Anti-fogging agent and Anti-fogging method for vehicle lamp structure

Abstract

To provide an anti-fogging agent and a method for preventing fogging of a vehicle lamp structure using the same, the anti-fogging agent being excellent in anti-fogging properties and capable of sufficiently maintaining rectilinearity and intensity of transmitted light when a water film is formed.SOLUTION: An anti-fogging agent is provided, wherein when a film of water is formed on a main surface of a base material treated with the anti-fogging agent, the water film uniformity index WE expressed by the following formula is 65% or higher. WE=(S / TS)×100SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an antifogging agent and a method for preventing fogging of a vehicle lamp structure. [Background technology]

[0002] A method is known in which an antifogging agent composition containing a surfactant is applied to the interior of a lamp chamber of a vehicle lamp structure for an automobile or the like, which is susceptible to fogging due to condensation (see, for example, Patent Document 1). When moisture adheres to a coating film formed by an antifogging agent containing a surfactant, the moisture instantly turns into a water film due to the effect of the surfactant, thereby suppressing the occurrence of fogging. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-027134 Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, in automobile headlight systems, a method of controlling the on / off of light sources in part has been adopted to prevent drivers of oncoming or preceding vehicles from feeling dazzled.

[0005] When an anti-fog agent is applied to such headlights, a water film is formed on the treated surface, suppressing fogging. However, it has been found that there is room for further improvement in the uniformity of the water film in anti-fog agents in order to make this control function more effectively. If the water film formed is not uniform, the straightness and intensity of the transmitted light are impaired, reducing the directionality and brightness of the light and raising concerns that the area to be turned off (area not exposed to light) may become blurred or distorted.

[0006] The present invention has been made in view of the above circumstances, and aims to provide an antifogging agent that has excellent antifogging properties and can sufficiently maintain the straightness and intensity of transmitted light when a water film is formed, and an antifogging method for a vehicle lamp structure using the same. [Means for solving the problem]

[0007] One aspect of the present invention relates to an anti-fogging agent, which has a water film uniformity index WE, represented by the following formula (a), of 65% or more when a water film is formed on a main surface of a substrate treated with the anti-fogging agent: WE=(S / TS)×100 …(a) [In formula (a), TS represents the total frequency of the area of ​​black regions generated in an evaluation image of 1824 × 1824 pixels obtained by capturing an image of an object having a checkerboard pattern composed of black and white squares with sides of 0.5 mm through the substrate on which a water film is formed, and the total frequency of the black regions in the area distribution indicates the frequency of the black regions. S represents the total frequency of the black regions included in a predetermined area range in the area distribution, and the predetermined area range indicates an area range having a frequency of 5% or more of the total frequency in an area distribution indicating the area of ​​black regions generated in a reference image of 1824 × 1824 pixels obtained by capturing an image of the object through the substrate. Note that the distance between the object and the substrate is 2.5 cm, and the position of the digital camera capturing the object is set so that 4900 black and white squares are included in the 1824 × 1824 pixel image.]

[0008] An anti-fogging agent having the above-mentioned water film uniformity index WE of 65% or more has excellent anti-fogging properties and can adequately maintain the straightness and intensity of transmitted light when a water film is formed.

[0009] The antifogging agent may have an antifogging index AFI, as shown by the following formula (b), of 7 or more when water vapor is brought into contact with the main surface of the substrate treated with the antifogging agent. AFI=(S1-S2)×10 / (S0-S2) …(b) [In formula (b), S1 represents the file size when an image for evaluating anti-fogging properties, obtained by photographing the subject through the substrate exposed to water vapor, is compressed using a predetermined compression method; S2 represents the file size when an image N, obtained by photographing the subject through an untreated substrate exposed to water vapor, is compressed using the predetermined compression method; and S0 represents the file size when an image O, obtained by photographing the subject through an untreated substrate, is compressed using the predetermined compression method. Note that the size of the image for evaluating anti-fogging properties, image N, and image O is 1824 x 1824 pixels, the distance between the subject and the substrate is 2.5 cm, and the predetermined compression method refers to compression at a compression rate of 20% and resizing to 820 x 820 pixels.]

[0010] The antifogging agent may contain colloidal silica, at least one selected from the group consisting of a crosslinking agent, a binder, and a metal chelate, and a liquid medium.

[0011] One aspect of the present invention relates to an antifogging method for a vehicle lamp structure, which comprises treating an inner surface of a lens of the vehicle lamp structure with the above-mentioned antifogging agent. This method can impart antifogging properties to the vehicle lamp structure and form an antifogging film that can sufficiently maintain the straightness and intensity of transmitted light when a water film is formed. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide an antifogging agent that has excellent antifogging properties and can sufficiently maintain the linearity and intensity of transmitted light when a water film is formed, and a method for antifogging a vehicle lamp structure using the same. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram for explaining a method for calculating the water film uniformity index WE. [Figure 2] FIG. 2 is a schematic diagram for explaining a method for calculating the water film uniformity index WE. [Figure 3]FIG. 3 is a diagram for explaining the sample image. [Figure 4] FIG. 4 is a diagram for explaining the reference image and the evaluation image. [Figure 5] FIG. 5 is a diagram showing an example of the area distribution. [Figure 6] FIG. 6 is a diagram schematically illustrating a vehicle lamp structure. [Figure 7] FIG. 7 shows the shape of the image projected onto the wall in a transmission test using a laser pointer. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail, with reference to the drawings where necessary. However, the present invention is not limited to the following embodiments. The materials exemplified below may be used singly or in combination, unless otherwise specified. When multiple substances corresponding to each component are present in the composition, the content of each component refers to the total amount of the multiple substances present in the composition, unless otherwise specified. Numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range may be replaced with the upper or lower limit of a numerical range of another stage. In the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with the values ​​shown in the examples.

[0015] <Anti-fogging agent> The antifogging agent of this embodiment has a water film uniformity index WE, represented by the following formula (a), of 65% or more when a water film is formed on the main surface of a substrate treated with the antifogging agent. WE=(S / TS)×100 …(a) [In formula (a), TS represents the total frequency in an area distribution showing the area and frequency of black regions generated from an evaluation image of 1824 × 1824 pixels obtained by capturing an image of an object having a checkerboard pattern consisting of black and white squares with sides of 0.5 mm through the substrate on which a water film is formed, and S represents the total frequency included in a predetermined area range in the area distribution, where the predetermined area range represents an area range whose frequency is 5% or more of the total frequency in an area distribution showing the area and frequency of black regions generated from a reference image of 1824 × 1824 pixels obtained by capturing an image of the object through the substrate. Note that the distance between the object and the substrate is 2.5 cm, and the position of the digital camera capturing the object is set so that 4900 black and white squares are included in the 1824 × 1824 pixel image.]

[0016] The antifogging agent of the present embodiment may also have an antifogging index AFI, as shown by the following formula (b), of 7 or more when water vapor is brought into contact with the main surface of the substrate treated with the antifogging agent. AFI=(S1-S2)×10 / (S0-S2) …(b) [In formula (b), S1 represents the file size obtained by compressing an anti-fogging property evaluation image of the subject through the substrate that has been exposed to water vapor using a predetermined compression method; S2 represents the file size obtained by compressing an image N of the subject through an untreated substrate that has been exposed to water vapor using the predetermined compression method; and S0 represents the file size obtained by compressing an image O of the subject through the untreated substrate using the predetermined compression method, where the anti-fogging property evaluation image, image N, and image O each have a size of 1824 × 1824 pixels, the distance between the subject and the substrate is 2.5 cm, the position of the digital camera that photographs the subject is set so that 4900 black squares and white squares are included in the 1824 × 1824 pixel image, and the predetermined compression method refers to compressing at a compression rate of 20% and resizing to 820 × 820 pixels.]

[0017] The methods for calculating the water film uniformity index WE and the anti-fogging index AFI will be described in detail.

[0018] <Water film uniformity index WE> The water film uniformity index WE can be calculated by the following method. First step: Prepare a sample by treating the main surface of the substrate with an anti-fogging agent. Second step: An object (hereinafter also referred to as a "sample image") having a pattern in which multiple regions with a predetermined brightness are arranged in a predetermined area is imaged through a sample having a water film formed on the main surface treated with an anti-fogging agent to obtain an image for evaluation. Third step: A water film uniformity index indicating the uniformity of the water film is derived based on the area distribution of regions having a predetermined brightness in the evaluation image.

[0019] (1st step) FIG. 1 is a schematic diagram for explaining a method for calculating the water film uniformity index WE and the anti-fogging index AFI, and shows an example of a method for preparing a sample in the first step. (A) in FIG. 1 shows a step (coating step) in which an anti-fogging agent 2 is applied to a main surface S1 of a substrate 1 by a spray 3 to form a coating film. (B) in FIG. 1 shows a sample 10 obtained by drying the coating film. The sample 10 has a film 5 formed from the anti-fogging agent on the main surface S1 of the substrate 1 (hereinafter also referred to as an "anti-fogging film").

[0020] When calculating the water film uniformity index WE and the antifogging index AFI, a polycarbonate substrate can be used as the substrate 1. The thickness of the substrate 1 can be 2 mm.

[0021] The size of the substrate 1 can be set to 10 cm square so that a sufficient number of pixels can be obtained in the image for evaluation.

[0022] The substrate 1 can have a visible light transmittance of 85% or more. The visible light transmittance of the substrate can be measured, for example, by a U-3500 type recording spectrophotometer (manufactured by Hitachi, Ltd.).

