WO2013099671A1 - Reflector, method for manufacturing reflector, and backlight panel - Google Patents

Description

Reflector, reflector manufacturing method and backlight panel

The present invention relates to a light guide plate type backlight panel used in a liquid crystal panel.

Conventionally, in a liquid crystal display device or the like, a backlight panel that emits light by illuminating light from the back side of a liquid crystal layer is used. In recent years, in particular, the use of an edge-light type backlight panel that can reduce the number of light sources and is advantageous for energy saving is increasing. A reflection plate is installed adjacent to the light guide plate of the edge light type backlight panel. The role of the reflecting plate is to return the light leaked to the reflecting plate side out of the light guided from the light source into the light guiding plate to the liquid crystal layer side to increase the luminance. Such an edge light type backlight panel is required to have uniform luminance over the entire light emission surface.

In the edge light type backlight panel, light emitted to the back side of the light guide plate is reflected by the reflection plate, returns to the inside of the light guide plate, and is emitted from the front side of the light guide plate. Therefore, high brightness can be obtained by reflection of light on the reflecting plate.

A gap is usually formed between the reflector and the light guide plate. This is because, when the reflecting plate and the light guide plate are brought into close contact with each other, a partially bright portion called a white spot is generated, and there is a risk of unevenness in luminance. For example, when the light guide plate or the like is partially deformed by heat or the like, if the part is strongly pressed against the reflective plate against other parts, the luminance of those parts is not the same as the other parts, and white It can be a factor such as a spot.

As a method of providing a gap between the light guide plate and the reflection plate, there is a method of applying a mixture of crosslinked acrylic beads or the like to a binder on the surface of the reflection plate (Patent Document 1).
As another method, there is a method of forming irregularities on the surface of the reflector. (Patent Documents 2 to 5).

JP 2005-25183 A JP 2003-121616 A JP 2003-270415 A WO2007 / 142260 Publication JP 2001-266629 A

However, as in Patent Document 1, in the method of maintaining the gap between the reflection plate and the light guide plate with beads, it is necessary to uniformly disperse and apply the beads. For this reason, it is necessary to use beads separately, and the material cost increases. In addition, since a bead coating step is required, a manufacturing process is required.

Further, in the method of directly forming the uneven shape on the surface of the foam as in Patent Documents 2 to 5, although the manufacturability is excellent, the resistance to the white spot is not sufficient only by adding arbitrary unevenness. On the other hand, the inventors have found that only irregularities satisfying a specific condition can suppress white spots.

The present invention has been made in view of such problems, and an object of the present invention is to provide a reflector plate that is excellent in manufacturability and can prevent the occurrence of white spots and the like.

In order to achieve the above-mentioned object, a first invention is a reflector for a backlight panel made of a thermoplastic resin foam, and a plurality of convex portions are formed on at least one surface of the reflector, A durometer A hardness of a surface having a convex portion is 95 or more and less than 100.

Further, it is desirable that the reflecting plate is characterized in that the arithmetic average roughness Ra of the surface having the convex portion is 6 or more and less than 30.

It is desirable that the reflecting plate has a first unfoamed layer on at least the surface of the convex forming surface, and the thickness of the first unfoamed layer is 5 to 30 μm.

It is desirable that the first unfoamed layer has a foamed layer on the inner side in the thickness direction, and further has a second unfoamed layer on the inner side of the foamed layer.

It is desirable that the total thickness of the reflector is 0.3 mm or more. It is desirable that the specific gravity of the reflector is 0.7 or less. The thermoplastic resin is preferably a thermoplastic polyester resin, and is preferably a polyethylene terephthalate resin.

According to the first invention, since the plurality of convex portions are formed on the surface of the reflecting plate, when the reflecting plate is disposed on the rear surface of the light guide plate, the gap between the light guide plate is maintained by the convex portions. be able to. At this time, since the reflecting plate is a foam, light can be efficiently diffused inside the reflecting plate and reflected to the front surface. Moreover, since the hardness of the convex portion is durometer A hardness 95 or more, the convex portion can be prevented from being crushed, and partial adhesion between the light guide plate and the reflecting plate due to the crushed convex portion can be prevented.

