JP2008274043A - Film and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent film excellent in dimensional stability, and capable of adjusting birefringence. <P>SOLUTION: The transparent film comprises a laminar inorganic compound (A), a birefringent substance (B) different from (A) and an additive (C), and has an oriented lamination layer structure of the laminar inorganic compound (A) wherein the proportion of (C) occupying in the film is greater than 0 mass% and not greater than 45 mass%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transparent film containing a layered inorganic compound. In addition, the present invention relates to a display at least a part of which is formed of such a film, a related member, a circuit board, and a gas barrier film.

  In recent years, the manufacturing technology of flat panel displays including liquid crystal displays (hereinafter referred to as FPD) has dramatically advanced, and thin displays that cannot be achieved with conventional cathode ray tubes have become a reality. Almost all current FPDs have devices formed on glass substrates, and there are no practical FPDs using substrates other than glass substrates. The reason for this is that the glass substrate has high heat resistance and is suitable for forming a display drive circuit or member that requires high-temperature formation, a low linear expansion coefficient, and stress applied to the drive circuit or member. Gas barrier that can be suppressed, that there is little breakage of wiring and characteristic fluctuation of parts, that it is easy to extract light because it is transparent in the visible light range, and that has high gas barrier properties and prevents entry of oxygen and water vapor from the outside It can be used as a material, and can maintain a high vacuum if necessary.

However, the glass substrate is not flexible and easily broken. In addition, the weight is heavy, and the deformation of the substrate and the difficulty in handling are problematic. In addition, glass substrates cannot be used for flexible displays such as electronic paper that can be bent, assuming applications such as bending and carrying. Because it has, it is not very suitable for mobile use. From such a point of view, it is desired to put a display substrate and a gas barrier film into practical use having heat resistance, linear expansion coefficient, transparency, gas barrier properties and the like equivalent to glass.
In addition, there is an increasing demand for high-density component mounting on circuit boards on which electronic components constituting electrical appliances such as displays, mobile phone terminals, and computers are mounted. In addition, with the increase in electrical appliances that require rotation and deformation as typified by mobile phone terminals, there is an increasing demand for flexibility. Therefore, the demand and demand for flexible circuit boards and copper clad laminates are also increasing.

  At present, as the flexible circuit board, a substrate formed of a resin such as polyethylene terephthalate, polycarbonate, polyimide, or a special glass epoxy substrate is used. However, when manufacturing a printed circuit board in which circuit wiring is formed by printing or coating using a conductive ink such as a conductive paste, the conductive ink is applied to obtain a sufficiently high conductive wiring. In general, it is necessary to fire at a high temperature of 300 ° C. or more later. However, in the case of a flexible circuit board using a substrate formed of the resin as described above, the heat resistance of the resin is low and the linear expansion coefficient is generally large. In addition, the above-mentioned high-temperature firing cannot be performed, and it must be performed at a relatively low temperature.

However, since the conductive ink does not sufficiently sinter at a low temperature, there is a problem that the conductive performance is generally inferior as compared with a metal foil or wiring obtained by vacuum deposition. Polyimide resin has a relatively high heat resistance, but is expensive, and therefore difficult to use in applications where cost is most important, such as an RFID (Radio frequency identification) tag. From such a point of view, there is a demand for practical use of an inexpensive flexible printed circuit board that has insulation and high heat resistance and flame retardancy.
On the other hand, there are many kinds of layered inorganic compounds represented by clay minerals in nature, many of which are inexpensive, harmless to the human body, and have the characteristics of not burning. As the name suggests, layered inorganic compounds are layered (plate-like) inorganic crystals. Typical examples include layered silicates such as smectite group clay and mica, layered silicates such as magadiite and kenyaite, hydro Layered double hydroxides such as talcite, layered phosphates, layered transition metal oxygenates such as titanium / niobate, hexaniobate or molybdate, layered manganese oxide, layered cobalt oxide, etc. There are layered inorganic compounds having different compositions.
Among layered inorganic compounds, especially clay minerals are present in large quantities in nature, and are suitably used for various applications in view of being inexpensive and excellent in dispersibility (see, for example, Non-Patent Document 1).

As one of the utilization methods of layered inorganic compounds including clay minerals as described above, extensive research has been conducted on nanocomposite materials in which a small amount of layered inorganic compounds (generally about 5% by mass or less) is added to the resin. Some have been put into practical use (for example, see Non-Patent Document 2). In the nanocomposite material system to which a small amount of these layered inorganic compounds is added, an effect of improving strength and flame retardancy or an effect of improving gas barrier properties is recognized.
However, since the ratio of the layered inorganic compound is small in these nanocomposite materials, the properties of the resin are not substantially improved. Most of them are not aligned in the layered inorganic compound, or have been aligned to some extent by stretching or the like. For example, taking gas barrier properties, the layered inorganic compound is added to cause gas permeation. Although there are cases where the gas transmission rate is reduced to a fraction of the distance because the moving distance becomes long, there are almost no cases where the gas barrier property is improved by an order of magnitude or more. In addition, for the purpose of improving the gas barrier property by extending the gas movement path when the gas permeates, layered inorganic compounds such as natural montmorillonite and synthetic mica having a large crystal size are often used. In this case, natural montmorillonite is used. It is difficult to obtain a colorless and highly transparent film with a small haze (cloudiness) that can be used for displays, etc. due to factors such as yellow coloration derived from light and scattering of light derived from the large crystal size of synthetic mica. It was. Similarly, when the amount of layered inorganic compound added is small, it is difficult to significantly improve other physical properties other than gas barrier properties, such as heat resistance and dimensional stability during temperature changes. It was difficult to say that the essential characteristics of the excellent layered inorganic compound were fully utilized.

In order to improve the dimensional stability and heat resistance, and to increase the transparency by suppressing the scattering of light, the layer of the layered inorganic compound is oriented, that is, the layer of the nanosheet which is a unit structure of the layered inorganic compound, It is thought that it is important to form a nanocomposite that is densely and highly oriented and stacked so that the orientation of the layer surfaces is as uniform as possible. In addition, it is necessary to reduce the proportion of components such as polymers that lack dimensional stability and heat resistance. This is considered to improve the gas barrier property.
Conventionally, for example, a layered inorganic compound or a dispersion in which a layered inorganic compound and an additive such as a polymer are mixed is spread on a glass plate or a film having releasability, and is allowed to stand and dry. It is known that a uniform film is formed. For example, reports of retardation plates for liquid crystal displays using the birefringence of layered inorganic compounds (see Patent Documents 1 and 2), reports of the same retardation plates with adjusted birefringence (see Patent Document 3), layered inorganic A report that succeeded in expressing transparency and high gas barrier properties by using a water-soluble resin having a good affinity for the compound and setting the weight ratio of the layered inorganic compound to the total solid to 70% or more (see Patent Document 4), water High-strength and water-resistant, consisting of a hydrophobic layered compound and transparent polyimide that have improved dispersibility in organic solvents by exchanging inorganic ions in the layered inorganic compound dispersed in organic ions such as organic ammonium salts Report on transparent film (see Patent Document 5), Report on transparent film with high strength and water resistance composed of resin and hydrophobic layered compound having a glass transition temperature of 250 ° C. or more (see Patent Document 6) There are any number of reports.

  However, the films in Patent Documents 1 and 2 have a large birefringence in the thickness direction (the refractive index in the thickness direction is smaller than the refractive index in the in-plane direction) and are generally required to have low birefringence. It cannot be applied to optical applications (for example, a display substrate or an optical lens). Patent Document 3 makes it possible to adjust the birefringence in the film thickness direction, but the actually implemented invention is the formation of a film on a support, and the strength and dimensional stability required for a self-supporting film or formed body There are no mentions of constituents necessary for the development of sex. Although the film in Patent Document 4 has a high ratio of layered inorganic compounds and exhibits high gas barrier properties, the additive is limited to water-soluble resins, so water resistance and hygroscopicity, and further elution of alkali metals provided in layered inorganic compounds The birefringence in the thickness direction is very large. In the film in Patent Document 5, if the content of the hydrophobic layered compound is not less than 20% by mass, the hydrophobic layered compound is partially agglomerated in the production process, and the haze increases and it is difficult to say that the film is transparent (in haze value). 50% or more), and the decrease in toughness becomes significant. Furthermore, transparent polyimide is expensive and has many problems from the viewpoint of cost. Similarly, Patent Document 6 describes that the upper limit of the proportion of the hydrophobic layered compound is 50% by mass due to the decrease in transparency, and the transparent film actually produced has a content of the hydrophobic layered compound of about Therefore, it is difficult to say that the value of the linear expansion coefficient, which is considered appropriate as an index of dimensional stability, is as small as 25 ppm / ° C. or more. In addition, in order to improve heat resistance, a resin that is not a general-purpose product having a Tg of 250 ° C. or higher must be used, which is hardly practical.

That is, films and formed bodies to which conventional layered inorganic compounds have been added have problems in transparency, birefringence, heat resistance, dimensional stability, strength, water resistance, etc. It is thought that a high-dimensional balance has not been developed yet.
Therefore, the present invention solves the problems of the prior art as described above, and does not deteriorate the linear expansion coefficient and elastic modulus even at a temperature exceeding the Tg of the resin to be added, and has high strength, dimensional stability and heat resistance. It is an object of the present invention to provide a transparent film that is high, has water resistance, can adjust birefringence, and can also achieve zero birefringence. It is another object of the present invention to provide a display material (for example, a substrate or a gas barrier film), a gas barrier film, and a circuit board having such a film.
Japanese Patent No. 3060744 JP-A-11-95030 JP 2005-274595 A JP 2007-63118 A JP 2006-37079 A JP 2006-265383 A Edited by Sudo Kodankai, “Invitation to Clay Science: Clay's Face and Charm”, Sankyo Publishing, p. 6 (2000) Nakasumi, edited by “Development of Polymer Nanocomposites”, Frontier Publishing, p. 25-90 (2004)

  An object of the present invention is to provide a transparent film having excellent dimensional stability and capable of adjusting birefringence.

As a result of intensive studies in order to solve the above-mentioned problems, the present inventor comprises a layered inorganic compound (A), a birefringent substance (B) different from (A), and an additive (C), and is layered. A transparent film having a structure in which the lamination of the inorganic compound (A) is oriented, and if the proportion of the film in (C) is greater than 0% by mass and 45% by mass or less, it can be adapted to the purpose. And the present invention was made based on this finding.
That is, the present invention relates to a transparent film containing a layered inorganic compound.

  The transparent film of the present invention has strength that can be handled as a self-supporting film, has a small linear expansion coefficient, excellent dimensional stability, can adjust birefringence, and can also achieve zero birefringence.

  In the present invention, the layered inorganic compound is cleaved as much as possible to the nanosheet which is its unit structure, the layer surface direction is as parallel as possible to the film surface, and a substance having birefringence, an additive such as a polymer, The film is stacked in a dense and highly uniform orientation with an antioxidant as required. For this purpose, the film is formed by a casting method from a dispersion in which a substance constituting the film is dispersed in a solvent. Then, the birefringence of the film is controlled by orienting a birefringent material having an anisotropic refractive index to the film, and the nanosheets are oriented and regularly laminated as described above. By increasing the proportion of the layered inorganic compound in and limiting the amount of additives such as polymers that have low heat resistance and dimensional stability, high transparency, dimensional stability, heat resistance, and their physical properties can be achieved. A major feature is that the birefringence can be controlled while being held.

