JP2009054348A - Vehicle lighting - Google Patents

Abstract

Provided is a vehicular lamp in which an anti-fogging coating film can exhibit excellent anti-fogging properties and can suppress appearance defects such as water dripping marks on the inner surface of a lens.
An automotive headlamp as a vehicular lamp includes a light source bulb in a housing, a front lens that transmits light from the light source bulb, and an atmospheric pressure fluctuation in the housing. A ventilation hole 18 is provided. On the inner surface 13a of the front lens 13, an anti-fogging coating film 16 is formed which is formed of a crosslinked body obtained by three-dimensionally crosslinking a water-soluble polymer and has a water absorption of 1.5 to 25 mg / cm ² . It is preferable that the cross-linked portion constituting the cross-linked body has an ether bond or a siloxane bond, and the coating film residual ratio after being immersed in water at 40 ° C. for 240 hours is 20 to 100% by mass. Moreover, it is preferable that the crosslinked body is formed of a random copolymer.
[Selection] Figure 1

Description

  In the present invention, for example, by forming a specific antifogging coating film on the inner surface of the front lens of the housing constituting the automotive headlamp, it is possible to exhibit excellent antifogging properties and The present invention relates to a vehicular lamp that can suppress the occurrence of poor appearance.

  Conventionally, in a vehicle lamp, in particular, an automotive headlamp, when a light source bulb is turned on, light generated from the light source bulb is reflected on the reflecting surface of the reflector, and the reflected light is transmitted through the front lens, so that a predetermined light distribution pattern is obtained. Irradiate outside. In this case, when the light source bulb generates heat, the air inside the housing is warmed and expanded, and when the light source bulb is turned off, the air inside the housing shrinks. In order to prevent such pressure fluctuations in the housing due to the expansion or contraction of the air in the housing, the housing is provided with a vent hole that is a vent means for communicating the inside of the housing with the outside. And microtex etc. which are the film | membrane materials which let air permeate | transmit and do not let water pass through the vent hole as needed.

  However, when high-humidity air enters the housing when the air pressure in the housing is adjusted by the vent holes, moisture is applied to the inner surface of the front lens when the front lens is cooled by the outside air or rain. Condensation may cause clouding. At that time, there is a problem that the brightness of the automotive headlamp is lowered, a predetermined light distribution characteristic cannot be obtained, or the aesthetic appearance of the lens surface is impaired, thereby causing discomfort to the user.

In order to prevent such fogging on the inner surface of the front lens, a vehicular lamp (see, for example, Patent Document 1) provided with a sealed space in a place where fogging is likely to occur, or a vehicle in which a resistance heating element is laid on the front lens. There have been proposed lamps (for example, see Patent Document 2), lamps (for example, see Patent Document 3) in which an antifogging agent is applied to the inner surface of a lens, and the like. In addition, as a coating composition capable of forming an antifogging film, it is formed from (meth) acrylic acid ester containing a quaternary ammonium salt, other (meth) acrylic acid ester and vinyl ester such as methoxysilane. What consists of a copolymer is known (for example, refer patent document 4).
JP-A-10-64304 (pages 2 and 3) Japanese Patent Laid-Open No. 10-109587 (pages 2 and 5) Japanese Utility Model Publication No. 5-87706 (2nd page) JP 2002-265853 A (pages 2 and 4)

  However, the vehicular lamp described in Patent Document 1 can prevent fogging only on a part of the inner surface of the front lens, and the vehicular lamp described in Patent Document 2 has a certain fog reduction effect and an effect of making the fog inconspicuous. Although obtained, there is a problem that the structure of the vehicular lamp is complicated and the manufacturing cost increases.

  In addition, in the lamp described in Patent Document 3, when a water film is formed on the surface of a coating film using a general antifogging agent containing a surfactant, the water may flow down locally, There was a problem that the surfactant dissolved out of the anti-fogging coating film after drying was deposited, leaving a trace of water dripping on the inner surface of the front lens. On the other hand, when no surfactant is added to suppress the occurrence of water dripping traces, sufficient antifogging properties cannot be obtained.

  In addition, in the anti-fogging coating composition described in Patent Document 4, since the quaternary ammonium salt is contained in the (meth) acrylic acid ester, particularly when it is placed in a heating environment for a long period of time. There was a problem in that decomposition easily occurred and the surface of the coating became rough and the appearance deteriorated. Furthermore, in the invention described in Patent Document 4, in order to improve the balance between hydrophilicity and hydrophobicity, hydrophilicity cannot be fully expressed at the expense of hydrophobicity, and the water absorption amount of the coating is insufficient. There was a problem.

  Therefore, the object of the present invention is that the anti-fogging coating film can exhibit excellent anti-fogging properties and can suppress occurrence of poor appearance such as water dripping marks on the inner surface of the lens. The object is to provide a vehicular lamp.

In order to achieve the above object, a vehicular lamp according to a first aspect of the present invention includes a light source in a housing, a lens that transmits light from the light source, and a vent hole for adjusting pressure fluctuations in the housing. The vehicular lamp includes a cross-linked body obtained by three-dimensionally cross-linking a water-soluble polymer on the inner surface of the lens, and an antifogging coating film having a water absorption of 1.5 to 25 mg / cm ² is formed. It is characterized by that.

  In the vehicular lamp of the second invention, in the first invention, the cross-linked portion constituting the cross-linked body has an ether bond or a siloxane bond, and the coating film remaining ratio after being immersed in water at 40 ° C. for 240 hours is 20 It is -100 mass%.

  According to a third aspect of the present invention, there is provided the vehicular lamp according to the second aspect, wherein the cross-linked body is formed from a monomer (A), a monomer (B), and a monomer (C) shown below. And the content of the monomer (C) is 0.2-5 parts by mass with respect to a total of 100 parts by mass of the monomer (A) and the monomer (B). The mass average molecular weight of the coalescence is 100,000 to 1,000,000.

Monomer (A): Non-crosslinkable water-soluble vinyl monomer Monomer (B): Non-crosslinkable water-insoluble vinyl monomer Monomer (C): By condensation reaction or addition reaction Vinyl monomer having a crosslinkable functional group capable of cross-linking The vehicle lamp of the fourth invention is characterized in that, in the third invention, the cross-linked product is formed of a random copolymer.

  According to a fifth aspect of the present invention, there is provided a vehicular lamp according to any one of the first to fourth aspects, wherein the vehicular lamp is an automotive headlamp, and light from a light source is forwarded through a lens in the housing. It is characterized by having a reflector to reflect.

According to the present invention, the following effects can be exhibited.
In the vehicular lamp according to the first aspect of the present invention, there is provided an anti-fogging coating film comprising a crosslinked body obtained by three-dimensionally crosslinking a water-soluble polymer on the inner surface of the lens and having a water absorption of 1.5 to 25 mg / cm ^2. Is formed. For this reason, the anti-fogging coating film can exhibit sufficient water absorption, can suppress fogging due to dew condensation on the inner surface of the lens, and at the same time, can suppress the occurrence of dripping of water drops. Therefore, the anti-fogging coating film can exhibit excellent anti-fogging properties and can suppress the appearance defects such as water dripping traces on the inner surface of the lens.

  In the vehicular lamp of the second invention, the cross-linked portion constituting the cross-linked body has an ether bond or a siloxane bond, and the coating film remaining ratio after being immersed in water at 40 ° C. for 240 hours is 20 to 100% by mass. . For this reason, in addition to the effects of the first invention, the water resistance of the anti-fogging coating film can be increased, the dissolution of the anti-fogging coating film can be suppressed and the residual rate can be increased, and the appearance of the vehicle lamp is poor. Can be suppressed over a long period of time.

