Resin film as well as preparation method and application thereof

Abstract

The invention discloses a resin film as well as a preparation method and application thereof, belongs to the technical field of polaroid compensation films, and overcomes the defect that a downstream polaroid manufacturer cannot realize continuous production due to relatively large film thickness deviation of most compensation films in the prior art. The film thickness deviation D% of the resin film is smaller than or equal to 2%, D% = (Dmax-Dmin) / D * 100%, Dmax represents the maximum film thickness, Dmin represents the minimum film thickness, and D represents the average film thickness; the in-film phase difference R0 ranges from 30 nm to 80 nm, and the film thickness phase difference Rth ranges from 110 nm to 160 nm. The film thickness deviation of the resin film is smaller than or equal to 2%, the attaching precision and the size stability can be improved, continuous production is achieved, the product yield is further increased, the manufactured liquid crystal display has the large visual angle, and the display effect is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polarizing plate compensation films, and particularly relates to a resin film and a preparation method and application thereof. BACKGROUND

[0002] As a key material of liquid crystal display (LCD), a polarizing plate is mainly composed of "five films and one glue", the "five films" are a protective film, a surface treatment film, a PVA film, a compensation film (PVA protective film) and a release film, and the "one glue" refers to PSA pressure sensitive adhesive. In the field of compensation films, two kinds of films are mainly used, which are COP film (cyclo-olefin polymer film) and TAC film (triacetyl cellulose film), and the COP film has good heat resistance and size stability, and has gradually occupied the main market in the field of large-size display screens.

[0003] However, the existing compensation film has a large film thickness deviation, which leads to problems such as reduction of fitting precision, inconsistency of optical performance, uneven stress distribution, size matching and the like in the assembly process of the polarizing plate, and thus needs to be adjusted during production, which leads to the problem that the downstream polarizing plate manufacturer cannot realize continuous production, and affects the production efficiency. In addition, the liquid crystal panel prepared by using the existing compensation film has poor display effect. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to overcome the defects that the existing compensation film has a large film thickness deviation, leading to that the downstream polarizing plate manufacturer cannot realize continuous production, and the display effect is poor, so as to provide a resin film and a preparation method and application thereof.

[0005] To this end, the present application provides the following technical solutions.

[0006] In a first aspect, the present application provides a resin film, and the film thickness deviation D% is ≤2%;

[0007] wherein D% = (Dmax-Dmin) ÷ D x 100%;

[0008] Dmax represents the maximum film thickness;

[0009] Dmin represents the minimum film thickness;

[0010] D represents the average film thickness;

[0011] The in-film retardation R0 of the resin film ranges from 30 to 80 nm, and the film thickness retardation Rth ranges from 110 to 160 nm.

[0012] The in-film retardation R0 is in the horizontal direction, and the film thickness retardation Rth is in the vertical direction.

[0013] In a possible implementation, the moisture permeability of the resin film in 24 hours is ≤20 g / m2 ;

[0014] In a possible implementation, the resin film has a light transmittance ≥ 91%;

[0015] In a possible implementation, the resin film has a haze ≤ 1%;

[0016] In a possible implementation, the resin film is made of one or more of polyolefin resin, cyclic olefin resin, polyester resin, polycarbonate resin, sulfone polymer resin, polymethyl methacrylate resin and triacetate cellulose resin; preferably, the resin film is made of cyclic olefin resin, more preferably, the resin film is made of COP resin.

[0017] In a possible implementation, the resin film has an average film thickness D of 15-60 μm.

[0018] In a second aspect, the application provides a method for preparing a resin film, comprising the following steps:

[0019] S1, drying resin raw material and controlling the mass content of fine powder in the resin raw material ≤ 10%;

[0020] The fine powder is resin raw material with a particle size ≤ 50 μm;

[0021] S2, using the product obtained in S1 to prepare a base film;

[0022] S3, preparing a stretched film by double-drawing process of the base film; the stretching temperature T1 in the double-drawing process satisfies Tg+5℃ ≤ T1 ≤ Tg+30℃;

[0023] S4, heat treating the stretched film to obtain the resin film.