[0023] The substrate 1 can have a haze of 1.0 or less. The haze of the substrate can be measured, for example, with a haze meter (NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd.).

[0024] The substrate 1 can have a YI of 1.5 or less. The YI of the substrate 1 can be measured, for example, by a colorimeter (300A, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0025] The main surface S1 of the substrate 1 is untreated (not treated) with any treatment other than an antifogging agent, and can be cleaned with isopropyl alcohol.

[0026] FIG. 1 shows a case where the treatment with the anti-fogging agent is carried out by spray coating and drying after application, but the treatment method can be selected as appropriate according to the practical application.

[0027] The antifogging agent may be applied by a method such as spin coating, dip coating, flow coating, bar coating, or gravure coating.

[0028] The amount of application is not limited because it depends on the components of the anti-fogging agent, its content, etc., but for example, 10 -9 ~10 3 g / m 2 It can be said that:

[0029] The temperature of the antifogging agent used in the coating step may be, for example, 1 to 50° C., or 10 to 30° C. The coating time of the antifogging agent may be, for example, 1 second to 1 hour, or 5 to 30 minutes.

[0030] The drying temperature may be, for example, 5 to 300° C., or 10 to 200° C. The drying time may be 30 seconds to 150 hours.

[0031] When calculating the water film uniformity index WE and the antifogging index AFI, the thickness of the antifogging film 5 can be set to 1 μm. The film thickness of the antifogging film can be measured, for example, with a non-contact film thickness meter, Optical NanoGauge C13027 (manufactured by Hamamatsu Photonics Co., Ltd.). The above-mentioned coating amount, coating temperature, coating time, drying temperature, and drying time can be appropriately set so that the thickness of the antifogging film 5 falls within the above-mentioned ranges.

[0032] (Second step) Fig. 2 shows an example of an apparatus for obtaining an evaluation image in the second step. In the apparatus shown in Fig. 2, water 20 is placed in a temperature-controllable water bath having an open top, and a sample image 30 is placed at a depth D2 from the water surface, with the patterned surface S2 facing the water surface. A digital camera 40 is placed above the water bath at a distance D3 from the surface S2 of the sample image 30, facing the water surface.

[0033] Sample image 30 is an object having a checkered pattern made up of black and white squares with a side length of 0.5 mm. Figure 3 shows a sample image. The image shown in Figure 3 is a checkered pattern in which black squares and white squares are arranged alternately vertically and horizontally, and black and white squares are provided. In this checkered pattern, the side length of the squares is 0.5 mm and their area is 0.25 mm. 2 The difference between the black square and the white square can be set so that when the reference image described later is converted into 8 bits of 0 to 255, the difference in brightness between the two areas is 150 or more.

[0034] The digital camera 40 that can be used is one that can output an 8-bit numerical value from 0 to 255 for each pixel.

[0035] The distance D3 between the digital camera 40 and the surface S2 of the sample image 30 can be set to 17 cm so that only the sample image is captured. When the sample image shown in Figure 3 (a checkerboard pattern of 0.5 mm x 0.5 mm squares) is used, the distance D3 can be set so that 4900 squares are included in the image, which is 1824 x 1824 pixels in size.

[0036] The sample image 30 is placed in water at a depth D2 from the water surface, where D2 may be 1 cm.

[0037] Although not shown in FIG. 2, a light source may be used to illuminate surface S2 of sample image 30 so as to obtain a properly exposed image.

[0038] In this embodiment, in order to form a water film on the main surface of the substrate treated with the antifogging agent, the sample 10 is placed above the water bath at a distance D1 from the surface of the water 20, with the main surface S1 of the substrate facing the water surface.

[0039] The distance D1 between the main surface S1 and the water surface can be set to 1.5 cm.

[0040] When the sample 10 is placed above the water bath, the water 20 may be heated to a predetermined temperature. Water vapor (steam) generated from the water surface can form a water film or cloudiness on the main surface of the substrate treated with the antifogging agent. In this specification, the term "water film" refers to a water film formed on the main surface of the substrate treated with the antifogging agent. The formation of the water film can be confirmed visually.

[0041] In the second step, the sample image 30 is captured through the sample on which the water film has been formed. By checking in advance the time from when the sample 10 is placed until when the water film is formed, the timing of capturing the image can be set using the passage of time as an indicator.

[0042] The time from placing the sample 10 until the water film is formed is 40 seconds, and the image can be taken when the temperature of the water 20 is 40° C. and the distance D1 is 1.5 cm.

[0043] (Third Step) In the third step, a water film uniformity index that indicates the uniformity of the water film is calculated based on the area distribution of the black regions (corresponding to the black squares) in the evaluation image.

[0044] Figure 4 shows evaluation images with different water film uniformity. Evaluation image (B) is an image with low water film uniformity, and it can be seen that there is greater variation in the area of ​​the black regions (corresponding to black squares) than in evaluation image (A). Therefore, the uniformity of the water film can be measured based on the area distribution of the black regions in the evaluation image.

[0045] The water film uniformity index can be calculated by comparing a sample image with a reference image taken through a substrate without a water film formed thereon. The reference image can be, for example, an image taken immediately after (0 seconds after placement) placing a substrate not treated with an anti-fogging agent.

[0046] The water film uniformity index is derived from the evaluation image and the reference image obtained under the following imaging conditions using the sample image having the checkered pattern shown in FIG. 3, by the following image processing.

[0047] [Imaging conditions] Digital camera: Canon PowerShot SX70 HS (focal length in 35mm film equivalent: 15mm, image size: 1824 x 1824 pixels, saved in jpg format)

[0048] [Image Processing] (1) Using image processing software (ImageJ), read the evaluation image and the reference image and convert them to 8 bits (Image → type → 8 bit). (2) Set the boundary threshold to "90~255" (Image→Adjust→Threshold→Set to "90~255"→apply). (3) Binarize (Process → Binary → Make Binary). (4) Set “Area” as the measurement condition (check Analyze → Set Measurements → Area). (5) Use particle analysis to calculate the area of ​​1 pixel or more squared (Analyze → Analyze Particles → Set "Size" to "1-Infinity", "Show" to "Outlines", check "Display results" and "Clear Results", and click OK). (6) From the information of the reference image (5), a frequency distribution is created in 20 pixel increments in the range of 0 to 1000 pixels as an area distribution, and the area range RA where the frequency is 5% or more of the total frequency is obtained. (7) From the information in (5) of the evaluation image, a frequency distribution is created in 20-pixel increments in the range of 0 to 1000 pixels as an area distribution, and the ratio (%) of the number of particles (frequency) included in the area range in (6) to the total number of particles (total frequency) is calculated, and this is used as the water film uniformity index.

[0049] Figure 5 shows examples of area distributions created in (6) and (7) above. The reference image and evaluation image are images obtained using the method shown in Figure 2. The reference image was captured immediately after (0 seconds after placement) placing a substrate (polycarbonate plate) that had not been treated with an antifogging agent. The evaluation image was captured 40 seconds after placing a sample obtained by applying an antifogging agent (here, one with low water film uniformity was selected) to a polycarbonate plate and drying it. D1, D2, and D3 in Figure 2 are 1 cm, 1.5 cm, and 17 cm, respectively, and the water temperature is 40°C.

[0050] The area range RA in the reference image is a range of 300 to 400 pixels (the range indicated by B in FIG. 5), and the water film uniformity index of the evaluation image is calculated to be 36%.

[0051] <Anti-fog index AFI> The anti-fogging index AFI can be determined by the following method. Fourth step: After bringing water vapor into contact with the main surface of the sample prepared in the first step, an image of a predetermined subject is taken through the sample to obtain an image for evaluating antifogging properties. Fifth step: An anti-fogging index indicating the anti-fogging properties of the anti-fogging agent is derived based on the file size after compression when the image for evaluating anti-fogging properties is compressed using a predetermined compression method.

[0052] (Step 4) The water vapor contact can be performed using the device shown in FIG. 2 described above. That is, D1, D2, and D3 in FIG. 2 and the temperature of the water 20 can be set to the values ​​described in the second step. Also, by checking in advance the time from when the substrate is placed until the cloudiness is generated, the timing of imaging can be set using the passage of time as an indicator. The time from when the substrate is placed until the cloudiness is generated depends on the type of substrate, the temperature of the water 20, the distance D1, etc., but when the substrate is a polycarbonate plate, the temperature of the water 20 is 40°C, and the distance D1 is 1.5 cm, imaging can be performed after 10 seconds have elapsed.

[0053] The image for evaluating anti-fogging properties can be obtained by arranging the sample prepared in the first step as shown in Figure 2 and capturing a sample image after a predetermined time has elapsed (e.g., 10 seconds).

[0054] The sample image can be a checkerboard pattern as shown in Fig. 3. In this case, the distance D3 can be set so that 4900 squares are included in an image of size 1824 x 1824 pixels.

[0055] (5th step) In the fifth step, an anti-fogging index indicating the anti-fogging properties of the anti-fogging agent is derived based on the file volume after compression when the anti-fogging property evaluation image obtained in the fourth step is compressed using a predetermined compression method.

[0056] Regarding the file size after compression, for example, when a JPG image is compressed, the information of the cloudy white areas is compressed, and the number of image files is reduced. In other words, when the image is compressed, the color gradation of the cloudy white areas disappears and is replaced with an average color, reducing the number of image files. On the other hand, the information of the non-cloudy areas is difficult to compress, so the number of image files remains high.

