JP4821157B2 - Polymer compound, highly transparent polyimide, resin composition and article - Google Patents

Description

  The present invention relates to a polymer compound having excellent transparency. Preferably, the polyimide is excellent in heat resistance and transparency, and in particular, a material for forming a product or member that has a high requirement for transparency as well as heat resistance (for example, an optical product, a molding material of an optical component, a layer forming material or The present invention relates to a polyimide that can be suitably used as an adhesive or the like, a resin composition containing the polyimide, and an article manufactured using the resin composition.

  Polymer materials are used in various products around us because of their easy processing and light weight. The polyimide developed by DuPont in 1955 in the United States has been under development because it has excellent heat resistance and its application to the aerospace field has been studied. Since then, detailed research has been conducted by many researchers, and it has become clear that performance such as heat resistance, dimensional stability, and insulation properties are among the highest in organic materials. Application to materials was promoted. At present, it has been used extensively as a chip coating film in a semiconductor element or as a base material for a flexible printed wiring board.

  Polyimide is a polymer synthesized from diamine and acid dianhydride. By reacting diamine and acid dianhydride in a solution, it becomes polyamic acid (polyamic acid) which is a precursor of polyimide, and then becomes a polyimide through a dehydration ring closure reaction. In general, since polyimide has poor solubility in a solvent and is difficult to process, it is often made into a polyimide by making it into a desired shape in the state of a precursor polyamic acid and then heating. Since polyamic acid is decomposed by heat or water, its storage stability is not good. In consideration of this point, a polyimide that has been improved so that it can be molded or applied by dissolving in a solvent after introducing a skeleton with excellent solubility in the molecular structure and making it into a polyimide is used. There is a tendency that the chemical resistance and the adhesion to the substrate are inferior to those of the precursor system. Therefore, a method using a precursor and a method using solvent-soluble polyimide are properly used depending on the purpose.

In recent years, as the market for thin displays typified by liquid crystals and plasmas grows, research is being conducted to make these thin displays flexible and deformable. In particular, organic EL displays, which are expected to be next-generation thin displays, are also expected to be flexible because their light-emitting sites are made of organic materials.
In order to put such a flexible display into practical use, an attempt has been made to change the glass currently used as a base material to a polymer that is a flexible material that can be bent. Such an alternative material is required to have transparency, heat resistance, chemical resistance, water vapor and oxygen barrier properties, dimensional stability, and the like equivalent to glass.
As a glass substitute material, the higher the heat resistance, the better. However, from the viewpoint of heat treatment conditions required at the time of post-processing, it is preferable that at least the glass transition temperature is 200 ° C. or higher, and it absorbs also in transparency. The one that does not have at all is ideal, but one that exhibits a transmittance of 85% or more in each wavelength of a wavelength region of 400 nm to 800 nm generally called a visible light region is preferable. In addition, the dimensional stability is preferably in the order of several ppm equivalent to that of glass, but is preferably at least 40 ppm or less.

  In addition to flexible display substrates, glass is the best choice for products that used conventional glass, such as optical fibers and lenses, or parts used in optical waveguides and optical circuits, optical elements, and surface protection films for optical elements. Investigations or proposals for changing the portion to be made into a polymer material are underway.

Polyimide resin is one of materials that have high heat resistance, light weight, high strength, and has been studied as a material that can be replaced with glass from an early stage. However, problems to be studied still remain.
One of them is transparency. Polyimide is generally colored reddish brown. The cause is said to be due to charge transfer, and recently, it has been reported that charge transfer in the molecule is particularly related to coloring. (Non-Patent Document 1)

That is, a transparent polyimide can be made by eliminating charge transfer in the molecule. Based on this principle, two methods have been proposed so far for making polyimide transparent.
The first is to introduce an aliphatic structure, especially an alicyclic structure, into the polyimide skeleton, which usually has many aromatic skeletons, and to block the π-electron conjugation in the skeleton, thereby inhibiting the movement of charges in the skeleton and making it transparent It is to plan. In particular, it is said that it is effective to introduce an alicyclic skeleton into a diamine as a raw material. (Non-patent document 1, Patent document 1)
The other is to introduce transparency into the polyimide skeleton, thereby imparting transparency by making the electronic state in the skeleton less susceptible to charge transfer. (Patent Document 2)

  Regarding polyimides using 2,2 ', 6,6'-biphenyltetracarboxylic dianhydride as an acid component, Non-Patent Document 2, 1968 US Goin et al., 2,2', 6,6'- The polyamic acid obtained by reacting biphenyltetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether in dimethylacetamide can be dissolved in dimethylacetamide again after reprecipitation purification using diethyl ether. It is described that the polyimide was obtained by casting the polyamic acid solution and gradually heating to 300 ° C., but only the thermal decomposition temperature of the polyimide is described here, and other physical properties The details of are not described.

Patent Document 3 also discloses that a polyimide synthesized by using 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether is used as a liquid crystal alignment film. Although described, only the ability to orient the liquid crystal is described here, and other physical properties are not described.
Patent Document 4 describes a polyimide using 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride in the examples. Here, the polyimide adheres to the polymer polymerization vessel. Although it is used as a protective film to prevent and describes the initial colorability of the polymer produced in the polymerization vessel provided with the protective film, it does not describe any physical properties of the polyimide itself.

Patent Document 5 discloses a method for producing a molded body of polyimide, and 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride is described as a representative example of the raw material. These are merely enumerations and no actual synthesis examples are described, so that specific physical properties cannot be known.
Patent Document 6 discloses a method for producing polyimide fine particles, which also describes 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride as a representative example of the raw material. Since it is merely an enumeration of names and no actual synthesis examples are described, specific physical properties cannot be known.

Patent Document 7 discloses a polyimide and a pressure-sensitive adhesive tape obtained using the same, and 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride is also described here as a representative example of the raw material. However, since it is merely an enumeration of compound names and no actual synthesis examples are described, specific physical properties cannot be known.
Patent Document 8 discloses a method for producing a photoconductive polymer, which also describes 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride as a representative raw material. However, since it is merely an enumeration of compound names and is not described as an example, specific physical properties cannot be known.

Japanese Patent Laid-Open No. 10-310639 Japanese Patent Laid-Open No. 05-1148 JP 56-52722 A JP-A-6-41205 JP-A-6-329799 Japanese Patent Laid-Open No. 11-140181 JP 2002-60489 A JP-A-3-275725 Polymer Preprints, Japan 48 [5] 939 (1999) POLYMER LETTERS Vol.6, p821-825 (1968)

Any of the above-described methods conventionally used for improving the transparency of polyimide causes a decrease in physical properties associated therewith.
In the first method, the alicyclic structure is more easily oxidized than the aromatic structure, and there is a problem that when heated in air, the alicyclic structure is colored by oxidation. For this reason, it is recommended that polyimides having an alicyclic structure be heated in an inert atmosphere. Moreover, since the polyimide which introduce | transduced the alicyclic structure has a low thermal decomposition temperature compared with an aromatic polyimide, it is inferior to heat resistance. In addition, when the linear thermal expansion coefficient is increased and an interface is formed with a material having a low coefficient of thermal expansion such as a metal, metal oxide or silicon wafer, the cause of warpage or poor adhesion due to the thermal history is applied. It becomes.

  In addition, when a diamine having an alicyclic structure is used as a raw material, a diamine having a alicyclic structure is higher in basicity than an aromatic diamine, so that a polyamide formed during the polymerization reaction with an acid dianhydride is used. Forms a salt with the carboxylic acid of the acid, making it difficult to increase the molecular weight. For this reason, a silylation method (a method in which an amino group is silylated and then polymerized with an acid dianhydride) is proposed, but this increases the cost because the number of synthesis steps increases by one.

  On the other hand, the second method has a problem that the introduction of fluorine into polyimide increases the cost of raw materials and increases the cost. In addition, the introduction of fluorine reduces the adhesion at the interface and easily peels off the substrate. Moreover, solvent resistance also falls and a glass transition temperature also falls. Furthermore, when the coefficient of linear thermal expansion is increased, when it is formed on a substrate having a small coefficient of thermal expansion, it causes warpage of the substrate and a decrease in adhesion.

  The present invention has been accomplished in view of the above circumstances, and its first object is to have a portion where unsaturated bonds and π-electron orbitals containing π-electron orbitals continue alternately, so that it is a polymer compound that is easily colored, For example, a polymer compound having a large portion occupied by an aromatic structure such as an aromatic polyimide, a polymer compound improved by a new method different from the conventional one, and a requirement for transparency using the polymer compound Another object of the present invention is to provide a resin composition useful as a resin material for forming a high product or member, and further a product or member having excellent transparency produced using the resin composition.

  The second object of the present invention is to provide a highly transparent polyimide without impairing the inherent properties of polyimide such as heat resistance.

  The third object of the present invention is to provide a polyimide resin composition useful as a resin material for forming a product or member having a high requirement for transparency in addition to heat resistance, using the polyimide having high transparency. There is.

A fourth object of the present invention is to provide a product or member excellent in heat resistance and transparency using the polyimide resin composition, or a glass substitute material that is lightweight and can be flexible. It is in.
The present invention solves at least one of these objects.

Highly transparent polyimide according to the present invention, have a repeating unit represented by the following formula (1), the light transmittance between the 400nm~800nm when deposited into a film having a thickness of 1μm is at each wavelength It is characterized by being 85% or more .