[0024] In a possible implementation, the screening step for controlling the mass content of fine powder in the resin raw material ≤ 10% is performed in air or inert atmosphere.

[0025] COP resin is brittle, and is prone to breakage during actual drying or conveying, therefore, there is a part of fine powder in the screened COP resin.

[0026] The double-drawing process refers to the process of producing a film by double-stretching, which is stretching in the longitudinal direction (MD) and the transverse direction (TD) simultaneously or in steps.

[0027] The double-drawing process is uniaxial stretching or biaxial stretching;

[0028] The double-drawing process is synchronous double-drawing or asynchronous double-drawing, preferably, asynchronous biaxial stretching.

[0029] In one possible implementation, the S1 satisfies at least one of the following conditions:

[0030] (1) The mass content of fine powder in the resin raw material is controlled to be 0.01% to 5%.

[0031] (2) The step of drying the resin raw material is performed in air or an inert atmosphere, preferably in a nitrogen atmosphere;

[0032] (3) The drying temperature is 90 to 130°C, preferably 100 to 110°C.

[0033] In one possible implementation, the S2 uses a casting method or a calendering method to prepare the base film, preferably a casting method.

[0034] Optionally, the casting method uses a single-screw or double-screw extruder, preferably a single-screw extruder.

[0035] Optionally, the casting method includes a conveying section with a controlled temperature of 230 to 270°C, preferably 250 to 260°C;

[0036] a melting section with a controlled temperature of 240 to 270°C, preferably 250 to 255°C;

[0037] a mixing section with a controlled temperature of 240 to 270°C, preferably 250 to 255°C;

[0038] a homogenizing section with a controlled temperature of 230 to 260°C, preferably 240 to 250°C;

[0039] a die with a controlled temperature of 230 to 250°C, preferably 240 to 250°C.

[0040] In one possible implementation, the base film prepared by the casting process is controlled to be in the range of 50 to 300μm.

[0041] In one possible implementation, the S3 satisfies at least one of the following conditions:

[0042] (1) Tg+15°C≤T1≤Tg+20°C;

[0043] (2) In the double-drawing process, the longitudinal stretching ratio is controlled to be 1.1≤MD≤6, preferably 1.5≤MD≤2.5;

[0044] (3) In the double-drawing process, the transverse stretching ratio is controlled to be 1.1≤TD≤4, preferably 1.2≤TD≤2.

[0045] By increasing the stretching ratio, the regularity or crystallinity of the polymer molecular chain can be increased, thereby regulating the moisture permeability.

[0046] In a possible implementation, the S4 satisfies at least one of the following conditions:

[0047] (1) The temperature T2 of the heat treatment is greater than or equal to Tg, and optionally, Tg+20℃≤T1≤Tg+50℃, preferably, Tg+30℃≤T1≤Tg+40℃.

[0048] (2) The time t of the heat treatment satisfies 10s≤t≤300s, preferably, 30s≤t≤60s.

[0049] In a third aspect, the present application provides a polarizing film compensation film using the resin film or the resin film prepared according to the preparation method.

[0050] In a fourth aspect, the present application provides a polarizing film comprising the polarizing film compensation film.

[0051] In a fifth aspect, the present application provides a liquid crystal display comprising the polarizing film.

[0052] In a possible implementation, the liquid crystal display is a VA type panel (Vertical Alignment).

[0053] The technical scheme of the present application has the following advantages:

[0054] 1. The film thickness deviation D% of the resin film of the present application is less than or equal to 2%, wherein D%=(Dmax-Dmin)÷D×100%, Dmax represents the maximum film thickness, Dmin represents the minimum film thickness, and D represents the average film thickness; the in-film retardation R0 of the resin film ranges from 30nm to 80nm, and the film thickness retardation Rth ranges from 110nm to 160nm.

