JP2005060583A - Method for producing block copolymer membrane having vertically oriented lamella structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of producing a block copolymer membrane which, even when it has a high molecular weight, has unidirectionally and regularly arranged lamellae in a wide area and has a microphase separated structure vertically to the membrane surface. <P>SOLUTION: The method comprises the consecutive steps of: dissolving a block copolymer comprising two types of recurring monomer units and developing a lamellar microphase separation structure in a thermal equilibrium state in a solvent acting as a good solvent for a block comprising one type of the recurring monomer units and acting as a poor solvent for a block comprising the other type of the recurring monomer units, forming the solution into a membrane of the block copolymer, removing the solvent from the membrane to develop a microphase separation structure other than the lamella structure, and heating the desolvented block copolymer membrane in a manner that the respective narrow regions of the membrane are successively heated to the glass transition temperature or higher. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a block copolymer film having a vertically aligned lamella structure in which lamellae (thin layers) are aligned perpendicularly to the film surface of the block copolymer. More specifically, a block copolymer film (see FIG. 12) having a microphase-separated structure in which lamellas are vertically aligned in a wide area, the normal of the lamella interface is parallel to the film surface, and arranged in one direction is manufactured. Regarding the method.

  When the above block copolymer film is used, for example, a polarizing film, a diffraction grating, an electronic device, a high-density memory, an optical waveguide, etc. can be produced using a regularly arranged lamellar microphase separation structure. Is possible.

  The block copolymer is a polymer compound composed of a plurality of repeating monomer units, and has a sequence continuously connected without branching in the middle, for example, a compound composed of monomers A and B. In the case, it means an array such as AAAAABBBBBAAAAABBBBBAAAAA. Here, the chain of A or B is referred to as a block, and is represented as an A block and a B block, respectively. A binary block copolymer composed of A block and B block is represented as A-b-B, a ternary block copolymer is represented as A-b-B-b-A, B-b-A-b-B, and a multi-component (n-element) block copolymer is represented as-(Ab-B) n-.

  A block copolymer creates an ordered and characteristic microdomain structure when different types of blocks undergo phase separation without sufficiently mixing with each other. This is called a microphase separation structure.

  The microphase-separated structure varies depending on the composition of the block copolymer, and a lamellar, cylindrical, spherical, gyloid, or other structure is formed. Here, the lamellar microphase separation structure refers to a structure in which, for example, two blocks of A and B are alternately arranged in layers as shown in FIG. The cylindrical microphase separation structure refers to a structure in which, for example, a cylinder (cylinder) made up of B blocks is present in a matrix made up of A blocks, as shown in FIG. The spherical microphase separation structure refers to a structure in which, for example, spheres composed of B blocks are present in a matrix composed of A blocks as shown in FIG. The guilloidal shape refers to a structure in which, for example, a mesh structure composed of B blocks exists in a matrix composed of A blocks.

  Here, if the orientation control is not performed at the time of forming the block copolymer, the block copolymer film has a narrow region of the film (this is shown in the transmission electron microscope (TEM) photograph of FIG. 4). Such a region is referred to as “grain”) and has a microphase separation structure that is regularly oriented, and the entire film has an irregularly oriented microphase separation structure in which a plurality of grains are aggregated. In FIG. 4, the boundaries between the grains are indicated by lines, and the regions surrounded by the boundaries represent different grains.

  On the other hand, when the orientation is controlled, it is possible to produce a block copolymer film having a microphase separation structure with a regular orientation as a whole film. From such a block copolymer film having a regularly oriented microphase separation structure as a whole film, for example, a polarizing film or the like can be produced.

  As an example of controlling the orientation, there is a method proposed by Bodycom et al. In this method, a block copolymer film having a vertically aligned lamellar structure regularly arranged in one direction is utilized by using a zone heating method and an order-disorder transition (ODT) of the block copolymer. Manufactured (see Non-Patent Document 1, Non-Patent Document 2, and Patent Document 1).

  Here, the zone heating method refers to a method in which the block copolymer film is sequentially heated to a predetermined temperature or more for each narrow region.

