JP4695024B2 - Light reflector - Google Patents

Description

  The present invention relates to a light reflecting plate that can be used as a component such as an illumination device such as a fluorescent lamp, a backlight unit of a liquid crystal display device, and a light reflection mechanism of a copying machine, and particularly constitutes a backlight unit of a liquid crystal display device. The present invention relates to a light reflector that can be suitably used as a constituent material of a reflector.

  As a backlight unit of a liquid crystal display device, a light source light is directly incident on a liquid crystal display panel, and a light source light is incident from an edge side of a light guide plate made of acrylic resin or the like. The sidelight method (also called the edge light method) that illuminates the liquid crystal display panel is known, and the latter is used in applications that require thinness, such as monitors, small LCD TVs, and notebook computers. Sidelight method is mainly adopted.

  For example, as shown in FIG. 2, the sidelight type backlight unit includes a light source such as a cold-cathode tube 2 disposed on the edge of the light guide plate 3 and a reflector so as to cover the outside of the light source. 1. A member called 1 is installed, light from the light source is guided by the reflector 1, incident from the edge of the light guide plate 3, and converted into a uniform surface light source by the light guide plate 3 to illuminate the liquid crystal display panel The ones are common.

  As a constituent member of this type of reflector, a reflection plate having a configuration in which a reflection film made of foamed white polyester is laminated on a metal plate is conventionally known (Patent Document 1).

  The reflective film made of such foamed white polyester is cheaper than, for example, a silver-deposited PET film, but is inferior in light reflectance when compared with the equivalent thickness. It has been proposed to add a particulate filler such as titanium oxide or barium sulfate and increase the reflectance by utilizing refractive scattering due to the refractive index difference between the polyester and the particulate filler (for example, Patent Document 2, Patent). Reference 3).

JP-A-10-177805 JP 2002-138150 A WO200404077

However, a light reflector having a structure in which a reflective film is laminated on a metal plate using a reflective film containing such a polyester resin and a particulate filler exhibits high reflection performance. If a cold cathode tube reflector is formed and incorporated in a backlight unit of a notebook computer and brought into contact with a resin light guide plate such as acrylic resin, noise may occur when the monitor is opened and closed. I understand.
Moreover, in order to use it as a component part of a personal computer or a household electrical appliance, it is necessary to satisfy predetermined standards in various environmental tests for quality assurance, but there is also a problem that evaluation of a wet heat resistance test is not sufficient.

  Accordingly, an object of the present invention is to eliminate the problem of noise generation and sufficiently enhance the heat and moisture resistance in a light reflector formed by laminating a light reflection layer containing a polyester resin and a fine filler on a metal plate. It is in.

  The present invention is a light reflector comprising a light reflection layer (B) containing a polyester resin and a fine particulate filler and an outermost surface layer (C) on at least one surface side of the metal plate (A), the outermost surface The layer (C) includes a silicone, and proposes a light reflector characterized in that the contact angle of the surface with distilled water is 95 degrees or more.

  Thus, the problem of noise generation can be solved by providing the outermost surface layer (C) containing silicone on the surface side of the light reflection layer (B) and setting the contact angle of the surface to 95 degrees or more. In addition, the heat and humidity resistance could be sufficiently improved.

  The light reflector of the present invention has solved the problem of noise generation and has sufficiently improved moisture and heat resistance. For example, the light reflector used in an illuminating device such as a fluorescent lamp and the direct backlight of a liquid crystal display device can be used. Suitable for use as a light reflection plate for surface light sources, a light reflection plate for edge-type backlights, a light reflection plate for reflectors arranged around LEDs and cold cathode tubes, a light reflection plate for a light reflection mechanism of a copying machine, etc. be able to. Among them, it is particularly suitable as a light reflecting plate used for an application in which it is placed in contact with a resin plate such as an acrylic resin such as a backlight unit of a notebook personal computer.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, an example of an embodiment of the present invention will be described in detail, but the scope of the present invention is not limited to the embodiment described below.

In the present invention, the expression “main component” includes the intention to allow other components to be contained within a range that does not interfere with the function of the main component, unless otherwise specified. Although the content ratio of the components is not specified, the main component (when two or more components are the main components, the total amount thereof) is 50% by mass or more, preferably 70% by mass or more, particularly in the composition. It preferably includes 90% by mass (including 100%).
Further, when “X to Y” (X and Y are arbitrary numbers) is described, “X to Y” is intended unless otherwise specified, and “it is preferably larger than X and smaller than Y”. Includes intentions.
In general, a “film” is a thin flat product whose thickness is extremely small compared to the length and width and whose maximum thickness is arbitrarily limited, and is usually supplied in the form of a roll. (Japanese Industrial Standard JISK6900), and “sheet” generally refers to a product that is thin according to the definition in JIS, and whose thickness is usually small instead of length and width. However, since the boundary between the sheet and the film is not clear and it is not necessary to distinguish the two in terms of the present invention, in the present invention, even when the term “film” is used, the term “sheet” is included and the term “sheet” is used. In some cases, “film” is included.

