WO2023173818A1 - Light diffusion plate capable of being used for long time, preparation method therefor and application thereof - Google Patents

Abstract

The present invention provides a light diffusion plate capable of being used for a long time, a preparation method therefor and an application thereof. According to the light diffusion plate of the present invention, polystyrene (GPPS) to which a light diffusion agent is added is used to make a light diffusion layer, a protective layer is compounded on each of the upper surface and the lower surface of the GPPS light diffusion layer, the protective layer is an SMA (styrene-maleic anhydride copolymer) resin blending modified PMMA resin layer, and the SMA resin added in the protective layer can achieve a tackifying effect, so that the interlayer bonding force between the two different material layers, i.e., the PMMA resin layer and the GPPS layer, can be effectively improved, thereby significantly prolonging the service life of the plate.

Description

A kind of light diffusion plate that can be used for a long time and its preparation method and application Technical field

The invention belongs to the technical field of light diffusion materials and specifically designs a light diffusion plate that can be used for a long time and its preparation method and application.

Background technique

Light diffusion material is a material that can allow light to pass through and effectively diffuse light. It can convert point and line light sources into line and surface light sources. It has a large scattering angle, good light conductivity, and uniform light transmission. Therefore, it is widely used in liquid crystal displays, LED lighting and imaging display systems. Its main function is to fully scatter the incident light to achieve a softer and more uniform illumination effect.

Light diffusion materials are generally made of transparent resin as a matrix and by adding a certain proportion of light diffusing agents and other additives. Commonly used transparent substrates include polycarbonate (PC), polymethylmethacrylate (PMMA), polystyrene (GPPS), and polypropylene (PP). Due to the advantages of polystyrene such as good rigidity, dimensional stability, high light transmittance, low haze and low cost, more and more backlight display devices and LED lamp covers are made of polystyrene-based light diffusion materials.

At present, polystyrene-based light diffusion materials are often prepared by blending, extruding and granulating polystyrene resin with a suitable proportion of light diffusing agent. Light diffusing agents mostly use organic polymer particles such as organic silicone, cross-linked PMMA microspheres, and polystyrene microspheres with a spherical structure. Although adding these light diffusing agents can better achieve higher light transmittance and effectively diffuse light, the overall cost is high and the preparation process is complicated, especially for light diffusing agents with microsphere structures.

Due to cost, the cost of polycarbonate (PC) and polymethyl methacrylate (PMMA) is much higher than that of polystyrene (GPPS). Therefore, the current low-end products in the market mainly use GPPS materials. However, the shortcomings of polystyrene (GPPS) light diffusion plates are also obvious, such as poor surface scratch resistance, poor weather resistance, easy yellowing, and poor solvent resistance. Therefore, most methods now improve the performance of polystyrene light diffusion panels by compounding a layer of protective material on the surface of the polystyrene light diffusion panels to prepare multi-layer composite light diffusion panels, such as the Chinese patent "Composite Light Diffusion Panels and Preparation Methods" It is disclosed that a polycarbonate layer is compounded on the upper and lower surfaces of a polystyrene light diffusion plate. Although the performance of the light diffusion plate can be improved, the surface hardness is low, the solvent resistance of polycarbonate is poor, and the long-term aging performance is poor. To guarantee.

Therefore, it is necessary to develop a light diffusion sheet that can be used for a long time and has good light diffusion performance, surface hardness and weather resistance.

Contents of the invention

The purpose of the present invention is to solve the problem that existing light diffusion sheets are prone to delamination during use, and to further improve the light diffusion performance, surface hardness and weather resistance of the light diffusion sheets, by providing a light diffusion sheet that can be used for a long time. Light diffusion sheet.

Another object of the present invention is to provide a method for preparing the light diffusion plate that can be used for a long time.

Another object of the present invention is to provide the application of the light diffusion plate that can be used for a long time in the field of imaging display.

In order to achieve the above objects, the present invention adopts the following technical solutions:

A light diffusion plate that can be used for a long time, including a GPPS light diffusion core layer and PMMA protective layers located on the upper and lower surfaces of the GPPS light diffusion core layer;

Among them, the GPPS light diffusion core layer includes GPPS resin and light diffusion agent;

The PMMA protective layer includes components calculated according to the following parts by weight:

The light diffusion plate of the present invention uses polystyrene (GPPS) added with a light diffusion agent as a light diffusion layer, and a protective layer is compounded on the upper and lower surfaces of the light diffusion layer. The protective layer is SMA (styrene maleic anhydride). Copolymer) resin blend modified PMMA resin layer.