Further, the order - disorder transition The order - a disorder transition temperature (T _ODT) phase transition occurring in the boundary, the block copolymer film and the boundary of T _ODT, ordered state where microphase-separated structure is formed To a disordered state having no specific structure, or from a disordered state to an ordered state.

Bodycom et al. Adopted a zone heating (or zone cooling) method in which a part of the block copolymer film was cooled and the other part was heated to T _ODT or more. A film having a vertically aligned lamellar structure regularly arranged is formed. This process will be described with reference to FIG. 5. First, in the first stage, the entire film is heated to a temperature higher than T _ODT . In the second stage, the cooling means set at a temperature lower than T _ODT is moved within the film surface to form nuclei having the same orientation. In the third stage, the cooling means is sequentially moved in the film plane to grow the nuclei formed in the second stage, and finally the lamellar microphase in which the lamella is regularly oriented perpendicular to the film plane in a wide area. A block copolymer membrane having a separation structure is obtained (fourth stage).

“Macromolecules”, (USA), 1999, Vol. 32, No. 6, p.952-954 “Macromolecules” (USA), 1999, Vol. 32, No. 6, p.2075-2077 Japanese Patent Laid-Open No. 10-330494

In the above-mentioned method by Bodycom et al., A block copolymer film having a vertically aligned lamellar structure is obtained using TO _ODT of the block copolymer. However, when the block copolymer has a large molecular weight, T _ODT becomes a high temperature exceeding 200 ° C., and at this temperature, the degree of deterioration due to thermal decomposition of the block copolymer increases, so the above method is used. I can't.

  The problem to be solved by the present invention is to provide a method for producing a block copolymer film having a vertically aligned lamellar structure even for a block copolymer having a large molecular weight.

The method for producing a block copolymer film having a vertically aligned lamellar structure according to the present invention, which has been made to solve the above-mentioned problems,
A block copolymer consisting of two types of repeating monomer units and expressing a lamellar microphase separation structure in a thermal equilibrium state is a good solvent for the block consisting of one repeating monomer unit, and from the other repeating monomer unit A step of dissolving in a solvent that is a poor solvent for the block comprising;
Forming the block copolymer film using the solution;
Removing the solvent from the membrane and developing a microphase separation structure other than lamellar,
A step of heating the block copolymer film from which the solvent has been removed to a glass transition temperature or higher sequentially for each narrow region;
It is characterized by including.

A homopolymer composed of a monomer that is compatible with only one of the blocks constituting the block copolymer (AbB, AbBbA, BbAbB,-(AbB) n-) and that is the same or different from the monomer constituting the block. , One or more kinds may be mixed in the block copolymer. The homopolymer is compatible with only one of the blocks (A block or B block). The homopolymer compatible with the A block and the homopolymer compatible with the B block are co-polymerized in the same block. It can be mixed into the polymer solution. Even when such a block copolymer is used, a block copolymer film having a vertically aligned lamellar structure can be produced by sequentially performing the same steps as described above. The homopolymer means a polymer composed of one kind of monomer.
In the following, unless otherwise specified, the term “block copolymer” includes the case where a homopolymer compatible with any block is mixed.

  In the method according to the present invention, a microphase-separated block copolymer (AbB, AbBbA, BbAbB,-(AbB) n-) is produced from a microphase-separated structure other than a lamellar structure that occurs at the glass transition temperature (Tg). Using a non-equilibrium structure-equilibrium structure transition to a lamellar microphase-separated structure, lamellas are regularly arranged in one direction and vertically oriented from a block copolymer consisting of two types of repeating monomer units. A block copolymer membrane having a microphase separation structure is produced.

  For example, a state in which a block copolymer film having a cylindrical microphase separation structure in a non-equilibrium state changes to a lamellar microphase separation structure is as shown in FIG. When a block copolymer membrane (first stage) in a non-equilibrium state (cylindrical microphase separation structure) is heated to Tg or higher, the interface curvature of the cylinder gradually changes (second stage) and eventually adjoins. The cylinders coalesce (third stage), and the interface structure newly formed by the coalescence propagates in the axial direction of the cylinder (fourth stage), and finally a lamella is formed (fifth stage) (“macro mole” Macromolecules ", (USA), 1993, 26, 485-491).

