CN106154367A - A kind of light diffusing sheet and preparation method - Google Patents

Abstract

The invention discloses a light diffusion sheet and a manufacturing method. The structure of the light diffusion sheet is characterized in that the transparent substrate layer is provided with a microstructure layer on one surface of the transparent substrate layer, and the concave structure of the microstructure layer is filled with diffusion particles. In order to realize the diffuser, the manufacturing method is characterized in that, the above-mentioned mold structure is copied on the transparent substrate by embossing with a mold having a convex structure of a topologically arranged pattern to obtain a concave structure complementary to the mold structure; by scraping Coating technology, the diffusion particles are scraped into the above-mentioned concave microstructure to form a patterned arrangement of diffusion particles. The invention solves the problem that the traditional random structure cannot be artificially optimized through the arrangement of patterned diffusion particles. Under the joint action of the patterned structure and the diffusion particles, it produces a light diffusion effect, which is used in the direction of backlight and beam shaping.

Description

A kind of light diffusion sheet and manufacturing method

technical field

The invention relates to a light diffusion sheet, which has the structure of filling light diffusion particles in patterned microstructure grooves. Under the joint action of patterned structure and diffusing particles, light diffusion effect is produced, which is used for backlight and beam shaping direction.

Background technique

Light diffusers are essential components in the display and lighting fields. Its main function is to diffuse light and uniformly convert point/line light sources into line/area light sources. Traditional diffusers add chemical particles to transparent plastic materials to form a diffusion layer. In the diffusion layer, the incident light propagates in two or more media with different refractive indices, refraction, reflection and scattering occur, forming the effect of diffused light.

At present, there are three main processing methods for light diffusion sheets: embossing processing, heat treatment injection molding and coating process. The embossing process melts the polymer on the surface of the film and processes it with rollers of most microstructures. The method is simple, but its main disadvantage is that it will cause uneven density of the diffusion film material. Heat treatment injection molding method, the main materials include methyl methacrylate, azobisisocyanate, diffusion powder and dyes. After fully stirring and mixing, pour it into the mold, and then bake and solidify in an oven for at least 4 to 8 hours, and the production cycle is long. The most common method of producing a diffusion film is the coating method, in which a diffusion layer is formed on the surface of a transparent substrate by electrostatic coating. This method is relatively mature in technology, but uses a variety of polymer materials. For example, the adhesive material is thermoplastic polymer resin (methacrylate monomer or polymer, polyester, polycarbonate, polystyrene, etc.) ethylene, polymethylpentene), acrylates, photoinitiators, diffusion powders, dyes, tougheners, wetting agents, defoamers, etc. are also required. Moreover, since adding a diffusion layer on the substrate increases the thickness of the diffusion sheet, the use of various polymers leads to greater light energy absorption loss, and the organic pollutants generated during production are not conducive to environmental protection.

With the widespread use of new solid-state light sources such as light-emitting diodes, in addition to requiring high transmittance and easy-to-adjust haze for the matching light diffusion sheet, it is also required to be able to achieve special features such as soft light without "hot spots" and directional diffusion. The optical effect poses new technical challenges for the development and manufacture of light diffusers.

The continuous improvement of micro-nano manufacturing technology has made it possible to manufacture large-scale micro-nano structures in batches. Processing a micro-nano structure with a certain topological arrangement on the surface of the plastic substrate as a light diffusion sheet meets the requirements of thinner, flexible, functional, high light energy utilization, low cost and low energy consumption in the production process of optical functional films, and has become a new technology. The darling of a generation of optical functional films. Light diffusers based on surface microstructure can also be subdivided into two categories: one is a completely random structure. For example, a random microlens array structure. Although it can diffuse and soften light very well, due to the random arrangement of its scattering units, it can only meet the needs of a certain type of optical film, such as the light diffusion sheet used in LCD TVs. The other is a regularly arranged structure. By designing the topological arrangement of micro-nano structures, optimized optical effects such as directional scattering and soft light can be achieved, and functions that are difficult to achieve with random arrangements can be obtained. The optimized microstructure diffuser has greater flexibility and wide adaptability, and will play an important role in the light modulation of the new generation of organic light-emitting diodes, solar cells, etc. and in improving the light energy utilization of devices.

