JP4936456B2 - Vehicle front lighting - Google Patents

Description

  The present invention relates to a vehicle front light having a projection lens made of methacrylic resin and a light source unit including a semiconductor light emitting element.

  Conventionally, halogen bulbs and metal halide discharge lamps used as light sources generate a large amount of heat, so the internal temperature rises and resin with poor heat resistance cannot achieve the light distribution performance as designed due to thermal deformation. Until now, it was difficult to use methacrylate resin or polycarbonate resin, and many glass lenses were used.

  FIG. 5 shows a conceptual diagram of a conventional vehicle front lighting using a metal halide discharge lamp as a light source. This lamp reflects the light emitted from the light source 8 attached to the reflector 6 to the front by the reflector 6 deposited with aluminum, and passes through the shade 5 (light shielding plate) fixed to the reflector 6 or the lens holder 4. Is projected forward by the aspherical lens 7 held or fastened by the lens holder 4 to form a light distribution.

  In Patent Document 1, as a projection-type automotive front lamp, inorganic nanoparticles having high thermal conductivity are dispersed in a resin lens, the thermal conductivity is improved, and heat dissipation is increased, thereby reducing thermal deformation of the resin lens. It is disclosed to do. However, it is difficult to stably disperse the inorganic nanoparticles, and the cost increases.

  Patent Document 2 discloses that a projector-type vehicle front lighting uses an LED as a light source, and a lens and a reflector are made of resin. However, when a general-purpose acrylic resin is used, the injection molding processing time is extremely short. If the length is not too long, sink marks are large, and it is difficult to form a predetermined light distribution.

JP 2006-302596 A JP 2005-209603 A

  An object of the present invention is to provide a vehicular front lamp with less unevenness in illuminance.

  As a result of intensive studies to solve these problems, the present inventors have achieved a balance between physical properties of heat resistance and mechanical strength by using a methacrylic resin having a specific low molecular weight component in a specific ratio range. It is possible to obtain a projection lens with reduced appearance defects, particularly sink marks, while maintaining the same, and further, by using this projection lens and using a semiconductor light emitting element as a light source, a vehicle headlamp with less unevenness in light distribution can be obtained. As a result, the present invention has been completed.

That is, the vehicle front lighting of the present invention is
A vehicle front light having a projection lens and a light source unit including a semiconductor light emitting element,
The projection lens is made of methacrylic resin;
The methacrylic resin is
Consists of 85 to 98.5 wt% of methyl methacrylate monomer units and 1.5 to 15 wt% of at least one other vinyl monomer unit copolymerizable with methyl methacrylate,
The weight average molecular weight measured by gel permeation chromatography (GPC) is 60,000 to 200,000,
It is characterized by containing 7 to 25% of a weight average molecular weight component of 1/5 or less of the peak weight average molecular weight (Mp) in the GPC elution curve.

  The methacrylic resin used in the present invention can lower the temperature at which it is plasticized in the screw cylinder of the molding machine injection unit by improving the flow characteristics during molding while maintaining the balance of physical properties of heat resistance and mechanical strength. As a result, the temperature of the resin to be injected and filled is low, the mold cooling time can be shortened, and the molding tact time can be greatly shortened. In the conventional method that brings about high flow by simply reducing the molecular weight, physical properties, particularly heat resistance and embrittlement have been reduced. The methacrylic resin used in the present invention is superior in that the flow is improved without deteriorating the physical properties.

  In addition, the swell effect is characteristic of the resin flow of the methacrylic resin used in the present invention, and there is a limit to the gate port of injection molding such as a projection lens, that is, from the flange part fixedly held or fastened to the lens holder part. In the shape of injection filling with a side gate, molding defects such as flow marks, jetting, and whitening are reduced when the resin flow has a diffusion effect like the methacrylic resin used in the present invention.

  From the above, the methacrylic resin used in the present invention has a feature that it can reduce appearance defects, particularly sink marks, of molded products made by injection molding. Therefore, it has become possible to provide a vehicular headlamp with little light distribution unevenness by having such a projection lens made of methacrylic resin and a light source unit having a semiconductor light emitting element.

  The present invention will be described in detail below. The embodiments described below are preferable specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. As long as there is no description of the effect, it is not restricted to these aspects.

  The vehicular front lamp of the present invention refers to a headlamp and a fog lamp. A vehicle headlamp will be described using a headlamp as an example.

  FIG. 1 is a conceptual diagram showing an example of a headlamp according to the present invention. In FIG. 1, 1 is a projection lens, 2 is a semiconductor light emitting element (LED), 3 is a light source unit, 4 is a lens holder, 5 is a shade, and 6 is a reflector. As shown in FIG. 1, the light source unit 3 includes an LED 2 and a reflector 6. The projection lens 1 is disposed so as to irradiate the light reflected from the reflector 6 forward. Between the light source unit 3 and the projection lens 1, a shutter (shade) 5 that blocks a part of the light reflected by the reflector 6 and a holder 4 that holds and fastens the projection lens 1 are configured.

