LIQUID CRYSTAL POLYMER PARTICLES, THERMOSETTING RESIN COMPOSITION, AND MOLDED ARTICLE

Abstract

Disclosed are liquid crystal polymer particles capable of reducing dielectric loss tangent while suppressing surface roughness of the resin film, when added to a resin film. The liquid crystal polymer particles have a melting point of 270° C. or higher, wherein cumulative distribution 50% diametre D.sub.50 in the particle size distribution is 20 μm or less, and cumulative distribution 90% diametre D.sub.90 is 2.5 times or less of D.sub.50.

Claims

1. Liquid crystal polymer particles having a melting point of 270° C. or higher, wherein cumulative distribution 50% diametre D.sub.50 in the particle size distribution is 20 μm or less, and cumulative distribution 90% diametre D.sub.90 is 2.5 times or less of D.sub.50.

2. The liquid crystal polymer particles according to claim 1, wherein dielectric loss tangent of the liquid crystal polymer particles is 0.001 or less.

3. The liquid crystal polymer particles according to claim 1, wherein the ratio of modal diametre Dp to D.sub.50 in the particle size distribution of the liquid crystal polymer particles is 0.7 or more and 1.3 or less.

4. The liquid crystal polymer particles according to claim 1, having a water absorption rate of 0.05% or less.

5. The liquid crystal polymer particles according to claim 1, comprising structural unit (I) derived from a hydroxycarboxylic acid, structural unit (II) derived from a diol compound, and structural unit (III) derived from a dicarboxylic acid.

6. The liquid crystal polymer particles according to claim 5, wherein the structural unit (I) derived from a hydroxycarboxylic acid is a structural unit derived from 6-hydroxy-2-naphthoic acid.

7. The liquid crystal polymer particles according to claim 5, wherein the composition ratio of the structural unit (I) is 40 mol % or more and 80 mol % or less with respect to the structural units of the entire liquid crystal polymer particles.

8. A thermosetting resin composition comprising the liquid crystal polymer particles according to claim 1 and a thermosetting resin.

9. The thermosetting resin composition according to claim 8, wherein the content of the liquid crystal polymer particles is 5 to 80% by mass with respect to 100 parts by mass of the thermosetting resin.

10. The thermosetting resin composition according to claim 8, wherein the thermosetting resin is at least one selected from the group consisting of an epoxy resin, phenol resin, polyimide resin, and bismaleimide triazine resin.

11. A method for producing the thermosetting resin composition according to claim 8, comprising the step of mixing at least the liquid crystal polymer particles and the thermosetting resin at a temperature lower than the melting point of the liquid crystal polymer particles.

12. A molded article using the thermosetting resin composition according to claim 8.

13. The molded article according to claim 12 in the form of a film, a sheet or a plate.

14. The molded article according to claim 13, being a resin film having a thickness of 25 μm or less.

15. The molded article according to claim 14, wherein surface roughness Ra of the resin film is 1.0 μm or less.

16. An electronic circuit board comprising the thermosetting resin composition according to claim 8.

17. The electronic circuit board according to claim 16, being a flexible circuit board.

Description

EXAMPLES

[0091] Hereinafter, the present invention shall be described more specifically with reference to the Examples, but the present invention shall not be limited to the Examples.

Synthesis of Liquid Crystal Polymer

Synthesis Example 1

[0092] 60 mol % of 6-hydroxy-2-naphthoic acid (HNA), 20 mol % of 4,4-dihydroxybiphenyl (BP), 15.5 mol % of terephthalic acid (TPA), and 4.5 mol % of 2,6-naphthalenedicarboxylic acid (NADA), and potassium acetate and magnesium acetate as catalysts were fed to a polymerization vessel having stirring blades, then the polymerization vessel was subjected to pressure reduction-nitrogen injection three times to substitute the nitrogen, and subsequently acetic anhydride (1.08 molar equivalent to the hydroxyl group) was further added, the temperature was raised to 150° C., and acetylation reaction was carried out under reflux for 2 hours.

[0093] After completion of acetylation, the polymerization vessel in an acetic acid-distilled state was heated at 0.5° C./min, the polymer was drawn out when the melt temperature in the vessel reached 310° C., and the polymer was solidified by cooling. The polymer thus obtained was pulverized to a size that passed through a sieve having a mesh opening of 2.0 mm to obtain a prepolymer.

