JPH01228539A - Formation of built-up film - Google Patents

Abstract

PURPOSE:To cover a solid base plate with a superthin film by separating a solid base plate in contact with the monomolecular film of amphiphilic organic molecules from the surface of a liquid inclined at an angle of 0-15 deg. to a gas- liquid surface. CONSTITUTION:A base plate 1 is attached from within a gas phase to the monomolecular film 2 of organic molecules preformed on the surface of a liquid approximately parallel to the liquid surface. The surface of the base plate 1 is then inclined at a small angle theta(0 deg.<theta<15 deg.) to a gas-liquid surface to thereby separate the base plate 1 from the liquid surface. The aforesaid inclination angle may be kept constant or gradually changed during the separation process. In the case of an aqueous phase instead of the liquid phase, the second layer 2 of the monomolecular film is formed in this process on the surface of the base plate with its hydrophilic group facing the same. Preferably, the separation speed is not more than 5mm/min. in terms of the moving speed in the vertical direction to the gas-liquid surface of the base plate.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for forming an organic ultra-thin film, and more particularly to a technique for accumulating an organic ultra-thin film with molecular orientation on a substrate in a short time.

(Prior art) A method for transferring a monomolecular film of amphiphilic molecules formed at a gas-liquid interface onto a solid substrate was already developed in the 1930s by Lang
Constructed by miuir and Blodgett, L
It is called the angmiutr-Blodgett method or the vertical immersion method. Further, a monolayer (m'onolayer) or a cumulative layer (multilayer) coated on a substrate using such a method is generally referred to as an LB film, and is used as a representative organic ultra-thin film. The needs for organic ultra-thin films formed in this way span a wide range of fields, including insulating thin films for semiconductor devices, thin films for nonlinear optical materials, functional thin films for sensors, and surface protective films for magnetic recording materials. This method successfully takes advantage of features that are difficult to obtain with other film formation methods, such as the orientation of organic molecules and the ultra-thinness of the film.

However, there are still many drawbacks in terms of productivity such as simplicity, speed, and controllability of film formation, and improvements in the film formation method for practical use are desired.

Therefore, recently, instead of the vertical dipping method, the use of the horizontal adhesion method by Fukuda et al. has become popular (Kiyonari Fukuda, "Materials Technology" Vol. 4, No. 6, p. 261, 1986).

It is said that this method requires less time to coat the film than the vertical dipping method, and often forms a film with excellent uniformity and orientation.

On the other hand, improvements are being made to equipment to increase the efficiency of monomolecular film coating. JP-A-60-183724 and JP-A-60-193533 disclose examples of methods in which the addition of a film-forming solution to the water surface and the coating on the substrate are carried out continuously. or,
Th1n 5olid Film is a method of continuously accumulating a monomolecular film by using a cylindrical substrate or a support for the substrate and rotating it across the gas-liquid interface.
ms+, Vol. 99, p. 221, 1983.

Furthermore, JP-A-61-42364 and JP-A No. 61-42365
This publication discloses a means for forming a cumulative film on a substrate having a lens-like curved surface by rotating the substrate reciprocatingly at the air-liquid interface based on the principle of the vertical immersion method.

(Problems to be Solved by the Invention) In order to accumulate a monomolecular film using the conventional method described above, the vertical dipping method and methods modeled on it require a considerable amount of time to move the substrate back and forth, and horizontal adhesion requires a considerable amount of time. This method requires a cleaning process to remove the monomolecular film on the liquid surface before peeling off the substrate from the liquid surface, which takes time. These are major disadvantages in terms of productivity.

In addition, if the horizontal deposition method is performed in a short time by omitting the cleaning process for convenience, one or more monolayers may unexpectedly adhere, but in this case, the coating will be uneven and a good Molecular orientation is rarely obtained.

These problems are related to the time required for the coating process.

In terms of coating possibilities, conventional methods usually coat the first layer efficiently, but since the accumulation from the second layer often involves peeling of the existing film, it is difficult to select a suitable substrate for coating. It is necessary to select the drying time in the accumulation process.
Accumulation is not always easy.

It is therefore an object of the present invention to provide a method for rapidly coating a solid substrate with an ultra-thin film consisting of an accumulated layer of organic molecules. The purpose is to provide a method for quickly forming a highly uniform cumulative film, and thirdly, it is possible to efficiently accumulate a monomolecular film even on a solid substrate where it is difficult to deposit using the conventional L-B method. The purpose of the present invention is to provide an accumulation method.

These objects of the present invention are to cover one plane of a solid substrate with a monomolecular film of amphiphilic organic molecules formed at a gas-liquid interface. This could be achieved by performing a series of operations in which the molecular film was peeled from the liquid surface while being tilted at an angle of less than 15°, not facing the film surface.