The currently researched microstructure diffuser with optimized topological arrangement, such as literature [1] S.M.Mahpeykar, etal.Stretchable hexagonal diffusion gratings as optical diffusers for insitu tunable broadband photon management, Adv.Opt.Mater.4(7):1106-1114 , 2016) reported that self-assembled polystyrene (Polystyrene, PS) microspheres with honeycomb dense arrangement on polydimethylsiloxane (polydimethylsiloxane, PDMS), using the stretchability of PDMS to realize the adjustable diffraction angle light field. Literature [2] C.L.Lai, J.S.Lin, T.Yoshimi, and W.H.Fan, A microstructure diffuser plate for LEDlighting, Proc. SPIE 6758, 2007. It is reported that the light diffuser plate made of regular microlens array is used to prevent LED glare, and the same The self-organization method is used to arrange polystyrene microspheres densely on the substrate. Self-organizing methods are not suitable for fabricating large-area structural templates. Literature [3] T.C.Huang1, J.R.Ciou1, P.H.Huang1, K.H.Hsieh, and Sen-Yeu Yang Fast fabrication of integrated surface-relief and particle-diffusingplastic diffuser by use of a hybrid extrusion roller embossing process, OpticsExpress 16(1), 440 -447,2008. Reported a light diffusion sheet with mixed microstructure and doped particles and its manufacturing method. Its technical route is to use a melt extruder to pass polycarbonate mixed with PMMA diffusion particles through a roller with a microstructure, and obtain an integrated light diffusion sheet after cooling and curing. The process of melt extrusion is complicated and the required equipment is expensive.

Contents of the invention

The object of the present invention is to provide a light diffusion sheet with patterned diffusion particles and a manufacturing method thereof. The idea of the light diffusion sheet of the present invention is to make a concave structure on the base material, and these preset concave structures present topological arrangement, such as square, hexagonal, strip, ring and other forms. The concave structure is filled with diffusion particles of organic or inorganic materials. The diffusion particles can be spherical, ellipsoidal, cylindrical, cuboid, or other heteromorphic shapes. The refractive index of the diffusion particles is different from that of the substrate, micro-nano structure layer and protective layer. When the incident light beam passes through the surface of the diffusion sheet, it will be affected by the patterned diffusion particles, and optical phenomena such as refraction, scattering, and diffraction will occur, forming a diffusion effect on light.

A light diffusion sheet, which includes a transparent substrate layer, a microstructure layer is provided on one side surface of the transparent substrate layer, the microstructure layer is provided with a microstructure, and the microstructure is a concave structure. Diffusion particles are filled in the concave structure of the structural layer.

In one of the embodiments, the microstructure in the microstructure layer is in a concave shape, which is used to induce the arrangement of diffusion particles. Arrangement in a symmetrical axis or an asymmetrical axis in a plane; the arrangement state of the diffusion particles can be continuous or discrete.

In one embodiment, the material of the microstructure layer may be the same as that of the substrate layer, or may be different.

In one embodiment, the width of the concave structure is greater than 1 micron, and the aspect ratio is greater than 0.3.

In one embodiment, the concave structure of the microstructure layer is filled with diffusion particles, which are distributed according to the topological arrangement of the concave structure; the diffusion particles can be larger than, smaller than or equal to the characteristic size of the concave structure, and their shape can be spherical , ellipsoid, cylinder, cuboid, or other special-shaped bodies.

In one embodiment, a transparent protective layer may be provided outside the microstructure layer, and the protective layer completely or partially covers the diffusion particles.

In one of the embodiments, the absolute value of the difference between the optical refractive index of the diffusing particles filled in the concave structure of the microstructure layer and the refractive index of the transparent substrate layer, the microstructure layer, the protective layer material, or one of them Not less than 0.01.

A method for manufacturing a light diffusion sheet, comprising the following steps:

S1. Using a mold with a raised structure, fabricate a structure on a transparent substrate by hot embossing or ultraviolet embossing, and obtain a concave structure complementary to the raised structure of the mold in the microstructure layer;

S2 Scrape-coating the diffusion particles into the recessed structure made in the above steps by using the scraping technology to form a patterned arrangement of the diffusion particles.

In one embodiment, step S3 is further included. Coating a protective layer on the surface of the microstructure layer.

In one of the embodiments, the absolute value of the difference between the optical refractive index of the diffusing particles filled in the concave structure of the microstructure layer and the refractive index of the transparent substrate layer, the microstructure layer, the protective layer material, or one of them Not less than 0.01.

The invention proposes a novel structure of a light diffusion sheet and a manufacturing method thereof. The diffusion sheet is made by micro-nano imprinting and scraping technology, and realizes the functions of directional scattering and homogenization of light spots by using the refraction and diffraction of light of the micro-nano topological structure and the scattering effect of diffusing particles on light. Micro-nano imprinting technology is a technology that can be used to prepare large-area patterned micro-nano structures in large quantities. Its processing resolution is only related to the size of the template pattern, and is not limited by the physical limitation of the shortest exposure wavelength of optical lithography. It has high The advantages of resolution, high output, and low cost. Scrape coating technology realizes the filling of diffused particles, the method is convenient, the process is simple, and it is easy to realize mass production.