<Light reflector>
As shown in FIG. 1, the light reflecting plate according to the present embodiment (hereinafter referred to as “the present light reflecting plate”) is a resin composition containing a polyester resin and a fine particulate filler on at least one side of the metal plate (A). The light reflecting layer (B) is made of, and the outer surface layer (C) containing silicone is provided on the surface of the light reflecting layer (B).

<Metal plate (A)>
The material of the metal plate (A) is not particularly limited, and examples thereof include various metals such as iron, various stainless steels, copper, copper alloys, aluminum, aluminum alloys, tin alloys, steel plates, nickel, and zinc. it can.

  The thickness of the metal plate (A) is 0.05 mm to 0.8 mm, but it is not limited to the metal plate having such a thickness, and can be appropriately selected depending on the application. For example, a stainless steel plate having a thickness of 0.05 mm to 0.4 mm, an aluminum alloy having a thickness of 0.1 to 0.6 mm, a thickness of 0.2 to 0. An example is a 4 mm brass plate. However, the present invention is not limited to this.

The surface of the metal plate (A) may be subjected to monolayer plating, multilayer plating or alloy plating, or may be subjected to immersion chromic acid treatment or phosphoric acid chromic acid treatment.
In addition, for the purpose of improving adhesion with the light reflecting layer (B), chemical treatment such as silane coupling agent, coupling agent treatment with titanium coupling agent, acid treatment, alkali treatment, ozone treatment, ion treatment, Various surfaces such as plasma treatment, glow discharge treatment, arc discharge treatment, discharge treatment such as corona treatment, ultraviolet ray treatment, X-ray treatment, gamma ray treatment, electromagnetic wave irradiation treatment such as laser treatment, and other surface treatment such as flame treatment and primer treatment Processing may be performed.

<Light reflection layer (B)>
The light reflection layer (B) is a layer containing a polyester resin and a fine particle filler, and refractive scattering due to a difference in refractive index between the polyester resin and the fine particle filler, and voids (empty in the light reflection layer (B)). In the case of having pores, light reflection performance can be obtained from refractive scattering due to a difference in refractive index between the polyester resin and the gap (air), and the reflectance is preferably 80% or more.

(Polyester resin)
The polyester resin which is the base resin (main component) of the light reflecting layer (B) is, for example, an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid or naphthalenedicarboxylic acid, or an ester thereof, ethylene glycol, diethylene glycol, 1,4- An aromatic polyester resin obtained by polycondensation with glycols such as butanediol, neopentyl glycol, 1.4 cyclohexanedimethanol, an aliphatic polyester resin obtained by ring-opening polymerization of a lactone, such as polyε-caprolactam, Polyethylene adipate, polyethylene azelate, polyethylene succinate, polybutylene adipate, polybutylene azelate, polybutylene succinate, polybutylene succinate adipate, polytetramethylene succinate, cyclohexane dica An aliphatic polyester resin obtained by polymerizing a dibasic acid and a diol, such as a boric acid / cyclohexanedimethanol condensate, an aliphatic polyester resin obtained by polymerizing a hydroxycarboxylic acid such as polylactic acid or polyglycol, the aliphatic Examples thereof include aliphatic polyesters in which a part of the ester bonds of the polyester, for example, 50% or less of the total ester bonds are replaced with amide bonds, ether bonds, urethane bonds, and the like.
Examples of aliphatic polyester resins fermented and synthesized by microorganisms include polyhydroxybutyrate, a copolymer of hydroxybutyrate and hydroxyvalerate, and the like.

Among them, aliphatic polyester resins that do not contain an aromatic ring in the molecular chain do not cause ultraviolet absorption, so that they are exposed to ultraviolet rays or by receiving ultraviolet rays emitted from a light source such as a liquid crystal display device. It does not deteriorate or yellow, and it is possible to suppress a decrease in light reflectivity over time.
Moreover, in order to obtain light reflectivity by utilizing refractive scattering, it is preferable to use a resin having a large refractive index difference from air or a filler. From this point, when mainly utilizing the refractive index difference from the filler, the base resin preferably has a smaller refractive index, and polylactic acid having a refractive index (n) of less than 1.46 is particularly suitable.

