JPH0384848A - Light diffusion film and its formation and tubular bulb and its manufacture - Google Patents

Abstract

PURPOSE:To obtain sufficient mechanical strength of a light diffusion film without employing excess requirements by fusing specific metal oxide granules to one another in chains to form a cluster of granules in branched, frizzled or nebulous configuration, and attaching the granules to the surface of a substrate while causing them to irregularly combine with one another. CONSTITUTION:A light-diffusing film 12 located on a substrate 10 comprises a turbid light diffusion film layer 14 including metal oxide particles and being substantially the main body that exhibits the light diffusion characteristic of the film, and a transparent protection film layer 16 formed and laid thereon. The surface of the light diffusion film layer 14 shows a unique pattern when observed by a scan electron microscope(SEM) and a more detailed observation of the same reveals that if this pattern is considered as a primary structure there exists a secondary structure wherein a cluster 20 of granules are formed while being irregularly combined together in branched, frizzled or nebulous configuration. Further the secondary structure includes a tertiary structure comprising granules of relatively regular grain size in the range 0.05 to 0.5mu fused to one another in chains. Thus an excellent light diffusion characteristic of the light diffusion film is obtained and also the mechanical strength of the film is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for forming a light-diffusing film, and particularly to improvements in the film-forming agent. The present invention also relates to an improvement in a tube having a light-diffusing film.

[Prior Art] Forming a metal oxide film having a property of scattering light (hereinafter referred to as "diffusion property") in order to impart light scattering property to the surface of an optical component or a substrate such as a light bulb or a bulb of a discharge lamp. There is.

Such a coating must be mechanically strong, resistant to wear, and resistant to peeling, and must also have light-diffusing properties (hereinafter referred to as a "diffusion film"). be.

Conventionally, a method for forming a light-diffusing film is a method of applying a metal oxide film-forming agent to the surface of a substrate in a high humidity atmosphere (Japanese Patent Application Laid-open Nos. 59-221967 and 59-221968 2 hereinafter referred to as prior art 1). Alternatively, a method in which a metal oxide film forming agent applied to the surface of a substrate is treated at a high temperature of 1000° C. or higher to generate metal oxide microcrystals in the film and impart light scattering properties (see the above-mentioned two publications and the following prior art) 2),
Furthermore, a method of imparting light scattering properties by forming minute bubbles in a continuous film of metal oxide (Japanese Patent Laid-Open No. 61-802
No. 02 Publication 2 (hereinafter referred to as Prior Art 3), etc. are disclosed.

In each of the above methods, an organic metal compound solution such as an alcoholic solution of a metal alkoxide is used as a raw material, a substrate is immersed in the solution, and the solution is applied to the surface of the substrate by pulling it up at a constant speed. It has a so-called immersion firing process to transform it into an oxide film. Each of the above methods has the advantage that it is easier to impart light scattering properties to the substrate surface and is suitable for mass production, compared to long-known methods such as honing treatment and coating of light scattering fine powder. have.

[Problems to be Solved by the Invention] However, the method for forming a light diffusing film such as Prior Art 1 or Prior Art 2 does not require high humidity of 95% or more or 100% humidity.
Extreme conditions such as high temperatures of 0°C or higher are required. Therefore, in order to cope with such extreme conditions, there were problems such as applying anti-rust treatment to various parts of the machine surface of the film forming device, or requiring large-scale high-temperature firing equipment and a large amount of thermal energy. .

Therefore, the work of pulling up the substrate immersed in the metal oxide film forming agent is carried out in a normal indoor atmosphere with a humidity of 30 to 80%, and the heat treatment is carried out in a normal room atmosphere with a humidity of 30 to 80%.
There has been a strong demand for a method for forming a light-diffusing film under mild conditions that can be carried out in the atmosphere at a temperature of ~600°C.

On the other hand, according to the method disclosed in the prior art 3,
Although the work can be carried out under relatively mild conditions compared to the first two methods, it is difficult to form a film with appropriate size bubbles in an appropriate distribution, and the film The problem was that mechanical strength and adhesion to the substrate were insufficient.

By the way, the light-diffusing film formed on the surface of the substrate does not originally have very strong mechanical strength, and it is inevitable that the film will be gradually scraped off from the surface and lost due to wear during use. Therefore, it is conceivable to cover the surface of the light-diffusing film with a protective layer that does not inhibit light-diffusing properties.