According to the present invention, one layer of a monomolecular film of amphiphilic organic molecules previously formed at the gas-liquid interface is transferred onto a solid substrate by a horizontal deposition method, and then the plane of the substrate is moved to the gas-liquid interface. By gradually pulling away from the liquid surface while tilting slightly (greater than 0° and less than 15°), a second layer is accumulated and two monolayers are molecularly oriented on the substrate in one continuous operation. coated with

The monomolecular film formed at the gas-liquid interface in the present invention can be a monomolecular film made of various amphiphilic organic molecules. Regarding the formation method and characterization of monolayers, see G.
Written by L. Ga1nes, Jr. [Insoluble
Monolayers at Liquid-Gas
InterfacesJ +Interscience
, Ne@york (1966), etc. A typical monomolecular film is formed at the water-air interface, that is, on the water surface, and these molecules are surface-active water-insoluble organic molecules in which hydrophilic and hydrophobic groups coexist. It is. A compound suitable for forming a monolayer is an amphipathic surface-active compound having both a hydrophilic group and a hydrophobic group in the molecule. By developing such a compound from a volatile organic solution onto the water surface and compressing it to an appropriate surface pressure, the molecules are oriented with the hydrophilic groups facing below the water surface and the hydrophobic groups facing above the water surface. Closely packed monolayers can be formed.

Insoluble compounds in which the entire molecule is hydrophobic have difficulty in orienting the molecules, which tends to cause aggregation, making it difficult to form a monomolecular film and apply stable surface pressure. Therefore, as a compound for forming a monomolecular film, it is necessary to use a water-insoluble and nonvolatile compound with a well-balanced hydrophilicity and hydrophobicity.

Compounds with such properties include, for example, carboxylic acids with long-chain alkyls (generally having 16 or more carbon atoms);
Examples include esters, alcohols, thiols, aldehydes, amides, ethers, amines, ammonium salts, and metal chelates. In addition, as a functional compound,
Pigments M (cyanine, merocyanine, squarylium compounds, xanthine compounds, triphenylmethane compounds, anthraquinone compounds, etc.), compounds that undergo photoisomerization (azobenzene, spiropyran and spirooxazine derivatives, indigo compounds, fulgide compounds, lenanol) ), compounds with catalytic and photocatalytic mechanisms (porphyrin derivatives, ruthenium bipyridinium complexes, etc.), compounds that interact with biological substances (phosphorus membranes, cholesterol, etc.), compounds with inclusion functions (e.g. crown ethers, cyclodextrins, etc.) Further, examples of compounds having reactive groups useful for fixing functional compounds include, for example, Japanese Patent Application No. 3155/1986.
No. 42, No. 62-158994, No. 62-21364
Compounds exemplified in No. 7 are also useful.

Many solid substrates for coating monomolecular films include inorganic materials such as metals, metal oxides, ceramics, carbon, and silicon compounds, organic materials such as polymer resins and natural resins, and composite materials of these materials. Can be used.

The surface coated with a monomolecular film may be part of these materials, and although it is desirable that the coated surface be flat, it does not have to be optically flat, and the entire surface may not necessarily be geometrically flat. It doesn't have to be academically flat.

In the present invention, a liquid phase (subph) in which a monomolecular film is formed
When the solid substrate is in an aqueous phase, the surface to be coated of the solid substrate is preferably hydrophobic.

This is because the first layer of monomolecular film, which is directly coated on the surface by horizontal adhesion, attaches to the substrate from the hydrophobic group side of the molecule, and a physically stable adsorption state is likely to be formed due to hydrophobic interaction. It's for a reason.

Here, hydrophobicity is defined as a solid surface having a contact angle with water of at least 25# at room temperature. Regarding hydrophobicity, the contact angle with water is preferably 40e or more, and more preferably 90' or more. Hydrophobic surfaces can be obtained using various organic and inorganic materials.

For example, organic materials include polystyrene, polyethylene,
Polymer resins such as polypropylene and fluorocarbons,
Many water-insoluble compounds can be used, such as organosilicon compounds, lipids, fats and oils, and natural proteins.

These may be part or all of the substrate, or may be coated on the surface of the substrate. Although most inorganic materials have poor hydrophobicity, they can be used by coating and modifying the surface with a suitable hydrophobic substance. For example, the surface of an oxide such as silica glass can be made hydrophobic by preliminarily chemically treating it with an organic silicon compound that can react with hydroxyl groups on the surface. As the organosilicon compound, for example, alkylalkoxysilane, arylalkoxysilane, alkylchlorosilane, arylchlorosilane, etc. are generally useful. Alternatively, a hydrophobic surface coated with a hydrophobic organic compound can also be obtained by simply immersing solid particles in a solution of a hydrophobic organic compound and then drying the solid particles.

