Patent Application
20240280733
The present invention relates to an antifog-film-attached glass article for security cameras, a security camera, and a method for manufacturing an antifog-film-attached glass article for security cameras.
Transparent bases typically made of glass may have antifog films formed thereon in order to impart antifog properties. For example, Patent Literature 1 discloses an antifog film containing a polyvinyl acetal resin, which is a water-absorbing resin, and a silica component such as colloidal silica.
Patent Literature 1: JP 2012-117025 A
According to studies by the present inventors, however, conventional antifog films are not suitable for maintaining the imaging function of security cameras for which the demand has been increasing. In view of this, the present invention aims to provide an antifog-film-attached glass article suitable for use in security cameras.
In the present description, the mention of QR code being a registered trademark is hereinafter omitted.
The present invention provides an antifog-film-attached glass article for security cameras, the antifog-film-attached glass article including:
In another aspect, the present invention provides an antifog-film-attached glass article for security cameras, the antifog-film-attached glass article including:
In still another aspect, the present invention provides a security camera including:
In yet another aspect, the present invention provides a method for manufacturing an antifog-film-attached glass article for security cameras, the antifog-film-attached glass article including a glass base and an antifog film on the glass base, the method including:
The present invention provides an antifog-film-attached glass article suitable for maintaining the imaging function of security cameras.
An embodiment of the present invention will be described below with reference to the drawings as appropriate. The present invention is not limited to the following embodiment. In the present description, a “main component” refers to a component contained in the highest content among the components contained. Furthermore, “principal surfaces” of a plate-shaped article refer to two surfaces facing away from each other at a predetermined distance, called the thickness.
As disclosed in Patent Literature 1, antifog films often have added thereto, together with a water-absorbing polymer, an inorganic component that compensates for a decrease in abrasion resistance, typically a silica component such as colloidal silica. Antifog-film-attached glass articles that achieve a high abrasion resistance as well as antifog properties are suitable for use as window panes for automobiles. In contrast, glass articles for use together with security cameras are not required to have a high-level abrasion resistance. It is appropriate to proceed with development of antifog-film-attached glass articles for security cameras from a perspective different from that of antifog-film-attached glass articles for automobiles.
The greatest emphasis for antifog-film-attached glass articles for security cameras that should be placed on is that even a long-time exposure of antifog films to a harsh environment does not impair the imaging function of security cameras. An antifog-film-attached glass article according to the present embodiment has been achieved through further studies made from such a perspective, and can exhibit a function of transmitting light without scattering at a high level even when the antifog film is exposed to a harsh environment.
The shape and material of the glass base 10 are not particularly limited. The glass base 10 is, for example, a glass sheet.
The glass composition of the glass sheet is not particularly limited, and may be soda-lime glass, aluminosilicate glass, borosilicate glass, alkali-free glass, or even multicomponent glass called C-glass, E-glass, etc. The multicomponent glass contains SiO2 as the main component, and further contains a component other than SiO2, for example, at least one oxide selected from the group consisting of B2O3, Al2O3, MgO, CaO, Li2O, Na2O, and K2O. The glass sheet, however, may be made of silica glass.
The glass sheet may be float glass. Float glass is shaped by a so-called float process. Since float glass is shaped in a float bath with one principal surface in contact with molten tin, the tin becomes diffused over the one principal surface. Accordingly, one principal surface, called a bottom surface, of float glass has a surface layer formed of tin diffused thereon, whereas the other principal surface, called a top surface, does not have such a surface layer. From another perspective, the tin concentration in float glass is higher on one principal surface than on the other principal surface. The glass sheet, however, may be shaped by a manufacturing process other than the float process, for example, the overflow downdraw process.
In the case where float glass is used as the glass base, the antifog film is desirably formed on the bottom surface of the float glass. Accordingly, in the case where the glass base 10 in
The thickness of the glass sheet is, for example, 0.5 to 7.0 mm, and may be 0.5 to 5.0 mm. In the case where impact resistance should be emphasized, the glass sheet that is non-strengthened glass has a thickness of preferably 3.5 mm or more. Note that the glass sheet that is strengthened glass having a thickness of 1.8 mm or more can have a sufficient impact resistance. The strengthened glass may be either thermally strengthened glass or chemically strengthened glass.
