JP5663220B2 - OPTICAL THIN FILM, ITS MANUFACTURING METHOD, AND OPTICAL MULTILAYER FILM - Google Patents

Description

  The present invention relates to an optical thin film, a method for producing the same, and an optical multilayer film, and more particularly to an optical thin film formed by alternating adsorption, a method for producing the same, and a technique for producing an optical multilayer film by laminating it with other optical thin films. .

  Various optical multilayer films in which optical thin films are laminated are used for optical products such as glasses and cameras, and devices that cause optical and visual phenomena such as display screens of display devices. For example, in order to prevent reflection of external light to the surface of a glass material or the like and to prevent reflection of an image, an antireflection film is used in optical products such as a display device and glasses / cameras. This antireflection film is a typical example of an optical multilayer film.

  The basic principle of a general single-layer antireflection film is that the refractive index is higher than that of a substrate having a thickness suitable for producing an optical path difference corresponding to ¼ of the wavelength λ of the light to be antireflection. By forming a low layer on the substrate surface, the optical path difference d between the reflected light from the upper surface of the layer and the reflected light from the lower surface is λ / 2, and the light of the opposite phase interferes with each other to reflect the reflected light. The strength is lowered. Usually, the antireflection film is often formed by an optical multilayer film having a laminated structure using a high refractive index layer and a low refractive index layer. For example, Patent Documents 1 and 2 below disclose antireflection films made of a multilayer structure. Patent Document 3 below discloses an optical multilayer film having a multilayer heterostructure in which layers formed by a sol-gel method and layers formed by an alternate adsorption method are alternately stacked. Patent Document 4 below discloses a technique for eliminating surface rainbow unevenness while ensuring flexibility by using a film containing inorganic fine particles and an organic binder.

  The essential function of the antireflection film is to reduce the reflectance of the substrate surface, but in order to use such an optical multilayer film as an industrial product, sufficient wear resistance can be ensured, It is required that the manufacturing cost can be reduced. Thus, for example, Patent Document 5 below discloses an antireflection film that improves wear resistance by using a layer containing silylated inorganic oxide fine particles. Patent Document 6 below discloses a coating composition suitable for high-speed production of an antireflection film having a uniform thickness by coating in order to reduce manufacturing costs.

  In general, there are various variations in the film formation process, and the quality, thickness accuracy, manufacturing cost, and the like of the generated film vary greatly depending on which film formation process is employed. For example, if a film forming process using a technique such as sputtering or vapor deposition in a vacuum chamber is adopted, the film thickness can be controlled with high accuracy. However, it is necessary to perform the work by placing the substrate in the vacuum chamber. For this reason, mass productivity is lacking, and manufacturing costs are inevitably high. On the other hand, a method of preparing a film forming tank in which a film forming material is dissolved in a solvent and pulling the substrate up after being immersed in this film forming tank (hereinafter referred to as a solution dipping method) is rich in mass productivity and vacuum. Since a large-scale apparatus such as a chamber is not necessary, the manufacturing cost can be greatly reduced. In particular, the method using an aqueous solution of a film forming material does not require an organic solvent, and is considered to be the method with the lowest manufacturing cost.

  However, the conventional solution dipping method in which a substrate is dipped in a solution and then pulled up to form a film on the surface thereof is inappropriate for use in the manufacturing process of an optical multilayer film. This is because the film thickness cannot be accurately controlled by a general solution immersion method. As described above, in the antireflection film, a layer having a thickness suitable for causing an optical path difference corresponding to ¼ of the wavelength λ of light to be antireflection is formed on the surface of the base material. It is very important to form it uniformly. In the case of an optical thin film or an optical multilayer film used for other purposes other than antireflection, it is necessary to sufficiently secure the accuracy of the thickness of each layer in order to perform its optical function normally. Therefore, generally, in order to form an optical thin film or an optical multilayer film, a film forming process capable of controlling the thickness with very high accuracy is required. However, in the conventional solution dipping method, the thickness of the film formed on the surface of the substrate depends on various factors such as the shape of the substrate, the concentration of the solution, the dipping time, and the influence of gravity when pulling up, For example, a film having a high thickness accuracy such as “a film having a thickness suitable for causing an optical path difference corresponding to ¼ of the wavelength λ” cannot be formed.

  Therefore, the applicant of the present invention based on the result of earnest study to provide an optical multilayer film that can be manufactured by using a solution immersion method, in Patent Document 7, a high refractive index layer showing a first refractive index. And a technique for forming an optical multilayer film obtained by laminating each optical thin film comprising a low refractive index layer having a second refractive index lower than the first refractive index on a substrate.

  In this optical multilayer film, the high refractive index layer is composed of an alternating adsorption film of the first material and the second material, and the low refractive index layer is composed of an alternating adsorption film of the third material and the fourth material. The first material layer is composed of PDDA (polydiallylamine dimethylammonium chloride), and the second material layer is composed of TALH (titanium (IV) bis (ammonium lacto) dihydroxide) which is a titanium compound. The third material layer is made of PDDA, and the fourth material layer is made of sodium silicate.

JP 2002-243902 A JP 2007-052345 A JP 2001-350015 A JP 2005-148376 A JP 2007-069471 A JP 2006-096861 A JP 2009-058703 A

  When an optical multilayer film is produced by such alternate adsorption, a high vacuum is not required unlike the dry method described above, and the mechanical strength of the thin film and double-sided coating on a curved surface do not become a problem. In addition, as in the sol-gel method, environmental control such as temperature and humidity is highly necessary because the hydrolysis and polymerization reaction proceeds depending on the stability of film-forming materials in organic solvents and temperature and humidity. Since it does not require high-temperature baking for stabilizing the thin film, it is suitable for film formation on a resin substrate. In addition, the optical multilayer film itself is characterized by excellent mechanical strength and optical characteristics.

  However, since TALH used as a precursor of titanium oxide has a fast hydrolysis reaction at the lactic acid site, a phenomenon occurs in which titania particles are precipitated and the solution becomes clouded. As a result, an optical multilayer is formed. Since the transparency of the film decreases due to the increase in surface roughness (10 nm or more) accompanying particle precipitation, further improvement has been desired.

  The present invention has been made to solve the above-mentioned conventional problems. An optical thin film having excellent transparency and excellent transparency compared with the case where a conventional titanium lactate ammonium salt is used as a film forming material, and It is an object to provide a technique capable of forming a laminated optical multilayer film.

The present invention relates to a water-soluble metal complex that becomes a multimer in an aqueous solution, wherein the raw material of the water-soluble metal complex is a compound of Ti, Zr, or Hf, and the ligand is acetylacetone, diamine, pyridine The above-mentioned problems are solved by forming an optical thin film characterized by being formed using at least one selected from the group consisting of a group .

Here, before hear compound is a metal alkoxide, an organic acid salt may be either an inorganic acid salt. Also, the diamines ethylenediamine, ethylenediaminetetraacetic acid, 1,2-propanediamine, may be at least one selected from the group consisting of 1,3-propanediamine, further, the pyridines, It may be one or more selected from the group consisting of pyridine and bipyridine.

The present invention also provides an aqueous solution of an electrolyte polymer and a water-soluble metal complex that becomes a multimer in the aqueous solution, wherein the raw material of the water-soluble metal complex is a compound of any one of Ti, Zr, and Hf. A method for producing an optical thin film characterized in that an alternating adsorption film is formed by alternately immersing a base material in an aqueous solution of one or more selected from the group consisting of acetylacetone, diamines, and pyridines, and By doing so, the above-mentioned problem is solved in the same manner.

  Here, the electrolyte polymer may be made of a material selected from the group consisting of polydiallylamine dimethylammonium chloride, polyallylamine hydrochloride, polyethylimine, polyacrylic acid, and polysulfonic acid.