Examples of polylactic acid include D-lactic acid or L-lactic acid homopolymers or copolymers thereof. Specifically, poly (D-lactic acid) whose structural unit is D-lactic acid, poly (L-lactic acid) whose structural unit is L-lactic acid, and a copolymer of L-lactic acid and D-lactic acid. Poly (DL-lactic acid) or a mixture thereof can be exemplified.
The DL ratio of polylactic acid, that is, the content ratio of D-lactic acid and L-lactic acid is D-lactic acid: L-lactic acid = 100: 0 to 85:15, or D-lactic acid: L-lactic acid = 0: It is preferable that it is 100-15: 85. More preferably, D-lactic acid: L-lactic acid = 99.5: 0.5 to 95: 5, or D-lactic acid: L-lactic acid = 0.5: 99.5 to 5:95.
In addition, you may blend the polylactic acid from which the copolymerization ratio of D-lactic acid and L-lactic acid differs.

As polylactic acid, a copolymer of lactic acid and other hydroxycarboxylic acid can also be used. At this time, as "other hydroxycarboxylic acid units" to be copolymerized, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, Examples thereof include bifunctional aliphatic hydroxycarboxylic acids such as 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, and 2-hydroxycaproic acid, and lactones such as caprolactone, butyrolactone, and valerolactone.
The polylactic acid may be a non-aliphatic carboxylic acid such as terephthalic acid and / or a non-aliphatic diol such as an ethylene oxide adduct of bisphenol A, or a component other than lactic acid and / or lactic acid, as a small amount copolymerization component. Hydroxycarboxylic acid may be included.

  The polylactic acid preferably has a high molecular weight. For example, the weight average molecular weight is preferably 50,000 or more, more preferably 60,000 to 400,000, and particularly preferably 100,000 to 300,000. . When the weight average molecular weight of polylactic acid is less than 50,000, the mechanical properties may be inferior.

(Fine particulate filler)
The particulate filler improves whiteness, provides refractive scattering due to the difference in refractive index between the base resin and the filler, and forms voids (holes) in the film when the film is stretched. It plays a role of providing refractive scattering due to a difference in refractive index between air and air (air).

  Examples of the fine particle filler include an organic fine particle filler and an inorganic fine particle filler.

  As the organic fine particulate filler, it is preferable to use at least one selected from cellulose powders such as wood powder and pulp powder, polymer beads made of olefin resin, polymer hollow particles such as styrene, and the like.

  As inorganic fine particulate filler, calcium carbonate, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, zinc oxide, magnesium oxide, calcium oxide, titanium oxide, alumina, aluminum hydroxide, magnesium hydroxide, hydroxyapatite It is preferable to use at least one selected from silica, mica, talc, kaolin, clay, glass powder, asbestos powder, zeolite, silicate clay and the like.

  Among these, a fine particle filler that can obtain an excellent reflection performance with a large refractive index difference from the base resin is preferable. From this viewpoint, it is preferable to use a fine particle filler having a large refractive index. Specifically, calcium carbonate, barium sulfate, titanium oxide or zinc oxide having a refractive index of 1.6 or more is preferable, and titanium oxide having a refractive index of 2.5 or more is particularly preferable. In view of long-term durability, barium sulfate that is stable against acids and alkalis is also preferable.

  The size of the fine filler is preferably 0.05 μm to 15 μm, more preferably 0.1 μm to 10 μm. If the average particle size of the fine filler is 0.05 μm or more, light scattering reflection occurs with the roughening of the surface, so that the obtained reflection directivity becomes smaller. Moreover, if the average particle diameter of a fine particle filler is 15 micrometers or less, since the interface of base resin and a fine particle filler is formed more densely, the outstanding light reflectivity can be obtained.

  A light reflection layer (B) may contain a well-known additive as needed. For example, it may contain a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistance agent, an impact resistance improver, and the like.

(Formation method of light reflection layer (B))
The light reflection layer (B) can be formed by bringing a resin composition containing a polyester resin and a fine particulate filler into a molten state and applying or extruding the resin composition onto the metal plate (A). It is also possible to form a film from the resin composition and laminate the film on the metal plate (A).
In order to obtain a higher reflectance, a film (cast sheet) is formed from a resin composition containing a polyester resin and a fine filler, and the film is stretched 1.1 times or more in a uniaxial direction or a biaxial direction. Is preferred. By stretching, a void having a fine powder filler as a core is formed inside the film, and an interface between the base resin and the void and an interface between the void and the fine powder filler are formed. Since it increases, light reflectivity can be improved.

Under the present circumstances, what is necessary is just to employ | adopt a well-known method for film forming and the extending | stretching method.
For example, as a biaxial stretching method, a film that has been melt-extruded from a T-die is stretched in the longitudinal direction with a roll stretching machine and then stretched in the transverse direction with a tenter stretching machine (sequential biaxial stretching method). In addition, it is also possible to employ a method (simultaneous biaxial stretching method) in which the end-stretched film is stretched in the longitudinal and lateral directions with a tenter type simultaneous biaxial stretching machine. It is also possible to employ a method (inflation method) in which a film melt-extruded in a tube shape is expanded by gas pressure and stretched, or other methods.