[0055] The film thickness deviation of the resin film of the present application is less than or equal to 2%, which can improve the bonding accuracy and the dimensional stability, realize continuous production, and further improve the product yield.

[0056] Moreover, the in-film retardation R0 of the film of the present application ranges from 30nm to 80nm, and the film thickness retardation Rth ranges from 110nm to 160nm, which can improve the display effect of the VA type panel. In the liquid crystal display (LCD) technology, the core function of the compensation film is to accurately compensate the undesired phase difference of the liquid crystal layer at different viewing angles. The compensation film with R0 and Rth satisfying the range of the present application can provide appropriate horizontal compensation and vertical compensation, so that the display has good color performance, stereoscopic effect and authenticity, and a large visual angle.

[0057] 2. The method for preparing the resin film comprises the following steps: S1, drying resin raw materials, and controlling the mass content of fine powder in the resin raw materials to be ≤10%; the fine powder is resin raw material with a particle size ≤50 μm; S2, preparing a base film using the product obtained in S1; S3, preparing a stretched film by double-drawing process of the base film; the stretching temperature T1 in the double-drawing process satisfies Tg+5℃≤T1≤Tg+30℃; S4, heat treating the stretched film to obtain the resin film.

[0058] In the resin melting and plasticizing process, the fine powder is more likely to melt earlier than the normal resin particles, resulting in the extension of the heating time of the fine powder part and the occurrence of degradation, cross-linking carbonization and other phenomena. If the content of fine powder is too high, the cast base film will have problems such as crystal points and defects, and when the base film is further drawn, the problems such as crystal points and defects will be further enlarged, resulting in a large deviation in film thickness uniformity. The present application controls the content of fine powder to reduce the film thickness deviation. The degradation and cross-linking carbonization of fine powder will also affect the refractive index of the resin film, and then affect the phase difference; in combination with the stretching temperature T1 in the double-drawing process of the present application satisfying Tg+5℃≤T1≤Tg+30℃, the in-film phase difference R0 and the film thickness phase difference Rth of the resin film can be controlled in a suitable range. If T1 is too low, the molecular chain is stretched and the disorientation rate is low, the orientation degree of the resin film is high, and the phase difference is high; if T1 is too high, the chain segment moves too much, the disorientation rate is too high, and the phase difference is too low. DETAILED DESCRIPTION

[0059] The following examples are provided to better further understand the present application, and are not limited to the best mode, and do not constitute a limitation on the content and scope of protection of the present application. Any person under the inspiration of the present application or the combination of the present application with other prior art features will fall within the scope of protection of the present application.

[0060] The specific experimental steps or conditions are not specified in the examples, and can be performed according to the conventional experimental steps described in the literature. The reagents or instruments used are not specified by the manufacturer, and are conventional reagent products that can be obtained by purchase.

[0061] The raw materials used in the following examples and comparative examples are as follows:

[0062] COP resin, Zeon Corporation, glass transition temperature Tg 150℃;

[0063] Example 1

[0064] The present example provides a method for preparing a resin film, comprising the following steps:

[0065] S1, pretreatment: dry the resin at 100°C for 4 hours in a nitrogen atmosphere, filter the fine powder (particle size ≤ 50 μm) after drying with a screening device, collect the resin on the screen, and measure the fine powder content to be 8%.

[0066] S2, casting process: a single screw extruder with a width of 600 mm is used to prepare the casting base film. First, set the control temperature of each section of the extruder, the conveying section is 250°C, the melting section is 260°C, the mixing section is 260°C, the homogenizing section is 255°C, and the die is 240°C. Then add the dried resin particles from the hopper opening, set the screw speed to 45 rpm. Adjust the pulling speed of the cooling roller to control the thickness of the base film to 240 μm, and wind it up.