  In the vehicular lamp of the third invention, the crosslinked body contains a copolymer formed from the monomer (A), the monomer (B) and the monomer (C), and the monomer ( The content of C) is 0.2 to 5 parts by mass with respect to a total of 100 parts by mass of the monomer (A) and the monomer (B), and the mass average molecular weight of the copolymer is 100,000 to 1,000,000. For this reason, the effect which concerns on 2nd invention can be improved, and also the heat resistance of an anti-fogging coating film can be improved by raising a crosslinking density and molecular weight.

  In the vehicular lamp of the fourth invention, since the crosslinked body is formed of a random copolymer, in addition to the effect according to the third invention, the random copolymer can exhibit a uniform function and is anti-fogging. The effect of the anti-fogging coating including the properties can be further enhanced, and the anti-fogging coating can be easily formed.

  A vehicular lamp according to a fifth aspect of the present invention is an automotive headlamp, and a housing includes a reflector that reflects light from a light source forward through a lens. Therefore, the effects according to any one of the first to fourth inventions can be effectively exhibited in the automotive headlamp.

In the following, embodiments that are considered to be the best of the present invention will be described in detail.
The vehicular lamp according to the present embodiment includes a light source in the housing, a lens that transmits light from the light source, and a vent hole for adjusting atmospheric pressure fluctuation in the housing. Furthermore, the vehicular lamp is, for example, an automotive headlamp, and a reflector that reflects light from the light source forward through a lens is provided in the housing. And the anti-fogging coating film which is comprised with the crosslinked body which water-soluble polymer was bridge | crosslinked three-dimensionally on the inner surface of the said lens, and has a water absorption of 1.5-25 mg / cm < ² > is formed. In vehicular lamps, the lens is cooled by the outside air and moisture is condensed on the inner surface of the lens, resulting in cloudiness, the brightness from the light source is reduced, and the desired light distribution characteristics cannot be obtained. A membrane is required. In addition to headlamps, auxiliary headlamps, vehicle width lights, number lights, tail lights, parking lights, brake lights, reverse lights, turn signal lights, auxiliary turn signal lights, emergency blinking lights, etc. Is mentioned.

FIG. 1 shows a longitudinal cross-sectional view of a preferred embodiment for a vehicle headlamp, and the vehicle headlamp will be described below.
That is, in the automotive headlamp 10 as a vehicle lamp, the engagement recess 12 provided at the front end of the cylindrical housing 11 is engaged with the engagement provided at the rear end of the front lens 13 as a lens. The convex portions 14 are engaged, and the engaging portions are bonded with an adhesive 15 such as a hot melt adhesive and are connected in an airtight manner. The housing 11 is made of, for example, a synthetic resin. The front lens 13 is formed of a material that is light transmissive (transparent) and has good thermal conductivity, such as a synthetic resin. On the inner surface 13a of the front lens 13, the above-described antifogging coating film 16 is formed with a predetermined thickness.

  A lamp chamber space 17 is formed between the front portion of the housing 11 and the front lens 13. A vent hole 18 is opened at the rear portion of the housing 11, and a cylindrical cap 19 is attached to the rear end portion of the housing 11. A reflector 20 having an arc shape in cross section is supported at the rear part in the housing 11 by a support member (not shown). The reflector 20 is formed of, for example, a thermosetting resin or the like, and the inner surface thereof is a reflecting surface 21 made of, for example, an aluminum deposition film. The reflector 20 is disposed in the housing 11 so as to be tiltable in the vertical and horizontal directions by a pivot bearing (not shown).

  A center portion of a light source bulb 23 as a light source is fitted and supported in the fitting hole 22 at the rear end portion of the reflector 20. The light source bulb 23 is configured by arranging a filament 25 in a glass tube bulb 24, and a connection terminal 27 is projected from a rear portion via a base 26 formed in a cylindrical shape. The light emitted from the light source bulb 23 is reflected on the reflecting surface 21 on the inner surface of the reflector 20, passes through the antifogging coating film 16 and the front lens 13, and is irradiated forward.

  The light source bulb 23 is inserted from behind the fitting hole 22 of the reflector 20, the flange portion 28 of the light source bulb 23 is brought into contact with the peripheral edge of the fitting portion 29 of the reflector 20, and the light source bulb 23 is attached by a light source bulb fitting (not shown). The reflector 20 is detachably attached. As a result, the light source bulb 23 protrudes to the front side of the reflector 20 and is disposed in the lamp chamber space 17 via the reflector 20.

  Between the base 26 of the light source bulb 23 and the rear end portion of the housing 11, a rubber waterproof cover 30 formed in an accordion shape is mounted so that water does not enter the housing 11. Yes. That is, the waterproof cover 30 includes a boss portion 31 provided on the inner peripheral edge portion and a seal portion 32 provided on the outer peripheral edge portion. The boss 31 of the waterproof cover 30 is attached to the base 26 of the light source bulb 23 in a watertight and detachable manner. The seal portion 32 of the waterproof cover 30 is sandwiched between the rear end edge of the housing 11 and the cap 19 in a watertight and detachable manner. As a result, water is prevented from entering the housing 11 and the lamp chamber space 17 from the rear end opening of the housing 11.

The antifogging coating film 16 of the thus configured automotive headlamp 10 is formed over substantially the entire inner surface 13 a of the front lens 13. The anti-fogging coating film 16 is composed of a crosslinked product obtained by three-dimensionally crosslinking a water-soluble polymer as described above, and its water absorption is 1.5 to 25 mg / cm ² , preferably 2.0 to ²⁰ mg / cm ^2. cm ² . Here, the water-soluble polymer means a polymer having a solubility of 10 parts by mass or more with respect to 100 parts by mass of water at 25 ° C. By cross-linking the water-soluble polymer three-dimensionally, the anti-fogging coating film 16 having good water absorption can be obtained.

The water absorption is the amount of water that can be absorbed per unit area (unit surface area) by the antifogging coating film 16. For example, in an actual use environment of the automotive headlamp 10, if an anti-fogging coating film 16 having a water absorption amount of 1.5 mg / cm ² or more is formed on the inner surface 13a of the front lens 13, fogging or water A good anti-fogging effect can be obtained without dripping. When the water absorption of the anti-fogging coating film 16 is less than 1.5 mg / cm ² , fogging occurs, or water that cannot be absorbed overflows and dripping occurs. On the other hand, when the water absorption amount of the anti-fogging coating film 16 exceeds 25 mg / cm ² , it is necessary to increase the water absorption of the anti-fogging coating film 16, so that the heat resistance, water resistance and the like deteriorate.

The film thickness of the antifogging coating film 16 is preferably 0.5 to 20 μm, and more preferably 1 to 10 μm, in order to obtain good antifogging properties and coating film appearance. When this film thickness is thinner than 0.5 μm, the antifogging property of the antifogging coating film 16 tends to decrease, and when it exceeds 20 μm, the coating film appearance tends to deteriorate. Generally, in the case of the water-absorbing anti-fogging coating film 16, the water absorption amount depends on the film thickness of the anti-fogging coating film 16. Therefore, in the antifogging coating film 16 of this embodiment, in order to obtain a water absorption amount of 1.5 mg / cm ² or more, the film thickness must be increased as the water absorption of the antifogging coating film 16 is lower. However, if the film thickness is too thick, it is difficult to obtain a smooth coating film, and the coating film appearance tends to deteriorate.

  The antifogging coating film 16 is preferably an ether bond or a siloxane bond from the viewpoint of enhancing the water resistance thereof. Unlike the ester bond and the like, these bonds are hardly hydrolyzed and have excellent water resistance and durability. The anti-fogging coating film 16 preferably has a coating film residual ratio of 20 to 100% by mass, more preferably 30 to 100% by mass after being immersed in water at 40 ° C. for 240 hours. Here, the coating film remaining rate is the anti-residue remaining on the inner surface without being dissolved in water after the front lens 13 having the anti-fogging coating film 16 formed on the inner surface 13a is immersed in water at 40 ° C. for 240 hours. The ratio of the cloudy coating film 16 is expressed by mass%. When the coating film residual ratio is less than 20% by mass, the water resistance of the antifogging coating film 16 is lowered, and when the moisture is absorbed, the antifogging coating film 16 may be dissolved and the coating film appearance may be lowered. .

