JP6683520B2 - Inner lens - Google Patents

Description

  The present invention relates to an inner lens.

The methacrylic resin composition is characterized by having higher light transmittance, weather resistance and rigidity than other plastic transparent resins as a transparent resin, and has been conventionally suitably used for outer lenses of tail lamps and the like.
On the other hand, in recent years, the number of headlamps having a structure using an inner lens (also referred to as a projector lens) is increasing (for example, refer to Patent Documents 1 to 6 below).
The "inner lens" is disposed on the front side of the light source bulb and has a focal point in the vicinity of the light emitting portion of the light source bulb, and receives direct light from the light source bulb to control light distribution. It refers to a lens component for emitting light to the lens side, that is, the outer lens side.

  Similar to the outer lenses of tail lamps, these inner lenses are required to have high light transmittance and weather resistance, so glass has been mainly used as a material from the past, but in recent years, productivity efficiency has been improved. From the viewpoint of the above, and from the viewpoint of the degree of design freedom that the portion for fixing the lens portion and other parts can be integrally molded, a methacrylic resin composition, particularly an acrylic resin (PMMA) is used. The reason why the methacrylic resin composition is selected among many resins is that it has high light transmittance and weather resistance, like glass. The injection molding method is usually selected as the molding method for the inner lens.

JP-A-10-003805 JP 2001-110212 A JP-A-2002-140906 JP, 2004-030985, A JP, 2007-053053, A JP, 2013-093105, A

However, the inner lens, particularly the inner lens for automobile headlamps, usually has a lens thickness of more than 10 mm and is thick. Therefore, when this is molded by injection molding, a molding cycle, especially a cooling time becomes long. have.
Further, since the methacrylic resin composition undergoes volume contraction during solidification, a vacuum void is generated in the molded product, or a dent called a sink mark is generated on the surface of the molded product, which is particularly thick. It also has a problem that it tends to occur in meat molded products.
The defective molding phenomenon such as the vacuum void and the sink mark described above causes the deterioration of the characteristics as a precise optical member such as a lens, and becomes a defect.

As a method for preventing the extension of the molding cycle as described above, for example, in selecting the grade of the methacrylic resin composition, a high flow type, that is, a low viscosity type is selected, and the resin temperature at the time of injection molding is set to be low. There is a method of setting and corresponding.
However, this method has the following problems.
For the high flow type grade, a method of lowering the viscosity is adopted by lowering the molecular weight of the methacrylic resin constituting it or by increasing the proportion of the comonomer amount of the methacrylic resin.
In the former method of lowering the molecular weight of the methacrylic resin to be constituted, the fluidity is improved, but the entanglement of the polymer is reduced, and thus there is a problem that the toughness is lowered. For this reason, sufficient design consideration should be given to the design of the parts to be fixed to other parts that are integrally molded with the lens described above, specifically thickening to increase the section modulus, corners of the molded product, etc. It is indispensable to give consideration to the design, such as attaching a corner R or C surface to a portion. For this reason, there is a problem that the design of the molded product is extremely restricted.
In addition, the latter method of increasing the proportion of comonomer amount of the methacrylic resin is to lower the glass transition point of the methacrylic resin that constitutes it to improve the fluidity, so inevitably in exchange for improved fluidity, heat resistance. It has a problem of causing a decrease. This decrease in heat resistance may not provide practically sufficient characteristics for automobile parts that are supposed to be used in a high temperature environment.

  Therefore, in the present invention, the occurrence of vacuum voids and sink marks is sufficiently suppressed, practically sufficient optical characteristics can be exhibited, and an inner lens having sufficient strength and heat resistance even in a portion for fixing with other parts is provided. The challenge is to provide.

As a result of intensive studies to solve the above-mentioned problems of the prior art, the inventors have solved the above-mentioned problems of the prior art by using a methacrylic resin composition having a specific range of pseudoplasticity (thixotropy). They have found that they can be solved and have solved the problems of the prior art.
That is, the present invention is as follows.

