A photo-alignment mask and its design method

Abstract

The present invention belongs to the technical field of liquid crystal photo-alignment, and discloses a photo-alignment mask and its design method. The photo-alignment mask includes: a plurality of adjacent and alternating first regions and second regions, where the first regions and the second regions are adjacent to each other with multiple parallel straight lines as the adjacent dividing lines, the incident surfaces and the exit surfaces of the first regions and the second regions are the same and parallel to each other, both the first regions and the second regions include a plurality of two-dimensionally closely arranged unit structures, and each unit structure includes a cylindrical dielectric body disposed at the center and a metal body disposed outside the dielectric body, and the cross-section of the metal body is square. By adjusting the waveguide parameters of each unit structure, the present invention can make the exit angles of ultraviolet light after passing through the two regions symmetrical. Therefore, the present invention only needs one exposure to achieve the alignment of the product, greatly improving the alignment efficiency and the yield of the liquid crystal panel. Moreover, its structure is simple and convenient to prepare.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid crystal photo-alignment, and particularly to a photomask suitable for photo-alignment and a design method thereof. Background Art

[0002] In the process of manufacturing liquid crystal panels, the alignment process has an important impact on the quality of products. The alignment process is mainly divided into rubbing alignment and non-rubbing alignment. The rubbing alignment method can provide strong alignment ability for liquid crystal molecules. However, during the production process, the friction between the flannelette and the substrate will generate electrostatic and particle contamination, and electrostatic and particles can often directly cause damage to liquid crystal elements. Therefore, both academia and industry are researching non-rubbing alignment methods, which can not only avoid electrostatic and particle contamination, but also be easier to control liquid crystal molecules.

[0003] Among them, the most widely used non-rubbing alignment method is to irradiate the alignment agent with photosensitizer with linearly polarized ultraviolet light, which is generally called ultraviolet photo-alignment method, or photo-alignment for short. Photo-alignment uses linearly polarized ultraviolet light to irradiate the polymer alignment film with photosensitizer, so that the polymer has alignment ability. Its advantages are that it can avoid the contamination of the glass substrate surface, can perform small-area alignment, can perform patterned alignment through a photomask, and can control the parameters of liquid crystal cells, such as pretilt angle, surface alignment strength, etc. by using the angle of incident light and the length of irradiation time.

[0004] UV2A (Ultra Violet Vertical Alignment) technology is a VA (Vertical Alignment) panel technology for liquid crystal alignment using ultraviolet light (UV = UltraViolet). Its name comes from the multiplication of ultraviolet light UV and the VA mode of the liquid crystal panel. After adopting the UV2A technology, the aperture ratio, contrast ratio and response speed can be improved, and the production process can be greatly reduced. In the alignment process, in order to achieve a wide viewing angle display effect, polarized state UV light needs to irradiate a single sub-pixel area of the same substrate at a certain tilt angle twice or more times (for example, first perform the first one-way irradiation, then rotate the substrate 180°, and then perform the second one-way irradiation. The combination of the two one-way irradiations forms a two-way irradiation) to form an alignment effect of 4Domain, 8Domain, etc. At present, in the exposure using a half-blocking photomask, only half of the UV light plays a role in each exposure, so the utilization rate of UV light is low, and multiple exposures also reduce the production efficiency. Summary of the Invention

[0005] In order to solve the technical problems of low production efficiency and low utilization rate of ultraviolet light in the existing UV2A alignment technology, the present invention proposes an optical alignment mask and its design method to improve the production efficiency of optical alignment products.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: an optical alignment mask, comprising: a plurality of adjacent and alternating first regions and second regions, the first region and the second region are adjacent demarcation lines with mutually parallel and equidistant straight lines, the incident surfaces and the exit surfaces of the first region and the second region are the same and mutually parallel, both the first region and the second region include a plurality of two-dimensionally closely arranged unit structures, each unit structure includes a cylindrical dielectric body arranged at the center and a metal body arranged outside the dielectric body, and the cross section of the metal body is square;

[0007] Along the straight line direction, the radii of the dielectric bodies of the respective unit structures in the first region and the second region change; along the direction perpendicular to the straight line, the radii of the dielectric bodies of the respective unit structures in the first region are the same, the radii of the dielectric bodies of the respective unit structures in the second region are the same, and the radii of the dielectric bodies of the respective unit structures in the first region and the second region are different.