  The layered inorganic compound (A) used in the present invention will be described. The layered inorganic compound (A) in the present invention is not particularly limited, and clay mineral, layered polysilicic acid, layered silicate, layered double hydroxide, layered phosphate, titanium / niobate and hexaniobium Examples thereof include layered transition metal oxyacid salts such as acid salts and molybdates, layered manganese oxides, and layered cobalt oxides. However, in order to obtain a transparent film, it is necessary that the layered inorganic compound is not colored or the degree of coloring is slight. Furthermore, when dispersed in a solvent, it is important to cleave and disperse the nanosheet as a unit layer as much as possible. Particularly suitable as these layered inorganic compounds are clay minerals. As the clay mineral, natural clay or synthetic clay may be used, and for example, mica, vermiculite, montmorillonite, beidellite, saponite, hectorite, stevensite, or magadiite, hydrotalcite, caryonite, halloysite, etc. may be used. However, the use of synthetic clay is preferred to improve the transparency of the film, and synthetic saponite, synthetic hectorite, synthetic stevensite, synthetic mica, synthetic hydrotalcite, synthetic caryonite, etc. are preferred, but dispersibility and the like are preferred. Thus, clay belonging to the smectite group is more preferable. From the viewpoint of gas barrier properties, natural montmorillonite having a large aspect ratio of the clay crystal layer, clay belonging to the mica group, smectite clay having a high aspect ratio, and the like are preferable.

Most of the layered inorganic compounds, especially clay minerals, have the property of being dispersed in water or a mixed solvent of water and a highly polar solvent. Therefore, the dispersion medium of such a layered inorganic compound is generally water or one containing water. However, when the dispersion medium of the layered inorganic compound is limited to water or one containing water, additives such as a birefringent material other than the layered inorganic compound and a polymer, which are constituents of the film of the present invention, are also used. , Water, water-containing or dissolved or dispersed in water-compatible solvents must be used, in which case the birefringent materials and additives that can be used are extremely limited .
In addition, the structure which orientated the lamination | stacking of the layered compound (A) in this invention means the state laminated | stacked so that the direction of the layer surface of a layered compound (A) may become as parallel as possible to a film surface.

In the present invention, the term “transparent” means that the total light transmittance is 70% or more and the haze (cloudiness) is 10% or less.
As the layered inorganic compound (A), it is also useful to use a hydrophobic layered compound obtained by subjecting the surface of the layered inorganic compound to an organophilic treatment. As the organophilic treatment, treatment can be performed using an organic ion such as an ammonium salt, a phosphonium salt, an imidazolium salt, a carboxylic acid, an amino acid, or a sulfonic acid. By carrying out the organophilic treatment using these organic ions, the inorganic ions provided in the nanosheet of the layered inorganic compound having a charge are exchanged with organic ions to improve the dispersibility in an organic solvent, and a hydrophobic layered compound is produced. be able to. For layered inorganic compounds such as caryonite, hydrotalcite, or layered silicate, where the hydroxyl group is exposed on the surface of the nanosheet, the hydrophobicity is obtained by bonding the hydroxyl group to an organic substance by dehydration reaction etc. Layered compounds are also suitable. By dispersing the layered inorganic compound in the organic solvent, a hydrophobic birefringent substance or additive that is similarly dispersed or dissolved in the organic solvent can be uniformly mixed in the dispersion in which the layered inorganic compound is dispersed. The types of additives such as birefringent substances and polymers that can be selected are dramatically increased, and not only water-resistant films can be obtained, but film properties such as birefringence, strength, and dimensional stability can be widely controlled. It becomes possible. In particular, an organic smectite obtained by making a clay belonging to the smectite group organophilic by the above-described method is preferable from the viewpoints of easiness of organic treatment, dispersibility, and the like. Among organic ions, ammonium salts include ammonium salts having alkyl groups, benzyl groups, polyoxyethylene groups, oxyethylene groups, oxypropylene groups, etc., and quaternary ammoniums such as dimethyl distearyl ammonium salts and trimethyl stearyl ammonium salts. Salt. Phosphonium salts and imidazolium salts have a higher decomposition and desorption temperature than quaternary ammonium salts, so the heat resistance of the hydrophobic layered compound itself that has been subjected to organophilic treatment with phosphonium salts or imidazolium salts. In addition, since the influence on the additive such as a polymer by a substance formed by decomposition and desorption is also reduced, it is suitable for comprehensively improving the heat resistance of the film.

The presence of organic ions in the hydrophobic layered compound has a relatively small influence on the transparency and dimensional stability of the film because it is strongly bonded to the surface of the tetrahedral sheet or octahedral sheet. That is, even if the proportion of the inorganic component (part as a layered inorganic compound) in the hydrophobic layered compound decreases due to the introduction of bulky organic ions, the organic ions are combined with the nanosheet, which is an inorganic component, and behaves as one. Therefore, it is a feature that the influence of these organic ions on the dimensional stability during heating and the decrease in elastic modulus is small.
In addition, since the hydrophobic layered compound is obtained by exchanging inorganic ions such as alkali metals existing between the layers of the charged layered inorganic compound with organic ions, if the hydrophobic layered compound that has been sufficiently ion-exchanged is used, the alkali metal etc. In principle, it is possible to obtain a film containing almost no inorganic salt, and it is considered that the film is suitable for use in electronic devices that dislike alkali metals. Furthermore, by selecting the type of organic solvent, the film can be dried with less heat energy than water, and a low-energy manufacturing process can be achieved.

The definition of the water-resistant film is that it does not dissolve when immersed in water, but the water absorption after 24 hours of impregnation with distilled water of at least 24 ° C. is 10% or less, preferably 7%. Hereinafter, it is desirable that the content is 5% or less. Here, the water absorption rate is mc for the weight before dipping in the water of the film that has been sufficiently dried (desirably dried at 100 ° C. or more for 1 hour or more), and md after being dipped in water. Next (1) type water absorption rate = (md−mc) / mc × 100 (%) (1)
Is defined by
Next, the birefringent material (B) used in the present invention will be described. As an index for defining the birefringence, the intrinsic birefringence value of the substance is suitable. In the present invention, the intrinsic birefringence Δn is a value of a refractive index in a direction showing a minimum refractive index in a plane in which the direction having the largest refractive index is one axis, the refractive index is nzz, and the axis is the normal direction. Can be defined as a value given by the following formula (2), where nxx is the refractive index value in the direction showing the maximum refractive index.
Δn = {nzz− (nxx + nyy) / 2} (2)
For example, in the case of a biphenyl molecule in which two benzene rings are connected in series, the refractive index value of the method is nzz, the direction of the refractive index of the method is nzz, the direction perpendicular to the benzene ring is nx, and parallel to the benzene ring. It is possible to estimate whether or not it has a suitable intrinsic birefringence by calculating the value of Δn in that case by electronic state calculation by, for example, first-principles calculation or density functional theory. it can.

  In the present invention, it is necessary that the direction of the axis having the highest refractive index in the birefringent material is oriented in a direction substantially perpendicular to the plane of the nanosheet. In this case, the value of Δn is From the viewpoint of refraction, it is preferably at least 0.03 or more, preferably 0.06 or more, more preferably 0.1 or more, still more preferably 0.15 or more, and most preferably 0.3 or more. When the degree of orientation is the same, the larger the Δn, the greater the change in birefringence with the addition of a small amount. However, if Δn is too large, Rth does not become a predetermined value due to a subtle change in the amount of addition of the birefringent material, or Rth changes greatly due to a subtle variation in the orientation of the birefringent material. Therefore, depending on the type of the birefringent material to be selected, it is not always good if the value of Δn is large. The value of Δn is at least 2.0 or less, preferably 1.5 or less.

As a birefringent substance, the intrinsic birefringence Δn is 0.03 or more, and as will be described later, the nzz direction of the layered inorganic compound in the film is generally in the normal direction of the nanosheet. It is not particularly limited as long as it can be oriented and oriented, and examples thereof include low molecular substances having a pi electron system, rod-like, needle-like, or plate-like inorganic microcrystals. In particular, from the viewpoint of ease of orientation, low molecular weight substances and low molecular weight substances having mesogenic groups are preferred.
In the present invention, nx, ny and nz mean the three main refractive indices of the x direction, the y direction and the z direction, respectively, the x direction and the y direction are in-plane directions of the film perpendicular to each other, and the z direction is It is defined as the film thickness direction. At this time, the retardation value often used for quantitatively expressing the birefringence of the film is Re (nm) as the retardation in the in-plane direction, and Rth (nm) as the retardation in the thickness direction. Where d (nm) is defined as the following formulas (3) and (4).
Re = (nx−ny) × d (3)
Rth = {(nx + ny) / 2−nz} × d (4)
Usually, since the layered inorganic compound is composed of nanosheets that are not equiaxed, when such nanosheets are oriented and laminated, a birefringent film having an optical axis in the normal direction of the film is formed. In general, the nanosheets constituting the layered inorganic compound have a smaller refractive index in the film thickness direction than the in-plane direction, and when laminated, the in-plane directions are oriented randomly in parallel to the plane of the nanosheet, Unless special measures (for example, orientation control by stretching, electron beam irradiation, or application of an electromagnetic field) are added, nx and ny are almost the same, and birefringence in the film plane hardly occurs (Re˜0). On the other hand, since the relationship of nx> nz and ny> nz is established in the film thickness direction, the film in which the nanosheets are oriented and laminated as described above exhibits optically negative uniaxiality (Rth> 0). Therefore, it can be suitably used for applications that preferably use optical negative uniaxiality, for example, for phase difference correction of a vertically aligned liquid crystal cell such as a VA type by adjusting the amount of a layered inorganic compound. Documents 1 and 2 are suitable examples.

  However, when the amount of the layered inorganic compound constituting the film increases, that is, when the constituent ratio of the layered inorganic compound increases even at the same film thickness, the layered inorganic compound constituting the film is further increased by increasing the film thickness itself. When the amount increases, Rth increases. For this reason, when the ratio of the layered inorganic compound as in the present invention is increased and a film having a sufficient strength that can be handled as a self-supporting film is obtained, a film having a large Rth value is necessarily formed. Will be formed. In addition, it is difficult to produce a film having a relationship of nx> nz> ny, which is necessary for phase difference correction of a polarizing plate suitably used for an IPS liquid crystal cell.

  When polarized light passes through a birefringent medium, its polarization state changes. When polarized light is transmitted through a film whose Rth value is not 0, the polarization state changes when the direction of light passing through the film deviates (tilts) from the normal direction of the film. The larger the absolute value of Rth, the more the direction of light passing through the film deviates from the normal direction of the film, and the greater the change in the polarization state of the light. Converted to elliptically or circularly polarized light. This greatly affects devices using polarization characteristics, such as liquid crystal displays. In a liquid crystal display, normally two polarizing plates are used, the polarization characteristics are converted by controlling the phase difference of the liquid crystal layer in the liquid crystal cell sandwiched between the polarizing plates by voltage, and the amount of light that can pass through the polarizing plate is determined. An image is formed by controlling. At present, the substrate that forms the liquid crystal cell is glass, and since glass has extremely low birefringence, the Rth value is also small. Therefore, even if polarized light passes through the glass substrate obliquely with respect to the normal direction, the state is almost the same. does not change. For this reason, the amount of light that can be transmitted through the polarizing plate can be controlled as designed even for light that has passed through the glass substrate obliquely.