As shown in
A glass base 20 shown in
On the principal surface of the glass base, an underlying film may be formed. In this case, the underlying film is interposed between the surface of the glass base and the antifog film. The underlying film is not particularly limited, and may be, for example, a barrier film preventing elution of an alkali metal from the glass. The barrier film is, for example, a silica film.
In the case where the antifog film is formed only on one principal surface of the glass base, a film other than the antifog film may be formed on the other principal surface. Examples of such a film include an antireflection film, a water-repellent film, a hydrophilic film, and a colored film.
The film thickness of each of the antifog films 11 and 21 is not limited to a specific value, and is 1.0 to 1000 nm, preferably 10 to 500 nm, and particularly preferably 30 to 150 nm.
The antifog films 11 and 21 each include, for example, an organic polymer having a betaine structure. The betaine structure is a structure in which a positive charge and a negative charge are not in adjacent positions in the same molecule and no dissociable hydrogen atom is directly bonded to a positively charged atom. Examples of the positively charged atom include a nitrogen atom, a sulfur atom, and a phosphorus atom. Examples of the negatively charged atom include an oxygen atom. The betaine structure may be a polymer of a betaine monomer which will be described later. The molecular weight of the organic polymer is not particularly limited, and may be 100,000 or more in terms of weight-average molecular weight.
The organic polymer may have a main chain and a side chain containing a betaine structure. The main chain may include a linear carbon chain, and is, for example, a linear alkyl group. The organic polymer may have a structure in which a plurality of side chains are bonded to one main chain. The organic polymer may further include a silicon atom bonded to one terminal of the main chain. The organic polymer may be bonded to the surface of the glass base via the silicon atom. This bond can be formed by a reaction between a hydroxy group on the surface of the glass base and a silanol group. The main chain chemically bonded to the surface of the glass base via the silicon atom can grow upward from the surface of the glass base to form a so-called polymer brush. This polymer brush may be exposed on the surface of the antifog film. The antifog film can be a monomolecular film formed of an organic polymer in which the side chain contains a betaine structure. The organic polymer may be supplied onto the surface of the glass base, for example, as a compound represented by the following Formula (I).
R in Formula (I) is an organic group containing a betaine structure. R may contain a polymer of a betaine monomer. Examples of the betaine monomer include sulfoxybetaine monomer, carboxybetaine monomer, and phosphorylbetaine monomer. These betaine monomers may be used alone or two or more thereof may be used in combination. R may contain the main chain and side chain containing a betaine structure described above.
X in Formula (I) is a hydroxy group, or a hydrolyzable group or a halogen atom. Examples of the hydrolyzable group include at least one selected from the group consisting of an alkoxyl group, an acetoxy group, an alkenyloxy group, and an amino group. Examples of the alkoxyl group include a C1-C4 alkoxyl group, and specifically a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. The hydrolyzable group is preferably an alkoxyl group, and more preferably a C1-C4 alkoxyl group. The halogen atom is, for example, chlorine.
The sulfoxybetaine monomer is represented by, for example, the following Formula (II).
In Formula (II), R1 is a (meth)acryloylaminoalkyl group having a C1-C4 alkyl group or a (meth)acryloyloxyalkyl group having a C1-C4 alkyl group. R2 and R3 are each independently a hydrogen atom, a C1-C4 alkyl group, a C1-C4 hydroxyalkyl group, or a (meth)acryloyloxyalkyl group having a C1-C4 alkyl group. R4 is a C1-C4 alkylene group or a C1-C4 oxyalkylene group.
The carboxybetaine monomer is represented by, for example, the following Formula (III).
In Formula (III), R8 and R9 are each independently a hydrogen atom or a C1-C4 alkyl group. R10 is a (meth)acryloyloxyalkyl group having a C1-C4 alkyl group. R11 is a C1-C4 alkylene group.
The phosphorylbetaine monomer is represented by, for example, the following Formula (IV).
In Formula (IV), R12 is a (meth)acryloyloxyalkyl group having a C1-C4 alkyl group. R13 is a C1-C4 alkylene group. R14, R15, and R16 are each independently a hydrogen atom or a C1-C4 alkyl group.
