JPH0961295A - Testing method for reflector degradation in light acceleration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce light degradation occurring in back light unit lighting test of a silver reflector in a short time by radiating visible light obtained from pseudo solar light with ultraviolet rays removed to a reflector to be tested. SOLUTION: Light from a visible light source 10 for generating light in a visible range of wavelength of 380 to 780nm is passed through an ultraviolet ray removing filter 20 for removing ultraviolet light substantially having a wavelength of 360nm or less to remove ultraviolet rays, and light with radiated light intensity preferably of 100mW/cm<2> -700mW/cm<2> is radiated to a reflector 30 using silver. At this time the reflector 30 is heated by a temperature adjusting stage 30 to a predetermined temperature of 60 deg.C-150 deg.C for example and kept at this temperature. Thus light degradation caused in a lamp reflector for a back light unit of a liquid crystal display device can be reproduced in an extremely short time, so that light degradation of the reflector 30 can to efficiently studied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photo-deterioration test method for reflectors used in electronic equipment, lighting equipment and the like, and more specifically, it is formed mainly of a polymer used in liquid crystal display devices and fluorescent lamps. The accelerated light degradation test of the reflectors described.

[0002]

2. Description of the Related Art Silver is a metal having a high reflectance in the visible light region. However, silver is sulfurized and blackened when exposed to the air, so that it was necessary to periodically re-form the silver film on an optical mirror or the like on which silver was vapor-deposited. Therefore, it was not generally used except for some applications. In recent years, a high-reflectance silver reflector using silver as a reflection film has been used mainly in a lamp reflector of a backlight portion of a liquid crystal display device, for a reflector of a fluorescent lamp, or the like. These are PET (polyethylene terephthalate) / silver thin film layer /
So-called silver reflector consisting of adhesive layer / aluminum plate and PET
/ Silver thin film layer / white coating / adhesive layer / aluminum thin film layer / polymer film / white coating
By using PET, which is a transparent polymer film, as a protective layer for silver, it has succeeded in preventing sulfuration and oxidation of silver due to atmospheric exposure, which has been a problem in the past, and maintaining high reflectance. For example, as an example of the reliability test results of the silver reflector and the silver reflector which are silver reflectors, a high temperature test (80 ° C, 1000 hours) and a low temperature test (-20
℃, 1000 hours), high temperature and high humidity test (60 ℃, 95% R
H, 1000 hours), no blackening due to sulfurization was observed, and no decrease in reflectance was observed.

However, the backlight unit high-temperature lighting test (the lamp reflector made of the above silver reflection sheet is incorporated in the backlight unit of the liquid crystal display device,
When a lighting test was performed in a high-temperature tank at 60 ° C.), a new problem occurred in that the reflecting surface turned purple in a few thousand hours and the reflectance drastically decreased. The present inventors conducted an irradiation test using a high-intensity xenon lamp light and a light irradiation test using an ultraviolet lamp light in order to reproduce the light deterioration of the silver reflector and to deteriorate it in a short time. However, although a decrease in reflectance was observed in both tests, the reflective surface turned yellow and the deterioration behavior was clearly different from that in the backlight unit high temperature lighting test.

[0004]

DISCLOSURE OF THE INVENTION The present invention relates to a reflector formed by using a polymer as a main material, and in particular, a silver reflection film comprising at least A and B of a transparent polymer film (A) and a silver thin film layer (B). It is an object of the present invention to provide a photo-accelerated deterioration test method for reproducing the photo-deterioration occurring in a backlight unit lighting test for a body in a short time.

[0005]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that the photodegradation of the silver reflector causes the transparent polymer film (A) to deteriorate and discolor. However, it was found that the surface of the silver thin film layer (B) turned purple. As a result of further intensive studies, it was found that the light irradiation mainly including visible light excluding ultraviolet rays can selectively deteriorate silver and turn it into purple. Furthermore, it was found that the deterioration of this silver rapidly progressed as the irradiation intensity increased and the test temperature increased. The present invention has been made based on such findings.

