These two products belong to textile screen printing. Because most of their substrates are all kinds of textiles, the technical process is basically based on the textile screen printing process.

1. Development of flag and its production technology

The flag occupies an important position in people's minds at all times and all over the world. The flag making process in various periods is very exquisite. The following is a brief introduction.

1) History of flag making. On October 1, 1949, the first national flag was raised in Tiananmen Square. It was made of red silk cloth and yellow five pointed stars. Therefore, for a period of time, the production of flags was limited to sewing, splicing, patching, embroidery and other processes, but the speed was slow and the output was small. In the early 1950s, when the industries were divided into centralized departments, flag making belonged to industry. The national flag is produced by several printing and dyeing enterprises designated by the state. As for a small number of flags, some also use screen printing technology, but the technology is relatively backward. In the 1960s and 1970s, man-made fibers and other textiles began to be used in the flag industry, but the technology was still relatively primitive. In the production of the national flag and the party flag, the white five pointed star or the party emblem were first extracted by the discharge dyeing technology, and then the yellow was dyed with the basic dye. Therefore, its color fastness was very poor. In 1990, the national flag law was promulgated. The people's governments of all provinces, municipalities and autonomous regions approved a number of designated production enterprises and formulated national standards for the national flag and its color. With the development of market economy, the increase of flag categories has brought a development opportunity to the flag making industry. At present, the flag making industry in large and medium-sized cities is still developing to a deeper level, and can meet the market needs in terms of scale and product quality.

2) Technology and evolution of flag making. At present, the scale of the flag making enterprises is relatively small, and their equipment is not perfect. Compared with the regular screen printing enterprises, the gap is not small. Generally, there are not many relatively perfect flag making enterprises that do their own work or external processing according to changing needs. As the flag making materials are all kinds of textiles, their performance specifications are constantly changing, so the flag making technology is also changing. The fabrics used for screen printing flags are from pure cotton, real silk and man-made fiber fabrics used in the early days to polyester fabrics commonly used at present. The printing materials are different. The printing processes are divided into direct printing and discharge dyeing. For example, China's national flag, party flag, regiment flag and military flag are all yellow badges with red background, and discharge dyeing technology is adopted. There are also some enterprises that use the pigment direct printing process, and enterprises with good conditions have adopted the disperse dye direct printing process. Because the main feature of the flag is that the front and back of the pattern color should be consistent, and at the same time, the fabric should not be too thick, and the color of the paint direct printing should not be consistent with the front and back.

2. Types of flags

There are many kinds of flags, and their shapes and colors are different. Their uses are targeted to a certain extent. They can be broadly divided into the following types.

① Political flags: there are national flags, Party flags, regiment flags, military flags, national flags of nearly 200 countries and international organizations and regional flags in the world. Their graphic colors are complex and it is difficult to make.

② Logo (Chronicle) banner: a banner with striking words or insignia of units, groups, schools, etc., which can display their own images.

③ Propaganda flag: such as the special flag for large-scale advertising activities to achieve the purpose of propaganda and agitation.

④ Ceremonial flags: flags used by protocol in international exchanges, team flags presented by sports teams and brocade flags used for awards.

⑤ Maritime flag: such as the information flag, communication flag and command flag for ships.

3. Specification and manufacturing method of flag

1) Flag specifications. Except for special requirements, the flags we see in our daily life are used to indicate their specifications by size. Specific dimensions are as follows:

1 # flag 288cm × 192cm； 2 # flag 240cm × 160cm； 3 # flag 192cm × 128cm； 4 # flag 144cm × 96cm； 5 # flag 96cm × 64cm； 6 # flag 30cm × 20cm； 7 # flag 21cm × 14cm； 8 # flag 15cm × 10cm。 long × The high ratio is 3:2.

The national flag of Tiananmen Square is 500cm × 333cm, the flag should not exceed this specification. In various large-scale activities, the entrance type pilot flag is determined according to its size, generally at 15m × Around 10m, the largest flag can only be made by sewing. Flag and commercial flag are basically selected according to this standard. The strip-shaped publicity materials with a ratio of less than 3:2 belong to banners or special flags.

2) Flag making process. The production process of the flag is relatively complicated. First, the design emblem and text must be compatible with the size of the flag. Therefore, the first step is to enlarge or reduce the graphics and text, and then color separation and black-and-white drawing, or drawing and engraving to make a screen printing plate. In the production process of screen printing, it involves the width setting of the printing platen, the preparation of the printing paste, the selection of the scraper, the color fixing of the post-treatment, water washing, ironing and leveling. After printing, it is also necessary to sew. While ensuring the size of the flag, it is also necessary to pay attention to the robustness of the suture to prevent it from being damaged by the wind during hanging. The flagpole cover (also known as Qiyong) is the symbol of the appearance of the flag. Without it, it can not be called a flag. Therefore, its width should be consistent with the size of the flag.