[0067] S3, double stretching process: before stretching, the base film obtained by winding is cut to remove the edge part to ensure an effective width of 450 mm. Then stretch, set the following parameters:

[0068] The stretching temperature is 180°C;

[0069] The stretching mode is asynchronous double stretching;

[0070] The longitudinal stretching ratio MD is 4 times, and the transverse stretching ratio TD is 3 times.

[0071] S4, shaping process: the prepared stretched film is shaped at high temperature, the temperature is set to 200°C, the shaping time (i.e. heat treatment time) is 200s, and the finished film A1 is obtained, the average film thickness D of the finished film A1 is 20 μm.

[0072] Example 2

[0073] The present embodiment provides a method for preparing a resin film, comprising the following steps:

[0074] S1, pretreatment: dry the resin at 110°C for 4 hours in an air atmosphere, filter the fine powder (particle size ≤ 50 μm) after drying with a screening device, collect the resin on the screen, and measure the fine powder content to be 4%.

[0075] S2, casting process: a single screw extruder with a width of 600 mm is used to prepare the casting base film. First, set the control temperature of each section of the extruder, the conveying section is 235°C, the melting section is 245°C, the mixing section is 250°C, the homogenizing section is 250°C, and the die is 235°C. Then add the dried resin particles from the hopper opening, set the screw speed to 45 rpm. Adjust the pulling speed of the cooling roller to control the thickness of the base film to 120 μm, and wind it up.

[0076] S3, double drawing process: before drawing, the base film obtained by winding is cut to remove the edge part to ensure that the effective width is 450 mm. Then drawing is performed, and the following parameters are set:

[0077] The drawing temperature is 160°C;

[0078] The drawing mode is synchronous double drawing;

[0079] The longitudinal drawing ratio MD is 2 times, and the transverse drawing ratio TD is 1.5 times.

[0080] S4, shaping process: the drawn film prepared is subjected to shaping treatment at high temperature, the temperature is set to 175°C, and the shaping time (i.e. heat treatment time) is 200 s, to obtain a finished film A2, and the average film thickness D of the finished film A2 is 40 μm.

[0081] Example 3

[0082] The present embodiment provides a preparation method of a resin film, comprising the following steps:

[0083] S1, pretreatment: the resin is dried at 100°C for 4 hours in a nitrogen atmosphere, and after drying, the fine powder (particle size ≤ 50 μm) is filtered by a screening device, and the resin on the screen is collected, and the fine powder content is measured to be 1%.

[0084] S2, casting process: a single screw extruder with a width of 600 mm is used to prepare a casting base film, first set the control temperature of each section of the extruder, the conveying section / melt section / mixing section / homogenization section / die temperature is 265 / 250 / 250 / 255 / 260°C. Then the dried resin particles are added from the hopper opening, and the screw rotation speed is set to 45 rpm. By adjusting the traction speed of the cooling roller, the thickness of the base film is controlled to be 360 μm, and winding is performed.

[0085] S3, double drawing process: before drawing, the base film obtained by winding is cut to remove the edge part to ensure that the effective width is 450 mm. Then drawing is performed, and the following parameters are set:

[0086] The drawing temperature is 155°C;

[0087] The drawing mode is asynchronous double drawing;

[0088] The longitudinal drawing ratio MD is 6 times, and the transverse drawing ratio TD is 4 times.

[0089] S4, shaping process: the drawn film prepared is subjected to shaping treatment at high temperature, the temperature is set to 185°C, and the shaping time (i.e. heat treatment time) is 200 s, to obtain a finished film A3, and the average film thickness D of the finished film A3 is 15 μm.

[0090] Example 4

[0091] The embodiment provides a preparation method of a resin film, and comprises the following steps:

[0092] S1, pretreatment: drying the resin at 90 DEG C for 4 hours in a nitrogen atmosphere, filtering the fine powder (particle size ≤ 50 μm) by using a screening device after drying, collecting the resin on the screen, and measuring that the fine powder content is 0.05%.