Due to the application of the above technical solutions, the present invention, as a structure-induced patterned diffusion particle scattering sheet, has the following two advantages compared with the prior art:

1. Realize artificially intervened diffuse particles and scattered light fields in multiple dimensions. The present invention realizes the patterned arrangement of diffusing particles by means of patterned structure induction, so that the scattering properties of a large number of scattering particles can be artificially optimized, such as directional scattering and soft light, and the light field is more flexible. Regulation, with wider adaptability.

2. Convenient and reliable process: Combining embossing and scraping technology, the whole process is smooth and simple, and it is easy to realize batch production and large-format manufacturing. The equipment is cheap and the running costs are lower.

Description of drawings

Fig. 1 is a schematic structural diagram of a light diffusion sheet with patterned arrangement of light diffusion particles according to Embodiment 1 of the present invention;

Among them: 11. Diffusion particles; 12. Substrate; 13. Micro-nano structure layer; 14. Micro-nano structure

Figure 2a-d is a flow chart of making a light-diffusing sheet with patterned light-diffusing particles in Embodiment 1; Figure 2a is the embossing mold in Embodiment 1; The stamping mold obtains a complementary concave structure on the substrate; FIG. 2c is a schematic diagram of filling diffusion particles using scrape coating technology in Example 1; FIG. 2d is a protective layer on the surface in Example 1.

Among them: 21. Micro-nano structure layer; 22. Substrate; 23. Diffusion particles; 24. Protective layer

Fig. 3 is a schematic diagram of a mold structure for embossing a concave structure in Embodiment 1;

4 is a schematic diagram of another mold structure for embossing a concave structure in Embodiment 1;

5 is a schematic diagram of another mold structure for embossing a concave structure in Embodiment 1;

6 is a schematic diagram of another mold structure for embossing a concave structure in Embodiment 1;

Fig. 7 is the situation in which the diffusion particles are arranged in a multi-layer stacked manner in the concave structure in the third embodiment;

Fig. 8 is a topological structure of the concave structure filled with diffusion particles in the fourth embodiment;

Fig. 9 is another topological structure of the concave structure filled with diffusion particles in the fourth embodiment;

Fig. 10 is another topological structure of the concave structure filled with diffusion particles in the fourth embodiment;

Fig. 11 is the case where the micro-nano structure layer completely covers the protective layer in Embodiment 5;

Wherein 111, protective layer

Fig. 12 is the case where the micro-nano structure layer partially covers the protective layer in the fifth embodiment.

121. Protective layer

detailed description

The present invention will be further described below in conjunction with accompanying drawing and embodiment:

Embodiment 1: Refer to FIG. 1 , a light diffusion sheet, a structural schematic diagram of a light diffusion sheet with patterned arrangement of light diffusion particles. On the substrate 12, there are recessed structures 14, these recessed structures 14 present a preset topological arrangement, such as square, hexagonal, strip, ring, etc., the width of the recessed structure is greater than 1 micron, and the aspect ratio is greater than 0.3 . The concave structure 14 is filled with diffusion particles 11 of organic or inorganic materials. The diffusion particles 11 can be spherical, ellipsoidal, cylindrical, cuboid, or other special-shaped bodies. Different from the protective layer, the absolute difference between the optical refractive index of the diffusing particles and the refractive index of the transparent substrate layer, microstructure layer, protective layer material, or one of them is not less than 0.01. When the incident light beam passes through the surface of the diffusion sheet, it is affected by the patterned diffusion particles 11, and optical phenomena such as refraction, scattering, and diffraction will occur to form a diffusion effect on light. The characteristic size of the diffusion particles 11 is 1-10 microns. The absolute value of the refractive index difference between the diffusing particles and one of the substrate 12 , the micro-nano structure layer material 13 , and the protective layer material is greater than 0.01; or the absolute value of the refractive index difference between them is greater than 0.05.

Embodiment 2: Referring to Figures 2a-2d, a production process of a light diffusion sheet proposed by the present invention. First, a mold with a topologically arranged patterned raised structure is fabricated. The patterned convex structure mold in Figure 2a can be realized by various methods, such as mask photolithography exposure, laser direct writing, chemical etching or mechanical scribing. The material of the mold can be metal materials, such as nickel, stainless steel, copper or metal alloy materials, organic materials, such as polycarbonate, polyvinyl chloride, polyester, perfluoropolyetherene, tetrafluoroethylene copolymer and acrylic; Inorganic non-metallic materials such as silica, silicon, carbon steel, silicon carbide. Next, FIG. 2 b is a schematic diagram of using a mold to make a concave structure on a transparent substrate 22 by embossing. Hot embossing or UV embossing can be used. Hot embossing is to first use a hard stamping blank to process it into a stamping mold, and then soften the polymer substrate 21 by high temperature, or coat the polymer substrate with a high molecular polymer material 21 with thermal softening properties, Put it into the embossing machine to heat and press the stamper on the polymer substrate with a certain pressure, then lower the temperature to near the solidification point of the polymer, and at the same time separate the stamper from the polymer layer, leaving the surface of the substrate with Complementary structures on the mold. The process of UV embossing is basically the same as that of hot embossing. It is necessary to use a polymer that can be cured under ultraviolet light as the imprinting layer material. transparent. Again, FIG. 2c is a schematic diagram of the concave structure in the microstructure layer filled with diffusion particles 23 . Through scrape coating technology, the diffused particles are scraped and filled in the concave microstructure with a scraper to form patterned diffused particles. Finally, a transparent material can be used to cover the outer surface of the micro-nano structure layer as the protective layer 24, and the appearance of a smooth surface can be realized. Since the refractive index of the diffusing particles is different from that of the substrate, the micro-nano structure layer and the protective layer, the patterned diffusing particles scatter the incident light.