  The stretching temperature is preferably within a predetermined temperature range (Tg to Tg + 50 ° C.) from the glass transition temperature (Tg) of the polyester resin. For example, in the case of polylactic acid, it is preferably 50 to 90 ° C. When the stretching temperature is within this range, stretching can be performed stably without breaking during stretching, and the stretching orientation can be increased. As a result, the porosity can be increased and the reflectance can be increased.

  Moreover, in order to provide heat resistance and dimensional stability to the obtained film, it is preferable to heat-process. At this time, the heat treatment temperature is preferably 90 to 160 ° C, more preferably 110 to 140 ° C. The treatment time required for the heat treatment is preferably 1 second to 5 minutes. Moreover, although there is no limitation in particular about extending | stretching equipment etc., it is preferable to perform the tenter extending | stretching which can perform a heat setting process after extending | stretching.

  In addition, it is also possible to use a commercially available white polyester film containing a fine particle filler for a reflective film. For example, Lumirror E60L and E60V (trade name) manufactured by Toray Industries, Melinex (trade name) manufactured by Teijin DuPont, Crisper (trade name) manufactured by Toyobo Co., Ltd., Ref White (trade name) manufactured by Kimoto, Mitsubishi Examples thereof include white polyester films such as resin ecologue (trade name). However, it is not limited to these.

  In order to improve adhesion and wettability, the surface of the light reflecting layer (B) may be subjected to surface treatment such as corona treatment, coating treatment or flame treatment.

  As a method of laminating the formed film on the metal plate (A), for example, the surface temperature of the metal plate (A) is heated so as to be about the melting point of the resin constituting the main component of the light reflecting layer (B). Then, a method of heat-sealing the film with a rubber roll, a method of supplying the heat-rolled metal plate (A) and the film in layers, or heat-sealing them, or a metal plate (A) with an adhesive in advance. The method of apply | coating and crimping | bonding a film can be mentioned.

  The thickness of the light reflecting layer (B) is not particularly limited, but is preferably in the range of 10 μm to 500 μm, for example, in terms of moldability and stackability.

<Outermost surface layer (C)>
The outermost surface layer (C) contains silicone and is characterized in that the contact angle of the surface with distilled water is 95 degrees or more.
When the contact angle (with respect to distilled water) of the surface of the outermost surface layer (C) is less than 95 degrees, the heat-and-moisture resistance as a reflector is deteriorated, and the light-reflecting layer (B) is removed from the metal plate (A) at the time of moisture-and-heat resistance. While being easy to peel, the outermost surface layer (C) becomes easy to peel from the light reflecting layer (B).

The outermost surface layer (C) is preferably a transparent layer having a light transmittance (JIS K 7361-1) of 80% or more, particularly 90% or more. When the light transmittance of the outermost surface layer (C) is 80% or more, the reflection characteristics of the light reflection layer (B) are not deteriorated.
Here, in order to increase the light transmittance of the surface of the outermost surface layer (C) to 80% or more, while forming the outermost surface layer (C) using “resin containing silicone” having a light transmittance of 80% or more. The thickness of the outermost surface layer (C) is preferably 0.01 μm to 10 μm.

The “silicone-containing resin” that is the main component of the outermost surface layer (C) is a resin containing an organopolysiloxane bond having a siloxane bond as a skeleton, for example, a silicone-modified resin containing a siloxane bond or a siloxane Examples thereof include a silicone resin having a bond as a skeleton, or a mixed resin thereof.
Specifically, for example, dimethyl silicone oil, methylphenyl silicone oil, methyl hydrogen silicone oil, cyclic polydimethylsiloxane, alkyl-modified silicone oil, amino-modified silicone oil, silicone-polyether copolymer, fatty acid-modified silicone oil, epoxy Silicone oil such as modified silicone oil and fluorosilicone oil, pure silicone resin, alkyd modified silicone resin, polyester modified silicone resin, epoxy modified silicone resin, acrylic modified silicone resin, silicone resin such as urethane modified silicone resin, millable silicone rubber, Deacetic acid-type silicone rubber, oxime-resistant silicone rubber, dealcohol-free silicone rubber, deacetone-type silicone rubber, deaeration Phenoxy type silicone rubber (or, one-pack type), condensed silicone rubber, addition type silicone rubber (or more, two-liquid type) other silicone rubbers such as an acryloyl group (CH ₂ = CHCO-) or methacryloyl group (CH ₂ = CCH ₃ CO—) is a compound having one to several molecular weights in the molecule and several hundred to several hundreds of molecular weight, typically mono (meth) acrylates such as epoxy, epoxidized oil, urethane, polyester, polyether, etc. , Di (meth) acrylate, tri (meth) acrylate, and polyfunctional (meth) acrylate, and compounds containing silicone, etc. It is not preferable.
Among these, (meth) acrylate containing silicone, comb-type graft polymer having silicone in the graft chain, silicone / acrylic copolymer resin (also referred to as silicone-modified acrylic resin) and the like are particularly preferable. It may be used alone, for example, acrylic resin, melamine resin, phenol resin, urea resin, epoxy resin, amino alkyd resin, urethane resin, polyester resin having a light transmittance of 80% or more A binder resin such as a resin may be added.

