Method for testing spectral transmittance of multilayer liquid crystal polymer film

Abstract

The invention discloses a method for testing the spectral transmittance of a multilayer liquid crystal polymer film, which comprises the following steps: respectively preparing a reference sample wafer and a sample wafer to be tested on two same glass substrates with liquid crystal orientation layers attached on the surfaces, only spin-coating one layer of liquid crystal polymer film on the reference sample wafer, spin-coating N layers of liquid crystal polymer films on the sample wafer to be tested, N = K + 1; k is the layer number of the liquid crystal polymer film with the spectral transmittance to be tested and is greater than or equal to 1; keeping the film orientation and the liquid crystal orientation of the reference sample wafer and the tested sample wafer consistent, and testing the spectral transmittance T0 (lambda) of the reference sample wafer and the spectral transmittance Ts (lambda) of the tested sample wafer through a spectrophotometer; and obtaining the spectrum transmittance TSk (lambda) of the K layers of liquid crystal polymer films according to the T0 (lambda) and the Ts (lambda). When the spectral transmittance of the multi-layer liquid crystal polymer film is tested, the influence of the glass substrate and the attached liquid crystal orientation layer is eliminated, and the testing method is simple and practical.

Description

Technical Field

[0001] The invention belongs to the technical field of photoelectric testing, and relates to a method for testing the spectral transmittance of an optical film, in particular to a method for testing the spectral transmittance of a multilayer liquid crystal polymer film. Background Art

[0002] With the breakthrough in the theoretical research of geometric phase (also called PB phase), PB phase optical devices based on liquid crystal polymer film materials have become a research hotspot, and new PB phase optical devices such as liquid crystal polarization gratings, liquid crystal lenses, liquid crystal lens arrays, liquid crystal q-wave plates, and liquid crystal fork gratings have been developed. Before these optical devices are actually applied, certain optical performance parameters of liquid crystal polymer film materials need to be accurately measured, and the basic data obtained can better support the exploration of their applications. The spectral transmittance of liquid crystal polymer film is one of the very important optical performance parameters, especially when used in high-energy lasers and high-power lasers, the spectral transmittance data of the film will play an important reference role.

[0003] At present, the mainstream method for testing the spectral transmittance of thin films is to place the film directly in the optical path of a spectrophotometer for testing, which can easily obtain the spectral transmittance parameters of the film.

[0004] However, for liquid crystal polymer films, it is very difficult to directly use a spectrophotometer to test the spectral transmittance. First, liquid crystal polymer films used in PB phase optical devices are usually prepared by the uniform coating method. A small amount of prepolymer solution is dropped on a glass substrate pre-coated with a liquid crystal orientation layer, spin-coated and dried, and then UV-cured to finally obtain an optical-grade PB phase film. In other words, the liquid crystal polymer film does not exist independently, but is attached to a flat glass substrate. Secondly, the liquid crystal polymer film can also be peeled off from the glass substrate, but because the film is very thin, only micron-level thick, it is easy to break and curl.

[0005] In order to test the spectral transmittance of liquid crystal polymer film, the best way is of course to peel the film off the glass substrate for measurement, but the actual operation is not very realistic. If the film with glass substrate is directly measured as a whole, the influence of glass substrate and liquid crystal orientation layer attached to it will be brought into play. For example, the influence of Fresnel reflection, glass and liquid crystal orientation layer with different refractive index will have different Fresnel reflection. Summary of the invention

[0006] Purpose of the invention: The purpose of the present invention is to provide a method for testing the spectral transmittance of a multilayer liquid crystal polymer film that can eliminate the influence of a glass substrate and a liquid crystal orientation layer attached thereto.

[0007] Technical solution: The method for testing the spectral transmittance of a multilayer liquid crystal polymer film of the present invention comprises:

[0008] A reference sample and a sample to be tested are prepared on two identical glass substrates with a liquid crystal alignment layer attached to the surface, wherein the reference sample is spin-coated with only one layer of liquid crystal polymer film, and the sample to be tested is spin-coated with N layers of liquid crystal polymer film, N = K + 1; K is the number of layers of the liquid crystal polymer film whose spectral transmittance is to be tested, K ≥ 1;

[0009] Keep the film orientation of the reference sample and the sample under test consistent with the liquid crystal orientation direction, and use a spectrophotometer to test the spectral transmittance T0(λ) of the reference sample and the spectral transmittance T0(λ) of the sample under test. s (λ);

[0010] According to the spectral transmittance T0(λ) of the reference sample and the spectral transmittance T0(λ) of the tested sample, s (λ), obtain the spectral transmittance T of the K-layer liquid crystal polymer film Sk (λ).