  The anti-fogging coating film 16 of this embodiment applies the anti-fog coating composition which has a water-soluble polymer as a main component to the inner surface of the front lens 13, and is dried and hardened so that the water-soluble polymer is three-dimensionally. It is comprised by the crosslinked body which is bridge | crosslinked. As such an antifogging coating composition, the following compositions are preferred. That is, the anti-fogging coating composition contains a copolymer formed from the monomer (A), monomer (B) and monomer (C) shown below. Here, the content of the monomer (C) is 0.2 to 5 parts by mass with respect to a total of 100 parts by mass of the monomer (A) and the monomer (B), and the mass of the copolymer. The average molecular weight is 100,000 to 1,000,000. According to this anti-fogging coating composition, good anti-fogging properties and heat resistance can be exhibited to a higher degree, and occurrence of appearance defects such as fogging and dripping marks on the inner surface 13a of the front lens 13 is remarkably suppressed. can do.

Monomer (A): Non-crosslinkable water-soluble vinyl monomer Monomer (B): Non-crosslinkable water-insoluble vinyl monomer Monomer (C): By condensation reaction or addition reaction First, the monomer (A) that forms the copolymer, that is, the non-crosslinkable water-soluble vinyl monomer will be described. This water-soluble vinyl-based monomer is a monomer that causes the copolymer to exhibit water absorption and exhibit a function of improving antifogging properties. Here, a water-soluble vinyl-type monomer means the vinyl-type monomer which has a solubility of 10 mass parts or more with respect to 100 mass parts of water at 25 degreeC. The solubility of the water-soluble vinyl monomer is not particularly limited as long as it is 10 parts by mass or more with respect to 100 parts by mass of water at 25 ° C. Moreover, non-crosslinking property means that the crosslinking reaction based on a condensation reaction or an addition reaction does not occur.

  Examples of the water-soluble vinyl monomer include (meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-ethyl (meth) acrylamide, and N, N-diethyl (meth). Acrylamide, Nn-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-dimethylaminoethyl (meth) acrylamide, N-dimethylaminopropyl (meth) acrylamide, diacetone (meth) acrylamide, N- (meta) ) (Meth) acrylamide monomers such as acryloylpiperidine, (meth) acryloylmorpholine; carboxyl group-containing vinyl monomers such as (meth) acrylic acid, itaconic acid, crotonic acid, and ammonium salts thereof, organic Amine salts, alkali metal salts; styrene Sulfonic acid group-containing vinyl monomers such as sulfonic acid, vinyl sulfonic acid, methallyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, and ammonium thereof Examples include salts, organic amine salts, alkali metal salts and the like.

  Among these water-soluble vinyl monomers, (meth) acrylamide monomers are preferable from the viewpoint that the adhesion of the antifogging coating film 16 to the inner surface of the front lens can be improved. Furthermore, from the viewpoint that the heat resistance of the anti-fogging coating film 16 can be improved, N, N-dialkyl (meth) acrylamide systems such as N, N-dimethyl (meth) acrylamide and N, N-diethyl (meth) acrylamide are used. Monomers are particularly preferred. One or two or more of these water-soluble vinyl monomers are appropriately selected and used.

  The content of the monomer (A) is preferably 50 to 95 parts by mass, and 65 to 90 parts by mass when the total of the monomer (A) and the monomer (B) is 100 parts by mass. More preferably, it is a part. When the content of the monomer (A) is less than 50 parts by mass, a water-soluble polymer is not obtained, so that a sufficient water absorption amount cannot be obtained. The film remaining rate tends to decrease.

  The antifogging coating composition includes a copolymer composed of a (meth) acrylate ester containing a quaternary ammonium salt, a (meth) acrylic acid ester, and a vinyl ester having methoxysilane or ethoxysilane, and other simple substances. A room temperature curable coating composition comprising a copolymer of a monomer can also be used.

  The (meth) acrylate ester containing the quaternary ammonium salt is a component for enhancing water absorption, and methyl chloride salt of dimethylaminoethyl methacrylate is preferable. The composition ratio of the (meth) acrylate ester containing a quaternary ammonium salt in the copolymer is 50 to 70% by mass. When the ratio of the (meth) acrylate ester containing a quaternary ammonium salt is lower than 50% by mass, it does not become a water-soluble polymer, so a satisfactory water absorption amount cannot be obtained, and when it is higher than 70 parts by mass. The water resistance of the copolymer is lowered. (Meth) acrylic acid ester is a component for increasing the water resistance and strength of the coating film. The composition ratio of the (meth) acrylic acid ester in the copolymer is 30 to 50% by mass. Vinyl ester having methoxysilane or ethoxysilane is a component for forming a three-dimensional crosslink by curing at room temperature, and γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropyltriethoxysilane, etc. Can be mentioned. The composition ratio of the vinyl ester having methoxysilane or ethoxysilane in the copolymer is 0.000 with respect to a total of 100 parts by mass of the (meth) acrylate ester containing a quaternary ammonium salt and the vinyl ester having methoxysilane or ethoxysilane. 1 to 10 parts by mass.

  Next, the monomer (B), that is, the non-crosslinkable water-insoluble vinyl monomer will be described. The monomer (B) water-insoluble vinyl monomer exhibits the function of increasing the strength and hardness of the copolymer and increasing the adhesion of the anti-fogging coating film 16 to the inner surface 13a of the front lens 13. It is a monomer. Here, the monomer (B) water-insoluble vinyl monomer means a vinyl monomer having a solubility of less than 10 parts by mass with respect to 100 parts by mass of water at 25 ° C. Moreover, non-crosslinking property means that the crosslinking reaction based on a condensation reaction or an addition reaction does not occur.

  Examples of water-insoluble vinyl monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth). (Meth) acrylate based monomers such as acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, etc. Body; aromatic vinyl monomers such as styrene, vinyltoluene and α-methylstyrene. Among these water-insoluble vinyl monomers, a (meth) acrylate-based monomer is used from the viewpoint that the anti-fogging coating film 16 is increased in hardness and excellent adhesion to the inner surface 13a of the front lens 13 is obtained. A monomer is preferred. One or two or more of these water-insoluble vinyl monomers are appropriately selected and used.

  The content of the monomer (B) is preferably 5 to 50 parts by mass, and 10 to 35 parts by mass when the total of the monomer (A) and the monomer (B) is 100 parts by mass. It is more preferable that When the content of the monomer (B) is less than 5 parts by mass, the coating film remaining rate of the resulting anti-fogging coating film 16 is reduced, and when it is more than 50 parts by mass, it does not become a water-soluble polymer. Satisfactory water absorption cannot be obtained.

  Next, the monomer (C), that is, a vinyl monomer having a crosslinkable functional group that can be crosslinked by a condensation reaction or an addition reaction will be described. The vinyl monomer of the monomer (C) is crosslinked by a condensation reaction such as a dehydration condensation reaction or a dealcoholization condensation reaction or an addition reaction (crosslinking reaction) to form a three-dimensional crosslinked structure in the copolymer molecule. It is a vinyl monomer having a crosslinkable functional group for formation. When the monomer (C) has such a crosslinkable functional group, a crosslinked structure can be formed in the copolymer by means such as heating after the production of the copolymer. Examples of the crosslinkable functional group that can be crosslinked by a condensation reaction include an N-methylol group, an N-alkoxymethylol group, and an alkoxysilyl group. Moreover, an epoxy group etc. are mentioned as a crosslinkable functional group which can be bridge | crosslinked by addition reaction.