[1]
An inner lens for a headlamp, which is obtained by injection molding a methacrylic resin composition containing a methacrylic resin,
The methacrylic resin composition,
Based on JIS K7210: 1999, a load of 3.80 kgf, a melt mass flow rate value a (g / 10 min.) Measured at a test temperature of 230 ° C., and a load of 10.19 kgf,
The value b (g / 10 min.) Of melt mass flow rate measured at a test temperature of 230 ° C.
An inner lens satisfying the conditions of the following formulas (1) and (2).
5.0 <b / a ... (1)
0.4 <a <2.0 ... (2)
[2]
The methacrylic resin is
Methacrylic acid ester monomer unit 80-99.9 mass%,
0.1 to at least one other vinyl monomer unit copolymerizable with methacrylic acid ester
20% by mass,
The inner lens according to the above [1], which comprises:
[3]
The methacrylic acid ester is
The inner lens according to the above [2], which is methyl methacrylate and / or ethyl methacrylate.
[4]
The other vinyl monomer copolymerizable with the methacrylic acid ester,
The inner lens according to the above [2] or [3], which is methyl acrylate and / or ethyl acrylate.
[5]
The inner lens as described in any one of [1] to [4] above, wherein the thickness of the central portion of the inner lens in the optical axis direction is 10 mm or more.
[6]
The inner lens as described in any one of [1] to [5] above, wherein the inner lens has a one-point gate in the peripheral portion and the gate thickness is 3 mm or less.

  According to the present invention, vacuum voids and sink marks generated by molding shrinkage are reduced, practically sufficient optical performance is obtained, and sufficient strength and heat resistance are obtained even in a portion for fixing with other parts. It is possible to obtain an inner lens having the same.

The schematic side view of an example of the inner lens of this embodiment is shown. The schematic perspective view of the rectangular parallelepiped molded article used in the characteristic evaluation of an Example and a comparative example is shown.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail, but the present invention is not limited to the following description and within the scope of the gist thereof. Various modifications can be implemented.

[Inner lens for headlamp]
The inner lens of this embodiment is
An inner lens for a headlamp, which is obtained by injection molding a methacrylic resin composition containing a methacrylic resin,
The methacrylic resin composition,
Melt mass flow rate value a (g / 10 min.) Measured at a load of 3.80 kgf and a test temperature of 230 ° C. based on JIS K7210: 1999, and melt mass flow rate value measured at a load of 10.19 kgf and a test temperature of 230 ° C. b (g / 10 min.) satisfies the conditions of the following formulas (1) and (2).
5.0 <b / a ... (1)
0.3 <a <15 ... (2)

The “inner lens” in the present embodiment is disposed on the front side of the light source bulb, and the focal point is located in the vicinity of the light emitting portion of the light source bulb. It refers to a lens component that is controlled to emit light to the lens side, that is, the outer lens side.
Typical examples of such "inner lens" include inner lenses for use in automobile headlamps, but also for headlights for motorcycles and bicycles, and inner lenses for use in projector lamps of office automation equipment. Can be mentioned.

The inner lens for the headlamp of this embodiment is also called a projector lens, and as described in the above-mentioned prior art document, an optical component installed and used in front of a halogen lamp, an HID lamp, an LED lamp, or the like. Is.
Since the inner lens of the present embodiment is an optical component, it needs to have a high light transmittance, and since it is expected to be widely used outdoors, it must have high weather resistance. High heat resistance is also required.

Usually, the inner lens often has a thickness of 10 mm or more in the optical axis direction at the center of the lens, and a preferable example of the inner lens of the present embodiment is 10 mm or more.
By targeting a lens in which the thickness of the central part of the lens in the optical axis direction is 10 mm or more, the inner lens having the configuration of the present embodiment can exhibit a more remarkable effect of improving the characteristics.

(Pseudoplasticity of methacrylic resin composition)
The inner lens of the present embodiment is obtained by injection molding a methacrylic resin composition containing a methacrylic resin.
This methacrylic resin composition is required to have high fluidity, high heat resistance, and high toughness in order to solve the problems of the prior art, but these have properties that are in a mutually contradictory relationship. Is.
However, the present inventor has found that the use of the methacrylic resin composition having the following pseudo-plasticity in a specific range satisfies all the above-mentioned contradictory relationships.
The specific range is, for example, a melt mass flow rate value a (g / 10 min.) Measured at a load of 3.80 kgf and a test temperature of 230 ° C. based on JIS K7210: 1999, a load of 10.19 kgf, and a test temperature of 230 ° C. The value b (g / 10 min.) Of the melt mass flow rate measured in 1. satisfies the conditions of the following formulas (1) and (2).
5.0 <b / a ... (1)
0.3 <a <15 ... (2)

  The value of b / a in the above formula (1) is one index showing the pseudoplasticity of the molten resin which is a non-Newtonian fluid, that is, a parameter which is a measure of the ratio of the viscosity at low shear and the viscosity at high shear. It is indicated that the larger the value of b / a, the greater the degree of decrease in viscosity due to shearing force.