[0008] For the optical alignment mask described above, along the straight line direction, the radii of the dielectric bodies of the respective unit structures in the first region are periodic, and change monotonically within each period, the radii of the dielectric bodies of the respective unit structures in the second region are periodic, and change monotonically within each period, and the change trends of the first region and the second region are opposite.

[0009] The metal width between each adjacent unit structure is greater than the skin depth of the metal.

[0010] The parameters of each unit structure satisfy the following conditions:

[0011]

[0012] Among them, (x, y) represents the position of a certain unit structure 6, a(x, y) represents the radius of the dielectric body 7 of the unit structure 6 at this position, h represents the thickness of the unit structure, β(a(x, y)) represents the transverse propagation constant of the unit structure 6 located at this position, represents the initial phase of light, n represents an integer, x represents the horizontal axis displacement, θ in represents the incident angle, θ out1 and θ out2 respectively represent the exit angles of the first region and the second region, θ out1 = -θ out2 , λ represents the wavelength.

[0013] The relationship between the waveguide transverse propagation constant β and the radius a of the dielectric body is:

[0014]

[0015] J m (au) represents the Bessel function of the first kind of order m, represents the Hankel function of the first kind, J′ m (au) and represent the corresponding derivatives, u represents the transverse propagation constant of the incident light in the dielectric part, v represents the transverse propagation constant of the incident light in the metal part, and its expression is:

[0016]

[0017] where k d represents the wave vector of the incident light in the dielectric, k metal represents the wave vector of the incident light in the metal.

[0018] In addition, the present invention also provides a design method for the above-mentioned photo-alignment mask, including the following steps:

[0019] Step 1: First, according to the parameters of the exposure equipment, determine the angular frequency ω, wavelength λ, and incident angle θ of the incident light in , according to the product to be aligned, determine the widths pl of the first region and the second region, determine the exit angle θ out1 , θ out2 , and thereby calculate the distribution of the phase change ;

[0020] Step 2: Select the materials of the dielectric body and the metal body, and determine the relative dielectric constants ε d , ε metal , and calculate the numerical relationship β(a) between the radius a of the cylinder and the transverse propagation constant β of the waveguide according to the above parameters;

[0021] Step 3: Determine the side length d, thickness h of the metal body and the radius a of the dielectric body according to ;

[0022] Step 4: Calculate or measure the conversion efficiency of the first region and the second region, and in combination with the incident light power distribution, adjust the lengths l of the first region and the second region so that the energy of the outgoing light is the same in each first region and each second region.

[0023] In the said step 3, it further includes the step of determining the range of the number of unit structures in each first region and each second region.

[0024] In the said step 3, there is:

[0025]

[0026] The relationship between the transverse propagation constant β of the waveguide and the radius a of the dielectric body (7) is as follows:

[0027]

[0028] J m (au) represents the Bessel function of the first kind of order m, represents the Hankel function of the first kind, J′ m (au) and represent the corresponding derivatives, u represents the transverse propagation constant of the incident light in the dielectric part, v represents the transverse propagation constant of the incident light in the metal part, and their expressions are:

[0029]

[0030] Among them, k d represents the wave vector of the incident light in the dielectric, k metal represents the wave vector of the incident light in the metal.

