TWI288844B - Light diffusion plate for LCD backlight - Google Patents

Abstract

The present invention related to a light diffusion plate for an LCD backlight with enhanced masking effect of lamp and light transmittance, which light diffusion plate is manufactured by coextrusion or multi-layer extrusion of at least two light diffusion layers each having a different light diffusion rate gradient, to weaken light diffusion at the inlet portion of an incident light and gradually intensifies light diffusion with the progress of light, thereby enhancing both the masking effect of lamp and the light transmittance. Accordingly, the light diffusion plate of the present invention is useful for a lighting fixture cover required to have uniform brightness and advertisement panels, particularly direct backlight type LCD devices required to have a thin structure.

Description

1288844 The Year of the Dance (Μ冰修(丨丨正替换页9, invention description: [Technical Field] The present invention relates to a light diffusing plate having an improved bulb masking effect and light transmittance, and a lighting fixing cover [0002] In general, the backlight in the conventional LCD element includes an edge illumination system and a direct illumination system. In the edge illumination system, A fluorescent lamp will be placed at the edge of a light guide plate, which is tilted downward to the bottom end, and a sheet-shaped reflector is placed underneath, and a pattern is printed on the bottom end of the light guide plate if necessary. The system that provides low brightness is mainly used in small-sized display elements. The direct illumination system does not use a light guide, but it will include a reflector, a plurality of bulbs mounted on the reflector, and a light diffuser with a specific The distance is placed on the bulb, because the bulb is completely hidden, the core of the system will have a uniform brightness, for this purpose, Diffusion should result in low light transmittance, which causes a certain reduction in brightness. Another way is to keep the light diffuser away from the bulb, making it difficult to turn it into a thin film. An improved method uses a geometry at the same time. The light guide plate and a light diffusing plate are disclosed in the Korean Patent Laid-Open No. 2-71-71358, but the system is still subject to problems such as complicated structure, increased complexity of the process, high manufacturing cost, and weight. [Abstract] 5 14416 pifl.doc 1288844 One of the objects of the present invention is to provide a light diffusing plate that effectively covers a bulb and has a high light transmittance to maintain high brightness uniformity, thereby allowing a thin backlight to have Improved efficacy. To provide a light diffusing plate for LCD backlights for the purposes of the present invention, a coextruded or multilayer extruded at least two light diffusing plate comprising a bonding resin with or without a light diffusing bead string ( Bead), the individual light diffusing plates have a light diffusivity to the incident light of a bulb inserted thereon, from the bottom of the light diffusing plate to the top of the light diffusing plate The present invention will be described in detail later. Generally, the 'light diffusing plate is produced by extrusion comprising a bonding resin and a light diffusing bead string, and the present invention relates to a co-extrusion or multilayer. A light diffusing plate that extrudes a plurality of light diffusing layers. In the light diffusing plate of the present invention, the first light diffusing layer having the incident light of the bulb inserted thereon does not include the light diffusing bead string. Light diffusing panels for LCD backlights, particularly light diffusing panels for direct moonlight LCD displays, may be formed by co-extrusion or multilayer extrusion of at least two layers of light diffusing layers, each having a different light diffusivity gradient. Coextruding or multi-layer extruding the multi-layer light diffusion layer to increase the light diffusivity of the bottom of the light diffusing plate from the bottom of the light diffusing plate of the incident light (λ) of a bulb inserted thereon, thereby avoiding the reflection at the bottom of the light diffusing plate The resulting light is removed again to avoid leakage of light and maximize the diffusion of light at the bottom of the light diffusing plate. This light diffusion is illustrated in Figure 1. This can be done in different ways, including, for example, an adjustment 6 14416pifl.doc 1288844 ^ $_咖修(粟.). Positive | Replace the density of distribution ("density distribution" is used here to define a quantitative density representation The number of light-diffusing bead strings in each volume) and the extrusion rate of the light-diffusing bead string in the light-diffusing layer to have different thicknesses and different light transmittances in the co-extrusion or multi-layer extruded multi-light diffusion layer And a method of forming a light diffusion layer comprising a light diffusion bead string each having a different reflection index than the bonding resin. In the example of using the density distribution of the light-diffusing bead string, the number of the light-diffusing bead strings is controlled such that the density distribution gradually increases from the bottom of the light-diffusing plate of the incident light of a bulb inserted thereon toward the top end of the light-diffusing plate. The light diffusion layer at the bottom of the light diffusion plate having the incident light of a bulb inserted thereon contains a light diffusion bead having a lower reflection coefficient than the bonding resin, and at this time, the light diffusion layer at the tip of the light diffusion plate contains a ratio A light diffusing bead string that bonds the reflection coefficient of the resin crucible. That is to say, a co-extrusion or multi-layer extrusion multilayer light diffusion layer having a different density distribution of light diffusion bead strings or a reflection coefficient gradient of a light diffusion bead string is formed in a multilayer light diffusion layer having a light diffusivity gradient. The light diffusing plate 0 is in the example of coextruding or multilayering two diffusion layers to form a light diffusing plate, such as one having a thickness of 1 to 3 min and a light transmittance of 20 to 75% (light diffusivity: 99 to 98) The light diffusing plate of %) can be made to pass through a light diffusing layer that controls the bottom of the light diffusing plate having incident light of a bulb inserted thereon to have a light transmittance of 70 to 93% (light diffusivity: 98~) 6%) and the thickness 〇·5 to 1.5 mm' and the light diffusion layer at the tip of the light diffusing plate has a light transmittance of 30 to 80% (light diffusivity: 99 to 96%) and a thickness of 0.5 to 7 14416 pifl. 1288844 Repair [1.5mm 〇 Compared with a single-layer light diffuser with the same light transmittance, the first diffuser plate has the ability to maintain high brightness uniformity, and it is necessary to increase the bulb and light diffusion. The ideal brightness is achieved at a distance between the boards, so it can be used for thin display systems. The direct backlight system required for the system. In the present invention, the number of co-extrusion or multi-layer extruded light diffusion layers and the thickness of the individual light diffusion layers can be controlled.曰 In the production of the light-diffusing sheet according to the present invention, the types of the bonding resin and the light-diffusing bead in the light-diffusing layer are generally obtained, and will be described in detail below. % Specific examples of the bonding resin used herein include acryl-, urethane-, or epoxy melamine-based polymer or unsaturated polyester, methacrylic acid. Methylmethacrylate, ethylmethacrylate, isobutylmethacrylate, n-butylmethacrylate, η·butylmercaptoacrylate (N-butyl methacrylate) N-butylmethylmethacrylate), acrylic acid, methacrylic acid, hydroxyethylmethacrylate, hydroxypropylmethacrylate, hydroxyethylacrylate ), acrylamide, methylolacrylamide, glycine citrate 8 14416pifl.doc

