Acrylate foamed reflective sheet, preparation method thereof and backlight module

Abstract

The present application provides an acrylic ester foaming reflective sheet, comprising PET substrate, foaming layer and protective layer in sequence; the foaming layer is acrylic ester resin with porous nano-particles and bubbles dispersed in it; the porous nano-particles are dispersed in the gaps between the bubbles; the particle size of the porous nano-particles is 10-50 nm, and the specific surface area is 300-500 m 2 / g. The present application uses light-curable acrylic ester resin as the foaming layer, adopts non-nuclear foaming process to foam, and the white reflective sheet finally obtained has the foaming point near the porous nano-particles. Since the size of the bubbles in the present application can be controlled at the nanometer level, compared with the stretched PET polyester foaming layer in the prior art, a thinner thickness can be achieved, and the stiffness is more excellent. The present application also provides a preparation method of the acrylic ester foaming reflective sheet and a backlight module.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of liquid crystal display, and particularly relates to an acrylic ester foaming reflective sheet, a preparation method thereof and a backlight module. BACKGROUND

[0002] The backlight module is a backlight component in an LCD display product, which is generally composed of a backlight light source, multiple layers of backlight material and a support frame. The backlight quality determines important parameters of the liquid crystal display screen, such as brightness, light uniformity and color step, and largely determines the light emitting effect of the liquid crystal display screen.

[0003] The backlight module includes an illuminating light source, a reflective sheet, a light guide plate, a diffusion sheet, a brightness enhancement film (prism sheet) and a frame. The function of the reflective sheet is to reflect light not directed to the light emitting surface, prevent the illuminating light from escaping to the back of the picture, and make the light of the light source fully utilized and uniformly distributed. The reflective sheet is divided into a metal reflective sheet and a white reflective sheet. The metal reflective sheet is mainly used for illuminating light source reflection, and the white reflective sheet is used for light guide plate reflection.

[0004] At present, the mainstream white reflective sheet on the market is mostly produced by foaming technology. TiO2 and other materials are mixed with a resin with high optical transparency, such as PET resin, and then finely foamed to form the reflective sheet. The refractive index of the bubbles in the reflective sheet is about 1, which has strong reflection ability and good refraction and reflection effect on light.

[0005] However, the reflective sheet using polyester resin as raw material needs to be stretched and oriented during film forming, or bubbles are formed in the film by stretching. The reflective sheet is too soft and lacks stiffness. SUMMARY

[0006] The purpose of the present application is to provide an acrylic ester foaming reflective sheet, a preparation method thereof and a backlight module. The acrylic ester foaming reflective sheet in the present application has excellent stiffness, small bubble size and can achieve a thinner thickness.

[0007] The present application provides an acrylic ester foaming reflective sheet, which comprises a PET substrate, a foaming layer and a protective layer in contact with each other in sequence.

[0008] The foaming layer is an acrylic ester resin with porous nanoparticles and bubbles dispersed therein. The porous nanoparticles are dispersed in the gaps between the bubbles, and the density of the bubbles away from the PET substrate is higher than that of the bubbles in contact with the PET substrate.

[0009] The particle size of the porous nanoparticles is 10-50 nm, and the specific surface area is 300-500 m 2 / g.

[0010] Preferably, the acrylate resin comprises one or more of tripropyleneglycol diacrylate, tetrahydrofurfuryl acrylate, ethoxylated bisphenol A diacrylate, polyethyleneglycol diacrylate, o-phenylphenethoxyethyl acrylate, 2-phenoxyethyl acrylate and p-phenylmethacrylate;

[0011] The viscosity of the acrylate resin is 1500-2500 cps.

[0012] Preferably, the porous nanoparticles comprise porous ceramic powder, porous polymer or porous carbon material.

[0013] Preferably, the diameter of the bubbles is 50 nm-3 μm.

[0014] The thickness of the foamed layer is 30-55 μm.

[0015] The present application provides a preparation method of the acrylate foamed reflective sheet as described above, comprising the following steps:

[0016] A) impregnating the porous nanoparticles in a foaming solvent, stirring to obtain the porous nanoparticles adsorbed with the foaming solvent;

[0017] The foaming solvent is acetone and / or n-heptane.

[0018] B) mixing the porous nanoparticles adsorbed with the foaming solvent with the UV acrylate resin, coating on the surface of the PET substrate, curing to obtain the foamed layer;

[0019] C) compounding a protective layer on the surface of the foamed layer to obtain the acrylate foamed reflective sheet.

