JP2006143943A - Polybenzoxazole and its production process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film with a high glass-transition temperature, high transparency, low birefringenece, a low water absorption coefficient and sufficient toughness, and polybenzoxazoles available to make the film, and others. <P>SOLUTION: The polybezoxazole has a repeated unit shown by formula (1) (wherein R represents a bivalent alicyclic ring group) with cutoff wavelengths of 300 nm or less in a film of 20 μm thickness and a transmittance of 70% or over at 400 nm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention has a high glass transition temperature, high transparency, low birefringence, low water absorption, sufficient toughness, etc., in various electronic devices (for example, electrical insulating films) and various substrates (for example, liquid crystal display substrates, The present invention relates to a substrate for organic EL display, a substrate for electronic paper, a substrate for solar cell, particularly a plastic substrate for flexible film liquid crystal display), polybenzoxazole useful as a protective film for polarizing film, a method for producing the same, and a polybenzoxazole film.

  Currently, a glass substrate is used as a liquid crystal display substrate. However, with the recent trend toward larger display screens, problems of weight reduction and productivity improvement have become apparent. Further, in mobile information / communication devices such as mobile phones, electronic notebooks, and portable personal computers, a problem has been pointed out that the glass substrate in the liquid crystal display is easily damaged even by a small impact. Therefore, recently, as a substitute material for a glass substrate that is heavy and easily broken, a plastic substrate that is lighter in weight, has high moldability, and is difficult to break is drawing attention. If a highly transparent and sufficiently tough plastic substrate such as glass is used, a flexible film liquid crystal panel that can be bent and rolled and stored can be realized.

  However, a plastic substrate has a disadvantage that it is inferior in heat resistance as compared with a glass substrate. In particular, since the TFT type liquid crystal panel is exposed to a high temperature of about 200 to 220 ° C. several times in the manufacturing process, the glass transition temperature of the plastic substrate is required to be higher than at least 220 ° C. However, existing typical transparent resins such as polymethyl methacrylate and polycarbonate have glass transition temperatures of 100 ° C. and 150 ° C., respectively, which are completely insufficient in terms of heat resistance. Furthermore, polyethersulfone is currently considered promising as a plastic substrate for flexible film liquid crystal displays that has both heat resistance and transparency, but its glass transition temperature is 220 ° C., which is sufficient in terms of heat resistance. The current situation is not to say.

  On the other hand, polyimide, polybenzoxazole, polybenzimidazole and the like are known as polymer materials having a high glass transition temperature. In Non-Patent Document 1, a polyimide having a high glass transition temperature, high transparency, and high toughness is studied (Non-Patent Document 1).

Polyimide film is generally obtained by casting and drying a polyimide precursor obtained by reacting tetracarboxylic dianhydride and diamine in equimolar polar solvent such as dimethylacetamide in an equimolar polar solvent. It is manufactured by a two-stage method in which it is heat-cured at a high temperature. This is because the polyimide itself is insoluble in a solvent and hardly has thermoplasticity, and it is difficult to mold the polyimide itself.
However, for example, a plastic substrate for a flexible film liquid crystal display usually requires a film thicker than 100 μm. However, it is difficult to produce such a thick polyimide film by a two-step method.

A more serious problem is that the polyimide film is colored. This is due to intramolecular conjugation through aromatic groups in the polyimide chain and intramolecular / intermolecular charge transfer interaction (Non-Patent Document 2). On the other hand, by using an aliphatic monomer for one or both of the tetracarboxylic dianhydride and the diamine used in the polymerization of the polyimide precursor, it is possible to prevent the charge transfer interaction.
However, when a polyimide precursor is polymerized from an aliphatic diamine and a tetracarboxylic dianhydride, salt formation occurs at the initial stage of the polymerization reaction, and it takes a long time to complete the polymerization or the polymerization reaction does not proceed at all. (Non-Patent Document 3).

Furthermore, since polyimide contains a highly polarizable imide group in the molecule at a high concentration, it has a high water absorption rate and may cause a malfunction of the liquid crystal display.
In addition, polybenzimidazole also has a highly polar secondary amine residue in the molecule, and therefore has a higher water absorption rate than polyimide.

On the other hand, polybenzoxazole does not contain a highly polarizable structural unit such as an imide group in the molecule, and low water absorption is expected. Furthermore, by introducing an alicyclic structure into the molecule of polybenzoxazole, it is expected that the transparency of the film is improved and at the same time the intermolecular interaction is lowered and the solubility in organic solvents is increased. . Here, for example, Patent Document 1 discloses polybenzoxazole having an alicyclic structure having both a low dielectric constant, a low linear thermal expansion coefficient, and a high glass transition temperature. Patent Document 2 discloses polybenzoxazole having an alicyclic structure in which a polybenzoxazole precursor has a high i-line transmittance. Furthermore, Patent Document 3 discloses polybenzoxazole having an alicyclic structure as an optical waveguide material at a wavelength of 1.3 μm or 1.55 μm. However, the polybenzoxazoles described in these are obtained by dehydration ring closure at high temperature after coating and drying the organic solvent solution of the precursor, and are colored in the high temperature cyclization process.
That is, at present, there is no disclosure of a technique for producing polybenzoxazole that satisfies all the properties and processability of the film suitable for a plastic substrate for flexible film liquid crystal displays.

