KR100851333B1 - Light reflector - Google Patents

Abstract

An optical reflective plate is provided to decrease a specific gravity and raise a reflective index of the reflective plate by injecting inert gas into polypropylene mixed with ethylene and heating the polypropylene. An optical reflective plate(10) reflects an incident beam. Inert gas is injected into the optical reflective plate. Polypropylene(11), which is mixed with ethylene, is heated, such that vapors(12) are formed. A mean diameter of the vapors lies between 0.5 and 30um A concentration of the ethylene, which is mixed with polypropylene, lies between 0 and 50 w%. A specific gravity of the reflective plate lies between 0.4 and 0.7.

Description

Light reflector {LIGHT REFLECTOR}

1 is a cross-sectional view of a conventional liquid crystal display device;

2 is a detailed view of the lightbox of FIG.

3 is a cross-sectional view of a light reflection plate according to the present invention;

4 is a perspective view showing a state in which a roll is formed by stacking a polypropylene sheet with a separator;

5 is an exemplary view of a light reflection plate manufacturing method according to the present invention;

6 is a flowchart of a method of manufacturing a light reflection plate according to the present invention.

* Description of the symbols for the main parts of the drawings *

10: light reflection plate 11: polypropylene

12: bubble 13: additive sheet

14: Linate 15: Roll

20: sealed container 30: heating device

40: cooling device 50: plate heater

101: upper polarizing plate 102: upper glass substrate

103: top electrode 104: liquid crystal

105: bottom electrode 106: bottom glass substrate

107: bottom polarizer 110: light box

111 diffuser 112 light guide plate

113: side light 114: light reflector

The present invention relates to a light reflector, and more particularly, to a light reflector capable of foaming polypropylene mixed with ethylene to reduce manufacturing cost and improve reflectance.

In general, the light reflection plate is installed on the rear surface of a liquid crystal display (LCD) or the like, wherein the liquid crystal display device is an application of the electrical and optical properties of a liquid crystal having an intermediate characteristic between a liquid and a solid.

As shown in FIG. 1, the LCD includes an upper polarizing plate 101, an upper glass substrate 102, an upper electrode 103, a liquid crystal 104, a rear electrode 105, a rear glass substrate 106, and a rear surface. The polarizing plate 107 and the light box 110 are stacked.

In this case, the liquid crystal display 104 is a liquid crystal display device having a liquid crystal 104 having a fluidity as a liquid, and having a state in which the liquid crystal 104 is regularly arranged as a crystal, and using a property in which molecular arrangements are changed by an external electric field.

In the liquid crystal display, when the voltage is applied to the liquid crystal 104, the arrangement of the liquid crystal 104 is changed. When the light scanned by the light box 110 passes through the liquid crystal 104 in this state, diffraction occurs. .

At this time, the light is transmitted through the polarizing plate to obtain a desired image.

On the other hand, the light box 110 has a structure as shown in FIG. 2 in order to obtain a function as a surface light source in the liquid crystal display device.

As shown in FIG. 2, the light box 110 is provided by stacking the light reflecting plate 114, the light guide plate 112, and the diffusion plate 111, and side lights 113 are provided on the side surfaces thereof. .

The light of the side light 113 is guided to the light guide plate 112, and is repeatedly displayed through the diffuser plate 111 while repeating diffuse reflection at an interface between the light guide plate 112 and the light reflection plate 114. It is emitted to cotton.

As described above, in order to cause diffuse reflection at the interface between the light guide plate 112 and the light reflection plate 114, the following method is used.

For example, a method of printing a pattern causing diffusion reflection on an interface between the light guide plate 112 and the light reflection plate 114, and a predetermined pattern is formed between the light guide plate 112 and the light reflection plate 114. A method of inserting a printed film, a method of forming a concave finely on the lower surface of the light guide plate 112, and the like.

In addition, since the light reflecting plate 114 is required to have a high light reflectance, various materials have conventionally been used. 114).

However, in the light reflection plate 114 having the metal mirror surface, diffuse reflection is less likely to occur, so that the amount of light directed to the display surface is rather small.

Moreover, the light reflection plate 114 which consists of a film containing white pigments, such as a titanium oxide, is also used.

In the light reflection plate 114 made of a film containing a white pigment such as titanium oxide, it is necessary to increase the amount of pigment added in order to suppress leakage of light to the rear surface.