[0020] Preferably, the stirring speed in step A) is 1500-2500 rpm; the stirring time in step A) is 5-20 min.

[0021] Preferably, the photocuring in step B) is three-stage curing, which is one-stage photocuring, two-stage infrared heating curing and three-stage photocuring.

[0022] Preferably, the UV energy of the one-stage photocuring is 10-50 mW / cm 2 ; the one-stage photocuring time is 0.5-1.5 s.

[0023] Preferably, the two-stage infrared heating curing time is 0.5-1.5 min.

[0024] Preferably, the UV energy of the three-stage photocuring is 300-400 mW / cm 2 ; the three-stage photocuring time is 0.5-1.5 min.

[0025] The present application provides a backlight module, comprising the above-mentioned acrylate foamed reflective sheet.

[0026] The present application provides an acrylate foamed reflective sheet, comprising PET substrate, foamed layer and protective layer in sequence; the foamed layer is acrylate resin with porous nanoparticles and bubbles dispersed in it; the porous nanoparticles are dispersed in the interstice of the bubbles; the particle size of the porous nanoparticles is 10-50nm, and the specific surface area is 300-500m 2 / g. The present application uses light-curable acrylate resin as the foamed layer, and adopts non-nuclear foaming process to foam, and the foaming point of the white reflective sheet obtained finally is near the porous nanoparticles. The present application can control the size of the foam and the density of the molding through the curing parameters such as UV energy, curing temperature or time during the curing process. Since the size of the bubbles in the present application can be controlled at the nanometer level, compared with the stretched molding PET polyester foamed layer in the prior art, the thickness can be thinner, and the stiffness is more excellent. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative effort on the basis of the provided drawings.

[0028] Figure 1 It is the optical microscope picture of the reflective sheet prepared in Example 1 of the present application under 2000 times magnification;

[0029] Figure 2 It is the electron microscope picture of the reflective sheet prepared in Example 1 of the present application under 8000 times magnification;

[0030] Figure 3 It is the structural schematic diagram of the acrylate foamed reflective sheet in the present application;

[0031] Figure 3 In the figure, 1 is the protective layer, 2 is the foamed layer, 3 is the PET substrate, 4 is the bubble, and 5 is the porous nanoparticle. DETAILED DESCRIPTION

[0032] The present application provides an acrylate foamed reflective sheet, comprising PET substrate, foamed layer and protective layer in sequence;

[0033] The foamed layer is acrylate resin with porous nanoparticles and bubbles dispersed in it; the porous nanoparticles are dispersed in the interstice of the bubbles;

[0034] The porous nanoparticles have a particle size of 10-50 nm and a specific surface area of 300-500 m 2 / g.

[0035] In the present application, the thickness of the PET substrate is preferably 80-200 μm, more preferably 100-150 μm.

[0036] In the present application, the foaming layer is preferably an acrylic resin layer having porous nanoparticles and circular bubbles dispersed therein; the thickness of the foaming layer is preferably 30-55 μm, more preferably 35-50 μm.

[0037] The porous nanoparticles are preferably porous ceramic powder, porous polymer or porous carbon material; the porous ceramic powder is preferably nano-TiO2 and / or nano-SiO2; the porous carbon material is preferably carbon nanotube and / or graphene; the mass ratio of the porous nanoparticles to the acrylate resin is preferably 1:(5-20), more preferably 1:(10-15), such as 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, preferably a range value with any of the above values as the upper limit or lower limit.

[0038] The particle size of the porous nanoparticles is preferably 10-50 nm, more preferably 20-40 nm, most preferably 20-30 nm; the specific surface area of the porous nanoparticles is preferably 300-500 m 2 / g, more preferably 400-450 m 2 / g.

[0039] In the present application, the diameter of the bubbles is preferably 50 nm-3 μm, more preferably 50-800 nm. Based on the foaming process in the present application, the bubbles have a rising tendency in the foaming layer after being generated, i.e. the density of the bubbles away from the PET substrate is higher than that of the bubbles in contact with the PET substrate.

[0040] In the present application, the center of the bubbles in the foaming layer is coreless, and the porous nanoparticles are located in the vicinity of the bubbles and dispersed in the gaps between the circular bubbles.

[0041] In the present application, the acrylate resin of the foaming layer is preferably one or more of tripropylene glycol diacrylate, tetrahydrofurfuryl acrylate, ethoxylated bisphenol A diacrylate, polyethylene glycol diacrylate, o-phenylphenethoxyethyl acrylate, 2-phenoxyethyl acrylate and p-phenyl methacrylate.