  Examples of acrylates containing silicone, in other words, commercially available acrylates containing an organopolysiloxane bond, include Sanrad Kasei's Sunrad (trade name), GE Toshiba Silicone UVH8558, UV9300, UVHC1101, etc. (all trade names). However, the present invention is not limited thereto, and these acrylates may be mixed with other acrylate compounds such as urethane, epoxy and polyester having a light transmittance of 80% or more. In addition, as commercially available silicone graft polymers, Saimak (trade name) manufactured by Toagosei Co., Ltd., Aquabrid (trade name) manufactured by Daicel Chemical Industries, SG-204 (trade name) manufactured by Nippon Shokubai Co., Ltd. Modiper (trade name) and the like, and silicone / acrylic copolymer resins such as Charine (trade name) manufactured by Nissin Chemical Co., Ltd., Bon Coat manufactured by Dainippon Ink Chemical Co., Ltd., and Ceranate (all trade names) are listed. be able to. However, it is not limited to these.

Next, the contact angle is set to 95 degrees or more. For this, the amount of silicone in the outermost surface layer (C) is set to a predetermined value or more, that is, the X-ray source is controlled by X-ray photoelectron spectroscopy (ESCA method). When measured from the spectral intensity distribution under the conditions of MgKa, output 15 Kv × 33 mA, vacuum degree 5 × 10 ⁻⁸ torr, Si / C is 0.05 or more, particularly 0.08 or more, and the upper limit is 0.20. It is preferable to adjust so that it may become less.
If the amount of silicone is 0.05 or more, the contact angle becomes 95 degrees or more, and the heat and humidity resistance is improved. For example, a reflector for a cold cathode tube is formed from this reflector, and is assembled so as to come into contact with the resin light guide plate. In addition, when a backlight unit of a notebook personal computer is configured, it is possible to suppress the generation of noise accompanying the opening and closing of the display. On the other hand, even if Si / C is 0.20 or more, the effect of improving the contact angle is not recognized, the effect of improving the moist heat resistance is not recognized, and the adhesion with the reflective film layer is lowered. Such problems will arise.

In the outermost surface layer (C), the content of the fine particle filler is preferably less than 3% by mass, and it is particularly preferable that the fine particle filler is not included.
Of course, the light transmittance can be increased by preventing the outermost surface layer (C) from containing a fine filler (as much as possible). For example, a reflector for a cold cathode tube is formed from the reflector. Even when the light guide plate and the outermost surface layer (C) are rubbed when the backlight unit of the notebook personal computer is configured so as to come into contact with the resin light guide plate, the fine particles from the outermost surface layer (C) The occurrence of noise can be more reliably suppressed without missing the filler, and without slippage.

  However, the outermost surface layer (C) may contain a known additive in addition to the “resin containing silicone”. For example, it may contain a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistance agent, an impact resistance improver, and the like.

  As a method of forming the outermost surface layer (C) on the light reflecting layer (B), for example, a resin composition containing silicone may be applied on the light reflecting layer (B), When the reflective layer (B) is extruded, it may be formed by overlapping and extruding (two-layer extrusion) at the same time. Moreover, a film may be formed from the resin composition containing silicone, and this film may be laminated on the light reflection layer (B). However, it is not limited to these methods.

  In addition, although this light reflection board is a thing of a structure formed by laminating | stacking a metal plate (A), a light reflection layer (B), and an outermost surface layer (C) sequentially, if these functions are not disturbed, these Other layers other than may be provided.