3) Flag material. In recent years, the textiles used for flag making have basically replaced pure cotton with polyester fiber like Chunya spinning (thin material) and Oxford cloth (thick material), as well as artificial fiber fabrics and real silk. Therefore, the printing pastes used are also changed. Among them, the coating printing pastes are generally understood and familiar. Therefore, the basic points of direct printing and discharge of some disperse dyes are briefly introduced here, because it is the development direction of screen printing flags in the future. The pigment printing process will be gradually reduced or eliminated.

4) Direct printing with disperse dyes. It is a special dye for polyester fabric. It has complete color spectrum, strong color and bright surface. Thousands of varieties are produced at home and abroad a few days ago, and there is a large choice. Direct printing with disperse dyes is a common process. As the name implies, it is made by mixing the disperse dyes into the printing paste with the desired color and directly printing on the white or light colored polyester fabric. After drying, it is fixed at high temperature, washed with water, soaped and dried. The process flow is as follows:

Color matching paste → screen printing → high temperature fixation → water washing → soaping → drying and finishing. In color matching, the amount of disperse dye is determined according to the color depth, generally not more than 5%. The slurry as the carrier accounts for 60% - 70%, and 1% ammonium sulfate and 5% urea are appropriately added according to different conditions, and the rest is synthesized with water. The color paste shall have good fluidity and stability. The printed platen shall be properly heated to prevent infiltration and improve production efficiency.

There are three methods for high temperature fixation: one is high temperature and high pressure steaming, 135 ℃ / 20-30 minutes. The second is high temperature and atmospheric pressure steaming, 175-185 ℃ / 8-10 minutes, and the other is dry heat baking, 190-195 ℃ / 2-3 minutes. Can be determined according to respective conditions. Water washing is to wash the slurry and non fixed dye at normal temperature. Soap washing is to wash with 2 g / L caustic soda solution at 80-85 ℃ / 10-15 minutes.

5) Screen printing discharge process. It is more difficult for disperse dyes to discharge than other dyes. The key is the supply of high-temperature equipment and heat energy. At the same time, the technical requirements for preparing color pastes are high, and the use of auxiliaries should be accurate. Discharge dyeing is to hydrolyze the color of the printed part into white under high temperature by using dark and medium color polyester fabric and auxiliaries in the printing pulp. The discharge is divided into white and color. For example, the Hong Kong SAR flag is white and the Chinese flag is color. In the whitening printing, the slurry used for the carrier must be resistant to various chemical additives, with an amount of about 70%, stannous chloride (whitening agent) 6% - 8%, citric acid 0.5% - 1%, whitening agent 1% - 2%, urea 3% - 5%, and water to synthesize 100%. The printing paste of color drawing is basically made of dispersive dye with reducing agent added according to the white drawing formula. Of course, there are many requirements in the specific operation. The fixing conditions of high temperature and direct printing are basically similar, and the best conditions can be selected according to local conditions.

There are many ways to make flags by screen printing. Because it is not limited by color registration, it is rich in color and bright in color. Therefore, it lays a good foundation for the production of propaganda banners.

4. The rise of banners

① Banners are rising in the reform and opening up. If people want to gain public recognition in commercial and social public welfare publicity in an economic way, one of the best ways is to print and hang banners. Therefore, banners have become a method used by many enterprises for advertising and publicity, hanging above and below commercial buildings. In its heyday, various buildings in the streets and lanes can be seen everywhere. Necessary provisions have been made in the rectification of the city appearance, so that the publicity method is standardized.

② The technology of making banners is relatively simple, and anyone with a little knowledge of screen printing can implement it. First, it does not need formal equipment, and the printed platen can be selected according to local conditions. It is equipped with some mesh frames of different specifications and stretched with screens for use. The preparation of paint white and paint color is also convenient. When there is no computer engraving machine, the required words or graphics are usually written or designed manually. The key to design is to calculate the area of words or patterns and the distance between them. Because the printing volume of the banner is not large, the bottom plate is used for printing the banner. Generally, there is no need for photographic plate making. Instead, paper, polyester film or red film can be used for lettering, and some can be used for lettering with instant stickers, which can be used for screen printing. Nowadays, computer lettering is widely used, and its effect and efficiency are much better than manual lettering.

③ The textiles used for the banner include pure cotton fabric, polyester silk, Oxford spinning, etc. generally, the paint color is printed on the colored cloth, which is very simple; Color banners are also printed color by color by using the color registration process.