However, when attempting to form a protective film layer on the light-diffusing film formed by each of the above methods, the protective film layer itself tends to peel off because the bond between the protective film layer and the light-diffusing film layer is insufficient. Alternatively, the entire light-diffusing film may be peeled off from the substrate. This is a particularly serious problem in the case of a light-diffusing film formed on the surface of a bulb whose shape is a curved surface.

The present invention has been made in view of the problems of the prior art described above, and its purpose is to provide a light diffusing film that can be formed without using extreme conditions and has sufficient mechanical strength, and a method for forming the same. An object of the present invention is to provide a tube to which such an excellent light-diffusing film is applied, and a method for manufacturing the same.

[Means for Solving the Problems] In order to achieve the above object, the inventors of the present invention conducted extensive studies and first discovered the following useful method for forming a light-diffusing film.

That is, an alkyl derivative of benzene (hereinafter referred to as "alkylbenzene J"), in particular an alkylbenzene whose alkyl side chain has 8 to 15 carbon atoms, is selected from water-insoluble organic solvents, and it is mixed with an organic metal in a predetermined ratio. When a solution prepared by adding to a compound solution is used as a metal oxide film forming agent, the substrate immersed in the film forming agent is pulled up from the film forming agent in a normal indoor atmosphere with a humidity of 30 to 80%, Next, 500 to 6, which is usually used in the immersion firing method.
It has been found that a metal oxide light-diffusing film having good properties can be formed by heat treatment in the atmosphere at a temperature of 00°C.

That is, the invention according to claim 2 provides a method for forming a light-diffusing film in which an organometallic compound solution is applied as a film-forming agent to the surface of a substrate, and this is heated to form a metal oxide fine particle film. The number of carbon atoms in is 8 or more and 1
This is a method for forming a light-diffusing film characterized by containing an alkylbenzene of 5 or less.

In the method for forming a light-diffusing film of the present invention, the humidity is 30 to 80%.
When the substrate is pulled up from the film-forming agent in a normal indoor atmosphere of about 100%, the volatile components in the liquid film of the adhesion-forming agent adhering to the substrate evaporate and dry, and at the same time, the liquid film becomes cloudy. Start. This white turbidity is then completely transformed into a cloudy, opaque metal oxide film by heat treatment at <500-600° C. and is fixed to the substrate surface.

In order to give the metal oxide film good white turbidity, it is preferable to dry the film on the surface of the substrate for 1 to 2 minutes after lifting the substrate from the film forming agent.

Electron microscopic findings on the surface of the cloudy and opaque metal oxide coating show that, at a magnification of about 3,000 times or more, groups of metal oxide granules are irregularly connected to form a complex pattern. This pattern is formed by a group of the above-mentioned granules having a branch-like, curly-hair-like, or cloud-like form, and furthermore, this group has a particle size of 0.0!5 to 0.05. 5μ,
It is composed of metal oxide granules of relatively uniform particle size that are fused together in a chain.

These electron microscopic findings are clearly different from the findings of a cloudy film obtained by the prior art. For example, when formed by the method of the prior art described above, the film has a spongy microstructure rich in vacuoles, and when formed by the method of the prior art 2, it contains microcrystals of metal oxide.

That is, in the invention according to claim 1, the particle size is 0.05 to 0.
5μ metal oxide granules are fused to each other in a chain to form a branch-like, curly-hair-like, or cloud-like group, and the group is irregularly connected and attached to the substrate surface. This is a light-diffusing film characterized by:

The light scattering film forming method of the present invention includes titanium oxide (TiO2),
Zirconium oxide (ZrOi), tantalum oxide (Ta2)
It is suitable for forming a light-diffusing film layer made of a metal oxide mainly composed of 0s) or a composite of these metal oxides.

In this case, as the organometallic compound in the film forming agent, an organic compound of a metal corresponding to the final form of the metal oxide is used. For example, when forming a light scattering film made of titanium oxide (Ties), titanium alkoxide (Ti(OR)4.
R represents an alkyl group), titanium chelate compound (
TiX, , Y+-□ (X represents a chelating agent, Y represents a group such as an alkoxyl group), etc. are used.

As the water-insoluble organic solvent to be included in the metal oxide film forming agent, alkylbenzene, which is liquid at room temperature and has 8 to 15 carbon atoms in the alkyl side chain, forms a metal oxide film with good white turbidity. give. If an alkylbenzene having 7 or less carbon atoms or 16 or more carbon atoms in the alkyl side chain is contained, the metal oxide coating after heat treatment will have insufficient white turbidity or will not be cloudy at all.