However, since the white pigment added to the film absorbs light of a specific wavelength, the increase in the amount of addition causes a problem that the increase in light loss cannot be neglected and the reflectance is lowered.

In addition, a light reflection plate 114 made of a polyester film containing fine bubbles is also used.

In addition, a light reflecting plate 114 is also used, which is made of a film obtained by laminating a polyester film containing this microbubble and another polyester film in which particles of calcium carbonate or silica having no light absorption are dispersed.

However, in the case described above, a polyester film containing microbubbles is produced by dispersing a polymer in a polyester and forming bubbles around the polymer particles when the polymer film is stretched in the vertical or horizontal axis.

However, it is rather difficult to uniformly disperse the polymer in the polyester, so that the dispersion of bubbles in the polyester is also uneven, and the light cannot be diffused and reflected sufficiently.

Moreover, since the stretched film becomes thinner than 200 micrometers in thickness, the light which leaks to the film back surface also becomes large, and it is difficult to achieve satisfactory reflectance.

Therefore, in order to obtain sufficient reflectance, there existed a problem that the need of arrange | positioning the other light reflection plate which has a metal mirror surface on the back surface of a film arises.

Similarly, in the light reflection boards, such as a lighting fixture, high light reflectivity may be calculated | required.

As the light reflection plate for this use, one made of a metal material such as a steel sheet or an aluminum plate, or a coating material containing a light reflective pigment on the surface of a plastic injection molded product is used.

In the case of using a light reflection plate made of a metal material, the total reflectance of the light is sufficiently high, but there is a problem that the reflected light is dazzling because there is little diffusion reflection.

On the other hand, in the light reflection plate which coated the coating material containing a light reflective pigment on the surface of a plastic injection molded object, there exists a limit to thickening a coating film, and since the pigment itself absorbs light, there existed a problem that the reflectance of light falls.

Accordingly, an object of the present invention is to provide a light reflection plate having a high reflectance and a low manufacturing cost without adding another light reflection plate by forming bubbles by heating polypropylene mixed with ethylene.

The above object is, according to the present invention, a light reflection plate for reflecting the incident light, the light reflection plate is a light reflection plate characterized in that the inert gas is injected at a high pressure, the bubble is formed by heating the polypropylene mixed with ethylene Is achieved by.

Preferably, the polypropylene may be mixed with less than 50weight% of the ethylene.

In addition, the average diameter of the bubbles may be formed to 0.5㎛ to 30㎛.

In addition, the light reflector may have a specific gravity of 0.4 to 0.7.

Preferably, the inert gas may be provided with carbon dioxide.

Here, the inert gas may be injected into the light reflection plate at a penetration pressure of 50 kg / cm 2 to 72 kg / cm 2.

Meanwhile, according to the present invention, there is provided a light reflection plate manufacturing method for reflecting incident light, comprising: rolling a polypropylene sheet mixed with ethylene to form a roll; Inserting the roll into a sealed container and supplying an inert gas at a high pressure to inject the inert gas into the light reflection plate; Heating to form bubbles in the light reflection plate; Cooling the light reflecting plate formed with the bubble; is achieved by a light reflecting plate manufacturing method comprising a.

Preferably, the polypropylene may be mixed with less than 50weight% of the ethylene.

Here, the average diameter of the bubbles may be formed to 0.5㎛ 30㎛.

In addition, the light reflector may have a specific gravity of 0.4 to 0.7.

Preferably, rolling the polypropylene sheet mixed with the ethylene to form a roll may further include overlapping the separator on the sheet to form a space between the sheet and the sheet.

Here, the inert gas may be provided with carbon dioxide.

On the other hand, the inert gas may be injected into the light reflection plate at a penetration pressure of 50kg / ㎠ to 72㎏ / ㎠.

In addition, the light reflection plate may be heated by one of a plate heater and an infrared heater.

Here, the plate heater or the infrared heater may heat the light reflection plate at a temperature of 135 ℃ to 160 ℃.

Hereinafter, with reference to the accompanying drawings, the present invention will be described in detail.

Referring to FIG. 3, the light reflection plate 10 according to the present invention is a light reflection plate 10 that reflects incident light. It is characterized in that the bubble 12 is formed by heating the propylene 11.