(In the formula, R ^{1 to} R ⁶ are each independently a hydrogen atom or a monovalent organic group, which may be bonded to each other. R ⁷ is a divalent organic group. The groups represented by the same symbols between the repeating units present in may be different atoms or structures.)

Since the imide skeleton contained in the repeating unit of the above formula (1) is unstable when arranged in a plane, the relative position of the benzene ring of the biphenyl structure contained in the imide skeleton is twisted, and the π bond conjugate is Be cut off.
Since the polyimide according to the present invention has such a spatial arrangement of the molecular structure, the charge transfer on the polyimide molecular chain is blocked while having heat resistance due to the aromatic polyimide, so that the polyimide becomes transparent.

  Next, the polyimide resin composition according to the present invention is characterized by containing the polyimide according to the present invention. This polyimide resin composition is a pattern forming material (resist), coating material, paint, printing ink, adhesive, filler, electronic material, molding material, resist material, building material, three-dimensional modeling, film for flexible display, optical It can be used in all known fields and products in which resin materials are used, such as members.

  In particular, the polyimide resin composition according to the present invention has high transparency in addition to the original properties of polyimide such as heat resistance, dimensional stability, insulation, etc., fields and products in which these properties are effective, For example, paints, printing inks, color filters, flexible display films, electronic parts, interlayer insulation films, wiring coating films, optical circuits, optical circuit parts, antireflection films, holograms, other optical members or building materials are formed. Suitable for

As described above, the polymer compound according to the present invention has a conjugated state that is easily formed in a polymer because it has a portion in which an unsaturated bond including a π-electron structure and a single bond are alternately continued. Depending on the structure, it can be cut or diluted so that excellent transparency can be achieved. According to such means, compared with the case where transparency is increased by introducing other chemical structures or substituents into the molecule, the polymer compound is excellent without deteriorating useful properties inherently provided. Transparency is obtained.
Therefore, the polymer compound according to the present invention is useful as a resin material for forming a product or a member having a high demand for transparency using the polymer compound, and a resin composition containing the polymer compound is used. By using it, it is possible to produce a product or member having excellent transparency.
In addition, the polyimide according to the present invention exhibits good transparency without introducing fluorine or an alicyclic skeleton. Therefore, it is possible to eliminate the problems that the original physical properties of polyimide such as heat resistance and dimensional stability, which have been unavoidable by the introduction of fluorine and alicyclic skeletons, and the problem of high cost can be solved. A highly transparent polyimide coating film, film or molded article having heat resistance equivalent to that of polyimide can be obtained.

  Since the resin composition containing the polyimide according to the present invention has high transparency in addition to heat resistance, dimensional stability, and insulation, films for all known members that require transparency and It is suitable as a coating film, and is expected to be used as, for example, a highly heat-resistant film or structure for optical members such as antireflection films, optical circuit components, and holograms.

  Furthermore, this polyimide resin composition is expected to be used for substrates of optical members such as thin display substrates such as liquid crystal displays and organic EL as a glass substitute material that is lightweight and can be flexible. The

The present invention is described in detail below. The inventor has designed a polyimide molecule based on a completely new concept, and is an aromatic polyimide having a high heat resistance, particularly preferably a fully aromatic polyimide, but a polyimide having high transparency without introducing fluorine. It came to invent. In other words, in order not to cause charge transfer on the polyimide molecular chain that causes coloring, the concept of applying a twist to the skeleton to cut the π-electron conjugated structure of the polyimide molecular chain is applied to polyimide. did.
Furthermore, the inventor is not limited to polyimide, and the conjugated state is formed in the molecule because unsaturated bonds and single bonds including π-electron orbits continue alternately. The inventors have also found that the present invention can be widely applied to molecular compounds, and have reached the present invention.

  The polymer compound of the present invention based on the above idea is a polymer compound having a portion in which unsaturated bonds including π electron orbitals and single bonds are alternately continued, and a conjugated state formed by π electron orbitals in the molecule. Assuming that at least a portion of the molecule is cleaved or dilute by the molecular conformation and that the transmissivity of at least some wavelengths between 400 nm and 800 nm is assumed that the conjugate state has not been cleaved or dilute. It is characterized by being larger than the transmitted transmittance.

Since the polymer compound of the present invention has a portion in which unsaturated bonds and single bonds including π electron orbitals are alternately continued, usually, a conjugated state is easily formed by π electron orbitals in the molecule. Because it is stabilized, it should be easy to absorb and color long-wave electromagnetic waves.
In general, a π-conjugated structure is observed when unsaturated bonds are connected via a single bond. In that case, the single bond has a double bond property due to the interaction between the unsaturated bonds. Electrons (π electrons) involved in π bonds of unsaturated bonds connected through a single bond are stable when they have a common π electron orbit. For this reason, the electrons are present on the same plane, including the electrons that are supposed to exist on a bond that should be a single bond.

The unsaturated bond in this case is not limited to those formed between carbon atoms, and includes those containing heteroatoms such as a carbonyl group.
Furthermore, in a broad sense, examples showing a π-conjugated structure include those in which an unsaturated bond is connected by a functional group composed of an atom having an unshared electron pair such as an amino group or an ether group.
The present invention is applicable to all structures having a π-conjugated structure known so far including these examples.
A typical example of the π-conjugated structure is an aromatic structure. The aromatic structure in the present invention is a chemical structure defined as a general aromatic, in which unsaturated bonds contained in the structure, such as benzene and naphthalene, are linked cyclically, and π Includes aromatic cyclic structures that are conjugated to planar structures.

In the present invention, at least a part of the conjugated state that would normally be formed by the π-electron orbitals existing in the molecule of the polymer compound is cut or diluted by the three-dimensional structure of the molecule. Here, when a planar primary structural formula of a polymer compound is drawn, a portion in which double bonds including π bonds and single bonds consisting only of σ bonds are alternately arranged is usually in a conjugated state. Is the part that should be formed.
Thus, by stabilizing or diluting at least a part of the conjugated state that would normally be formed, the stabilization of the π-electron orbitals existing in the molecule of the polymer compound is inhibited. That is, charge transfer in the molecule due to integration of the π electron orbitals is hindered.

  The three-dimensional structure in the present invention includes both the molecular configuration and the conformation. The configuration is a spatial arrangement of atoms or atomic groups bonded to an asymmetric carbon atom around the asymmetric carbon atom, or a structure that is difficult to move in a molecule, for example, in a cis-trans isomer. It means a spatial arrangement of atoms and atomic groups that bind to it. Conformation means various spatial arrangements of atoms in a molecule realized by the rotation of two atomic groups connected by this bond around a single bond in the molecule. .

Cutting or diluting the π-conjugated structure described in the present invention means that an unsaturated bond is connected through a single bond and usually becomes a conjugated structure. It means that it is impossible or difficult to do.
Specifically, the π-electron orbitals of two unsaturated bonds at both ends of a single bond are not in the same plane. Generally, as the angle between the planes approaches 0 ° to 90 ° It is considered that the interaction is most difficult when it becomes 90 degrees.
In general, the two π-electron orbitals are considered to be the most stable and stable when they are in the same plane, and the interaction is the most dilute and unstable when the angle of the two π-electron orbits is orthogonal. It appears to be. Since a stable electron orbit is excited by a low-energy electromagnetic wave, that is, a long-wave electromagnetic wave, absorption of the portion becomes large. That is, the greater the degree of inhibition of the orbital stabilization of π electrons, the more the absorption wavelength shifts to the single wavelength side than the original absorption wavelength.

  Here, the action of steric hindrance is to form a π plane, that is, a conjugated state in order to stabilize, that is, integrate two or more adjacent π electron orbitals due to the three-dimensional structure of the molecule. The tendency or driving force and the tendency or driving force to increase the stability of the configuration due to causes other than stabilization of the π electron orbital compete at a common position in the molecular structure, resulting in the formation of the π plane. Or completely distort the π plane.

As a cause of steric hindrance, for example, distortion of a cyclic structure and a spatial hindrance due to a relatively large substituent can be mentioned.
In the case of a highly transparent polyimide containing a 7-membered ring imide structure, which will be described later, the driving force for releasing the distortion of the imide ring is identical to the two benzene rings contained in the biphenyl structure integrated with the imide ring. It is superior to the driving force to be arranged in the π plane, and as a result, the conjugate of the π bond is cut off.
In addition, 2,2′-dimethyl-4,4′-diaminobiphenyl has a methyl group in which the free rotation of a single bond between the benzene rings is inhibited by two methyl groups introduced at the 2-position and the 2′-position. As compared with 4,4′-diaminobiphenyl, in which is not introduced, conjugation is difficult.
Whether the conjugated state is cleaved or diluted by the three-dimensional structure of the molecule in the molecule of the polymer compound can be estimated from the results of molecular orbital calculations of the polymer compound or a model compound similar thereto.