  Here, when the film is heated without controlling the heating region, adjacent cylinders in an arbitrary direction are united, and grains are grown using this as a nucleus. For this reason, the block copolymer film has an irregular grain structure as shown in the TEM photograph of FIG.

  Therefore, in order to orient the lamella regularly in a wide region, as shown in FIG. 7, only a narrow region of the block copolymer film in a non-equilibrium state is heated to a temperature of Tg or higher. This prevents the formation of free nuclei, and the transition from cylinder to lamella appears only in the relevant narrow region. Thereafter, by sequentially moving the heating region, a micro phase separation structure in which lamellas are regularly oriented perpendicular to the membrane surface is formed in a wide region of the membrane.

Even when a block copolymer membrane having a microphase-separated structure such as a sphere or gyroid is used, the same control is performed to change to a lamellar microphase-separated structure.
In the present invention, the order of the microphase separation structure in the nonequilibrium state is not questioned, and the above control is performed even when the order of the microphase separation structure in the nonequilibrium state is low. As a result, a block copolymer film having a regular lamellar microphase separation structure having a vertical orientation can be obtained.

  According to the method of the present invention, a block copolymer film having a microphase-separated structure in which lamellas are regularly arranged in one direction and oriented perpendicularly to the film surface can be produced in a wide region. The method according to the present invention is a vertically aligned lamella structure regularly arranged in one direction using a high molecular weight block copolymer that has been difficult to produce from the conventional method using zone heating and order-disorder transition. It is particularly suitable for producing a block copolymer film having

  From the block copolymer film having the vertically aligned lamella structure regularly arranged in one direction, the polarizing film, diffraction grating, electronic device, high-density memory are utilized by utilizing the regularity of the structure. An optical waveguide or the like can be manufactured.

  The microphase separation structure of the block copolymer membrane in the non-equilibrium state and the equilibrium state is the type and combination of monomers constituting the block copolymer, their volume fraction, and the solvent that dissolves the block copolymer during film formation. It depends on the type. In the present invention, monomers that have a microphase separation structure other than lamellar in a non-equilibrium state and a lamellar microphase separation structure in an equilibrium state are styrene, p-chlorostyrene, acrylonitrile, vinyl acetate, vinyl chloride. , Methyl methacrylate, isoprene, and other commonly used monomers are used in appropriate combination, and the solvent is appropriately selected according to the combination of monomers.

  For example, in a polystyrene-polyisoprene block copolymer (hereinafter referred to as “PS-b-PI”) composed of a combination of styrene and isoprene, a lamellar microphase separation is performed in an equilibrium state when the PS volume fraction is 0.51. Take the structure. In addition, when cyclohexane, which is a good solvent for PI and a poor solvent for PS, is used as a solvent, the PI polymer chain extends in a domain composed of PI in a non-equilibrium state, and PS in a domain composed of PS. Since the polymer chain shrinks, it takes a cylindrical microphase separation structure with PS as the cylinder part and PI as the matrix.

  A method for producing a block copolymer membrane having a lamellar microphase separation structure using a block copolymer and a solvent having the above conditions will be described in detail below.

  First, a block copolymer consisting of two types of repeating monomer units is a good solvent for the block consisting of one repeating monomer unit, and a poor solvent for the block consisting of the other repeating monomer unit. Dissolve in (selective solvent). Since this selective solvent is removed later, it is desirable to use a solvent having a relatively high volatility.

The block copolymer solution is applied to a metal plate or the like by using a general coating method such as a spin coating method, a solvent casting method, a roll coating method, a dip coating method, or a curtain coating method to form a block copolymer film. Form.
Then, heating etc. are performed and a solvent is removed from this block copolymer film | membrane.

  In a state where the solvent is removed, the block copolymer film has a non-equilibrium non-lamellar microphase separation structure and is in an unstable state in terms of energy. However, the microphase-separated structure is frozen in this state, and the structural change of the block copolymer film does not occur on a daily time scale even when heated at a temperature below the Tg of the block copolymer.