The content of alkylbenzene in the metal oxide coating formulation is preferably adjusted to 10 to 35% by volume, more preferably 5 to 35% by volume. When the alkylbenzene content is less than 10% by volume, the metal oxide coating after heat treatment is not cloudy at all, or the coating has insufficient white turbidity. Furthermore, when the content exceeds 40% by volume, the metal oxide coating often becomes sufficiently cloudy, but at the same time, the thickness of the coating is not uniform and the adhesion to the substrate is weak. Inconveniences arise in film formation.

In the case of a titanium oxide film, Table 1 shows the relationship between the number of carbon atoms in the alkyl side chain of the alkylbenzene contained in the film forming agent (type of alkylbenzene) and the content of alkylbenzene, and the white turbidity of the film. be. Table 1 shows that in order to obtain a titanium oxide film with good white turbidity, compounds with a chemical structure in which an alkyl side chain is bonded to a benzene ring, that is, alkylbenzene, are effective, but the number of carbon atoms in the alkyl side chain is This indicates that the content is limited to those in the range of 8 to 15, and that the optimum content is common to all alkylbenzenes having alkyl side chain carbon numbers in the above range of 15 to 35% by volume. There is.

Table 1 deals with alkylbenzenes in which the alkyl side chain has a linear shape, but even if other structural isomers having a branched alkyl side chain are used as the alkylbenzene, the same results as in Table 1 are shown. Obtain a similar relationship.
(Left below) The light-diffusing film produced by the method of the present invention will not peel off even if a transparent dielectric film or conductive film is further layered thereon, and the light-diffusing film layer below it will not peel off. The accompanying peeling is also extremely unlikely to occur. Furthermore, this transparent coating layer can be made sufficiently resistant to wear if it is formed by a conventionally known appropriate method.

Therefore, this transparent film layer functions as a protective layer for the light-diffusing film layer below, which is a layer that substantially exhibits light-diffusing properties, and does not inhibit the light-diffusing property of the light-diffusing film layer, so that the transparent film layer itself and the transparent film layer function as a protective layer. The protective film layer as a whole constitutes a light-diffusing film with enhanced peel resistance and wear resistance. This means that
When the light-diffusing film is applied to a bulb, it is possible to provide a bulb having a light-diffusing film formed on the bulb surface, which is particularly useful and has excellent mechanical strength.

Therefore, we present the following invention. First, the invention according to claim 3 provides the light scattering film according to claim 1, which is formed directly on the substrate surface or on at least one dielectric coating and/or conductive coating formed on the substrate surface. layer and
The light scattering film is characterized in that it is composed of a transparent dielectric film layer and/or a transparent conductive film layer formed on the light scattering film layer. Further, the invention according to claim 5 is a tube characterized in that the light diffusing film is formed on the surface of the tube bulb.

Furthermore, the invention according to claim 4 provides a method for forming a light-diffusing film by the method according to claim 2 directly on the substrate surface or after forming at least one dielectric coating and/or conductive coating on the substrate surface. This is a method for forming a light-diffusing film, the method comprising: then forming a transparent dielectric film layer and/or a transparent conductive film layer on the light-diffusing film layer. The invention as set forth in claim 6 is a method for manufacturing a tube, characterized in that a light-diffusing film is formed on the surface of the bulb by the method as set forth in claim 4.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 schematically shows a state in which a light diffusing film according to the present invention is formed, and shows a substrate 10 such as a glass bulb of a tube.
A light scattering film 12 is formed thereon.

The light-diffusing film 12 is composed of a cloudy light-diffusing film layer 14 that contains metal oxide fine particles and is a main body that substantially exhibits light-diffusing properties, and a transparent protective film layer 16 formed in a layered manner thereon. There is.

The transparent protective film layer 16 is made of a transparent dielectric film such as a silicon oxide (SiO□) film, or a transparent conductive film such as a tin (Sn)-doped indium oxide (Ingot) film.

Further, FIG. 2 schematically shows another embodiment of the light-diffusing film of the present invention, and parts corresponding to those in FIG.

In the figure, a dielectric coating or a conductive coating 18 is provided between a base 10 and a light-diffusing film 12.

Here, the dielectric film or the conductive film 18 is made of the same material as the transparent protective film layer 16, but if the film 18 does not need to be transparent due to its function, it may not be transparent. good. Further, the coating layer 8 may have either a -layer structure or a multilayer structure of two or more layers, but the constituent material of each layer must be heat resistant to temperatures of at least about 600°C. No.

Next, the present invention will be explained using more specific examples.