  In the present embodiment, the magnitude of the parameters is particularly important, and as a result of earnest studies, it has been found that when the value of b / a exceeds 5.0, they conflict with each other such as high fluidity, high heat resistance and high toughness. At the same time, the characteristics that have the relationship of

Further, in the formula (2), by setting a> 0.3, sufficient fluidity can be obtained to suppress vacuum voids and sink marks.
Further, a <15 means that the region where a is 15 or more cannot be reached unless the molecular weight is considerably reduced, and when the molecular weight is such that a is 15 or more, sufficient toughness and mechanical properties are obtained. However, since a <15, practically sufficient toughness and mechanical strength can be obtained, and practically also in the part for fixing with other parts attached to the inner lens. Sufficient strength is obtained.
In addition, in order to satisfy the range of 0.3 <a <15, and further to satisfy the relationship of 5.0 <b / a, which is necessary for achieving both fluidity and long-term characteristics, pseudoplasticity of the molten resin is required. Is increased, that is, it is effective to obtain a methacrylic resin composition having a broadened molecular weight distribution.

The methacrylic resin composition used for the inner lens of the present embodiment has 0.3 <a <15, preferably 0.4 <a <2.0, and 0.5 <a <1.0. More preferably.
Further, 5.0 <b / a is preferable, 5.1 <b / a is preferable, and 5.8 <b / a is more preferable.

  As a method for broadening the molecular weight distribution of the methacrylic resin composition, for example, as disclosed in WO 2007/60891, methacrylic resins having extremely different molecular weights are continuously added in one polymerization reaction tank. Examples of the method include suspension polymerization. The values of a and b / a can be controlled by adjusting the molecular weight of each methacrylic resin.

In addition, as another method for obtaining the methacrylic resin composition having a broadened molecular weight distribution as described above, continuous bulk polymerization or continuous solution polymerization method may be used in which two or more polymerization reaction tanks arranged in parallel are used to measure the molecular weight Another method is to polymerize different methacrylic resins, combine the polymerization solutions in which the respective polymers are dissolved and mix them, and then remove the solvent and unreacted monomers to obtain the polymers.
Examples of the polymerization apparatus in which two or more polymerization reaction tanks are arranged in parallel include the apparatuses described in JP2012-153805A and JP2012-153807A.
Further, as another method for obtaining a methacrylic resin composition having a broadened molecular weight distribution as described above, a continuous bulk polymerization or a continuous solution polymerization method is used, in which two or more polymerization reaction tanks arranged in series are used to control the molecular weight A method of continuously polymerizing different methacrylic resins may also be mentioned.
An example of a polymerization apparatus in which two or more polymerization reaction tanks are arranged in series is an apparatus described in JP 2012-102190 A.
Furthermore, as another method of obtaining a methacrylic resin composition having a broadened molecular weight distribution as described above, a method of compounding two or more kinds of methacrylic resin compositions having different molecular weights with an extruder or the like, in a reactor And the like, and a method of carrying out the polymerization with a temperature gradient, a monomer concentration gradient, a catalyst system concentration gradient, and combinations thereof.
The values of a and b / a can be controlled by producing a methacrylic resin by using the various methods described above.

Further, as a method of controlling the values of a and b / a, the temperature condition and the discharge amount at the time of methacrylic resin composition extrusion at the time of manufacturing the inner lens of the present embodiment are adjusted, and at the time of injection molding. The method of adjusting the molding temperature and the molding residence time in step 1 is also effective.
Specifically, the temperature condition during extrusion is 300 ° C. or lower, and / or the discharge rate is 3 kg / hr. The above is preferable. Further, at the time of molding, the molding temperature is preferably 290 ° C. or lower, and / or the molding residence time is preferably 15 minutes or shorter.
By setting the temperature conditions at the time of extrusion, the discharge amount of the methacrylic resin composition, the molding temperature at the time of injection molding, and the molding residence time within the above ranges, the values of a and b / a are appropriately defined in this embodiment. The methacrylic resin composition can be controlled to various ranges, and the methacrylic resin composition can be prevented from discoloring, and excellent appearance characteristics peculiar to the methacrylic resin composition can be obtained.

(Composition of methacrylic resin composition)
The inner lens of the present embodiment is an injection-molded methacrylic resin composition, and the methacrylic resin composition contains a methacrylic resin.
The methacrylic resin contains 80 to 99.9% by mass of a methacrylic acid ester monomer unit and 0.1 to 20% by mass of another vinyl monomer unit copolymerizable with at least one methacrylic acid ester. It is preferable that it is toxic.