  Examples of vinyl monomers having a crosslinkable functional group that can be crosslinked by a condensation reaction include N-methylol (meth) acrylamide, N-methoxymethylol (meth) acrylamide, N-butoxymethylol (meth) acrylamide, and the like. Vinyl monomers having a methylol group or an N-alkoxymethylol group; alkoxysilyl groups such as γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropyltriethoxysilane, vinyltrimethoxysilane, etc. Examples thereof include vinyl monomers. Examples of the vinyl monomer having a crosslinkable functional group that can be cross-linked by addition reaction include vinyl monomers having an epoxy group such as glycidyl (meth) acrylate, vinyl glycidyl ether, and allyl glycidyl ether.

  Among these monomers, vinyl having an N-methylol group or an N-alkoxymethylol group from the viewpoint of enhancing the water resistance of the antifogging coating film 16 and capable of crosslinking by a simple method of heat curing or room temperature curing. A vinyl monomer having an alkoxy monomer or an alkoxysilyl group is preferred. A vinyl monomer having an N-methylol group or an N-alkoxymethylol group generates an ether bond by curing, and a vinyl monomer having an alkoxysilyl group generates a siloxane bond by curing. Furthermore, it is more preferable that it is a vinyl-type monomer which has N-methylol group or N-alkoxy methylol group from a viewpoint that it is excellent in the storage stability of an anti-fog coating composition, and can be heat-hardened in a short time. Further, together with a vinyl monomer having an N-methylol group or an N-alkoxymethylol group, a vinyl monomer having a hydroxyl group capable of undergoing a heat condensation reaction with these may be used in combination. Examples of such a vinyl monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxyethyl (meta). ) Hydroxyl group-containing vinyl monomers such as ε-caprolactone adduct of acrylate.

  Among these, N-methylol (meth) acrylamide or N-alkoxymethylol (meth) acrylamide or a combined system of these and a hydroxyl group-containing vinyl monomer is particularly preferable in terms of excellent curability. One or two or more vinyl monomers having these crosslinkable functional groups are selected and used. Here, the first (heating) curing reaction is a crosslinking reaction based on a dehydration condensation reaction between N-methylol groups, and the second is a crosslinking reaction based on a dealcoholization condensation reaction between N-methylol groups and N-alkoxymethylol groups. is there. Further, the third is a crosslinking reaction based on a dehydration condensation reaction with an N-methylol group and a hydroxyl group, and the fourth is a crosslinking reaction based on a dealcoholization condensation reaction with an N-alkoxymethylol group and a hydroxyl group. From the viewpoint of excellent reactivity, it is particularly preferable to use the first, second, or third heat curing reaction.

  The content of the monomer (C) is preferably 0.2 to 5 parts by mass, more preferably 0.5 to 100 parts by mass in total of the monomer (A) and the monomer (B). ~ 3 parts by mass. When the content of the monomer (C) is less than 0.2 parts by mass, the crosslinking density of the copolymer is lowered and the coating film residual ratio of the anti-fogging coating film 16 is reduced, and when the content is more than 5 parts by mass Is not preferable because the crosslink density of the copolymer is increased and the antifogging property of the antifogging coating film 16 is lowered.

  The copolymer in this embodiment contains a polyfunctional vinyl monomer in addition to the monomer (A), monomer (B) and monomer (C) for the purpose of increasing the mass average molecular weight. Can be polymerized. Although these vinyl monomers have a crosslinkable functional group, they are not crosslinkable functional groups by condensation reaction or addition reaction. Such polyfunctional vinyl monomers include N, N′-methylenebis [(meth) acrylamide], neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri ( Meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, or the like is used. The copolymerization amount of the polyfunctional vinyl monomer is preferably 1 part by mass or less with respect to 100 parts by mass in total of the monomer (A) and the monomer (B).

  The mass average molecular weight of the copolymer in the present embodiment is an average molecular weight based on mass (weight) shown in terms of polystyrene measured by gel permeation chromatography (GPC). The measurement conditions are as follows.

Column: Three connected columns (first column: Shodex KD-802.5, second column: Shodex KD-803, third column: Shodex KD-80M, all manufactured by Showa Denko KK), column temperature: 55 ° C, developing solvent: N, N-dimethylformamide, flow rate: 1.0 ml / min
The mass average molecular weight measured by GPC of the copolymer in this embodiment is preferably 100,000 to 1,000,000, more preferably 150,000 to 700,000. When the weight average molecular weight of the copolymer is less than 100,000, the amount of water that can be absorbed in the resulting anti-fogging coating film 16 is reduced, and the anti-fogging coating film 16 has fogging and dripping traces. As it occurs, the coating film residual ratio also decreases. On the other hand, when the mass average molecular weight exceeds 1,000,000, the viscosity of the anti-fogging coating composition becomes high and handling as a coating becomes difficult. As a result, it becomes difficult to apply the antifogging coating composition, and problems such as deterioration of the appearance of the antifogging coating film 16 occur.

  The copolymer of the present embodiment may have any structure of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer. A random copolymer is preferable from the viewpoint that the effect can be improved and an antifogging coating composition can be easily prepared. As a polymerization method for obtaining a copolymer, various known polymerization methods such as a radical polymerization method, a cationic polymerization method, an anion living polymerization method, and a cation living polymerization method are adopted, but industrial productivity is particularly easy. The radical polymerization method is preferable from the viewpoint of performance over a variety of meanings. As the radical polymerization method, a normal bulk polymerization method, suspension polymerization method, solution polymerization method, emulsion polymerization method and the like are employed, but the solution polymerization method is preferable in that it can be used as a coating after polymerization.

Next, the manufacturing method of the anti-fogging coating composition in this embodiment, especially the manufacturing method by the solution polymerization method of a copolymer are demonstrated below.
In a reaction vessel equipped with a stirrer, a thermometer, a nitrogen introduction tube and a reflux tube, an organic solvent as a polymerization solvent, a monomer (A), 70% by mass or less of the total amount of the monomer (B) and a monomer ( C) is charged and heated to a predetermined temperature while blowing nitrogen gas. Next, the remainder of the monomer (B) and the radical polymerization initiator are added dropwise over 30 minutes to 10 hours, and a copolymer solution is further obtained by performing a polymerization reaction for 30 minutes to 10 hours.

  A monomer (A) or a monomer (C) can make the mass average molecular weight of the copolymer obtained high by charging all into an reaction container first with an organic solvent. However, it is not always necessary to initially charge the whole in the reaction vessel, and if it is desired to adjust the mass average molecular weight or the heat generation due to polymerization, 30% by mass or more of the total amount can be initially charged in the reaction vessel together with the polymerization solvent. The remainder can be added dropwise to carry out the polymerization. If the initially charged amount is less than 30% by mass of the total amount, the mass average molecular weight of the resulting copolymer tends to be low, which is not preferable.

  For the monomer (B), 70% by mass or less of the total amount is first charged into the reaction vessel together with the monomer (A), the monomer (C) and the organic solvent, and the remainder is dropped to perform polymerization. Thus, by dripping a monomer (B) in reaction container and superposing | polymerizing, since the heat_generation | fever by a polymerization reaction can be made small, it is preferable when manufacturing industrially. When the amount charged initially exceeds 70% by mass of the total amount, heat generation due to polymerization increases, and it tends to be difficult to control the polymerization reaction in industrial production.

  In most cases, the polymerization reaction rates of the monomer (A) and the monomer (B) are different. Therefore, the monomer (A) is polymerized by adding the monomer (B) dropwise. ) And the monomer (B) to compensate for the difference in the polymerization reaction rate and to suppress the deviation of the copolymer composition. Further, the amount of the monomer (B) initially charged is preferably 10 to 50% by mass of the total amount from the viewpoint that the heat generated by the polymerization can be more easily controlled.