  The present invention further includes an optical multilayer film, wherein the first optical thin film according to claim 1 and one or more second optical thin films formed by a dry process or a wet process are laminated. By doing so, the above-mentioned problems are solved.

  Here, the first optical thin film is a high refractive index layer exhibiting a first refractive index, and the second optical thin film is a low refractive index layer exhibiting a second refractive index lower than the first refractive index. The high refractive index layer is constituted by an alternating adsorption film of a first material and a second material, and the low refractive index layer is constituted by an alternating adsorption film of a third material and a fourth material, The first material and the third material are each composed of a material selected from the group consisting of polydiallylamine dimethylammonium chloride, polyallylamine hydrochloride, polyethylimine, polyacrylic acid, and polysulfonic acid. Also good.

  According to the present invention, by using a water-soluble metal complex that becomes a multimer in an aqueous solution, it is possible to form a film by using a solution immersion method, and it is possible to control the thickness with high accuracy, and extremely It has become possible to provide an optical thin film with high transparency. This is thought to be because the hydrolysis reaction is suppressed because the metal complex forms a multimer in the aqueous solution.

  In particular, the alternately adsorbing membrane comprises a layer mainly composed of an electrolyte polymer selected from the group consisting of polydiallylamine dimethylammonium chloride, polyallylamine hydrochloride, polyethylimine, polyacrylic acid, and polysulfonic acid, and the water-soluble layer. By forming a film having a metal complex as a main component and alternating layers, a film having sufficient wear resistance can be uniformly formed on the substrate surface.

  In the method for producing an optical thin film according to the present invention, the base material is alternately immersed a plurality of times in a film formation tank containing an aqueous solution of an electrolyte polymer and a film formation tank containing an aqueous solution of the water-soluble metal complex. Thus, a high refractive index layer or a low refractive index layer composed of alternating adsorption films can be formed, and the film thickness can be controlled by the number of times of immersion in each film formation tank. Therefore, mass productivity can be improved and manufacturing cost can be reduced.

Side sectional view showing the structure of a general antireflection film having a laminated structure of a high refractive index layer H and a low refractive index layer L Conceptual diagram showing the principle of manufacturing a general alternating adsorption film Conceptual diagram showing how the electrolyte polymer is adsorbed on the substrate surface based on the manufacturing principle shown in FIG. The conceptual diagram which shows the more concrete adsorption state in the 2nd immersion process based on the manufacturing principle shown in FIG. The conceptual diagram which shows the structure of the alternating adsorption film formed when the immersion process shown in FIG. 4 is performed 6 times in total Side sectional view showing the basic structure of an antireflection film according to the present invention The figure which shows the molecular structure of PDDA used as the raw material of the layer 11 and the layer 13 which are shown in FIG. The figure which shows the molecular structure of ACPT used as the raw material of the layer 12 shown in FIG. The figure which shows the molecular structure of the sodium silicate used as the raw material of the layer 14 shown in FIG. The graph which shows the measured value of the single-sided reflectance of the antireflection film shown in FIG. The figure which shows the molecular structure of some examples of the electrolyte polymer which can be used instead of PDDA in this invention. Photomicrograph showing the surface state of each multilayer film of conventional TALH and ACPT of the present invention The conceptual diagram which shows the image data of the result of having measured the surface roughness of each multilayer film of conventional TALH and ACPT of this invention with an atomic force microscope Diagram showing contrast of transmittance of each multilayer film of conventional TALH and ACPT of the present invention The diagram which shows the antireflection characteristic of the multilayer film which consists of ACPT of this invention

  Hereinafter, the present invention will be described based on the illustrated embodiments.

<<< §1. Basic structure of antireflection film according to the present invention >>
The present invention can be widely applied to a technique for forming various optical multilayer films using a solution immersion method. Hereinafter, embodiments in which the present invention is used for a technique for forming an antireflection film will be described. . The antireflection film according to the present invention has a structure in which a high-refractive index layer H and a low-refractive index layer L are laminated on a base material 10, as shown in the side sectional view of FIG. In general, an antireflection film having a thickness (corrected thickness in consideration of the refractive index n) suitable for generating an optical path difference corresponding to one-fourth of the wavelength λ of light to be antireflective is used. When formed on the surface of the material 10, when light is irradiated from above, the reflected light path from the upper surface of the film (interface with the atmosphere) and the reflected light from the lower surface of the film (interface with the substrate 10) An optical path difference of λ / 2 (half wavelength) is generated between the optical paths and cancel each other. The antireflection film suppresses reflection from the surface of the base material 10 using such a principle.

  For example, in order to prevent reflection of light irradiated on the substrate surface, a film having a thickness of λ / (4 · n) may be formed (n is the refractive index of the film).

  As shown in FIG. 1, an antireflection film having a two-layer structure is also widely used. For example, in an antireflection film having a structure in which a high refractive index layer H having a thickness λ / (4 · nH) and a low refractive index layer L having a thickness λ / (4 · nL) are laminated on the substrate 10. , It is known that the light reflected at the illustrated interfaces S0, S1, and S2 weakens each other with respect to light having an incident angle θ = 0 °, and a good antireflection effect is obtained (nH is a high refractive index layer H). NL is the refractive index of the low refractive index layer L). Therefore, the antireflection film having the structure shown in FIG. 1 is widely used not only for display devices but also for optical products such as glasses and cameras.

  Theoretically, if the refractive index of the atmosphere and the low refractive index layer L are different, reflection at the interface S0 occurs, and if the refractive index of the low refractive index layer L and the high refractive index layer H is different, the reflection at the interface S1. If the refractive index of the high refractive index layer H and the base material 10 are different, reflection at the interface S2 occurs. Therefore, even if the magnitude relationship between the refractive indexes of the layers is not as shown in the illustrated example, theoretically, an antireflection effect can be obtained. For example, the refractive index of the low refractive index layer L and the base material 10 may be equal. In practice, as shown in the figure, a structure in which a high refractive index layer H and a low refractive index layer L are laminated on the base material 10 in the order shown is often used.

  Further, the “low refractive index” of the low refractive index layer L in the present application means that the refractive index is low in comparison with the high refractive index layer H, and the “high refractive index” of the high refractive index layer H in the present application is Means that the refractive index is high in comparison with the low refractive index layer L, and does not mean “high or low” with the base material 10 as a comparison target. However, practically, a material having a higher refractive index than the base material 10 is used as the material for the high refractive index layer H, and a material having a lower refractive index than the base material 10 is used as the material for the low refractive index layer L. Is often used.

  Therefore, in each of the embodiments described later, a high refractive index layer H having a higher refractive index than the material of the base material 10 is formed on the upper surface of the base material 10, and the refractive index of the upper surface of the base material 10 is higher than that of the material of the base material 10. In this example, a low low refractive index layer L is formed. FIG. 1 shows an antireflection film formed by laminating one high refractive index layer H and one low refractive index layer L on the upper surface of the base material 10. Alternatively, an antireflection film in which the high refractive index layer H and the low refractive index layer L are alternately laminated a plurality of times may be formed.

  In short, the antireflection film according to the present invention is based on the high refractive index layer H exhibiting the first refractive index and the low refractive index layer L exhibiting the second refractive index lower than the first refractive index. It is a film formed by laminating on a material, and the thickness of each layer is suitable for producing an optical reflection difference corresponding to one-fourth of the wavelength λ of light to be antireflective (the antireflection effect). It is only necessary to be set to (dimension).

  The visible wavelength range of human beings is about 400 nm to 650 nm, and theoretically, all light in these wavelength ranges should be the light to be subjected to antireflection, but in determining the thickness of each layer. Then, it is necessary to determine a representative wavelength λ. In general anti-reflection coating design, λ = 550 nm is often set as the wavelength of light to be anti-reflection as a wavelength value that is near the center of the visible wavelength range and has high visibility with the naked eye. Therefore, also in each of the embodiments described later, the wavelength λ of light that is an object of antireflection is set to 550 nm. Therefore, for example, if the refractive index of the high refractive index layer H shown in FIG. 1 is nH = 1.8, the thickness is about 76 nm by the calculation of 550 / (4 × 1.8).

