阅读说明：本技术 碳酸锶颗粒、光学膜和图像显示装置 (Strontium carbonate particles, optical film, and image display device ) 是由 日元武史 河野孝史 井东优忠 长井淳 于 2019-04-26 设计创作，主要内容包括：[课题]提供一种相位差表现性高的碳酸锶。[解决手段]碳酸锶颗粒具有10～100nm的范围内的平均长径和在c轴方向上为15nm以上的微晶粒径。([ problem ] to provide strontium carbonate having high phase difference expression. The strontium carbonate particles have an average long diameter in the range of 10 to 100nm and a crystallite diameter of 15nm or more in the c-axis direction.)

1. Strontium carbonate particles having an average major axis in the range of 10 to 100nm and a crystallite diameter of 15nm or more in the c-axis direction.

2. The strontium carbonate particles according to claim 1, wherein the average major axis is in the range of 20 to 70nm, and the crystallite diameter in the c-axis direction is 20nm or more.

3. The strontium carbonate particles according to claim 1 or 2, wherein the ratio of the average major axis to the crystallite diameter is 2.5 or less.

4. Strontium carbonate particles according to any of claims 1 to 3, having a surfactant attached to the surface.

5. The strontium carbonate particles according to any one of claims 1 to 4, wherein the surfactant has a phenyl group.

6. The strontium carbonate particles of claim 5, wherein the surfactant is a polyoxyethylene styrenated phenyl ether phosphate.

7. A resin composition comprising:

strontium carbonate particles according to any one of claims 1 to 6; and

a resin comprising the strontium carbonate particles.

8. The resin composition according to claim 7, wherein a content of the strontium carbonate particles relative to the entire resin composition is in a range of 0.1 to 50 mass%.

9. The resin composition according to claim 8, wherein the content is in the range of 1 to 35% by mass.

10. The resin composition according to any one of claims 7 to 9, wherein the resin is at least one selected from the group consisting of polycarbonate, polymethyl methacrylate, cellulose ester, polystyrene, styrene acrylonitrile copolymer, polyfumarate diester, polyarylate, polyethersulfone, polyolefin, maleimide copolymer, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, and polyurethane.

11. The resin composition according to any one of claims 7 to 10, wherein the resin is polyimide.

12. A resin composition comprising the strontium carbonate particles according to any one of claims 1 to 6 and a polyimide precursor.

13. A strontium carbonate-containing polyimide film obtained from the resin composition according to claim 11 or 12.

14. An optical film comprising the resin composition according to any one of claims 7 to 12 or the strontium carbonate-containing polyimide film according to claim 13.

15. An image display device comprising the optical film according to claim 14.

Technical Field

The present invention relates to strontium carbonate particles, an optical film including the strontium carbonate particles, and an image display device including the optical film.

Background

For example, optical films for controlling a phase difference of light are used in various devices such as liquid crystal display devices. In order to adjust the properties of the optical film, it has been attempted to control the retardation (in-plane retardation) and birefringence (in-plane birefringence) of the optical film. Patent documents 1 to 5 disclose the following: the birefringence is adjusted by incorporating fine particles of strontium carbonate into an optical material made of a polymer resin.

Disclosure of Invention

Problems to be solved by the invention

Patent documents 1 to 5 describe: although birefringence is adjusted by incorporating fine particles of strontium carbonate into an optical material made of a polymer resin, there is room for improvement in improving the expression of retardation inherent to strontium carbonate.

Means for solving the problems

One embodiment of the strontium carbonate particles has an average long diameter in the range of 10 to 100nm and a crystallite diameter of 15nm or more in the c-axis direction.

According to a preferable mode, the average length is in the range of 20 to 70nm, and the crystallite diameter in the c-axis direction is 20nm or more.

According to a preferred embodiment, the ratio of the average major axis to the crystallite diameter is 2.5 or less.

According to a preferred mode, the strontium carbonate particles have a surfactant attached to the surface.

According to a preferred embodiment, the surfactant has a phenyl group.

According to a preferred embodiment, the surfactant is polyoxyethylene styrenated phenyl ether phosphate.

One embodiment of the resin composition includes the strontium carbonate particles and a resin including the strontium carbonate particles.

According to a preferred embodiment, the content of the strontium carbonate particles is in the range of 0.1 to 50 mass% with respect to the entire resin composition.

According to a preferred embodiment, the content of the strontium carbonate particles is in the range of 1 to 35 mass% with respect to the entire resin composition.

According to a preferred embodiment, the resin is at least one selected from the group consisting of polycarbonate, polymethyl methacrylate, cellulose ester, polystyrene, styrene acrylonitrile copolymer, polyfumarate diester, polyarylate, polyethersulfone, polyolefin, maleimide copolymer, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, and polyurethane.

According to a preferred embodiment, the resin is polyimide.

One embodiment of the resin composition includes the above-described strontium carbonate particles and a polyimide precursor.

One embodiment of the strontium carbonate-containing polyimide film is obtained from the resin composition.

An optical film of one embodiment includes the resin composition or the polyimide film containing strontium carbonate.

An image display device according to one embodiment includes the above optical film.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the above aspect, strontium carbonate having high phase difference expression performance, an optical film including the strontium carbonate, and an image display device can be provided.

Detailed Description

The inventors of the present application paid attention to the crystallite size of the strontium carbonate particles and found that the expressivity of the phase difference inherent to the strontium carbonate particles can be improved. Specifically, the inventors found that: by increasing the crystallite diameter in the c-axis direction of the strontium carbonate particles, the phase difference of the transmitted light can be further expressed.

More specifically, the strontium carbonate particles of the present embodiment have an average long diameter in the range of 10 to 100nm and a crystallite diameter of 15nm or more in the c-axis direction. Preferably, the strontium carbonate particles have an average length of 20 to 70nm and a crystallite diameter of 20nm or more in the c-axis direction. The ratio of the average major axis to the crystallite diameter in the c-axis direction (average major axis/crystallite diameter) is 2.5 or less, preferably 2.0 or less, and more preferably 1.5 or less. Here, if the crystallite diameter in the c-axis direction is less than 15nm, the phase difference expressiveness inherent to strontium carbonate is reduced. Further, when the crystallite diameter in the c-axis direction is 15nm or more and the ratio of the average major axis to the crystallite diameter in the c-axis direction exceeds 2.5, the haze is deteriorated.