That is, the present invention provides (1) a light accelerated deterioration test method for a reflector, which is performed by irradiating the reflector with light mainly composed of visible light, (2) Light mainly composed of visible light is obtained from pseudo-sunlight (1) Light accelerated deterioration test method for reflector, (3) Through filter capable of substantially removing ultraviolet light, (1) or (2) the photo-accelerated deterioration test method of the reflector, which is performed by irradiating with pseudo sunlight having an irradiation intensity of 100 mW / cm ² or more, (4) a wavelength of substantially 360
Irradiation intensity is 100 mW / cm ² or more and 700 mW / c through a filter that can remove UV light of nm or less.
The light accelerated deterioration test method for the reflector according to any one of (1) to (3), which is performed by irradiating pseudo sunlight of m ² or less, (5) Performed by heating the reflector (1) to (4) ) Light accelerated deterioration test method for any of the reflectors in (6),
(5) Photo-accelerated deterioration test method of reflector performed by heating at 0 ° C. or higher and 150 ° C. or lower, (7) The reflector is a reflector formed mainly of a polymer (1) to (6) (8) The light accelerated deterioration test method for a reflector, and (8) the reflector is a silver reflector composed of at least a transparent polymer film and a silver thin film layer, and is irradiated with light from the transparent polymer film side (1). )
(7) The present invention relates to the light-accelerated deterioration test method for a reflector according to any one of (7) to (7).

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, referring to the attached drawings, FIG. 1 is a schematic view of an apparatus using the photo-accelerated deterioration test method of the present invention. The light emitted from the visible light source 10 has its ultraviolet rays removed by the ultraviolet ray cut filter 20 and is applied to the reflector 30. The reflector 30 is heated by the temperature adjustment stage 40 and kept at a constant temperature.

The temperature control stage used in the present invention comprises, for example, a sheet heater, a thermocouple, and a temperature controller. The thermocouple measures the temperature of the reflector, which is a sample, and the sheet heater is operated by the temperature controller. By turning on / off, the temperature of the reflector is kept constant.

The visible light source is a light source that emits light in the visible region having a wavelength of 380 nm to 780 nm.
Examples thereof include a tungsten lamp, a halogen lamp, a xenon lamp, and a fluorescent lamp. Especially the xenon lamp
It is used for light resistance tests, etc. because it provides high irradiation intensity and its spectrum is close to outdoor exposure. Among the visible light sources, pseudo sunlight is preferable. Pseudo-sunlight is a light source called a solar simulator, and its spectrum is a light source having a spectrum similar to that of the sun's rays outdoors in fine weather, and can be said to be a standardized light source of the xenon lamp. It is desirable to use such a standardized light source for the test in order to eliminate the difference between the lamps.

In the present invention, the light mainly composed of visible light means a light obtained by cutting the ultraviolet light among the lights obtained from the above-mentioned visible light source, particularly preferably pseudo sunlight,
As an example, it refers to light obtained by passing through a so-called ultraviolet cut filter. The ultraviolet cut filter is a filter that can substantially remove ultraviolet rays, and is a filter that cuts ultraviolet light as much as possible and transmits light having a longer wavelength such as visible light as much as possible.

In the present invention, a filter capable of substantially removing ultraviolet light having a wavelength of 360 nm or less means a wavelength of 3
A filter having a transmittance at 60 nm of 5% or less, more preferably 3% or less, and further preferably 1% or less. Here, there is a transmission limit wavelength (for example, an intermediate value between the wavelength at which the transmittance is 72% and the wavelength at which the transmittance is 5%) as an index representing the cut wavelength of the filter. Those skilled in the art know that the values are different. FIG. 2 shows an example of a spectrum of pseudo sunlight obtained through a filter capable of substantially removing ultraviolet light having a wavelength of 360 nm or less. The irradiation intensity of these lights is preferably 100 m
W / cm ² or more, more preferably 100 mW / c
m is ² or more 700 mW / cm ² or less, further preferably 300 mW / cm ² or more 700 mW / cm ² or less. Light weaker than 100 mW / cm ² is not realistic because it takes a long time to deteriorate. On the other hand, if it exceeds 700 mW / cm ² , the transparent polymer film deteriorates and breaks although the time required for the deterioration is short. Moreover, the need for cooling arises because of the high heat.

In order to accelerate the light deterioration of the reflector, it is preferable to heat the reflector. The heating temperature is not particularly limited, but it is 60 ° C. or higher and 150 ° C. or lower if it is forced. At a temperature lower than 60 ° C, a sufficient promoting effect cannot be obtained. Further, at a temperature exceeding 150 ° C., the polymer film deteriorates and breaks or the like occurs.

The reflector that can be tested in the present invention is an object that returns the light incident on the reflector to the original medium, and here mainly 70% or more of the light in the visible region is returned to the original. An object that returns to the medium, more preferably an object that returns 80% or more of the light in the visible region to the original medium, and further preferably, returns 90% or more of the light in the visible region to the original medium. An object. Specifically, a silver reflector using silver as a reflective metal, a so-called mirror using aluminum as a reflective metal, a white sheet in which a white pigment such as barium sulfate or alumina is dispersed in a polymer, or the like is used. Can be mentioned.