  Of course, the effect of the light intensity being weakened by mutual interference is not limited to the case where light whose phases are accurately shifted by half a wavelength interfere with each other. The effect of reducing the strength is sufficiently obtained. In addition, considering that the wavelength of light to be antireflective extends from 400 nm to 650 nm and the incident angle θ varies, the thickness of each layer is accurately set to a specific value calculated under specific conditions. There is no need to set to. However, if the thickness dimension deviates significantly, the antireflection effect cannot be obtained.

  Therefore, in order to form the antireflection film, it is essential to control the film thickness at a dimensional level close to the wavelength of light. For this reason, conventionally, an antireflection film has generally been generated using a film forming process suitable for film thickness control such as sputtering or vapor deposition in a vacuum chamber. However, the film forming process using the vacuum chamber has an advantage that the film thickness can be controlled with high accuracy, but it is necessary to put the base material in the vacuum chamber to perform the operation, so that the mass productivity is lacking. There is a problem that the manufacturing cost increases.

  The basic idea of the present invention is a method in which a high refractive index layer H and a low refractive index layer L shown in FIG. Therefore, it is possible to form a film and to control the film thickness with high accuracy. If such a method is adopted, mass productivity can be improved, and a large-scale device such as a vacuum chamber is not necessary, so that the manufacturing cost can be greatly reduced.

  Thus, in understanding the present invention, it is very important to deepen the understanding of the alternately adsorbed film. Therefore, in the next section 2, the configuration of the alternating adsorption film and the process for producing the same will be described in detail.

<<< §2. Alternating adsorption film configuration and process for making it >>
A method for producing a composite organic thin film using a technique called layer-by-layer electrostatic self-assembly was originally described in 1992 by G.C. It is a method published by Decker et al. (Decher. G, Hong. JD and J. Schmit: Thin Solid Films, 210/211, p.831 (1992)). In this method, an aqueous solution of a positive electrolyte polymer (cation) and an aqueous solution of a negative electrolyte polymer (anion) are prepared in separate containers, and an initial surface charge is applied to these containers (film forming material). ) Are alternately immersed to obtain a composite organic ultrathin film (alternate adsorption film) having a multilayer structure on the substrate.

  For example, when a glass substrate is used as a base material to be a film forming material, the surface of the glass substrate is subjected to a hydrophilic treatment to introduce OH-groups on the surface to give a negative charge as an initial surface charge. Then, if this negatively charged glass substrate is dipped in a positive electrolyte polymer aqueous solution, the positive electrolyte polymer is adsorbed on the surface by Coulomb force until at least the surface charge is neutralized. Is formed. The surface portion of the ultrathin film thus formed is positively charged. Therefore, this time, if this glass substrate is immersed in a negative electrolyte polymer aqueous solution, the negative electrolyte polymer is adsorbed by the Coulomb force, and one ultra-thin film is formed. In this way, by alternately immersing the glass substrate in two containers, it is possible to alternately form an ultrathin film layer made of a positive electrolyte polymer and an ultrathin film layer made of a negative electrolyte polymer. It is possible to form a composite organic thin film having

  FIG. 2 is a conceptual diagram showing the manufacturing principle of a general alternating adsorption film. In the figure, an aqueous solution of a positive electrolyte polymer (cation) is placed in a first tank 100, and an aqueous solution of a negative electrolyte polymer (anion) is placed in a second tank 200. Here, the base material 10 which consists of a glass substrate etc. is prepared, the surface is hydrophilized, OH-group is introduce | transduced into the surface, and a negative charge is given as an initial surface charge. FIG. 3A is a conceptual diagram showing a state in which the surface of the substrate 10 is negatively charged in this way. Subsequently, when the negatively charged substrate 10 is placed in the first tank 100, the positive electrolyte polymer comes into contact with the surface of the substrate 10 and is adsorbed by the Coulomb force. FIG. 3B is a conceptual diagram showing a state in which the positive electrolyte polymer is adsorbed. Here, if this base material 10 is put in the 2nd tank 200, a negative electrolyte polymer will contact the surface of the base material 10 this time, and will adsorb | suck with a Coulomb force. FIG.3 (c) is a conceptual diagram which shows the state which the negative electrolyte polymer adsorb | sucked. Thus, if the base material 10 is alternately immersed in the 1st tank 100 and the 2nd tank 200, on the surface of the base material 10, the layer which consists of a positive electrophilic polymer, and a negative electrolyte polymer As a result, the alternating adsorption film having a multilayer structure is finally formed.

  However, the conceptual diagram shown in FIG. 3 shows a simplified model for explaining the principle. In practice, the thin film is formed in a state close to the conceptual diagram shown in FIG. 4 or FIG. Seem. FIG. 4 is a conceptual diagram showing an adsorption state in the second immersion process (a process when the base material 10 is taken out from the first tank 100 and immersed in the second tank 200). The first layer thin film A1 made of a positive electrolyte polymer has already been formed on the surface of the base material 10 by the first dipping treatment, and the second tank is formed by the Coulomb force acting on the thin film A1. The negative electrolyte polymer b in 200 will be adsorbed on the surface. If the base material 10 is immersed in the second tank 200 for a certain period of time, the negative electrolyte polymer b in the second tank 200 is successively adsorbed on the surface, and a second layer of thin film B2 is formed. It will be. However, when a certain amount of time has passed and the second layer thin film B2 made of the negative electrolyte polymer b becomes thicker, the Coulomb force by the thin film A1 no longer acts, and at that time the adsorption reaches the saturation point. Will be greeted.

  FIG. 5 is a conceptual diagram showing the structure of the alternating adsorption film formed when such immersion treatment is performed a total of six times. Here, the thin films A1, A3, A5 constituting the odd-numbered layers are layers made of a positive electrolyte polymer, and the thin films B2, B4, B6 constituting the even-numbered layers are layers made of a negative electrolyte polymer. It is. As described above, the adsorption of the electrolyte polymer is caused by the action of the Coulomb force. Therefore, if a sufficient immersion time is secured until the Coulomb force stops acting due to electrical neutralization, the adsorption reaches the saturation point. As a result, the thickness of each layer no longer increases. In other words, the film thickness of each layer can be accurately controlled to a predetermined value. As described above, the fact that the film thickness can be accurately controlled regardless of the solution immersion method is an advantage of using the alternately adsorbing film.

  Since the progress of the adsorption phenomenon of the electrolyte polymer changes depending on conditions such as the concentration of the electrolyte polymer in the solution and the pH value, the packing density of molecules in each layer also depends on these conditions. For this reason, even when sufficient immersion time until the adsorption reaches the saturation point is secured, the thickness of the actually formed layer varies depending on conditions such as the concentration of the electrolyte polymer in the solution and the pH value. Therefore, when mass production is performed, it is necessary to always use an electrolyte polymer solution having a specific concentration and a specific pH value, and manage the film thickness so as not to fluctuate.

  In addition, when the base material is pulled up from the solution layer before reaching the saturation point, the thickness of each layer is smaller than the thickness when immersed until reaching the saturation point, but the thickness is controlled by the immersion time. It is possible. Therefore, if the immersion time can be accurately controlled during the film formation process, it is not always necessary to perform the immersion until the saturation point is reached, and the immersion time may be raised halfway.

  Alternatively, if the quartz resonator is alternately immersed in each solution tank together with the base material 10 to form an alternate adsorption film equivalent to the surface of the base material 10 on the surface of the quartz resonator, By monitoring the change in the oscillation frequency (corresponding to the change in the mass of the alternately adsorbed film formed), it is possible to accurately control the film thickness. Such a film thickness control method is disclosed in, for example, International Publication No. WO 00/13806.