<Application>
The light reflector is a light reflector used in an illumination device such as a fluorescent lamp, a light reflector of a surface light source of a direct type backlight of a liquid crystal display device, a light reflector of an edge type backlight, an LED or a cold cathode tube. It can be suitably used as a light reflecting plate for a reflector disposed around, a light reflecting plate of a light reflecting mechanism of a copying machine, or the like.
For example, as shown in FIG. 2, one side portion of the light reflection plate is bent so that the light reflection layer (B) is turned inside and rounded back at 180 ° C., so that the cold cathode tube has a J-shaped cross section. The reflecting plate 1 can be formed. The cold-cathode tube reflector 1 accommodates the cold-cathode tube 2 inside the folded portion, and inserts the end portion of the light guide plate 3 into the inner side from the opening of the folded portion. The backlight unit (light guide plate type) of the liquid crystal display device can be configured. At this time, even if the light reflection plate and the light guide plate 3 are arranged so as to be in contact with each other, noise is not generated when the display is opened and closed.

Examples of the present invention will be described below and will be described in more detail. However, the present invention is not limited to these examples, and various applications are possible without departing from the technical idea of the present invention.
First, the evaluation method will be described.

<Contact angle>
A “reflective film laminated metal plate” described below was formed as a test specimen, and the contact angle with respect to distilled water was measured for this reflective film laminated metal plate using DROP MASTER500 (manufactured by Kyowa Interface Science Co., Ltd.).

<Transmissivity>
The coating agent shown in Table 1 was pre-dried at room temperature for 15 hours, and then dried at 80 ° C. for 6 hours and 120 ° C. for 20 minutes to produce a film having a thickness of 10 μm.
About this sheet | seat, the total light transmittance was measured based on JISK7361-1, and the thing higher than 80% evaluated it as (circle) and 80% or less.

<Reflectivity>
An integrating sphere was attached to a spectrophotometer U-4000 (manufactured by Hitachi, Ltd.), and the reflectance with respect to light having a wavelength of 550 nm was measured.
In the state of the reflective film before being laminated on the metal plate (A), the reflectance is measured for each of the case where the outermost surface layer (C) is provided and the case where the outermost layer (C) is not provided. When small, it evaluated as (circle) and when larger than 0.3%, it evaluated as x.

<Noise>
As shown in FIG. 3, the “reflective film laminated metal plate” (length 30 mm × width 30 mm) and the light guide plate made of acrylic as the test body do not have the outermost surface layer (C) or the outermost surface layer (C). In this case, the light reflection layer (B) is overlapped so as to be in contact with the acrylic light guide plate, and both are fixed with clips. The acrylic light guide plate is bent 50 times forward and backward ± 20 degrees, and noise noise is generated at the 51st time. When noise noise was not generated, it was evaluated as ○, and when noise sound was generated, it was evaluated as ×.

<Heat and heat resistance>
The reflective film laminated metal plate described below was cut to 60 mm × 60 mm and immersed in boiling water for 5 hours. The sample was taken out after 5 hours and evaluated as ◯ when there was no abnormality such as peeling of the outermost surface layer (C), and × when peeling occurred.

(Preparation of reflective film with outermost layer)
Pellets of polylactic acid having a weight average molecular weight of 200,000 (L-form content 99.5 mol%, D-form content 0.5 mol%, glass transition temperature 65 ° C.) and titanium oxide having an average particle size of 0.25 μm The mixture was mixed at a mass ratio of 50:50 and pelletized using a twin screw extruder to prepare a master batch.
This master batch and the polylactic acid were mixed at a mass ratio of 40:60 to prepare a resin composition. Thereafter, this resin composition was extruded from a T die at 220 ° C. using a single screw extruder, and cooled and solidified to form a film. The obtained film was biaxially stretched 3 times in the MD direction and 3 times in the TD direction at a temperature of 65 ° C. and then heat treated at 140 ° C. to obtain a biaxially stretched aliphatic polyester reflective film having a thickness of 80 μm.
Furthermore, on the obtained biaxially stretched aliphatic polyester reflective film, the coating agent shown in Table 1 was applied so as to have a coating thickness of 1 μm after drying to produce a “reflective film with an outermost surface layer”.

(Production of reflective film laminated metal plate)
As a metal plate (A), an adhesive having the following composition was applied on a stainless steel plate (SUS304) having a thickness of 0.1 mm so that the coating thickness after drying was 3 μm, and after baking at 220 ° C., The reflective film with a surface layer was laminated at 200 ° C. and immediately cooled to obtain a “reflective film laminated metal plate” as a test specimen.

  As the above-mentioned adhesive, water-dispersed polyisocyanate (Aquanate 100 (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd.) with respect to 100 parts by mass of a polycarbonate-based urethane emulsion (Permarin UA310 (trade name) manufactured by Sanyo Chemical Industries). ) An adhesive comprising 10 parts was used.