Examples of the methacrylic acid ester monomer include, but are not limited to, butyl methacrylate, ethyl methacrylate, methyl methacrylate, propyl methacrylate, isopropyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, and methacrylic acid. Examples thereof include acid (2-ethylhexyl), methacrylic acid (t-butylcyclohexyl), benzyl methacrylate, and methacrylic acid (2,2,2-trifluoroethyl). From the viewpoint of easy availability and price, methyl methacrylate and ethyl methacrylate are preferable.
The said methacrylic acid ester monomer may be used individually by 1 type, or may be used in combination of 2 or more type.
The methacrylic resin contained in the methacrylic resin composition preferably has a methacrylic acid ester monomer unit content of 99.9% by mass or less. When the content of the methacrylic acid ester monomer unit is 99.9% by mass or less, decomposition of the resin at the time of molding can be prevented, generation of a methacrylic acid ester monomer that is a volatile component and molding failure called silver. Can be effectively prevented.
Further, when the methacrylic acid ester monomer unit is 80% by mass or more, the heat resistance generally required for the molded article can be secured.
By having sufficient heat resistance, rigidity can be ensured, and reduction of the bonding force at the joint can be effectively prevented especially at high temperature.
The content of the methacrylic acid ester monomer unit is more preferably 90 to 99.8% by mass, further preferably 94 to 99.8% by mass.

The vinyl monomer copolymerizable with the methacrylic acid ester monomer is not limited to the following, and examples thereof include methyl acrylate, ethyl acrylate, n-propyl acrylate, and n-acrylate. Examples thereof include acrylic acid ester monomers having one acrylate group such as butyl, sec-butyl acrylate, and 2-ethylhexyl acrylate.
In addition, ethylene glycol such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene glycol di (meth) acrylate having two or more (meth) acrylate groups. Or, the both-end hydroxyl groups of its oligomer are esterified with acrylic acid; the two hydroxyl groups of neopentyl glycol di (meth) acrylate, di (meth) acrylate, etc. are esterified with acrylic acid; trimethylolpropane , An ester of a polyhydric alcohol derivative such as pentaerythritol esterified with acrylic acid;
In particular, methyl acrylate, ethyl acrylate, and n-butyl acrylate are preferable, and methyl acrylate and ethyl acrylate are more preferable because they are easily available.
These may be used alone or in combination of two or more.
The content of the other vinyl monomer unit copolymerizable with the methacrylic acid ester monomer is preferably 0.1% by mass or more, and when it is 0.1% by mass or more, it is It is possible to prevent the resin from decomposing, and it is possible to effectively prevent the generation of a methacrylic acid ester monomer as a volatile component and a defective molding called silver. Further, when the vinyl monomer unit is 20% by mass or less, heat resistance generally required for a molded article can be secured.
By having sufficient heat resistance, rigidity can be ensured, and reduction of the bonding force at the joint can be effectively prevented especially at high temperature.
The content of the other vinyl monomer unit copolymerizable with the methacrylic acid ester monomer is more preferably 0.1 to 18% by mass, further preferably 0.2 to 16% by mass. .

  The vinyl monomer other than the acrylic acid ester monomer copolymerizable with the methacrylic acid ester monomer is not limited to the following, and examples thereof include acrylic acid and methacrylic acid. Α, β-unsaturated acids; unsaturated group-containing divalent carboxylic acids such as maleic acid, fumaric acid, itaconic acid, cinnamic acid and their alkyl esters; styrene, o-methylstyrene, m-methylstyrene, p- Methyl styrene, 2,4-dimethyl styrene, 2,5-dimethyl styrene, 3,4-dimethyl styrene, 3,5-dimethyl styrene, p-ethyl styrene, m-ethyl styrene, o-ethyl styrene, p-tert- Styrene-based monomers such as butylstyrene and isopropenylbenzene (α-methylstyrene); 1-vinylnaphthalene, 2-vinylnaphthalene, , 1-diphenylethylene, isopropenyltoluene, isopropenylethylbenzene, isopropenylpropylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, isopropenylhexylbenzene, isopropenyloctylbenzene and other aromatic vinyl compounds; acrylonitrile, methacrylonitrile Cyanide vinyl compounds such as; unsaturated carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; maleimide, N-methylmaleimide, N-ethylmaleimide, N-phenylmaleimide, N-cyclohexylmaleimide and other N- Examples include substituted maleimides; amides such as acrylamide and methacrylamide; and polyfunctional monomers such as divinylbenzene.

The methacrylic resin may be copolymerized by appropriately adding a vinyl monomer other than the above-exemplified vinyl monomers for the purpose of improving properties such as heat resistance and processability.
The acrylic acid ester monomer copolymerizable with the methacrylic acid ester monomer and vinyl monomers other than the acrylic acid ester monomer exemplified above may be used alone or in combination. You may use it in combination of 2 or more types.

