KR102607476B1 - Imaging lens - Google Patents

Abstract

An imaging lens made of polycarbonate containing formula (1) and formula (2) in the ratio shown below, has a specific refractive index and Abbe number, and has physical properties of low birefringence and low absorption.
50 mol% ≤ (1) < 70 mol%
30 mol% < (2) ≤ 50 mol%

Description

IMAGING LENS {IMAGING LENS}

The present invention relates to an imaging lens made of a specific polycarbonate resin.

In recent years, most mobile phones have been equipped with a camera function, and recently, mobile phones equipped with a high-resolution camera function comparable to a digital still camera have been appearing. The pixel size of the imaging device has become smaller, and the pixel pitch is less than 1.4 microns. Meanwhile, in response to miniaturization and thinning of mobile phones, there is also a demand for miniaturization of imaging lenses. Therefore, in order to cope with higher resolution of imaging devices and miniaturization of imaging lenses, there is a strong demand for lower birefringence and improvement in aberration correction capabilities of imaging lenses. Conventionally, imaging lenses for portable devices such as mobile phones and smartphones are made of aspherical plastic, and aberration correction is achieved by combining lenses with different optical properties (refractive index, Abbe number) and lens shapes.

Among the optically transparent resins commercialized for lens use, polycarbonate resin (nd = 1.584) made from bisphenol A as a raw material with high refractive index and low Abbe number has been widely used. However, polycarbonate resin made from bisphenol A has a weak point of large birefringence, so it cannot be used in recent high-resolution cameras.

As a method of reducing birefringence, a polycarbonate copolymer containing a fluorene group or an oxaspiroundecane group is disclosed (Patent Documents 1 and 2). Patent Document 1 discloses information recording media such as optical disks, and Patent Document 2 discloses optical disks, optical films, optical prisms, and pickup lenses (which only identify 0 or 1 of optical signals), but does not assume an imaging lens. Therefore, the characteristics necessary for an imaging lens, such as refractive index, Abbe number, orientation birefringence, and absorptivity, are not known. Additionally, a camera lens made of polycarbonate resin and styrene resin having a specific structure is disclosed (Patent Document 3). However, the patent document contained a polystyrene component, and furthermore, due to mixing of incompatible components, there was a problem in that the resin was weak and had low heat resistance.

Japanese Patent Publication No. 9-268225 Japanese Patent Publication No. 2004-67990 Japanese Patent Publication No. 2009-93146

Therefore, the purpose of the present invention is to provide an imaging lens that has a specific refractive index and Abbe number, and is low birefringent and low absorptivity by using a specific polycarbonate resin.

In order to achieve the above-mentioned problem, the present inventor conducted extensive research on new resins for imaging lenses, and as a result, 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene and 3,9-bis( By copolymerizing 1,1-dimethyl-2-hydroxyethyl)2,4,8,10-tetraoxaspiro[5.5]undecane at a specific composition ratio to obtain a polycarbonate resin for an imaging lens, and using the resin, It was discovered that an imaging lens with a specific refractive index and Abbe number could be produced with low birefringence and low absorption.

That is, according to the present invention, an imaging lens made of the polycarbonate resin shown below is provided.

1. An imaging lens made of polycarbonate containing formula (1) and formula (2) in the ratio of the following formula.

50 mol% ≤ (1) < 70 mol%

30 mol% < (2) ≤ 50 mol%

[Formula 1]

[Formula 2]

2. The imaging lens according to 1 above, wherein the polycarbonate resin has a refractive index of 1.57 to 1.60 and an Abbe number of 27 to 31.

3. The imaging lens according to 1 or 2 above, wherein the film made of polycarbonate resin has an orientation birefringence of 2 × 10 ^-3 or less.

4. The imaging lens according to any one of items 1 to 3 above, wherein the polycarbonate resin has a refractive index of 1.58 to 1.59.

5. The imaging lens according to any one of items 1 to 4 above, wherein the polycarbonate resin has an Abbe number of 27.5 to 29.5.

