JP2018087116A - Glass tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass tube for protecting an imaging device capable of obtaining a clear imaged image having less distortion, etc., by solving the problem that a streak-like projection extended in the direction of tube axis may appear since molten glass is wound around a molding, such as a sleeve and is extended and molded in a tube shape by a method for manufacturing a glass tube, so called the Danner method or the Bellow method, and a refraction state of light transmitting the glass tube may become uneven when the projection exists in the glass tube.SOLUTION: The glass tube for protecting an imaging device consists of a glass tube and does not have a projection defined below on the outer surface and the inner surface. The projection is an acute depression or projection in a shape obtained when measuring the outer and inner surfaces of the glass tube in the circumferential direction around the tube axis. The tip angle of the depression or projection is 90° or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a glass tube that protects an imaging apparatus.

  Surveillance cameras that can image the surroundings are used on streets and construction sites. These cameras are made of a transparent cylinder such as a glass tube for the purpose of protecting the surrounding environment (wind, rain, dust, etc.) or holding a reflecting mirror for imaging the surroundings with one camera. A camera is provided inside (Patent Document 1).

JP 2004-343297 A

The glass tube is manufactured by a method called the Danner method or Bellow method. In these glass tube manufacturing methods, melted glass is wound around a molded body such as a sleeve and stretched into a tube shape, so that a streak-like protrusion extending in the tube axis direction may appear. If there is a protrusion on the glass tube, the refractive state of the light transmitted through the glass tube may be non-uniform.
Therefore, when a camera is installed inside a glass tube and a captured image is obtained via the glass tube, streaky protrusions on the glass tube may affect the captured image.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a glass tube that protects an imaging apparatus that has little influence on a captured image.

  The glass tube for protection of the imaging device of the present invention is made of a glass tube, and is characterized in that there are no protrusions defined below on the outer surface and the inner surface. Here, the protrusion refers to an acute-angle concave portion or convex portion in a shape obtained when the outer surface and inner surface of the glass tube are measured in the circumferential direction around the tube axis.

  Since the protective glass tube of the imaging device of the present invention has no projections that affect the captured image, a clear captured image can be obtained.

It is a figure which shows the result of having measured the glass tube provided with a protrusion with a roundness measuring device. It is a figure which shows the result of having measured the glass tube which does not have a processus | protrusion with the roundness measuring apparatus. It is a figure which shows the imaging device (camera) using the glass tube for protection of the imaging device of this invention. 2 is a captured image obtained through the protective glass tube of Example 1. FIG. 6 is a captured image obtained through the protective glass tube of Example 2.

  Hereinafter, an embodiment of a protective glass tube (hereinafter referred to as a glass tube of the present invention) of an imaging apparatus according to the present invention will be described.

  The glass tube of the present invention is characterized in that there are no protrusions on the outer and inner surfaces as defined below. A protrusion means the acute-angle recessed part or convex part in the shape obtained when measuring the outer surface and inner surface of a glass tube in the circumferential direction centering on a tube axis.

  Since glass tubes are made by a method called the Danner method or bellows method, in which molten glass raw material is supplied to the molded body and the glass is pulled while forming the tube axis method, rarely streaky protrusions are formed on the surface of the glass tube. May occur. The streak-like protrusion appears in a direction substantially parallel to the tube axis, and is considered to be caused by a foreign body adhering to the molded body or the outer surface used when the above-described glass tube is molded.

The streak-like protrusions make the thickness of the glass tube uneven. Therefore, the light transmitted through the glass tube may be locally distorted due to the lens effect resulting from the uneven thickness of the glass tube. In particular, there is a greater concern about distortion of transmitted light as the degree of protrusion is locally acute. The glass tube of the present invention does not have such sharp projections, and the surface (outer surface or inner surface) of the glass tube has a surface shape close to a perfect circle or a smooth surface. Therefore, it is possible to obtain a captured image that is not distorted.
In addition, the shape of the above-mentioned glass tube can be measured using a roundness measuring apparatus. The roundness is measured using, for example, a roundness measuring instrument RONDCOM 31C manufactured by Tokyo Seimitsu Co., Ltd.