  As for the organic solvent, the use of the organic solvent having a remarkably high boiling point is that the antifogging coating film 16 adheres to the inner surface 13a of the front lens 13 as an object to be coated due to the solvent remaining during drying and heat curing of the antifogging coating film 16. The organic solvent having a boiling point of less than 180 ° C. is preferably used. Examples of the organic solvent include alcohol solvents such as methanol, ethanol, isopropanol, diacetone alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, 3-methoxy-1- Alcohol ether solvents such as butanol and 3-methoxy-3-methyl-1-butanol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ether solvents such as tetrahydrofuran and dioxane; methyl acetate, ethyl acetate, Ester solvents such as n-butyl acetate, isobutyl acetate, t-butyl acetate, methyl lactate and ethyl lactate; aromatic solvents such as benzene, toluene and xylene; Formamide, amide solvents such as dimethylformamide is used. These polymerization solvents are used alone or in combination of two or more.

  The ratio of the total amount of the monomer (A) and the monomer (B) and the organic solvent used for the polymerization reaction is a mass ratio, the total amount of the monomer (A) and the monomer (B) / organic. The solvent is preferably 20/80 to 80/20, and more preferably 30/70 to 70/30. When the ratio of the organic solvent exceeds 80% by mass, the molecular weight of the obtained copolymer tends to be low, and when it is less than 20% by mass, heat generation due to polymerization tends to increase and industrial production tends to be difficult. The content (solid content) of the copolymer in the copolymer solution is preferably 3 to 70% by mass, more preferably 20 to 50% by mass. When the content of this copolymer is less than 3% by mass, the content of the copolymer is too low, the amount of the copolymer in the antifogging coating composition is reduced, and the coating film becomes too thin. Productivity tends to decrease, and when it exceeds 70% by mass, the viscosity of the copolymer solution becomes high and handling becomes difficult.

  As the radical polymerization initiator, generally used organic peroxides, azo compounds and the like can be used. Examples of the organic peroxide include benzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, and t-butyl peroxypivalate. Examples of the azo compound include 2,2′-azobisisobutyro Nitriles, 2,2′-azobis-2-methylbutyronitrile and the like can be mentioned. It is preferable that content of a radical polymerization initiator is 0.01-3 mass parts with respect to a total of 100 mass parts of a monomer (A) and a monomer (B). The radical polymerization initiator is preferably polymerized while being dropped into the reaction vessel in terms of easy control of heat generated by the polymerization. The temperature at which the polymerization reaction is carried out is appropriately changed depending on the type of radical polymerization initiator to be used, but the preferred polymerization temperature for industrial production is 30 to 150 ° C, and the more preferred polymerization temperature is 40 to 100 ° C. is there.

  Next, the copolymer or copolymer solution obtained by polymerization is dissolved, dispersed or diluted by adding a solvent for the purpose of adjusting the viscosity suitable for coating. Examples of such a solvent include alcohol solvents such as water, methanol, ethanol, isopropanol, diacetone alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, 3-methoxy Alcohol ether solvents such as -1-butanol and 3-methoxy-3-methyl-1-butanol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ether solvents such as tetrahydrofuran and dioxane; methyl acetate; Esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, methyl lactate and ethyl lactate; aromatics such as benzene, toluene and xylene Agents, formamide, amide solvents such as dimethylformamide; n- hexane, cyclohexane, n- heptane, n- octane, hydrocarbon solvents such n- decane, and the like. These solvents are used alone or in combination of two or more.

  If necessary, various conventional additives such as a leveling agent, an antioxidant, an ultraviolet absorber, a light stabilizer, and a curing catalyst can be added to the antifogging coating composition. In particular, the effect of increasing the speed of the crosslinking reaction can be obtained by blending a curing catalyst. Curing catalysts include inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid; acidic phosphoric acid alkyl esters such as monoalkyl phosphates and dialkyl phosphates; and aromatics such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid and naphthalenesulfonic acid Aromatic sulfonic acids and the like can be used, and aromatic sulfonic acids are preferred because they have a large effect of increasing the curing rate. One or more of these curing catalysts are appropriately selected and used.

  The content of the curing catalyst is preferably 0.1 to 15 parts by mass with respect to 100 parts by mass of the copolymer contained in the antifogging coating composition. When the content of the curing catalyst is less than 0.1 parts by mass, the effect of increasing the curing rate is not sufficiently exhibited, and when it is more than 15 parts by mass, the antifogging coating film turns yellow and the appearance is poor. There is a case. The curing catalyst is preferably blended immediately before the antifogging coating composition is applied to the inner surface 13a of the front lens 13. When a curing catalyst is previously blended in the antifogging coating composition, the antifogging coating composition may thicken or color over time.

  In order to further increase the coating film strength, a known curing agent can be added to the antifogging coating composition. Specific examples of the curing agent include methylols such as dimethylol urea, methylated trimethylol melamine, hexamethylol melamine, hexamethoxymethylol melamine, hexabutoxymethylol melamine, and the like. Examples thereof include compounds having two or more in the molecule. The content of these curing agents is preferably 20 parts by mass or less with respect to 100 parts by mass of the copolymer contained in the antifogging coating composition. When this content exceeds 20 mass parts, since the anti-fogging property of the obtained anti-fogging coating film 16 falls, it is not preferable.

  The antifogging coating composition thus obtained preferably contains 3 to 30% by mass of the copolymer, and more preferably 5 to 20% by mass. When the copolymer content is less than 3% by mass, the antifogging coating film 16 becomes too thin when the antifogging coating composition is applied to the inner surface 13a of the front lens 13, and satisfactory antifogging properties are obtained. Cannot be expressed. On the other hand, when it is more than 30% by mass, the viscosity of the antifogging coating composition becomes high and the coating work becomes difficult, and the antifogging coating film 16 becomes thick and the appearance tends to be deteriorated.

  Next, a method for forming the antifogging coating film 16 on the inner surface 13a of the front lens 13 using the above-described antifogging coating composition will be described. The antifogging coating film 16 is formed by first coating the antifogging coating composition on the inner surface 13a of the front lens 13 by a coating method performed in a normal paint. As the coating method, a dipping method, a flow coating method, a roll coating method, a bar coating method, a spray coating method and the like are suitable. At this time, for the purpose of improving the wettability of the anti-fogging coating composition to the inner surface 13a and preventing the repelling, it is preferable to remove adhered foreign matter, degrease and wash the inner surface 13a before coating. Specific examples include dust removal with high-pressure air or ionized air, ultrasonic cleaning with an aqueous detergent solution or an alcohol solvent, wiping using an alcohol solvent, cleaning with ultraviolet rays and ozone, and the like.

  After application of the antifogging coating composition, the solvent contained in the antifogging coating film 16 is volatilized and dried at a temperature of 30 to 60 ° C. for 1 to 15 minutes. Subsequently, the anti-fogging coating film 16 composed of a cross-linked water-soluble polymer is formed by heating and curing at a temperature of 75 to 150 ° C. for 5 to 180 minutes, preferably 10 to 120 minutes at a temperature of 100 to 150 ° C. It is formed on the inner surface 13 a of the lens 13. At this time, a heat condensation reaction (crosslinking reaction) occurs based on the crosslinkable functional group contained in the monomer (C) in the copolymer, and a crosslinked structure of the copolymer is formed. This crosslinking reaction is accelerated by the above-mentioned curing catalyst, and the crosslinking rate can be increased. However, when the front lens 13 is made of a synthetic resin material, it is necessary to set the curing temperature to be equal to or lower than the thermal deformation temperature of the synthetic resin material.

