of HAZE (%) = (DIF / TT) × 100.
Since there is a correlation between the appearance defect of the optical component and the HAZE value, the samples after the oil / chemical resistance test were evaluated based on the HAZE value according to the following criteria.
“◯”: Less than 1% “Δ”: 1% or more to less than 2% “×”: 2% or more Table 2 shows the evaluation results.
In addition, about the samples 1, 2, and 4, the external appearance of the lens after an oil-proof and chemical-resistance test, etc. were shown in FIGS.

(4) Summary As shown in Table 2, in any of Samples 1 to 6, resistance to strong acid (pH 1) was good.
However, in Sample 1 (ZEONEX E48R), resistance to engine oil and body grease was not recognized, and the oil resistance was poor.
In sample 3 (AD5503), resistance to brake fluid and light removal liquid (acetone) was not recognized, and the oil resistance and chemical resistance were poor.
In sample 4 (WF100), resistance to brake fluid, water repellent coating agent, alcohol, and light removal liquid (acetone) was not recognized, and the oil resistance and chemical resistance were poor.
Sample 5 (VH4) and Sample 6 (VH5) were also inferior in resistance to brake fluid, water repellent coating agent, alcohol, and light removal liquid (acetone).

On the other hand, Sample 2 (APL5514ML) was not excellent in resistance to engine oil and body grease, but was excellent in overall oil resistance and chemical resistance.
From the above, the polyorene fin-based resin (ZEONEX E48R) that has been widely used as a lens material conventionally, the polycarbonate resin that is used in Patent Document 2 (see paragraph 0016, etc.), and Patent Document 3 (paragraph 0021). It is difficult to ensure oil resistance and chemical resistance with acrylic resins such as those used in the above), and in order to ensure such performance, it is useful to select a certain polyolene fin resin (APL5514ML). I know that there is.

In Example 2, a hard coat layer was formed on Samples 1 to 6 produced in Example 1, and these were designated as “Samples 1A to 6A”.
Samples 1A to 6A were subjected to the same oil / chemical resistance test and evaluation as in Example 1.
The hard coat layer was formed by first performing oxygen plasma treatment on the resin molded articles of Samples 1 to 6, and then applying and drying a hard coat agent by a spray method.
In the oxygen plasma treatment, after making a vacuum environment of 10 Pa, oxygen plasma was generated at an oxygen gas flow rate of 50 sccm and a power of 150 W, and the treatment was performed for 30 seconds.
In the coating treatment, a silicon-based thermosetting resin (Tosguard 510 manufactured by Momentive Performance Materials Japan) was used as a hard coating agent, and the layer thickness after drying was set to 2 to 4 μm.
The evaluation results are shown in Table 3.
In addition, as demonstrated in Example 1, since resistance to strong acid (pH 1) was good in any of Samples 1 to 6, strong acid was excluded from test chemicals in Example 2 (same in Examples 3 and 4). .)

As shown in Table 3, the results of Sample 1A (ZEONEX E48R) and Sample 4A (WF100) did not vary.
Sample 2A (APL5514ML) improved the resistance of engine oil and body grease, resulting in excellent oil resistance and chemical resistance for all test chemicals.
In sample 3A (AD5503), the resistance to car shampoo was improved and the weak alkali resistance was improved.
In sample 5A (VH4), the resistance of the weak acid detergent was improved, and the weak acid resistance was improved.
In sample 5A (VH4) and sample 6A (VH5), the alcohol resistance was improved and the alcohol resistance was improved.

Thus, oil resistance and chemical resistance were improved in many samples. This seems to be due to the effect of the hard coat layer protecting the surface of the molded product. However, the hard coat layer formation (adhesion) cannot be secured continuously, such as the outer periphery and side surfaces of the molded product, and the hard coat layer is not fully protected, preventing erosion of the molded product itself. It seems not.
In contrast, sample 2A (APL5514ML) has excellent oil resistance and chemical resistance for all test chemicals as described above, and a hard coat layer can be formed on certain cycloolefin-based resins (APL5514ML). It turns out that it is useful.
In particular, the formation (adhesion) of the hard coat layer is conventionally considered to be unsuitable for cycloolefin resins and suitable for polycarbonate resins having a higher refractive index with respect to d-line than cycloolefin resins, but sample 1A (ZEONEX E48R) and sample 2A (APL5514ML) are compared, sample 2A (APL5514ML) has improved oil resistance and chemical resistance, and a certain cycloolefin resin (APL5514ML) is selected to form a hard coat layer. It turns out to be useful.