Here, the average major axis can be measured by a method of visually observing or image-processing a Scanning Electron Microscope (SEM) photograph of the strontium carbonate particles. The long diameter of the strontium carbonate particles can be measured as the length in the longitudinal direction (length of the long side) when the strontium carbonate particles are regarded as rectangles, for example. The short diameter of the strontium carbonate particles can be measured as the length in the width direction (length of the short side) when the strontium carbonate particles are regarded as a rectangle.

Specifically, a rectangle having a minimum area circumscribing the strontium carbonate particles in the image is calculated, and the major axis and the minor axis are determined from the lengths of the long side and the short side of the rectangle. The term "average" means an average value obtained by measuring a certain number (N number) of statistically reliable strontium carbonate particles. The number (N number) is usually 300 or more, preferably 500 or more, and more preferably 1000 or more.

The average aspect ratio of the strontium carbonate particles is not particularly limited, and may be, for example, in the range of 1.0 to 10.0. The average aspect ratio of the strontium carbonate particles is more preferably in the range of 2.0 to 5.0.

The aspect ratio referred to herein means "major axis/minor axis" of the particles. The average aspect ratio is an average value of aspect ratios. That is, the average aspect ratio is calculated as follows: the aspect ratios of the plurality of particles were measured and calculated from the average of the aspect ratios obtained from the plurality of particles. The number of particles (N number) used for calculating the average value is as described above. The content of the strontium carbonate particles in the entire resin composition may be in the range of 0.1 to 50 mass%. The content of the strontium carbonate particles is more preferably in the range of 1 to 35 mass% with respect to the entire resin composition. Here, when the content of the strontium carbonate particles is 35 mass% or less with respect to the entire resin composition, the haze can be 2% or less; when the content of the strontium carbonate particles is 50 mass% or less with respect to the entire resin composition, the haze can be 5% or less.

Preferably, a surfactant is attached to the strontium carbonate particles. This can improve the dispersibility of the strontium carbonate particles in the resin composition or in the solvent before mixing into the resin composition.

Although not particularly limited, a surfactant in which a hydrophilic group is bonded to a hydrophobic group and a hydrophilic group is bonded to a group that forms an anion in water is preferable. The anion-forming group is preferably a carboxylic acid group (-CO)₂H) Sulfuric acid radical (-OSO)₃H) Or a phosphate group (-OPO)₃H₂). The hydrogen atoms of these acid groups may be replaced by an alkali metal such as sodium or potassium or ammonium. The hydrophilic group is preferably an oxyalkylene group having 1 to 4 carbon atoms. The hydrophobic group is preferably an alkyl group having 3 to 30 carbon atoms, a phenyl group, or an alkylphenyl group having 7 to 30 carbon atoms. The surfactant in which the anion-forming group is a carboxylic acid group is preferably a compound represented by the following formula (I).

[ solution 1]

In the formula (I), R1 represents an alkyl group having 3 to 30 carbon atoms, a phenyl group or an alkylphenyl group having 7 to 30 carbon atoms, L1 represents an alkylene group having 1 to 4 carbon atoms, M1 represents hydrogen, an alkali metal or ammonium, and k represents a number in the range of 2 to 10. R1 is preferably an alkyl group or an alkylphenyl group having 10 to 18 carbon atoms. L1 is preferably ethylene. The surfactant in which the anion-forming group is a sulfate group is preferably a compound represented by the following formula (II).

[ solution 2]

In the formula (II), R2 represents an alkyl group having 3 to 30 carbon atoms, a phenyl group or an alkylphenyl group having 7 to 30 carbon atoms, L2 represents an alkylene group having 1 to 4 carbon atoms, M2 represents hydrogen, an alkali metal or ammonium, and M represents a number in the range of 2 to 10. R2 is preferably an alkyl group or an alkylphenyl group having 12 to 18 carbon atoms.

The surfactant in which the anion-forming group is a phosphoric acid group is preferably a compound represented by the following formula (III).

[ solution 3]

In the formula (III), R3 represents an alkyl group having 3 to 30 carbon atoms, a phenyl group or an alkylphenyl group having 7 to 30 carbon atoms, L3 represents an alkylene group having 1 to 4 carbon atoms, M3 and M4 each independently represent hydrogen, an alkali metal or ammonium, and n represents a number in the range of 2 to 10. R3 is preferably an alkyl group or an alkylphenyl group having 12 to 18 carbon atoms.

Among the above surfactants, the surfactant preferably has a phenyl group. More preferably, the surfactant is a polyoxyethylene styrenated phenyl ether phosphate represented by the following chemical formula.

[ solution 4]

[ solution 5]

The surfactant having a phenyl group has high heat resistance. Therefore, the strontium carbonate particles coated with the surfactant having a phenyl group can maintain high dispersibility when the optical film (resin composition) is formed at a high temperature. Further, since the strontium carbonate particles reduce the shielding or scattering of transmitted light, the transparency of the optical film (resin composition) can be ensured. The optical film has a haze of 3% or less, preferably 2% or less, and more preferably 1% or less.

The method for producing the strontium carbonate granular particles includes, for example, a reaction step: while stirring an aqueous solution or an aqueous suspension of strontium hydroxide, carbon dioxide gas is introduced into the aqueous solution or the aqueous suspension to carbonate strontium hydroxide, thereby producing strontium carbonate. The concentration of the aqueous solution or aqueous suspension of strontium hydroxide is usually in the range of 1 to 20 mass%, preferably in the range of 2 to 15 mass%, and more preferably in the range of 3 to 8 mass%. The amount of carbon dioxide gas introduced is usually in the range of 0.5 to 200 mL/min, preferably 0.5 to 100 mL/min, and more preferably 1 to 50 mL/min, relative to 1g of strontium hydroxide in the aqueous solution or aqueous suspension of strontium hydroxide. When the strontium hydroxide is carbonated, it is preferable that a carboxylic acid having a hydroxyl group be dissolved in an aqueous solution or an aqueous suspension of the strontium hydroxide as a grain growth inhibitor for the strontium carbonate grains to be produced. The crystal growth inhibitor is preferably an organic acid having 2 carboxyl groups and 3 to 6 hydroxyl groups and carboxyl groups in total. Preferred examples of the crystal growth inhibitor include tartaric acid, malic acid, and tartronic acid. As the crystal growth inhibitor, an organic acid having 2 carboxyl groups and hydroxyl groups and at least 3 carboxyl groups and hydroxyl groups in total can be used, and from the viewpoint of controlling particle growth by adhering to the surface of the produced particles and improving dispersibility in a fine state, a dicarboxylic acid or an anhydride thereof containing 1 or more hydroxyl groups in the molecule is more preferable, and DL-tartaric acid is particularly preferable. The amount of the crystal growth inhibitor to be used is usually in the range of 0.1 to 20 parts by mass, preferably 1 to 10 parts by mass, based on 100 parts by mass of strontium hydroxide. As another example of the crystal growth inhibitor, citric acid and gluconic acid may be cited.