First, an example of the method for forming a light scattering film according to the present invention will be described.

(1) Preparation of metal oxide film forming agent for light-diffusing film layer 14 type
Prepare an alcoholic solution of titanium alkoxide such as -nBu)4), add water etc. to it to partially polymerize the titanium compound, and partially chelate the titanium compound with a chelating agent such as acetylacetone. A solution was prepared by adjusting the concentration to an appropriate concentration using a volatile organic solvent such as ethanol or ethyl acetate. Then,
To this, n-dodecylbenzene (CsHs(CH*)
CHm) was added at a content of 15 to 35% by volume, and the entire solution was stirred well.

Finally, an organic solvent such as ethanol was added to adjust the desired concentration to obtain a film forming agent.

(2) Formation of light-diffusing film layer 14 Substrate 10 is immersed in the above-mentioned film forming agent at a humidity of 30 to 80%.
After the base body 10 is pulled up at a constant speed in an atmosphere of about 1 to
The liquid film adhering to the surface of the substrate 10 was dried by holding it in the atmosphere for 2 minutes. Next, heat treatment was performed in the atmosphere at about 500 to 600° C. for about 3 to 7 minutes to obtain a film containing fine particles of titanium oxide that was cloudy in appearance, that is, a light-diffusing film layer 14.

When using dodecylbenzene as the alkylbenzene contained in the film forming agent, the content is 15
When the amount was 35% by volume, the titanium oxide light scattering film layer exhibited the best light scattering properties and was also strong in terms of strength.

In addition to the above-mentioned n-dodecylbenzene (hereinafter referred to as "normal type") in which the alkyl side chain is linear and a phenyl group (CsHs-) is bonded to the end of the alkyl side chain, commercially available dodecylbenzene includes: The alkyl side chain is linear, but there are "soft ties" in which the phenyl group is bonded to random positions on the alkyl side chain (e.g., structural formula is attached to a random position on the alkyl side chain (hard type) (
Example: There is a structural formula ■).

Structural formula I Structural formula■ In addition, the number of carbon atoms in the alkyl side chain of soft type and hard type dodecylbenzene is 12 and 10.
It is distributed in the range of ~14 and is not constant. However, the alkylbenzene contained in the film forming agent was three types of dodecylbenzene, normal type, soft type, and hard type.Titanium oxide light scattering film layers having light scattering properties were provided, and there was almost no difference in characteristics between them.

FIG. 3 is a photograph of a scanning electron microscope (SEM) image of the surface of the titanium oxide diffusion film layer 14 of the present invention at a magnification of 5,000 times (A) and a magnification of 10,000 times (B). Further, FIG. 4 is a photograph of a SEM image at a magnification of 5,000 times (A) and a magnification of 10,000 times (B) of the surface of a titanium oxide diffusion film layer prepared under high humidity by the method of Prior Art 1.

When the surface of the light-diffusing film layer 14 of the present invention is observed by SEM, the S, EM image exhibits a unique pattern as shown in FIG. 3(A) at a magnification of about aooo times or more. S.E.
Detailed observation of the M image shows that if this pattern is a primary structure, it is formed by a group of granules connected irregularly, and that this group of granules is branched, It can be seen that there is a secondary structure having a curly hair-like or cloud-like morphology (Figure 3 (B)). Furthermore, within this secondary structure, grain sizes of 0.05 to 0. It can also be seen that it contains a tertiary structure consisting of granules of relatively uniform particle size of 5μ fused together in a chain (Figure 3 (C)).
. Since the SEM image of the granules matches the characteristic X-ray image of titanium, it can be confirmed that the granules are composed of titanium oxide. Thus, it can be seen that the above-mentioned unique pattern is woven by a complex collection of fine titanium oxide granules.

On the other hand, in the case of a titanium oxide light diffusing film layer formed by a conventional technique, for example, the method of the prior art 1, as shown in FIG. 4(A).
As shown in FIG. 1 and (B), the pattern resembles a cross section of a sponge rich in vacuoles, and the findings are clearly different from those obtained by the method of the present invention. The same applies to the methods of Prior Art 2 and 3 above.

In the above explanation, the SEM images were observed on the surface of the bare light-diffusing film layer without any thin layer overlaid thereon, but as described later, the surface of the light-diffusing film layer was layered on top of the light-diffusing film layer. Even when observing the surface of the light-diffusing film through the transparent protective layer, the pattern of the SEM image of the light-diffusing film can be observed as clearly as when observing the bare surface of the light-diffusing film at the same magnification. Therefore, it is possible to distinguish the light diffusing film of the present invention from the conventional one even by observing through the transparent protective film layer.

