Resin molded products, resin molded products for car windows, and methods for manufacturing resin molded products

Abstract

The present invention provides: a resin molded article which has improved abrasion resistance and improved weather resistance, while maintaining heat resistance; a resin molded article for vehicle windows; and a method for producing a resin molded article. Each of a resin molded article and a resin molded article for vehicle windows according to the present invention is provided with a resin base material (10), a primer layer (11) and a hard coat layer (12). The thickness of the primer layer (11) and the thickness of the hard coat layer (12) are adjusted on the basis of the total light transmittance of the resin base material (10) and the respective inclination angles of the layers in a state where the resin molded article is assembled to a vehicle body (2). In addition, the hard coat layer (12) has a modified layer (13) that is modified by a light modification method, and the degree of modification of the modified layer (13) is also adjusted on the basis of the inclination angle and the total light transmittance.

Description

Technical Field

[0001] The present invention relates to a resin molded product, a resin molded product for vehicle windows, and a method for manufacturing a resin molded product.

Background Art

[0002] Today, technological development is underway to replace glass materials, which have been used for vehicle parts that require translucency such as vehicle lamps, sunroofs, and windows, with resin materials such as polycarbonate and acrylic. Resin materials are lightweight compared to glass materials and can be formed into desired designs using injection molding technology, making them suitable for reducing vehicle body weight and improving vehicle design.

[0003] However, resin materials have the drawback of having lower scratch resistance and weather resistance compared to glass materials. Therefore, when resin materials are used for vehicle windows and the like, there is a problem that scratches due to the friction of wipers and discoloration due to sunlight are likely to occur.

[0004] To solve this problem, conventionally, a technique of applying a special hard coat to the surface of a resin material to improve scratch resistance and weather resistance is known. For example, in Patent Documents 1 and 2, a transparent resin plate (resin substrate) is coated with a primer layer and a hard coat layer, and ultraviolet light is irradiated onto the surface of the hard coat layer to form a modified layer (cured film), thereby enhancing scratch resistance and weather resistance.

[0005] Further, in Patent Document 3, a primer layer is formed on the surface of a substrate, a hard coat layer of a silicone polymer is formed on the surface of the primer layer, and ultraviolet light having a wavelength of 200 nm or less is irradiated onto the surface of the hard coat layer to modify only the exposed portion into a modified portion mainly composed of silicon dioxide. Patent Document 4 discloses a technique of a transparent resin plate in which a transparent cured layer (hard coat layer) composed of two layers, an inner layer made of a cured product formed from an ultraviolet curable coating composition and an outermost layer made of silica derived from polysilazane in contact with the inner layer, is formed.

Prior Art Documents

[0006] [Patent Document 1] Patent No. 4536824 [Patent Document 2] Patent No. 5708499 [Patent Document 3] International Public Gazette WO2009 / 110152 [Patent Document 4] Japanese Patent Publication No. 2000-71380 [Overview of the project] [Problems that the invention aims to solve]

[0007] Incidentally, vehicle components such as lights, sunroofs, and windows are partially blackened or smoked to conceal imperfections or improve appearance, resulting in different heat absorption capacities from sunlight in each section. Furthermore, the surfaces of these vehicle components include flat and curved surfaces with varying curvatures depending on the design, and when mounted on the vehicle body, each section is tilted at a different angle, resulting in different angles of sunlight irradiation for each section. Thus, these vehicle components have different heat absorption capacities and different irradiation angles in each section, leading to different thermal stresses on each part.

[0008] Furthermore, with resin materials, increasing the thickness of the primer layer, hard coat layer, and modified layer improves scratch resistance and weather resistance, but also has the problem of decreasing heat resistance (see Figure 9).

[0009] However, according to the technology described in Patent Documents 1 and 2, since a primer layer, a hard coat layer, and a modified layer are uniformly formed on the surface of the transparent resin plate, the heat resistance is uniformly reduced, and there is a problem that areas with high localized heat stress are created, making them prone to cracking.

[0010] Furthermore, according to the technologies described in Patent Documents 3 and 4, thermal curing of silicone polymers causes condensation reactions such as dehydration and dealcoholization, leading to shrinkage of the hard coat layer and accumulation of internal stress. This results in a hard coat layer with an incomplete bonding state and many defects, making it prone to peeling, cracking, clouding, and solvent cracking. Moreover, in such hard coat layers, irradiating the outermost surface of the silicone polymer with ultraviolet light to remove organic groups further accumulates internal stress.

[0011] Therefore, the object of the present invention is to provide a resin molded product, a resin molded product for car windows, and a method for manufacturing a resin molded product that enables both scratch resistance and durability (heat resistance and weather resistance). [Means for solving the problem]

[0012] (1) The resin molded article and the resin molded article for car windows of the present invention are resin molded articles comprising a resin substrate, a hard coat layer covering at least a part of the resin substrate, and a primer layer provided between the resin substrate and the hard coat layer, wherein the hard coat layer and / or primer layer are characterized in that their thickness is adjusted based on the inclination angle and the total light transmittance of the resin substrate when the resin molded article is assembled to a predetermined product. In this case, the hard coat layer includes a modified layer obtained by photomodifying the hard coat layer with ultraviolet light, and the degree of modification of the modified layer is adjusted based on the inclination angle and the total light transmittance.