[0031] The present invention has the following beneficial effects compared with the prior art:

[0032] The present invention proposes an optical alignment mask and its design method. By using the metasurface phase modulation method, the mask is divided into multiple unit structures to form multiple adjacent and alternating first regions and second regions. By optimizing the waveguide parameters of the first region and the second region, the exit angles of the ultraviolet light after passing through the two regions can be made symmetric. Therefore, the optical alignment mask of the present invention can achieve the alignment of the product with only one exposure, greatly improving the alignment efficiency and the yield rate of the liquid crystal panel. Moreover, its structure is simple and it is convenient to prepare. Description of the Drawings

[0033] Figure 1 is a schematic structural diagram of an optical alignment mask provided in Embodiment 1 of the present invention;

[0034] Figure 2 is a schematic diagram of the unit structures in the first region and the second region in Embodiment 1 of the present invention;

[0035] Figure 3 is a schematic diagram of the unit structure in Embodiment 1 of the present invention;

[0036] Figure 4 is a schematic diagram of light passing through the optical alignment mask in Embodiment 1 of the present invention;

[0037] Figure 5 is a schematic diagram of propagation in the cross-section AA of the mask in Embodiment 1 of the present invention;

[0038] Figure 6 is the relationship between the cylindrical radius a and in the unit structure provided by the present invention;

[0039] In the figure, 1 is the first region, 2 is the second region, 3 is a straight line, 4 is the incident surface, 5 is the exit surface, 6 is the unit structure, 7 is the dielectric body, 8 is the metal body, and 9 is the transition region. Specific Embodiment

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0041] Embodiment 1

[0042] As Figures 1 to 3 shown, Embodiment 1 of the present invention provides a photo-alignment mask, including: a plurality of adjacent and alternating first regions 1 and second regions 2, where the first regions 1 and the second regions 2 are adjacently divided by a plurality of mutually parallel straight lines 3, the incident surfaces 4 and the exit surfaces 5 of the first regions 1 and the second regions 2 are the same and mutually parallel, the first regions 1 and the second regions 2 each include a plurality of two-dimensionally closely arranged unit structures 6, and each unit structure 6 includes a cylindrical dielectric body 7 disposed at the center and a metal body 8 disposed outside the dielectric body 7, and the cross-section of the metal body 8 is square;

[0043] Specifically, as Figure 2 shown, in this embodiment, along the direction of the straight line 3, the radii of the dielectric bodies 7 in the respective unit structures 6 in the first regions 1 and the second regions 2 change periodically; along the direction perpendicular to the straight line 3, the radii of the dielectric bodies 7 in the respective unit structures 6 in the first regions 1 are the same, the radii of the dielectric bodies 7 in the respective unit structures 6 in the second regions 2 are the same, and the radii of the dielectric bodies 7 in the respective unit structures 6 in the first regions 1 and the second regions 2 are different.

[0044] Furthermore, in this embodiment, along the direction of the straight line 3, the radii of the dielectric bodies 7 in the respective unit structures 6 in the first regions 1 show periodicity and monotonically change within each period, the radii of the dielectric bodies 7 in the respective unit structures 6 in the second regions 2 show periodicity and monotonically change within each period, and the change trends in the first region and the second region are opposite.

[0045] Specifically, in this embodiment, the metal width between adjacent unit structures 6 is greater than the skin depth of the metal.

[0046] Furthermore, in this embodiment, the parameters of each unit structure 6 satisfy the following conditions:

[0047]

[0048] Among them, (x, y) represents the position of the unit structure 6, a(x, y) represents the radius of the dielectric body 7 of the unit structure at this position, h represents the thickness of the unit structure, and β(a(x, y)) represents the transverse propagation constant of the unit structure 6 at this position. represents the initial phase of the light, n represents an integer, x represents the horizontal axis displacement parallel to the direction of the straight line 3, and θ in represents the incident angle, and θ out1 and θ out2 respectively represent the exit angles of the first region and the second region, and θ out1 = -θ out2 , and λ represents the wavelength.

[0049] Further, in this embodiment, the relationship between the waveguide transverse propagation constant β and the radius a of the dielectric body 7 is:

[0050]

[0051] Among them, J m (au) represents the Bessel function of the first kind of order m, represents the Hankel function of the first kind, J′ m (au) and represent the corresponding derivatives, u represents the transverse propagation constant of the incident light in the dielectric part, v represents the transverse propagation constant of the incident light in the metal part, and its expression is:

[0052]

[0053] Among them, k d represents the wave vector of the incident light in the dielectric, and k metal represents the wave vector of the incident light in the metal, and there is:

[0054]

[0055] Among them, ε d and ε metal respectively represent the dielectric constants in the dielectric body and the metal, c represents the speed of light, and ω represents the angular frequency of the incident light.