Further, if the arithmetic average roughness Ra is 6 or more, a certain gap or more can be secured between the light guide plate and the reflection plate without excessively collapsing the convex portion.

Also, if the reflecting plate has the first unfoamed layer on at least the surface of the convex forming surface, the hardness of the convex can be increased efficiently. Further, if the thickness of the first unfoamed layer is 5 to 30 μm, the effect of improving the hardness is high, and it is possible to suppress a decrease in reflectance due to light absorption in the unfoamed layer.

Further, by forming the first unfoamed layer and the second unfoamed layer and forming the foamed layer therebetween, it is easy to achieve both high reflectivity and the hardness of the surface having the convex portion.

Also, if the total thickness of the reflector is 0.3 mm or more, the occurrence of wrinkles on the reflector can be suppressed. Moreover, if the specific gravity of a reflecting plate is 0.7 or less, weight reduction can be achieved and material cost can be reduced. In addition, by applying a polyethylene terephthalate resin, which is a thermoplastic polyester resin, as the thermoplastic resin, a reflector having excellent heat resistance and cost can be obtained.

2nd invention is the manufacturing method of the reflecting plate for backlight panels, Comprising: The process a which contains the inert gas in the reflecting plate base material which consists of thermoplastic resin foams, The embossing to the said reflecting plate base material And a step c of heating the reflector substrate and performing a foaming process.

According to the second invention, when the convex portion is formed, the surface area of the reflector substrate is increased, so that the gas component inside the convex portion is easily released during foaming. Therefore, it is easy to form an unfoamed layer on the convex portion forming surface, and the hardness of the convex portion can be increased.

3rd invention comprises the reflecting plate concerning 1st invention, the light-guide plate provided in the front surface of the said reflecting plate, and the light source provided in the side of the said light-guide plate, The said convex part WHEREIN: The backlight panel is characterized in that a gap is formed between the reflector and the light guide plate.

According to the third invention, a gap can be maintained between the light guide plate and the reflection plate by the convex portion on the surface of the reflection plate. Moreover, since the convex part on the surface of the reflecting plate has a high hardness, the convex part is not easily crushed. For this reason, it is possible to prevent the light guide plate from being partially adhered to the surface of the reflection plate due to partial deformation of the light guide plate. For this reason, a backlight panel with uniform brightness can be obtained over the entire surface.

According to the present invention, it is possible to provide a reflector that is excellent in manufacturability and can prevent the occurrence of white spots and the like.

1 is a schematic diagram showing a configuration of a backlight panel 1. FIG. It is an enlarged view which shows the boundary part vicinity of the light-guide plate 3 and the reflecting plate 5, and is the A section enlarged view of FIG. FIG. 3 is an enlarged view showing the vicinity of the boundary between the light guide plate 3 and the reflective plate 5, and is an enlarged view of a portion B in FIG. (A)-(c) is a figure which shows the manufacturing process of the reflecting plate 5. FIG. It is an enlarged view which shows the boundary part vicinity of the light-guide plate 3 and the reflecting plate 5, and is the E section enlarged view of FIG.4 (c). The figure which shows other embodiment of the reflecting plate.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 is a view showing a backlight panel 1 used in a liquid crystal display device, etc. FIG. 2 is an enlarged view of a portion A in FIG. 1, and FIG. 3 is an enlarged view of a portion B in FIG. The backlight panel 1 is a so-called edge-light type backlight panel, and mainly includes a light guide plate 3, a reflection plate 5, a light source 9, and the like.

The light source 9 is disposed on the side (edge) of the light guide plate 3 and surrounded by the reflector 2 and the like. As the light source 9, for example, LED (Light Emitting Diode), CCFL (Cold Cathode Fluorescent Lamp), EEFL (External Electrofluorescent Lamp), HCFL (Hot Cathode Fluorescent LED) can be used. Those arranged in a line can also be applied.