  On the other hand, when polyimide or polybenzoxazole is insoluble in an organic solvent, usually after applying and drying an organic solvent solution of a polyimide or polybenzoxazole precursor, a dehydration cyclization reaction is performed at a high temperature of 300 ° C. or higher. A method of forming a heat-resistant insulating film is used. However, if the thermal expansion coefficient of the insulating film is not sufficiently low (not close to that of the metal substrate) at this time, a large thermal stress is generated in the cooling process to return to room temperature after the thermal cyclization reaction, and the insulating film is Peeling, cracking, warping of the laminate, etc. occur, leading to a decrease in device reliability.

“Proceedings of Polymer Discussion Group”, Volume 53, 2004, p. 3985-3986 “Progress in Polymer Science”, 26, 2001, p. 259-335 “High Performance Polymers”, Vol. 15, 2003, p. 47-64 JP 2002-327060 A JP 2004-18594 A JP 2004-118123 A

  An object of the present invention is to solve the above-mentioned problems, and has a high glass transition temperature, a high transparency, a low birefringence, a low water absorption rate, and a sufficient toughness. Display substrate, organic EL display substrate, electronic paper substrate, solar cell substrate, polarizing film protective film, especially polybenzoxazole which can be used for polybenzoxazole film useful as plastic substrate for flexible film liquid crystal display and The manufacturing method and the like are provided.

（一般式（１）中、Ｒは２価の脂環族基である）
（２）２，２−ビス（３−アミノ−４−ヒドロキシフェニル）−ヘキサフルオロプロパンまたはその誘導体と脂環式ジカルボン酸またはその誘導体を縮合剤の存在下で重縮合反応させる工程を含む、下記一般式（１）で表される反復単位を有するポリベンゾオキサゾールの製造方法。
一般式（１）

（一般式（１）中、Ｒは２価の脂環族基である）
（３）（２）に記載の製造方法により得られるポリベンゾオキサゾール。
（４）下記一般式（２）で表される反復単位を有するポリベンゾオキサゾール。
一般式（２）

（５）０．５質量％溶液としたときの、オストワルド粘度計を用いて３０℃で測定したときの固有粘度が０．４ｄＬ／ｇ以上である、（１）、（３）および（４）のいずれかに記載のポリベンゾオキサゾール。
（６）有機溶媒に可溶である（１）、（３）〜（５）のいずれかに記載のポリベンゾオキサゾール。
（７）（１）、（３）〜（６）のいずれかに記載のポリベンゾオキサゾールを含むポリベンゾオキサゾールフィルム。
（８）ガラス転移温度が２４０℃以上である、（７）に記載のポリベンゾオキサゾールフィルム。
（９）ポリベンゾオキサゾールフィルムに平行な方向（ｎ_in）と垂直な方向（ｎ_out）の屈折率の差が０．０１５以下である（７）または（８）に記載のポリベンゾオキサゾールフィルム。
（１０）膜厚２０μｍのポリベンゾオキサゾールフィルムを２５℃の水に２４時間浸漬した後の重量増加分から求められる吸水率が１％以下である（７）〜（９）のいずれかに記載のポリベンゾオキサゾールフィルム。
（１１）１ＭＨｚにおける誘電率ε（ε＝１．１×ｎ_av ²、ｎ_avは平均屈折率を示す）が２．８以下である、（７）〜（１０）のいずれかに記載のポリベンゾオキサゾールフィルム。 As a result of intensive studies by the inventors under the above problems, it has been found that the problem can be solved by the following means.
(1) A polybenzoxazole having a repeating unit represented by the following general formula (1), the cut-off wavelength when the polybenzoxazole is a 20 μm-thick film is 300 nm or less, and transmission at 400 nm Polybenzoxazole having a rate of 70% or more.
General formula (1)

(In general formula (1), R is a divalent alicyclic group)
(2) A step of polycondensation reaction of 2,2-bis (3-amino-4-hydroxyphenyl) -hexafluoropropane or a derivative thereof with an alicyclic dicarboxylic acid or a derivative thereof in the presence of a condensing agent, A method for producing polybenzoxazole having a repeating unit represented by the general formula (1).
General formula (1)

(In general formula (1), R is a divalent alicyclic group)
(3) Polybenzoxazole obtained by the production method according to (2).
(4) Polybenzoxazole having a repeating unit represented by the following general formula (2).
General formula (2)

(5) (1), (3) and (4) having an intrinsic viscosity of 0.4 dL / g or more when measured at 30 ° C. using an Ostwald viscometer when a 0.5 mass% solution is obtained. The polybenzoxazole according to any one of the above.
(6) The polybenzoxazole according to any one of (1) and (3) to (5), which is soluble in an organic solvent.
(7) A polybenzoxazole film containing the polybenzoxazole according to any one of (1) and (3) to (6).
(8) The polybenzoxazole film as described in (7) whose glass transition temperature is 240 degreeC or more.
(9) The polybenzoxazole film according to (7) or (8), wherein the difference in refractive index between the direction parallel to the polybenzoxazole film (n _in ) and the direction perpendicular to the direction (n _out ) is 0.015 or less.
(10) The polysorbent according to any one of (7) to (9), wherein the water absorption obtained from a weight increase after immersing a polybenzoxazole film having a thickness of 20 μm in water at 25 ° C. for 24 hours is 1% or less. Benzoxazole film.
(11) The poly according to any one of (7) to (10), wherein a dielectric constant ε (ε = 1.1 × n _av ² , n _av represents an average refractive index) at 1 MHz is 2.8 or less. Benzoxazole film.