  However, if instead of a glass substrate, for example, a film having a non-zero absolute value of Rth in which nanosheets are oriented and laminated as described above is used as the substrate, the linearly polarized light that has passed obliquely with respect to the normal direction of the substrate is elliptical. As a result of being converted into polarized light or the like and changing its state, the light that should originally be shielded by the polarizing plate passes through the polarizing plate. For this reason, the amount of transmitted light cannot be controlled as designed. This causes an undesired phenomenon such as a decrease in viewing angle (a decrease in contrast when viewed from an oblique direction) due to black floating (light leakage) in a liquid crystal display. Therefore, a film having a large absolute value of Rth, at least a film having an absolute value of Rth exceeding 2000 nm is not suitable as a member for controlling polarization in a liquid crystal display, and is generally at most 2000 nm or less and 1000 nm or less. The most common is 500 nm or less.

  Therefore, when a film material is used as an alternative to the current glass substrate, it is generally preferable that the absolute value of Rth is close to 0 nm as in the case of glass. However, strictly speaking, even though glass has a Rth value of, for example, a value of several tens of nanometers in the case of a thickness of 800 μm, it is difficult to completely form a film having an Rth of 0 nm. And there is little need. Therefore, the value of Rth that can be regarded as practically 0 nm is at least −50 nm to 50 nm, preferably −20 nm to 20 nm. The above value is preferably achieved at a film thickness of 150 μm, and more preferably at a film thickness of 200 μm or more. Also, it is generally preferable that the absolute value of Re is close to 0 nm. A value close to 0 nm is preferably -10 nm or more and 10 nm or less.

  The above is about Rth required when the present glass substrate for liquid crystal display is replaced with the film of the present invention, and actually protects polarizing plates and other optical films such as retardation plates and polarizing plates. In many cases, triacetylcellulose (TAC) film has birefringence, and therefore, considering that Rth is compensated, a film material like the present invention can be used as an alternative to the current glass substrate. When R is used, its Rth is not necessarily close to 0 nm, and can be controlled to an appropriate value within an absolute value of 2000 nm or less. Although the amount of Rth and the sign of the polarizing plate, retardation plate, TAC film, etc. have a width depending on the material, a suitable value cannot be defined unconditionally, but the Rth of all the materials constituting the liquid crystal panel excluding the liquid crystal molecules The total is generally 2000 nm or less in absolute value, often 1000 nm or less, and most commonly 500 nm or less. Therefore, the range of the Rth value that should be carried by the film of the present invention is at least an absolute value of 2000 nm or less as a range in which the inherent Rth value of various materials constituting the liquid crystal panel can be suitably compensated. The absolute value is preferably 1000 nm or less, more preferably 500 nm or less, and in view of compatibility with many current members, the absolute value is preferably 350 nm or less. It is done. The above value is preferably achieved at a film thickness of 150 μm, and more preferably at a film thickness of 200 μm or more. In addition, if it is used for the substrate of the IPS liquid crystal panel, a part of the role of the phase difference plate having a relationship of nx> nz> ny, which is currently limited in production method, by previously setting Rth of the substrate to be negative. It is also possible to make the substrate bear.

  In the present invention, the birefringence of the film generated when the nanosheets as described above are oriented and laminated can be controlled by orienting a birefringent substance different from the layered inorganic compound and imparting it to the film. is there. For example, the birefringence of the film in the present invention can be controlled by adding a low-molecular substance having intrinsic birefringence or an inorganic microcrystal sufficiently smaller than the wavelength of light to the film and orienting the film in the film. In the present invention, the low molecular weight having the above-mentioned intrinsic birefringence is utilized by utilizing physical and chemical interaction with the layered inorganic compound that is oriented and laminated in the film or the substance bonded to the layered inorganic compound. Substances and inorganic microcrystals can also be easily oriented in the film. Depending on the amount of addition of the birefringent substance and the control of the orientation direction and the degree of orientation (orientation degree), Rth can be made larger, or conversely, Rth can be made smaller to make the Rth value too large. Rth can be adjusted freely by making adjustments, making Rth negative in some cases, and adjusting the type and amount of addition of birefringent substances to produce a zero birefringence film with zero Rth. Can be adjusted.

  Examples of the low molecular substance having birefringence include molecules having a mesogenic group. The mesogenic group means a rigid linear intermediate portion that exhibits liquid crystallinity in liquid crystal molecules. The mesogenic group has rigidity so that the molecules do not deform during orientation and the polarizability anisotropy does not decrease, and in order to increase the polarizability anisotropy, two or more aromatic rings or It preferably has an alicyclic ring. Two or more aromatic rings or alicyclic rings may have a linking group connecting them, and examples of the aromatic ring include an aromatic hydrocarbon ring such as a benzene ring, or an aromatic heterocycle. Among these, those having two or more benzene rings are preferable because they are molecules having large anisotropy and rigidity. Such molecules include fluorene, naphthalene, carbazole, biphenyl, 4-biphenylcarboxylic acid, 4-hydroxybiphenyl, 2-hydroxybiphenyl, diphenyl ether, benzophenone, stilbene, diphenylacetone, 1,4-diphenyl-1,3- Examples thereof include butadiene, benzaldehyde azine, 4-benzoylbiphenyl, chalcone, 1,3-diphenoxybenzene, phenanthrene, and tolane, and low molecular weight substances having a mesogenic group described in Patent Document 3. In particular, 4-hydroxybiphenyl is preferable from the viewpoint of heat stability, and phenanthrene and 4-biphenylcarboxylic acid are preferable from the viewpoint of a large Rth reduction effect.

  This low molecular weight substance with a mesogenic group has a delocalized electron density distribution in the long axis direction of the molecule, and therefore the polarizability in the long axis direction of the molecule is larger than the polarizability in the other direction. Intrinsic birefringence in the major axis direction of the molecule is large. Further, in such a low-molecular substance having a mesogenic group, when interacting with the nanosheet, the interaction with the nanosheet or a substance bound to the nanosheet (for example, an organic ion bound to the nanosheet surface), and the Due to the interaction between the low-molecular substances, a large number of molecules can be recognized that are oriented with the long axis direction of the molecules arranged in a direction substantially perpendicular to the surface of the nanosheet. As a result, due to the effect of intrinsic birefringence in the major axis direction of the low molecular weight substance oriented approximately perpendicular to the nanosheet, refraction in the film thickness direction of the film in which the nanosheets containing the low molecular weight substance are oriented and laminated The rate is larger than that without the low molecular weight substance, and the value of Rth is small. Increasing the amount of the low molecular weight substance, using a molecule having a larger intrinsic birefringence in the long axis direction of the low molecular weight substance, or the degree of vertical orientation of the low molecular weight substance with respect to the surface of the nanosheet is closer to 90 degrees By using such a molecule, the value of Rth can be further reduced, and it is easy to set Rth <0 nm. Of course, by optimizing the above-described elements that change Rth, it is possible to make Rth 20 nm or less in absolute value, that is, approximately 0 nm. In this method, even if the film thickness is increased, the Rth adjustment effect can be freely controlled by adjusting the variable element relating to the low molecular weight substance. Therefore, even if the film is thick to obtain sufficient self-supporting strength, Rth is 0 nm. Or it is excellent in that it can be a negative value. By this method, the retardation of the alignment film of the nanosheet that usually has Rth> 0 nm can be arbitrarily adjusted.

  In addition to the low-molecular substance having a mesogenic group, the value of Rth can be controlled by adding inorganic microcrystals having birefringence. Any inorganic microcrystal having birefringence may be used as long as it can be oriented with respect to at least one axis in the film. For example, in the case of an elongated needle-like crystal, it is considered that the longitudinal direction of the needle is parallel to the film surface, and the direction in which the needle faces in the surface is randomly oriented so as to be sandwiched between nanosheets in the film. If it is a plate-like crystal similar to the nanosheet, it is considered that it is oriented and laminated in parallel like the nanosheet. In order to reduce Rth, it is necessary to be an inorganic microcrystal that increases the refractive index in the film thickness direction when oriented in the film as described above, and such an inorganic microcrystal is not so many. For example, needle-shaped strontium carbonate can be mentioned. The size of the needle-like inorganic crystallites is preferably such that the average length in the longitudinal direction is 200 nm or less and the needle diameter is about 20 nm or less on average. If the size of the crystal is larger than this, it causes scattering when visible light is transmitted, and there is a possibility that the decrease in transmittance becomes remarkable particularly on the short wavelength side.

In a film containing a layered inorganic compound in which Rth is not controlled by a birefringent substance or the like, the value of Rth depends on the volume ratio of the layered inorganic compound in the film, the size of the birefringence of the layered inorganic compound itself, and the film surface. It is determined by the degree of orientation. That is, when the nanosheets are completely separated in the film, the degree of orientation is 0%, and the birefringence of each nanosheet is canceled out, and Rth is almost 0 nm. On the other hand, when the nanosheets are oriented and laminated as in the present invention, depending on how much the surface of each nanosheet is inclined from the film surface on average, that is, how much the orientation degree is disturbed from the state of 100%. , Rth is considered to have a slight width. However, in the present invention and a conventionally reported laminate of nanosheets made by a casting method similar to that of the present invention, it can be considered that each nanosheet is generally laminated substantially parallel to the film surface. . At this time, unless the birefringence is controlled by addition of a birefringent substance or the like, when the film thickness is dnm and the ratio of the layered inorganic compound in the film is a mass%, Rth is approximately represented by the following formula (5).
Rth> P × a × d (5)
The value is in the range of and does not fall below a certain value. Here, P is a value that depends on the birefringence of the layered inorganic compound itself and the degree of orientation relative to the film surface, and is at least 0.00005 or more, generally 0.0001 or more, and more generally 0.00015. As described above, it is usually 0.0002 or more. In particular, in the case of orientation lamination using smectite group clay or mica group clay, the value of P is usually 0.0002 or more, at least 0.00015 or more, and if the value of P is smaller than that, Nanosheets in the film are difficult to say in an oriented state.

Here, a is the ratio of the layered inorganic compound in the film, but corresponds to the ratio of the crystalline inorganic component that develops birefringence, and the organic ions bonded to the nanosheet with the hydrophobic layered compound, etc. It should be noted that is not included. The value a can be easily obtained from the composition ratio of the film by calculation. For example, the hydrophobic layered compound in which the organic cation, which is an organic component, is bound to 6 parts of the nanosheet, which is an inorganic component, is 65% by mass, the birefringent material is 10% by mass, and the polymer is 25% by mass. In the case of a membrane, the calculated value of a is 39% by mass. Alternatively, it can be estimated from the interlayer distance distribution of nanosheets by X-ray diffraction spectrum and image analysis by transmission electron microscope (TEM). Moreover, if it is a film | membrane which does not have an inorganic component other than a layered inorganic compound, it is determined as follows experimentally. That is, for example, when the mass of the film measured immediately after drying the film at 150 ° C. for 1 hour or more sufficiently is ma, and the mass of ash remaining after heating the film at 800 ° C. for 2 hours is mb, the value of a is Following formula (6)
a = mb / ma × 100 (6)
Can be used. Alternatively, when the birefringent substance or additive is not affected, it is possible to dissolve only the layered inorganic compound with an acid and obtain a from the weight change at that time.

  However, in the present invention, by orienting the birefringent material, a film having an Rth smaller than the conventional range given by the formula (4) can be produced. As described above, a film having an Rth of approximately 0 nm, Furthermore, a film with Rth <0 nm can also be produced. When Rth <0, it is difficult to define the lower limit, but considering the intrinsic birefringence value of the birefringent material, the upper limit of the amount that can be added, and the usage, etc., the Rth is about −3000 nm. Is considered to be the lower limit, and generally up to about -2000 nm is considered to be a suitable range of use. In particular, when considering the use of a substrate for a liquid crystal display, at least −2000 nm, usually −1000 nm, preferably about −500 nm, and considering the compatibility with many current members, a range up to −350 nm is preferable. It is.

