Optical Components

Abstract

To provide an optical component that has an adhesive structure of an optical lens and a metal housing using a low cure shrinkage UV curable adhesive, and prevents positional deviation over time in use environments (high temperature, high temperature and high humidity, and temperature cycle) to allow high positional accuracy.SOLUTION: In an optical component having an adhesion part formed of an adhesive structure that bonds and fixes an optical lens and a metal housing using a UV curable adhesive including a filler formed of metal oxide in an amount of 50 mass% or more and at least one or more types of adhesives, the adhesion part is such that the UV curable adhesive satisfying the following first requirement and second requirement is arranged at a center part, and 50% or more of a surface of the UV curable adhesive not including a part to be bonded with an addition polymerization silicone rubber adhesive satisfying the following third requirement. First requirement: a water absorption of 0.5% or less in an environment of 85°C and 85%; second requirement: Tg of 105°C or more; third requirement: a heat loss of 0.3% or less in an environment of 105°C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical section Product Regarding. [Background technology]

[0002] Optical components that can be applied to devices equipped with optical components, such as head-up displays, are known. To fix the position of optical components (lenses, etc.), UV-curable adhesives are often used, which have low cure shrinkage, short cure times, and good productivity. In particular, acrylic radical polymerization adhesives and epoxy cationic polymerization adhesives are often used.

[0003] The installation of optical components may require high positioning accuracy, with even minute displacements of a few microns unacceptable within a storage temperature range of, for example, -40°C to +60°C. However, the adhesive used to secure the optical components to the holding member can experience a decrease in adhesive strength or changes in the internal stress of the adhesive due to factors such as moisture in the air, fine dust particles, or deterioration over time. This can cause changes in the state of fixation, leading to minute positional deviations in the secured optical components.

[0004] One known technique for solving the above-mentioned conventional problems is to cover the exposed parts of the UV-curable adhesive with a coating material (such as silicone resin or epoxy resin) to prevent moisture and fine dust from coming into contact with the UV-curable adhesive (see Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0005] The technology disclosed in Patent Document 1 makes it possible to prevent, for example, displacement over time due to reaction of a UV-curable adhesive within the storage temperature range of optical components (-40°C to +60°C). However, there are issues with using the technology of Patent Document 1 for optical components used in in-vehicle devices.

[0006] For example, consider the case where components using UV-curable adhesives such as acrylic radical polymerization adhesives or epoxy cationic polymerization adhesives are applied to in-vehicle equipment. In this case, it is possible to suppress misalignment over time in a temperature cycle environment within the storage temperature range of the in-vehicle equipment (-40°C to +105°C) or in a high-temperature, high-humidity environment (85°C, 85%).

[0007] Generally, when exposed to high temperatures of 105°C (the highest temperature in the storage temperature range) for a long period of time, oxygen is activated to form oxygen radicals, which can attack polymer materials. UV-curable adhesives are susceptible to attack by activated oxygen radicals. Therefore, when exposed to high temperatures for a long period of time, the initiators and additives in the UV-curable adhesive volatilize and oxidize and decompose, causing weight loss. Therefore, when exposed to a 105°C environment for a long period of time, the UV-curable adhesive shrinks due to weight loss, causing misalignment over time.

[0008] That is, in a long-term environment at 105°C, it is necessary to limit the physical properties of the adhesive (Tg, heat loss), but the physical properties of the adhesive are not taken into consideration in conventional technologies including Patent Document 1. Therefore, when conventional technologies are used to apply optical components to a long-term environment at 105°C, there is a problem in reliably preventing positional deviation over time.

[0009] Furthermore, assuming that the optical component-equipped device is an in-vehicle device, the environment in which the in-vehicle device is used will be high temperature and humidity (85°C, 85%), so the optical components are required to be durable in that environment. In other words, durability is required in a harsher environment than the general high temperature and humidity (45°C, 90%) that is assumed for the technology disclosed in Patent Document 1.

[0010] Additionally, in-vehicle devices require longer durability than optical pickup components such as those exemplified in Patent Document 1. The technology disclosed in Patent Document 1 fails to consider the moisture-proofing properties of the coating material, allowing moisture to penetrate the coating material. Therefore, while the technology disclosed in Patent Document 1 can delay moisture penetration into the UV-curable adhesive, this is insufficient for the service life of the in-vehicle device. Therefore, when the technology disclosed in Patent Document 1 is applied to optical components used in in-vehicle devices, moisture may penetrate the UV-curable adhesive, causing it to swell due to water absorption, resulting in misalignment. In other words, conventional technologies, including Patent Document 1, have a problem in that it is necessary to limit the water absorption rate of the adhesive under long-term high-temperature and high-humidity conditions.

[0011] As described above, conventional technology does not take into account the physical properties of UV-curing adhesives, and therefore poses challenges when used for components that require reliable prevention of positional shifting over time, even when used for long periods in high-temperature, high-humidity environments, such as optical components used in automotive equipment.

[0012] The present invention aims to provide an optical component that has a bonding structure between an optical lens and a metal housing using a low-cure shrinkage UV-curable adhesive, and that enables high positional accuracy by suppressing positional deviation over time in the usage environment (high temperature, high temperature and humidity, temperature cycles). [Means for solving the problem]

[0013] In order to solve the above technical problems, one aspect of the present invention is an optical component having an adhesive part having an adhesive structure in which an optical lens and a metal housing are adjacently bonded and fixed with a UV-curable adhesive containing 50% by mass or more of a filler made of a metal oxide and at least one type of adhesive, wherein the adhesive part is under A UV-curable adhesive that satisfies the first and second requirements above Between the optical lens and the metal housing The surface of the UV-curable adhesive is placed on the surface of the adhesive layer, and the surface of the adhesive layer is not included in the adhesive layer. Face , coated with an addition polymerization type silicone rubber adhesive that satisfies the third requirement below. Coverage rate is between 50% and 100% It is characterized by: First requirement: 85℃ Water absorption rate of 0.5% or less in an 85% humidity environment Second requirement: Tg105℃ or higher Third requirement: Heat loss of 0.3% or less in a 105°C environment [Effects of the Invention]

