JPH1159333A - Transparent substrate with function to detect droplet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the sensitivity of an optical sensor for detecting water droplets. SOLUTION: A sensor device 2 has diffraction gratings 5, 6 formed on the surface of a glass substrate 4 by laser beams. The diffraction grating 5 is for causing detection light rays from a light emission element 7 such as a light emitting diode to impinge on the inside of a windshield 1, while the diffraction grating 6 is for causing the light rays totally reflected by the inside of the windshield 1 to exit from the windshield 1 and impinge on a photo-detector 8. The outdoor surface of the windshield 1 is made water-repellent, and the area of the outdoor surface of the windshield 1 where the sensor 2 detects whether or not water droplets exist is not made water-repellent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent substrate such as a glass plate or a resin plate having a function of detecting the presence or absence of a liquid such as a raindrop, the number and amount of a droplet per unit area with high accuracy.

[0002]

2. Description of the Related Art Conventionally, attempts have been made to automatically operate a wiper by detecting that raindrops have adhered to a windshield of an automobile. The detection method is roughly divided into two types. There are a method of detecting by a change and a change of electric capacity, and a method of detecting optically by using a change of a reflected light amount.

A method of detecting a change in electric resistance between electrodes, a change in electric capacity, and the like is inferior to an optical type in terms of durability and sensitivity. Particularly, in a windshield for an automobile, a driver or a driver is required. It is important that the signal follows the visibility of the passenger, and an optical sensor is desirable.

[0004] As an example of an optical detection system, Japanese Patent Laid-Open No.
-70554, JP-A-2-70555, JP-T-8-505101 and European Patent No. 56
There are those disclosed in Japanese Patent No. 2275, all of which detect the attachment of a droplet by a change in the amount of reflected or transmitted light.

[0005]

FIG. 1 (a) and FIG. 1 (b)
Indicates a state in which water droplets adhere to the glass surface, and (a)
(B) shows the case where the contact angle (θ) is 40 °, and (b) shows the case where the contact angle (θ) is 110 °.

When the volume (V) of the water droplet adhering to the glass surface is calculated based on FIG. 1, V = 1 / 3πh ² (3r−h) (1) h = (r−rcos θ) (2) From the equations (1) and (2), V = 1 / 3π (r−rcosθ) ² (3r−r + rcosθ) = 1 / 3πr ³ (1−cosθ) ² (2 + cosθ) (3) θ = 40 ° in equation (3) (glass not subjected to water-repellent treatment)
And θ = 110 ° (glass that has been subjected to a water-repellent treatment), and the radius (x) of a water droplet on the glass surface when V = 1 is obtained. When θ = 40 °, x = 1.15. When θ = 110 °, x = 0.63. The above calculation formula is described in "Surface" vol. 17 No. 12 (1979).
The book “The fogging of glass and how to prevent it” is written by Yoshito Raft.

As is apparent from the above, the detection sensitivity is greatly affected by the state of the glass surface even when the volume of the attached water droplets is the same. For example, x = 1.15 when θ = 40 ° and x = 0.63 when θ = 110 °,
The area ratio is (1.15) ² /(0.63) ² = 3.33, and the sensitivity is more than three times higher without water-repellent treatment than without water-repellent treatment.

However, windshields of automobiles and the like are generally formed with a coating of silicone resin or fluorine resin on the entire surface thereof to exhibit water repellency. Sensitivity drops for the reasons described above.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to optically detect that a droplet has adhered to one surface of a transparent substrate by a sensor device provided on the other surface of the transparent substrate. In the transparent substrate provided with the droplet detecting function described above, a water-repellent treatment is performed on one surface side of the transparent substrate, and the liquid-repellent treatment is not performed on the droplet detection region on the one surface side. In order to increase the droplet detection sensitivity,
It is possible to apply a hydrophilic treatment to the droplet detection area.

Further, the sensor device includes an optical element for causing a light beam for detection to enter the transparent substrate, and an optical element for emitting, from the transparent substrate, a light beam totally reflected in the transparent substrate among the light beams for detection. Can be considered. As the optical element, a prism or a diffraction grating can be considered. In particular, a diffraction grating is excellent in application to a curved glass plate or the like, and as a manufacturing method, it can be formed by, for example, an ablation phenomenon generated by irradiating the surface of a glass substrate with laser light. .