[0057] The compression method used is lossy compression and resizing.

[0058] In this embodiment, the file size when an image for evaluating anti-fogging properties is compressed using the above compression method is S1, the file size when an image N obtained by imaging the specified subject through a fogged substrate after contacting water vapor with the untreated substrate is compressed using the above compression method is S2, and the file size when an image O obtained by imaging the subject through the untreated substrate is compressed using the above compression method is S0. The anti-fogging index AFI calculated by the following formula can be used. AFI = (S1-S2) x 10 / (S0-S2)

[0059] When calculating the anti-fogging index AFI, the imaging and compression conditions for the anti-fogging evaluation images, image N and image O, are as follows: a jpg image of 1824 x 1824 pixels is obtained, compressed at a compression rate of 20% (compression level 20), and then resized to 820 x 820 pixels.

[0060] Images O and N can be obtained by placing a substrate not treated with an antifogging agent and capturing sample images immediately after (0 seconds after placement) and after a predetermined time has elapsed (e.g., 10 seconds). Also, S0 and S1 may be calculated in advance from these images.

[0061] The antifogging agent of this embodiment may have a water film uniformity index WE of 65% or more, 70% or more, 80% or more, or 90% or more.

[0062] Methods for increasing the water film uniformity index (WE) of an anti-fogging agent include, for example, combining colloidal silica (described later) with a specific colloidal silica binding material, increasing the hydrophilicity of the material, and increasing the smoothness of the coating surface.

[0063] The antifogging agent of the present embodiment may have an antifogging index AFI of 6.0 or more, 7.0 or more, or 8.0 or more.

[0064] Methods for increasing the antifogging index AFI of an antifogging agent include, for example, increasing the amount of hydrophilic groups and adding a hydrophilic material.

[0065] The antifogging agent of this embodiment may be capable of forming a film having a contact angle with water of 10° or less, 8° or less, or 5° or less.

[0066] The contact angle can be calculated by using a contact angle meter, for example, by averaging 10 measurements on a 1 μL droplet of ultrapure water.

[0067] The antifogging agent of this embodiment may be a non-surfactant-based antifogging agent from the viewpoint of antifogging properties and transparency when a water film is formed. Here, "non-surfactant-based" means that the content of a surfactant known as a component of an antifogging agent is 1% by mass or less based on the total non-volatile content of the antifogging agent. The antifogging agent may in particular not contain a surfactant such as an anionic surfactant, a cationic surfactant, a nonionic surfactant, or an amphoteric surfactant, or the content of such a surfactant may be 1% by mass or less based on the total non-volatile content of the antifogging agent.

[0068] The antifogging agent may contain colloidal silica, at least one material selected from the group consisting of a crosslinking agent, a binder, and a metal chelate (colloidal silica binding material), and a liquid medium.

[0069] (colloidal silica) Colloidal silica having an average particle size (secondary particle size) of 1 to 1,000 nm can be used. When the average particle size is 1 nm or more, the particles are less likely to aggregate in the anti-fogging agent, and therefore the particles are more likely to adhere to the substrate. On the other hand, when the average particle size is 1,000 nm or less, the specific surface area of ​​the particles increases, and the particles are more likely to adhere to the substrate. From this perspective, the average particle size of the colloidal silica may be 3 to 700 nm or 5 to 500 nm.

[0070] The average particle size can be measured, for example, by the following procedure. First, approximately 100 μL (L stands for liter; the same applies below) of colloidal silica dispersion is measured out and diluted with ion-exchanged water to obtain a diluted solution so that the colloidal silica content is approximately 0.05% by mass (a content that results in a transmittance (H) of 60 to 70% during measurement). The diluted solution is then placed in the sample chamber of a laser diffraction particle size analyzer (manufactured by Horiba, Ltd., product name: LA-920, refractive index: 1.93, light source: He-Ne laser, absorption 0), and the average particle size can be measured.

[0071] The number of silanol groups per gram of colloidal silica is 10 x 10 18 ~1000×10 18 50 x 10 18 ~800×10 18 pieces / g or 100 x 10 18 ~700×10 18 The number of silanol groups per 1 g of colloidal silica may be 10 × 10 18 When the number of silanol groups is 1000×10 / g or more, the number of chemical bonding points with the functional groups of the substrate increases, which makes it easier to improve adhesion to the substrate. 18 By keeping the content at or less than 1 / g, a sudden polycondensation reaction between colloidal silica particles can be suppressed during preparation of the anti-fogging liquid, and a decrease in the number of chemical bonding points with the functional groups of the substrate can be suppressed.

[0072] In this embodiment, the number of silanol groups (ρ [groups / g]) can be measured and calculated by the following titration.

[0073] [1] First, weigh out 15 g of colloidal silica into a container whose mass has been measured (X [g]) and disperse it in an appropriate amount (100 ml or less) of water. If the colloidal silica is in the form of a dispersion in a medium such as water, measure out the dispersion into the container so that the amount of colloidal silica is 15 g.

[0074] [2] Next, adjust the pH to 3.0-3.5 with 0.1 mol / L hydrochloric acid, measure the mass (Y [g]) at this point, and calculate the total mass of the liquid (YX [g]).

[0075] [3] Weigh out 1 / 10 of the mass obtained in [2] ((YX) / 10[g]) of the liquid into a separate container. At this stage, the colloidal silica (A[g]) contained in the liquid is 1.5g.

[0076] [4] Add 30 g of sodium chloride and then add ultrapure water to bring the total volume to 150 g. Adjust the pH to 4.0 with 0.1 mol / L sodium hydroxide solution to use as the titration sample.

[0077] [5] Add 0.1 mol / L sodium hydroxide to this titration sample until the pH reaches 9.0, and determine the amount of sodium hydroxide (B [mol]) required to change the pH from 4.0 to 9.0.

[0078] [6] Calculate the number of silanol groups in the colloidal silica using the following formula (1). ρ=B·N A / A·S BET ···(1) (In formula (1), N A [mol / mol] indicates Avogadro's number. BET [m 2 / g] indicates the BET specific surface area of ​​the colloidal silica.)

[0079] The above-mentioned BET specific surface area S BETis determined according to the BET specific surface area method. Specific measurement methods include, for example, placing colloidal silica in a dryer, drying it at 150°C, placing it in a measurement cell, and vacuum-degassing it at 120°C for 60 minutes. The sample is then subjected to a single-point or multi-point method of adsorbing nitrogen gas using a BET specific surface area measuring device. More specifically, the colloidal silica dried at 150°C is first crushed into small pieces in a mortar (magnetic, 100 ml), placed in a measurement cell as a measurement sample, and the BET specific surface area, S, is measured using a BET specific surface area measuring device (product name NOVE-1200) manufactured by Yuasa Ionics Co., Ltd. BET Measure.

[0080] The degree of association of the colloidal silica may be, for example, 5.0 or less, 4.0 or less, 3.0 or less, 2.5 or less, or 2.0 or less. The degree of association may be 1.0 or more, 1.3 or more, or 1.5 or more.

[0081] Herein, the degree of association of colloidal silica in a colloidal silica dispersion refers to the ratio of the average particle size of secondary particles of colloidal silica in the dispersion to the biaxial average primary particle size of colloidal silica (average particle size of secondary particles / biaxial average primary particle size). The average primary particle size can be measured, for example, using a known transmission electron microscope (e.g., H-7100FA, manufactured by Hitachi High-Tech Corporation). For example, images of particles are taken using an electron microscope, and the biaxial average primary particle size of a predetermined number of particles is calculated, and the average value of these is obtained. In the case of colloidal silica, since the particle size is generally uniform, the number of particles measured may be, for example, about 20 particles. The average particle size of secondary particles refers to the value obtained by the above-mentioned method.

[0082] The shape of the colloidal silica is not particularly limited, and examples thereof include pearl necklace-like, chain-like, spherical, cocoon-like, association-like, and confetti-like shapes. Of these, the pearl necklace-like and chain-like shapes are preferred from the viewpoint of water retention, and the pearl necklace-like shape is more preferred from the viewpoint of moisture resistance and water resistance.

[0083] The surface of the colloidal silica may be subjected to a coupling treatment with a modifying agent. The modifying agent is not particularly limited, but examples thereof include a silane coupling agent having a cationic group represented by the following general formula (2), a silane coupling agent having a sulfonic acid group which is an anionic group, or a compound having a functional group that can be converted into a silane coupling agent for the purpose of hydrophobic treatment.

[0084] [ka] (In formula (2), R is an alkyl group having 1 to 6 carbon atoms, R' is an alkyl group having 1 to 3 carbon atoms, and R" is a hydrocarbon group having 1 to 4 carbon atoms or a hydrocarbon group having 1 to 4 carbon atoms substituted with an amino group. m is an integer of 0 to 2, p is 1 or 2, and n is an integer of 1 to 3, and m+n+p=4.)

[0085] Specific examples of R include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, an isopentyl group, a neopentyl group, a hexyl group, and an isohexyl group. An alkyl group having 1 to 3 carbon atoms is preferred, and a methyl group or an ethyl group is more preferred.

[0086] Specific examples of R' include a methyl group, an ethyl group, a propyl group, an isopropyl group, etc., with a methyl group and an ethyl group being preferred.