[0013] (2) Furthermore, the present invention relates to a method for manufacturing a resin molded product, comprising the steps of: providing a primer layer on at least a part of a resin substrate; and covering the primer layer with a hard coat layer, wherein the steps of providing the primer layer and / or covering with a hard coat layer are characterized in that the thickness is adjusted based on the inclination angle and the total light transmittance of the resin substrate when the resin molded product for a car window is assembled to a car body. In this case, the hard coat layer includes a modified layer obtained by photomodifying the hard coat layer with ultraviolet light, and the degree of modification of the modified layer is adjusted based on the inclination angle and the total light transmittance.

[0014] (3) The resin molded article of the present invention is a resin molded article comprising a resin substrate, a hard coat layer covering at least a part of the resin substrate, and a primer layer formed between the resin substrate and the hard coat layer, wherein the hard coat layer comprises a first hard coat layer made of a silicone compound and a second hard coat layer made of a polysilazane compound, and the thickness of the second hard coat layer is 1 μm or less.

[0015] (4) The thickness of the second hard coat layer is preferably 0.5 μm or less.

[0016] (5) The hard coat layer may include a first modified layer obtained by modifying the hard coat layer with silica using ultraviolet light.

[0017] (6) The second hard coat layer may include a second modified layer obtained by modifying the second hard coat layer to silica by ultraviolet light in an oxygen atmosphere, or by modifying it to silicon nitride by ultraviolet light in a nitrogen atmosphere.

[0018] (7) The resin molded product for a car window of the present invention comprises a resin molded product according to any one of (3) to (6) above, and is characterized in that a second hard coat layer is formed on the outside of the car interior.

[0019] (8) The present invention provides a method for manufacturing a resin molded article, comprising the steps of forming a primer layer on a resin substrate and covering the primer layer with a hard coat layer, wherein the step of covering with a hard coat layer includes the steps of covering the primer layer with a first hard coat layer made of a silicone compound and covering the first hard coat layer with a second hard coat layer made of a polysilazane compound, characterized in that the thickness of the second hard coat layer is 1 μm in the step of covering with the second hard coat layer.

[0020] (9) In the case of (8) above, it is preferable that the thickness of the second hard coat layer be 0.5 μm or less in the step of coating with a second hard coat layer.

[0021] (10) The step of coating with the hard coat layer may include a step of irradiating the hard coat layer with ultraviolet light to form a first modified layer obtained by photo-modifying at least a part of the hard coat layer into silica.

[0022] (11) The step of coating with the second hard coat layer may include a step of irradiating the second hard coat layer with ultraviolet light in a nitrogen atmosphere to form a second modified layer obtained by photo-modifying at least a part of the second hard coat layer into silicon nitride. [Effect of the Invention]

[0023] According to the resin molded product, the resin molded product for vehicle windows, or the method for manufacturing the resin molded product of the present invention, the layer thickness of the hard coat layer and the primer layer is adjusted according to the heat absorption ability of sunlight and the tilt angle (the tilt angle in the state assembled to the vehicle), and the degree of modification of the modified layer is adjusted. Therefore, for the part with a high heat load, the heat resistance is maintained, and for the part with a low heat load, the scratch resistance and weather resistance are enhanced.

[0024] Further, according to the resin molded product, the resin molded product for vehicle windows, and the method for manufacturing the resin molded product of the present invention, since the second hard coat layer is composed of a polysilazane compound capable of forming a dense film even at a low temperature, the effect of achieving both scratch resistance and durability is achieved. Also, when photo-modified with ultraviolet light, a denser silicon dioxide film can be formed, and when reacted with ultraviolet light in a nitrogen atmosphere, a harder silicon nitride film can be formed. In this case, there is also an effect that the scratch resistance and durability can be further enhanced. [Brief Description of the Drawings]