The betaine monomer may have a structure represented by the following Formula (V).
In Formula (V), R20 may be a (meth)acryloyloxyalkyl group having a C11 alkyl group.
The above organic polymer, which has a main chain and a plurality of side chains and in which a silicon atom is bonded to a terminal of the main chain and the side chains contain a betaine structure, can be, for example, LAMBIC 771W manufactured by OSAKA ORGANIC CHEMICAL INDUSTRY LTD.
The organic polymer having a betaine structure may be the main component of the antifog film.
The antifog film may contain an ultraviolet absorber, an infrared absorber, a leveling agent (surface conditioner), a light stabilizer, and the like as appropriate in addition to the above components. These components, however, are added in desirably 5 mass % or less, more desirably 3 mass % or less, and particularly desirably 1 mass % or less, relative to the antifog film. The antifog film is not required to have a high abrasion resistance, and accordingly may or may not contain colloidal silica or other silica fine particles. The content of the silica fine particles in the antifog film may be, for example, 10 to 60 mass %, and may be limited to less than 5 mass %, even less than 3 mass %, or particularly less than 1 mass %. The content of oxide fine particles including silica fine particles may also be about the same as described above for the silica fine particles. The antifog film may or may not contain oxide fine particles typified by silica fine particles.
The antifog film according to the present embodiment can exhibit a function of transmitting transmission light without scattering at a high level, even after a long-time exposure to a harsh environment for antifog films, for example, contact with water. To exhibit this function, the antifog film desirably has, in addition to transparency, water resistance and even hydrophilicity. An antifog film having an insufficient water resistance may cause elution of its components when exposed to moisture for a long time. Furthermore, in the case where an antifog film has hydrophilicity to such an extent that water is retained as a continuous film on the surface of the antifog film, transmission light can be transmitted without excessive scattering.
The antifog-film-attached glass article according to the present embodiment can transmit transmission light without excessive scattering. Specifically, the antifog-film-attached glass article can have a haze ratio of, for example, 5% or less, even 3% or less, particularly 1% or less, and in some cases, 0.4% or less. The haze ratio is specified in JIS K 7136: 2018.
The antifog-film-attached glass article according to the present embodiment can have both water resistance and hydrophilicity. These properties can be evaluated by a method called a high-temperature water vapor evaluation which will be described in detail in the Examples section. This method supplies high-temperature and excessive water vapor to the antifog film with the antifog film turned vertically downward. When the antifog film is brought into contact with this water vapor, a transparent continuous film of water is formed on a portion directly exposed to the water vapor on the surface of the antifog film that is excellent in hydrophilicity and water resistance. Being a “transparent continuous film” can be determined by visually confirming that the continuity as a film, not a water drops, is ensured and that the film has not become fogged. Fogging of a film can be caused by whitening of the film due to an insufficient water resistance or by dew condensation on the film surface due to insufficient antifog properties. On the surface of a film having an insufficient hydrophilicity, water is not retained as a continuous film but is dispersed and adhered as water drops. On a film having an insufficient water resistance, whitening of the film due to contact with high-temperature water vapor is observed, and elution of the components of the film, a defect of the film, or the like may occur. The hydrophilicity of the surface is evaluated typically by the contact angle of water. However, this evaluation method only drops an extremely small amount of water drops onto the film, and accordingly does not adequately reproduce a harsh environment. Additionally, the transparent continuous film may coat 80% or more or even 90% or more of the surface of the antifog film exposed to water vapor.
For a more detailed or more phased film evaluation, an information reading evaluation using a QR code can be performed. The details of this evaluation method will be described later in the Examples section as well. In this evaluation method, the antifog-film-attached glass article according to the present embodiment even after immersion in water at room temperature for 100 hours can exhibit a good hydrophilicity to such an extent that it is possible to read preferably a QR code “A” of a 30 mm square size, more preferably a QR code “S” of a 20 mm square size, still more preferably a QR code “SS” of a 15 mm square size, and particularly preferably a QR code “SSS” of a 10 mm square size.