The actions and effects exerted by the above embodiment are collectively described below.
In the automotive headlamp 10 as the vehicle lamp in the present embodiment, the automotive headlamp 10 is configured by a cross-linked body in which a water-soluble polymer is three-dimensionally cross-linked to the inner surface 13a of the front lens 13, and is 1.5 to 25 mg / cm ^2. The anti-fogging coating film 16 having the water absorption amount is formed. For this reason, the anti-fogging coating film 16 can exhibit sufficient water absorption, can suppress fogging due to condensation on the inner surface 13a of the front lens 13, and at the same time, water is absorbed into the anti-fogging coating film 16. In this way, it is possible to suppress the occurrence of dripping water drops. Therefore, the anti-fogging coating film 16 can exhibit excellent anti-fogging properties, and it is possible to suppress appearance defects such as water dripping marks on the inner surface 13 a of the front lens 13.

  -The crosslinked part which comprises the said crosslinked body has an ether bond or a siloxane bond, and the coating-film residual rate after being immersed in 40 degreeC water for 240 hours is 20-100 mass%, Water resistance can be increased, and dissolution of the anti-fogging coating film 16 can be suppressed to increase its residual rate. As a result, the appearance defect of the automotive headlamp 10 can be suppressed over a long period of time.

  The cross-linked product contains a copolymer formed from the monomer (A), monomer (B) and monomer (C) described above, and the monomer (C) content is simple. It is 0.2 to 5 parts by mass with respect to a total of 100 parts by mass of the monomer (A) and the monomer (B), and the mass average molecular weight of the copolymer is 100,000 to 1,000,000. . Thus, by setting the content of the monomer (C) small and setting the mass average molecular weight of the copolymer large, the crosslinked body has a large molecular weight and has a crosslinked structure with an appropriate crosslinking density. Can do. Therefore, the crosslinked body can exhibit excellent water absorption and water resistance, and can also exhibit good heat resistance.

  In addition, since the crosslinked body is formed of a random copolymer, the random copolymer can exhibit a uniform function and can further enhance the effect of the antifogging coating film 16 including antifogging properties. At the same time, the anti-fogging coating film 16 can be easily formed by random copolymerization.

Hereinafter, the embodiment will be described more specifically with reference to reference examples, examples, and comparative examples, but the present invention is not limited to the scope of these examples. In the reference example, the manufacturing method of the material used in the examples and comparative examples is shown.
[Reference Example 1, Production of Antifogging Coating Composition 1]
In a reaction vessel equipped with a thermometer, a stirrer, a nitrogen introduction tube and a cooling tube, 50 g of isopropanol as an organic solvent, 80 g of N, N-dimethylacrylamide as a monomer (A), and as a monomer (B) 5 g of methyl methacrylate and 1.5 g of N-methylolacrylamide as the monomer (C) were charged and heated to 65 ° C. while blowing nitrogen gas. Thereto, 0.27 g of hydrocarbon diluted product of 3,5,5-trimethylhexanoyl peroxide [trade name: Perroyl 355 (S)] manufactured by NOF Corporation was dissolved in 30 g of isopropanol as a radical polymerization initiator. Was added dropwise over 1 hour. Simultaneously, 15 g of methyl methacrylate dissolved in 150 g of isopropanol was added dropwise over 3 hours. Furthermore, after superposing | polymerizing for 6 hours, it heated up at 80 degreeC and superposed | polymerized for 1 hour at the temperature, and the random copolymer solution 1 was obtained.

  And when GC (gas chromatograph) measured the polymerization conversion rate of the preparation monomer, it was 100%. Moreover, it was 267,000 when the mass mean molecular weight was measured by GPC (gel permeation chromatograph). Furthermore, the solid content of the random copolymer solution was 31.0% by mass.

To 32.3 g of the above random copolymer solution 1, 27.7 g of isopropanol, 30 g of methyl ethyl ketone, 10 g of 3-methoxy-3-methyl-1-butanol [trade name: Solfit manufactured by Kuraray Co., Ltd.] The solid content is adjusted to 10% by mass, and 0.2 g of p-toluenesulfonic acid is used as a curing catalyst, and 0.1 g of polyether-modified polydimethylsiloxane [trade name: BYK302 manufactured by Big Chemie Japan Co., Ltd.] is used as a leveling agent. Thus, an antifogging coating composition 1 was obtained.
[Reference Example 2, production of anti-fogging coating composition 2]
Polymerization was performed in the same manner as in Reference Example 1 except that N-methylolacrylamide was changed to 0.2 g in Reference Example 1 to obtain Random Copolymer Solution 2. The polymerization conversion rate of the charged monomer was measured by GC and found to be 100%. Moreover, it was 260,000 when the mass mean molecular weight was measured by GPC. Furthermore, the solid content of the random copolymer solution was 30.8% by mass.

22.5 g of isopropanol, 30 g of methyl ethyl ketone, and 10 g of solfit are added to 32.5 g of the random copolymer solution 2 to adjust the solid content to 10% by mass, 0.2 g of p-toluenesulfonic acid as a curing catalyst, a leveling agent As a result, 0.1 g of BYK302 was mixed to obtain an antifogging coating composition 2.
[Reference Example 3, production of anti-fogging coating composition 3]
Antifogging coating composition 3 was produced as shown below. That is, 60 g of dimethylaminoethyl methacrylate methyl chloride, 10 g of methyl methacrylate, 20 g of n-butyl methacrylate, 10 g of 2-ethylhexyl methacrylate, γ-methacryloxy in a reaction vessel equipped with a thermometer, a stirrer, a nitrogen introduction tube and a cooling tube. Add 2.5 g of propyltrimethoxysilane, 77 g of methyl ethyl ketone as an organic solvent, 77 g of methanol, 0.89 g of azobisisobutyronitrile as a polymerization initiator, perform polymerization at 70 ° C. for 8 hours while blowing nitrogen gas, and perform random copolymerization A combined solution 3 was obtained.

The polymerization conversion rate of the charged monomer was measured by GC and found to be 100%. Moreover, it was 152,000 when the mass mean molecular weight was measured by GPC. Furthermore, the solid content of the random copolymer solution was 40.0% by mass. To 20 g of the random copolymer solution 3, 35 g of isopropanol, 5 g of cyclohexanone, and 40 g of propylene glycol monomethyl ether were added to adjust the solid content to 8% to obtain an antifogging coating composition 3.
[Reference Example 4, Production of Antifogging Paint Composition 4]
A reactor equipped with a thermometer, a stirrer, a nitrogen introducing tube and a cooling tube was charged with 185 g of propylene glycol monomethyl ether as an organic solvent, and heated to 70 ° C. while blowing nitrogen gas. Thereto, 1.67 g of polymer peroxide as a polymerization initiator represented by the following formula (1), 45 g of N, N-dimethylacrylamide as a monomer (A), and as monomer (C) What melt | dissolved 5 g of N-methylol acrylamide was dripped over 2 hours. Further, a polymerization reaction was carried out for 2 hours to synthesize a block copolymer precursor. Thereafter, a mixed solution of 46.7 g of methyl methacrylate as the monomer (B) and 3.3 g of acrylic acid was dropped over 1 hour, and a polymerization reaction was performed at 80 ° C. for 3 hours. Obtained.

