JPH10298237A - Lamp lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lamp lens which is lightweight and has high transparency and heat resistance and excellent weathering resistance by molding a polymer comprising repeating units having a specified structure. SOLUTION: The polymer used to form the lamp lens comprises repeating units represented by the formula (R<1> is H, a 1-25C hydrocarbon group or a substituted hydrocarbon group; and n is a positive integer). From the viewpoints of specific gravity and heat resistance, R<1> is desirably of 6C or higher and is desirably exemplified by cyclohexyl or adamantyl. The component other than the repeating units is exemplified by methyl methacrylate. Although not particularly limited, the molecular weight of the polymer is desirably in the range of 10,000-1,000,000 in terms of a number-average molecular weight. This lens can be produced by a known process such as melt molding or solution molding. It is necessary that the lens can transmit light from the lamp at good efficiency, and it is therefore desirable that it has a Y1 value of 3 or below as measured with a color difference meter and a total light transmittance of 87% or above as measured with an integral spherical hazemeter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic lamp lens used for headlamps, fog lamps, signal lights, and the like for vehicles.

[0002]

2. Description of the Related Art A lamp lens usually made of inorganic glass is mounted on the front of a headlamp, a fog lamp or a signal lamp for a vehicle in order to maintain light transmission.
However, although inorganic glass is excellent in heat resistance, transparency and weather resistance, it has drawbacks such as being easily broken and heavy, and recently a plastic lamp lens has been partially developed and put into practical use. .

As a thermoplastic polymer having excellent transparency and weather resistance, there is an acrylic polymer typified by a methyl methacrylate polymer. However, since the heat resistance is low, a lamp molded with these polymers is used. The lens has a disadvantage that it is easily deformed by heat generated when the lamp is turned on. Also has relatively good transparency, weather resistance,
Examples of the thermoplastic polymer having a high heat resistance temperature include polycarbonate.

[0004]

However, polycarbonate has a problem in that it has a relatively high specific gravity among plastics. Further, polycarbonate cannot be said to have sufficient heat resistance yet, and in practical use, it is necessary to consider a shape such that the lens does not become too hot, or to take special measures for heat shielding. That is, there is no known lamp lens made of a thermoplastic polymer having excellent transparency and weather resistance, low specific gravity, and high heat resistance temperature.

[0005]

The gist of the present invention resides in a lamp lens formed of a polymer containing a repeating unit represented by the following general formula (1).

[0006]

Embedded image

In the formula, R ¹ represents a hydrogen atom or a hydrocarbon group having 1 to 25 carbon atoms, an alicyclic hydrocarbon group or a substituted hydrocarbon group, and n represents a positive integer.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the polymer used in the lamp lens of the present invention, the content of the repeating unit represented by the general formula (1) is not particularly limited. The content of the unit is preferably at least 30% by weight, more preferably at least 50% by weight. If the content is too small, the heat resistance tends to be insufficient.

As the repeating unit component of the general formula (1) of the polymer, R ¹ preferably has 6 or more carbon atoms from the viewpoint of specific gravity and heat resistance, and cyclohexyl, tricyclodecanyl, An adamantyl group is particularly preferred.

Further, examples of the component other than the repeating unit of the general formula (1) of the polymer include (meth) acrylates such as methyl methacrylate and methyl acrylate, styrene, α-methylstyrene, acrylonitrile and the like. From the viewpoint of transparency, methyl methacrylate is most preferred.

Although the molecular weight of the polymer is not particularly limited, it is preferable that the number average molecular weight Mn is in the range of 10,000 to 1,000,000. More preferably, it is in the range of 30,000 to 500,000.

The lamp lens of the present invention can be manufactured by a known melt molding method, solution molding method or the like. Among these molding methods, the injection molding method is most preferable from the viewpoint of efficiency. At the time of molding, an appropriate amount of a plasticizer, a cross-linking agent, a heat stabilizer, a coloring agent, an ultraviolet absorber, a release agent, and the like can be added.

The shape of the lamp can be any shape according to the purpose of use and design as a headlamp, fog lamp or signal lamp. It is preferable to have a structure having a lens group on the light surface (inner surface).