(Test Example 1)
In the production of the reflective film with the outermost surface layer as a test body, an ultraviolet curable silicone acrylate (Sunrad RC610 (trade name) manufactured by Sanyo Chemical Industries) is used as a coating agent to be applied onto the biaxially stretched aliphatic polyester reflective film. Coat prepared by adding 10 parts of diluted monomer (acrylamide derivative ACMO (trade name) manufactured by Kojin Co., Ltd.) and 3 parts of reaction initiator (IRUGACURE 184 (trade name) manufactured by Ciba Specialty Chemicals) to 100 parts by mass This coating agent is applied onto the reflective film so that the film thickness after UV irradiation becomes 1 μm, and cured by irradiating with ultraviolet rays at a UV illuminance of 170 mJ / cm ² to form the outermost surface layer (C). Then, as described above, the reflective film with the outermost surface layer and the reflective film laminated metal plate were produced.
The above-described evaluation test was performed on the obtained reflective film with the outermost surface layer and the reflective film-laminated metal plate, and the results are shown in Tables 1 and 2.

In addition, the silicone content in the outermost surface layer (C) was measured by X-ray photoelectron spectroscopy (ESCA method) under a condition where the X-ray source was MgKa, the output was 15 Kv × 33 mA, and the degree of vacuum was 5 × 10 ⁻⁸ torr. Si / C was measured from the intensity distribution and indicated by the Si / C value (the same applies hereinafter).

(Test Example 2)
In the production of a reflective film with an outermost surface layer as a test body, a coating agent comprising an acrylic emulsion (Aquabrid AST4635 (trade name) manufactured by Daicel Chemical Industries, Ltd.) is applied as a coating agent to be applied onto a biaxially stretched aliphatic polyester reflective film. And coating the coating agent so that the thickness is 3 μm after drying at 100 ° C., forming the outermost surface layer (C), and producing the reflective film with the outermost surface layer and the reflective film laminated metal plate as described above did. The above evaluation was performed in the same manner as in Test Example 1, and the results are shown in Tables 1 and 2.

(Test Example 3)
In the production of a reflective film with an outermost surface layer as a test body, as a coating agent applied on a biaxially stretched aliphatic polyester reflective film, from silicone graft acrylic emulsion (Symac US-270 (trade name) manufactured by Toa Gosei Co., Ltd.) The reflective film with the outermost surface layer was the same as in Test Example 2 except that polyisocyanate (Coronate HL (trade name) manufactured by Nippon Polyurethane Co., Ltd.) was blended in the coating agent so that the solid content ratio was 5% by mass. In addition, a reflective film-laminated metal plate was prepared and subjected to the above evaluation test, and the results are shown in Tables 1 and 2.

(Test Example 4)
In the production of the reflective film with the outermost surface layer as a test body, an acrylic emulsion (Aquabrid AST4635 (trade name) manufactured by Daicel Chemical Industries, Ltd.) is used as a coating agent to be applied onto the biaxially stretched aliphatic polyester reflective film. Using a coating agent in which ether-modified silicone oil (YF3842 (trade name) manufactured by Toshiba Silicone Co., Ltd.) is blended so as to have a solid content ratio of 5 mass%, this coating agent has a coating thickness after drying. A reflective film with an outermost surface layer and a reflective film-laminated metal plate were prepared in the same manner as in Test Example 2 except that the coating was applied to a thickness of 3 μm, the evaluation test was performed, and the results are shown in Tables 1 and 2. .

(Test Example 5)
In the production of the reflective film with the outermost surface layer as a test body, 100 parts by mass of acrylic emulsion (Aquabrid AST4635 (trade name) manufactured by Daicel Chemical Industries, Ltd.) as a coating agent to be applied on the biaxially stretched aliphatic polyester reflective film. On the other hand, 10 parts of polyisocyanate (Aquanate 100 (trade name) manufactured by Nippon Polyurethane Co., Ltd.) and 5 parts of silicone acrylic copolymer resin (Modiper FS770 (trade name) manufactured by Nippon Oil & Fats Co., Ltd.) in solid content ratio. The reflective film with the outermost surface layer and the reflective film laminated metal plate were used in the same manner as in Test Example 2, except that the coating agent was added and this coating agent was applied so that the coating thickness after drying was 3 μm. It produced, the said evaluation test was done, and the result was shown in Table 1 and Table 2.

(Test Example 6)
In the production of a reflective film with an outermost surface layer as a test body, a silicone acrylic copolymer resin (Modiper FS770 (trade name) manufactured by NOF Corporation) is used as a coating agent to be applied on a biaxially stretched aliphatic polyester reflective film. A reflective film with an outermost surface layer and a reflective film-laminated metal plate were prepared in the same manner as in Test Example 5 except that the amount was 30 parts by mass, and the evaluation test was performed. The results are shown in Tables 1 and 2. .