Embodiment 3: Referring to Figures 3-4, a light diffusion sheet proposed by the present invention, the shape of the concave structure filled with diffusion particles depends on the microstructure shape of the mold. Microstructure shapes such as spheres, ellipsoids, triangular pyramids, quadrangular pyramids, etc., and cross-sections of circles, ellipses, triangles, quadrilaterals or other irregular polygons, and shapes that can be filled with diffusion particles are all within the protection scope of the present invention. Diffusion particles are filled in the processed concave structure, and its state is shown in Figures 5-6. When the structure on the mold has a high aspect ratio, the concave structure of the microstructure layer will also have a large aspect ratio, and the diffusion particles will be arranged in a multi-layer stacked manner in the concave structure, as shown in Fig. 7 . This provides an additional spatial dimension for designing the light modulation of the diffuser.

Embodiment 4: Referring to Figures 8-10, a light diffusion sheet proposed by the present invention, the topological structure of the concave structure filled with diffusion particles determines the distribution of the center position of the light diffusion spot. Its topology can be a linear grating, such as square, hexagonal, strip, ring, etc.

Embodiment 5, referring to Figures 11-12, a light diffusion sheet proposed by the present invention, the micro-nano structure layer can be covered with a protective layer 111 or 112, and the protective layer can completely cover the diffusion particles, or partially cover the diffusion particles.

Claims (10)

1. a light diffusing sheet, it is characterised in that: including transparent substrate layer, the side surface in described transparent substrate layer is provided with micro- Structure sheaf, described microstructured layers is provided with micro-structural, and described micro-structural is sunk structure, fills in the sunk structure of microstructured layers There is diffusion particle.

2. a kind of light diffusing sheet according to claim 1, it is characterised in that in microstructured layers, micro-structural is recessed, uses In induction diffusion particle arrangement, its arrangement mode can be wire grating, rectangle, annular and hexagon arrangement, or, in plane The inside symmetrically arrangement of axle or the planar arrangement in asymmetric shaft；Described diffusion particle arrangement state can continuously or from Dissipate.

3. a kind of light diffusing sheet according to claim 2, it is characterised in that can be with to the material of microstructured layers therein Substrate layer material is identical, it is also possible to different.

4. a kind of light diffusing sheet according to claim 1, it is characterised in that described sunk structure width is more than 1 micron, deeply Wide ratio is more than 0.3.

5. a kind of light diffusing sheet according to claim 1, it is characterised in that fill in the sunk structure of described microstructured layers There is diffusion particle, be distributed according to the topology arrangement of sunk structure；Diffusion particle can be more than, be less than or equal to sunk structure Characteristic size, its shape can be spherical, elliposoidal, cylinder, cuboid, or other obform bodies.

6. a kind of light diffusing sheet according to claim 1, it is characterised in that can be provided with transparent outside microstructured layers Protective layer, protective layer is completely or partially coated with diffusion particle.

7. a kind of light diffusing sheet according to claim 5, it is characterised in that be filled in the sunk structure of microstructured layers Diffusion particle, its light refractive index and transparent substrate layer, microstructured layers, protective layer material or their refractions of one of them The difference absolute value of rate is not less than 0.01.

8. the preparation method of a light diffusing sheet, it is characterised in that comprise the following steps:

S1, use there is the mould of bulge-structure, make structure over the transparent substrate by hot padding or ultraviolet stamping mode, The sunk structure complementary with mould bulge-structure is obtained in microstructured layers；

S2 utilizes doctor blade technique, scratches diffusion particle in the sunk structure making in above-mentioned steps, forms patterned expansion Shot arrangement.

9. the preparation method of a kind of light diffusing sheet according to claim 8, it is characterised in that also include step S3. micro- Structure sheaf surface applies protective layer.

10. the preparation method of a kind of light diffusing sheet according to claim 9, it is characterised in that be filled in microstructured layers Diffusion particle in sunk structure, its light refractive index and transparent substrate layer, microstructured layers, protective layer material or they its One of specific refractivity absolute value be not less than 0.01.