[0011] Furthermore, the spectral transmittance T of the K-layer liquid crystal polymer film is Sk (λ) is calculated as: Sk (λ) = T s (λ) / T0(λ).

[0012] Furthermore, the spectral transmittance of the reference sample and the sample to be tested is tested by the same spectrophotometer.

[0013] Furthermore, first, the reference sample is placed in the test light path of the spectrophotometer, the film orientation and liquid crystal orientation direction of the reference sample are recorded, and the spectral transmittance T0(λ) of the reference sample is collected; then, the reference sample is taken out, and the sample to be tested is placed, the film orientation of the sample to be tested is kept consistent with that of the reference sample, the liquid crystal orientation direction of the sample to be tested is kept consistent with that of the reference sample, and the spectral transmittance T0(λ) of the sample to be tested is collected. s (λ).

[0014] Furthermore, the glass substrate includes ITO glass and white glass.

[0015] Furthermore, the liquid crystal alignment layer on the surface of the glass substrate is prepared by spin coating.

[0016] Furthermore, only one layer of liquid crystal alignment layer is spin-coated on the surface of the glass substrate.

[0017] Furthermore, the liquid crystal alignment layer adopts an SD1 photo alignment layer, and the SD1 photo alignment layer obtains an alignment effect through exposure.

[0018] Furthermore, the liquid crystal alignment layer adopts a polyimide PI alignment layer, and the polyimide PI alignment layer obtains an alignment effect through a friction treatment.

[0019] Furthermore, a method for preparing N layers of liquid crystal polymer films is as follows: on a glass substrate with a liquid crystal orientation layer attached thereto, a layer of liquid crystal polymer film is first prepared by spin coating, and then a second layer of liquid crystal polymer film is prepared by spin coating, and this operation is repeated until N layers of liquid crystal polymer films are prepared.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the present invention can eliminate the influence of the glass substrate and the liquid crystal orientation layer attached thereto when testing the spectral transmittance of the multilayer liquid crystal polymer film, and the testing method is simple and practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of a method for testing spectral transmittance of a multilayer liquid crystal polymer film provided by an embodiment of the present invention;

[0022] Figure 2 is a schematic diagram of the spectral transmittance test of a reference sample in an embodiment of the present invention;

[0023] Figure 3 It is a schematic diagram of the spectral transmittance test of the sample under test in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] like Figure 1 As shown, an embodiment of the present invention provides a method for testing spectral transmittance of a multilayer liquid crystal polymer film, comprising the following steps:

[0026] S1. Prepare a reference sample and a test sample on two identical glass substrates with a liquid crystal alignment layer attached to the surface, respectively, wherein the reference sample is spin-coated with only one layer of liquid crystal polymer film, and the test sample is spin-coated with N layers of liquid crystal polymer film, N = K + 1; K is the number of layers of the liquid crystal polymer film whose spectral transmittance is to be tested, K ≥ 1;

[0027] The glass substrates of the reference sample and the sample to be tested are the same, for example, ITO glass is used as the substrate, or white glass or other flat glass is used as the substrate.

[0028] A liquid crystal alignment layer, such as an SD1 photo-alignment layer or a polyimide PI alignment layer, is prepared on the surface of the glass substrate by spin coating, and the liquid crystal alignment layers on the two glass substrates are made using the same process conditions. If it is an SD1 photo-alignment layer, it needs to be exposed to obtain an alignment effect; if it is a polyimide PI alignment layer, it needs to be rubbed to obtain an alignment effect.

[0029] On the basis of preparing the liquid crystal alignment layer, a layer of liquid crystal polymer film is prepared by spin coating. One of the samples is completed and is called the reference sample. The other one is used to prepare the second layer of liquid crystal polymer film by spin coating, and then the third layer of liquid crystal polymer film is prepared by spin coating. This operation is repeated until N layers of liquid crystal polymer film are prepared, which is called the tested sample.