[0025] [Figure 1] It is a schematic view of a rear module showing an embodiment of the resin molded product of the present invention and a vehicle equipped with the rear module. [Figure 2] It is a schematic diagram showing the resin layer structure of the rear module of Example 1. [Figure 3](a) A schematic diagram showing parts with different total light transmittances, and (b) A schematic diagram showing parts with different inclination angles (θ) when assembled on a vehicle. [Figure 4] This is a comparison table showing examples of resin layer structure patterns. [Figure 5] This is a comparison table showing examples of surface modification methods for hard coat layers. [Figure 6] (a) A graph showing the relationship between integrated light intensity and surface Young's modulus, and (b) A graph showing the relationship between surface Young's modulus and scratch resistance. [Figure 7] (a) A graph showing the relationship between illuminance and surface Young's modulus, and (b) A graph showing the relationship between illuminance and the thickness of the modified layer. [Figure 8] This table shows the results of scratch resistance and weather resistance tests. [Figure 9] (a) A table showing the relationship between layer thickness and weather resistance / heat resistance, and (b) A table showing the relationship between the degree of modification and weather resistance / heat resistance. [Figure 10] This is a schematic diagram showing the resin layer structure of the rear module in Examples 2-1 and 2-2. [Figure 11] This is a schematic diagram showing the resin layer structure of the rear module in Example 2-3. [Figure 12] This is a schematic diagram showing the resin layer structure of the rear module in Example 2-4. [Figure 13] (a) Chemical structural formula of a conventional hard coat layer, (b) Chemical structural formula of Examples 2-1 to 2-4. [Figure 14] This is a comparison table showing the experimental results of conventional comparative examples 1 to 8. [Figure 15] This is a comparison table showing the experimental results for Examples 2-1 to 2-4. [Figure 16] This is a photograph of a sample after a Taber abrasion test. [Modes for carrying out the invention]

[0026] Embodiments of the present invention implemented in a resin rear module will be described with reference to the drawings. In each embodiment, common or similar components are denoted by the same reference numerals in the drawings. [Examples]

[0027] As shown in Figure 1, the rear module 1 consists of a rear window 3, a rear combination lamp (RCL) 4, a window cleaner 5, a high-mounted stop lamp (HMSL) 6, a license plate lamp (LPL) 7, a display 8, and a spoiler 9, and is attached to the vehicle body 2 so as to cover the rear of the vehicle.

[0028] As shown in Figure 2, the rear module 1 consists of a polycarbonate (PC) resin base material 10, a hard coat layer 12 in which at least a portion of the resin base material 10 is coated with a silicone resin, and a primer layer 11 made of acrylic resin placed between the resin base material 10 and the hard coat layer 12. The hard coat layer 12 also includes a modified layer 13 made of silicon dioxide (SiO2). In this case, the configuration may also be made without the primer layer 11. When attached to the vehicle body 2, the side with the modified layer 13 is positioned to face outwards.

[0029] In the step of applying the primer layer 11, a primer solvent is applied to the surface of the resin substrate 10 by a dip-coating method (wet method), dried at room temperature, and then heated for a predetermined time to cure and dry, thereby forming the primer layer 11. The primer layer 11 relieves the stress between the resin substrate 10 and the hard coat layer 12, improving the adhesion of the hard coat layer 12 and preventing peeling of the hard coat layer 12. Furthermore, the application of the primer layer 11 also enhances weather resistance.

[0030] In the process of coating the primer layer 11 with a hard coat layer 12, a hard coat solvent is applied to the surface of the primer layer 11 by a dip coat method, dried at room temperature, and then heated for a predetermined time to cure and dry, thereby forming the hard coat layer 12. The hard coat layer 12 provides hard protection to the surface of the resin substrate 10 and also improves its weather resistance.

[0031] In the process of photomodifying the hard coat layer 12 with ultraviolet light, ultraviolet light is irradiated onto the surface of the hard coat layer 12, and the modified layer 13 is formed by modifying the silicone resin of the hard coat layer 12 to silicon dioxide (SiO2). In particular, in Example 1, a high-power, high-intensity excimer lamp capable of irradiating ultraviolet light with a peak at a wavelength of 172 nm is used. This is because using high-power, high-intensity ultraviolet light allows for the formation of a thicker modified layer 13 compared to when low-power, low-intensity ultraviolet light is used.

[0032] As shown in Figure 3(a), the rear module 1 is composed of multiple parts with different total light transmittances, such as the black part 21, the visible part 22, and the clear part 23. The visible part 22 is smoked or otherwise treated to have a lower total light transmittance than the clear part 23. In the following description, the visible part 22 and the clear part 23 refer to parts with a total light transmittance exceeding 70%, and the black part 21 refers to parts with a total light transmittance of 70% or less. Conventionally, regardless of the total light transmittance, the primer layer 11 was composed of 2 μm and the hard coat layer 12 of 6 μm. However, in the present invention, for example, the parts with a total light transmittance of 70% or less, such as the black part 21, are composed in the following patterns (1) to (3). (1) Primer layer 11 is 1 μm thick, hard coat layer 12 is 6 μm thick (2) Primer layer 11 is 2 μm thick, hard coat layer 12 is 4 μm thick (3) Primer layer 11 is 1 μm thick, hard coat layer 12 is 4 μm thick In (1), only the thickness of the primer layer 11 is thinner than conventional methods; in (2), only the thickness of the hard coat layer 12 is thinner than conventional methods; and in (3), both the thickness of the primer layer 11 and the hard coat layer 12 are thinner than conventional methods.

[0033] As shown in Figure 3(b), the rear module 1 includes planes or curved surfaces with different curvatures in each part. When assembled to the vehicle body 2, the inclination angle (θ) from the horizontal H differs in each part, resulting in different angles of incidence of sunlight and consequently different heat absorption capacities in each part. Conventionally, a uniform modified layer 13 with a uniform degree of modification (surface hardness) was formed regardless of the inclination angle. However, in the present invention, the degree of modification is suppressed in parts with small inclination angles when assembled to the vehicle. In particular, it is preferable not to form the modified layer 13 in parts with an inclination angle of 30° or less.