[0042] In the present application, the refractive index of the foaming layer can be adjusted as required, and in the embodiments of the present application, three refractive indexes of 1.562, 1.583 and 1.602 are selected for testing.

[0043] In the present application, the protective layer is preferably an acrylate resin, which is preferably one or more of tripropylene glycol diacrylate, tetrahydrofuran acrylate, ethoxylated bisphenol A diacrylate, polyethylene glycol diacrylate, o-phenylphenethoxyethyl acrylate, 2-phenoxyethyl acrylate and p-phenyl methacrylate; the type of acrylate resin in the protective layer can be the same as or different from that in the foaming layer. The thickness of the protective layer is preferably 5-20 μm, more preferably 8-15 μm, and most preferably 8-10 μm.

[0044] The present application also provides a preparation method of the acrylate foaming reflective sheet, comprising the following steps:

[0045] A) impregnating the porous nanoparticles in a foaming solvent, and stirring to obtain the porous nanoparticles adsorbed with the foaming solvent;

[0046] The foaming solvent is one or more of acetone, n-heptane and n-hexane;

[0047] B) mixing the porous nanoparticles adsorbed with the foaming solvent with a UV acrylate resin, coating on the surface of a PET substrate, and curing to obtain the foaming layer;

[0048] C) compounding a protective layer on the surface of the foaming layer to obtain the acrylate foaming reflective sheet.

[0049] In the present application, the porous nanoparticles are impregnated in the foaming solvent, and stirring is performed to fill the foaming solvent into the pore structure of the porous material. In order to avoid premature volatilization of the adsorbed foaming solvent, the porous nanoparticles adsorbed with the foaming solvent should be stored at low temperature (≤20℃).

[0050] In the present application, the type and amount of the porous nanoparticles are consistent with those described above, and will not be repeated here.

[0051] In the present application, a low-boiling organic solvent is used as the foaming solvent, which is preferably one or more of acetone and / or n-heptane.

[0052] In the present application, the temperature of the impregnation is preferably below 20℃, the time of the impregnation is preferably 0.1-2 hours, more preferably 0.5-1.5 hours, and most preferably 0.5 hours; preferably, mechanical stirring is applied during the impregnation to make the foaming solvent more uniformly absorbed inside the porous nanoparticles. The stirring speed is preferably 200-300 rpm, more preferably 250-300 rpm; the stirring time is 1-5 min, more preferably 2-4 min.

[0053] After obtaining the porous nanoparticles with the foaming solvent absorbed, the present application adds the porous nanoparticles with the foaming solvent absorbed into the UV acrylate glue, stirs to make them uniformly dispersed in the UV acrylate glue, to obtain a mixed glue;

[0054] In the present application, the UV acrylate glue is preferably one or more of tripropylene glycol diacrylate, tetrahydrofuran acrylate, ethoxylated bisphenol A diacrylate, polyethylene glycol diacrylate, o-phenylphenethoxyethyl acrylate, 2-phenoxyethyl acrylate, and p-phenyl methacrylate; the viscosity of the UV acrylate glue is preferably 100-2500 cps, more preferably 300-1500 cps.

[0055] In the present application, the stirring speed is preferably 100-500 rpm, more preferably 200-300 rpm; the stirring time is preferably 10-15 min.

[0056] After obtaining the mixed glue, the present application applies the mixed glue to the surface of a PET substrate, and cures to obtain a foaming layer.

[0057] In the present application, the method of application is a conventional application method in the art, and the present application does not make special limitations thereto.

[0058] In the present application, the curing process is accompanied by a foaming process, and the curing process in the present application is divided into three stages. The first stage is a UV curing process, in which the UV acrylate resin is cured under UV irradiation. The UV curing process is an exothermic process, and the heat generated makes the foaming solvent absorbed inside the porous nanoparticles rapidly volatilize to generate bubbles, and escape from the inside of the porous nanoparticles, to form micro-bubbles inside the acrylate glue layer, which are about 3-10 nm in size under transmission electron microscopy.

[0059] In the present application, in the UV curing of the first stage, the UV energy is preferably 10-50 mW / cm 2 , more preferably 20-40 mW / cm 2 , and most preferably 20-30 mW / cm 2The UV curing time is preferably 0.5-1.5 s, more preferably 0.8-1.0 s.