The reflector formed by using a polymer as a main material means a reflector containing a resin such as a polymer film in a member constituting a so-called reflector. In particular, it refers to a reflector in which a polymer is used in a portion that transmits or reflects light, and examples thereof include a silver reflector, a silver reflector sheet, a white reflector sheet, and a metal vapor deposition film.

The term "silver reflector" means a reflector using silver as a light-reflecting substance, which corresponds to a silver reflector or a silver reflector sheet. The silver reflector is a reflector composed of at least A, B, C and D of a transparent polymer film (A), a silver thin film layer (B), an adhesive layer (C) and a metal plate (D), and light is The light enters from the transparent polymer film (A) side and is reflected by the silver thin film layer (B).

The silver reflective sheet is a reflector composed of at least A, B, C and D of a transparent polymer film (A), a silver thin film layer (B), an adhesive layer (C) and a polymer film (D). For example, a reflection sheet composed of PET / silver thin film layer / white pigment layer / adhesive layer / aluminum thin film layer / PET / white pigment layer is also included. Light enters from the transparent polymer film (A) and is reflected by the silver thin film layer (B) like the silver reflector.

The transparent polymer film is a polymer film which is transparent in the visible light range, and for example, polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyether sulfone ( PES), polycarbonate (P
C), cellulose triacetate-based resin, polyarylate-based resin, polysulfone-based resin and the like. However, the material is not necessarily limited to these, and may be transparent in the visible light region. As for transparency, it is preferable that the light transmittance at a wavelength of 550 nm is 80% or more. More preferably, the light transmittance is 80% or more with respect to the light in the wavelength range of 500 to 700 nm, and further preferably the wavelength of 3
The light transmittance is 80 for light in the range of 80 to 780 nm.
% Or more.

The white reflective sheet means so-called alumina, titania (titanium white), lead oxide (lead white), zinc oxide (zinc white), calcium carbonate, barium carbonate, barium sulfate,
It is a polymer sheet containing white pigments such as potassium titanate and sodium silicate. The metal vapor deposition film is a film in which a metal thin film is formed on a polymer film, and an aluminum vapor deposition film or the like corresponds to this. The present invention
It is a light-accelerated deterioration test method for the reflector, which is performed by irradiating the reflector with light mainly containing visible light from the transparent polymer film side.

[0019]

The present invention will be described below with reference to examples. The reflectance is measured by Hitachi automatic recording spectrophotometer (U-340
The measurement was performed by setting a 150φ integrating sphere in 0). The reflectance shown below is a value at a wavelength of 550 nm. [Example 1] As a light source, a solar simulator (using a xenon lamp) model YSS-505H manufactured by Yamashita Denso Co., Ltd.
For the ultraviolet cut filter, Toshiba Chemical Industry Co., Ltd. Sharp cut filter L-39 (transmission limit wavelength 39
Using 0 nm and a transmittance of 1% or less at a wavelength of 360 nm), pseudo sunlight having an irradiation intensity of 500 mW / cm ² was obtained by removing light having a wavelength of 360 nm or less. This light was applied to a silver reflection sheet kept at 100 ° C. by a temperature adjustment stage. As a result, the reflectance, which was 95% before the test, decreased to 50% after 200 hours.
The deterioration rate was about 47%. After examining the deteriorated part,
It was found to be the surface of the silver thin film layer. This was similar to the deterioration that occurred in the backlight unit high temperature lighting test, and could be reproduced in a short time of 200 hours.

[Example 2] As a light source, a solar simulator (using a xenon lamp) model YSS manufactured by Yamashita Denso Co., Ltd.
-505H is used as an ultraviolet ray cut filter by Toshiba Chemical Industry Co., Ltd. Sharp cut filter L-39 (transmission limit wavelength 390 nm, transmittance at wavelength 360 nm is 1
% Or less) to obtain pseudo-sunlight having an irradiation intensity of 500 mW / cm ^{2 from} which light having a wavelength of 360 nm or less was substantially removed. This light was applied to a silver reflection sheet kept at 70 ° C. by a temperature adjustment stage. As a result, 95 before the test
%, The reflectance decreased to 85% after 200 hours. The deterioration rate was about 11%. When the deteriorated portion was examined, it was found to be the surface of the silver thin film layer. This was similar to the deterioration that occurred in the backlight unit high temperature lighting test, and could be reproduced in a short time of 200 hours.