[0034] In this case, the portion with a total light transmittance of 70% or less and the portion with an inclination angle of 30° or less may exist separately or overlap. Therefore, when they overlap, it is preferable to adjust both the thickness of the primer layer 11 and the hard coat layer 12, and the degree of modification of the modified layer 13.

[0035] The following provides a detailed explanation of the technology used in the present invention, the experimental methods for evaluating the invention, and the experimental results.

[0036] (Pattern of resin layer structure) As shown in Figure 4, there are multiple patterns for the layer structure consisting of the primer layer 11, hard coat layer 12, and modified layer 13. For example, there is a pattern in which an acrylic or silicone hard coat layer is directly formed on the surface of the resin substrate 10, a pattern in which a primer layer 11 is formed on the surface of the resin substrate 10 and a silicone hard coat is applied on top of it, and a pattern in which the surface of the hard coat layer 12 is modified to form a reinforcing modified layer 13. Of these, the method of forming the modified layer 13 in particular provides particularly high scratch resistance compared to conventional glass materials (ΔHaze value after Taber abrasion is about 2%) in tests to evaluate scratch resistance (Taber abrasion test).

[0037] (Method for surface modification of hard coat layer) As shown in Figure 5, in addition to the photomodification method used in Example 1, there are other methods for reinforcing the surface of the hard coat layer 12, such as forming a hard layer using a vacuum deposition process like chemical vapor deposition (CVD).

[0038] The photomodification method involves irradiating a resin substrate 10 with ultraviolet light at atmospheric pressure while flowing nitrogen through an already coated silicone-based hard coat layer 12, thereby modifying the surface and forming a modified layer 13. For example, when a hard coat layer 12 made of a silicone-based polymer is irradiated with ultraviolet light with a wavelength of 360 nm or less, the polymer's bonding chains (Si-C bonding chains) are broken, and oxygen atoms and silicon atoms present in small amounts in the atmosphere, the hard coat layer 12, and the resin substrate 10 recombine, forming a modified layer 13 mainly composed of silicon dioxide. On the other hand, the vacuum deposition process involves blowing a raw material gas containing hard layer components onto a resin substrate in a vacuum chamber, depositing a film on the surface or gas phase of the resin substrate through a chemical reaction to form a hard layer.

[0039] Compared to vacuum deposition processes, photomodification has the advantage of being less expensive because it does not require large-scale equipment such as vacuum chambers. Furthermore, in vacuum deposition processes, a hard layer is deposited by blowing in a raw material gas, which creates an interface between the hard layer and the hard coat layer, potentially leading to delamination of the hard layer at the interface. However, photomodification does not create an interface between the hard layer and the hard coat layer, eliminating the risk of delamination and resulting in superior scratch resistance and weather resistance.

[0040] (Method for evaluating the degree of modification by photomodification) In Example 1, the modified layer 13 refers to the portion of the hard coat layer 12 that has been modified to have a hardness of 5 GPa or more. The degree of modification is evaluated by measuring the Young's modulus in the layer thickness direction using a nanoindenter under the conditions (1) to (5) below, and confirming the correlation between the layer thickness and Young's modulus. (1) Equipment: KLA G200 nanoindenter, high resolution DCM-II head (maximum load: 30mN), Berkovich indenter (2) Measurement mode: Continuous stiffness measurement method (CSM) (3) Indentation depth: 1000nm (4) Vibration frequency: 65Hz (5) Vibration amplitude: 1nm

[0041] (Method for evaluating scratch resistance) For the evaluation of scratch resistance, a Taber abrasion test is performed on the surface of the modified layer 13 under the conditions of "abrasion wheel CS-10F, 0.5 kg load". The smaller the ΔHaze value (%) around 1000 rotations of Taber abrasion, the higher the scratch resistance. The higher the surface Young's modulus, the lower the ΔHaze value and the higher the scratch resistance (see Figure 6(b)).

[0042] (Method for evaluating weather resistance) For weather resistance evaluation, the accelerated weathering test, the Super UV test, is conducted under the following conditions (1) to (3). The longer the lifespan, the higher the weather resistance rating. (1) Equipment: iSuper UV Tester S-UV-161 (manufactured by Iwasaki Electric Co., Ltd.) (2) Test method: Repeated cycle of irradiation → darkness → condensation (3) Illuminance during irradiation: 900 w / m 2 (300~400nm)

[0043] (Method for evaluating heat resistance) For heat resistance evaluation, the material is subjected to an environment of 110°C for 720 hours, followed by an adhesion test after at least one hour. The evaluation is based on the result of 0 / 100 adhesion and confirmation that there are no significant appearance abnormalities such as film delamination or cracking.