Next, the coating operation of the present invention will be explained based on FIG.

The coating operation consists of two steps.

The first step of the present invention, as shown in FIGS. 1a and b,
With respect to the monomolecular film 2 of organic molecules formed in advance on the liquid surface,
This is a process in which the substrate l is bonded to a monomolecular film from a gas phase at an angle substantially horizontal to the liquid level, and this is similar to a part of the process of the conventionally known horizontal adhesion method. In this step, it is preferable that the substrate surface involved in coating be brought into contact with the surface of the monomolecular film horizontally, but in preparation for the second step, the surface of the substrate is tilted at a low angle θ (Q*<θ<15°). There is no practical problem in doing so. When the liquid phase is an aqueous phase, one layer of monomolecular film is coated in this step with the hydrophobic groups facing the substrate surface.

The second step, as shown in FIGS. 1C and d, is a step in which the substrate to which the monomolecular film is bonded is peeled off from the liquid surface, and this step involves setting the substrate surface at a low angle θ (0 ″′kuθ
<15°). this,
The angle of inclination may be kept constant during the process of separation, or may be gradually changed.

When the liquid phase is an aqueous phase, a second layer of monomolecules is coated in this step with the hydrophilic groups directed toward the substrate surface. The speed of peeling is important in this step, and it is preferable that this speed be controlled to be sufficiently slow so that the molecular density of the coated monomolecular film does not become smaller than that at the liquid surface. Such a speed largely depends on the fluidity of molecules in the monomolecular film on the liquid surface, and a film with poor fluidity needs to be slowed down. The peeling speed is preferably lower than at least 5 layers m/min as a moving speed of the substrate surface in the direction perpendicular to the air-liquid interface.

Although FIG. 1 shows an example of coating on the water surface, the object of the present invention can be achieved by similar operations when a hydrophobic developing solvent is used.

In the coating process, it is preferable to keep the surface pressure of the monomolecular film on the liquid phase sufficiently high. Sufficiently high means that the surface pressure of the monomolecular film is 41! In the (π-A) characteristic,
This is a region that is lower than the burst pressure (πC) and higher than the pressure at which the formation of a so-called coagulated film or solid film, which shows a remarkable rise in pressure, begins.

Although this pressure depends on the molecule, it is generally 5 dyne/
The range is from cm to 60 dyne/cm. It is preferable to maintain the surface pressure at a constant pressure, especially during the IM process of the substrate.The pressure is controlled by monitoring the pressure in a trough equipped with a surface pressure sensor and at the same time interlocking the membrane barrier in response to changes in pressure. method, it can be controlled to a constant value. Alternatively, it is also possible to control by means of interlocking the barrier in accordance with the number of falling particles.

The trough for monolayer production used in the method of the present invention includes commonly used troughs (such as float type barrier type and belt barrier type), as well as those shown in JP-A-60-183724 and JP-A-60-209245. Continuous accumulation troughs such as No. 60-196934 and No. 60-19720
Various improved troughs can be used, such as a vibration application type trough as shown in No. 8, or a moving wall type (Miyata method) trough suitable for coating highly viscous films.

Next, the present invention will be explained with examples, but the application of the method of the present invention is not limited to these examples.

[Example 1] A glass slide (2.5X, 7.5c+a) was treated with a hot sulfuric acid aqueous solution, washed with water, dried, immersed in a 10% toluene solution of trimethylchlorosilane for 6 hours, and then washed with toluene to remove the surface. The contact angle of the hydrophobic surface with water was measured and was approximately 90''.

A boric acid buffer aqueous solution (10-3M) containing 2×10-'M cadmium chloride at pH 5.
) was prepared, and a chloroform fI solution of alaxic acid (10-'M) was spread on the water surface at room temperature to form a monomolecular film containing alaxic acid and cadmium alaxic acid.

The monomolecular film was gradually compressed using a pelt-dove barrier, and the surface pressure was controlled at 30 dyne/cm.

Fix the previously treated slide glass substrate on a substrate support with the short axis of the substrate surface inclined by 3 degrees from the horizontal, move it onto the monomolecular film on the water surface as shown in Figure 1 a and b, and then horizontally Adhesion was carried out. Next, with the substrate surface tilted, it was first lifted vertically above the water surface at a speed of 20 m/min, and when the water surface began to peel off from the substrate surface, the speed was quickly reduced to 2 m/min and gradually peeled off. continued. In this way, the substrate was moved up and down once, and the entire process took about 1 minute to complete the coating operation. After this operation, the cumulative ratio was calculated from the ratio of the area reduction of the monomolecular film on the water surface to the effective area covered by the substrate, and the cumulative ratio was 2.0 per operation, which was 2.
It was found that a monolayer of layers was coated with this operation.