A method for manufacturing the antifog-film-attached glass article according to the present embodiment will be described below.
The surface of a glass base on which an antifog film is to be formed is preferably cleaned prior to antifog film formation. Examples of the cleaning method include alkaline cleaning and plasma cleaning. Alkaline cleaning is cleaning using an alkaline cleaning liquid. The alkaline cleaning liquid is, for example, an aqueous solution containing a water-soluble alkali metal salt. The cleaning liquid, for example, may contain a surfactant or other components. Plasma cleaning is cleaning by plasma exposure. The plasma cleaning may be cleaning using plasma in a reduced pressure atmosphere or cleaning using atmospheric-pressure plasma (AP plasma cleaning). Alkaline cleaning and plasma cleaning may be performed alone, or both may be performed. In a preferred embodiment, alkaline cleaning and AP plasma cleaning are performed. In this case, the organic polymer can be more strongly bonded to the surface of the glass base.
In the case where the glass base is float glass, the following cleaning is preferably performed.
The antifog film can be formed by applying, onto the surface of the glass base, a coating liquid for forming the antifog film, and heating the glass base on which the coating film has been formed from the coating liquid. The solvent used for preparing the coating liquid and the application method for the coating liquid should be any conventionally known material and method. Examples of the application method include spin coating, roll coating, spray coating, dip coating, flow coating, screen printing, and brush coating. The coating film may be appropriately dried before the heating.
The heating temperature for the glass base on which the coating film has been formed is, for example, 90° C. or higher, preferably 100° C. or higher, and in some cases, 120° C. or higher. Furthermore, the heating temperature for the coating film is 190° C. or lower, preferably 180° C. or lower, and particularly preferably 160° C. or lower. The heating time is not particularly limited, and may be 5 to 60 minutes, 5 to 45 minutes, 10 to 45 minutes, or 15 to 30 minutes.
The present invention will be described below in more detail with reference to examples. First, a method for evaluating the properties of samples according to the examples and comparative examples will be described.
The antifog-film-attached glass article was immersed in a plastic container containing pure water at room temperature (about 25° C.) and held in this state for 24 hours or 100 hours. Subsequently, the antifog-film-attached glass article was removed and leaned against a holder for drying. The sample dried was subjected to the following appearance evaluation and high-temperature water vapor evaluation.
The state of the film surface was evaluated with the naked eye to determine which of the following is met.
As shown in
The QR codes used were of the five types shown in
The case where none of the QR codes had been readable was evaluated as “X”, and the case where the film had been eluted or peeled off due to contact with high-temperature water vapor was evaluated as “Y”.
The QR code “SSS” shown in
The camera used was smartphone “Xperia XZ2” manufactured by Sony Corporation (model name: SO-03K, OS: Android (registered trademark) (ver. 10)). For QR code reading, the QR code reading function of LINE (registered trademark) application (ver. 11.7.2) was used.
An amount of 20 mass % of LAMBIC 771W (manufactured by OSAKA ORGANIC CHEMICAL INDUSTRY LTD.) and 80 mass % of purified water were mixed to prepare a coating liquid.
The glass sheet used was float glass (size: 50 mm×50 mm, thickness: 1.1 mm) subjected in advance to alkaline cleaning. Onto the bottom surface of this float glass, the coating liquid was applied by spin coating (at 1500 rpm for 10 seconds) to form a coating film. Next, the float glass on which the coating film had been formed was heated in an oven under conditions of 100° C. and 15 minutes. Thus, an antifog-film-attached glass article was obtained. The cleaning liquid used for the alkaline cleaning was a 25% aqueous solution of potassium hydroxide (LBC-1 manufactured by LEYBOLD Co., Ltd.).
An antifog-film-attached glass article according to Example 2 was obtained in the same manner as in Example 1 except the following points. The float glass was subjected in advance to alkaline cleaning and then further subjected to atmospheric-pressure plasma cleaning (AP plasma cleaning). The AP plasma cleaning was performed with controller CSM-SSC1 (nozzle: CSM-BG, power: 1000 W, treatment time: 10 seconds) manufactured by CSM Instruments Inc.