The curing process comprises the following steps: the aqueous slurry containing spherical strontium carbonate microparticles obtained in the reaction step is aged at a predetermined temperature and for a predetermined time while being stirred, and the particles grow into acicular strontium carbonate microparticles. The aging step may be carried out in warm water. The curing temperature is in the range of 75 to 115 ℃, preferably 80 to 110 ℃, and particularly preferably 85 to 105 ℃. When the aging temperature is less than 75 ℃, the crystal growth of the spherical strontium carbonate fine particles tends to be insufficient and the average aspect ratio tends to be too low; when the aging temperature is higher than 115 ℃, crystal growth of the short diameter of the spherical strontium carbonate fine particles tends to be promoted, and the aspect ratio tends to be low. The aging time is not particularly limited, but is usually in the range of 1 to 100 hours, preferably 5 to 50 hours, and particularly preferably 10 to 30 hours. This enables the crystallite size of the generated strontium carbonate particles to grow and also enables variation to be reduced. In general, the reynolds number obtained by the following equation is 10000 or more, preferably 50000 or more, and more preferably 100000 or more with respect to stirring. Thereafter, the slurry was naturally cooled to room temperature to prepare an aqueous slurry of strontium carbonate fine particles.

R (Reynolds number) ═ d²×n×ρ/μ

d: blade diameter [ m ]]N: rotational speed [ 1/s]ρ: liquid density [ kg/m ]³]μ: viscosity coefficient [ kg/(m sec)]

The solvent used in the surface treatment is not particularly limited, and as a method for treating the surface of the strontium carbonate particles with the surfactant, a method in which the strontium carbonate particles are dried after the surfactant and the strontium carbonate particles are brought into contact with each other in the aqueous suspension can be used.

When the aging step is performed on the dispersion used in the surface treatment step, an aqueous slurry after the aging step may be used. The surface treatment step can be performed by adding a surfactant to the dispersion while applying a shearing force. The content of the strontium carbonate particles in the aqueous slurry is preferably in the range of 1 to 30 mass%. The total amount of the surfactant added to the aqueous slurry is usually in the range of 1 to 60% by mass, preferably in the range of 10 to 50% by mass, and more preferably in the range of 20 to 40% by mass. The shear force can be applied by using a known stirring apparatus such as a stirring blade mixer, a homomixer, a magnetic stirrer, an air stirrer, an ultrasonic homogenizer, CLEARMIX, FilMix, or a wet jet mill.

The drying step can be performed by a known drying method using a thermal dryer such as a spray dryer, a drum dryer, or a tray dryer.

The strontium carbonate particles have high dispersibility in a resin such as an organic solvent. The strontium carbonate particles can be dispersed in the resin (organic solvent) as primary particles or fine particles close to the primary particles by being put into the resin and subjected to a usual dispersion treatment such as a stirring treatment or an ultrasonic treatment. The type of the organic solvent is not particularly limited, and may be appropriately selected and used in accordance with the properties of the resin and the like. Examples of the organic solvent capable of appropriately dispersing the strontium carbonate particles include alcohols (e.g., ethanol, 1-propanol, 2-propanol, 1-butanol, and ethylene glycol), methylene chloride, N-methyl-2-pyrrolidone, γ -butyl lactone, dimethylacetamide, and tetrahydrofuran. These organic solvents may be used alone (1 type), or two or more types may be used in combination.

In addition, an optical film of one embodiment includes a resin and strontium carbonate particles dispersed in the resin. As the strontium carbonate particles dispersed in the resin, the above-described strontium carbonate particles are used.

The resin constituting the optical film is at least one selected from the group consisting of polycarbonate, polymethyl methacrylate, cellulose ester, polystyrene, styrene acrylonitrile copolymer, polyfumarate diester, polyarylate, polyethersulfone, polyolefin, maleimide copolymer, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, and polyurethane.

Preferably, the resin constituting the optical film is polyimide. Polyimide is known to have excellent heat resistance due to its chemical structure. In addition, it is known that polyimide has excellent bending resistance due to the ordered structure of the molecular chain of polyimide. However, polyimides that are also excellent in bending resistance cause optical birefringence. Here, by dispersing the strontium carbonate particles in polyimide, birefringence of the entire optical film can be controlled by utilizing a retardation inherent to strontium carbonate. Thus, an optical film having excellent heat resistance and bending resistance and in which birefringence is appropriately controlled can be provided. The dimensional shrinkage of the polyimide film is 0.05% or more, preferably 0.08% or more, in at least one direction, at any temperature of 250 ℃ to 400 ℃ when the temperature is raised monotonously from 25 ℃/min to 10 ℃/min.

Dimensional shrinkage (%) of [ { (dimension at 25 ℃ -dimension after temperature rise) }/(dimension at 25 ℃) × 100

The polyimide composition of the above embodiment includes a polyimide precursor (a1) and fine particles (B) having optical anisotropy. The polyimide precursor (a1) contains at least one of the repeating units represented by the following chemical formulae, for example.

[ solution 6]

(in the formula, X₁Is a 4-valent group having an aromatic ring or alicyclic structure, Y1 is a 2-valent group having an aromatic ring or alicyclic structure, and R1 and R2 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms. )

The polyimide precursor (a1) may be, for example, a partially imidized polyamic acid including a repeating unit of an imide structure, which is partially imidized.