The polybenzoxazole of the present invention has, for example, a high glass transition temperature, high transparency, low birefringence, low water absorption, sufficient toughness and the like when formed into a film. In particular, it can have all of these. The polybenzoxazole film of the present invention is an electrical insulating film in various electronic devices, a substrate for liquid crystal display, a substrate for organic EL display, a substrate for electronic paper, a substrate for solar cell, a protective film for polarizing film, a plastic for a flexible film liquid crystal display. It can be preferably used as a substrate or the like.
In addition, when a polybenzoxazole film is used as an electrical insulating film in a multilayer substrate or the like, the organic solvent solution of the polybenzoxazole is applied to form an insulating film on a metal substrate, and then the solvent is evaporated at a relatively low temperature. It only needs to be dried, which is advantageous for reducing thermal stress in the metal substrate / insulating film laminate.

  Hereinafter, the contents of the present invention will be described in detail. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

一般式（１）中、Ｒは２価の脂環族基であり、Ｒは、炭素数４〜２０であることが好ましい。さらに、環は６〜１２員環が好ましく、６員環がより好ましい。また、単環でも多環（縮合環を含む）でもよいが、好ましくは、単環である。具体的には、以下のものが挙げられるが、本発明はこれに限定されるものではない。 First, the compound represented by General formula (1) of this invention is demonstrated.
General formula (1)

In general formula (1), R is a divalent alicyclic group, and R preferably has 4 to 20 carbon atoms. Further, the ring is preferably a 6-12 membered ring, more preferably a 6 membered ring. Further, it may be monocyclic or polycyclic (including fused ring), but is preferably monocyclic. Specific examples include the following, but the present invention is not limited thereto.

一般式（１）で表される化合物のうち、より好ましくは、一般式（２）で表される化合物である。
一般式（２）

Of the compounds represented by the general formula (1), the compound represented by the general formula (2) is more preferable.
General formula (2)

The compound represented by the general formula (1) is obtained by, for example, polycondensation reaction of 2,2-bis (3-amino-4-hydroxyphenyl) -hexafluoropropane and its derivative with dicarboxylic acid or its derivative. sell. The polycondensation reaction is preferably carried out in the polymerization solvent and / or in the presence of a condensing agent, more preferably in the presence of a condensing agent.
2,2-bis (3-amino-4-hydroxyphenyl) -hexafluoropropane and derivatives thereof are preferably 2,2-bis (3-amino-4-hydroxyphenyl) represented by the following formula (2): ) -Hexafluoropropane. Such a 2,2-bis (3-amino-4-hydroxyphenyl) -hexafluoropropane and its derivative and a cycloaliphatic dicarboxylic acid are subjected to a polycondensation reaction, thereby satisfying the above-mentioned required characteristics. The polybenzoxazole represented by this is obtained.
Formula (2)

2,2-bis (3-amino-4-hydroxyphenyl) -hexafluoropropane and derivatives thereof used in the present invention are preferably 2,2-bis (3-amino-4-hydroxyphenyl) -hexafluoropropane. .
Furthermore, in the present invention, other bis (o-aminophenol) derivatives may be used in combination. Examples of such other bis (o-aminophenol) derivatives include 4,6-diaminoresorcinol, 2,5-diaminohydroquinone, 3,3′-dihydroxybenzidine, 3,3′-diamino-4,4′-. Dihydroxybiphenyl, 3,3′-diamino-4,4′-dihydroxybiphenyl ether, 4,4′-diamino-3,3′-dihydroxybiphenyl ether, 3,3′-diamino-4,4′-dihydroxybiphenyl sulfone 4,4′-diamino-3,3′-dihydroxybiphenylsulfone, 3,3′-diamino-4,4′-dihydroxybiphenylmethane, 4,4′-diamino-3,3′-dihydroxybiphenylmethane, 2, Preferred examples include 2-bis (3-amino-4-hydroxyphenyl) -propane and the like. Two or more of these may be used in combination.
The content of the other bis (o-aminophenol) derivative is 30 masses of the total amount of the other bis (o-aminophenol) derivative and 2,2-bis (3-amino-4-hydroxyphenyl) -hexafluoropropane. % Or less is preferable.
2,2-bis (3-amino-4-hydroxyphenyl) -hexafluoropropane and derivatives thereof, and other bis (o-aminophenol) derivatives may be used as salts such as hydrochloride.

式（４）

Although the alicyclic dicarboxylic acid used by this invention is not specifically limited unless it deviates from the meaning of this invention, Preferably, it is a C4-C20 thing. The cyclic portion is preferably a 6-12 membered ring, more preferably a 6 membered ring. Further, it may be a monocycle or a polycycle (including a condensed ring), but a monocycle is preferred.
Examples of the alicyclic dicarboxylic acid used in the present invention include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,1-cyclopropanedicarboxylic acid, and 1,1-cyclobutane. Preferred examples include dicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 2,5-norbonanedicarboxylic acid, 1,3-adamantanedicarboxylic acid, and the like. 1,3-cyclohexanedicarboxylic acid (formula (3)) and 1,4-cyclohexanedicarboxylic acid (formula (4)) is more preferred.
The alicyclic dicarboxylic acid used in the present invention can be used alone or in combination of two or more. Furthermore, the alicyclic dicarboxylic acid used in the present invention preferably contains at least 1,3-cyclohexanedicarboxylic acid from the viewpoint of polymerization reactivity of polybenzoxazole and solubility in an organic solvent. The content at this time is preferably 20% or more of the total alicyclic dicarboxylic acid amount.
Formula (3)

Formula (4)