Hereinafter, each configuration will be described in detail.

In the light reflecting plate 10 according to the present invention, a thermoplastic polypropylene (11) resin mixed with ethylene is used, and the polypropylene (11) is homopolypropylene (Homo PP), block polypropylene (Block PP), random poly Propylene (Random PP), terpolypropylene (Ter-PP) and the like.

Here, the light reflection plate 10 according to the present invention may be used any of the polypropylene (11) resin, in particular, block polypropylene is most preferred among the polypropylene (11) resin.

This is because the foamed light reflecting plate 10 is a bubble 12 that serves as a reflection, the more bubbles 12, the higher the reflectance.

Therefore, the block polypropylene has a higher reflectance because of higher bubble ratio, that is, higher density of bubbles than other polypropylene.

On the other hand, ethylene mixed in the polypropylene (11) resin is preferably copolymerized within 50weight%.

In addition, the light reflection plate 10 according to the present invention may copolymerize any one of butylene, hexane, and octane in addition to the ethylene to the polypropylene 11 resin.

The light reflector 10 according to the present invention has a crystallization nucleating agent, a crystallization accelerator, a foaming nucleating agent, an antioxidant, an antistatic agent, and an ultraviolet ray preventing agent in the polypropylene 11 resin before foaming within a range that does not affect the light reflecting properties. Various additives, such as a light stabilizer, a pigment, dye, and a lubricating agent, can also be mix | blended.

Here, it is preferable that the addition amount of the crystallization nucleating agent in the said additive is 5 weight% or less, More preferably, it is 2 weight% or less.

Table 1 shows the specific gravity and the reflectance of the light reflector 10 according to the additives added to the polypropylene (11) resin.

Referring to Table 1, it can be seen that the specific gravity of the light reflection plate 10 is low and the reflectance is high when the additive is added at 2weight% than when the additive is not added to the polypropylene (11) resin.

In addition, it can be seen that the use of block polypropylene and random polypropylene has a lower specific gravity and a higher reflectance than the case of using homo polypropylene and terpolypropylene.

In addition, there is a case where in the additive, the addition of CaCO ₃ can be seen that a low specific gravity higher reflectance than the addition of other additives.

 Additive-free CaCO3 (2weight%) TiO2 (2weight%) TaIc (2weight%) importance reflectivity importance reflectivity importance reflectivity importance reflectivity Homo PP 0.80 88 0.76 92 0.77 87 0.78 87 Co- PP Block PP 0.55 99 0.51 101 0.53 99 0.53 97 Random PP 0.60 97 0.55 98 0.56 97 0.54 96 Ter-PP 0.60 94 0.54 96 0.55 96 0.54 95

In addition, when the UV inhibitor and the antioxidant is added to the light reflector 10 according to the present invention, as shown in Table 2, it can be seen that it is effective in preventing yellowing without affecting the reflectance of the light reflector 10. have.

Here, it can be seen that the light reflection plate 10 is effective in preventing yellowing when the amount of the ultraviolet ray inhibitor and the antioxidant added is a predetermined amount or more.

UV Stabilizer contents (%) Oxidation prevention (%) Reflectivity (%) Yellowing test    Example  0.5 0 96.7 Little bit yellowing 0.1 96.7 ok 0.15 96.7 ok  One 0 96.7 ok 0.1 96.7 ok 0.15 96.7 ok   Comparative example   0 0 96.7 Yellowing 0.1 96.7 Little bit yellowing 0.15 96.7 Little bit yellowing

On the other hand, the light reflector 10 according to the present invention, after the foaming of the polypropylene (11) resin, the additive is blended, or as shown in Figure 3, the additive sheet 13 containing the additive as shown in the poly It is also possible to use a laminating method for adhering to the surface of the propylene 11.

Here, when the additive sheet 13 is adhered to the surface of the polypropylene 11 by the laminating method, the thickness of the additive sheet 13 is preferably formed to be smaller than the thickness of the polypropylene 11. .

On the other hand, the method of manufacturing the light reflection plate of the present invention can be a variety of methods, such as a method using a molten salt bus, a method using a hot air, a method using a plate heater 50, a method using an infrared heater.

