JPS6180202A - Light diffusive film and its formation - Google Patents

Abstract

PURPOSE:To obtain a light diffusive film which is easily formable, is suitable for mass production, is hardly worn mechanically, and can be formed regardless of the material of a base body or the inside and outside surfaces thereof by incorporating foam into the continuous film body formed on the surface of the base body thereby providing light diffusivity thereto. CONSTITUTION:For example, dioctyl phthalate (DOP) is added as a high boiling solvent at about 5-10vol% to an a low boiling solvent for an org. metallic compd., for example, tetraisopropyl titanate and such soln. is coated on the surface of the base body 1 of a halogen electric bulb, etc. and is dried to form a gel-like coated film 24 and thereafter the film is calcined for about 5min at about 600 deg.C. The DOP liquid drops 25 diffused into the film 24 evaporate and the org. metallic compd. decomposes so that the drops 25 expand diametrally to form foam 22 while evaporating. The drops 25 existing near the surface of the film 24 are burst to communicate with the external air and form recessed holes 23 in the stage of expanding diametrally. The light diffusive film 2 contg. the foam 22 and the holes 23 in the body 21 is thus formed. The resultant film 2 exhibits the excellent light diffusivity even if the film is extremely thin.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a light-diffusing film that is formed on the surface of a substrate such as a light bulb, a high-pressure discharge lamp bulb, an optical filter, a window glass, etc. to impart light-diffusion properties, and a method for forming the same. .

[Technical background of the invention and its problems]

For example, in a halogen light bulb for a copying machine, in order to make the illuminance distribution uniform on the irradiated surface, the light-emitting portions and non-light-emitting portions of the filament are arranged alternately in the tube axis direction, but this is not sufficient. For this reason, the bulb surface is generally honed to provide light scattering properties, but this method has the disadvantage of requiring a lot of labor. Another conceivable method is to apply light-diffusing fine powder such as silica to the outer surface of the bulb by electrostatic coating or hot water drop method to form a light-diffusing film. These types of light-diffusing films are generally mechanically weak and easily abraded, and in some cases their light-diffusing properties decrease after long-term use.Also, depending on the type of light-diffusing fine powder, they do not fit well with quartz bulbs and are likely to peel off. There are some things.

[Purpose of the invention]

The present invention provides a light-diffusing film that is easy to form, suitable for mass production, mechanically strong and resistant to wear, and can be formed regardless of the material of the substrate such as a bulb, or on either the internal or external surfaces, and exhibits excellent light-diffusing properties. The purpose is to provide a forming method.

[Summary of the Invention] - The first aspect of the present invention is a light-diffusing film that has light-diffusing properties by containing air bubbles in a continuous film formed on the surface of a substrate.

The second aspect of the present invention is to mix a high boiling point organic solvent with an organometallic compound, apply it to the surface of the substrate, and sinter it to decompose the organometallic compound. This is a method for easily forming the light-diffusing film of the first invention by incorporating.

[Embodiments of the invention]

The details of the invention will be explained with reference to the illustrated embodiments. 1st
The figure shows an example of a halogen light bulb for a copying machine provided with the light diffusing film of this embodiment. In the figure, (1) is a tube-shaped transparent quartz bulb, that is, the base, (2) is a light-diffusing film formed on the outer surface of this base (1), and (3), (3) are crushed and sealed both ends of the base (1). The sealing part formed by sealing (4), (4) is this sealing part (3),
(3) Molybdenum introduction foil embedded in (5), (5
) is connected to these introduction foils (4), (4) and the base (1)
The inner conductor wires (6), (6), etc. introduced inside are short-circuit wires (7).

A plurality of filaments (8), (8), which are connected in series through (7) and installed between inner conductors (5), (5).
・ is the reed force supporting the shorting wires (7), (7), (9),
Reference numeral (9) denotes a lead-in foil, and terminals connected to (4) and (4) via external groove wires (not shown) and attached to the end faces of the sealing parts (3) and (3). Then, the required halogen is sealed in the base (1) along with an inert gas such as argon.

As is clear from the electron micrograph of FIG. 2, the light-diffusing film (2) is a thin film that contains bubbles and has circular holes on its surface, and its detailed structure is schematically shown in FIG. 3. That is, a continuous film (21) made of a metal oxide such as titanium oxide (Ti02) formed on the surface of the base (1) contains a large number of bubbles (22), and some of these bubbles are part of the film. Body (2
1) A circular concave hole (23) is opened on the surface. These air bubbles (22) and recesses (23) scatter the transmitted light, making it appear cloudy to the naked eye. Then, the membrane body (
21) The thickness of 3000-8000 people (0.3-0.8
μ).