(Test Example 7)
In the production of the reflective film with the outermost surface layer as the test body, as a coating agent to be applied on the biaxially stretched aliphatic polyester reflective film, an acrylic emulsion (Aquabrid AST4635 (trade name) manufactured by Daicel Chemical Industries, Ltd.) Using a coating agent in which PTFE (tetrafluoroethylene resin) powder with a diameter of 3 μm (sampler PTFE powder TFW300F (trade name) manufactured by Sampler Tech Co., Ltd.) is blended so as to have a solid content ratio of 3% by mass is used. A reflective film with an outermost surface layer and a reflective film-laminated metal plate were prepared in the same manner as in Test Example 2 except that the coating agent was applied so that the coating thickness after drying was 3 μm, and the evaluation test was performed. Are shown in Tables 1 and 2.

(Test Example 8)
In the production of the reflective film with the outermost surface layer as the test body, acrylic emulsion (Aquabrid AST4635 (trade name) manufactured by Daicel Chemical Industries), polyethylene as a coating agent to be applied on the biaxially stretched aliphatic polyester reflective film. Using a coating agent prepared by blending a wax emulsion (M2211 (trade name) manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) so that the solid content ratio is 5% by mass, the coating thickness after drying is 3 μm. A reflective film with an outermost surface layer and a reflective film-laminated metal plate were prepared in the same manner as in Test Example 2 except that the coating was applied so that the above evaluation test was performed. The results are shown in Tables 1 and 2.

Tables 1 and 2 revealed the following.
In the case where the main component of the outermost surface layer (C) is silicone acrylate (Test Example 1) or silicone-grafted acrylic resin (Test Example 3), the contact angle of the outermost surface layer (C) is 95 degrees or more, and light is transmitted. The rate was higher than 80%, and even in the result of the evaluation test, there were no problems in any of the reflectivity, noise property, and heat and humidity resistance.
On the other hand, the one using a polyether-modified silicone oil having high solubility in water (Test Example 4) had a contact angle of less than 95 degrees and was inferior in noise resistance and moist heat resistance.

In the case where the main component of the outermost surface layer (C) is an acrylic resin emulsion containing no silicone (Test Example 2), the contact angle of the outermost surface layer (C) was smaller than 95 degrees, and there was no problem with respect to reflectivity. However, noise resistance and moist heat resistance were inferior.
However, a silicone acrylic resin added to this acrylic resin emulsion so that the contact angle was 95 degrees or more (Test Example 6) sufficiently improved noise resistance and moist heat resistance.
However, when the amount of the silicone acrylic resin added was small and the contact angle was less than 95 degrees (Test Example 5), the noise and wet heat resistance could not be sufficiently improved.

  In the case where PTFE powder was added to the acrylic resin emulsion (Test Example 7), the contact angle was 95 degrees or more, but the main component of the outermost surface layer (C) did not contain silicone and contained fine particle filler. Therefore, although there was no problem with heat and humidity resistance, there was a problem that the transmittance was low, the reflectivity was poor, and particles were missing in the noise test.

  An acrylic resin emulsion to which a polyethylene wax emulsion was added (Test Example 8) had a contact angle of 95 degrees or more, and had no problem with reflectivity and wet heat resistance, but had a problem with noise.

It is sectional drawing which showed an example of the light reflector of this invention. It is the figure which showed the structural example of the backlight unit of a sidelight system using the reflecting plate (reflector) for cold cathode tubes formed by processing a light reflector. It is the front view which showed the method of the noise property test.

Explanation of symbols

A Metal plate B Light reflection layer C Outermost surface layer 1 Cold cathode tube reflection plate 2 Cold cathode tube 3 Light guide plate

Claims (5)

A light reflector comprising a light reflection layer (B) containing a polyester resin and a fine particulate filler in a single layer on at least one side of the metal plate (A), and an outermost surface layer (C),
The outermost surface layer (C) contains silicone and has a contact angle of 95 ° or more with distilled water on the surface thereof.   2. The light reflection according to claim 1, wherein the main component of the outermost surface layer (C) is a silicone-modified resin containing a siloxane bond, a silicone resin having a siloxane bond as a skeleton, or a mixed resin thereof. body.   The light reflection according to claim 1 or 2, wherein the silicone content in the outermost surface layer (C) is such that Si / C is 0.05 or more as measured by X-ray photoelectron spectroscopy. body.   A reflector comprising the light reflector according to claim 1. A reflective plate for a cold cathode tube is formed from a light reflector provided with a light reflecting layer (B) containing a polyester resin and a particulate filler on at least one side of the metal plate (A), and is in contact with the resin light guide plate. In the case where a backlight unit is configured in combination, a method for preventing the occurrence of noise accompanying opening and closing of the monitor unit,
A method comprising forming the outermost surface layer (C) containing silicone and having a contact angle of 95 ° or more with distilled water on the surface of the reflector.

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