That is, the separator 14 is laminated on the sheet of the thermoplastic polypropylene 11 and then rolled to form a roll 15, and the inert gas is contained in the roll 15 by maintaining it for a predetermined time under high pressure conditions. A method in which foaming proceeds by applying heat at normal pressure to the polypropylene (11) sheet containing the inert gas is used.

On the other hand, the inert gas is carbon dioxide, nitrogen, helium, argon, etc. Among them, carbon dioxide is advantageous compared to the other in that it can contain a large amount in the polypropylene (11).

Table 3 shows the reflectance according to the method of applying heat to the thermoplastic polypropylene (11) sheet.

Referring to Table 3, when the plate heater and the infrared heater are used in the method of applying heat to the thermoplastic polypropylene 11 sheet, the process time for applying heat is minimized, the specific gravity of the foamed polypropylene 11 is lowered, and It is possible to obtain a light reflector 10 having a reflectance.

In addition, when the block polypropylene and the random polypropylene are used, the light reflection plate 10 having a higher reflectance can be obtained than when the homopolypropylene and the terpolypropylene are used.

Glycerin sirocco Plate heater Infrared heater Process times 30 120 20 20  Specific gravity (g / cm 3) Homo PP 0.80 0.83 0.79 0.77 Co- PP Block PP 0.55 0.64 0.53 0.50 Random PP 0.60 0.66 0.57 0.56 Ter PP 0.60 0.68 0.58 0.55  Reflectance (%) Homo PP 88 87 89 90 Co- PP Block PP 99 97 99 100 Random PP 97 96 98 98 Ter PP 94 92 95 96

Here, referring to FIG. 3, the average diameter of the bubbles 12 formed inside the polypropylene 11 may be heated to be 0.5 μm to 30 μm.

Preferably, the polypropylene 11 may be heated so that the average diameter of the bubble 12 is 10 μm or less.

This is because if the average diameter of the bubble 12 exceeds 10 μm, incident light penetrates into the light reflection plate 10 or the number of diffuse reflections decreases at the bubble interface, thereby decreasing the diffuse reflectance.

In addition, when the average diameter of the bubble 12 exceeds 10 μm, when the light reflection plate 10 is used for the liquid crystal display device, the light reflection plate 10 may be caused by light loss from the end of the light reflection plate 10. This is because the amount of light returned to the surface is reduced, and the diffusion reflectance is lowered.

On the other hand, since the incident light transmits when the average diameter of the bubble 12 is smaller than the wavelength of visible light, the average diameter of the bubble 12 should be at least the wavelength of the visible light.

Here, Table 4 shows the reflectance of the light reflector 10 according to the type of various polypropylene 11, the average diameter of the bubble 12 and the specific gravity of the light reflector.

Referring to Table 4, it can be seen that the reflectance of the light reflection plate 10 is higher the smaller the average diameter of the bubble 11, the lower the specific gravity.

In particular, it can be seen that the reflectance of the light reflector 10 formed of block polypropylene and random polypropylene is higher than that of the light reflector 10 formed of homopolypropylene and terpolypropylene.

Specific gravity (g / cm 3) Cell diameter (㎛) reflectivity(%)      Homo PP   0.85 One 85 5 82 10 80 20 72   0.80 One 87 5 85 10 81 20 75   0.75 One 88 5 85 10 83 20 72      Ter-PP   0.75 One 91 5 88 10 85 20 77   0.60 One 92 5 90 10 86 20 80   0.50 One 94 5 91 10 88 20 82            Co-PP      Block PP   0.70 One 97 5 97 10 96 20 89   0.60 One 99 5 98 10 96 20 91   0.50 One 99 5 98 10 97 20 90      Random PP   0.70 One 95 5 93 10 90 20 83   0.60 One 97 5 96 10 94 20 88   0.50 One 97 5 95 10 94 20 86

On the other hand, if the thickness of the light reflection plate 10 is less than 200 µm, even if other requirements are satisfied, the light reflectance on the back surface of the light reflection plate 10 increases, so that the diffusion reflectance decreases.

In addition, if the thickness of the light reflection plate 10 is too thin, the shape retaining property is inferior when molded into a predetermined shape.

Therefore, as for the thickness of the light reflection board 10, it is more preferable that it is 500 micrometers or more.

On the other hand, the specific gravity of the light reflection plate 10 according to the present invention may be formed to be 0.4 to 0.7.