The light guide plate 3 has a flat plate shape, and the light emission surface (the side on which the liquid crystal panel not shown is arranged on the upper surface side in FIG. 1) and the back surface are configured to be smooth. A reflector 5 is provided on the back side of the light guide plate 3 through a gap. A dot pattern for light diffusion may be printed on the back side of the light guide plate 3. For example, an acrylic resin can be used as the light guide plate 3.

As shown in FIG. 2, the reflector 5 is a porous body having fine bubbles 7 which are closed cells, and is formed of, for example, a resin foam. More specifically, a thermoplastic resin sheet having fine bubbles or pores having an average cell diameter of 50 nm or more and 50 μm or less inside can be suitably used.

The reflecting plate 5 is preferably made of a thermoplastic polyester resin in view of its heat resistance. The thermoplastic polyester resin used in the present invention is not limited, but for example, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate and the like can be appropriately selected. These may be used individually by 1 type, and may mix and use 2 or more types. Among these, polyethylene terephthalate is preferable in terms of availability, economy, heat resistance, and the like.

In the present invention, a crystallization nucleating agent, a crystallization accelerator, a bubble nucleating agent, an antioxidant, an antistatic agent are added to the thermoplastic resin sheet before foaming within a range that does not affect the properties of the obtained reflector 5. Agents, UV inhibitors, light stabilizers, fluorescent brighteners, pigments, dyes, compatibilizers, lubricants, reinforcing agents, flame retardants, crosslinking agents, crosslinking aids, plasticizers, thickeners, thickeners, etc. Various additives may be blended. Moreover, you may laminate | stack resin containing the said additive on the obtained reflecting plate, and may coat the coating material containing the said additive. Applying a layer containing a UV inhibitor to at least one surface of the polyester resin foam is sufficient to prevent UV deterioration even when thermoplastic polyester resins or polyester elastomers that are susceptible to UV deterioration are used. Is particularly preferable.

In addition, it is desirable that the thickness of the reflecting plate 5 is 0.1 mm or more. If the thickness of the reflecting plate 5 is less than 0.1 mm, the rigidity is low and wrinkles are likely to occur, which is not preferable. From the viewpoint of increasing rigidity, the thickness of the reflector 5 is preferably 0.2 mm or more, and more preferably 0.3 mm or more.

The specific gravity of the reflector 5 is preferably 0.7 or less, more preferably the specific gravity is less than 0.6, and the specific gravity is more preferably less than 0.5. If the specific gravity is large, the distribution amount of the fine bubbles 7 is not sufficient, and the effect of the fine bubbles is reduced. Moreover, the reflectance of the reflecting plate 5 is not limited, but when used as a reflecting plate of a liquid crystal panel, the total reflectance of the reflecting plate 5 is desirably 90% or more. Further, from the viewpoint of energy saving, the reflectance is preferably 95% or more, and more preferably 98% or more.

A plurality of convex portions 11 are formed on the surface of the reflecting plate 5. That is, the light guide plate 3 contacts the convex portion 11 on the surface of the reflective plate 5, and a gap is formed between the light guide plate 3 and the reflective plate 5 by the convex portion 11. The shape of the convex portion 11 is not limited to the illustrated example, but may be other shapes, but it is desirable that the convex portion 11 has a circular arc-shaped tip shape so that the tip of the convex portion 11 is not easily crushed. In addition, the shape of the convex portion 11 needs to have a certain height or higher so that the gap does not collapse even when compressed. Specifically, the arithmetic average roughness Ra is preferably 5 or more. In order to suppress white spots more reliably, Ra is preferably 6 or more, and more preferably Ra is 7 or more. In addition, when Ra exceeds 30, it is not preferable because the convex portion is easily crushed even with a small pressure.

Further, it is desirable that the convex portions 11 are randomly dispersed without being aligned with the surface of the reflecting plate 5. By arranging the projections 11 at random, when the reflector 5 is arranged on the rear surface of the light guide plate 3 and used as a backlight panel unit, there is no occurrence of a striped pattern due to light interference or the like, and it is uniform. Brightness can be obtained. In addition, the formation method of the convex part 11 is mentioned later.