  In practice, when the base material 10 is lifted from the first tank 100 and moved to the second tank 200, or when it is lifted from the second tank 200 and moved to the first tank 100, pure water is used. It is preferable to pass through a rinsing bath.

  G. At the beginning of the announcement by Decker et al., This alternate adsorption film formation method was understood as a method of alternately immersing the substrate in a positive electrolyte polymer (cation) aqueous solution and a negative electrolyte polymer (anion) aqueous solution, Recently, it has become clear that it is not always necessary to use an aqueous solution of an electrolyte polymer. Specifically, examples using inorganic electrolytes and examples using organic solvents have been reported (for example, T. Ito, Y. Okayama, S. Shiratori: Thin Solid Films 393 (2001) 138). Therefore, the “alternate adsorption film” referred to in the present specification means that a positive electrolyte (cation) solution and a negative electrolyte (anion) solution are prepared in separate containers, and the substrates are alternately immersed in these containers. By doing this, the film formed on the surface of the substrate is widely meant.

<<< §3. Configuration of Antireflection Film According to the Present Invention >>
As shown in FIG. 1, the antireflection film according to the present invention basically has a high refractive index layer H exhibiting a first refractive index and a second refractive index lower than the first refractive index. The low-refractive index layer L shown in FIG. 1 is laminated on the base material 10 and is characterized in that the high-refractive index layer H and the low-refractive index layer L are configured by alternating adsorption films, respectively. It is in the point made.

  FIG. 6 is a side sectional view showing the basic structure of the antireflection film according to the present invention. The portion indicated by H in FIG. 6 is the high refractive index layer H shown in FIG. 1, and the portion indicated by L in FIG. 6 is the low refractive index layer L shown in FIG. As described in §2, since the alternating adsorption film has a structure in which layers of two kinds of materials are alternately stacked, the high refractive index layer H includes the first material layer 11 and the second material layer. The low refractive index layer L has a structure in which the third material layers 13 and the fourth material layers 14 are alternately stacked.

  For convenience of illustration, FIG. 6 shows each layer enlarged in the thickness direction as compared with FIG. 1, but the thicknesses of the high refractive index layer H and the low refractive index layer L are both reflected. There is no change in that the layer has a thickness suitable for producing an optical path difference corresponding to ¼ of the wavelength λ of the light to be prevented. That is, in the example shown in FIG. 6 as well, if λ = 550 nm is set as the wavelength of the light to be prevented from being reflected, and the conditions are set so as to prevent reflection of light incident from vertically above, high refraction The thickness of the refractive index layer H may be set to a value close to 550 / (4 · nH) nm, and the thickness of the low refractive index layer L may be set to a value close to 550 / (4 · nL) nm (here , NH, and nL are the refractive indexes of the high refractive index layer H and the low refractive index layer L as a whole, as will be described later).

  Further, FIG. 6 shows an example in which each of the high refractive index layer H and the low refractive index layer L is composed of 10 material layers (adsorption layers formed by being immersed once in the solution layer). (For example, the high refractive index layer H includes five first material layers 11 and five second material layers 12 in total, and the low refractive index layer L includes five third material layers 13. The total number of the fourth material layer 14 is 10), and the actual number of the material layers is determined based on what is used for each material, the concentration in the solution, and the pH value of the solution. It depends on the conditions such as how much it should be and how to raise the substrate in the alternate adsorption film forming process. This is because the thickness of the high refractive index layer H and the low refractive index layer L must be set to a thickness suitable for producing an optical path difference corresponding to ¼ of the wavelength λ of the light, and the individual materials. This is because the thickness of one layer depends on the above conditions.

  For example, as described in §2, in the process of forming the alternating adsorption film, when the base material is pulled up from the solution tank before reaching the saturation point, the thickness of one material layer depends on the immersion time. Different. If it is pulled up quickly, the thickness of one material layer becomes small. Therefore, in order to form the high refractive index layer H or the low refractive index layer L having a predetermined thickness, the shorter the immersion time, the shorter the material layer Need to be increased (increase the number of times of alternately immersing in the solution tank). Further, in the process of forming the alternately adsorbing film, even when the base material is immersed in the solution tank for a sufficient time until the saturation point is reached, the thickness of one material layer is determined depending on the type of material and the solution. Therefore, the actual number of material layers differs depending on these conditions.

  In short, the high-refractive index layer H has the first material layer 11 and the second material until the final thickness becomes a thickness that causes an optical path difference of ¼ of the wavelength λ of the light to be antireflection. The low refractive index layer L may be configured by alternately stacking the third material layer 13 and the fourth material layer 14 until the same thickness is obtained. What is necessary is just to comprise. The number of individual material layers to be finally stacked may be determined by trial and error for each film formation condition.

  In the case of the basic embodiment of the present invention described in §6, the first material layer is composed of PDDA (polydiallylaminedimethylammonium chloride), and the second material layer is composed of a water-soluble titanium complex that becomes a multimer in an aqueous solution. The third material layer is composed of PDDA, and the fourth material layer is composed of sodium silicate. In this embodiment, the high refractive index layer H is formed by alternately laminating 15 PDDA material layers and 15 ammonium citratoperoxotitanate (IV): ammonium citratoperoxotitanate (hereinafter referred to as ACPT) material layers. The low refractive index layer L is formed by alternately laminating 40 PDDA material layers and 40 sodium silicate material layers, and finally a total of 110 laminated structures. As shown, an antireflection film is formed.

<<< §4. Optical characteristics of antireflection film according to the present invention >>
As shown in FIG. 6, the antireflection film according to the present invention is composed of four types of material layers: a first material layer 11, a second material layer 12, a third material layer 13, and a fourth material layer 14. In contrast to the multilayer structure, the antireflection film shown in FIG. 1 is a two-layer structure of a high refractive index layer H and a low refractive index layer L. From this point of view, the physical structure of the structure shown in FIG. 1 is greatly different from the physical structure of the structure shown in FIG. However, the inventor of the present application has found that both are structures that behave optically in an equal manner.

  That is, in the structure shown in FIG. 6, if each material layer is considered to be an optically independent layer having an individual refractive index, light is reflected at each interface of each material layer. . For example, the interface between the upper surface of the base material 10 and the first material layer 11 positioned above it, the interface between the upper surface of the first material layer 11 and the second material layer 12 positioned above it, and Considering the interface between the upper surface of the second material layer 12 and the first material layer 11 located above the second material layer 12, the interface between these material layers is the boundary between the material layers having different refractive indexes. Therefore, reflection of light occurs at each interface.

  However, in practice, the optical behavior of the structure shown in FIG. 6 is close to the optical behavior of the structure shown in FIG. That is, the high refractive index layer H shown as a multilayer structure in FIG. 6 behaves as a single optical layer having a predetermined refractive index as a whole, and is shown as a multilayer structure in FIG. The low refractive index layer L also behaves as a single optical layer having a predetermined refractive index as a whole. Eventually, from the high refractive index layer H and the low refractive index layer L shown in FIG. The resulting structure can function as an antireflection film, similarly to the structure shown in FIG.

  As described above, at this stage, the detailed theoretical consideration about the reason why the alternating adsorption film composed of the multilayer material layers shown in FIG. 6 has the same optical characteristics as the two-layer antireflection film shown in FIG. Not done. However, since the thickness of each material layer 11, 12, 13, 14 is very small compared to the wavelength of light, the inventor of the present application has a unique refraction in terms of optical behavior in each individual material layer. It is not functioning as a single layer having a refractive index, and it is a unique refractive index for the first time in a block unit called a high refractive index layer H or a block unit called a low refractive index layer L having a thickness closer to the wavelength of light I think that it may function as a single layer.