[0087] Specific examples of the hydrocarbon having 1 to 4 carbon atoms in R" include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, and an isobutylene group, and an alkylene group having 2 to 4 carbon atoms is preferred, with an ethylene group, a propylene group, and a butylene group being more preferred.

[0088] Of R", specific examples of the hydrocarbon group having 1 to 4 carbon atoms substituted with an amino group include an aminomethylene group, an aminoethylene group, an aminopropylene group, an aminoisopropylene group, an aminobutylene group, and an aminoisobutylene group, with an aminoethylene group and an aminopropylene group being preferred.

[0089] Examples of the compound represented by the general formula (2) include aminopropyltrimethoxysilane, (aminoethyl)aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxysilane, aminobutyltriethoxysilane, etc. These may be used alone or in combination.

[0090] Examples of silane coupling agents having a functional group that can be chemically converted into a sulfonic acid group include 1) silane coupling agents having a sulfonate ester group that can be converted into a sulfonic acid group by hydrolysis, and 2) silane coupling agents having a mercapto group and / or a sulfide group that can be converted into a sulfonic acid group by oxidation. Because the sulfonic acid modification of the colloidal silica surface is carried out in solution, it is preferable to use the latter silane coupling agents having a mercapto group and / or a sulfide group in order to increase the modification efficiency.

[0091] Examples of silane coupling agents having a mercapto group include 3-mercaptopropyltrimethoxysilane, 2-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane.

[0092] An example of a silane coupling agent having a sulfide group is bis(3-triethoxysilylpropyl) disulfide.

[0093] The mercapto group-containing silane coupling agent and the sulfide group-containing silane coupling agent may be used alone or in combination.

[0094] Examples of silane coupling agents used for hydrophobic treatment include silylating agents. A disiloxane compound and / or a monoalkoxysilane compound is added to the silylating agent to carry out the silylation reaction. Examples of disiloxane compounds used as silylating agents include compounds represented by the following general formula (I):

[0095] [ka] (In formula (I), R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are each independently an alkyl group having 1 to 20 carbon atoms or a phenyl group.

[0096] Examples of disiloxane compounds include hexamethyldisiloxane, 1,3-dibutyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, 1,3-divinyltetramethyldisiloxane, hexaethyldisiloxane, and 3-glycidoxypropylpentamethyldisiloxane, with hexamethyldisiloxane being preferred.

[0097] The monoalkoxysilane compound as the silylating agent includes a compound represented by the following general formula (II).

[0098] [ka] (In formula (II), R 7 , R 8 and R 9 are each independently an alkyl group having 1 to 20 carbon atoms or a phenyl group, and Q is an alkyl group having 1 to 3 carbon atoms.

[0099] Examples of the monoalkoxysilane compound include trimethylmethoxysilane, trimethylethoxysilane, trimethylpropoxysilane, phenyldimethylmethoxysilane, and chloropropyldimethylmethoxysilane, with trimethylmethoxysilane, trimethylethoxysilane, and trimethylpropoxysilane being preferred.

[0100] The silylating agents may be used alone or in combination of two or more kinds.

[0101] The colloidal silica may contain a metal oxide other than silicon dioxide. The type of metal oxide is not particularly limited, but alumina may be used. Examples of such colloidal silica include colloidal silica in which a sufficient amount of aluminosilicate is firmly formed on the surface of the colloidal silica to stabilize the silica sol.

[0102] The content of colloidal silica can be 1 to 20% by mass based on the total amount of the antifogging agent. A content of 1% by mass or more facilitates the development of sufficient antifogging properties, while a content of 20% by mass or less inhibits the polycondensation reaction of silanol groups between particles, making it easier to maintain antifogging properties (hydrophilicity). From this perspective, the content of colloidal silica may be 1.5 to 15% by mass, 2 to 13% by mass, or 3 to 10% by mass.

[0103] Colloidal silica is available as a colloidal silica dispersion. Examples of the dispersion medium include water, isopropyl alcohol, 1-methoxy-2-propyl alcohol, ethyl alcohol, methyl alcohol, ethylene glycol, ethylene glycol-n-propyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, dimethylacetamide, N-methylpyrrolidone, toluene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, and ethyl acetate. The dispersion medium may be water, an alcohol, or a mixture of water and an alcohol. Of these, water is preferred from the viewpoint of versatility.

[0104] The pH of the colloidal silica dispersion may be 2 to 10. By setting the pH to 6 to 8, if alkoxy groups are present on the surface of the colloidal silica, the hydrolysis reaction rate is slowed. This makes it easier to form a coating film from colloidal silica with remaining alkoxy groups. In this case, the polycondensation reaction of silanol groups due to moisture absorption can be suppressed, making it easier to maintain the anti-fogging properties (hydrophilicity) of the film surface. By setting the pH to 2 to 5 or 8 to 10, if alkoxy groups are present on the surface of the colloidal silica, the hydrolysis reaction rate is increased. This makes it possible to generate more silanol groups, making it easier to improve adhesion to substrates.

[0105] The pH of the colloidal silica dispersion can be measured with a pH meter (for example, Model PHL-40, manufactured by Denki Kagaku Keiki Co., Ltd.). The measured pH is measured by performing three-point calibration using standard buffer solutions (phthalate pH buffer solution, pH: 4.01 (25°C), neutral phosphate pH buffer solution, pH: 6.86 (25°C), and borate pH buffer solution, pH: 9.18 (25°C)), then immersing the electrode in the dispersion and allowing it to stabilize for at least two minutes, and then using the value.

[0106] The zeta potential of the colloidal silica in the dispersion is preferably -50 mV to 40 mV. A zeta potential of -10 mV to 10 mV reduces the repulsion between particles when coated, allowing the particles to adhere closely to the substrate, which tends to improve the hydrophilicity of the substrate. A zeta potential of -50 mV to -11 mV or 11 mV to 40 mV increases the repulsion between particles in the dispersion, increasing dispersibility and facilitating suppression of particle aggregation.

[0107] The zeta potential of colloidal silica can be measured using a zeta potential meter (e.g., Beckman Coulter, Model: Coulter Delsa 440). To measure zeta potential, first add pure water to a colloidal silica dispersion to achieve a silica particle concentration of 5 ppm based on the total volume of the test solution, and then disperse the silica particles using ultrasonic treatment to prepare a test solution. The test solution is then placed in a measurement cell equipped with platinum electrodes on both sides, and a voltage of 10 V is applied to both electrodes. The charged silica particles migrate to the electrode with the opposite polarity. The migration speed of these charged silica particles is then determined.

[0108] The raw material for colloidal silica is not particularly limited and may be water glass or alkoxysilane.

[0109] The preparation process when the raw material is water glass is not particularly limited, but for example, sodium silicate is heated and concentrated by hydrothermal synthesis to prepare particles. For example, agglomerates with a three-dimensional network structure may be prepared under an acidic pH condition to suppress the growth of primary particles, and then disintegrated, or agglomerates with an alkaline pH condition to accelerate the growth of primary particles may be prepared and then disintegrated.

[0110] When the raw material is alkoxysilane, the production process is not particularly limited, but for example, particles are produced by sol-gel synthesis of the alkoxysilane. For example, after promoting the hydrolysis reaction of the alkoxysilane, the polycondensation reaction may be promoted to obtain a gel, and then the internal solvent may be removed by heat treatment. Alternatively, after obtaining the gel, solvent substitution with a predetermined solvent may be performed.