[0056] Next, the alignment principle of the present invention will be introduced in combination with Figures 4 to 6 .

[0057] The incident light is incident on the point (x, y, 0) of the incident surface in a direction parallel to the xz plane. The angular frequency of the incident light is ω, the wavelength is λ, and the angle between the incident light and the normal direction is θ in , the angle between the exit light passing through the first region Area1 and the normal is θ out1 , and the angle between the exit light passing through the second region Area2 and the normal is θout2 = -θ out1 , the phase change of the incident light and the outgoing light satisfies the following relational expression:

[0058]

[0059] By attaching different phases to the light at different positions the deflection of light can be achieved.

[0060] In this embodiment, using the metasurface phase modulation method, the photomask is divided into multiple unit structures, and each unit structure will attach different phases to the light according to its different parameters. In this embodiment, each unit structure is a cylinder embedded in a cuboid. The height of the cuboid is h, the side length of the bottom of the cuboid is d, the height of the central cylinder is h, the radius is a, the material of the cylinder is dielectric, and the material of the remaining part of the cuboid is metal. Each unit structure can be regarded as a circular waveguide. The unit structure utilizes the fact that the propagation constant β of the surface plasmon mode in the waveguide changes with the radius a, and the unit structure can achieve the phase change of light in the range of 0 to 2π using this law.

[0061] The distribution of the radius a of the dielectric body 7 on the photomask satisfies then the above formula (1) can be obtained. According to formula (1) and θ out1 = -θ out2 the constraint relationship, the waveguide, that is, the geometric parameters of the unit structure 6, can be determined. In addition, in this embodiment, the width of the metal between adjacent unit structures should be greater than the skin depth of this kind of metal.

[0062] Embodiment 2

[0063] Embodiment 2 of the present invention provides a design method for an optical alignment photomask described in Embodiment 1, including the following steps:

[0064] Step 1: First, according to the parameters of the exposure equipment, determine the angular frequency ω, wavelength λ, and incident angle θ of the incident light in , according to the product to be aligned, determine the widths pl of the first region and the second region, and determine the outgoing angle θ out1 , θ out2 , and thus calculate the phase change

[0065] Step 2: Select the materials of the dielectric body 7 and the metal body 8, and determine the relative dielectric constants ε d , ε metal , and calculate the numerical relationship β(a) between the radius a of the cylinder and the transverse propagation constant β of the waveguide according to the above parameters. The calculation formula is the above formula (2).

[0066] Step 3: Determine the side length d, thickness h of the metal body 8, and radius a of the dielectric body 7.

[0067] Specifically, in Step 3, to determine each parameter, follow the following steps:

[0068]

[0069] Specifically, according to Formulas (7) and (8), the above Formula (1) can be obtained. Therefore, determine each of the above parameters according to Formula (1).

[0070] In the said Step 3, it also includes the step of determining the range of the number of unit structures in each first region 1 and second region 2.

[0071] Step 4: Calculate or measure the conversion efficiency of the first region 1 and second region 2, and adjust the length l of the first region 1 and second region 2 according to the conversion efficiency, in combination with the incident light power distribution, so that the energy of the outgoing light is the same in each first region 1 and each second region 2.

[0072] A transition method of this embodiment also includes the process of determining the transition region and other positions. Generally speaking, the UV2A technology is simultaneous exposure of multiple photomasks, and the connection position between the photomasks is regarded as the transition region. The specific processing method has nothing to do with the present invention, so no description is made.

[0073] After the design is completed, process a metal film with a thickness of h on the photomask according to the determined parameters, determine the position of each unit structure, and process a cylindrical hole in the center of each unit structure. Finally, fill the selected dielectric in the cylindrical hole to form a cylindrical dielectric body, thus completing the processing of the alignment mask.

[0074] After the previous manufacturing process is completed, only one exposure of the product is required, and then the subsequent manufacturing process of the product can be carried out.