The protrusions of the glass tube have a sharp concave or convex tip angle of 90 ° or less in a shape obtained when the outer surface and inner surface of the glass tube are measured in the circumferential direction around the tube axis.
The streak-like protrusion appears locally when the shape is measured in the circumferential direction, and the tip of the protrusion (true) is either a concave shape or a convex shape in the thickness direction of the glass tube. The point farthest or closest to the center of the circularity measurement is an acute angle.
Therefore, the sharp tip (one point) is determined from the result obtained by the shape measurement. Next, only the deformed part is taken out from the result obtained by the shape measurement, and two approximate curves passing through the tip part are drawn. Then, the angle formed by the two approximate curves is defined as the tip angle of the acute concave portion or convex portion.
When the tip angle of the acute concave portion or convex portion exceeds 90 °, the distortion of light transmitted through the glass tube is small, so that the glass tube of the present invention has no tip having a tip angle of 90 ° or less on the outer surface and the inner surface. This is an essential configuration.

  The protrusion of the glass tube is illustrated in FIG. The illustrated glass tube is made of soda lime glass and has a tubular shape with an outer diameter of 32 mm and a wall thickness of 0.8 mm. FIG. 1 shows the shape of the glass tube in a direction perpendicular to the tube axis measured by a roundness measuring device RONDCOM 31C manufactured by Tokyo Seimitsu Co., Ltd. Of the two measurement lines, the outer shape is the outer surface and the inner surface is the inner surface. Show shape. In FIG. 1, a portion surrounded by a one-dot chain line is a protrusion of the present invention. This protrusion is a deformation existing on the inner surface of the glass tube and has a tip angle of about 60 °. FIG. 2 shows the result of measuring the shape of a glass tube having the same glass composition and dimensions as in FIG. 1 by the same method. The glass tube of FIG. 2 has no protrusions although the shape of the inner and outer surfaces of the glass tube is recognized to be flat. For this reason, when the light transmitted through the glass tube is imaged, there is no possibility that a problem such as distortion of the captured image occurs.

The glass tube can use a glass composition according to desired properties such as soda lime glass, aluminosilicate glass, borosilicate glass, and the like. The glass tube, for example, puts a glass raw material prepared so as to have a desired glass composition into a melting furnace, heats and melts the glass raw material at 1000 to 1600 ° C., and clarifies the molten glass. Thereafter, the molten glass is formed into a tubular shape using a forming apparatus, cut into a predetermined length, and gradually cooled.
As a method of forming the glass tube main body into a tube shape, a known method such as a Dunner method, a bellow method, or a blow method can be used. Moreover, you may obtain a glass tube of a desired tube diameter by extending a glass tube using a glass lathe.

As one embodiment, the glass tube main body has, as a glass composition, an oxide-based mass%, an oxide-converted mass percentage display, SiO ₂ 40-80%, Al ₂ O ₃ 0.1-4%, Na ₂ O 10 to 25%, RO 1 to 20%. Hereinafter, the content of chemical components related to the composition is expressed in terms of mass% based on oxide unless otherwise specified.

SiO ₂ is a component constituting the skeleton of glass and is essential. The content of SiO ₂ in this embodiment is 40 to 80%. When the content of SiO ₂ is less than 40%, the stability as glass is lowered or the weather resistance is lowered. This content is preferably 50% or more, more preferably 58% or more. On the other hand, if the content of SiO ₂ exceeds 80%, the viscosity of the glass increases and the meltability decreases significantly. This content is preferably 75% or less, typically 70% or less.

Al ₂ O ₃ is a component that improves the weather resistance of glass and is essential. The content of Al ₂ O ₃ in this embodiment is 0.1 to 4%. If the content of Al ₂ O ₃ exceeds 4%, the viscosity of the glass becomes high and uniform melting becomes difficult. This content is preferably 3.5% or less, typically 3% or less. When the Al ₂ O ₃ content is less than 0.1%, the weather resistance is lowered. This content is preferably 0.2% or more, and more preferably 0.3% or more.

Na ₂ O is a component that improves the meltability of the glass and is essential. The content of Na ₂ O in this embodiment is 10-25%. If the Na ₂ O content is less than 10%, the meltability is poor. This content is preferably 11% or more, typically 12% or more. When the Na ₂ O content exceeds 25%, the weather resistance is lowered. This content is preferably 23% or less, typically 21% or less.

  Alkaline earth metal oxide RO (R represents at least one alkaline earth metal selected from the group consisting of Mg, Ca, Sr and Ba. RO represents MgO, CaO, SrO and BaO. Is a component that improves the meltability and moldability, and is essential. If the RO content exceeds 20%, the glass tends to be devitrified, which is not preferable. The RO content is preferably 18% or less, more preferably 17% or less. If the RO content is less than 1%, the effect of improving the meltability and moldability cannot be obtained sufficiently. The RO content is preferably 2% or more, more preferably 3% or less.