FIG. 3 is an enlarged view of part B of FIG. As shown in the figure, the top of the convex portion 11 is in contact with the light guide plate 3. Here, the upper part (C in the figure) above the base of the convex part 11 (the bottom part of the convex part 11) is the convex part range, and the lower part (D in the figure) than the base part of the convex part 11 is the range other than the convex part. To do. That is, a gap corresponding to the convex portion range C is formed between the light guide plate 3 and the reflection plate 5.

In the present invention, even if a surface pressure is applied due to thermal deformation or the like of the reflecting plate or the light guide plate, the surface of the reflecting plate 5 needs to have a hardness that does not crush the gap. Therefore, high hardness is required for the surface having the convex portion 11. Specifically, a durometer A hardness of 95 or more is required. If the durometer A hardness is less than 95, the possibility of white spots is greatly increased. In order to reliably suppress white spots, the durometer A hardness is preferably 96 or more, more preferably 97 or more.

In order to obtain such a configuration, it is desirable to form the surface non-foamed layer 8 on the surface of the reflecting plate 5. The non-foamed surface layer 8 is a region that is formed on the surface of the reflecting plate 5 where the convex portions 11 are formed, and in which no fine bubbles are present (or there are only minute portions compared to the inside of the reflecting plate). If the surface unfoamed layer 8 is too thin, the effect of improving the hardness is small. On the other hand, if the thickness is too thick, the specific gravity of the entire reflecting plate 5 is increased, and there is a concern that the reflectance is reduced due to light absorption by the surface unfoamed layer 8. Therefore, the thickness range of the unfoamed surface layer 8 is preferably about 3 to 50 μm, more preferably 5 to 30 μm.

Next, the function of the backlight panel 1 will be described. The light emitted from the light source 9 enters the light guide plate 3 directly or by the reflector 2 or the like disposed behind the light source. The light beam incident on the inside of the light guide plate 3 is totally reflected at the interface because of the air layer existing on the front surface of the light guide plate 3. On the other hand, on the back side of the light guide plate 3, a part of the light is transmitted and enters the reflection plate 5. The light incident on the reflecting plate 5 is reflected by the reflecting plate 5 and returns into the light guide plate 3. A part of the returned light is totally reflected again on the front surface of the light guide plate 3, but the remaining light is emitted to the front surface of the light guide plate 3. Thus, light can be uniformly emitted from the entire surface of the backlight panel.

In the reflection plate 5, the light guide plate 3 is totally reflected or diffused at the interface with a large number of fine bubbles 7 (the inside is, for example, an air layer and the refractive index is smaller than that of the resin constituting the reflection plate 5). Emitted to the side. The light beam diffused by the reflection plate 5 returns into the light guide plate 3, and a part of the light is totally reflected again on the front surface of the light guide plate 3, and the remaining light is emitted to the front surface of the light guide plate 3.

At this time, the reflecting plate 5 for diffusing light is a porous body and absorbs light much less than white paint or the like. Further, the diffusion and reflection of light can be easily controlled by the average hole diameter and density of the reflecting plate 5. In addition, since a predetermined gap is maintained between the reflecting plate 5 and the light guide plate 3, a white spot or the like does not occur due to surface contact between the light guide plate 3 and the reflecting plate 5. That is, uniform brightness can be ensured on the front surface of the light guide plate 3.

Next, a method for manufacturing the reflector 5 will be described. FIG. 4 is a schematic view showing a manufacturing process of the reflector 5. The method for introducing bubbles into the sheet is not limited. For example, a batch foaming method in which a resin sheet is impregnated with gas in a pressure vessel and then heated and foamed, or a thermoplastic resin sheet is extruded from a die of an extruder. There are an extrusion foaming method in which foaming is performed, and a stretching method in which a void is formed at the interface between the filler and the resin by extruding a thermoplastic resin sheet containing a filler and then stretching. Here, the manufacturing method of the reflecting plate 5 by the batch foaming method is shown as an example. In the case of the batch foaming method, there are advantages that the bubbles are more easily refined than the extrusion foaming method, thicker than the stretching method, and easy to reduce the specific gravity.