[0075] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photo-alignment mask, characterized in that: include: A plurality of adjacent and alternating first regions (1) and second regions (2), wherein the first regions (1) and the second regions (2) are adjacently divided by a plurality of mutually parallel and equidistant straight lines (3), the incident surfaces (4) and the exit surfaces (5) of the first regions (1) and the second regions (2) are identical and mutually parallel, and the first regions (1) and the second regions (2) each comprise a plurality of two-dimensionally closely arranged unit structures (6), each unit structure (6) comprising a cylindrical dielectric body (7) arranged at the center and a metal body (8) arranged outside the dielectric body, and the cross section of the metal body (8) is a square; Along the straight line (3), the radius of the dielectric body (7) of each unit structure (6) in the first area (1) and the second area (2) changes; along the direction perpendicular to the straight line (3), the radius of the dielectric body (7) of each unit structure (6) in the first area (1) is the same, the radius of the dielectric body (7) of each unit structure (6) in the second area (2) is the same, and the radius of the dielectric body (7) of each unit structure (6) in the first area (1) is different from the radius of the dielectric body (7) of each unit structure (6) in the second area (2); along the straight line (3), the radius of the dielectric body (7) of each unit structure (6) in the first area (1) is periodic and changes monotonically in each period, the radius of the dielectric body (7) of each unit structure (6) in the second area (2) is periodic and changes monotonically in each period, and the change trends of the first area (1) and the second area (2) are opposite; The parameters of each unit structure (6) satisfy the following conditions: in, represents the position of the unit structure (6), represents the radius of the dielectric body (7) of the location unit structure (6), represents the thickness of the unit structure, represents the lateral propagation constant of the unit structure (6) at this location, represents the initial phase of light, n represents an integer, x represents the horizontal axis displacement, represents the angle of incidence, and denote the emission angles of the first and second zones respectively, , Indicates wavelength; Transverse propagation constant of waveguide The relationship with the radius a of the dielectric body (7) is: ； represents the m-th order Bessel function of the first kind, represents the Hankel function of the first kind, and represents the corresponding derivative, u represents the lateral propagation constant of the incident light in the dielectric part, v It represents the lateral propagation constant of the incident light in the metal part, and its expression is: ； ； in, represents the wave vector of the incident light in the dielectric, Represents the wave vector of incident light in the metal.

2. The optical alignment mask according to claim 1, characterized in that: The metal width between each adjacent unit structure (6) is greater than the skin depth of the metal.

3. A method for designing a photo-alignment mask according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step 1: First, determine the angular frequency of the incident light based on the parameters of the exposure equipment ,wavelength , and the angle of incidence , determine the width of the first and second zones according to the product to be aligned , determine the exit angle , , calculate the phase change The distribution of is calculated as follows: ； represents the initial phase of light, n represents an integer, x represents the horizontal axis displacement, represents the angle of incidence, and denote the emission angles of the first and second zones respectively, , Indicates wavelength; Step 2: Select the material of the dielectric body (7) and the material of the metal body (8), determine the relative dielectric constants of the two materials, and calculate the radius of the cylinder. The lateral propagation constant of the waveguide The numerical relationship ; The relationship between the waveguide lateral propagation constant and the radius a of the dielectric body (7) is: ； represents the m-th order Bessel function of the first kind, represents the Hankel function of the first kind, and represents the corresponding derivative, u represents the lateral propagation constant of the incident light in the dielectric part, v It represents the lateral propagation constant of the incident light in the metal part, and its expression is: ； ； in, represents the wave vector of the incident light in the dielectric, represents the wave vector of the incident light in the metal; Step 3: According to , determine the radius of the dielectric body (7) ; Represents the phase change between the incident light and the outgoing light; Step 4: Calculate or measure the conversion efficiency of the first zone (1) and the second zone (2), and adjust the length of the first zone (1) and the second zone (2) based on the incident light power distribution. , so that the energy of the emitted light in each first area (1) and each second area (2) is the same.

4. The method for designing a photo-alignment mask according to claim 3, characterized in that: The step 3 also includes the step of determining the number range of the unit structures in each of the first area (1) and the second area (2).

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