The polyimide composition comprises a polyimide (a2) and strontium carbonate particles (B) having optical anisotropy. The polyimide (a2) contains at least one of the repeating units represented by the following chemical formulae, for example.

[ solution 7]

(in the formula, X₂Is a 4-valent group having an aromatic ring or alicyclic structure, and Y2 is a 2-valent group having an aromatic ring or alicyclic structure. )

The polyimide precursor (a1) used in the polyimide precursor composition and the polyimide (a2) used in the polyimide composition will be described in detail below.

< polyimide precursor (A1) >

The polyimide precursor (a1) contains at least one of the repeating units represented by formula 6.

Although not particularly limited, the polyimide composition obtained is excellent in heat resistance, and therefore the above [ chemical formula 6] is preferable]X in (1)₁Is a 4-valent group having an aromatic ring, and Y is a 2-valent group having an aromatic ring. Further, since the polyimide composition obtained is excellent in heat resistance and also excellent in transparency, X is preferable₁Is a 4-valent group having an alicyclic structure, and Y is a 2-valent group having an aromatic ring. Further, since the polyimide composition obtained is excellent in heat resistance and also excellent in dimensional stability, X is preferably a 4-valent group having an aromatic ring and Y is preferably a 2-valent group having an alicyclic structure.

X is X in view of the properties of the polyimide composition obtained, for example, transparency, mechanical properties, heat resistance and the like₁(iii) the above-mentioned formula 6 is a group having a valence of 4 having an alicyclic structure and Y is a group having a valence of 2 having an alicyclic structure]The content of the repeating unit is preferably 50 mol% or less, more preferably 30 mol% or less, or less than 30 mol%, and still more preferably 10 mol% or less, based on the total repeating units.

In one embodiment, a polyimide precursor (A1)In, X₁(formula 6) above wherein Y is a group having a valence of 2 and an aromatic ring]The total content of 1 or more kinds of the repeating units in (b) is preferably 50 mol% or more, more preferably 70 mol% or more, more preferably 80 mol% or more, further preferably 90 mol% or more, and particularly preferably 100 mol% based on the total repeating units. In this embodiment, particularly in the case of a polyimide composition which is required to have high transparency, the polyimide precursor (a1) preferably contains a fluorine atom. That is, the polyimide precursor (A1) preferably contains X₁The above formula 6 of the 4-valent group having an aromatic ring containing a fluorine atom]And/or Y is a 2-valent group having an aromatic ring containing a fluorine atom]1 or more of the repeating units (c).

In one embodiment, in the polyimide precursor (A1), X₁(iii) the above-mentioned 6-valent group being a 4-valent group having an alicyclic structure and Y being a 2-valent group having an aromatic ring]The total content of 1 or more kinds of the repeating units in (b) is preferably 50% or more, more preferably 70% or more by mole, more preferably 80% or more by mole, further preferably 90% or more by mole, and particularly preferably 100% by mole based on the total repeating units.

In one embodiment, in the polyimide precursor (A1), X₁(iii) the above formula 6 is a group having a valence of 4 in an aromatic ring and Y is a group having a valence of 2 in an alicyclic structure]The total content of 1 or more kinds of the repeating units in (b) is preferably 50 mol% or more, more preferably 70 mol% or more, more preferably 80 mol% or more, further preferably 90 mol% or more, and particularly preferably 100 mol% based on the total repeating units.

As X₁The 4-valent group having an aromatic ring of (4) is preferably a 4-valent group having an aromatic ring having 6 to 40 carbon atoms.

Examples of the 4-valent group having an aromatic ring include the following groups.

[ solution 8]

(in the formula, Z₁Is a direct bond, or the following 2-valent group:

[ solution 9]

Any one of the above. Wherein, Z in the formula₂Is a 2-valent organic group. )

As Z₂Specific examples thereof include aliphatic hydrocarbon groups having 2 to 24 carbon atoms and aromatic hydrocarbon groups having 6 to 24 carbon atoms.

The following group is particularly preferable as the 4-valent group having an aromatic ring because the polyimide composition obtained can achieve both high heat resistance and high transparency.

[ solution 10]

(in the formula, Z₁Is a direct bond or a hexafluoroisopropylidene bond. )

Here, since the polyimide composition obtained can satisfy all of high heat resistance, high transparency and low linear thermal expansion coefficient, Z is₁More preferably a direct bond.

As provision of X₁[ formula 6] above for a group having a valence of 4 to an aromatic ring]Examples of the tetracarboxylic acid component of the repeating unit of (a) include 2, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane, 4- (2, 5-dioxotetrahydrofuran-3-yl) -1,2,3, 4-tetrahydronaphthalene-1, 2-dicarboxylic acid, pyromellitic acid, 3,3 ', 4,4 ' -benzophenonetetracarboxylic acid, 3,3 ', 4,4 ' -biphenyltetracarboxylic acid, 2,3,3 ', 4 ' -biphenyltetracarboxylic acid, 4,4 ' -oxydiphthalic acid, bis (3, 4-dicarboxyphenyl) sulfone, m-terphenyl-3, 4,3 ', 4 ' -tetracarboxylic acid, p-terphenyl-3, 4,3 ', 4 ' -tetracarboxylic acid, biscarboxyphenyldimethylsilane, biscarboxyphenoxydiphenyl sulfide, bis (3, 4-dicarboxyphenoxy) diphenyl sulfide, bis (3, 4-dicarboxyphenyl) hexafluoropropane, 4- (2, Sulfonyl diphthalic acids, tetracarboxylic dianhydrides thereof, tetracarboxylic silyl esters, tetracarboxylic acid chlorides, and the like. As provision of X₁Being aromatic rings having fluorine atoms[ formula 6] of a 4-valent group]Examples of the tetracarboxylic acid component of the repeating unit of (2) include derivatives such as 2, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane, tetracarboxylic dianhydride thereof, tetracarboxylic silyl ester, tetracarboxylic ester and tetracarboxylic acid chloride. The tetracarboxylic acid component may be used alone, or two or more kinds may be used in combination.

As X₁The alicyclic 4-valent group of (2) is preferably a 4-valent group having an alicyclic structure having 4 to 40 carbon atoms, more preferably having at least one aliphatic 4-to 12-membered ring, and still more preferably an aliphatic 4-or 6-membered ring.