First, as shown in FIG. 4A, the reflector base 13 is manufactured. In addition, illustration of a separator is abbreviate | omitted in Fig.4 (a). First, a thermoplastic resin sheet is produced, and a roll is formed by overlapping and winding a thermoplastic resin sheet and a separator. The separator used here may be any one as long as it has a void through which an inert gas or an organic solvent used as needed freely enters and exits, and the permeation of the inert gas into itself can be ignored. . As the separator, a resin nonwoven fabric or a metal net is particularly suitable.

On the other hand, the thermoplastic resin sheet is preferably unstretched. This is because when the thermoplastic resin sheet is stretched, the gas does not sufficiently permeate into the sheet, and the intended foamed sheet cannot be obtained.

In the above method, an organic solvent may be contained in the resin sheet before the roll made of the resin sheet and the separator is held in a pressurized inert gas atmosphere and the resin sheet contains the inert gas. When an organic solvent is contained in the sheet, the crystallinity of the thermoplastic resin sheet can be increased to 30% or more. As a result, the rigidity of the sheet is increased and it is difficult for the trace of the separator to remain on the surface of the sheet, and the permeation time of the inert gas can be shortened. Depending on the type of separator, the trace of the separator may not remain on the surface of the sheet, so that the treatment containing the organic solvent is not necessarily required. However, from the viewpoint of shortening the gas permeation time, it is preferable to carry out a treatment containing an organic solvent.

Organic solvents used to increase the crystallinity of the resin sheet include benzene, toluene, methyl ethyl ketone, ethyl formate, acetone, acetic acid, dioxane, m-cresol, aniline, acrylonitrile, dimethyl phthalate, nitroethane, nitromethane, benzyl alcohol Etc. Of these, acetone is more preferable from the viewpoints of handleability and economy.

Next, as shown in FIG. 4B, a large number of convex portions 11 are formed on the surface of the reflector base 13. For forming the convex portion 11, for example, a resin sheet is passed between a pair of embossing rolls having a concave portion corresponding to the convex portion 11, and the convex portion 11 (for example, embossing processing) is formed on the surface of the reflector plate base 13 by the roll. ) May be formed. The foamed sheet may be passed between the embossing rolls described above to give irregularities. From the viewpoint of ease of applying unevenness, the sheet before gas permeation has an advantage that unevenness is easily provided because the deformation of the central layer of the sheet is small.

Next, the reflector base material 13 on which the convex portions 11 are formed is placed in a high-pressure vessel and held in a pressurized inert gas atmosphere so that the thermoplastic sheet contains an inert gas serving as a foaming agent. Examples of the inert gas include helium, nitrogen, carbon dioxide, and argon. Among these, carbon dioxide is preferable because it can be contained in a large amount in the thermoplastic polyester. The osmotic pressure of the inert gas is preferably 30 to 70 kg / cm ² , more preferably 50 kg / cm ² or more. The infiltration time of the inert gas is 1 hour or more, and more preferably the gas is infiltrated until it becomes saturated.

Next, the reflector base material 13 is taken out from the high-pressure vessel, and while removing the separator, the reflector base material 13 on which the convex portions 11 are formed is heated to a temperature equal to or higher than the softening temperature of the resin sheet under normal pressure. By doing in this way, as shown in FIG.4 (c), the reflecting plate base material 13 is made to foam. Under the present circumstances, after taking out from a high pressure container, the bulk specific gravity of the foam obtained can be adjusted by adjusting the time until it makes it foam.

Specifically, the longer this time, the larger the bulk specific gravity. In addition, the heating temperature at the time of foaming is set to the melting point or less above the glass transition point of the resin.