[0044] (Experimental results: Evaluation of the degree of modification by photomodification) The surface Young's modulus was measured by varying the cumulative light intensity and illuminance, and the following experimental results (1) to (3) were obtained. (1) As shown in Figure 6(a), the larger the cumulative light intensity (product of illuminance and time), the larger the surface Young's modulus of the modified layer 13. As shown in Figure 6(b), the higher the surface Young's modulus, the lower the ΔHaze value and the higher the scratch resistance. (2) As shown in Figure 7(a), when the cumulative light amount is the same, the surface Young's modulus does not change even if the illuminance is changed and the time is increased or decreased. (3) As shown in Figure 7(b), when the cumulative light amount is the same, increasing the illuminance allows ultraviolet light to penetrate deeper into the hard coat layer 12, increasing the thickness of the modified layer 13.

[0045] (Experimental results: Evaluation of scratch resistance and weather resistance) Figure 8(a) shows the experimental results for the thickness, scratch resistance, and weather resistance of the modified layer 13 when the cumulative light intensity is fixed and the irradiation distance and illuminance are changed. From these experimental results, it can be seen that the thickness of the modified layer 13 increases in proportion to the illuminance, and that the scratch resistance and weather resistance improve with increasing thickness of the modified layer 13. In particular, the improvement in weather resistance is thought to be due to the fact that when the thickness of the modified layer 13 is thicker, the slope of Young's modulus from the modified layer 13 to the hard coat layer 12 becomes gentler, and the stress on the hard coat layer 12 is relieved. On the other hand, as shown in Figure 8(b), test results have also shown that when the cumulative light intensity of ultraviolet light irradiated onto the silicone-based hard coat is increased to strengthen scratch resistance, the weather resistance weakens.

[0046] (Experimental results: Evaluation of the thickness and heat resistance of the primer layer and hard coat layer) Figure 9(a) shows the experimental results of weather resistance and heat resistance when the layer thickness of the primer layer 11 and the hard coat layer 12 is varied. The experimental results show that weather resistance improves in proportion to the layer thickness, while heat resistance decreases. In particular, a favorable balance of scratch resistance, weather resistance, and heat resistance is achieved when one or more of the following conditions (a1) to (a4) are met. (a1) In the primer layer 11, the thickness of the visible portion 22 and the clear portion 23 is greater than 2 μm and 20 μm or less, and the thickness of the black portion 21 is 0.01 μm or more and 2 μm or less. (a2) In the hard coat layer 12, the thickness of the visible portion 22 and the clear portion 23 is greater than 6 μm and 20 μm or less, and the thickness of the black portion 21 is 0.01 μm or more and 6 μm or less. (a3) In the primer layer 11, the thickness of the portion with an inclination angle of 30° or less is 0.01 μm or more and 2 μm or less, and the thickness of the portion with an inclination angle exceeding 30° is greater than 2 μm and 20 μm or less. (a4) In the hard coat layer 12, the thickness of the portion with an inclination angle of 30° or less is 0.01 μm or more and 6 μm or less, and the thickness of the portion with an inclination angle exceeding 30° is greater than 6 μm and 20 μm or less.

[0047] (Experimental results: Evaluation of degree of modification and heat resistance) Figure 9(b) shows the experimental results for scratch resistance and heat resistance when the cumulative light intensity and the surface hardness (degree of modification) of the modified layer 13 are changed. The experimental results show that scratch resistance improves in proportion to the degree of modification, while heat resistance decreases. In particular, a favorable balance of scratch resistance, weather resistance, and heat resistance is achieved when the following conditions (b1) or (b2) are met. (b1) The degree of modification of the visible portion 22 and the clear portion 23 shall be such that the surface hardness is 0.02 or less, and the degree of modification of the black portion 21 shall be such that it is not modified or the degree of modification shall be such that the surface hardness is greater than 0.02. (b2) The portion with an inclination angle of 30° or less will not be modified, while the portion with an inclination angle exceeding 30° will be modified to achieve a surface hardness of 0.02 or higher.

[0048] With the rear module 1 configured as described above, the thickness of the primer layer 11 and the hard coat layer 12 are adjusted according to the heat absorption capacity of sunlight and the inclination angle when assembled to the vehicle, and the degree of modification of the modified layer 13 is adjusted. As a result, heat resistance is maintained in areas with high heat load, while scratch resistance and weather resistance are enhanced in areas with low heat load. [Examples]

[0049] The configuration and operation of the rear module 1 in Examples 2-1 to 2-4 will be described below based on Figures 1, 10 to 16. Configurations common to Example 1 will be omitted from the description.

[0050] (Example 2-1) As shown in Figure 10, the rear module 1 of Example 2-1 includes a polycarbonate (PC) resin substrate 10 and a hard coat layer covering at least a portion of the resin substrate 10. In this case, the hard coat layer includes a first hard coat layer 12a made of a silicone compound and a second hard coat layer 12b made of perhydroxypolysilazane (see Figure 13(b)), which is a polysilazane compound. The rear module 1 also includes a primer layer 11 made of an acrylic resin provided between the resin substrate 10 and the first hard coat layer 12a. When the rear module 1 is attached to the vehicle body 2, it is positioned so that the side with the second hard coat layer 12b faces outwards.