  The projection lens 1 also includes an aspheric lens called planoconvex, a biconvex lens that is convex on both the incident and output sides, and a meniscus lens that is a concave lens on the incident side. In order to further improve the illuminance unevenness of the present invention, a biconvex lens that is convex on both the entrance and exit sides is preferable. Further, the maximum thickness of the projection lens 1 is preferably 8 mm or more, more preferably 10 mm to 30 mm. More preferably, it is 12 mm-25 mm.

  The projection lens 1 is preferably molded by injection molding or injection compression molding using a methacrylic resin described later. Depending on the required performance, a polycarbonate resin or the like may be used, but it is difficult to remove the molecular orientation strain inside the lens and the light dispersibility is poor, and there are great demerits in optical characteristics when used as a lens. In addition, when the light source is a semiconductor light emitting device, the amount of heat generated is smaller than that of a conventional light source, so the temperature inside the vehicle front lighting unit does not become high, and the heat resistance of the resin is not highly demanded. Can be used.

  An example of a specific molding method of the projection lens 1 is shown below.

  In order to avoid an optical influence by the gate portion, a gate port for injection molding is set from a flange portion fixed and held or fastened to the holder portion. In the molding process of injection molding, the mold is closed and the mold is clamped, and after touching the nozzle, the molten resin is injected and filled into the mold cavity through the sprue, runner and gate in the mold. Thereafter, a pressure holding step is performed. For this purpose, since the molten resin cooled and solidified by the mold contracts, the injection pressure is continuously applied for a while to supply and compensate the molten resin. The holding pressure is effective until the molten resin can be filled into the mold cavity through the gate. When the gate, which is the passing point, is cooled and solidified, the further holding step is wasted. After the pressure holding is completed, cooling is performed until deformation does not occur when taking out from the mold, and the mold is opened to take out the projection lens as a molded product.

  The methacrylic resin used in the present invention comprises methyl methacrylate and at least one other vinyl monomer copolymerizable with methyl methacrylate.

Other vinyl monomers copolymerizable with methyl methacrylate affect fluidity and heat resistance. Examples of other vinyl monomers copolymerizable with methyl methacrylate include the following.
Alkyl methacrylate having 2 to 18 carbon atoms in the alkyl group, alkyl acrylate having 1 to 18 carbon atoms in the alkyl group;
Α, β-unsaturated acids such as acrylic acid and methacrylic acid, unsaturated group-containing divalent carboxylic acids such as maleic acid, fumaric acid and itaconic acid, and alkyl esters thereof;
Aromatic vinyl compounds such as styrene, α-methylstyrene, styrene having a substituent on the benzene ring;
Vinyl cyanide compounds such as acrylonitrile and methacrylonitrile;
Maleic anhydride, maleimide, N-substituted maleimide and the like;
Ethylene glycol such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, etc. Esterified;
What esterified the hydroxyl group of two alcohols, such as neopentylglycol di (meth) acrylate and di (meth) acrylate, with acrylic acid or methacrylic acid;
Esterification of polyhydric alcohol derivatives such as trimethylolpropane and pentaerythritol with acrylic acid or methacrylic acid;
Polyfunctional monomers such as divinylbenzene.

  These can be used alone or in combination of two or more. Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoints of light resistance, heat resistance, and fluidity. Used. Methyl acrylate, ethyl acrylate, and n-butyl acrylate are particularly preferable, and methyl acrylate is most preferable because it is easily available.

  The content of methyl methacrylate units is 98.5 wt% or less from the viewpoint of the thermal decomposability of the resin. If it is this range, generation | occurrence | production of the bubble which a monomer called foaming produced | generated by decomposition | disassembly of the resin called silver at the time of shaping | molding will be suppressed. Moreover, it is 85 wt% or more from the point of heat resistance. If the heat resistance is high, distortion of the molded product can be suppressed during the environmental test. Preferably it is 90-98 wt%, More preferably, it is 92-97 wt%.

  The content of other vinyl monomer units copolymerizable with methyl methacrylate is 1.5 wt% or more from the viewpoint of fluidity and heat resistance with respect to the methacrylic resin, and 15% or less from the viewpoint of heat resistance. is there. Preferably it is 2-10 wt%, More preferably, it is 3-8 wt%.

  The methacrylic resin used in the present invention has a weight average molecular weight measured by gel permeation chromatography (GPC) of 60,000 or more from the viewpoint of mechanical strength and 200,000 or less from the viewpoint of fluidity. In this range, the molding process is easy. Moreover, from a fluid viewpoint, Preferably it is 60,000-160,000, More preferably, it is 60,000-140,000.

  The weight average molecular weight is measured by gel permeation chromatography (GPC). Specifically, using a monodispersed standard methacrylic resin with a known weight average molecular weight and available as a reagent, and an analytical gel column that elutes a high molecular weight component first, a calibration curve is obtained from the elution time and the weight average molecular weight. Create it. The molecular weight of each sample can be obtained from the obtained calibration curve.