[0014] According to the present invention, the optical lens and metal housing are bonded together using a UV-curable adhesive with low cure shrinkage, which enables high positional accuracy by suppressing positional deviation over time in the usage environment (high temperature, high temperature and humidity, temperature cycles). [Brief explanation of the drawings]

[0015] [Figure 1] 1A and 1B are diagrams showing examples of the structure of an embodiment of an optical component according to the present invention. [Figure 2] 3 is a graph illustrating the properties of a UV-curable adhesive used in the optical component. [Figure 3] 3 is a graph illustrating the properties of a UV-curable adhesive used in the optical component. [Figure 4] 3 is a graph illustrating the properties of an addition polymerization type silicone rubber adhesive used in the optical component. [Figure 5] 3 is a graph illustrating the properties of an addition polymerization type silicone rubber adhesive used in the optical component. [Figure 6] 3A and 3B are diagrams illustrating a first embodiment of the optical component. [Figure 7] 5A to 5C are diagrams illustrating a bonding process for the optical component according to the first embodiment. [Figure 8] FIG. 3 is a diagram illustrating the film thickness direction in the first embodiment of the optical component. [Figure 9] FIG. 10 is a table showing the results of misalignment evaluations in tests conducted using a plurality of examples and comparative examples of the optical component according to the embodiment. [Figure 10] FIG. 10 is a plan view showing an embodiment of an optical component mounting device including the embodiment. [Figure 11] FIG. 2 is a configuration diagram of the optical component mounting device. DETAILED DESCRIPTION OF THE INVENTION

[0016] [Adhesive structure] 1A and 1B are a front view and a side view, respectively, showing an example of the structure of an optical lens structure 10 as an embodiment of an optical component according to the present invention. As shown in Fig. 1, the optical lens structure 10 according to this embodiment includes an optical lens 1, which is a type of optical component, a metal housing 2 as a member to which the optical component is fixed, a UV-curable adhesive 3, and an addition polymerization type silicone rubber adhesive 4.

[0017] The metal housing 2 is a holding member for fixing and holding the optical lens 1 in a predetermined position and state. The UV-curing adhesive 3 is an adhesive member for fixing the optical lens 1 to the metal housing 2. The addition polymerization type silicone rubber adhesive 4 is a coating material for covering the surface of the UV-curing adhesive 3, not including the adhesive portion between the UV-curing adhesive 3 and the object to be bonded (the optical lens 1 and the metal housing 2).

[0018] [Optical component mounting device] Here, as an example of an optical component mounting device that operates by mounting the optical lens structure 10 according to this embodiment, a configuration example of a head-up display device 100 as an in-vehicle device will be described with reference to Fig. 10 and Fig. 11. Fig. 10 is a plan view of the head-up display device 100. Fig. 11 is a diagram showing an example of the configuration of a display device 101 that includes the optical lens structure 10.

[0019] 10 , the head-up display device 100 includes a display device 101 as an example of utilization of the optical lens structure 10, and a free-form surface mirror 103. The display device 101 also includes a light source device 11, an optical deflection device 13, and a screen 15.

[0020] The light source device 11 is a device that irradiates laser light emitted from a light source to the outside of the device. The light source device 11 may irradiate laser light that is a combination of laser light of three colors, R, G, and B, for example.

[0021] The optical deflection device 13 is an example of an image forming unit that receives the irradiation light emitted from the light source device 11 and emits image light that forms an image, and is a device that changes the direction of travel of laser light using MEMS (Micro Electro Mechanical Systems) or the like.

[0022] The screen 15 is an example of a component on which an image is formed by focusing the image light emitted from the optical deflection device 13, and is a diverging component that has the function of diverging the laser light at a predetermined divergence angle. The screen 15 is configured, for example, in the form of an EPE (Exit Pupil Expander) using a transmissive optical element having a light diffusing effect, such as a micro lens array (MLA) or a diffusion plate.

[0023] Here, the projection method of the display device 101 is a "panel method" in which an intermediate image is formed using an imaging device such as a liquid crystal panel, a DMD panel (digital mirror device panel), or a fluorescent display tube (VFD), and a "laser scanning method" in which an intermediate image is formed by scanning laser light emitted from the light source device 11 with a scanning means.

[0024] 11 is a diagram showing an example of the configuration of display device 101. In addition to light source device 11, optical deflection device 13, and screen 15 described with reference to FIG. 10, display device 101 further includes a filter 307 that optically modulates the laser light emitted from light source device 11, a condenser lens 410 that condenses the modulated light optically modulated by filter 307 toward optical deflection device 13, a mirror 401 that reflects the deflected light deflected by optical deflection device 13, and a second mirror 402 that reflects the light reflected by mirror 401 toward screen 15.

[0025] Light source device 11 includes light source elements 111R, 111G, and 111B (hereinafter referred to as light source element 111 when there is no need to distinguish between them), collimator lenses 112R, 112G, and 112B, apertures 113R, 113G, and 113B, combining elements 114, 115, and 116, and a lens 117.

[0026] The light source elements 111R, 111G, and 111B that emit three-color (R, G, and B) laser beams are, for example, laser diodes (LDs) each having one or more light-emitting points. The light source elements 111R, 111G, and 111B emit laser beams (light beams) of different wavelengths λR, λG, and λB (for example, λR=640 nm, λG=530 nm, and λB=445 nm).

[0027] The emitted laser beams (beams) are coupled by collimator lenses 112R, 112G, and 112B, respectively, to form a substantially parallel beam. The coupled laser beams (beams) are combined by three combining elements 114, 115, and 116. The combining elements 114, 115, and 116 are plate-shaped or prism-shaped dichroic mirrors that reflect or transmit the laser beams (beams) according to their wavelengths, and combine them into a single beam. The combined beam passes through filter 307 and condenser lens 410 and is guided to optical deflection device 13.

[0028] The display device 101 is constructed by assembling a housing 10A, a mirror unit (mirror holding member) 305, and a screen unit 300. The housing 10A holds and accommodates light source elements 111R, 111G, and 111B, collimator lenses 112R, 112G, and 112B, combining elements 114, 115, and 116, a filter 307, a condenser lens 410, and an optical deflection device 13. The mirror unit 305 holds a mirror 401 and a second mirror 402. The screen unit 300 is an example of a holding member that holds a screen 15.