(3) Formation of transparent protective film layer 16 On the light-diffusing film layer 14 formed by the operation in (2) above, the transparent protective film layer 16 is formed by the following procedure using an appropriate method, for example, the immersion baking method. did. That is, a silicon compound polymer obtained by hydropolymerizing a silicon compound, such as silicon alkoxide (Si(OR) 4, where R is an alkyl group), is applied to the substrate 10 on which the light-diffusing film layer 14 has been formed by the operation (2) above. The substrate 1 is immersed in a film forming agent consisting of an alcohol solution of
0 at a constant speed and dry it, about 500 to 60
A transparent silicon oxide (Sift) coating layer 16 was formed on the light-diffusing film layer 14 by heat treatment in the atmosphere at 0° C. for about 3 to 7 minutes.

When forming a film structure in which a dielectric film or a conductive film 18 is present between the base 10 and the light-diffusing film 12, the film 18 is coated on the base 10 in advance by a conventionally known appropriate method.
After forming, the operations (2) and (3) above may be performed in this order.

Next, the characteristics of the light-diffusing film according to the present invention will be explained.

Assuming that the diffuser film would be applied to a halogen light bulb, a halogen light bulb with a cylindrical glass bulb was prepared, and films with four types of film configurations were formed on the outer surface of the glass bulb using various methods. The peeling resistance, abrasion resistance, and heat resistance of the material were investigated. The results are shown in Table 2 below.

(The following is a margin) The following layers constitute the light-diffusing film 12 in each of the films of Film Structure I to Film Structure (2) in Table 2.

That is, in the film layer [I, the titanium oxide diffuser film layer 1
In film configuration (2), there are only two layers, the first and second layers in film configuration (2), the first to third layers in film configuration (2), and the second and third layers in film configuration (2). It is. Furthermore, in film configurations (1) to (2), a layer of a transparent protective film layer 16 functioning as a protective film is coated on the light-diffusing film layer 14. Furthermore, in the membrane configuration ①, the substrate 1
A transparent film layer 18 of titanium oxide, which is one of the dielectric films, is present between the light scattering film 12 and the light scattering film 12 .

The method for forming each layer of the coating with the four types of film configurations is the general method used in the immersion firing method described in the description of the example above for each layer except the titanium oxide light scattering film layer 14. A method was used.

Three methods were used to form the light scattering film layer 14 of titanium oxide: the method according to the present invention described in the description of each example above, and the method according to two types of conventional techniques, and the differences were examined.

In Table 2, the method for forming the titanium oxide diffusion film layer in Comparative Example I is the method shown as Prior Art 1, and Comparative Example
The method for forming the titanium oxide light scattering film layer is the method shown as Prior Art 3 above.

Here, the membrane strength test was conducted as follows.

First, a peel resistance test was conducted by pasting a cellophane tape on the surface of the film, peeling it off vigorously, and then examining whether the film peeled off or not.

The abrasion resistance test was conducted by strongly rubbing the surface of the film with a finger and then examining the state of damage to the film.

The heat resistance test was conducted by examining the state of the film after leaving the sample in the atmosphere at 500° C. for 100 hours.

As is clear from Table 2 above, in the case of film configuration I, the strength of the film is low regardless of whether the titanium oxide light scattering film layer 14 is formed using the conventional method or the method according to the present invention. It was not sufficient, especially in terms of wear resistance.

On the other hand, regarding the film configurations (1) to (2) in which the transparent protective film layer 16 is formed on the light-diffusing film layer 14, when the light-diffusing film layer 14 of titanium oxide is formed by the conventional method,
It was poor in terms of peeling resistance and abrasion resistance (Comparative Example I), or it was difficult to form a film of three or more layers because peeling easily occurred (Comparative Example ■).

On the other hand, when the diffuser film layer 14 of titanium oxide is formed by the method according to the present invention, the function of the transparent protective film layer 16 is fully utilized, and in any of film configurations ① to ②, peeling resistance is achieved. It was possible to obtain a light-diffusing film 12 that was excellent in all aspects of properties, abrasion resistance, and heat resistance (Example 1).

In the above explanation, the case where the alkylbenzene contained in the film forming agent for forming the light-diffusing film layer is n-dodecylbenzene in which the number of carbon atoms in the alkyl side chain is 12 was exemplified. Carbon number is 8~
In all cases, alkylbenzenes in the range of 15 to 35% by volume gave similar results to those in Example 1 above.