Although this halogen bulb has filaments (6) and (6) arranged intermittently, the light is transmitted through the diffuser film (2).
Since the light is diffused and emitted, there is no unevenness in illuminance on the irradiated surface. Furthermore, although there is a large difference in coefficient of thermal expansion between the quartz that makes up the bulb (1) and the titanium oxide that makes up the light-diffusing film (2), the light-diffusing film (2) is extremely thin, and the film body (21) Since it contains air bubbles (22) and concave holes (23), the mechanical strain caused by the difference in thermal expansion is alleviated, and the light diffusing film (2) does not peel off even after repeated blinking for a long period of time. In addition, since the light scattering film (2) is extremely thin, the light loss is 3~
It is only about 4%, which is extremely advantageous. In addition, a light-diffusing film (
Since the film body (21) in 2) is a continuous body, it is mechanically strong and has no fear of wear, and its light scattering properties do not change during long-term use.

To form such a light-diffusing film (2), first, a high-boiling organic solvent such as di-2-ethylhexyl phthalate (dioctyl phthalate, abbreviated as dioctyl phthalate) is added to a low-boiling organic solvent solution of an organic titanium compound such as tetraisopropyl titanate. DOP) is added in an amount of 5 to 10% by volume, and if necessary, an appropriate amount of a low boiling point organic solvent such as butyl acetate is added thereto to adjust the viscosity. Then, the sealed halogen bulb is immersed in this solution and pulled back to dry at a speed of 30 to 50 cm/min. Therefore, the above-mentioned DOP is a colorless oily liquid that boils at 231° C. under a pressure of 5 mmHg and is mutually soluble in various low-boiling point organic solvents in arbitrary proportions. Therefore, in the drying step, only the low boiling point organic solvent is evaporated.

After drying, as shown in FIG. 4, minute droplets of DOP (25) are dispersed in the gel-like coating film (24) made of an organic titanium compound, making it cloudy.

Next, the halogen bulb on which this gel-like coating film (24) has been formed is fired in air at about 600° C. for about 5 minutes.

Then, DOP droplets (
The evaporation of 25) and the decomposition of the organotitanium compound occur one after the other, and as a result, the droplet (25) expands in diameter while evaporating almost at that position, becoming a bubble (22), and further inside the bubble (22). of DOP vapor is gradually replaced by atmospheric air.

In addition, the droplet (25) near the surface of the gel-like coating (24)
) ruptures in the process of expanding its diameter and communicates with the outside air, forming a concave hole (23
), and finally, as shown in FIG. 3, a light-diffusing film (2) containing air bubbles (22) and concave holes (23) is formed in a continuous film body (21) made of titanium oxide. As is clear from this formation process, in the present invention, air bubbles (22) and concave holes (2
3) are essentially the same.

In this way, DOP not only improves the film formation of the organic titanium compound but also forms droplets (25) in the gel coating (24).
) and become spores of air bubbles (22), so that even though the gel-like coating film (24) is extremely thin, it foams effectively. Furthermore, even if the organic titanium compound starts to decompose due to the high boiling point of DOP, sufficient vapor pressure is maintained within the bubbles (22), so the bubbles (22) can be maintained before the organic titanium compound decomposes and solidifies.
2) will not be crushed, and the recessed hole (23) will not be flattened.

Note that if the amount of DOP added is too small, the bubbles (22) and the recessed holes (23) will be too small, resulting in a decrease in light scattering properties. On the contrary, DO
If the amount of P added is too large, the variations in the size of the bubbles (22) and the concave holes (23) will become large, resulting in local variations in light scattering properties, and large concave holes (23) that can be seen with the naked eye.
3) may be formed.

Further, in the present invention, the constituent material of the membrane body (21) is not limited to the above-mentioned titanium oxide, and for example, silica (S
i(h), zinc oxide (ZnO), aluminum oxide (A
Q203), oxidized di) Li ml (Zr02),
Tantalum oxide (Ta205), tin oxide (Sn02), indium oxide (In203), etc. may also be used, and the diffusion film may be formed using an organic compound of these metals in the same manner as described above.

Furthermore, the high boiling point organic solvent is not limited to the above-mentioned DoP, but any solvent may be used as long as it has similar physical properties and does not produce a decomposition residue upon calcination.

Next, various high-boiling point organic solvents were added to the organic titanium compound in various proportions to form light-diffusing films in the same manner as described above, and the light-diffusing properties of the films were investigated. The results are shown in Table 1 below.