[0029] The light source unit 110 is detachable from the housing 10A and holds the light source elements 111R, 111G, and 111B.

[0030] [Position accuracy required in an in-vehicle environment] Assume that the head-up display device 100 described above is mounted on a vehicle. To ensure the optical properties of the head-up display device 100, it is necessary to adjust (align) its position with other optical components and then fix it to an adherend such as a vehicle housing. For this reason, a UV-curable adhesive 3 that can be cured immediately after aligning the optical lens 1 included in the optical lens structure 10 is often used. Therefore, the UV-curable adhesive 3 is required to have low cure shrinkage and high positional accuracy under the following storage environment.

[0031] First condition: High temperature (105℃) Second condition: Temperature cycle within a specified temperature range (-40℃ to +105℃) Third condition: High temperature and high humidity (85℃85%)

[0032] Furthermore, in a structure in which an optical lens 1 serving as an optical component is bonded to a metal housing 2 serving as an adherend to which the optical component is fixed (hereinafter, this structure may be referred to as "optical component bonding"), the thickness of the adhesive layer varies by approximately 100 μm to 400 μm during alignment of the optical lens 1 serving as an optical component. In order to achieve high positional accuracy under various environments despite variations in the adhesive layer thickness, it is necessary to suppress the positional deviation over time under each environment to within ±1% of the adhesive layer thickness. For example, in the case of a 200 μm thickness, it is necessary to suppress the positional deviation over time to within ±200 μm.

[0033] [About adhesives] Next, the properties of the UV-curable adhesive 3 according to this embodiment will be described. As the UV-curable adhesive 3, it is possible to use an epoxy-based or acrylic-based UV-curable adhesive containing 50 mass % or more of a filler made of a metal oxide such as silica. In general, filling the adhesive with silica filler enables low cure shrinkage during UV irradiation.

[0034] In addition, the UV-curable adhesive 3 is configured to satisfy the following first and second requirements, which will be described in detail below.

[0035] First requirement: Water absorption rate of 0.5% or less in an 85°C / 85% humidity environment Second requirement: Tg 105℃ or higher

[0036] [Water absorption rate of 0.5% or less in an 85°C, 85% humidity environment] The water absorption rate, which is one of the first requirements for the UV-curable adhesive 3 according to this embodiment, is measured by the following method. Specifically, the weight of the cured product of the prepared UV-curable adhesive 3 alone before the test and after leaving it at 85°C and 85% humidity for 1000 hours are measured. The water absorption rate is calculated by the following formula (1) using the measured weight.

[0037] (Formula 1) Water absorption rate [%] = 100 × (weight after 1000 hours at 85°C and 85% humidity - weight before testing) / weight before testing

[0038] Here, the relationship between water absorption rate and misalignment over time will be explained using the graph in Fig. 2. In the graph in Fig. 2, the horizontal axis represents the water absorption rate of the UV-curable adhesive 3 in an environment of 85°C and 85% humidity, and the vertical axis represents misalignment over time of the UV-curable adhesive 3 in an environment of 85°C and 85% humidity. When the misalignment over time is within ±1% of the adhesive layer thickness, it is plotted as "◯", and when it is greater than ±1% of the adhesive layer thickness, it is plotted as "X".

[0039] In an 85°C, 85% humidity environment, the UV-curable adhesive 3 absorbs water and swells. Therefore, the greater the water absorption rate of the UV-curable adhesive 3 in an 85°C, 85% humidity environment, the greater the positional deviation over time due to the effects of water absorption and swelling. If the water absorption rate of the UV-curable adhesive 3 in an 85°C, 85% humidity environment is 0.5% or less, it is possible to ensure that the positional deviation over time in an 85°C, 85% humidity environment is ±1% or less.

[0040] [Tg 105℃ or higher] Next, a method for measuring Tg, which is included in the second requirement for the UV-curable adhesive 3 according to this embodiment, will be described. In this embodiment, the glass transition temperature is measured by TMA using a cured adhesive alone of the prepared UV-curable adhesive 3. Then, based on the measurement results, the inflection point temperature derived from the glass transition temperature is determined to be Tg.

[0041] Here, the relationship between Tg and temporal positional shift in a temperature cycle over a predetermined temperature range will be explained using the graph in Fig. 3. In the graph in Fig. 3, the horizontal axis represents Tg, and the vertical axis represents temporal positional shift in a temperature cycle (-40°C to +105°C). When the temporal positional shift is within ±1% of the adhesive layer thickness, it is plotted with "◯", and when it is greater than ±1% of the adhesive layer thickness, it is plotted with "X".

[0042] If Tg is less than 105°C, the maximum temperature in the storage temperature range, the UV-curable adhesive 3 will suddenly soften in a temperature environment above Tg. Therefore, in a temperature environment above Tg, the UV-curable adhesive 3 will be unable to withstand (will succumb to) the internal stress caused by the weight of the optical lens 1, etc., causing the adhesive layer of the UV-curable adhesive 3 to compress and deform, resulting in misalignment.

[0043] On the other hand, if the Tg of the UV-curable adhesive 3 is 105°C or higher, the Tg will not be exceeded within the storage temperature range, preventing the UV-curable adhesive 3 from suddenly softening and preventing the UV-curable adhesive 3 from succumbing to internal stress, ensuring that positional deviation over time is within ±1%. For these reasons, to achieve high positional accuracy in various environments (high temperature, high temperature and high humidity, and temperature cycles), the Tg of the UV-curable adhesive 3 must be set to a maximum temperature of 105°C or higher for each environment.

[0044] [UV-curing adhesive 3 positional deviation over time in a long-term 105°C environment] A UV-curable adhesive 3 configured to satisfy the first and second requirements can suppress misalignment over time in an 85°C / 85% humidity environment and a temperature cycle (-40°C to +105°C) environment. Compared to a temperature cycle (-40°C to +105°C) environment, if the UV-curable adhesive 3 is exposed to a 105°C environment for a long period of time, oxygen is activated to become oxygen radicals, which may attack the polymer material.