FIG. 5 is an enlarged view of part E in FIG. As shown in FIG. 5, the surface unfoamed layer 8 is usually formed on the surface layer of such a foam. The surface unfoamed layer 8 is formed, for example, when gas that has permeated into the inside escapes from the surface of the reflector substrate 13 before foaming (in the direction of arrow F in the figure). By reducing the amount of gas on the surface of the reflecting plate substrate 13, the fine bubbles 7 are not generated in the vicinity of the surface layer of the reflecting plate substrate 13 during the subsequent foaming process, or the generation amount thereof is reduced. Therefore, in the surface non-foamed layer 8, the fine bubbles 7 are hardly observed and become a solid resin portion.

When the convex part 11 is formed on the surface of the reflector base 13, the surface area of the convex part 11 increases. For this reason, the amount of escape of this gas increases, and the amount of fine bubbles 7 inside the convex portion 11 becomes smaller than other parts (inside the reflecting plate 5). That is, the volume ratio of the fine bubbles 7 in the convex portion 11 is smaller than the volume ratio of other portions. Therefore, the hardness of the convex part 11 can be made higher than the hardness in parts other than the convex part 11.

Note that the thickness of the unfoamed surface layer 8 is usually about 5 to 10 μm, but the thickness of the unfoamed surface layer 8 can be increased by appropriately setting the manufacturing conditions. In the present invention, for example, the thickness of the surface unfoamed layer 8 may be about 30 μm.

Next, another embodiment of the reflector will be described. As shown in FIG. 6, an intermediate unfoamed layer 10 may be further formed on the inner side in the thickness direction of the surface unfoamed layer 8. That is, the surface unfoamed layer 8, the foamed layer 12, and the intermediate unfoamed layer 10 may be formed in order from the surface on the convex 11 forming surface of the reflector. The intermediate non-foamed layer 10 is a region where the fine bubbles 7 are not present (or are present only minutely compared to the inside of the reflector), like the surface unfoamed layer 8. The foam layer 12 is a layer in which a predetermined amount of fine bubbles 7 are formed.

As described above, the surface non-foamed layer 8 can improve the hardness of the reflector surface. However, if only the thick unfoamed layer 8 is disposed on the surface of the reflector in order to make the surface predetermined hardness only by the unfoamed layer 8, the reflectance is reduced due to light absorption by the unfoamed layer 8. There are concerns. Therefore, a high reflectance is obtained by forming the foamed layer 12 on the inner side of the surface unfoamed layer 8 as shown in FIG. 6 and further forming the intermediate unfoamed layer 10 on the inner side of the foamed layer 12. And the hardness of the convex part are easily compatible.

The surface unfoamed layer 8 can increase the thickness of the surface unfoamed layer by promoting gas detachment from the surface by heating after removing the resin sheet containing the inert gas. At this time, when heated under appropriate conditions, an intermediate unfoamed layer can also be generated due to the effect of thermal crystallization of the resin.

According to the present invention, since the plurality of convex portions 11 are formed on the surface of the reflection plate 5, a gap can be formed between the light guide plate 3 and the reflection plate 5 without applying beads or the like. Moreover, since the hardness of the convex part 11 is 95 or more in durometer A hardness, even when a part of the light guide plate 3 is pressed against the reflecting plate 5 due to deformation of the light guide plate 3 or the like, the convex part 11 is crushed. This can be prevented. Therefore, it is possible to prevent the gap between the light guide plate 3 and the reflection plate 5 from being crushed and coming into surface contact with each other. For this reason, formation of a white spot can be suppressed and a backlight panel with high luminance can be obtained.

(Measurement evaluation method)
Hereinafter, the present invention will be described in detail by way of examples. Measurement and evaluation were performed by the following methods.

(1) Sheet thickness The thickness at the four corners, four sides of the sample and the center of the sheet was measured with a micrometer, and the average value of a total of nine points was taken as the sheet thickness.