Further, as X₁The 4-valent group having an alicyclic structure of (2) preferably has at least one aliphatic 6-membered ring in the chemical structure and no aromatic ring because heat resistance and transparency can be achieved at the same time. X₁The 6-membered ring in the (4-valent group having an alicyclic structure) may be two or more, and two or more 6-membered rings may be composed of two or more carbon atoms in common. The 6-membered ring may be a crosslinked ring type in which carbon atoms constituting the ring (the carbon atoms in the 6-membered ring) are bonded to each other to further form the ring.

X₁The (alicyclic group-having 4-valent group) is preferably a 6-membered ring structure having high symmetry, since the polymer chain can be densely packed and the polyimide has excellent solvent resistance, heat resistance and mechanical strength. Further, X₁In the case where two or more 6-membered rings of the (4-valent group having an alicyclic structure) are composed of two or more carbon atoms in common and carbon atoms constituting the rings in the 6-membered rings are bonded to each other to form further rings, the polyimide is more preferable because good heat resistance, solvent resistance and low linear expansion coefficient can be easily achieved.

Preferred 4-valent groups having an aliphatic 4-membered ring or an aliphatic 6-membered ring include the following groups.

[ solution 11]

(in the formula, R₃₁～R₃₆Each independently is directA linkage, or a 2-valent organic group. R₄₁～R₄₇Each independently represents a compound selected from the group consisting of: -CH₂-、-CH＝CH-、-CH₂CH₂-, -O-, -S-or a combination thereof. )

As R₃₁、R₃₂、R₃₃、R₃₄、R₃₅、R₃₆Specific examples thereof include direct bonding, aliphatic hydrocarbon groups having 1 to 6 carbon atoms, oxygen atoms (-O-), sulfur atoms (-S-), carbonyl bonds, ester bonds, and amide bonds.

The alicyclic group-having 4-valent group is particularly preferably the following group because the polyimide obtained can achieve high heat resistance, high transparency, and a low linear thermal expansion coefficient.

[ solution 12]

As provision of X₁[ formula 6] above for a group having a 4-valent alicyclic structure]Examples of the tetracarboxylic acid component of the repeating unit of (3) include 1,2,3, 4-cyclobutanetetracarboxylic acid, isopropylidenedioxybisphthalic acid, cyclohexane-1, 2,4, 5-tetracarboxylic acid and [1, 1' -bis (cyclohexane)]-3,3 ', 4,4 ' -tetracarboxylic acid, [1,1 ' -bis (cyclohexane)]-2,3,3 ', 4 ' -tetracarboxylic acid, [1,1 ' -bis (cyclohexane)]-2,2 ', 3,3 ' -tetracarboxylic acid, 4 ' -methylenebis (cyclohexane-1, 2-dicarboxylic acid), 4 ' - (propane-2, 2-diyl) bis (cyclohexane-1, 2-dicarboxylic acid), 4 ' -oxybis (cyclohexane-1, 2-dicarboxylic acid), 4 ' -thiobis (cyclohexane-1, 2-dicarboxylic acid), 4 ' -sulfonylbis (cyclohexane-1, 2-dicarboxylic acid), 4 ' - (dimethylsilanediyl) bis (cyclohexane-1, 2-dicarboxylic acid), 4 ' - (tetrafluoropropane-2, 2-diyl) bis (cyclohexane-1, 2-dicarboxylic acid), octahydropentalene-1, 3,4, 6-tetracarboxylic acid, bicyclo [2.2.1]Heptane-2, 3,5, 6-tetracarboxylic acid, 6- (carboxymethyl) bicyclo [2.2.1]Heptane-2, 3, 5-tricarboxylic acid, bicyclo [2.2.2 [ ]]Octane-2, 3,5, 6-tetracarboxylic acid, bicyclo [2.2.2]Oct-5-ene-2, 3,7, 8-tetracarboxylic acid, tricyclo [4.2.2.02,5]Decane-3, 4,7, 8-tetracarboxylic acid, tricyclo [4.2.2.02, 5]]Dec-7-ene-3, 4,9, 10-tetracarboxylic acid, 9-oxatricyclo [4.2.1.02, 5]]Nonane-3, 4,7, 8-tetracarboxylic acid, norbornane-2-spiro- α -cyclopentanone- α '-spiro-2', -norbornane 5,5 ", 6, 6" -tetracarboxylic acid (4arH,8acH) -decahydro-1 t,4 t: 5c,8 c-dimethylnaphthalene-2 c,3c,6c,7 c-tetracarboxylic acid, (4arH,8acH) -decahydro-1 t,4 t: 5c,8 c-dimethylnaphthalene-2 c,3c,6c,7 c-tetracarboxylic acid, their derivatives such as tetracarboxylic dianhydride, tetracarboxylic silyl ester, tetracarboxylic ester, tetraacylcarboxylic acid, etc. the tetracarboxylic acid component may be used alone or in combination of two or more.

As Y₁The 2-valent group having an aromatic ring of (2) is preferably a 2-valent group having an aromatic ring having 6 to 40 carbon atoms, more preferably 6 to 20 carbon atoms.

Examples of the 2-valent group having an aromatic ring include the following groups.

[ solution 13]

(in the formula, W₁N 11-n 13 are directly bonded or 2-valent organic groups, each independently represents an integer of 0-4, R₅₁、R₅₂、R₅₃Each independently is an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group, or a trifluoromethyl group. )

As W₁Specific examples thereof include a 2-valent group represented by formula 14 below and a 2-valent group represented by formula 15 below.

[ solution 14]

[ solution 15]

(formula R)₆₁～R₆₈Each independently represents any of the 2-valent groups represented by the above formula. )

Here, the polyimide obtained can satisfy both high heat resistance and high transparency,Low coefficient of linear thermal expansion, therefore W₁Particularly preferably a direct bond, or a group selected from the group consisting of: -NHCO-, -CONH-, -COO-, -OCO-. In addition, W₁Is also particularly preferably R₆₁～R₆₈Is a direct bond, or is selected from the group consisting of: 1 of the group consisting of-NHCO-, -CONH-, -COO-, -OCO- [ formula 14]]Any of the 2-valent groups shown.