[0111] Commercially available colloidal silica dispersions may be used, for example, ST-PS-SO (manufactured by Nissan Chemical Industries, Ltd.), ST-PS-MO (manufactured by Nissan Chemical Industries, Ltd.), ST-PS-M (manufactured by Nissan Chemical Industries, Ltd.), ST-PS-S (manufactured by Nissan Chemical Industries, Ltd.), ST-UP (manufactured by Nissan Chemical Industries, Ltd.), ST-OUP (manufactured by Nissan Chemical Industries, Ltd.), IPA-ST-UP (manufactured by Nissan Chemical Industries, Ltd.), MA-ST-UP (manufactured by Nissan Chemical Industries, Ltd.), PGM-ST-UP (manufactured by Nissan Chemical Industries, Ltd.), MEK-ST-UP (manufactured by Nissan Chemical Industries, Ltd.), IPA-ST (manufactured by Nissan Chemical Industries, Ltd.), IPA- ST-L (Nissan Chemical Co., Ltd.), IPA-ST-ZL (Nissan Chemical Co., Ltd.), MA-ST-M (Nissan Chemical Co., Ltd.), MA-ST-L (Nissan Chemical Co., Ltd.), MA-ST-ZL (Nissan Chemical Co., Ltd.), EG-ST (Nissan Chemical Co., Ltd.), EG-ST-XL-30 (Nissan Chemical Co., Ltd.), NPC-ST-30 (Nissan Chemical Co., Ltd.), PGM-ST (Nissan Chemical Co., Ltd.), DMAC-ST (Nissan Chemical Co., Ltd.), DMAC-ST-ZL (Nissan Chemical Co., Ltd.), NMP-ST (Nissan Chemical Co., Ltd.), TOL-ST (Nissan Chemical Co., Ltd.) (Nissan Chemical Co., Ltd.), MEK-ST-40 (Nissan Chemical Co., Ltd.), MEK-ST-L (Nissan Chemical Co., Ltd.), MEK-ST-ZL (Nissan Chemical Co., Ltd.), MIBK-ST (Nissan Chemical Co., Ltd.), MIBK-ST-L (Nissan Chemical Co., Ltd.), CHO-ST-M (Nissan Chemical Co., Ltd.), EAC-ST (Nissan Chemical Co., Ltd.), PMA-ST (Nissan Chemical Co., Ltd.), MEK-EC-2130Y (Nissan Chemical Co., Ltd.), MEK-EC-2430Z (Nissan Chemical Co., Ltd.), MEK-EC-2140Z (Nissan Chemical Co., Ltd.), MEK-AC-4130Z (Nissan Chemical Co., Ltd.) Nissan Chemical Co., Ltd.), MEK-AC-5140Z (Nissan Chemical Co., Ltd.), PGM-AC-2140Y (Nissan Chemical Co., Ltd.), PGM-AC-4130Y (Nissan Chemical Co., Ltd.), MIBK-AC-2140Z (Nissan Chemical Co., Ltd.), MIBK-SD-L (Nissan Chemical Co., Ltd.), ST-XS (Nissan Chemical Co., Ltd.), ST-OXS (Nissan Chemical Co., Ltd.), ST-NXS (Nissan Chemical Co., Ltd.), ST-CXS (Nissan Chemical Co., Ltd.), ST-S (Nissan Chemical Co., Ltd.), ST-OS (Nissan Chemical Co., Ltd.), ST-NS (Nissan Chemical Co., Ltd.),ST-30 (Nissan Chemical Co., Ltd.), ST-O (Nissan Chemical Co., Ltd.), ST-N (Nissan Chemical Co., Ltd.), ST-C (Nissan Chemical Co., Ltd.), ST-AK (Nissan Chemical Co., Ltd.), ST-50-T (Nissan Chemical Co., Ltd.), ST-O-40 (Nissan Chemical Co., Ltd.), ST-N-40 (Nissan Chemical Co., Ltd.), ST-CM (Nissan Chemical Co., Ltd.), ST-30L (Nissan Chemical Co., Ltd.), ST-OL (Nissan Chemical Co., Ltd.), ST-AK-L (Nissan Chemical Co., Ltd.), ST-YL (Manufactured by Nissan Chemical Co., Ltd.), ST-OYL (Manufactured by Nissan Chemical Co., Ltd.), ST-AK-YL (Manufactured by Nissan Chemical Co., Ltd.), ST-ZL (Manufactured by Nissan Chemical Co., Ltd.), MP-1040 (Manufactured by Nissan Chemical Co., Ltd.), MP-2040 (Manufactured by Nissan Chemical Co., Ltd.), MP-4540M (Manufactured by Nissan Chemical Co., Ltd.), PL-1-IPA (Manufactured by Fuso Chemical Co., Ltd.), PL-1-TOL (Manufactured by Fuso Chemical Co., Ltd.), PL-2L-PGME (Manufactured by Fuso Chemical Co., Ltd.), PL-2L-MEK (Manufactured by Fuso Chemical Co., Ltd.), PL-2L (Manufactured by Fuso Chemical Co., Ltd.) PL-3 (manufactured by Fuso Chemical Co., Ltd.), PL-4 (manufactured by Fuso Chemical Co., Ltd.), PL-5 (manufactured by Fuso Chemical Co., Ltd.), PL-1H (manufactured by Fuso Chemical Co., Ltd.), PL-3H (manufactured by Fuso Chemical Co., Ltd.), PL-5H (manufactured by Fuso Chemical Co., Ltd.), BS-2L (manufactured by Fuso Chemical Co., Ltd.), BS-3L (manufactured by Fuso Chemical Co., Ltd.), BS-5L (manufactured by Fuso Chemical Co., Ltd.), HL-2L (manufactured by Fuso Chemical Co., Ltd.), HL-3L (manufactured by Fuso Chemical Co., Ltd.), HL-4L (manufactured by Fuso Chemical Co., Ltd.), PL-3-C (manufactured by Fuso Chemical Co., Ltd.), PL-3-D (manufactured by Fuso Chemical Co., Ltd.), TCSOL800 (manufactured by Tama Chemicals Co., Ltd.), SI-40 (manufactured by JGC Catalysts and Chemicals Co., Ltd.), SI-50 (manufactured by JGC Catalysts and Chemicals Co., Ltd.), SI-45P (manufactured by JGC Catalysts and Chemicals Co., Ltd.), SI-80P (manufactured by JGC Catalysts and Chemicals Co., Ltd.), SIK-23 (manufactured by JGC Catalysts and Chemicals Co., Ltd.), S-30H (manufactured by JGC Catalysts and Chemicals Co., Ltd.), SIK-15 (manufactured by JGC Catalysts and Chemicals Co., Ltd.), SI-550 (manufactured by JGC Catalysts and Chemicals Co., Ltd.), etc.

[0112] (liquid medium) The liquid medium disperses colloidal silica in the anti-fogging agent and dissolves the colloidal silica binding material. The liquid medium has a boiling point lower than 185°C. The liquid medium volatilizes when heated during anti-fogging film formation, thereby bringing the colloidal silica particles closer together and facilitating bonding. The liquid medium may be the same as or different from the dispersion medium contained in the colloidal silica dispersion.

[0113] Examples of the liquid medium include water, organic solvents, and mixtures thereof. Examples of the organic solvent include alcohols such as methyl alcohol, ethyl alcohol, 1-propanol, isopropyl alcohol, 1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, diacetone alcohol, 1-butoxy-2-propanol, 1-hexanol, 1-octanol, 2-octanol, and 3-methoxy-3-methyl-1-butanol, glycols such as polyethylene glycol, glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol mono-tert-butyl ether, propylene glycol monomethyl ether acetate, propylene glycol n-propyl ether, and propylene glycol monomethyl ether, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran and dioxane, esters such as ethyl acetate and butyl acetate, cyclic hydrocarbons such as cyclohexane, and acetonitrile. These may be used alone or in combination, but it is preferable that they can be uniformly dispersed in the colloidal silica dispersion. For example, when the dispersion medium of the colloidal silica dispersion is water, ethylene glycol monobutyl ether is preferred.

[0114] (metal chelate) The metal chelate functions as a binding material for the colloidal silica, and can form an anti-fogging film with excellent moisture and water resistance.

[0115] The metal chelate is not particularly limited and can be appropriately selected from known metal chelates, such as zirconium chelate compounds, titanium chelate compounds, nickel chelate compounds, aluminum chelate compounds, and tin chelate compounds.

[0116] Examples of zirconium chelate compounds include zirconium tetrakis(acetylacetonate) and zirconium bis(butoxy)bis(acetylacetonate).

[0117] Examples of titanium chelate compounds include titanium tetrakis(acetylacetonate) and titanium bis(butoxy)bis(acetylacetonate).

[0118] Examples of nickel chelate compounds include CR12 (manufactured by Momentive Performance Materials Japan) and Ni(AcAc)2.

[0119] Examples of aluminum chelate compounds include aluminum bis(ethylacetoacetate) mono(acetylacetonate), aluminum tris(acetylacetonate), and aluminum ethylacetoacetate diisopropylate.

[0120] Examples of tin chelate compounds include dibutyltin diacetate, dibutyltin dilaurate, and dibutyltin dioctiate.

[0121] Among the above, the metal chelate is more preferably a zirconium chelate compound, a titanium chelate compound, or a nickel chelate compound from the viewpoint of moisture resistance and water resistance.

[0122] The metal chelate may be a commercially available product. For example, a zirconium chelate compound is available as ZC-150 (manufactured by Matsumoto Fine Chemical Co., Ltd.), an aluminum chelate compound is available as Aluminum Chelate D (manufactured by Kawaken Fine Chemical Co., Ltd.) or Plain Act AL-M (manufactured by Ajinomoto Fine-Techno Co., Ltd.), and a nickel chelate compound is available as acetylacetonate nickel(II) hydrate (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0123] The antifogging agent may contain one type of metal chelate, or may contain two or more types of metal chelates.

[0124] The content of the metal chelate may be 0.01 to 5.0 parts by mass, 0.05 to 2.0 parts by mass, or 0.1 to 1.0 parts by mass relative to 100 parts by mass of colloidal silica, from the viewpoints of the moisture resistance, water resistance, contamination resistance, water dripping resistance, etc. of the anti-fogging film.

[0125] When a metal chelate is used, for example, an antifogging agent can be obtained by adding a liquid medium, a metal chelate, and an acid catalyst (nitric acid) in this order to a water-dispersed silica sol.

[0126] (binder) The binder functions as a binding material for the colloidal silica, and can form an anti-fogging film with excellent moisture and water resistance. The binder is a medium with a boiling point of 185°C or higher.

[0127] Examples of binders include sugars such as cellulose, carboxymethyl cellulose, dextrin, chitin, chitosan, and xanthan gum; glycol ethers such as ethylene glycol monobutyl ether, ethylene glycol monopropyl ether, ethylene glycol mono-tert-butyl ether, triethylene glycol butyl methyl ether, propylene glycol n-butyl ether, dipropylene glycol methyl ether, and dipropylene glycol n-butyl ether; alcohols such as polyvinyl alcohol, modified polyvinyl alcohol, and polyvinyl acetal; glycols such as polyoxyethylene polyoxypropylene glycol, ethylene glycol, diethylene glycol, propylene glycol, and polyethylene glycol; ethers such as lauryl alcohol glycidyl ether, glycerol polyglycidyl ether, polyethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether; glycerin, polyacrylic acid, acrylic resin, epoxy resin, urethane resin, polyvinylpyrrolidone, polyvinylpyrrolidone-vinyl acetate copolymer (vinyl acetate pyrrolidone copolymer), N-methylpyrrolidone, dimethyl sulfoxide, and polysaccharides such as cellulose nanofibers; and silane oligomers.