[0093] S2, casting process: using a 600 mm width single screw extruder to prepare a casting base film, first setting the control temperature of each section of the extruder, the conveying section / melting section / mixing section / homogenizing section / die temperature is 250 / 250 / 250 / 255 / 240 DEG C. Then the dried resin particles are added from the hopper, and the screw rotation speed is set to 45 rpm. By adjusting the traction speed of the cooling roller, the thickness of the base film is controlled to be 92 μm, and the winding is carried out.

[0094] S3, double stretching process: before stretching, the winding obtained base film is cut to remove the edge part, and the effective width is 450 mm. Then stretching is carried out, and the following parameters are set:

[0095] The stretching temperature is 170 DEG C;

[0096] The stretching mode is asynchronous double stretching;

[0097] The longitudinal stretching ratio MD is 1.5 times, and the transverse stretching ratio TD is 1.5 times.

[0098] S4, shaping process: the prepared stretching film is subjected to shaping treatment at high temperature, the temperature is set to 175 DEG C, the shaping time (i.e. heat treatment time) is 200 s, and the finished product film A4 is prepared. The average film thickness D of the finished product film A4 is 41 μm.

[0099] Comparative Example 1

[0100] The comparative example provides a preparation method of a resin film, which is basically the same as that of the embodiment 1, and the main difference lies in that the fine powder content is 15% in the pretreatment, and the finished product film B1 is prepared.

[0101] Comparative Example 2

[0102] The comparative example provides a preparation method of a resin film, which is basically the same as that of the embodiment 1, and the main difference lies in that the stretching temperature is 150 DEG C in the double stretching process, and the finished product film B2 is prepared.

[0103] Test Example 1

[0104] The prepared resin film is subjected to the following performance test:

[0105] The maximum film thickness Dmax and the minimum film thickness Dmin are tested by a film thickness tester with a precision of 0.1 μm.

[0106] The in-film retardation R0 and the film thickness retardation Rth are tested by a retardation meter, model: RETS-100nx, Otsuka, Japan.

[0107] The light transmittance and haze are tested by a transmission haze meter, model: 4775, BYK-Gardner.

[0108] The moisture permeability is tested by an oxygen / water vapor permeability tester, and the test standard refers to ISO 15106-2.

[0109] The relevant test results are shown in Table 1 below.

[0110] Table 1 Test results of resin film

[0111]

[0112] From the table, it can be seen that by controlling the preparation process, the film thickness deviation is <1%, and the downstream polaroid manufacturer can realize continuous production by using the compensation film of the present application.

[0113] Test Example 2

[0114] The resin films prepared by using the examples and the comparative examples are used to prepare polaroids, and the prepared polaroids are assembled into complete display modules with liquid crystal cells; the modules are lighted, full white field and full black field signals are inputted; a luminance meter is used to test the center point, the screen normal of the display module is 0°, the luminance meter is rotated from 0° to left or right or up and down, and the luminance is recorded every 5° until the CR is reduced to below the threshold value (CR < 10):

[0115] CR(θ) = L white (θ) / L black (θ) L white (θ): white field luminance, L black (θ): black field luminance.

[0116] The sum of the left / right / up / down symmetry angles is calculated, which is the viewing angle.

[0117] The test results are shown in Table 2.

[0118] Table 2 Viewing angle

[0119] No. Viewing angle ° (left-right) Viewing angle ° (up-down) A1 158 149 A2 165 155 A3 171 160 A4 163 148 B1 55 37 B2 78 101

[0120] As can be seen from Table 2, the liquid crystal display using the compensation film of the present application can obtain a larger viewing angle, and the display effect of the liquid crystal display is improved.

[0121] Obviously, the above embodiments are merely example for clearly illustrating but not limitation to the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments need not and can not be enumerated. The obvious changes or variations derived from this still fall within the protection scope of the present application.