As provision of Y₁[ formula 6] above for a 2-valent group having an aromatic ring]Examples of the diamine component of the repeating unit of (a) include p-phenylenediamine, m-phenylenediamine, benzidine, 3 '-diaminobiphenyl, 2' -bis (trifluoromethyl) benzidine, 3 '-bis (trifluoromethyl) benzidine, m-tolidine, 4' -diaminobenzinilide, 3,4 '-diaminobenzanilide, N' -bis (4-aminophenyl) terephthalamide, N '-p-phenylenebis (p-aminobenzamide), 4-aminophenoxy-4-diaminobenzoate, bis (4-aminophenyl) terephthalate, bis (4-aminophenyl) ester of biphenyl-4, 4' -dicarboxylic acid, p-phenylenebis (p-aminobenzoate), bis (4-aminophenyl) - [1, 1' -Biphenyl]-4,4 '-dicarboxylic acid ester, [1, 1' -biphenyl]-4,4 '-diylbis (4-aminobenzoate), 4' -oxydianiline, 3 '-oxydianiline, p-methylenebis (phenylenediamine), 1, 3-bis (4-aminophenoxy) benzene, 1, 3-bis (3-aminophenoxy) benzene, 1, 4-bis (4-aminophenoxy) benzene, 4' -bis (4-aminophenoxy) biphenyl, 4 '-bis (3-aminophenoxy) biphenyl, 2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane, 2-bis (4-aminophenyl) hexafluoropropane, bis (4-aminophenyl) sulfone, 3' -bis (trifluoromethyl) benzidine, 3,3 '-bis ((aminophenoxy) phenyl) propane, 2' -bis (3-amino-4-hydroxyphenyl) hexafluoropropane, bis (4- (4-aminophenoxy) diphenyl) sulfone, bis (4- (3-aminophenoxy) diphenyl) sulfone, octafluorobenzidine, 3 '-dimethoxy-4, 4' -diaminobiphenyl, 3 '-dichloro-4, 4' -diaminobiphenyl, 3 '-difluoro-4, 4' -diaminobiphenyl, 2, 4-bis (4-aminoanilino) -6-amino-1, 3, 5-triazine, 2, 4-bis (4-aminoanilino) -6-methylamino-1, 3, 5-triazine, 2, 4-bis (4-aminoanilino) -6-ethylamino-1, 3, 5-trisOxazine, 2, 4-bis (4-aminoanilino) -6-anilino-1, 3, 5-triazine. As provision of Y₁The above formula 6 of the 2-valent group having an aromatic ring containing a fluorine atom]Examples of the diamine component of the repeating unit of (3) include 2,2 '-bis (trifluoromethyl) benzidine, 3' -bis (trifluoromethyl) benzidine, and 2, 2-bis [4- (4-aminophenoxy) phenyl group]Hexafluoropropane, 2-bis (4-aminophenyl) hexafluoropropane, and 2, 2' -bis (3-amino-4-hydroxyphenyl) hexafluoropropane. The diamine component may be used alone, or two or more thereof may be used in combination.

As Y₁The alicyclic structure-having 2-valent group of (2) is preferably a group having a carbon number of 4 to 40 and having a 2-valent alicyclic structure, more preferably having at least one aliphatic 4 to 12-membered ring, and still more preferably an aliphatic 6-membered ring.

Examples of the 2-valent group having an alicyclic structure include the following groups.

[ solution 16]

(in the formula, V₁、V₂Each independently represents a direct bond or a 2-valent organic group, n21 to m26 each independently represents an integer of 0 to 4, R₈₁～R₈₆Each independently is an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group, or a trifluoromethyl group, R₉₁、R₉₂、R₉₃Each independently selected from the group consisting of: -CH₂-、-CH＝CH-、-CH₂CH₂-, -O-, -S-or a combination thereof. )

As V₁、V₂Specifically, the above chemical formula 14 can be mentioned]The 2-valent radical shown.

The following group is particularly preferable as the alicyclic group-having 2-valent group because the polyimide obtained can achieve both high heat resistance and a low linear thermal expansion coefficient.

[ solution 17]

Among the 2-valent groups having an alicyclic structure, the following groups are preferred.

[ solution 18]

As provision of Y₁[ formula 6] above for a 2-valent group having an alicyclic structure]Examples of the diamine component having the repeating unit of (a) include 1, 4-diaminocyclohexane, 1, 4-diamino-2-methylcyclohexane, 1, 4-diamino-2-ethylcyclohexane, 1, 4-diamino-2-n-propylcyclohexane, 1, 4-diamino-2-isopropylcyclohexane, 1, 4-diamino-2-n-butylcyclohexane, 1, 4-diamino-2-isobutylcyclohexane, 1, 4-diamino-2-sec-butylcyclohexane, 1, 4-diamino-2-tert-butylcyclohexane, 1, 2-diaminocyclohexane, 1, 3-diaminocyclobutane, 1, 4-bis (aminomethyl) cyclohexane, 1, 3-bis (aminomethyl) cyclohexane, diaminobicycloheptane, diaminomethylbicycloheptane, diaminooxydicycloheptane, diaminomethoxybicycloheptane, isophoronediamine, diaminotricyclodecane, diaminomethyltricyclodecane, bis (aminocyclohexyl) methane, bis (aminocyclohexyl) isopropylidene, 6 '-bis (3-aminophenoxy) -3,3, 3', 3 '-tetramethyl-1, 1' -spirobiindane, 6 '-bis (4-aminophenoxy) -3,3, 3', 3 '-tetramethyl-1, 1' -spirobiindane. The diamine component may be used alone, or two or more thereof may be used in combination.

The polyimide precursor (a1) containing at least one of the repeating units represented by formula [ 6] above may contain a repeating unit other than the repeating unit represented by formula [ 6 ].

The tetracarboxylic acid component and the diamine component which provide other repeating units are not particularly limited, and other known aliphatic tetracarboxylic acids and known aliphatic diamines can be used. The other tetracarboxylic acid components may be used alone, or two or more of them may be used in combination. Other diamine components may be used alone, or two or more thereof may be used in combination.

The content of the repeating unit other than the repeating unit represented by [ chemical formula 6] is preferably 30 mol% or less than 30 mol%, more preferably 20 mol% or less, and still more preferably 10 mol% or less, based on the total repeating units.