[0051] In the step of applying the primer layer 11, a primer solvent is applied to the surface of the resin substrate 10 by a dip-coat method (wet method), dried at room temperature, and then heated for a predetermined time to cure and dry, thereby forming the primer layer 11. The primer layer 11 relieves the stress between the resin substrate 10 and the first hard coat layer 12a, improving the adhesion of the first hard coat layer 12a and preventing peeling of the first hard coat layer 12a. Furthermore, the application of the primer layer 11 also enhances weather resistance.

[0052] In the step of coating the primer layer 11 with the first hard coat layer 12a, a hard coat solvent is applied to the surface of the primer layer 11 by a dip coat method, dried at room temperature, and then heated for a predetermined time to cure and dry, thereby forming the first hard coat layer 12a. The first hard coat layer 12a hardens and protects the surface of the resin substrate 10, improving its weather resistance.

[0053] In the step of covering the first hard coat layer 12a with the second hard coat layer 12b, a polysilazane compound, perhydroxypolysilazane, is applied to the surface of the hard coat layer 11 and cured and dried at room temperature to form the second hard coat layer 12b.

[0054] (Example 2-2) The rear module 1 of Example 2-2 has a resin layer structure similar to that of the rear module 1 of Example 2-1, but the thickness of the second hard coat layer 12b is thinner than that of Example 2-1.

[0055] (Examples 2-3) As shown in Figure 11, the rear module 1 of Example 2-3 includes a first modified layer 13a, which is formed by modifying the hard coat layers 12 and 13 to silica using ultraviolet light, in addition to the resin layer structure of the rear module 1 of Example 2-2. The thickness of the second hard coat layer 12b in Example 2-3 is the same as the thickness of the second hard coat layer 12b in Example 2-2.

[0056] In the process of modifying the hard coat layers 12 and 13 into the first modified layer 13a, ultraviolet light is irradiated onto the surface of the hard coat layers 12 and 13 to modify the silicone resin and perhydroxypolysilazane of the hard coat layers 12 and 13 into silica, i.e., silicon dioxide (SiO2), thereby forming the first modified layer 13a. In particular, in Example 2-3, a high-power, high-intensity excimer lamp capable of irradiating ultraviolet light with a peak at a wavelength of 172 nm is used. This is because using high-power, high-intensity ultraviolet light allows for the formation of a thicker first modified layer 13a compared to when low-power, low-intensity ultraviolet light is used.

[0057] (Examples 2-4) As shown in Figure 12, the rear module 1 of Example 2-4 includes a second modified layer 13b, which is obtained by modifying the second hard coat layer 12b to silicon nitride using ultraviolet light in a nitriding atmosphere, in addition to the resin layer structure of the rear module 1 of Example 2-2. The thickness of the second hard coat layer 12b is the same as that of the second hard coat layer 12b in Example 2-2.

[0058] In the process of modifying the second hard coat layer 12b into the second modified layer 13b, ultraviolet light is irradiated onto the surface of the second hard coat layer 12b to modify the perhydroxypolysilazane in the second hard coat layer 12b to silicon nitride (Si3N4), thereby forming the second modified layer 13b. Similar to Example 2-3, Example 2-4 employs a high-power, high-intensity excimer lamp capable of irradiating ultraviolet light with a peak at a wavelength of 172 nm. This is because using high-power, high-intensity ultraviolet light allows for the formation of a thicker second modified layer 13b compared to using low-power, low-intensity ultraviolet light.

[0059] Next, the experimental results demonstrating the effects of the present invention in terms of scratch resistance, heat resistance, and weather resistance will be explained based on Figures 14-16. In Figures 14 and 15, "◎>〇>△>×" indicates the degree of quality, with 〇 or higher being considered a passing grade.

[0060] (Method for evaluating scratch resistance) In accordance with the safety glass standard (UN / ECE R43), a workpiece cut to 100 x 100 mm was placed on a Taber abrasion tester, and a load of 4.9 N (500 g) was applied to the abrasion wheel CS-10, rotating it 1000 times to create scratches. The difference in haze (cloudiness) before and after the test was observed, and a ΔHaze of 2% or less was considered acceptable. This is because a ΔHaze of 2% or less indicates scratch resistance close to that of glass, making it suitable for use as a vehicle window (see Figure 16). Note that "workpiece" refers to a resin molded product cut to 100 x 100 mm.

[0061] (Method for evaluating heat resistance) Workpieces cut to 50 x 50 mm were placed in a constant temperature bath at 100°C and inspected for appearance every 100 hours. Workpieces were deemed unacceptable if cracks or clouding appeared in the coating (hard coat layer), and the time elapsed until this point was defined as their lifespan (h).