  As a method for adjusting the value of Rth as described above, a method of controlling the amount of addition of the birefringent substance is effective. In particular, a birefringent substance composed of a low molecule is different from a polymer such as a polymer, and it has little influence on the physical properties of the film, such as tensile strength, elastic modulus, and linear expansion coefficient, when added, and the mass of the film If it is up to about 20% by mass, there is almost no effect. The preferred addition amount of the birefringent material is at least 0.1% by mass, preferably 1% by mass or more, based on the mass of the film, although it depends on the intrinsic birefringence and orientation degree of the birefringent material More preferably, it is 3 mass% or more, More preferably, it is 7 mass% or more, and may be 10 mass% or more. From the viewpoint of transparency and Rth value, the preferred addition amount of the birefringent material is at least 40% by mass, preferably 30% by mass or less, more preferably 25% by mass or less, and most preferably 20% by mass. It is as follows.

Even when the amount of the layered inorganic compound constituting the film is large, when the orientation of the nanosheets is dispersed and averaged, the birefringence is also averaged and birefringence hardly occurs, and Rth to 0 nm. Become. However, in such a film, since the nanosheets are not oriented and laminated, a low linear expansion coefficient as in the present invention, a high viscoelastic modulus at high temperature, a tensile strength, etc. cannot be obtained. It is difficult to obtain high transparency due to increased scattering.
The additive (C) used in the present invention will be described. In the present invention, various additives can be used as necessary in order to improve the physical properties of the film, such as improving the strength of the film, improving transparency, and suppressing heat-resistant yellowing. For example, if you want to impart flame retardancy, use an inorganic flame retardant such as antimony trioxide. If you want to impart plasticity, use a plasticizer such as methyl phthalate to suppress oxidative degradation during heating. Hindered phenols, hindered amines, phosphorus-based or sulfur-based antioxidants and the like may be added. These additives may be used alone or in combination of two or more.

  As the additive, an additive that imparts self-supporting property to the film and improves strength and flexibility is particularly important. Preferred as such an additive is a polymer. In general, a film made of only a layered inorganic compound or the above-described hydrophobic layered compound is fragile, poor in flexibility, and often has a self-supporting strength. In the film made of natural montmorillonite having a large aspect ratio of nanosheets and excellent dispersibility, it is possible to produce a film having only a certain strength even with a film made of only natural montmorillonite. When the ratio is increased, it is difficult to obtain transparency. In the present invention, by optimizing the type and amount of additives, the birefringence is controlled, the film self-sustainability is improved, and the film has a transparent, heat-resistant strength, and dimensional stability. it can.

  When water is used as a solvent using a layered inorganic compound that is dispersed in water, it is necessary to use an additive that is also hydrophilic and highly dispersible or soluble in water. For example, epsilon caprolactam, dextrin, starch, cellulosic resin, cellulose fiber, gelatin, agar, flour, gluten, alkyd resin, polyurethane resin, epoxy resin, fluororesin, acrylic resin, methacrylic resin, phenolic resin, polyamide resin, polyester resin Polyimide resin, polyvinyl resin, polyethylene glycol, polyacrylamide, polyethylene oxide, protein, deoxyribonucleic acid, ribonucleic acid, polyamino acid, polyhydric phenol, and benzoic acid compounds are preferred. Alternatively, an aqueous dispersion material such as latex or emulsion may be used. In addition, since they are highly dispersible or soluble in water, many films have low water resistance. Therefore, the water resistance of the additive itself may be improved by adding a salt, other reactive monomer, polymer, oligomer or the like. In the present invention, among these, hydrophilic polymers such as polyvinyl resins, methacrylic resins, and polyamide resins are preferred as additives.

  As described above, when a hydrophobic layered compound having high water resistance is used and a solvent other than water is used as a dispersion medium, an additive that can be similarly dissolved or dispersed in an organic solvent may be used. it can. In this case, generally a water-resistant film can be obtained. In the present invention, among these, a hydrophobic polymer is preferable as an additive. For example, styrene resin, acrylic resin, aromatic polycarbonate resin, aliphatic polycarbonate resin, aromatic polyester resin, aliphatic polyester resin, aliphatic polyolefin resin, cyclic olefin resin, polyamide resin, polyphenylene ether It is possible to use thermoplastic resins such as thermoplastic resins, thermoplastic polyimide resins, polyacetal resins, modified polyvinyl alcohol resins, polyvinyl acetal resins, polysulfone resins, polyethersulfone resins, and amorphous fluorine resins. Of these, polyvinyl acetal resins and polyethersulfone resins are preferable from the viewpoint of heat resistance, dimensional stability, and the like. From the viewpoint of gas barrier properties, an ethylene-vinyl alcohol copolymer (eval) is also suitable.

Also, epoxy resin, thermosetting modified polyphenylene ether resin, thermosetting polyimide resin, urea resin, allyl resin, silicon resin, benzoxazine resin, phenol resin, unsaturated polyester resin, bismaleimide triazine resin, alkyd resin, furan resin Thermosetting resins such as melamine resin, polyurethane resin, and aniline resin can also be used.
In addition, a thermosetting or photocurable resin can also be used, and examples thereof include an epoxy resin containing a latent photocationic polymerization initiator and a silicone resin. In addition, when hardening the said photocurable resin, you may apply heat simultaneously with light irradiation. In the present invention, a curing agent, a curing catalyst or the like may be used in combination with the thermosetting resin and the photocurable resin, but they are generally used for curing the thermosetting resin and the photocurable resin. If it is a thing, it will not specifically limit. Specific examples of the curing agent include polyfunctional amines, polyamides, acid anhydrides, and phenol resins, and specific examples of the curing catalyst include imidazole. These curing agents and curing catalysts can be used alone or in combination. Furthermore, the resin mentioned above may be used independently and may use 2 or more types together. In addition, it is preferable that said additive is also transparent or little colored from the necessity of setting it as a transparent film | membrane.

  In the present invention, polyvinyl acetal resin can be mentioned as a particularly suitable additive as one of additives for increasing the strength and flexibility of the film while controlling the birefringence. Polyvinyl acetal has a structure in which various aldehydes or ketones are acetalized with polyvinyl alcohol to introduce an acetal group into the side chain. Further, when the acetal group is introduced, the reaction does not proceed completely, and a structure having an acetyl group or a hydroxyl group is taken. The physical and chemical properties can be changed by changing the composition ratios of the acetal group, acetyl group, and hydroxyl group. Further, the thermal properties, mechanical properties, and solution viscosity can be changed by changing the degree of polymerization. Representative examples of commercially available products include SLECK K and SLECK B (trade name) manufactured by Sekisui Chemical Co., Ltd. The kind of the polyvinyl acetal resin used in the present invention is not particularly limited. However, when a transparent film is produced, the polyvinyl acetal resin is also preferably transparent or less colored. Examples of the substituent on the acetal carbon of the polyvinyl acetal resin include a butyl group, an acetyl group, a phenyl group, a naphthyl group, and a hydrogen group. The above-described resins may be used alone or in combination of two or more. Moreover, the polymer mentioned above may have a 2 or more types of said substituent on acetal carbon. The polyvinyl acetal resin may contain a hydroxyl group in addition to the acetal group. The amount of the hydroxyl group is preferably 25% or more because it mixes well with the layered inorganic compound such as clay. Moreover, since there will be no water resistance when there are too many hydroxyl groups, 60% or less is preferable, Especially preferably, it is 40% or less. As a polyvinyl acetal resin that satisfies the above characteristics, Sekisui Chemical Co., Ltd. polyvinyl butyral resin ESREC B can be mentioned. In Eslek B, the amount of hydroxyl groups is 25% to 40%, and particularly preferred is BX-1, which has a hydroxyl group content of 33 ± 3 wt%.

Furthermore, unlike expensive resins such as transparent polyimide, polyvinyl acetal resin is inexpensive at about 1000 yen or less per kg, and can be applied to a wide range of uses in terms of cost.
As a solvent for dissolving the polyvinyl acetal resin, in terms of excellent solubility, methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, n-octanol, diacetone alcohol, benzyl alcohol, methyl Cellosolve, ethyl cellosolve, butyl cellosolve, acetone, methyl ethyl ketone, isobutyl ketone, cyclohexane, isophorone, N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, methyl acetate, ethyl acetate, isopropyl acetate, Acetic acid-n-butyl, dioxane, tetrahydrofuran, methylene chloride, propylene chloride, ethylene chloride, chloroform, toluene, xylene, pyridine, dimethyl Sulfoxide, is preferably used as a solvent and acetic acid. Among them, tetrahydrofuran is very preferable as a solvent for polyvinyl acetal resin, and a solution in which polyvinyl acetal resin is dissolved in tetrahydrofuran is prepared. Separately, a layered inorganic compound is dispersed in an easily dispersible solvent other than tetrahydrofuran such as toluene. A method of preparing a dispersion liquid prepared and preparing a liquid containing nanosheets dispersed by mixing the two is desirable. In addition, since the suitable solvent of polyvinyl acetal resin is an organic solvent as described above, the layered inorganic compound to be dispersed is preferably the hydrophobic layered compound described above. Furthermore, when dissolving the polyvinyl acetal resin, first adding a solvent that swells the resin, and then adding a solvent that is excellent in solubility of the polyvinyl acetal resin is easy to dissolve the resin and shortens the time required for dissolution. Is preferred. Addition of alcohol as an additive solvent is preferable in that the viscosity of the solution can be kept low and the change in viscosity during storage is reduced.

  In the film of the present invention, it is important to reduce the addition amount of the polymer among the additives as described above. Generally, polymers, especially organic polymers, have low dimensional stability and heat resistance, and when heated to a temperature above the glass transition temperature, they stretch greatly or become soft with reduced elasticity. There were restrictions. For this reason, it was difficult to use it for the application which requires a high temperature process, for example, the substrate of a display. In order to solve these problems, the addition of a conventional layered inorganic compound has been studied. However, in a film containing a conventional layered inorganic compound, an additive other than the layered inorganic compound is used in order not to deteriorate the physical properties such as transparency. For example, the ratio of the polymer for strength development is more than 45% by mass, and therefore it is extremely possible to achieve a sufficiently low linear expansion coefficient, for example, a value of 20 ppm / ° C. or less without lowering transparency or the like. It was difficult.

  In the present invention, in order to solve such a problem, the nanosheet layer is densely and highly oriented, and the additive is intercalated on average between layers (the target substance is inserted between the nanosheet layers). The layer of nanosheets that are unit structures are stacked so that the direction of the layer surface is as uniform as possible, and a nanosheet alignment film having high periodicity in the direction perpendicular to the layer surface is formed, and the polymer occupies the composition of the film The addition amount is at least 45% by mass or less, usually 40% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less, and most preferably 10% by mass or less. It has high dimensional stability (low coefficient of linear expansion) with little expansion and contraction due to heating, and can be characterized by low decrease in viscoelasticity even at high temperatures. . In particular, when a polyvinyl acetal resin is used, the amount of the polymer added is preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less from the viewpoint of gas barrier properties and dimensional stability. .