(2) Average cell diameter It was determined according to ASTM D3576-77. An SEM photograph of the cross section of the sheet was taken, straight lines were drawn in the horizontal direction and the vertical direction on the SEM photograph, and the length t of the bubble chord crossed by the straight line was averaged. Assuming that the magnification of the photograph is M, the average bubble diameter d was determined by substituting it into the following equation (d = t / (0.616 × M)).

(3) Foaming ratio It calculated as ratio (rho) / rho of the specific gravity ((rho) f) of the foam sheet measured by the underwater substitution method and the specific gravity ((rho) s) of the resin before foaming.

(4) Reflectance The reflectance was measured with a spectrophotometer (U-4100, manufactured by Hitachi High-Tech Co., Ltd.) under the condition of a spectral slit of 4 nm and a light wavelength of 550 nm. As a reference, an aluminum oxide white plate (210-0740: manufactured by Hitachi High-Tech Fielding Co., Ltd.) was used, and the measured value was a value relative to the reference.

(5) Durometer A hardness In the present invention, the hardness of the reflective sheet was evaluated by the durometer A hardness based on JIS K 7215 (1986). JIS K 7215 (1986) is a standard corresponding to ISO 868.

(6) Surface roughness In this invention, the surface roughness of the reflective sheet was evaluated by arithmetic mean roughness Ra based on JIS B0601 (2001). JIS B0601 (2001) is a standard corresponding to ISO 4287.

(7) White spot tolerance In this invention, the white spot tolerance evaluation of the reflective sheet was performed as follows. Remove the LCD panel from the commercially available edge light type LCD monitor and take out the backlight. Next, the reflective sheet was taken out from the backlight, and a metal disk having a diameter of 25 mm and a thickness of 1 mm was laid under the reflective sheet, and then the backlight was reassembled as it was. A glass petri dish having a diameter of 50 mm was allowed to stand on the surface of the backlight so that the above-described metal disk was at the center. At the center of the petri dish, a Φ10 mm indenter was set up at a right angle, and the petri dish was compressed while measuring the load. The compression was continued until a white spot appeared around the metal disk, and the load (unit N: Newton) when the white spot appeared for the first time was read as white spot resistance. The white spot resistance was judged to be acceptable if it was 40N or more, and rejected if it was less than 40N.

Example 1
After adding 2 parts by weight of a polyester elastomer (grade: Hytrel 2551, manufactured by Toray DuPont) to 100 parts by weight of polyethylene terephthalate (grade: SA-1206, unitika, ρs = 1.34) The sheet was formed into a sheet of 5 mm thickness × 250 mm width × 60 m length. The sheet thus obtained was passed between rolls heated above the glass transition point of the resin, and a predetermined pressure was applied to make the surface of the sheet uneven. An olefin-based nonwoven fabric separator was stacked on this sheet and wound into a roll shape.

Thereafter, the roll was put into a pressure vessel, pressurized to 6 MPa with carbon dioxide gas, and carbon dioxide gas was infiltrated into the resin sheet. The penetration time was 72 hours. After completion of the infiltration, the roll was taken out from the pressure vessel, and while removing the separator, only the resin sheet was supplied to a hot air oven set at a temperature lower than the melting point of the resin and foamed.

(Example 2)
A foam sheet was obtained by changing only the temperature and pressure conditions for embossing the sheet having the same composition as in Example 1.

(Comparative Example 1)
After adding 2 parts by weight of a polyester elastomer (grade: Hytrel 2551, manufactured by Toray DuPont) to 100 parts by weight of polyethylene terephthalate (grade: SA-1206, unitika, ρs = 1.34) The sheet was formed into a sheet of 5 mm thickness × 250 mm width × 60 m length. An olefin-based nonwoven fabric separator (grade: FT300, manufactured by Japan Vilene) was layered on this sheet and wound into a roll.