[0045] The UV-curable adhesive 3 is easily attacked by activated oxygen radicals, and so in a long-term 105°C environment, thermal weight loss occurs due to the volatilization and oxidative decomposition of the initiator and additives of the UV-curable adhesive 3. Therefore, in a long-term 105°C environment, the UV-curable adhesive 3 shrinks due to thermal weight loss, causing misalignment over time.

[0046] Therefore, in the optical lens structure 10 according to this embodiment, the surface of the UV-curable adhesive 3, which does not include the adhesive portion (adhesion section) between the optical lens 1 and the metal housing 2 as the objects to be adhered, is covered with an addition polymerization silicone rubber adhesive 4 that satisfies the third requirement. This prevents the UV-curable adhesive 3 from losing weight due to heat in a long-term 105°C environment, and makes it possible to suppress positional displacement over time in a long-term 105°C environment. Details of the addition polymerization silicone rubber adhesive 4 will be described below.

[0047] [Addition polymerization type silicone rubber adhesive 4] Generally, silicone rubber adhesives are known to be of the condensation polymerization type and the addition polymerization type. Condensation polymerization type silicone rubber generates small amounts of outgassing, such as acetone, alcohol, and oxime, during the reaction, and there is a concern that if this outgas adheres to the optical lens 1, it may impair the optical properties. For this reason, this embodiment is limited to the addition polymerization type silicone rubber adhesive. Heat-curing and room-temperature-curing addition polymerization type silicone rubber adhesives can be used as the addition polymerization type silicone rubber adhesive 4.

[0048] Silicone rubber is not easily attacked by oxygen radicals activated in a 105°C environment, so by covering the surface of the UV-curing adhesive 3, which does not include the bonded portion between the objects to be bonded (optical lens 1 and metal housing 2), with an addition polymerization silicone rubber adhesive 4, it acts as follows in a 105°C environment: The activated oxygen radicals are adsorbed or consumed by the addition polymerization silicone rubber adhesive 4, so that the oxygen radicals do not reach the UV-curing adhesive 3.

[0049] Therefore, even in a long-term environment of 105°C, oxygen does not come into direct contact with the UV-curable adhesive 3, preventing the initiator and additives of the UV-curable adhesive 3 from volatilizing or oxidizing decomposition, and preventing shrinkage of the UV-curable adhesive 3 due to weight loss caused by heating.

[0050] Generally, silicone rubber adhesives have high moisture resistance, so the addition polymerization type silicone rubber adhesive 4 does not specify a water absorption rate in an 85°C / 85% humidity environment like the UV-curing adhesive 3. Also, generally, silicone rubber adhesives have a Tg of -40°C or lower, and are always above the Tg of the silicone rubber adhesive in a storage environment (-40°C to +105°C). If the storage environment temperature crosses the Tg, the adhesive will suddenly soften when it exceeds the Tg. If the storage environment (-40°C to +105°C) is always above the Tg, the temperature will not cross the Tg and the adhesive will not suddenly soften, so the addition polymerization type silicone rubber adhesive 4 does not specify a Tg like the UV-curing adhesive 3.

[0051] The addition polymerization type silicone rubber adhesive 4 having the above properties is constituted by the following third requirement, which will be explained in detail below.

[0052] Third requirement: Heat loss of 0.3% or less in a 105°C environment

[0053] [Loss of weight at heat of 0.3% or less in a 105°C environment] The heat loss of the addition polymerization type silicone rubber adhesive 4 in a 105°C environment was measured as follows. Specifically, the weight of the prepared cured addition polymerization type silicone rubber adhesive 4 alone was measured before testing and after leaving it at 105°C for 1000 hours. The measured weights were used to calculate the heat loss in a 105°C environment using the following equation (2).

[0054] Formula (2) Heat loss [%] = 100 x (weight before test - weight after 1000 hours at 105°C) / weight before test

[0055] The properties of the addition polymerization type silicone rubber adhesive 4 will now be described using the graph in Fig. 4. In the graph in Fig. 4, the horizontal axis represents the heat loss in a 105°C environment, and the vertical axis represents the positional shift over time in a 105°C environment of an adhesive structure in which the surface of the UV-curing adhesive 3, excluding the bonded portions between the objects to be bonded (optical lens 1 and metal housing 2), is completely covered with the addition polymerization type silicone rubber adhesive 4.

[0056] When the positional deviation over time is within ±1% of the adhesive layer thickness, it is plotted with "◯", and when it is ±1% or more of the adhesive layer thickness, it is plotted with "X".

[0057] In a long-term 105°C environment, thermal weight loss occurs due to the volatilization and oxidative decomposition of the adhesive's initiator and additives. Therefore, the greater the thermal weight loss of the addition polymerization silicone rubber adhesive 4, the greater the adhesive contraction, and the greater the positional misalignment over time in the direction of compression of the adhesive layer. Therefore, as shown in Figure 4, if the addition polymerization silicone rubber adhesive 4 has a thermal weight loss of 0.3% or less in a 105°C environment, it can ensure that the positional misalignment over time in a 105°C environment is within ±1%.

[0058] If 50% or more of the surface of the UV-curable adhesive 3, not including the adhesive portion between the objects to be bonded (optical lens 1 and metal housing 2), is covered with the addition polymerization type silicone rubber adhesive 4, high positional accuracy is possible in an environment of 105°C. Details of the coverage rate are explained below.

[0059] [Coverage rate of addition polymerization type silicone rubber adhesive 4] The coverage rate of the addition polymerization type silicone rubber adhesive 4 according to this embodiment can be measured by the following method: Using a microscope, the following surface area A and surface area B are measured, and the coverage rate is calculated using the following formula (3).

[0060] Surface area A: The surface area of ​​the UV-curable adhesive 3, excluding the bonded portion between the objects to be bonded (optical lens 1 and metal housing 2) after the optical component and metal housing are released in the sixth step of the bonding process described below.

[0061] Surface area B: The surface area of ​​the portion of the UV-curable adhesive 3 exposed from the surface of the addition polymerization type silicone rubber adhesive 4, excluding the bonded portion between the silicone rubber adhesive thermally cured and the bonded objects (optical lens 1 and metal housing 2) in the eighth step of the bonding process described below.