  The methacrylic resin contained in the methacrylic resin composition can be produced by a bulk polymerization method, a cast polymerization method, or a suspension polymerization method, but is not limited to these methods.

(Components that can be mixed with the methacrylic resin composition)
<Other resins>
The methacrylic resin composition may be mixed with other conventionally known resins within a range that does not impair the effects of the present invention, particularly within a range that does not impair the transparency of the inner lens.
The other resin is not particularly limited, and a known curable resin or thermoplastic resin is preferably used.

<Additives>
Various additives may be mixed in the methacrylic resin composition in order to impart predetermined various properties such as weather resistance and releasability to the extent that the effects of the present embodiment are not impaired.
Examples of additives that can be used include, but are not limited to, phthalic acid ester-based, fatty acid ester-based, trimellitic acid ester-based, phosphoric acid ester-based, polyester-based plasticizers; higher fatty acids, higher fatty acids Releasing agent such as fatty acid ester, higher fatty acid mono-, di-, or triglyceride type; antistatic agent such as polyether type, polyether ester type, polyether ester amide type, alkyl sulfonate, alkylbenzene sulfonate, etc .; oxidation Stabilizers such as inhibitors, UV absorbers, heat stabilizers, light stabilizers; flame retardants, lubricants, impact imparting agents, slidability improvers, compatibilizers, flow control agents, dyes, sensitizers, coloring Pigments, rubbery polymers, antibacterial and antifungal agents, antifouling agents and the like.

Further, the ultraviolet absorber is not limited to the following, for example, benzotriazole compounds, benzotriazine compounds, benzoate compounds, benzophenone compounds, oxybenzophenone compounds, phenol compounds, oxazole compounds. Examples thereof include compounds, malonic acid ester-based compounds, cyanoacrylate-based compounds, lactone-based compounds, salicylic acid ester-based compounds, benzoxazinone-based compounds, and the like, with benzotriazole-based compounds and benzotriazine-based compounds being preferred.
These may be used alone or in combination of two or more.
The melting point (Tm) of the ultraviolet absorber is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, further preferably 130 ° C. or higher, still more preferably 160 ° C., from the viewpoint of preventing thermal deformation of the molded product. That is all.
The ultraviolet absorber preferably has a mass reduction rate of 50% or less when heated from 23 ° C. to 260 ° C. at a rate of 20 ° C./min, from the viewpoint of preventing the occurrence of molding defects such as silver in a molded product. It is more preferably 30% or less, still more preferably 15% or less, even more preferably 10% or less, still more preferably 5% or less.

In the methacrylic resin composition for obtaining the inner lens of the present embodiment, the content of the above-mentioned other resins and additives is to maintain the transparency of the methacrylic resin composition and prevent molding defects such as bleed-out. From the viewpoint of 100 parts by mass of the methacrylic resin composition, 0 to 60 parts by mass is preferable, 0.01 to 34 parts by mass is more preferable, and 0.02 to 25 parts by mass is further preferable.
When the content is within the above numerical range, the function of each material can be exhibited.

[Method for producing methacrylic resin composition]
The methacrylic resin composition, which is a raw material for the inner lens of the present embodiment, is obtained by mixing and kneading the methacrylic resin, the various additives described above, and other predetermined resins.
For example, it can be produced by kneading using a kneader such as an extruder, a heating roll, a kneader, a roller mixer, a Banbury mixer.
In particular, kneading with an extruder is preferable from the viewpoint of productivity.
The kneading temperature may be in accordance with the preferable processing temperature of the methacrylic resin composition, and is preferably in the range of 140 to 300 ° C, more preferably 180 to 280 ° C.

Various injection molding methods can be applied to the method of molding the methacrylic resin composition to obtain the inner lens of the present embodiment. Further, for example, a special molding method other than the usual injection molding method such as an injection compression molding method and an ultra-high speed injection molding method can be applied.
FIG. 1 shows a schematic side view of an example of the inner lens of the present embodiment.
The inner lens of FIG. 1 includes a lens portion 1 and a portion 2 for fixing to other parts.
The inner lens of the present embodiment has pseudoplasticity of the methacrylic resin composition even when the inner lens in which the lens portion 1 and the portion 2 are integrated is injection-molded using the methacrylic resin composition. By specifying as described above, good fluidity and moldability can be obtained, and practically sufficient strength can be obtained even in the portion 2 for fixing to other parts.