As described above, as a result of the conjugated state of the polymer compound being cut or diluted, the light absorption wavelength region of the polymer compound is shortened, and the transmittance of light having a wavelength in the visible light region is improved. Can do.
Here, whether or not the absorption wavelength region of light has shifted to the short wavelength side is the absorption wavelength estimated by molecular mechanical or molecular orbital calculations such as MM2, AM1, and PM5 of the polymer compound or similar model compounds. This can be confirmed by comparing the approximate value of the region and / or intensity with the actual measurement value. In addition, if there is no compound to be compared, at least if the π-conjugated structure is cut and / or diluted, it can be confirmed that it is the most stable structure of the molecular mechanical or molecular orbital calculation result. good.
As another method, when a model compound having a similar structure with a continuous conjugated structure is present stably, the absorption wavelength of the model compound and a compound obtained by cutting or diluting the conjugated structure may be compared and confirmed. .
According to the present invention, superior transparency can be achieved without deteriorating useful properties inherent to the polymer compound, compared with the case where transparency is increased by introducing other chemical structures or substituents into the molecule. Sex is obtained.
The polymer compound according to the present invention has improved light transmittance or improved total light transmittance at all wavelengths in the visible light region (400 nm to 800 nm) according to the principle of improving transparency according to the present invention. It is desirable that However, depending on the use of the polymer compound or the wavelength of the light source used in the use, it is sufficiently useful if the light transmittance is increased at some wavelengths among wavelengths between 400 nm and 800 nm. Therefore, in the present invention, the transmittance of light of at least some wavelengths between 400 nm and 800 nm can be improved by cutting or diluting the conjugated state in the polymer compound by the three-dimensional structure of the molecule. That's fine.

When aromatic structures, which are typical examples of π-conjugated structures, are abundantly contained in the molecules of polymer compounds, the π-conjugated chains of each aromatic structure are integrated to form a more stable conjugated state. Cheap. In the present invention, such a polymer compound is very effective.
Specifically, a polymer compound in which the aromatic structure occupies 50% by weight or more of the entire molecular structure is a typical example in which a conjugated state is easily formed by a π electron orbital in the molecule, and is easily colored. Although it has a molecular structure, the polymer compound according to the present invention is a film having a thickness of 1 μm, preferably 2 μm, particularly preferably 2 μm or more even when the aromatic structure occupies 50% by weight or more of the entire molecular structure. When the film is formed, very excellent transparency can be achieved such that the transmittance between 400 nm and 800 nm is 85% or more, particularly preferably 90% or more at each wavelength. Further, the total light transmittance (JIS K7105) of the film is more preferably 90% or more.

Here, “the aromatic structure occupies 50% by weight or more” means that the proportion of the constituent unit forming the aromatic structure in the polymer is 50% or more of the total weight of the polymer. Say something. The structural unit forming the aromatic structure is composed of an atom having an π electron involved in an unsaturated bond forming an aromatic structure, and a hydrogen atom and a halogen atom directly bonded to the atom. In the case of xylene having a chemical structure of CH ₃ —C ₆ H ₄ —CH ₃ , the C ₆ H ₄ portion is an aromatic structure.
The method for confirming whether the aromatic structure occupies 50% by weight or more is not particularly limited. For example, solid and liquid ¹ H- and ¹³ C-NMR spectra (nuclear magnetic resonance spectra) or red Techniques such as external spectroscopy and gas chromatography can be used.

  In order to sufficiently obtain the effect of improving the transparency, the polymer compound according to the present invention has a three-dimensional structure of the molecule that cleaves or dilutes the conjugated state, an aromatic ring or aromatic that becomes a part of the polymer skeleton. The molar ratio with respect to the amount of the repeating unit including a condensed ring including a group ring is preferably 50% or more, and more preferably 70% or more.

In the case where a large number of aromatic rings are included as part of the polymer skeleton, a conjugated state is very easily formed in the molecule, so that the benefit obtained by improving the transparency by applying the present invention Will grow that much.
From this point of view, as one of preferred embodiments belonging to the present invention, an aromatic ring in which 50 mol% or more, particularly 70 mol% or more of the repeating unit constituting the polymer skeleton is a part of the polymer skeleton, or Occupied by a repeating unit containing a condensed ring containing an aromatic ring and cutting at least a part of the conjugated state between the aromatic ring or the condensed ring, which becomes a part of the polymer skeleton, by the three-dimensional structure of the molecule Examples include diluted polymer compounds.

Here, the repeating unit constituting the polymer skeleton includes both the main chain skeleton and the side chain skeleton repeating unit, but particularly when only limited to the repeating unit constituting the main chain skeleton is described above. It is preferable that the conditions are satisfied.
The aromatic ring contained in the repeating unit may be either a monocyclic aromatic ring or a condensed polycyclic aromatic ring. Moreover, the condensed ring containing an aromatic ring may contain two or more aromatic rings. The aromatic ring contained in the condensed ring may be either a monocyclic structure or a condensed polycyclic structure.
When the repeating unit can be further divided into two or more repeating units, the molar ratio is determined by dividing into the smallest repeating units.

As a preferred embodiment belonging to the present invention, the polymer compound contains two or more aromatic rings as repeating units constituting the polymer skeleton, particularly preferably the main chain skeleton, and conjugation between the aromatic rings of the repeating units. Examples thereof include a polymer compound whose state is cut or diluted by the three-dimensional structure of the molecule.
In this embodiment, 50 mol% or more, particularly 70 mol% or more of the repeating units constituting the polymer skeleton, particularly preferably the main chain skeleton, cleave the conjugated state between the aromatic rings by the configuration of the molecular structure. Alternatively, it is preferably occupied by dilute repeat units.

When the condensed ring that is part of the polymer skeleton contains two or more aromatic rings, the conjugated state between the aromatic rings contained in the same condensed ring is cleaved or diluted by the three-dimensional structure of the molecule. Thus, the transparency of the polymer compound can be effectively improved.
That is, as another preferred embodiment belonging to the present invention, a repeating unit including a condensed ring that is a part of the polymer skeleton is included, and at least two aromatic rings included in the same condensed ring of the repeating unit are included. Examples thereof include a polymer compound in which a conjugated state is cut or diluted by a three-dimensional structure of a molecule. In addition, the highly transparent polyimide containing the 7-membered ring imide structure mentioned later is one of this aspect.
In this embodiment, two or more aromatic rings in which 50 mol% or more, particularly 70 mol% or more of the repeating units constituting the polymer skeleton, particularly preferably the main chain skeleton, are cut or diluted with respect to each other in the conjugated state. More preferably, it is occupied by the above repeating unit containing a condensed ring containing.

  The polymer compound according to the present invention described above is useful as a resin material for forming a product or member having a high requirement for transparency using the polymer compound, and a resin composition containing the polymer compound It is possible to produce a product or member excellent in transparency using an object.

Hereinafter, a highly transparent polyimide containing a 7-membered ring imide structure will be described in detail as an example of the polymer compound according to the present invention. The features, advantages, and other contents described with respect to the following highly transparent polyimide are descriptions common to all the polymer compounds according to the present invention unless otherwise contradicted.
The highly transparent polyimide of the present invention is characterized by having a repeating unit represented by the following formula (1) including a 7-membered imide structure.

(In the formula, R ^{1 to} R ⁶ are each independently a hydrogen atom or a monovalent organic group, which may be bonded to each other. R ⁷ is a divalent organic group. The groups represented by the same symbols between the repeating units present in may be different atoms or structures.)

Aromatics typified by polyimides derived from pyromellitic dianhydride-derived polyimides having an aromatic 5-membered ring imide structure and polyimides derived from 1,4,5,8-naphthalenetetracarboxylic dianhydride 6 Polyimide having a membered ring imide structure arranges all atoms related to the imide bond stably in a planar shape, so that the conjugated structure of π electrons tends to spread on the polyimide molecular chain, and in particular, an aromatic acid dianhydride as an acid component. In the case of a wholly aromatic polyimide that uses an aromatic diamine as well as a diamine component, the conjugated structure tends to spread over a wide range on the polyimide molecular chain, and thus a coloring phenomenon is likely to occur.
In addition, polyimide derived from 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride also has a five-membered ring structure imide group having a planar structure although the imide group is bonded to a different benzene ring. Therefore, the benzene ring and the imide group are π-conjugated. In addition, a single bond connecting two benzene rings derived from an acid anhydride can freely rotate, and they can form a π-conjugated structure.

  In contrast, the polyimide according to the present invention has an imide skeleton contained in the repeating unit of the formula (1), that is, 2,2 ′, 6 ′, 6′-biphenyltetracarboxylic dianhydride or an aromatic ring thereof. It has a 7-membered ring imide structure derived from a compound having a substituent, and is unstable when it is arranged on a plane. Therefore, the relative position of the benzene ring of the biphenyl structure contained in the imide skeleton is twisted, and the π bond conjugation is broken.

  FIG. 1 shows a spatial arrangement inferred from the result of molecular orbital calculation of a model compound having a skeleton of formula (1). Since 2,2 ', 6', 6'-biphenyltetracarboxylic dianhydride can rotate the bond connecting the benzene rings of the biphenyl skeleton, when imidization is performed, a 7-membered ring imide structure is formed. It is presumed from the results of MM2 molecular orbital calculation that the two benzene rings and the imide bond do not exist in the same plane, and that the benzene rings take an inclined configuration of about 30 to 40 °.

From this calculation result, it can be seen that not only the planarity of the benzene rings of biphenyl but also the planarity of the imide bond is lost, and the structure is taken in the direction of breaking the π conjugation in the molecular chain.
Since the polyimide according to the present invention has such a spatial arrangement of the molecular structure, the charge transfer on the polyimide molecular chain is blocked while having heat resistance due to the aromatic polyimide, so that the polyimide becomes transparent.

  The polyimide according to the present invention also exhibits good dimensional stability, which is a characteristic of aromatic polyimide. Furthermore, the raw material 2,2 ′, 6 ′, 6′-biphenyltetracarboxylic dianhydride can be obtained at a low cost because it can be obtained by a relatively simple synthesis method such as an oxidation reaction of pyrene. .