In order to obtain a film in which the layered inorganic compound, the birefringent substance, and the additive are uniformly dispersed in the film and the birefringent substance is oriented to obtain a desired Rth in the present invention, the following production method is used. Is preferred.
A layered inorganic compound to be used is dispersed in a solvent to prepare a dispersion liquid that is cleaved as much as possible into a single-layer nanosheet. As a dispersion method, a known method that has been used for dispersion of a conventional layered inorganic compound, such as a method of stirring or shaking for a long time, a method of applying a shearing force with an apparatus such as a homogenizer, or the like can be used. The birefringent material is put into this dispersion and stirred well to prepare a nanosheet dispersion in which the nanosheet and the birefringent material are uniformly mixed and dispersed. At this time, in order to improve the dispersibility of the birefringent substance and suppress the occurrence of aggregation, a dispersion liquid in which the layered inorganic compound is dispersed in a state where the birefringent substance is sufficiently dissolved or dispersed in a solvent in advance. It is more preferable to mix with. At this time, the solvent used for dispersing the layered inorganic compound need not be the same as the solvent used for dissolving or dispersing the birefringent substance, and different solvents may be used as long as they are compatible with each other.

  Next, another additive such as a polymer or an antioxidant is added to the nanosheet dispersion liquid to form a nanosheet-containing liquid containing a predetermined ratio of a predetermined component. As a method for adding these additives, a method of adding these additives as they are in a solid state to the nanosheet dispersion liquid and mixing them may be used, but an additive-containing liquid in which the additives are dispersed or dissolved in a solvent is prepared separately. And the method of mixing both and preparing a nanosheet containing liquid is desirable. If this method is used, the solubility of the additive in the solvent used to disperse or dissolve the additive or the layered inorganic compound or the birefringent substance that exhibits a thickening effect in the dissolution process or dispersion process in the solvent is low. Even in the case, it is possible to disperse more in the nanosheet-containing liquid. Therefore, it is possible to widely study the types and amounts of additives that can be used. Further, by mixing the layered inorganic compound and the additive in a sufficiently dispersed or dissolved state, the layered inorganic compound can be prevented from aggregating and forming a non-uniform lump by the action of the additive. The same applies to the birefringent material. As a result, a nanosheet-containing liquid in which the layered inorganic compound, the birefringent substance, and the additive are more uniformly dispersed is obtained, so that the generation of aggregates is suppressed and the birefringent substance is interposed between the nanosheet layers in the film forming process. As a result, it is possible to produce a film having sufficient mechanical strength and flexibility, in which the constituent substances constituting the film are uniformly distributed, and high transparency can be obtained. Can be granted.

  In some cases, the birefringent material forms a state of being bonded with a certain orientation to the surface of the nanosheet at the stage of the nanosheet dispersion liquid in which the layered inorganic compound and the birefringent material are mixed. In particular, this tendency often appears in mesogenic low-molecular substances. In this case, in order to control the orientation of the birefringent substance with respect to the layered inorganic compound as designed, it is preferable to add the birefringent substance before adding other additives such as a polymer to the nanosheet dispersion. . On the other hand, in the case of a birefringent material whose orientation is determined by being taken in between layers in the process of orientation lamination of nanosheets during film formation, the order of adding the birefringent material to the liquid in which the nanosheets are dispersed is as described above. It is not always necessary, for example, to be added at the same time as the polymer or the antioxidant, or after adding them.

  In addition, the layered inorganic compound contained in the nanosheet-containing liquid may be one type, or two or more different types of layered inorganic compounds may be used. Similarly, one type of birefringent material may be used, or two or more different types of birefringent materials may be used. Furthermore, one type of additive may be used, or two or more different types of additives may be used. In preparing the nanosheet-containing liquid, the nanosheet-containing liquid may be prepared by using two or more types of nanosheet dispersion liquids having different types of layered inorganic compounds, or two or more types of additives having different types of additives. You may produce a nanosheet containing liquid using an agent containing liquid. Alternatively, a nanosheet-containing liquid may be prepared by mixing a plurality of types of nanosheet dispersion liquids and a plurality of types of additive-containing liquids.

  It is desirable that the layered inorganic compound in the nanosheet-containing liquid obtained by the above method is cleaved as far as possible into the nanosheet that is a unit component and is uniformly dispersed. When cleavage of the layered inorganic compound is insufficient, additives such as birefringent substances and polymers are not sufficiently intercalated between nanosheets, Rth is not controlled as designed, film strength is reduced, and heat resistance is low Problems such as a decrease in transparency and a decrease in transparency due to light scattering by the aggregated layered inorganic compound occur. Furthermore, even if a film is produced in a state in which a large number of nanosheets are aggregated, the orientation of the nanosheets is reduced, resulting in a decrease in dimensional stability. However, it is generally difficult to make a dispersion in which all the layered inorganic compounds are dispersed into a single nanosheet, and there are usually some aggregated states. Although it is difficult to evaluate the cleavage state of the layered inorganic compound, for example, for a dispersion in which only the layered inorganic compound is dispersed, the particle size distribution is measured by a dynamic scattering method. The approximate cleaved state can be known by carrying out a technique for measuring the thickness of each nanosheet with an atomic force microscope, viscosity measurement, and the like. Alternatively, as will be described later, the interlayer distance of the nanosheets in the film can also be estimated by a method of observing with an X-ray diffraction spectrum or TEM. Alternatively, as a widely known method for indicating the standard of the dispersion state, there is a method for examining the sedimentation height ratio of the dispersion in the standing state. Since the dispersion of the layered inorganic compound in which cleavage is advanced and the particle volume is reduced and uniformly dispersed has a feature that it is difficult to settle even if left standing, in the state of the dispersion in which only the layered inorganic compound is dispersed, that is, It is desirable to prepare a nanosheet-containing liquid using a dispersion having a sedimentation height ratio of at least 50% or more, preferably 70% or more, more preferably 90% or more when left in an atmosphere of at least 24 ° C. for 12 hours. . Since this sedimentation height ratio depends on the solid content concentration of the layered inorganic compound in the dispersion, it is necessary to prepare a dispersion having a solid content that satisfies the above conditions. In the dispersion liquid in which the sedimentation height ratio is smaller than this, that is, the gravity is superior to the swelling power (dispersion ability) of the layered inorganic compound and the layered inorganic compound is precipitated, the cleavage of the layered inorganic compound is insufficient and there are many nanosheets. A film in which nanosheets such as those of the present invention are oriented and laminated, and an additive such as a birefringent material or a polymer is inserted between the layers on an average basis. Is generally difficult to form.

In many cases, the nanosheet-containing liquid obtained by the above method contains mainly gas components derived from air. Therefore, when the nanosheet-containing liquid is formed by reducing the gas components contained in such a nanosheet-containing liquid, they are formed. It is necessary to remove such gas components so that bubbles and voids derived from the gas components do not occur. As a removing method, any known method such as vacuum degassing under reduced pressure, irradiation with ultrasonic waves, or the like can be used.
The solid content concentration of the nanosheet-containing liquid in the present invention is suitably 1 to 20% by mass, more preferably 3 to 15% by mass, and still more preferably 5 to 12% by mass. At this time, when the concentration of the solid content is too thin, there is a problem that it takes too much time for drying. If the solid content is too high, the layered inorganic compound, the birefringent material and the additive are difficult to disperse well, the viscosity increases too much, or the thixotropy becomes too remarkable to remove the gas component. As a result, there is a problem that the orientation of the obtained film is poor and the uniformity is lowered, and the transparency, gas barrier properties, dimensional stability, and the like are deteriorated.

Although the kind of solvent used in this invention is not specifically limited, Water and an organic solvent can be used. Further, water in which a small amount of an organic substance such as acetamide, N, N-dimethylformamide, ethanol, methanol, or a salt is dissolved can also be used. The purpose of adding organic substances, salts, etc. is to change the dispersibility of clay in the nanosheet-containing liquid, change the viscosity of the nanosheet-containing liquid, change the ease of drying of the film, improve the uniformity of the film, etc. It is.
In particular, as the solvent for dispersing the hydrophobic layered compound, aromatic hydrocarbons (eg, toluene, xylene), ethers (eg, ethyl ether, tetrahydrofuran), ketones (eg, acetone, methyl ethyl ketone), aliphatic hydrocarbons (eg, n -Octane), alcohols (eg methanol, ethanol, isopropanol), halogenated hydrocarbons (eg chloroform, dichloromethane, 1,2-dichloroethane), N, N-dimethylformamide, N-methylpyrrolidone, dioctyl phthalate, dimethyl Sulfoxide, methyl cellosolve, etc. can be used.

  In order to sufficiently disperse the hydrophobic layered compound, it is effective to add a highly polar solvent such as methanol, particularly a solvent composed of molecules having a dipole moment of 1.60 debye or more. When a small amount of methanol is added to the dispersion of the hydrophobic layered compound, methanol penetrates between the layers of the aggregated hydrophobic layered compound to widen the gap between layers, and when sufficient time and shear force are applied, the hydrophobic layered compound Can be dispersed to near the unit layer. This greatly promotes dispersion of the hydrophobic layered compound and extremely reduces the aggregates of the nanosheet, so that the hydrophobic layered compound peels almost to the nanosheet that is the unit layer, and the birefringent material, additive, and hydrophobic layered material are peeled off. A nanosheet-containing liquid in which the compounds are extremely uniformly mixed can be obtained, and physical properties such as transparency are exhibited. Such solvents include water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, isobutyl alcohol and other alcohols, acetone, methyl ethyl ketone, 2-pentanone, cyclohexanone and other ketones, formic acid, acetic acid, Propionic acid, methyl formate, propyl formate, butyl formate, ethyl acetate, formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, N-methylpyrrolidone, dimethyl Examples thereof include sulfoxide, acetonitrile, tetrahydrofuran and the like. Among these, methanol is preferable because it has a dipole moment of 1.67 debye, a molecular weight of 32.04, and high compatibility with many solvents. Although somewhat inferior, ethanol is preferable from the viewpoint of safety because it has a dipole moment of 1.68 Debye, a small molecular weight of 46.07, and is similarly compatible with many solvents.

The type of the organic solvent in which the hydrophobic layered compound can be dispersed greatly depends on the type of the organic substance bonded to the surface of the nanosheet that develops the hydrophobic property, and thus it is necessary to select an appropriate one. In addition, it is necessary to select the birefringent substance and additives that are finally mixed in the nanosheet-containing liquid while paying attention to the solubility and dispersibility of the additive. Although it is generally preferable to select an organic solvent that is good for both the dispersibility of the hydrophobic layered compound and the solubility and dispersibility of the birefringent material and additives, the dispersion solvent of the nanosheet dispersion and the birefringent material It is not always necessary that the solvent of the additive-containing liquid is the same, and the layered inorganic compound, the birefringent substance, and the additive can be well dispersed when the nanosheet-containing liquid is obtained by mixing. If it does not specifically limit.
The method of solid-liquid separation means for reducing the solvent in the nanosheet-containing liquid is preferably a heat evaporation method, but is not particularly limited, and any known solid-liquid separation technique such as centrifugation, filtration, and compression is used. be able to. The concentration step for increasing the solid content concentration may be performed under reduced pressure. In particular, if the thickness of the nanosheet-containing liquid is thin and the liquid is flowed by stirring or the like, the amount of evaporation of the solvent increases and the amount is short. It is effective because it can be concentrated over time. Importantly, if the nanosheet-containing liquid is concentrated as described above, it becomes difficult to remove the remaining gas components as described above. Therefore, the gas components contained in the nanosheet-containing liquid are sufficiently reduced. After that, it is necessary to concentrate.
After the nanosheet-containing liquid thus obtained is applied to the surface of the support with a certain thickness, the solvent is slowly removed to form a film. The method for removing the solvent is not particularly limited, and for example, centrifugation, filtration, vacuum drying, freeze vacuum drying, standing in an inert gas atmosphere, and heat evaporation are preferable. Alternatively, a plurality of these methods may be combined.