[0062] Formula (3) Coverage [%] = 100 × (surface area A – surface area B) / surface area A

[0063] The graph in Figure 5 shows the relationship between the coverage of the addition polymerization type silicone rubber adhesive 4 that satisfies the third requirement above and the positional misalignment over time in a 105°C environment. In the graph in Figure 5, the horizontal axis represents the coverage of the addition polymerization type silicone rubber adhesive 4, and the vertical axis represents the positional misalignment over time in a 105°C environment. When the positional misalignment over time is within ±1% of the adhesive layer thickness, it is plotted with a "◯", and when it is greater than ±1% of the adhesive layer thickness, it is plotted with an "X".

[0064] If the coverage of the addition polymerization silicone rubber adhesive 4 is less than 50%, the oxygen radicals activated in a 105°C environment cannot be adsorbed or consumed by the addition polymerization silicone rubber adhesive 4. Therefore, as shown in Figure 5, if the coverage of the addition polymerization silicone rubber adhesive 4 is less than 50%, oxygen comes into contact with the UV-curable adhesive 3, causing thermal weight loss due to volatilization and oxidative decomposition of the initiator and additives of the UV-curable adhesive 3. As a result, contraction of the UV-curable adhesive 3 causes displacement of the adhesive layer in the compression direction over time.

[0065] Furthermore, if the coverage rate of the addition polymerization type silicone rubber adhesive 4 is 50% or more, oxygen radicals activated in a 105°C environment can be adsorbed to or consumed by the addition polymerization type silicone rubber adhesive 4, thereby suppressing heat loss of the UV-curing adhesive 3. As a result, it is possible to ensure that the positional deviation over time in a 105°C environment is within ±1%.

[0066] [About the adhesive process] Next, a process (adhesion process) for adhering objects (optical lens 1 and metal housing 2) according to this embodiment will be described. The adhesion process according to this embodiment includes the following first to eighth steps. Each step will be described below.

[0067] [First process: Surface treatment] The first step is a surface treatment step. Surface treatment is performed to improve the wettability of the adherends (optical lens 1 and metal housing 2) and to improve the bonding strength between the adhesive and the adherend. Examples of surface treatment methods include atmospheric pressure plasma treatment, reduced pressure plasma treatment, corona treatment, plasma treatment, and UV treatment.

[0068] [Second step: Fixing optical components and metal housing] The second step is the "fixing of the optical component and metal housing" step. This is the step of fixing the surface-treated optical lens 1 and the metal housing 2 in place. Fixing is performed using the optical component and metal housing fixing function of the optical component bonding device. Methods for fixing the optical lens 1 include chucks and clamps, and methods for fixing the metal housing 2 include screw fastening and toggle clamps.

[0069] [Third process: UV adhesive application] The third step is a UV adhesive application step. The UV curing adhesive 3 is applied using the application function of the optical component bonding device. Examples of application methods include using a dispenser.

[0070] [Fourth step: Optical component alignment] The fourth step is the optical component alignment step. The fixed optical lens 1 is aligned to a predetermined position. Optical component alignment is performed using the position adjustment function of the optical component bonding device. Possible methods for position adjustment include an active alignment device, a precision desktop three-axis robot, and an XYZ-axis linear ball.

[0071] [Fifth step: UV curing of adhesive] The fifth step is a UV curing step of the adhesive. In this step, the applied UV-curable adhesive 3 is irradiated with UV light from above the optical lens 1 to cure it. The UV curing of the adhesive is performed using the UV irradiation function of the optical component bonding device. Examples of UV irradiation methods include ultraviolet lamps, visible light lamps, and infrared lamps. Examples of ultraviolet lamps include high-pressure mercury lamps, low-pressure mercury lamps, metal halide lamps, high-power metal halide lamps, gallium lamps, xenon lamps, xenon flash lamps, excimer lamps, UV-LEDs, and electrodeless lamps. One or more UV irradiators may be used as long as they can cure the adhesive.

[0072] [Sixth step: Unfixing the optical components and metal housing] The sixth step is the optical component / metal housing release step. In this step, after the UV-curing adhesive 3 has cured, the optical lens 1 and metal housing 2 are released from their fixed state and removed from the optical component bonding device. The optical component / metal housing 2 is released from their fixed state using the optical component / metal housing fixing function of the optical component bonding device. Methods for fixing the optical lens 1 include a chuck and a clamp, and methods for fixing the metal housing 2 include a screw fastening and a toggle clamp.

[0073] [Seventh step: Applying silicone rubber adhesive] The seventh step is a silicone rubber adhesive application step. The addition polymerization type silicone rubber adhesive 4 is applied using the application function of the optical component bonding device. Examples of application methods include using a dispenser.

[0074] [Eighth process: Heat curing of silicone rubber adhesive] The eighth step is a silicone rubber adhesive thermal curing step. In this step, after the addition polymerization type silicone rubber adhesive 4 is applied, it is thermally cured using a heating device. Examples of heating devices include an oven, a heater plate, a near-infrared halogen lamp, and a far-infrared heater.

[0075] [Example 1] Next, as the first example described in the above embodiment, an example will be described in which a "collimator lens in an Al housing" is used as the optical lens 1, and the thickness of the adhesive layer with the metal housing 2 is set to "200 μm" to fix the adherend.

[0076] (glue) In addition, in the first example, an acrylic UV-curable adhesive 3 was used as the UV-curable adhesive, and a heat-curable addition-polymerization silicone rubber adhesive 4 was used as the addition-polymerization silicone rubber adhesive 4. The water absorption rate and Tg of the UV-curable adhesive 3 in an 85°C / 85% humidity environment, and the heat loss evaluation of the heat-curable addition-polymerization silicone rubber adhesive 4 in a 105°C environment were measured using the following methods.

[0077] (Water absorption measured in an 85℃ 85% humidity environment) The water absorption rate of the UV-curable adhesive 3 was measured using an electronic balance (GR-202 (A&D)). The weight of the cured product of the prepared UV-curable adhesive 3 before the test and the weight after leaving it at 85°C and 85% humidity for 1000 hours were measured, and the water absorption rate in an 85°C and 85% humidity environment was calculated using the following equation (4).