6. The imaging lens according to any one of items 1 to 5 above, wherein the polycarbonate resin has a specific viscosity of 0.12 to 0.32.

7. The imaging lens according to any one of 1 to 6 above, wherein the polycarbonate resin has an absorption rate of 0.2% or less.

8. The imaging lens according to any one of 1 to 7 above, used in any of mobile phones, smartphones, tablet terminals, personal computers, digital cameras, video cameras, in-vehicle cameras, and surveillance cameras.

The resin used in the imaging lens of the present invention is 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene and 3,9-bis(1,1-dimethyl-2-hydroxyethyl). A polycarbonate resin for an imaging lens is obtained by copolymerizing 2,4,8,10-tetraoxaspiro[5.5]undecane at a specific composition ratio, and by using the resin, it has a specific refractive index and Abbe number, is low birefringent, and has low absorption. Since it becomes an imaging lens with , the industrial effect it exhibits is exceptional.

Hereinafter, the imaging lens of the present invention will be described sequentially and in detail.

<Polycarbonate resin>

The polycarbonate resin used in the imaging lens of the present invention has a refractive index of 1.57 to 1.60, more preferably 1.58 to 1.59, at a measurement temperature of 25°C and a measurement wavelength of 589 nm.

The polycarbonate resin used in the imaging lens of the present invention preferably has an Abbe number of 27.0 to 31.0 at a measurement temperature of 25°C, and more preferably 27.5 to 29.5. The Abbe number is calculated using the following formula from the refractive indices of measurement temperature: 25°C and measurement wavelength: 486 nm, 589 nm, and 656 nm.

ν = (nD-1)/(nF-nC)

nD: Refractive index at a wavelength of 589 nm

nC: Refractive index at wavelength 656 nm

nF: Refractive index at a wavelength of 486 nm

The polycarbonate resin used in the imaging lens of the present invention contains formulas (1) and (2).

[Formula 3]

[Formula 4]

The polycarbonate resin used in the imaging lens of the present invention contains 50 mol% or more but less than 70 mol% of formula (1), preferably 55 to 65 mol%, and more preferably 57 to 64 mol%. do. Moreover, it contains Formula (2) in an amount greater than 30 mol% but not more than 50 mol%, preferably 35 to 45 mol%, and more preferably 36 to 43 mol%.

The polycarbonate resin used in the imaging lens of the present invention contains repeating units represented by formulas (1) and (2), but may be copolymerized with other diol components to the extent that the characteristics of the present invention are not impaired. The other diol component is preferably 10 mol% or less based on the total repeating units. As other diol components, ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, tricyclo[5.2.1.0 ^2,6 ]decane dimethanol, cyclohexane-1,4- Dimethanol, decalin-2,6-dimethanol, norbornane dimethanol, pentacyclopentadecanedimethanol, cyclopentane-1,3-dimethanol, isosorbide, hydroquinone, resorcinol, 2,2-bis. (4-hydroxyphenyl)propane, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, bis(4-hyde) Roxyphenyl)diphenylmethane, 1,3-bis(2-(4-hydroxyphenyl)-2-propyl)benzene, bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl)sulfide, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)cyclohexane, biphenol, bisphenol fluorene, bisresol fluorene, etc. can be mentioned.

The polycarbonate resin used in the imaging lens of the present invention preferably has a specific viscosity in the range of 0.12 to 0.32, and more preferably in the range of 0.18 to 0.30. If the specific viscosity is 0.12 to 0.32, the balance between formability and strength is excellent.

The polycarbonate resin used in the imaging lens of the present invention has an absolute value of orientation birefringence (Δn) of preferably 0 to 6 × 10 ^-3 , more preferably 0 to 4 × 10 ^-3 , even more preferably The range is 0 to 2 × 10 ^-3 . Orientation birefringence (Δn) is measured at a wavelength of 589 nm when a cast film with a thickness of 100 μm obtained from the polycarbonate resin is stretched twice at Tg + 10°C.