PMMA resin itself has good light transmittance and high surface hardness. While protecting the polystyrene light diffusion sheet, it does not affect the light diffusion (light transmittance and haze) of the light diffusion sheet. It can also be added by adding Weathering agents and other additives can improve the weather resistance of materials. However, studies have found that due to the high surface hardness of PMMA resin, its bonding performance with the GPPS light diffusion layer is poor. If conventional adhesives are used, it will affect the light diffusion performance of the board, especially the light transmittance. The inventor of the present invention found through a large number of experimental studies that if the SMA resin added to the PMMA protective layer is blended and modified, the hardness and transmittance of the PMMA resin can be effectively improved without affecting the hardness and light transmittance of the PMMA resin layer. The interlayer bonding force between the two different material layers of the GPPS layer can significantly increase the service life of the material.

Conventional GPPS light diffusion core layer can be used in the present invention, and the GPPS light diffusion core layer includes components calculated according to the following parts by weight:

GPPS resin 70~90 parts;

Light diffusion masterbatch 10 to 30 parts;

Other additives 0 to 1 part.

It should be noted that conventional commercially available high-viscosity GPPS resins can be used in the present invention. Optionally, the melt flow rate of the GPPS resin at 200°C and 5kg is ≤5g/10min. Higher melt viscosity is beneficial to the light diffusing agent masterbatch being better dispersed in the GPPS resin matrix.

Further preferably, the melt flow rate of the GPPS resin under the conditions of 200°C and 5kg is 3 to 5g/10min.

Preferably, the melt flow rate of the SMMA resin at 230°C and a load of 3.16kg is 2.0-10g/10min.

In the present invention, the melt flow rate of GPPS resin and PMMA resin is detected according to the ISO 1133-1:2011 standard method.

The light diffusion masterbatch is a masterbatch obtained by melt extrusion of a light diffusion agent and GPPS resin. Preparing the light diffusing agent into a masterbatch can improve the dispersion performance of the light diffusing agent in the matrix resin and further improve the light dispersing effect.

Preferably, the weight content of the light diffusing agent in the light diffusing masterbatch is 2 to 10%.

Optionally, the light diffusing agent is one or a combination of organic silicon light diffusing agents or inorganic light diffusing agents.

Existing commercially available SMA resins with conventional MA (maleic anhydride) content can be used in the present invention. Optionally, the weight content of MA in the SMA resin is 15 to 30%.

Optionally, the weathering agent is an ultraviolet absorber and/or a light stabilizer.

Preferably, the weather-resistant agent is a mixture of ultraviolet absorber and light stabilizer at a ratio of 1:1 to 1.5.

Preferably, the ultraviolet absorber is a benzotriazole ultraviolet absorber, including but not limited to 2-(2'-hydroxy-5'-methylphenyl) benzotriazole (UV-P) or 2- One or a combination of (2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole (UV-327).

Preferably, the light stabilizer is a hindered amine light stabilizer (HALS), including but not limited to one or a combination of HALS 944, HALS 770DF.

Preferably, in the light diffusion plate that can be used for a long time, the thickness ratio of the GPPS light diffusion core layer and the PMMA protective layer (referring to the protective layer of the single-sided surface layer, that is, the upper surface layer or the lower surface layer) is 1:0.05~ 0.08.

The thickness of the light diffusion plate of the present invention can be 1.0 to 2.0 mm.

Preferably, other additives described in the GPPS light diffusion core layer and PMMA protective layer are independently selected from one or a combination of lubricants, antioxidants or colorants.

Preferably, the PMMA protective layer includes components calculated according to the following parts by weight:

The preparation method of the light diffusion plate that can be used for a long time includes the following steps:

After the raw materials of each component of the GPPS light diffusion core layer and the raw materials of each component of the PMMA protective layer are mixed evenly, they are added to the co-extrusion extruder from different feeding ports. After melting and extruding, we obtain The light diffusion plate can be used for a long time.