[Example 3] As a light source, a solar simulator (using a xenon lamp) model YSS manufactured by Yamashita Denso Co., Ltd.
-505H is used as an ultraviolet ray cut filter by Toshiba Chemical Industry Co., Ltd. Sharp cut filter L-39 (transmission limit wavelength 390 nm, transmittance at wavelength 360 nm is 1
% Or less) to obtain pseudo-sunlight having an irradiation intensity of 500 mW / cm ^{2 from} which light having a wavelength of 360 nm or less was substantially removed. This light was applied to a silver reflection sheet kept at 140 ° C. by a temperature adjustment stage. As a result, 9 before the test
The reflectance, which was 5%, decreased to 20% after 200 hours. The deterioration rate was about 79%. When the deteriorated portion was examined, it was found to be the surface of the silver thin film layer. This was similar to the deterioration that occurred in the backlight unit high temperature lighting test, and could be reproduced in a short time of 200 hours.

[Example 4] As a light source, a solar simulator (using a xenon lamp) model YSS manufactured by Yamashita Denso Co., Ltd.
-505H is used as an ultraviolet ray cut filter by Toshiba Chemical Industry Co., Ltd. Sharp cut filter L-39 (transmission limit wavelength 390 nm, transmittance at wavelength 360 nm is 1
% Or less) to obtain pseudo sunlight having an irradiation intensity of 150 mW / cm ^{2 from} which light having a wavelength of 360 nm or less was substantially removed. This light was applied to a silver reflection sheet kept at 100 ° C. by a temperature adjustment stage. As a result, 9 before the test
The reflectance, which was 5%, decreased to 85% after 200 hours. The deterioration rate was about 11%. When the deteriorated portion was examined, it was found to be the surface of the silver thin film layer. This was similar to the deterioration that occurred in the backlight unit high temperature lighting test, and could be reproduced in a short time of 200 hours.

[Example 5] As a light source, a solar simulator (using a xenon lamp) model YSS manufactured by Yamashita Denso Co., Ltd.
-505H is used as an ultraviolet ray cut filter by Toshiba Chemical Industry Co., Ltd. Sharp cut filter L-39 (transmission limit wavelength 390 nm, transmittance at wavelength 360 nm is 1
% Or less) to obtain pseudo-sunlight having an irradiation intensity of 400 mW / cm ^{2 from} which light having a wavelength of 360 nm or less is substantially removed. This light was applied to a silver reflection sheet kept at 100 ° C. by a temperature adjustment stage. As a result, 9 before the test
The reflectance, which was 5%, decreased to 60% after 200 hours. The deterioration rate was about 37%. When the deteriorated portion was examined, it was found to be the surface of the silver thin film layer. This was similar to the deterioration that occurred in the backlight unit high temperature lighting test, and could be reproduced in a short time of 200 hours.

[Sixth Embodiment] As a light source, a solar simulator (using a xenon lamp) model YSS manufactured by Yamashita Denso Co., Ltd.
-505H is used as an ultraviolet ray cut filter by Toshiba Chemical Industry Co., Ltd. Sharp cut filter L-39 (transmission limit wavelength 390 nm, transmittance at wavelength 360 nm is 1
% Or less) to obtain pseudo-sunlight having an irradiation intensity of 600 mW / cm ^{2 from} which light having a wavelength of 360 nm or less is substantially removed. This light was applied to a silver reflection sheet kept at 100 ° C. by a temperature adjustment stage. As a result, 9 before the test
The reflectance, which was 5%, decreased to 40% after 200 hours. The deterioration rate was about 58%. When the deteriorated portion was examined, it was found to be the surface of the silver thin film layer. This was similar to the deterioration that occurred in the backlight unit high temperature lighting test, and could be reproduced in a short time of 200 hours.

[Comparative Example 1] A lamp reflector made of a silver reflection sheet was incorporated into a backlight unit of a liquid crystal display device and assembled, and a backlight unit lighting test (25 ° C) was performed.
Lighting test conducted at room temperature. The light source is a cold cathode tube. After 200 hours, the lamp reflector made of a silver reflective sheet was taken out and the reflectance was measured in the same manner as in Example 1. The reflectance was 95%, and no decrease in reflectance was observed. Moreover, discoloration was not observed.