The polymerization conversion rate of the charged monomer was measured by GC and found to be 100%. Moreover, it was 88,000 when the mass mean molecular weight was measured by GPC. Further, the solid content of the block copolymer solution was 35.4% by mass.
[CO (CH ₂ ) ₄ COO (C ₂ H ₄ O) ₃ CO (CH ₂ ) ₄ COOO] ₁₀ (1)
71.8 g of propylene glycol monomethyl ether was added to 28.2 g of the block copolymer solution 4 to adjust the solid content to 10% by mass, and 0.01 g of diisobutyl phosphate as a curing catalyst, a fluorosurfactant Perfluoroalkyltrimethylammonium salt [trade name: Surflon S-121 (active ingredient 30% by mass as a fluorosurfactant)] manufactured by Asahi Glass Co., Ltd. Obtained.
[Example 1]
The antifogging coating composition 1 of Reference Example 1 was applied to the inner surface 13a of the front lens 13 by the spray coating method, dried at 40 ° C. for 5 minutes, and then heated and cured at 120 ° C. for 90 minutes. The anti-fogging coating film 16 having the film thickness and water absorption shown in 1 was formed. The following evaluation was performed on the front lens 13 having the antifogging coating film 16 formed on the inner surface 13a.
(Appearance of coating film)
The appearance of the anti-fogging coating film 16 was visually evaluated in the following four stages. In addition, if evaluation is more than (circle), there is no problem practically, and (double-circle) is more preferable.

A: Smooth.
○: Slightly inferior in smoothness
(Triangle | delta): Smoothness is inferior.

X: It is not smooth but has an orange peel shape (coconut skin shape).
(Water absorption)
The front lens 13 having the anti-fogging coating film 16 formed on the inner surface 13a was cut into an appropriate size to obtain a test piece, and the mass was measured. Next, it is placed at a height of 5 cm from the water surface of a warm water bath maintained at 80 ° C. so that the coating surface of the test piece faces down, and the anti-fogging coating film 16 is cloudy or dripping. The mass immediately after irradiation was measured by applying steam from a warm water bath until just before. The amount of water absorption was calculated from the measured mass by the following formula.

Water absorption (mg / cm ² ) = (ML) / S
However, L is a mass (mg) before 80 ° C. steam irradiation, M is a mass (mg) after 80 ° C. steam irradiation, and S is an area (cm ² ) irradiated with 80 ° C. steam.
(Coating film residual rate)
The front lens 13 having the anti-fogging coating film 16 formed on the inner surface 13a was cut into an appropriate size to obtain a test piece, and the mass was measured. Next, the mass of the test piece after being immersed in warm water at 40 ° C. for 240 hours and dried at room temperature for 5 hours was measured. Furthermore, after removing all the anti-fogging coating film 16 which remained on the test piece, the mass was measured again. The coating film residual ratio was calculated from the measured mass by the following formula.

Coating film residual ratio (% by mass) = (NP) × 100 / (LP)
However, L is a mass (mg) before being immersed in 40 ° C. warm water, N is immersed in 40 ° C. warm water for 240 hours, and is dried at room temperature for 5 hours (mg), and P is an antifogging coating film from a test piece. This is the mass (mg) after all 16 is removed.

Furthermore, the automotive headlamp 10 in which the housing 11 was formed by the front lens 13 having the anti-fogging coating film 16 formed on the inner surface 13a was produced as a vehicular lamp. This automobile headlamp 10 was attached to an actual automobile. This car was actually used for one year and tested in an actual use environment. During this test period, the ambient temperature was raised to 60-140 ° C. During the test period, the inner surface 13a and the anti-fogging coating film 16 were observed and visually evaluated for appearance defects, cloudiness, and water dripping traces. The evaluation method is shown below.
(Appearance of coating film)
The appearance of the anti-fogging coating film 16 formed on the inner surface 13a of the front lens 13 during the test period was visually evaluated in the following four stages. In addition, if evaluation is more than (circle), there is no problem practically, and (double-circle) is more preferable.

A: Smooth.
○: Slightly inferior in smoothness
(Triangle | delta): Smoothness is inferior.

X: The anti-fogging coating film 16 melt | dissolves and the inner surface 13a of the front lens 13 is exposed.
(Cloudy)
The presence or absence of fogging of the inner surface 13a of the front lens 13 during the test period was visually evaluated in the following four stages. In addition, if evaluation is more than (circle), there is no problem practically, and (double-circle) is more preferable.

(Double-circle): Cloudiness is not recognized at all.
○: No fogging is observed, but the surface of the antifogging coating film 16 is slightly rough or a water film is formed on the surface of the antifogging coating film 16.

Δ: Slight fogging is observed, or clouding is not recognized, but the surface of the anti-fogging coating film 16 is not smooth but rough.
X: Cloudiness is clearly recognized.
(Water dripping trace)
The presence or absence of water dripping traces on the inner surface 13a of the front lens 13 during the test period was visually evaluated in the following four stages. In addition, if evaluation is more than (circle), there is no problem practically, and (double-circle) is more preferable.

A: No dripping trace is observed.
◯: No water dripping trace is observed, but the surface of the anti-fogging coating film 16 is slightly rough.
(Triangle | delta): The state where the trace of water dripping is recognized or the surface of the anti-fogging coating film 16 is rough.

X: A dripping trace is recognized clearly.
The above evaluation results are summarized in Table 1.
[Examples 2 to 5]
In Example 2 and Example 3, the film thickness of the anti-fogging coating film 16 in Example 1 was increased as shown in Table 1 to increase the water absorption. In Example 4, the antifogging coating composition 1 in Example 1 was changed to the antifogging coating composition 2 of Reference Example 2, and the film thickness of the antifogging coating film 16 was increased as shown in Table 1. In Example 5, the antifogging coating composition 1 in Example 1 was changed to the antifogging coating composition 3 of Reference Example 3, the film thickness of the antifogging coating film 16 was increased as shown in Table 1, and The heat curing conditions were one week at 20 ° C. and 65% RH.

And the film thickness of the anti-fogging coating film 16 obtained in Examples 2-5, the water absorption, and the coating-film residual rate were evaluated according to Example 1. FIG. The results are summarized in Table 1. Moreover, the automotive headlamp 10 in which the housing 11 was formed by the front lens 13 in which the anti-fogging coating film 16 obtained in Examples 2 to 5 was formed on the inner surface 13a was produced. It was installed in an actual vehicle, and this vehicle was actually used for one year and tested in an actual use environment. The results are summarized in Table 1.
[Comparative Example 1 and Comparative Example 2]
In Comparative Example 1 and Comparative Example 2, except that the antifogging coating composition 4 of Reference Example 4 was used, the heat curing condition was 20 minutes at 120 ° C., and the film thickness of the antifogging coating film was changed as shown in Table 1. Was carried out in the same manner as in Example 1. As a result, an anti-fogging coating film having the coating film appearance, water absorption and coating film residual rate shown in Table 1 was obtained. Further, as a vehicular lamp, an automotive headlamp in which a housing is formed by a front lens in which the antifogging coating film obtained in Comparative Example 1 and Comparative Example 2 is formed on the inner surface is produced. Then, it was mounted on an actual vehicle, and this vehicle was actually used for one year and tested in an actual use environment. The results are summarized in Table 1.
[Comparative Example 3]
In Comparative Example 3, the same test as in Example 1 was performed using a front lens in which an antifogging coating film was not formed on the inner surface. The evaluation results obtained are summarized in Table 1.