In Example 3, an antireflection layer was further formed on Samples 1A to 6A produced in Example 2 and designated as “Samples 1B to 6B”. That is, in samples 1B to 6B, the hard coat layer and the antireflection layer were laminated in this order on samples 1 to 6.
Samples 1B to 6B were also subjected to the same oil resistance / chemical resistance test and evaluation as in Example 1.
The anti-reflective layer is made of a high refractive index material using Ti oxide and a low refractive index material using Si oxide. A total of four layers of material layers were alternately stacked.
In this case, a high refractive index material layer (first layer) was formed immediately above the hard coat layer.
The thickness of the antireflection layer is 15 nm for the first high refractive index material layer (TiO ₂ layer), 30 nm for the second low refractive index material layer (SiO ₂ layer), and the third layer. The high refractive index material layer (TiO ₂ layer) was 120 nm, the fourth low refractive index material layer (SiO ₂ layer) was 85 nm, and the total layer thickness was 250 nm.
The evaluation results are shown in Table 4.

  As shown in Table 4, the resistance of the water repellent coating agent was improved in sample 5B (VH4), and the resistance of alcohol was improved in sample 6B (VH5). was gotten.

In Example 4, a water / oil repellent layer was further formed on Samples 1B to 6B produced in Example 3 to obtain “Samples 1C to 6C”. That is, in samples 1C to 6C, the hard coat layer, the antireflection layer, and the water / oil repellent layer were laminated in this order on samples 1 to 6.
Samples 1C to 6C were subjected to the same oil / chemical resistance test and evaluation as in Example 1.
The water / oil repellent layer was formed by depositing a fluorine-based material by a vacuum deposition method.
In this case, Merck substance WR1 was used as the fluorine-based material, and the layer thickness was 5 to 20 nm.
The evaluation results are shown in Table 5.

  As shown in Table 5, sample 1C (ZEONEX E48R) has body grease resistance, sample 3C (AD5503) has brake fluid resistance, sample 4C (WF100) has alcohol resistance, and sample 5C (VH4) has brake fluid resistance. However, in sample 6C (VH5), the resistance of the water-repellent coating agent was improved. This is probably because the test chemical was repelled by the water / oil repellent layer, and the protective effect increased somewhat.

DESCRIPTION OF SYMBOLS 1 Lens unit for vehicle-mounted cameras 10 Object side lens 12 Exposed surface 20 Image side lens group 22, 24, 26 Lens 30, 32 Diaphragm 40 Hard coat layer 50 Antireflection layer 52 Antireflection structure 60 Water repellent / oil repellent layer 70 Haze meter 72 Light source 74 Lens 76 Aperture 78 Lens 80 Sample 82 Integrating sphere 84 Receiver

Claims (5)

In the in-vehicle camera lens unit mounted on the in-vehicle camera,
A resin object side lens having a surface exposed to the outside air;
An image side lens group which is disposed on the image side from the object side lens and is composed of one or a plurality of resin lenses,
All the lenses of the object side lens and the image side lens group are made of resin,
An in-vehicle camera lens unit, wherein the object side lens is made of a certain cycloolefin resin. The in-vehicle camera lens unit according to claim 1,
The exposed surface of the object side lens is subjected to a certain surface treatment,
An in-vehicle camera lens unit, wherein a hard coat layer is formed on an exposed surface of the object side lens after the surface treatment. The in-vehicle camera lens unit according to claim 1 or 2,
An in-vehicle camera lens unit, wherein an antireflection layer is formed on an outermost surface of the exposed surface of the object side lens. In the vehicle-mounted camera lens unit according to any one of claims 1 to 3,
A lens unit for an in-vehicle camera, wherein a water-repellent / oil-repellent layer is formed on an outermost surface of the exposed surface of the object side lens. In the vehicle-mounted camera lens unit according to any one of claims 1 to 4,
An in-vehicle camera lens unit, wherein an antireflection structure is formed on a surface of at least one lens of the image side lens group.