The polycarbonate resin used in the imaging lens of the present invention has a total light transmittance of preferably 80% or more at a thickness of 1 mm, more preferably 85% or more, and even more preferably 88% or more.

The polycarbonate resin used in the imaging lens of the present invention preferably has a water absorption of 0.20% or less after immersion at 23°C for 24 hours, and is more preferably 0.17% or less.

The polycarbonate resin used in the imaging lens of the present invention preferably has a glass transition point of 120 to 160°C, and more preferably 125 to 150°C.

<Method for producing polycarbonate resin>

The polycarbonate resin used in the imaging lens of the present invention is produced by a reaction method known per se for producing a conventional polycarbonate resin, for example, a method of reacting a diol component with a carbonate precursor such as diester carbonate. do. Next, the basic means of these manufacturing methods will be briefly explained.

The transesterification reaction using carbonic acid diester as a carbonate precursor is carried out by heating and stirring a predetermined ratio of aromatic dihydroxy components with carbonic acid diester under an inert gas atmosphere, and distilling off the resulting alcohol or phenol. do. The reaction temperature varies depending on the boiling point of the produced alcohol or phenol, etc., but is usually in the range of 120 to 300°C. The reaction is completed under reduced pressure from the beginning while distilling off the produced alcohol or phenol. Additionally, end stoppers, antioxidants, etc. may be added as needed.

Examples of the carbonic acid diester used in the transesterification reaction include esters such as aryl groups and aralkyl groups having 6 to 12 carbon atoms which may be substituted. Specifically, diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl)carbonate, and m-cresyl carbonate are exemplified. Among them, diphenyl carbonate is particularly preferable. The amount of diphenyl carbonate used is preferably 0.95 to 1.10 mol, more preferably 0.98 to 1.04 mol, based on a total of 1 mol of the dihydroxy compound. In addition, in the melt polymerization method, a polymerization catalyst can be used to speed up the polymerization rate, and examples of such polymerization catalysts include alkali metal compounds, alkaline earth metal compounds, basic phosphorus compounds, nitrogen-containing compounds, and metal compounds. As such compounds, organic acid salts, inorganic salts, oxides, hydroxides, hydrides, alkoxides, quaternary ammonium hydroxides, etc. of alkali metals or alkaline earth metals are preferably used, and these compounds can be used individually or in combination. .

Alkali metal compounds include sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium hydroxide, sodium bicarbonate, sodium carbonate, potassium carbonate, cesium carbonate, lithium carbonate, sodium acetate, potassium acetate, cesium acetate, lithium acetate, sodium stearate, and stear. Potassium acid, cesium stearate, lithium stearate, sodium borohydride, sodium benzoate, potassium benzoate, cesium benzoate, lithium benzoate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate, disodium phenyl phosphate, bisphenol A Examples include disodium salt, dipotassium salt, dicesium salt, dilithium salt, sodium salt of phenol, potassium salt, cesium salt, and lithium salt.

Alkaline earth metal compounds include magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, calcium bicarbonate, barium bicarbonate, magnesium bicarbonate, strontium bicarbonate, magnesium diacetate, Examples include calcium acetate, strontium diacetate, and barium diacetate. Basic boron compounds include, for example, tetramethyl boron, tetraethyl boron, tetrapropyl boron, tetrabutyl boron, trimethylethyl boron, trimethylbenzyl boron, trimethylphenyl boron, triethylmethyl boron, triethylbenzyl boron, and triethyl. Sodium salts, potassium salts, lithium salts, calcium salts, barium salts, magnesium salts such as phenyl boron, tributylbenzyl boron, tributyl phenyl boron, tetraphenyl boron, benzyl triphenyl boron, methyl triphenyl boron, butyl triphenyl boron, etc. , or strontium salt, etc.

Basic phosphorus compounds include, for example, triethylphosphine, tri-n-propylphosphine, triisopropylphosphine, tri-n-butylphosphine, triphenylphosphine, tributylphosphine, or quaternary Phosphonium salts, etc. can be mentioned.