In order to suppress transmission of ultraviolet rays through the glass tube, the glass may contain Fe ₂ O ₃ 0.01 to 0.3% and / or TiO ₂ 0.0001 to 0.1%. When the resin member is provided inside the glass tube, the resin member may be deteriorated if the ultraviolet ray transmittance of the glass tube is high. By containing each component of Fe ₂ O ₃ and TiO ₂ in the glass, it is possible to suppress the transmission of ultraviolet rays through the glass tube.
If Fe ₂ O ₃ is less than 0.01%, the ultraviolet transmittance of the glass tube is increased, which is not preferable. Further, if Fe ₂ O ₃ is more than 0.3%, the glass tube is colored, and the transmittance of light having a wavelength in the visible region is lowered, which is not preferable. Fe ₂ O ₃ is preferably 0.02 to 0.15%, more preferably 0.03 to 0.18%. When TiO ₂ is less than 0.0001%, the ultraviolet transmittance of the glass tube is increased, which is not preferable. Further, if TiO ₂ is more than 0.1%, the glass tube is colored and the transmittance of light having a wavelength in the visible region is lowered, which is not preferable. TiO ₂ is preferably 0.0005 to 0.08%, more preferably 0.001 to 0.01%. Only one of Fe ₂ O ₃ and TiO ₂ may be contained in the glass tube, or both may be contained. In the present invention, ultraviolet light means light having a wavelength of 400 nm or less.

In addition to the aforementioned components, suitable components may be contained for the purpose of obtaining desired characteristics. Further, as a fining _{agent, Sb 2 O 3, CeO 2} , F, SO 3, is selected from the group of Cl were one or two or more may be contained from 0.001 to 3%.

The glass tube of the present invention may include an ion exchange layer having a lower sodium concentration than the central portion in the glass thickness direction on the outer peripheral surface.
The ion exchange layer is provided on the outer peripheral surface of the glass tube, and can suppress the occurrence of weathering in the glass tube even when the glass tube is used, for example, outdoors or in a high humidity environment. Moreover, the intensity | strength of a glass tube can be raised and the failure | damage when external force is added can be suppressed.

  The ion exchange layer has a lower sodium concentration than the central portion in the thickness direction of the glass by replacing the sodium component on the glass surface with the potassium component. The weathering of glass is visually recognized as white cloudy on the glass surface when moisture in the atmosphere reacts with the sodium component on the glass surface to precipitate fine crystals. Therefore, the above-mentioned crystal precipitation can be suppressed by lowering the sodium concentration on the glass surface.

The ion exchange layer can be performed, for example, by immersing a glass tube in a molten salt at 400 ° C. to 550 ° C. for about 1 to 96 hours. The molten salt used for the ion exchange treatment is not particularly limited as long as it contains potassium ions. For example, a molten salt of potassium nitrate (KNO ₃ ) is preferably used. In addition, a molten salt in which potassium nitrate (KNO ₃ ) and sodium nitrate (NaNO ₃ ) are mixed may be used.

  The ion exchange layer is preferably provided in a depth direction of 3 μm to 50 μm on the surface of the glass tube. If the depth is less than 3 μm, the ion exchange layer is too thin to sufficiently suppress weathering. If the depth exceeds 50 μm, it takes time to form the ion exchange layer, and the productivity is not good.

Since the ion exchange layer replaces the sodium component on the glass surface with the potassium component, it has a surface compressive stress in the depth direction of the surface of the glass tube. In order to obtain high strength while reducing the weight by making the glass tube thin, the ion exchange layer is a layer having a surface compression stress of 3 μm to 50 μm in the depth direction of the surface of the glass tube (hereinafter referred to as DOL). Preferably).
If the DOL is less than 3 μm, the mechanical strength of the glass tube may be lowered when the contact scratch enters deeper than the DOL. If the DOL is more than 50 μm, it is difficult to cut the glass tube after the tempering treatment. DOL is preferably 5 μm to 40 μm, and more preferably 7 μm to 30 μm.