[ formula 6] of polyimide precursor (A1)]In, R₁、R₂Each of which is an alkylsilyl group having 3 to 9 carbon atoms. R₁、R₂In the case of hydrogen, the polyimide tends to be easily produced.

R₁、R₂The kind of the functional group and the introduction ratio of the functional group can be changed by the production method described later.

Polyimide precursor (A1) (containing the above [ formula 6]]Polyimide precursor of at least one of the repeating units shown) according to R₁、R₂The chemical structures adopted can be classified as:

1) polyamic acid (R)₁、R₂Is hydrogen);

2) polyamic acid ester (R)₁、R₂At least a part of (a) is an alkyl group),

3)4) Polyamic acid silyl ester (R)₁、R₂At least a portion of (a) is an alkylsilyl group).

In addition, the polyimide precursor (a1) can be easily produced by the following production method for each classification. The method for producing the polyimide precursor (a1) is not limited to the following production method.

1) Polyamic acid

The polyimide precursor (a1) can be suitably obtained as a polyimide precursor solution composition by reacting a tetracarboxylic dianhydride and a diamine component as tetracarboxylic acid components in a solvent in a ratio of approximately equimolar amounts, preferably a molar ratio of the diamine component to the tetracarboxylic acid component [ the number of moles of the diamine component/the number of moles of the tetracarboxylic acid component ] of preferably 0.90 to 1.10, more preferably 0.95 to 1.05, at a relatively low temperature of, for example, 1200 ℃.

More specifically, the diamine is dissolved in an organic solvent or water, and the tetracarboxylic dianhydride is slowly added to the solution while stirring, and the solution is maintained at 0 to 120 ℃, preferably 5 to 80 ℃ for 1 to 72 hours, thereby obtaining a polyimide precursor. In the case of the reaction at 800 ℃ or higher, the molecular weight changes depending on the temperature history at the time of polymerization, and imidization proceeds by heat, so that there is a possibility that a polyimide precursor cannot be stably produced. Since the molecular weight of the polyimide precursor is easily increased, the order of addition of the diamine and the tetracarboxylic dianhydride in the above-mentioned production method is preferable. In addition, the order of addition of the diamine and the tetracarboxylic dianhydride in the above production method may be reversed, and the precipitation is preferably reduced. When water is used as the solvent, an imidazole such as 1, 2-dimethylimidazole or a base such as triethylamine is preferably added in an amount of 0.8 equivalent or more to the carboxyl group of the produced polyamic acid (polyimide precursor).

2) Polyamide acid ester

The tetracarboxylic dianhydride is reacted with an arbitrary alcohol to obtain a diester dicarboxylic acid, and then reacted with a chlorinating agent (thionyl chloride, oxalyl chloride, or the like) to obtain a diester dicarboxylic acid dichloride. The diester dicarboxylic acid chloride and the diamine are stirred at-20 to 120 ℃, preferably-5 to 80 ℃ for 1 to 72 hours to obtain a polyimide precursor. When the reaction is carried out at 800 ℃ or higher, the molecular weight may vary depending on the temperature history at the time of polymerization, and the imidization may proceed by heat, so that the polyimide precursor may not be stably produced. Further, a polyimide precursor can also be obtained simply by subjecting a diester dicarboxylic acid and a diamine to dehydration condensation using a phosphorus-based condensing agent, a carbodiimide condensing agent, or the like.

Since the polyimide precursor obtained by this method is stable, it may be purified by reprecipitation or the like by adding a solvent such as water or alcohol.

3) Polyamic acid silyl ester (Indirect method)

The diamine is reacted with a silylating agent in advance to obtain a silylated diamine. If necessary, the silylated diamine is purified by distillation or the like. Then, the silylated diamine is dissolved in the dehydrated solvent in advance, and the tetracarboxylic dianhydride is slowly added while stirring, and the mixture is stirred at 0 to 120 ℃, preferably 5 to 80 ℃ for 1 to 72 hours, thereby obtaining a polyimide precursor. When the reaction is carried out at 800 ℃ or higher, the molecular weight may vary depending on the temperature history at the time of polymerization, and the imidization may proceed by heat, so that the polyimide precursor may not be stably produced.

4) Polyamic acid silyl ester (direct Process)

Mixing the polyamic acid solution obtained by the method of 1) above with a silylating agent, and stirring the mixture at 0 to 120 ℃, preferably 5 to 80 ℃ for 1 to 72 hours to obtain a polyimide precursor. When the reaction is carried out at 800 ℃ or higher, the molecular weight may vary depending on the temperature history at the time of polymerization, and the imidization may proceed by heat, so that the polyimide precursor may not be stably produced.

As the silylating agent used in the method 3) or the method 4), a silylating agent containing no chlorine is preferably used, and in this case, it is not necessary to purify the silylated polyamic acid or the resulting polyimide. Examples of the silylating agent containing no chlorine atom include N, 0-bis (trimethylsilyl) trifluoroacetamide, N, 0-bis (trimethylsilyl) acetamide, and hexamethyldisilazane. N, 0-bis (trimethylsilyl) acetamide and hexamethyldisilazane are particularly preferable because they contain no fluorine atom and are inexpensive.

In addition, in order to accelerate the reaction, an amine-based catalyst such as pyridine, piperidine, triethylamine or the like can be used in the silylation reaction of the diamine in the method 3). The catalyst can be used as it is as a polymerization catalyst for a polyimide precursor.

The solvent (C) used for preparing the polyimide precursor (a1) is preferably water or an aprotic solvent such as N, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, 1, 3-dimethyl-2-imidazolidinone, or dimethyl sulfoxide, and any solvent can be used without any problem as long as the raw material monomer components and the produced polyimide precursor are dissolved, and the structure thereof is not particularly limited. As the solvent, water is preferably used; amide solvents such as N, N-dimethylformamide, N-dimethylacetamide, and N-methylpyrrolidone; cyclic ester solvents such as γ -butyrolactone, γ -valerolactone, γ -caprolactone, α -methyl- γ -butyrolactone, and the like; carbonate solvents such as ethylene carbonate and propylene carbonate; glycol solvents such as triethylene glycol; phenol solvents such as m-cresol, p-cresol, 3-chlorophenol, and 4-chlorophenol; acetophenone, 1, 3-dimethyl-2-imidazolidinone, sulfolane, dimethyl sulfoxide, and the like. Other common organic solvents, that is, phenol, o-cresol, butyl acetate, ethyl acetate, isobutyl acetate, propylene glycol methyl acetate, ethyl cellosolve, butyl cellosolve, 2-methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, tetrahydrofuran, dimethoxyethane, diethoxyethane, dibutyl ether, diethylene glycol dimethyl ether, methyl isobutyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methyl ethyl ketone, acetone, butanol, ethanol, xylene, toluene, chlorobenzene, terpene, mineral essential oils, naphtha solvents, and the like can also be used. Two or more solvents may be used in combination.