1288844 (glycidylmethyacrylate), copolymerization of ethyl acrylate, isobutyl acrylate, n-butyl acrylate, or 2-ethylhexy acrylate Or a terpolymer. Organic or inorganic bead strings can be used as a light diffusing bead string to enhance the light transmittance and the light diffusivity of the copper of the general bonding resin. The specific examples of these light diffusing bead strings used herein include organic Beads, such as propylene-based polymers, or methyl methacrylate, methyl methacrylate, isobutyl methacrylate, methyl butyl acrylate, dibutyl methacrylate, acrylic, A Acrylic acid, methyl hydroxyethyl acrylate, methyl hydroxypropyl acrylate, ethyl hydroxy acrylate, acrylamide, acesulfame & amine, decyl methacrylate, ethyl acrylate, acrylic acid Copolymer of butyl ester, butyl acrylate or 2-ethyl hexyl acrylate or a mixture of two copolymers, polyethylene, polystyrene or polypropylene (验lefm) beads Or a single-polymer bead string ίίί multi-layered porridge prepared by coating a bead string on a different monomer, such as dioxin, oxygen, oxidized, oxygen- ΙΜ Wait, the organic beads are in the light The ratio of the degree of diffusion to the inorganic bead string [Embodiment] is not intended to limit the present invention. The scope of the present invention will be described in detail by way of examples. The difference in the distribution of the bead string is used to control the light spread: the light diffusivity of the light diffusing layer is 14416pifl.doc 9 1288844