表１において、実施例１〜３の自動車用前照灯１０は前面レンズ１３の内面１３ａに２．１〜１８．１ｍｇ／ｃｍ^２の吸水量を有する防曇塗膜１６が形成されており、実使用環境下において曇りや水垂れ跡が発生することはなかった。従って、実施例１〜３の自動車用前照灯１０は、その前面レンズ１３の内面１３ａに極めて長期に防曇性を付与することができ、格別有用であることが確認された。ここで、実施例４では防曇塗膜１６の塗膜残存率が好ましい範囲よりも若干小さいため、１年間試験後において曇りや水垂れ跡は認められないが防曇塗膜１６の表面がわずかに荒れた状態であった。さらに、実施例５では１年間試験後において、曇りや水垂れ跡は認められないが、防曇塗膜１６の外観の低下がみられ、防曇塗膜１６の表面がわずかに荒れた状態であった。これは、防曇塗膜１６を形成する共重合体中に第４級アンモニウム塩が含まれているためである。第４級アンモニウム塩は熱によってホフマン脱離を起こして分解する。１年間の実使用環境下における試験期間において、環境温度は６０〜１４０℃まで上昇している。そのため、第４級アンモニウム塩の分解が起こり、防曇塗膜１６の外観が低下する結果となった。

In Table 1, in the automotive headlamps 10 of Examples 1 to 3, the antifogging coating film 16 having a water absorption of 2.1 to 18.1 mg / cm ² is formed on the inner surface 13a of the front lens 13; No cloudiness or dripping traces occurred in the actual use environment. Therefore, it was confirmed that the automotive headlamps 10 of Examples 1 to 3 can impart antifogging properties to the inner surface 13a of the front lens 13 for a very long time and are particularly useful. Here, in Example 4, since the coating film remaining rate of the anti-fogging coating film 16 is slightly smaller than the preferred range, no fogging or dripping trace is observed after one year test, but the surface of the anti-fogging coating film 16 is slightly It was in a rough state. Further, in Example 5, no fogging or dripping marks were observed after the test for one year, but the appearance of the antifogging coating film 16 was deteriorated, and the surface of the antifogging coating film 16 was slightly roughened. there were. This is because the quaternary ammonium salt is contained in the copolymer forming the antifogging coating film 16. The quaternary ammonium salt decomposes by causing Hoffman elimination by heat. In the test period under the actual use environment for one year, the environmental temperature has increased to 60 to 140 ° C. Therefore, decomposition of the quaternary ammonium salt occurred, resulting in a decrease in the appearance of the antifogging coating film 16.

  On the other hand, in Comparative Example 1, since the water absorption amount of the anti-fogging coating film is small, a water film is formed on the inner surface of the front lens after one year test, and water flows down from this water film to cause dripping. After drying, water traces derived from the surfactant were observed. In Comparative Example 2, although the film thickness was increased, the amount of water absorption was small, and the occurrence of water dripping traces could not be suppressed. In Comparative Example 3, fogging occurred on the inner surface of the front lens after the test for one year, which was not suitable as an automotive headlamp.

In addition, this embodiment can also be changed and embodied as follows.
The anti-fogging coating film 16 can be formed on the reflection surface 21 of the reflector 20 in addition to the inner surface 13 a of the front lens 13 of the automotive headlamp 10.

  As the cross-linked product, a non-crosslinkable water-soluble vinyl monomer of monomer (A) and a vinyl type having a crosslinkable functional group that can be cross-linked by condensation reaction or addition reaction of monomer (C) It is also possible to use a copolymer with a monomer.

-As a crosslinked body, a three-dimensionally crosslinked water-soluble polymer formed from monomers other than the monomer (A), monomer (B) and monomer (C) is used. Is also possible.
The anti-fogging coating film 16 may be configured by including a non-crosslinked body of a water-soluble polymer or a crosslinked body of a water-insoluble polymer in the crosslinked body.

The reflector 20 provided in the housing 11 can be omitted.
Furthermore, the technical idea grasped from the embodiment will be described below.

  The ratio of the monomer (A) is 50 to 95 parts by mass and the ratio of the monomer (B) is 50 to 5 with respect to a total of 100 parts by mass of the monomer (A) and the monomer (B). The vehicular lamp according to claim 3, wherein the vehicular lamp is a mass part. In such a configuration, since the monomer (A) is set to be a main component, in addition to the effect of the invention according to claim 3, the water absorption of the antifogging coating film can be increased. The antifogging property of the coating film can be improved.

  The vehicle lamp according to claim 3, wherein the monomer (C) is a vinyl monomer having an N-methylol group or an N-alkoxymethylol group. When comprised in this way, in addition to the effect of the invention which concerns on Claim 3, a crosslinked structure can be easily formed in a copolymer by a condensation reaction.

  The vehicle lamp according to claim 3, wherein the monomer (A) is an N, N-dialkyl (meth) acrylamide monomer. When comprised in this way, in addition to the effect of the invention which concerns on Claim 3, the adhesiveness of the anti-fogging coating film with respect to the inner surface of a lens can be improved.

  The vehicle lamp according to claim 3, wherein the monomer (B) is a (meth) acrylate monomer. When comprised in this way, in addition to the effect of the invention which concerns on Claim 3, while being able to raise the hardness of an anti-fogging coating film, the adhesiveness of the anti-fogging coating film with respect to the inner surface of a lens can be improved.

  The vehicle lamp according to claim 3, wherein the copolymer is copolymerized using a curing catalyst. When constituted in this way, in addition to the effect of the invention according to claim 3, the condensation reaction or addition reaction (crosslinking reaction) of the copolymer can be promoted.

  The vehicle lamp according to claim 3, wherein the copolymer is cured by heating using a curing catalyst. When comprised in this way, in addition to the effect of the invention which concerns on Claim 3, hardening of a copolymer can be performed easily and rapidly.

  A method for manufacturing a vehicular lamp according to the invention of claim 3, wherein the anti-fogging coating film is formed from the monomer (A), monomer (B) and monomer (C) shown below. Copolymer is included, and the content of the monomer (C) is 0.2 to 5 parts by mass with respect to 100 parts by mass in total of the monomer (A) and the monomer (B). And an antifogging coating composition having a weight average molecular weight of 100,000 to 1,000,000 is applied to the inner surface of the lens, and dried and cured. The manufacturing method of the vehicle lamp of description.

Monomer (A): Non-crosslinkable water-soluble vinyl monomer Monomer (B): Non-crosslinkable water-insoluble vinyl monomer Monomer (C): By condensation reaction or addition reaction Vinyl monomer having a crosslinkable functional group capable of crosslinking When configured in this manner, an antifogging coating film for a vehicle lamp having the effect of the invention according to claim 3 can be easily formed.

The longitudinal cross-sectional view for demonstrating the headlamp for motor vehicles as a vehicle lamp in embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Automotive headlamp as a vehicle lamp, 11 ... Housing, 13 ... Front lens as lens, 13a ... Inner surface, 16 ... Anti-fogging coating film, 18 ... Air vent, 20 ... Reflector, 23 ... As light source Light source bulb.

Claims (5)

In a vehicular lamp having a light source in a housing, a lens that transmits light from the light source, and a vent for adjusting atmospheric pressure variation in the housing, a water-soluble polymer is three-dimensionally crosslinked on the inner surface of the lens A vehicular lamp characterized in that an antifogging coating film comprising a crosslinked body and having a water absorption of 1.5 to 25 mg / cm ² is formed. The crosslinked part which comprises the said crosslinked body has an ether bond or a siloxane bond, and the coating-film residual rate after being immersed in 40 degreeC water for 240 hours is 20-100 mass%, It is characterized by the above-mentioned. Vehicle lamps. The crosslinked product contains a copolymer formed from the monomer (A), monomer (B) and monomer (C) shown below, and the content of the monomer (C) is It is 0.2-5 mass parts with respect to a total of 100 mass parts of the monomer (A) and the monomer (B), and the mass average molecular weight of the copolymer is 100,000-1,000,000. The vehicular lamp according to claim 2, wherein the vehicular lamp is provided.
Monomer (A): Non-crosslinkable water-soluble vinyl monomer Monomer (B): Non-crosslinkable water-insoluble vinyl monomer Monomer (C): By condensation reaction or addition reaction Vinyl monomer having a crosslinkable functional group The vehicular lamp according to claim 3, wherein the crosslinked body is formed of a random copolymer. 5. The vehicle lamp according to claim 1, wherein the vehicular lamp is an automobile headlamp, and a reflector is provided in the housing to reflect light from the light source forward through a lens. Item 1. A vehicle lamp according to item 1.

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