The lamp lens of the present invention needs to efficiently transmit the internal lamp light. For this purpose, the YI value measured by a color difference meter is 3 or less, and the total light transmittance measured by an integrating sphere haze meter is required. It is desirable that it be 87% or more. Also,
Since abrasion resistance of the surface is required, it is preferable to form a cured film of a cross-linkable curable resin on at least the outer surface side as necessary. Examples of the cross-linkable curable resin include those made of an acrylic polyfunctional compound, a silicon compound, and the like.

The present invention will be described below with reference to the drawings. FIG.
2 shows an entire vehicle lamp lens, and FIG. 2 and FIG. 3 are enlarged sectional views of main parts thereof. In the figure, 1 is a lamp lens substrate formed of a thermoplastic polymer, 2 is a lens group provided on its inner surface, and 3 is a cross-linked cured resin film provided on the outer surface of the substrate.

[0016]

The present invention will be described below in detail with reference to examples. In the examples, “parts” and “%” are all parts by weight and% by weight. In the following examples, lamp lenses and cured films were evaluated by the following methods. 1) Molecular weight of polymer Determined by GPC method (solvent: chloroform) using PMMA as a standard. 2) Polymer composition Quantified by 1H NMR (solvent: chloroform-d, measurement temperature: 60 ° C).

3) After drying at a saturated water absorption of 80 ° C., the weight was measured, and then immersed in warm water of 25 ° C. until the weight reached equilibrium. The weight after equilibrium was measured and determined by the following equation.

Saturated water absorption (%) = [(water absorption−dry weight) / dry weight] × 100 4) Total light transmittance Measured with an integrating sphere haze meter according to ASTM D1003. 5) VICAT softening temperature Measured according to ASTM D1525.

6) Yellowness index (YI value) The yellowness index was measured according to JIS K-7103 using a color difference analyzer (type 307, manufactured by Hitachi, Ltd.). The YI values are X, Y,
It was calculated by the following equation based on the Z stimulus value. YI value = 100 (1.28X-1.06Z) / Y 7) Specific gravity Measured using an auto pycnometer 1320 (manufactured by Shimadzu Corporation).

8) Abrasion resistance (Steel wool abrasion resistance) A # 000 steel wool ("Bonstar" manufactured by Nippon Steel Wool Co., Ltd.) was mounted on a circular pad having a diameter of 25 mm and placed on a reciprocating abrasion tester stand. The pad was placed on the surface of the held sample and subjected to 50 reciprocal scratches under a load of 1000 g. This sample was washed with a neutral detergent, and the haze value was measured with a haze meter. The resistance to steel wool abrasion is indicated by "haze value after abrasion-haze value before abrasion".

9) Adhesion of the cured film The surface of the sample was scribed with a razor to make 11 vertical and horizontal scratches at 1.5mm intervals to make 100 squares, and a cellophane tape 25mm width
(Nichiban Co., Ltd.) is pressed against the squares and rapidly removed upward. The evaluation of this result is the number of remaining squares / the number of all squares.
(100).

10) Weather resistance Sunshine weatherometer (WE-produced by Suga Test Instruments Co., Ltd.)
Using SUN-DC), exposure was performed at a black panel temperature of 63 ° C. and a cycle of 12 minutes of water / 60 minutes of drying for 1000 hours and 1500 hours. This sample was observed for the following appearance items. The appearance of the coating such as cracks, crazing, delamination, haze, yellowish color and the like was observed.

Example 1 In a flask having a capacity of 2 liters, 824 g (4 mol) of tricyclodecanyl acrylate, 160 g (4 mol) of paraformaldehyde having a purity of 75%, and 60 g (0.53 g) of 1,4-diazabicyclo [2,2,2] octane mol), p-methoxyphenol 616mg, t-
120 g of butyl alcohol while air bubbling
The reaction was performed at 80 ° C. for 5 days. After the completion of the reaction, the reaction solution was poured into 3 L of methanol and stirred for 30 minutes. Then
This mixed solution was allowed to stand at −20 ° C. overnight, and bis (α) as white crystals was formed.
Thus, 712 g (yield 79.2%) of -hydroxymethylacrylic acid tricyclodecanyl) ether was obtained.