  However, when the block copolymer film in a non-equilibrium state is heated to Tg or more, the block copolymer film comes to have a stable equilibrium structure (lamellar microphase separation structure).

  In order to make this lamellar microphase-separated structure regularly vertically aligned in one direction in a wide region, only a narrow region of the block copolymer film in a non-equilibrium state, preferably depending on the type of block copolymer. A region substantially the same as the period of the lamellar structure in a fixed thermal equilibrium state is heated to a temperature of Tg or higher. For heating the film, it is desirable to use a temperature control means capable of forming a steep temperature gradient (see [0042]) that can be rapidly heated and cooled. Further, in order to orient the lamella regularly in one direction in a wider region, it is desirable that the moving speed of the temperature control means is equal to or less than the grain growth speed (see [0043]). Furthermore, it is desirable to provide an orientation interface so as to be in contact with the first heating region of the block copolymer film and to control the direction of the block copolymer chain. As a result, in the block copolymer consisting of two blocks, the block having higher affinity to the orientation interface is arranged so as to be in contact with the orientation interface, and the direction perpendicular to the orientation interface (the moving direction of the temperature gradient) It is easy to obtain a block copolymer film having a vertically aligned lamellar structure regularly arranged in (1).

  According to the above method, it is possible to produce a block copolymer film having a microphase separation structure in which lamellas are regularly arranged in one direction in a wide region and oriented perpendicular to the film surface. The lamella spacing can be changed by changing the number of monomer units (degree of polymerization) of each block chain constituting the block copolymer.

  Also, a homopolymer composed of a monomer that is compatible with only one of the blocks constituting the block copolymer (AbB, AbBbA, BbAbB,-(AbB) n-) and that is the same or different from the monomer constituting the block. It is also possible to change the lamellar spacing by mixing one or more of these in the block copolymer. For example, when a homopolymer compatible with the A block and a homopolymer compatible with the B block are both mixed with the block copolymer, the homopolymer compatible with the A block has a lamella thickness composed of the A block. A homopolymer that changes and is compatible with the B block changes the lamellar thickness of the B block.

  The block copolymer film that is regularly arranged in one direction and has a vertically oriented lamellar structure manufactured as described above can be used as, for example, a polarizing film, a diffraction grating, an optical waveguide, and the like. In addition, an electronic device is manufactured by treating such a block copolymer film with a specific reagent, or removing only one part that is not resistant to the reagent by plasma treatment, ultraviolet irradiation, etc. It is also possible to manufacture a high-density memory or the like in which the resin removal portion is replaced with a magnetic material or an optical material.

  Furthermore, by using a block copolymer composed of two types of repeating monomer units having different dielectric constants, a block copolymer film is produced in the same manner as described above, thereby having a vertically aligned lamella structure. It is also possible to produce photonic crystals. The period of the crystal can be performed by changing the period of the lamella by changing the number of monomer units (degree of polymerization) of each block chain constituting the block copolymer.

A block copolymer (PS-b-PI) consisting of polystyrene and polyisoprene with a number average molecular weight of 8.9 × 10 ⁴ , a [weight average molecular weight] / [number average molecular weight] of 1.04, and a polystyrene volume fraction of 0.51. After dissolving polyisoprene in a good solvent cyclohexane, a PS-b-PI film was prepared by a casting method.

  The PS-b-PI membrane was dried at room temperature under vacuum to remove the solvent. A transmission electron microscope (TEM) photograph of the PS-b-PI film excluding the solvent is shown in FIG. According to FIG. 8, it can be seen that the PS-b-PI membrane has a microphase separation structure in which the cylinders form a hexagonal lattice and exist in the matrix. In this embodiment, since a selective solvent of a good solvent is used for polyisoprene, the bright region (cylinder portion) is made of polystyrene and the dark region (matrix portion) is made of polyisoprene in FIG.