[0128] The binder components may be used alone or in combination of two or more depending on the purpose, application, etc. However, from the viewpoint of excellent water resistance and moisture resistance, the binder component may be cellulose, polyethylene glycol, glycerol polyglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin, acrylic resin, polyacrylic acid, polyvinyl alcohol, or polyvinylpyrrolidone.

[0129] The antifogging agent may contain one type of binder or two or more types of binders.

[0130] The content of the binder may be 0.001 to 5.0 parts by mass, 0.005 to 2.0 parts by mass, or 0.01 to 1.0 parts by mass relative to 100 parts by mass of colloidal silica, from the viewpoint of the moisture resistance, water resistance, contamination resistance, water dripping resistance, etc. of the anti-fogging film.

[0131] When a binder component is used, for example, an antifogging agent can be obtained by adding a liquid medium, a binder component (added as a dispersion of the binder component), and an acid catalyst (nitric acid) in this order to a water-dispersed silica sol.

[0132] (Crosslinking agent) The crosslinking agent functions as a binder for the colloidal silica, and can form an anti-fogging film having excellent moisture resistance and water resistance. Examples of the crosslinking agent include a silane coupling agent.

[0133] Examples of the silane coupling agent include silane compounds having a vinyl group, an epoxy group, a styryl group, an acryloyl group, a methacryloyl group, an amino group, a ureido group, an isocyanate group, an isocyanurate group, a mercapto group, a fluoro group, an alkyl group, or the like, and silane oligomers having a silanol group.

[0134] Examples of the silane coupling agent having a vinyl group include KBM-1003 and KBE-1003 (both trade names, manufactured by Shin-Etsu Chemical Co., Ltd.; the same applies hereinafter).

[0135] Examples of silane coupling agents having an epoxy group include KBM-303, 402, 403, 4803, KBE-402, 403, X-12-981S, and X-12-984S.

[0136] Examples of silane coupling agents having a styryl group include KBM-1403.

[0137] Examples of silane coupling agents having a methacryloyl group include KBM-502, 503, KBE-502, 503, and the like.

[0138] Examples of silane coupling agents having an acryloyl group include KBM-5103, X-12-1048, and X-12-1050.

[0139] Examples of silane coupling agents having an amino group include KBM-602, 603, 903, 573, 575, 6803, KBE-903, 9103P, and X-12-972F.

[0140] Examples of silane coupling agents having a ureido group include KBE-585A.

[0141] Examples of silane coupling agents having an isocyanate group include KBE-9007 and X-12-1159L.

[0142] An example of a silane coupling agent having an isocyanurate group is KBM-9659.

[0143] Examples of silane coupling agents having a mercapto group include KBM-802, 803, X-12-1154, and X-12-1156.

[0144] Examples of silane coupling agents having a fluoro group include KBM-7103.

[0145] Other silane coupling agents include KBE-04, KBM-13, KBM-22, KBM-103, KBM-202SS, KBM-3033, KBM-3063, KBM-3103C, KBM-3066, KBM-7103, KBE-22, KBE-103, KBE-3033, KBE-3063, and KBE-3083.

[0146] Examples of silane oligomers having silanol groups include ethyl silicate 28, ethyl silicate 28P, ethyl silicate 40, ethyl silicate 48, EMS-485, methyl silicate 51, methyl silicate 53A, N-propyl silicate, N-butyl silicate, Colcoat PX, and Colcoat N-103X.

[0147] The above silane coupling agents may be used alone or in combination of two or more depending on the purpose, application, etc. However, from the viewpoint of achieving excellent anti-fogging properties of the anti-fogging film, the silane coupling agent may be a silane coupling agent having an epoxy group, an amino group, or a ureido group.

[0148] The content of the silane coupling agent may be 1.0 to 100.0 parts by mass, 5.0 to 100.0 parts by mass, 6.0 to 50.0 parts by mass, or 7.0 to 20.0 parts by mass relative to 100 parts by mass of colloidal silica, from the viewpoints of the moisture resistance, water resistance, contamination resistance, water dripping resistance, etc. of the anti-fogging film.

[0149] When a silane coupling agent is used, for example, a liquid medium, a silane coupling agent, and an acid catalyst (nitric acid) can be added in this order to a water-dispersed silica sol to obtain an antifogging agent.

[0150] (Other ingredients) The antifogging agent may contain various conventional additives such as antioxidants, ultraviolet absorbers, and light stabilizers, as necessary. Furthermore, the antifogging agent may contain, as an antifoaming agent, a catalyst, and the like used in preparing the raw materials, nitric acid, acetic acid, hydrochloric acid, nitric acid, phosphoric acid, sulfate, paratoluenesulfonic acid, benzenesulfonic acid, methanesulfonic acid, phenolsulfonic acid, oxalic acid, maleic acid, malonic acid, tartaric acid, citric acid, malic acid, acetic acid, lactic acid, succinic acid, benzoic acid, ammonia, urea, imidazole, sodium carbonate, calcium carbonate, and the like. Furthermore, a thickener may be used in view of the viscosity of the solution.

[0151] <Hydrophilic agent> The antifogging agent can hydrophilize the target surface, so it can be called a hydrophilizing agent. For specific aspects of the hydrophilizing agent, please refer to the above description of the antifogging agent. The hydrophilizing agent may have the same water film uniformity index WE and antifogging index AFI as the antifogging agent according to the above-mentioned embodiment, and may have the same composition as the antifogging agent according to the above-mentioned embodiment.

[0152] By using a hydrophilizing agent, the substrate can be subjected to a hydrophilizing treatment.

[0153] Examples of materials constituting the substrate include, in addition to the above-mentioned polycarbonate, resin materials such as acrylic polymer, polyamide, polyacrylate, polyimide, acrylonitrile-styrene copolymer, styrene-acrylonitrile-butadiene copolymer, polyvinyl chloride, polyethylene, and polycarbonate, metal materials such as aluminum, magnesium, copper, zinc, iron, titanium, chromium, manganese, cobalt, and nickel, ceramic materials such as silicon oxide, aluminum oxide, magnesium oxide, copper oxide, zinc oxide, iron oxide, titanium oxide, chromium oxide, manganese oxide, cobalt oxide, and nickel oxide, and glass. Examples of articles comprising such a substrate include the above-mentioned vehicle lamp structures (automobile headlights, etc.), as well as vehicle windshields, eyeglasses, goggles, mirrors, storage containers, windows, and camera lenses.

[0154] <Anti-fogging method for vehicle lamp structure> The antifogging method for a vehicle lamp structure involves treating the inner surface of a lens included in the vehicle lamp structure with the antifogging agent of the present embodiment described above. The treatment with the antifogging agent may include, for example, a step of applying the antifogging agent to the inner surface of the lens to form a coating film (a coating step), and a step of drying the coating film (a drying step). Prior to the coating step, a cleaning step may be performed to remove any release agent that may be adhering to the lens surface.

[0155] (Cleaning process) The cleaning liquid used in the cleaning step is not particularly limited, but considering that the lens inner surface substrate of the most commonly used vehicle lamp structure is polycarbonate, a liquid that does not dissolve the polycarbonate substrate is preferred, and water, alcohols, etc. are more preferred. Specifically, water, isopropyl alcohol, methanol, ethanol, etc. are preferred. The cleaning step may be performed by wiping the substrate with a cloth or the like soaked in the cleaning liquid.

[0156] (Coating process) The coating step is, for example, a step of coating the antifogging agent on the inner surface of the lens. The antifogging agent may be coated on the entire inner surface of the lens, or may be selectively coated on a portion of the inner surface.

[0157] The coating method is not particularly limited, and examples thereof include spin coating, dip coating, spray coating, flow coating, bar coating, and gravure coating. Spray coating is particularly preferred because it is easy to form an anti-fogging film of uniform thickness even on uneven surfaces, and it has high productivity and high use efficiency of the anti-fogging agent. These methods may be used alone or in combination of two or more. The anti-fogging agent may be applied by soaking it in a cloth or the like.

[0158] The amount of application is not limited because it depends on the components of the anti-fogging agent, its content, etc., but for example, 10 -9 ~10 3 g / m 2 It can be said that:

[0159] The temperature of the antifogging agent used in the coating step may be, for example, 1 to 50° C., or 10 to 30° C. By setting the temperature at 1° C. or higher, the antifogging properties and adhesion tend to be further improved, and by setting the temperature at 50° C. or lower, the transparency of the antifogging film tends to be easily obtained. The treatment time with the antifogging agent can be, for example, 1 second to 1 hour, or 5 to 30 minutes.

[0160] (drying process) In this step, after applying the anti-fogging agent, the liquid medium is volatilized from the anti-fogging agent. The liquid medium can be volatilized, for example, by leaving it at room temperature. However, by carrying out this step at a higher temperature, the adhesion between the inner surface of the lens and the anti-fogging film can be further improved. The drying temperature is not particularly limited and varies depending on the heat resistance temperature of the lens, but may be, for example, 5 to 300°C or 10 to 200°C. By setting the temperature at 5°C or higher, better adhesion can be achieved, and by setting it at 300°C or lower, deterioration due to heat can be further suppressed. The drying time can be 30 seconds to 150 hours. By this step, an anti-fogging film containing colloidal silica is formed on the inner surface of the lens.