[0078] Formula (4) Water absorption rate [%] = 100 × (weight after 1000 hours at 85°C and 85% humidity - weight before testing) / weight before testing

[0079] The measurement results under the above conditions showed that the water absorption rate in an environment of 85°C and 85% humidity was 0.3%.

[0080] (Tg measurement) The Tg of UV-curable adhesive 3 was measured using a TMA4000SA (manufactured by Netsch Japan). The cured product of UV-curable adhesive 3 prepared for glass transition temperature measurement was measured under the following conditions: width 4 mm, length 20 mm, load 10 gf, temperature rise rate 10°C / min, and air atmosphere. The inflection point temperature derived from the glass transition temperature was determined to be Tg. The measurement result was Tg = 123°C.

[0081] (Measurement of heat loss in a 105℃ environment) An electronic balance GR-202 (A&D) was used to measure the heat loss of addition polymerization type silicone rubber adhesive 4 in a 105°C environment. The weight of the cured product of addition polymerization type silicone rubber adhesive 4 prepared alone before testing and after leaving it at 105°C for 1000 hours were measured, and the heat loss in a 105°C environment was calculated using the following equation (5).

[0082] Formula (5) Heat loss [%] = 100 x (weight before test - weight after 1000 hours at 105°C) / weight before test

[0083] Measurements under the above conditions showed that the weight loss upon heating in a 105°C environment was 0.2%.

[0084] (Optical Lens 1) A collimator lens was used as the optical lens 1. The material of the collimator lens was L-BSL7, and the dimensions were Φ5.1 and a thickness of 2.35 mm.

[0085] (Metal case 2) An Al housing was used for the metal housing 2. The material of the Al housing was ADC12. The overall dimensions of the Al housing were 13.5 mm x 51.8 mm x t2.5 mm.

[0086] As shown in Fig. 6, the optical lens structure 10 according to the first embodiment uses a collimator lens with a circular optical surface as the optical lens 1. An Al housing is used as the metal housing 2. As shown in Fig. 6, the side surface of the collimator lens is fixed to one location on the surface (flat surface) of the Al housing with an adhesive layer thickness of 200 µm. An adhesive layer thickness of 200 µm means that the distance from the surface of the Al housing to the lowest point Lp of the collimator lens is 200 µm.

[0087] (Adhesive device) The bonding process in the first embodiment is shown in Figure 7. An optical component bonding apparatus 200 that can perform this bonding process includes a holder 210 that holds an optical lens 1, an adhesive applicator 220, and an ultraviolet ray irradiator 230. The optical component bonding apparatus 200 has the functions of fixing the optical component and metal housing, applying adhesive, adjusting position, and irradiating UV light.

[0088] The holder 210 operates as a pair, for example, a first chuck 211 with a groove formed on one side and a second chuck 212 with a flat surface on one side. The optical component bonding device 200 also has a fixing jig that fixes the metal housing 2 by screw fastening. The function of fixing the optical component and the metal housing is realized by the holder 210 and the fixing jig.

[0089] The adhesive applicator 220 is a so-called dispenser, and in the first embodiment, an "MS-1D" manufactured by Musashi Engineering Co., Ltd. The adhesive application function is realized by the dispenser.

[0090] The position adjustment function is realized by using an XYZ-axis linear ball micrometer head (XYZGS80, manufactured by Misumi Corporation) to fine-tune the relative positional relationship between the metal housing 2 and the optical lens 1 and achieve alignment of the optical components.

[0091] The ultraviolet irradiator 230 has a plate for so-called ultraviolet irradiation, and in the first embodiment, a Panasonic UV-LED curing device (ANUJ3500 (controller)), ANUJ6186 (smart head), and ANUJ6428 (φ8 spot lens) are used. The UV irradiation function is realized by the ultraviolet irradiator 230.

[0092] (Bonding process according to the first embodiment) Next, a first example of a process (adhesion process) for adhering objects (optical lens 1 and metal housing 2) according to this embodiment will be described. Note that Fig. 2 shows a process image from the second step to the seventh step.

[0093] [First process: Surface treatment] Surface treatment of the metal housing 2 was performed using an atmospheric pressure plasma treatment device (Piezobrush PZ2: manufactured by ARS Corporation). The surface treatment time was set to the time it took for the surface free energy of the collimator lens (optical lens 1) and the Al housing (metal housing 2) to increase and saturate. For each adhesive joint, surface treatment was performed on the collimator lens using a standard nozzle from a distance of 10 mm (recommended by the manufacturer), and on the Al housing using a near-field nozzle (for conductors) from a distance of 2 mm (recommended by the manufacturer).

[0094] [Second step: Fixing optical components and metal housing] 7(a), the collimator lens (optical lens 1) is held and fixed by a first chuck tool 211 and a second chuck tool 212, and the Al housing (metal housing 2) is fixed with screws provided in the optical component bonding device 200. Note that the screws are not shown in FIG.

[0095] [Third process: UV adhesive application] Next, as shown in Fig. 7(b), a UV-curable adhesive 3 is applied to the surface of the Al housing (metal housing 2). The application is performed using a dispenser (MS-1D, manufactured by Musashi Engineering Co., Ltd.) as an adhesive applicator 220. The amount of adhesive applied here is 3 mg, which is sufficient to achieve an adhesive layer thickness of 200 µm without adhering to the effective optical range of the collimator lens.

[0096] [Fourth step: Optical component alignment] 7(c), the fixed collimator lens is adjusted so that it is placed 200 μm above the Al housing using an XYZ-axis linear ball micrometer head (XYZGS80, manufactured by Misumi Corporation) provided in the optical component bonding apparatus 200. Normally, the position of the collimator lens needs to be adjusted to ensure the optical characteristics, but in the first example, the film thickness was limited to 200 μm in order to evaluate the positional deviation.

[0097] [Fifth step: UV curing of adhesive] 7(d), the applied UV-curing adhesive 3 is cured by a UV-LED curing device (ANUJ3500 (controller), ANUJ6186 (smart head), ANUJ6428 (φ8 spot lens), all manufactured by Panasonic) provided in the optical component bonding device 200. Ultraviolet light with a wavelength of 365 nm is irradiated from above the collimator lens in two directions.