  A component having a weight average molecular weight of 1/5 or less of the peak weight average molecular weight (Mp) present in the methacrylic resin used in the present invention is important with respect to the mechanical strength of the resin and the appearance defect of the molded product. A component having a weight average molecular weight of 1/5 or less of Mp has a plasticizing effect. When the abundance of this component is in the range of 7 to 25% with respect to the methacrylic resin component, the effect of improving moldability and suppressing distortion of the molded product after molding can be obtained. It is necessary to be 7% or more from the viewpoint of plasticizing effect and fluidity, the injection pressure during molding can be suppressed, and distortion of the molded product due to residual strain can be prevented. On the other hand, it is necessary to be 25% or less from the viewpoint of heat resistance, distortion of the molded product, and strength. Preferably, it is 8-23%, More preferably, it is 8-20%. In addition, the methacrylic resin component having a weight average molecular weight of 500 or less tends to cause a foam-like appearance defect called silver at the time of molding.

  Here, in the present invention, the peak weight average molecular weight (Mp) refers to the weight average molecular weight showing a peak in the GPC elution curve. When there are a plurality of peaks in the GPC elution curve, the peak is indicated by the weight-average molecular weight having the largest abundance. The content of the weight average molecular weight component of 1/5 or less of Mp can be determined as follows. That is, the area area (FIG. 2) in the GPC elution curve described below is divided by the elution time corresponding to 1/5 of the weight average molecular weight of Mp, and GPC elution corresponding to the weight average molecular weight component of 1/5 or less of Mp. Find the area of the area on the curve. From the ratio of the area and the area area in the GPC elution curve, the ratio of the weight average molecular weight of 1/5 or less of Mp can be determined.

  The other vinyl monomer copolymerizable with methyl methacrylate used in the present invention preferably has a higher composition ratio in the high molecular weight component of the resulting methacrylic resin than the composition ratio in the low molecular weight component. This is because heat resistance and appearance defects of molded products can be reduced, and fluidity can be further improved while maintaining mechanical strength.

  This point will be described with reference to FIGS. 2 to 4 are GPC elution curve measurement graphs, where the vertical axis is RI (differential refraction) detection intensity (mV), the horizontal axis is the elution time (min.) On the lower side, and the entire GPC area area is on the upper side. Indicates the cumulative area area (%). Moreover, in FIGS. 2-4, since the column eluted from a high molecular weight component is used, the high molecular weight component is observed at the beginning of the elution time, and the low molecular weight component is observed at the end of the elution time.

  In the present invention, the area of the hatched portion shown in FIG. 2 is referred to as “area area in GPC elution curve”. A specific method for determining the area of the area in the GPC elution curve is as follows. First, the point A at which the baseline 12 automatically drawn by the measuring instrument and the GPC elution curve 11 intersect the GPC elution curve 11 obtained from the elution time obtained by the GPC measurement and the detection intensity by the RI (differential refraction detector). And point B is determined. Point A is a point where the GPC elution curve 11 and the baseline 12 at the beginning of the elution time intersect. Point B is, as a rule, a position where the weight average molecular weight is 500 or more and the baseline 12 and the GPC elution curve 11 intersect. If the weight average molecular weight does not intersect within the range of 500 or more, the value of RI detection intensity at the elution time when the weight average molecular weight is 500 is defined as point B. A hatched portion surrounded by the GPC elution curve between the points A and B and the line segment AB is an area in the GPC elution curve. This area is the “area area in the GPC elution curve”.

  The “cumulative area area (%)” of the area area in the GPC elution curve is the high molecular weight side, that is, the point A shown in FIG. 2 is 0% which is the standard of the cumulative area area (%), and the low molecular weight side, that is, the elution time. From this point of view, the detection intensity corresponding to each elution time is accumulated, and the area area in the GPC elution curve is formed. A specific example of the accumulated area area is shown in FIG. In FIG. 3, a point on the baseline at a certain elution time is a point X, and a point on the GPC elution curve is a point Y. The ratio of the area surrounded by the curve AX, the line segment AB, and the line segment XY to the area area in the GPC elution curve is defined as the value of “cumulative area area (%)” at a certain elution time.

Let Mh (wt%) be the average composition ratio of other vinyl monomer units copolymerizable with methyl methacrylate in the weight average molecular weight component (high molecular weight component) in the cumulative area of 0 to 2%. Meanwhile, the average composition ratios of weight average molecular weight component (the low molecular weight component) methyl methacrylate and other copolymerizable vinyl monomer unit in which in the cumulative area dimension 98% to 100% and Ml (wt%) . FIG. 4 shows a schematic diagram of positions on the measurement graph of the accumulated area area of 0 to 2% and 98 to 100%.

  The values of Mh and Ml can be obtained by fractionating several times or several tens of times according to the column size based on the elution time obtained from GPC. The composition of the collected sample may be analyzed by a known pyrolysis gas chromatography method.

It is preferable that the relationship of the following formula (1) is established between Mh (wt%) and Ml (wt%) in the present invention.
(Mh-4.1) ≧ Ml ≧ 0 (1)

  This is because the average composition of other vinyl monomer units copolymerizable with methyl methacrylate is more than 4.1 (wt%) in the high molecular weight component than in the low molecular weight component, It shows that the vinyl monomer is not necessarily copolymerized. The difference between Mh (wt%) and Ml (wt%) is preferably 4.1 (wt%) or more, and more preferably 4.2 (wt%) or more for the effect of improving fluidity.