[0094] Next, the prepolymer obtained as described above was heated over 14 hours from room temperature to 295° C. by using a heater in an oven manufactured by Yamato Kagaku Co., Ltd., and then solid phase polymerization was performed while maintaining the temperature at 295° C. for 1 hour. Then, the heat in the prepolymer was naturally released at room temperature to obtain Liquid crystal polymer A. By using a polarizing microscope (product name: BH-2) manufactured by Olympus Co., Ltd. equipped with a microscope hot stage (product name: FP82HT) manufactured by Mettler, it was confirmed that liquid crystallinity was exhibited by heating and melting the Liquid crystal polymer A on a microscope heating stage and confirming from the presence or absence of optical anisotropy.

Synthesis Example 2

[0095] Liquid crystal polymer B was obtained in the same manner as in Synthesis Example 1, except that the monomer feed was changed to 60 mol % of p-hydroxybenzoic acid (HBA), 20 mol % of BP, 15 mol % of TPA, and 5 mol % of IPA, and the final temperature of solid phase polymerization was set at 265° C. and the retention time was set at 1 hour. Subsequently, it was confirmed in the same manner as described above that the obtained Liquid crystal polymer B exhibited liquid crystallinity.

Production of Liquid Crystal Polymer Particles

Example 1

[0096] Powder (average diametre: 80 μm) of the Liquid crystal polymer A synthesized above was pulverized for 15 minutes using a Nano Jetmizer NJ-50 type jet mill manufactured by Aishin Nanotechnologies Co., Ltd. under conditions of a pulverization pressure of 1.4 MPa and a resin feed rate of 120 g/h to obtain a pulverized product. Using a vibration sieving machine equipped with an ultrasonic oscillator, the pulverized product thus obtained was passed through a sieve having a mesh opening of 20 μm and those which passed the sieve was collected. As a result, substantially spherical liquid crystal polymer particles A1 were obtained.

Example 2

[0097] Regarding 2 minutes of pulverization time and 1 minute of cooling time using a freezer mill type 6775 manufactured by SPEX Co., Ltd. as one cycle, powder of the liquid crystal polymer A was subjected to the cycle for ten times, thereby obtaining a pulverized product. The obtained pulverized product was passed through a sieve having a mesh opening of 20 μm using a vibration sieving machine equipped with an ultrasonic oscillator, and the pulverized object which passed through the sieve was collected. As a result, substantially spherical liquid crystal polymer particles A2 were obtained.

Example 3

[0098] Pulverization was performed three times under the same pulverization apparatus and pulverization conditions as in Example 1 to obtain a pulverized product. The obtained pulverized product was passed through a sieve having a mesh opening of 20 μm using a vibration sieving machine equipped with an ultrasonic oscillator, and the pulverized object which passed through the sieve was collected. As a result, substantially spherical liquid crystal polymer particles A3 were obtained.

Example 4

[0099] Powder of the liquid crystal polymer A was continuously pulverized under conditions of a pulverizing pressure of 0.65 MPa and a resin supply amount of 5 kg/h using an apparatus in which a DSF-10 type classifier manufactured by Nippon Pneumatic Mfg. Co., Ltd. was combined with a SPK-12 type jet mill manufactured by Nippon Pneumatic Mfg. Co., Ltd., to obtain a substantially spherical liquid crystal polymer A4.

Comparative Example 1

[0100] Substantially spherical liquid crystal polymer particles A5 were obtained in the same manner as in Example 1, except that the sieve having a mesh opening of 20 μm was not used.

Comparative Example 2

[0101] Substantially spherical liquid crystal polymer particles B1 were obtained in the same manner as in Example 1, except that Liquid crystal polymer B was used instead of Liquid crystal polymer A and the sieve having an opening of 20 μm was not used.

Evaluation of Liquid Crystal Polymer

Measurement of Particle Size Distribution

[0102] Particle size distribution of the liquid crystal polymer particles obtained as described above was measured by a laser diffraction/scattering method particle size distribution measuring device (manufactured by Beckman Coulter, LS13 320 dry system, equipped with tornado dry powder module). The parameters D.sub.50, D.sub.90 and D.sub.p indicating the particle size distribution were obtained as calculation results from the measurement data. The results are shown in Table 1.

Measurement of Melting Point

[0103] Melting point of each liquid crystal polymer obtained above was measured by a differential scanning calorimeter (DSC) manufactured by Hitachi High-Tech Science Co., Ltd. in accordance with the test method of ISO11357 and ASTM D3418. At this time, the temperature was raised from room temperature to 360 to 380° C. at a heating rate of 10° C./min to completely melt the polymer, then the melting point (Tm.sub.2) was determined from the peak of the endothermic peak obtained when the temperature was lowered to 30° C. at a rate of 10° C./min, and further raised to 380° C. at a rate of 10° C./min. The measurement results are shown in Table 1.