  Polyimides produced using 2,2 ', 6,6'-biphenyltetracarboxylic dianhydride have been known in the past, but their physical properties are not known in detail, and the transparency is particularly good. The property of being has never been known in the past.

  The present invention is based on a novel molecular design for increasing the transparency of polyimide, and polyimides produced using 2,2 ', 6,6'-biphenyltetracarboxylic dianhydride are highly transparent. It has been found that transparency is good due to a mechanism that is not found in conductive polyimide, and shows suitable applications in the field where high transparency can be utilized together with properties such as heat resistance inherent to polyimide.

In the repeating unit represented by the above formula (1), a substituent other than a hydrogen atom may be introduced at the positions of R ^{1 to} R ⁶ . The polyimide in the present invention has good transparency if the repeating unit of the formula (1) has a 7-membered ring imide skeleton derived from 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride. The same effect can be expected even when a substituent is introduced into R ^{1 to} R ⁶ .
Examples of the monovalent organic group that can be introduced at the positions of R ^{1 to} R ⁶ other than a hydrogen atom include, for example, a halogen atom, a hydroxyl group, a mercapto group, a primary amino group, a secondary amino group, a tertiary amino group, and a cyano group. , Silyl group, silanol group, alkoxy group, nitro group, carboxyl group, acetyl group, acetoxy group, sulfone group, saturated or unsaturated alkyl group, saturated or unsaturated halogenated alkyl group, or aromatic such as phenyl or naphthyl Group, allyl group and the like. R ^{1 to} R ⁶ may be the same as or different from each other. Two or more groups of R ^{1 to} R ⁶ , in particular two or three of R ^{1 to} R ³ and / or two or three of R ^{4 to} R ⁶ May be bonded to each other to form a cyclic structure.

Substituents R ^{1 to} R ⁶ may be introduced in the raw material state and may be used in the state of an acid dianhydride in which a substituent has already been introduced, or may be reacted with a diamine in the state of polyimide or polyamic acid. It may be introduced. Moreover, it is possible to adjust the wavelength of light to be absorbed by introducing a substituent, and it is also possible to absorb a desired wavelength by introducing a substituent.

  Interpretation of the Ultraviolet Spectra of Natural Products (AIScott 1964) and identification methods by spectrum of organic compounds as a guide to what substituents should be introduced to shift the absorption wavelength with respect to the desired wavelength You can refer to the table described in the fifth edition (RMSilverstein 1993).

R ⁷ in the formula (1) is a divalent organic group, and specific examples thereof include a divalent organic group corresponding to each diamine component described later, that is, both involved in the formation of a polyimide chain from the diamine component. Examples include a structure in which the terminal amino group is removed. In addition, between each repeating unit which exists in the same polyimide chain | strand, the atom or structure from which the group represented with the same code | symbol differs may be sufficient.

The polyimide according to the present invention is an aromatic polyimide in which at least a portion derived from an acid dianhydride has an aromatic imide structure. From the viewpoint of improving the heat resistance and dimensional stability of the polyimide, it is further derived from a diamine. The part is also preferably a wholly aromatic polyimide containing an aromatic structure. Therefore, R ⁷ which is a structure derived from a diamine component is also preferably a structure derived from an aromatic diamine. Here, the wholly aromatic polyimide is a polyimide obtained by copolymerization of an aromatic acid component and an aromatic amine component or polymerization of an aromatic acid / amino component. The aromatic acid component is a compound in which all four acid groups forming the polyimide skeleton are substituted on the aromatic ring, and the aromatic amine component is the two amino groups forming the polyimide skeleton. Both are compounds substituted on the aromatic ring, and the aromatic acid / amino component is a compound in which both the acid group and amino group forming the polyimide skeleton are substituted on the aromatic ring. However, as is clear from the specific examples of raw materials described later, it is not necessary for all acid groups or amino groups to be present on the same aromatic ring.

The polyimide of this invention can also improve solubility by introduce | transducing a substituent into molecular structure. From this viewpoint, the substituents R ^{1 to} R ⁶ are a saturated and unsaturated alkyl group having 1 to 15 carbon atoms, a saturated and unsaturated alkoxy group having 1 to 15 carbon atoms, a bromo group, a chloro group, a fluoro group, A nitro group, a primary to tertiary amino group and the like are preferable. Moreover, these groups may be present in the divalent organic group R ⁷ .

  The polyimide of the present invention may have a repeating unit other than the formula (1) as long as the object of the present invention of improving properties such as transparency, heat resistance, and dimensional stability can be achieved. . For example, the polyimide of the present invention may contain a repeating unit having an imide structure other than the formula (1), or a repeating unit that is not an imide structure such as a repeating unit of an amide structure (a repeating unit of polyamide). You can leave.

  The repeating unit having an imide structure other than the formula (1) can be represented by the following formula (2), and a polyimide including the repeating unit represented by the formula (1) and the repeating unit represented by the formula (2). Can be represented by the following formula (3). In addition, the polyimide represented by Formula (3) may contain repeating units other than Formula (1) and Formula (2).

(In the above formula (2), X is a tetravalent organic group, and Y is a divalent organic group.)

(In the above formula (2) and formula (3), R ^{1 to} R ⁶ , R ⁷ , X and Y are the same as those in formula (1) or formula (2). The same among repeating units present in the same molecule. The groups represented by the symbols may be different atoms or structures, m is a natural number of 1 or more, n is a natural number of 0 or more, and the unit of formula (1) and the unit of formula (2) are (It may be a random array or an array with regularity.)

  The imide structure other than the formula (1) is introduced into the polyimide chain by using an acid dianhydride other than 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride and its derivatives.

  A conventionally known method can be applied as a method for producing the polyimide of the present invention. For example, (1) A method in which a polyamic acid as a precursor is synthesized from an acid dianhydride and a diamine, molded in the state of the polyamic acid, and then imidized by heating. (2) A method in which amic acid is heated in a solution or a polyimide solution is obtained using a dehydration catalyst such as acetic anhydride or dicyclohexylcarbodiimide, and then the polyimide solution is molded by a method such as coating. (3) First, there is a method of synthesizing diimide monomers using acid dianhydride and a monoamine having 2 equivalents of reaction sites, and then bonding diimide monomers together to form polyimide.

The polyimide of the present invention is improved in transparency by ring-closing to the intramolecular imide ring from the mechanism for expressing the transparency. That is, the higher the intramolecular imide cyclization rate at the synthesis stage, the better the transparency. Conversely, when the crosslinking reaction proceeds at the site of the precursor molecule closing to the imide ring and a large number of crosslinking bonds are formed with other precursor molecules, the intramolecular imide cyclization rate decreases. Cause coloration.
Therefore, when pursuing transparency, the method (2) or (3) is preferable, and when pursuing transparency particularly strictly, the intramolecular imide cyclization rate should be surely set to 100%. It is preferable to synthesize by the above method (3).

From the viewpoint of obtaining excellent transparency, in the present invention, the intramolecular imide cyclization rate is preferably 80 mol% or more, particularly 90 mol% or more. Here, the intramolecular imide cyclization rate is actually the intramolecular imide cyclization with respect to the theoretical value when it is assumed that the intramolecular imide cyclization site contained in the polyimide precursor is 100% intramolecular imide cyclization. The ratio of the part. In order to determine the intramolecular imide cyclization rate for a specific polyimide, it may be determined by infrared spectroscopy, liquid or solid ¹ H-NMR, ¹³ C-NMR, or the like.

  The loss of the intramolecular imide cyclization reaction is caused by the fact that reactive sites that can undergo imide cyclization reaction are consumed by the crosslinking reaction or remain unreacted. large. Therefore, in this invention, you may evaluate whether the intramolecular imide cyclization was fully performed by measuring the quantity of the crosslink bond contained in the obtained polyimide. For example, when a rubber-like region is not observed in the dynamic viscoelasticity measurement of polyimide, it can be determined that the intramolecular imide cyclization rate is high. On the other hand, when a rubber-like region is observed in the dynamic viscoelasticity measurement of polyimide, it is a cross-linked product, and therefore, the intramolecular imide cyclization rate is lower than that which does not show a rubber-like region. Can be judged. In fact, when a rubbery region is observed, the transparency of the polyimide is slightly reduced.

As described above, the acid dianhydride used here is not only 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride, but any one of R ^{1 to} R ⁶ according to the purpose. You may use the derivative | guide_body in which the substituent was introduce | transduced more than the location. As the acid dianhydride, other than 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride and / or a derivative thereof may be used in combination. 2,2 ', 6,6'-biphenyltetracarboxylic dianhydride and / or its derivatives, and other acid dianhydrides are used in combination of two or more as long as the transparency of the polyimide can be secured can do.
The acid dianhydride that can be used in combination with 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride and / or its derivative is preferably an aromatic dianhydride from the viewpoint of heat resistance. Depending on the desired physical properties, acid dianhydrides other than 2,2 ', 6,6'-biphenyltetracarboxylic dianhydride are within a range not exceeding 50 mol%, preferably 30 mol% of the total acid dianhydride. May be used.