  Further, Ml is more preferably less than 0.5 (wt%), and further preferably less than 0.3 (wt%).

  That is, the average composition of other vinyl monomer units copolymerizable with methyl methacrylate of the methacrylic resin in the high molecular weight component is 4.1 (wt%) or more higher than the average composition of the low molecular weight component, and Ml is 0. It is preferable that the amount be less than 0.5 wt% because the heat resistance and the appearance defect of the molded product are reduced, and a dramatic fluidity improving effect is obtained while maintaining the mechanical strength.

  The methacrylic resin used in the present invention can be produced using the copolymer (1) and copolymer (2) shown below.

  The copolymer (1) is composed of at least one monomer selected from 99.9 to 100 wt% of a methyl methacrylate monomer and another vinyl monomer copolymerizable with methyl methacrylate. It is preferable that the amount of other vinyl monomers copolymerized with less than 1 wt% and copolymerizable with methyl methacrylate is small, and may not be used. The molecular weight is preferably 5,000 to 30,000 in terms of weight average weight measured by gel permeation chromatography. Since the number of components having a weight average molecular weight of 500 or less causing problems in molding is reduced, the weight average molecular weight of the copolymer (1) is preferably 5,000 or more. In this case, when the copolymer (2) is produced in the presence of the copolymer (1), the molecular weight of the copolymer (2) is preferably stabilized during continuous production. 30,000 or less is preferable from the viewpoint of fluidity. More preferably, it is 5,000-25,000, More preferably, it is 6,000-20,000. The optimum range is 60,00 to 150,000.

  Copolymer (2) is a monomer composed of 80 to 99.5 wt% of methyl methacrylate monomer and 0.5 to 20 wt% of monomer composed of at least one other vinyl monomer copolymerizable with methyl methacrylate. The weight average molecular weight measured by gel permeation chromatography is preferably 70,000 or more from the viewpoint of mechanical strength, and is preferably 230,000 or less from the viewpoint of fluidity. . More preferably, it is 70,000-200,000, More preferably, it is 75,000-180,000.

  The ratio of the copolymer (1) is preferably 5 wt% or more in order to obtain the effect of improving fluidity, and is preferably 20 wt% or less from the viewpoint of the mechanical strength of the resin. More preferably, it is 5-17 wt%, More preferably, it is 5-15 wt%.

  The ratio of the copolymer (2) is preferably 95 wt% or less in order to obtain the effect of improving fluidity, and preferably 80 wt% or more from the viewpoint of the mechanical strength of the resin.

  There is no restriction | limiting in particular as a manufacturing method of the composition of the methacryl resin used for this invention, Specifically, the following method is mentioned.

  1. The polymer (A) is produced in advance, and the polymer (A) is mixed with the raw material composition mixture of the polymer (B) having a molecular weight different from that of the polymer (A). A method of producing the mixture by polymerizing the mixture.

  2. After the polymer (A) is produced in advance, a raw material composition mixture of the polymer (B) having a molecular weight different from that of the polymer (A) is sequentially added to the polymer (A), or the polymer (A) is overlapped. A method of producing by sequentially adding to the raw material composition mixture of the combined body (B) and polymerizing.

  3. A method in which a polymer (B) having a molecular weight different from that of the polymer (A) and the polymer (A) is separately produced in advance and blended.

  These methods relate to the case where the two types of molecular weight components are different. However, with respect to methods 1 and 2, polymers (C) and polymers (D) having different molecular weight compositions can be produced in the same procedure. good. Further, with respect to method 3, polymers (C) and polymers (D) having different molecular weight compositions may be further blended and melt kneaded with an extruder.

  Preferably, the polymer (A) is produced, and the polymer (B) is produced in a state where the polymer (A) is present in the raw material composition mixture of the polymer (B). This is because the compositions of the polymer (A) and the polymer (B) can be easily controlled, the temperature rise due to polymerization heat generation during polymerization can be suppressed, and the viscosity in the system can be stably obtained. In this case, the raw material composition mixture of the polymer (B) may be in a state where the polymerization is partially started. As a polymerization method for that purpose, bulk polymerization, solution polymerization, suspension polymerization or emulsion polymerization is preferred. More preferred are bulk polymerization, solution polymerization and suspension polymerization.

  Either the polymer (A) or the polymer (B) may have a high molecular weight, and either one may have a low molecular weight. The compositions of the polymer (A) and the polymer (B) are preferably different.

  For example, if the content of other vinyl monomers copolymerizable with methyl methacrylate is 1 to 20 wt% with respect to the methacrylic resin, the content differs between the polymer (A) and the polymer (B). It is preferable.

  Preferably, the polymer (A) is a copolymer (1) having a low molecular weight, the polymer (B) is a copolymer (2) having a high molecular weight, and more preferably the polymerization method is a copolymer. After producing (1), the copolymer (2) is produced in the presence of the copolymer (1).