  For example, in the case of the basic embodiment described later, since the high refractive index layer H is composed of a total of 30 material layers (since the material layers 11 and 12 are alternately laminated 15 times each), λ / (4 · nH) = about 80 nm, the thickness of one material layer is only about 2 nm. It is considered that a single material layer having such a small thickness can no longer function as a single layer having an intrinsic refractive index in terms of optical behavior. Therefore, in considering the optical phenomenon, it is not appropriate to take a microscopic view of each material layer such as the material layers 11 and 12, and it is necessary to grasp from a macro viewpoint.

  Here, if the structure shown in FIG. 6 is observed from a macro viewpoint, the high refractive index layer H is configured such that the first material layer 11 and the second material layer 12 having a minute thickness are alternately arranged repeatedly. As a whole, it behaves as one optical layer made of a fusion material of the first material and the second material, and the low refractive index layer L has a minute thickness. Since the third material layer 13 and the fourth material layer 14 have a structure in which the third material layer 14 and the fourth material layer 14 are alternately and repeatedly arranged, one optical device made of a fusion material of the third material and the fourth material as a whole. It is thought that it may behave as a typical layer.

  Therefore, the actual behavior of light when there is incident light from above in FIG. 6 may be treated as light reflection occurs at the interfaces S0, S1, and S2, which are the boundary portions of the layers in a macro view. It will be. Of course, actually, the light is not reflected only at the positions of the interfaces S0, S1, and S2, and it is considered that a more complicated phenomenon occurs from a microscopic viewpoint. Is considered that there is no problem in treating light at the interfaces S0, S1, and S2 as reflecting light at least for capturing the optical behavior as an antireflection film. As a result, the optical characteristics of the structure shown in FIG. 6 as the antireflection film are almost the same as those of the conventional antireflection film shown in FIG.

  The refractive index of the high refractive index layer H as a whole is determined based on the refractive index of the first material and the refractive index of the second material (it is expected that the average value of both will be obtained). ) Similarly, the refractive index of the low refractive index layer L as a whole is determined based on the refractive index of the third material and the refractive index of the fourth material (again, an average value of both). Is expected). Here, the refractive index of the high refractive index layer H (the refractive index of the entire layer) needs to be set higher than the refractive index of the low refractive index layer L (the refractive index of the entire layer). As the fourth material, it is necessary to select a material having a predetermined refractive index so that such setting is possible.

  Specifically, the material selection is performed such that the refractive index of the first material and the refractive index of the second material are both higher than the refractive index of the third material and the refractive index of the fourth material. This is one method, but is not necessarily limited to a selection method that satisfies such conditions. For example, even if the refractive index of the second material and the refractive index of the fourth material are equal, if the refractive index of the first material is higher than the refractive index of the third material, the refractive index of the high refractive index layer H Can be set to be higher than the refractive index of the low refractive index layer L.

<<< §5. Preferred materials for each material layer >>
The antireflection film according to the present invention has, for example, a high refractive index layer H exhibiting a first refractive index nH and a second refractive index nL lower than the first refractive index, as in the example shown in FIG. And a low refractive index layer L shown in FIG. The example shown in FIG. 6 has a two-layer structure in which a high refractive index layer H and a low refractive index layer L are laminated one by one, but of course, high refractive index layer H / low refractive index layer L / high refractive index. A structure in which a plurality of layers are stacked, such as a refractive index layer H / a low refractive index layer L /.

  An important feature of the present invention is that, as shown in the figure, the high refractive index layer H is constituted by an alternating adsorption film in which the first material layers 11 and the second material layers 12 are alternately laminated, and the low refractive index layer L Is constituted by an alternating adsorption film in which the third material layer 13 and the fourth material layer 14 are alternately laminated. Therefore, here, it will be examined what kind of material should be used as the material constituting each material layer.

  First, from an optical point of view to fulfill the function as an antireflection film, it is necessary to use a material having a specific refractive index that satisfies specific conditions. That is, as described above, the refractive index of the high refractive index layer H (the refractive index of the entire layer) is higher than the refractive index of the low refractive index layer L (the refractive index of the entire layer). A fourth material needs to be selected.

  On the other hand, considering the process of forming the antireflection film, the first to fourth materials need to be materials suitable for forming the alternating adsorption film. As described in section 2 with reference to FIG. 2, the alternating adsorption film is formed by preparing a positive electrolyte (cation) solution and a negative electrolyte (anion) solution in separate containers. The base material is alternately immersed in the container. As described above, each material does not necessarily need to be a water-soluble polymer, but it needs to be at least an electrolyte. In addition, regarding the relationship between the first material and the second material, and the relationship between the third material and the fourth material, one must be a positive electrolyte while the other must be a negative electrolyte. .

  Further, considering that an antireflection film is supplied as an industrial product, durability that can withstand practical use is required. That is, as an antireflection film used for optical products such as display screens and glasses / cameras, it is necessary to ensure sufficient hardness so that they are not easily damaged. Furthermore, in applications such as display screens, glasses / cameras, etc., it is premised that the substrate on which the film is to be formed is transparent, so the antireflection film itself must also be made of a transparent material.

  As a result of comprehensively considering these various conditions, the present inventor used an electrolyte polymer (specifically, polydiallylamine) as the first material and the third material in forming the antireflection film according to the present invention. Dimethylammonium chloride, polyallylamine hydrochloride, polyethylimine, polyacrylic acid, polysulfonic acid, etc.), and the second material and the fourth material are composed of inorganic electrolyte as a main component. I think it is preferable to configure. The reason is as follows.

  First, the first reason that the second material and the fourth material are made of a material mainly composed of an inorganic electrolyte is that a combination of transparent materials having various refractive indexes can be prepared. The electrolyte polymer also has a specific refractive index for each material, but in general, the refractive indexes of many electrolyte polymers are all about 1.5 to 1.6, and the refractive indexes are large. It is difficult to select two different materials. On the other hand, since the refractive index of the inorganic electrolyte is relatively widely distributed, it is possible to select two materials having greatly different refractive indexes. In the present invention, since it is necessary to prepare a high refractive index layer H and a low refractive index tank L having different refractive indexes, the second material and the fourth material are made of a material mainly composed of an inorganic electrolyte. Convenient.

  The second reason why the second material and the fourth material are composed of a material mainly composed of an inorganic electrolyte is advantageous for practical use as an industrial product and for ensuring sufficient hardness that is not easily damaged. Because it becomes. In general, since the polymer layer has a lower hardness than the inorganic material layer, the antireflection film formed only from the polymer layer is easily damaged. If the second material and the fourth material are composed of a material mainly composed of an inorganic electrolyte, sufficient hardness can be secured by the portions of the second material layer 12 and the fourth material layer 14. Specifically, a metal compound such as a metal oxide is optimal for use as the second material and the fourth material.

  On the other hand, the reason why the first material and the third material are made of a material whose main component is an electrolyte polymer is that there is an effect in promoting smooth film formation of the alternating adsorption film. Originally, the alternately adsorbing film was conceived using two types of electrolyte polymer aqueous solutions, and from the viewpoint of uniform film formation, it is preferable that all materials are constituted by the electrolyte polymer. Therefore, in carrying out the present invention, it is preferable to promote smooth film formation by using the first material and the third material as electrolyte polymers. Specifically, when any one of polydiallylamine dimethylammonium chloride, polyallylamine hydrochloride, polyethylimine, polyacrylic acid, and polysulfonic acid is used as the first material and the third material, uniform film formation is achieved. It became possible.