  Other acid dianhydrides that can be used in combination with 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride and / or its derivatives include, for example, ethylenetetracarboxylic dianhydride, butanetetracarboxylic dianhydride. Anhydride, cyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 2 , 2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) -Terdianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane Dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane Anhydride, 2,2-bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3-bis [(3,4-dicarboxy ) Benzoyl] benzene dianhydride, 1,4-bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] Phenyl} propane dianhydride, 2, -Bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, 4,4′-bis [4- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, 4,4 '-Bis [3- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [ 3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfone dianhydride, bis {4- [3- (1,2-dicarboxy Phenoxy] phenyl} sulfone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] Phenyl} sulfide dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-hexaflupropane dianhydride, 2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-propane dianhydride, 2,3,6,7-naphthalene Tetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic Acid dianhydride, 3,4,9,10- Examples include perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, and the like. These may be used alone or in combination of two or more. And as a particularly preferred tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetra Carboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoro Examples include propane dianhydride.

  When acid dianhydride into which fluorine is introduced or acid dianhydride having an alicyclic skeleton is used as the acid dianhydride to be used in combination, the physical properties such as solubility and thermal expansion coefficient are adjusted without significantly impairing transparency. It is possible. Also, rigid acid dianhydrides such as pyromellitic acid anhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, etc. If used, the coefficient of linear thermal expansion becomes small, but it tends to hinder the improvement of transparency, so it may be used in combination while paying attention to the copolymerization ratio.

  On the other hand, the amine component can also be used alone or in combination of two or more diamines. The diamine component used is not limited, but p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diamino. Diphenyl ether, 3,3′-diaminodiphenyl sulfide, 3,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 4,4 '-Diaminodiphenylsulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4' -Diaminodiph Nylmethane, 2,2-di (3-aminophenyl) propane, 2,2-di (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2,2 -Di (3-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-di (4-aminophenyl) -1,1,1,3,3,3-hexa Fluoropropane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 1,1-di (3-aminophenyl) -1 -Phenylethane, 1,1-di (4-aminophenyl) -1-phenylethane, 1- (3-aminophenyl) -1- (4-aminophenyl) -1-phenylethane, 1,3-bis ( 3-Aminophenoxy) benzene, 1,3 Bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminobenzoyl) benzene, 1, 3-bis (4-aminobenzoyl) benzene, 1,4-bis (3-aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 1,3-bis (3-amino-α, α -Dimethylbenzyl) benzene, 1,3-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,4-bis ( 4-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,3-bis (4-amino-α, α-dito Trifluoromethylbenzyl) benzene, 1,4-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 2 , 6-bis (3-aminophenoxy) benzonitrile, 2,6-bis (3-aminophenoxy) pyridine, 4,4′-bis (3-aminophenoxy) biphenyl, 4,4′-bis (4-amino) Phenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide,

Bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-amino) Phenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3- (3-Aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3 3,3-hexafluoropropane, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (4-aminophenoxy) benzoyl] ben 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-amino Phenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (3-aminophenoxy) -Α, α-dimethylbenzyl] benzene, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 4,4'-bis [4- (4-aminophenoxy) benzoyl ] Diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethylbenzen) ) Phenoxy] diphenylsulfone, 4,4′-bis [4- (4-aminophenoxy) phenoxy] diphenylsulfone, 3,3′-diamino-4,4′-diphenoxybenzophenone, 3,3′-diamino-4 , 4′-Dibiphenoxybenzophenone, 3,3′-diamino-4-phenoxybenzophenone, 3,3′-diamino-4-biphenoxybenzophenone, 6,6′-bis (3-aminophenoxy) -3,3 3 ′, 3′-tetramethyl-1,1′-spirobiindane, 6,6′-bis (4-aminophenoxy) -3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, , 3-bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, α, ω-bis ( -Aminopropyl) polydimethylsiloxane, α, ω-bis (3-aminobutyl) polydimethylsiloxane, bis (aminomethyl) ether, bis (2-aminoethyl) ether, bis (3-aminopropyl) ether, bis ( 2-aminomethoxy) ethyl] ether, bis [2- (2-aminoethoxy) ethyl] ether, bis [2- (3-aminoprotoxy) ethyl] ether,

1,2-bis (aminomethoxy) ethane, 1,2-bis (2-aminoethoxy) ethane, 1,2-bis [2- (aminomethoxy) ethoxy] ethane, 1,2-bis [2- (2 -Aminoethoxy) ethoxy] ethane, ethylene glycol bis (3-aminopropyl) ether, diethylene glycol bis (3-aminopropyl) ether, triethylene glycol bis (3-aminopropyl) ether, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1, 11-diaminoundecane, 1,12-diaminododecane, 1,2-diaminocyclohex 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,2-di (2-aminoethyl) cyclohexane, 1,3-di (2-aminoethyl) cyclohexane, 1,4-di (2- Aminoethyl) cyclohexane, bis (4-aminocyclohexyl) methane, 2,6-bis (aminomethyl) bicyclo [2,2,1] heptane, 2,5-bis (aminomethyl) bicyclo [2,2, 1] A diamine obtained by substituting some or all of the hydrogen atoms on the aromatic ring of the above diamine with a substituent selected from a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group. Can be used. Furthermore, depending on the purpose, any one or two or more of the ethynyl group, benzocyclobuten-4′-yl group, vinyl group, allyl group, cyano group, isocyanate group, and isopropenyl group serving as a crosslinking point, Even if it introduce | transduces into some or all of the hydrogen atoms on the aromatic ring of diamine as a substituent, it can be used.

The diamine can be selected depending on the desired physical properties, and if a rigid diamine such as p-phenylenediamine is used, the expansion coefficient is low. Rigid diamines include p-phenylenediamine, m-phenylenediamine, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2, 6 as diamines in which two amino groups are bonded to the same aromatic ring. -Diaminonaphthalene, 2,7-diaminonaphthalene, 1,4-diaminoanthracene and the like can be mentioned.
In addition, diamines in which two or more aromatic rings are bonded by a single bond, and two or more amino groups are each bonded directly or as part of a substituent on a separate aromatic ring, for example, There exists what is represented by following formula (4). Specific examples include benzidine and the like.

(A is a natural number of 1 or more, and the amino group is bonded to the meta position or para position with respect to the bond between benzene rings.)

Furthermore, in the above formula (4), it is also possible to use a diamine having a substituent at a position where the amino group on the benzene ring is not substituted without being involved in the bond with other benzene. These substituents are monovalent organic groups, but they may be bonded to each other.
Specific examples include 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2′-ditrifluoromethyl-4,4′-diaminobiphenyl, 3,3′-dichloro-4,4′-diamino. Biphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, 3,3′-dimethyl-4,4′-diaminobiphenyl and the like can be mentioned.
When used as an optical waveguide or an optical circuit component, the transmittance for electromagnetic waves having a wavelength of 1 μm or more can be improved by introducing fluorine as a substituent of the aromatic ring.

On the other hand, when a diamine having a siloxane skeleton such as 1,3-bis (3-aminopropyl) tetramethyldisiloxane is used as the diamine, the elastic modulus is lowered and the glass transition temperature can be lowered.
Here, the selected diamine is preferably an aromatic diamine from the viewpoint of heat resistance. However, depending on the desired physical properties, the diamine may be an aliphatic diamine or siloxane within a range not exceeding 60 mol%, preferably not exceeding 40 mol%. Non-aromatic diamines such as diamines may be used.

  Next, a method for synthesizing 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride, which is a raw material for the polyimide according to the present invention, and a method for synthesizing a polyimide will be specifically exemplified. However, the present invention is not limited to this.

  2,2 ', 6,6'-biphenyltetracarboxylic dianhydride having the most basic structure among the acid component raw materials can be obtained by an oxidation reaction of pyrene. That is, first, pyrene is dissolved in dichloromethane. When completely dissolved, add acetonitrile and water and stir. Thereto are added sodium periodate as an oxidizing agent and ruthenium trichloride as a catalyst, and the mixture is stirred at room temperature for 10 to 30 hours. After completion of the reaction, the precipitate is filtered, and the precipitate is extracted with acetone and filtered. The extracted acetone is concentrated and dried, and then refluxed with dichloromethane for 4 to 10 hours. The white solid obtained by filtering it is 2,2 ′, 6,6′-biphenyltetracarboxylic acid, which is a precursor of 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride. The 2,2 ′, 6,6′-biphenyltetracarboxylic acid thus obtained was refluxed with acetic anhydride for 3 hours, and then the solvent was distilled off. The resulting solid was obtained at a pressure of 0.8 mmHg (106.4 Pa). By subjecting it to sublimation purification at 230 ° C., the desired product, 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride can be obtained.

  Next, an example of synthesizing polyimide using the above 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride as an acid component and 4,4′-diaminodiphenyl ether as an amine component will be described. First, equimolar 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride is gradually added to dimethylacetamide in which 4,4′-diaminodiphenyl ether is dissolved, and the mixture is stirred at room temperature. After stirring for about 1 to 20 hours, the reaction solution is dropped into the stirred diethyl ether and reprecipitated to obtain polyamic acid. The polyamic acid is dissolved again in dimethylacetamide, applied onto a substrate such as glass and dried, a polyamic acid coating film is formed, and heated to obtain a polyimide coating film.

  In addition, when chemical imidation is performed instead of heat dehydration, known compounds such as amines such as pyridine and β-picolinic acid, carbodiimides such as dicyclohexylcarbodiimide, and acid anhydrides such as acetic anhydride are used as dehydration catalysts. May be. Examples of the acid anhydride include, but are not limited to, acetic anhydride, propionic acid anhydride, n-butyric acid anhydride, benzoic acid anhydride, trifluoroacetic acid anhydride, and the like. At that time, a tertiary amine such as pyridine or β-picolinic acid may be used in combination.