[0060] After the first UV curing reaction, the foaming solvent is volatilized in the acrylate adhesive to form micro-bubbles, and the UV acrylate adhesive is cured to increase the viscosity. The second stage uses an IR lamp to further cure the acrylate adhesive by infrared heating, which makes the bubbles grow and increases the bubble density. The IR lamp can increase the temperature of the acrylate adhesive by 800℃ in 1 s; the infrared heating curing time is preferably 0.5-1.5 s, more preferably 0.8-1.0 s; the frequency of the IR lamp is preferably 3-6 times per second, more preferably 4-5 times per second.

[0061] Finally, the third stage of the second UV curing is performed, which fixes and shapes the bubbles grown to the required size in the second stage. The UV curing energy of the third stage is preferably 300-400 mW / cm 2 , more preferably 330-350 mW / cm 2 ; the three-stage light curing time is 0.5-1.5 s, more preferably 0.8-1.0 s.

[0062] After the foaming layer is obtained, the present application composites an acrylate layer on the foaming layer to make the surface flat. The composition of the acrylate layer is consistent with the protective layer described above, and the present application will not be described here.

[0063] The present application also provides a backlight module comprising the acrylate foaming reflective sheet described above.

[0064] The present application provides an acrylate foaming reflective sheet, which comprises a PET substrate, a foaming layer and a protective layer in contact with each other in sequence; the foaming layer is an acrylate resin dispersed with porous nanoparticles and bubbles; the porous nanoparticles are dispersed in the gaps between the bubbles; the particle size of the porous nanoparticles is 10-50 nm, and the specific surface area is 300-500 m 2 / g. The present application uses an acrylate resin capable of light curing as the foaming layer, adopts a coreless foaming process to foam, and finally obtains a white reflective sheet with the foaming point near the porous nanoparticles. The present application can control the size and density of the foaming by curing parameters such as UV energy, curing temperature, or time during the curing process. Since the size of the bubbles in the present application can be controlled at the nanometer level, compared with the existing technology of stretching and molding the PET polyester foaming layer, a thinner thickness can be achieved, and the stiffness is more excellent.

[0065] In order to further illustrate the present application, the following embodiments of the present application provide a kind of acrylic ester foaming reflective sheet, its preparation method and backlight module are described in detail, but it cannot be understood as limiting the scope of protection of the present application.

[0066] The acrylic resins with different refractive indexes used in the following examples are prepared according to the proportions in Table 1, and the refractive indexes of the prepared acrylic resins are 1.483, 1.562, 1.583 and 1.602.

[0067] Table 1 Composition of acrylic resins with different refractive indexes

[0068]

[0069] Example 1

[0070] 20 g of SiO2 with a particle size of 20 nm and a specific surface area of 385 m 2 / g was soaked in 50 mL of acetone, and was mixed at room temperature or 20°C by centrifugal rotation at 1800 rpm / 10 min, and then was taken out and placed in an environment below 20°C for standby.

[0071] 5 g of the mixed SiO2 was taken out and uniformly stirred and dispersed in 50 g of ultraviolet acrylic resin with a refractive index of 1.562 at room temperature or below 20°C to obtain a coating liquid.

[0072] The PET base film after 100 μm was taken, and the coating liquid was coated onto the surface of the PET base film at a coating machine speed of 10 m / min, and the coating layer thickness was controlled to be 30 μm.

[0073] The curing process was as follows:

[0074] The first section light source energy was 20 mW / cm2 for pre-curing, the light curing wavelength was LED 365 nm light source, the machine speed was 10 m / min, the acetone in the porous SiO2 in the UV glue generated bubbles with a size of about 3-10 nanometers, and the coating thickness was 30 μm,

[0075] The second section IR lamp tube irradiation made the bubbles in the UV glue grow and increase in density, and the bubbles filled the entire UV with a size of 50-800 nanometers.

[0076] The third section mercury lamp UV energy was 330 mW / cm 2 , the light curing wavelength was 365 nm, the machine speed was 10 m / min, and the bubbles generated in the second section were cured to obtain a foaming layer.

[0077] An 8 μm UV acrylic resin layer with a refractive index of 1.483 was coated on the surface of the foaming layer to obtain a white reflective sheet.

[0078] Examples 2-3

[0079] White reflective sheets were prepared according to the method of Example 1, except that in Examples 2 and 3, acrylic resins having refractive indices of 1.583 and 1.602, respectively, were used instead of the acrylic resin having a refractive index of 1.562 in Example 1.

[0080] Examples 4-6

[0081] White reflective sheets were prepared according to the methods of Examples 1-3, respectively, except that in Examples 4, 5, and 6, 60 mL of n-heptane was used instead of 50 mL of acetone in Examples 1-3.