[Comparative Example 2] A lamp reflector made of a silver reflection sheet was incorporated into a backlight unit of a liquid crystal display device and assembled, and a backlight unit high temperature lighting test (6
A lighting test was performed at room temperature of 0 ° C. The light source is a cold cathode tube. After 200 hours, the lamp reflector made of a silver reflective sheet was taken out and the reflectance was measured in the same manner as in Example 1. The reflectance was 95%, and no change in the reflectance was observed. Moreover, discoloration was not observed.

[Comparative Example 3] An ultraviolet lamp (QP) was used as a light source.
UVA-351 lamp manufactured by ANEL) was used. This light was applied to a silver reflection sheet kept at 100 ° C. by a temperature adjustment stage. When the reflectance was measured after 200 hours as in Example 1, the reflectance was 95%, and no change in the reflectance was observed. Moreover, discoloration was not observed.

[Comparative Example 4] As a light source, a solar simulator (using a xenon lamp) model YSS-of Yamashita Denso Co., Ltd.
Using 505H, pseudo sunlight having an irradiation intensity of 500 mW / cm ² was obtained. No UV cut filter was used. This light was applied to a silver reflection sheet kept at 100 ° C. by a temperature adjustment stage. As a result, 9 before the test
The reflectance, which was 5%, decreased to 55% after 200 hours. The deterioration rate was 42%. However, the discoloration was yellow, and when the deteriorated portion was examined, it was found that it was a polymer film and the silver thin film layer was not deteriorated.
Therefore, it was found that the deterioration was different from the deterioration observed in the long-term test in the backlight unit high-temperature lighting test.

Table 1 shows the deterioration rates and deteriorated parts by the test methods shown in Example 1 and Comparative Examples 1 to 4. In the light deterioration test of the present invention, it can be seen that the deterioration (decrease in reflectance and discoloration of purple) observed in a long-term test of several thousand hours in the backlight unit high-temperature lighting test is achieved in a short time of 200 hours. .

[0030]

[Table 1]

Table 2 shows the difference in the deterioration rate depending on the heating temperature of the reflector when the pseudo sunlight except the light having the irradiation intensity of 500 mW / cm ² and the wavelength of substantially 360 nm or less was removed. It can be seen that photodegradation is promoted by heating.

[0032]

[Table 2]

Table 3 shows the change in deterioration rate due to the difference in irradiation intensity of the pseudo-sunlight except for light having a wavelength of substantially 360 nm or less when the heating temperature of the reflector is 100 ° C. It can be seen that the deterioration rate increases as the irradiation intensity increases.

[0034]

[Table 3]

[0035]

By using the photodegradation test method of the present invention, the photodegradation that occurs in the lamp reflector for the backlight unit of the liquid crystal display device can be reproduced in a very short period of time. This has made it possible to efficiently study the optical deterioration of the reflector.

[Brief description of drawings]

FIG. 1 is a schematic view of a photo-accelerated deterioration test apparatus of the present invention.

FIG. 2 is a spectrum diagram of pseudo-sunlight obtained through a filter capable of substantially removing ultraviolet light having a wavelength of 360 nm or less.

[Explanation of symbols]

 10 Visible Light Source 20 UV Cut Filter 30 Reflector 40 Temperature Control Stage

Claims (8)

[Claims] 1. A test method for light-accelerated deterioration of a reflector, comprising:
A light accelerated deterioration test method for a reflector, which is performed by irradiating the reflector with light mainly composed of visible light. 2. The light-accelerated deterioration test method for a reflector according to claim 1, wherein the light mainly composed of visible light is obtained from pseudo sunlight. 3. A photo-accelerated deterioration test of the reflector according to claim 1 or 2, which is carried out by irradiating pseudo sunlight having an irradiation intensity of 100 mW / cm ² or more through a filter capable of substantially removing ultraviolet light. Method. 4. Irradiation intensity of 10 through a filter capable of substantially removing ultraviolet light having a wavelength of 360 nm or less.
0 mW / cm ² or more 700 mW / cm ² light accelerated deterioration test method of the reflector according to claim 1, performed by irradiating with a pseudo solar light or less. 5. The photo-accelerated deterioration test method for a reflector according to claim 1, which is carried out by heating the reflector. 6. The photo-accelerated deterioration test method for a reflector according to claim 5, wherein the reflector is heated to 60 ° C. or higher and 150 ° C. or lower. 7. The photo-accelerated deterioration test method for a reflector according to claim 1, wherein the reflector is formed mainly of a polymer. 8. The reflector according to claim 1, wherein the reflector is a silver reflector composed of at least a transparent polymer film and a silver thin film layer, and is irradiated with light from the transparent polymer film side. Light accelerated deterioration test method.