In a 5 L flask containing 2500 ml of toluene as a solvent, 250 g of bis (α-hydroxymethyl acrylate tricyclodecanyl) ether and 250 g of methyl methacrylate (MMA) were added and dissolved. To this solution was added 3 g of pertetra A (manufactured by NOF Corporation, purity: 20 wt.%) As an initiator, and the mixture was stirred for 40 minutes while purging with nitrogen. Thereafter, the mixture was heated to 95 ° C. to start the polymerization, and the polymerization was performed for 7 hours.

This reaction solution was put into a large amount of methanol to precipitate a polymer, which was filtered and washed with methanol. This is vacuum dried to obtain 455 g of a powdery polymer (yield:
91%).

An extruder equipped with this polymer and having a 30φ double vent
(Barrel temperature: about 250 ° C.) to form a strand and pelletize. Using the obtained pellets, a lamp lens is injection-molded to form an outer dimension of 200 mm × 100 mm ×
A 50 mm lamp lens was manufactured. Using an injection molding machine IS-100 manufactured by Toshiba Machine Co., molding was performed under the conditions of a cylinder temperature of 250 ° C., a mold temperature of 100 ° C., and an injection pressure of 1350 kg / cm ² .

A part of the obtained lamp lens was cut and its physical properties were measured. The result was as follows. 1) Molecular weight of polymer: Mn = 95000 2) Polymer composition: tricyclodecanyl ester / methyl methacrylate = 50/50 3) Saturated water absorption: 0.9% 4) Total light transmittance: 91% 5) VICAT softening temperature 6) Yellowness index (YI value): 1.5 7) Specific gravity: 1.15 g / cm ³ .

Example 2 The following two types of curing liquids were prepared. 1) Composition of curing liquid 1 Dipentaerythritol hexaacrylate 39 parts Dipentaerythritol pentaacrylate 28 parts Tetrahydrofurfuryl acrylate 35 parts 2-hydroxy-4-n-octoxybenzophenone 10 parts Benzoin / isopropyl ether 4 parts Then, 75 parts of isopropyl alcohol and 75 parts of toluene were added as organic solvents to obtain a curing liquid 1.

2) Composition of curing liquid 2 33 parts of dipentaerythritol hexaacrylate 22 parts of dipentaerythritol pentaacrylate Trimethylolethane / succinic acid / acrylic acid = esterified compound synthesized from 2/1 / 4.4 (molar ratio) 10 parts Tetrahydrofurfuryl acrylate 35 parts 2,4-dihydroxybenzophenone 10 parts Benzoin ethyl ether 4 parts Based on the above composition, 75 parts of isopropyl alcohol and 75 parts of n-butyl acetate were added as an organic solvent to obtain a curing liquid 2. .

After coating these two types of curing liquids on the outer surface of the lamp lens, the organic solvent was removed by evaporation at room temperature for 5 minutes. Then, it was cured by irradiation with a high-pressure mercury lamp (“I-Graphic” H08L21). With respect to the obtained lamp lens, the abrasion resistance of the cured film, the adhesion of the cured film, and the weather resistance of the lamp lens were evaluated, and the results shown in Table 1 were obtained.

[0031]

[Table 1]

[0032]

The lamp lens of the present invention is lightweight, has high transparency and heat resistance, and has excellent weather resistance.

[Brief description of the drawings]

FIG. 1 is a perspective view of a vehicle lamp lens.

FIG. 2 is an enlarged sectional view of a lens portion of FIG.

FIG. 3 is an enlarged sectional view of a lens portion of a lamp lens having a cured film formed on an outer surface.

[Explanation of symbols]

 1 base material for lamp lens 2 lens group 3 cured film

Claims (2)

[Claims] 1. A lamp lens formed of a polymer containing a repeating unit represented by the following general formula (1). Embedded image (In the formula, R ¹ represents a hydrogen atom or a hydrocarbon group having 1 to 25 carbon atoms, an alicyclic hydrocarbon group, or a substituted hydrocarbon group, and n represents a positive integer.) 2. The lamp lens according to claim 1, wherein a cured film of a cross-linkable curable resin material is formed on an outer surface.