Composition ratio Mal (wt%) of other vinyl monomer units copolymerizable with methyl methacrylate of copolymer (1) in the present invention and other copolymerizable with methyl methacrylate of copolymer (2) It is preferable that the relationship of the formula (2) is established in the composition ratio Mah (wt%) of the vinyl monomer unit.
(Mah-4.1) ≧ Mal ≧ 0 (2)

  The composition ratios Mal and Mah can be determined by measuring each of the copolymer (1) and the copolymer (2) by a pyrolysis gas chromatography method. Each value is almost the same as the composition ratio used in the preparation.

  The difference between Mah (wt%) and Mal (wt%) is preferably 4.1 (wt%) or more from the viewpoint of fluidity. When the high molecular weight copolymer (1) contains more vinyl monomer copolymerizable with methyl methacrylate as a composition ratio, fluidity is improved while maintaining heat resistance and mechanical strength. It is preferable because it can be achieved.

  That is, maintaining the difference between Mah (wt%) and Mal (wt%) to 4.1 (wt%) or more reduces the heat resistance and the appearance defect of the molded product, while maintaining the mechanical strength. It is preferable for improving fluidity.

  As a polymerization initiator for producing the highly fluid methacrylic resin of the present invention, the following general radical polymerization initiator can be used when free radical polymerization is used.

Di-t-butyl peroxide, lauroyl peroxide, dilauroyl peroxide, t-butylperoxy 2-ethylhexanoate, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane Peroxide systems such as 1,1-bis (t-butylperoxy) cyclohexane;
Azo series such as azobisisobutyronitrile, azobisisovaleronitrile, 1,1-azobis (1-cyclohexanecarbonitrile);

  These may be used alone or in combination of two or more. A combination of these radical initiators and an appropriate reducing agent may be used as a redox initiator. These initiators are generally used in the range of 0.001 to 1 wt% with respect to the monomer mixture.

  As a method for producing a methacrylic resin used in the present invention, a chain transfer agent generally used for adjusting the molecular weight of the polymer (A) and the polymer (B) when producing by a radical polymerization method. Can be used. Examples of the chain transfer agent include n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, 2-ethylhexyl thioglycolate, ethylene glycol dithioglycolate, trimethylolpropane tris (thioglycolate), pentaerythritol tetrakis (thioglycolate). Etc.) are preferably used. Generally, it is used in the range of 0.001 to 1 wt% with respect to the monomer mixture. The chain transfer agent used for the polymer (A) and the polymer (B) may be the same or different. The amount of chain transfer agent of polymer (A) and polymer (B) is determined depending on the desired molecular weight.

In the methacrylic resin in the present invention, the following additives may be used as necessary.
Heat stabilizers such as dyes, pigments, hindered phenols and phosphates;
UV absorbers such as benzotriazole, 2-hydroxybenzophenone, and salicylic acid phenyl ester;
Plasticizers such as phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, etc .;
Mold release agents such as higher fatty acids, higher fatty acid esters, mono-, di- or triglycerides of higher fatty acids;
Higher fatty acid esters, polyolefin-based lubricants;
Antistatic agents such as polyether-based, polyetherester-based, polyetheresteramide-based, alkyl sulfonate, alkylbenzene sulfonate;
Phosphorus, phosphorus / chlorine, phosphorus / bromine flame retardants;
Acrylic rubber obtained by multistage polymerization as a reinforcing agent;
Organic and organic inorganic light diffusing agents such as methyl methacrylate / styrene polymer beads and organic siloxane beads;
Inorganic light diffusing agents such as barium sulfate, titanium oxide, calcium carbonate, talc;

  Note that the light diffusing agent is effective in preventing glare of reflected light.

  There are no particular limitations on the method of blending these additives. For example, the additive is dissolved in the monomer mixture in advance and polymerized, or the resulting methacrylic resin is uniformly blended using a blender, tumbler, etc., and then added by compounding with an extruder. It is done.

  The methacrylic resin used in the present invention may be used alone or mixed with other resins. When mixing with other resins, they may be blended and mixed by heating and melting, or a plurality of pellets extruded by heating and melting and mixing may be blended and then mixed by heating and melting. The additives mentioned above may be blended and mixed at this time.

  The methacrylic resin obtained in the present invention may be a combination of a plurality of methacrylic resin compositions of the present invention having different compositions, or may be combined with an existing methacrylic resin. As a combination method, they may be used by blending, or each resin may be once heated and melted, extruded, blended again, and pelletized.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[material]
The raw materials used are as follows.

Methyl methacrylate (MMA): manufactured by Asahi Kasei Chemicals (2.5 ppm of 2,4-di-6-tert-butylphenol) is added as a polymerization inhibitor. What)
Methyl acrylate (MA): manufactured by Mitsubishi Chemical (14 ppm of 4-methoxyphenol manufactured by Kawaguchi Chemical Industry as a polymerization inhibitor)
n-octyl mercaptan (manufactured by Arkema,
2-ethylhexyl thioglycolate: manufactured by Arkema, used as a polymerization molecular weight regulator Lauroyl peroxide: manufactured by Nippon Oil & Fats Co., Ltd., tricalcium phosphate: manufactured by Nippon Kagaku Kogyo, as a suspending agent Use Calcium carbonate: manufactured by Shiraishi Kogyo Co., Ltd., used as a suspending agent, sodium lauryl sulfate: manufactured by Wako Pure Chemical Industries, Ltd., used as a suspending aid

[Measurement method]
[I. Measurement of resin composition and molecular weight]
1. Composition analysis of methacrylic resin The composition analysis of methacrylic resin was performed by pyrolysis gas chromatography and mass spectrometry.