[0062] (Method for evaluating weather resistance) Ultraviolet exposure was performed using a long-arc xenon lamp as the irradiation source for the exposure device. The total amount of ultraviolet radiation to the exposed workpiece (wavelength 400 nm or less, 1 m) 2 The joules per unit were measured, and the result was 50 MJ / m³.2 Each workpiece was removed and its appearance was observed. Workpieces showing cracks, clouding, or peeling of the coating were deemed unacceptable, and the radiation dose up to that point was considered the lifespan (h). Ultraviolet radiation dose: 300 MJ / m 2 However, this is equivalent to one year's worth of UV exposure in the natural environment.

[0063] The exposure apparatus temperature was set to 63±3°C and measured using a Black standard thermometer. The relative humidity inside the exposure apparatus was controlled to 50±5% during the dry phase of the test cycle. Deionized water was used in the water spray cycle. The exposure apparatus performed continuous light irradiation and intermittent water spraying in a 2-hour cycle. The workpiece was exposed to ultraviolet light for 102 minutes without water spraying, and then exposed to ultraviolet light for 18 minutes with water spraying.

[0064] (Test results of scratch resistance, heat resistance, and weather resistance) The experimental results for Comparative Examples 1-8 are shown below in (1)-(8). (1) In Comparative Example 1, an acrylic hard coat currently used in headlamps was directly applied to a polycarbonate resin substrate. However, it failed to meet the scratch resistance requirements for automotive safety windows. (2) In Comparative Example 2, a silicone-based hard coat, which was expected to have higher hardness and superior scratch resistance than an acrylic-based hard coat, was directly applied to a polycarbonate resin substrate. However, it had poor adhesion to the polycarbonate resin and peeled off. (3) In Comparative Example 3, a perhydroxypolysilazane hard coat was applied directly to a polycarbonate resin substrate. However, similar to the silicone type, adhesion was poor and peeling occurred. (4) In Comparative Example 4, in order to improve adhesion with the polycarbonate resin substrate, an acrylic primer was applied to the polycarbonate resin substrate, and then a silicone hard coat was applied on top of it. Adhesion was good, and heat resistance and weather resistance were improved, but scratch resistance was insufficient. (5) In Comparative Example 5, aiming for an effect equivalent to that of Comparative Example 4, an acrylic primer was applied to a polycarbonate resin substrate, and then perhydroxy PolyAlthough silazane was applied, the adhesion was insufficient. (6) In Comparative Example 6, perhydroxy is hard and prone to accumulating stress. Poly We tried reducing the thickness of the silazane layer. However, delamination occurred. (7) In Comparative Example 7, considering that it is the same silicon compound, a silicone-based hard coat was applied, and then perhydroxy Poly Silazane was applied. While it was hoped that this would improve adhesion, it peeled off. (8) In Comparative Example 8, the outermost surface of the silicone-based hard coat was converted to silica using ultraviolet light. Scratch resistance improved, but heat resistance and weather resistance were unsatisfactory.

[0065] The experimental results for Examples 2-1 to 2-4 are shown below in (1) to (4). (1) In Example 2-1, an acrylic primer was applied to improve adhesion with the polycarbonate resin substrate, and then a silicone hard coat and perhydroxy Poly Silazane was applied. Considering that perhydroxypolysilazane has high hardness and is prone to peeling and cracking, a thin film of 1 μm was deposited to ensure conformability with the substrate. As a result, it passed all tests for scratch resistance, heat resistance, and weather resistance. (2) In Example 2-2, a thinner layer of perhydroxypolysilazane was applied. As a result, we succeeded in further extending the heat resistance life. (3) In Examples 2-3, the applied perhydroxypolysilazane was converted to silica using ultraviolet light. As a result, even higher scratch resistance was achieved. (4) In Examples 2-4, perhydroxypolysilazane was converted to silicon nitride by irradiating it with ultraviolet light in a nitrogen atmosphere. Silicon nitride has higher hardness than silica and improved scratch resistance. In addition, since silicon nitride has the effect of absorbing ultraviolet light, the silicone-based hard coat was protected and the weather resistance life was also improved.

[0066] As described above, the rear module 1 of Examples 2-1 to 2-4 comprises a resin substrate 10, a primer layer 11, a first hard coat layer 12a, and a second hard coat layer 12b, and since the thickness of the second hard coat layer 12b is 1,000 μm or less, it has the effect of improving scratch resistance, weather resistance, and heat resistance. Furthermore, as in Examples 2-2 to 2-4, by making the second hard coat layer 12b thin, heat resistance can be further improved, as in Example 2-3, by modifying the hard coat layers 12 and 13 to form a first modified layer 13a, scratch resistance can be further improved, and as in Example 2-4, by modifying the second hard coat layer 12b in a nitriding atmosphere to form a second modified layer 13b, silicon nitride absorbs ultraviolet light and protects the first hard coat layer 12a, thus improving weather resistance.