[0030] S2. Turn on the spectrophotometer and place the reference sample into the test light path of the spectrophotometer. Figure 2 As shown, the film orientation and liquid crystal orientation direction of the reference sample are recorded, and the spectral transmittance T0(λ) of the reference sample is collected.

[0031] S3, take out the reference sample, put in the sample to be tested, keep the film orientation of the sample to be tested consistent with that of the reference sample, and keep the liquid crystal orientation direction of the sample to be tested consistent with that of the reference sample, such as Figure 3 As shown, the spectral transmittance T of the sample under test is collected. s (λ).

[0032] S4, according to the spectral transmittance T0(λ) of the reference sample and the spectral transmittance T0(λ) of the tested sample s (λ), obtain the spectral transmittance T of the K-layer liquid crystal polymer film Sk (λ).

[0033] Spectral transmittance T of K-layer liquid crystal polymer film Sk (λ) is calculated as: Sk (λ) = T s (λ) / T0(λ).

Claims

1. A method for testing the spectral transmittance of a multilayer liquid crystal polymer film, characterized in that: include: A reference sample and a sample to be tested are prepared on two identical glass substrates with a liquid crystal alignment layer attached to the surface, wherein the reference sample is spin-coated with only one layer of liquid crystal polymer film, and the sample to be tested is spin-coated with N layers of liquid crystal polymer film, N = K + 1; K is the number of layers of the liquid crystal polymer film whose spectral transmittance is to be tested, K ≥ 1; Keep the film orientation of the reference sample and the sample under test consistent with the liquid crystal orientation direction, and use a spectrophotometer to test the spectral transmittance T0(λ) of the reference sample and the spectral transmittance T0(λ) of the sample under test. s (λ); According to the spectral transmittance T0(λ) of the reference sample and the spectral transmittance T0(λ) of the tested sample, s (λ), obtain the spectral transmittance T of the K-layer liquid crystal polymer film Sk (λ).

2. The method for testing spectral transmittance of a multilayer liquid crystal polymer film according to claim 1, characterized in that: Spectral transmittance T of K-layer liquid crystal polymer film Sk (λ) is calculated as: Sk (λ) = T s (λ) / T0(λ).

3. The method for testing spectral transmittance of a multilayer liquid crystal polymer film according to claim 1, characterized in that: The spectral transmittance of the reference sample and the sample under test is tested by the same spectrophotometer.

4. The method for testing spectral transmittance of a multilayer liquid crystal polymer film according to claim 3, characterized in that: First, place the reference sample into the test light path of the spectrophotometer, record the film orientation and liquid crystal orientation direction of the reference sample, and collect the spectral transmittance T0(λ) of the reference sample; Then, take out the reference sample, put in the sample to be tested, keep the film orientation of the sample to be tested consistent with that of the reference sample, keep the liquid crystal orientation direction of the sample to be tested consistent with that of the reference sample, and collect the spectral transmittance T of the sample to be tested. s (λ).

5. The method for testing spectral transmittance of a multilayer liquid crystal polymer film according to claim 1, characterized in that: The glass substrate includes ITO glass and white glass.

6. The method for testing spectral transmittance of a multilayer liquid crystal polymer film according to claim 1, characterized in that: The liquid crystal alignment layer on the surface of the glass substrate is prepared by spin coating.

7. The method for testing spectral transmittance of a multilayer liquid crystal polymer film according to claim 6, characterized in that: The liquid crystal alignment layer on the surface of the glass substrate is only spin-coated in one layer.

8. The method for testing spectral transmittance of a multilayer liquid crystal polymer film according to claim 1, characterized in that: The liquid crystal alignment layer adopts an SD1 optical alignment layer, and the SD1 optical alignment layer obtains an alignment effect through exposure.

9. The method for testing spectral transmittance of a multilayer liquid crystal polymer film according to claim 1, characterized in that: The liquid crystal alignment layer adopts a polyimide PI alignment layer, and the polyimide PI alignment layer obtains an alignment effect through a friction treatment.

10. The method for testing spectral transmittance of a multilayer liquid crystal polymer film according to claim 1, characterized in that: The preparation method of N layers of liquid crystal polymer film is as follows: on a glass substrate with a liquid crystal orientation layer attached thereto, a layer of liquid crystal polymer film is first prepared by spin coating, and then a second layer of liquid crystal polymer film is prepared by spin coating, and this operation is repeated until N layers of liquid crystal polymer film are prepared.

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