Pyrolysis device: PY-2020D made by FRONTIER LAB
Column: DB-1 (length 30 m, inner diameter 0.25 mm, liquid phase thickness 0.25 μm)
Column temperature program: Hold at 40 ° C. for 5 min, then increase the temperature to 320 ° C. at a rate of 50 ° C./min, hold 320 ° C. for 4.4 minutes Pyrolysis furnace temperature: 550 ° C.
Column inlet temperature: 320 ° C
Gas chromatography: Agilent GC6890
Carrier: pure nitrogen, flow rate 1.0 ml / min
Injection method: Split method (split ratio 1/200)
Detector: JEOL mass spectrometer Automass Sun
Detection method: electron impact ionization method (ion source temperature: 240 ° C., interface temperature: 320 ° C.)
Sample: 10 μl of 10 g chloroform solution of 0.1 g methacrylic resin

  A sample was collected in a platinum sample cup for a thermal decomposition apparatus, vacuum-dried at 150 ° C. for 2 hours, and then the sample cup was placed in a thermal decomposition furnace, and composition analysis of the sample was performed under the above conditions. The composition ratio of the methacrylic resin was determined based on the peak area on total ion chromatography (TIC) of methyl methacrylate and methyl acrylate and the calibration curve of the following standard sample.

<Creation of standard sample for calibration curve>
The ratio of methyl methacrylate and methyl acrylate is (methyl methacrylate / methyl acrylate) = (100% / 0%), (98% / 2%), (94% / 6%), (90% / 10% ) (80% / 20%) were added to 50 g of each of the five solutions in total, 0.25% lauroyl peroxide and 0.25% n-octyl mercaptan. Each of these mixed solutions was put into a 100 cc glass ampule bottle, and the air was replaced with nitrogen and sealed. The glass ampoule bottle was placed in an 80 ° C. water bath for 3 hours and then in an oven at 150 ° C. for 2 hours. After cooling to room temperature, the glass was crushed and the methacrylic resin inside was taken out and subjected to composition analysis. A graph of (methyl acrylate area value) / (methyl methacrylate area value + methyl acrylate area value) and methyl acrylate charge ratio obtained by measurement of a standard sample for a calibration curve is used as a calibration curve. It was.

2. Measurement of weight-average molecular weight of methacrylic resin Measuring device: Gel analysis chromatography (LC-908) manufactured by Nippon Analytical Industry
Column: one JAIGEL-4H and two JAIGEL-2H, connected in series
In this column, the high molecular weight elutes early and the low molecular weight elutes slowly.

Detector: RI (differential refraction) detector Detection sensitivity: 2.4 μV / sec
Sample: 0.450 g of methacrylic resin in chloroform 15 ml Injection amount: 3 ml
Developing solvent: chloroform, flow rate 3.3 ml / min

  Under the above conditions, the RI detection intensity with respect to the elution time of the methacrylic resin was measured. The average molecular weight of the methacrylic resin was determined based on the area area in the GPC elution curve and the calibration curve.

  The following 10 methacrylic resins (manufactured by EasiCal PM-1 Polymer Laboratories) having different molecular weights and known monodispersed weight average molecular weights were used as standard samples for calibration curves.

Weight average molecular weight Standard sample 1 1,900,000
Standard sample 2 790,000
Standard sample 3 281,700
Standard sample 4 144,000
Standard sample 5 59,800
Standard sample 6 28,900
Standard sample 7 13,300
Standard sample 8 5,720
Standard sample 9 1,936
Standard sample 10 1,020

  When the polymer (1) and the polymer (2) are mixed, the GPC elution curve of the polymer (1) alone is measured in advance to determine the weight average molecular weight, and the polymer (1) is present. GPC in which the polymer (1) and the polymer (2) are mixed with each other by multiplying the GPC elution curve of the polymer (1) by the ratio (the charge ratio used in this example). By subtracting from the elution curve, a GPC elution curve of the polymer (2) alone is obtained. From this, the weight average molecular weight of the polymer (2) was determined.

  Moreover, the peak weight average molecular weight (Mp) in the GPC elution curve was calculated | required from the GPC elution curve and a calibration curve, and content of the weight average molecular weight component of 1/5 or less of Mp was calculated | required as follows.

  First, the area area (shaded area in FIG. 2) in the GPC elution curve of methacrylic resin is obtained. Next, the area area in the GPC elution curve is divided by the elution time corresponding to the weight average molecular weight of 1/5 of Mp, and the area area in the GPC elution curve corresponding to the weight average molecular weight component of 1/5 or less of Mp is calculated. Ask. From the ratio of the area and the area area in the GPC elution curve, the ratio of the weight average molecular weight of 1/5 or less of Mp was determined.