Measurement of Dielectric Loss Tangent (10 GHz)

[0104] Flat test pieces were obtained using each liquid crystal polymer obtained above by heating and melting under conditions of individual melting point to melting point +30° C., and then injection-molding using a mold of 30 mm×30 mm×0.4 mm (thickness). Subsequently, using the flat test pieces, dielectric loss tangent at a frequency of 10 GHz was measured by a split post dielectric resonator method (SPDR method) using a network analyzer N5247A of Keysight Technologies. Samples of each type were measured every N=4, and the average values of 4 measurements are shown in Table 1.

Measurement of Water Absorption Rate

[0105] Water absorption rate of each of the liquid crystal polymer particles produced above was measured by the following procedure. Approximately 0.1 g of liquid crystal polymer particles were cut out, dried in a vacuum oven set at 100° C. for 1 hour, then precisely weighed, and the dry weight was measured. After the liquid crystal polymer particles were immersed in pure water for 24 hours, the moisture adhered was wiped off with Kimwipes, precisely weighed, and the weight at the time of water absorption was measured. The difference between the weight at water absorption and the weight at the time of drying was divided by the weight at the time of drying to calculate the water absorption rate. The calculation results are shown in Table 1.

TABLE-US-00001 TABLE 1 Composition (mol %) Liquid Constituting Constituting Water Crystal Unit Unit Constituting Unit Particle Size Distribution Melting Dielectic Absorption Polymer (I) (II) (III) D.sub.50 D.sub.90/D.sub.50 Point Tangent Rate Particles HNA HBA BP TPA NADA IPA (μm) (μm) Dp/D.sub.50 (° C.) tanδ (%) Ex. 1 A1 60 — 20 15.5 4.5 — 9.0 1.6 1.1 319 0.0007 Less than 0.02 Ex. 2 A2 60 — 20 15.5 4.5 — 10.5 1.7 1.2 319 0.0007 Less than 0.02 Ex. 3 A3 60 — 20 15.5 4.5 — 7.5 1.8 1.2 319 0.0007 Less than 0.02 Ex. 4 A4 60 — 20 15.5 4.5 5.3 1.7 1.0 319 0.0007 Less than 0.02 Comp. A5 60 — 20 15.5 4.5 — 12.5 2.6 0.7 319 0.0007 Less than 0.02 Ex. 1 Comp. B1 — 60 20 15 — 5 8.3 4.3 0.9 355 0.004 Less than 0.02 Ex. 2

Film Production 1

Example 5

[0106] To a polyimide varnish (SPIXAREA GR003, manufactured by SOMAR CORPORATION) was added 30 parts by weight of Liquid crystal polymer particles Al based on 100 parts by weight of the polyimide in the varnish to obtain a suspension. The resulting suspension was applied to a glass substrate, dried and cured to produce a film having a thickness of 60 μm.

Example 6

[0107] A film was produced in the same manner as in Example 5, except that the thickness of the film was changed to other than 20 μm.

Example 7

[0108] A film having a thickness of 20 μm was produced in the same manner as in Example 6, except that the amount of Liquid crystal polymer particles A1 added was changed from 30 parts by mass to 50 parts by mass.

Example 8

[0109] A film having a thickness of 20 μm was produced in the same manner as in Example 6, except that 30 parts by mass of Liquid crystal polymer particles A2 were added instead of Liquid crystal polymer particles A1.

Example 9

[0110] A film having a thickness of 20 μm was produced in the same manner as in Example 6, except that 30 parts by mass of Liquid crystal polymer particles A3 were added instead of Liquid crystal polymer particles A1.

Reference Example

[0111] A film having a thickness of 60 μm was produced in the same manner as in Example 5, except that Liquid crystal polymer particles A1 were not added.

Comparative Example 3

[0112] A film having a thickness of 20 μm was produced in the same manner as in Example 6, except that 30 parts by mass of Liquid crystal polymer particles A4 were added instead of Liquid crystal polymer particles A1.

Comparative Example 4

[0113] A film having a thickness of 20 μm was produced in the same manner as in Example 6, except that 30 parts by mass of Liquid crystal polymer particles B1 were added instead of Liquid crystal polymer particles A1.