Of these methods, for example, when the heating evaporation method is used, for example, a flat tray may be used as a support, and the nanosheet-containing liquid may be applied thereto. The material of the support is not particularly limited, but it is necessary to be unaffected by the solvent and to withstand the temperature during heating. For example, a resin film such as polyethylene terephthalate (PET) or polypropylene or Examples thereof include a resin substrate, a glass or silicon wafer, or a substrate made of a metal such as brass, copper, stainless steel, or aluminum. They generally have a higher thermal conductivity.
In the process of solidifying and drying the nanosheet-containing liquid as the solvent evaporates, volume shrinkage occurs, and stress resulting from the volume shrinkage acts on the resulting film. Therefore, if the strength of the film cannot withstand this stress, the film may break during the drying process, which makes it difficult to produce a large-area film, and the applicable applications are limited. There's a problem.
In such a case, it is assumed that the support is flexible enough to absorb the stress accompanying drying shrinkage, and the film itself is deformed together with the support during drying, or a shape that relaxes the shrinkage stress. By drying while actively deforming the support, the stress remaining in the film can be relieved and the occurrence of cracks in the film can be suppressed.

The support is not particularly limited as long as it is easily deformable and has flexibility, but the film peelability after drying, the continuous production of the film in the form of a roll, and the production cost of the film In consideration of the influence, a resin film such as PET is preferable.
It is preferable that at least a portion of the surface of the support that comes into contact with the film is subjected to a peeling facilitating treatment so that the film can be easily peeled off from the support. Examples of the separation facilitating treatment include an ultraviolet irradiation treatment, an electron beam irradiation treatment, an ion beam irradiation treatment, a corona discharge treatment, a plasma treatment (eg, remote plasma treatment, flame plasma treatment), and a physical treatment (eg, a contact area is reduced). Machine processing for processing the surface). Also, a treatment to apply a resin that lowers the adhesiveness such as silicone resin, and a peelability imparting that lowers the adhesiveness when the softness or Young's modulus changes or foams under physical stimulation such as light, heat, etc. An example of the treatment is to apply an agent. Or you may combine two or more among these processes.

The surface of the support is preferably as smooth as possible. When the surface is not smooth, the surface roughness of the support is transferred to the surface of the film, which reduces the surface smoothness of the film. Furthermore, the light is irregularly reflected, causing a decrease in transmittance and an increase in haze.
As described above, by using a deformable support, it is possible to suppress damage to the film due to shrinkage stress during film production. This makes it possible to produce a film with a large area with a high yield, which is suitable for applications requiring a film with a large area such as a display. In addition, according to the present invention, when continuous production by a roll is performed using a support made of a film wound in a roll shape, it is easy to obtain a continuous film. It becomes easy to produce a clay tape.

  As a specific example of the solvent removal of the nanosheet-containing liquid in the case of the heating evaporation method, for example, in a forced air oven, etc., 30 ° C. or higher and 150 ° C. or lower, preferably 30 ° C. or higher and 120 ° C. or lower, more preferably 50 ° C. or higher and 90 ° C. Under the following temperature conditions, the film is dried for 10 minutes to 7 hours, preferably 20 minutes to 3 hours, more preferably 20 minutes to 2 hours to obtain a film. However, the optimal drying time greatly depends on the composition of the nanosheet-containing liquid because it varies depending on the film thickness, the solid content concentration of the nanosheet-containing liquid, the solvent used, and the like. However, if the boiling point is too low, not only will the solvent volatilize during the preparation of the nanosheet-containing liquid and the solids concentration will increase, but also the risk of flammable explosion will increase, so mass productivity and It is preferable to select and use as appropriate from both aspects of safety.

  By passing through such a manufacturing method, the film of the present invention becomes a film having excellent uniformity in which nanosheets are highly oriented and laminated, and birefringent substances and additives are averagely inserted between the layers. . Moreover, there is little damage of the film | membrane by the mixed bubble. As a result, the obtained film obtains high mechanical strength. Moreover, it becomes transparent by using a layered inorganic compound having a small coefficient of linear expansion, high viscoelasticity up to a high temperature, and no coloring such as synthetic clay. Although it is difficult to define the mechanical strength that can be used as a self-supporting film, it is generally defined that the tensile strength is at least 10 MPa or more, preferably 15 MPa or more, more preferably 20 MPa or more, and has a strength that can be handled by hand. Is possible.

In order to have mechanical strength that can be used as a free-standing film that is easy to handle, the film thickness of the film needs to be at least 10 μm, preferably 15 μm or more, more preferably 30 μm or more, and even more preferably 50 μm or more. It is desirable that There are not many factors that define the upper limit of the film thickness, but if the film thickness is too thick, there may be a problem of cost due to a decrease in transparency or an increase in raw material costs, so at least 20000 μm or less, preferably 1000 μm or less, The thickness is most preferably 500 μm or less.
The film of the present invention has improved gas barrier properties due to the oriented lamination of nanosheets, and can be made to function as a gas barrier layer by being formed thin on the surface of the same film of the present invention or other resin film. In that case, the film thickness is preferably 0.1 μm or more, more preferably 0.5 μm or more, and further preferably 1 μm or more in order to have sufficient gas barrier properties. More preferably, it is more preferably 6 μm or more, and most preferably 10 μm or more. However, if it is too thick, the film may be warped due to the generation of stress or the interface may be peeled off. Similarly, it is preferably 1000 μm or less, more preferably 200 μm or less, and less than 100 μm. More preferably, it is less than 50 μm.

In the film of the present invention, it is possible to obtain a film having high transparency over the entire visible light range, small haze, no coloration, and little transparency in-plane unevenness. As the transparency, a total light transmittance of at least 70% or more, preferably 80% or more, more preferably 85%, and still more preferably 88% or more can be obtained. Moreover, the haze (cloudiness) is preferably 10% or less, preferably 7% or less, more preferably 5% or less. Further, a light transmittance of at least 75%, preferably 80% or more, more preferably 85% or more can be obtained as a light transmittance in a wavelength range of 400 nm to 800 nm. By appropriately selecting the kind of layered inorganic compound, birefringent substance and additive, by optimizing the process during film formation, etc., a plurality of those optical characteristics are satisfied. For example, the total light transmittance is 85 % Or more, a haze of 5% or less, and a film having a light transmittance of 85% or more in a wavelength range of 400 nm to 800 nm.
Further, the upper limit of the light transmittance of parallel light is determined by the refractive index of the film. Of the layered inorganic compounds, the refractive index of a general clay is often around 1.5, so even if an additive having a low refractive index is added, the light transmittance of parallel light generally has an upper limit of about 95%. It is thought that. Therefore, the total light transmittance is considered to be 95% as an upper limit. Of course, it is possible to further improve the transmittance by, for example, laminating an antireflection film having a low refractive index, a multilayer antireflection film utilizing optical interference, or an antiglare film on the surface of the film. .

  The film according to the present invention is also characterized by high dimensional stability, that is, a small amount of dimensional change with respect to temperature change. The dimensional stability against temperature change can be evaluated by the linear expansion coefficient. The linear expansion coefficient of the film in the present invention is at least 20 ppm or less as an absolute value of an average linear expansion coefficient from 50 ° C. to at least around 160 ° C., preferably around 200 ° C., more preferably around 260 ° C. Yes, preferably 15 ppm or less, more preferably 10 ppm or less, even more preferably 7 ppm or less, particularly preferably 5 ppm or less, and it is also possible to obtain 3 ppm or less. In particular, when the proportion of the additive is 30% by mass or less, a film having a very small linear expansion coefficient of 1 ppm or less can be obtained by optimizing the type of resin and curing conditions. In addition, the film is not an average value in the above temperature range, but does not cause a sudden dimensional change even when the dimensional stability with respect to a temperature change in a narrow temperature range of, for example, about 30 ° C. is observed. It is also a feature. For example, the value of the linear expansion coefficient in the temperature range of 50 ° C to 80 ° C, the value in the temperature range of 65 ° C to 95 ° C, and the value in the temperature range of 130 ° C to 160 ° C are all absolute values of 20 ppm or less. The same is true when viewed in other temperature ranges. Furthermore, it is a great feature that the above characteristics are manifested regardless of the glass transition temperature of the resin to be added. Usually, since the resin greatly expands when the glass transition temperature is exceeded, the linear expansion coefficient changes greatly with the glass transition temperature as a boundary. However, in the film of the present invention in which the ratio of the resin is suppressed, the influence of the glass transition temperature of the resin is practically hardly exhibited in terms of dimensional stability, and shows high dimensional stability against temperature changes. It is a feature.

The characteristic that the value of the linear expansion coefficient does not change greatly even when the value of such a small linear expansion coefficient and the glass transition temperature of the added resin is exceeded includes a film made of a conventional resin or a layered inorganic compound. However, the conventional nanocomposite film, in which the resin was the main component and the nanosheet layer was not highly oriented and laminated, was an extremely small value that could not be reached, especially for transparent films. It can be said that this characteristic is extremely suitable for applications such as a substrate on which an electronic device made of an inorganic material having a small linear expansion coefficient is mounted.
Furthermore, the film of the present invention is characterized by little decrease in storage elastic modulus even at high temperatures. In general, ordinary resins, especially amorphous ones, tend to have their storage elastic modulus rapidly reduced when their glass transition temperature is exceeded. Therefore, when they are heated above their glass transition temperature, they tend to be deformed. The film in the present invention is characterized by having a high storage elastic modulus up to a high temperature, and is characterized in that a rapid decrease in storage elastic modulus does not occur even when the glass transition temperature is exceeded. Such temperature dependence of the storage elastic modulus can be measured by a dynamic viscoelasticity measuring apparatus. The film according to the present invention is added at a storage elastic modulus measured by a dynamic viscoelasticity measuring device up to at least 160 ° C, preferably up to 200 ° C, more preferably up to 260 ° C, and even more preferably up to a temperature of 300 ° C or more. The storage elastic modulus is at least 100 MPa or more, preferably 500 MPa or more, and more preferably 1000 MPa or more regardless of the glass transition temperature of the resin to be used.

  In addition, the orientation lamination form as in the film of the present invention as described above can be formed to some extent by a method of stretching a resin formed body in which a conventional layered inorganic compound is randomly dispersed in a resin. There is a limit to the degree of orientation of the layered inorganic compound obtained at a possible stretching ratio in the resin processing, and as described above, the proportion of the extendable additive such as a polymer can be increased by increasing the proportion of the layered inorganic compound. If the amount is reduced, the amount of components that can be stretched decreases, making stretching itself difficult, and it is difficult to form an oriented laminated structure of layered inorganic compounds that only exhibits the physical properties of the film of the present invention. Therefore, the film forming method by the casting method from the solution as described above is suitable for the film in the present invention.

  In the film of the present invention, as a method for confirming whether the layered inorganic compound, the birefringent material and the additive are uniformly mixed and dispersed and the nanosheet layer is highly oriented and laminated, X-ray diffraction is used. Analysis of an X-ray diffraction spectrum by an apparatus and direct observation of a laminated state by a TEM are effective. Conventionally, various studies and evaluations such as the orientation lamination state of a film formed on a support such as a glass substrate by X-ray diffraction measurement and the dispersion and peeling state of a nanosheet in a nanocomposite containing clay have been performed. Generally, the intensity and position of the main peak (bottom reflection peak at the lowest 2θ side) generated in the X-ray diffraction spectrum by the first-order diffraction of the 001 plane of the layered inorganic compound, and the background of the X-ray diffraction spectrum in the low 2θ region It is possible to know the lamination state (average interval between layers) and the dispersion state of the nanosheets by lifting of the sheet. The film of the present invention is a laminate in which nanosheet layers are highly oriented, whereas the amount of additive is large as in the case of conventional nanocomposite materials, and the additive is intercalated between the nanosheet layers. In the case where the spacing between the nanosheet layers is increased and the orientation of the nanosheet layers is disturbed, the linear expansion coefficient is larger than 20 ppm, and the performance is low.