Examples of nitrogen-containing compounds include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and trimethylbenzylammonium hydroxide, which have an alkyl or aryl group, etc. Examples include graded ammonium hydroxides. Additionally, tertiary amines such as triethylamine, dimethylbenzylamine, and triphenylamine, and imidazoles such as 2-methylimidazole, 2-phenylimidazole, and benzoimidazole can be mentioned. Additionally, bases or basic salts such as ammonia, tetramethylammonium borohydride, tetrabutylammonium borohydride, tetrabutylammonium tetraphenyl borate, and tetraphenylammonium tetraphenyl borate are exemplified.

Examples of metal compounds include zinc aluminum compounds, germanium compounds, organic tin compounds, antimony compounds, manganese compounds, titanium compounds, and zirconium compounds. These compounds may be used alone or in combination of two or more types.

The amount of these polymerization catalysts used is preferably 1 × 10 ^-9 to 1 × 10 ^-2 equivalents, preferably 1 × 10 ^{-8 to 1 × 10 -3 equivalents, more preferably 1 × 10 -9} to 1 × 10 ^-3 equivalents, based on 1 mole of diol component. It is selected from the range of × 10 ^-7 to 1 × 10 ^-5 equivalent weight.

Additionally, if necessary, a catalyst deactivator may be added at a later stage of the reaction. Known catalyst deactivators are effectively used as catalyst deactivators, but ammonium salts and phosphonium salts of sulfonic acids are preferred. Furthermore, salts of dodecylbenzenesulfonic acid, such as tetrabutylphosphonium salt of dodecylbenzenesulfonate, and salts of paratoluenesulfonic acid, such as tetrabutylammonium salt of paratoluenesulfonic acid, are preferable.

Also, as esters of sulfonic acid, methyl benzenesulfonate, ethyl benzenesulfonate, butyl benzenesulfonate, octyl benzenesulfonate, phenyl benzenesulfonate, methyl p-toluenesulfonate, ethyl p-toluenesulfonate, butyl p-toluenesulfonate, octyl p-toluenesulfonate, phenyl p-toluenesulfonate. etc. are preferably used. Among them, tetrabutylphosphonium dodecylbenzenesulfonate salt is most preferably used.

When using at least one type of polymerization catalyst selected from alkali metal compounds and/or alkaline earth metal compounds, the amount of these catalyst deactivators used is preferably 0.5 to 50 moles per mole of the catalyst, more preferably 0.5 to 10 moles. It can be used in a molar ratio, more preferably in a molar ratio of 0.8 to 5 moles.

In addition, the polycarbonate resin of the present invention can be blended with additives such as heat stabilizers, plasticizers, light stabilizers, polymerized metal deactivators, flame retardants, lubricants, antistatic agents, surfactants, antibacterial agents, ultraviolet absorbers, and mold release agents, depending on the application or need. You can.

Additionally, depending on the application or need, additives such as heat stabilizers, plasticizers, light stabilizers, polymerized metal deactivators, flame retardants, lubricants, antistatic agents, surfactants, antibacterial agents, ultraviolet absorbers, and mold release agents can be added.

<Manufacturing method of imaging lens>

The imaging lens of the present invention can be molded and processed by any method such as injection molding, compression molding, injection compression molding, melt extrusion molding, or casting, and injection molding is particularly preferable.

The molding conditions for injection molding are not particularly limited, but the cylinder temperature of the molding machine is preferably 180 to 320°C, more preferably 220 to 300°C, and even more preferably 240 to 280°C. Moreover, the mold temperature is preferably 70 to 130°C, more preferably 80 to 125°C, and even more preferably 90 to 120°C. The injection pressure is preferably 50 to 1,700 kgf/cm2, more preferably 500 to 1,600 kgf/cm2, and more preferably 1,000 to 1,500 kgf/cm2.

The imaging lens of the present invention can be used in imaging lenses for smartphones, digital cameras, video cameras, etc.

Example

The present invention will be further explained below with reference to examples.

Examples 1 to 3, Comparative Examples 1 to 4

The evaluation was conducted according to the method described below.