Table 1 (blank below) where DBP is an abbreviation for dibutyl phthalate DOP is an abbreviation for dioctyl phthalate DAP is an abbreviation for diallyl phthalate From this table 1, when forming a light diffusing film using an organic titanium compound, DBP or DOP It turns out that it is sufficient to add 5 to 2% by volume of. In addition, if low light scattering properties are acceptable, 10 to 10 b of DAP may be added.

Next, various high-boiling point organic solvents were added to the organosilicon compound in various proportions to form a light-diffusing film in the same manner as described above, and the light-diffusing properties thereof were investigated. The results are shown in Table 2 below.

Table 2 From Table 2, it can be seen that when forming a light scattering film using an organosilicon compound, it is sufficient to add 5 to 20% by volume of DBP or DOP. However, when formed under the same conditions, a titanium oxide light scattering film has better light scattering properties than a silica light scattering film. This seems to be due to the difference in refractive index.

In addition, although the above-mentioned embodiment was formed on the outer surface of a halogen light bulb, the present invention is not limited to this, and the present invention is not limited to this. It can be formed on any surface, including the inner and outer surfaces of light bulbs and infrared light bulbs, the inner and outer surfaces of the outer bulb of high-pressure discharge lamps, optical filters, and plate glass such as window glass. Therefore, such a surface to be formed is referred to as a substrate surface.

Further, the light-diffusing film of the present invention can increase the diffusion effect by closely stacking a plurality of thin light-diffusing films of around 0.1 μm on the same substrate surface. In this case, a first thin light-diffusing film may be formed on the surface of the substrate by the method described above, and second and subsequent thin light-diffusing films may be successively formed and stacked on that surface. In this case, as shown in FIG. 5, the concave holes in the lower layer (21A) and (21B) are the same as those in the upper layer (21B) and (21C).
Although the upper part is buried by the bubble (22A), (
22B) remains as it is, and the result is the same as when a very large number of bubbles are contained in a thick light-diffusing film, exhibiting excellent light-diffusing properties.

Furthermore, the light diffusing film of the present invention may be provided in a layered manner with another optical film, such as a visible light transmitting infrared reflective film, and its position may be above, below, or in an intermediate layer of such optical film. Even if it is installed at a certain position, the light scattering properties will not be affected.

Furthermore, the method of forming a plurality of layers of light-diffusing films is as follows:
Even if coating and firing are repeated for each layer, it will not work as soon as multiple layers are coated and then fired.

〔Effect of the invention〕

The light-diffusing film of the present invention exhibits light-diffusing properties by containing air bubbles within the continuous film made of metal oxide formed on the surface of the substrate.
Despite its extremely thin film thickness, it exhibits excellent light scattering properties,
Mechanical distortion caused by the difference in thermal expansion with the base material is alleviated, and it can withstand long-term repeated thermal shock without the risk of peeling.It is mechanically strong and its light scattering properties do not deteriorate even after long-term use.
Light loss is also extremely low.

In addition, the method for forming the light scattering film of the present invention involves blending a high boiling point organic solvent with an organometallic compound, applying it to the substrate surface, and baking to decompose the organometallic compound and form a metal oxide film. After that, the high boiling point organic solvent becomes small droplets and disperses in the coating film, and these small droplets evaporate at that position to form bubbles, which are extremely easy to form, extremely thin, and have excellent light scattering properties. A light-diffusing film can be formed.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of an example of a halogen light bulb using an embodiment of the light diffusing film of the present invention, Fig. 2 is an electron micrograph of the outer surface of the part surrounded by chain lines in Fig. A schematic cross-sectional view based on a photograph, Fig. 4 is a schematic cross-sectional view of a coating film before firing in this method of forming a light-diffusing film, and Fig. 5 is a cross-sectional view schematically showing a state in which multiple layers of light-diffusing film are layered. It is. (1)...Substrate (2)...Diffusing film (2
1)...Membrane body (22)...Bubble 1l-

Claims (3)

[Claims] (1) A light-diffusing film characterized in that it exhibits light-diffusing properties by containing air bubbles within a continuous film made of a metal oxide formed on the surface of a substrate. (2) The light-diffusing film according to claim 1, wherein some of the bubbles are open on the surface of the film body. (3) A metal oxide film formed by blending a high boiling point organic solvent with an organometallic compound and applying it to the surface of the substrate, baking it and decomposing the above organometallic compound. Bubbles formed by the evaporation of the above high boiling point organic solvent inside the metal oxide film body. A method for forming a light-diffusing film, characterized by containing.