式（４）の１，４−シクロヘキサンジカルボン酸には式（６）に示すようにトランス体とシス体が存在するが、本発明に係るポリベンゾオキサゾールを重合する場合、特に立体構造の制約はなく、トランス体、シス体どちらも使用可能であり、これらの混合物であってもなんら差し支えない。
式（６）

In 1,3-cyclohexanedicarboxylic acid, a trans isomer and a cis isomer exist as shown in Formula (5), but when the polybenzoxazole according to the present invention is polymerized, there is no particular restriction on the three-dimensional structure, Both cis isomers can be used, and a mixture of these can be used.
Formula (5)

The 1,4-cyclohexanedicarboxylic acid of the formula (4) has a trans isomer and a cis isomer as shown in the formula (6). However, when the polybenzoxazole according to the present invention is polymerized, the steric structure is particularly limited. In addition, both a trans isomer and a cis isomer can be used, and a mixture thereof may be used.
Formula (6)

  In addition to the alicyclic dicarboxylic acid, another dicarboxylic acid may be used in combination. Examples of dicarboxylic acids in this case include terephthalic acid, isophthalic acid, phthalic acid, 2,5-dimethylterephthalic acid, 2,3-pyridinedicarboxylic acid, 2,4-pyridinedicarboxylic acid, 2,6-pyridinedicarboxylic acid, 2 , 6-pyridinedicarboxylic acid, 3,4-pyridinedicarboxylic acid, 3,5-pyridinedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, 2,2′-biphenyldicarboxylic acid, 4,4′-diphenylether dicarboxylic acid, 4,4′-diphenylmethanedicarboxylic acid, 4,4′-diphenylsulfonedicarboxylic acid, 1,2-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1 3-adamantane dicarboxylic acid, 1,8-anthracene dicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, peric acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, 1,2 Examples include cyclohexanedicarboxylic acid. Two or more of these may be used in combination. These dicarboxylic acids are preferably 0 to 30% by mass based on the amount of the alicyclic dicarboxylic acid.

  More specifically, the polybenzoxazole represented by the general formula (1) is obtained by the following method. That is, 2,2-bis (3-amino-4-hydroxyphenyl) -hexafluoropropane in an equimolar amount with the total amount of the alicyclic dicarboxylic acid component is placed in a reaction vessel, and a polymerization solvent and / or a condensing agent is added. While stirring with a stirrer, in a nitrogen atmosphere, the temperature is raised stepwise from 100 ° C. to 10 ° C. to the final temperature (held at each temperature for 10 minutes), and finally held at 200 to 230 ° C. for 10 minutes to 4 hours. After cooling to room temperature, the mixture is precipitated in water, washed with a large amount of water until the washing water becomes neutral, further washed with methanol, and finally dried under vacuum at 100 ° C. to obtain a white precipitate of polybenzoxazole.

 The monomer concentration at the time of polymerization is 5 to 30% by mass, preferably 10 to 20% by mass. By setting the monomer concentration to 5% by mass or more, the degree of polymerization of polybenzoxazole can be maintained at a more preferable level. By setting the monomer concentration to 30% by mass or less, the monomer is more fully dissolved and a more uniform solution is obtained. can get.

  The polymerization solvent and the condensing agent employed in the present invention are not particularly limited. For example, as described in US Pat. No. 4,931,532, a chlorinated hydrocarbon solvent may contain niline pentoxide, phosphorus oxychloride, five Condensing agents such as phosphorus chloride, trifluoroacetic anhydride-pyridine, thionyl chloride and trimethylsilyl phosphate may be added. In addition, polymerization and polymerization with a condensing agent such as polyphosphoric acid or phosphorous pentoxide-methanesulfonic acid described in Polymer Science Society, New Polymer Experimental Studies, Vol. 3, Synthesis and Reaction of Polymers (2) p178-179 (1996) What used also as a solvent is more preferable.

The polymerization reaction using the alicyclic dicarboxylic acid is preferably carried out by gradually raising the temperature as described above without increasing the temperature rapidly (for example, by increasing the temperature stepwise by 5 to 10 ° C. at each temperature). Hold for 60 minutes). By gradually raising the temperature, it is possible to more effectively prevent the polybenzoxazole obtained by the partial decomposition of the alicyclic structure from being colored, and to further increase the degree of polymerization. can do.
The final polymerization temperature is preferably 180 to 240 ° C, more preferably 200 to 240 ° C. By carrying out the polymerization reaction while maintaining at the final polymerization temperature for 5 minutes to 5 hours, more preferably for 10 minutes to 4 hours, the degree of polymerization can be made more sufficient.

 Since the polybenzoxazole production method of the present invention using an alicyclic dicarboxylic acid does not require a high-temperature thermal cyclization step, there is no fear of coloring the resulting polybenzoxazole film, which is preferable. In addition, since it is synthesized without going through the precursor, for example, it does not include a complicated chlorination step of dicarboxylic acid, etc., and it is a compound that is not preferable for an electronic device if it remains even in a trace amount as a reagent used in precursor polymerization Has the advantage of not requiring any use. Furthermore, the polybenzoxazole production method of the present invention does not require the use of polymer dissolution accelerators (for example, metal salts such as lithium bromide and lithium chloride) that are often added during polymerization of the polybenzoxazole precursor. . When these metal salts remain in the polybenzoxazole film even if there are trace amounts of metal ions, the reliability as an electronic device is remarkably lowered. Therefore, the production method of the present invention is preferable from this viewpoint.