Preferably, the mixing is performed in a high-speed mixer, and the rotation speed of the high-speed mixer is 500 to 800 rpm.

Preferably, the extruder is a three-layer co-extrusion extruder. It should be noted that in the light diffusion plate, the thickness of each layer can be controlled by controlling the screw speed ratio of the extruder, and the thickness of the plate can be adjusted by the traction speed of the traction roller.

Preferably, the extrusion temperature (screw temperature) is 80-220°C. Specifically, from the feeding port to the machine head, the temperature is set to: the temperature in the first zone is 80-100°C, the temperature in the second zone is 180-200°C, and the temperature in the third zone is 200-220°C. ℃, the four zone temperature is 200~220℃, the screen changer temperature is 200~220℃, the transition zone temperature is 200~220℃, and the die head temperature is 200~220℃.

The application of the above-mentioned light-diffusion plate that can be used for a long time in the field of imaging and display is also within the scope of protection of the present invention, and can be specifically used to prepare lampshades and panels for liquid crystal displays or LED lighting lamps.

Compared with the prior art, the beneficial effects of the present invention are:

The light diffusion plate of the present invention uses polystyrene (GPPS) added with a light diffusing agent masterbatch as a light diffusion layer, and a protective layer is compounded on the upper and lower surfaces of the light diffusion layer. The protective layer is SMA (styrene styrene). The PMMA resin layer modified by blending and modifying the poly(acetic anhydride copolymer) resin can effectively improve the interlayer bonding force between the PMMA resin layer and the GPPS layer, which are two different material layers, thereby significantly increasing the service life of the material. Among them, the total light transmittance of the light diffusion plate of the present invention is more than 65%, which can be as high as 76%; the haze is >78%, which can be as high as 90%; the surface hardness level can reach 2H level; after 600 hours of irradiation, photoaging The color difference value reaches the level of △E≤1.5 and can be as low as 0.5.

Description of the drawings

Figure 1 is a schematic structural diagram of the light diffusion plate of the present invention.

Detailed ways

The present invention will be further described below with reference to specific embodiments and drawings, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field. Unless otherwise stated, the reagents and materials used in the present invention are all commercially available.

Examples of the present invention use the following raw materials:

Polystyrene (GPPS):

1#: GPPS-1050, the melt flow rate under 200℃ and 5kg load is 2.0g/10min, purchased from Foshan Total;

2#: GPPS-500N, the melt flow rate under 200℃ and 5kg load is 3.0g/10min, purchased from Dushanzi Petrochemical;

3#: GPPS WD-500E, the melt flow rate under 200℃ and 5kg load is 5.0g/10min, purchased from Shanghai Secco;

4#: GPPS, brand name GPPS-525, melt flow rate under 200℃ and 5kg load is 8.0g/10min, purchased from CITIC Guoan;

Light diffusing agent:

1#: Silicone light diffusing agent, KMP-590, purchased from Shin-Etsu, Japan;

2#: Silica, HDK H2000, purchased from Wacker, Germany;

PMMA resin:

1#: PMMA 205, the melt flow rate under 230℃ and 3.16kg load is 2.5g/10min, purchased from Zhenjiang Chimei;

2#: PMMA 207, the melt flow rate under 230℃ and 3.16kg load is 8.0g/10min, purchased from Zhenjiang Chimei;

SMA resin:

SMA-1: SZ10010, MA weight content is 25%, purchased from POLYSCOPE in the Netherlands;

SMA-2: SMA-700, MA weight content is 18%, purchased from Shanghai Huawen;

EMA resin: AC1330, purchased from DuPont in the United States;

Weathering agent:

1#-UV absorber UV-P: RIASORB, commercially available;

2#-Light stabilizer HALS 770DF: RIASORB, commercially available;

Other additives:

Lubricant: calcium stearate, commercially available;

It should be noted that in the present invention, the weathering agent and other additives used in each embodiment and comparative example are the same.