  The compressive stress (hereinafter sometimes referred to as CS) of the layer having surface compressive stress is preferably strengthened so as to be, for example, 300 MPa or more, 500 MPa or more, 700 MPa or more, 900 MPa or more. The mechanical strength of the tempered glass increases as the CS value increases. On the other hand, if the CS becomes too high, the tensile stress inside the glass may become extremely high. Therefore, the CS is preferably 1400 MPa or less, and more preferably 1300 MPa or less.

  CS and DOL formed on the surface of the glass tube can be determined by observing the number of interference fringes and the interval between them using, for example, a surface stress meter (FSM-6000LE manufactured by Orihara Seisakusho Co., Ltd.).

  The ion exchange layer may be provided not only on the outer peripheral surface of the glass tube but also on the inner peripheral surface. When an ion exchange layer is provided on the outer peripheral surface and inner peripheral surface of the glass tube, it is possible to suppress the occurrence of weathering on the inner surface of the glass tube. Moreover, since compressive stress is generated on each of the outer peripheral surface and the inner peripheral surface of the glass tube, the glass tube can be provided with high mechanical strength.

  The thickness of the glass tube is preferably 2 mm or less, more preferably 1.5 mm or less, and particularly preferably 1.0 mm or less. Moreover, since there exists concern about an intensity | strength when the thickness of a glass tube main body is too thin, Preferably it is 0.2 mm or more, More preferably, it is 0.4 mm or more, Most preferably, it is 0.5 mm or more.

The glass tube preferably has an average transmittance of 94% to 99% in a wavelength range of 380 nm to 780 nm with a thickness of 1 mm. In addition, the average transmittance | permeability when the thickness of a glass tube is 1 mm means the value which measured the average transmittance | permeability of the glass tube whose thickness is not 1 mm, and converted the result into thickness.
When the average transmittance of the glass tube is less than 94%, the amount of light transmitted through the glass tube is attenuated, which may affect the captured image. Further, when the average transmittance of the glass tube exceeds 99%, the structure of the antireflection film provided on the surface of the glass tube becomes complicated, which may increase the manufacturing cost. 94.5% to 98.5% is preferable and 95% to 98% is more preferable as an average transmittance in a wavelength range of 380 nm to 780 nm when the thickness of the glass tube is 1 mm.

In the glass tube of the present invention, a moisture shielding layer may be provided on the surface of the glass tube or the surface of the ion exchange layer.
The surface of glass may be deteriorated by the influence of moisture in the atmosphere. This deterioration of the glass surface is a cloudy phenomenon called weathering that appears as a cloudy change on the glass surface during storage or use of the so-called semi-finished product before the glass tube is assembled as an imaging device. . Specifically, it is considered that the moisture in the atmosphere reacts with the sodium component on the glass surface and fine crystals are precipitated, so that the glass surface is visually recognized as white cloudy.
Therefore, by providing a moisture shielding layer on the surface of the ion exchange layer, the reaction between the moisture in the atmosphere and the sodium component on the glass surface can be suppressed, and the occurrence of weathering can be more effectively suppressed.

The moisture shielding layer may be composed of a single layer or multiple layers as long as it can suppress the reaction between the moisture in the glass tube surface or the atmosphere and the sodium component on the glass surface.
In the case of a multilayer, a plurality of thin films having different refractive indexes are alternately laminated. As the multilayer structure, for example, an optical multilayer film in which about 10 layers of SiO ₂ films and TiO ₂ films are alternately stacked may be used. The optical multilayer film can be formed by a known method such as vacuum deposition or sputtering.
In the case of a single layer, a silica layer in which hollow silica is dispersed in a resin can be used. The silica layer can be obtained by immersing a glass tube in a coating solution in which hollow silica is dispersed in a resin, and then baking the glass tube.

  The glass tube of the present invention can be used as a protective member that protects these devices by providing an imaging device inside as shown in FIG. 3, for example. This imaging device 10 includes a glass tube 1 of the present invention, a lid 2 that hermetically seals the internal space, and cameras 3 (two) installed in the internal space. These imaging devices are installed on an appropriate base or device. Since the camera 3 is disposed in a space constituted by the glass tube 1 and the lid 2, dust or the like does not adhere to the lens even when used outdoors, for example. The camera 3 captures an image transmitted through the glass tube 1. However, the glass tube 1 has no protrusions on the inner and outer surfaces, and the captured image is not distorted.