  The polybenzoxazole according to the present invention can be dissolved in an organic solvent to obtain a uniform, transparent and highly storage-stable solution. Furthermore, this solution is cast on a substrate of silicon, copper, glass or the like and dried in a hot air dryer, for example, in the range of 50 to 150 ° C. for 10 minutes to 10 hours. The dried one is preferably heat-treated at 150 to 300 ° C., more preferably 180 to 250 ° C., to obtain a transparent and tough polybenzoxazole film. By heat-processing at 300 degrees C or less, it can prevent more effectively that polybenzoxazole (polybenzoxazole film) will color. In order to suppress coloring, the heat treatment is desirably performed in a vacuum or in an inert gas atmosphere such as nitrogen, but may be performed in air unless the temperature is too high.

  Although it does not specifically limit as an organic solvent used when obtaining a polybenzoxazole solution, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, hexamethylphospho Luamide, dimethylsulfoxide, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, 1,2-dimethoxyethane-bis (2-methoxyethyl) ether, terahydrofuran, 1,4-dioxane, picoline , Pyridine, acetone, toluene, xylene, dichloromethane, chloroform, 1,2-dichloroethane and the like, and phenol, o-cresol, m-cresol, p-cresol, o-chlorophenol, m-chlorophenol, p-chlorophenol, Protic solvents such as ethanol, ethanol, 2-propanol can be used, and aprotic solvents are preferable, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, γ-butyrolactone 1,3-dimethyl-2-imidazolidinone, terahydrofuran and dichloromethane are more preferred. These solvents may be used alone or in combination of two or more.

The glass transition temperature (Tg) as used in the field of this invention means what was calculated | required from the loss peak in frequency 0.1Hz and the temperature increase rate of 5 degree-C / min by dynamic viscoelasticity measurement.
The glass transition temperature of the polybenzoxazole of the present invention is preferably 240 ° C. or higher, and more preferably 250 ° C. or higher.
Since the polybenzoxazole of the present invention has an alicyclic structure, its long-term thermal stability is inferior to that of a wholly aromatic polybenzoxazole that does not contain it, but is required for the production of flexible film liquid crystal displays, multilayer substrates, etc. Short-term heat resistance is sufficiently high, and there is no problem in application to the industrial field.

In the present invention, the intrinsic viscosity of polybenzoxazole refers to an intrinsic viscosity when a 0.5 mass% polybenzoxazole solution is measured at 30 ° C. using an Ostwald viscometer.
The intrinsic viscosity of the polybenzoxazole according to the present invention is preferably 0.4 dL / g or more, and more preferably 0.5 dL / g or more. By setting it as 0.4 dL / g or more, it can prevent more effectively that the toughness of a polybenzoxazole film falls rapidly and it becomes difficult to apply to a flexible film liquid crystal display.

The cut-off wavelength in the present invention means a wavelength at which the visible / ultraviolet transmittance from 200 nm to 900 nm is measured with a spectrophotometer and the transmittance is 0.5% or less.
The cut-off wavelength of the polybenzoxazole (polybenzoxazole film) of the present invention is preferably shorter than 320 nm, and more preferably shorter than 300 nm. Such polybenzoxazole (polybenzoxazole film) is particularly preferable when applied to a flexible film liquid crystal display substrate.
The polybenzoxazole (polybenzoxazole film) of the present invention preferably has a transmittance at 400 nm of 70% or more, more preferably 80% or more.

In the present invention, the birefringence of the polybenzoxazole film is measured by an Abbe refractometer (using a sodium lamp, wavelength 589 nm) in the direction parallel to the polybenzoxazole film (n _in ) and perpendicular to the direction (n _out ). And a value (Δn = n _in −n _out ) obtained from the difference between these refractive indexes.
The birefringence tends to be preferably as low as possible. For example, when it is 0.015 or less (more preferably 0.010 or less, more preferably 0.005 or less), it is suitably used for a liquid crystal display substrate or the like. It is done.

The water absorption rate of the polybenzoxazole film in the present invention means that after a polybenzoxazole film (film thickness: 20 μm) vacuum-dried at 50 ° C. for 24 hours is immersed in water at 25 ° C. for 24 hours, excess moisture is wiped off and weight The water absorption rate (%) calculated from the increase.
The water absorption rate of the polybenzoxazole film in the present invention tends to be low, but for example, when it is 1% or less (more preferably 0.5% or less), it is suitably used for a liquid crystal display substrate or the like. .

 The linear thermal expansion coefficient (CTE) of the polybenzoxazole film in the present invention is 100 to 200 ° C. from the elongation of the test piece at a load of 0.5 g / thickness of 1 μm and a heating rate of 5 ° C./min. The linear thermal expansion coefficient obtained as an average value in the range of. The linear thermal expansion coefficient of the polybenzoxazole film in the present invention is preferably 80 ppm / K or less, more preferably 70 ppm / K or less.

The dielectric constant of the polybenzoxazole film in the present invention is the following average refractive index n _av
n _av = (2n _in + n _out ) / 3
Is a dielectric constant (ε = 1.1 × n _av ² ) at 1 MHz calculated based on
The dielectric constant of the polybenzoxazole film in the present invention is preferably 3.0 or less, more preferably 2.7 or less.