The logarithmic viscosity of the polyimide precursor (A1) is not particularly limited, but the logarithmic viscosity in a solution of N, N-dimethylacetamide having a concentration of 0.5g/dL at 300 ℃ is preferably 0.2dL/g or more, more preferably 0.3dL/g or more, and particularly preferably 0.4dL/g or more. When the logarithmic viscosity is 0.2dL/g or more, the molecular weight of the polyimide precursor is high, and the obtained polyimide is excellent in mechanical strength and heat resistance.

< polyimide (A2) >

The polyimide (a2) is not particularly limited, and is obtained from the polyimide precursor (a1), and contains at least one of the repeating units represented by the above formula 7.

[ chemical formula 7] above]Corresponding to [ formation 6] above]，X₁Corresponds to X₂，Y₁Corresponds to Y₂. As the above [ chemical formula 7]]X in (1)₂、Y₂Examples thereof include compounds similar to the above formula 6]X in (1)₁、Y₁The same substances, preferably the same substances, are used.

Although not particularly limited, since it is excellent in heat resistance, poly (arylene sulfide) is preferredX in chemical formula (7) of imide (A2)₂Is a 4-valent group having an aromatic ring, Y₂Is a 2-valent group having an aromatic ring. Further, X is preferable because of excellent heat resistance and excellent transparency₂Is a 4-valent group having an alicyclic structure, Y₂Is a 2-valent group having an aromatic ring. Further, X is preferable because of excellent heat resistance and excellent dimensional stability₂Is a 4-valent group having an aromatic ring, Y₂Is a 2-valent group with an alicyclic structure.

In order to obtain a polyimide composition having a small retardation in the thickness direction and in the in-plane direction and excellent characteristics such as transparency, mechanical characteristics, and heat resistance, the polyimide (a2) is preferably a polyimide containing a fluorine atom and obtained from an aromatic tetracarboxylic acid component and an aromatic diamine; or a polyimide obtained from an alicyclic tetracarboxylic acid component and an aromatic diamine; or a polyimide obtained from an aromatic tetracarboxylic acid component and an alicyclic diamine. The tetracarboxylic acid component includes a tetracarboxylic acid and a tetracarboxylic acid derivative such as a tetracarboxylic dianhydride, a tetracarboxylic acid silyl ester, a tetracarboxylic acid ester, or a tetracarboxylic acid chloride.

X is relative to the total repeating units in view of the properties of the polyimide composition, such as transparency, mechanical properties, heat resistance, etc₂Is a 4-valent group having an alicyclic structure, Y₂[ formula 7] above for a 2-valent group having an alicyclic structure]The content of the repeating unit is preferably 50 mol% or less, more preferably 30 mol% or less, or less than 30 mol%, more preferably 10 mol% or less.

In one embodiment, in the polyimide (A2), X₂Is a 4-valent group having an aromatic ring, Y₂[ formula 7] above for a 2-valent group having an aromatic ring]The total content of 1 or more kinds of the repeating units in (b) is preferably 50 mol% or more, more preferably 70 mol% or more, more preferably 80 mol% or more, further preferably 90 mol% or more, and particularly preferably 100 mol% based on the total repeating units. In this embodiment, particularly when high transparency is required, the polyimide (a2) preferably contains a fluorine atom. Namely, polyimide(A2) Preferably containing X₂The above formula 7 being a 4-valent group having an aromatic ring containing a fluorine atom]Repeating unit of (a) and/or Y₂[ formula 7] above for 2-valent group having fluorine atom-containing aromatic ring]1 or more of the repeating units (c).

In one embodiment, in the polyimide (A2), X₂Is a 4-valent group having an alicyclic structure, Y₂[ formula 7] above for a 2-valent group having an aromatic ring]The total content of 1 or more kinds of the repeating units in (b) is preferably 50% or more, more preferably 70% or more by mole, more preferably 80% or more by mole, further preferably 90% or more by mole, and particularly preferably 100% by mole based on the total repeating units.

In one embodiment, in the polyimide (A2), X₂Is a 4-valent group having an aromatic ring, Y₂[ formula 7] above for a 2-valent group having an alicyclic structure]The total content of 1 or more kinds of the repeating units in (b) is preferably 50 mol% or more, more preferably 70 mol% or more, more preferably 80 mol% or more, further preferably 90 mol% or more, and particularly preferably 100 mol% based on the total repeating units.

The polyimide (a2) containing at least one of the repeating units represented by formula 7 may contain 1 or more kinds of repeating units other than the repeating unit represented by formula 7.

The content of the repeating unit other than the repeating unit represented by the above formula 7 is preferably 30 mol% or less than 30 mol%, more preferably 20 mol% or less, and still more preferably 10 mol% or less based on the total repeating units.

The polyimide (a2) can be produced by imidizing the polyimide precursor (a1) (i.e., subjecting the polyimide precursor (a1) to a dehydration ring-closure reaction). The method of imidization is not particularly limited, and a known thermal imidization or chemical imidization method can be suitably used.

In the optical film comprising the resin containing strontium carbonate particles, the average length of the strontium carbonate particles is as small as 10 to 100nm, and the surface of the strontium carbonate particles is coated with a surfactant, so that the dispersibility of the strontium carbonate particles in the resin is improved. This can reduce the haze of the optical film.

For example, optical films having a haze of 1% or less and positive out-of-plane birefringence can be provided. In addition, an optical film having a haze of 1% or less and zero out-of-plane birefringence can also be provided. Further, an optical film having a haze of 1% or less and a negative out-of-plane birefringence can also be provided.

In addition, such an optical film can be suitably used for an image display device.