  The polyimide of the present invention synthesized in this way has a copolymerization ratio of the aromatic acid component and / or aromatic amine component as large as possible in order to improve the heat resistance and dimensional stability inherent in the polyimide. Is preferred. Specifically, the proportion of the aromatic acid component in the acid component constituting the repeating unit of the imide structure is preferably 50 mol% or more, particularly preferably 70 mol% or more, and the amine component constituting the repeating unit of the imide structure The proportion of the aromatic amine component in the total is preferably 40 mol% or more, particularly preferably 60 mol% or more, and particularly preferably a wholly aromatic polyimide.

  From the viewpoint of achieving transparency, the polyimide of the present invention is a repeating unit represented by the formula (1) in which 50 mol% or more, particularly 70 mol% or more of the repeating unit of the imide structure present in the polyimide chain is represented. It is preferable. From the viewpoint of heat resistance and dimensional stability, the repeating unit represented by the formula (1) is preferably a repeating unit of wholly aromatic polyimide.

  The polyimide of the present invention synthesized in this way is characterized by having high transparency, and transmits light at each wavelength in the wavelength region of 400 nm to 800 nm when formed on a film having a thickness of 1 μm, preferably 2 μm. The rate is preferably 85% or more. Further, the total light transmittance (JIS K7105) is more preferably 90% or more.

  The weight average molecular weight of the polyimide of the present invention is preferably in the range of 3,000 to 1,000,000, more preferably in the range of 5,000 to 500,000, although it depends on the application. More preferably, it is in the range of 10,000 to 500,000. When the weight average molecular weight is 3,000 or less, it is difficult to obtain sufficient strength when a coating film or film is used. Further, if it is less than 10,000, coloring may occur because the number of polymer ends that cause coloring becomes relatively large. On the other hand, when it exceeds 1,000,000, the viscosity increases and the solubility also decreases, so that it is difficult to obtain a coating film or film having a smooth surface and a uniform film thickness.

The polyimide of the present invention is good because the original characteristics of the polyimide such as heat resistance, dimensional stability and insulation are not impaired.
For example, the 5% weight loss temperature measured in nitrogen is preferably 250 ° C. or higher, more preferably 300 ° C. or higher. In particular, when used in applications such as electronic parts that pass through the solder reflow process, if the 5% weight loss temperature is 300 ° C. or less, defects such as bubbles occur due to the decomposition gas generated in the solder reflow process. There is a fear. Here, the 5% weight reduction temperature is the time when the weight of the sample is reduced by 5% from the initial weight when the weight loss is measured using a thermogravimetric analyzer (in other words, the sample weight becomes 95% of the initial weight). Temperature). Similarly, the 10% weight reduction temperature is a temperature at which the sample weight is reduced by 10% from the initial weight.

The glass transition temperature is preferably as high as possible from the viewpoint of heat resistance. However, in applications where a thermoforming process is considered, such as an optical waveguide, it is preferable to exhibit a glass transition temperature of about 120 ° C. to 380 ° C. More preferably, it exhibits a glass transition temperature of about 380C to 380C.
From the viewpoint of dimensional stability, the linear thermal expansion coefficient is preferably 60 ppm or less, and more preferably 40 ppm or less. When used as a film substrate for a flexible display as a glass substitute, 20 ppm or less is more preferable.

  As described above, the polyimide according to the present invention exhibits good transparency without introducing fluorine or an alicyclic skeleton. Therefore, it is possible to eliminate the problems that the original physical properties of polyimide such as heat resistance and dimensional stability, which have been unavoidable by the introduction of fluorine and alicyclic skeletons, and the problem of high cost can be solved. A highly transparent polyimide coating film, film or molded article having heat resistance equivalent to that of polyimide can be obtained.

  The polyimide according to the present invention may be subjected to a coating or molding process for producing a product or member as it is, but the polyimide is dissolved or dispersed in a solvent as necessary, and further, a light or thermosetting component, A polyimide resin composition may be prepared by blending a non-polymerizable binder resin other than polyimide according to the present invention and other components.

Various general-purpose solvents can be used as a solvent for dissolving, dispersing or diluting the polyimide resin composition.
Usable general-purpose solvents include, for example, diethyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether and other ethers; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, Glycol monoethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether (so-called cellosolves); ketones such as methyl ethyl ketone, acetone, methyl isobutyl ketone, cyclopentanone, cyclohexanone; acetic acid Ethyl, butyl acetate, acetic acid n-propyl, i-propyl acetate, n-butyl acetate, i-butyl acetate, acetate esters of the above glycol monoethers (for example, methyl cellosolve acetate, ethyl cellosolve acetate), methoxypropyl acetate, ethoxypropyl acetate, dimethyl oxalate , Esters such as methyl lactate and ethyl lactate; alcohols such as ethanol, propanol, butanol, hexanol, cyclohexanol, ethylene glycol, diethylene glycol, glycerin; methylene chloride, 1,1-dichloroethane, 1,2-dichloroethylene, 1- Halogenated hydrocarbons such as chloropropane, 1-chlorobutane, 1-chloropentane, chlorobenzene, bromobenzene, o-dichlorobenzene, m-dichlorobenzene; N, N-dimethylform Amides, amides such as N, N-dimethylacetamide; pyrrolidones such as N-methylpyrrolidone; lactones such as γ-butyrolactone; sulfoxides such as dimethyl sulfoxide, and other organic polar solvents, etc. , Aromatic hydrocarbons such as benzene, toluene and xylene, and other organic nonpolar solvents. These solvents are used alone or in combination.

As the photocurable component, a compound having one or more ethylenically unsaturated bonds can be used. For example, an amide monomer, a (meth) acrylate monomer, a urethane (meth) acrylate oligomer, a polyester (meth) Aromatic vinyl compounds such as acrylate oligomers, epoxy (meth) acrylates, hydroxyl group-containing (meth) acrylates, and styrene can be exemplified. Here, (meth) acrylate means that either acrylate or methacrylate may be used.
When using a photocurable compound having such an ethylenically unsaturated bond, a photoradical generator may be further added.

  Moreover, as a light or thermosetting component other than the photocurable compound having an ethylenically unsaturated bond, or other non-polysynthetic binder resin, any known polymer compound or radical reaction or other curing reactivity may be used. Compounds can be used. For example, organic polyisocyanates such as tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate; vinyl acetate, vinyl chloride, acrylate ester, methacrylate ester, etc. Polymers and copolymers of acrylic or vinyl compounds; styrene resins such as polystyrene; acetal resins such as formal resins and butyral resins; silicone resins; phenoxy resins; epoxy resins typified by bisphenol A type epoxy resins; polyurethanes, etc. Urethane resin; phenol resin; ketone resin; xylene resin; polyamide resin and precursor thereof; polyimide resin and precursor thereof; polyether resin; Polybenzoxazole resin; Cyclic polyolefin resin; Polycarbonate resin; Polyester resin; Polyarylate resin; Polystyrene resin; Novolak resin; Cycloaliphatic polymer such as polycarbodiimide, polybenzimidazole, polynorbornene; Siloxane polymer Any known high molecular compound or curing reactive compound may be mentioned, but it is not limited thereto. These may be used alone or in combination of two or more.

  When a non-polymeric polymer binder resin is used, the weight average molecular weight is usually preferably 3000 or more, depending on the use of the resin composition. In addition, if the molecular weight is too large, the solubility and processing characteristics are deteriorated. Therefore, the weight average molecular weight is usually preferably 10,000,000 or less.

  In order to impart processing characteristics and various functionalities to the resin composition according to the present invention, various organic or inorganic low-molecular or high-molecular compounds may be blended. For example, dyes, surfactants, leveling agents, plasticizers, fine particles, sensitizers, and the like can be used. The fine particles include organic fine particles such as polystyrene and polytetrafluoroethylene, inorganic fine particles such as colloidal silica, carbon, and layered silicate, and these may have a porous or hollow structure. The function or form includes pigments, fillers, fibers, and the like.

  In the polyimide resin composition according to the present invention, the polyimide represented by the formula (1) is usually contained within a range of 5 to 99.9% by weight with respect to the entire solid content of the resin composition. Further, the blending ratio of other optional components is preferably in the range of 0.1 wt% to 95 wt% with respect to the entire solid content of the polyimide resin composition. When the amount is less than 0.1% by weight, the effect of adding the additive is hardly exhibited, and when the amount exceeds 95% by weight, the characteristics of the resin composition are hardly reflected in the final product. In addition, solid content of a polyimide resin composition is all components other than a solvent, and a liquid monomer component is also contained in solid content.

  The polyimide resin composition according to the present invention is for pattern forming materials (resists), coating materials, paints, printing inks, adhesives, fillers, electronic materials, molding materials, resist materials, building materials, three-dimensional modeling, and flexible displays. It can be used in all known fields and products in which resin materials are used, such as films and optical members.

  In particular, the polyimide resin composition according to the present invention has high transparency in addition to the original properties of polyimide such as heat resistance, dimensional stability, insulation, etc., fields and products in which these properties are effective, For example, paints, printing inks, color filters, flexible display films, electronic parts, interlayer insulation films, wiring coating films, optical circuits, optical circuit parts, antireflection films, holograms, other optical members or building materials are formed. Suitable for

  Moreover, since it has high transparency in addition to heat resistance, dimensional stability, and insulation, this polyimide resin composition is suitable as a film or coating film for all known members that require transparency. For example, it is expected to be used as a highly heat-resistant film or structure for optical members such as antireflection films, optical circuit components, and holograms.