This operation was repeated 12 times, and finally a cumulative film of 24 layers could be coated on the substrate. The total time required for this accumulation was 64 minutes. For comparison, Table 1 compares an example of the time required for various steps required in an experiment in which a 24-layer LB film was formed by the conventional vertical dipping method and the time required by the method of the present invention.

[Example 2] A gold-coated substrate was prepared by vacuum-depositing chromium as a base to a thickness of 200 mm on the surface of a slide glass as a solid substrate, and then vacuum-depositing gold to a thickness of 1000 mm on top of this.

On the surface of this substrate, α-divalmitoylphosphatidylcholine (DPPC), a type of phospholipid, is present.
We tried coating it with a monomolecular film.

DPPC and dichloromethane as lO-”Mi solution p
A monomolecular film was prepared by developing it on a H6,8 neutral phosphate buffer (10 −3 M) and compressed to a surface pressure of 20 dyn/cs. Under this constant pressure, the gold substrate was coated with the first layer of the monomolecular film by lifting the substrate from below the water surface to above the water surface using a vertical immersion method. The cumulative ratio was 1.0. The substrate was dried at room temperature for 10 minutes and then dried in a vacuum dryer for 1 hour. An operation was performed to further accumulate a monomolecular film of DPPC on this substrate.

As a result of repeating horizontal continuous two-layer deposition by basically the same operation as that of the present invention in Example 1, nine layers of DPPC were obtained.
was transferred onto the gold surface with an average cumulative ratio of 0.95. On the other hand, as a comparison, we tried coating the second layer and above using the vertical dipping method, but the first layer peeled off during the 2nd N coating process, and it was difficult to continue the accumulation after that. .

[Example 3] A monomolecular film of cadmium araxinate used in Example 1 was coated on the gold surface of the same gold-deposited slide glass as used in Example 2 under a surface pressure of 30 dyn/cm in the same manner as in Example 2. 251'i accumulation was carried out by this operation. The average cumulative ratio was 1.1.

In order to investigate the molecular orientation of the cadmium araxinate film formed in this way, FT was performed using a high-sensitivity reflection-absorption method.
-IR spectrum was measured.

The measurements were carried out using a JEOL JIR-106 model FT-IR equipped with a high-sensitivity reflectance measuring device (JEOL IR-R3C20). The measurement conditions were a resolution of 4 cm-' and a number of integrations of 1.
000 times, the scan speed of the mirror of the interferometer is 4
win/sec, a water-cooled glow light source was used, and an MCT was used as a detector.

In addition, high-sensitivity reflection measurements were performed at an incident angle of 806.

The IR spectrum of the resulting cadmium araxinate film was analyzed using an araxinate solid powder sample (bulk po
wder).

There is a significant difference between the two, and compared to the spectrum of the powder sample in the cumulative film prepared by the method of the present invention, the absorption of symmetrical stretching vibrations (near 1430c*-') by carbonyl groups is greatly enhanced; Absorption of stretching vibration by CHz (
29620II-') was weakening. This fact confirms that the axes of the alkyl chains are sharply oriented in the direction perpendicular to the substrate surface (i.e., the direction of the electric field created by the incident light and reflected light for measurement), and the cumulative method of the present invention can detect molecular orientation. It also shows that it is excellent in terms of formation.

Furthermore, the X-ray diffraction spectrum of the same sample was measured. A Rigaku Ru-200 model X-ray diffractometer was used for measurement
Measurement using alpha rays for u- revealed that cadmium araxinate was regularly arranged, and the number of interlayer cavities was estimated to be 55.3.

[Brief explanation of the drawing]

FIG. 1 is a drawing explaining the steps of the cumulative film forming method of the present invention. In FIG. 1, 1 represents a solid substrate, and 2 represents a monomolecular film. Figures 1a and b show the horizontal adhesion process (first process);
Figures 1c and d show the subsequent water surface peeling process (second step).
process). The coating process proceeds in the order of a, b, c, and d. Arrows indicate the direction of movement of the substrate. Patent applicant: Fuji Photo Film Co., Ltd. Figure 1 Procedural Amendment

Claims (1)

[Claims] (1) In the step of coating a monomolecular film of amphiphilic organic molecules formed at the gas-liquid interface on one plane of a solid substrate, the plane of the solid substrate is the film surface of the monomolecular film on the liquid phase. The substrate was moved from the gas phase to contact with the film surface of the monomolecular film while facing the gas-liquid interface, and then the substrate surface was tilted at an angle greater than 0° and smaller than 15° with respect to the gas-liquid interface from the liquid surface. A cumulative film forming method characterized by coating a monomolecular film on a substrate surface by peeling.