(1) Specific viscosity: After completion of polymerization, the obtained polycarbonate resin was sufficiently dried, and the specific viscosity (ηsp) of the solution at 20°C was measured from a solution in which 0.7 g of the pellets were dissolved in 100 ml of methylene chloride.

(2) Copolymerization ratio: Measured using proton NMR of JNM-AL400 manufactured by Nippon Electronics. It was obtained from the integral ratio of the peak resulting from the structure of equation (1) around 7.6 to 7.8 ppm and the peak resulting from the structure of equation (2) around 0.8 to 1.1 ppm.

(3) Refractive index (nD), Abbe number (ν): The refractive index at 25°C of a circular plate with a thickness of 0.3 mm and ϕ5 mm obtained by injection molding using an Abbe refractometer made by ATAGO DR-M2. was measured. The Abbe number was calculated using the following formula from the refractive indices of the measurement wavelengths: 486 nm, 589 nm, and 656 nm.

ν = (nD-1)/(nF-nC)

nD: Refractive index at wavelength 589 nm

nC: Refractive index at wavelength 656 nm

nF: Refractive index at wavelength 486 nm

(4) Orientation birefringence (Δn): After dissolving the polycarbonate resin in methylene chloride, it was cast on a glass petri dish and thoroughly dried to produce a cast film with a thickness of 100 μm. The film was stretched twice at a glass transition point (Tg) + 10°C, the retardation (Re) at 589 nm was measured using an ellipsometer M-220 manufactured by Nippon Spectroscope Co., Ltd., and the orientation was obtained from the following formula: Birefringence (Δn) was determined. In addition, the glass transition point was measured using DSC-60A manufactured by Shimadzu Corporation at a temperature increase rate of 20°C/min.

Δn = Re/d

Δn: Orientation birefringence

Re: phase difference

d: thickness

(5) Water absorption: The plate-shaped molded piece obtained by injection molding was measured based on ISO62.

(6) Evaluation of optical deformation of the lens: Using a SE30DU injection molding machine manufactured by Sumitomo Heavy Industries Co., Ltd., at a cylinder temperature of 280°C and a mold temperature of 120°C, the thickness was 0.2 mm, the convex surface curvature radius was 5 mm, and the concave surface curvature radius was 4 mm. , an aspherical lens of Φ5 mm was injection molded. Optical deformation was evaluated by placing an aspherical lens between two polarizing plates and visually observing light leakage using the orthogonal Nicole method. Evaluation was conducted based on the following standards.

◎: Almost no light leakage.

○: Slight light leakage is recognized.

×: Light leakage is significant.

(7) Evaluation of moldability of the lens: The aspherical lens molded by the same method as (6) was visually confirmed for poor filling, molding defects, lens fragility, and presence or absence of mold attachments. In the evaluation, the probability of a defective product when 500 sheets were molded was classified as less than 1% (◎), less than 1 to 5% (○), less than 5 to 10% (△), and more than 10% (×).

[Example 1]

9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene (hereinafter abbreviated as BPEF) 110.50 parts, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)- 45.05 parts of 2,4,8,10-tetraoxaspiro[5.5]undecane (hereinafter abbreviated as SPG), 87.40 parts of diphenyl carbonate, and 8.00 × 10 ^-5 parts of sodium hydroxide as a catalyst, tetramethylammonium hydroxide 3.65 × 10 ^-3 parts of the side were placed in a reaction pot equipped with a stirrer and a distillation discharge device, and nitrogen substitution was performed three times, and then the jacket was heated to 180°C to melt the raw materials. After complete dissolution, the pressure was reduced to 20 kPa over 20 minutes, and the jacket was heated to 260°C at a rate of 60°C/hr to perform a transesterification reaction. After that, the pressure was reduced to 0.13 kPa over 80 minutes while the jacket was maintained at 260°C, and a polymerization reaction was performed for 30 minutes under conditions of 260°C and 0.13 kPa or less. After completion of the reaction, the produced polycarbonate resin was extracted while pelletizing, and polycarbonate resin pellets were obtained. Using the pellets, specific viscosity, copolymerization ratio, and orientation birefringence were measured, and the results are listed in Table 1. In addition, after drying the pellet at 110°C for 4 hours, a measurement piece was formed by injection molding, and the results of measurement of refractive index (nD), Abbe number (ν), water absorption, evaluation of optical deformation of the lens, and moldability of the lens are shown in Table 1. It is described in .