  Furthermore, since it becomes a highly transparent polyimide with high transparency, a polymer having an aliphatic carbon-hydrogen bond has absorption in the vicinity of 1.55 μm, which is the wavelength range used for optical signals, and is difficult to apply. The present invention can also be applied to optical circuit components such as optical signal waveguides and splitters. In particular, the transmittance is high even in a visible light region such as 800 nm, which is effective when a plurality of wavelengths are simultaneously used for wavelength multiplexing.

  Furthermore, this polyimide resin composition is expected to be used for substrates of optical members such as thin display substrates such as liquid crystal displays and organic EL as a glass substitute material that is lightweight and can be flexible. The

(Production Example 1)
Pyrene (15 g, 74 mmol) was placed in a 2 L (liter) flask and dissolved in 320 ml of dichloromethane. When completely dissolved, 320 ml of acetonitrile and 480 ml of distilled water were added and stirred. Thereto were added 150 g of sodium periodate as an oxidizing agent and 650 mg of ruthenium trichloride as a catalyst, and the mixture was stirred at room temperature for 22 hours. After completion of the reaction, the precipitate was filtered, and the precipitate was extracted with acetone and filtered. The extracted acetone was concentrated and dried, then refluxed with dichloromethane for 4 hours, and filtered to obtain a powder. Extraction with acetone and refluxing with dichloromethane were repeated until the powder was completely white, and 10.2 g of 2,2 ′, 6,6′-biphenyltetracarboxylic acid was obtained.
The obtained 2,2 ′, 6,6′-biphenyltetracarboxylic acid was refluxed with acetic anhydride for 3 hours, and then the solvent was distilled off. The resulting solid matter was 230 mm at a pressure of 0.8 mmHg (106.4 Pa). Purification by sublimation under the condition of ° C. gave a white powder of 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride (2,2 ′, 6,6′-BPDA), which was the target product.

(Production Example 2)
0.82 g (6 mmol) of p-aminobenzoic acid was put into a 50 ml three-necked flask and dissolved in 10 ml of dimethylformamide (DMF). Thereto was added 0.88 g (3 mmol) of 2,2 ′, 6,6′-BPDA little by little, and the mixture was stirred at room temperature for 5 hours. Thereafter, 10 ml of acetic anhydride was added and stirred at 120 ° C. for 5 hours. After completion of the reaction, the reaction solution was cooled to room temperature, and the reaction solution was added dropwise to 500 ml of saturated sodium hydrogen carbonate solution for reprecipitation to obtain a white powder of diimide compound 1 having a carboxylic acid at the terminal.

Example 1
The diimide compound 1 1.64 g (2 mmol) and 20 ml of toluene were put into a 200 ml flask and stirred. There, 50 ml of thionyl chloride was added, and it stirred at 120 degreeC for 5 hours. After completion of the reaction, the solvent and thionyl chloride were distilled off with a rotary evaporator to obtain acid chloride. 20 ml of dehydrated dichloromethane was added thereto to dissolve the acid chloride, and then the dehydrated tetrahydrofuran solution in which 0.45 g (2 mmol) of 4,4′-isopropylidenediphenol and 0.30 g (3 mmol) of triethylamine were dissolved was added. Add dropwise and stir at 50 ° C. for 4 hours. After reprecipitation with distilled water including the precipitate, it was dissolved in DMF and reprecipitated again with hexane to obtain the target polyimide as a white powder (polyimide 1).

(Example 2)
(1) Synthesis of precursor solution 1
4,4'-Diaminodiphenyl ether 1.20 g (6 mmol) was put into a 50 ml three-necked flask, dissolved in 5 ml of dehydrated N-methyl-2-pyrrolidone (NMP) and cooled in an ice bath under a nitrogen stream. While stirring. To this, every 30 minutes, 10 parts of 2,2 ', 6,6'-BPDA (1.77 g, 6 mmol) was added every 30 minutes, and after the addition was completed, the mixture was stirred in an ice bath for 5 hours. A viscous liquid (precursor solution 1) was obtained.
(2) Synthesis of Polyimide 2 In a 50 ml eggplant flask, 1 g of the above precursor solution 1 and 4 ml of dehydrated NMP were placed and stirred. Thereto, 2 ml of acetic anhydride was added and stirred at 100 ° C. for 24 hours. The solution was reprecipitated with diethyl ether to obtain 370 mg of white powder. (Polyimide 2). The weight average molecular weight in terms of polystyrene by GPC (gel permeation chromatography) was 64,000.

(Example 3)
In a 50 ml eggplant flask, 11 g of the precursor solution 1 synthesized in Example 2 and 4 ml of dehydrated NMP were placed and stirred. Thereto, 2 ml of trifluoroacetic anhydride was added and stirred at 100 ° C. for 24 hours. The solution was reprecipitated with diethyl ether to obtain 370 mg of white powder (Polyimide 3). The weight average molecular weight in terms of polystyrene by GPC was 13,000.

Example 4
The precursor solution 1 synthesized in Example 2 was directly spin-coated on glass and dried on a hot plate heated to 140 ° C. for 30 minutes. Thereafter, heating was performed in an air oven at 300 ° C. for 1 hour to obtain a polyimide (polyimide 4) insoluble in NMP.

(Example 5)
(1) Synthesis of precursor solution 2
4,4′-Diaminodiphenyl ether 1.20 g (6 mmol) was put into a 50 ml three-necked flask, dissolved in 5 ml N-methyl-2-pyrrolidone (NMP), and stirred at room temperature under a nitrogen stream. Thereto was added 1.77 g (6 mmol) of 2,2 ′, 6,6′-BPDA all at once. A large exotherm was observed with the addition. After completion of the addition, the mixture was stirred for 5 hours to obtain a light brown liquid (precursor solution 2).
(2) Synthesis of Polyimide 5 In a 50 ml eggplant flask, 1 g of the above precursor solution 2 and 4 ml of NMP were placed and stirred. Thereto, 2 ml of acetic anhydride was added and stirred at 100 ° C. for 24 hours. The solution was reprecipitated with diethyl ether to obtain 350 mg of a light brown powder (polyimide 5). The weight average molecular weight in terms of polystyrene by GPC was 6,800.

[Transparency evaluation]
A coating film having a thickness of about 2 μm was formed on glass by spin coating using a 15 wt% DMF solution of the above polyimide. When the transmittance of the coating film at 400 to 800 nm was measured with a spectrophotometer (UV-2550 (PC) S GLP manufactured by SHIMADZU), the transmittance was 90% or more at all wavelengths.

[Transparency evaluation 2]
The polyimides 2, 4, 5 and the precursor solution 1 are formed on glass by a spin coating method, and the transmittance of the coating film at 400 to 800 nm is measured by a spectroscopic device (UV-2550 (PC) S manufactured by SHIMADZU). GLP). Polyimides 2 and 5 were prepared by dissolving polymer powder in NMP, spin-coating the precursor solution 1 as it was, and drying it on a hot plate at 140 ° C. for 30 minutes. The polyimide 4 used in Example 4 was used as it was.
The measurement results are shown in the graph of FIG. The polyimide 5 having a small molecular weight had a transmittance of 85% or less at a wavelength of about 470 nm or less at a film thickness of about 1 μm. On the other hand, the polyimides 2 and 4 derived from the precursor solution 1 with a large molecular weight show a transmittance of 85% or more in the range of 400 nm to 800 nm including those precursors even though the thickness is 1 μm or more. The transmittance was found to be good. If the molecular weight of the precursor is low, the number of polymer ends is large, and coloring derived from the polymer ends occurs, which is considered to cause a decrease in transmittance.
In addition, as in Example 1, a method in which a diimide compound is connected to form a polyimide is not used, but as in Examples 2 to 5, a polyimide is chemically or heat-induced by a catalytic reaction rather than a precursor polyamic acid. In the case of a chemical imidation represented by polyimide 2 (an imidation by a chemical dehydration ring closure reaction), the dehydration cyclization reaction within the molecule is likely to proceed, but it is represented by polyimide 4. The thermal imidized product (imidized product by heat dehydration cyclization reaction) undergoes a cross-linking reaction between some molecules in addition to the dehydration cyclization reaction. In the case of the polyimide of the present invention, since the polyimide has a seven-membered ring imide structure, the conjugation of π electrons is cut and transparency is exhibited, so intermolecular crosslinking is considered to cause coloring. Therefore, it is considered that the transmittance of polyimide 4 is slightly lower than that of polyimide 2.

[Thermal properties evaluation]
The NMP solution of polyimide 2 described above was applied to an Upilex S 50S (trade name: Ube Industries) film affixed on glass, dried on a hot plate at 140 ° C. for 30 minutes, then peeled off, and a film thickness of 5 μm. Film was obtained.
Similarly, the precursor solution 1 was applied to an Upilex S 50S (trade name: Ube Industries) film pasted on glass, dried on a hot plate at 140 ° C. for 30 minutes, and then peeled off to obtain a film obtained. In the air, heating was performed at 300 ° C. for 1 hour in an oven to obtain a polyimide film having a thickness of 45 μm. This polyimide film is substantially a film of the polyimide 4 described above.