When it was observed the PS-b-PI film using small angle X-ray scattering (SAXS), in the scattering profile of the membrane, high-order peaks at 3 ^1/2 and 2 times the wave number of first peak In addition, the gentle peak seen on the wide-angle side was satisfactorily fitted by the theoretical scattering function of the cylindrical particles ((a) of FIG. 9). This also indicates that the microphase separation structure of the PS-b-PI membrane has a cylinder structure.

  Next, zone heating of this PS-b-PI film was performed using the zone heating apparatus 10 shown in FIG. The zone heating apparatus 10 includes a heating block 11 having an elongated rectangular head portion, a cooling block 12 having an elongated rectangular head portion, a sample cell 13 for fixing a sample (PS-b-PI film), and a heating block. 11 and a driving device 14 for controlling the moving speed of the cooling block 12 are provided. The sample fixed in the sample cell 13 is brought into contact with the head portions of the heating block 11 and the cooling block 12 to be heated and cooled. The interval in the moving direction (oz direction in the figure) of the head portions of the heating block 11 and the cooling block 12 is very short, and the block copolymer film can be heated under a steep temperature gradient.

  An orientation interface (glass in this embodiment) 15 is provided at the end of the sample cell 13, and the sample is fixed in the sample cell 13 so as to be in contact with the orientation interface 15. By providing the orientation interface 15 in this manner, among the block copolymer samples composed of two blocks, blocks with higher affinity are arranged in contact with the orientation interface 15.

  10A is a longitudinal sectional view of the apparatus, and FIG. 10B is a view of the apparatus as viewed from above the apparatus. However, in (b), the upper heating block 11 and cooling block 12 are omitted.

  In the present embodiment, the heating block 11 and the cooling block 12 were used with an interval in the moving direction of the head portion of 4 mm. In addition, the heating block 11 temperature is 180 ° C higher than the Tg of PS-b-PI, the cooling block 12 temperature is 3 ° C, and the maximum temperature in the sample is adjusted to 160 ° C and the minimum temperature is 10 ° C did. Furthermore, by setting the distance between the heads of the heating block 11 and the cooling block 12 to 2 mm, a temperature gradient within the sample of 75 ° C./mm was formed. The sample was sandwiched between two polyimide films and then fixed in the sample cell 13.

Using the apparatus 10 as described above, the heating block 11 and the cooling block 12 were moved in the oz direction at a speed of 25 nm / sec to control the orientation of the PS-b-PI film. A PS-b-PI film having a lamellar microphase separation structure oriented perpendicular to the film surface (xz plane) was obtained. The profile in (b) of FIG. 9 is a scattering profile obtained by observing this PS-b-PI film with SAXS, and has a wave number that is an integral multiple (1, 3, 5 times) of the primary peak. The next peak appears. Further, when the two-dimensional small angle scattering measurement of the obtained PS-b-PI film was performed, the scattering pattern was observed when observed from the ox direction and the oy direction in terms of the film arrangement in the apparatus diagram of FIG. As shown in 11 (a) and 11 (b), strong scattering appeared in the _qz direction. Therefore, the PS-b-PI film after heating to a temperature above Tg has a lamellar surface parallel to the xy plane and perpendicular to the film surface (xz plane), and the normal direction of the lamella is in the oz direction. It is inferred that the microphase separation structure is arranged as shown in FIG.

  The reason why the PS-b-PI film has a lamellar surface parallel to the xy plane and perpendicular to the film surface (xz surface) is to be normal to the moving direction (oz direction) of the heating block 11 and the cooling block 12 When the lamella interface grows so that the vector has an angle, the PS block and the PI block extend or contract more than necessary near the orientation interface, so the lamella interface grows in a direction parallel to the orientation interface. Compared to the case, it is considered that the block polymer chain packing in the lamella becomes unreasonable and is in a disadvantageous form-entropy state.

  As described above, according to the method of the present invention, as shown in FIG. 12, a microphase separation structure in which lamellas are regularly arranged in one direction (oz direction) and oriented perpendicularly to the film surface in a wide region. The block copolymer film | membrane which has can be obtained.