In the inner lens of the present embodiment, it is preferable that the inner lens has a one-point gate in the peripheral portion and the gate thickness is 3 mm or less.
It is not preferable to directly install the gate on the lens, which is a thick portion, because defective molding due to jetting may occur and the defective molding rate may increase. Furthermore, since the molding strain tends to be larger near the gate than other parts in the molded product, the optical characteristics such as birefringence may be affected, and the function as an optical member is reduced. There is a possibility that it will end. Therefore, the defective molding can be effectively reduced by disposing the gate on the peripheral portion of the inner lens.
Further, by using the one-point gate, the effect that the weld line is not formed on the molded product can be obtained.
Since the weld line may reduce the optical characteristics and the product strength of the molded product, the effect of improving the optical characteristics and the product strength can be obtained by not forming the weld line.
The thicker the gate is, the more sufficient resin pressure is applied to the cavity in the mold during injection molding, and as a result, the effect of suppressing sink marks or voids can be obtained. However, if it is too thick, it becomes difficult to cut the sprue runner from the peripheral portion, that is, the gate cut. Therefore, the thicker is not preferable. As described above, by setting the gate thickness to 3 mm or less, it is possible to suppress the occurrence of sink marks and the occurrence of voids, and to make the balance of the ease of gate cutting good.

[Use of inner lens]
The inner lens of the present embodiment can be preferably used as a part for a headlamp, but is particularly suitable as an inner lens for a headlamp of an automobile, and also has a similar structure, that is, the light of a light source is used as an inner lens. It can be used as various lamp parts that collect light with a lens.
For example, headlights for motorcycles and bicycles other than automobiles, projector lamps for OA equipment, etc. may be mentioned.

  Hereinafter, the present embodiment will be described with reference to specific examples and comparative examples, but the present embodiment is not limited to the examples described below.

[1. Pseudoplasticity; melt mass flow rate (MFR) measurement under different loading conditions]
A rectangular parallelepiped molded product (100 mm × 40 mm × 20 mm) was manufactured using the resin pellets manufactured in Examples and Comparative Examples described later.
The rectangular parallelepiped molded product (100 mm × 40 mm × 20 mm) was finely crushed using a precision cut saw and a nipper, and dried under a reduced pressure condition of 80 ° C. for 24 hours to obtain a measurement sample.
Using the measurement sample, the melt mass flow rate value a (g / 10 min.) Measured at a load of 3.80 kgf and a test temperature of 230 ° C. based on JIS K7210: 1999, and among the measurement conditions, only the load condition was 10 Melt mass flow rate value b (g / 10 min.) Measured as 0.19 kgf was measured, and b / a was calculated.
The measurement results are shown in Table 3 below.

[2. Heat resistance; Measurement of glass transition temperature (Tg)]
Similar to the measurement of the pseudoplasticity, a rectangular parallelepiped molded product (100 mm × 40 mm × 20 mm) was manufactured using the resin pellets manufactured in Examples and Comparative Examples described later.
This direct molded article (100 mm × 40 mm × 20 mm) was finely crushed with a precision cut saw and nippers, and dried under reduced pressure at 80 ° C. for 24 hours to obtain a measurement sample.
The measurement is carried out by Tg measurement in accordance with the DCS method which is an evaluation method used in Identification (ID) certification with UL standard Follow Up Service (FUS), and a glass transition point of 110 ° C. which is one of the heat resistance is measured. It was confirmed whether or not it exceeded. Those having a glass transition point of more than 110 ° C. are indicated by ◯, and those not exceeding 110 ° C. are indicated by x, which are shown in Table 3 below.

[3. Strength; measurement of tensile modulus and tensile breaking strain]
After drying the resin pellets manufactured in Examples and Comparative Examples described below at 80 ° C. for 24 hours, a test piece (dumbbell test piece) for a tensile test based on the ISO standard was molded, and ISO 527-2 / 1A / 1. And tensile elastic modulus and tensile breaking strain were measured based on ISO 527-2 / 1A / 5.
The use of a methacrylic resin composition having these high values is suitable because it can exhibit sufficient strength in the portion 2 for fixing to other parts when used as a molding material for the inner lens part illustrated in FIG. I decided.
It was confirmed whether the tensile modulus, which is a measure of the required strength, exceeds 3000 MPa and the tensile breaking strain exceeds 5%.
And, those which exceeded each were represented by O, and those which did not exceed were represented by X, and are shown in Table 3 below.