When the specific gravity of the light reflection plate 10 exceeds 0.7, that is, when the bubble ratio of the light reflection plate 10 is small, the light absorption or light reflection plate 10 in the non-foamed polypropylene (11) resin portion This is because the light loss increases due to light transmission due to the transparency of the light and the diffusion reflectance decreases.

On the other hand, the method of manufacturing the light reflection plate 10 of the present invention is not particularly limited, but considering the productivity, it is preferable to use the method using the plate heater 50 as described below.

That is, as shown in FIG. 4, the roll 15 is formed by winding the sheet of the thermoplastic polypropylene 11 overlapped with the separator 14, and the roll 15 is sealed, as shown in FIG. 5. It was placed in the vessel 20 and supplied with an inert gas at a high pressure to contain the inert gas in the thermoplastic polypropylene 11 sheet, and the thermoplastic polypropylene 11 sheet containing the inert gas was heated by a heating device 30. And foaming is used.

In the above method, the roll 15 made of the thermoplastic polypropylene 11 sheet and the separator 14 is placed in an airtight container 20 before the inert gas is contained in the thermoplastic polypropylene 11 sheet. It can also be contained.

Hereinafter, the method of manufacturing the light reflection plate 10 of the present invention will be described in detail with reference to FIGS. 5 and 6.

Here, FIG. 5 is an example of a method of manufacturing a light reflection plate using the plate heater 50, and the method of manufacturing the light reflection plate may be formed using various methods as well as a method of using the plate heater 50.

First, an additive is blended into a polypropylene (11) resin copolymerized with ethylene (S11).

Here, the additive may be blended in the sheet after the foaming of the polypropylene 11 resin, or as shown in FIG. 3, the additive sheet 13 may be adhered in a laminating manner.

Next, as shown in FIG. 4, the rolls 15 obtained by stacking the thermoplastic polypropylene 11 sheet and the separator 14 are formed (S12 and S13).

At this time, the separator 14 maintains a gap between the polypropylene 11 sheets such as nonwoven fabric, nylon mesh, metal mesh, and paper, does not cause physical and chemical reactions with the polypropylene 11 sheet, and the inert gas passes freely. As a gap which can be made, any material having a thickness of 500 µm or less may be used.

Next, the roll 15 formed as described above is placed in the high pressure sealed container 20 and completely sealed, and then the inert gas is supplied to the inside of the sealed container 20 at high pressure (S14).

Here, the penetration pressure of the inert gas is 30 kg / cm 2 to 72 kg / cm 2, more preferably 50 kg / cm 2 to 72 kg / cm 2.

This is because the penetration pressure of the inert gas should be a section in which the inert gas becomes a liquid state, because when the penetration pressure exceeds 72 kg / cm 2, the inert gas becomes a supercritical state.

In addition, the filling time of the inert gas into the high pressure sealed container 20 is 1 hour or more, but the gas is continuously supplied until the saturation state is reached.

The time and amount of penetration of the inert gas into the polypropylene 11 in a saturated state may be set differently depending on the type of resin to be foamed, the type of inert gas, the penetration pressure, and the thickness of the sheet.

Here, the light reflector 10 according to the present invention uses a polypropylene (11) resin, using carbon dioxide as an inert gas, when the pressure of carbon dioxide is 70㎏ / ㎠, the thickness of the sheet is 0.8mm or more 30 hours It is preferable to set it as.

At this time, the amount of carbon dioxide contained in the polypropylene 11 resin is approximately 4.7weight% to 5.5weight%.

Next, the roll 15 is taken out from the high pressure sealed container 20, the separator 14 is removed (S15), and then heat is applied to the polypropylene 11 containing the inert gas using the heating device 30. The polypropylene 11 is foamed (S16).

Here, the shorter the time until the roll 15 is taken out of the sealed container 20 to apply heat, the specific gravity of the foamed polypropylene 11 is lowered.

In addition, a heating temperature is set in the range which is 5 degreeC-30 degreeC lower than the melting temperature of resin.

Accordingly, the light reflection plate 10 according to the present invention may heat the light reflection plate 10 at a temperature of 135 ° C. to 160 ° C., which is 5 ° C. to 30 ° C., lower than 165 ° C., which is the melting temperature of the polypropylene 11. .