Performance Evaluation

Measurement of Surface Roughness

[0114] Each of the films produced above was cut out into 3 mm×80 mm strips to obtain film samples. Subsequently, surface roughness of the film sample was measured using an OLS5000 type laser microscope manufactured by Olympus Co., Ltd. The measurement results are shown in Table 2.

Measurement of Dielectric Constant and Dielectric Loss Tangent

[0115] Each of the film samples produced above were measured for the dielectric constant and dielectric loss tangent at 10 GHz were using a measuring device in which a cavity resonator manufactured by AET, Inc. is connected to spectrum network analyzer MS46122B type manufactured by Anritsu Corporation. The measurement results are shown in Table 2.

Measurement of Water Absorption Rate

[0116] The water absorption rate of each film produced above was measured by the following procedure. Approximately 0.1 g of the film was cut out, dried in a vacuum oven set at 100° C. for 1 hour, then precisely weighed, and the dry weight was measured. After the film was immersed in pure water for 24 hours, the moisture adhered was wiped off with Kimwipes, precisely weighed, and the weight at the time of water absorption was measured. The difference between the weight at water absorption and the weight at the time of drying was divided by the weight at the time of drying to calculate the water absorption rate. The calculation results are shown in Table 2.

TABLE-US-00002 TABLE 2 Liquid Surface Water Crystal Addition Film Roughness Dielectric Absorption Polymer Amount thickness Ra Tangent Dielectric Rate Particles (%) (μm) (μm) tanδ Constant (%) Ex.5 A1 30 60 0.28 0.014 3.06 1.5 Ex.6 A1 30 20 0.63 0.014 3.05 1.4 Ex.7 A1 50 20 0.96 0.010 3.05 1.1 Ex.8 A2 30 20 0.80 0.014 3.05 1.4 Ex.9 A3 30 20 0.53 0.014 3.05 1.4 Ref. — — 60 0.08 0.020 2.93 1.9 Ex. Comp. A5 30 20 2.43 0.014 3.05 1.4 Ex.3 Comp. B1 30 60 3.01 0.016 3.21 1.4 Ex.4

Production of Film 2

Example 10

[0117] To a glass container equipped with a stirrer were added 60% m-toluidine (tol), 40% 4,4′-diaminodiphenyl ether (DDE) and N,N-dimethylacetamide so that a predetermined concentration is obtained, and the mixture was stirred at 25° C. under a nitrogen atmosphere to obtain a solution. 100% of pyromellitic dianhydride (PMDA) was added to this solution in several batches and stirred at 25° C. under a nitrogen atmosphere to obtain a polyamic acid varnish. To the polyamic acid varnish thus obtained was added 30 parts by mass of Liquid crystal polymer particles A4 based on 100 parts by mass of polyamic acid in the varnish to obtain a suspension. The suspension thus obtained was applied to a glass substrate, dried and then cured at 300° C. to produce a film having a thickness of 25 μm.

Example 11

[0118] A film having a thickness of 25 μm was produced in the same manner as in Example 10, except that the addition amount of Liquid crystal polymer particles A4 was 50 parts by mass with respect to 100 parts by mass of the polyamic acid.

Example 12

[0119] A film having a thickness of 25 μm was produced in the same manner as in Example 11, except that the temperature at which the suspension applied on the glass substrate was dried and then cured was set to 350° C.

(Reference Example 2

[0120] A film having a thickness of 25 μm was produced in the same manner as in Example 10, except that Liquid crystal polymer particles A4 were not added.

Performance Evaluation

[0121] Performance evaluation was performed in the same manner as in Film Production 1 described above. The evaluation results are shown in Table 3.

TABLE-US-00003 TABLE 3 Liquid Surface Dielectric Crystal Addition Baking Film Roughness loss Polymer amount temperature thickness Ra tangent Dielectric Particles (%) (° C.) (μm) (μm) tanδ constant Ex. 10 A4 30 300 25 0.23 0.0017 3.26 Ex. 11 A4 50 300 25 0.26 0.0016 3.30 Ex. 12 A4 50 350 25 0.45 0.0015 2.93

[0122] Generally, when the powder of liquid crystal polymer particles is mixed with polyamic acid which is a precursor of polyimide, burning conditions are appropriately adjusted to 300° C. or higher in order to sufficiently increase the imidization rate of polyimide. According to the above results, use of the liquid crystal polymer of the present invention makes it possible to suppress adverse effects on the dielectric loss tangent, relative dielectric constant, and surface roughness of the film as much as possible even when the burning conditions are adjusted in that manner.