<<< §6. Antireflective coating according to basic embodiment >>
In view of the situation described in §5, the inventor of the present application configures the first material layer 11 and the third material layer 13 of a material mainly composed of an electrolyte polymer in the antireflection film shown in FIG. It is considered best to form the material layer 12 and the fourth material layer 14 of a material mainly composed of an inorganic electrolyte. Then, sufficient hardness can be ensured by the second material layer 12 and the fourth material layer 14, and materials having different refractive indexes are selected as the second material and the fourth material. In addition, the first material layer 11 and the third material layer 13 made of the electrolyte polymer serve as a binder layer, and smooth film formation (uniform film formation) of the alternately adsorbed films can be achieved. Can be encouraged.

  As described above, since there is no great difference in the refractive index of the electrolyte polymer, the first material layer 11 and the third material layer 13 are substantially made of an electrolyte polymer having the same refractive index. It doesn't matter. In other words, the first material and the third material need only be able to serve as a binder layer, and thus there is no need to consider the refractive index. Therefore, practically, the first material and the third material may be composed of the same electrolyte polymer.

  In the basic embodiment of the present invention, both the first material layer 11 and the third material layer 13 are made of PDDA. This PDDA (polydiallylamine dimethylammonium chloride) is a water-soluble positive electrolyte polymer represented by the structural formula shown in FIG. 7, and its aqueous solution is used as a cationic aqueous solution in the first tank 100 shown in FIG. can do.

  Thus, even if the refractive index of the first material layer 11 and the refractive index of the third material layer 13 are the same (that is, the first material and the third material are made of the same material such as PDDA). However, if the material is selected such that the refractive index of the second material layer 12 is higher than the refractive index of the fourth material layer 14, the refractive index nH of the high refractive index layer H (as the entire layer) Can be set to be higher than the refractive index nL of the low refractive index layer L (the refractive index of the entire layer).

  In terms of the relationship with the refractive index of the substrate 10, the refractive index nH of the high refractive index layer H (the refractive index of the entire layer) is practically lower than the refractive index of the substrate 10. It is preferable to set the refractive index nL of the refractive index layer L (the refractive index of the entire layer) to be lower than the refractive index of the substrate 10. For this purpose, a material having a refractive index higher than that of the base material 10 is selected as the material (inorganic electrolyte) of the second material layer 12, and the material (inorganic electrolyte) of the fourth material layer 14 is selected. A material having a refractive index lower than that of the substrate 10 may be selected.

In the basic embodiment of the present invention, the second material layer 12 is composed of a titanium compound generated from ACPT (ammonium citatoperoxotitanate (IV)), and the fourth material layer 14 is composed of sodium silicate. ing. ACPT is a water-soluble negative electrolyte composed of a tetranuclear complex represented by the structural formula shown in FIG. 8, and its aqueous solution should be used as an anion aqueous solution in the second film formation tank 200 shown in FIG. Can do. This ACPT is a material known as a precursor of titanium oxide. When the substrate 10 is dipped in the ACPT aqueous solution and pulled up, a titanium compound containing titanium oxide (titanium oxide “TiO ₂ ”, titanate “ A film of a compound including a compound such as “Ti (OH) ₄ ” is formed.

On the other hand, sodium silicate (Na ₂ SiO ₃ ) is a water-soluble negative electrolyte represented by the structural formula shown in FIG. 9, and its aqueous solution is also used as an anion aqueous solution in the second tank 200 shown in FIG. Can be used. When the base material 10 is dipped in the aqueous solution of sodium silicate and pulled up, a sodium silicate film is formed.

  As a result, the antireflection film according to the basic embodiment of the present invention has a layer structure as shown in FIG. 6, and the first material layer 11 is a layer made of PDDA which is an electrolyte polymer. The material layer 12 is a layer mainly composed of titanium oxide, which is an inorganic electrolyte, the third material layer 13 is a layer made of PDDA, which is an electrolyte polymer, and the fourth material layer 14 is silicic acid, which is an inorganic electrolyte. This is a layer mainly composed of sodium.

  Here, as general measurement values, the refractive index of PDDA is 1.5 to 1.6, the refractive index of titanium oxide is 1.7 to 2.0, and the refractive index of sodium silicate is 1.50. Although the measured value in the case of the antireflection film prepared as the basic embodiment is about 1.52, the refractive index nH of the high refractive index layer H as a whole is 1.8, and the low refractive index layer L The refractive index nL of the entire layer was 1.5. Therefore, the thickness of the high refractive index layer H is set to λ / (4 · nH) = 76 nm using λ = 550 nm and nH = 1.8, and the thickness of the low refractive index layer L is λ = 550 nm, Using nL = 1.5, λ / (4 · nL) = 92 nm was set.

  FIG. 10 is a graph showing measured values of the single-sided reflectance of the antireflection film according to such a basic embodiment, in which the horizontal axis represents the wavelength (unit: nm) and the vertical axis represents the single-sided reflectance (unit:%). ing. A graph G1 indicated by a solid line indicates the characteristics of the antireflection film according to the basic embodiment described above. The single-sided reflectance of a general glass plate that has not been subjected to any antireflection processing is about 4%, whereas in the antireflection film according to this basic embodiment, single-sided reflection in the wavelength range of 500 to 600 nm. The rate is 1% or less, and a sufficient antireflection effect is obtained.

  In addition, the graph G2 shown with a broken line is a sample in which only the high refractive index layer H is formed on the substrate 10 (that is, a sample having a structure in which the low refractive index layer L is removed from the basic embodiment shown in FIG. 6). The measurement result of the reflectance about is shown. As shown in the figure, the sample has a single-sided reflectance of 8% or more over a wide range of wavelengths, and rather has an effect of increasing the reflectance, and does not function as an antireflection film. This is because, in the case of the material according to this basic embodiment, the refractive index of the high refractive index layer H is about 1.8, which is higher than the refractive index of the glass substrate (about 1.5). Alone, it is considered that the reflectance has increased to about 8%. When the material according to at least the basic embodiment is used, the effect as an antireflection film cannot be obtained unless a two-layer structure of the high refractive index layer H and the low refractive index layer L is adopted.

<<< §7. Manufacturing method of antireflection film according to basic embodiment >>
Here, a specific manufacturing process of the antireflection film according to the basic embodiment described in §6 will be described. The antireflection film according to the present invention has a structure in which a plurality of layers having different refractive indexes (layers composed of alternating adsorption films) are stacked. In particular, in the antireflection film according to the basic embodiment, FIG. 2, a two-layer structure of a high refractive index layer H that is a first optical thin film and a low refractive index layer L that is a second optical thin film is employed.

  Here, in order to form the high refractive index layer H, a first film formation tank containing an aqueous solution of an electrolyte polymer and a second film formation tank containing an aqueous solution of a first water-soluble inorganic electrolyte are prepared. Then, the substrate 10 to be formed with an antireflection film on the surface is immersed in the aqueous solution in the first film formation tank and the aqueous solution in the second film formation tank alternately multiple times, so that the first alternating An adsorption film may be formed and used as the high refractive index layer H. On the other hand, in order to form the low refractive index layer L, an aqueous solution of a second water-soluble inorganic electrolyte having a refractive index different from that of the third film-forming tank containing an aqueous solution of an electrolyte polymer and the first water-soluble inorganic electrolyte. And a substrate having the surface on which the first alternating adsorption film (high refractive index layer H) is formed, the aqueous solution in the third film formation tank and the fourth. A second alternating adsorption film may be formed by alternately immersing it in the aqueous solution in the film forming tank several times, and this may be used as the low refractive index layer L.

  Specifically, a first film formation tank containing an aqueous PDDA solution represented by the structural formula of FIG. 7 and a second film formation tank containing an ACPT aqueous solution represented by the structural formula of FIG. 8 are prepared. Then, a high refractive index layer H is formed by alternately immersing a glass substrate or the like serving as the base material 10 a plurality of times, and a structural formula shown in FIG. 9 shows a PDDA aqueous solution. A fourth film formation tank containing an aqueous solution of sodium silicate is prepared, and a low refractive index layer L is formed by alternately immersing a glass substrate having a high refractive index layer H formed on the surface a plurality of times. Good.