  The average interlayer distance in the film of the present invention is at least 10 nm or less, preferably 7 nm or less, more preferably 5 nm or less, more preferably 4 nm or less as a value converted from the position of the first-order diffraction peak of the 001 plane in the X-ray diffraction spectrum. More preferably, it is 3.5 nm or less, and most preferably 3 nm or less. This preferable average interlayer distance is the thickness of one layer of the nanosheet when using a wavelength of 1.54 mm which is a general Kα ray of copper when converted to the top position (value of 2θ) of the first-order diffraction peak. In a film made of smectite group clay or synthetic mica group clay having a thickness of about 1 nm, it corresponds to a region of 0.8 to 9.0 in 2θ.

The minimum value of the interlayer distance corresponds to that of a composition consisting only of nanosheets. However, in the film of the present invention, since the birefringent substance and additive are averaged intercalated, the composition consisting only of nanosheets It is necessary that the average interlayer distance is larger than that of the object. As a method for confirming this, whether or not the peak top position of the first-order diffraction peak in the X-ray diffraction spectrum is shifted to the lower 2θ side than that of the composition consisting only of the nanosheet is a standard.
Note that whether or not the average interlayer distance of the nanosheets in the film is in the preferred range can also be confirmed by directly measuring the interlayer distance by TEM observation.
In the present invention, the degree to which the birefringent material is intercalated between the nanosheet layers and the orientation are determined by observation with a scanning electron microscope (SEM) other than the above-described analysis by X-ray diffraction and measurement by TEM. , Circular dichroism spectroscopy (polarization IR measurement), etc. It can also be estimated by the amount extracted into the solvent when the film is immersed in a solvent in which the birefringent substance is soluble. Separation methods such as sequential dissolution, sequential precipitation, dialysis, ultrafiltration, gel permeation chromatography are the methods of separation and analysis by dissolving, extracting and separating components with such solvents (including alkaline and acidic water). , Gel filtration chromatography, column chromatography, ion exchange chromatography, gas chromatography, electrophoresis, electrodialysis and the like.

  For alteration of birefringent substances and additives such as polymers due to chemical reactions, liquid or gas chromatography, or time-of-flight mass spectrometers can be used for substances generated (decomposed and generated) by solvent extraction or heating as described above. Analysis, nuclear magnetic resonance (NMR) structure analysis, X-ray diffraction, X-ray photoelectron spectroscopy, infrared absorption spectroscopy, Raman spectroscopy, UV-visible absorption spectrum, fluorescence / phosphorescence analysis, photoacoustic spectroscopy Analysis by a method, light scattering method, neutron scattering method, osmotic pressure method, ultracentrifugation method, viscosity method, gel permeation chromatography and the like. Alternatively, the layered inorganic compound can be dissolved with acid to leave only the organic component, and the birefringent material can be eluted as described above to separate only the polymer component and analyze the polymer state. it can. As described above, the state of the composition of the membrane in the present invention can be analyzed by using these generally known separation / analysis methods. Analysis of the polymer as an additive can also be performed by separating and analyzing fragments generated by chemical decomposition such as thermal decomposition, hydrolysis, and oxidative decomposition by the above-described method.

  And since the film | membrane of this invention has the intensity | strength which can be utilized as a self-supporting film | membrane, it can be used for various uses. For example, taking advantage of birefringence controllability, flexibility, low linear expansion, heat resistance strength, transparency, etc., it can be used for a wide range of applications as a general-purpose optical film. Especially, it is suitable to use for the board | substrate of a liquid crystal display, an organic electroluminescent display, and electronic paper. In particular, since the birefringence of the film can be arbitrarily controlled, it is suitable as a member for a liquid crystal display. In other words, the active matrix drive circuit serving as the backplane can be directly formed on the film at a high temperature. By doing so, it is not necessary to use a conventional method such as transfer to a resin film after forming the drive circuit on a heat-resistant support such as a glass substrate, so that the manufacturing process of the display can be reduced. It is also superior in terms of cost. These drive circuits may be constituted by conventional silicon-based semiconductors, but organic semiconductors such as pentacene and thiophenes and amorphous inorganic semiconductors may also be used. In addition, if it is the direction opposite to the organic EL display or electronic paper backplane, that is, the direction in which light is extracted, transparency is generally unnecessary, but it is on the viewing side of the display by taking advantage of the transparency of the film of the present invention. It can also be used on the front plane side. Note that liquid crystal display systems to which the film of the present invention can be applied include TN, STN, VA, and IPS, but are not particularly limited because Rth can be freely adjusted. Absent. Further, the organic EL display can be applied to both a top emission type and a bottom emission type. Furthermore, as electronic paper, for example, an electrophoretic drive system, an electronic powder fluid system, a system using liquid crystal, and the like can be used without any particular limitation. Circuits for driving them can be used for both the passive matrix system and the active matrix system.

In addition, the film can be widely used as a flexible substrate of an electric circuit by taking advantage of the insulating property. Even when used as a substrate for an electric circuit, image processing is often used for alignment when mounting an electronic component, and in this case, transparency is required. Therefore, the film of the present invention is suitable. In particular, in a flexible printed circuit board in which a conductive portion on a substrate is formed by applying or printing a conductive ink, the conductive ink can be baked at a higher temperature by taking advantage of the heat resistance of the film and a low linear expansion coefficient. The resistivity of the conductor portion formed by coating or printing can be further reduced. Suitable applications of such flexible substrates and flexible printed substrates include RFID tag substrates and copper clad laminates. Furthermore, if it is a transparent film | membrane, it can apply also to the device which needs to permeate | transmit light like a solar cell.
When the film of the present invention is applied to the display, flexible substrate, flexible printed substrate, solar cell, electronic device having an organic semiconductor or an amorphous inorganic semiconductor, etc., the film may be applied as it is. If necessary, a film having another function (for example, a water vapor barrier film made mainly of an inorganic material, a reinforcing material made of a resin material, a protective layer for preventing scratches, a smoothing layer for smoothing the surface), etc. May be used.
Hereinafter, the present invention will be described more specifically with reference to examples.

[Example 1]
Organic modified synthetic smectite (Lucentite SAN manufactured by Co-op Chemical Co., Ltd.) as a hydrophobic layered compound, polyvinyl butyral (Surek Chemical Co., Ltd., ESREC BX-1 manufactured by Sekisui Chemical Co., Ltd.), and phenanthrene (Wako Pure Chemical Industries, Ltd.) as a birefringent substance Used).
8.5 g of hydrophobic layered compound, 8.5 g of methanol and 68 g of toluene were placed in a 300 ml Erlenmeyer flask together with a rotor and stirred at 25 ° C. for 2 hours to obtain a uniform dispersion of hydrophobic layered compound. Further, 1.5 g of polyvinyl butyral, 1.5 g of toluene and 12.0 g of tetrahydrofuran were placed in a 300 ml Erlenmeyer flask together with a rotor and stirred at 25 ° C. for 2 hours to obtain a uniform additive-containing liquid. Moreover, 0.76 g of phenanthrene and 6.74 g of toluene were put into a 50 ml Erlenmeyer flask together with a rotor, and stirred at 25 ° C. for 2 hours to obtain a uniform birefringent substance-containing liquid.
Next, the dispersion liquid of the hydrophobic layered compound, the additive-containing liquid, and the birefringent substance-containing liquid are placed in a 500 ml Erlenmeyer flask together with a rotor and stirred at 25 ° C. for 2 hours to obtain a uniform nanosheet-containing liquid. It was. And about 25 degreeC nanosheet containing liquid was put into the vacuum deaeration apparatus, and it fully deaerated, stirring with a rotor for about 5 minutes.

Next, a PET film with a release agent applied to a flat portion of a metal tray having a depth of 3 mm is laid, and the nanosheet-containing liquid is poured thereon, and a glass rod is used to slide the upper part of the metal tray. Then, by removing the excess nanosheet-containing liquid, a nanosheet-containing liquid film having a uniform thickness was formed. This metal tray was placed on a hot plate and dried by heating at 60 ° C. for about 4 hours. The produced film was peeled from the tray to obtain a uniform film having a thickness of 115 μm and a layered inorganic compound content of 47 to 55 wt% and a polymer content of 14 wt%.
In order to confirm the flexibility of the film, it was curved into a cylindrical shape with a radius of 6 mm, but no cracks were generated and no defects were generated. In order to confirm the transparency of the film, the transmittance in the wavelength range of 200 nm to 800 nm was measured with an ultraviolet-visible spectrophotometer “UV-2500PC” manufactured by Shimadzu Corporation. The range from 380 nm to 800 nm And a transmittance of 85% or more, and no coloring was observed. Furthermore, the total light transmittance of the film measured with a turbidimeter “NDH2000” manufactured by Nippon Denshoku Industries Co., Ltd. was 91.7%, and the haze (haze) was 4.5%. The total light transmittance and haze referred to here are the total light transmittance test method JIS K 7361, the plastic optical test method JIS K 7105, and the plastic transparent material defined in Japanese Industrial Standards. How to determine haze It is determined according to JIS K 7136.

  In order to confirm the dimensional stability of this film, the linear expansion coefficient was measured by “TMA-60” manufactured by Shimadzu Corporation. At the time of measurement, the sample width was 5 mm, the load was 10 g, the sample was heated to 260 ° C. at a temperature rising rate of 5 ° C./min, cooled to 31 ° C., and then similarly heated to 260 ° C. at a temperature rising rate of 5 ° C./min. As a result, the absolute value of the average linear expansion coefficient in the range of 50 ° C. to 260 ° C. was 1.1 ppm / ° C., and the coefficient was substantially constant in the temperature range. That is, in any arbitrary range from 50 ° C. to 260 ° C., the value of the linear expansion coefficient calculated from the change in the expansion coefficient at the time of temperature increase of at least 30 ° C. is actually 20 ppm or less. When the temperature was increased from 50 ° C. to 260 ° C., a phenomenon that greatly expanded or contracted in a specific temperature range was not observed.

  In order to confirm whether or not the layer of the nanosheet was densely laminated with a highly oriented nanosheet, analysis by X-ray diffraction was performed with an X-ray diffractometer “RINT-2500” manufactured by Rigaku Corporation. The X-ray wavelength used is 1.54056 mm of Cu / Kα. In the obtained X-ray diffraction spectrum, a clear peak is observed at 2.89 at 2θ (3.05 nm in terms of interlayer distance), and the nanosheet layer in the film is highly laminated and dense. It was shown to be oriented. In addition, the interlayer distance of the nanosheet is 2.25 nm in the case of a film composed only of a hydrophobic layered compound without adding an additive (a layered inorganic compound dispersion composed of only the hydrophobic layered compound is dropped onto a silicon substrate and dried. Since the obtained film is increased from the value obtained by X-ray diffraction analysis in the same manner, the additive polymer and birefringent substance are intercalated between the nanosheet layers and regularly stacked. Was confirmed.

In order to confirm whether or not the membrane is water resistant, the water absorption rate was measured for one day. Cut out the above-prepared membrane to a size of 5 cm square, put it in a 500 ml beaker containing 200 ml of purified water, leave it in a constant temperature room at 24 ° C. for 24 hours, lift the membrane, wipe the surface moisture, and When the increase / decrease was measured, an increase of 4.1% in weight was observed, but no change visually recognized.
In order to confirm the strength of this film, tensile strength measurement was performed using “TG-1kN” manufactured by Minebea equipped with a 100N load cell. At the time of measurement, the sample width was 1 cm, the sample length was 10 cm, the distance between chucks was 2 cm, and the pulling speed was 10 cm / min. As a result, the strength was 20.9 MPa, and the mechanical strength usable as a self-supporting film was obtained. Had enough.