Further, the elongation at break (%) of the polybenzoxazole film in the present invention is based on the elongation at the time when the test piece (3 mm × 30 mm) was subjected to a tensile test (stretching speed: 8 mm / min) and the test piece was broken. The required elongation (%). The breaking elongation (%) of the polybenzoxazole film in the present invention is preferably as high as possible, but is preferably 10% or more, more preferably 20% or more.
The 5% weight reduction temperature in the present invention refers to a temperature at which the weight is reduced by 5% in nitrogen (T _d5N2 ) or air (T _{d5 Air} ) at a heating rate of 10 ° C./min. In the present invention, T _{d5 N2} is preferably as high as possible, but is preferably 450 ° C. or higher, more preferably 470 ° C. or higher. In the present invention, T _{d5 Air} is preferably as high as possible, but is preferably 350 ° C. or higher, more preferably 380 ° C. or higher.

  The polybenzol of the present invention can be used in the form of a film. In the polybenzoxazole film of the present invention, additives such as an oxidation stabilizer, a terminal blocking agent, a filler, a silane coupling agent, a photosensitizer, a photopolymerization initiator, and a sensitizer are mixed as necessary. It can be done.

  The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

<Intrinsic viscosity>
About 0.5 mass% polybenzoxazole solution, the intrinsic viscosity in 30 degreeC temperature was measured using the Ostwald viscometer.
<Glass transition temperature>
The dynamic viscoelasticity was measured from the loss peak at a frequency of 0.1 Hz and a heating rate of 5 ° C./min.
<Linear thermal expansion coefficient>
By thermomechanical analysis, the linear thermal expansion coefficient (average value in the range of 100 to 200 ° C.) is obtained for the elongation of the test piece (5 mm × 20 mm) at a load of 0.5 g / thickness of 1 μm and a heating rate of 5 ° C./min. It was.
<Cutoff wavelength (transparency)>
Visible / ultraviolet transmittance from 200 nm to 900 nm was measured with a spectrophotometer. The wavelength (cutoff wavelength) at which the transmittance was 0.5% or less was used as an index of transparency. The shorter the cutoff wavelength, the better the transparency.
<Transmittance% at a wavelength of 400 nm (transparency)>
The transmittance at a wavelength of 400 nm was measured with a spectrophotometer, and the value of a film thickness of 20 μm was calculated.
<Birefringence>
The refractive index _{in the} direction parallel to the polybenzoxazole film (n _in ) and the direction perpendicular to the (n _out ) is measured with an Abbe refractometer (using a sodium lamp, wavelength 589 nm), and birefringence (Δn = N _in −n _out ).
<Dielectric constant>
Based on the average refractive index n _av = (2n _in + n _out ) / 3 of the polybenzoxazole film, the dielectric constant (ε) at 1 MHz was calculated by the following formula (ε = 1.1 × n _av ² ).
<Elastic modulus, elongation at break>
A tensile test (stretching speed: 8 mm / min) was performed on a polybenzoxazole film test piece (3 mm × 30 mm), and the elastic modulus was determined from the initial gradient of the stress-strain curve, and the elongation was determined from the elongation at the time the film was broken. Elongation (%) was determined.
<Water absorption rate>
A polybenzoxazole film (thickness: 20 to 30 μm) vacuum-dried at 50 ° C. for 24 hours was immersed in water at 25 ° C. for 24 hours, and then excess water was wiped off, and the water absorption (%) was determined from the weight increase.
<5% weight loss temperature>
The temperature at which the weight decreased by 5% in nitrogen (T _{d5 N2} ) or in air (T _{d5 Air} ) was measured at a heating rate of 10 ° C./min.

Example 1
In a closed reaction vessel equipped with a stirrer, 10 mmol of 1,3-cyclohexanedicarboxylic acid (cis, trans mixture) and 10 mmol of 2,2-bis (3-amino-4-hydroxyphenyl) -hexafluoropropane were added, and the monomer concentration was 10 mass. % Polyphosphoric acid was added. While stirring with a stirrer, the temperature was raised stepwise from 100 ° C. to 10 ° C. in an oil bath (held at each temperature for 10 minutes), and finally held at 200 ° C. for 1 hour. After completion of the reaction, the reaction mixture was cooled to room temperature, precipitated in water, and washed with a large amount of water until the washing water became neutral. Furthermore, it wash | cleaned with methanol and finally it vacuum-dried at 100 degreeC, and obtained the white precipitation of polybenzoxazole.
The intrinsic viscosity of polybenzoxazole measured in N-methyl-2-pyrrolidone at 30 ° C. was 0.501 dL / g, which was confirmed to be a high polymer. Moreover, it showed high solubility in various solvents (N-methyl-2-pyrrolidone, N, N-dimethylacetamide, tetrahydrofuran, m-cresol, hexamethylphosphoramide, etc.). Next, this polybenzoxazole was dissolved in N-methyl-2-pyrrolidone (10% by mass). This solution was uniform and transparent, and did not precipitate or gel at all even when allowed to stand at room temperature for one month, and showed extremely high solution storage stability. This solution was cast on a glass substrate, dried at 100 ° C. for 1 hour, and further heat-treated in vacuum at 230 ° C. for 1 hour to obtain a transparent and flexible polybenzoxazole film. According to the 180 ° bending test, the film showed toughness without breaking. Film properties are glass transition temperature 244 ° C., cut-off wavelength (Cut Off) 290 nm, elongation at break 10.0%, birefringence Δn = 0.007, coefficient of linear thermal expansion (CTE) 53.4 ppm / K, 5% weight reduction The temperature (temperature increase rate 10 ° C./min) is 482 ° C. in nitrogen (T _d5 N ₂ ), 404 ° C. in air (T _d5 Air), the dielectric constant is 2.61, and the water absorption rate is 0.14%. A polybenzoxazole satisfying all the required properties was obtained (Table 1). The infrared absorption spectrum of this polybenzoxazole film is shown in FIG.