[0161] The thickness of the anti-fogging film is not particularly limited, but may be about 1 nm to 5 mm, 5 nm to 10 μm, or 10 nm to 5 μm from the viewpoints of transparency, anti-fogging properties, etc. The film thickness of the anti-fogging film can be measured, for example, with a non-contact film thickness meter, Optical NanoGauge C13027 (manufactured by Hamamatsu Photonics Co., Ltd.).

[0162] The water contact angle of the anti-fogging film can be 40° or less with respect to a 1 μL droplet of ultrapure water, and may be 20° or less. This allows the anti-fogging properties to be fully exhibited. The contact angle can be calculated using a contact angle meter, for example, as the average value of 10 measurements.

[0163] The anti-fog film can have a visible light transmittance of 85% or more, 90% or more, or 95% or more. This allows the brightness of the vehicle lamp to be maintained at a sufficiently high level. The visible light transmittance of the anti-fog film can be measured, for example, using a U-3500 type recording spectrophotometer (manufactured by Hitachi, Ltd.).

[0164] The anti-fog film may have a haze of 6.0 or less, 3.0 or less, or 1.0 or less. This allows the brightness of the vehicle lamp to be maintained at a sufficiently high level. The haze of the anti-fog film can be measured, for example, using a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0165] The anti-fog film may have a YI of 4.0 or less, 3.0 or less, or 1.5 or less. This allows the brightness of the vehicle lamp to be maintained at a sufficiently high level. The YI of the anti-fog film can be measured, for example, using a chromaticity meter (300A, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0166] FIG. 6 is a schematic diagram illustrating a vehicle lamp structure. The inner surface of the lens of the vehicle lamp structure is antifogging-treated by the antifogging method for a vehicle lamp structure using the antifogging agent described above. The lamp structure 100 shown in FIG. 6 includes a lamp housing 103 having a recessed shape with one open end and a lens 101 closing the open end of the lamp housing 103. The lens 101 is made of, for example, polycarbonate. The lamp housing 103 and the lens 101 form a lamp chamber S. A light source 104 is mounted in the lamp housing 103 and disposed within the lamp chamber S. The light source 104 may be an incandescent bulb, an LED bulb, a halogen bulb, or the like, as appropriate. As shown in the figure, a reflector 105 that functions as a reflector for the light from the light source 104 may be provided within the lamp chamber S so as to surround the light source 104 from the rear. The inner surface of the lens 101, i.e., the surface facing the lamp chamber S, is provided with an antifogging film 102 formed from the antifogging agent described above. The anti-fogging film 102 may be provided on the entire inner surface of the lens 101, or may be provided selectively on a portion thereof as shown in FIG.

[0167] The vehicle lamp structure is anti-fogging treated with the anti-fogging agent of this embodiment, which has a water film uniformity index WE of 65% or more, and therefore has excellent anti-fogging properties and can sufficiently maintain the straightness and intensity of transmitted light when a water film is formed. [Example]

[0168] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0169] <Preparing the anti-fogging agent> The following coating solutions were prepared as anti-fogging agents.

[0170] Example 1 A 0.05% by weight aqueous cellulose dispersion was obtained by mixing 0.05 g of 60L (manufactured by Daido Chemical Industry Co., Ltd.) with 99.95 g of a water and ethanol mixture (1:1 by weight ratio of water to ethanol). 4.00 g of ST-PS-SO (manufactured by Nissan Chemical Co., Ltd., 15 wt% water, pearl necklace-shaped silica) water-dispersed silica sol, 6.86 g of water, 3.27 g of ethylene glycol monobutyl ether, 0.12 g of the 0.05% by weight aqueous cellulose dispersion, and 0.75 g of nitric acid diluted to 10% by weight were mixed and stirred for 1 hour to obtain a coating solution.

[0171] Example 2 A 0.05% by mass aqueous cellulose dispersion was obtained by mixing 0.05 g of 60 L of cellulose with 99.95 g of a water and ethanol mixture (1:1 by mass ratio of water to ethanol). 4.00 g of ST-PS-SO4, a water-dispersed silica sol, 6.68 g of water, 3.27 g of ethylene glycol monobutyl ether, 0.02 g of a ureido group-containing silane coupling agent KBE-585A, 0.12 g of the 0.05% by mass aqueous cellulose dispersion, and 0.75 g of nitric acid diluted to 10% by mass were mixed and stirred for 1 hour to obtain a coating solution.

[0172] Example 3 0.12 g of polyacrylic acid 1WX-049 (manufactured by Taisei Fine Chemical Co., Ltd., solids content 40.7% by mass) was mixed with 99.88 g of water to obtain a 0.05% by mass aqueous polyacrylic acid dispersion. 4.00 g of water-dispersed silica sol ST-PS-SO, 6.43 g of water, 3.27 g of ethylene glycol monobutyl ether, 0.1 g of KBE-585A, and 0.12 g of the 0.05% by mass aqueous polyacrylic acid dispersion were mixed and stirred for 1 hour to obtain a coating solution.

[0173] Example 4 A coating solution was obtained in the same manner as in Example 3, except that 0.10 g of E535 (manufactured by Ashland Japan Co., Ltd., solid content 50%), a vinyl acetate pyrrolidone copolymer, was mixed with 99.9 g of water instead of 1WX-049 to obtain a 0.05 mass % vinyl acetate pyrrolidone copolymer solution.

[0174] Example 5 A coating liquid was obtained in the same manner as in Example 3, except that glycerin was used instead of 1WX-049.

[0175] Example 6 A coating solution was obtained in the same manner as in Example 3, except that dextrin was used instead of 1WX-049.

[0176] Example 7 A coating solution was obtained in the same manner as in Example 3, except that PEG200, a polyethylene glycol, was used instead of 1WX-049.

[0177] Example 8 A 0.05% by mass aqueous cellulose dispersion was obtained by mixing 0.05 g of 60 L of cellulose with 99.95 g of a water and ethanol mixture (1:1 water:ethanol ratio). A 0.05% by mass aqueous cellulose dispersion was obtained by mixing 4.00 g of ST-PS-SO4 (a water-dispersed silica sol), 6.75 g of water, 3.27 g of ethylene glycol monobutyl ether, 0.12 g of the 0.05% by mass aqueous cellulose dispersion, 0.1 g of KBE-585A, 0.01 g of aluminum chelate D (Al-D: Kawaken Fine Chemicals Co., Ltd.), and 0.75 g of nitric acid diluted to 10% by mass. The mixture was stirred for 1 hour to obtain a coating solution.

[0178] Example 9 A coating solution was obtained in the same manner as in Example 8, except that 0.0005 g of a zirconium chelate compound, Zr(acac)4 (manufactured by Tokyo Chemical Industry Co., Ltd.), was added instead of aluminum chelate D, and 6.78 g of water was added instead of 6.75 g of water.

[0179] Example 10 4.00 g of ST-PS-SO, which is a water-dispersed silica sol, 10.01 g of isopropyl alcohol, 0.24 g of KBE-585A, and 0.75 g of nitric acid diluted to 10% by mass were mixed and stirred for 1 hour to obtain a coating liquid.

[0180] Example 11 A coating solution was obtained in the same manner as in Example 10, except that 10.00 g of ST-PS-SO was added instead of 4.00 g of ST-PS-SO, and 0.20 g of KBE-04 (manufactured by Shin-Etsu Chemical Co., Ltd.), which is ethyl orthosilicate, was added instead of 0.24 g of KBE-585A.

[0181] Example 12 4.00 g of ST-PS-SO, which is a water-dispersed silica sol, 6.97 g of water, 3.27 g of ethylene glycol monobutyl ether, 0.01 g of CR12, which is a nickel chelate compound, and 0.75 g of nitric acid diluted to 10% by mass were mixed and stirred for 1 hour to obtain a coating solution.

[0182] The compositions of the coating solutions obtained above (however, the liquid medium and nitric acid are omitted) are shown in Tables 1 and 2. In the tables, the amounts of silane coupling agent, binder, and metal chelate are shown in parts by mass relative to 100 parts by mass of silica.

[0183] (Comparative Example 1) 4.00 g of IPA-ST-UP (Nissan Chemical Industries, Ltd., 15 wt% isopropyl alcohol), a silica sol dispersed in isopropyl alcohol, 6.98 g of water, 3.27 g of isopropyl alcohol, and 0.75 g of nitric acid diluted to 10% by mass were mixed and stirred for 1 hour to obtain a coating solution.

[0184] (Comparative Example 2) A coating liquid was obtained in the same manner as in Comparative Example 1, except that 4.00 g of IPA-ST (manufactured by Nissan Chemical Co., Ltd., 30 wt %-isopropyl alcohol), which is a silica sol dispersed in isopropyl alcohol, was added instead of IPA-ST-UP.

[0185] (Comparative Example 3) 1.5 g of 1WX-049 (a quaternary ammonium salt type hydrophilic polymer manufactured by Taisei Fine Chemical Co., Ltd.) and 13.5 g of ethylene glycol monobutyl ether were mixed and stirred for 1 hour to obtain a coating liquid.