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 2 is a perspective view of a front portion of an automobile to which the transparent substrate according to the present invention is applied, and FIG. 3 is an enlarged sectional view of a portion where a sensor device is attached. 2 is attached with an adhesive (adhesive tape) 3. An adhesive (adhesive tape) 3 having a refractive index substantially equal to the refractive index (1.48) of the windshield 1 was selected. Note that a soda-lime glass substrate having a thickness of 5 mm and containing SiO ₂ as a main component was used as a front glass.

The sensor device 2 has diffraction gratings 5 and 6 formed on the surface of a glass substrate 4 by laser light. Here, the diffraction grating 5 is for allowing a light beam for detection from a light emitting element 7 such as a light emitting diode to enter the windshield 1, and the diffraction grating 6 is for transmitting a light beam totally reflected inside the windshield 1 to the windshield 1. The light is emitted from the light receiving element 1 and made incident on the light receiving element 8.

The exterior surface of the windshield 1 is water-repellent. However, windshield 1
No water-repellent treatment is applied to a region of the outdoor surface of the sensor where the presence or absence of water droplets is detected by the sensor device 2. Here, the fact that the water-repellent coating is not applied means that the water-repellent coating once formed is peeled off, the structure in which the water-repellent coating is not formed from the beginning by using a mask or the like, and the hydrophilic treatment is applied on the water-repellent coating. And the like.

The adhesive 3 is not applied to the entire surface but is applied with a space between the sensor device 2 and the windshield 1 so that a closed space is provided between the sensor device 2 and the windshield 1 so that even if dew condensation occurs on the indoor side surface, the dew condensation can be prevented. I do not detect it.

As shown in FIG. 4, the diffraction grating generates first-order diffracted light at a fixed angle with respect to incident light. Although high-order diffracted light is also generated, first-order diffracted light is mainly used because the amount of light is small.

When incident light is transmitted, the relationship between the angle of the incident light and the angle of the diffracted light is expressed by the following equation (1). That is, the angle of the incident light is θ ₀ , the angle of the m-th order diffracted light is θ, the wavelength of the incident light is λ, the pitch of the groove is d, the refractive index on the output side is n, and the refractive index of the medium on the incident side is If n ₀ , the angle can be determined as follows. n · sin θ−n ₀ · sin θ ₀ = mλ / d (m = 0, ± 1, ± 2,...) (1)

When the entrance side is air and the exit side is a transparent plate, n
₀ = 1.0, and the angle of light traveling through the transparent plate can be adjusted by changing the angle of light incident on the diffraction grating.

As described above, light can be introduced into the transparent plate at an arbitrary angle by using the diffraction grating. Also, by appropriately selecting the angle of incidence on the diffraction grating, it is possible to set so that the introduced light is totally reflected in the transparent plate. It is also possible to emit light totally reflected in the transparent plate to the air from the transparent plate based on the same principle. When the water droplet W adheres to the outer surface of the windshield 1, the total amount of reflected light incident on the light receiving element 8 changes, and the adhesion of the water droplet W is detected based on this change.

As a general method of manufacturing a diffraction grating, a metal such as soft aluminum is precisely cut into grooves with a diamond needle, and this is transferred as a master to an epoxy resin or the like applied to the surface of a transparent plate such as glass. Gain by doing. Alternatively, a photo-sensitive resin applied to the surface of a transparent plate such as glass is exposed by two-beam interference, and only the exposed portion is etched, or only the unexposed portion is etched to realize a fine groove shape. ing.

The diffraction grating according to the above-described manufacturing method can be applied to the present invention. However, the diffraction grating transferred to an epoxy resin or the diffraction grating formed on a photosensitive resin has weather resistance and mechanical strength. However, using it for an application that requires a small amount of problems remains. Furthermore, when a large window glass or a windshield glass is used, it is difficult to apply the above-described transfer technology and exposure technology, and it is not practically appropriate.

Therefore, more preferably, a diffraction grating is formed directly on a transparent plate such as glass by a laser processing method using an ablation phenomenon in which a glass surface is partially evaporated by a laser beam.

The ablation phenomenon is a phenomenon that occurs when glass absorbs laser light energy, and Ag atoms, Ag colloids or Ag colloids extend from the surface of the glass substrate to a predetermined depth.
When silver is contained in the form of ions, and the silver concentration is the highest at the surface to be laser-processed, and a concentration gradient is provided so that the silver concentration gradually decreases to a predetermined depth, the surface layer portion Ablation phenomena occur sequentially from the inside toward the inside, so that cracking and chipping hardly occur during processing.