In order to confirm the retardation value in the thickness direction of this film, a three-dimensional refractive index was measured at an incident angle of 40 ° using a phase difference measuring device “KOBRA-WR” manufactured by Oji Scientific Instruments Co., Ltd. When the retardation value converted into γ was measured, the Rth of this film was −17 nm. The Re of this film was 0.3 nm.
In order to confirm the storage elastic modulus of the membrane, dynamic viscoelasticity measurement was performed using a dynamic viscoelastic device Vibron “DDV-01FP” manufactured by Orientec Co., Ltd. When measuring, the sample size is 3mm x 57mm, the distance between chucks is 50mm, the frequency is 1Hz, the load is 6g, the heating rate is 3 ℃ / min, the temperature range is 30 ℃ to 350 ℃, and the sample amplitude is 16μm As a result, the storage elastic modulus at the start of the measurement was 3645 MPa, and although the minimum value was 1129 MPa at 100 ° C., the storage elastic modulus was not drastically lowered, and the temperature was maintained at 1000 MPa or higher in all temperature ranges. It was. (See Figure 1)
The intrinsic birefringence of phenanthrene was calculated using Gaussian 03 as the calculation program, density functional method as the calculation method, B3LYP as the functional, and 6-311 ++ G ** level as the basis function. A value of 1.20 to 1.32 was obtained as Δn, and it was found that it had a sufficiently large intrinsic birefringence.

[Example 2]
A film was prepared in the same manner as in Example 1 except that the birefringent substance was changed to 4-hydroxybiphenyl and 0.85 g of 4-hydroxybiphenyl (manufactured by Wako Pure Chemical Industries, Ltd.) was added. The obtained film had a film thickness of 150 μm, a layered inorganic compound content of 47 to 55 wt%, and a polymer content of 14 wt%. When the transmittance was measured in the same manner as in Example 1, the shape of the ultraviolet-visible absorption spectrum was almost the same as that of the film of Example 1, and the light transmittances of 400 nm or more were all 85% or more.
Further, the water absorption of the membrane was measured in the same manner as in Example 1. As a result, although an increase of 2.1 g in weight was observed, no visually observable change was observed.
Furthermore, when the total light transmittance of the film was measured in the same manner as in Example 1, it was 90.9%. Furthermore, when the haze (cloudiness) of the film was measured in the same manner as in Example 1, it was 3.2%.
Furthermore, when the tensile strength measurement was carried out in the same manner as in Example 1, it was 30.0 MPa.
Further, when the water absorption rate was measured in the same manner as in Example 1, an increase in weight of 2.1% was observed.

Furthermore, when the absolute value of the linear expansion coefficient was measured in the same manner as in Example 1, it was 0.9 ppm, and the coefficient was substantially constant in the temperature range. That is, in any arbitrary range from 50 ° C. to 260 ° C., the value of the linear expansion coefficient calculated from the change in the expansion coefficient when the temperature is increased by 10 ° C. is 20 ppm or less, actually 10 ppm or less. When the temperature rose to 0 ° C., there was no phenomenon that greatly expanded or contracted in a specific temperature range.
Further, retardation measurement was carried out in the same manner as in Example 1. As a result, Rth was 1033 nm and Re was 1.5 nm.
Further, this film was heated in an oven at 160 ° C. for 1 hour, and then Rth was performed in the same manner as in Example 1. As a result, it was +893 nm, and Rth did not increase by heating. It was found that Rth was well reduced by the effect of the refractive material.
Furthermore, when the dynamic viscoelasticity measurement was carried out in the same manner as in Example 1, no place where the storage elastic modulus suddenly decreased was observed as in Example 1, and 100 MPa or higher was maintained over the entire temperature range. It was.
As a result of calculating the intrinsic birefringence of 4-hydroxybiphenyl in the same manner as in Example 1, it was found that Δn had a value of 0.92 to 0.97 and had a sufficiently large intrinsic birefringence.

Example 3
A film was produced in the same manner as in Example 1 except that the amount of phenanthrene was changed to 0.95 g in Example 1. The obtained film had a film thickness of 115 μm, a layered inorganic compound content of 47 to 54 wt%, and a polymer content of 14 wt%.
When retardation measurement was carried out in the same manner as in Example 1, Rth was -613 nm and Re was 0.4 nm.
Further, when the total light transmittance of the film was measured in the same manner as in Example 1, it was 91.6%. Furthermore, when the haze (cloudiness) of the film was measured in the same manner as in Example 1, it was 4.9%.
Furthermore, when the tensile strength measurement was carried out in the same manner as in Example 1, it was 21.8 MPa.
Furthermore, when the absolute value of the linear expansion coefficient was measured in the same manner as in Example 1, it was 0.9 ppm, and the coefficient was substantially constant in the temperature range. That is, in any arbitrary range from 50 ° C. to 260 ° C., the value of the linear expansion coefficient calculated from the change in the expansion coefficient when the temperature is increased by 10 ° C. is 20 ppm or less, actually 10 ppm or less. When the temperature rose to 0 ° C., there was no phenomenon that greatly expanded or contracted in a specific temperature range.

[Comparative Example 1]
In Example 1, a film was prepared in the same manner using only the dispersion liquid of the layered inorganic compound without using the birefringent substance-containing liquid. The obtained film had a film thickness of 138 μm, a layered inorganic compound content of 51-60 wt%, and a polymer content of 15 wt%. When Rth of this film was measured in the same manner as in Example 1, it was +2427 nm.
Further, when the total light transmittance of the film was measured in the same manner as in Example 1, it was 91.4%. Furthermore, when the haze (cloudiness) of the film was measured in the same manner as in Example 1, it was 3.2%.
Furthermore, when the tensile strength measurement was carried out in the same manner as in Example 1, it was 28.6 MPa.
Further, when the absolute value of the linear expansion coefficient was measured in the same manner as in Example 1, it was 0.6 ppm, and the coefficient was substantially constant in the temperature range. That is, in any arbitrary range from 50 ° C. to 260 ° C., the value of the linear expansion coefficient calculated from the change in the expansion coefficient when the temperature is increased by 10 ° C. is 20 ppm or less, actually several ppm or less. When the temperature rose to 260 ° C., a phenomenon that greatly expanded or contracted in a specific temperature range was not recognized.

[Comparative Example 2]
Under the same conditions as in Example 1, the mixing ratio of the dispersion of the layered inorganic compound and the polyvinyl butyral resin solution was changed, and a film was prepared so that the resin ratio in the film was 46 wt%. The obtained film had a film thickness of 131 μm, a layered inorganic compound content of 28 to 32 wt%, and a polymer content of 46 wt%.
Furthermore, when the total light transmittance of the film was measured in the same manner as in Example 1, it was 91.7%. Furthermore, when the haze (cloudiness) of the film was measured in the same manner as in Example 1, it was 3.6%.
Furthermore, when the tensile strength measurement was carried out in the same manner as in Example 1, it was 40.5 MPa.
Further, when the absolute value of the linear expansion coefficient was measured in the same manner as in Example 1, it was 21 ppm.

[Comparative Example 3]
Using only the additive-containing liquid in Example 1, a film having a thickness of 228 μm made of only polyvinyl butyral resin was produced in the same manner as in Example 1. When the absolute value of the linear expansion coefficient of this membrane was measured in the same manner as in Example 1, the elongation of the membrane was very large and measurement was impossible.
Furthermore, when dynamic viscoelasticity measurement was carried out in the same manner as in Example 1, the storage elastic modulus at the start of measurement was 1451 MPa, the storage elastic modulus suddenly decreased from around 60 ° C., and 1.6 MPa at 93 ° C. As a result, the storage elastic modulus was practically zero. (See Figure 1)
Furthermore, when the total light transmittance of the film was measured in the same manner as in Example 1, it was 92.3%. Furthermore, when the haze (cloudiness) of the film was measured in the same manner as in Example 1, it was 0.6%.
Furthermore, when the tensile strength measurement was carried out in the same manner as in Example 1, it was 27.0 MPa.

It is a graph showing the storage elastic modulus in each temperature of a film | membrane.

Claims (25)

  A transparent layered inorganic compound (A), a birefringent substance (B) different from (A), and an additive (C), and having a structure in which the lamination of the layered inorganic compound (A) is oriented A film characterized in that the ratio of the additive (C) to the film is more than 0% by mass and 45% by mass or less.   The film according to claim 1, wherein the additive (C) is a polymer.   The film according to claim 1 or 2, wherein the birefringent substance (B) includes a low molecular substance having an intrinsic birefringence of 0.03 or more.   The film according to claim 3, wherein the low-molecular substance has a mesogenic group.   The said additive (C) is a polyvinyl acetal resin, The film | membrane as described in any one of Claims 1-4 characterized by the above-mentioned. When the film thickness is dnm and the ratio of the layered inorganic compound (A) is a mass%, the retardation value (Rth, unit nm) in the thickness direction satisfies the following formula (1). The film | membrane as described in any one of 1-5.
−3000 <Rth <0.0002 × a × d (1)   The film according to any one of claims 1 to 6, wherein a retardation value in a thickness direction of the film is -50 nm or more and 50 nm or less in terms of a film thickness of 150 µm.   The film according to any one of claims 1 to 7, further comprising an antioxidant.   The said layered inorganic compound (A) consists of 1 or more types of synthetic clay, The film | membrane as described in any one of Claims 1-8 characterized by the above-mentioned.   The hydrophobic layered compound obtained by subjecting the surface of the layered inorganic compound (A) to organophilic treatment is used. The film according to any one of claims 1 to 9,   The film according to any one of claims 1 to 10, wherein the film thickness is 0.1 µm or more and 1000 µm or less.   The storage elastic modulus measured with a dynamic viscoelasticity measuring device under the conditions of a measurement frequency of 1 Hz, a sample amplitude of 16 μm, and a load of 0.05 g per 1 μm of thickness is 100 MPa or more in a temperature range from 30 ° C. to 350 ° C. The film according to claim 1, wherein:   The film according to any one of claims 1 to 12, wherein an average film linear expansion coefficient in the range of 50 ° C to 260 ° C is -20 ppm or more and 20 ppm or less.   14. The linear expansion coefficient of the film when the temperature is raised by 30 ° C. in the range of 50 ° C. to 260 ° C. is −20 ppm or more and 20 ppm or less in any temperature range. The membrane according to item.   The film according to any one of claims 1 to 14, which has a tensile strength of 10 MPa or more.   The membrane according to any one of claims 1 to 15, wherein the water absorption after impregnation in distilled water at 24 ° C is 5% or less.   The film according to any one of claims 1 to 16, wherein an in-plane retardation value of the film is -10 nm or more and 10 nm or less.   The film according to any one of claims 1 to 17, wherein the total light transmittance is 85% or more.   The optical film material which consists of a film | membrane as described in any one of Claims 1-18.   The display element material which consists of a film | membrane as described in any one of Claims 1-18.   The display element material according to claim 20, wherein the display element is a liquid crystal display.   The display element material according to claim 20, wherein the display element is electronic paper.   The display element material according to claim 21, wherein the display element uses organic or inorganic electroluminescence.   A gas barrier film comprising the film according to any one of claims 1 to 18.   The electronic circuit using the film | membrane as described in any one of Claims 1-18 for a board | substrate.

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