In this example, the light diffusing plate is fabricated by co-extruding a light diffusing layer having a thickness of 1.5 mm, a light transmittance of 90% (light diffusivity: 3%), and a thickness of 〇.5 mm having 70. A light diffusing layer of % light transmittance (light diffusivity: 98%). Here, the measurement of the light diffusivity and the transmittance is carried out by a standard method of ASTM D 1003, using NDH 2000 (Denshoku of Sakamoto as a measuring device) to measure a single extrusion to a sheet of a corresponding thickness. In this example, the transmittance of the light diffusing layer can be adjusted by controlling the distribution of the light diffusing bead string, and the thickness of the light diffusing layer can be adjusted by controlling the extrusion rate of the extruder. • This light-diffusing layer was prepared by using polymethyl methacrylate (VH〇〇1 supplied by UbiShi Rayon, Japan) as a bonding resin, and a cross-linked polystyrene bead string (Korean κ〇1〇η) Diasphere supplied as a string of light diffusing beads, details are listed in Table J. The known light diffusing plate has a total thickness of 2 mm and a light transmittance of 63%. This light surplus will be cut into n-ray (four) units, placed 13mm above a specific interval of one ^ eight cold cathode fluorescent, with the brightness on the bulb and at the midpoint of the bulb, on the bulb The average ratio of the degree to the brightness in the bulb is (10). 14416pifl.doc 10 1288844 Ocean P month ♦ repair instrument) replacement page 丨 Table 1 brand name manufacturer refractive index (%) content (wt·%) distribution dense light on the incident light side of the light diffusion layer Dissphere SPB-X10 Kolon 1.57 0.3 liA 6.5x1 〇6 Light diffusing layer on the light output side Diasphere SPB-X10 Kolon 1.57 10 2.2x1 08 Production example 2. Using the refractive index gradient of the light diffusing bead string to control the light diffusivity of the light diffusing layer' In this example The light diffusing plate is produced by coextruding a light diffusing layer having a thickness of 15 mm and having a light transmittance (light diffusivity: 30%) of 90% in the same manner as the example 丨. 5 mm is formed by a light diffusing layer having a light transmittance (light diffusivity: 98%) of 7 %. Here, the measurement of the light diffusivity and the transmittance is measured by ASTM D, using NDH 2000 (Denshoku, Japan) as a measuring device, and measuring a single extrusion to a sheet having a corresponding thickness. In the present example, the transmittance of the light-diffusing layer can be adjusted by controlling the difference in refractive ratio between the light-diffusing bead string and the bonding resin, and the thickness of the light-diffusing layer can be adjusted by controlling the extrusion rate of the extruder. This light diffusion layer was prepared using polymethyl methacrylate (Japanese

VH001 (refractive index: ι·49%) supplied by Mitsubishi Rayon as a bonding resin, a polystyrene-methyl methacrylate copolymer bead string (Diasphere MSP_Xl〇) and a polystyrene bead series (10) SPB -X10) as a light diffusing bead string of individual layers, the refractive index of the light diffusing bead string is 14416pifl.doc