[Example 2]

Polycarbonate resin pellets were obtained in the same manner as in Example 1 except that BPEF was 105.24 parts and SPG was 48.70 parts. Using the pellet, measurements were made in the same manner as in Example 1, and the results are listed in Table 1.

[Example 3]

Polycarbonate resin pellets were obtained in the same manner as in Example 1 except that BPEF was 98.22 parts and SPG was 53.57 parts. Using the pellet, measurements were made in the same manner as in Example 1, and the results are listed in Table 1.

[Example 4]

Polycarbonate resin pellets were obtained in the same manner as in Example 1 except that BPEF was 87.70 parts and SPG was 60.88 parts. Using the pellet, measurements were made in the same manner as in Example 1, and the results are listed in Table 1.

[Comparative Example 1]

Polycarbonate resin pellets were obtained by the method described in Example 17 of Japanese Patent No. 3160209. Using the pellet, measurements were made in the same manner as in Example 1, and the results are listed in Table 1. When evaluating lens formability, lens cracks and sprue bends occurred frequently, indicating that formability was poor.

[Comparative Example 2]

Polycarbonate resin pellets were obtained in the same manner as in Example 1 except that BPEF was 52.62 parts and SPG was 85.23 parts. Using the pellet, measurements were made in the same manner as in Example 1, and the results are listed in Table 1.

[Comparative Example 3]

Measurements were made in the same manner as in Example 1 using polycarbonate resin AD-5503 manufactured by Teijin Co., Ltd., and the results are shown in Table 1.

[Comparative Example 4]

Polycarbonate resin pellets were obtained by the method described in Example 3 of Japanese Patent No. 5217644. That is, 50.0 parts of Eupilon H-4000 (manufactured by Mitsubishi Engineering Plastics Co., Ltd.) as a polycarbonate resin and 50.0 parts of Dyrak D-232 (manufactured by Nova Chemical Co., Ltd.) as a styrene resin are mixed in an extruder at 255°C. It was kneaded and pelletized to obtain pellets of a resin composition for optical lenses.

Using the pellet, measurements were made in the same manner as in Example 1, and the results are listed in Table 1.

The imaging lens of the present invention has a specific refractive index, Abbe number, low birefringence, and low absorption, so it can be used for imaging with mobile phones, smartphones, tablet terminals, personal computers, digital cameras, video cameras, in-vehicle cameras, surveillance cameras, etc. It is very useful because it can be used on lenses.

Claims (8)

An imaging lens made of polycarbonate resin containing formula (1) and formula (2) in the ratio of the following formula,
50 mol% ≤ (1) < 70 mol%
30 mol% < (2) ≤ 50 mol%
[Formula 1]

[Formula 2]

The specific viscosity of the polycarbonate resin is 0.12 to 0.32,
An imaging lens having an orientation birefringence of 0.7 × 10 ^-3 or less at a wavelength of 589 nm when a film made of polycarbonate resin is stretched twice at Tg + 10°C. According to claim 1,
An imaging lens in which the polycarbonate resin has a refractive index of 1.57 to 1.60 and an Abbe number of 27 to 31. delete The method of claim 1 or 2,
An imaging lens whose refractive index of polycarbonate resin is 1.58 to 1.59. The method of claim 1 or 2,
An imaging lens made of polycarbonate resin with an Abbe number of 27.5 to 29.5. delete The method of claim 1 or 2,
An imaging lens with a polycarbonate resin absorption rate of 0.2% or less. The method of claim 1 or 2,
Imaging lenses used in any of mobile phones, smartphones, tablet terminals, personal computers, digital cameras, video cameras, in-vehicle cameras, and surveillance cameras.