3. Measurement of composition ratio of vinyl copolymer copolymerizable with methyl methacrylate in high molecular weight component and low molecular weight component of methacrylic resin Molecular weight component having cumulative area of 0-2% shown in FIG. A certain molecular weight component was fractionated from the column based on the corresponding elution time, and the composition analysis was performed. Measurement and fractionation of each component are as described in 1. above. The same apparatus and conditions were used.

  That is, the fractionation was performed twice, and 10 μl of the fractionated sample was added to the above 1. The sample was collected in a platinum sample cup for a pyrolysis apparatus of the pyrolysis gas chromatography analysis and mass spectrometry method used in the above, and dried in a vacuum dryer at 100 ° C. for 40 minutes. Above 1. The composition of the methacrylic resin corresponding to the accumulated area area fractionated under the same conditions as above was determined.

[II. Measurement of practical properties]
1. Heat resistance (measurement of VICAT softening temperature)
Molding machine: 30t press molding machine Test piece: 4mm thickness
Measurement conditions: Conforms to ISO 306 B50

  The VICAT softening temperature of the methacrylic resin was determined under the above conditions. This was used as an index for heat resistance evaluation.

2. Molding fluidity evaluation (measurement of spiral length)
This is a test for determining the relative fluidity based on the distance of the resin flowing through a spiral cavity having a constant cross-sectional area.

Injection molding machine: Toshiba Machine IS-100EN
Mold for measurement: Mold with a groove of 2mm depth and 12.7mm width dug into the surface of the mold in an Archimedean spiral shape from the center of the surface

Injection conditions Resin temperature: 250 ° C
Mold temperature: 55 ° C
Injection pressure: 98 MPa
Injection time: 20 sec

A methacrylic resin was injected into the center of the mold surface under the above conditions. After 40 seconds from the end of the injection, the spiral molded product was taken out, the length of the spiral portion was measured, and used as an index for fluidity evaluation as follows.
◎: Excellent fluidity during molding and sufficiently good state ○: Fluidity during molding is good △: Fluidity during molding is slightly inferior ×: Fluidity during molding is poor and undesirable

3. Mechanical strength evaluation (crack when releasing mold of thin molded product)
Injection molding machine: JSW 350t electric injection molding machine Molded article size: Flat plate with 240mm width, 135mm length, 0.8mm thickness Gate: Film gate with 240mm width, 0.8mm thickness Gate installation position: Center in the width direction of the molded article portion

Injection conditions Barrel temperature: 275 ° C
Mold temperature: 75 ℃
Injection speed: 800 mm / sec, constant holding pressure and holding time: 200 MPa, 20 sec
Removal of molded product: 40 seconds after the start of injection

Under the above conditions, methacrylic resin was injection molded. The cracking state at the time of mold release was confirmed and used as an index for evaluating the mechanical strength as follows.
◎: Good state with sufficient strength without cracking when mold is released ○: Good condition when molded product is not cracked when releasing mold △: Cracked product when mold is released There is a state X: The molded product often breaks when the mold is released

4). Molded product sink amount The molded product appearance was visually observed and evaluated according to the following criteria.
◎: good condition without sink marks: good condition with small sink marks Δ: condition with slightly large sink marks ×: condition with large sink marks and unfavorable condition

5. Light distribution performance evaluation The light cut-off (bright / dark boundary line) clarity and light distribution unevenness were comprehensively evaluated when a screen 10 m ahead was irradiated with a headlamp.
A: State where cut-off sharpness and light distribution unevenness are sufficiently good ○: State where cut-off sharpness and light distribution unevenness are both good Δ: State where cut-off sharpness and light distribution unevenness are both slightly unfavorable x: Unfavorable state of both cut-off sharpness and light distribution unevenness

[Examples 1-7, Comparative Examples 1-3]
Into a 60 L reactor, the raw material of the polymer (1) was added in the blending amount shown in Table 1, stirred and mixed, and suspension polymerization was carried out at a reaction temperature of 80 ° C. for 150 minutes to obtain a polymer (1). . This polymer (1) was sampled and the weight average molecular weight was measured. The results are shown in Table 1.

  Thereafter, the temperature is maintained at 80 ° C. for 60 minutes, and then the raw material of the polymer (2) is charged into the reactor at the blending amount shown in Table 1, followed by suspension polymerization at 80 ° C. for 90 minutes, and subsequently at 92 ° C. The temperature was raised at a rate of 1 ° C./min and ripened for 60 minutes to substantially complete the polymerization reaction. Next, the mixture was cooled to 50 ° C. and 20 wt% sulfuric acid was added to dissolve the suspending agent, followed by washing, dehydrating and drying treatment to obtain a bead polymer. The weight average molecular weight of this bead polymer was measured, and the weight average molecular weight of the polymer (2) was determined from the ratio of the polymer (1) shown in Table 1. The results are shown in Table 1.

  The bead polymer thus obtained was extruded at 240 ° C. with a twin screw extruder and pelletized. The results of measuring the composition and molecular weight of this pellet are shown in Table 2. Table 3 shows the results of evaluating the heat resistance, molding fluidity, and mechanical strength of the pellets.