[0098] [Sixth step: Unfixing the optical components and metal housing] 7(e), after the UV irradiation is completed, the first chuck 211 and the second chuck 212 are opened and the screws of the Al housing (metal housing 2) are released. This completes the process of removing the optical lens structure 10 from the optical component bonding device 200 and UV-curing the collimator lens (optical lens 1) to the Al housing (metal housing 2).

[0099] [Seventh step: Applying silicone rubber adhesive] Next, as shown in Fig. 7(f), an addition polymerization type silicone rubber adhesive 4 was applied to the Al housing (metal housing 2) using a dispenser (MS-1D, manufactured by Musashi Engineering Co., Ltd.) As shown in Fig. 7(f), 3 mg of UV-curable adhesive 3 was applied to both ends.

[0100] [Eighth process: Heat curing of silicone rubber adhesive] Finally, the optical lens structure 10 was subjected to a heat treatment in an oven (DX302, manufactured by Yamato Scientific Co., Ltd.) at 105° C. for 1 hour.

[0101] [Second Example] Next, a second example of the embodiment described above will be explained. The second example differs from the first example described above only in the seventh step (application of silicone rubber adhesive).

[0102] In the seventh step of the second embodiment, 2.0 mg of addition polymerization type silicone rubber adhesive 4 was applied to both ends of the UV curing type adhesive 3. The other steps were the same as those described in the first embodiment, and the collimator lens was fixed to the Al housing.

[0103] Below, comparative examples will be described first to explain the effectiveness of the first and second embodiments, and then each comparative example will be compared with the first and second embodiments.

[0104] [First Comparative Example] In the first comparative example, a UV-curable adhesive 3 was used, which has a water absorption rate of 1.5% in an 85°C / 85% humidity environment and a Tg of 90°C in an 85°C / 85% humidity environment. The other materials used were the same as in first example 1, and the collimator lens was fixed to the Al housing by the process described in the first example.

[0105] [Second Comparative Example] In the second comparative example, an addition polymerization type silicone rubber adhesive 4 was used, which has a heat loss of 1.2% in an environment of 105°C. Other materials were the same as in the first example 1, and the collimator lens was fixed to the Al housing by the process described in the first example.

[0106] [Third comparative example] In the third comparative example, in the seventh step (silicone rubber adhesive application process) in the first example, an addition polymerization type silicone rubber adhesive 4 was applied in an amount of 1.5 mg to each end of the UV curing type adhesive 3. Other than this, the materials and processes used were the same as in the first example, and the collimator lens was fixed to the Al housing.

[0107] [Fourth comparative example] In the fourth comparative example, in the seventh step (silicone rubber adhesive application process) in the first example, an addition polymerization type silicone rubber adhesive 4 was applied in an amount of 1.0 mg to each end of the UV curing type adhesive 3. Other than this, the materials and processes used were the same as in the first example, and the collimator lens was fixed to the Al housing.

[0108] [Fifth comparative example] In the fifth comparative example, the seventh step (the silicone rubber adhesive application process) and the eighth step (the silicone rubber adhesive thermal curing process) in the first example were not performed. Other than this, the materials and processes used were the same as those in the first example, and the collimator lens was fixed to the Al housing.

[0109] [Evaluation of coverage of addition polymerization type silicone rubber adhesive 4] Next, a method for measuring values ​​used to evaluate the coverage of the addition polymerization type silicone rubber adhesive 4 in the first and second examples and the first to fifth comparative examples will be described.

[0110] In the sixth step (optical component / metal housing release process) already explained, after the optical lens 1 (collimator lens) is released, the surface area of ​​the UV-curable adhesive 3, excluding the adherend, is measured using a microscope (VHK5000 (manufactured by Keyence Corporation)). This measurement result is referred to as the "first surface area."

[0111] Next, after the eighth step (thermal curing of the silicone rubber adhesive), the surface of the addition polymerization type silicone rubber adhesive 4, excluding the adherend, is observed, and the surface area of ​​the exposed portion of the UV-curable adhesive 3 is measured. This measurement result is designated as the "second surface area."

[0112] Next, the coverage of the addition polymerization type silicone rubber adhesive 4 was calculated using the following formula (6). The calculated values ​​are included in the table in FIG.

[0113] Formula (6) Coverage rate [%] = 100 × (first surface area - second surface area) / first surface area

[0114] [Test conditions] Using the optical lens structures 10 manufactured in the first and second examples and the first to fifth comparative examples, storage tests were carried out in various environments (105°C, 85°C 85%, temperature cycle (-40°C to +105°C)). The test methods for each environment will now be described.

[0115] (105℃ environmental test) The fabricated optical lens structure 10 was placed in a constant temperature incubator (DKN402 (manufactured by Yamato Scientific Co., Ltd.)) and left at 105°C for 1000 hours.

[0116] (85℃ 85% environmental test) The manufactured optical lens structure 10 was placed in a low-humidity (low-temperature) thermo-hygrostat (PDL-4J (manufactured by Espec Corp.)) and left at 85°C and 85% for 1000 hours.

[0117] (Temperature cycle environmental test) The manufactured optical lens structure 10 was placed in a thermal shock tester (TSA-72ES-A, manufactured by Espec Corporation), and 1000 temperature cycles were performed from "-40°C for 30 minutes" to "+105°C for 30 minutes" and "+105°C for 30 minutes" to "-40°C for 30 minutes."

[0118] (Evaluation of misalignment) A microscope (VHX-5000, Keyence, 200x magnification) was used to measure the misalignment. Images of the adhesive joint were taken with the microscope before each test (high temperature, high temperature and humidity, temperature cycle). Then, one feature point was set by scratching the optical lens 1 (collimator lens) in advance, and one feature point was set on the metal part (Al housing). The normal direction of the line segment connecting the collimator lens feature point and the Al housing feature point on the adhesive surface of the collimator lens was then measured.

[0119] The normal direction of the line segment connecting the collimator lens characteristic point and the Al housing characteristic point to the collimator lens bonding surface is the "film thickness direction FL" shown in Fig. 8. For misalignment evaluation, the direction of the arrow in the film thickness direction FL shown in Fig. 8 is the positive direction.