Examples 1 to 14

This embodiment provides a series of light diffusion plates that can be used for a long time, prepared according to the formulas in Tables 1 to 3 and a preparation method including the following steps:

S1. Preparation of light diffusion masterbatch

According to the formula in Table 1, the light diffusing agent and GPPS resin are mixed evenly in a high-speed mixer, then added to a twin-screw extruder, and prepared by melt extrusion at 180 to 210°C;

S2. Preparation of light diffusion plate

According to the formula shown in Tables 2 to 3, mix the raw materials of each component of the GPPS light diffusion core layer in a high-speed mixer evenly, and then add them to the main feed port of the three-layer co-extrusion extruder; each component of the PMMA protective layer After the component raw materials are mixed evenly in the high-speed mixer, they are added to the auxiliary feed port of the three-layer co-extrusion extruder; the above raw materials are melted and plasticized by each single-screw extruder (wherein, the extrusion temperature (screw temperature ) is 80~220℃. The specific settings from the feeding port to the machine head are: the temperature in the first zone is 80~100℃, the temperature in the second zone is 180~200℃, the temperature in the third zone is 200~220℃, and the temperature in the fourth zone is 200~220℃. The screen changer temperature is 200~220℃, the transition zone temperature is 200~220℃, and the die head temperature is 200~220℃), and then it is extruded from the T-shaped die into a sheet. The extruded sheet is made of multiple The cooling roller is cooled, and the light diffusion plate is obtained after being pulled by a traction roller and cut (the schematic diagram is shown in Figure 1).

Table 1 Formula of light diffusion masterbatch (parts by weight)

Table 2 Contents of each component in the light diffusion plates of Examples 1 to 9 (parts by weight)

Note: In each embodiment of the present invention, the upper and lower protective layers have the same thickness by default.

Table 3 Contents of each component in the light diffusion plates of Examples 10 to 14 (parts by weight)

Note: In each embodiment of the present invention, the upper and lower protective layers have the same thickness by default.

Comparative example 1

This comparative example provides a light diffusion plate. The difference between the formula and Example 2 is that no SMA resin is added.

Comparative example 2

This comparative example provides a light diffusion plate. The difference between the formula and Example 2 is that the added amount of SMA resin is replaced by 13 parts.

Comparative example 3

This comparative example provides a light diffusion plate. The difference between the formula and Example 2 is that the SMA resin is replaced with EMA.

Comparative example 4

This comparative example provides a light diffusion plate. The difference between the formula and Example 2 is that the SMA resin in the PMMA protective layer is replaced and added to the GPPS light diffusion core material.

Performance Testing

The light diffusion plates prepared in the above examples and comparative examples were cut into square plate samples of 100mm×100mm, and their performance was tested. The specific test items and test methods are as follows:

1. Light diffusion performance test:

Test the light transmittance of the sample in accordance with the GB/T2410-2008 standard; use a haze meter to test the haze of the sample in accordance with the ASTM D1003-2013 standard.

2. Surface hardness: measured using a pencil hardness tester according to the national standard GB/T 6739-1996.

3. Photoaging resistance: tested according to the ISO 4892.2-2013 standard, test conditions: 0.51W/m ² , including 102 minutes of drying, 18 minutes of spraying, and 30 continuous cycles of irradiation, totaling 600 hours;

In addition, the present invention also tested the light transmittance of the light diffusion plate after 600 hours of simulation in the above-mentioned simulated environment.

The test results are detailed in Table 3:

Table 3 Performance test results

It can be seen from the above results:

The multi-layer (three-layer) co-extruded light diffusion sheet prepared in various embodiments of the present invention has good optical properties, high surface hardness and light aging resistance. Specifically: the light transmittance of the light diffusion sheet is 65%. Above, it can be as high as 76%; haze >78%, can be as high as 90%; surface hardness can reach 2H level; after 600h xenon lamp aging test, photoaging color difference △E≤1.5, can be as low as 0.5; it also has relatively After a long use time, the light transmittance can be maintained above 90% after a 600h xenon lamp aging simulation test, which can be as high as 98.6%.

The results of Example 2 and Examples 4 to 6 show that the GPPS resin matrix within the melt flow rate range selected by the present invention can be used in the present invention, and the light diffusion performance (light transmittance and Haze) is better, but the performance of low melt flow rate (high viscosity) substrate is better; as the GPPS resin melt flow rate increases (for example, Example 6), the viscosity of the matrix decreases, and after a long time After use, the stability of the board will deteriorate (especially the retention rate of light transmittance and photoaging performance).