  As described above, the number of times of alternately dipping is determined so as to obtain a thickness necessary for functioning as an antireflection film. Actually, the optimum number of times may be determined by trial and error. In the case of the basic embodiment described here, a total of 30 sheets are immersed in the first film formation tank containing the PDDA aqueous solution and the second film formation tank containing the ACPT aqueous solution, 15 times each. After forming the high refractive index layer H made of the material layer, each was immersed 40 times in the third film formation tank containing the PDDA aqueous solution and the fourth film formation tank containing the sodium silicate aqueous solution. The low refractive index layer L composed of a total of 80 material layers is formed.

  In the basic embodiment, a baking step for heating the entire glass substrate is added thereafter. This firing step is a step intended to remove moisture by firing one or both of the first alternating adsorption film and the second alternating adsorption film. This firing step is not necessarily a necessary step, but in the case of the basic embodiment described here, it is very effective in increasing the refractive index and hardness of the second material layer 12.

  The second material layer 12 is a layer mainly composed of titanium oxide formed using an ACPT aqueous solution contained in the second film formation tank as a raw material. As described above, ACPT is a precursor of titanium oxide, but it is considered that the formation of titanium oxide is promoted and the refractive index and hardness of the second material layer 12 are increased by performing the firing step. When the baking process is added, the film thickness is slightly reduced. Therefore, it is necessary to determine the number of layers of each material layer in consideration of the reduced size of the thickness (that is, in the stage before baking, the final product It should be slightly thicker than the thickness).

<<< §8. Material modification >>>
In the basic embodiment described so far, the first material layer 11 and the third material layer 13 are constituted by PDDA (polydiallylamine dimethyl ammonium chloride) represented by the structural formula of FIG. In addition to this, the layer 11 and the third material layer 13 can be composed of various electrolyte polymers. For example, polyallylamine hydrochloride (PAH) represented by the structural formula of FIG. 11 (a) and polyethylimine (PEI) represented by the structural formula of FIG. 11 (b) are both positive electrolyte polymers (cations). As the first film formation tank and the third film formation tank, tanks containing these aqueous solutions may be used.

  In addition, polyacrylic acid (PAA) represented by the structural formula of FIG. 11 (c) and polysulfonic acid (PSS) represented by the structural formula of FIG. 11 (d) are materials that can be a negative electrolyte polymer (anion). Also, as the first film formation tank and the third film formation tank, tanks containing these aqueous solutions can be used. However, in this case, the aqueous solution of the inorganic electrolyte prepared in the second film formation tank and the fourth film formation tank needs to be an aqueous solution that can be a positive electrolyte (cation).

  In the basic embodiment described so far, the second material layer 12 is constituted by a layer mainly composed of titanium oxide, and the fourth material layer 14 is constituted by a layer mainly composed of sodium silicate. In addition, the second material layer 12 and the fourth material layer 14 can be made of various inorganic electrolyte materials (for example, metal compounds).

  In particular, the second material layer 12 for constituting the high refractive index layer H (first optical thin film) is considered to be suitable for group 4 or 5 metal oxide fine particles or metal alkoxide. Specifically, it is preferable to use oxides such as titanium, zirconium, hafnium, tellurium, tantalum, and niobium. For this purpose, an aqueous solution of titanium oxide, zirconium oxide, hafnium oxide, tellurium oxide, tantalum oxide, niobium oxide precursors (all of which are affinity precursors) is used as the second film formation tank. What is necessary is just to use the tank which accommodated.

  As such a precursor, it is preferable to use a water-soluble metal complex that becomes a multimer in an aqueous solution. As the raw material for the water-soluble metal complex, the group 4A element compound is preferable, and the ligand is preferably one or more selected from the group consisting of carboxylic acid, acetylacetone, diamines, and pyridines.

  The 4A group element can be any of the titanium (Ti), zirconium (Zr), and hafnium (Hf), and the compound includes any of metal alkoxide, organic acid salt, and inorganic acid salt. Can be mentioned.

As the pre-Symbol diamines that make up the ligand, ethylenediamine, ethylenediaminetetraacetic acid, 1,2-propanediamine, at least one selected from the group consisting of 1,3-propanediamine, further, the pyridine Examples of the class include one or more selected from the group consisting of pyridine and bipyridine.

More specifically, as a precursor of titanium oxide, ACPT (ammonium citatoperoxotitanate (IV)) represented by the structural formula of FIG. 8: The formula is ((NH ₄ ) ₈ [Ti ₄ (C An aqueous solution of a water-soluble titanium peroxo complex represented by ₆ H ₄ O ₇ ) ₄ (O ₂ ) ₄ ] · 8H ₂ O) is used as the aqueous solution for the second film formation tank.

On the other hand, as the fourth material layer 14 for constituting the low refractive index layer L (second optical thin film), a silicate compound other than sodium silicate (Na ₂ SiO ₃ ) can be used, and its aqueous solution. Can also be used as an aqueous solution for the fourth film formation tank. For example, an oligosilicate (Oligosilsesquioxane) having a functional group such as an epoxy side chain or an amine group, or a silicate (silicate salt) such as Na or K can be used as the fourth material layer 14.

<<< §9. Application to other than anti-reflective coating >>>
In the embodiments described so far, the example in which the present invention is applied to the antireflection film has been described. However, the technology according to the present invention is not limited to the antireflection film, and various other optical multilayers can be used. This technology can be widely applied to membranes. Specifically, in addition to the antireflection film, various optical filters (for example, ND filter, band pass filter, short wave pass filter (short wavelength band pass filter), long wave pass filter (long wavelength band pass filter), minus The present invention can also be applied to filters, etc., mirrors, half mirrors, various polarizing plates (polarizing beam splitter (PBS), etc.), protective films (so-called barrier films formed for surface protection), and the like.

<First film formation tank>
An aqueous solution containing PDDA at a concentration of 10 mM / l and having a pH value adjusted to 5.5 with sodium hydroxide was prepared.

<Second film formation tank>
An aqueous solution containing ACPT at a concentration of 1% by weight and having a pH value adjusted to 7.2 with nitric acid was prepared.

<Third film formation tank>
An aqueous solution containing PDDA at a concentration of 10 mM / l and having a pH value adjusted to 10 with sodium hydroxide was prepared.

<Fourth film formation tank>
An aqueous solution containing sodium silicate at a concentration of 0.1% by weight and having a pH value adjusted to 10 with hydrochloric acid was prepared.

  The surface of the glass substrate used as the base material 10 is subjected to a hydrophilic treatment with potassium hydroxide to introduce an OH group into the surface, thereby giving a negative charge as an initial surface charge. This is dipped in the first film formation tank for 10 minutes (a time sufficiently longer than the time for reaching the alternate adsorption saturation point) and then pulled up, and then passed through the pure water rinse bath to the second film formation tank. After soaking for 10 minutes (a time sufficiently longer than the time for reaching the saturation point of the alternate adsorption), it was pulled up and immersed in a pure water rinse bath. This alternate adsorption operation was repeated a total of 15 times. Thereafter, it is dipped in the third film formation tank for 10 minutes (a time sufficiently longer than the time for reaching the saturation point of the alternate adsorption) and then pulled up, and then passed through the pure water rinse bath to the fourth film formation tank for 10 minutes. After soaking for a minute (a time sufficiently longer than the time to reach the saturation point of the alternate adsorption), it was lifted and immersed in a pure water rinse bath. This alternate adsorption operation was repeated 40 times in total. Thereafter, it was naturally dried, and further subjected to a baking step by being housed in a thermostat at 200 ° C. for 5 hours.