(Example 2)
Except that 1,4-cyclohexanedicarboxylic acid (cis, trans mixture) was used as the alicyclic dicarboxylic acid, polybenzoxazole was polymerized in the same manner as described in Example 1, and a film was prepared to evaluate the physical properties. went. Table 1 shows physical property values. According to the 180 ° bending test, the film showed toughness without breaking. Since 1,3-cyclohexanedicarboxylic acid was not used, it exhibited solubility only in limited solvents (m-cresol, hexamethylphosphoramide, etc.), but almost satisfied the required characteristics as in Example 1. Polybenzoxazole (polybenzoxazole film) was obtained.

(Example 3)
Except that trans-1,4-cyclohexanedicarboxylic acid was used as the alicyclic dicarboxylic acid, polybenzoxazole was polymerized in the same manner as in the method described in Example 1 to produce a film, and physical properties were evaluated. Table 1 shows physical property values. According to the 180 ° bending test, the film showed toughness without breaking. Since 1,3-cyclohexanedicarboxylic acid was not used, it exhibited solubility only in limited solvents (m-cresol, hexamethylphosphoramide, etc.), but almost satisfied the required characteristics as in Example 1. Polybenzoxazole (polybenzoxazole film) was obtained.

Example 4
According to the method of Example 1, 7.5 mmol of 1,3-cyclohexanedicarboxylic acid (cis, trans mixture), 2.5 mmol of 1,4-cyclohexanedicarboxylic acid (cis, trans mixture) and 2,2-bis (3 A polybenzoxazole copolymer was synthesized from 10 mmol of -amino-4-hydroxyphenyl) -hexafluoropropane. Moreover, the polybenzoxazole film was produced similarly to Example 1, and physical property evaluation was performed. Table 1 shows physical property values. According to the 180 ° bending test, the film showed toughness without breaking. Since 1,3-cyclohexanedicarboxylic acid was used, it was soluble in the same organic solvent as the polybenzoxazole (polybenzoxazole film) described in Example 1. Further, as in Example 1, all required characteristics were satisfied.
(Example 5)
According to the method of Example 1, 5 mmol of 1,3-cyclohexanedicarboxylic acid (cis, trans mixture), 5 mmol of 1,4-cyclohexanedicarboxylic acid (cis, trans mixture) and 2,2-bis (3-amino-4) A polybenzoxazole copolymer was synthesized from 10 mmol of -hydroxyphenyl) -hexafluoropropane. Moreover, the polybenzoxazole film was produced similarly to Example 1, and physical property evaluation was performed. Table 1 shows physical property values. According to the 180 ° bending test, the film showed toughness without breaking. Since 1,3-cyclohexanedicarboxylic acid was used, it was soluble in the same organic solvent as the polybenzoxazole (polybenzoxazole film) described in Example 1. Further, as in Example 1, all required characteristics were satisfied.
(Example 6)
According to the method of Example 1, 2.5 mmol of 1,3-cyclohexanedicarboxylic acid (cis, trans mixture), 7.5 mmol of 1,4-cyclohexanedicarboxylic acid (cis, trans mixture) and 2,2-bis (3 A polybenzoxazole copolymer was synthesized from 10 mmol of -amino-4-hydroxyphenyl) -hexafluoropropane. Moreover, the polybenzoxazole film was produced similarly to Example 1, and physical property evaluation was performed. Table 1 shows physical property values. According to the 180 ° bending test, the film showed toughness without breaking. Since 1,3-cyclohexanedicarboxylic acid was used, it was soluble in the same organic solvent as the polybenzoxazole (polybenzoxazole film) described in Example 1. Further, as in Example 1, all required characteristics were satisfied.

(Comparative Example 1)
A polybenzoxazole was polymerized in the same manner as described in Example 1 except that terephthalic acid was used in place of the alicyclic dicarboxylic acid, and a film was prepared to evaluate the physical properties. Table 1 shows physical property values. Since 1,3-cyclohexanedicarboxylic acid was not used, it was hardly soluble in organic solvents other than protic m-cresol and hexamethylphosphoramide, and the transparency of the film was insufficient.
(Comparative Example 2)
Except that isophthalic acid was used in place of the alicyclic dicarboxylic acid, polybenzoxazole was polymerized in the same manner as described in Example 1, a film was prepared, and physical properties were evaluated. Table 1 shows physical property values. Since 1,3-cyclohexanedicarboxylic acid was not used, it was hardly soluble in organic solvents other than protic m-cresol and hexamethylphosphoramide, and the transparency of the film was insufficient.
(Comparative Example 3)
In a sealed reaction vessel equipped with a stirrer, 5 mmol of 2,2-bis (3-amino-4-hydroxyphenyl) -hexafluoropropane was placed and sealed with a septum cap. 22 mL of N-methyl-2-pyrrolidone was added by a syringe to dissolve the monomer, and 3 mL of pyridine was further added. To this solution, 3.2 ml (25 mmol) of trimethylsilyl chloride was slowly added dropwise with a syringe, and after completion of the addition, the mixture was stirred at room temperature for 1 hour to carry out a silylation reaction. To this solution, 5 mmol of trans-1,4-cyclohexanedicarboxylic acid was slowly added, and a polymerization reaction was performed at room temperature for 24 hours to obtain a transparent and viscous polybenzoxazole precursor solution. This is cast on a glass substrate, dried at 60 ° C. for 2 hours, and then subjected to heat treatment stepwise at 200 ° C. for 1 hour and 270 ° C. for 1 hour under reduced pressure to complete the thermal dehydration cyclization reaction. A tough polybenzoxazole film of 20 μm was obtained. Completion of the ring closure reaction was confirmed from the infrared absorption spectrum of the film. The physical property values are shown in Table 1. The obtained polybenzoxazole film exhibited the same physical properties as the polybenzoxazole film described in Example 3, but remarkable coloring was observed, and the transmittance at 400 nm was as low as 26.4%. This is because the alicyclic structural unit was slightly thermally decomposed during the thermal dehydration ring closure reaction at 270 ° C.