[4. Evaluation of molded products; measurement of sink marks, confirmation of vacuum voids)
After drying the resin pellets manufactured in Examples and Comparative Examples described later at 80 ° C. for 24 hours, a rectangular parallelepiped molded product (100 mm × 40 mm × 20 mm) shown in FIG. 2 was injection-molded under the same conditions shown below.
<Injection conditions>
Resin temperature: 230 ℃
Mold temperature: 120 ℃
Holding pressure: 110 MPa
Priority time: 56 seconds Cooling time: 900 seconds And the amount of sink marks generated on the surface of 100 mm x 40 mm of the rectangular parallelepiped molded article, that is, the total value of the amount of sink marks on both the front surface 4 and the back surface is measured, and The presence or absence of vacuum voids generated inside the molded product was confirmed.
Regarding the amount of sink marks, those in which the total value on both the front and back sides did not exceed 2000 μm were expressed as ◯, and those in which the total value exceeded 2000 μm as x.
Regarding the vacuum voids, those that were not observed were represented by O, and those that were observed were represented by X.
The evaluation results are shown in Table 3 below.
The evaluation of this rectangular parallelepiped molded product is a model experiment performed in place of the inner lens shown in FIG. 1. Since it can be assumed that the thickness of the central part of the lens is 3 in the optical axis direction, it was judged to be effective for the effect verification, and was used as the verification method in this example and the comparative example.
That is, if it was possible to reduce the amount of sink marks and the vacuum voids by this evaluation method, it was judged that the same effect could be expected with an actual inner lens.

The method for producing the methacrylic resin will be described below.
The blending amounts are shown in Table 1 and Table 2.

The abbreviations in Tables 1 and 2 indicate the following compounds.
MMA; methyl methacrylate, MA; methyl acrylate, LPO; lauroyl peroxide, 2EHTG; 2-ethylhexyl thioglycolate, NOM; n-octyl mercaptan

[Example 1]
<Polymerization of methacrylic resin>
The methacrylic resin was polymerized by a suspension polymerization method.
First, as the preparation of the suspension agent, 2 kg of water, 65 g of tricalcium phosphate, 39 g of calcium carbonate and 0.39 g of sodium lauryl sulfate were added to a 5 L container having a stirrer, and the suspension agent was prepared by stirring and mixing them. did.
Next, 25 kg of water was charged into a 60 L reactor and the temperature was raised to 80 ° C. to prepare for suspension polymerization. After confirming that the temperature reached 80 ° C. and became a constant temperature state, as a polymerization raw material, the raw material described in the column of polymer (I) of resin 1 in the following Table 1 and the total amount of the suspending agent were added to a 60 L reactor. It was put in and stirred.
Then, when suspension polymerization was carried out at about 80 ° C., an exothermic peak was observed 80 minutes after the raw materials and the suspending agent were added. After confirming the exothermic peak, the temperature was raised to 92 ° C at a rate of 1 ° C / min, the temperature was maintained at 92 ° C to 94 ° C for 30 minutes, and then the temperature was lowered to 80 ° C at a rate of 1 ° C / min.
After confirming that the temperature reached 80 ° C., 2.5 g of ADEKA ADEKA STAB LA-32 manufactured by ADEKA Co., Ltd. as a UV absorber was added to the raw materials described in the column of polymer (II) of resin 1 in Table 1 below as a lubricant. What added 10g of Calcol 8098 by Kao Co., Ltd. was thrown in to the same reactor additionally, and suspension polymerization was continuously performed maintaining about 80 degreeC.
An exothermic peak was observed 105 minutes after the starting material for the polymer (II) was charged.
After confirming the exothermic peak, the temperature was raised to 92 ° C at a rate of 1 ° C / min, and the temperature was maintained at 92 ° C for 60 minutes.
Then, after cooling to 50 ° C., 20 mass% sulfuric acid was added to dissolve the suspending agent.
Then, the polymerization reaction solution was taken out of the 60 L reactor, passed through a sieve with a sieve opening of 1.68 mm to remove a huge aggregate, and then the aqueous layer and the solid matter were separated with a Buchner funnel to obtain a bead-shaped polymer.
The bead-like polymer was washed 5 times with about 20 L of distilled water on a Buchner funnel and then dried in a steam oven to obtain fine polymer particles corresponding to Resin 1.
<Granulation>
The obtained polymer fine particles were discharged at a discharge rate of 9.8 kg / hr. , Melted and kneaded with a vented twin-screw extruder having a pressure reduction degree of 0.05 MPa and a barrel temperature of 240 ° C., and the strand was cooled and cut at a cooling bath temperature of 45 ° C. to obtain resin pellets corresponding to the resin 1. Obtained.
<Evaluation>
The above-mentioned evaluations (1. pseudoplasticity, 2. heat resistance, 3. strength, 4. evaluation of molded product) were carried out using the resin pellets of the above resin 1. The results are shown in Table 3 below.