[0067] It should be noted that the present invention is not limited to the embodiments described above, and the configuration of each part can be arbitrarily changed without departing from the spirit of the present invention, such as by appropriately changing the material, combination, and area to which the resin substrate 10 and coating layer are applied. For example, the area in which the modified layer 13 is formed can be limited to specific locations such as the wiper sliding part, or a transparent resin substrate such as acrylic resin, cycloolefin polymer (COP), or polyethylene terephthalate (PET) can be used as the resin substrate 10 instead of polycarbonate. Furthermore, an anti-fogging layer or an anti-fouling functional layer may be formed on top of the modified layer 13. [Explanation of Symbols]

[0068] 1 Rear Module 2 car bodies 3 Rear window 4. Rear combination lamps 5 Window Cleaner 6. High-mounted stop lamp 7. License plate lamp 8 Display 9 Spoiler 10 Resin substrate 11. Primer layer 12. Hard court layers (a: first hard court layer, b: second hard court layer) 13. Modified layers (a: first modified layer, b: second modified layer) 21 Black part 22 Visible area 23 Clear part L Sunlight

Claims

1. A resin molded product comprising a resin substrate, a hard coat layer covering at least a portion of the resin substrate, and a primer layer provided between the resin substrate and the hard coat layer, The thickness of the hard coat layer and the primer layer is adjusted based on the inclination angle from the horizontal when the resin molded product is assembled into a predetermined product and the total light transmittance of the resin substrate. The resin substrate comprises a first portion having a total light transmittance of 70% or less and an inclination angle of 30° or less, and a second portion which is the remaining portion. The thickness of the primer layer included in the first part is 0.01 μm or more and 2 μm or less, and the thickness of the primer layer included in the second part is greater than 2 μm and 20 μm or less. A resin molded product characterized in that the thickness of the hard coat layer included in the first portion is 0.01 μm or more and 6 μm or less, and the thickness of the hard coat layer included in the second portion is greater than 6 μm and 20 μm or less.

2. The hard coat layer includes a modified layer obtained by photomodifying the hard coat layer with ultraviolet light. The degree of modification of the modified layer is adjusted based on the tilt angle and the total light transmittance. The resin substrate comprises a first portion having a total light transmittance of 70% or less and an inclination angle of 30° or less, and a second portion which is the remaining portion. The resin molded article according to claim 1, wherein the first portion does not include the modified layer.

3. A resin molded product for a car window, comprising the resin molded product described in claim 1 or 2.

4. A method for manufacturing a resin molded product, A method for manufacturing a resin molded product, comprising the steps of: providing a primer layer on at least a portion of a resin substrate; covering the primer layer with a hard coat layer; and photomodifying the hard coat layer with ultraviolet light, The steps of providing the primer layer and covering it with the hard coat layer include adjusting the thickness based on the inclination angle from the horizontal when the resin molded product is assembled to the vehicle body and the total light transmittance of the resin substrate. The photomodification step includes a step of adjusting the degree of modification based on the tilt angle and the total light transmittance, The resin substrate comprises a first portion having a total light transmittance of 70% or less and an inclination angle of 30° or less, and a second portion which is the remaining portion. In the process of adjusting the thickness, The thickness of the primer layer included in the first portion is adjusted to be between 0.01 μm and 2 μm. The thickness of the primer layer included in the second part is adjusted to be greater than 2 μm and 20 μm or less. The thickness of the hard coat layer included in the first portion is adjusted to be between 0.01 μm and 6 μm. The thickness of the hard coat layer included in the second portion is adjusted to be greater than 6 μm and 20 μm or less. A method for manufacturing a resin molded product, characterized in that the first portion is not photomodified in the photomodification step.

5. A resin molded product comprising a resin substrate, a hard coat layer covering at least a portion of the resin substrate, and a primer layer formed between the resin substrate and the hard coat layer, The hard coat layer comprises a first hard coat layer made of a silicone-based compound and a second hard coat layer made of a polysilazane compound. The thickness of the second hard coat layer is 1 μm or less. A resin molded article characterized in that the first hard coat layer and the second hard coat layer include a first modified layer obtained by modifying the first hard coat layer and the second hard coat layer with silica using ultraviolet light.

6. The resin molded article according to claim 5, wherein the thickness of the second hard coat layer is 0.5 μm or less.

7. A resin molded product for a car window comprising the resin molded product according to claim 5 or 6, characterized in that the second hard coat layer is formed on the exterior side of the car interior.

8. The process comprises the steps of forming a primer layer on a resin substrate and covering the primer layer with a hard coat layer. The step of coating with the hard coat layer includes the steps of coating the primer layer with a first hard coat layer made of a silicone compound and coating the first hard coat layer with a second hard coat layer made of a polysilazane compound. In the step of coating with the second hard coat layer, the thickness of the second hard coat layer is set to 1 μm or less. A method for manufacturing a resin molded article, characterized in that the step of coating with the hard coat layer includes a step of irradiating the first hard coat layer and the second hard coat layer with ultraviolet light to form a first modified layer obtained by photomodifying at least a portion of the first hard coat layer and the second hard coat layer with silica.

9. The method for manufacturing a resin molded article according to claim 8, wherein in the step of coating with the second hard coat layer, the thickness of the second hard coat layer is 0.5 μm or less.

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