Thereafter, the roll was put into a pressure vessel, pressurized to 6 MPa with carbon dioxide gas, and carbon dioxide gas was infiltrated into the resin sheet. The penetration time was 72 hours. After completion of the infiltration, the roll was taken out from the pressure vessel, and while removing the separator, only the resin sheet was supplied to a hot air oven set at a temperature lower than the melting point of the resin and foamed. The foamed sheet thus obtained was passed between rolls heated above the glass transition point of the resin, and a predetermined pressure was applied to make the surface of the sheet uneven.

(Comparative Example 2)
A foamed sheet was obtained by changing only the conditions for embossing the sheet having the same composition as Comparative Example 1.

The results are shown in Table 1.

As shown in Table 1, in Example 1, the thickness of the foamed sheet was 0.75 mm, and the specific gravity was 0.35. When the arithmetic average roughness of the surface of the foam sheet having the convex portions was measured, Ra was 7.9, and the durometer A hardness was 96.8. It was a pass level when the white spot tolerance of the obtained reflective sheet was measured.

Moreover, in Example 2, the thickness of the foam sheet was 0.55 mm, and the specific gravity was 0.35. The arithmetic average roughness of the surface of the foam sheet having the convex portions was measured to find 6.4, and the durometer A hardness measured to be 95.8. It was a pass level when the white spot tolerance of the obtained reflective sheet was measured.

On the other hand, in Comparative Example 1, the thickness of the foamed sheet was 0.73 mm, and the specific gravity was 0.36. The arithmetic mean roughness of the surface of the foamed sheet having the convex portions was measured and found to be 3.5, and the durometer A hardness was measured to be 92.4. Since the arithmetic average roughness was small and the duro A hardness was low, the white spot resistance of the obtained reflective sheet was measured and found to be a rejected level.

In Comparative Example 2, the thickness of the foam sheet was 0.60 mm, and the specific gravity was 0.35. The arithmetic average roughness of the surface of the foam sheet having the convex portions was measured and found to be 5.9, and the durometer A hardness was 92. Since the arithmetic average roughness was small and the duro A hardness was low, the white spot resistance of the obtained reflective sheet was measured and found to be a rejected level.

The embodiment of the present invention has been described above with reference to the accompanying drawings, but the technical scope of the present invention is not affected by the above-described embodiment. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the technical idea described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

1 ... Backlight panel 3 ... Light guide plate 5 ... Reflector plate 7 ... Fine air bubbles 9 ... Light source 11 ... Convex portion 13 ... Reflector plate base material 15 ... Skin layer 17 ......... Melting part 19 ......... Non-melting part

Claims (10)

A reflector for a backlight panel made of a thermoplastic resin foam,
A plurality of convex portions are formed on at least one surface of the reflecting plate,
A reflector having a durometer A hardness of 95 to less than 100 on the surface having the convex portion. 2. The reflector according to claim 1, wherein an arithmetic average roughness Ra of the surface having the convex portion is 6 or more and less than 30. 2. The reflection plate has a first unfoamed layer on at least a surface of the convex forming surface, and the thickness of the first unfoamed layer is 5 to 30 μm. The reflector as described. 4. The reflector according to claim 3, wherein the first unfoamed layer has a foamed layer on the inner side in the thickness direction, and further has a second unfoamed layer on the inner side of the foamed layer. 2. The reflector according to claim 1, wherein a total thickness of the reflector is 0.3 mm or more. 2. The reflector according to claim 1, wherein the reflector has a specific gravity of 0.7 or less. 2. The reflector according to claim 1, wherein the thermoplastic resin is a thermoplastic polyester resin. The reflector according to claim 1, wherein the thermoplastic resin is a polyethylene terephthalate resin. A method of manufacturing a reflector for a backlight panel,
A step a of incorporating an inert gas into the reflector substrate made of a thermoplastic resin foam;
B) embossing the reflector substrate;
A step c of heating the reflector substrate to perform a foaming treatment;
The manufacturing method of the reflecting plate characterized by comprising. The reflector according to any one of claims 1 to 8,
A light guide plate provided in front of the reflector;
A light source provided on a side of the light guide plate;
Comprising
The backlight panel is characterized in that a gap is formed between the reflection plate and the light guide plate by the convex portion.

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