(Comparative Example 4)
A polybenzoxazole precursor was polymerized in the same manner as described in Comparative Example 3 except that 1,3-cyclohexanedicarboxylic acid was used as the alicyclic dicarboxylic acid. When this polybenzoxazole precursor solution was cast on a glass substrate and dried at 60 to 100 ° C. for 2 hours, no film-forming property was shown. This is because the polybenzoxazole precursor has an intrinsic viscosity as low as 0.139 dL / g and a molecular weight that is too low. Since a polybenzoxazole film could not be produced, physical properties were not evaluated.
(Comparative Example 5)
A polybenzoxazole precursor was polymerized in the same manner as described in Comparative Example 3 except that terephthalic acid was used in place of the alicyclic dicarboxylic acid. This was cast on a glass substrate, dried at 80 ° C. for 1 hour, and then heat-treated at 360 ° C. for 30 minutes under reduced pressure to complete the thermal dehydration ring-closing reaction, thereby obtaining a tough polybenzoxazole film having a thickness of 15 μm. . Completion of the ring closure reaction was confirmed from the infrared absorption spectrum of the film. However, the polybenzoxazole film showed almost no solubility in organic solvents, and the film was colored.
(Comparative Example 6)
A polybenzoxazole precursor was polymerized in the same manner as described in Comparative Example 3 except that isophthalic acid was used in place of the alicyclic dicarboxylic acid. This was cast on a glass substrate, dried at 60 ° C. for 2 hours, and then heat-treated at 300 ° C. for 1 hour under reduced pressure to complete the thermal dehydration cyclization reaction to obtain a tough polybenzoxazole film having a thickness of 15 μm. . Completion of the ring closure reaction was confirmed from the infrared absorption spectrum of the film. A relatively transparent film was obtained, but showed almost no solubility in organic solvents.

(Comparative Example 7)
Polyimides corresponding to the polybenzoxazole described in Example 1 were synthesized, and the physical properties of the films were compared. That is, 5 mmol of trans-1,4-cyclohexanediamine was put in a reaction vessel and dissolved in N, N-dimethylacetamide. To this solution, 5 mmol of 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride powder was gradually added and stirred for 48 hours to obtain a transparent and viscous polyimide precursor solution. This was cast on a glass substrate, dried at 60 ° C. for 2 hours, and then subjected to a thermal imidization reaction at 300 ° C. for 1 hour to obtain a flexible polyimide film. However, despite having substantially the same intrinsic viscosity (molecular weight) as that of the polybenzoxazole of Example 5, the elongation at break was much lower. The transparency of the film was very high, but it showed little solubility in organic solvents. Moreover, compared with the polybenzoxazole film as described in Examples 1-6, the slightly high water absorption was shown. This is because the molecule contains a highly polarizable imide group.

FIG. 1 shows an infrared absorption spectrum of the polybenzoxazole film described in Example 1.

Claims (11)

A polybenzoxazole having a repeating unit represented by the following general formula (1), the cut-off wavelength when the polybenzoxazole is a 20 μm-thick film is 300 nm or less, and the transmittance at 400 nm is 70 % Polybenzoxazole.
General formula (1)

(In general formula (1), R is a divalent alicyclic group) 2,2-bis (3-amino-4-hydroxyphenyl) -hexafluoropropane or a derivative thereof and an alicyclic dicarboxylic acid or a derivative thereof are subjected to a polycondensation reaction in the presence of a condensing agent. A method for producing a polybenzoxazole having a repeating unit represented by 1).
General formula (1)

(In general formula (1), R is a divalent alicyclic group) Polybenzoxazole obtained by the production method according to claim 2. The polybenzoxazole which has a repeating unit represented by following General formula (2).
General formula (2)

5. The polycrystal according to claim 1, which has an intrinsic viscosity of 0.4 dL / g or more when measured at 30 ° C. using an Ostwald viscometer when a 0.5 mass% solution is obtained. Benzoxazole. 6. The polybenzoxazole according to claim 1, which is soluble in an organic solvent. The polybenzoxazole film containing the polybenzoxazole in any one of Claim 1, 3-6. The polybenzoxazole film of Claim 7 whose glass transition temperature is 240 degreeC or more. The polybenzoxazole film according to claim 7 or 8, wherein a difference in refractive index between a direction parallel to the polybenzoxazole film (n _in ) and a direction perpendicular to the direction (n _out ) is 0.015 or less. The polybenzoxazole film according to any one of claims 7 to 9, wherein a water absorption obtained from a weight increase after a polybenzoxazole film having a thickness of 20 µm is immersed in water at 25 ° C for 24 hours is 1% or less. The polybenzoxazole film according to claim 7, wherein a dielectric constant ε (ε = 1.1 × n _av ² , n _av represents an average refractive index) at 1 MHz is 2.8 or less.

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