  In the glass tube of the present invention, streak-like protrusions are suppressed, and a clear captured image without distortion or the like can be obtained even through the glass tube. There may be one or more imaging devices provided in the glass tube. When the surroundings are imaged using one imaging device, a conical reflecting mirror may be provided inside the glass tube, and a surrounding image may be obtained by photographing the reflecting mirror. In addition, when a plurality of imaging devices are provided, images may be simultaneously captured by these imaging devices, and a plurality of obtained images may be processed to obtain surrounding images.

  As mentioned above, although embodiment of this invention was described, these embodiment was shown as an example and is not intending limiting the range of invention. The configuration can be changed as appropriate within the limits not departing from the spirit of the present invention.

  EXAMPLES Hereinafter, although it demonstrates in detail based on the Example of this invention, this invention is not limited only to these Examples. Example 1 is an example of the present invention and Example 2 is a comparative example.

(Example 1)
First, SiO _{2 is} 70%, B ₂ O ₃ 1%, Al ₂ O ₃ 2%, Na ₂ O 16%, K ₂ O 2%, CaO 6%, and MgO 3% in terms of mass% in terms of oxide. Thus, the glass raw material was prepared. The glass raw material was melted, stirred and clarified, and formed into a tubular shape by the Danner method. This glass was cut to obtain a glass tube having an outer diameter of 40 mm, a height of 100 mm, and a wall thickness of 0.85 mm.
Next, using the following method and apparatus, the shapes of the outer surface and the inner surface of the glass tube were measured to confirm the presence or absence of protrusions.
Using a roundness measuring device (RONDCOM 31C, manufactured by Tokyo Seimitsu Co., Ltd.), the shapes of the outer and inner surfaces of the glass tube were measured. As a result, there were no protrusions having a concave or convex tip angle of 90 ° or less on the outer and inner surfaces of the glass tube.

(Example 2)
A glass tube having the same glass composition as in Example 1 was used and formed into a tubular shape by the Danner method. At this time, the molding time was different from Example 1. When the presence or absence of protrusions on the outer and inner surfaces of the glass tube was confirmed by the same method as in Example 1, three protrusions having a recess or protrusion with a tip angle of 90 ° or less were confirmed.

(Evaluation)
About each glass tube of Example 1 and Example 2, the glass tube was arrange | positioned just before the lens of a digital still camera, and the captured image was obtained. Each captured image is shown in FIGS. The camera took a picture of the fluorescent tube. The obtained captured image was subjected to exposure correction so that the boundary portion between the light (bright portion) of the fluorescent tube and the other portion (dark portion) could be clearly distinguished.

  As shown in FIG. 4, in the captured image obtained through the glass tube of Example 1, no distortion or the like due to the streak-like deformation of the glass tube was observed. On the other hand, the distortion resulting from the stripe-like processus | protrusion (projection which appears by shape measurement) of a glass tube was confirmed by the captured image obtained via the glass tube of Example 2 from FIG. Specifically, when the streak-like projections of the glass tube straddle the boundary between the bright part and the dark part to be imaged, distortion was confirmed at a part of the boundary in the captured image.

By using the protective glass tube of the imaging device of the present invention, a clear captured image with little distortion or the like can be obtained.

Claims (6)

A glass tube for protection of an imaging device which is made of a glass tube and has no projections defined below on the outer surface and the inner surface.
A protrusion means the acute-angle recessed part or convex part in the shape obtained when measuring the outer surface and inner surface of a glass tube in the circumferential direction centering on a tube axis.   The glass tube for protection of an imaging device according to claim 1, wherein the concave portion or the convex portion has a tip angle of 90 ° or less. The glass tube, as a glass composition, by mass% based on _{oxides, SiO 2 40~80%, Al 2} O 3 0.1~4%, Na 2 O 10~25%, RO (R is, Mg And at least one alkaline earth metal selected from the group consisting of Ca, Sr, and Ba, and RO means the total amount of MgO, CaO, SrO, and BaO.) 1-20% inclusive The glass tube for protection of the imaging device of Claim 1 or Claim 2 to do.   The glass tube for protection of an imaging device according to any one of claims 1 to 3, wherein an ion exchange layer having a lower sodium concentration than a central portion in the thickness direction of the glass is provided on the outer peripheral surface.   The glass tube for protection of an imaging device according to claim 4, wherein an ion exchange layer having a sodium concentration lower than that of a central portion in the glass thickness direction is provided on the inner peripheral surface. 6. The glass for protecting an imaging apparatus according to claim 1, wherein the glass tube has an average transmittance of 94% to 99% in a wavelength range of 380 nm to 780 nm with a thickness of 1 mm. tube.