Here, the heating means of the light reflector 10 includes an oil booth, a hot air blowing furnace, a plate heater 50 and the like, but in consideration of the efficiency of the process, it is preferable to use a plate heater 50 or a hot air blowing furnace method. Do.

Foaming conditions in the plate heater 50 may be set in various ways, for example, the foaming temperature may be set to a linear speed of 140 ℃ and foaming time is 30 seconds or more.

Finally, when the foamed resin is cooled through the cooling device 40, a light reflection plate 10 made of a thermoplastic polypropylene 11 foam is obtained (S17).

The light reflector 10 produced by the method of manufacturing a light reflector according to the present invention has a high diffuse reflectance component among the total reflectance components, and as shown in Tables 1 to 3, 90 in all wavelength ranges of 380 nm to 800 nm. Diffuse reflectivity of at least%

Therefore, the method of manufacturing a light reflection plate according to the present invention does not add pigments or fine particles which induce diffuse reflection of light, and has high reflectance without additionally disposing a metal having a specular reflection component on the back surface of the light reflection plate 10. The reflecting plate 10 can be obtained.

On the other hand, the light reflector 10 is not limited to the shape may be formed in various shapes.

Therefore, the shape of the sheet of light reflecting plate 10 obtained in the above process may be used as the light reflecting plate 10 for enhancing the light diffusion reflection of a liquid crystal display (LCD) or the like.

In addition, the light reflecting plate 10 may be formed in a bent form by a method such as heating vacuum molding, and may be used as a light reflecting plate 10 for a general lighting fixture such as a fluorescent lamp.

Therefore, the light reflector according to the present invention, by injecting an inert gas into the polypropylene mixed with ethylene and heated to form a bubble, it is possible to obtain a light reflector with a low specific gravity and a high reflectance with a high foam ratio.

In addition, the light reflector according to the present invention does not add pigments or fine particles for inducing diffuse reflection of light, and high reflectance can be obtained without additionally arranging a metal having a specular reflection component on the back side of the light reflector, so that the light is inexpensive. The reflector can be manufactured.

Claims (15)

A light reflector for reflecting incident light, The light reflection plate is injected with an inert gas, bubbles are formed by heating the polypropylene mixed with ethylene, Light reflecting plate, characterized in that the average diameter of the bubble is 0.5㎛ 30㎛. The method of claim 1, The polypropylene is a light reflection plate, characterized in that the ethylene is mixed in more than 0 50weight% or less. delete The method according to claim 1 or 2, The light reflection plate is a light reflection plate, characterized in that the specific gravity is 0.4 to 0.7. The method of claim 1, The inert gas is a light reflection plate, characterized in that the carbon dioxide. The method of claim 5, wherein The inert gas is a light reflection plate, characterized in that injected into the light reflection plate at a penetration pressure of 50kg / ㎠ to 72kg / ㎠. In the light reflecting plate manufacturing method for reflecting the incident light, Rolling the polypropylene sheet mixed with ethylene to form a roll; Inserting the roll into a sealed container and supplying an inert gas at a high pressure to inject the inert gas into the light reflection plate; Heating the bubble to form a bubble having an average diameter of 0.5 μm to 30 μm; And cooling the light reflection plate on which the bubbles are formed. The method of claim 7, wherein The polypropylene is a method for producing a light reflection plate, characterized in that the ethylene is mixed at 50weight% or less. delete The method according to claim 7 or 8, The light reflection plate has a specific gravity of 0.4 to 0.7, characterized in that the light reflection plate manufacturing method. The method of claim 7, wherein Rolling the polypropylene sheet mixed with the ethylene to form a roll, the step of overlapping the separator on the sheet to form a space between the sheet and the sheet; light reflection plate manufacturing method further comprising a . The method of claim 7, wherein The inert gas is a light reflection plate manufacturing method characterized in that the carbon dioxide. The method of claim 12, The inert gas is a light reflection plate manufacturing method, characterized in that injected into the light reflection plate at a penetration pressure of 50kg / ㎠ to 72kg / ㎠. The method of claim 7, wherein The light reflection plate is a method of manufacturing a light reflection plate, characterized in that the heating by any one of a plate heater or an infrared heater. The method of claim 14, The plate heater or infrared heater is a method of manufacturing a light reflection plate, characterized in that for heating the light reflection plate at a temperature of 135 ℃ to 160 ℃.

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