Claims

1. A resin film, characterized in that Film thickness deviation D%≤2%; Where, D% = (Dmax - Dmin) ÷ D × 100%; Dmax represents the maximum film thickness; Dmin represents the minimum film thickness; D represents the average film thickness; The film internal phase difference R0 ranges from 30 to 80 nm, and the film thickness phase difference Rth ranges from 110 to 160 nm.

2. The resin film according to claim 1, wherein The resin film satisfies at least one of the following conditions: (1) The moisture permeability of the resin film for 24 hours is ≤ 20 g / m 2 ; (2) The light transmittance of the resin film is ≥91%, (3) Haze ≤ 1%; (4) The material of the resin film includes one or more of polyolefin resin, cycloolefin resin, polyester resin, polycarbonate resin, sulfone polymer resin, polymethyl methacrylate resin and triacetyl cellulose resin; preferably cycloolefin resin; (5) The average film thickness D of the resin film is 15 to 60 μm.

3. A method for preparing the resin film according to claim 1 or 2, characterized in that: The following steps are involved: S1. Drying the resin raw material and controlling the mass content of fine powder in the resin raw material to be ≤10%; The fine powder is a resin raw material with a particle size of ≤50 μm; S2, using the product obtained in S1 to prepare a basement membrane; S3, preparing a stretched film by subjecting the base film to a double-stretching process; The stretching temperature T1 in the double-stretching process satisfies Tg+5°C≤T1≤Tg+30°C; S4. Heat-treating the stretched film to obtain the resin film.

4. The method for preparing the resin film according to claim 3, wherein: The S1 satisfies at least one of the following conditions: (1) controlling the mass content of fine powder in the resin raw material to be 0.01% to 5%; (2) drying the resin raw material in air or an inert atmosphere, preferably in a nitrogen atmosphere; (3) The drying temperature is 90 to 130°C, preferably 100 to 110°C.

5. The method for preparing the resin film according to claim 3, wherein: Said S2 adopts a casting method or a calendaring method to prepare the base film, preferably a casting method; Optionally, the casting method uses a single-screw or twin-screw extruder, preferably a single-screw extruder; Optionally, the casting method includes: a conveying section, controlling the temperature to be 230-270°C, preferably 250-260°C; Melting section, the temperature is controlled at 240-270°C, preferably 250-255°C; In the mixing section, the temperature is controlled at 240-270°C, preferably 250-255°C; Homogenization section, control the temperature to 230-260°C, preferably 240-250°C; The die head is controlled at a temperature of 230-250°C, preferably 240-250°C.

6. The method for preparing a resin film according to any one of claims 3 to 5, characterized in that: S3 satisfies at least one of the following conditions: (1)Tg+15℃≤T1≤Tg+20℃; (2) In the double-stretching process, the longitudinal stretching ratio is controlled to be 1.1≤MD≤6, preferably 1.5≤MD≤2.5; (3) In the double-stretching step, the transverse stretching ratio is controlled to be 1.1≤TD≤4, preferably 1.2≤TD≤2.

7. The method for preparing a resin film according to any one of claims 3 to 5, characterized in that: The S4 satisfies at least one of the following conditions: (1) The temperature of the heat treatment is T2 ≥ Tg, optionally, Tg + 20 ° C ≤ T1 ≤ Tg + 50 ° C, preferably Tg + 30 ° C ≤ T1 ≤ Tg + 40 ° C; (2) The heat treatment time is t, which satisfies 10s≤t≤300s, preferably 30s≤t≤60s.

8. A polarizer compensation film, characterized in that: A resin film according to any one of claims 1-2 or a resin film prepared according to the preparation method according to any one of claims 3-7.

9. A polarizer, characterized in that: Including the polarizer compensation film according to claim 8.

10. A liquid crystal display, characterized in that: Including the polarizer according to claim 9.

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