The results of Example 2 and Examples 7 to 9 show that ordinary light diffusion masterbatch can be used in the present invention, but the light transmittance of inorganic light diffusion masterbatch is poor, but in the case of a small amount of addition, the light transmittance can be reaches 65%.

The results of Example 2 and Examples 10-11 show that both conventional PMMA resin and SMA resin can be used in the present invention, and the prepared light diffusion plate has good light diffusion properties (light transmittance and haze).

The results of Example 2 and Example 12 show that the addition of other additives has little impact on the performance of the prepared light diffusion plate.

The results of Example 2 and Examples 13-14 show that the thickness ratio of the protective layer surface layer to the core layer is within the range selected by the present invention and has little impact on the performance of the prepared light diffusion plate.

The results of Example 2 and Comparative Examples 1 to 2 show that adding an appropriate amount of SMA resin to the protective layer can enhance the interlayer adhesion without affecting the light diffusion performance of the material; Comparative Example 1 Without adding SMA resin, the interlayer adhesion effect is not good, and it is easy to age and delaminate, resulting in a significant decrease in light transmittance after aging. In Comparative Example 2, a larger amount of SMA resin was added, and the overall light diffusion performance of the prepared light diffusion plate was improved. and a significant decrease in hardness.

Comparative Example 3 adds conventional interlayer adhesive, but it will significantly affect the light transmission performance, haze and weather resistance of the light diffusion plate; Comparative Example 4 adds SMA resin to the GPPS light diffusion core layer, and the SMA resin also has an effect. It can enhance the inter-layer adhesion, but it will significantly affect the light transmission performance and haze of the light diffusion plate, and cannot meet the demand for simultaneous improvement of light transmittance and haze.

The above results show that only when an appropriate amount of SMA resin is added to the PMMA protective layer, it will enhance the interlayer adhesion.

The above-described specific embodiments further describe the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above-mentioned are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. A light diffusion plate that can be used for a long time, characterized by including a GPPS light diffusion core layer and PMMA protective layers located on the upper and lower surfaces of the GPPS light diffusion core layer;

   Among them, the GPPS light diffusion core layer includes GPPS resin and light diffusion agent;

   The PMMA protective layer includes components calculated according to the following parts by weight:

   
2. The light diffusion plate that can be used for a long time according to claim 1 is characterized in that the GPPS light diffusion core layer includes components calculated according to the following parts by weight:

   GPPS resin 70~90 parts;

   Light diffusion masterbatch 10 to 30 parts;

   Other additives 0 to 1 part.
3. The light diffusion plate that can be used for a long time according to claim 2 is characterized in that the melt mass flow rate of the GPPS resin under the conditions of 200°C and 5kg is ≤5g/10min.
4. The light diffusion plate that can be used for a long time according to claim 3 is characterized in that the melt mass flow rate of the GPPS resin under the conditions of 200°C and 5kg is 3 to 5g/10min.
5. The light diffusion plate that can be used for a long time according to claim 2 is characterized in that the light diffusion masterbatch contains a light diffusing agent and a GPPS resin, and the weight content of the light diffusing agent is 2 to 10%.
6. The light diffusion plate that can be used for a long time according to claim 2 is characterized in that in the light diffusion masterbatch, the light diffusing agent is one or a combination of organic silicon light diffusing agent or inorganic light diffusing agent. .
7. The light diffusion plate that can be used for a long time according to claim 1 is characterized in that the thickness ratio of the GPPS light diffusion core layer and the PMMA protective layer on one side is 1: (0.05~0.08).
8. The light diffusion plate that can be used for a long time according to any one of claims 1 or 2, characterized in that the other additives are one or a combination of lubricants, antioxidants or colorants.
9. The method for preparing a light diffusion plate that can be used for a long time according to any one of claims 1 to 8, characterized in that it includes the following steps:

   After the raw materials of each component of the GPPS light diffusion core layer and the raw materials of each component of the PMMA protective layer are mixed evenly, they are added to the co-extrusion extruder from different feeding ports. After melting and extruding, we obtain The light diffusion plate can be used for a long time.
10. Application of the long-term usable light diffusion plate described in any one of claims 1 to 8 in the field of imaging and display.

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