There are the following methods for introducing silver on the surface of the glass substrate. (1) A method in which a glass substrate containing monovalent alkali ions is immersed in a molten salt containing silver ions to perform ion exchange. (2) A method in which a mixture of silver-containing salts such as silver nitrate with talc or the like or a paste of silver powder is applied to the surface of a glass substrate and heated.

As the laser beam, a laser beam having the same periodicity as the target groove interval is used, and fine grooves are formed directly on the glass. As a method of obtaining a laser beam having a periodic intensity distribution, as shown in FIG. 5A, a mask is provided on the surface of a glass substrate, and the mask is irradiated with the laser beam through a lens, or FIG. 5
As shown in (b), a method of forming a periodic light intensity distribution in the overlapping portion by dividing the laser beam into two by a beam splitter and overlapping them at a certain angle can be applied. .

[0026]

According to the present invention as described above,
Since the water-repellent treatment is not performed or the water-repellent film is removed from the droplet detection area on the surface of the transparent substrate such as a window glass that has been subjected to the water-repellent treatment, the droplet and the transparent substrate surface are removed. And the detection area can be increased.

Further, if a diffraction grating is used as an optical element for allowing a light beam for detection to enter the transparent substrate or for emitting a light beam totally reflected in the transparent substrate from the transparent substrate, the thickness of the sensor itself can be reduced. In addition, the present invention can be easily applied to a curved transparent substrate such as an automobile windshield.

[Brief description of the drawings]

FIG. 1 (a) is an enlarged view of a water droplet attached to a glass plate at a contact angle (θ) of 40 °, and FIG. 1 (b) is a contact angle (θ) of 11
Enlarged view of water droplets attached to a glass plate at 0 °

FIG. 2 is a perspective view of a front portion of an automobile to which the transparent substrate according to the present invention is applied.

FIG. 3 is an enlarged sectional view of a portion where the sensor device is attached.

FIG. 4 is a diagram for explaining the function of a diffraction grating;

FIGS. 5A and 5B are diagrams showing an example of a method for manufacturing a diffraction grating.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Windshield of an automobile, 2 ... Sensor device, 3 ... Adhesive, 4 ... Glass substrate which comprises a sensor device, 5, 6 ...
Diffraction grating, 7: light emitting element, 8: light receiving element.

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[Procedure amendment]

[Submission date] December 18, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

[0026]

According to the present invention as described above,
Since the water-repellent treatment is not performed or the water-repellent film is removed from the droplet detection area on the surface of the transparent substrate such as a window glass that has been subjected to the water-repellent treatment, the droplet and the transparent substrate surface are removed. And the detection area can be increased. In addition, the droplet detection area
Do not perform water treatment or remove water-repellent coating
So that it is not affected by the white cloudiness unique to water-repellent treated glass.
Droplets can be detected, and the sensitivity accompanying deterioration of water repellency
Never bring about a change.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hideki Imanishi 3-5-1, Doshumachi, Chuo-ku, Osaka-shi, Osaka Nippon Sheet Glass Co., Ltd.

Claims (5)

[Claims] 1. A transparent substrate having a droplet detection function wherein a sensor device provided on the other surface of the transparent substrate optically detects that a droplet has adhered to one surface of the transparent substrate. A transparent substrate having a droplet detection function, wherein a water-repellent treatment is performed on one surface side of the transparent substrate, and a water-repellent treatment is not performed on a droplet detection region on the one surface side. 2. The transparent substrate having a droplet detecting function according to claim 1, wherein a hydrophilic treatment is applied to a droplet detecting area on one surface side of the transparent substrate. A transparent substrate with functions. 3. A transparent substrate provided with a droplet detecting function according to claim 1 or 2, wherein said sensor device comprises: an optical element for causing a light beam for detection to enter the transparent substrate; A transparent substrate having a droplet detecting function, comprising: an optical element for emitting a light beam totally reflected in the transparent substrate from the transparent substrate. 4. The transparent substrate having a droplet detection function according to claim 3, wherein the optical element is a diffraction grating. 5. The transparent substrate according to claim 4, wherein the diffraction grating is formed by an ablation phenomenon generated by irradiating the surface of the glass substrate with laser light. A transparent substrate with a drop detection function.