[0082] Examples 7-9

[0083] White reflective sheets were prepared according to the methods of Examples 1-3, respectively, except that in Examples 7, 8, and 9, 20 g of TiO2having a particle size of 25 nm and a specific surface area of 385 m2 / g was used instead of SiO2in Examples 1-3. 2

[0084] Examples 10-12

[0085] White reflective sheets were prepared according to the methods of Examples 7-9, respectively, except that in Examples 10, 11, and 12, 60 mL of n-heptane was used instead of 50 mL of acetone in Examples 7-9.

[0086] Table 2 Performance tests of white reflective sheets in Examples 1-12

[0087]

[0088]

[0089] wherein the reflectance test is a Konica 3600A tester test, the stiffness test is a standard test according to ISO 5628 Paper and board - Determination of static bending stiffness - General principles, sample width: 38 ± 0.2 mm, sample length: 76 mm, and the test thickness is 138 μm

[0090] Examples 13-24

[0091] White reflective sheets were prepared according to the methods of Examples 1-12, respectively, except that in Examples 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, and 24, the coating thickness of the foamed layer was 55 μm.

[0092] Table 3 Performance tests of white reflective sheets in Examples 13-24

[0093] ​

[0094]

[0095] Wherein the reflectivity test is Konica 3600A tester test, stiffness test is in accordance with ISO5628 paper and paperboard-static bending stiffness determination general principles standard test, sample width: 38±0.2mm, sample length: 76mm, test thickness is 163 μm.

[0096] From the above experiment, the white reflective sheet prepared by the application can have reflectivity higher than 90% at wavelength 550nm.

[0097] The bubble in the acrylic acid obtained by using low-boiling acetone is greater than that obtained by using n-heptane, and in our experiment, it is also found that when the thickness is 55 μm, the bubble size obtained is greater than that of 30 μm coating thickness, and the bubble density covering the glue is also greater, which is specifically reflected in the contribution of reflectivity.

[0098] In the embodiment of the application, not all bubbles will fill the entire foaming layer, the outermost protective layer uses low-refractive n=1.436 UV acrylic resin, under the same conditions, only the high and low refractive index difference between the foaming layer and the protective layer, the greater the refractive index difference between the foaming layer and the protective layer, the better the reflectivity obtained.

[0099] The above is only the preferred embodiment of the application, it should be pointed out that for ordinary skilled in the art, without departing from the principles of the application, can make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the application.

Claims

1. A kind of acrylate foaming reflective sheet, comprising PET substrate, foaming layer and protective layer in turn contact; The foaming layer is that acrylate resin is dispersed with porous nano-particle and bubble;The porous nano-particle is dispersed in the interstice of the bubble, and the density of the bubble far from the PET substrate end is higher than the density of the bubble in contact with the PET substrate; The porous nanoparticle has a particle size of 10-50 nm, a specific surface area of 300-500 m 2 / g; The diameter of the bubble is 50nm-800nm;The thickness of the foaming layer is 30-55 μm; The preparation method of the acrylate foaming reflective sheet, comprising the following steps: A) porous nano-particle is immersed in foaming solvent, and stirring is carried out, and porous nano-particle adsorbed with foaming solvent is obtained; The foaming solvent is acetone and / or n-heptane; B) porous nano-particle adsorbed with foaming solvent is mixed with UV acrylate resin, and coated on the surface of PET substrate, and solidified, and foaming layer is obtained; The solidification in step B) is three-stage solidification; Respectively, one-stage photocuring, two-stage infrared heating solidification and three-stage photocuring; The first light-cured UV energy is 10-50 mW / cm 2 ; the first light-cured time is 0.5-1.5 s; the second infrared heating-cured time is 0.5-1.5 s; the third light-cured UV energy is 300-400 mW / cm 2 ; the third light-cured time is 0.5-1.5 s; C) composite protective layer on the surface of the foaming layer, and obtain acrylate foaming reflective sheet.

2. The acrylate foamed reflective sheet according to claim 1, characterized in that, The acrylate resin includes one or several of tripropylene glycol diacrylate, tetrahydrofurfuryl acrylate, ethoxylated bisphenol A diacrylate, polyethylene glycol diacrylate, o-phenylphenyl ethoxy ethyl acrylate, 2-phenoxyethyl acrylate and p-phenyl methacrylate; The viscosity of the acrylate resin is 1500-2500cps.

3. The acrylate foamed reflective sheet according to claim 2, characterized in that, The porous nano-particle includes porous ceramic powder, porous polymer or porous carbon material. 4.A backlight module comprising the acrylate foaming reflective sheet according to any one of claims 1-3.

Images