  As a result, an antireflection film composed of a high refractive index layer H having a thickness of 75 nm and a low refractive index layer L having a thickness of 80 nm was formed on the glass substrate. The single-sided reflectance characteristics of the antireflection film are as shown in the graph G1 of FIG. Further, when the hardness of the antireflection film was measured, it was confirmed that the hardness was 3H or more. This indicates that it is considerably harder than a general antireflection film (hardness 2B to HB), and the wear resistance is greatly improved. When the same process was repeated under the same conditions, an antireflection film having the same performance could be formed.

  For comparison, an optical multilayer film having the same configuration using TALH formed by the same method as in Patent Document 7 was prepared.

  The water-soluble titanium complex ACPT (ammonium citatoperoxotitanate (IV)) used in the alternating adsorption film of this example forms a peroxo complex in which oxygen is coordinated to Ti element in an aqueous solution. Since the octamer is constituted, it is considered that the hydrolysis reaction between the Ti element and the ligand is suppressed. The fact that ACPT forms an octamer in an aqueous solution is described in a paper published by Masato Kakihana et al. In Inorg. Chem. 2001, 40.891-894.

  Accordingly, the transparency of the aqueous solution is high because the rate of precipitation of titania particles is slower than that of the conventional TALH present in the aqueous solution as a monomer. Since the precipitation of particles is alleviated even when the alternate adsorption film is used, the optical multilayer film composed of the conventional TALH and the optical multilayer film composed of ACPT according to the present invention are shown in FIGS. 12 (a) and 12 (b). As shown in each of the electron micrographs, it was found that the ACPT had finer precipitated particles on the surface.

  As shown in FIGS. 13A and 13B, the surface roughness of the same two optical multilayer films is measured with an atomic force microscope, and the surface roughness is as low as several nm, for example, 5.3 nm. I found out.

  Further, when the transmittance was measured for the same optical multilayer film, the conventional TALH (a) was 70% at a wavelength of 450 nm as shown in FIG. 14, whereas the ACPT (b) according to the present invention was 90%. In other words, it was found that a multilayer film having a very high transparency with a transmittance of 90% or more in the visible light region was formed.

  The optical multilayer film produced in this example is a thin film composed of a water-soluble metal oxide precursor and a polymer electrolyte, and the surface of the glass substrate serving as the substrate 10 is flat by controlling the amount of adsorption. Even a curved surface can be uniformly coated. In addition, since adsorption is performed by self-assembly of a medium in an aqueous solution, a large-scale apparatus such as a vacuum deposition method is unnecessary, and an organic solvent is not used, so that the environmental load is low.

  Since this multilayer film has a high refractive index of 1.71 when formed at room temperature, it is promising as a high refractive index layer of an optical multilayer film. As shown in FIG. 15, the antireflection film in which the low refractive index layer is combined with a multilayer film made of a polymer electrolyte and sodium silicate and the high refractive index layer is made of ACPT has a maximum transmittance of 98% near 520 nm. Indicated.

  Therefore, since it has sufficient optical properties even at room temperature, it can be effectively used for a substrate made of an organic material.

  Also, the heat treatment (200 ° C.) strengthens the bonding of the inorganic compound, adhesion (no peeling by tape test), moisture resistance (temperature: 60 degrees, humidity: 90%, 72 hours of tape) Excellent properties were also exhibited for the case of no peeling by test.

  From the above, it can be seen that if the method according to the present invention is used, it is possible to mass-produce the antireflection film under a highly accurate film thickness control. And since the film-forming process can be performed by the method immersed in aqueous solution under normal temperature normal pressure, a manufacturing cost can be reduced significantly.

  In the above-described embodiment, the optical thin film made of ACPT has been described as an example of constituting an antireflection film having a two-layer structure. However, the present invention is not limited to this. It is good also as a highly transparent protective film.

  The water-soluble metal complex that becomes a multimer in the aqueous solution that constitutes the first optical thin film is not limited to ACPT that constitutes the octamer, and any metal complex that exists in the aqueous solution as a dimer or more. Is optional.

  In addition, as a dry process used for forming the second optical thin film, a vacuum deposition method, a sputtering method, or the like can be used. As a wet process, a dipping method, a spin coating method, or the like can be used. it can.

In addition, the optical multilayer film in which one or more layers of the first optical thin film and the second optical thin film are laminated, and the number of layers and the layer structure are arbitrary as long as one or more layers are included. If it is a structure,
First layer: the first optical thin film (high refractive index layer) according to claim 1
Second layer: second optical thin film (intermediate refractive index layer) formed by a dry process
Third layer: second optical thin film (low refractive index layer) formed by a dry process
Fourth layer: second optical thin film (ultra low refractive index layer) formed by a wet process
Or
First layer: second optical thin film (intermediate refractive index layer) formed by a dry process
Second layer: the first optical thin film (high refractive index layer) according to claim 1
Third layer: second optical thin film (low refractive index layer) formed by a dry process
Fourth layer: second optical thin film (ultra low refractive index layer) formed by a wet process
Can be given as a specific example.

  Furthermore, specific examples of the optical multilayer film in which one or more layers of the first optical thin film and the second optical thin film are laminated include an optical thin film having two or more layers, an antireflection film, an optical filter, and the like. it can.

10 ... Base material (for example, glass substrate)
DESCRIPTION OF SYMBOLS 11 ... 1st material layer 12 ... 2nd material layer 13 ... 3rd material layer 14 ... 4th material layer 100 ... 1st tank 200 ... 2nd tank A1, A3, A5 ... Thin film B2, B4 , B6 ... thin film b ... electrolyte polymer G1, G2 ... graph showing reflectance H ... high refractive index layer L ... low refractive index layer nH ... refractive index of high refractive index layer nL ... refractive index of low refractive index layer S0, S1 , S2: layer interface λ: wavelength of light to be antireflection

Claims (8)

A water-soluble metal complex that becomes a multimer in an aqueous solution, wherein the raw material of the water-soluble metal complex is a compound of Ti, Zr, or Hf, and the ligand is acetylacetone, a diamine, or a pyridine An optical thin film formed using at least one selected from the group consisting of: Before hear compound is a metal alkoxide, an optical thin film according to claim 1, wherein the organic acid salt, either an inorganic acid salt. 2. The optical thin film according to claim 1 , wherein the diamine is at least one selected from the group consisting of ethylenediamine, ethylenediaminetetraacetic acid, 1,2-propanediamine, and 1,3-propanediamine. The optical thin film according to claim 1 , wherein the pyridine is at least one selected from the group consisting of pyridine and bipyridine. An aqueous solution of an electrolyte polymer;
A water-soluble metal complex that becomes a multimer in an aqueous solution, wherein the raw material of the water-soluble metal complex is a compound of Ti, Zr, or Hf, and the ligand is acetylacetone, a diamine, or a pyridine In an aqueous solution of one or more selected from
A method for producing an optical thin film, comprising alternately adsorbing films formed by alternately immersing a substrate. Said electrolyte polymer, polydiallylamine dimethyl ammonium chloride, polyallylamine hydrochloride, polyethylenimine, polyacrylic acid, according to claim 5, characterized in that configured by a material selected from the group consisting of polysulfonic acid Manufacturing method of optical thin film. A first optical thin film according to claim 1;
A second optical thin film formed by a dry process or a wet process;
An optical multilayer film characterized by laminating one or more layers. The first optical thin film is a high refractive index layer exhibiting a first refractive index, and the second optical thin film is a low refractive index layer exhibiting a second refractive index lower than the first refractive index;
The high refractive index layer is constituted by an alternating adsorption film of a first material and a second material, and the low refractive index layer is constituted by an alternating adsorption film of a third material and a fourth material,
The first material and the third material are each composed of a material selected from the group consisting of polydiallylaminedimethylammonium chloride, polyallylamine hydrochloride, polyethylimine, polyacrylic acid, and polysulfonic acid. The optical multilayer film according to claim 7 .