  Using this pellet, an aspherical convex lens having a diameter of 60 mmφ and a maximum thickness of 20 mm was molded under the following conditions.

Injection molding machine: Sumitomo Heavy Industries SE-180 Injection molding machine Gate: Side gate with thickness of 3 mm, width of 10 mm, and gate land length of 10 mm Gate installation position: Periphery of bottom plane of hemisphere Runner: Thickness of 8 mm, width of 10 mm, length 20mm
Molding temperature: 190 ° C
Mold temperature: 105 ° C
Molding cycle: 240 sec

Injection conditions Injection speed: 3mm / sec
Injection time: 5 sec
Holding pressure and holding time: 140 MPa, held for 10 sec, and then held at 60 MPa for 20 sec.

  The obtained lens was cooled all day and night in a desiccator, and the amount of molded product sink was evaluated. The results are shown in Table 3.

  Moreover, the obtained lens was used as the projection lens 1 of the headlamp shown in FIG. 1, and the light distribution performance was evaluated. The results are shown in Table 3.

[Comparative Examples 4 and 5]
The raw material of the polymer (2) is charged into a 60 L reactor at the blending amount shown in Table 1, suspended and polymerized at a reaction temperature of 80 ° C. for 150 minutes, and heated to 92 ° C. at a rate of 1 ° C./min. The polymerization was substantially completed after aging for 60 minutes. Next, the mixture was cooled to 50 ° C. and 20 wt% sulfuric acid was added to dissolve the suspending agent, followed by washing, dehydrating and drying treatment to obtain a bead polymer.

  Using this bead-shaped polymer, a lens and a headlamp were obtained in the same manner as in Example 1.

  The evaluation results are shown in Tables 1 to 3.

  Specifically, the highly fluid methacrylic resin of the present invention can be applied to molded products having secondary processing in the vehicle material field, thin-walled and large-sized molded products, and molded products that are prone to sink marks due to thick product shapes. While maintaining appearance quality by using it for head lenses in the vehicle field, especially projection lenses, aspherical lenses called planoconvex, biconvex lenses that are convex on both the entrance and exit sides, and meniscus lenses that are concave on the entrance side The molding characteristics during molding are improved and sink marks are reduced. For this reason, it is possible to provide a vehicular headlamp having a light distribution characteristic according to a predetermined design.

It is a conceptual diagram which shows an example of the vehicle front lighting of this invention. It is explanatory drawing of the area of an area in a GPC elution curve. It is the figure which showed an example of the accumulation area area. It is the schematic which shows the position of 0-2% of accumulation area areas, and 98-100% of accumulation area areas. It is a conceptual diagram of the conventional vehicle front lighting using a metal halide discharge lamp as a light source.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Projection lens 2 Semiconductor light emitting element 3 Light source unit 4 Lens holder 5 Shade 6 Reflector 7 Aspherical lens 8 Light source 11 GPC elution curve 12 Base line

Claims (8)

A vehicle front light having a projection lens and a light source unit including a semiconductor light emitting element,
The projection lens is made of methacrylic resin;
The methacrylic resin is
Consists of 85 to 98.5 wt% of methyl methacrylate monomer units and 1.5 to 15 wt% of at least one other vinyl monomer unit copolymerizable with methyl methacrylate,
The weight average molecular weight measured by gel permeation chromatography (GPC) is 60,000 to 200,000,
A vehicle headlamp comprising 7 to 25% of a weight average molecular weight component equal to or less than 1/5 of a peak weight average molecular weight (Mp) in a GPC elution curve. The other at least one vinyl monomer copolymerizable with the methyl methacrylate is an alkyl methacrylate having an alkyl group having 2 to 18 carbon atoms and / or an acrylic acid having an alkyl group having 1 to 18 carbon atoms. The vehicle headlamp according to claim 1, wherein the vehicle front lamp is alkyl. Average composition of other vinyl monomer units copolymerizable with methyl methacrylate in the weight average molecular weight component in the cumulative area area 0-2% from the high molecular weight side of the area area in the GPC elution curve of the methacrylic resin the ratio Mh (wt%), the average composition ratio of methacrylic acid methyl copolymerizable with other vinyl monomer units having a weight average molecular weight component in the cumulative area dimension 98~100% Ml (wt%) and There front headlamp for a vehicle according to claim 1 or 2, characterized in that a relation of the expression (1).
(Mh-4.1) ≧ Ml ≧ 0 (1) The vehicle front light according to claim 3 , wherein the Ml is less than 0.5 wt%. The vehicle headlamp according to any one of claims 1 to 4 , wherein the weight average molecular weight is 60,000 to 160,000. The vehicle headlamp according to any one of claims 1 to 4, wherein the weight average molecular weight is 60,000 to 91,000. The vehicular headlamp according to any one of claims 1 to 6 , further comprising 8 to 20% of a weight average molecular weight component equal to or less than 1/5 of the peak weight average molecular weight (Mp). The vehicular headlamp according to any one of claims 1 to 7 , wherein a maximum thickness of the projection lens is 8 mm or more.

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