[0186] Comparative Example 4 1.5 g of KBE-9103P, a silane coupling agent having an amino group, 12.8 g of isopropyl alcohol, and 0.75 g of nitric acid diluted to 10% by mass were mixed and stirred for 1 hour to obtain a coating liquid.

[0187] (Comparative Example 5) A coating liquid was obtained in the same manner as in Comparative Example 4, except that KBE-403, a silane coupling agent having an epoxy group, was used instead of KBE-9103P.

[0188] (Comparative Example 6) A coating liquid was obtained in the same manner as in Comparative Example 4, except that KBM-5103, a silane coupling agent having an acryloyl group, was used instead of KBE-9103P.

[0189] [Table 1]

[0190] [Table 2]

[0191] [Table 3]

[0192] [Anti-fogging treatment for polycarbonate substrate] A 10 cm square x 2 mm thick polycarbonate substrate (visible light transmittance: 90%, haze: 0.1, YI: 0.2) was washed with isopropyl alcohol. Using an applicator, the coating solution obtained in each Preparation Example and Comparative Preparation Example was applied to the substrate so that the thickness after drying would be 1 μm, and the substrate was heated at 110°C for 30 minutes to obtain a polycarbonate substrate with an anti-fogging film having a thickness of 1 μm as a sample. Note that the thickness of the coating solutions in Comparative Preparation Examples 3 to 6 was adjusted by repeatedly applying and drying.

[0193] <Evaluation> The samples obtained above were evaluated as follows.

[0194] (Anti-fog index) Using the device shown in Figure 2, images for evaluating anti-fogging properties and reference images were obtained under the following photographing conditions. The anti-fogging index AFI was calculated using the obtained evaluation images and reference images according to the calculation method shown below.

[0195] [Imaging conditions] Sample image: Checkerboard pattern of black and white squares, square side length 0.5mm Water temperature: 40℃ Distance D1: 1.5cm Depth D2: 1cm Distance D3: 17cm (distance from the sample image to the center surface of the front lens) Digital camera: Canon PowerShot SX70 HS (focal length in 35mm film equivalent: 15mm, saved image size: 1824 x 1824 pixels, saved format: jpg), captured so that the 1824 x 1824 pixel image contained 4900 squares. Anti-fogging evaluation image: Taken 10 seconds after placing the sample. Reference images: A polycarbonate substrate not treated with anti-fog agent was taken immediately after placement (0 seconds after placement) (Image O) and 10 seconds later (Image N). Compression method: Compressed at 20% compression rate, resized to 820 x 820 pixels and output

[0196] [Calculation of anti-fogging index AFI] The anti-fogging index AFI was calculated using the following formula from the file size S1 when the image for evaluating anti-fogging properties was compressed using the above compression method, the file size S2 when image N was compressed using the above compression method, and the file size S0 when image O was compressed using the above compression method. AFI = (S1-S2) x 10 / (S0-S2)

[0197] (Water film uniformity index) Using the device shown in Figure 2, evaluation images and reference images were obtained under the following photographing conditions. The obtained evaluation images and reference images were subjected to the image processing described below to calculate the water film uniformity index.

[0198] [Imaging conditions] Sample image: Checkerboard pattern of black and white squares, square side length 0.5mm Water temperature: 40℃ Distance D1: 1.5cm Depth D2: 1cm Distance D3: 17cm (distance from the sample image to the center surface of the front lens) Digital camera: Canon PowerShot SX70 HS (focal length in 35mm film equivalent: 15mm, saved image size: 1824 x 1824 pixels, saved format: jpg), captured so that the 1824 x 1824 pixel image contained 4900 squares. Evaluation image: Taken 40 seconds after placing the sample. Reference image: Photographed immediately after placing a polycarbonate substrate not treated with anti-fogging agent (0 seconds after placement).

[0199] [Image Processing] (1) Using image processing software (ImageJ), read the evaluation image and the reference image and convert them to 8 bits (Image → type → 8 bit). (2) Set the boundary threshold to "90~255" (Image→Adjust→Threshold→Set to "90~255"→apply). (3) Binarize (Process → Binary → Make Binary). (4) Set “Area” as the measurement condition (check Analyze → Set Measurements → Area). (5) Use particle analysis to calculate the area of ​​1 pixel or more squared (Analyze → Analyze Particles → Set "Size" to "1-Infinity", "Show" to "Outlines", check "Display results" and "Clear Results", and click OK). (6) From the information of the reference image (5), a frequency distribution is created in 20 pixel increments in the range of 0 to 1000 pixels as an area distribution, and the area range RA where the frequency is 5% or more of the total frequency is obtained. (7) From the information in (5) of the evaluation image, a frequency distribution is created in 20-pixel increments in the range of 0 to 1000 pixels as an area distribution, and the ratio (%) of the number of particles (frequency) included in the area range in (6) to the total number of particles (total frequency) is calculated, and this is taken as the water film uniformity index WE.

[0200] Furthermore, the following evaluations were carried out.

[0201] (Water contact angle measurement) The water contact angle of the anti-fogging film was measured. A DropMaster DM-50 (Kyowa Interface Science Co., Ltd.) was used for the measurement. The volume of water dropped was 1 μL. The number of drops was set to 3.

[0202] (Water film uniformity) In the same manner as when capturing the evaluation image for the water film uniformity index, a sample with a water film formed thereon was prepared, and a transmission test using the laser pointer described below was carried out. The shape of the image projected onto the wall was visually confirmed, and the water film uniformity was evaluated according to the evaluation criteria described below. [Permeation test] Laser Pointer: Sakura Cray-Pas Rabbit Laser Pointer RX-5N Shape of the emitted light: Linear Distance between laser pointer and sample: 2cm Distance from sample to wall: 13cm Projected line length: approx. 7cm [Evaluation criteria] Uniform: The shape of the projected line does not change even when the laser pointer is moved. Uneven: The shape of the projected line is distorted depending on the position of the laser pointer. FIG. 7 shows the shape of an image projected onto a wall, where (A) is an example of a uniform image and (B) is an example of a non-uniform image.

[0203] (water resistance) The sample was immersed in pure water, placed in a thermostatic chamber heated to 40°C, and heated for 120 hours. After heating, the following steam test was performed, and the presence or absence of clouding was visually observed. [Steam test] The anti-fogging film of the sample was exposed to steam from a water bath set at 40°C for 10 seconds. The height of the sample (anti-fogging film) was 1.5 cm above the water surface. The presence or absence of fogging was visually observed.

[0204] (moisture resistance) The sample was placed in a thermostatic chamber heated to 50°C and heated for 120 hours at a humidity of 95%. After heating, the sample was subjected to the steam test in the same manner as above, and the presence or absence of clouding was visually confirmed. The humidity was also monitored with a hygrometer during heating.

[0205] [Table 4] [Explanation of symbols]

[0206] 1...substrate, 2...anti-fogging agent, 3...spray, 5...anti-fogging film, 10...sample, 20...water, 30...sample image, 40...digital camera, 101...lens, 102...anti-fogging film, 103...lamp housing, 104...light source, 105...reflector, S...lamp chamber.

Claims

1. An anti-fogging agent, wherein when a water film is formed on a main surface of a substrate treated with the anti-fogging agent, the water film uniformity index WE, as expressed by the following formula (a), is 65% or more: WE=(S / TS)×100...(a) [In formula (a), TS represents the total frequency of the area of ​​black regions generated from an evaluation image of 1824 x 1824 pixels obtained by capturing an image of an object having a checkerboard pattern composed of black and white squares with sides of 0.5 mm through the substrate on which a water film is formed, and the total frequency of the area in an area distribution showing the frequency of the black regions; S represents the total frequency of the area included in a predetermined area range in the area distribution, and the predetermined area range represents an area range whose frequency is 5% or more of the total frequency in an area distribution showing the area of ​​black regions generated from a reference image of 1824 x 1824 pixels obtained by capturing an image of the object through the substrate, the distance between the object and the substrate being 2.5 cm; and the position of the digital camera capturing the object is set so that 4900 black and white squares are included in the 1824 x 1824 pixel image.]

2. 2. The antifogging agent according to claim 1, wherein the antifogging index AFI, as represented by the following formula (b), is 7 or more when water vapor is brought into contact with the main surface of a substrate treated with the antifogging agent: AFI=(S1-S2)×10 / (S0-S2)...(b) [In formula (b), S1 represents the file size obtained by compressing an anti-fogging property evaluation image of the subject through the substrate in contact with water vapor using a predetermined compression method; S2 represents the file size obtained by compressing an image N of the subject through an untreated substrate in contact with water vapor using the predetermined compression method; and S0 represents the file size obtained by compressing an image O of the subject through an untreated substrate using the predetermined compression method, wherein the anti-fogging property evaluation image, image N, and image O each have a size of 1824 x 1824 pixels, the distance between the subject and the substrate is 2.5 cm, the position of the digital camera photographing the subject is set so that 4900 black squares and white squares are included in the 1824 x 1824 pixel image, and the predetermined compression method refers to compressing at a compression rate of 20% and resizing to 820 x 820 pixels.]

3. The antifogging agent according to claim 1 or 2, comprising colloidal silica, at least one selected from the group consisting of a crosslinking agent, a binder, and a metal chelate, and a liquid medium.

4. A method for preventing fogging of a vehicle lamp structure, comprising treating an inner surface of a lens provided in the vehicle lamp structure with the antifogging agent according to any one of claims 1 to 3.

Images