[0120] Next, images of the adhesive joint after each test (high temperature exposure, high temperature and high humidity, temperature cycle) are obtained, and the value of the line segment connecting the collimator lens feature point and the Al housing feature point in the normal direction (film thickness direction FL) of the collimator lens adhesive surface is measured. The amount of change from before each test (high temperature, high temperature and high humidity, temperature cycle) is set as the amount of positional deviation.

[0121] (Position misalignment evaluation results) The results of the misalignment evaluation after each of the tests described above (high temperature, high temperature and high humidity, and temperature cycle) are shown in Figure 9. If the misalignment over time was within ±1% of the adhesive layer thickness of 200 μm, that is, within ±200 μm, then a "Good" was entered in the evaluation column, and if it was greater than that, then an "Unfavorable" was entered in the evaluation column.

[0122] In Figure 9, "A" in the "Adhesive Type" column refers to an acrylic UV-curable adhesive 3 that simultaneously meets the first and second requirements. Similarly, "B" in the "Adhesive Type" column refers to a heat-curable addition polymerization silicone rubber adhesive 4 that meets the third requirement.

[0123] As shown in Figure 9, the coverage of the addition polymerization type silicone rubber adhesive 4 in the first and second examples is 100% and 50%, respectively. When the coverage is 50% or more, activated oxygen radicals are adsorbed to or consumed by the addition polymerization type silicone rubber adhesive 4, and do not reach the UV-curable adhesive 3. Therefore, oxygen does not come into direct contact with the UV-curable adhesive 3 in a 105°C environment, preventing the volatilization and oxidative decomposition of the initiator and additives in the UV-curable adhesive 3 and preventing shrinkage due to thermal weight loss of the UV-curable adhesive 3. This prevents positional deviation over time in a 105°C environment.

[0124] In the first comparative example, the water absorption of the UV-curable adhesive 3 is 1.5% and its Tg is 90°C, which does not satisfy either the first or second requirement. Because the water absorption is 0.5% or more, in an 85°C / 85% humidity environment, the UV-curable adhesive 3 absorbs water and swells, causing increased positional displacement over time. Furthermore, because the Tg is 105°C or less, in a 105°C environment or a temperature cycle environment, the UV-curable adhesive 3 softens, causing it to succumb to internal stress and undergo compressive deformation, resulting in positional displacement over time.

[0125] In the second comparative example, the heat loss of the addition polymerization type silicone rubber adhesive 4 was 1.2%, which does not satisfy the third requirement. Because the heat loss in a 105°C environment was 0.5% or more, the shrinkage caused by the heat loss of the addition polymerization type silicone rubber adhesive 4 increased the positional shift over time in the compression direction of the adhesive layer thickness.

[0126] In the third to fifth comparative examples, the coverage of the addition polymerization type silicone rubber adhesive 4 is less than 50%. When the coverage is less than 50%, activated oxygen radicals cannot be adsorbed or consumed by the addition polymerization type silicone rubber adhesive 4 in a 105°C environment, and the oxygen comes into direct contact with the UV-curable adhesive 3. As a result, in a 105°C environment, the initiator and additives of the UV-curable adhesive 3 volatilize or oxidize and decompose, causing the UV-curable adhesive 3 to shrink due to heat loss and resulting in misalignment over time. When the coverage is less than 50%, the smaller the coverage of the addition polymerization type silicone rubber adhesive 4, the greater the heat loss of the UV-curable adhesive 3, and the greater the misalignment over time in the direction of compression of the adhesive layer thickness.

[0127] As described above, in the optical lens structure 10 according to this embodiment, an adhesive is used to bond optical components, and the UV-curable adhesive 3 that satisfies the first and second requirements is placed at the center of the bonded portion using the adhesive. Then, 50% or more of the surface of the UV-curable adhesive 3, excluding the bonded portion, is covered with an addition polymerization type silicone rubber adhesive 4 that satisfies the third requirement.

[0128] With these structural features, the silicone rubber of the optical lens structure 10 according to this embodiment is less susceptible to attack by activated oxygen radicals. By covering 50% or more of the UV-curable adhesive 3 with the addition polymerization silicone rubber adhesive 4, the activated oxygen radicals are adsorbed to or consumed by the addition polymerization silicone rubber adhesive 4, and the oxygen radicals do not reach the UV-curable adhesive 3.

[0129] This action prevents oxygen from coming into direct contact with the UV-curable adhesive 3 even in a long-term environment of 105°C. As a result, it is possible to prevent the initiator and additives of the UV-curable adhesive 3 from volatilizing or oxidative decomposition, and it is possible to prevent shrinkage due to thermal weight loss of the UV-curable adhesive 3. As described above, the optical lens structure 10 according to this embodiment can suppress positional deviation over time in usage environments (high temperature, high temperature and high humidity, temperature cycles).

[0130] The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the technical gist thereof. The present invention covers all technical matters included in the technical ideas described in the claims. The above-described embodiments are preferred examples, but a person skilled in the art can realize various modifications from the disclosed contents. Such modifications are also included in the technical scope described in the claims. [Explanation of symbols]

[0131] 1: Optical lens 2: Metal housing 3: UV curing adhesive 4: Addition polymerization type silicone rubber adhesive 10: Optical lens structure 100: Head-up display device 200: Optical parts bonding equipment 210: Holder 211: First chuck 212: Second chuck 220: Adhesive applicator 230: Ultraviolet irradiation equipment [Prior art documents] [Patent documents]

[0132] [Patent Document 1] Japanese Patent Application Publication No. 05-210851

Claims

[Claim 1] An optical component having an adhesive part having an adhesive structure in which an optical lens and a metal housing are adjacently bonded and fixed with a UV-curable adhesive containing 50% by mass or more of a filler made of a metal oxide and at least one type of adhesive, The adhesive portion is a UV-curable adhesive that satisfies the following first and second requirements is disposed between the optical lens and the metal housing; An optical component characterized in that the surface of the UV-curable adhesive, excluding the portion to be adhered, is covered with an addition polymerization type silicone rubber adhesive that satisfies the third requirement below at a coverage rate of 50% or more and 100% or less. First requirement: Water absorption rate of 0.5% or less in an 85°C, 85% humidity environment Second requirement: Tg 105℃ or higher Third requirement: Heat loss of 0.3% or less in a 105°C environment

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