Antifog-film-attached glass articles according to Examples 3 to 6 were obtained in the same manner as in Example 1 except that the heating conditions were changed to those described in Table 1.
In each of Examples 1 to 6, the film thickness of the antifog film was measured with an SEM. The antifog film according to each of Examples 1 to 6 had a film thickness of about 55 nm.
An antifog-film-attached glass article according to Example 7 was obtained in the same manner as in Example 1 except that the conditions for spin coating were changed to 300 rpm and 10 seconds. The antifog film according to Example 7 had a film thickness of about 395 nm.
An antifog-film-attached glass article according to Example 8 was obtained in the same manner as in Example 1 except that the coating liquid was applied by dropping onto the glass sheet instead of spin coating.
An antifog-film-attached glass article according to Example 8 was obtained in the same manner as in Example 2 except that the coating liquid was applied onto the top surface of the float glass.
Antifog-film-attached glass articles according to Comparative Examples 1 to 5 were obtained in the same manner as in Example 1 except that the cleaning of the float glass, the application method for the coating liquid, and the heating conditions for the float glass on which the coating film had been formed were changed as described in Table 2. Note that, in Comparative Examples 1 to 3, the heating of the coating film was omitted. Furthermore, in Comparative Example 3, the float glass was subjected to alkaline cleaning twice.
The results of the water immersion test are shown in Tables 1 and 2.
In Comparative Examples 1 to 3, according to the high-temperature water vapor evaluation performed prior to the water immersion test, fogging due to dew condensation was observed on the antifog film to such an extent that the QR code was not readable (evaluated as X). Accordingly, the water immersion test was omitted. Additionally, the antifog film according to Example 8, which had been formed by dropping, had a slightly large film thickness, about 330 nm.
The antifog-film-attached glass articles according to the examples were each evaluated as “SSS” in the high-temperature water vapor evaluation performed after the water immersion test (for 100 hours). In each of the antifog films of the glass articles according to the examples, at the stop time point of the supply of high-temperature water vapor, a continuous film of water having a uniform thickness was formed on the surface of the antifog film, and the transparency of the antifog-film-attached glass article was ensured while neither whitening of the film itself nor fogging due to dew condensation was observed. Additionally, the transparent continuous films of the examples evaluated as “SSS” each coated 90% or more of the surface of the antifog film exposed to water vapor, more specifically, coated substantially the entirety of the above surface. In contrast, in each of Comparative Examples 4 and 5, fogging due to dew condensation occurred on the film, and consequently even the QR code of the largest size was not readable.
Next, the following evaluations were performed on the examples and Comparative Examples 4 and 5. The results are shown in Tables 3 and 4.
The antifog-film-attached glass article in the initial state where the antifog film had been formed was subjected to an appearance evaluation in the same manner as described above, and furthermore subjected to a haze ratio measurement.
The antifog-film-attached glass article in the initial state where the antifog film had been formed was subjected to supply of high-temperature water vapor to the antifog film in the same manner as in the high-temperature water vapor evaluation. Subsequently, the antifog-film-attached glass article was removed and leaned against a holder for drying. The sample dried was again repeatedly subjected to supply of high-temperature water vapor to the antifog film and drying, where high-temperature water vapor was supplied to the antifog film 10 times. Subsequently, an appearance evaluation and a high-temperature water vapor evaluation were performed in the same manner as described above. Additionally, in the high-temperature water vapor evaluation, the QR code photographing was performed without performing the 11th water vapor supply (immediately after the completion of the 10th water vapor supply).
An amount of 0.5 cc of an alcohol solvent containing ethanol as the main component (“FineeterA-10” manufactured by FUTABA PURE CHEMICAL CO, LTD.) was dropped for impregnation onto a nonwoven fabric wiper (“BEMCOT M-3II” manufactured by Asahi Kasei Corporation) cut into a width of 25 mm, and then the wiper and the antifog-film-attached glass article were set in a reciprocating abrasion tester. With a load of 400 g applied to the wiper, reciprocation for a length of 30 mm was performed 20 times. Subsequently, an appearance evaluation and a high-temperature water vapor evaluation were performed in the same manner as described above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-098340 | Jun 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/023353 | 6/9/2022 | WO |