1288844 can be adjusted by the amount of the monomer used in the preparation of the light diffusing bead string. For example, the lower the stupid ethylene content will result in a low refractive index and a high transmittance, the details of which are listed in Table 2. . The known light diffusing plate has a total thickness of 2 mm and a light transmittance of 63%. The light diffuser will be cut into 17-inch units and placed above a 13rnm with eight cold cathode fluorescent lamps placed at specific intervals to measure 1 at the bulb and at the midpoint between the bulbs. Brightness, the average ratio of the shell on the bulb to the brightness at the midpoint of the bulb is 1〇2. Table 2 _Light diffusion bead string brand name manufacturer refractive index difference with the refractive index of the bonding resin (wt·%) Optical expansion on the incident light side Dissphere MSPX10 Kolon 1.51 0.02 3 Optical expansion layer on the light output side Diasphere SPB- X10 Kolon 1.57 0.09 10 Comparative Example 1 In this example, a light diffusing layer having a thickness of 2 mm and a light transmittance of 63% (light diffusivity·) was produced using the same bonding resin as the above example and the same light diffusing bead string extruded light diffusion layer. · 99%) light diffuser. Using the standard method of ASTM D 1003, using NDH 2000 (Japan's 14416pifl.doc 12 1288844

Month 43⁄4 repair $)

Denshoku) As a measuring device, measures the transmittance and light diffusivity of a single extruded sheet to a corresponding thickness. This light diffusion layer was prepared using polymethyl methacrylate (Japanese

VH001 (refractive index: 丨.49%) supplied by Mitsubishi Rayon was used as a bonding resin, and a polystyrene bead string (Diasphere SPB-X10) was used as a light-diffusing bead. The details are shown in Table 3. In the same manner as in Example 1, it was decided to provide a distance of 18 lnm between the bulb and the light diffusing plate having an average luminance ratio of 1.02. Table 3 Light-Diffusing Beads Brand Name Manufacturer Refractive Index Content (wt·%) Single-layer light diffuser Diasphere SPB-X10 Kolon 1.57 3 According to the results of Examples 1 and 2 and Comparative Example 1, the bulb required to achieve the specified brightness ratio The distance from the light diffusing plate is 13 mm in Examples 1 and 2, and the light diffusing plate made of a single light diffusing layer in Comparative Example 1 is 18 mm, so the light diffusing plate used in the present invention can reduce the backlight thickness by about 5 mm. 〇 As described above, according to the present invention, the light diffusing plate made of the multilayer light diffusing layer having different light diffusivity gradients by co-extrusion or multilayer extrusion can reduce the thickness of the backlight unit without losing the light transmittance. And the light diffusing plate made by extrusion with a single light diffusing layer having the same transmittance is not relatively blurred. 13 14416pifl.doc 1288844

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing a state of light diffusion of light on a light diffusing plate having a plurality of layers of light diffusing layers according to a preferred embodiment of the present invention. [Graphic Marking Description] None 14 14416pifl.doc

Claims (1)

X. Patent application scope: 1. A light diffusing plate for liquid crystal display backlight, which is used for co-extrusion or multi-layer extrusion of at least two light diffusing plates, which comprises a bonding resin, and the individual light diffusing plate pairs are inserted therein The incident light of a light bulb has a light diffusing rate which gradually increases from the bottom of the light diffusing plate to the top end of the light diffusing plate. 2. The light diffusing plate for liquid crystal display backlight according to claim 1, wherein the bonding resin has a plurality of light diffusing bead strings, and a refractive index of the light diffusing bead strings and a refractive index of the bonding resin different. 3. The light diffusing plate for liquid crystal display backlight according to claim 2, wherein each of the light diffusing bead strings of each of the two light diffusing plates has a different density gradient to allow the light to diffuse a density of the bead string is gradually increased from the bottom of the light diffusing plate to which the bulb having the incident light is inserted toward the top of the light diffusing plate, and the density distribution is defined as a light diffusing bead string per unit volume. quantity. The light diffusing plate for liquid crystal display backlight according to claim 2 or 3, wherein the at least two light diffusing plates comprise the light diffusing strings having a refractive index different from that of the bonding resin, The bottom of the light diffusing plate on which the bulb having the incident light is inserted gradually increases toward the top end of the light diffusing plate. 15 14416pifl.doc 1288844月#!修 (致) is replacing the page VII. Designation of the representative figure: (1) The representative representative of the case is: Figure (1). (2) A brief description of the symbol of the symbol of the representative figure: None 8. If there is a chemical formula in this case, please disclose the chemical formula that best shows the characteristics of the invention: None 4 14416pifl.doc