Further, in the above description, titanium oxide was used as an example of the metal oxide constituting the light-diffusing film layer 14, but other metal oxides such as zirconium oxide (ZrO*) and tantalum oxide (T
Even in the case of metal oxides such as atom (Os) or composite oxides of these oxides, the same results as in Example I were obtained regarding the strength of the light-diffusing film 12.

Furthermore, although the transparent protective film layer 16 that functions as a protective film has been described using a silicon oxide (SiOs) film as an example,
In addition, the same results as in Example r were obtained for other transparent dielectric films such as magnesium fluoride (MgF2), or transparent conductive films such as indium oxide (In20s) doped with tin (Sn). Obtained.

[Effects of the Invention] As explained above, the light-diffusing film of the present invention has the microstructure as described in claim 1, so it provides excellent light-diffusing properties, and as described in claim 3, it can be integrated with a transparent protective film layer. Therefore, it has excellent mechanical strength.

Moreover, according to the method for forming a light-diffusing film according to claim 2, since the film-forming agent contains alkylbenzene, it is possible to easily form a light-diffusing film made of metal oxide granules under mild conditions.

According to the method for forming a light-diffusing film according to claim 4, it is possible to form a transparent protective film layer on top of a light-diffusing film layer made of metal oxide granules, thereby improving mechanical strength. It becomes possible to obtain an excellent light-diffusing film.

Furthermore, in the bulb according to the fifth aspect of the present invention, since the light-diffusing film is formed integrally with the transparent protective film layer, the mechanical strength of the light-diffusing film is excellent. Further, according to the method for manufacturing a bulb according to claim 6, it is possible to form a transparent protective film layer on a light-diffusing film layer made of metal oxide granules, so that mechanical strength can be improved. It becomes possible to obtain a tube having an excellent light-diffusing film.

[Brief explanation of drawings]

FIG. 1 is a schematic partially enlarged cross-sectional view of a light-diffusing film according to an embodiment of the present invention, and FIG. 2 is a schematic partially enlarged cross-sectional view of a light-diffusing film according to another embodiment of the present invention. FIG. 3 shows metal oxide structure photographs of scanning electron microscope (SEM) images of the surface of the titanium oxide diffusion film layer 14 of the present invention at a magnification of 5,000 times (A) and a magnification of 10,000 times (B), and a photograph of the metal oxide structure at a magnification of 10,000 times. It is a partial schematic diagram (C) of a SEM image. FIG. 4 shows the surface of the titanium oxide light scattering film layer prepared by the method of Prior Art 1 at magnifications of 5,000 times (A) and 1,000 times.
It is a metal oxide structure photograph diagram of a 0x (B) SEM image. O...Substrate 2...Diffusing film 4...Diffusing film layer 6...Transparent protective film layer 8...Dielectric film layer or conductive film layer O...Titanium oxide granules

Claims (6)

[Claims] (1) Metal oxide granules with a particle size of 0.05 to 0.5μ are fused together in a chain to form a branch-like, curly-hair-like, or cloud-like group, and the group is irregularly formed. A light-diffusing film characterized by being attached to the substrate surface in a series. (2) A method for forming a light-diffusing film in which an organometallic compound solution is applied as a film-forming agent to the surface of a substrate and heated to form a metal oxide fine particle film, wherein the film-forming agent has an alkyl side chain having 8 or more carbon atoms. A method for forming a light-diffusing film, characterized in that it contains an alkyl derivative of benzene having a molecular weight of 15 or less. (3) The light-diffusing film layer according to claim 1, which is formed directly on the substrate surface or on at least one dielectric film and/or conductive film formed on the substrate surface, and the light-diffusing film layer according to claim 1. 1. A light-diffusing film comprising a transparent dielectric film layer and/or a transparent conductive film layer formed thereon. (4) Directly on the substrate surface or after forming at least one dielectric coating and/or conductive coating on the substrate surface, a light-diffusing film layer is formed by the method according to claim 2, and then the light-diffusing film layer is A method for forming a light-diffusing film, comprising forming a transparent dielectric film layer and/or a transparent conductive film layer thereon. (5) A bulb made of heat-resistant glass, characterized in that the light-diffusing film according to claim 3 is formed on the surface of the bulb as a base. (6) A method for manufacturing a tube in which the bulb is made of heat-resistant glass, characterized in that the bulb is used as a base and a light-diffusing film is formed on the surface thereof by the method according to claim 4. Method.