The figure of the block copolymer film | membrane which has a lamellar micro phase separation structure. The figure of the block copolymer film | membrane which has a cylindrical micro phase-separation structure. The figure of the block copolymer film | membrane which has a spherical micro phase-separation structure. A transmission electron microscope (TEM) photograph of a block copolymer film formed without performing orientation control. The figure showing a mode that the block copolymer film | membrane which is arranged in one direction by the zone heating method and has a vertical alignment lamellar structure is formed. The figure showing a mode that the micro phase-separation structure of a block copolymer changes from a cylinder shape to a lamellar shape by heating. Using a glass transition temperature, a block copolymer film having a vertically aligned lamellar structure in which lamella normals are regularly arranged in a direction perpendicular to the orientation interface and parallel to the temperature gradient direction in a wide area is shown. Figure representing. TEM photograph of PS-b-PI film before heating to a temperature above Tg. Small angle X-ray scattering (SAXS) profiles of PS-b-PI films before and after heating to temperatures above Tg. (a) It is one Example of the zone heating apparatus for implementing this invention, Comprising: The figure (vertical sectional view) which shows the mode before starting zone heating, The apparatus of (b) (a) is apparatus upper direction (C) The figure showing the state in the middle of the zone heating process using the apparatus of (a), (d) The figure showing the temperature distribution in a sample in a zone heating process. (A) Two-dimensional small-angle scattering profile observed from the ox direction and (b) Two-dimensional small-angle scattering profile observed from the oy direction of the PS-b-PI film after zone heating to a temperature above Tg. Image of the microphase separation structure of PS-b-PI membrane after zone heating to a temperature above Tg.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Temperature control apparatus 11 ... Heating block 12 ... Cooling block 13 ... Sample cell 14 ... Drive apparatus 15 ... Orientation interface

Claims (8)

A block copolymer consisting of two types of repeating monomer units and expressing a lamellar microphase separation structure in a thermal equilibrium state is a good solvent for the block consisting of one repeating monomer unit, and from the other repeating monomer unit A step of dissolving in a solvent that is a poor solvent for the block comprising;
Forming the block copolymer film using the solution;
Removing the solvent from the membrane and developing a microphase separation structure other than lamellar,
A step of heating the block copolymer film from which the solvent has been removed to a glass transition temperature or higher sequentially for each narrow region;
A method for producing a block copolymer film having a vertically aligned lamellar structure, comprising:   One or more homopolymers that are compatible with only one of the blocks constituting the block copolymer and composed of the same or different monomers as the monomers constituting the block are mixed with the block copolymer. A method for producing a block copolymer film having a vertically aligned lamellar structure.   The size of the heating region above the glass transition temperature of the block copolymer film is substantially the same as the period of the lamellar structure in a thermal equilibrium state determined by the type of the block copolymer. 3. A method for producing a block copolymer film having a vertically aligned lamella structure according to 2.   The method for producing a block copolymer film having a vertically aligned lamellar structure according to any one of claims 1 to 3, wherein the block copolymer comprises styrene and isoprene.   The method for producing a block copolymer film having a vertically aligned lamellar structure according to claim 4, wherein the solvent is cyclohexane.   The block copolymer having a vertically aligned lamella structure according to any one of claims 1 to 5, wherein the lamella spacing is changed by changing the number of monomer units of each block chain constituting the block copolymer. A method for producing a polymer film. A block copolymer consisting of two repeating monomer units having different dielectric constants and expressing a lamellar microphase separation structure in a thermal equilibrium state is a good solvent for a block consisting of one repeating monomer unit, For the other block composed of repeating monomer units, a step of dissolving in a solvent that is a poor solvent;
Forming the block copolymer film using the solution;
Removing the solvent from the membrane and developing a microphase separation structure other than a lamellar microphase separation structure;
A step of heating the block copolymer film from which the solvent has been removed to a glass transition temperature or higher sequentially for each narrow region;
A method for producing a photonic crystal having a vertically aligned lamellar structure, comprising:   8. The method for producing a photonic crystal according to claim 7, wherein the period of the crystal is changed by changing the number of monomer units of each block chain constituting the block copolymer.

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