[Examples 2 to 4]
In Examples 2 to 4, the contents of Resins 2 to 4 in Table 1 below were respectively polymerized in the same manner as in Example 1 to obtain polymer fine particles corresponding to Resins 2 to 4.
Further, resin pellets were obtained by granulating in the same manner as in Example 1, and a test piece for a tensile test based on ISO standard and a rectangular parallelepiped molded article were manufactured, and each evaluation was performed.
The results are shown in Table 3 below.

[Comparative Example 1]
2 kg of water, 65 g of tricalcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate were charged into a 5 L container having a stirrer, and they were mixed and stirred to prepare a suspension agent.
Next, 26 kg of water was charged into a 60 L reactor and the temperature was raised to 80 ° C. to prepare for suspension polymerization.
After confirming that the temperature reached 80 ° C. and reached a constant temperature, each raw material shown in Table 2 below as a polymerization raw material and the suspension agent were charged into a 60 L reactor.
After that, suspension polymerization was carried out at about 80 ° C., an exothermic peak was observed, then the temperature was raised to 92 ° C. at a rate of 1 ° C./min, and the temperature was kept at 92 ° C. for 60 minutes.
Then, after cooling to 50 ° C., 20 mass% sulfuric acid was added to dissolve the suspending agent.
Then, the polymerization reaction solution was taken out of the 60 L reactor, passed through a sieve with a sieve opening of 1.68 mm to remove a huge aggregate, and then the aqueous layer and the solid matter were separated with a Buchner funnel to obtain a bead-shaped polymer.
The bead-like polymer was washed 5 times on a Buchner funnel with about 20 L of distilled water and then dried in a steam oven to obtain polymer fine particles corresponding to the resin 5.
Hereinafter, the granulation, the production of the test piece and the rectangular parallelepiped molded article, and each evaluation were performed in the same manner as in Example 1.
The results are shown in Table 3 below.

[Comparative Examples 2 and 3]
Polymerization was carried out in the same manner as in Comparative Example 1 using the raw materials shown in Table 2 below to obtain polymer fine particles corresponding to the resins 6 and 7.
Further, the granulation, the production of the test piece and the rectangular parallelepiped molded article, and the respective evaluations were carried out in the same manner as in Example 1.
The results are shown in Table 3 below.

  INDUSTRIAL APPLICABILITY The inner lens of the present invention is an inner lens for an automobile headlamp, various lamp parts in which light from a light source is condensed by the inner lens, a headlight for motorcycles and bicycles other than automobiles, and a projector lamp for OA equipment. It has industrial applicability as above, and is particularly suitable as an inner lens for an automobile headlamp.

1: Lens part of the inner lens 2: Part for fixing other parts of the inner lens 3: Thickness in the optical axis direction of the lens center part of the inner lens 4: Rectangular solid molded product (100 mm ×) used in Examples and Comparative Examples 40
mm × 20 mm), the front surface (40 mm × 1) on which the amount of sink marks is measured.
00 mm)

Claims (6)

An inner lens for a headlamp, which is obtained by injection molding a methacrylic resin composition containing a methacrylic resin,
The methacrylic resin composition,
Based on JIS K7210: 1999, a load of 3.80 kgf, a melt mass flow rate value a (g / 10 min.) Measured at a test temperature of 230 ° C., and a load of 10.19 kgf,
The value b (g / 10 min.) Of melt mass flow rate measured at a test temperature of 230 ° C.
An inner lens satisfying the conditions of the following formulas (1) and (2).
5.0 <b / a ... (1)
0.4 <a <2.0 ... (2) The methacrylic resin is
Methacrylic acid ester monomer unit 80-99.9 mass%,
0.1 to 20 mass% of at least one other vinyl monomer unit copolymerizable with methacrylic acid ester,
The inner lens according to claim 1, which comprises: The methacrylic acid ester is
The inner lens according to claim 2, which is methyl methacrylate and / or ethyl methacrylate. The other vinyl monomer copolymerizable with the methacrylic acid ester,
The inner lens according to claim 2 or 3, which is methyl acrylate and / or ethyl acrylate.   The inner lens according to any one of claims 1 to 4, wherein a thickness of a central portion of the inner lens in the optical axis direction is 10 mm or more.   The inner lens according to any one of claims 1 to 5, wherein the inner lens has a one-point gate at a peripheral portion thereof and has a gate thickness of 3 mm or less.

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