[Dynamic viscoelasticity evaluation]
The dynamic viscoelasticity measurement of the film produced in the above thermophysical property evaluation was performed at a frequency of 3 Hz and a heating rate of 5 ° C./min using a viscoelasticity measuring apparatus Solid Analyzer RSA II (manufactured by Rheometric Scientific).
The measurement results of the polyimide 2 and polyimide 4 films are shown in the graph of FIG. Since both have a tan δ peak at around 350 ° C., it can be said that the Tg (glass transition temperature) of these polyimides is 350 ° C. Also, from the behavior of storage elastic modulus (E ′) and loss elastic modulus (E ″) above Tg, polyimide 4 is constant between two temperatures above Tg and rubbery regions (E ′ and E ″). It was suggested that it was a crosslinked product. On the other hand, since polyimide 2 has E ′ and E ″ lowered as they are at a temperature of Tg or higher, it is suggested that polyimide 2 is a non-crosslinked body.

[Evaluation of linear thermal expansion coefficient]
Using the thermomechanical analyzer Thermo Plus TMA8310 (manufactured by Rigaku Corporation), the linear thermal expansion coefficient of the film produced in the above-mentioned thermophysical property evaluation was 10 ° C./min. The polyimide 2 film had a tensile load of 1 g and polyimide 4 The film was measured with a tensile load of 5 g (about 1 g per 5 μm thickness).
As a result, the linear thermal expansion coefficients at 50 ° C. to 100 ° C. were 27 ppm for polyimide 2 and 25 ppm for polyimide 4. The inflection points of film expansion were both 315 ° C.
From these results, the polyimide having the 7-membered ring imide structure of the present invention has good heat resistance, high transparency, and can produce a film having a low expansion coefficient. Applicable fields / products such as paints, printing inks, color filters, flexible display films, electronic parts, interlayer insulation films, wiring coating films, optical circuits, optical circuit parts, antireflection films, holograms, other optics Suitable for forming parts or building materials.
Furthermore, it is suitable as a film or coating film for all known members requiring transparency, for example, a high heat-resistant film or structure for optical members such as antireflection films, optical circuit components, and holograms. The use as is expected.

It is a three-dimensional structure model of a compound having a skeleton of formula (1). It is a graph which shows the result of having measured the transmittance | permeability in 400-800 nm about each coating film of the polyimide 2, 4, 5 and the precursor solution 1 synthesize | combined in the Example. It is a graph which shows the result of having performed dynamic viscoelasticity measurement about each film of the polyimide 2 and the polyimide 4 synthesize | combined in the Example.

Claims (24)

A highly transparent polyimide having a repeating unit represented by the following formula (1) and having a light transmittance between 400 nm and 800 nm of 85% or more at each wavelength when formed on a film having a thickness of 1 μm.

(In the formula, R ^{1 to} R ⁶ are each independently a hydrogen atom or a monovalent organic group, which may be bonded to each other. R ⁷ is a divalent organic group. The groups represented by the same symbols between the repeating units present in may be different atoms or structures.) The highly transparent polyimide according to claim 1, further comprising a repeating unit represented by the following formula (2).

(In the formula, X is a tetravalent organic group, and Y is a divalent organic group. The groups represented by the same reference sign between different repeating units present in the same molecule are different atoms or structures. Is also good.) In the following formula (1), the divalent organic group represented by R ⁷ is p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4. '-Diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4′-diaminodiphenylsulfone, 3,3′-diaminobenzophenone, 4,4′-diaminobenzophenone, 3,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 3 , 4′-Diaminodiphenylmethane, 2,2-di (3 -Aminophenyl) propane, 2,2-di (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2,2-di (3-aminophenyl)- 1,1,1,3,3,3-hexafluoropropane, 2,2-di (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2- (3-amino Phenyl) -2- (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 1,1-di (3-aminophenyl) -1-phenylethane, 1,1-di (4-aminophenyl) -1-phenylethane, 1- (3-aminophenyl) -1- (4-aminophenyl) -1-phenylethane, 1,3-bis (3-aminophenoxy) benzene, 1, 3-bis (3-aminobenzoyl Benzene, 1,3-bis (4-aminobenzoyl) benzene, 1,4-bis (3-aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 1,3-bis (3-amino) -Α, α-dimethylbenzyl) benzene, 1,3-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (3-amino-α, α-dimethylbenzyl) benzene, 1, 4-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,3-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (4-amino-α, α-ditrifluoromethylben) Di) benzene, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2- Bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1, 1,3,3,3-hexafluoropropane, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (4-aminophenoxy) ben Yl] benzene, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3 -Aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (3-amino Phenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 4,4′-bis [4- (4-aminophenoxy) ) Benzoyl] diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethyl) Benzyl) phenoxy] diphenylsulfone, 4,4′-bis [4- (4-aminophenoxy) phenoxy] diphenylsulfone, 3,3′-diamino-4,4′-diphenoxybenzophenone, 3,3′-diamino- 4,4′-dibiphenoxybenzophenone, 3,3′-diamino-4-phenoxybenzophenone, 3,3′-diamino-4-biphenoxybenzophenone, 6,6′-bis (3-aminophenoxy) -3,3 , 3 ′, 3′-tetramethyl-1,1′-spirobiindane, 6,6′-bis (4-aminophenoxy) -3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, 1,3-bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, α, ω-bis (3-aminopropyl) Pyr) polydimethylsiloxane, α, ω-bis (3-aminobutyl) polydimethylsiloxane, bis (aminomethyl) ether, bis (2-aminoethyl) ether, bis (3-aminopropyl) ether, bis (2- Aminomethoxy) ethyl] ether, bis [2- (2-aminoethoxy) ethyl] ether, bis [2- (3-aminoprotoxy) ethyl] ether, 1,2-bis (aminomethoxy) ethane, 1,2 -Bis (2-aminoethoxy) ethane, 1,2-bis [2- (aminomethoxy) ethoxy] ethane, 1,2-bis [2- (2-aminoethoxy) ethoxy] ethane, ethylene glycol bis (3- Aminopropyl) ether, diethylene glycol bis (3-aminopropyl) ether, triethylene glycol bis (3- Minopropyl) ether, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1, 9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,2- Di (2-aminoethyl) cyclohexane, 1,3-di (2-aminoethyl) cyclohexane, 1,4-di (2-aminoethyl) cyclohexane, bis (4-aminocyclohexyl) methane, 2,6- Bis (aminomethyl) bicyclo [2,2,1] heptane, 2,5-bis (aminomethyl) The structure according to claim 1 or 2, wherein the amino groups at both ends are removed from one or more diamines selected from the group consisting of bicyclo [2,2,1] heptane and a diamine represented by the following formula (4): The highly transparent polyimide described.

(A is a natural number of 1 or more, and the amino group is bonded to the meta position or para position with respect to the bond between benzene rings.)   The highly transparent polyimide according to any one of claims 1 to 3, wherein the linear thermal expansion coefficient is 60 ppm or less.   The highly transparent polyimide according to any one of claims 1 to 4, wherein the glass transition temperature is 120 ° C or higher.   The highly transparent polyimide according to any one of claims 1 to 5, wherein an intramolecular imide cyclization rate is 80% or more.   The highly transparent polyimide according to any one of claims 1 to 6, which does not show a rubber-like region in dynamic viscoelasticity measurement.   The highly transparent polyimide according to any one of claims 1 to 7, having a weight average molecular weight of 10,000 or more.   The highly transparent polyimide according to claim 1, wherein the formula (1) is a repeating unit of wholly aromatic polyimide.   A polyimide resin composition containing the polyimide according to any one of claims 1 to 9.   The polyimide resin composition according to claim 10, wherein the polyimide resin composition is used as a pattern forming material.   Used as paint or printing ink, or color filter, flexible display film, electronic component, interlayer insulation film, wiring coating film, optical circuit, optical circuit component, antireflection film, hologram, optical member or building material The polyimide resin composition according to claim 10. A printed matter, at least part of which is formed of a cured product of the polyimide resin composition according to any one of claims 10 to 12. The color filter in which at least one part is formed with the hardened | cured material of the polyimide resin composition as described in any one of the said Claims 10 thru | or 12. The film for flexible displays in which at least one part is formed with the hardened | cured material of the polyimide resin composition as described in any one of the said Claims 10 thru | or 12. The electronic component in which at least one part is formed with the hardened | cured material of the polyimide resin composition as described in any one of Claims 10 thru | or 12. An interlayer insulating film, at least part of which is formed of a cured product of the polyimide resin composition according to any one of claims 10 to 12. A wiring coating film, at least part of which is formed of a cured product of the polyimide resin composition according to any one of claims 10 to 12. An optical circuit, at least a part of which is formed of a cured product of the polyimide resin composition according to any one of claims 10 to 12. An optical circuit component, at least part of which is formed of a cured product of the polyimide resin composition according to any one of claims 10 to 12. An antireflection film, at least part of which is formed of a cured product of the polyimide resin composition according to any one of claims 10 to 12. The hologram in which at least one part is formed with the hardened | cured material of the polyimide resin composition as described in any one of the said Claims 10 thru | or 12. The optical member in which at least one part is formed with the hardened | cured material of the polyimide resin composition as described in any one of the said Claims 10 thru | or 12. The building material in which at least one part is formed with the hardened | cured material of the polyimide resin composition as described in any one of the said Claims 10 thru | or 12.

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